Tehran, Iran

Tarbiat Modares University is an exclusively graduate university with its main campus in Tehran, Iran. It was founded in 1982 and is consistently ranked among top universities in Iran. Tarbiat Modares University is the only exclusively graduate university in Iran and was founded to train university professors. Admission to the university is through national level university exams and in most programs is limited to top performers. Wikipedia.

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Mohammad-Zamani M.J.,Tarbiat Modares University | Moravvej-Farshi M.K.,Tarbiat Modares University | Neshat M.,University of Tehran
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2017

We propose an array of unbiased antennaless continuous wave (CW) THz photomixers made of subwavelength buried metal-semiconductor-metal (MSM) gratings with dissimilar Schottky barriers. These dissimilar metals in each unit cell are in intimate contact, and yet the maximum electric field appearing in the semiconducting material, unlike that in the planar structures, is far below its breakdown threshold. This relaxes the breakdown constraint that is normally confronted in the design of similar THz emitters with planar gratings. Besides, as compared with a similar array with subwavelength but planar MSM gratings, use of the buried MSM has increased the volume in which the carriers' photogeneration occurs, enhancing the resultant CW THz radiation by an order of magnitude. This is also five orders of magnitude greater than the THz power that can be radiated by a similar array of the same size with diffraction-limited planar electrodes. Moreover, calculating the frequency dependence of the THz output power, the newly proposed plasmons-assisted emitters are shown to be tunable in a wide range of 0.1-3 THz. We have also numerically demonstrated that 4.5% of the 1.58 mW optical pump can efficiently be converted to the THz power at the radiation frequency of 0.5 THz. © 1995-2012 IEEE.

Abbasi S.,Tarbiat Modares University
Current Opinion in Colloid and Interface Science | Year: 2017

Over the past few decades scientists have paid special attention to studying novel and natural polysaccharides due to the growing demand for ready meals, public awareness about the importance of natural fibers in the daily diet, as well as their wide range of applications especially in foods, pharmaceuticals and herbal medicines. Moreover, they are preferred to the biotechnologically produced ones as they are usually non-toxic, natural, biodegradable, biocompatible and ecologically friendly. Persian gum is one of these potential novel hydrocolloids which has been introduced and studied during the past few years. As well as outlining its botanical source, this review uses Persian gum as an example of the types of characterization that are necessary for such a new polysaccharide: physicochemical, structural, rheological, functional properties, interaction with other macromolecules (proteins and polysaccharides), as well as highlighting its key possible applications in foodstuffs. © 2017 Elsevier Ltd

Pahlavan S.,Tarbiat Modares University | Ahmadi V.,Tarbiat Modares University
IEEE Photonics Technology Letters | Year: 2017

In this letter, we report a novel approach in demultiplexer design by performing wavelength separation in hetero photonic crystal (HPC) with an oblique boundary. First step, demultiplexing action is considered like ordinary demultiplexers using wavelength dispersion in photonic crystals. Contrary to ordinary demultiplexers, the oblique boundary in HPC causes components of Bloch wave-vectors of different wavelengths not to be equal in the second step. This change in Bloch wave-vector results in ultra-high separation angles for incident wavelengths. A beam divergence of 133° is obtained for an input range from λ = 1521 to λ= 1550 nm. © 1989-2012 IEEE.

Seifouri M.,Shahid Rajaee Teacher Training University | Sharaf R.,Tarbiat Modares University
Optical and Quantum Electronics | Year: 2017

In this work new plasmonic assisted metal-semiconductor-metal photodetectors are presented. The new devices incorporate symmetric triangular and elliptic gratings, subwavelength slit and metal pads that is extended into the active layer made up of GaAs. Simulations are carried out using the 2-D finite difference time domain method. It is shown that with elliptic nanogratings and optimized horned shape extended metal pads, light transmission through the subwavelength slit of the proposed structure is 17 times that of a plasmonic photodetector consisting of only a subwavelength slit at the middle of the metal contacts with no gratings. It is also demonstrated that the triangular shaped nanogratings fixes the peak transmission around the desired wavelength of 830 nm, while the rectangular and elliptic counterparts red shift the maximum transmission to about 900 nm. © 2017, Springer Science+Business Media New York.

Saberi Moghaddam M.H.,Tarbiat Modares University | Saei Moghaddam M.,Quchan University of Advanced Technology | Khorramdel M.,Tarbiat Modares University
Energy | Year: 2017

This paper investigates the geometric parameters related to thermal efficiency and pollution emission of a multi-hole flat flame burner. Recent experimental studies indicate that such burners are significantly influenced by both the use of distribution mesh and the size of the diameter of the main and retention holes. The present study numerically simulated methane-air premixed combustion using a two-step mechanism and constant mass diffusivity for all species. The results indicate that the addition of distribution mesh leads to uniform flow and maximum temperature that will reduce NOx emissions. An increase in the diameter of the main holes increased the mass flow which increased the temperature, thermal efficiency and NOx emissions. The size of the retention holes should be considered to decrease the total flow velocity and bring the flame closer to the burner surface, although a diameter change did not considerably improve temperature and thermal efficiency. Ultimately, under temperature and pollutant emission constraints, the optimum diameters of the main and retention holes were determined to be 5 and 1.25 mm, respectively. © 2017 Elsevier Ltd

Basirat S.,Islamic Azad University | Salehi Neyshabouri S.A.A.,Tarbiat Modares University
River Sedimentation - Proceedings of the 13th International Symposium on River Sedimentation, ISRS 2016 | Year: 2017

Local scour around hydraulic structures have a significant impact on the design of them. Therefore, understanding the behavior of flow and changes of bed, influenced by the presence of structure on flow field is inevitable. © 2017 Taylor & Francis Group, London.

Sadeghi S.H.,Tarbiat Modares University | Hazbavi Z.,Tarbiat Modares University
Science of the Total Environment | Year: 2017

Quantitative response of the watershed health to climate variability is of critical importance for watershed managers. However, existing studies seldom considered the impact of climate variability on watershed health. The present study therefore aimed to analyze the temporal and spatial variability of reliability (Rel), resilience (Res) and vulnerability (Vul) indicators in node years of 1986, 1998, 2008 and 2014 in connection with Standardized Precipitation Index (SPI) for 24 sub-watersheds in the Shazand Watershed of Markazi Province in Iran. The analysis was based on rainfall variability as one of the main climatic drivers. To achieve the study purposes, the monthly rainfall time series of eight rain gauge stations distributed across the watershed or neighboring areas were analyzed and corresponding SPIs and RelResVulindicators were calculated. Ultimately, the spatial variation of SPI oriented RelResVulwas mapped for the study watershed using Geographic Information System (GIS). The average and standard deviation of SPI-RelResVulindex for the study years of 1986, 1998, 2008 and 2014 was obtained 0.240 ± 0.025, 0.290 ± 0.036, 0.077 ± 0.0280 and 0.241 ± 0.081, respectively. In overall, the results of the study proved the spatiotemporal variations of SPI-RelResVulwatershed health index in the study area. Accordingly, all the sub-watersheds of the Shazand Watershed were grouped in unhealthy and very unhealthy conditions in all the study years. For 1986 and 1998 all the sub-watersheds were assessed in unhealthy status. Whilst, it declined to very unhealthy condition in 2008 and then some 75% of the watershed ultimately referred again to unhealthy and the rest still remained under very unhealthy conditions in 2014. © 2017 Elsevier B.V.

Bagheri M.,Tarbiat Modares University | Masoomi M.Y.,Tarbiat Modares University | Morsali A.,Tarbiat Modares University
Journal of Hazardous Materials | Year: 2017

Synthesis of a new porous cobalt based metal-organic framework, [Co6(oba)6(CH3O)4(O)2]n·3DMF (TMU-11) has been carried out to introduce a new and highly efficient adsorbent of dibenzothiophene (DBT). This compound has been synthesized by solvothermal method using a nonlinear dicarboxylate ligand and characterized by single-crystal X-ray crystallography. To study the adsorption properties of the synthesized compound, TMU-11, for DBT removal, various factors, such as amount of adsorbent, contact time and temperature were examined. On the basis of the results, maximum efficiency and reusability in DBT removal occur under the mild reaction conditions. Furthermore, the DBT removal follows the pseudo-second order reaction kinetic. The maximum adsorption value is 825 mg/g. The selectivity test of DBT over naphthalene (NA) clearly shows that π−π interactions between organic linkers of TMU-11 and the aromatic ring of DBT are not responsible for the adsorption desulfurization (ADS) process and the main part of adsorption takes place on unsaturated site around Co centres. Our findings may provide some insight into the preparation of the adsorbent with superior performance in practical applications. © 2017 Elsevier B.V.

Bayat A.,Tarbiat Modares University | Saievar-Iranizad E.,Tarbiat Modares University
Journal of Luminescence | Year: 2017

Blue photoluminescent WS2 quantum dots (QDs) were synthesized using a simple top-down method from natural raw mineral tungsten disulfide via tip ultrasonication followed by centrifugation in a water-ethanol (0.7/0.3 ratio) as eco-friendly solvent. Cavitation process at a high power (300 W) led to the breaking of bulk WS2 flakes to its quantum dots. The as synthesized WS2 QDs showed blue photoluminescence upon UV excitation. The synthesized WS2 QDs were analysed by UV–vis and photoluminescence spectrophotometry, transmission electron microscopy, atomic force microscopy and X-ray diffraction. According to the transmission electron microscopy images, the size of WS2 QDs was obtained as 5 nm in average. © 2017

Ghorbanzadeh M.,Tarbiat Modares University | Moravvej-Farshi M.K.,Tarbiat Modares University | Darbari S.,Tarbiat Modares University
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2017

An optophoresis system based on surface plasmons in a simple microfluidic environment is proposed, which introduces new functionalities, including three-dimensional trapping of particles, bidirectional manipulation, controllable sorting, and in situ sensing. Its operating principle is based on plasmonic field, which is excited by the Kretschmann configuration on a gold stripe. In this system, trapping, manipulating, and sorting mechanisms are based on the balance of two oppositely exerted scattering forces induced by two counter-propagating surface plasmons. Moreover, for detecting particle's intrinsic properties and in situ position monitoring, we take advantage of the particle's lens-like behavior and stripe's edge effects. The proposed low-power functional system that can be simply and inexpensively integrated into lab-on-a-chip devices is a promising candidate for biological applications and developing integrated optical manipulation chips. © 2016 IEEE.

Imani M.,Tarbiat Modares University | Ghassemian H.,Tarbiat Modares University
Remote Sensing Letters | Year: 2017

A spectral–spatial hyperspectral image classification method is proposed in this article. The proposed method is local histogram and discriminative based classification (LHD). It is implemented in two steps. In the first step, a projection matrix is obtained by maximizing the class discrimination and preserving the local structure of data using both the spectral and spatial neighbours. In the second step, the contextual features are extracted from the local regions using the histogram as a nonparametric statistical estimate. Finally, with incorporating spectral and spatial features, the classification map is obtained. The experimental results demonstrate that the proposed method is superior to some state-of-the-art alternatives. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Khorasani A.C.,Tarbiat Modares University | Shojaosadati S.A.,Tarbiat Modares University
Food Hydrocolloids | Year: 2017

The present research evaluated the effects of starch and carboxymethylcellulose (CMC) incorporation with bacterial nanocellulose-pectin bionanocomposite (BNC-pec) on the protection of Bacillus coagulans under drying and simulated gastrointestinal (SGI) conditions. The BNC-pec used for the bacteria entrapment was coated with starch and CMC. This was followed by the investigation of the surface morphology, molecular bondings and crystallinity of such hydrocolloids. SEM images revealed that starch created smooth and compact surface compared to CMC did disrupted and patchy for BNC-pec. FTIR analysis revealed the hydrogen bonds as the most important intermolecular interactions in the matrices, and there existed no evidence of the formation of chemical bonds via coating, thus entrapping the cells without chemical reactions. In addition, the coating transformed the semi-crystallinity structure of the BNC-pec into amorphous. Prebiotic score of BNC-pec increased more in the case of the CMC-coated compared to starch-coated. Although the BNC-pec increased the survivability to approximately 95%, CMC and starch coating could not improve it during microwave drying. CMC and starch caused an upgrade in the survival rate resulting from the BNC-pec from 75 to 92.68 and 97.37%, respectively under SGI conditions. In order to improve the cell viability under both drying and SGI conditions, the prebiotic matrix was prepared using 60% BNC, 15% pectin and 25% CMC or starch as coating. The matrices yielded high survivability of B. coagulans at 66.67 (CMC-coated) and 61.67% (starch-coated) compared to free cell (47.93%). The present findings proposed novel prebiotic bionanocomposites as good promises for probiotics protection. © 2016 Elsevier Ltd

Ghasemi Estahbanati E.,Tarbiat Modares University | Omidkhah M.,Tarbiat Modares University | Ebadi Amooghin A.,Arak University
ACS Applied Materials and Interfaces | Year: 2017

In this research, Pebax1657 as an organic phase and silver nanoparticles as an inorganic phase were used for preparation of binary mixed matrix membranes (MMMs). Silver nanoparticles as a filler could enter the polymer chains and enhance the gas permeability by increasing the fractional free volume of membranes. Afterward, ternary MMMs were fabricated by addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid, in order to have better polymer/filler adhesion and eliminate interfacial defects and nonselective voids. In addition, positively polarized silver nanoparticles in the presence of the IL could interact with PEO segment of the polymer and increase the CO2 affinity of membranes, which results in increasing the CO2/light gases permselectivity of MMMs. Gas permeation properties of MMMs were studied at a temperature of 35 °C and operating pressures from 2 to 10 bar. Moreover, fabricated membranes were characterized by fourier transform infrared-attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimeter (DSC). The analysis revealed that there is a proper adhesion between positively charged surface of nanoparticles and the polymer, and both filler and IL decrease the crystallinity of the membranes, which could enhance the polar gas transport properties. Gas permeation results showed significant enhancement in CO2 permeability (325 Barrer) for binary membrane (Pebax 1657/1%Ag) at 35 °C and 10 bar. Moreover, ternary MMM (Pebax 1657/0.5%Ag/50%IL) encountered significant increase in both permeability and selectivity in comparison with neat membrane. Indeed, the CO2 permeability increased from 110 Barrer to 180 (about 64%). Moreover, the related CO2/CH4 and CO2/N2 selectivities were increased from 20.8 to 61.0 (more than 193%) and from 78.6 to 187.5 (about 139%), respectively. © 2017 American Chemical Society.

Zare M.H.,Tarbiat Modares University | Mohamadian M.,Tarbiat Modares University | Beiranvand R.,Tarbiat Modares University
IEEE Transactions on Industrial Electronics | Year: 2017

In this paper, a novel single-stage three-port inverter that connects photovoltaic (PV) panel to a single-phase power grid is introduced. In a single-phase grid-connected PV panel, the input power is constant during the line-frequency period, while the output power oscillates at double-line frequency. A series active power decoupling circuit utilizing thin-film capacitors is incorporated to a conventional flyback inverter to handle input and output power differences. Therefore, popularly low-reliable electrolytic capacitors are replaced with small long-lifetime thin film. The proposed inverter can extract the maximum power from PV, deliver a low total harmonic distortion sinusoidal current to the output, and decouple the input and output powers. The proposed power decoupling circuit shares the inverter main switch. Thus, these functions are achieved using just three switches and a simple control scheme which is applicable for both charging and discharging states. Operation principle and control strategy are discussed in detail. Experimental results based on a 100-W prototype inverter verify feasibility and functionality of the proposed inverter. © 2016 IEEE.

Feiz R.,Tarbiat Modares University | Rezghi M.,Tarbiat Modares University
Journal of Visual Communication and Image Representation | Year: 2017

Color image restoration is an important problem in image processing. Using the structured total least squares (STLS) for fidelity term of the restoration process gives better results in comparison with the least squares (LS) approach. The main drawback of the STLS approach is its complexity. To overcome this issue, in this paper by an appropriate transformation the color image restoration is substituted with two smaller subproblems corresponding to smooth and oscillatory parts of the image. The first and second subproblems are modeled via STLS and LS approaches, respectively. We show that the proposed method is faster than STLS and gives competitive solutions with it. Also, we demonstrate that Haar wavelet perseveres the structure of the blurring operator, which causes a considerable reduction in computational and storage complexity of the proposed method. © 2017 Elsevier Inc.

Keshavarz H.,Tarbiat Modares University | Abadeh M.S.,Tarbiat Modares University
Knowledge-Based Systems | Year: 2017

Sentiment analysis is about classifying opinions expressed in text. The aim of this study is to improve polarity classification of sentiments in microblogs by building adaptive sentiment lexicons. In the proposed method, corpora-based and lexicon-based approaches are combined and lexicons are generated from text. The sentiment classification is formulated as an optimization problem, in which the goal is to find optimum sentiment lexicons. A novel genetic algorithm is then proposed to solve this optimization problem and find lexicons to classify text. The algorithm generates adaptive sentiment lexicons, and then a meta-level feature is extracted based on it, which is then used alongside Bing Liu's lexicon and n-gram features. The experiments are conducted on six datasets. In terms of accuracy, the results outperform the state-of-the-art methods proposed in the literature in two of the datasets. Also, in four of the datasets, the proposed approach outperforms in terms of F-measure. Applying the proposed method on six datasets, the accuracy is higher than 80% in all six datasets and the F-measure is higher than 80% in four of these datasets. Using the sentiment lexicons created by the proposed algorithm, one can get a better understanding of the specific language and culture of Twitter users and sentiment orientation of words in different contexts. It is also shown that it is useful not to omit the conventional stop-words, as each word can have its sentimental implications. © 2017.

Poor H.M.,Tarbiat Modares University | Sadrameli S.M.,Tarbiat Modares University
Fluid Phase Equilibria | Year: 2017

Flash point (FP) is a key property and play an important role in hazard classification, safe handling, transportation, and it is used to characterize the fire hazards of liquids. The prediction of this important property of mixtures, leads to design process to avoid the occurrence of fire or explosion. Activity coefficient models are vital to impose the non-ideality of the mixture and accurately predict the flash point of the system. In the present work, correlative local composition activity coefficient models such as Wislon, NRTL, UNIQUAC, and predictive models such as UNIFAC, UNIFAC-LBY, UNIFAC-DMD, and NIST modified UNIFAC (UNIFAC-NIST) together with the general flash point model of Liaw et al. were used to predict the flash point of 15 binary mixtures. The deviations on the flash point using the Ideal, Wilson, NRTL, UNIQUAC, UNIFAC, UNIFAC-LBY, UNIFAC-DMD, and UNIFAC-NIST, are 1.68, 1.72, 1.73, 1.80, 2.04, 2.11, 2.36, and 4.02 K, respectively. Finally, one can conclude that the results of predictive model are superior respect to the correlative models. UNIFAC-LBY model gives the minimum deviation amongst the predictive models, even rather than UNIFAC-NIST model, which in it development, the quality of experimental data critically evaluated. So, UNIFAC-LBY model successfully can be used to predict the unreported FP data, and those materials that are toxic, explosive, and radioactive. Finally, in the absence of phase equilibria data, the local composition parameters regressed through the flash point data. © 2017 Elsevier B.V.

Nozohour Yazdi M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University
New Journal of Chemistry | Year: 2017

A rapid, sensitive, high clean-up and economic three phase hollow fiber liquid phase microextraction method followed by HPLC-UV was applied for speciation of inorganic selenium in water and biological samples. The most sensitive absorption line at 332 nm was used for all determinations. Selenium(iv) was reacted with o-phenylenediamine to form piazselenol in an acidic medium (pH = 2). Subsequently the piazselenol complex was extracted into 20 μL of n-dodecane in the pores of the hollow fibers (membrane solvent), and then into the methanol that fills the lumen of the hollow fibers. After separation, preconcentrated Se(iv) in the organic phase was determined using HPLC-UV. Total inorganic selenium was obtained by reduction of Se(vi) to Se(iv) with hydrochloric acid. Then the concentration of Se(vi) was calculated by subtracting the concentration of Se(iv) from the total inorganic selenium concentration. The parameters that could have an effect on extraction, including pH, amount of complex reagent, HF length, extraction time, salt concentration and stirring rate, were optimized by using the one variable at a time method and central composite design. Under optimum conditions, a linear range of 0.05-200 μg L−1 (R2 > 0.998), a limit of detection (S/N = 3) of 0.02 and a preconcentration factor of 195 with a relative standard deviation of 5.1% were achieved. The proposed method was successfully applied to the speciation of inorganic selenium in different water and biological samples with recoveries of 95-103% for spiked samples. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Khosravian-Arab H.,Amirkabir University of Technology | Dehghan M.,Amirkabir University of Technology | Eslahchi M.R.,Tarbiat Modares University
Journal of Computational Physics | Year: 2017

This paper is intended to provide exponentially accurate Galerkin, Petrov–Galerkin and pseudo-spectral methods for fractional differential equations on a semi-infinite interval. We start our discussion by introducing two new non-classical Lagrange basis functions: NLBFs-1 and NLBFs-2 which are based on the two new families of the associated Laguerre polynomials: GALFs-1 and GALFs-2 obtained recently by the authors in [28]. With respect to the NLBFs-1 and NLBFs-2, two new non-classical interpolants based on the associated- Laguerre–Gauss and Laguerre–Gauss–Radau points are introduced and then fractional (pseudo-spectral) differentiation (and integration) matrices are derived. Convergence and stability of the new interpolants are proved in detail. Several numerical examples are considered to demonstrate the validity and applicability of the basis functions to approximate fractional derivatives (and integrals) of some functions. Moreover, the pseudo-spectral, Galerkin and Petrov–Galerkin methods are successfully applied to solve some physical ordinary differential equations of either fractional orders or integer ones. Some useful comments from the numerical point of view on Galerkin and Petrov–Galerkin methods are listed at the end. © 2017 Elsevier Inc.

Partovi S.M.A.,Tarbiat Modares University | Sadeghnejad S.,Tarbiat Modares University
Computers and Geosciences | Year: 2017

The aim of well-to-well correlation is to detect similar geological boundaries in two or more wells across a formation, which is usually done manually. The construction of such a correlation by hand for a field with several wells is quite complex and also time-consuming as well. The aim of this study is to speed up the well-to-well correlation process by providing an automated approach. The input data for our algorithm is the depths of all geological boundaries in a reference well. The algorithm automatically searches for similar depths associated with those geological boundaries in other wells (i.e., observation wells). The fractal parameters of well-logs, such as wavelet exponent (Hw), wavelet standard deviation exponent (Hws), and Hausdorff dimension (Ha), which are calculated by wavelet transform, are considered as pattern recognition dimensions during the well-to-well correlation. Finding the proper fractal dimensions in the automatic well-to-well correlation approach that provide the closest geological depth estimation to the results of the manual interpretation is one of the prime aims of this research. To validate the proposed technique, it is implemented on the well-log data from one of the Iranian onshore oil fields. Moreover, the capability of gamma ray, density, and sonic log in automatic detection of geological boundaries by this novel approach is also analyzed in detail. The outcome of this approach shows promising results. © 2017 Elsevier Ltd

Khodkar F.,Tarbiat Modares University | Golshan Ebrahimi N.,Tarbiat Modares University
Journal of Applied Polymer Science | Year: 2017

Coaxial electrospinning is a method for producing fibrous mats with optional features, such as antibacterial properties, controllable release, and hydrophobicity based on shell materials. Because these features are important in biomedical applications, in this study, biocompatible hydrophobic polymer (polycaprolactone) and hydrophilic polymer [poly(vinyl alcohol)] with silver nanoparticles loaded in the core solution were coaxially electrospun. The effect of silver addition on the conductivity and viscosity of the solutions, chemical structure of the fiber mats, mechanical properties, porosity, hydrophobicity, water vapor transmission rate (WVTR), silver release, and antibacterial properties were investigated. Fibers with silver exhibited less porosity and a lower WVTR and a greater contact angle than the fibers without silver. Furthermore, the core–shell fibers reduced the burst release of silver and successfully prevented the growth of Escherichia coli and Staphylococcus aureus bacteria. Therefore, it seems that these fibers are suitable for providing electrospun mats with long-term antibacterial properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44979. © 2017 Wiley Periodicals, Inc.

Bathaie S.Z.,Tarbiat Modares University | Ashrafi M.,Shiraz University | Azizian M.,Tarbiat Modares University | Tamanoi F.,University of California at Los Angeles
Current Molecular Pharmacology | Year: 2016

Mevalonate (MVA) is synthesized from 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) by HMG-CoA reductase (HMG-CoAR). MVA is further metabolized to farnesyl pyrophosphate (FPP), a precursor of cholesterol and sterols. FPP is also converted to geranylgeranyl pyrophosphate, and these lipids are used for post-translational modification of proteins that are involved in various aspects of tumor development and progression. Many studies showed that the MVA pathway is up-regulated in several cancers such as leukemia, lymphoma, multiple myeloma; as well as breast, hepatic, pancreatic, esophageal and prostate cancers. Several mechanisms may be involved in dysregulation of this pathway. They include p53 mutation, a mutation in HMG-CoAR and sterol-regulatory element binding protein (SREBP) cleavageactivating protein SCAP as its regulator, PKB/Akt activation, decreased AMPK activation, and activation of transcription factors such as: SREBP and HIF-1. Statins as inhibitors of MVA pathway might be useful for cancer prevention and/or treatment through their interactions with essential cellular functions, such as cell proliferation and differentiation. Other inhibitors are also designed for inhibition of this key pathway and their mechanism of action was investigated. In the present review, we will first describe about some inhibitors of MVA, including statins that have been suggested for cancer treatment. We will then discuss about the mechanisms involved in MVA dysregulation, especially in cancer. © 2016 Bentham Science Publishers.

Ibrahim W.,Tarbiat Modares University | Abadeh M.S.,Tarbiat Modares University
Journal of Theoretical Biology | Year: 2017

Protein fold recognition is an important problem in bioinformatics to predict three-dimensional structure of a protein. One of the most challenging tasks in protein fold recognition problem is the extraction of efficient features from the amino-acid sequences to obtain better classifiers. In this paper, we have proposed six descriptors to extract features from protein sequences. These descriptors are applied in the first stage of a three-stage framework PCA-DELM-LDA to extract feature vectors from the amino-acid sequences. Principal Component Analysis PCA has been implemented to reduce the number of extracted features. The extracted feature vectors have been used with original features to improve the performance of the Deep Extreme Learning Machine DELM in the second stage. Four new features have been extracted from the second stage and used in the third stage by Linear Discriminant Analysis LDA to classify the instances into 27 folds. The proposed framework is implemented on the independent and combined feature sets in SCOP datasets. The experimental results show that extracted feature vectors in the first stage could improve the performance of DELM in extracting new useful features in second stage. © 2017 Elsevier Ltd

Binesh N.,Tarbiat Modares University | Rezghi M.,Tarbiat Modares University
Applied Soft Computing Journal | Year: 2017

Clustering or community detection is one of the most important problems in social network analysis, and because of the existence of overlapping clusters, fuzzy clustering is a suitable way to cluster these networks. In fuzzy clustering, in addition to the correctness of the clusters assigned to each node, the produced membership of one node to each cluster is also important. In this paper, we introduce a new fuzzy clustering algorithm based on the nonnegative matrix factorization (NMF) method. Despite the well-known fuzzy clustering techniques like FCM, the proposed method does not depend on any parameter. Also, it can produce appropriate memberships based on the network structure and so identify the overlap nodes from non-overlap nodes, well. Also, to evaluate the validity of such fuzzy clustering algorithms, we propose two new evaluation criteria (SFEC and UFEC), which are constructed based on the neighborhood structure of nodes and can evaluate the memberships. Experimental results on some real-world networks and also many artificial networks show the effectiveness and reliability of our proposed criteria. © 2017 Elsevier B.V.

Shanei A.,Isfahan University of Medical Sciences | Shanei M.M.,Tarbiat Modares University
Ultrasonics Sonochemistry | Year: 2017

When a liquid is irradiated with high intensities of ultrasound irradiation, acoustic cavitation occurs. Acoustic cavitation generates free radicals from the breakdown of water and other molecules. Cavitation can be fatal to cells and is utilized to destroy cancer tumors. The existence of particles in liquid provides nucleation sites for cavitation bubbles and leads to decrease the ultrasonic intensity threshold needed for cavitation onset. In the present investigation, the effect of gold nanoparticles with appropriate amount and size on the acoustic cavitation activity has been shown by determining hydroxyl radicals in terephthalic acid solutions containing 15, 20, 28 and 35 nm gold nanoparticles sizes by using 1 MHz low level ultrasound. The effect of sonication intensity in hydroxyl radical production was considered. The recorded fluorescence signal in terephthalic acid solutions containing gold nanoparticles was considerably higher than the terephthalic acid solutions without gold nanoparticles at different intensities of ultrasound irradiation. Also, the results showed that the recorded fluorescence signal intensity in terephthalic acid solution containing finer size of gold nanoparticles was lower than the terephthalic acid solutions containing larger size of gold nanoparticles. Acoustic cavitation in the presence of gold nanoparticles can be used as a way for improving therapeutic effects on the tumors. © 2016 Elsevier B.V.

Amin F.,Tarbiat Modares University | Malek A.,Tarbiat Modares University
Numerical Heat Transfer, Part B: Fundamentals | Year: 2017

This paper presents some novel problems associated with the steady natural convection flow in an inclined square cavity filled with a saturated porous medium. The proposed method is a high-accurate spectral method based on the Fourier–Galerkin technique. The numerical results have demonstrated the advantage for the following reasons. (a) The high-accurate method deals with inclined geometries successfully. (b) The streamlines, isotherms, and the average Nusselt numbers are affected significantly by the inclination of the cavity for high values of Rayleigh number. (c) In contrast with the finite element method a highly accurate and efficient solution with less computational effort is obtained. © 2017 Taylor & Francis

Mousavi S.,Tarbiat Modares University | Saeedi S.,Tarbiat Modares University
International Journal of Circuit Theory and Applications | Year: 2017

This paper describes selectivity and sensitivity performance evaluations and improvement methods for an on-off keying super-regenerative (SR) receiver. A slope-controlled quasi-exponential quench waveform, generated by a low-complexity PVT-tolerant quench generator circuit, is proposed to increase data rate and reduce the receiver 3-dB bandwidth, thereby preventing oscillation caused by out-of-band injected signals and improving the receiver selectivity. The SR receiver sensitivity is also enhanced by a noise-canceling front-end topology with single-ended to differential (S2D) signal converter. To exemplify these techniques, we designed an SR receiver with the proposed front-end and quench waveform generator in a 0.18-μm CMOS technology. Theoretical analyses and circuit simulations show 30% and 65% reduction in 3-dB bandwidth of the SR receiver at 25 Mbps data rate by employing the proposed quench signal compared with piecewise-linear and trapezoidal quench waveforms, respectively. Performance of the proposed front-end is evaluated by a fast bit-error-rate estimation procedure, based on circuit noise simulations and statistical analyses, without the need for time-consuming transient-noise simulations. Accuracy of the procedure has been verified by comparing its results with transient-noise simulations. According to the estimated bit-error-rate curves, the noise-canceling topology with S2D converter enhances the SR receiver sensitivity by 9 dB. © 2017 John Wiley & Sons, Ltd.

Zakian P.,Tarbiat Modares University | Khaji N.,Tarbiat Modares University | Kaveh A.,Iran University of Science and Technology
Computers and Structures | Year: 2017

Stochastic finite element method (StFEM) is a robust tool for uncertainty quantification of engineering systems having random properties. Nevertheless, the matrices involved in this method are very large compared to their deterministic counterparts. Thus, the computational aspects of StFEM are of great importance to be optimized. In this paper, an efficient StFEM is developed for analysis of structures. For this purpose, a method based on graph concepts is presented and extended to StFEM and recently developed stochastic spectral finite element method (StSFEM) procedures. Here, mathematical remedies are incorporated to enhance the analysis performance. Firstly, a graph theoretical method is presented for swift numerical solution of Fredholm integral equation arising from Karhunen–Loève expansion, which greatly reduces the existing computational cost, and can even be applied to the domain without symmetry. Secondly, a preconditioner is applied to decompose the matrices to Kronecker products of sub-matrices, and then graph product rules are utilized to solve the governing linear equation of cyclically symmetric models without inversing the final matrix, while only a small matrix is inversed instead. The proposed method provides significant improvement in the stochastic structural analysis. Illustrative examples demonstrate the efficiency and accuracy of the present method as a swift analysis. © 2016 Elsevier Ltd

Moshaii A.,Tarbiat Modares University
Scientia Iranica | Year: 2016

Improvement of the efficiency of a Rhodamine 6G dye laser by adding proper concentrations of gold colloidal nanoparticles into the dye solution has experimentally been investigated. Gold colloidal nanoparticles, due to their strong plasmonic peak in the visible region, are expected to have a considerable interaction with Rhodamine 6G dye molecules with broad emission spectrum in the visible range. It is shown that with addition of enough low concentrations (less than 0.4 μ M/l) of gold nanoparticles to the dye solution, both the output power and the efficiency of the dye laser increase. The best improvement of the laser effciency reaches 15%. Two amplifying mechanisms exist for efficiency improvement by the nanoparticles, which are resonant energy transfer from the plasmonic nanoparticles to the dye molecules and the high near field around the nanoparticles. The results indicate that in low concentrations of gold nanoparticles, the amplifying mechanisms dominate the dissipating mechanism of scattering of the pumped light by the nanoparticles. This leads to the efficiency improvement by addition of the nanoparticles. © 2016 Sharif University of Technology. All rights reserved.

Nozohour Yazdi M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University
Journal of Separation Science | Year: 2017

The speciation of chromium(VI) and chromium(III) was investigated by using hollow fiber liquid-phase microextraction based on two immiscible organic solvents followed by high performance liquid chromatography with ultraviolet detection. In this method, chromium(VI) and chromium(III) reacted with ammonium pyrrolidine dithiocarbamate to produce hydrophobic complexes. Subsequently, the complexes were first extracted into a thin layer of organic solvent (n-dodecane) present in the pores of a porous hollow fiber, and then into a μL volume of an organic acceptor (methanol) located inside the lumen of the hollow fiber. Then, the extracting organic phase was injected into the separation column of the high-performance liquid chromatograph for the analysis of both chromium species. Effective parameters on extraction were optimized using one-variable-at-a-time method and central composite design. Under optimized conditions, a linear range of 0.25-100 and 0.5-100 μg/L (R2 > 0.998), the limits of detection of (S/N = 3) 0.08 and 0.1 μg/L and a preconcentration factor of 625 and 556 were achieved for chromium(VI) and chromium(III), respectively. The method was successfully applied to the speciation and determination of chromium species in different water samples and satisfactory results were obtained. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yousefi Seyf J.,Tarbiat Modares University | Haghtalab A.,Tarbiat Modares University
Fluid Phase Equilibria | Year: 2017

A connection is established between molecular level phenomena (molecular dynamics simulation) and macroscopic properties to obtain the solubility of solutes in a solvent. Condensed phase Optimized Molecular Potential for Atomistic Simulation Studies (COMPASS) was applied as a force field in Molecular Dynamics (MD) simulation. Radial distribution function (RDF) is used to calculate the interaction parameters of the local composition (LC) activity coefficient models, so that a specific range of RDF was considered. Using the present approach, the solubility of pharmaceuticals in the various solvents are calculated and compared with the experiment. The results demonstrate that the interaction parameters are radius dependent, but from engineering and practical point of view, the averaged interaction parameters are used in calculation of solid-liquid equilibrium. The upper limits of the integral for the average interaction parameters are determined at the specified radius which the slope of its tangent was zero. The important feature of the present study is that using RDF through MD simulation gives a pair of interaction parameter that could well predict the experimental solubility data. To validate the present method, the solubility of pharmaceutical solutes such as aspirin, acetaminophen, defriprone, and ephedrine were simulated in the selected solvents at 298.15 K and 1 atm. Thus, the MD simulations of these pharmaceutical systems are simulated and their RDFs are obtained to calculate the energy parameters of the LC models so that their solubility in a given solvent are calculated. The calculated solubility using LC models show that NRTL model presents the lowest deviation from the experimental solubility data. © 2017 Elsevier B.V.

Kamari Kaverlavani S.,Tarbiat Modares University | Moosavifard S.E.,Islamic Azad University at Tehran | Bakouei A.,Tarbiat Modares University
Chemical Communications | Year: 2017

Multilevel interior nanoporous CuCo2O4 microspheres have been for the first time developed using a facile self-templated method. Electrochemical results in three- and two-electrode systems show that the double-shelled hollow microsphere electrode is a promising candidate for high-performance supercapacitors. © The Royal Society of Chemistry.

Talebi Bezmin Abadi A.,Tarbiat Modares University
Journal of Global Antimicrobial Resistance | Year: 2017

Infection with Helicobacter pylori plays an essential role in the development of duodenal and gastric ulcers as well as in the pathobiology of gastric adenocarcinoma. Thus, successful elimination of the bacterium can reduce the risk of development of these diseases. Currently, most guidelines recommend standard triple therapy (amoxicillin + clarithromycin + proton pump inhibitor), although its efficacy is rapidly falling. Notably, traditional first-line therapy fails in almost 32% of H. pylori-carrying cases, suggesting the importance of choosing the best formulation for first-line therapy. Hence, due to the decreasing effectiveness of first-line treatment, we should be prepared to confront increasing H. pylori therapeutic defeat. Owing to increasing reports of antibiotic resistance worldwide, newer approaches and directions are necessary for managing this problematic infection. Developing and providing better anti-H. pylori strategies (probiotics, antibiotic therapy and non-traditional medicine) without using current clinical experience in treating the infection is impossible. Furthermore, development and examination of new preventive vaccines may also be a new therapeutic direction. Taken together, with regard to current experience, clinicians are highly recommended to consider all alternatives to eradicate H. pylori until a universal vaccine becomes practically available. This article aims to give an overview regarding the current status of H. pylori treatment, accordingly designing an actual overview to gain optimal strategies against this infection. © 2017 International Society for Chemotherapy of Infection and Cancer

Ahmadieh H.,Tarbiat Modares University | Asl B.M.,Tarbiat Modares University
Computer Methods and Programs in Biomedicine | Year: 2017

Background and Objective We proposed a noninvasive method for separating the fetal ECG (FECG) from maternal ECG (MECG) by using Type-2 adaptive neuro-fuzzy inference systems. Methods The method can extract FECG components from abdominal signal by using one abdominal channel, including maternal and fetal cardiac signals and other environmental noise signals, and one chest channel. The proposed algorithm detects the nonlinear dynamics of the mother's body. So, the components of the MECG are estimated from the abdominal signal. By subtracting estimated mother cardiac signal from abdominal signal, fetal cardiac signal can be extracted. This algorithm was applied on synthetic ECG signals generated based on the models developed by McSharry et al. and Behar et al. and also on DaISy real database. Results In environments with high uncertainty, our method performs better than the Type-1 fuzzy method. Specifically, in evaluation of the algorithm with the synthetic data based on McSharry model, for input signals with SNR of -5 dB, the SNR of the extracted FECG was improved by 38.38% in comparison with the Type-1 fuzzy method. Also, the results show that increasing the uncertainty or decreasing the input SNR leads to increasing the percentage of the improvement in SNR of the extracted FECG. For instance, when the SNR of the input signal decreases to -30 dB, our proposed algorithm improves the SNR of the extracted FECG by 71.06% with respect to the Type-1 fuzzy method. The same results were obtained on synthetic data based on Behar model. Our results on real database reflect the success of the proposed method to separate the maternal and fetal heart signals even if their waves overlap in time. Moreover, the proposed algorithm was applied to the simulated fetal ECG with ectopic beats and achieved good results in separating FECG from MECG. Conclusions The results show the superiority of the proposed Type-2 neuro-fuzzy inference method over the Type-1 neuro-fuzzy inference and the polynomial networks methods, which is due to its capability to capture the nonlinearities of the model better. © 2017 Elsevier B.V.

Samari-Khalaj M.,Tarbiat Modares University | Abbasi S.,Tarbiat Modares University
International Journal of Biological Macromolecules | Year: 2017

Persian gum (PG), mountain almond tree (Amygdalus scoparia) exudate, is a transparent and natural edible gum which consists of soluble (SFPG, 25–30 wt%) and insoluble (IFPG, 70–75 wt%) fractions. Therefore, in the present study, using response surface methodology (RSM), the influence of concentration (0.64–7.36 wt%), acrylamide (0.070–0.120 mol), temperature (19.77–70.23 °C), and time (0.32–3.68 h) on solubilizing and some other properties of IFPG were investigated. Based on our findings, the highest solubility (64 wt%) was achieved at the presence of 6 wt% IFPG, and 0.08 mol acrylamide at 60 °C after 3 h. Intrinsic viscosity and molecular weight determination also confirmed modification reaction which led to reduction in molecular weight. In addition, the effect of pH and electrolytes on rheological properties showed that the soluble part of IFPG which modified at optimum conditions had an anionic structure similar to conventional SFPG. © 2017 Elsevier B.V.

Moallemi S.,Tarbiat Modares University | Jannesari A.,Tarbiat Modares University
ICCAS 2012 - 2012 IEEE International Conference on Circuits and Systems: "Advanced Circuits and Systems for Sustainability" | Year: 2012

A new architecture for increasing the resolution of Delta-Sigma Analog to Digital Converter (ADC) is presented. The proposed technique also reduced the area of the modulator significantly. Also the feed forward topology is used for reducing the total power consumption. The modulator has been simulated in 0.18μm standard CMOS technology with 1.8V power supply in Hspice circuit simulator. The modulator achieves the Dynamic Range of 95.6dB and 80dB for GSM and Bluetooth standards respectively while consumes 4.02mW and 4.04mW in each case. © 2012 IEEE.

Mortazavi M.,Kerman Graduate University of Technology | Hosseinkhani S.,Tarbiat Modares University
Enzyme and Microbial Technology | Year: 2017

Protein engineering can provide useful approaches for loop anchoring and mutation of surface-exposed loop residues to Arg for the design of thermostable proteins. In this context and due to the high proportion of surface loops, some of the solvent-exposed residues in the Lampyris turkestanicus luciferase were mutated to Arg. Using the red-emitter mutant luciferase (E354R/Arg356), the single (-Q35R, -I182R, -I232R and -L300R), double (-Q35R/I232R) and triple (-Q35R/I232R/I182R) mutant luciferases were introduced. The relative remaining activity of -I232R, double and triple mutants increased significantly compared to the wild-type at 40 °C. The optimal temperature of these mutants increased up to 40 °C which were 15 °C more than wild-type luciferase. It is anticipated that these mutations increased the local interactions that finally improved the thermostability and optimum temperature of luciferase. It should be noted that Arg substitution at amino acid positions 35, 182 and 232 had no effect on the bioluminescence emission spectra. Furthermore, these mutations have not significantly changed the specific activities of firefly luciferases. Finally, with the use of the homology modeling and molecular docking, the effects of these substitutions were evaluated. In conclusion, this study provides beneficial insights on how the thermal stability of luciferase can be improved by protein engineering for biological applications. © 2016 Elsevier Inc.

Khorasani A.C.,Tarbiat Modares University | Shojaosadati S.A.,Tarbiat Modares University
International Journal of Biological Macromolecules | Year: 2017

Incorporation of nanofibers of chitin (NC), lignocellulose (NLC) and bacterial cellulose (BNC) in pectin was studied to improve prebiotic activity and gastrointestinal resistance of the pectin-nanofibers biocomposites for protection of probiotics under simulated gastrointestinal conditions. The biocomposites were prepared using various compositions of pectin and nanofibers, which were designed using D-optimal mixture method. The incorporation of the nanofibers in pectin led to a slow degradation of the pectin-nanofibers biocomposites in contrast to their rapid swelling. AFM analysis indicated the homogenous distribution of interconnected nanofibers network structure in the pectin-nanofibers biocomposite. FTIR spectra demonstrated fabrication of the biocomposites based on the inter- and intra-molecular hydrogen bonding and ionic interaction of pectin-Ca2+. XRD patterns revealed the amorphous structures of the biocomposites as compared to the crystalline structures of the nanofibers. Among the compositions, the optimal compositions were as follows: 60% pectin + 40% NC, 50% pectin + 50% NLC and 60% pectin + 40% BNC, where the prebiotic score, probiotic survival under simulated gastric and intestinal conditions were optimum. The optimal biocomposite pectin-NC exhibited the highest survival of the entrapped probiotic bacteria under simulated gastric (97.7%) and intestinal (95.8%) conditions when compared with the corresponding to free cells (76.2 and 73.4%). © 2016

Azadegan M.,Tarbiat Modares University | Beheshti M.T.H.,Tarbiat Modares University
Asian Journal of Control | Year: 2017

This paper presents a new model for networked control systems (NCSs) under transmission control protocol (TCP) as a multiple-delay system by considering both sensor to controller and controller to actuator delays. An analytical TCP model has been considered for the network part, and an active queue management (AQM) controller is designed to regulate the desired queue length, which ensures holding the network induced delay and its variation within their lower bounds. The model is assumed to possess structured uncertainties due to the stochastic nature of the network. Robust stability and stabilization conditions are derived in terms of linear matrix inequalities (LMIs) by applying the Lyapunov-Krasovskii stability criterion. Illustrative examples are presented and it has been shown that the proposed method will obtain less conservative results compared to the existing approaches in the literature. © 2017 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd.

Akhbari K.,Tarbiat Modares University | Morsali A.,Tarbiat Modares University | Retailleau P.,CNRS Natural Product Chemistry Institute
Ultrasonics Sonochemistry | Year: 2013

Micro and nano-structures of a lead(II) coordination polymer, [Pb 2(2-Me-8-Hq)2(MeOH)2]n (1), [2-Me-8-HqH = 2-methyl-8-hydroxyquinoline], were synthesized by two sonochemical methods. These new micro and nano-structures were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction and consists of primary dimeric unit of [Pb 2(2-Me-8-Hq)2(MeOH)2]. Self assembly between the dimmeric units of [Pb2(2-Me-8-Hq)2(MeOH)2] from Pb-O bonds results in formation of a one-dimensional lead(II) coordination polymer. The PbII-ion in compound 1 has PbO6N1 coordination sphere with a stereo-chemically 'active' electron lone pair on the metals. By a reversible solid-state structural transformation, we successfully prepared [Pb2(2-Me-8-Hq)2]n (2) by thermal desolvation of 1. Thermal stability of compound 1 was studied by thermo gravimetric and differential thermal analyses. In addition nano-structure of PbO was prepared from calcination process of compound 1 at 873 K. © 2013 Elsevier B.V. All rights reserved.

Alibeigloo A.,Tarbiat Modares University
Composite Structures | Year: 2014

Based on theory of elasticity, static analysis of a simply supported sandwich panel with functionally graded material (FGM) core subjected to thermo-mechanical mechanical load is carried out. The thermo-elastic constants of the FGM core layer are assumed to be graded in the radial direction according to the power-law of constituents while the Poisson's ratio is assumed to be constant. Analytical solutions for the temperature, stress and displacement fields for the sandwich panel with simply-supported edges are derived by using the Fourier series expansions along the axial and circumferential direction and state-space technique along the radial direction. Accuracy and convergence of the presents approach are validated by comparing the numerical results with those found in literature. In addition, the effects of surface boundary conditions, gradient index, span angle, facing layers thickness and axial length to mid radius ratio on the behavior of the sandwich panel are studied. © 2013 Elsevier Ltd.

Seidi S.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Feizbakhsh R.,Tarbiat Modares University
Journal of Chromatography A | Year: 2011

Electromembrane extraction (EME) coupled with high performance liquid chromatography and ultraviolet detection was developed for determination of amphetamine-type stimulants in human urine samples. Amphetamines migrated from 3mL of different human urine matrices, through a thin layer of 2-nitrophenyl octyl ether (NPOE) containing 15% tris-(2-ethylhexyl) phosphate (TEHP) immobilized in the pores of a porous hollow fiber, and into a 15μL acidic aqueous acceptor solution present inside the lumen of the fiber. Equilibrium extraction conditions were obtained after 7min of operation. Experimental design and response surface methodology (RSM) were used for optimization of EME parameters. Under optimal conditions, amphetamines were effectively extracted with recoveries in the range of 54-70%, which corresponded to preconcentration factors in the range of 108-140. The calibration curves were investigated in the range of 0-7μgmL -1 and good linearity was achieved with a coefficient of estimation better than 0.991. Detection limits and inter-day precision (n=3) were less than 0.01μgmL -1 and 11.2%, respectively. © 2011 Elsevier B.V.

Zavvari M.,Islamic Azad University at Urmia | Ahmadi V.,Tarbiat Modares University
Infrared Physics and Technology | Year: 2014

In this paper a single photon detector with operating wavelength of 6 μm is proposed and its performance characteristics are studied. Intersubband absorption of single photons in quantum dot layers leads to creation of photoelectrons which are injected to multiplication region and under above breakdown condition a large output pulse is generated. The detector is designed for self quenching operation in which an additional layer called transient carrier buffer (TCB) is used for trapping of backward avalanche generated holes at the interface of TCB and charge layer. The accumulated holes impose an additional charge in such a way that the voltage across the multiplication region drops and the output is quenched. A model is developed to analyze the performance of detector and results of simulation predict detection efficiency about 12% at T = 150 K. Also the quenching and recovering performance of detector is studied and results show that both higher temperatures and higher bias improve dynamics of detector. However higher temperatures result in higher dark count rate. © 2013 Elsevier B.V. All rights reserved.

Moghaddam M.P.,Tarbiat Modares University | Abdollahi A.,Tarbiat Modares University | Rashidinejad M.,Shahid Bahonar University of Kerman
Applied Energy | Year: 2011

In recent years, extensive researches have been conducted on implementation of demand response programs (DRPs), aimed to electricity price reduction, transmission lines congestion resolving, security enhancement and improvement of market liquidity. Basically, DRPs are divided into two main categories namely, incentive-based programs (IBPs) and time-based rate programs (TBRPs). Mathematical modeling of these programs helps regulators and market policy makers to evaluate the impact of price responsive loads on the market and system operational conditions. In this paper, an economic model of price/incentive responsive loads is derived based on the concept of flexible price elasticity of demand and customer benefit function. The mathematical model for flexible price elasticity of demand is presented to calculate each of the demand response (DR) program's elasticity based on the electricity price before and after implementing DRPs. In the proposed model, a demand ratio parameter has been introduced to determine the appropriate values of incentive and penalty in IBPs according to the level of demand. Furthermore, the importance of determining optimum participation level of customers in different DRPs has been investigated. The proposed model together with the strategy success index (SSI) has been applied to provide an opportunity for major players of the market, i.e. independent system operator (ISO), utilities and customers to select their favorite programs that satisfy their desires. In order to evaluate the performance of the proposed model, numerical studies are conducted on the Iranian interconnected network load profile on the annual peak day of the year 2007. © 2011 Elsevier Ltd.

Shariati S.,Islamic Azad University at Rasht | Faraji M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Rajabi A.A.,Tarbiat Modares University
Desalination | Year: 2011

The object of this study was to evaluate the efficiency of safranin O dye removal with application of magnetite nanoparticles (Fe3O4 NPs) as adsorbent. For this propose, NPs of Fe3O4 were synthesized via a chemical precipitation method with addition of sodium hydroxide to solutions of Fe2+ and Fe3+. The prepared NPs were characterized by XRD and TEM and the applicability of the synthesized NPs for removing of safranin O as a cationic dye from aqueous solutions was investigated. The surface of Fe3O4 NPs was modified with addition of sodium dodecyl sulfate as an anionic surfactant. The effects of various parameters on the removal efficiency of safranin O such as the type and amount of surfactant, pH of solution, salt effect and contact time were studied and optimized. The studies of sorption kinetics of the dye showed a rapid sorption dynamics by a second-order kinetic model, suggesting chemisorption mechanism. Dye adsorption equilibrium data were fitted well to the Langmuir isotherm and the maximum monolayer capacity qmax was calculated from the Langmuir as 769.23mg g-1.The obtained results indicate that sodium dodecyl sulfate modified Fe3O4 NPs can be used as an efficient adsorbent material for adsorption of cationic dyes from aqueous solutions. © 2010 Elsevier B.V.

Hamzeh A.,Tarbiat Modares University | Reti T.,Óbuda University
Match | Year: 2014

For the structural characterization of a connected graph G with n vertices and m edges two novel graph irregularity measures are introduced, they are defined as IRM1(G)=M1(G)-4m2/n and IRM2(G)=M2(G)-4m3/n2 where M1(G) and M2(G) are the first and second Zagreb indices of graph G, respectively. For irregularity indices IRM1(G) and IRM2(G) of trees, unicyclic, bicyclic and tricyclic graphs, upper bounds as a function of vertex number n are given. Moreover, it has been proved, that if the Zagreb indices inequality M2(G)/m ≥ M1G)/n is fulfilled for a connected graph G, then the relation IRM2(G)/m ≥ IRM1G)/n holds for G, as well. Tests performed on the sets of dual graphs of C66 fullerene isomers verified that the topological invariant IRM2 has a good discriminatory power and can be successfully applicable to the stability prediction of fullerenes.

Darvishi Cheshmeh Soltani R.,Arak University of Medical Sciences | Rezaee A.,Tarbiat Modares University | Khataee A.,University of Tabriz
Industrial and Engineering Chemistry Research | Year: 2013

The aim of this work was to enhance the efficiency of a photocatalytic process involving carbon black (CB)-modified ZnO nanoparticles using an electrochemical process consisting of powdered activated carbon (PAC), carbon nanotubes (CNTs), and CB-polytetrafluoroethylene (PTFE)-coated gas-diffusion cathode (GDC) to degrade Acid Red 18. Hydrogen peroxide generated by PAC-PTFE-, CNT-PTFE-, and CB-PTFE-coated GDC was 58.45, 100.9, and 112.3 μM, respectively. The efficiency of the combined process equipped with CB-PTFE-coated GDC was assessed as the function of different operational parameters. With the increase of initial pH from 3 to 10, decolorization efficiency decreased from 94.5% to 57.61%. Increasing the dye concentration from 2 to 20 mg/L led to a decrease in the decolorization efficiency from 100% to 50.45%. The increase of the current intensity from 30 to 300 mA resulted in increasing decolorization efficiency from 37.45% to 95.31%. TOC analysis showed 51.13% mineralization of 10 mg/L dye solution in 20 min. © 2013 American Chemical Society.

Abdollahi A.,Tarbiat Modares University | Parsa Moghaddam M.,Tarbiat Modares University | Rashidinejad M.,Shahid Bahonar University of Kerman | Sheikh-El-Eslami M.K.,Tarbiat Modares University
IEEE Transactions on Smart Grid | Year: 2012

In recent years, load management (LM) programs are introduced as an impressive option in all energy policy decisions. Under deregulation, the scope of LM programs has considerably been expanded to include demand response programs (DRPs). Basically, DRPs are divided into two main categories namely, incentive-based programs (IBPs) and time-based rate (TBR) programs. In this paper, an economic model of responsive loads is derived based upon price elasticity of demand and customers' benefit function. In order to investigate the economic-driven and environmental-driven measures of demand response programs, a new linearized formulation of cost-emission based unit commitment problem associated with DRPs (UCDR) is presented. Here, UCDR is modeled as a mixed-integer programming (MIP) problem. The proposed model is applied to determine loads provided by DRPs and schedule commitment status of generating units. Moreover, the optimum value of incentive as a crucial issue for implementing DRPs is derived. Several analyses are conducted to investigate the impact of some important factors such as elasticity on the UCDR problem. The strategy success index (SSI) is employed to prioritize DRPs from the independent system operator (ISO) perspective. The conventional 10-unit test system is used to demonstrate effectiveness of the proposed methodology. © 2011 IEEE.

Arasteh H.R.,Tarbiat Modares University | Parsa Moghaddam M.,Tarbiat Modares University | Sheikh-El-Eslami M.K.,Tarbiat Modares University | Abdollahi A.,Shahid Bahonar University of Kerman
International Journal of Electrical Power and Energy Systems | Year: 2013

This paper investigates the impact of demand response resources (DRRs) as the consequence of implementing demand response programs (DRPs) on power markets. Indeed, this paper incorporates commercial concept of DRPs with unit commitment (UC) to solve "unit and DR commitment" problem. This mixed problem will decrease the network operation cost by using of DRPs' potential to mitigate some UC constraints and avoiding some highly priced generation of units. Here, employing the proposed DRPs model is considered as a new concept in electricity market. In this paper, a dynamic approach is proposed for participating DR service providers in power markets in order to maximize their profits. This paper also aims to concurrently consider the aforementioned commercial DRPs supply model with the generators supply curves in the unit commitment problem, which is solved to minimize operational costs considering multifarious constraints. Performance of the proposed approach is investigated through numerical studies using a standard IEEE 10-unit test system. The results show the efficiency and advantage of the proposed methodology.© 2013 Elsevier Ltd. All rights reserved.

Azadi M.,Shahid Bahonar University of Kerman | Azadi M.,Tarbiat Modares University | Mohebbi A.,Shahid Bahonar University of Kerman
Journal of Hazardous Materials | Year: 2010

A three-dimensional Eulerian-Lagrangian fluid dynamics (CFD) model was developed to simulate the gas particulate flow inside cyclones with different sizes. Cyclones of different sizes, were used which named as cyclones I, II, and III. Cyclone I was considered as the biggest and cyclone III was considered as the smallest cyclone. The effects of cyclone size and inlet velocity on hydrodynamics behavior and performance parameters including cut-off diameter and pressure drop were investigated. The renormalization group (RNG) k-e{open} model and Reynolds stress model (RSM) were used to study the effect of turbulent modeling. Particle trajectories were calculated via discrete phase model (DPM). The velocity fluctuations were simulated with discrete random walk (DRW) model to study the turbulent dispersion of particles. The cut-off size and pressure drop were increased with increasing the cyclone size. The RSM predicted the cut-off diameter very well with the deviations of 2.3%, 3.4%, and 3.6% of the experimental data, for cyclones I, II, and III, respectively. CFD model was developed using Fluent code to simulate the gas particulate flow inside cyclone. The simulation results also confirmed the applicability of CFD modeling with RSM as a promising tool to study the cyclone size effect on performance parameters. © 2010 Elsevier B.V.

Mirmomeni M.,Abadgaran Construction Company | Zarezadeh Mehrizi M.,Tarbiat Modares University | Marino M.A.,University of California at Davis
Computational Optimization and Applications | Year: 2010

Effective project management requires the development of a realistic plan and a clear communication of the plan from the beginning to the end of the project. The critical path method (CPM) of scheduling is the fundamental tool used to develop and interconnect project plans. Ensuring the integrity and transparency of those schedules is paramount for project success. The complex and discrete nature of the solution domain for such problems causes failing of traditional and gradient-based methods in finding the optimal or even feasible solution in some cases. The difficulties encountered in scheduling construction projects with resource constraints are highlighted by means of a simplified bridge construction problem and a basic masonry construction problem. The honey-bee mating optimization (HBMO) algorithm has been previously adopted to solve mathematical and engineering problems and has proven to be efficient for searching optimal solutions in large-problem domains. This paper presents the HBMO algorithm for scheduling projects with both constrained and unconstrained resources. Results show that the HBMO algorithm is applicable to projects with or without resource constraints. Furthermore, results obtained are promising and compare well with those of well-known heuristic approaches and gradient-based methods. © 2008 Springer Science+Business Media, LLC.

Zavvari M.,Islamic Azad University at Urmia | Ahmadi V.,Tarbiat Modares University
Applied Optics | Year: 2013

A novel design for a quantum dot infrared photodetector (QDIP) is proposed based on avalanche multiplication and is expected to be used as a single photon detector at mid-IR. A high field multiplication region is added to a conventional QDIP in separate absorption, charge, and multiplication structures to intensify incoming photocurrent generated in the absorption region. The absorption region of the photodetector consists of quantum dot layers that are responsible for absorption of mid-IR wavelengths. Because of higher operation voltages in gated-mode operation, resonant tunneling barriers are also included in the absorption region to prevent higher dark currents. The absorption region is designed for operation at ?8 ?m. During the gate pulse period, photo-generated electrons can trigger an avalanche and produce an output pulse. For this detector, the dark count rate (DCR) and single photon quantum efficiency (SPQE) are calculated at different temperatures. SPQE with peak of about 0. 3 for T50 K is obtained. For higher temperatures, about T 120 K, SPQE is very low due to the contribution of dark carriers generated in the quantum dot absorption region. © 2013 Optical Society of America.

Moradi M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Baheri T.,Research Centers of Antinarcotics Police
Journal of Separation Science | Year: 2011

The process of surfactant-assisted dispersive liquid-liquid microextraction (SA-DLLME) followed by high-performance liquid chromatography-UV detection was successfully applied for the extraction and determination of selected cannabinoids (cannabidiol, Δ 9-tetrahydrocannabinol, and cannabinol) in urine samples. The effective parameters on the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time (OVAT) and face center design (FCD). Under the optimum conditions (extraction solvent and its volume, toluene, 85 μL; disperser agent and its concentration, 1.0 mL of ultra-pure water containing 0.5 mmol/L tetradecyl tremethyl ammonium bromide (TTAB); sample pH, 2.0 and salt concentration, 11% w/v NaCl), the limits of detection of the method were in the range of 0.1-0.5 μg/L and the repeatability and reproducibility of the proposed method, expressed as relative deviation, varied between 4.1 and 8.5% and 6.7 and 11.6%, respectively. Linearity was found to be in the range of 1.0-200 μg/L and under the optimum conditions, the preconcentration factors (PFs) were between 190 and 292. This proposed method was successfully applied in the analysis of three male advocate urine samples and good recoveries were obtained. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Khoshkholgh M.G.,Tarbiat Modares University | Navaie K.,Tarbiat Modares University | Yanikomeroglu H.,Carleton University
IEEE Transactions on Mobile Computing | Year: 2010

In this paper, we analyze the achievable capacity of the secondary service for overlay and underlay access strategies. We then propose a novel mixed access strategy in which in contrast to the underlay strategy, the secondary service transmits during the idle periods without considering the interference threshold constraint. In contrast to the overlay strategy, mixed strategy makes transmission during the busy periods with a probability p-a subject to satisfying the interference threshold constraint. Parameter p-a is a secondary service parameter, which can be adjusted based on the spectrum status. Moreover, we show that the secondary service can adjust p-a to select appropriate access strategy with the objective of maximizing the achieved capacity based on the interference at the secondary service receiver, I, imposed by the primary service transmitter. The proposed spectrum-sharing technique developed in this paper based on I significantly reduces the system complexity comparing to the system in which for spectrum sharing, the imposed interference at the primary receiver is required. We further suggest a simple power allocation scheme for the mixed strategy that its achieved capacity is very close to the maximum achievable capacity of the secondary service. © 2006 IEEE.

Ghiassi B.,University of Minho | Soltani M.,Tarbiat Modares University | Tasnimi A.A.,Tarbiat Modares University
Journal of Structural Engineering (United States) | Year: 2012

Coating the walls with reinforced concrete layers is a conventional method of strengthening masonry structures in Iran. However, because of the lack of analytical and experimental information about the behavior of strengthened masonry walls with this method, the design of these walls is generally conducted based on empirical relations and decisions that may result in uneconomical or underdesigned strengthening details. This paper aims to develop a rational method for design and seismic evaluation of unreinforced masonry walls strengthened with reinforced concrete layers. In the proposed method, four failure modes are considered for these walls, and the strength relations and acceptance criteria for each of them are provided in accordance with FEMA 356 and ASCE 41 relations for reinforced concrete and masonry walls. The accuracy of the proposed method in predicting the nonlinear behavior and governing failure modes of the strengthened walls is validated by comparing the results with available experimental and performed numerical results. © 2012 American Society of Civil Engineers.

Mokari N.,Tarbiat Modares University | Navaie K.,Tarbiat Modares University | Navaie K.,University of Leeds | Navaie K.,Carleton University | Khoshkholgh M.G.,Tarbiat Modares University
IEEE Transactions on Wireless Communications | Year: 2011

Here our focus is on the downlink radio resource allocation in underlay spectrum sharing based on OFDMA technology. Both continuous and discrete rate strategies are investigated. We consider the practical case in which for the wireless channel between the secondary base station and secondary users only partial channel state information (CSI) is available at the secondary base station. We formulate the resource allocation problem in the secondary network as an optimization problem in which the objective is to maximize the secondary users weighted sum rate. Two main constraints at the secondary base station are the maximum total transmission power, and the primary service collision probabilities. The only available a priori information is the channel distribution information (CDI) for the channel between the secondary base station and the primary receivers. Since the optimal radio resource allocation is non convex we utilize dual optimization method to obtain suboptimal solutions. The computational complexity due to the constraints in the original radio resource allocation is then reduced by exploiting system specifications and substituting the original constraints with the equivalent constraints on the transmission power and rate. Simulations studies are conducted to investigate the impact of the different system parameters. We also compare the proposed algorithm with the conventional radio resource allocation and show that by the proposed algorithm we are able to enforce the collision probability constraint in the primary service which in return results in a slight decreasing in the sum rate of the secondary system. Furthermore, we show that the proposed schemes are able to keep the outage probability imposed by imperfect CSI below a given threshold. © 2011 IEEE.

Husseinzadeh Kashan A.,Tarbiat Modares University | Husseinzadeh Kashan M.,Tarbiat Modares University | Karimiyan S.,International Institute of Earthquake Engineering and Seismology
Information Sciences | Year: 2013

Many combinatorial optimization problems comprise a grouping phase (the grouping problem) in which the task is to partition a set of items into disjoint sets. Introduced in 1994, grouping genetic algorithm (GGA) is the only evolutionary algorithm heavily modified to suit the structure of grouping problems. In this paper we adapt the structure of the well-known particle swarm optimization algorithm (PSO) for grouping problems. To propose the grouping version of the PSO algorithm, which is called GPSO algorithm, we develop new particle position and velocity updating equations which preserve the major characteristics of the original equations and are respondent to the structure of grouping problems. The new updating equations work with groups of items rather than items isolatedly. One of the main characteristics of the new equations is that they work in continuous space but their outcome is used in discrete space through a two phase procedure. Applications of GPSO algorithm are made to the single batch-machine scheduling problem and bin packing problem, and results are compared with the results reported by GGA. Computational results testify that our algorithm is efficient and can be regarded as a new solver for the wide class of grouping problems. © 2012 Published by Elsevier Inc.

Farahpour M.M.,Tarbiat Modares University | Hessami K.,International Institute of Earthquake Engineering and Seismology
Journal of the Geological Society | Year: 2012

Several major zones across the Zagros fold-thrust belt have been interpreted as indicating that orogeny took place progressively from NE to SW through discrete orogenic episodes during Tertiary time. This paper uses field evidence of growth onlaps and angular unconformities within the Cretaceous stratigraphic column as well as existing geological maps and cross-sections to indicate that deformation started as early as the Late Aptian and folded the whole width of the Zagros belt simultaneously. Later events are indicated by folding at the end of the Cenomanian, and in the Late Turonian and Santonian. Following the Late Cretaceous deformation phases, the SE Zagros basin was divided into several longitudinal intra-shelf basins, which were separated by NW-SE-trending Cretaceous anticlines. However, with reference to our previous work, it can be suggested that each of the sub-basins was folded serially from NE to SW through a series of tectonic phases during the next episode of Zagros orogeny in Tertiary time. The change of deformation style from concomitant to serial folding, during the Cretaceous and Tertiary respectively, is attributed to the existence of the Hormuz Salt and shearing at the base of the former basin and its absence at the base of the Tertiary intra-shelf basins.

Abdollahzadeh E.,Tarbiat Modares University | Rezaei M.,Tarbiat Modares University | Hosseini H.,Shahid Beheshti University of Medical Sciences
Food Control | Year: 2014

Food poisoning caused by Listeria monocytogenes leads to a 30% rate of mortality among patients. The antibacterial activity of cinnamon, thyme, and rosemary essential oils (EOs) and shallot and turmeric extracts was tested against L.monocytogenes using agar well and disc diffusion techniques. Results showed that thyme EO had the highest antimicrobial activity, followed by cinnamon and rosemary EOs, respectively. The antilisterial activity of thyme EO at 0.4%, 0.8%, and 1.2% levels, nisin at 500 or 1000IU/g level, and their combination against L.monocytogenes was examined in minced fish samples. The antilisterial properties of nisin were also investigated in cooked minced fish treatments. Nisin at 500 or 1000IU/g in the minced fish meat demonstrated bacteriostatic activity against L.monocytogenes. The use of thyme EO at 0.8% and 1.2% reduced the L.monocytogenes viable count below 2 log cfu/g after 6 days. Furthermore, simultaneous use of thyme EO at 0.8% and 1.2%, and nisin at 500 or 1000IU/g level, reduced the L.monocytogenes viable count below 2 logcfu/g after the second day of storage. The antilisterial activity of nisin in the cooked minced fish samples was slightly stronger than that of the raw group. © 2013 Elsevier Ltd.

Zafarani H.,International Institute of Earthquake Engineering and Seismology | Soghrat M.,Tarbiat Modares University
Bulletin of the Seismological Society of America | Year: 2012

Physically based ground-motion prediction equations for soil and rock sites in the Zagros region have been developed based on the specific barrier model (SBM) used within the context of the stochastic model. Instead of direct timedomain simulation, random vibration theory was used to estimate measures of peak motion in terms of the pseudospectral velocity of anelastic harmonic oscillator with 5% viscous damping. To avoid the uncertainties, calibration of the source model uses a database of carefully selected strong motion data without ambiguity about the site condition. Therefore, only rock sites are selected for determining source parameters. Also, to avoid any inconsistencies caused by magnitude conversion formulas, we restricted the dataset only to events with available moment magnitudes. Regression analysis is performed using the random effects model that considers both interevent and intraevent variabilities to effectively deal with the problem of an unequal number of records from different earthquakes. No sign of self-similarity breakdown is observed between the source radius and its seismic moment. The local and global stress drops derived for the Zagros region (39 and 116 bars, respectively) are more consistent with the values obtained by other authors for an interplate regime than the values for an intraplate region. However, from the viewpoint of source heterogeneity (as the ratio of the stress drops is an indicator of the complexity of the source and heterogeneity of slip on the fault) the Zagros events, which have a stress-drop ratio of about three are more homogeneous than other interplate events. Stochastic simulations are then implemented to predict peak ground motion and response spectra parameters for rock and soil site conditions.

Soghrat M.R.,Tarbiat Modares University | Khaji N.,Tarbiat Modares University | Zafarani H.,International Institute of Earthquake Engineering and Seismology
Geophysical Journal International | Year: 2012

In this study, based upon the calibrated specific barrier model (SBM) against the latest available strong motion data, ground motion prediction equations for soil and rock sites in northern Iran are developed. The SBM may provide the most complete, simple and self-consistent description of the faulting process, which is applicable in both 'near-fault' and 'far-field' regions. Consequently, the SBM may provide consistent ground motion simulations over the entire necessary frequency range and for all distances of engineering interests. To determine source parameters in this study, we used 163 three-component records of 32 earthquakes with magnitude ranging from M W 4.9 to 7.4 in northern Iran. In the database, records with hypocentral distances less than 200 km are chosen and only earthquakes whose moment-magnitude estimates are available have been used. Furthermore, using the best available information, recording sites are classified into two main geologic categories: rock and soil. Because of the lack of site amplification information in the most regions of the world including Iran, we used the H/V ratio method for estimating the site amplification. Moreover, the Kappa factor that shows diminishing the high-frequency amplitude is determined. In this study, two data sets are considered for determining the source parameters (Δσ G and Δσ L) and the H/V ratio and the Kappa factor. Only S-wave part of signals is used in each analysis. Regression analysis is performed using 'random effects' method that considers both interseismic (event-to-event) and coseismic (within-event) variabilities to effectively deal with the problem of weighting observations from different earthquakes. The residuals are controlled against available northern Iranian strong ground motion data to verify that the model predictions are unbiased and that there are no significant residual trends with magnitude and distance. At first, it is assumed that no sign of self-similarity breakdown is observed between the source radius and its seismic moment. After controlling the results, the modified SBM should be used as some deviations have been observed. To verify the robustness of the results, the number of observations is changed by removing various randomly selected data sets from the original database, which results in unchanged results of the model. Stochastic simulations are then implemented to predict peak ground motion and response spectra parameters. The stochastic SBM predictions are in relatively good agreement with other available attenuation relationships proposed for Iran, Europe and Middle East. It has been shown that the proposed SBM of this study provides unbiased ground motion estimates over the entire frequency range of most engineering applications. It provides a reliable and physically realistic, yet computationally efficient, way to model strong ground motions. © 2011 The Authors Geophysical Journal International © 2011 RAS.

Mehrjoo M.,Islamic Azad University at Tehran | Khaji N.,Tarbiat Modares University | Ghafory-Ashtiany M.,International Institute of Earthquake Engineering and Seismology
Applied Soft Computing Journal | Year: 2013

In this paper, a crack identification approach is presented for detecting crack depth and location in beamlike structures. For this purpose, a new beam element with a single transverse edge crack, in arbitrary position of beam element with any depth, is developed. The crack is not physically modeled within the element, but its effect on the local flexibility of the element is considered by the modification of the element stiffness as a function of crack's depth and position. The development is based on a simplified model, where each crack is substituted by a corresponding linear rotational spring, connecting two adjacent elastic parts. The localized spring may be represented based on linear fracture mechanics theory. The components of the stiffness matrix for the cracked element are derived using the conjugate beam concept and Betti's theorem, and finally represented in closed-form expressions. The proposed beam element is efficiently employed for solving forward problem (i.e., to gain accurate natural frequencies of beam-like structures knowing the cracks' characteristics). To validate the proposed element, results obtained by new element are compared with two-dimensional (2D) finite element results as well as available experimental measurements. Moreover, by knowing the natural frequencies, an inverse problem is established in which the cracks location and depth are identified. In the inverse approach, an optimization problem based on the new beam element and genetic algorithms (GAs) is solved to search the solution. The proposed approach is verified through various examples on cracked beams with different damage scenarios. It is shown that the present algorithm is able to identify various crack configurations in a cracked beam. © 2012 Elsevier B.V. All rights reserved.

Mohajjel M.,Tarbiat Modares University | Fergusson C.L.,University of Wollongong
International Geology Review | Year: 2014

The Zagros Mountains of Iran formed by continental collision from closure of the Neo-Tethyan Ocean. The Zagros Orogen underlying the mountain range reflects a much longer history with the Pan-African basement and Phanerozoic successions. New mapping, radiometric ages, and stratigraphic analyses have enabled advances in our understanding of the Jurassic to Cenozoic tectonic history. The northwestern Zagros Orogen consists of three belts: (1) the Zagros Fold and Thrust Belt, divided into the outer Zagros Simply Folded Belt and the inner High Zagros Belt; (2) the Zagros Suture Zone including radiolarite, ophiolite, and Bisotun limestone thrust sheets; and (3) the Sanandaj-Sirjan Zone, which contains abundant metamorphic rocks. Late Cretaceous ophiolites of the Kermanshah region are part of the outer ophiolite belt of the Zagros Orogen and have formed in passive margin and supra-subduction zone settings. Major events include early Mesozoic rifting, Jurassic subduction followed by a more cryptic interval of subduction in the Cretaceous, multiple ophiolite emplacement on the Arabian margin in the Late Cretaceous to Eocene, and collision of central Iran and the Arabian margin in the Oligocene with final closure of the shallow Tethyan seaway in the mid-Miocene. A Middle to Late Jurassic plutonic belt, the Qorveh-Aligodarz Plutonic Belt, formed a magmatic arc with subdued topography related to a moderately NE-dipping subduction zone under the Sanandaj-Sirjan Zone. An Early Cretaceous unconformity reflects limited uplift followed by widespread marine deposition with intercalated volcanic rocks in the Sanandaj region. Subduction continued with a low-lying arc that underwent trenchward advance. In the Late Cretaceous to Oligocene interval, the Neo-Tethyan Ocean closed with ophiolite obduction over the Arabian Peninsula margin and major shortening affected the Sanandaj-Sirjan Zone with uplift and plutonism. Much of the forearc of the Jurassic to Cretaceous arc system has been lost by tectonic erosion along a low-angle Eocene subduction zone prior to collision. Flattening of the subducting slab in the Late Cretaceous and Palaeogene explains the inland retreat of the arc to central Iran. Continental collision initiated in the Oligocene but the Tethyan seaway remained open until the mid-Miocene. © 2013 Taylor and Francis.

Rasti M.,Tarbiat Modares University | Rasti M.,Shiraz University of Technology | Sharafat A.R.,Tarbiat Modares University | Zander J.,KTH Royal Institute of Technology
IEEE Transactions on Information Theory | Year: 2011

We formally define the gradual removal problem in wireless networks, where the smallest number of users should be removed due to infeasibility of the target-SIR requirements for all users, and present a distributed power-control algorithm with temporary removal and feasibility check (DFC) to address it. The basic idea is that any transmitting user whose required transmit power for reaching its target-SIR exceeds its maximum power is temporarily removed, but resumes its transmission if its required transmit power goes below a given threshold obtained in a distributed manner. This enables users to check the feasibility of system in a distributed manner. The existence of at least one fixed-point in DFC is guaranteed, and at each equilibrium, all transmitting users reach their target-SIRs consuming the minimum aggregate transmit power. Furthermore, in contrast to the existing algorithms, no user is unnecessarily removed by DFC, i.e., DFC is Pareto and energy-efficient. We also show that when target-SIRs are the same for all users, DFC minimizes the outage probability. Simulation results confirm our analytical developments and show that DFC significantly outperforms the existing schemes in addressing the gradual removal problem in terms of convergence, outage probability, and power consumption. © 2006 IEEE.

Fakour H.,Tarbiat Modares University | Esmaili-Sari A.,Tarbiat Modares University | Zayeri F.,Shahid Beheshti University of Medical Sciences
Journal of Hazardous Materials | Year: 2010

The aim of this study was to determine the relationship between mercury concentrations in saliva and hair in women with amalgam fillings and its relation with age and number of amalgam fillings. Eighty-two hair and saliva samples were collected randomly from Iranian women who have the same fish consumption pattern and free from occupational exposures. The mean ± SD age of these women was 29.37 ± 8.12 (ranged from 20 to 56). The determination of Hg level in hair samples was carried out by the LECO, AMA 254, Advanced Mercury Analyzer according to ASTM, standard No. D-6722. Mercury concentration in saliva samples was analyzed by PERKIN-ELMER 3030 Cold Vapor Atomic Absorption Spectrophotometer. The mean ± SD mercury level in the women was 1.28 ± 1.38. μg/g in hair and 4.14 ± 4.08. μg/l in saliva; and there were positive correlation among them. A significant correlation was also observed between Hg level of saliva (Spearman's ρ=0.93, P<0.001) and hair (Spearman's ρ=0.92, P<0.001) with number of amalgam fillings. According to the results, we can conclude that amalgam fillings may be an effective source for high Hg concentration in hair and releasing the mercury to the saliva samples. © 2009 Elsevier B.V.

Noori S.,Shahid Beheshti University of Medical Sciences | Hassan Z.M.,Tarbiat Modares University
Free Radical Biology and Medicine | Year: 2012

Tehranolide, a novel natural sesquiterpene lactone with an endoperoxide group, bears a structural similarity to artemisinin and has been shown to inhibit cell growth. However, the underlying mechanisms of these activities remain obscure. The purpose of this study was to investigate the fundamental mechanisms by which tehranolide inhibits growth in MCF-7 cells. Cell growth was determined by using the MTT viability assay and counting cells. Apoptosis and cell-cycle progression were evaluated by means of Hoechst 33258 staining, flow cytometry with annexin-V/propidium iodide double staining, and ROS formation. The protein expression of Bax and Bcl-2 was demonstrated by Western blotting. Moreover, to determine the molecular mechanism whereby tehranolide mediates G0/G1 arrest, the expression of PI3K, p-PI3K, Akt, p-Akt, p27kip1, cyclin D1, and CDK4 was monitored. Cell proliferation was significantly inhibited by tehranolide in a dose- and time-dependent manner. This compound inhibited cell proliferation and induced G0/G1 arrest through the PI3K/Akt/cyclin D1 pathway. It also induced apoptosis and an increase in ROS. In addition, an increase in cytochrome c and Bax, as well as a decrease in Bcl-2, was observed. Moreover, blocking the CD95 receptor with an anti-CD95 antibody (ZB4) had no effect on tehranolide-mediated apoptosis. This study has yielded promising results, which show for the first time that tehranolide does inhibit the growth of cancer cells. The selective inhibition of cancer cell growth, the apoptosis induction via the mitochondrial pathway, and the G0/G1 arrest by modulating the PI3K/AKT signaling pathway and downregulating cyclin D1, which leads to the release of p27kip1 and the association of this inhibitor with the cyclin E/CDK2 complex, ultimately preventing cell-cycle progression from G1 to S phase, all serve to provide support for further studies of tehranolide as a possible anticancer drug in the clinical treatment of cancer. © 2012 Elsevier Inc. All rights reserved.

Saadati R.,Shahid Beheshti University of Medical Sciences | Dadashzadeh S.,Shahid Beheshti University of Medical Sciences | Abbasian Z.,Shahid Beheshti University of Medical Sciences | Soleimanjahi H.,Tarbiat Modares University
Pharmaceutical Research | Year: 2013

Purpose: To investigate accelerated blood clearance (ABC) induction upon repeated injections of PLGA-PEG nanoparticles as a commonly used polymeric drug carrier. Methods: Etoposide-loaded PLGA-PEG NPs were developed and administered as the test dose to rats pre-injected with various NP treatments at certain time intervals. Pharmacokinetic parameters of etoposide and production of anti-PEG IgM antibody were evaluated. Results: A notable ABC effect was induced by a wide range of polymer doses (0.1 to 20 mg) of empty NPs, accompanied by IgM secretion. However, a further increase in polymer dose resulted not only in the abrogation of the observed ABC induction but also in distinctly a higher value for AUC of the NPs relative to the control. The data from the PEG-negative group verified the fundamental role of PEG for ABC induction. The first injection of etoposide-containing PEGylated nanoparticles (a cell cycle phase-specific drug) produced a strong ABC phenomenon. Three sequential administrations of etoposide-loaded NPs abolished ABC, although a high level of IgM was still detected, which suggests saturation with insignificant poisoning of immune cells. Conclusion: The presented results demonstrate the importance of clinical evaluations for PLGA-PEG nanocarriers that consider the administration schedule in multiple drug delivery, particularly in cancer chemotherapy. © 2012 Springer Science+Business Media New York.

Saeedi H.,Tarbiat Modares University | Saeedi H.,Sharif University of Technology | Banihashemi A.H.,Carleton University
IEEE Transactions on Information Theory | Year: 2010

In this paper, new sequences (λn,ρn) of capacity achieving low-density parity-check (LDPC) code ensembles over the binary erasure channel (BEC) is introduced. These sequences include the existing sequences by Shokrollahi as a special case. For a fixed code rate R, in the set of proposed sequences, Shokrollahi's sequences are superior to the rest of the set in that for any given value of n, their threshold is closer to the capacity upper bound 1 - R. For any given δ, 0 < δ < 1 - R, however, there are infinitely many sequences in the set that are superior to Shokrollahi's sequences in that for each of them, there exists an integer number n0, such that for any n > n0, the sequence (λn, ρn) requires a smaller maximum variable node degree as well as a smaller number of constituent variable node degrees to achieve a threshold within δ-neighborhood of the capacity upper bound 1-R. Moreover, it is proven that the check-regular subset of the proposed sequences are asymptotically quasi-optimal, i.e., their decoding complexity increases only logarithmically with the relative increase of the threshold. A stronger result on asymptotic optimality of some of the proposed sequences is also established. © 2006 IEEE.

News Article | October 23, 2015
Site: www.nature.com

Graduate students in the sciences generally keep a tight focus on their area of study, whether it is mice, molecules or lasers. But when it comes to plans for the future, they are willing to take a wide-angle view. The 2015 Nature survey of graduate students, which drew more than 3,400 responses from early-career researchers across the world, uncovered a strong and far-reaching enthusiasm for jobs in academia. Some 78% of respondents said that they are likely or very likely to pursue a research career in academia, a bold stance given the global shortage of permanent positions at universities. But the survey also revealed uncertainty and ambivalence. More than 60% of respondents said that they are “likely” or “very likely” to pursue a job in industry (see 'Industry appeal'). And 61% said that they are “likely” or “very likely” to pursue a research job with a government or foundation, which makes it clear that many graduate students are unclear about their futures. Indeed, when it comes to job plans, even a firm conviction can quickly fade. Daria Bulanova, a PhD student in molecular biology at the University of Helsinki, noted in her survey response that she expected to pursue a career in industry. “I was influenced by friends and relatives who had careers in big pharma and big biotech,” she explains. “They all had a really good career track.” Yet in the several months since she took the survey, Bulanova, who studies mutations in breast cancer, reveals that she has taken a 180-degree turn towards academia. Through company visits and consultations, she has been able to assess the reality of taking on an industry job. “I decided that I wasn't mature enough for that kind of shark tank,” Bulanova says. In retrospect, she also is uncertain that a job in a large company could satisfy her scientific curiosity. “Research in industry is very narrow and settled,” she says. “It doesn't lead to other questions.” Bulanova's determination to stay in academia solidified after she attended seminars at which research luminaries — such as Peter Jackson, a microbiologist and immunologist at Stanford University School of Medicine in California — discussed their own career paths. “That was inspirational,” she says. “You start dreaming.” The survey tapped into an eclectic, global crowd. Respondents were roughly evenly distributed between Europe, Asia and North America, with some respondents living in South America, Africa and Australia. They are a well-travelled bunch: 40% of respondents live away from their home country, a group that includes Bulanova, who is from Russia. Interest in academia is widespread across the continents. More than 90% of respondents in Asia revealed that they see academia as a possible career option, with more than half declaring that they are “very likely” to go down that path. Enthusiasm for academia is only slightly cooler in North America and in Europe, where 32% and 41% of respondents, respectively, said that they are “very likely” to take the academic route. Respondents in biology, chemistry and medicine — the most common areas of study for survey participants — reported similar career goals. In all three fields, about three-quarters of those polled ticked the “likely” or “very likely” boxes for following an academic career, compared with more than half indicating that they would opt for a career in industry. Dreams of academia endure even in parts of the world in which prospects seem daunting. Parisa Naeli, a PhD student in molecular genetics at Tarbiat Modares University in Tehran says that so far, her vision for the future exceeds her actual opportunities. “I don't want to just be a doctor or a professor,” she explains. “I want to be a great researcher. I want to have a fully equipped lab and work on my dream project, but I don't have that.” Naeli is keenly aware of the obstacles ahead. “I think the academic market is better in other countries than in Iran,” she observes. “It's hard to find a teaching job, but it's even harder to get a research job. I could do a lot for people, like drug discovery. But I can't because I don't have the facilities.” Enthusiasm for academia is not evident everywhere, however, and it certainly has not swept the Pennsylvania State Milton S. Hershey Medical Center in Harrisburg, says Robert Nwokonko, a PhD student in molecular biology there. “It doesn't seem like a lot of people here think that an academic career is the way to go,” he says. “I know a lot of students who decided to finish with a master's degree and get into industry as soon as possible.” For his part, Nwokonko intends to buck the local trend and become an academic. “I'd like to have my principal investigator's job in the future,” he declares. “He gets to set the focus. I want to be able to run my own lab and put out some quality research.” Nwokonko took time to develop that particular ambition. He started out as a medical student but came to realize that he preferred research. A year-long internship at a biotechnology company sealed the deal. “It was very hard work for not much money,” he rues. “I figured if I still liked research after that, I should apply to graduate school.” Nwokonko acknowledges that the really hard part might not be over yet. “I believe I have a sense of the challenges,” he says. “There are a lot of postdocs in their thirties, even late thirties. It takes a long time to get a foot in the door.” Some who see professorships in their future are already thinking about back-up plans. Sean Leonard, a 31-year-old PhD student in bioinformatics at the University of Texas in Austin, states that he wants to give academia a try but is willing to consider other options. Before entering science, he spent four years in the US Army, which included deployments in Afghanistan and Iraq. Compared to combat, he notes, there is nothing especially scary about academia. “A lot of my peers are stressed out and worried,” he says. “They think, 'If I don't get an academic job, my life is over.' But with my experience, I don't feel that pressure. I'll be able to find something that's fulfilling.” Although he could probably make more money as an army officer, Leonard affirms that he is committed to scientific research. “The intellectual endeavour is a strong motivator for me,” he declares. And whereas many students at his university have given up on the idea of academia, he is sticking with it. “I like the collegiate atmosphere, and I like the idea of teaching.” As for his fallback position, he admits that companies might not be especially interested in his current research subject — microbial communities in the gut of the honeybee. But he hopes that the specialized research skills that he is developing will make him more attractive to industry. Where are early-career researchers getting their zeal for academic jobs? Judging from the survey responses, at least some encouragement comes from their mentors. A little more than one-third of respondents revealed that their advisers had helped to shape their career plans. And notably, only half of respondents stated that their supervisor is open to the possibility of their pursuing a career outside academia. The main source of inspiration — reported by more than half of respondents — was their own online research, which suggests that graduate students do not routinely go to great lengths to explore their career options. Both formal career training and helpful colleagues fell behind advisers and online research as sources of career guidance. Chelsea Lowther, a PhD student in clinical genetics at the University of Toronto, Canada, has sought career advice from many sources. However, her decision to pursue academia is almost entirely her own. “My supervisor is great to talk to about career planning,” Lowther notes. “But she doesn't tell us exactly what she thinks we should do. She doesn't want to influence us.” Lowther has good reason to believe that she is on the right path. Earlier this year, she won a three-year, Can$105,000 (US$80,600) grant from the Canadian Institutes of Health Research to study the genetics of schizophrenia and intellectual disabilities. “My adviser expects her graduate students to get their own funding,” she explains. “She thinks it will be good for our careers.” Like Nwokonko, Lowther originally planned to go to medical school until the lure of research pulled her in another direction. Now in her third year of graduate school, she is approaching principal investigators at conferences to scope out potential postdoctoral opportunities. “I'm not concerned about finding a postdoc,” she insists. “That's not where the bottleneck is. I would just love to think that I'll only have to do one postdoc.” Lowther maintains that she is not naive about the difficulties of moving from a postdoctoral role to an elusive tenure-track position. “I don't think I'll be blindsided,” she says. “I'm aware of how bleak the prospects are. I try to stay confident and work as hard as I can. It will fall into place.” Some respondents disclosed that they already knew that a PhD was not for them before embarking on lower-level graduate qualifications. Dan Upsher was finishing a master's degree in fisheries research at the University of Hull, UK, when he filled out the survey. At the time, he stated that he was interested in an industry career — and he has stayed on course. Instead of moving on to a PhD, Upsher has launched an aquatic-rehabilitation consultancy. “River rehabilitation is where my true passion lies.” he says. By his own estimate, the years of practical experience will be better for his career than a few more years of graduate school. Although he could always go back to university later on, for now, Upsher is glad to avoid the crowd. “Getting a PhD has become such a thing to do,” he remarks. “It's a fad.” Students who do move on to PhD programmes often run into unexpected difficulties. Nearly half of survey respondents reported that they were surprised to discover how hard it is to get a grant, and a similar fraction revealed that finding a work–life balance is more challenging than expected. Forty per cent said that they were surprised to discover that many researchers with PhDs have already done multiple postdoctoral stints — an increasingly common scenario. Still, those surprises were not enough to sour most students' opinions of graduate school. Seventy per cent of respondents said that they are “satisfied” or “very satisfied” with their graduate-school experience, and only 3% reported being “very dissatisfied”. Despite her own share of surprises, Bulanova still has her eyes on the academic path: one or two postdoctoral positions in Europe or the United States, followed by a tenure-track job. She accepts that it will not be easy. “In northern Europe, especially in Finland, there are cuts in funding and the positions are very limited,” she says. “Somehow I want to try.” She has ideas that she wants to test, preferably in her own laboratory. Those ideas might not pan out exactly as she planned but, she admits, that is the beauty of science — and, for that matter, of careers in science. “If you already know all of the answers,” she says, “what's the fun?”

Hosseini S.A.,Islamic Azad University at Tehran | Ghassemian H.,Tarbiat Modares University
International Journal of Remote Sensing | Year: 2011

The support vector machine (SVM) has been a dominant machine-learning technique in the last decade and has demonstrated its efficiency in many applications. Research on classification of hyperspectral images have shown the efficiency of this method to overcome the Hughes phenomenon for classification of such images. A major drawback of classification by SVM is that this classifier was originally developed to solve binary problems, and the algorithms for multiclass problems usually have a high-computational load. In this article, a new and fast method for multiclass problems is proposed. This method has two stages. In the first stage, samples are classified by a maximum likelihood (ML) classifier, and in the second stage, SVM selects the final label of a sample among high-probability classes for that sample by a tree structure. So, for each sample, only some classes must be searched by SVM to find its label. The uncertainty of ML classification for a sample is obtained by the entropy of probabilities, and the number of classes that must be searched by SVM for a sample is obtained based on the uncertainty of that sample in the primary ML classification. This approach is compared with two widely used multiclass algorithms: one-against-one (OAO) and directed acyclic graph (DAGSVM). The obtained results on real data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) revealed less computational time and better accuracy compared to these multiclass algorithms. © 2011 Taylor & Francis.

Hosseinifar M.,Islamic Azad University at Tehran | Ahmadi V.,Tarbiat Modares University | Abaeiani G.,Laser and Optics Research School
Journal of Lightwave Technology | Year: 2011

A novel structure of unitraveling carrier photodiodes (UTC-PDs) with high-speed, high-efficiency, and wavelength selective characteristics is presented. Including the essential features of resonant cavity enhanced photodiodes and waveguide photodiodes, we propose microring-based UTC-PDs (MR-UTC-PDs) which can achieve excellent high-speed and high-quantum efficiency characteristics simultaneously. The photoresponse of MR-UTC-PDs is based on a drift-diffusion model. Photoresponse characteristics of MR-UTC-PDs, which depend on device parameters and coupling conditions, are investigated and it is shown that the overcoupled structures are suitable for high-speed photodetection. The important features of the device, such as efficiency enhancement and wavelength selectivity are discussed and the trade-off between 3 dB bandwidth and efficiency is solved for nanoscaled absorption layer. Additionally, the bandwidth-efficiency product in the order of several hundreds gigahertz can be obtained even with low photoabsorption layers. © 2006 IEEE.

Saghaei H.,Islamic Azad University at Tehran | Ebnali-Heidari M.,Shahrekord University | Moravvej-Farshi M.K.,Tarbiat Modares University
Applied Optics | Year: 2015

Using numerical analysis, we compare the results of optofluidic and rod filling techniques for the broadening of supercontinuum spectra generated by As2Se3 chalcogenide photonic crystal fibers (PCFs). The numerical results show that when air-holes constituting the innermost ring in a PCF made of As2Se3-based chalcogenide glass are filled with rods of As2S3-based chalcogenide glass, over a wide range of mid-IR wavelengths, an ultra-flattened near-zero dispersion can be obtained, while the total loss is negligible and the PCF nonlinearity is very high. The simulations also show that when a 50 fs input optical pulse of 10 kW peak power and center wavelength of 4.6 μm is launched into a 50mm long rod-filled chalcogenide PCF, a ripple-free spectral broadening as wide as 3.86 μm can be obtained. © 2015 Optical Society of America.

Khalesi N.,Islamic Azad University at Tehran | Rezaei N.,Islamic Azad University at Tehran | Haghifam M.-R.,Tarbiat Modares University
International Journal of Electrical Power and Energy Systems | Year: 2011

Distribution system companies intend to supply electricity to its customers in an economical and reliable manner whereas customers in most distribution system are outspread and connect to distribution system with different type of equipments. These equipment usually have various types and resistance together, that produce highest loss and lowest reliability for distribution systems and customers that are not appreciated in networks. Distributed generations (DGs) are one of the best reliable solutions for these problems if they are allocated appropriately in the distribution system. This paper presents multi-objective function to determine the optimal locations to place DGs in distribution system to minimize power loss of the system and enhance reliability improvement and voltage profile. Time varying load is applied in this optimization to reach pragmatic results meanwhile all of the study and their requirement are based on cost/benefit forms. Finally to solve this multi-objective problem a novel approach based on dynamic programming is used. The proposed methodology is successfully applied to a study case and simulation results are reported to verify the proposed approach. © 2010 Elsevier Inc. All rights reserved.

Haghifam M.R.,Tarbiat Modares University | Manbachi M.,Islamic Azad University at Tehran
International Journal of Electrical Power and Energy Systems | Year: 2011

Many subsystems are involved in the reliability modeling of combined heat and power (CHP) systems, but in most studies these subsystems have not been classified and in many cases have been considered separately. Furthermore, calculating the reliability from the generation point to the consumer has not yet been studied. Herein, we classify combined heat and power subsystems and model their reliability, availability and mean-time-to-failure indices based on interactions between subsystems from the generation site to consumer delivery. The proposed CHP reliability and availability model is based on the state space and the continuous Markov method with electricity-generation, fuel-distribution and heat-generation subsystems. The effects of fuel- and water-distribution networks at the CHP site and the hot-water-distribution network on the consumer-utility reliability of CHP systems were fully assessed in an applicable case study. Additionally, we present a sensitivity analysis for island, standby and parallel operational modes of CHP systems. The results from the case study prove that improving the gas-distribution network, the network delivering hot water to the consumers and the water-delivery network to the CHP, in addition to optimizing the failure and repair rates of CHP systems, have considerable effects on the reliability improvement of the complete integrated system and have major roles in technical and economic feasibility studies of CHP systems. © 2010 Elsevier Ltd. All rights reserved.

Nasiri S.H.,Islamic Azad University at Tehran | Moravvej-Farshi M.K.,Tarbiat Modares University | Faez R.,Sharif University of Technology
IEEE Electron Device Letters | Year: 2010

We present a Nyquist stability criterion based on transmission line modeling for graphene nanoribbon (GNR) interconnects. This is the first instance that such an analysis has been presented for GNR, so far. In this analysis, the dependence of the degree of relative stability for multilayer GNR (MLGNR) interconnects on the geometry of each ribbon has been acquired. It is shown that, increasing the length and width, MLGNR interconnects become more stable. © 2006 IEEE.

Yousefi R.,Islamic Azad University at Tehran | Saghafi K.,Shahed University | Moravvej-Farshi M.K.,Tarbiat Modares University
IEEE Transactions on Electron Devices | Year: 2010

In this paper, we investigate the transport properties of carbon nanotube field-effect transistors (CNTFETs), with a nonequilibrium Green's function (NEGF) method. Tunneling leakage currents with respect to gate voltages are known effects for MOSFET-like CNTFETs (MOSCNTs). To minimize this phenomenon, we have proposed a structure with a simple modification of the MOSCNT by using lightly doped regions between the intrinsic channel and the highly doped source and drain regions, which we call the lightly doped drain and source CNTFET (LDDS-CNTFET). Simulations have shown that LDDS-CNTFET characteristics are related to the lightly doped region concentration. In comparison with an MOSCNT and a linearly doped CNTFET (LD-CNTFET), an LDDS-CNTFET with appropriately doped lightly doped drain and source regions has demonstrated a larger on current (Ion), a larger on off ratio (Ion/Ioff), a superior ambipolar characteristic, a shorter delay time, and also a smaller powerdelay product. Furthermore, our results show that the channel length for an LDDS-CNTFET is shorter than that for an LD-CNTFET having the same off-state characteristics. Finally, the effect of the unavoidable Schottky barriers at the interface of the heavily doped source/drain regions and their metal electrodes has been taken into account. Simulations have demonstrated that these Schottky barriers have almost the same deteriorating effects on the characteristics for both LD-CNTFETs and LDDS-CNTFETs. Hence, all discussions regarding the superiority of the proposed structure are also valid in presence of the Schottky barriers. © 2010 IEEE.

Fard M.J.S.,Islamic Azad University at Tehran | Morsali A.,Tarbiat Modares University
Journal of Inorganic and Organometallic Polymers and Materials | Year: 2010

Nano-structure of a new 1D double-chain Pb(II) coordination polymer, [Pb(μ-HPDC)(μ-Br)(H 2O)] n (1), {H 2PDC = 2,3-pyrazinedicarboxylic acid} was synthesized by a sonochemical method. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The structure of compound 1 was determined by single crystal X-ray diffraction and consists of 1D double-chain polymeric units. The coordination number in compound 1 is six and each lead atom is coordinated by two oxygen atoms of HPDC -, two nitrogen atoms of HPDC - ligands, one bromide atom and one oxygen of H 2O molecule. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses. Calcination of the nano-belts of compound 1 at 500 °C under air atmospheres yielded nano-sized particles of PbBr(OH) that characterized by scanning electron microscopy and X-ray powder diffraction. © 2010 Springer Science+Business Media, LLC.

Gholami R.M.,Islamic Azad University at Tehran | Borghei S.M.,Sharif University of Technology | Mousavi S.M.,Tarbiat Modares University
Hydrometallurgy | Year: 2011

A spent processing catalyst from an Iranian oil refinery was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize Al, Co, Mo and Ni from the spent catalysts under optimized conditions in batch cultures. The characteristics of the bioleach solution (pH, Eh, cell concentration and Fe(II)/Fe(III) concentration) were determined along with the concentration of metal values extracted from the catalyst. The results showed that after bioleaching using A. ferrooxidans in the presence of ferrous sulfate, maximum extractions of 63% Al, 96% Co, 84% Mo and 99% Ni were achieved after 30 days at pH 1.8-2.0. However, the highest extractions using A. thiooxidans in the presence of sulfur were 2.4% Al, 83% Co, 95% Mo and 16% Ni after 30 days at pH 3.9-4.4. The recovery of these metals decreases the environmental impact of the waste catalyst and the recycled product can be further used for industrial purposes. © 2010 Elsevier B.V.

Ahmadi A.,Tarbiat Modares University | Hadipour N.L.,Tarbiat Modares University | Kamfiroozi M.,Islamic Azad University at Shiraz | Bagheri Z.,Islamic Azad University at Tehran
Sensors and Actuators, B: Chemical | Year: 2012

Semiconductive carbon nanotubes (CNTs) have demonstrated great sensitivity toward molecules such as NH 3, NO, and NO 2. Nevertheless, pristine CNTs cannot be used for detection of some highly toxic molecules such as formaldehyde (HCOH). In the present study, we examined the possibility of using aluminum nitride nanotubes (AlNNTs) as a potential gas sensor for HCOH detection by performing density functional theory (DFT) calculation. It was found that HCOH molecule can be chemisorbed on the surface of AlNNTs with Gibbs free energies of -0.59 to -0.64 eV, at standard temperature and pressure (STP, 1 atm and 298 K). In view of the high change of HOMO/LUMO energy gap of the tube during the chemisorption, it is expected that the process induce a significant change in its electrical conductivity. Hence, the AlNNT can be used as a potential efficient gas sensor for HCOH detection. Furthermore, it was shown that H 2O molecules cannot significantly change the electronic properties of AlNNTs. © 2011 Elsevier B.V. All rights reserved.

Peyghan A.A.,Tarbiat Modares University | Rastegar S.F.,Islamic Azad University at Tehran | Hadipour N.L.,Tarbiat Modares University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

The electronic sensitivity of pristine, Ni- and Si-doped graphynes to ammonia (NH3) molecule was investigated using density functional theory, including dispersion correction. It was found that NH3 is weakly adsorbed on the sheet, releasing energy of 2.9-4.4 kcal/mol, and the electronic properties of the sheet are not significantly changed. Although both Ni-doping and Si-doping make the sheet more reactive and sensitive to NH 3, Si-doping seems to be a better strategy to manufacture NH 3 chemical sensors because of higher sensitivity. Our calculations show that the HOMO/LUMO gap of the Si-doped sheet is significantly decreased from 2.13 to 1.46 eV after the adsorption of NH3, which may increase the electrical conductance of the sheet. Therefore, the doped sheet might convert the presence of NH3 molecules to electrical signals. Moreover, the shorter recovery time of the Si-doped sheet is because of the middle adsorption energy of 39.3 kcal/mol in comparison with 55.1 kcal/mol for the Ni-doped sheet. © 2014 Elsevier B.V.

Gorji M.R.,Islamic Azad University at Tehran | Sanjabi S.,Tarbiat Modares University
Materials Letters | Year: 2012

In this paper, the corrosion behavior of NiTi thin films implanted with argon, carbon and nitrogen ions was investigated by potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) methods. PDS results showed that the i corr was decreased after implantation with carbon and nitrogen and increased with argon ions. EIS measurements also indicated that the corrosion resistance (R p) of the films implanted with carbon and nitrogen was increased and with argon implantation decreased. Scanning electron microscopy (SEM) images showed a lesser amount of corrosion defects in nitrogen and carbon implanted thin films and more amounts in argon implanted and unimplanted film surfaces. The cracks are also observed on argon implanted surface. © 2011 Elsevier B.V. All rights reserved.

Andervazh M.-R.,Islamic Azad University at Tehran | Olamaei J.,Islamic Azad University at Tehran | Haghifam M.-R.,Tarbiat Modares University
IET Generation, Transmission and Distribution | Year: 2013

This study proposes a Pareto-based multi-objective distribution network reconfiguration (DNRC) method using discrete particle swarm optimisation algorithm. The objectives are minimisation of power loss, the number of switching operations and deviations of bus voltages from their rated values subjected to system constraints. Probabilistic heuristics and graph theory techniques are employed to improve the stochastic random search of the algorithm self-adaptively during the optimisation process. An external archive is used to store non-dominated solutions. The archive is updated iteratively based on the Pareto-dominance concept to guide the search towards the Pareto optimal set. The method is implemented on the IEEE 33-bus and IEEE 70-bus radial distribution systems, simulations are carried out and results are compared with other available approaches in the literature. To assess the performance of the proposed method, a quantitative performance assessment is done using several performance metrics. The obtained results demonstrate the effectiveness of the proposed method in solving multi-objective DNRC problems by obtaining a Pareto front with great diversity, high quality and proper distribution of non-dominated solutions in the objective space. © The Institution of Engineering and Technology 2013.

Ahmadi Peyghan A.,Tarbiat Modares University | Hadipour N.L.,Tarbiat Modares University | Bagheri Z.,Islamic Azad University at Tehran
Journal of Physical Chemistry C | Year: 2013

By using density functional theory, we investigated the reactivity and electronic sensitivity of pristine and structurally manipulated BC2N nanotubes (BC2NNT) to a HCN molecule. It was mainly found that (i) the pristine BC2NNT can weakly adsorb the HCN with adsorption energy of -1.1 kcal/mol, and its electronic properties are not sensitive to HCN; (ii) doping the tube by an Al atom can largely improve its reactivity to HCN, but it does not have a significant effect on its sensitivity; (iii) B-B antisite defect on the tube wall can improve both reactivity and sensitivity of the tube to HCN; (iv) N-N antisite could improve neither the reactivity nor the sensitivity. Upon the adsorption of HCN on the B-B antisite defect, the HOMO-LUMO energy gap of the tube is significantly reduced from 2.23 to 1.82 eV and energy of 6.3 kcal/mol is released. © 2013 American Chemical Society.

Haghighi Mood S.,Islamic Azad University at Tehran | Hossein Golfeshan A.,Islamic Azad University at Tehran | Tabatabaei M.,Agricultural Biotechnology Research Institute of Iran | Salehi Jouzani G.,Agricultural Biotechnology Research Institute of Iran | And 4 more authors.
Renewable and Sustainable Energy Reviews | Year: 2013

Pretreatment technologies are aimed to increase enzyme accessibility to biomass and yields of fermentable sugars. In general, pretreatment methods fall into four different categories including physical, chemical, physico-chemical, and biological. This paper comprehensively reviews the lignocellulosic wastes to bioethanol process with a focus on pretreatment methods, their mechanisms, advantages and disadvantages as well as the combinations of different pretreatment technologies. Moreover, the new advances in plant "omics" and genetic engineering approaches to increase cellulose composition, reduce cellulose crystallinity, produce hydrolases and protein modules disrupting plant cell wall substrates, and modify lignin structure in plants have also been expansively presented. © 2013 Published by Elsevier Ltd. All rights reserved.

Koohestani M.,Islamic Azad University at Tehran | Golpour M.,Tarbiat Modares University
IET Microwaves, Antennas and Propagation | Year: 2010

In this study, a novel compact microstrip antenna with an ultra wide bandwidth is presented. The proposed antenna is a U-shaped square patch combined with two parasitic tuning stubs which is fed by a coplanar waveguide (CPW). The total size of the fabricated antenna is 24×28×0.787 mm3. The dimensional parameters for the antenna are introduced and their effects on the frequency characteristic have been investigated through a parametric study. Simulated and experimental results indicate that the antenna achieved an ultra wideband impedance bandwidth (S11 < -10 dB) as high as 129%. The radiation patterns of the antenna are measured and presented. The simulated results show good agreement with the measured results. The measured gains range from 1.6 to 5.3 dBi against frequency. These characteristics make the antenna suitable for UWB applications. © 2010 The Institution of Engineering and Technology.

Haroonabadi H.,Islamic Azad University at Tehran | Haghifam M.-R.,Tarbiat Modares University
Applied Soft Computing Journal | Year: 2011

Deregulation policy has caused some changes in the concepts of power systems reliability assessment and enhancement. In the present research, generation reliability is considered, and a method for its assessment is proposed using intelligent systems. Also, due to the stochastic behavior of power market and generators' forced outages, Monte Carlo Simulation is used for reliability evaluation. Generation reliability merely focuses on the interaction between generation complex and load. Therefore, in this research, based on the type of market and concentration, reserve margin and various future times, a Neuro-Fuzzy system is proposed for evaluation of generation reliability, which is valid and usable for all kinds of power pool markets. Finally, the proposed method is assessed on IEEE-Reliability Test System with satisfactory results. The results further showed that if market becomes more concentrated or price elasticity of demand increases, reliability will improve. © 2011 Elsevier B.V. All rights reserved.

Koohestani M.,Islamic Azad University at Tehran | Golpour M.,Tarbiat Modares University
Microwave and Optical Technology Letters | Year: 2010

This letter presents a rectangular slot antenna with a novel coplanar waveguide fed diamond patch covering frequency range from 2.27 to 10.63 GHz based on S11 < - 10 dB, 129φ%. The fabricated antenna has a small size as high as 42 x 42 mm2. The measured results are in good agreement with simulation results. The measured radiation patterns are nearly omni-directional over the most of the frequency bandwidth. The antenna gain ranges from 1.6 to 7.6 dBi. The simple structure, compact size, and good characteristics make the antenna easy to use in commercial ultra wideband systems. © 2009 Wiley Periodicals, Inc.

Uromeihy A.,Tarbiat Modares University | Farrokhi R.,Islamic Azad University at Tehran
Bulletin of Engineering Geology and the Environment | Year: 2012

Water leakage from a dam is always important, but particularly where the preservation of water is essential in semi-dry areas, such Iran. At Kamal-Saleh Dam, the rock mass rating (RMR) and geological strength index(GSI) systems were used to identify the quality of the rock mass, which is particularly important in a foliated material. The RMR results were compared with Lugeon tests undertaken in vertical and oblique holes along the dam foundation and abutments. Although the rock quality designation values could not be used to indicate the quality of the rock mass, they had a direct relationship with the Lugeon values. © 2011 Springer-Verlag.

Eskandari M.,Islamic Azad University at Tehran | Homaee M.,Tarbiat Modares University | Mahmodi S.,University of Tehran
Waste Management | Year: 2012

Landfill site selection is a complicated multi criteria land use planning that should convince all related stakeholders with different insights. This paper addresses an integrating approach for landfill siting based on conflicting opinions among environmental, economical and socio-cultural expertise. In order to gain optimized siting decision, the issue was investigated in different viewpoints. At first step based on opinion sampling and questionnaire results of 35 experts familiar with local situations, the national environmental legislations and international practices, 13 constraints and 15 factors were built in hierarchical structure. Factors divided into three environmental, economical and socio-cultural groups. In the next step, the GIS-database was developed based on the designated criteria. In the third stage, the criteria standardization and criteria weighting were accomplished. The relative importance weights of criteria and subcriteria were estimated, respectively, using analytical hierarchy process and rank ordering methods based on different experts opinions. Thereafter, by using simple additive weighting method, the suitability maps for landfill siting in Marvdasht, Iran, was evaluated in environmental, economical and socio-cultural visions. The importance of each group of criteria in its own vision was assigned to be higher than two other groups. In the fourth stage, the final suitability map was obtained after crossing three resulted maps in different visions and reported in five suitability classes for landfill construction. This map indicated that almost 1224. ha of the study area can be considered as best suitable class for landfill siting considering all visions. In the last stage, a comprehensive field visit was performed to verify the selected site obtained from the proposed model. This field inspection has confirmed the proposed integrating approach for the landfill siting. © 2012 Elsevier Ltd.

Ebrahimpour A.,Islamic Azad University at Tehran | Maerefat M.,Tarbiat Modares University
Energy Conversion and Management | Year: 2011

External shading affects the solar energy incident on a window and the transferred energy within the room through the window. In present study, the effect of advanced glazing and overhangs on the solar energy transmitted into or lost from the room through the fenestration areas have been evaluated for typical residential buildings in Tehran, using EnergyPlus× software. It was found that appropriate overhangs or side fins in the south, west and east windows would lead to the optimal reduction of the annual energy transferred into the buildings and can have an energetic behaviour equivalent to high performance glazing. The results have been summarized in a table to simple selecting the best window with different glazings, overhangs and side fins based on energy rating. © 2010 Elsevier Ltd. All rights reserved.

Heidari S.M.,Tarbiat Modares University | Ghaderi M.,Tarbiat Modares University | Afzal P.,Islamic Azad University at Tehran
Applied Geochemistry | Year: 2013

The aim of this study is to delineate and separate mineralization phases based on surface lithogeochemical Au, Ag, As and Cu data, using the Concentration-Area (C-A) fractal method in the Touzlar epithermal Au-Ag (Cu) deposit, NW Iran. Four mineralization phases delineated by multifractal modeling for these elements are correlated with the findings of mineralization phases from geological studies. The extreme phase of Au mineralization is higher than 3.38. ppm, which is correlated with the main sulfidation phase, whereas Ag extreme phase (higher than 52.48. ppm) is associated with silicic veins and veinlets. The resulting multifractal modeling illustrates that Au and Ag have two different mineralization trends in this area. Extreme (higher than 398.1. ppm) and high mineralization phases of Cu from the C-A method correlate with hydrothermal breccias and main sulfidation stage in the deposit, respectively. Different stages of Au mineralization have relationships with As enrichment, especially in high and extreme (higher than 7.9%) phases. The obtained results were compared with fault distribution patterns, showing a positive correlation between mineralization phases and the faults present in the deposit. Moreover, mineralization phases of these elements demonstrate a good correlation with silicification and silicic veins and veinlets. © 2013 Elsevier Ltd.

Ghadikolaei H.M.,Iran University of Science and Technology | Tajik E.,Iran University of Science and Technology | Aghaei J.,Shiraz University of Technology | Charwand M.,Tarbiat Modares University
Applied Energy | Year: 2012

This paper proposes a new framework for the operation of distribution companies (discos) in the liberalized electricity market environment considering distributed generation (DG) units and carbon dioxide (CO2) emission penalty cost. The proposed short-term framework is a two-stage model. The first stage, namely day-ahead stage, deals with the activities of discos. This stage includes a optimization problem to minimize the costs of distribution company (operational and CO2 emission costs). The first stage is formulated as a mixed integer nonlinear programming (MINLP) framework using the Benders decomposition to determine the decisions of discos to buy power from grid, schedule the DG units and contract with interruptible loads (ILs). The results of the first stage are imposed as the boundary constraints in the second stage which deals with the activities of discos in an hour-ahead period. In the hour-ahead stage, the retailers determine the amount of purchased active and reactive power from the grid and the production of each DG unit in the energy and reserve market keeping in mind its day-ahead decision to maximize the desired short-term profit. Finally, the efficiency of the proposed framework is studied on a case study. © 2012 Elsevier Ltd.

Milani A.E.,Islamic Azad University at Tehran | Haghifam M.R.,Tarbiat Modares University
Mathematical and Computer Modelling | Year: 2013

Power loss is one of the most important issues when dealing with distribution networks. Due to the nature of power loss, it can be an inseparable part of these networks. This is while an optimal reconfiguration is a great optimization procedure to power loss reduction in distribution networks. Moreover, to perform optimal dynamic reconfiguration, determining optimal time intervals and detecting the most proper time points greatly affects the total benefit achieved from this process. This benefit includes the cost of reconfiguration and the benefit of power loss reduction. This paper proposes an evolutionary approach for optimal time interval determination. In this paper basic reconfiguration models are discussed to form an optimal time interval model gradually. The Genetic Algorithm (GA) is used to solve the suggested model while the proposed method is implemented on an IEEE-33 Bus network. In order to examine the effectiveness of the proposed method, a comparison is done with other similar procedures. Also, in order to validate the numerical results, further compression is done with a method using a Binary Particle Swarm Optimization (BPSO) algorithm rather than the GA. © 2011 Elsevier Ltd.

Ahmadi A.,Iran University of Science and Technology | Charwand M.,Tarbiat Modares University | Aghaei J.,Shiraz University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2013

In the medium term planning, the objective of an electricity retailer is to configure its forward contract portfolio and to determine the selling price offered to its clients. To procure the electricity energy to be sold to the clients, a retailer has to face by two major challenges. Firstly, at buying electricity energy, it must cope with uncertain pool prices and sign forward contracts at higher average prices. Secondly, at selling electricity, it should handle the demand uncertainty and consider this fact that customers might choose a different retailer if the selling price is not competitive enough. In this paper the financial risk associated with the market price uncertainty is modeled using expected downside risk, which is incorporated explicitly as a constraint in the mixed-integer stochastic optimization problem. Roulette wheel mechanism and Lattice Monte Carlo Simulation (LMCS) are employed for random scenario generation wherein the stochastic optimization problem is converted into its respective deterministic equivalents. The proposed optimization problem is solved by a decomposition technique using Benders decomposition algorithm. A realistic case study is implemented to demonstrate the capability of the proposed method. © 2013 Elsevier Ltd. All rights reserved.

Anafcheh M.,Tarbiat Modares University | Ghafouri R.,Islamic Azad University at Tehran | Hadipour N.L.,Tarbiat Modares University
Solar Energy Materials and Solar Cells | Year: 2012

A quantum chemical computational study has been performed at B3LYP/6-311G(d, p) level to investigate electronic structures of the C60 and C70 fullerene derivatives, as electron acceptor in bulk heterojunction solar cells, seeking ways to improve their efficiency in corresponding photovoltaic devices. The key point of the present survey is to achieve a significant linear correlation between the electrophilicity index calculated for the fullerene derivatives and the corresponding open-circuit voltage of the photovoltaic device. This index is a prominent feature in determining tendency of the fullerene derivative towards acquiring an additional electron from the adjacent electron-rich donor molecule, and also its resistance to give the electron back transfer. The results reveal that replacing butyric acid ester by propionic acid ester in the aliphatic part or increasing the donating strength of the substituent in the esteric part will cause an increase in electrophilicity. Considering the derivatives of C70 generally yields higher electrophilicity than those of C60 derivatives. Also for indene-C60 derivatives a significant increase in the electrophilicity is observed by increasing the number of adducts, leading to raise in the V OC values. © 2012 Elsevier B.V.

Nikoukar J.,Islamic Azad University at Tehran | Haghifam M.R.,Tarbiat Modares University
International Journal of Electrical Power and Energy Systems | Year: 2012

In the deregulated power system, it is necessary to develop an appropriate pricing scheme that can provide the useful economic information to market users, such as generation companies, transmission companies and customers. However, accurately assessment and allocating the transmission cost in the transmission pricing scheme is a challenge, although many methods have been proposed. The objective of this paper is to propose a simple transmission pricing scheme using tracing method based on the proportional tree, in which transmission fixed cost, congestion cost and loss cost are considered. A case study based on IEEE 24-bus test system is applied to assess the effectiveness of the cost allocation procedure. © 2012 Elsevier Ltd. All rights reserved.

Fazilat H.,Islamic Azad University at Tehran | Akhlaghi S.,Islamic Azad University at Tehran | Shiri M.E.,Iran University of Science and Technology | Sharif A.,Tarbiat Modares University
Polymer | Year: 2012

A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive-neuro-fuzzy-interference system (ANFIS) and radial basis function (RBF) were developed to predict thermal degradation kinetics (TDK) of nylon6 (NY6)/feather keratin (FK) blend films. By simultaneous implementation of back-propagation ANN and feed-forward ANFIS modeling on the experimental data obtained from thermogravimetric analysis (TGA) method, thermal degradation behavior of various compositions of NY6/FK blends was successfully predicted with minimum mean square errors (MSE). RBF networks were then trained on the TGA data at one heating rate for predicting analogs information at different heating rates, providing sufficient feed for TDK modeling. According to the comparison made between experimental and predicted kinetic parameters of thermal degradation process calculated from Friedman and Kissinger methods, the proposed prediction effort could effectively contribute to the estimation of precise activation energy (E a) and reaction order (n) values with least amount of experimental work and most accuracy. © 2012 Elsevier Ltd. All rights reserved.

Ebrahimpour A.,Islamic Azad University at Tehran | Maerefat M.,Tarbiat Modares University
Energy Conversion and Management | Year: 2010

The correct selecting of typical meteorological year is an important factor for accurate building energy simulation. In this study, the Sandia method has been applied to analyze the measured weather data of a 14-year period (1992-2005) in Bandarabass and to select the proper data for the typical meteorological year. Also, typical meteorological year has been generated by using Meteonorm and Weathergenrator softwares. Then the results of Sandia method and the two mentioned softwares have been compared with long-term average measured data for main parameters in the weather data file. Finally, those results which have the minimum difference in every month with the long-term average measured data and have best meet the persistence criterion of Hall's have been used to select the typical meteorological year. It is found that, the results of Sandia method and Meteonorm software have good agreement with the long-term average measured data during the year and have best meet with the persistence criterion of the Hall's. © 2009 Elsevier Ltd. All rights reserved.

Khaburi M.A.,Islamic Azad University at Tehran | Haghifam M.R.,Tarbiat Modares University
International Journal of Electrical Power and Energy Systems | Year: 2010

Available Transfer Capability (ATC) is a key concept in the restructuring of power systems. ATC is used by system operators to determine the ability of transmission system to transfer power and by system planners to indicate a system's strength. ATC calculation involves determination of Total Transfer Capability (TTC) and two margins, Transmission Reliability Margin (TRM) and Capacity Benefit Margin (CBM). In fact, if the values of TRM and CBM are assumed to be constant, ATC is directly expressed by TTC. Therefore, improvement of TTC is an important topic in the current deregulation environments. Due to the uncertainty of power system behavior, the events such as transmission line outage can cause the transfer capability to decrease. Accordingly, transmission capability analysis needs a statistical forecast for an expected range of transfer capability. Thus, it is necessary to study TTC problem from a probabilistic point of view and consider the probabilistic feature of the power systems and the related contingencies. © 2009.

Koleini S.M.J.,Tarbiat Modares University | Aghazadeh V.,Tarbiat Modares University | Sandstrom A.,Lule University of Technology
Minerals Engineering | Year: 2011

Copper concentrates with mineralogy dominated by chalcopyrite have slow leaching kinetics at atmospheric pressure in sulphate media because of the formation of passivation layer on its surface during the leaching. To enhance the leaching rate of the copper concentrate, pyrite was added to act as a catalyst. Pyrite and copper sulphide minerals then form a galvanic cell which increases both the copper leaching rate and yield. Effect of parameters such as solution redox potential, temperature, initial acid concentration, solids content, total initial iron concentration and pyrite to copper sulphide minerals mass ratio were investigated. Mineralogical analyses by XRD were performed on selected leach residues and the feed materials. A copper recovery higher than 80% in 24 h was achieved at a redox potential of 410 mV vs Ag, AgCl, a temperature of 85 °C, 15 g/L of initial acid concentration, a solid content of 7.8% (w/v), a total initial iron concentration 5 g/L and pyrite to copper sulphide minerals mass ratio 2:1. XRD patterns on leach residues showed that candidates for surface passivation, i.e. jarosite and elemental sulphur, were formed at high total initial iron concentrations. © 2010 Elsevier Ltd. All rights reserved.

News Article | December 14, 2016
Site: www.sciencemag.org

During the 1920s and 1930s, Viennese physician and adventurer Alfons Gabriel fell under the spell of Iran's Lut Desert. Gabriel had crisscrossed arid parts of the Middle East, Pakistan, and Afghanistan by camel, observing and mapping areas into which few dared venture—lands with names such as Dasht-i-Naumid (the Desert without Hope) and Dasht-i-Margo (the Desert of Death). But a "confused mass of impassable tangled dunes" stymied his efforts to probe the interior of the Lut Desert, a tract of sand and fantastical rock formations in southeastern Iran that was said to be the hottest place on Earth. In March 1937, Gabriel finally conquered the central Lut—and barely made it out alive. He described his experiences a year later in a spellbinding talk to the Royal Geographical Society in London. Late one afternoon, Gabriel recounted, "the landscape darkened under red clouds … and a noise like the roaring of the sea began." The dust storm raged into the night. "For several anxious hours we lay, motionless and helpless, outstretched on the ground." Later, the voyagers were disoriented by mirages that were most vivid when the air was coolest, just before sunrise. Near the end of the 3-week journey, even their parched camels had had enough: "Their legs trembled; they panted, knelt down, and sometimes crept along on their knees." The allure of the Lut persists. Last month, a convoy of five SUVs carried 10 researchers and their guides, along with cameras, instruments, and hundreds of liters of water and fuel, into the heart of the desert. These modern explorers from Iran, the United States, and Europe were drawn not so much by the exotic landscape as by the puzzle of its unusual ecosystem. Many researchers had assumed that the Lut Desert is too hostile to sustain life, says Hossein Akhani, a plant biologist at the University of Tehran. The interior of the desert, an area nearly as big as West Virginia, is mostly devoid of plant life. But adventurers and the occasional scientist who traveled into the Lut had spotted diverse animal life, including insects, reptiles, and desert foxes. How that food web holds together without plants has been a mystery. A morbid, and possibly unique, phenomenon may be the answer. Dead birds are a frequent sighting in the desert. A few years ago, scientists in Iran began wondering whether migratory birds stray into the Lut and, overcome by the intense heat, fall from the sky like manna, forming the base of a food web. The expedition, organized by Akhani and Bahman Izadi, head of an environmental nonprofit in Shiraz, Iran, and a Lut explorer, set out to test the idea. Colleagues warned that in the fall, right after the heat of summer, the team might not find enough living things to tell. Creatures that burrowed or migrated to escape the heat would not have had time to venture back into the desert. Instead, the team confirmed the existence of a vibrant ecosystem and saw compelling signs that migratory birds do help nourish it. They also found that the bone-dry landscape conceals what they are calling a "hidden sea": a surprisingly shallow layer of salty groundwater that may also help sustain life. The Lut Desert also offers a less uplifting lesson—at least for people living on the knife edge of sustainability in arid regions. Climate change models predict that as temperatures rise, tracts of the Middle East that are naturally uninhabitable—not survivable without air conditioning—will expand. Those areas may come to resemble the transition zone between settlements on the Lut's edges and its supremely hostile core. After Gabriel's pioneering venture, the scientific literature on the Lut Desert remained sparse. One point was settled, though: Gabriel had noted that a contemporary, the German geographer Gustav Stratil-Sauer, "was of the opinion that the hottest region of the earth was not, as hitherto supposed, to be found in Sind, or Abyssinia, or in the Death Valley of California, but in the southern Lut." In 2005, an infrared radiometer on NASA's Aqua satellite measured a ground temperature of 70.7°C (159.3°F) at one spot in the Lut—the hottest satellite reading of ground temperature ever. And in April 2014, Morteza Djamali, a paleoecologist at the Mediterranean Institute of Marine and Terrestrial Biodiversity and Ecology in Marseilles, France, and his colleagues ventured into the central Lut to install a temperature logger at the same spot. In an experience worthy of Alfred Hitchcock, a swarm of locusts descended, picking nearby bird carcasses clean, cannibalizing each other, and biting the researchers. "I can imagine that a lonely traveler could be killed by these small creatures" in a few days, Djamali says. The hardship paid off, Djamali says. In July, the thermometer, planted 30 centimeters above the surface in the shade of a wooden cylinder, registered 61°C—some 5°C higher than the official shade record set in Death Valley in 1913. Bands of heat-absorbing black sand, primarily magnetite, together with topography that limits air movement help explain the blazing temperatures, Djamali says. That same year Akhani paid his first visit to the Lut, a quick scouting trip. A specialist in salt-loving plants, which grow in salty seeps in a few spots in the desert, he also had noticed the birds' carcasses and wondered what role they might play in the ecosystem. Cobbling together backing from the Iranian National Science Foundation, the Saeedi Institute for Advanced Studies at Kashan University in Iran, and other sources, he assembled a team of specialists from Iran and abroad that will spend the next 5 years prizing scientific secrets from the desert. The team set off last month on its maiden expedition, departing from Shahdad, an oasis on the Lut's western edge, and heading due north before arcing south in a path that bisected the desert. In some areas, yardangs, wind-sculpted rock formations several meters tall, sprouted from the desert like mushrooms. Heftier formations called kaluts reminded Akhani of "the ruins of an old city." Relics of what Djamali calls a "complex geoclimatic history," some are made of sandstone, whereas others were eroded from the beds of saline and playa lakes that dotted the landscape some 10 million years ago. The topography, whimsical or majestic, is a major reason the United Nations Educational, Scientific and Cultural Organization inscribed the Lut Desert on its World Heritage List last July. (Iran hopes it will beckon intrepid ecotourists.) Along their 700-kilometer journey, the researchers sampled soil and biota at 37 sites before emerging from the desert east of Bam, a city that suffered catastrophic damage from a 2003 earthquake. One day, the team struck out on foot into a canyon called Zabone Mar, which means "snake's tongue." By satellite, the canyon, about 15 meters wide with walls reaching 30 meters high, looks like a bifurcated tongue. "I noticed a weird noise," recalls expedition member Amir AghaKouchak, a hydrologist at the University of California (UC), Irvine. A continuous, soft crackling emanated from the walls. He speculates that the sound was the rock expanding as temperatures soared from nightly lows near 0°C up to fall daily maximums of about 40°C. "I just stopped and listened to this beautiful music." Or perhaps it was a siren call: The canyon is a death trap. Within its walls, the researchers found the remains of dozens of migratory birds. The birds may have sought shelter in the canyon's shade, but without water they would have quickly perished, AghaKouchak says. Mahmoud Ghasempouri, an ornithologist at Tarbiat Modares University in Tehran, collected carcasses of several migratory species. Why the birds make a fatal detour into the desert is a puzzle, he says. Even outside the canyon dead migratory birds were plentiful, and they often bore signs of having been scavenged by foxes. "I think that's their main food source," AghaKouchak says. Insects, too, are critical to the Lut's food web. Many nibble on plants on the desert's periphery and are in turn eaten by spiders, reptiles, and foxes in the Lut's interior, supplementing the nutrients in the ill-fated birds, says expedition member Hossein Rajaei, curator of Lepidoptera—moths and butterflies—at the Stuttgart State Museum of Natural History in Germany. Yet some live in the heart of the desert. When Rajaei set up light traps at night, he was surprised to count large numbers of moth species. "What do they do there? What do they eat there?" he asks. How the fly larvae he found in a pool of hypersaline water survive is another enigma, he says. And so is the question of how the Lut's denizens stay hydrated. The answer may lie just below the surface. Before the expedition began, AghaKouchak had scrutinized satellite sensor data from the Lut. To his surprise, microwaves emanating from the ground suggested that in some parts of the oven-hot desert, the soil is moist. Perplexed, AghaKouchak consulted a colleague, who proposed that the Lut's soil is so dry that microwaves were radiating from deeper layers of soil or even rocks, falsely indicating shallow moisture. Last month, in the heart of the desert, the team's convoy entered "a flat landscape, as far as you can see," the hydrologist says. A short distance onto the plain, one of the trucks broke through several centimeters of hard, crusty soil and sank, up to its axles—in mud. After another SUV pulled out the stricken vehicle, "you could actually see water" where the tires had been. "It was hard to believe," AghaKouchak says, "but the area is really, really wet." He thinks the moisture comes from distant mountains that ring the table-flat playa. Occasional rainfalls in the spring and early fall drain into the flat basin, he says. According to the team's guides, other areas of the Lut have similar features. Back at UC Irvine, AghaKouchak will attempt to correlate the local knowledge with satellite moisture data to map the extent of the hidden sea. No one lives in the heart of the Lut, and after a 6-year-long drought in Iran, settlements on the desert's fringes are in retreat. That may foreshadow the fate of other parts of the Middle East as global warming pushes summer temperatures still higher, says Elfatih Eltahir, an environmental engineer at the Massachusetts Institute of Technology in Cambridge. Last year, in Nature Climate Change, Eltahir and a colleague defined a naturally uninhabitable climate as one in which the heat index—temperature adjusted for humidity—exceeds 35°C for more than six straight hours. "What we are talking about are really extreme conditions," Eltahir says. "If a human being is exposed to that, very likely that person would die." In summer, areas of the Persian Gulf already exceed that threshold and would be unbearable without air-conditioning. Barring "significant mitigation," the uninhabitable areas near the Persian Gulf are likely to expand, including arid but still habitable regions of Iran. "Lut would be a good lab to study what an extreme environment would look like," AghaKouchak says. To probe such questions more deeply, Akhani's team plans to return in the spring. Among other things, they will bring more sophisticated instruments for measuring soil moisture and set up camera traps to study the ecology of the desert fox and other creatures in more detail. They also hope to decipher at a molecular level how the life forms adapt to broiling heat, Akhani says. In 2018, they may even attempt a summer expedition. "If we go then, we probably need to bring a physician," says AghaKouchak, who hastens to add, "I can't wait to go back."

Shafizadeh Moghadam H.,University of Heidelberg | Shafizadeh Moghadam H.,Tarbiat Modares University | Helbich M.,University of Heidelberg
Applied Geography | Year: 2013

Several factors contribute to on-going challenges of spatial planning and urban policy in megacities, including rapid population shifts, less organized urban areas, and a lack of data with which to monitor urban growth and land use change. To support Mumbai's sustainable development, this research was conducted to examine past urban land use changes on the basis of remote sensing data collected between 1973 and 2010. An integrated Markov Chains-Cellular Automata (MC-CA) urban growth model was implemented to predict the city's expansion for the years 2020-2030. To consider the factors affecting urban growth, the MC-CA model was also connected to multi-criteria evaluation to generate transition probability maps. The results of the multi-temporal change detection show that the highest urban growth rates, 142% occurred between 1973 and 1990. In contrast, the growth rates decreased to 40% between 1990 and 2001 and decreased to 38% between 2001 and 2010. The areas most affected by this degradation were open land and croplands. The MC-CA model predicts that this trend will continue in the future. Compared to the reference year, 2010, increases in built-up areas of 26% by 2020 and 12% by 2030 are forecast. Strong evidence is provided for complex future urban growth, characterized by a mixture of growth patterns. The most pronounced of these is urban expansion toward the north along the main traffic infrastructure, linking the two currently non-affiliated main settlement ribbons. Additionally, urban infill developments are expected to emerge in the eastern areas, and these developments are expected to increase urban pressure. © 2013 Elsevier Ltd.

Yasavol N.,Tarbiat Modares University | Mahboubi F.,Amirkabir University of Technology
Materials and Design | Year: 2012

Plasma nitriding is a surface treatment process, which is widely used to improve wear, fatigue and corrosion resistance of the industrial parts. Nevertheless, corrosion resistance can be enhanced by oxidizing of the nitrided components. This paper considers the duplex treatment of plasma nitriding and post-oxidizing of AISI 4130 low alloy steel. After plasma nitriding, the post-oxidizing treatment was done in the various gas mixtures of O2/H2 and temperatures. The treated samples were characterized using metallographic techniques, XRD, SEM, micro-hardness and potentiodynamic test. The X-ray diffraction confirmed the development of gamma prime and epsilon iron nitride phases during the nitriding, and hematite (Fe2O3) and magnetite (Fe3O4) phases under the oxidizing process. The sample oxidized under O2/H2 volume ratio of 1/3 showed the best corrosion resistance, which is attributed to the formation of an almost single phase magnetite oxide layer on the top of the compound layer. © 2012.

Eslahchi M.R.,Tarbiat Modares University | Dehghan M.,Amirkabir University of Technology
Computers and Mathematics with Applications | Year: 2011

In this research first we explicitly obtain the relation between the coefficients of the Taylor series and Jacobi polynomial expansions. Then we present a new method for computing classical operational matrices (derivative, integral and product) for general Jacobi orthogonal functions (polynomial and rational). This method can be used for many classes of orthogonal functions. © 2011 Elsevier Ltd. All rights reserved.

Kavussi A.,Tarbiat Modares University | Qorbani M.,Tarbiat Modares University | Khodaii A.,Amirkabir University of Technology | Haghshenas H.F.,Amirkabir University of Technology
Construction and Building Materials | Year: 2014

Warm Mix Asphalt (WMA), an alternative to Hot Mix Asphalt, has gained popularity in the recent years. In this research, the effects of aggregate gradation, hydrated lime and Sasobit has been investigated in WMA mixes. Indirect Tensile Testing was performed on dry and saturated samples. Response Surface Methodology was applied to analyze the data. The results indicated that in the case of Indirect Tensile Strength at saturation condition (ITS sat) all the first and second order terms of the aggregate grading, hydrated lime and Sasobit contents, as well as their interactive terms, were statistically significant at 90% confidence level. In the case of Tensile Strength Ratio (TSR) and Indirect Tensile Strength at dry condition (ITS dry) parameters, the interactions between grading and Sasobit contents were rather poor. © 2013 Elsevier Ltd. All rights reserved.

Nimvari M.E.,Tarbiat Modares University | Maerefat M.,Tarbiat Modares University | El-Hossaini M.K.,Research Institute of Petroleum Industry RIPI
International Journal of Thermal Sciences | Year: 2012

In the present study, turbulent flow and heat transfer through a partially porous channel is investigated numerically. Two common arrangements of a porous layer in the channel are considered; central arrangement and boundary arrangement. Different values of the porous layer thickness as well as Darcy number are studied for both arrangements. The peak of the turbulent kinetic energy takes place at the porous/fluid interface. A special thickness exists in which the Nusselt number is maximum for the central arrangement and minimum for the boundary arrangement, due to channeling effect. For the central arrangement, the thickness which yields the highest Nusselt number is found to be 0.83, 0.88 and 0.9 for Darcy numbers 10 -2, 10 -3 and 10 -4 respectively. Also, for the boundary arrangement, the Nusselt number takes on its minimum value for thicknesses between 0.6 and 0.7, depending on the value of the Darcy number; the smaller is the Darcy number, the larger is the value of thickness at which the minimum Nusselt number occurs. Besides, for both arrangements, an optimum thickness of the porous layer is defined, taking into account the Nusselt number together with a reasonable pressure drop. Hence an effective Nusselt number has been employed and via its values, an optimum thickness of the porous layer is proposed. © 2012 Elsevier Masson SAS. All rights reserved.

Salmasnia A.,Tarbiat Modares University | Baradaran kazemzadeh R.,Tarbiat Modares University | Mohajer Tabrizi M.,Amirkabir University of Technology
Neurocomputing | Year: 2012

Many real world applications consist of finding optimal inputs (design variables) to the system that yields in desirable values for stochastic outputs (Responses). Several studies in the literature have suggested approaches addressing these problems but most of them assume that the responses are independent and their variances are constant over the experimental space. Furthermore, in many situations the relationship between the response variables and design variables is too complex to be efficiently estimated using traditional surface fitting approaches. In this paper, a method is presented for optimizing the problem of correlated multiple responses where relationship among response and design variables is highly nonlinear by means of Neuro-Fuzzy and principal component analysis derived desirability function. As another advantage over existing works, we have relaxed the assumption that variance of each response is invariant over the feasible region. Finally, effectiveness of the proposed method is illustrated through a numerical example. © 2012 Elsevier B.V.

Keyvanloo K.,Tarbiat Modares University | Mohamadalizadeh A.,Research Institute of Petroleum Industry RIPI | Towfighi J.,Tarbiat Modares University
Applied Catalysis A: General | Year: 2012

Carbon nanotubes (CNTs) supported ceria catalysts coated with silica were used in catalytic cracking of naphtha to increase the yield of ethylene and propylene. Coating of CNTs was carried out with a pH control chemical deposition method using Si precursor. TGA results on coated CNTs showed 80 °C improvement in the thermal stability compared to uncoated CNT. XRD, SEM, and TEM analysis indicated that the structure of the CNT remained intact after modification. The silicon partly coated the CNT walls and the CeO 2 entered the CNT channel or was deposited on the wall. Measurement of the total acidity and number of Brønsted acid sites with NH 3-TPD and FTIR measurements exhibited that the total acid concentration and Brønsted acid sites of modified CNTs increased. TPR results showed that the presence of Si species slightly improved the reduction of CeO 2. As a result, catalyst Si-Ce/CNT showed a better catalytic cracking performance than catalysts Ce/CNT, Si/CNT or CNT. © 2011 Elsevier B.V. All rights reserved.

Sajadieh M.S.,Amirkabir University of Technology | Fallahnezhad M.S.,University of Yazd | Khosravi M.,Tarbiat Modares University
International Journal of Production Economics | Year: 2013

This paper considers an integrated production-inventory model for a three-stage supply chain involving multiple suppliers, multiple manufacturers and multiple retailers. The suppliers/manufacturers produce the raw materials/final goods at a finite rate and deliver the materials/goods in a number of batches to the manufacturers/retailers. We analyze the problem where the lead times from the manufacturers to the retailers are stochastic and shortage is allowed. We also explicitly include the transportation costs from the manufacturers to the retailers into the model. The numerical analysis shows that the coordination mechanism employed is more beneficial for the cases with less unpredictable lead times, lower shortage prices, and no transportation cost. © 2013 Elsevier B.V.

Ghoddousi P.,Iran University of Science and Technology | Eshtehardian E.,Tarbiat Modares University | Jooybanpour S.,Amirkabir University of Technology | Javanmardi A.,Iran University of Science and Technology
Automation in Construction | Year: 2013

Minimizing both project time and cost is an important matter in today's competitive environment. Therefore trade-off between project time and cost is necessary. In projects, each activity can be started at different time points, depending on its precedence relationship and resource availability. Also cost and duration of the activities could be changed depending on the allocated resources. In addition, another strategy that affects the project total time and cost is resource leveling, which is applied to reduce excessive fluctuations in the resource usage. In this paper multi-mode resource-constrained project scheduling problem (MRCPSP), discrete time-cost trade-off problem (DTCTP) and also resource allocation and resource leveling problem (RLP) are considered simultaneously. This paper presents the multi-mode resource-constrained discrete time-cost-resource optimization (MRC-DTCRO) model in order to select starting the time and the execution mode of each activity satisfying all the project constraints. To solve these problems, non-domination based genetic algorithm (NSGA-II) is employed to search for the non-dominated solutions considering total project time, cost, and resources moment deviation as three objectives. The results of MRC-DTCRO model presented in this paper show that adding the resource leveling capability to the previously developed multi-mode resource-constrained discrete time-cost trade-off problem (MRC-DTCTP) models provides more practical solutions in terms of resource allocation and leveling, which makes this research applicable to both construction industry and researchers. © 2012 Elsevier B.V. All rights reserved.

Ebadi Amooghin A.,Tarbiat Modares University | Omidkhah M.,Tarbiat Modares University | Kargari A.,Amirkabir University of Technology
RSC Advances | Year: 2015

A novel mixed matrix membrane (MMM) was fabricated by incorporating micro-sized nano-porous sodium zeolite-Y (NaY zeolite) into Matrimid®5218 matrix. The filler and the prepared membranes were characterized by X-ray diffraction (XRD), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), and thermal gravimetric and derivative thermal gravimetric (TG/DTG) analyses. The effects of filler content (0-20 wt%), feed pressure (2-12 bar), operating temperature (35-75°C) and mixed feed gas on CO2/CH4 transport properties of Matrimid/NaY were investigated. The results revealed that the Matrimid/NaY (15 wt%) displayed a CO2 permeability of 17.52 Barrer, more than two-fold increase with respect to the NaY-free counterpart. The corresponding CO2/CH4 selectivity was increased from 36.3 for Matrimid to 43.3 for Matrimid/NaY (15 wt%), (about 20%). The CO2 permselectivities of MMMs were greater than that of the Matrimid over the entire pressure range. As the operating temperature increased from 35 to 75°C, CH4 permeability increased about 175% and 215% for Matrimid and Matrimid/NaY (15 wt%), respectively. While the CO2 permeability enhanced about 78% and 98%. The corresponding decreases in the CO2/CH4 selectivities were 35.27% and 37.14%, respectively. Moreover, the mixed gas experiment results indicated that CO2 permeability and CO2/CH4 selectivity for all membranes were lower than those of pure gas experiments, but with less severity for MMMs. The best CO2-selective membrane, Matrimid/NaY (15 wt%), represented the CO2 permeability of 15.19 Barrer with CO2/CH4 selectivity of 39.5 for a 10/90 vol% mixture of CO2 and CH4. © The Royal Society of Chemistry 2015.

Farmahini Farahani M.,Tarbiat Modares University | Heidarinejad G.,Tarbiat Modares University | Delfani S.,Building Research Institute, Egypt
Energy and Buildings | Year: 2010

In this paper, the results of an investigation on a two-stage cooling system have been studied. This system consists of a nocturnal radiative unit, a cooling coil, and an indirect evaporative cooler. During the night in summer, requisite chilled water for a cooling coil unit is provided by nocturnal radiative cooling and is stored in a storage tank. During the next day, the water in the tank provides chilled water for the cooling coil unit and hot outdoor air passes through two-stages: the cooling coil unit and an indirect evaporative cooler. Three sources provide secondary air for the indirect evaporative cooler. The sources are outdoor air, the air leaving from the cooling coil, and the air leaving from the indirect stage (regenerative). The investigation has been conducted in weather conditions in the city Tehran. The results obtained demonstrate that the first stage of the system increases the effectiveness of the indirect evaporative cooler. Also, the regenerative model provides the best comfort conditions. Therefore, this environmentally friendly and energy-efficient system can be considered as an alternative to the mechanical vapor compression systems. © 2010 Elsevier B.V. All rights reserved.

Davoodi M.R.,Tarbiat Modares University | Khorasani K.,Tarbiat Modares University | Talebi H.A.,Concordia University at Montréal | Momeni H.R.,Amirkabir University of Technology
IEEE Transactions on Control Systems Technology | Year: 2014

In this brief a distributed fault detection and isolation (FDI) methodology for a network of heterogeneous multiagent systems with different dynamics and order from one another is proposed. An FDI filter is designed such that the effects of disturbances and control inputs on the residual signals are minimized (for accomplishing the fault detection task) subject to the constraint that the transfer matrix function from the faults to the residuals is equal to a preassigned diagonal transfer matrix (for accomplishing the fault isolation task). Moreover, by utilizing the proposed methodology, isolation of simultaneous occurring faults can also be handled. Sufficient conditions for solvability of the problem are obtained in terms of linear matrix inequality (LMI) feasibility conditions. The extended LMI characterization is then used to reduce the conservativeness of the solution by eliminating the couplings between the Lyapunov matrices and the agents' matrices. Simulation results presented demonstrate the effectiveness and capabilities of our proposed design methodology. © 2014 IEEE.

Kateb M.,Tarbiat Modares University | Ahmadi V.,Tarbiat Modares University | Mohseni M.,Amirkabir University of Technology
Solar Energy Materials and Solar Cells | Year: 2013

The present work reports preparation of an electrochromic device based on poly(3,4-ethylenedioxythiophene) (PEDOT) modified ZnO nanowires. The vertically aligned ZnO nanowires, being 70 nm in diameter, were prepared as a template by hydrothermal process on 65 nm ZnO seed layer sputtered on transparent conductive fluorine doped tine oxide substrate. PEDOT was synthesized by electropolymerization using two approaches. The first was prepared at 1.6 V constant potential (CP) and the second by 0-2 V cyclic voltammetry (CV). The PEDOT nanotubes were successfully grown on ZnO nanowires array by CV electrochemical polymerization but CP method led to formation of PEDOT thin film. The average wall thickness of nanotubes was 20 nm. The CV and CP electrodes and devices were characterized by scanning electron microscope, cyclic voltammetry analysis and UV-visible spectrophotometery to study the effect of preparation method on electrode morphology and device stability, response time (tR) and contrast. The CV approach gave rise to t R and contrast of 66 ms and 46.1%, respectively; CP method resulted in tR and contrast of 300 ms and 37.84%, respectively. While the conventional thin films had response time in order of second. © 2013 Elsevier B.V.

Parsaeefard S.,Tarbiat Modares University | Van Der Schaar M.,University of California at Los Angeles | Sharafat A.R.,Tarbiat Modares University
IEEE Transactions on Wireless Communications | Year: 2014

We develop a robust formalism for power control games in unlicensed bands between two groups of users competing for the spectrum: informed-users (leaders) who have advanced capabilities to extract side-information about other users and their strategies, and uninformed-users (followers) who can only observe the aggregate interference caused by others. Such nominal leader-follower games have been previously studied in the power control literature; however, these prior works fail to capture an important aspect of such interactions: the side-information and observations made by users may be uncertain, which has an important impact on users' strategies and network performance. Thus, in this paper we propose a new, robust game-theoretic formalism and solution which takes these uncertainties into account. Specifically, each group chooses its actions by solving its respective worst-case robust optimization problems. We show how various types of uncertainties affect the social utility of each group, and identify in which deployment scenarios the social utility of the robust game is higher than that of the nominal game. Importantly, we show that robust solutions in such games are more energy efficient. Finally, our theoretical formalism, analysis and solutions are complemented by simulations. © 2002-2012 IEEE.

Javadian S.,Tarbiat Modares University | Yousefi A.,Tarbiat Modares University | Neshati J.,Research Institute of Petroleum Industry RIPI
Applied Surface Science | Year: 2013

The corrosion inhibition characteristics of cation-rich and anion-rich catanionic mixtures of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), as corrosion inhibitor of mild steel (MS), in aqueous solution of 3.5% NaCl were investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscopy (SEM). Solutions of CTAB/SDS mixtures showed more appropriate inhibition properties compared to the solutions of the individual surfactants, due to strong adsorption on the metal surface and formation of a protective film. Potentiodynamic polarization investigations indicated that the inhibitors studied were mixed type inhibitors. Adsorption of the inhibitors on the mild steel surface obeyed the Flory-Huggins adsorption isotherm. Furthermore, the values of the adsorption free energy (ΔG ads) in both mixtures decreased compared with a single surfactant which is attributed to stronger interactions in mixtures. © 2013 Elsevier B.V. All rights reserved.

Veisi H.,Payame Noor University | Gholami J.,Tarbiat Modares University | Ueda H.,Tokyo Institute of Technology | Mohammadi P.,Payame Noor University | Noroozi M.,Research Institute of Petroleum Industry RIPI
Journal of Molecular Catalysis A: Chemical | Year: 2015

A Pd supported on diaminoglyoxime (DAG)-functionalized Fe3O4 (Fe3O4/DAG/Pd) hybrid materials was fabricated for the first time. In this fabrication, DAG played an important role as a capping agent. The immobilized palladium catalyst was an efficient catalyst without added phosphine ligands for the Suzuki cross-coupling reaction of several aryl halides with phenylboronic acid in aqueous phase at room temperature. The yields of the products were in the range from 70% to 98%. The prepared heterogeneous nanocatalyst was characterized by XRD, XPS, EDS, FT-IR, ICP, FESEM, VSM and TEM. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled eight times without any significant loss in activity. © 2014 Elsevier B.V. All rights reserved.

Jahangiri A.,Tarbiat Modares University | Pahlavanzadeh H.,Tarbiat Modares University | Aghabozorg H.,Research Institute of Petroleum Industry RIPI
International Journal of Hydrogen Energy | Year: 2012

A series of Sm doped LaNiO 3 nanoparticles by solids denoted as La 1-xSm xNiO 3-δ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) were synthesized by the modified citrate sol-gel method. The prepared compounds were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), BET specific surface area and scanning and transmission electron microscopy (SEM-TEM) techniques. The results showed that highly homogeneous and crystalline oxides with particle sizes in the range of nanometers were obtained through this synthesis method. The XRD patterns of the prepared La 1-xSm xNiO 3-δ solids confirmed the perovskite structure for the samples up to x = 0.1. When the degree (x > 0.1) of substitution increase the formation of spinel-type La 2NiO 4 and mixed NiO, Sm 2O 3 phases are favored thermodynamically and the rate of perovskite structure formation decreased drastically. The effects of the partial substitution of La by Sm, reaction temperatures and feed gas ratio at atmospheric pressure were investigated in process of combined carbon dioxide reforming and partial oxidation of methane (CDRPOM), after reduction of the samples under hydrogen. All samples presented similar activity at 1073 K while at lower temperatures, the La 1-xSm xNiO 3-δ catalysts with x = 0, 0.1, 0.9 and 1 showed the highest activity. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Sadeghi Meresht E.,Tarbiat Modares University | Shahrabi Farahani T.,Tarbiat Modares University | Neshati J.,Research Institute of Petroleum Industry RIPI
Engineering Failure Analysis | Year: 2011

In January 2010, stress corrosion cracking was occurred in a high-pressure gas pipeline steel in northern regions of Iran, after almost 40. years since its installation. In this study, failure mechanisms were determined based on available documents and metallographic studies conducted on this pipeline. The results showed that the applied polyethylene tape coating on the external surface of the pipeline became opened and disbonded in the corroded area causing external surface of buried pipeline to be exposed to wet soil around it. As a result of the chemical interactions and formation of carbonate/bicarbonate solution and with the presence of tensile stresses, stress corrosion cracking occurred in the longitudinal direction and at the outer surface of the pipe. In addition, mechanisms and morphology of cracks propagation due to stress corrosion cracking to internal side of the pipe wall were studied. © 2010 Elsevier Ltd.

Pendashteh A.,Tarbiat Modares University | Rahmanifar M.S.,Shahed University | Kaner R.B.,University of California at Los Angeles | Mousavi M.F.,Tarbiat Modares University | Mousavi M.F.,University of California at Los Angeles
Chemical Communications | Year: 2014

CuCo2O4 nanostructures were synthesized through a facile solution combustion method. Electrochemical investigations demonstrate a novel electrode material for supercapacitors with remarkable performance including high-rate capability, high-power density (22.11 kW kg-1) and desirable cycling stability at different current densities. © 2014 The Royal Society of Chemistry.

Jahangiri A.,Tarbiat Modares University | Aghabozorg H.,Research Institute of Petroleum Industry RIPI | Pahlavanzadeh H.,Tarbiat Modares University
International Journal of Hydrogen Energy | Year: 2013

LaNiO3 and LaNi1-xFexO3 (x = 0.2, 0.4, 0.6, 0.8 and 1) perovskites were prepared by the citrate solegel method. The prepared compounds were characterized by using thermogravimetric analysis (TGA) and X-ray diffraction (XRD), temperature programmed reduction (TPR), and inductively coupled plasma (ICP) techniques. Specific surface area of the samples was measured by BET method. Morphology study of the prepared catalysts was performed using scanning and transmission electron microscopy (SEM and TEM, respectively). The XRD patterns of fresh catalysts indicated the formation of well-crystallized perovskite structure as the main phase present in the prepared samples. The results showed that the highly homogeneous and pure solids with particle sizes in the range of nanometers were obtained through this synthesis method. TPR analysis revealed that by increasing the degree of substitution (x) the reduction of the prepared samples became difficult. The effects of the partial substitution of Ni by Fe and reaction temperatures at atmospheric pressure were investigated in the combined reforming of methane with CO2 and O2 (CRM), after reduction of the samples under hydrogen. LaNiO3 exhibited high activity and selectivity without coke formation between all of the studied perovskites. Among Fe-substituted catalysts, the following order of activity was observed: LaNiO 3>LaNi0.4Fe0.6O3>LaNi 0.6 Fe0.4O3 > LaNi0.8Fe 0.2O3 > LaNi0.2Fe0.8O3 > LaFeO3. Copyright © 2013, Hydrogen Energy Publications, LLC.

Ganji F.,Tarbiat Modares University | Vasheghani-Farahani S.,Research Institute of Petroleum Industry RIPI | Vasheghani-Farahani E.,Tarbiat Modares University
Iranian Polymer Journal (English Edition) | Year: 2010

During the past decades, hydrogels have been introduced suitable as novel materials for a variety of applications such as biomedical engineering, sanitary products, agriculture, bioseparation, enhanced oil recovery, etc. They have been successfully used as superabsorbent materials and in drug delivery, cell encapsulation and tissue repair due to their high water content and consequent biocompatibility. Considering the fact that water retention in the hydrogels provides a suitable drug diffusion pathway; many hydrogel-based networks have been designed and fabricated as intelligent carriers of drugs. The rate and degree of hydrogel swelling are the most important parameters which control the release patterns of solvents and drugs from these polymeric networks. Therefore, the precise account of hydrogel behaviour as well as mathematical description of equilibrium swelling, dimensional changes due to solvent uptake, desorption and drug release profiles were the main objectives in many investigations. The objective of this manuscript is to give a brief review on existing mathematical models and theories in the field of hydrogel swelling as well as the description of the drug release mechanism from swelling-controlled networks. The most important properties of hydrogels relevant to their swelling behaviour as well as kinetics and thermodynamic of swelling are also presented.

Forouzanfar M.,Amirkabir University of Technology | Doustmohammadi A.,Amirkabir University of Technology | Hasanzadeh S.,Tarbiat Modares University | Shakouri G H.,University of Tehran
Applied Energy | Year: 2012

In this paper, a new multi-level genetic programming (MLGP) approach is introduced for forecasting transport energy demand (TED) in Iran. It is shown that the result obtained here has smaller error compared with the result obtained using neural network or fuzzy linear regression approach. The forecast uses historical energy data from 1968 to 2002 and it is based on three parameters; gross domestic product (GDP), population (POP), and the number of vehicles (VEH). The approach taken in this paper is based on genetic programming (GP) and the multi-level part of the name comes from the fact that we use GP in two different levels. At the first level, GP is used to obtain the time series model of the three parameters, GDP, POP, and VEH, and forecast those parameters for the time interval that their actual data are not available, and at the second level GP is used one more time to forecast TED based on available data for TED along with the data that are either available or predicted for the three parameters discussed earlier. Actual data from 1968 to 2002 are used for training and the data for years 2003-2005 are used to test the GP model. We have limited ourselves to these data ranges so that we could compare our results with the existing ones in the literature. The estimation GP for the model is formulated as a nonlinear optimization problem and it is solved numerically. © 2011 Elsevier Ltd.

Farahani R.Z.,Kingston University | Hekmatfar M.,Amirkabir University of Technology | Arabani A.B.,Wayne State University | Nikbakhsh E.,Tarbiat Modares University
Computers and Industrial Engineering | Year: 2013

Hub location problem (HLP) is a relatively new extension of classical facility location problems. Hubs are facilities that work as consolidation, connecting, and switching points for flows between stipulated origins and destinations. While there are few review papers on hub location problems, the most recent one (Alumur and Kara, 2008. Network hub location problems: The state of the art. European Journal of Operational Research, 190, 1-21) considers solely studies on network-type hub location models prior to early 2007. Therefore, this paper focuses on reviewing the most recent advances in HLP from 2007 up to now. In this paper, a review of all variants of HLPs (i.e., network, continuous, and discrete HLPs) is provided. In particular, mathematical models, solution methods, main specifications, and applications of HLPs are discussed. Furthermore, some case studies illustrating real-world applications of HLPs are briefly introduced. At the end, future research directions and trends will be presented. © 2013 Elsevier Ltd. All rights reserved.

Sadeghi Meresht E.,Tarbiat Modares University | Shahrabi Farahani T.,Tarbiat Modares University | Neshati J.,Research Institute of Petroleum Industry RIPI
Corrosion Science | Year: 2012

The inhibition effects of 2-butyne-1,4-diol on the corrosion susceptibility of grade API 5L X65 steel pipeline in 2M Na2CO3/1M NaHCO3 solution were studied by electrochemical techniques and weight loss measurements. The results indicated that this inhibitor was a mixed-type inhibitor, with a maximum percentage inhibition efficiency of approximately 92% in the presence of 5mM inhibitor. Atomic force microscopy revealed that a protective film was formed on the surface of the inhibited sample. The adsorption of the inhibitor was found to conform to the Langmuir isotherm with the standard adsorption free energy of -21.08kJmol-1. © 2011 Elsevier Ltd.

Delfani S.,Building Research Institute, Egypt | Pasdarshahri H.,Tarbiat Modares University | Karami M.,University of Tehran
Energy and Buildings | Year: 2012

Nowadays, use of air-to-air heat recovery system combined to the cooling system is becoming necessary. Types of combination heat recovery and air conditioner must provide the comfort conditions and better indoor air quality for occupants in any climatic conditions. In this research, four types of air conditioning systems are evaluated experimentally. In each case, the amount of energy consumption by the aim of providing the thermal comfort, for various outdoor climatic conditions in hot and humid regions is evaluated and compared. The contour plot of each experimental case is made, which shows the net energy consumption of systems based on the outdoor design condition. Finally, according to the experimental results, for selected hot and humid cities of Asia's south and west countries (such as Abadan, Kuwait, Doha, Dehli, Bangkok), the rate of energy consumption of each cooling systems is calculated. It is shown that by using the heat recovery, energy consumption will reduce about 11-32% based on the system approach. © 2012 Elsevier B.V. All rights reserved.

Research Institute of Petroleum Industry RIPI and Tarbiat Modares University | Date: 2014-09-18

The present invention is related to the synthesis of a nano-hybrid catalyst made of carbon nanotubes and metal ferrite materials for the removal of NO_(x )compounds, which are emitted from stationary sources, through an ammonia selective catalytic reduction process. Weight ratios of carbon nanotube (x) to metal ferrite (y) is preferably about (x/y) 0.1 to 10. The present invention is also directed to the synthesis of a nano-hybrid catalyst to improve the efficiency of the conventional NO_(x )reduction process at lower reaction temperatures. By use of the preferred nano-hybrid catalyst, it is possible to locate a selective catalytic reduction (SCR) unit capable of operating at lower temperatures, e.g., below 260 C., and from about 50 C. to about 250 C., after the desulfurizer and the particle removal equipment. With the exhaust gas cleaner, the lifetime of the catalyst can be increased. This nano-hybrid catalyst provides higher NO_(x )removal efficiencies at low temperatures, typically from about 50 C. to about 250 C.

Tarbiat Modares University and Research Institute of Petroleum Industry RIPI | Date: 2010-10-21

The invention relates to a salt resistant water absorbing compound including a polymeric phase that includes polyacrylamide and at least one of di or poly saccharide, wherein the polyacrylamide is cross-linked in the presence of at least one of di or poly saccharide by a cross-linking agent including multivalent cations, complexes thereof, organic cross-linking agents, or any combination thereof.

Ashrafizadeh S.N.,Iran University of Science and Technology | Ameri Ghasrodashti A.,Tarbiat Modares University
Chemical Engineering Research and Design | Year: 2011

Miscible gas injection is generally used as one of the most efficient methods in the enhanced oil recovery. Minimum miscibility pressure (MMP) is an important parameter in the miscible gas injection projects, since local displacement efficiency in the reservoir media is highly dependent on the MMP. Therefore, an appropriate estimation of MMP would bring significant economic benefits. This paper presents a comparative study on five representative equations of state (EoSs) for predicting MMP using Parachor model together with the criterion of zero interfacial tension (IFT) at the miscibility conditions. The predicted MMP values are compared with the experimental data obtained from the most reliable measurement technique, so called slim tube method. Such a prediction would enables us to judge the accuracy of the results obtained from different equations of state as well as the capability of Parachor model to calculate the MMP. The results of predictions obtained for five oil-gas systems in this study reveal reliable MMP values within 5% of accuracy. © 2010 The Institution of Chemical Engineers.

Dashti R.,Iran University of Science and Technology | Yousefi S.,Tarbiat Modares University
Reliability Engineering and System Safety | Year: 2013

Asset management (AM) is composed of distribution system activities that lead to realize the system administration targets based on the stakeholders' benefits and correspondingly satisfying them. In this paper, asset management structure is represented and employing the AM structure, asset management processes are proposed. Furthermore, corresponding revisory actions are represented based on distribution asset wastages in order to structure a novel reliability based asset assessment model. The proposed model has been applied in a real distribution company, which provides 1 million customers with their requisite electrical energy. Crown Copyright © 2012 Publishedby Elsevier Ltd.All rights reserved.

Niknejad A.,Yasouj University | Abedi M.M.,Yasouj University | Liaghat G.H.,Tarbiat Modares University | Zamani Nejad M.,Yasouj University
Materials and Design | Year: 2012

In this article, some theoretical relations are derived to predict the mean folding force, total absorbed energy per unit of tube length and specific absorbed energy per unit of total mass by the polyurethane foam-filled grooved tubes with circular cross section under the axial compression process. During the folding process, a new theoretical model of deformation is introduced for the polyurethane foam-filler. The theoretical analysis is developed on the basis of the energy method. Some foam-filled grooved specimens were prepared and axially compressed to obtain the experimental diagram of the folding force versus the axial displacement. Comparison of the theoretical predictions with the experimental results showed a good agreement. Then, by considering the interaction effect between the polyurethane foam and the inner wall of grooved tubes, a semi-empirical relation was derived. Predictions along with considering the interaction factor obtained from the semi-empirical relation indicate a better correlation with those of the experiments. © 2012 Elsevier Ltd.

Niknejad A.,Yasouj University | Elahi S.A.,Yasouj University | Liaghat G.H.,Tarbiat Modares University
Materials and Design | Year: 2012

This paper investigates the effect of polyurethane foam-filler on the lateral plastic deformation in the circular tubes under radial quasi-static loading, experimentally. For this purpose, the specimens were prepared with five different diameters and thicknesses. For each constant diameter of specimens, several tubes with different lengths were prepared. All geometrical groups of specimens in the lateral compression tests (flattening) were used in empty and polyurethane foam-filled conditions. The effect of length, diameter and wall thickness of tubes on the lateral load, energy absorption and the specific absorbed energy were studied. The experimental results show that the polyurethane foam-filler increase the energy absorption capability of tubes and furthermore the increment of the energy absorption in thinner tubes is more than thicker specimens. Results show that using the polyurethane foam in the circular tubes under the lateral compression works as an excellent filler. © 2011 Elsevier Ltd.

Zohdi H.,Tarbiat Modares University | Shahverdi H.R.,Tarbiat Modares University | Hadavi S.M.M.,Iran University of Science and Technology
Electrochemistry Communications | Year: 2011

The corrosion behavior of Fe 55-xCr 18Mo 7B 16C 4Nb x (x = 0, 3, and 4 at.%) amorphous ribbons in Ringer's solution with pH value 6.5, open to air at 37 °C, was investigated by linear polarization and electrochemical impedance spectroscopy (EIS) methods, aiming to estimate the feasibility of Fe-based metallic glasses as potential biomaterials. It was shown that the corrosion resistance in Ringer's solution significantly increases with an increase in Nb content. The linear polarization and EIS measurements indicated that the Fe 51Cr 18Mo 7B 16C 4Nb 4 possesses larger polarization resistance value than that of 316L stainless steel and Ti-6Al-4V which are used in the human body in biomedical applications. In addition, the ICP test was carried out to measure the concentrations of ions which had dissolved into the electrolyte. It was seen that amorphous alloys do not release any significant ions into the Ringer's solution, implying good biocompatibility of these alloys. © 2011 Elsevier B.V. All rights reserved.

Hu M.-L.,Wenzhou University | Morsali A.,Tarbiat Modares University | Aboutorabi L.,Tarbiat Modares University
Coordination Chemistry Reviews | Year: 2011

In recent years, the chemistry of metal-coordination polymers has been advanced due to their diverse topologies and potential applications in smart optoelectronic, magnetic, microporous and biomimetic materials with specific structures, properties, and reactivities. Metal carboxylates have emerged as a large family of open framework materials. Recently, metal carboxylate chemistry has enhanced because of the increasing importance of hybrid inorganic-organic compounds with potential applications in separation, catalysis, and gas storage. So far, research on coordination polymers has considerably been concentrated on incorporation of s-, d-, and even f-block metal ions as coordination centers. As a heavy p-block metal ion, lead(II), with its large radius, flexible coordination environment, and variable stereo-chemical activity, is suitable for formation of unusual network topologies with interesting properties. This review provides an overview of all lead(II) carboxylate supramolecular compounds reported since 1990 and an investigation of their coordination modes, properties and structures. The variety of coordination modes of carboxylate groups increase the strength and stability of the resulting architectures. These modes include (η1), (μ2-η1:η1), (η2), (μ2-η2), (μ3-η1:η2), (μ3-η1:η2), (μ2-η2:η1), (μ3-η1:η2:η1) and (μ4-η2:η2) that have created multiplicity polymeric structures with different dimensions. In this study it was found that carboxylate groups in many of lead(II) coordination polymers form more than a single type of coordination mode and among all of these modes maximum number belonged to chelating (η2) mode. © 2011 Elsevier B.V.

Alinia Kashani A.H.,Iran University of Science and Technology | Maddahi A.,Tarbiat Modares University | Hajabdollahi H.,Vali e Asr University of Rafsanjan
Applied Thermal Engineering | Year: 2013

Thermodynamic modeling and optimal design of an air-cooled heat exchanger (ACHE) unit are developed in this study. For this purpose, ε-NTU method and mathematical relations are applied to estimate the fluids outlet temperatures and pressure drops in tube and air sides. The main goal of this study is minimizing of two conflicting objective functions namely the temperature approach and the minimum total annual cost, simultaneously. For this purpose, fast and elitist non-dominated sorting genetic-algorithm (NSGA-II) is applied to minimize the objective functions by considering ten design parameters. In addition, a set of typical constraints, governing on the ACHE unit design, is subjected to obtain more practical optimum design points. Furthermore, sensitivity analysis of change in the objective functions, when the optimum design parameters vary, is conducted and the degree of each parameter on conflicting objective functions has been investigated. Finally, a selection procedure of the best optimum point is introduced and final optimum design point is determined. © 2013 Elsevier Ltd. All rights reserved.

Mohammadi A.,University of Bojnord | Manteghian M.,Tarbiat Modares University | Mohammadi A.H.,Institute Of Recherche En Genie Chimique Et Petrolier Irgcp | Mohammadi A.H.,University of KwaZulu - Natal
Journal of Chemical and Engineering Data | Year: 2013

One of the limitations in the process of hydrate formation to benefit its positive application is high pressure and low temperature conditions. Design and construction of a unit with the aforementioned conditions is therefore expensive and unsafe. Thus, an investigation of methods for moderation of hydrate formation conditions seems to be very important. As mentioned in literature, utilization of ammonium salts in water normally promotes the hydrate formation conditions. One of these salts is tetra-n-butylammonium fluoride (TBAF). In this research, the dissociation data of semiclathrate hydrates for the systems of methane + TBAF + water, carbon dioxide + TBAF + water, and nitrogen + TBAF + water have been measured and reported. Experimental measurements were performed at three concentrations of TBAF, that is, (0.02, 0.05, and 0.15) mass fraction. A comparison of hydrate dissociation data in the presence or absence of TBAF shows the promotion effect of TBAF on methane, carbon dioxide, and nitrogen hydrate formation. By increasing the concentration of TBAF from (0.02 to 0.15) mass fraction, its promotion effect increases, and the p-T curves of the double gas + TBAF semiclathrate systems shift to the low pressure and high temperature regions (moderate conditions). Results of the experiments show that, contrary to clathrate hydrates, a small increase in temperature of semiclathrate hydrates, studied herein, leads to a noticeable increase in dissociation pressure. © 2013 American Chemical Society.

Ghannad M.,Shahrood University of Technology | Rahimi G.H.,Tarbiat Modares University | Nejad M.Z.,Yasouj University
Composites Part B: Engineering | Year: 2013

In this paper, using the first-order shear deformation theory (FSDT) and matched asymptotic method (MAM) of the perturbation theory, an analytical solution for deformations and stresses of axisymmetric clamped-clamped thick cylindrical shells with variable thickness made of functionally graded materials (FGMs) subjected to internal pressure are presented. The governing equations are a system of ordinary differential equations with variable coefficients. Using the MAM of the perturbation theory, these equations could be converted into a system of algebraic equations and two systems of differential equations with constant coefficients. The displacements and stresses along the radius and length have been plotted and distribution of these is compared with the solution using finite element method (FEM). © 2012 Elsevier Ltd. All rights reserved.

Gharibi H.,Tarbiat Modares University | Gharibi H.,University of Utah | Golmohammadi F.,Tarbiat Modares University | Kheirmand M.,Yasouj University
Electrochimica Acta | Year: 2013

Carbon supported Pd and PdxCo alloy electrocatalysts of different PdxCo atomic ratios (x = 1, 2, 3 and 10) were prepared by the impregnation synthesis method at room temperature without heat treatment by ethylene glycol (EG) reduction. As prepared PdxCo bimetallic nanoparticles show a single-phase face-centered-cubic (fcc) disordered structure. The performance of these electrodes in the ORR was measured with cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), inductive coupled plasma (ICP), X-ray diffraction (XRD); scanning electron microscopy coupled to energy dispersive X-ray (SEM-EDX) and transmission electron microscope (TEM). For synthesized PdxCo/C electrocatalysts, the highest catalytic activity for the ORR, was found for a Pd:Co atomic ratio of 3:1 in acid media at the presence and absence of methanol with optimal Pd-Pd bond distance (0.2729 nm). Since the PdxCo/C alloy electrocatalysts are inactive for the adsorption and oxidation of methanol, it can act as a methanol-tolerant ORR catalyst in a direct methanol fuel cell (DMFC). A membrane-electrode assembly (MEA) has been prepared by employing of the Pd3Co/C as a cathode for passive direct methanol fuel cell and characterized by polarization curves and impedance diagrams. The DMFC test results indicate that the MEA prepared from Pd3Co/C cathode exhibits better performance compared to the MEA prepared from Pt/C (Electrochem) and an in-house Pd/C catalyst synthesized, in terms of maximum power density and minimum charge transfer resistance. © 2012 Elsevier Ltd. All Rights Reserved.

Saremi A.,Arak University | Asghari M.,Tarbiat Modares University | Ghorbani A.,Arak University
Journal of Sports Sciences | Year: 2010

Omentin-1 is a newly discovered protein expressed and secreted from visceral adipose tissue that increases insulin sensitivity. We examined the effects of 12 weeks of aerobic training on serum omentin-1 concentrations together with cardiovascular risk factors in overweight and obese men. Eighteen overweight and obese participants (age 43.1±4.7 years, BMI≥25 kg·m-2) were assigned to exercise training (n=9) and control (n=9) groups. A matched control group of normal weight participants (n=8; age 42.2±3.8 years, BMI<25 kg·m-2) were also recruited for baseline comparison. The obese exercise group participated in 12 weeks of progressive aerobic training 5 days a week. Measures of serum omentin-1, insulin resistance, lipid profiles, blood pressure, and body composition were obtained before and after the 12 weeks. At baseline, normal weight participants had significantly higher serum omentin-1 concentrations than overweight and obese participants, and there were inverse correlations between omentin-1 and each of waist circumference, fasting glucose, insulin resistance, total cholesterol, triglyceride, and systolic blood pressure (P<0.05). After the aerobic training, waist circumference, percent body fat, fasting glucose, insulin resistance, triglyceride, total cholesterol, low-density lipoprotein cholesterol, and systolic blood pressure were all significantly decreased (P<0.05). In contrast, serum omentin-1 concentration was significantly increased after the aerobic programme (P<0.05), and correlated with changes in insulin resistance (r=-0.67, P=0.04), glucose (r=-0.65, P=0.05), waist circumference (r=-0.70, P=0.03), and aerobic fitness r=-0.68, P=0.04). Aerobic training resulted in an improvement in cardiometabolic risk factors in obese participants, and this improvement was accompanied by increased omentin-1 concentrations. © 2010 Taylor & Francis.

Abrishamifar A.,Iran University of Science and Technology | Ahmad A.A.,Iran University of Science and Technology | Mohamadian M.,Tarbiat Modares University
IEEE Transactions on Power Electronics | Year: 2012

Sliding mode control (SMC) is recognized as robust controller with a high stability in a wide range of operating conditions, although it suffers from chattering problem. In addition, it cannot be directly applied to multiswitches power converters. In this paper, a high performance and fixed switching frequency sliding mode controller is proposed for a single-phase unipolar inverter. The chattering problem of SMC is eliminated by smoothing the control law in a narrow boundary layer, and a pulsewidth modulator produces the fixed frequency switching law for the inverter. The smoothing procedure is based on limitation of pulsewidth modulator. Although the smoothed control law limits the performance of SMC, regulation and dynamic response of the inverter output voltage are in an acceptable superior range. The performance of the proposed controller is verified by both simulation and experiments on a prototype 6-kVA inverter. The experimental results show that the total harmonic distortion of the output voltage is less than 1.1% and 1.7% at maximum linear and nonlinear load, respectively. Furthermore, the output dynamic performance of the inverter strictly conforms the standard IEC62040-3. Moreover, the measured efficiency of the inverter in the worst condition is better than 95.5%. © 2006 IEEE.

Bahrami A.,Shiraz University | Besharati-Seidani A.,Tarbiat Modares University | Abbaspour A.,Shiraz University | Shamsipur M.,Razi University
Electrochimica Acta | Year: 2014

This work reports the preparation of a voltammetric sensor for selective recognition and sensitive determination of lead ions using a carbon paste electrode (CPE) impregnated with novel Pb2+-ion imprinted polymeric nanobeads (IIP) based on dithizone, as a suitable ligand for complex formation with Pb2+ ions. The differential pulse anodic stripping voltammetric technique was employed to investigate the performance of the prepared IIP-CPE for determination of hazardous lead ions. The designed modified electrode was revealed linear responses in the ranges of 3.0 × 10-10 - 1.0 × 10-9 mol dm-3 and 1.0 × 10-8 - 1.0 × 10-6 mol dm-3 with a limit of detection (LOD) of 1.0 × 10-10 mol dm-3 (S/N =3). It was found that the peak currents of the modified electrode for Pb2+ ions were at maximum value in acetate buffer of pH 4.0. The optimized preconcentration potential and accumulation time were to be -1.0 V and 25 s, respectively. The applicability of the proposed sensor to lead determination in tap water and lipstick samples are reported. © 2013 Elsevier Ltd.

Heidarzadeh M.,Tarbiat Modares University | Kijko A.,University of Pretoria
Natural Hazards | Year: 2011

A probabilistic tsunami hazard assessment is performed for the Makran subduction zone (MSZ) at the northwestern Indian Ocean employing a combination of probability evaluation of offshore earthquake occurrence and numerical modeling of resulting tsunamis. In our method, we extend the Kijko and Sellevoll's (1992) probabilistic analysis from earthquakes to tsunamis. The results suggest that the southern coasts of Iran and Pakistan, as well as Muscat, Oman are the most vulnerable areas among those studied. The probability of having tsunami waves exceeding 5 m over a 50-year period in these coasts is estimated as 17.5%. For moderate tsunamis, this probability is estimated as high as 45%. We recommend the application of this method as a fresh approach for doing probabilistic hazard assessment for tsunamis. Finally, we emphasize that given the lack of sufficient information on the mechanism of large earthquake generation in the MSZ, and inadequate data on Makran's paleo and historical earthquakes, this study can be regarded as the first generation of PTHA for this region and more studies should be done in the future. © 2010 Springer Science+Business Media B.V.

Jenabali Jahromi S.A.,Islamic Azad University at Marvdasht | Khajeh A.,Shiraz University | Mahmoudi B.,Tarbiat Modares University
Materials and Design | Year: 2012

AISI 410 martensitic stainless steel (MSS) samples were conventionally heat treated in diverse quenching environments to obtain three different microstructures: fine ferrite, fine and coarse martensite. Furthermore, laser surface treatment (LST) was done by pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser to compare the effect of short-term diffusion on the hardness of the different microstructures. The microstructure and microhardness of the samples were investigated by means of an optical microscope and Vickers microhardness tester respectively. Moreover, finite element simulation was done using ABAQUS finite element software to predict cooling curves and temperature histories at different depths of workpiece and to calculate the depth of fully hardened and partially hardened material. A comparison between theoretical and experimental results showed a good conformity and that LST is an effective approach to improve the hardness of the ferrite, despite the coarse and fine martensite phases. © 2011 Elsevier Ltd.

Sadeghi S.H.,Tarbiat Modares University | Moosavi V.,Tarbiat Modares University | Karami A.,Hormozgan University | Behnia N.,Shiraz University
Journal of Hydrology | Year: 2012

Assessment of factors affecting soil erosion processes is very important for managerial activities. However, full factorial design of an experiment is time consuming and expensive when there are a large number of factors and corresponding levels. Using the Taguchi method, this study assessed several factors affecting soil erosion. To the best of our knowledge, no study has been conducted to apply the Taguchi method in order to investigate the effects of different factors on soil erosion or sediment yield. The factors used in this study consisted of silt content, slope, aspect and vegetation cover, each of which had four levels in the study area in Lar Township, Iran. A L 16 orthogonal array was selected according to the aforementioned factors and levels and experimental tests were performed according to the Taguchi's orthogonal array. Analysis of the signal-to-noise (S/N) ratio was used to evaluate the experimental results. The optimum conditions for quantifying soil erosion were determined. A test experiment was also conducted in small-sized plots under the optimum conditions, and the prediction of other combinations of factors/levels was evaluated. The results showed that the Taguchi method could predict soil erosion with an average relative error of 12.4%. The percentage contribution of each factor was also determined. Silt and slope aspect made the greatest (49.4%) and the lowest (1.3%) contribution, respectively. The results showed that the Taguchi method is able to model the soil erosion process well (R 2>0.95) and can therefore be applied in future studies conducted in various fields. Additionally, comprehensive conclusions can be drawn if this method is applied under different plot sizes and considering further potential affective factors with different agroclimatic circumstances. © 2012 Elsevier B.V..

Moosavi V.,Tarbiat Modares University | Vafakhah M.,Tarbiat Modares University | Shirmohammadi B.,Tarbiat Modares University | Behnia N.,Shiraz University
Water Resources Management | Year: 2013

Artificial neural network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) have an extensive range of applications in water resources management. Wavelet transformation as a preprocessing approach can improve the ability of a forecasting model by capturing useful information on various resolution levels. The objective of this research is to compare several data-driven models for forecasting groundwater level for different prediction periods. In this study, a number of model structures for Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), Wavelet-ANN and Wavelet-ANFIS models have been compared to evaluate their performances to forecast groundwater level with 1, 2, 3 and 4 months ahead under two case studies in two sub-basins. It was demonstrated that wavelet transform can improve accuracy of groundwater level forecasting. It has been also shown that the forecasts made by Wavelet-ANFIS models are more accurate than those by ANN, ANFIS and Wavelet-ANN models. This study confirms that the optimum number of neurons in the hidden layer cannot be always determined by using a specific formula but trial-and-error method. The decomposition level in wavelet transform should be determined according to the periodicity and seasonality of data series. The prediction of these models is more accurate for 1 and 2 months ahead (for example RMSE = 0. 12, E = 0. 93 and R2 = 0. 99 for wavelet-ANFIS model for 1 month ahead) than for 3 and 4 months ahead (for example RMSE = 2. 07, E = 0. 63 and R2 = 0. 91 for wavelet-ANFIS model for 4 months ahead). © 2013 Springer Science+Business Media Dordrecht.

Aliofkhazraei M.,Tarbiat Modares University | Rouhaghdam A.S.,Boston Scientific Inc. | Gupta P.,Tarbiat Modares University
Critical Reviews in Solid State and Materials Sciences | Year: 2011

Cathodic plasma electrolytic (CPE) techniques are new groups of coating processes, which can be used for fabrication of nanostructured layers on surface of a wide range of metallic substrates. The most exciting visible feature of these atmospheric-based plasma techniques is continuous sparking on processed surface inside an electrolyte. Unlike the anodic part of plasma electrolysis (usually known as plasma electrolytic oxidation (PEO) or micro arc oxidation (MAO)), which is commonly used for oxidation of light metals/alloys such as aluminum, titanium and magnesium, CPE techniques can clean and coat different metals and alloys such as steel, copper, and light metals/alloys with formation of wide range of nanostructures including complex carbides, carbonitrides, intermetallics, and even oxides. It has been observed that the properties of obtained layers depend on the characteristics of achieved nanostructures such as average size, distribution and average coordination number of nanocrystallites. Furthermore, the properties of the processed surface can be tailored by tailoring the nanostructure characteristics. There is limited literature available on the mechanism of CPE and its connection to the morphology of nanostructured layers. This article addresses the two important aspects of CPE, namely characterization of nanostructured layers and mechanism of cathodic plasma electrolysis, which are reviewed in accordance to the morphology of fabricated nanostructures. © Taylor and Francis Group, LLC.

Tarbiat Modares University and Industrial Development And Renovation Organizatio | Date: 2010-04-13

The embodiments herein provide an improved Zymotis solid-state bioreactor and its operation for cultivation of microorganisms aseptically. In one embodiment, a bioreactor has two compartments containing three cooling plates. These plates have internal baffles instead of cooling tubes. The bioreactor has temperature sensors are loaded at different heights of the outer cooling plates for recoding and monitoring bed temperature during fermentation. Short space between two cooling plates with suitable material construction permits metabolic heat removal by conduction. The distance between two compartments is adjustable manually to achieve the best width. The product is extracted and harvested in the bioreactor using a trickle solvent. All of the on-line data are monitored on screen and recorded in the computer. Microorganisms are cultivated in such a manner that the bioreactor carries out all steps for cultivating microorganisms in an aseptic environment.

Saffarzadeh A.,Payame Noor University | Saffarzadeh A.,Institute for Research in Fundamental Sciences | Farghadan R.,Tarbiat Modares University
Applied Physics Letters | Year: 2011

The coherent spin-polarized electron transport through a zigzag-edge graphene flake (ZGF), sandwiched between two semi-infinite armchair graphene nanoribbons, is investigated by means of Landauer-Buttiker formalism. To study the edge magnetism of the ZGF, we use the half-filled Hubbard model within the Hartree-Fock approximation. The results show that the junction acts as a spin filter with high degree of spin polarization in the absence of magnetic electrodes and external fields. By applying a gate voltage the spin-filtering efficiency of this device can be effectively controlled and the spin polarization can reach values as high as 90%. © 2011 American Institute of Physics.

Pourghasemi H.R.,Tarbiat Modares University | Moradi H.R.,Tarbiat Modares University | Fatemi Aghda S.M.,Kharazmi University
Natural Hazards | Year: 2013

The current research presents a detailed landslide susceptibility mapping study by binary logistic regression, analytical hierarchy process, and statistical index models and an assessment of their performances. The study area covers the north of Tehran metropolitan, Iran. When conducting the study, in the first stage, a landslide inventory map with a total of 528 landslide locations was compiled from various sources such as aerial photographs, satellite images, and field surveys. Then, the landslide inventory was randomly split into a testing dataset 70 % (370 landslide locations) for training the models, and the remaining 30 % (158 landslides locations) was used for validation purpose. Twelve landslide conditioning factors such as slope degree, slope aspect, altitude, plan curvature, normalized difference vegetation index, land use, lithology, distance from rivers, distance from roads, distance from faults, stream power index, and slope-length were considered during the present study. Subsequently, landslide susceptibility maps were produced using binary logistic regression (BLR), analytical hierarchy process (AHP), and statistical index (SI) models in ArcGIS. The validation dataset, which was not used in the modeling process, was considered to validate the landslide susceptibility maps using the receiver operating characteristic curves and frequency ratio plot. The validation results showed that the area under the curve (AUC) for three mentioned models vary from 0.7570 to 0.8520 (AUCAHP = 75.70 %, AUCSI = 80.37 %, and AUCBLR = 85.20 %). Also, plot of the frequency ratio for the four landslide susceptibility classes of the three landslide susceptibility models was validated our results. Hence, it is concluded that the binary logistic regression model employed in this study showed reasonably good accuracy in predicting the landslide susceptibility of study area. Meanwhile, the results obtained in this study also showed that the statistical index model can be used as a simple tool in the assessment of landslide susceptibility when a sufficient number of data are obtained. © 2013 Springer Science+Business Media Dordrecht.

Seyfabadi J.,Tarbiat Modares University | Ramezanpour Z.,International Sturgeon Research Institute | Khoeyi Z.A.,Tarbiat Modares University
Journal of Applied Phycology | Year: 2011

The effects of irradiance and photoperiod on growth rates, chlorophyll a, β-carotene, total protein, and fatty acid content of Chlorella vulgaris were determined. The maximum growth rate (1. 13 day-1) was at 100 μmol photons m-2 s-1 and 16:8-h light/dark photoperiod. Chlorophyll a and β-carotene contents significantly differed under different light regimes with chlorophyll a content lower at high irradiance and longer light duration, while β-carotene showed the inverse trend. The total protein and fatty acid content also significantly differed in different light regimes; the maximum percentage of protein (46%) was at 100 μmol photons m-2 s-1 and 16:8 h photoperiod, and minimum (33%) was at 37.5 μmol photons m-2 s-1 and 8:16 h photoperiod; the total saturated fatty acids increased, while monounsaturated and polyunsaturated fatty acids decreased with increasing irradiance and light duration. © 2010 Springer Science+Business Media B.V.

Azadegan A.,Rutgers Business School | Patel P.C.,Ball State University | Zangoueinezhad A.,Tarbiat Modares University | Linderman K.,University of Minnesota
Journal of Operations Management | Year: 2013

Increasingly manufacturers implement lean practices to improve operational performance. In addition, manufacturers operate in ever more complex and volatile environments. This research investigates the effects of environmental complexity and dynamism on lean operations and lean purchasing practices. It empirically examines these relationships using archival and survey data from 126 manufacturers. The results show that environmental complexity positively moderates the effects of lean operations and lean purchasing on performance. However, environmental dynamism reduces the benefits of lean operations on performance, but enhances the benefits of lean purchasing on performance. Robustness tests further confirm the contingent effects of complexity and dynamism on lean operations and lean purchasing. This research offers a more nuanced understanding of the effect of external environmental context on lean practices, and suggests that practitioners should carefully consider the external environment when implementing different types of lean practices. © 2013 Elsevier B.V. All rights reserved.

Shamsipur M.,Razi University | Asgari M.,Tarbiat Modares University | Maragheh M.G.,Electrochemistry Laboratory | Moosavi-Movahedi A.A.,University of Tehran
Bioelectrochemistry | Year: 2012

A robust and effective nanocomposite film-glassy carbon modified electrode based on multi-walled carbon nanotubes and a room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was prepared by a layer-by-layer self-assembly method. The fabricated modified electrode was used as a novel impedimetric catalase nanobiosensor for the determination of H 2O 2. Direct electron transfer and electrocatalysis of catalase were fully investigated. The results suggested that catalase could be firmly adsorbed at the modified electrode. A pair of quasi-reversible redox peaks of catalase was observed in a 0.20M degassed phosphate buffer solution of pH 7.0. The nanocomposite film showed a pronounced increase in direct electron transfer between catalase and the electrode. The immobilized catalase exhibited an excellent electrocatalytic activity towards the reduction of H 2O 2. The electrochemical impedance spectroscopy measurements revealed that the charge transfer resistance decreases significantly after enzymatic reaction with hydrogen peroxide, so that the prepared modified electrode can be used for the detection of ultra traces of H 2O 2 (5-1700nM). © 2011 Elsevier B.V.

Neyshabur B.,Sharif University of Technology | Khadem A.,Sharif University of Technology | Hashemifar S.,University of Tehran | Arab S.S.,Tarbiat Modares University | Arab S.S.,Institute for Research in Fundamental Sciences
Bioinformatics | Year: 2013

Motivation: The interactions among proteins and the resulting networks of such interactions have a central role in cell biology. Aligning these networks gives us important information, such as conserved complexes and evolutionary relationships. Although there have been several publications on the global alignment of protein networks; however, none of proposed methods are able to produce a highly conserved and meaningful alignment. Moreover, time complexity of current algorithms makes them impossible to use for multiple alignment of several large networks together.Results: We present a novel algorithm for the global alignment of protein-protein interaction networks. It uses a greedy method, based on the alignment scoring matrix, which is derived from both biological and topological information of input networks to find the best global network alignment. NETAL outperforms other global alignment methods in terms of several measurements, such as Edge Correctness, Largest Common Connected Subgraphs and the number of common Gene Ontology terms between aligned proteins. As the running time of NETAL is much less than other available methods, NETAL can be easily expanded to multiple alignment algorithm. Furthermore, NETAL overpowers all other existing algorithms in term of performance so that the short running time of NETAL allowed us to implement it as the first server for global alignment of protein-protein interaction networks. © The Author 2013.

Tawakoli T.,Furtwangen University of Applied Sciences | Hadad M.J.,Furtwangen University of Applied Sciences | Hadad M.J.,Tarbiat Modares University | Sadeghi M.H.,Tarbiat Modares University
International Journal of Machine Tools and Manufacture | Year: 2010

Promising alternatives to conventional dry and fluid coolant applications are minimum quantity lubricant (MQL) or near dry grinding. Despite several researches, there have been a few investigations about the influence of MQL parameters on the process results, such as oil flow rate, air pressure, MQL nozzle position and distance from the wheel-workpiece contact zone. The current study aims to show through experiment and modeling, the effects of the above parameters on grinding performance such as grinding forces and surface roughness. The results show that the setting location of the nozzle is an important factor regarding the effective application of MQL oil mist. It has been shown that optimal grinding results can be obtained when the MQL nozzle is positioned angularly toward the wheel (at approximately 10-20° to the workpiece surface). In addition, it is found that the efficient transportation of oil droplets to the contact zone requires higher mass flow rate of the oil mist towards the grains flat area and longer deposition distance of an oil droplet. Applying the new setup, considerable reduction in the grinding forces and surface roughness has been achieved. © 2010 Elsevier Ltd. All rights reserved.

Abdollahi M.,Tarbiat Modares University | Rezaei M.,Tarbiat Modares University | Farzi G.,Kharazmi University
International Journal of Food Science and Technology | Year: 2012

Rosemary essential oil (REO) was used to develop an active film from chitosan. The effects of REO concentration (0.5, 1.0 and 1.5% v/v) on film properties were studied by measuring the physical, mechanical and optical properties of the REO-loaded films. Scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy were used to study microstructure and the interaction of the chitosan-based films. The solubility and water gain of the chitosan film decreased about 25% and 85%, respectively, by REO incorporation, up to 1.5% v/v, because of the interaction between hydrophilic groups of chitosan and REO as confirmed by FTIR. It was determined that REO improved the transparency of the films from 4.97 in neat chitosan up to 7.61; moreover, it reduced the films' light transmission in UV light more than 25%. Films containing REO showed more antibacterial activity and total phenol content. The films containing REO showed potential to be used as active film in food preservation. © 2012 The Authors. International Journal of Food Science and Technology © 2012 Institute of Food Science and Technology.

Hadad M.J.,Furtwangen University of Applied Sciences | Tawakoli T.,Furtwangen University of Applied Sciences | Sadeghi M.H.,Tarbiat Modares University | Sadeghi B.,Tarbiat Modares University
International Journal of Machine Tools and Manufacture | Year: 2012

An investigation is reported of the temperature and energy partition in grinding with minimum quantity lubrication (MQL) technique. Temperature distributions were determined in the subsurface of a hardened 100Cr6 steel workpieces through measuring by means of an embedded thermocouple during grinding in dry, MQL and fluid environments. The experiments were carried out with Al 2O 3 and CBN wheels. The energy partition to the workpiece was estimated using temperature matching. It is shown that the energy partition, and consequently the contact zone temperature, depends on the type of abrasives and coolantlubricant conditions. For MQL grinding with Al 2O 3 abrasive wheels, the energy partition varies in the range 73%77%. However, the energy partition is about of 82% for dry grinding. In fluid grinding with Al 2O 3 wheels, cooling by the fluid at the contact zone reduces the energy partition to less than 36%. For dry and MQL grinding with CBN superabrasive wheels, the energy partition is respectively about 52% and 46% due to the high thermal conductivity of the CBN abrasive. However, this can be reduced to 14% for grinding with CBN wheel and cooling by the fluid. © 2011 Elsevier Ltd. All rights reserved.

Shahbazi A.,Tarbiat Modares University | Younesi H.,Tarbiat Modares University | Badiei A.,University of Tehran
Chemical Engineering Journal | Year: 2011

Functionalized SBA-15 mesoporous silica with amine (-NH2) and melamine-based dendrimer amines (MDA) were synthesized. The materials were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption, thermogravimetric analysis and Fourier transform infrared (FTIR) spectroscopy. Tests were then conducted to study the adsorption of Pb(II), Cu(II) and Cd(II) ions onto SBA-15, NH2-SBA-15 and MDA-SBA-15 from a single metal aqueous solution for the effect of contact time, adsorbent dose, solution pH and concentration of metal ions in batch systems. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm by nonlinear regression analysis. The kinetics analysis revealed that the overall adsorption process was successfully fitted with the pseudo-first-order kinetic model. The adsorption of Pb(II), Cu(II) and Cd(II) onto MDA-SBA-15 was strongly dependent on temperature, and the adsorption capacity decreased with increasing the temperature of the system, indicating the exothermic and spontaneous nature of adsorption. For continuous adsorption experiments, MDA-SBA-15 adsorbent was used for the removal of single and ternary metal ions solutions of Pb(II), Cu(II) and Cd(II). Breakthrough curves were analyzed at different bed heights, flow rates and initial ternary metal ion concentrations. The Thomas and Yan models were used to determine the kinetic constants and to predict the breakthrough curves of each component. MDA-SBA-15 was regenerated and found to be suitable for reuse in successive adsorption-desorption cycles four times without significant loss in adsorption capacity. The results suggest that MDA-SBA-15 can be used as an adsorbent for an efficient removal of metal ions from aqueous solution. © 2010 Elsevier B.V.

Alizadeh N.,Tarbiat Modares University | Saburi N.,Islamic Azad University | Hosseini S.E.,Islamic Azad University
Food Control | Year: 2012

Benzoate-doped polypyrrole (PPy-Bz) was prepared electrochemically by anodic polymerization of pyrrole in the presence of benzoate ion (Bz) in an aqueous solution and was used as a solid-state PPy-Bz ion selective sensor. The effect of polymerization conditions on the characteristics of the potential response of the sensors was also discussed. The solid-state PPy-Bz sensor, showed a near-Nernstian behavior over 9 × 10 -5-2 × 10 -2 mol L -1 Bz - with a detection limit of 5 × 10 -5 mol L -1 in an aqueous solution. The potential response of the sensor was reproducible in the range pH 2-9 and was not affected by pH between 6 and 8. Selectivity of the sensor over diverse preservative reagents (sorbate, acetate and citrate) and inorganic salts was evaluated. The PPy-Bz sensor was applied for determination of Bz - ions in carbonated soft drinks by using potentiometry and the results are similar with values obtained by high-performance chromatography. © 2012 Elsevier Ltd.

Askarinejad A.,Tarbiat Modares University | Bagherzadeh M.,Sharif University of Technology | Morsali A.,Tarbiat Modares University
Applied Surface Science | Year: 2010

A simple sonochemical method was developed to synthesis uniform sphere-like Co3O4 and Mn3O4 nanocrystals. Epoxidation of styrene and cyclooctene by anhydrous tert-butyl hydroperoxide over the prepared Co3O4 and Mn3O4 nanocatalysts was investigated. The results of conversion activity were compared with bulk Co3O4 and Mn3O4. Under optimized reaction conditions, the nanocatalysts showed a superior catalytic performance as compared to the bulk catalysts. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area, were used to characterize and investigate the nanocatalysts. © 2010 Elsevier B.V.

Shidpour R.,Sharif University of Technology | Manteghian M.,Tarbiat Modares University
Nanoscale | Year: 2010

In this study a low-width MoS2 ribbon has been used for probing the electronic structure and local magnetic moment near vacancies. A theoretical study with the full-potential Density Functional Theory (DFT) approach (Wien2K code) have shown that when the dimension of MoS2 is reduced from 2-D to 1-D the nonmagnetic semi-conductor MoS2 becomes a magnetic conductor. Our study has shown that a vacancy on the S-edge with 50% coverage intensifies the magnetization of the edge of the MoS2 nanoribbon but such a vacancy on S-edge with 100% coverage causes this magnetic property to disappear. It is concluded that in both of them, there are positive or negative strong gradients of local magnetic moment near the vacancy. This may explain why lattice defects are essential for catalysis processes. © 2010 The Royal Society of Chemistry.

Barani K.,Tarbiat Modares University | Koleini S.M.J.,Tarbiat Modares University | Rezaei B.,University of Tehran
Separation and Purification Technology | Year: 2011

The effect of microwave radiation on the magnetic properties of an iron ore was investigated. Four samples from Choghart Iron ore were used in this research. Three samples were treated for 30, 60 and 120 s respectively, in a multi mode microwave oven with a frequency of 2.45 GHz and a maximum power of 1100 W. The magnetizations of non-treated and microwave-treated samples were determined using a vibrating sample magnetometer (VSM). With increasing in radiation time to 60 s, the total magnetism saturation and remanent magnetization of the samples were increased. The results show that with further increasing in microwave radiation time up to 120 s, localized sample melting was occurred and the total magnetism saturation and remanent magnetization were decreased. The results showed that the sample composes ferromagnetic and paramagnetic fractions. With increasing in microwave radiation time the magnetic susceptibility of the paramagnetic fraction was decreased from 0.0111 to zero whereas the magnetic susceptibility of the ferromagnetic fraction initially was increased from 0.0687 to 0.3879 then decreased to 0.1894 (at 120 s radiation time). It was confirmed that microwave radiation has a significant effect upon magnetic properties of iron ore. However, there is a limited condition, excessive radiation has a negative effect and reduces the magnetic susceptibility of iron ore. © 2010 Elsevier B.V.

Gholami A.,University of Tehran | Hosseini S.M.,Tarbiat Modares University
IEEE Transactions on Signal Processing | Year: 2011

Estimating a reliable and stable solution to many problems in signal processing and imaging is based on sparse regularizations, where the true solution is known to have a sparse representation in a given basis. Using different approaches, a large variety of regularization terms have been proposed in literature. While it seems that all of them have so much in common, a general potential function which fits most of them is still missing. In this paper, in order to propose an efficient reconstruction method based on a variational approach and involving a general regularization term (including most of the known potential functions, convex and nonconvex), we deal with i) the definition of such a general potential function, ii) the properties of the associated "proximity operator" (such as the existence of a discontinuity), and iii) the design of an approximate solution of the general "proximity operator" in a simple closed form. We also demonstrate that a special case of the resulting "proximity operator" is a set of shrinkage functions which continuously interpolate between the soft-thresholding and hard-thresholding. Computational experiments show that the proposed general regularization term performs better than ℓp -penalties for sparse approximation problems. Some numerical experiments are included to illustrate the effectiveness of the presented new potential function. © 2011 IEEE.

Amiri F.,Sharif University of Technology | Mousavi S.M.,Tarbiat Modares University | Yaghmaei S.,Sharif University of Technology
Separation and Purification Technology | Year: 2011

Statistically based experimental designs were applied to screen and optimize the bioleaching of spent hydrocracking catalyst by Penicillium simplicissimum. Eleven factors were examined for their significance on bioleaching using a Plackett-Burman factorial design. Four significant variables (pulp density, sucrose, NaNO3, and yeast extract concentrations) were selected for the optimization studies. The combined effect of these variables on metal bioleaching was studied using a central composite design (CCD). Second-order polynomials were established to identify the relationship between the recovery percent of the metals and the four significant variables. The optimal values of the variables for maximum metals bioleaching were as follows: pulp density (4.0%, w/v), sucrose (90 g/L), NaNO3 (2 g/L) and yeast extract (0.36 g/L). The maximum metals recovery percentages from the predicted models were 97.6% Mo, 45.7% Ni, and 14.3% Al. These values were in perfect agreement with the actual experimental values, which were (98.8 ± 0.9)% Mo, (46.5 ± 0.6)% Ni, and (13.7 ± 0.4)% Al. The growth kinetics of the fungus in the presence of the spent catalyst at various pulp densities (2-11%) and optimal condition was modeled using the modified Gompertz model. The kinetic parameters in the system were estimated using MATLAB R2008a. Results showed that the modified Gompertz model fit the experimental data well. The relationship between the specific growth rate and pulp density was found by modifying the Luong inhibition model which gave maximum specific growth rate of 0.034 day-1, optimal pulp density of 3.95% w/v and critical inhibitor concentration of 10.9% w/v. © 2011 Elsevier B.V. All rights reserved.

Hamedani N.F.,Tarbiat Modares University | Mahjoub A.R.,Tarbiat Modares University | Khodadadi A.A.,University of Tehran | Mortazavi Y.,University of Tehran
Sensors and Actuators, B: Chemical | Year: 2011

ZnO nanocrystals with various morphologies were synthesized via a fast and facile microwave assisted method using zinc acetate as starting material, guanidinium and acetyl acetone as structure directing agents, and water as solvent. Reaction conditions, templates and pH of the reaction medium were adjusted in order to achieve nanorod, nanoparticle, and flower-like morphologies. As synthesized ZnO samples were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption analysis (BET). Response and selectivity of the samples to CO, CH 4 and ethanol were measured in a flow system. It is shown that different morphologies of ZnO nanoparticles exhibit different responses and selectivities. Flower-like morphology is highly selective to CO, while nanorods and nanoparticles are selective to methane and ethanol, respectively. Moreover, in a wide range of temperatures, response of ZnO nanorods and nanoparticles towards CO is temperature independent. © 2011 Elsevier B.V. All Rights Reserved.

Sheykhan M.,Tarbiat Modares University | Ma'Mani L.,University of Tehran | Ebrahimi A.,Tarbiat Modares University | Heydari A.,Tarbiat Modares University
Journal of Molecular Catalysis A: Chemical | Year: 2011

A highly efficient and green system is introduced to chemical synthesis. Magnetic nanoparticle-supported propylsulfamic acid deposited onto hydroxyapatite [γ-Fe2O3-HAp-(CH2) 3-NHSO3H] synthesized as a unique heterogeneous acid catalyst of excellent activity and recyclable for at least 10 reaction runs without significant loss of activity. The facile recovery of the catalyst is carried out by applying an external magnet device. It is both "green" and efficient. The catalyst was fully characterized by spectroscopic, magnetic, adsorptive and thermal techniques (TEM, SEM, FTIR, TGA, XRD, BET, elemental analysis (CHNOS) and VSM). © 2010 Elsevier B.V.

Mafi Gholami R.,Islamic Azad University at Ahvāz | Mousavi S.M.,Tarbiat Modares University | Borghei S.M.,Sharif University of Technology
Journal of Industrial and Engineering Chemistry | Year: 2012

The present study examines the biorecovery of heavy metals from a spent refinery catalyst obtained from one of the oil refineries in Iran using Aspergillus niger. Bioleaching experiments were carried out in batch cultures using A. niger in the one-step process to mobilize Co, Mo and Ni from hazardous spent catalysts. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of pH, temperature, inoculum percentage, pulp density and rotation speed during the bioleaching of the metals. Experiments were designed as per the central composite design (CCD) technique. Three cubic mathematical models were derived for prediction of the responses. In process optimization, maximal values of Co, Mo and Ni recoveries were achieved as 71%, 69% and 46%, respectively, with a pH of 5.0, a temperature of 31°C, a pulp density of 2. g/L, a rotation speed of 115. rpm, and using a 12% inoculum. © 2011 The Korean Society of Industrial and Engineering Chemistry.

Badiei A.,University of Tehran | Goldooz H.,Tarbiat Modares University | Ziarani G.M.,Alzahra University
Applied Surface Science | Year: 2011

8-Hydroxyquinoline (8-HQ) was attached to mesoporous silica by sulfonamide bond formation between 8-hydroxyquinoline-5-sulfonyl chloride (8-HQ-SO 2Cl) and aminopropyl functionalized SBA-15 (designated as SBA-SPS-Q) and then aluminum complexes of 8-HQ was covalently bonded to SBA-SPS-Q using coordinating ability of grafted 8-HQ.The prepared materials were characterized by powder X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FT-IR), thermal analysis (TGA-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis and fluorescence spectra. The environmental effects on the emission spectra of grafted 8-HQ and its complexes were studied and discussed in details. © 2010 Elsevier B.V. All rights reserved.

Varasteh F.,Tarbiat Modares University | Arzani K.,Tarbiat Modares University | Barzegar M.,Tarbiat Modares University | Zamani Z.,University of Tehran
Food Chemistry | Year: 2012

Edible coatings as chitosan treatments (0%, 1% and 2%) were applied to 'Rabbab-e-Neyriz' pomegranate (Punica granatum L.). The effect of chitosan coating on individual anthocyanins and colour parameters of the juice during storage at 2 °C or 5 °C was examined. Six predominant anthocyanins were identified in the juice, with up to 935 mg/L total anthocyanins at the time of harvest. Cyanidin 3,5-diglucoside (402 mg/L) was the major pigment. The total anthocyanin content and chroma decreased with storage time in all applied treatments, although lightness and hue angle increased. These changes were reduced with chitosan treatments and at lower storage temperature (2 °C as compared to 5 °C). Based on the obtained results, the diglucoside anthocyanins were more stable than the monoglucosides. Chitosan coating followed by cold storage delayed anthocyanin degradation and prevented colour deterioration in the pomegranate arils. © 2011 Elsevier Ltd. All rights reserved.

Heidari B.,Islamic Azad University | Bakhtiari A.R.,Tarbiat Modares University | Shirneshan G.,Tarbiat Modares University
Food Chemistry | Year: 2013

This study examines concentrations of Cd, Cu, Pb and Zn in the soft tissue of Saccostrea cucullata in the intertidal zones of Lengeh Port, Persian Gulf, Iran, to survey whether heavy metals are within the acceptable limits for public health? The results revealed that the average metal concentrations (μg/g dry weight) ranged from 10.28 to 12.03 for Cd, 294.10 to 345.80 for Cu, 20.64 to 58.23 for Pb and 735.60 to 760.40 for Zn in the soft tissue of oysters. From the human public health point of view, comparison between the mean concentrations of the metals in the soft tissue of oyster and global guidelines clearly indicates that nearly in all cases concentrations are higher than the permissible amounts for human consumption. In addition, levels of Zn, Pb and Cu were well below their recommended oral maximum residue level (MRLs), whereas levels of Cd were observed two times higher. © 2013 Elsevier Ltd. All rights reserved.

Amiri F.,Sharif University of Technology | Yaghmaei S.,Sharif University of Technology | Mousavi S.M.,Tarbiat Modares University | Mousavi S.M.,Lappeenranta University of Technology
Bioresource Technology | Year: 2011

Adaptation of Penicillium simplicissimum with different heavy metals present in a spent hydrocracking catalyst, as well as one-step, two-step, and spent medium bioleaching of the spent catalyst by the adapted fungus, was examined in batch cultures. Adaptation experiments with the single metal ions Ni, Mo, Fe, and W showed that the fungus could tolerate up to 1500. mg/L Ni, 8000. mg/L Mo, 3000. mg/L Fe, and 8000. mg/L W. In the presence of multi-metals, the fungus was able to tolerate up to 300. mg/L Ni, 200. mg/L Mo, 150. mg/L Fe and 2500. mg/L W. A total of 3% (w/v) spent catalyst generally gave the maximum extraction yields in the two-step bioleaching process (100% of W, 100% of Fe, 92.7% of Mo, 66.43% of Ni, and 25% of Al). The main lixiviant in the bioleaching was shown to be gluconic acid. The red pigment produced by the fungus could also possibly act as an agent in Al leaching. © 2010 Elsevier Ltd.

Shahbeyk S.,Tarbiat Modares University | Hosseini M.,Tarbiat Modares University | Yaghoobi M.,Sharif University of Technology
Computational Materials Science | Year: 2011

The present paper studies the failure of concrete from the mesoscopic point of view. Biphasic cubic concrete samples containing spherical aggregates embedded in a homogenized mortar have been simulated using standard finite element method. Linear elasticity and damage-plasticity hypotheses are considered for the aggregates and mortar, respectively. Various triaxial loading conditions are assumed for each sample to generate adequate discrete failure points within the stress space. In the next step, the approximated failure surfaces of specimens are constructed using the Delaunay triangulation technique. The effects of mesostructural features such as aggregate grading curve, aggregate volumetric share, and more importantly the controlling parameters of mortars damage-plasticity constitutive model have been investigated. Finally, the failure modes of some selected samples have been reported and discussed. © 2011 Elsevier B.V. All rights reserved.

Asosheh A.,Tarbiat Modares University | Nalchigar S.,University of Tehran | Jamporazmey M.,University of Tehran
Expert Systems with Applications | Year: 2010

Information technology (IT) is a tool crucial for enterprises to achieve a competitive advantage and organizational innovation. A critical aspect of IT management is the decision whereby the best set of IT projects is selected from many competing proposals. The optimal selection process is a significant strategic resource allocation decision that can engage an organization in substantial long-term commitments. However, making such decisions is difficult because there are lots of quantitative and qualitative factors to be considered in evaluation process. This paper has two main contributions. Firstly, it combines two well-established managerial methodologies, balanced scorecard (BSC) and data envelopment analysis (DEA), and proposes a new approach for IT project selection. This approach uses BSC as a comprehensive framework for defining IT projects evaluation criteria and uses DEA as a nonparametric technique for ranking IT projects. Secondly, this paper introduces a new integrated DEA model which identifies most efficient IT project by considering cardinal and ordinal data. Applicability of proposed approach is illustrated by using real world data of Iran Ministry of Science, Research and Technology. © 2010 Elsevier Ltd. All rights reserved.

Safaei A.S.,Tarbiat Modares University | Kazemzadeh R.B.,Tarbiat Modares University | Niaki S.T.A.,Sharif University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2012

Shewhart charts are the most popular control charts that can be used to monitor variable quality characteristics in a production process. In this paper, a multi-objective model of the economic statistical design of the X-bar control chart is first proposed by incorporating the Taguchi loss function and the intangible external costs. The model minimizes the mean hourly loss cost while minimizing out-of-control average run length and maintaining reasonable in-control average run length. A multiobjective evolutionary algorithm, namely NSGA-II, is then developed and used to obtain the Pareto optimal solution of the model. Some sensitivity analyses are next performed to investigate the effect of parameter estimation on the chart performances. Finally, a comparison study with a traditional economic design model reveals that the proposed multiple objective design of the X-bar control chart offers a better approach and more practical outcomes for the practitioners. © Springer-Verlag London Limited 2011.

Mobayen S.,Tarbiat Modares University | Yazdanpanah M.J.,University of Tehran | Majd V.J.,Tarbiat Modares University
Proceedings of the American Control Conference | Year: 2011

A novel recursive singularity free FTSM (Fast Terminal Sliding Mode) strategy for finite time tracking control of nonholonomic systems is proposed. As a result, the singularity problem around the origin resulting from the fractional power of conventional terminal sliding mode is resolved. Simulation results are given for two benchmark examples of extended chained-form nonholonomic systems: a wheeled mobile robot and an underactuated surface vessel. The results show the effectiveness of the proposed strategy. © 2011 AACC American Automatic Control Council.

Miri M.S.,University of Iowa | Mahloojifar A.,Tarbiat Modares University
IEEE Transactions on Biomedical Engineering | Year: 2011

Retinal images can be used in several applications, such as ocular fundus operations as well as human recognition. Also, they play important roles in detection of some diseases in early stages, such as diabetes, which can be performed by comparison of the states of retinal blood vessels. Intrinsic characteristics of retinal images make the blood vessel detection process difficult. Here, we proposed a new algorithm to detect the retinal blood vessels effectively. Due to the high ability of the curvelet transform in representing the edges, modification of curvelet transform coefficients to enhance the retinal image edges better prepares the image for the segmentation part. The directionality feature of the multistructure elements method makes it an effective tool in edge detection. Hence, morphology operators using multistructure elements are applied to the enhanced image in order to find the retinal image ridges. Afterward, morphological operators by reconstruction eliminate the ridges not belonging to the vessel tree while trying to preserve the thin vessels unchanged. In order to increase the efficiency of the morphological operators by reconstruction, they were applied using multistructure elements. A simple thresholding method along with connected components analysis (CCA) indicates the remained ridges belonging to vessels. In order to utilize CCA more efficiently, we locally applied the CCA and length filtering instead of considering the whole image. Experimental results on a known database, DRIVE, and achieving to more than 94% accuracy in about 50 s for blood vessel detection, proved that the blood vessels can be effectively detected by applying our method on the retinal images. © 2006 IEEE.

Shirmohammadi B.,Tarbiat Modares University | Vafakhah M.,Tarbiat Modares University | Moosavi V.,Tarbiat Modares University | Moghaddamnia A.,University of Tehran
Water Resources Management | Year: 2013

In this study, several data-driven techniques including system identification, time series, and adaptive neuro-fuzzy inference system (ANFIS) models were applied to predict groundwater level for different forecasting period. The results showed that ANFIS models out-perform both time series and system identification models. ANFIS model in which preprocessed data using fuzzy interface system is used as input for artificial neural network (ANN) can cope with non-linear nature of time series so it can perform better than others. It was also demonstrated that all above mentioned approaches could model groundwater level for 1 and 2 months ahead appropriately but for 3 months ahead the performance of the models was not satisfactory. © 2012 Springer Science+Business Media Dordrecht.

Naeni L.M.,Sharif University of Technology | Shadrokh S.,Sharif University of Technology | Salehipour A.,Tarbiat Modares University
International Journal of Project Management | Year: 2011

The earned value technique is a crucial technique in analyzing and controlling the performance of a project which allows a more accurate measurement of both the performance and the progress of a project. This paper presents a new fuzzy-based earned value model with the advantage of developing and analyzing the earned value indices, and the time and the cost estimates at completion under uncertainty. As the uncertainty is inherent in real-life activities, the developed model is very useful in evaluating the progress of a project where uncertainty arises. A small example illustrates how the new model can be implemented in reality. © 2010 Elsevier Ltd and IPMA.

Modarres M.,University of Tehran | Younesizadeh Y.,Tarbiat Modares University
Physical Review C - Nuclear Physics | Year: 2012

In this work, the two-nucleon spectral functions (TNSFs) are defined in terms of the state- and the density-dependent correlation functions in the framework of the lowest-order constrained variational (LOCV) method to calculate the TNSF of the 16O nucleus in the 16O(e,e ′NN)14C reaction. The Reid soft-core (Reid68) and the Av 18 potentials are used as the internucleon interactions. Since, the short-range correlation effects are imposed on the wave functions for the individual channels (e.g., the 1S 0 and 3P J channels); therefore, the defect wave functions are obtained for various channels such that the high relative momenta (p>4fm -1) are ignored. The resulting TNSFs for the 16O nucleus are compared with those of the dressed random phase approximation (DRPA) calculations of Geurts and the experimental predictions, especially those of Onderwater, (NIKHEF group), where reasonable agreement is found. It is shown that the optimized state-dependent defect wave functions have substantial effects on the TNSF and it is not justified to use the simplified parametrized two-body correlation functions in all of the channels. In agreement with the experimental data of Onderwater, the knockout of a 1S 0 pair proton dominates the above reaction cross section. Finally, it is demonstrated that the 0 + and 2 + peaks, which are expected to be observed in the above reaction cross section, are moved to the lower momenta of out-going protons when the state-dependent correlation functions are imposed. © 2012 American Physical Society.

Hajjari M.,Tarbiat Modares University | Behmanesh M.,Tarbiat Modares University | Sadeghizadeh M.,Tarbiat Modares University | Zeinoddini M.,University of Tehran
Medical Oncology | Year: 2013

HOTAIR is a known long non-coding RNA which has recently been associated with the progression of some cancer types. It has been reported that HOTAIR expression is correlated with SUZ12 expression level and therefore may affect the epigenetic state of cancer tissues. Here, we found aberrant up-regulation of HOTAIR in gastric adenocarcinoma samples compared with normal adjacent gastric epithelium tissues. Besides, we found that the aberrant expression of HOTAIR was associated with TNM staging and lymph node metastasis of gastric tumors. Here, a potential cooperative expression between HOTAIR and SUZ12 genes in gastric adenocarcinoma tissues is deduced. This result suggests a role for HOTAIR long noncoding RNA in gastric cancer progression. © Springer Science+Business Media New York 2013.

Hamedani N.F.,Tarbiat Modares University | Mahjoub A.R.,Tarbiat Modares University | Khodadadi A.A.,University of Tehran | Mortazavi Y.,University of Tehran
Sensors and Actuators, B: Chemical | Year: 2012

CeO 2-doped ZnO nanostructures, with different Ce/Zn ratios, were synthesized via a very fast microwave-assisted method using zinc acetate dihydrate and cerium nitrate as starting materials and water as solvent. The samples were characterized via SEM, EDX, XRD, and BET analyses. Gas sensitivity of the fabricated sensor was studied for selective detection of ethanol in presence of CO and CH 4 and effect of CeO 2 with different concentrations as a dopant was investigated. 5 wt% CeO 2 doped sample was shown to improve the sensor response to 500 ppm ethanol with high selectivity in presence of CO and CH 4. Furthermore presence of ceria reduced the recovery time of the sensor significantly. The CeO 2-doped ZnO may be considered a promising sensing material for selective detection of ethanol. © 2012 Elsevier B.V. All rights reserved.

Motaghian H.,University of Tehran | Hassanzadeh A.,Tarbiat Modares University | Moghadam D.K.,University of Tehran
Computers and Education | Year: 2013

In many societies e-learning has become the main mechanism supporting distance education. Although e-learning efforts are considered to be a significant corporate investment, many surveys indicate high drop-out rates or failures. This research uses an integrated model in order to assessing the influence of IS-oriented, psychological and behavioral factors on instructors' adoption of web-based learning systems. Survey data collected from 115 university instructors were analyzed using structural equation modeling to examine the theoretical model. The research results show that perceived usefulness, perceived ease of use and system quality increase instructors' intention to use web-based learning systems; however, perceived usefulness is the most important factor affecting on intention and actual use of the system (adoption). © 2012 Elsevier Ltd. All rights reserved.

Maghanaki M.M.,Tarbiat Modares University | Ghobadian B.,Tarbiat Modares University | Najafi G.,Tarbiat Modares University | Galogah R.J.,University of Tehran
Renewable and Sustainable Energy Reviews | Year: 2013

Biomass is the only renewable energy source which can deliver electricity, provide heating, cooling and fuel in form of solid, liquid and gas. Biomass supplies more than 11.5% of the world's primary energy and about 79.7% of the world's energy consumption. In 2012, about 194.8 million ton of renewable energy was consumed in the world and about 0.1 million ton was consumed in Iran. Biogas is produced by anaerobic fermentation. Global biogas capacity will reach 22,000 MW by 2025. European biogas electricity production in 2006 was 17,272 GWh per year, of which 7338 GWh was by Germany alone. Biogas now represents 1.2% of the annual production of electricity and nearly 10% of renewable energy, with an installed power close to 1500 MW. Global biogas installed capacity is expected to achieve moderate growth over the next 12 years, reaching 22.040 MW by 2025 and making a compound annual growth rate (CAGR) of 7.2%, a recently published analysis by Global Information Inc (GII) showed. The world biogas market has grown considerably between 2001 and 2011, with installed capacity expanding to 8.377 MW in 2011 from 2.388 MW in 2001. This equals a CAGR of 13.4%. The potential of biomass sources in Iran is estimated to be 132 million ton (oil equivalent) in the form of agricultural and forest wastes, livestock wastes, municipal wastes, sewage and industrial wastes. Taking into account the usual amount of biogas yield from agricultural wastes, animal wastes, municipal wastes and industrial and municipal wastewater and with good safety factor, biogas in Iran will generate about 16146.35 million m3 which is approximately 323 petajoule (1015) of energy. This paper investigates the potential of biogas production from biomass sources in Iran and presents the energy carriers, examples of biogas production, applications and quantitative potential of different sources in Iran. © 2013 Published by Elsevier Ltd. All rights reserved.

Maghanki M.M.,Tarbiat Modares University | Ghobadian B.,Tarbiat Modares University | Najafi G.,Tarbiat Modares University | Galogah R.J.,University of Tehran
Renewable and Sustainable Energy Reviews | Year: 2013

Micro-cogeneration, also termed micro combined heat and power (MCHP) or residential cogeneration, is an emerging technology with the potential to provide energy efficiency and environmental benefits by reducing primary energy consumption and associated greenhouse gas emissions. MCHP can help to meet a number of energy and social policy aims. These are the reduction of greenhouse gas emissions from energy supply, increased decentralization of energy supply, improved energy security, possible avoidance of investment in and energy losses from electricity transmission and distribution networks, and potentially reduced energy cost to consumers. Micro-cogeneration systems have the potential to reduce energy demands of the residential sector for space heating, domestic hot water heating, and electricity. The reduced greenhouse gas emissions and reduced reliance upon central electrical generation, transmission, and distribution systems are the possible benefits. Also in the present paper, a comparison has been made between the MCHP technology and the other ones such as prime mover, electrical and thermal power, efficiency and emissions. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Afazeli H.,University of Tehran | Jafari A.,University of Tehran | Rafiee S.,University of Tehran | Nosrati M.,Tarbiat Modares University
Renewable and Sustainable Energy Reviews | Year: 2014

Fossil fuel resources are severely limited and their combustion is a major source of environmental pollution. As a result, scientists avidly seek alternatives to fossil fuels, and biomass can be a viable alternative source of energy. Anaerobic digestion is one of way of converting biomass to biogas. Slaughterhouse wastes and animal husbandry residues are from among the organic waste types utilized to generate biogas. Every year, large amounts of livestock waste discharges and slaughterhouse waste materials are produced worldwide, which provoke environmental pollution and are thus a cause of much concern. In lieu of what is discussed, it is intelligent to use animal wastes to generate biogas and hence reduce pollution. In view of that, the researchers in this study intend to investigate biogas production potential from animal manure in Iran. To this aim, biogas production potential from heavy and light livestock and poultry wastes were examined. Slaughterhouse wastes, containing rumen, intestines, stomach and blood from heavy and light livestock, and also poultry blood were examined. The results indicate that biogas production potential from the available livestock manure in this country is 8600 million m3 per year, 70% of which is obtained from heavy livestock, 23% of it from poultry, and only 7% from light livestock. Biogas yields potential from slaughterhouse wastes in Iran is approximately 54 million m3 per annum of which 40% is produced from light livestock rumen, 24% from heavy livestock rumen, 17% from heavy livestock blood, 14% from poultry blood, and 5% from light livestock blood. Tehran Province, as the capital, had the greatest potential for biogas production from slaughterhouse waste; that is about 9 million m3. From among all other provinces in Iran, Mazandaran Province had the greatest potential, with 828 million m3 biogas yield per year. © 2014 Elsevier Ltd.

Kazemipour A.,Islamic Azad University | Khormali O.,Tarbiat Modares University
Journal of Computational and Theoretical Nanoscience | Year: 2012

The vertex and edge versions of P I index were introduced in last years. In this paper, we introduce a new edge version for P I index and at following we compute this new index for some nanotubes. Copyright © 2012 American Scientific Publishers.

Gholami A.,University of Tehran | Hosseini S.M.,Tarbiat Modares University
Signal Processing | Year: 2013

This paper introduces a novel method to combine total variation and ℓ2 regularizations to reconstruct piecewise smooth signals. The main idea is to consider the signal as a sum of two components: a piecewise constant component and a smooth component. For the solution of ill-posed problems, the Tikhonov method with a special stabilizer in the form of a sum of two different stabilizers is used: the total variation for the first component and the Sobolev norm for the second one. An iteratively re-weighted least squares technique is used as a fast and an efficient algorithm for minimization of the Tikhonov functional. A method is also presented for determining the regularization parameters. Numerical experiments, among the many performed, in denoising, deblurring, and compressed sensing demonstrate high performance of the new regularization for reconstruction of piecewise-smooth solutions with sharp discontinuities. © 2012 Elsevier B.V.

Razminia A.,Tarbiat Modares University | Dizaji A.F.,University of Tehran | Majd V.J.,Tarbiat Modares University
Mathematical and Computer Modelling | Year: 2012

In this paper, we discuss the existence of the solution for a generalized fractional differential equation with non-autonomous variable order operators. In contrast to constant order fractional calculus, some standard relations including composition and sequential derivative rules do not remain correct under this generalization. Therefore, solving such a generalized fractional differential equation requires a different methodology, essential modifications, and generalizations for the basic concepts such as existence and uniqueness of the solution. The main goal of this paper is the proof of existence for the solution of a variable order fractional differential equation which is achieved by presenting four theorems. It is shown that if Lebesgue measurability, the continuity of the nonlinear term, and the conditions of differintegration operation are satisfied, then a solution for the variable order fractional differential equation exists. © 2011 Elsevier Ltd.

Akhavan O.,Sharif University of Technology | Azimirad R.,Malek-Ashtar University of Technology | Safa S.,Tarbiat Modares University | Hasani E.,Islamic Azad University at Karaj
Journal of Materials Chemistry | Year: 2011

Various morphologies of CuO/Cu(OH)2 nanostructures with different adsorbed -OH contents were synthesized on an acid-treated Cu foil through variation of NaOH concentration from 0 to 50 mM with an in situ oxidation method. X-ray diffractometry and X-ray photoelectron spectroscopy (XPS) indicated formation of CuO on the Cu(OH)2 crystalline phase at a growth temperature of 60°C for 20 h. Antibacterial activity of the nanostructures against Escherichia coli bacteria was studied in the dark and under light irradiation. The nanostructures grown at a NaOH concentration of 30 mM showed the highest surface area and the strongest antibacterial activity among the samples. After elimination of the contribution of the effective surface area of the nanostructures to the antibacterial activity, it was found that the surface morphology and chemical composition of the nanostructures were the other most important parameters in the antibacterial activity of the nanostructures. Using XPS analysis, the better photocatalytic activity per surface area of the nanostructures prepared at higher NaOH concentrations was substantially attributed to the amount of adsorbed OH bonds on the surface of the nanostructures. © 2011 The Royal Society of Chemistry.

Akbari Moornani K.,Tarbiat Modares University | Haeri M.,Sharif University of Technology
Transactions of the Institute of Measurement and Control | Year: 2013

This paper considers a closed-loop system consisting of a fractional/integer order system and a fractional PID controller. Assuming that the uncertain coefficients of the fractional PID controller lie in some known intervals independently (i.e. that controller is a member of an interval family), the paper presents some easy to use theorems to investigate the robust bounded-input bounded-output stability of the resultant closed-loop system. Moreover, a finite frequency bound required in drawing the related graphs has also been provided. Finally, some numerical examples are presented to illustrate the results. © 2012 The Author(s).

Naderi E.,Tarbiat Modares University | Seifi H.,Tarbiat Modares University | Sepasian M.S.,University of Tehran
IEEE Transactions on Power Delivery | Year: 2012

Deregulation in the power system industry and invention of new technologies for producing electrical energy have led to innovations in distribution system planning (DSP). Distributed generation (DG) is one of the most attractive technologies that brings different kinds of advantages to a wide range of entities, engaged in power systems. In this paper, a new model for considering DGs in the DSP problem is presented. In this model, an optimal power flow (OPF) is proposed to minimize capital costs for network upgrading, operation and maintenance costs, and the cost of losses for handling the load growth for the planning horizon. The term "dynamic" is used to refer to the planning over a specific period so that dynamic distribution system planning is, in fact, proposed. Besides, a modified genetic algorithm is used to find the optimal topology solution. The effectiveness of this method is demonstrated through examination on a radial distribution network. © 2012 IEEE.

Ojagh S.M.,Tarbiat Modares University | Rezaei M.,Tarbiat Modares University | Razavi S.H.,University of Tehran | Hosseini S.M.H.,University of Tehran
Food Chemistry | Year: 2010

Combining antimicrobial agents such as plant essential oils directly into a food packaging is a form of active packaging. In this work chitosan-based films containing cinnamon essential oil (CEO) at level of 0.4%, .0.8%, and 1.5% and 2% (v/v) were prepared to examine their antibacterial, physical and mechanical properties. Scanning electron microscopy was carried out to explain structure-property relationships. Incorporating CEO into chitosan-based films increased antimicrobial activity. CEO decreased moisture content, solubility in water, water vapour permeability and elongation at break of chitosan films. It is postulated that the unique properties of the CEO added films could suggest the cross-linking effect of CEO components within the chitosan matrix. Electron microscopy images confirmed the results obtained in this study. © 2010.

Ojagh S.M.,Tarbiat Modares University | Rezaei M.,Tarbiat Modares University | Razavi S.H.,University of Tehran | Hosseini S.M.H.,University of Tehran
Food Chemistry | Year: 2010

The effects of a chitosan (Ch) coating enriched with cinnamon oil (Ch + C) on quality of rainbow trout (Oncorhynchus mykiss) during refrigerated storage (4 ± 1 °C) were examined over a period of 16 days. A solution of Ch (2%, w/v) and Ch + C (2%, w/v Ch + 1.5%, v/v C) was used for the coating. The control and the coated fish samples were analysed periodically for microbiological (total viable count, psychrotrophic count), chemical (TVB-N, PV, TBA), and sensory (raw and cooked fish) characteristics. The results indicated that the effect of the Ch + C coating on the fish samples was to enable the good quality characteristics to be retained longer and to extend the shelf life during the refrigerated storage. © 2009.

Keramati A.,University of Tehran | Afshari-Mofrad M.,Tarbiat Modares University | Kamrani A.,University of Tehran
Computers and Education | Year: 2011

Although many researchers have studied different factors which affect E-Learning outcomes, there is little research on assessment of the intervening role of readiness factors in E-Learning outcomes. This study proposes a conceptual model to determine the role of readiness factors in the relationship between E-Learning factors and E-Learning outcomes. Readiness factors are divided into three main groups including: technical, organizational and social. A questionnaire was completed by 96 respondents. This sample consists of teachers at Tehran high schools who are utilizing a technology-based educating. Hierarchical regression analysis is done and its results strongly support the appropriateness of the proposed model and prove that readiness factors variable plays a moderating role in the relationship between E-Learning factors and outcomes. Also latent moderated structuring (LMS) technique and MPLUS3 software are used to determine each variable's ranking. Results show that organizational readiness factors have the most important effect on E-Learning outcomes. Also teachers' motivation and training is the most important factor in E-Learning. Findings of this research will be helpful for both academics and practitioners of E-Learning systems. © 2011 Elsevier Ltd. All rights reserved.

Seyyedi S.M.Y.,Sharif University of Technology | Akbari B.,Tarbiat Modares University
2011 International Symposium on Computer Networks and Distributed Systems, CNDS 2011 | Year: 2011

There are two main scalable methods for streaming live video over the Internet: Content Delivery Networks (CDNs) and Peer-to-Peer (P2P) networks. Though both have their own problems, P2P streaming systems challenge delivering video with constant quality and CDNs approaches require deployment of large number of servers throughout the Internet that is costly. Recently, using hybrid architectures based on both CDN and P2P networks has shown to be an efficient approach for large-scale video distribution over the Internet. This paper is compared the performance of two main hybrid CDN-P2P architectures includes: (i) CDN-P2P unconnected mesh in which independent P2P mesh networks are constructed under each CDN node, and (ii) CDN-P2P connected mesh in which CDN nodes and peers participate in construction of a single P2P mesh network. The comparison is preformed in addition, to the pure mesh-based P2P video streaming, using extensive simulation and based on different QoS metrics. © 2011 IEEE.

Mokhatab Rafiei F.,Isfahan University of Technology | Manzari S.M.,Tarbiat Modares University | Bostanian S.,Tarbiat Modares University
Expert Systems with Applications | Year: 2011

The purpose of this study is to design a model to predict financial health of companies. Financial ratios for 180 manufacturing companies quoted in Tehran Stock Exchange for one year (year ended March 21, 2008) have been used. Three models; based on artificial neural networks (ANN), genetic algorithm (GA), and multiple discriminant analysis (MDA) are utilized to classify the bankrupt from non bankrupt corporations. ANN model achieved 98.6% and 96.3% accuracy rates in training and holdout samples, respectively. To evaluate the reliability of the model, the data were examined with genetic algorithm and Multivariate discriminate analysis method. GA model attained only 92.5% and 91.5% accuracy rates and MDA reached 80.6% and 79.9 in training and holdout samples, respectively. © 2011 Published by Elsevier Ltd.

Hatami A.,Bu - Ali Sina University | Seifi H.,Tarbiat Modares University | Sheikh-El-Eslami M.K.,Tarbiat Modares University
IEEE Transactions on Power Systems | Year: 2011

This paper proposes a decision-making framework, based on stochastic programming, for a retailer: 1) to determine the sale price of electricity to the customers based on time-of-use (TOU) rates, and 2) to manage a portfolio of different contracts in order to procure its demand and to hedge against risks, within a medium-term period. Supply sources include the pool, self-production facilities and several instruments such as forward contracts, call options, and interruptible contracts. The objective is to maximize the profit and simultaneously to minimize the risks in terms of a multi-period risk measure. Moreover, the risks are measured using conditional value at risk (CVaR) methodology. The reaction of the customers to the retailers' selling prices as well as the competition between the retailers is modeled through a market share function. The problem is formulated as a mixed-integer stochastic programming. It is solved by a decomposition technique, and the decomposed parts are solved by a branch-and-bound algorithm. © 2006 IEEE.

Arabi Jeshvaghani R.,Tarbiat Modares University | Shamanian M.,Isfahan University of Technology | Jaberzadeh M.,Isfahan University of Technology
Materials and Design | Year: 2011

This paper deals with the improvement of the wear resistance of ductile iron surface alloyed by a hypoeutectic stellite 6 alloy. In this regard, the surface alloyed layer with 3. mm thickness deposited on ductile iron using tungsten inert gas (TIG) surface processing. The microstructure, hardness and wear resistance of surface alloyed layer were investigated using optical microscopy, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis, Vickers hardness (HV0.3) and pin-on-plate tests. The results showed that the microstructure of the surface alloyed layer consisted of carbides dispersed in a Co-based solid solution matrix with dendritic structure. This microstructure was responsible for the improvement of the hardness and wear resistance of the coating. Further investigations showed that the dominant mechanism of the wear in the coated and uncoated samples was delamination wear. © 2010 Elsevier Ltd.

Alibeigloo A.,Tarbiat Modares University | Simintan V.,Bu - Ali Sina University
Composite Structures | Year: 2011

Based on three-dimensional theory of elasticity axisymmetric static analysis of functionally graded circular and annular plates imbedded in piezoelectric layers is investigated using differential quadrature method (DQM). The plate has various edges boundary conditions and its material properties are assumed to vary in an exponential law with the Poisson ratio to be constant. This method can give an analytical solution along the graded direction using the state space method (SSM) and an effective approximate solution along the radial direction using the one-dimensional DQM. The method is validated by comparing numerical results with the results obtained in the literature. Both the direct and the inverse piezoelectric effects are investigated and the influence of piezoelectric layers on the mechanical behavior of plate is studied. The effects of the gradient index, thickness to radius ratio, and edges boundary conditions on the static behavior of FG circular and annular plates are investigated. © 2011 Elsevier Ltd.

Hosseini A.,Tarbiat Modares University | Wang J.,Chinese University of Hong Kong | Wang J.,Dalian University of Technology | Hosseini S.M.,Tarbiat Modares University
Neural Networks | Year: 2013

In this paper, we propose a penalty-based recurrent neural network for solving a class of constrained optimization problems with generalized convex objective functions. The model has a simple structure described by using a differential inclusion. It is also applicable for any nonsmooth optimization problem with affine equality and convex inequality constraints, provided that the objective function is regular and pseudoconvex on feasible region of the problem. It is proven herein that the state vector of the proposed neural network globally converges to and stays thereafter in the feasible region in finite time, and converges to the optimal solution set of the problem. © 2013 Elsevier Ltd.

Arabi Jeshvaghani R.,Tarbiat Modares University | Harati E.,Tarbiat Modares University | Shamanian M.,Isfahan University of Technology
Materials and Design | Year: 2011

In this study, the effect of surface alloying on the microstructure and wear behavior of ductile iron was studied. In this regard, ductile iron samples were coated by single and double pass welds of a nickel-based electrode (ENiCrFe3) using shielded metal arc welding. The effects of number of passes on microstructure, hardness and wear resistance of cladded layers were investigated. Optical microscopy and X-ray diffractometry were used to identify the microstructure and phase composition of cladded layers and interfaces. The results revealed that cladded layers consist of austenite (Fe, C), γ(Fe, Ni) and small quantities of carbides such as Cr7C3. It was also found that the hardness of the cladded layers was higher than that of substrate. In samples processed with a single and double passes, hardness reached up to 500 and 450 HV, respectively. Pin-on-plate wear tests showed that the wear mechanism is predominantly delamination in the cladded layers and substrate. © 2010 Elsevier Ltd.

Gharibi H.,Tarbiat Modares University | Kakaei K.,Tarbiat Modares University | Zhiani M.,Isfahan University of Technology
Journal of Physical Chemistry C | Year: 2010

A film of PANI nanowires (PANI (NWs)) was deposited onto the surface of a stainless steel electrode via cyclic voltammetry. During the polymerization of aniline (ANI), PANI(NWs) were doped with trifluoromethane sulfonic acid, and the doped PANI were utilized for the fabrication of a Vulcan (C) PANI composite. Pt particles were subsequently deposited by reduction onto the C-PANI composite to produce a Pt/C-PANI electrocatalyst. The current peak during methanol oxidation, the electrochemical surface area, and the stability of the Pt/C-PANI electrocatalysts were better than those observed using Pt/C+PANI (commercial Pt/C composites containing PANI) or Pt/C electrodes. The ionic resistance of the two electrodes containing PANI were only slightly larger than those of the Pt/C and Nafion solution catalysts, but electrochemical impedance spectroscopy measurements using the modified electrodes did not show a negative impedance after measurement of the open current voltage. The methanol diffusion coefficients in the Pt/C-PANI and Pt/C+PANI electrocatalysts were found to be 2.5 and 2 times higher than in the Pt/C electrode. X-ray diffractometer and scanning electron microscopy technique have been applied to investigate the crystallite size and the surface morphologies respectively. The Pt/C-PANI modified catalysts is more suitable for applying in the direct methanol fuel cells in comparison with the standard Pt catalysts. © 2010 American Chemical Society.

Asadzadeh Shahir A.,Tarbiat Modares University | Javadian S.,Tarbiat Modares University | Razavizadeh B.B.M.,Khorasan Research Institute for Food Science and Technology | Gharibi H.,Tarbiat Modares University
Journal of Physical Chemistry B | Year: 2011

Interaction of a food dye, tartrazine, with some cationic conventional and gemini surfactants, tetradecyltrimethylammonium bromide (TTAB), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl- diammonium dibromide (14,4,14), and N,N′-didodecyl-N,N,N′,N′- tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12), were first investigated comprehensively employing conductometry, tensiometry, and UV-visible spectroscopy. Tartrazine was found to behave in the same manner as aromatic counterions. The formation of ion pairs reflected as a considerable increase of the surfactant efficiency in tensiometry plots and their stoichiometry were determined by Job's method of continuous variations. For the tartrazine/TTAB system, nonionic DS3, ionic DS2-, and/or DS2 - ion pairs, their small premicelles, and tartrazine-rich micelles were constituted as well as dye-containing TTAB-rich micelles. Insoluble J-aggregates of DS- ion pairs and cylindrical surfactant-rich micelles were also formed in tartrazine/gemini surfactant systems and recognized by transmission electron microscopy. The zeta potential and the size of the aggregates were determined using dynamic light scattering and confirmed the suggested models for the processes happening in each system. Cyclic voltammetry was applied successfully to track all of these species using tartrazine's own reduction peak current for the first time. © 2011 American Chemical Society.

Pahlavanzadeh H.,Tarbiat Modares University | Keshtkar A.R.,Nuclear Science and Technology Research Institute, Iran | Safdari J.,Nuclear Science and Technology Research Institute, Iran | Abadi Z.,Tarbiat Modares University
Journal of Hazardous Materials | Year: 2010

The biosorption characteristics of nickel(II) ions using the brown algae (Cystoseria indica, Nizmuddinia zanardini, Sargassum glaucescens and Padina australis) were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, initial metal concentration and temperature were studied. The equilibrium data fitted very well to the Langmuir adsorption model in the concentration range of nickel(II) ions and at all the temperatures studied. Evaluation of the experimental data in terms of biosorption dynamics showed that the biosorption of nickel(II) onto algal biomass followed the pseudo-second-order dynamics well. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed that the biosorption of nickel(II) ions were feasible, spontaneous and endothermic at the temperature ranges of 293-313 K. © 2009 Elsevier B.V. All rights reserved.

Shadidi B.,Bu - Ali Sina University | Yusaf T.,University of Southern Queensland | Alizadeh H.H.A.,Bu - Ali Sina University | Ghobadian B.,Tarbiat Modares University
Applied Energy | Year: 2014

Diesohol fuel is a mixture of diesel and bioethanol fuels in which the ratio of bioethanol is less than 15%. In this research work, performance of a tractor engine (Massey Ferguson 399) using diesohol fuel was investigated. In these circumstances, the concentration of UHC and CO2 emissions in the exhaust pipe were measured and analyzed. The engine was run at several speeds (1600-2000rpm). The obtained results reveal that, when using diesohol fuels, the power and torque of the MF-399 tractor engine are increased by 3.17-8.50% and 1.75-10.28% respectively when compared to diesel fuel. This is due to a relatively more complete combustion of ethanol because of its high oxygen content. The fuel consumption and specific fuel consumption are also increased by 7.32-15.81% and 4.37-7.44% respectively due to low calorific value of ethanol compared to diesel fuel. The analysis showed that when diesohol is used, the rate of UHC is decreased but CO2 emission is increased. In brief, by using diesohol fuels, especially E6 blend in comparison to diesel fuel, engine performance and emissions are improved without any changes in engine structure for diesohol application. © 2013 Elsevier Ltd.

Pirhadi A.,Shahid Beheshti University | Bahrami H.,Tarbiat Modares University | Nasri J.,Tarbiat Modares University
IEEE Transactions on Antennas and Propagation | Year: 2012

in this communication a high directive electromagnetic bandgap (EBG) antenna operating in wide frequency band for both return loss (RL) and directivity is examined. In this EBG antenna an aperture coupled microstrip antenna (ACMA) is used as a feeding source and a frequency selective surface (FSS) is used as a superstrate layer. Suitable use of the superstrate layer, microstrip patch and coupling aperture simultaneously, leads to produce separate resonance frequencies and therefore the wide frequency band for RL. Also, high directivity is achieved only by using the superstrate layer that has been made by the FSS layer with square loop elements. At first, a wideband ACMA is designed to operate in x-band. In this step appropriate design of coupling aperture is of a great importance. Secondly, after the design of optimum superstrate layer by the FSS structure, it is added to the ACMA in order to increase both bandwidth and directivity. © 2012 IEEE.

Nejati H.R.,Tarbiat Modares University | Ahmadi M.,Tarbiat Modares University | Hashemolhosseini H.,Isfahan University of Technology
Tunnelling and Underground Space Technology | Year: 2012

The purpose of this study is the simulation of train movement and calculation of ground surface vibration induced by train movement in the subway tunnel. Tehran metro line 4 that is located in a populated area was considered as a case study. For simulation of train movement, effective factors on dynamic load magnitude and frequency have been studied and variation of wagon force in a longitude model is considered. Then Fourier amplitude spectrum was computed by means of Fast Fourier Transformation (FFT) of the dynamic train load and then the frequency range of train load was determined. In the next step, low energy frequencies were filtered and the dynamic load as a point load was applied on the numerical model of the tunnel and the ground surface vibration was determined. Finally, the result of the numerical model is verified by Metrikine and Vrouwenvelder's analytical model. Comparisons of numerical and analytical solutions shows that the numerical results have a good agreement with the analytical output and the maximum displacement in the horizontal and vertical directions are 3.75 and 5.25. mm, respectively. © 2011 Elsevier Ltd.

Shakouh I M.,Tarbiat Modares University | Mohamadian M.,Tarbiat Modares University | Afjei E.,Shahid Beheshti University
IEEE Transactions on Industrial Electronics | Year: 2015

In some industries, continuous operation of motors even under faults until scheduled maintenance time is necessary. However, conventional control methods are inefficient for eccentricity faults. In a conventional brushless direct current (BLDC) motor control method, stator current commands are similar in shape and delayed by corresponding phase differences in each phase. However, if the actual shape of the back electromotive force (EMF) waveform of an eccentric motor and phase inductance variations due to eccentricity are not considered, undesirable torque ripples may occur. Hence, a new control strategy must be developed for improving motor performance. In this paper, a method for controlling BLDC motors under static rotor eccentricity is proposed. The proposed control method is based on online estimation of phase inductances and back-EMFs of the BLDC motor under eccentricity faults. Therefore, in contrast to conventional methods, stator currents are injected considering the estimated back-EMFs of the conducting phases. The experimental results verify that the proposed method reduces electromagnetic torque pulsations under static rotor eccentricity. © 2014 IEEE.

Ultrasound-assisted emulsification microextraction with solidification of floating organic droplet (USAEME-SFO) followed by high performance liquid chromatography-diode array detection (HPLC-DAD), was applied for preconcentration and determination of phthalate esters in cosmetic and water samples. The effects of different variables on the extraction efficiency were studied simultaneously using an experimental design. The variables of interest in the USAEME-SFO were extraction solvent volume, salt effect, extraction time and centrifugation time. A factorial experimental design was employed for screening to determine the variables significantly affecting the extraction efficiency. Then, the significant factors were optimized by using a Box-Behnken design (BBD) and the response surface equations were derived. The optimum experimental conditions were extraction solvent volume, 30μL; sodium chloride concentration, 20% (w/v); extraction time, 12min and centrifugation time, 5min. Under optimal conditions, the preconcentration factors were between 355 and 409. The limit of detections (LODs) ranged from 0.005μgL -1 (for Diethylphthalate) to 0.01μgL -1 (for Dimethylphthalate). Dynamic linear ranges; (DLRs) of 0.05-800 and 0.05-1000μgL -1 were obtained for Diisobutyl- and Dimethylphthalate, respectively. The performance of the method was evaluated for extraction and determination of phthalate esters in cosmetic and environmental water samples in micrograms per liter and satisfactory results were obtained (RSDs<12.6%). © 2011 Elsevier B.V.

Aghayan H.,Tarbiat Modares University | Khanchi A.R.,Nuclear Science and Technology Research Institute, Iran | Mahjoub A.R.,Tarbiat Modares University
Applied Surface Science | Year: 2013

A series of cesium molybdo vanado phosphate (CsMVP) supported on platelet SBA-15 (SBA-15-%xCsMVP, x = 20, 30, 40 and 50 wt.%) was synthesized to develop an efficient inorganic composite ion-exchanger for gadolinium ion removal from aqueous solution. The preparation has been carried out using two-step aqueous impregnation methods. The obtained products were characterized by inductively coupled plasma (ICP), XRD, N2 adsorption-desorption isotherms, scanning electron microscopy (SEM) and FT-IR. In order to examine adsorption behavior of this compound on gadolinium removal, the effect of heteropoly metalate loading, pH, contact time, concentration of metal ion and temperature were investigated under batch system conditions. The SBA-15-30%CsMVP showed maximum adsorption capacity toward gadolinium removal. The results suggested that this methodology provides the general synthesis of supported heteropolymetalate with large surface areas, and ordered nano porous structures that can be used as inorganic composite ion-exchanger for efficient removal of gadolinium ions from aqueous solution. © 2013 Elsevier B.V. All rights reserved.

Kamarei F.,Shahid Beheshti University | Ebrahimzadeh H.,Shahid Beheshti University | Yamini Y.,Tarbiat Modares University
Journal of Hazardous Materials | Year: 2010

Solvent bar microextraction (SBME) combined with gas chromatography-flame ionization detector (GC-FID), was used for preconcentration and determination of some aliphatic amines in waste water samples. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the SBME were ionic strength, organic additive effect, sodium hydroxide concentration, stirring rate and extraction time and temperature. A Plackett-Burman design was performed for screening in order to determine the significant variables affecting the extraction efficiency. Then, the significant factors were optimized by a Box-Behnken design (BBD) and the response surface equations were derived. The optimum experimental conditions were sodium chloride concentration, 20% (w/v); sodium hydroxide concentration, 1molL-1; stirring rate, 700rpm; extraction temperature, 45°C; extraction time, 30min, and without addition of acetone. Under the optimum conditions, the preconcentration factors were between 260 and 1130. The limit of detections (LODs) ranged from 0.01μgL-1 (for dibutylamine) to 0.06μgL-1 (for N-ethyldiisopropylamine). The linear dynamic ranges (LDRs) of 0.05-800 and 0.1-600μgL-1 were obtained for most of the analytes. The performance of the method was evaluated for extraction and determination of aliphatic amines in waste water samples in the range of microgram per liter and satisfactory results were obtained (RSDs<13.6%). © 2010 Elsevier B.V.

Yamini Y.,Tarbiat Modares University | Rezaee M.,Tarbiat Modares University | Khanchi A.,Nuclear Science and Technology Research Institute, Iran | Faraji M.,Tarbiat Modares University | Saleh A.,Tarbiat Modares University
Journal of Chromatography A | Year: 2010

A simple, rapid and efficient dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA16 (45) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140μL of 1-undecanol; disperser solvent: 2.0mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5-250μgL-1 for Mn, 1.25-250μgL-1 for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3μgL-1. Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained. © 2009 Elsevier B.V.

Kamarei F.,Shahid Beheshti University | Ebrahimzadeh H.,Shahid Beheshti University | Yamini Y.,Tarbiat Modares University
Talanta | Year: 2010

Temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of chlorobenzenes in well water samples. The proposed method used 1-butyl-3-methylimidazolium hexafluorophosphate ([C 4mim][PF 6]) as the extraction solvent. The effect of different variables on extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the TCIL-DLPME were extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time, and heating time. The Plackett-Burman design was employed for screening to determine the variables significantly affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design (CCD) and the response surface equations were developed. The optimal experimental conditions obtained from this statistical evaluation included: extraction solvent volume, 75 μL; extraction time, 20 min; centrifugation time, 25 min; heating time, 4 min; solution temperature, 50 °C; and no addition of salt. Under optimal conditions, the preconcentration factors were between 187 and 298. The limit of detections (LODs) ranged from 0.05 μg L -1 (for 1,2-dichlorobenzene) to 0.1 μg L -1 (for 1,2,3-trichlorobenzene). Linear dynamic ranges (LDRs) of 0.5-300 and 0.5-500 μg L -1 were obtained for dichloro- and trichlorobenzenes, respectively. The performance of the method was evaluated for extraction and determination of chlorobenzenes in well water samples in micrograms per liter and satisfactory results were obtained (RSDs < 9.2%). © 2010 Elsevier B.V.

Shayesteh E.,Islamic Azad University at Garmsar | Yousefi A.,Tarbiat Modares University | Parsa Moghaddam M.,Tarbiat Modares University
Energy | Year: 2010

Spinning Reserve is one of the ancillary services which is essential to satisfy system security constraints when the power system faces with a contingency. In this paper, Day Ahead Demand Response Program as one of the incentive-based Demand Response programs is implemented as a source of spinning reserve. In this regard, certain number of demands are selected according to a sensitivity analysis, and simulated as virtual generation units. The reserve market is cleared for Spinning Reserve allocation considering a probabilistic technique. A comparison is performed between the absence and existence of Day Ahead Demand Response Program from both economical and reliability viewpoints. Numerical studies based on IEEE 57 bus test system is conducted for evaluation of the proposed method. © 2010 Elsevier Ltd. All rights reserved.

Naeeni M.H.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Rezaee M.,Nuclear Science and Technology Research Institute, Iran
Journal of Supercritical Fluids | Year: 2011

Supercritical fluid extraction (SFE) coupled with dispersive liquid-liquid microextraction (DLLME) and followed by gas chromatography-flame ionization detection (GC-FID) was applied for extraction and determination of ultra-trace amounts of seven organophosphorus pesticides (OPPs) (o,o,o-triethyl phosphorothioate, thionazin, sulfotepp, disulfoton, methyl parathion, parathion, and famphur) in soil and marine sediment samples. Supercritical CO 2 at 150 bar, 60 °C, 10 min static and 30 min dynamic extraction times was used to extract the pesticides. The extracts were collected in 1.0 mL of acetonitrile. Seventeen μL of carbon tetrachloride was dissolved in the collecting solvent and the mixture was then injected rapidly into 5.0 mL of aqueous solution. About (5.0 ± 0.2 μL) of sediment phase was collected after centrifuging and finally 2.0 μL of it was injected into gas chromatography (GC) injection port for analyses. The extraction recoveries for the target analytes were in the range of 44.4% and 95.4% and relative standard deviation (RSD%) for four-replicate measurements was below 7.5%. The limit detections of the method for determining the pesticides were in the range of 0.001-0.009 mg kg -1. The method was successfully applied for analysis of OPPs in real soil and marine sediment samples and satisfactory results were obtained. © 2011 Elsevier B.V. All rights reserved.

Jamshidi B.,Tarbiat Modares University | Minaei S.,Tarbiat Modares University | Mohajerani E.,Shahid Beheshti University | Ghassemian H.,Tarbiat Modares University
Computers and Electronics in Agriculture | Year: 2012

The feasibility of reflectance Vis/NIR spectroscopy was investigated for taste characterization of Valencia oranges based on taste attributes including soluble solids content (SSC) and titratable acidity (TA), as well as taste indices including SSC to TA ratio (SSC/TA) and BrimA. The robustness of multivariate analysis in terms of prediction was also assessed. Several combinations of various preprocessing techniques with moving average and Savitzky-Golay smoothing filters, standard normal variate (SNV) and multiplicative scatter correction (MSC) were used before calibration and the models were developed based on both partial least squares (PLS) and principle component regression (PCR) methods. The best models obtained with PLS method had root mean square errors of prediction (RMSEP) of 0.33°Brix, 0.07%, 1.03 and 0.37, and prediction correlation coefficients (r p) of 0.96, 0.86, 0.87 and 0.92 for SSC, TA, SSC/TA, and BrimA, respectively. It was concluded that Vis/NIR spectroscopy combined with chemometrics could be an accurate and fast method for nondestructive prediction of taste attributes and indices of Valencia oranges. Moreover, the application of this technique was suggested for taste characterization, directly based on BrimA which is the best index related to fruit flavor rather than determination of SSC or TA alone. © 2012 Elsevier B.V..

Ebrahiminia A.,Tarbiat Modares University | Mokhtari-Dizaji M.,Tarbiat Modares University | Toliyat T.,Tehran University of Medical Sciences
Ultrasonics Sonochemistry | Year: 2013

Acoustic cavitation plays an important role in sonochemical processes and the rate of sonochemical reaction is influenced by sonication parameters. There are several methods to evaluate cavitation activity such as chemical dosimetry. In this study, to comparison between iodide dosimetry and terephthalic acid dosimetry, efficacy of sonication parameters in reactive radical production has been considered by iodide and terephthalic acid dosimetries. For this purpose, efficacy of different exposure parameters on cavitations production by 1 MHz ultrasound has been studied. The absorbance of KI dosimeter was measured by spectrophotometer and the fluorescence of terephthalic acid dosimeter was measured using spectrofluorometer after sonication. The result of experiments related to sonication time and intensity showed that with increasing time of sonication or intensity, the absorbance is increased. It has been shown that the absorbance for continuous mode is remarkably higher than for pulsing mode (p-value < 0.05). Also results show that with increasing the duty cycles of pulsed field, the inertial cavitation activity is increased. With compensation of sonication time or intensity in different duty cycles, no significant absorbance difference were observed unless 20% duty cycle. A significant correlation between the absorbance and fluorescence intensities (count) at different intensity (R = 0.971), different sonication time (R = 0.999) and different duty cycle (R = 0.967) were observed (p-value < 0.05). It is concluded that the sonication parameters having important influences on reactive radical production. These results suggest that there is a correlation between iodide dosimetry and terephthalic acid dosimetry to examine the acoustic cavitation activity in ultrasound field. © 2012 Elsevier B.V. All rights reserved.

Aghapour A.A.,Tarbiat Modares University | Moussavi G.,Tarbiat Modares University | Yaghmaeian K.,Tehran University of Medical Sciences
Bioresource Technology | Year: 2013

The main objective of this study was to investigate the performance of a cyclic rotating-bed biological reactor (CRBR) in comparison to a sequencing continuous-inflow reactor (SCR) for the biodegradation and mineralization of catechol. Results showed that catechol degradation and mineralization in the SCR at the organic loading of 7.82kgCOD/m3d and the hydraulic retention time (HRT) of 9h were 28.2% and 10.3%, respectively. Under similar operating conditions to SCR, steady-state performance of CRBR with polyurethane foam (PUF) media for degradation and mineralization of catechol achieved was 98.7% and 97.9%, respectively. In comparison, the CRBR with 2H media attained average steady-state catechol degradation and mineralization of 89.1% and 83.6%, respectively, under similar conditions. Accordingly, the CRBR with PUF media presents a promising process for efficiently treating wastewater containing high concentrations of toxic, inhibitory and resistant compounds at a relatively short HRT. © 2013 Elsevier Ltd.

MohammadTaghvaei N.,Ahvaz Jundishapur University of Medical Sciences | Taheripak G.,Tehran University of Medical Sciences | Taghikhani M.,Tarbiat Modares University | Meshkani R.,Tehran University of Medical Sciences
Cellular Signalling | Year: 2012

Palmitate induces PTP1B expression in skeletal muscle cells. The purpose of this study was to investigate the mechanisms responsible for palmitate-induced PTP1B expression in mouse skeletal muscle cells. Three truncated fragments of PTP1B promoter were cloned into PGL3-basic vector and the promoter activity of PTP1B was assessed in C2C12 cells exposed to palmitate either in the presence or in the absence of several inhibitors to study the biochemical pathways involved. EMSA was performed to examine binding of NF-κB to NF-κB consensus sequence and PTP1B oligonucelotides in the cells treated with palmitate. Lentiviral PTP1B-shRNA was used to knockdown PTP1B in myotubes. The phosphorylation and protein levels of IRS-1 and Akt were detected by western blot. 0.5. mM palmitate induced PTP1B promoter activity in fragment -1715/+. 59 by 50% (p < 0.01). Palmitate increased NF-κB binding to both NF-κB consensus sequence and one NF-κB sequence (-920 to -935) in PTP1B promoter. Incubation of C2C12 cells with different concentrations of C2-ceramide enhanced PTP1B promoter activity dose-dependently. Inhibitors of de novo ceramide synthesis prevented palmitate-induced PTP1B promoter activity in myotubes. In addition, inhibitor of JNK pathway prevented ceramide-induced PTP1B promoter activity in myotubes. Knockdown of PTP1B also prevented ceramide-reduced IRS-1 and Akt phosphorylations in the myotubes. Exposure of the cells to PMA and calphostin C, an inhibitor of PKC, did not affect the activity of PTP1B promoter. Our data provide the evidence that the mechanism by which palmitate increased the expression of PTP1B seems to be through a mechanism involving the activation of ceramide-JNK and NF-κB pathways. © 2012 Elsevier Inc.

Ghambarian M.,Iranian Research and Development Center for Chemical Industries | Yamini Y.,Tarbiat Modares University | Esrafili A.,Tehran University of Medical Sciences
Microchimica Acta | Year: 2013

Microextraction of organic or inorganic analytes using solidified floating drops of organic solvents is a fairly new method that is simple and rapid, and requires only small quantities of solvents and reagents. This review (with 109 references) covers published work up to Sep. 2012, and describes how the method was combined with analytical techniques such as GC, HPLC, ICP-OES and electrothermal atomic absorption spectrometry. We discuss basic principles and the main parameters that affect the extraction efficiency, and give specific applications of the technique. © 2013 Springer-Verlag Wien.

Shamsipur M.,Razi University | Asgari M.,Tarbiat Modares University | Mousavi M.F.,Tarbiat Modares University | Davarkhah R.,Electrochemistry Laboratory FCR
Electroanalysis | Year: 2012

MWCNTs-nanoNiO composite was used as a glassy carbon electrode modifier for construction of a novel catalase nanobiosensor for hydrogen peroxide. The immobilized catalase exhibited excellent electrocatalytic activity towards the reduction of H 2O 2. The resulting amperometric biosensor exhibited a linear response over a concentration range of 200μM to 2.53mM with a low detection limit of 19.0μM. Electrochemical impedance measurements revealed that the modified electrode can be used for the sensitive detection of H 2O 2. The charge transfer resistance found to decrease significantly after enzymatic reaction of nanobiosensor with H 2O 2. The resulting impedance was highly sensitive to H 2O 2 over a linear range of 19-170nM with a detection limit of 2.4nM. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shirani A.,Islamic Azad University at Ahvāz | Momenzadeh M.,Islamic Azad University at Ahvāz | Sanjabi S.,Tarbiat Modares University
Surface and Coatings Technology | Year: 2012

The influence of sodium dodecyl sulfate (SDS) as anionic surfactant and cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant on the morphology, composition, and texture and corrosion behavior of electrodeposited Co-TiO 2 coatings was investigated. The polarization test revealed that the coatings deposited from SDS containing solution formed passive layer in low current densities and high positive voltages than coatings deposited in CTAB containing solution. The corrosion resistance of deposited coatings from SDS containing solution was improved in NaOH and H 2SO 4 solutions than CTAB one. The performed impedance test results in both corrosive media were compatible with the results of polarization test. The coatings deposited with CTAB had grains structure of 62nm whilst SDS ones showed finer grains around 45nm, which it was evaluated by XRD analysis and chronoamperometry extrapolation. © 2011 Elsevier B.V.

Moussavi G.,Tarbiat Modares University | Majidi F.,Tarbiat Modares University | Farzadkia M.,Tehran University of Medical Sciences
Desalination | Year: 2011

The electrocoagulation process (ECP) was investigated for the removal of cyanide from wastewater in batch and continuous operation under different conditions. The batch experiments indicated that an iron-aluminum electrode arrangement as anode-cathode attained the highest removal efficiency. The increase of the current densities of 2 to 15mA/cm2 resulted in an increase of cyanide removal from 43% to 91.8% after 20min of reaction in the absence of aeration. Under similar conditions, aeration of the reactor enhanced removal efficiencies from 45% to 98%. Continuous operation of the ECP reactor with various hydraulic retention times (HRT) led to an increase of cyanide removal from 57% at an HRT of 15min to complete elimination at an HRT of 140min. Thus, we conclude that electrocoagulation is a cost-effective promising process for efficient treatment of cyanide-laden wastewater. © 2011 Elsevier B.V.

Rahimi G.H.,Tarbiat Modares University | Gazor M.S.,Tarbiat Modares University | Hemmatnezhad M.,Islamic Azad University at Takestan | Toorani H.,Tarbiat Modares University
Composite Structures | Year: 2013

The postbuckling behavior of functionally graded beams is investigated by means of an exact solution method. The Von-Karman type nonlinear strain-displacement relationships are employed. The effects of the transverse shear deformation and rotary inertia are also included based upon the Timoshenko beam theory. After writing the kinetic and potential energy functionals, the governing equations of motion including the axial, transverse deflections and also the cross sectional rotation are derived using the Hamilton's principle. The material properties are assumed to be graded in the thickness direction according to the power-law distribution. Neglecting the inplane inertia, the three equations of motion are reduced to two nonlinear partial-integral-differential equations in terms of the transverse mid-plane deflection and the cross sectional rotation. FG beams are considered to have fixed-fixed, fixed-hinged, and hinged-hinged end conditions. A closed-form solution is achieved for the postbuckling deformation as a function of the exerted axial load which is beyond the critical buckling load. In order to study the vibrations taking place in the vicinity of a buckled equilibrium position, the linear vibration problem is exactly solved around the first buckled configuration of a hinged-hinged FG beam. This leads to a characteristic equation whose eigenvalues are the natural frequencies and the corresponding eigenvectors also determine the mode shapes. The influences of power-law exponent, some commonly used boundary conditions and beam geometrical parameters on the static deflection and free vibration frequencies are studied. A comparison of the present results with those obtained via Euler-Bernoulli beam theory clarifies the overestimation of the frequencies by the later one. © 2012.

Ziyadi H.,Tarbiat Modares University | Heydari A.,Tarbiat Modares University | Rezayat S.M.,Tehran University of Medical Sciences
Ceramics International | Year: 2014

Magnetic composite fibers with α-Fe2O3/SiO 2 core-shell structure were prepared by the electrospinning and sol-gel method. The α-Fe2O3 ceramic nanofibers were prepared by electrospinning of solution of poly (vinyl alcohol) (PVA) and Fe(NO3)3·9H2O composite nanofibers followed by calcinations. Controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS) caused a dense silica layer deposit on the surface of α-Fe2O3 nanofibers with a desired thickness using the sol-gel method (denoted as α-Fe2O3@SiO 2). The products were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscope (EDX), vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). The α-Fe2O 3@SiO2 core/shell fibers showed a high value of specific saturation magnetization. © 2013 Elsevier Ltd and Techna Group S.r.l.

Kent J.T.,University of Leeds | Mohammadzadeh M.,Tarbiat Modares University | Mosammam A.M.,University of Zanjan
Biometrika | Year: 2011

Gneiting (2002) proposed a nonseparable covariance model for spatial-temporal data. In the present paper we show that in certain circumstances his model possesses a counterintuitive dimple. In some cases, the magnitude of the dimple can be nontrivial. © 2011 Biometrika Trust.

Tavafian S.S.,Tarbiat Modares University | Jamshidi A.R.,Shariati Hospital | Mohammad K.,Tehran University of Medical Sciences
Clinical Journal of Pain | Year: 2011

Objective: This randomized clinical trial examined the efficacies of a group-based multidisciplinary rehabilitation program and oral drug treatment versus oral drug treatment alone in Iran. Methods: A total of 197 patients with chronic low back pain were randomized to either intervention group (n=97) receiving a group-based, 5-session multidisciplinary rehabilitation program plus oral medication or to control group (n=100) receiving just oral medication. At baseline and at 3 and 6-month follow-ups, patients filled out questionnaires on health-related quality of life (36-item Short-form General Health Survey) and disability Questionnaires (Quebec Disability Scale and Ronald-Morris Disability). Repeated measure analysis of variance was used to compare 2 groups during time. Results: The 2 groups were comparable regarding all baseline characteristics (P>0.05). There were significant differences within each group by time in terms of all subscales of 36-item Short-form (P<0.01) except for mental health (P=0.7). Furthermore, there were significant deferences between groups in terms of all domains of SF-36 scale except for general health (P=0.06), social function (P=0.08) and role emotional (P=0.7). Furthermore, according to the scores of Ronald-Morris Disability Questionnaire and Quebec Disability Scale, the disability of patients in the intervention group was improved over time significantly (P=0.01 and P<0.0001, respectively). Discussion: The findings revealed that the group-based multidisciplinary program could improve most domains of quality of life in chronic low back pain patients in the 6-month period. However, there were no significant differences between two groups in sub scales such as general health, social function and role emotional. © 2011 by Lippincott Williams & Wilkins.

Sedighi M.,Tarbiat Modares University | Keyvanloo K.,Brigham Young University | Towfighi J.,Tarbiat Modares University
Industrial and Engineering Chemistry Research | Year: 2011

To predict the main product yields of thermal cracking of heavy liquid hydrocarbon, four models, kinetic, artificial neural networks (ANN), neuro-fuzzy (NF), and polynomial, were developed. The models investigated the influence of COT, steam ratio, and feed flow rate on product yields at the reactor tube outlet. A semimechanistic kinetic model based on free radical chain reactions was developed using experimental results. This semimechanistic kinetic model contains 148 reactions for 43 species. An objective function was defined to optimize the kinetic parameters. For the artificial intelligence systems, a three-layer perceptron neural network with back-propagation (BP) training algorithm and Sugeno inference system were used. To compare the accuracy of artificial intelligence method, another empirical method based on response surface methodology was also developed. Finally, the models were compared to experimental data, and a comparison between the results of kinetic model, designed ANN, and NF was also carried out by analysis of variance (ANOVA) calculation. The obtained results demonstrate that these four models are in good agreement with experimental data, while the ANN and NF models show better results than do the kinetic model and polynomial model. © 2011 American Chemical Society.

Rezazadeh M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Seidi S.,Tarbiat Modares University | Esrafili A.,Tehran University of Medical Sciences
Analytica Chimica Acta | Year: 2013

In the present work, pulsed electromembrane extraction (PEME) was performed for the first time, as a new concept of electrically enhanced microextraction method, for extraction and quantification of histidine, phenylalanine and tryptophan in different matrices. PEME offers an alternative to conventional electromembrane extraction (EME), which faces problems such as serious instabilities in the analysis of real samples with high concentration levels of ions. In these samples, increasing of the ion transportation across the liquid membrane results in Joule heating during the extraction process which may follow by punctuation of the organic membrane, increasing of the current level and bubble formation due to electrolysis reactions. A mixture of 2-nitrophenyl octyl ether (NPOE), di-(2-ethylhexyl) phosphate (DEHP) and tris-(2-ethylhexyl) phosphate (TEHP) was immobilized in the pores of hollow fiber as the organic liquid membrane. Other effective parameters such as extraction time, ion balance and pulse frequency were optimized using the experimental design. Extraction recoveries in the range of 7.1-21.6% and satisfactory repeatability (2.1

Falaghi H.,Birjand University | Singh C.,Texas A&M University | Haghifam M.-R.,Tarbiat Modares University | Ramezani M.,Birjand University
International Journal of Electrical Power and Energy Systems | Year: 2011

In this paper, a framework is presented to solve the problem of multistage distribution system expansion planning in which installation and/or reinforcement of substations, feeders and distributed generation units are taken into consideration as possible solutions for system capacity expansion. The proposed formulation considers investment, operation, and outage costs of the system. The expansion methodology is based on pseudo-dynamic procedure. A combined genetic algorithm (GA) and optimal power flow (OPF) is developed as an optimization tool to solve the problem. The performance of the proposed approach is assessed and illustrated by numerical studies on a typical distribution system. © 2011 Elsevier Ltd. All rights reserved.

Teimouri Sendesi S.M.,Tarbiat Modares University | Towfighi J.,Tarbiat Modares University | Keyvanloo K.,Brigham Young University
Catalysis Communications | Year: 2012

To investigate the effect of Si/Al ratio, Fe and P loadings on the stability of HZSM-5 in the catalytic cracking of naphtha, experimental tests were done over 20 h time on stream on modified HZSM-5 with different Si/Al molar ratios. NH 3-TPD and TPO analyses showed that the more number of weak acid sites, the greater amount of coke is formed. According to TPO and XRD results, it was demonstrated that dealumination had a significant role in catalytic stability. Among catalysts, Fe(6)-P(2)/HZSM-5(25) showed the highest catalytic stability (1.86 wt.% propylene reduction). © 2012 Elsevier B.V.

Azizi-Shotorkhoft A.,University of Agriculture and Natural Resources Ramin | Rezaei J.,Tarbiat Modares University | Fazaeli H.,Animal Science Research Institute
Animal Feed Science and Technology | Year: 2013

A 28-d experiment was performed to evaluate the influence of replacing dietary corn/barley with molasses at levels of 0 (M0), 50 (M50) and 100 (M100) g/kg dietary dry matter (DM), as energy sources, in the diets containing heat-processed broiler litter (HBL) (240. g/kg DM) in male Moghani sheep. Digestibility, microbial protein supply (MPS), ruminal parameters and blood metabolites were measured. The digestibility of DM and crude protein (CP) in experimental sheep linearly increased (L, P=0.01) as level of molasses enhanced in the diets. Addition of molasses to diet linearly increased MPS (L, P=0.01) compared to sheep fed the control diet. Ruminal pH and ammonia concentrations linearly declined (L, P<0.05) as level of molasses increased in the diet. There was no difference (P>0.05) in ruminal volatile fatty acid concentrations, except a linear increase in the molar proportion of butyrate (L, P=0.02) among the molasses supplemented groups. Blood urea-N linearly decreased (L, P=0.02) in sheep fed molasses compared to the control group. It can be concluded that replacing corn/barley with molasses in sheep diet improved the utilization of the diet containing HBL. © 2012 Elsevier B.V.

Eskandari M.,Alzahra University | Yamini Y.,Tarbiat Modares University | Fotouhi L.,Alzahra University | Seidi S.,Tarbiat Modares University
Journal of Pharmaceutical and Biomedical Analysis | Year: 2011

In the present study, extraction of mebendazole across a supported-liquid membrane (SLM) was performed based on two different driving forces: (1) pH gradient over the SLM, and (2) electrical field sustained over the SLM. The extracted drug concentration was studied using reversed-phase HPLC-UV. At passive extraction conditions, mebendazole was extracted from alkaline samples (0.01mmolL -1 NaOH) into 1-undecanol immobilized in the pores of a porous hollow fiber of polypropylene (SLM), and then transported into 25μL of 100mM HCl as the acceptor solution. Under electrokinetic migration conditions, mebendazole transported under applied voltage from acidic solutions (100mmolL -1 HCl) through 2-nitrophenyl octyl ether (NPOE) immobilized in the pores of hollow fiber, into 25μL of 100mmolL -1 HCl as the acceptor solution. The effects of several factors including the nature of organic solvent, pH of donor and acceptor solutions, extraction time and stirring speed on the extraction efficiency of the drug were investigated and optimized. Under optimal conditions, preconcentration factors (PF) of 211 and 190 were obtained for the drug based on passive transport and electromembrane extraction (EME), respectively. Also, linear range of 0.5-1000μgL -1 with estimation of coefficient higher than 0.994 was obtained for both of the proposed methods. The results showed that EME has higher speed in comparison with simple passive transport. The methods were successfully applied to extract mebendazole from plasma and urine samples and satisfactory results were obtained. © 2010 Elsevier B.V.

Sarah Bakhshi,Tarbiat Modares University | Moravvej-Farshi M.K.,Tarbiat Modares University | Ebnali-Heidari M.,Shahrekord University
Applied Optics | Year: 2011

We are proposing a procedure to enhance the transmission efficiency of 60° photonic crystal (PhC) waveguide bends by means of selective optofluidic infiltration of an air hole, which is created as a point defect at the center of the conventional 60° PhC bend. Numerical studies demonstrate that by varying the defect radius and indices of optical fluids, one may enhance the bend transmission level and tune its 3 dB bandwidth over a substantial range of 88-138nm. In order to perform the numerical simulations, we have used two-dimensional (2D) finite difference time domain plane wave method, keeping in mind that the spectral features obtained by these 2D calculations are about 15% redshifted from those of real threedimensional structures. © 2011 Optical Society of America.

Bitarafan M.H.,Tarbiat Modares University | Moravvej-Farshi M.K.,Tarbiat Modares University | Ebnali-Heidari M.,Shahrekord University
Applied Optics | Year: 2011

We are proposing a procedure to reconfigure a three-port photonic crystal channel drop filter with two point-defect resonant cavities coupled to a bus and a drop W1-type waveguide, by means of selective optofluidic infiltration. Simulations show that, by selective infiltration of cavities and the air holes of the two parallel line defects that are partially surrounding the bus waveguide of the proposed channel drop filter (CDF), besides fine-tuning of the cavities resonant frequencies to the desired values, one can also fine-tune the CDF phase to an optimum condition for achieving optimum drop efficiency for any given resonant frequency. We have used the 2D finite difference time domain and plane wave method to perform the numerical simulations. © 2011 Optical Society of America.

Masoomi M.Y.,Tarbiat Modares University | Morsali A.,Tarbiat Modares University | Junk P.C.,James Cook University
CrystEngComm | Year: 2015

Two new three-dimensional porous Cd(ii)-based metal-organic frameworks, [Cd2(oba)2(4-bpdb)2]n·(DMF)x (TMU-8) and [Cd(oba)(4,4′-bipy)]n·(DMF)y (TMU-9), have been synthesized via mechanosynthesis by using nonlinear dicarboxylate and linear N-donor ligands and then characterized by single-crystal X-ray crystallography. The effect of using different N-donor ligands 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb) and 4,4′-bipyridine (4,4′-bipy) as pillars on the final structure has been studied. Also, the removal efficiency and order reaction kinetics of these MOFs in the presence of Congo red were investigated. © The Royal Society of Chemistry 2015.

Bakhshi S.,Tarbiat Modares University | Moravvej-Farshi M.K.,Tarbiat Modares University | Ebnali-Heidari M.,Shahrekord University
Applied Optics | Year: 2012

We present the design procedure for an ultracompact low-power all-optical modulator based on a dispersion-engineered slow-light regime in a photonic crystal Mach-Zehnder interferometer (PhC MZI), selectively infiltrated by nonlinear optical fluids. The dispersionless slow-light regime enhancing the nonlinearities enabled a 22 μm long PhC MZI to operate as a modulator with an input power as low as 3 mW/μm. Simulations reveal that the switching threshold can be controlled by varying the optofluidic infiltration. © 2012 Optical Society of America.

Sayadi A.R.,Tarbiat Modares University | Lashgari A.,Tarbiat Modares University | Paraszczak J.J.,Laval University
Tunnelling and Underground Space Technology | Year: 2012

In feasibility studies and mine planning, accurate and effective tools and methods facilitating cost estimation play an important role. Load-Haul-Dump (LHD) machines are a key loading and haulage equipment in most of the underground metal mines and hard rock tunnels. In this paper, a cost estimation model of these vehicles has been presented in the form of single and multivariable functions. These functions have been provided on the basis of costs types (i.e. capital and operating costs) and motor types (diesel and electric). Independent variables, in the single regression analysis is bucket capacity and in Multiple Linear Regression (MLR) analysis include bucket capacity, overall width, overall machine height and horse power (HP). The MLR is conducted in three steps. First, with the help of Principal Component Analysis (PCA), correlation between independent variables is omitted. Thereafter, significant PCs are selected and used as independent variables in the MLR functions. Finally, the cost relationships are established as functions of initial LHD variables. The mean absolute error rates are 11.59% and 6.87% for the single and multiple linear regression functions, respectively. © 2011 Elsevier Ltd.

Manoj K.,Maharana Pratap University of Agriculture and Technology | Monjezi M.,Tarbiat Modares University
International Journal of Mining Science and Technology | Year: 2013

Flyrock is one of the most hazardous events in blasting operation of surface mines. There are several empirical methods to predict flyrock. Low performance of such models is due to the complexity of flyrock analysis. Existence of various effective parameters and their unknown relationships are the main reasons for inaccuracy of the empirical models. Presently, the application of new approaches such as artificial intelligence is highly recommended. In this paper, an attempt has been made to predict flyrock in blasting operations of Soungun Copper Mine, Iran incorporating rock properties and blast design parameters using support vector machine (SVM) method. To investigate the suitability of this approach, the predictions by SVM have been compared with multivariate regression analysis (MVRA), too. Coefficient of determination (CoD) and mean absolute error (MAE) were taken as performance measures. It was found that CoD between measured and predicted flyrock was 0.948 and 0.440 by SVM and MVRA, respectively, whereas MAE between measured and predicted flyrock was 3.11 and 7.74 by SVM and MVRA, respectively. © 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.

Fotouhi L.,Alzahra University | Yamini Y.,Tarbiat Modares University | Molaei S.,Alzahra University | Seidi S.,Tarbiat Modares University
Journal of Chromatography A | Year: 2011

In the present study, hollow fiber liquid phase microextraction (HF-LPME) based on pH gradient and electromembrane extraction (EME) coupled with high-performance liquid chromatography (HPLC) was compared for the extraction of ephedrine from biological samples. The influences of fundamental parameters affecting the extraction efficiency of ephedrine were studied and optimized for both methods. Under the optimized conditions, preconcentration factors of 120 and 35 for urine and 51 and 8 for human plasma were obtained using EME and HF-LPME, respectively. The calibration curves showed good linearity for urine and plasma samples by both methods with the coefficient of estimations higher than 0.98. The limits of detection were obtained 5 and 10ngmL -1 using EME and 60 and 200ngmL -1 by HF-LPME for urine and plasma samples respectively. The relative standard deviations of the analysis were found in the range of 5.2-8.6% (n=3). The results showed that in comparison with HF-LPME based on pH gradient, EME is a much more effective transport process, providing high extraction efficiencies in very short time. © 2011 Elsevier B.V.

Salimi M.,Tarbiat Modares University | Mozdarani H.,Tarbiat Modares University | Majidzadeh K.,Breast Diseases Research Center
Medical Oncology | Year: 2012

ATM protein kinase plays a critical role in maintaining genome integrity by activating a biochemical chain reaction that in turn leads to cell cycle checkpoint activation and repair of DNA damage. Cyclin D1 acts in regulating the G1 phase of the cell cycle. Experimental and clinical studies suggest them to be involved in transformation and tumour progression. To elucidate the role of ATM and cyclin D1 expression in sporadic breast cancer, we investigated the possible link between their RNA expression levels in ductal carcinoma and normal adjacent versus normal breast tissues measured by Taqman realtime PCR in 119 breast tissues. Results showed that cyclin D1 over-expressed in 51.4% of breast tumours, whereas ATM expression was down regulated in 55% of breast tumours compared to both normal adjacent and normal controls (P ≤ 0.01). Cyclin D1 expression in adjacent normal and normal tissues was not significantly differed, whereas ATM expression in normal adjacent was lower than normal control (P ≤ 0.01). Over-expression of cyclin D1 correlated with ER+ and/or PR+ (oestrogen/progesterone receptor) status, whereas it mostly under-expressed in HER2+ (human epidermal growth factor 2) tumours. ATM under-expression was more observed in triple-negative tumours (ER -, PR- and HER2-). Our results indicated that reduced expression of the ATM and aberrant cyclin D1 expressions may contribute to the development and/or malignant progression of breast carcinomas also the latter could be involved in the regulation of hormone sensitivity associated with ER and PR. © Springer Science+Business Media, LLC 2011.

Khandelwal M.,Maharana Pratap University of Agriculture and Technology | Monjezi M.,Tarbiat Modares University
Rock Mechanics and Rock Engineering | Year: 2013

Backbreak is an undesirable phenomenon in blasting operations. It can cause instability of mine walls, falling down of machinery, improper fragmentation, reduced efficiency of drilling, etc. The existence of various effective parameters and their unknown relationships are the main reasons for inaccuracy of the empirical models. Presently, the application of new approaches such as artificial intelligence is highly recommended. In this paper, an attempt has been made to predict backbreak in blasting operations of Soungun iron mine, Iran, incorporating rock properties and blast design parameters using the support vector machine (SVM) method. To investigate the suitability of this approach, the predictions by SVM have been compared with multivariate regression analysis (MVRA). The coefficient of determination (CoD) and the mean absolute error (MAE) were taken as performance measures. It was found that the CoD between measured and predicted backbreak was 0.987 and 0.89 by SVM and MVRA, respectively, whereas the MAE was 0.29 and 1.07 by SVM and MVRA, respectively. © 2012 Springer-Verlag.

Kaleji B.K.,Tarbiat Modares University | Sarraf-Mamoory R.,Tarbiat Modares University | Fujishima A.,Kanagawa Academy Of Science And Technology
Materials Chemistry and Physics | Year: 2012

In this study, preparation of Nb-doped (0-20 mol% Nb) TiO 2 dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO 2 thin films were measured in the TiO 2-1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb 5+ dopant presented substitutional Ti 4+ into TiO 2 lattice. © 2011 Elsevier B.V.

Masoomi M.Y.,Tarbiat Modares University | Morsali A.,Tarbiat Modares University | Junk P.C.,James Cook University
RSC Advances | Year: 2014

A 3D, porous Zn(ii)-based metal-organic framework {[Zn2(oba)2(4-bpdb)]·2DMF}n (TMU-4) with double interpenetration was prepared by using a non-linear dicarboxylate (H2oba = 4,4′-oxybisbenzoic acid) and a linear N-donor (4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) ligand. Also micro- and nano-plates of this MOF were synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. The thermal stability was studied by thermogravimetric analysis (TGA). Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs, were studied. Calcination of TMU-4 at 500 °C under air atmosphere yields ZnO nanoparticles. This journal is © the Partner Organisations 2014.

Rostamnia S.,Islamic Azad University at Maragheh | Rostamnia S.,Tarbiat Modares University
Research Journal of Chemistry and Environment | Year: 2011

Nanoparticles based on toxic properties of quantum dot (Q.D.) have some limitation in environment and green applications. In view of the great attention paid to the development of eco-friendly and green chemistry approaches and based on recent advances in green support media, eco-friendly supported nanoparticles are used as catalyst that have led to a rational approach to the design of new heterogeneous green catalysts. Amongst the advantages of supported nanoparticles, the most significant is their large size (no Q.D.) and hence they can accommodate a greater number of eco-friendly surfaces such as clays, zeolites etc. for better catalytic activity and green media under controlled conditions.

Atighehchian A.,Tarbiat Modares University | Sepehri M.M.,Tarbiat Modares University
European Journal of Industrial Engineering | Year: 2013

In this paper, the dynamic single-machine scheduling problem with a sequence-dependent setup time and with minimising total weighted tardiness of jobs as the objective is investigated. Due to the dynamic nature of the problem, a function-based approach is developed that can capture dynamic characteristics associated with the environment. In order to find a function which maps the environment's states to an action at each decision point, a combination of simulated annealing and a multi-layer feed-forward neural network is employed in an algorithm named SANN. The efficiency of the proposed function-based approach is compared with the most commonly used dispatching rules and with an agent-based approach, which employs the Q-learning algorithm to develop a decision-making policy. Numerical results reveal that the proposed approach outperforms dispatching rules and the Q-learning algorithm. The mean value of the results is about 93% better than the mean of the best results obtained with dispatching rules. Copyright © 2013 Inderscience Enterprises Ltd.

Sohrab A.P.,Tarbiat Modares University | Atlasbaf Z.,Tarbiat Modares University
IEEE Antennas and Wireless Propagation Letters | Year: 2013

A wideband circuit analog absorber in X-band is proposed. The design is discussed by the unit cell and equivalent circuit model. A unit cell of the periodic structure for the absorber is designed and simulated. The absorber consists of two RO 4003 layers separated by air distance. With the thickness of 3 mm, the absorber offers a-20-dB bandwidth of 40%. A novel method for estimating the optimality ratio of planar absorbers is also proposed. The optimality ratio of the designed X-band absorber is calculated with the proposed method, and the result is about 80% optimality in frequency response and total thickness. © 2002-2011 IEEE.

Jamshidi H.,Tarbiat Modares University | Nategh M.J.,Tarbiat Modares University
International Journal of Machine Tools and Manufacture | Year: 2013

The frictional behavior of the tool-chip interface has a significant role in the cutting mechanics. The frictional and normal forces, the contact length between the cutting tool and chip, the coefficient of friction and the stress distribution are the influential parameters. The behavior of the tool-chip interface in ultrasonic-vibration assisted cutting is different from conventional cutting and needs to be investigated. The ultrasonic-vibration assisted cutting has several advantages compared with conventional process. In the present study a frictional model has been developed for studying the above mentioned parameters and predicting the tool-chip behavior in ultrasonic-vibration assisted turning at different cutting speeds and vibration amplitudes. The results have been verified by experiments. © 2012 Elsevier Ltd. All rights reserved.

Torabi A.,Tarbiat Modares University | Forooraghi K.,Tarbiat Modares University
IEEE Microwave and Wireless Components Letters | Year: 2011

A miniature harmonic-suppressed microstrip bandpass filter (BPF) with a new triple-mode stub-loaded resonator is presented in this letter. Four distinct mechanisms are utilized to create five transmission zeros (TZs), leading to sharp skirts and wide stopband. Both simulation and measurement results are presented. The simulated/measured minimum passband insertion loss is 0.66 dB/0.78 dB and the 20 dB rejection bandwidth is extended up to 4f0. The size of the filter is about 0.23 λg× 0.17 λg, where λg is the guided wavelength at the center frequency. © 2011 IEEE.

Rahimi G.H.,Tarbiat Modares University | Zandi M.,Tarbiat Modares University | Rasouli S.F.,Tarbiat Modares University
Aerospace Science and Technology | Year: 2013

In this paper, the buckling behavior of thin-walled GFRP cylindrical shells with triangular lattice patterned reinforcements formed by helical and circumferential ribs under axial force is analyzed. In this analysis, various models of composite isogrid stiffened cylindrical shells with outer diameter of 150 millimeters, shell thickness of 0.5 millimeters and height of 280 millimeters, stiffened with 6 helical and 2 circumferential ribs and all with the same material properties of shell and ribs are used. Ribs have constant section areas but different shapes and cross section profiles. The effects of these differences on buckling strengths of structures under axial load are studied. For analysis and modeling of structures, Finite Element Analysis method and ANSYS software were used. The results (elastic buckling load) for each model were derived and based on these results, ratio of buckling strengths to weight parameters were calculated for each model and were compared to results obtained from other models. The effect of profile of the ribs on the buckling of shells under axial loading can be concluded from the results. Results showed that stiffening the shells increased the buckling load from 10% up to 36% while decreased the buckling load to weight ratio to 42% up to 52% of an unstiffened shell. © 2011 Elsevier Masson SAS. All rights reserved.

Ghobadi M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Ebrahimpour B.,Tarbiat Modares University
Journal of Separation Science | Year: 2014

SPE combined with dispersive liquid-liquid microextration was used for the extraction of ultra-trace amounts of benzodiazepines (BZPs) including, diazepam, midazolam, and alprazolam, from ultra-pure water, tap water, fruit juices, and urine samples. The analytes were adsorbed from large volume samples (60 mL) onto octadecyl silica SPE columns. After the elution of the desired compounds from sorbents with 2.0 mL acetone, 0.5 mL of eluent containing 40.0 μL chloroform was injected rapidly into 4.5 mL pure water. After extraction and centrifugation, 2 μL of the sedimented phase was injected into a GC equipped with a flame ionization detector. Several parameters affecting this process were investigated and optimized. Under the optimal conditions, LODs ranged from 0.02 to 0.05 μg/L, a linear dynamic range of 0.1-100 μg/L and relative SDs in the range of 4.4-10.7% were attained. Very high preconcentration factors ranging from 3895-7222 were achieved. The applicability of the method for the extraction of BZPs from different types of complicated matrices, such as tap water, fruit juices, and urine samples, was studied. The obtained results reveal that the proposed method is a good technique for the extraction and determination of BZPs in complex matrices. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Masehian E.,Tarbiat Modares University | Nejad A.H.,Tarbiat Modares University
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2010

In this paper, the multi robot motion planning problem is solved through a decoupled approach, where a new algorithm for prioritizing the robots moves is developed. Assuming that the workspace is mapped into a tree graph and the initial and final configurations of robots are known, the robots' shortest start-to-goal paths on the tree are calculated independently. Then, a new rule-based prioritization scheme is applied in two phases: (a) Path Prioritization, which determines which robot can directly move along its shortest path and which robot should deviate from it, and (b) Motion Prioritization, which decides the order of robots' sequential moves. Furthermore, an algorithm is presented for minimizing the number of moves by adding extra vertices to the tree. ©2010 IEEE.

Mahmoudi Y.,Tarbiat Modares University | Maerefat M.,Tarbiat Modares University
International Journal of Thermal Sciences | Year: 2011

Forced convection through a channel partially filled with a porous medium is investigated analytically in the present work. Thermally developed condition is considered and the local thermal non-equilibrium model is utilized to obtain the exact solutions of both fluid and solid temperature fields for flow inside the porous material as well as for flow in the clear region. Nusselt number is obtained in terms of the porous insert thickness (S), porosity (ε) as well as pertinent parameters such as thermal conductivity ratio (k), Biot number (Bi), and Darcy number (Da). The values of S by which the temperature difference between the two phases approach to zero, for different values of Bi, k, and Da number are obtained. It is found that three mechanisms affect the Nu number i: clear fluid conduction ii: internal heat exchange in the porous medium iii: channeling effect in the clear flow. The value of S, which yields the highest Nu number is found to vary linearly from 0.8 to 0.97 as the value of Da decreases from 10-3 to 10-7. At the expense of reasonable pressure drop the optimum thickness of porous material in order to enhance the heat transfer rate is found S = 0.8. © 2011 Elsevier Masson SAS. All rights reserved.

In this work, a dodecylsulfate-doped nano porous polypyrrole gas sensor (PPy-DS) has been prepared by vapor deposition polymerization of pyrrole on surfaces of commercial polymer fiber in the presence of dodecyl sulfate (DS) as an anion dopant. The sensing behavior of PPy-DS in the presence of several aromatic hydrocarbons: benzene (B), ethyl benzene (E), toluene (T), 1,3,5-trimethylbenzene (TMB), and some other volatile organic compounds were studied experimentally. The PPy-DS had demonstrated fast response time (< 1s), sensitive for BTE and TMB with good reproducibility when reused. The sensitivity of the PPy-DS for various organic hydrocarbons was in the following order: BTE, TMB ≫ alcohol, acetone, acetonitrile, chloroform, and carbon disulfide. The PPy-DS coupled to a gas chromatograph and used for speciation determination of BTE and TMB in water samples by using a dispersive liquid-liquid microextraction (DLLME) method. © 2011 IEEE.

Asl B.M.,Tarbiat Modares University | Mahloojifar A.,Tarbiat Modares University
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2011

In adaptive ultrasound imaging, accurate estimation of the array covariance matrix is of great importance, and biases the performance of the adaptive beamformer. The more accurately the covariance matrix can be estimated, the better the resolution and contrast can be achieved in the ultrasound image. To this end, in this paper, we have used the forwardbackward spatial averaging for array covariance matrix estimation, which is then employed in minimum variance (MV) weights calculation. The performance of the proposed forwardbackward MV (FBMV) beamformer is tested on simulated data obtained using Field II. Data for two closely located point targets surrounded by speckle pattern are simulated showing the higher amplitude resolution of the FBMV beamformer in comparison to the forward-only (F-only) MV beamformers, without the need for diagonal loading. A circular cyst with a diameter of 6 mm and a phantom containing wire targets and two cysts with different diameters of 8 mm and 6 mm are also simulated. The simulations show that the FBMV beamformer, in contrast to the F-only MV, could estimate the background speckle statistics without the need for temporal smoothing, resulting in higher contrast for the FBMV-resulted image in comparison to the MV images. In addition, the effect of steering vector errors is investigated by applying an error of the sound speed estimate to the ultrasound data. The simulations show that the proposed FBMV beamformer presents a satisfactory robustness against data misalignment resulted from steering vector errors, outperforming the regularized F-only MV beamformer. These improvements are achieved without compromising the good resolution of the MV beamformer and resulted from more accurate estimation of the covariance matrix and consequently, the more accurate setting of the MV weights. © 2006 IEEE.

Asl B.M.,Tarbiat Modares University
Ultrasonic Imaging | Year: 2016

In recent years, adaptive minimum-variance (MV) beamforming has been successfully applied to medical ultrasound imaging, resulting in simultaneous improvement in imaging resolution and contrast. MV has high resolution and hence can provide accurate estimates of the target locations. However, the MV amplitude estimates are significantly biased downward, especially when occurring the errors in model parameters. The amplitude and phase estimation (APES) beamformer gives much more accurate amplitude estimates at the target locations, but at the cost of lower resolution. To reap the benefits of both MV and APES, we have proposed a modified APES (MAPES) beamformer by adding a parameter which controls the trade-off between spatial and amplitude resolutions. We have also proposed an adaptive beamformer which combines the MV and APES. The proposed beamformer first estimates the peak locations using the MV estimator and then refines the amplitude estimates at these locations using the MAPES estimator. By using simulated and experimental data-point targets as well as cyst phantoms-we show the efficacy of the proposed beamformers. © 2016 The Author(s).

Boroujeni E.A.,Tarbiat Modares University | Momeni H.R.,Tarbiat Modares University
Nonlinear Dynamics | Year: 2015

In this paper, the stability of a nonlinear non-fragile $$H_\infty $$H∞ fractional-order observer, based on the fractional-order Lyapunov theorem, is investigated in detail. It is the first time to derive the optimal gain of desired observer among a solution set that satisfies the nonlinear robust non-fragile fractional-order observer stability conditions systematically using linear matrix inequality approach. An iterative linear matrix inequality algorithm is introduced while a boundary condition is unknown during the design procedure. Finally, a fractional-order financial system is introduced to show the effectiveness of the proposed method. It has been shown that not only the iterative method is successful to find the proper boundary condition, but also the performance of the proposed observer is satisfying both non-fragility and robustness to external disturbances with an acceptable accuracy. © 2015, Springer Science+Business Media Dordrecht.

Husseinzadeh Kashan A.,Tarbiat Modares University
Applied Soft Computing Journal | Year: 2014

League Championship Algorithm (LCA) is a recently proposed stochastic population based algorithm for continuous global optimization which tries to mimic a championship environment wherein artificial teams play in an artificial league for several weeks (iterations). Given the league schedule in each week, a number of individuals as sport teams play in pairs and their game outcome is determined in terms of win or loss (or tie), given the playing strength (fitness value) along with the intended team formation/arrangement (solution) developed by each team. Modeling an artificial match analysis, each team devises the required changes in its formation (generation of a new solution) for the next week contest and the championship goes on for a number of seasons (stopping condition). An add-on module based on modeling the end season transfer of players is also developed to possibly speed up the global convergence of the algorithm. Extensive analysis to verify the rationale of the algorithm and suitability of the updating equations together with investigating the effect of different settings for the control parameters are carried out empirically on a large number of benchmark functions. Results indicate that LCA exhibits promising performance suggesting that its further developments and practical applications would be worth investigating in the future studies. © 2013 Elsevier B.V.

Ghaseminezhad S.M.,Tarbiat Modares University | Hamedi S.,Tarbiat Modares University | Shojaosadati S.A.,Tarbiat Modares University
Carbohydrate Polymers | Year: 2012

This study presents a novel green method using starch for the synthesis of silver nanoparticles (AgNPs). In this method, the fungal supernatant was added to a mixture of starch and silver nitrate solutions. The characteristics of AgNPs synthesized by three independent processes - a modified polysaccharide method, a microbial method, and our novel method - were compared. Dynamic light scattering (DLS) analysis revealed that the average sizes of AgNPs synthesized by the microbial method, the modified polysaccharide method, and our novel method were 84, 20, and 15 nm, respectively. The most stable AgNPs were generated by our novel method. The X-ray diffraction (XRD) spectrum of the products from the novel method showed that these AgNPs have high crystallinity. Fourier-transform infrared spectroscopy (FTIR) spectra demonstrated that the functional groups present in the products prepared by the novel method are a combination of the functional groups present in the AgNPs synthesized by the other two methods. © 2012 Elsevier Ltd. All rights reserved.

Rezazadeh M.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Seidi S.,Tarbiat Modares University | Esrafili A.,Tarbiat Modares University
Journal of Chromatography A | Year: 2012

In the present work, pulsed electromembrane extraction (PEME) is introduced for the first time as an efficient and inexpensive method for the extraction of ionizable compounds from different matrices. The setup proposed for electromembrane extraction (EME) provides a very stable system and satisfactory repeatability (RSDs<4.4) in comparison with existing methods. In this paper, PEME is conducted for the extraction of model analytes from biological fluids. The effective parameters such as extraction time, applied voltage and the duration of pulse and outage period are optimized using the experimental design. Preconcentration factors in the range of 100-140 and recoveries in the range of 95-108 were obtained in different biological matrices. The linear dynamic ranges of 5-200ngmL-1 (with correlation coefficient higher than 0.9955) and limits of detection of 1.0ngmL-1 were obtained for both of the drugs. The figures of merit of PEME were compared with the results from conventional EME, which proves the advantages of the proposed technique. © 2012 Elsevier B.V.

Ebrahimpour B.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Moradi M.,Tarbiat Modares University
Journal of Pharmaceutical and Biomedical Analysis | Year: 2012

A simple microextraction method based on emulsification of organic extraction solvent in aqueous sample using an ionic surfactant was evaluated for extraction and preconcentration of trace amounts of ofloxacin and ciprofloxacin as polar model drugs. In this method, the surfactant was used as carrier and disperser agent simultaneously. The target analytes were converted into their ion-pair complexes with Aliquat-336 and then extracted into an organic solvent (1-octanol) dispersed in aqueous solution. After extraction and phase separation, the organic solvent on top of the solution was withdrawn into the syringe and 20μL of it was injected into a HPLC instrument for analysis. The factors influential to extraction were investigated and optimized. Under optimum extraction conditions, the limits of detection (LODs) as small as 0.06 and 0.02ngmL -1 and linear dynamic range of 0.1-100 and 0.06-100ngmL -1 were obtained for ofloxacin and ciprofloxacin, respectively. For analysis of real samples such as waste water, river water and urine samples, solid-phase extraction (SPE) was applied prior to liquid phase microextraction in order to avoid/remove matrix effect. The obtained results indicate that the proposed method is efficient, fast and inexpensive for extraction and determination of fluoroquinolones in environmental aqueous and urine samples. © 2012 Elsevier B.V.

Seidi S.,Tarbiat Modares University | Yamini Y.,Tarbiat Modares University | Rezazadeh M.,Tarbiat Modares University | Esrafili A.,Tarbiat Modares University
Journal of Chromatography A | Year: 2012

In the present work, for the first time a new set-up was presented for simultaneous extraction of acidic and basic drugs using a recent novel electrically-enhanced microextraction technique, termed electromembrane extraction at low voltages followed by high performance liquid chromatography with ultraviolet detection. Nalmefene (NAL) as a basic drug and diclofenac (DIC) as an acidic drug were extracted from 24mL aqueous sample solutions at neutral pH into 10μL of each acidified (HCl 50mM) and basic (NaOH 50mM) acceptor solution, respectively. Supported liquid membranes including 2-nitrophenyl octyl ether containing 5% di-(2-ethylhexyl) phosphate and 1-octanol were used to ensure efficient extraction of NAL and DIC, respectively. Low voltage of 40V was applied over the SLMs during 14min extraction time. The influences of fundamental parameters affecting the transport of target drugs were optimized using experimental design. Under optimal conditions, NAL and DIC were extracted with extraction recoveries of 12.5 and 14.6, respectively, which corresponded to preconcentration factors of 300 and 350, respectively. The proposed technique provided good linearity with correlation coefficient values higher than 0.9956 over a concentration range of 8-500μgL -1 and 12-500μgL -1 for NAL and DIC, respectively. Limits of detection and quantifications, and intra-day precisions (n=3) were less than 4μgL -1, 12μgL -1, and 10.1%, respectively. Extraction and determination of NAL and DIC in human urine samples were successfully performed. In light of the data obtained in the present work, this new set-up for EME with low voltages has a future potential as a simple, selective, and fast sample preparation technique for simultaneous extraction and determination of acidic and basic drugs in different complicated matrices. © 2012 Elsevier B.V.

Valizadeh M.,Tarbiat Modares University | Kabir E.,Tarbiat Modares University
International Journal on Document Analysis and Recognition | Year: 2012

In this paper, we propose a new algorithm for the binarization of degraded document images. We map the image into a 2D feature space in which the text and background pixels are separable, and then we partition this feature space into small regions. These regions are labeled as text or background using the result of a basic binarization algorithm applied on the original image. Finally, each pixel of the image is classified as either text or background based on the label of its corresponding region in the feature space. Our algorithm splits the feature space into text and background regions without using any training dataset. In addition, this algorithm does not need any parameter setting by the user and is appropriate for various types of degraded document images. The proposed algorithm demonstrated superior performance against six well-known algorithms on three datasets. © 2010 Springer-Verlag.

Kashan M.H.,Tarbiat Modares University | Nahavandi N.,Tarbiat Modares University | Kashan A.H.,Tarbiat Modares University
Applied Soft Computing Journal | Year: 2012

Artificial bee colony (ABC) algorithm is one of the recently proposed swarm intelligence based algorithms for continuous optimization. Therefore it is not possible to use the original ABC algorithm directly to optimize binary structured problems. In this paper we introduce a new version of ABC, called DisABC, which is particularly designed for binary optimization. DisABC uses a new differential expression, which employs a measure of dissimilarity between binary vectors in place of the vector subtraction operator typically used in the original ABC algorithm. Such an expression helps to maintain the major characteristics of the original one and is respondent to the structure of binary optimization problems, too. Similar to original ABC algorithm, DisABC's differential expression works in continuous space while its consequence is used in a two-phase heuristic to construct a complete solution in binary space. Effectiveness of DisABC algorithm is tested on solving the uncapacitated facility location problem (UFLP). A set of 15 benchmark test problem instances of UFLP are adopted from OR-Library and solved by the proposed algorithm. Results are compared with two other state of the art binary optimization algorithms, i.e., binDE and PSO algorithms, in terms of three quality indices. Comparisons indicate that DisABC performs very well and can be regarded as a promising method for solving wide class of binary optimization problems. © 2011 Elsevier B.V. All rights reserved.

Moussavi G.,Tarbiat Modares University | Heidarizad M.,Tarbiat Modares University
Separation and Purification Technology | Year: 2011

This paper presents experimental results for the simultaneous removal of formaldehyde (CH2O) and ammonia nitrogen using three bioreactors: a sequencing batch reactor (SBR), a sequencing continuous-inflow reactor (SCR), and a novel modified moving-bed SCR (MSCR). The performance of these bioreactors was first investigated in terms of removal of CH2O and COD. The MSCR achieved the highest removal capacity: 100% of the CH2O and 97% of the COD at an inlet loading rate of 1.25 kg CH2O/m3 d (1.8 kg COD/m3 d) over a 24-h cycle time. The SCR was the next most efficient bioreactor. The nitrogen removal performance of the SCR and the MSCR was also studied. Results indicated that the MSCR removed approximately 99.9% of the nitrogen at a loading rate of 1.25 kg N/m3 d in the presence of 1.25 kg CH2O/m3 d. This work showed the MSCR to be an efficient modification of the activated sludge process for concurrently obtaining CH2O and nitrogen removal. © 2010 Elsevier B.V.

Karimi Z.,Tarbiat Modares University | Mahjoub A.R.,Tarbiat Modares University
Catalysis Communications | Year: 2011

K6P2W18O62 and K 14[NaP5W30O110] polyoxometalate salts are synthesized and immobilized within MCM-48, SBA-3, SBA-15 and NH 3 + functionalized mesoporous silicas. The newly designed hybrid materials are studied as catalysts for oxidation of thioethers. Preyssler complex is found to be a more active catalyst compared to its Dawson analog. Texture and chemical composition of the silica framework is shown to have indispensable effect on oxidation efficiency, stability, and reusability of catalysts. Catalysts with larger pores are proved to be more proper for the oxidation of relatively large thioethers and functionalization improves catalyst's properties. © 2011 Elsevier B.V. All rights reserved.

Abedini R.,Tarbiat Modares University | Omidkhah M.,Tarbiat Modares University | Dorosti F.,Tarbiat Modares University
International Journal of Hydrogen Energy | Year: 2014

The effect of MIL 53 (Al) metal organic framework on gas transport properties of poly (4-methyl-1-pentyne) (PMP) was determined based on reverse selectivity. Mixed matrix membranes (MMMs) were fabricated considering various weight percent of MIL 53 particles. The reverse MMMs permselectivities were evaluated through measurement of pure CO2 and H2 permeation together with calculation of CO2/H2 selectivity. The PMP/MIL 53 (Al) MMMs exhibited privileged CO2/H 2 permselectivity in comparison with the neat PMP. In addition, CO2 solubility coefficient was significantly increased with increasing the MIL 53 loading, while the H2 solubility coefficient was almost remained unchanged. Moreover with increasing the feed pressure the permeability of CO2 and CO2/H2 selectivity were dramatically enhanced, especially at higher filler loadings. Therefore, it was observed that the reverse selectivity of MMMs was enhanced so that the Robeson upper bound was overcome. The best yielding membranes (PMP/30 wt.% MIL 53) represented the CO2 permeability and CO2/H2 selectivity of 377.24 barrer and 24.91 for pure gas experiments respectively. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Mojaver R.,Tarbiat Modares University | Shahverdi H.R.,Tarbiat Modares University
Wear | Year: 2011

An end-chill cast was conducted on Zn-27%Al-2%Cu and Zn-27%Al-4%Cu alloys to produce a variety of microstructural features. In order to study the relationship between microstructure features and wear behavior of these alloys, microstructural characteristics of three sections at distances of 1, 10 and 90. mm from the chill were investigated by optical and scanning electron microscopy and their wear behaviors were examined using a pin-on disk machine. It was found that the grain size, secondary dendrite arm spacing, density of e{open} precipitates and amount of eutectoid α+ η increased with decreasing cooling rates. In addition, it was observed that the morphology of e{open} precipitates varied from semi-plate-like precipitates to fairly spherical precipitates along the height of the casting, i.e. with decreasing cooling rate.Microscope observations showed that the wear process proceeded by subsurface deformation, crack nucleation and crack growth, i.e. principle mode of wear was delamination. Also, wear tests showed that microstructures which solidified in the highest cooling rate displayed the maximum wear loss and rate in both alloys and also, the wear rate increased with increasing copper content.As a result of these investigations, the differences in wear behaviors of microstructures of as-cast Zn-27%Al-(more than 2%)Cu alloys were explained based on the relative contribution of each microstructural characteristic on fracture properties, crack nucleation mechanism and crack growth rate. © 2011 Elsevier B.V.

Shirmohammadi R.,Tarbiat Modares University
Nanoscale and Microscale Thermophysical Engineering | Year: 2011

The thermal response predicted by hyperbolic heat conduction model is studied for a microspherical particle exposed to laser pulse heating. Using the obtained analytical solution, the temperature distribution, propagation, and reflection of the temperature wave due to such a heat pulse is investigated for different thermal relaxation times and laser pulse durations. The effect of geometry on the temperature profile is also studied, and the results of the hyperbolic and Fourier model are compared. The solution and analysis are expected to be useful for selecting suitable parameters such as laser pulse duration and particle size in experimental research and practical works. Copyright © Taylor &Francis Group, LLC.

Arefi M.,University of Kashan | Khoshgoftar M.J.,Tarbiat Modares University
Smart Structures and Systems | Year: 2014

The present paper develops piezo-thermo-elastic analysis of a thick spherical shell for generalized functionally graded piezoelectric material. The assumed structure is loaded under thermal, electrical and mechanical loads. The mechanical, thermal and electrical properties are graded along the radial direction based on a power function with three different non homogenous indexes. Primarily, the non homogenous heat transfer equation is solved by applying the general boundary conditions, individually. Substitution of stress, strain, electrical displacement and material properties in equilibrium and Maxwell equations present two non homogenous differential equation of order two. The main objective of the present study is to improve the relations between mechanical and electrical loads in hollow spherical shells especially for functionally graded piezoelectric materials. The obtained results can evaluate the effect of every non homogenous parameter on the mechanical and electrical components. Copyright © 2014 Techno-Press, Ltd.

Masehian E.,Tarbiat Modares University | Sedighizadeh D.,Tarbiat Modares University
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2010

In this paper a novel method is presented for robot motion planning with respect to two objectives, the shortest and smoothest path criteria. A Particle Swarm Optimization (PSO) algorithm is employed for global path planning, while the Probabilistic Roadmap method (PRM) is used for obstacle avoidance (local planning). The two objective functions are incorporated in the PSO equations in which the path smoothness is measured by the difference of the angles of the hypothetical lines connecting the robot's two successive positions to its goal. The PSO and PRM are combined by adding good PSO particles as auxiliary nodes to the random nodes generated by the PRM. The proposed algorithm is compared in path length and runtime with the mere PRM method searched by Dijkstra's algorithm, and the results showed that the generated paths are shorter and smoother and are calculated in less time. ©2010 IEEE.

Rezghi M.,Tarbiat Modares University | Obulkasim A.,Erasmus Medical Center
Expert Systems with Applications | Year: 2014

Principal component analysis (PCA) is one of the powerful dimension reduction techniques widely used in data mining field. PCA tries to project the data into lower dimensional space while preserving the intrinsic information hidden in the data as much as possible. Disadvantage of PCA is that, extracted principal components (PCs) are linear combination of all features, hence PCs are may still contaminated with noise in the data. To address this problem we propose a modified version of PCA called noise free PCA (NFPCA), in which regularization is introduced during the PCs extraction step to mitigate the effect of noise. Potentials of the proposed method is assessed in two important application of high-dimensional molecular data: classification and survival prediction. Multiple publicly available real-world data sets are used for this illustration. Experimental results show that, the NFPCA produce highly informative than the ordinary PCA method. This is largely due to the fact that the NFPCA suppress the effect of noise in the PCs more efficiently with minimum information lost. The NFPCA is a promising alternative to existing PCA approaches not only in terms of highly informative PCs, but also its relatively cheap computational cost. © 2014 Elsevier Ltd. All rights reserved.

Ahmadi A.,Tarbiat Modares University | Beheshtian J.,Shahid Rajaee Teacher Training University | Hadipour N.L.,Tarbiat Modares University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

The interaction of NH3 with aluminum nitride nanotubes (AlNNTs) has been investigated on the basis of density functional theory calculations. Unlike the case of carbon nanotubes, it was found that the NH3 can be chemically adsorbed on the top of the aluminum atom of AlNNTs. The NH 3 adsorption energy of AlNNTs is typically more than that of BNNTs. Despite the strong interaction, the chemical modification of AlNNTs with the NH3 results in little changes in the electronic properties of AlNNTs. Morokuma, NBO and density of states analyses reveal that the nature of this interaction is mainly electrostatic rather than covalent. © 2011 Elsevier B.V. All rights reserved.