Mearaji F.,Islamic Azad University at Tehran |
International Journal of Refractory Metals and Hard Materials | Year: 2014
In this study, AlN whiskers were prepared in a tube furnace at 1000 °C for 1 h under 500 cc/min nitrogen gas flow. Al powders with particle sizes of 3 μm and 45 μm and NH4Cl were used as raw materials. SEM, TEM and XRD analyses were applied to characterize AlN whiskers. The diameters of AlN whiskers were from 140 nm to 340 nm by using different amounts of NH 4Cl and 3 μm Al powder. In the case of using NH4Cl more than 40 wt.%, pure AlN without any unreacted Al was formed as final product. Using NH4Cl and Al powder with a particle size of 45 μm leads to obtain AlN whiskers with 630 nm to 870 nm in diameter. By adding 50 wt.% NH 4Cl, pure AlN was formed. The diameter of the whiskers was increased by increasing the NH4Cl content in starting materials (about 200 nm). Also increase in diameter of AlN whisker was resulted by using coarse Al powder. By adding NH4Cl to Al, thermodynamically spontaneous chlorination-nitridation reactions in vapor phase were increased and whiskers and pure AlN powder were produced. It seems that the formation of whiskers in this work was related to solid-gas (VS) mechanisms. © 2014 Elsevier Ltd.
Abdali M.,Islamic Azad University at Tehran |
Materials Science in Semiconductor Processing | Year: 2014
Recent advances in etching agents and techniques on the fabrication of double-walled carbon nanotubes (DWCNTs) have introduced various techniques and devices based on nanotube technology. The present study evaluates the inter-shell interaction of DWCNT through density functional theory (DFT) and charge transfer model. The results showed that the band structure of a DWCNT is determined by super positioning of the band structures of the two individual CNT constituting the DWCNT. In next step, interwall conductance the electronic properties of DWCNT were studied through the band-structure approach. Our assessments have shown that at lower potentials the amount of intershell leakage current is negligible. © 2013 Elsevier Ltd. All rights reserved.
Karimyan P.,Amirkabir University of Technology |
Gharehpetian G.B.,Amirkabir University of Technology |
Abedi M.,Amirkabir University of Technology |
International Journal of Electrical Power and Energy Systems | Year: 2014
This paper proposes a new long term scheduling for optimal allocation and sizing of different types of Distributed Generation (DG) units in the distribution networks in order to minimize power losses. The optimization process is implemented by continuously changing the load of the system in the planning time horizon. In order to make the analysis more practical, the loads are linearly changed in small steps of 1% from 50% to 150% of the actual value. In each load step, the optimal size and location for different types of DG units are evaluated. The proposed approach will help the distribution network operators (DNOs) to have a long term planning for the optimal management of DG units and reach the maximum efficiency. On the other hand, since the optimization process is implemented for the entire time period, the short term scheduling is also possible. The proposed method is applied to IEEE 33-bus test system using both the analytical approach and particle swarm optimization (PSO) algorithm. The simulation results show the effectiveness and acceptable performance of the proposed method. © 2013 Elsevier Ltd. All rights reserved.
Keramati M.,Semnan University |
Akbari A.,IUST |
Keramati M.,University of Tehran
Proceedings of the 3rd International Conference on Computer and Knowledge Engineering, ICCKE 2013 | Year: 2013
Attack graphs are efficient tools for detecting possible attacks in the network and their causes. By analyzing attack graphs and eliminating causes of attacks in the networks, we can immune networks against known intrusions. The main shortcoming of attack graphs is that they give no information about the damages of the possible attacks in the network. On the other hand by attack graphs, we can only analyze network security qualitatively. In this paper we propose a method that can measure the impact of each shown attack in the attack graph on the security parameters (Confidentiality, Availability and Integrity) of the network. In the proposed approach we have defined some security metrics by combining CVSS framework and attack graph. The main problem with the existing approaches is that, they cannot consider interrelation between vulnerabilities of the network efficiently. Our defined security metrics can address this issue and help us to assess network security quantitatively by analyzing attack graphs. By applying proposed security metrics on each network's attack graph we can find the most perilous vulnerability in the network. © 2013 IEEE.
Ramak R.,K. N. Toosi University of Technology |
Valadan Zouj M.J.,K. N. Toosi University of Technology |
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2015
There are a considerable number of mixed pixels in remotely sensed images. Different sub-pixel analyses have been recently developed correspondingly. A well-known method is linear spectral unmixing which obtains an abundance of each endmember in a given pixel. This model assumes that each pixel is a linear combination of all endmembers in a scene. This assumption is not correct since each pixel can only be a composition of some surrounding endmembers. Even though, a fully mathematical technique is used for spectral analysis, the output of the model may not represent the physical nature of the objects over the pixel under test. In this regard, this paper proposes a Local Linear Spectral Unmixing which is based on neighbor pixels classes. Having classified the image, using a supervised classifier, it is scanned through a window of an appropriate size. For each pixel at the center of the window, the endmember matrix is formed only based on the majority classes existed in the window. Then the amount of each one is calculated. The LLSU method was evaluated on an AVIRIS data set collected from an agricultural area of northern Indiana. The results of the proposed method demonstrate a significant improvement in comparison with the LSU results. Moreover, due to the dimension reduction of the endmember matrix in this method, the computation time of the LLSU speeds up by three to eight times compared to the conventional Linear Spectral Unmixing method. As a result, the proposed method is efficient over the spectral unmixing tasks.
Tabatabaei S.M.,IUST |
2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 | Year: 2013
Vertebroplasty is an invasive treatment which not only reduces pain in patient but also stabilize fractured vertebra. Usage of Vertebroplasty has increasing rate among surgeons in recent decay. In this study we investigate the effects of cement properties and distribution on mechanical response of lumbar spine. A three-dimensional finite element model created from CT images of L1-L3. According to clinical observations and recent studies we considered that L2 augmented with three different volumes. Loadings were assumed to be pure momentum which applied in three anatomical directions (axial rotation, flexion and lateral bending). Segments range of motion, ligaments forces and intradiscal pressure had a good agreement with experimental results. Cement augmentation increases max von misses stress in L2 cancellous bone. Cement augmentation decreased segments range of motion and increased total stiffness of model. © 2013 IEEE.
Peyvandi-Pour A.,IUST |
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011
Existing Statistical fault localization approaches locate bugs by testing statistical behavior of each predicate and propose fault relevant predicates as nearest points to faults. In this paper, we present a novel statistical approach employing a weighted graph, elicited from run-time information of a program. The predicates are considered as nodes; an edge is denoting a run-time path between two predicates and its label is the number of simultaneous occurrence of connected predicates in the run. Firstly, a typical graph, representing failed run is contrasted with whole graphs of passed runs to find the two most similar graphs of the passed runs and failed runs and discriminative edges are chosen as suspicious edges. In next phase, we statistically test the distribution of the suspicious edges to find the most fault relevant edges; to this end, we apply a normality test on the suspicious edges and based on the test result, we use a parametric or non-parametric hypothesis testing to discover the most fault relevant edges. We conduct the experimental study based on Siemens test suite and the results show the proposing approach is remarkable. © 2011 Springer-Verlag.
Nasiri M.,IUST |
Minaei B.,IUST |
3rd International Conference on eLearning and eTeaching, ICeLeT 2012 | Year: 2012
In this paper, we describe an educational data mining (EDM) case study based on the data collected from learning management system (LMS) of e-learning center and electronic education system of Iran University of Science and Technology (IUST). Our main goal is to illustrate the applications of EDM in the domain of e-learning and online courses by implementing a model to predict academic dismissal and also GPA of graduated students. The monitoring and support of freshmen and first year students are considered very significant in many educational institutions. Consequently, if there are some ways to estimate probability of dismissal, drop out and other challenges within the process of the graduation, and also capable tools to predict GPA or even semester by semester grades, the university officials can design and improve more efficient strategies for education systems especially for e-learning ones which include less known and more complicated problems. To achieve the mentioned goal, a common methodology of data mining has been utilized which is called CRISP. Our results show that there can be confident models for predicting educational attributes. Currently there is an increasing interest in data mining and educational systems, making educational data mining as a new growing research community. © 2012 IEEE.
Keramati M.,IUST |
2012 6th International Symposium on Telecommunications, IST 2012 | Year: 2012
Nowadays computer networks face with multi-step attacks, during which, intruder exploits multiple vulnerabilities in a specific manner to attack his victim. So for assessing network security it is essential to understand which vulnerabilities and how must be exploited by the attacker to reach his goal. Such information can be obtained by modeling the network with attack graph. Current approaches for security assessment lack quantitative nature whereas for accurate decision making in security improvement of the network, it is necessary to measure security risk of possible attacks in the network quantitatively. In this paper an attack graph based security metric was proposed that can measure security risk of possible attacks in the network quantitatively. This metric can compute risk degradation options in terms of maximizing security and minimizing cost. Our security metric can be used to calculate total network security quantitatively and can be used for performing cost-benefit tradeoff in network hardening systems. The result of using the proposed metric with one network hardening framework on one well-known example is shown in this paper. © 2012 IEEE.
PubMed | Punjab Agricultural University and IUST
Type: | Journal: International journal of food science | Year: 2016
Cereal brans singly and in combination were blended at varying levels (5 and 10%) for development of Chapattis. Cereal bran enriched Chapattis were assessed for quality and physicochemical characteristics. On the basis of quality assessment, 10% enrichment level for Chapatti was the best. Moisture content, water activity, and free fatty acids remained stable during the study period. Quality assessment and physicochemical characteristics of bran enriched Chapattis carried out revealed that dough handling and puffing of bran enriched Chapattis prepared by 5 and 10% level of bran supplementation did not vary significantly. All types of bran enriched Chapattis except rice bran enriched Chapattis showed nonsticky behavior during dough handling. Bran enriched Chapattis exhibited full puffing character during preparation. The sensory attributes showed that both 5 and 10% bran supplemented Chapattis were acceptable.