Taghavifar H.,Islamic Azad University at Urmia
Energy Conversion and Management | Year: 2017
Optimization process of energy-related devices is gaining an undivided attention of industrial sectors due to cost effectiveness and practicality attributes. Diesel engines are the most efficient in producing power, although there is a great capacity that has not been fully exploited. Therefore the simplex-based optimization is addressed to enhance the indicated torque (IT), combustion noise (CN), and swirl ratio (SR) of the engine at the same time. The optimum solution is reached at RunID 27, which demonstrates 7.7% increase in IT, 0.19% decrease in CN, and 21.98% increase in SR compared to those of baseline mode. In the present study, IT and CN vary inversely, thus the modification in injection schemes and chamber geometry have to be considered without putting a penalty on another. It was indicated that Min. swirl and torque cases have significantly reduced bowl volume, however, the case with the lowest swirl has lower centerline depth. In addition, it is determined that Max. torque and swirl are obtainable with a big bowl segment, although it was observed that a shallow combustion chamber is expected to induce higher torque. The higher torque is associated with more uniformity of mixture (0.8484) and pressure peak (13.98 MPa) that is plausible with a fitted spray injection with chamber walls coordination, reducing the spray-wall impingement. © 2017 Elsevier Ltd
Zavvari M.,Islamic Azad University at Urmia
Journal of the Optical Society of America B: Optical Physics | Year: 2015
A single-photon detector is presented with quantum dot (QD) layers in its absorption region. The proposed detector is a three-terminal device in which a QD-based absorption region is integrated with an avalanche multiplication region through a tunneling barrier and the applied bias of each region can be controlled separately. The mid-infrared single photons (λ 3 5 μm) can be absorbed in QDs and the photogenerated electrons are drifted to the avalanche region to trigger an avalanche and generate an output pulse. Since the absorption region consists of doped QD layers, it is expected to have higher orders of dark count. However, by separately controlling the bias and keeping the electric field of absorption region low, the dark current of this region can be reduced. Our simulations predict a single-photon detection efficiency (SPQE) of about 0.7 at T = 50 K for the proposed detector. At higher temperatures, the dark count rate increases and results in reduced SPQE. To increase the operation temperature, resonant tunneling barriers (RTB) are included in the absorption region to inhibit the thermally excited electrons from contributing to the dark current generation. Our results show that the SPQE for the RTB-based device is about 0.65 at T = 77 K, which is approximately equivalent to the SPQE of the device without RTB at T= 50 K. © 2015 Optical Society of America.
Golshannavaz S.,Islamic Azad University at Urmia
Journal of Intelligent and Fuzzy Systems | Year: 2014
This research investigates the simultaneous allocation of optimally sited and sized distributed generation (DG) units along with the capacitor banks for power loss minimization in smart automated distribution systems (ADSs). Moreover, network reconfiguration as one of the salient features of ADSs realized by remotely controlled switches (RCSs) is proposed to be incorporated in the simultaneous optimal siting and sizing process of DGs and capacitors. As the structure of the system would vary in the solution process, all of the buses are considered as the candidate bus to connect DGs and capacitors. Several scenarios have been considered for concurrent allocation of DGs, capacitors and also reconfiguration in loss minimization problem to interrogate the performance of the proposed method. Binary genetic algorithm (BGA) is employed to simultaneously identify the optimal site and size of DGs and capacitors as well as the system structure. The proposed algorithm is effectively implemented and then validated on the well-known IEEE 33-bus standard distribution system. Assessing the different scenarios reveals that incorporating network reconfiguration in combined allocation of DG and capacitor, would result in superior power loss minimization and also affects the optimal site and size of DGs and capacitors. © 2014-IOS Press and the authors. All rights reserved.
Jafarian A.,Islamic Azad University at Urmia
International Journal of Artificial Intelligence | Year: 2014
Recently, there has been a considerable amount of interest and practice in solving many problems of several applied fields by fuzzy polynomials. In this paper, we intend to offer a new method for finding a solution of fully fuzzy polynomial with degree n, by using an artificial fuzzified feed-forward neural network. This neural net has the ability to get fuzzy vector as an input, and calculates its corresponding fuzzy output. It is clear that the input-output relation for each unit of fuzzy neural network is defined by the extension principle of Zadeh. In this work, a cost function is also defined for the level sets of fuzzy output and fuzzy target. Then we derive a learning algorithm from the cost function for adjusting three parameters of each triangular fuzzy weight. Consequently, our approach is illustrated by computer simulations on numerical examples. It is worthwhile to mention that, the application of this method in fluid mechanics has been shown by an example. © 2014 by IJAI CESER PUBLICATIONS.
Mostafaei H.,Islamic Azad University at Urmia |
Meybodi M.R.,Amirkabir University of Technology
Wireless Personal Communications | Year: 2013
In wireless sensor networks, when each target is covered by multiple sensors, we can schedule sensor nodes to monitor deployed targets in order to improve lifetime of network. In this paper, we propose an efficient scheduling method based on learning automata, in which each node is equipped with a learning automaton, which helps the node to select its proper state (active or sleep), at any given time. To study the performance of the proposed method, computer simulations are conducted. Results of these simulations show that the proposed scheduling method can better prolong the lifetime of the network in comparison to similar existing methods. © 2012 Springer Science+Business Media New York.
Zavvari M.,Islamic Azad University at Urmia |
Ahmadi V.,University of Tehran
IEEE Electron Device Letters | Year: 2013
A single-photon detector based on an avalanche quantum dot IR photodetector is presented and designed for self-quenching and self-recovering operation at IR wavelength. The device consists of dot layers and resonant tunneling barriers in the absorption region. An additional layer, called the transient carrier buffer, is added to trap the backward holes. For an avalanche process, the accumulation of backward-traveling-avalanche-generated holes leads to a reduction in the electric field of the multiplication region and avalanche gain, and consequently, the detector is quenched. The detector is self-recovered by thermionic emission and tunneling currents. We study the self-quenching and self-recovery performance of the device. A detection efficiency of around 8% is obtained. © 1980-2012 IEEE.
Mostafaei H.,Islamic Azad University at Urmia
Computer Communications | Year: 2015
Barrier coverage is one of the most important applications of wireless sensor networks. It is used to detect mobile objects are entering into the boundary of a sensor network field. Energy efficiency is one of the main concerns in barrier coverage for wireless sensor networks and its solution can be widely used in sensor barrier applications, such as intrusion detectors and border security. In this work, we take the energy efficiency as objectives of the study on barrier coverage. The cost in the present paper can be any performance measurement and normally is defined as any resource which is consumed by sensor barrier. In this paper, barrier coverage problem is modeled based on stochastic coverage graph first. Then, a distributed learning automata-based method is proposed to find a near optimal solution to the stochastic barrier coverage problem. The stochastic barrier coverage problem seeks to find minimum required number of sensor nodes to construct sensor barrier path. To study the performance of the proposed method, computer simulations are conducted. The simulation results show that the proposed algorithm significantly outperforms the greedy based algorithm and optimal method in terms of number of network barrier paths. © 2014 Elsevier B.V. All rights reserved.
Abdollahi A.,Islamic Azad University at Urmia
Physica B: Condensed Matter | Year: 2013
Ab initio calculations for the thermal properties of ZrC and ZrN have been performed by using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA). Pressure-temperature-dependent thermodynamic properties including the bulk modulus, thermal expansion, thermal expansion coefficient, heat capacity at constant volume and constant pressure were calculated using three different models based on the quasi-harmonic approximation (QHA): the Debye-Slater model, Debye-Grüneisen model and full quasi-harmonic model (that requires the phonon density of states at each calculated volume). Also the empirical energy corrections are applied to the results of three models. The calculated values are in good agreement with experimental results. It is found that the full quasi-harmonic model provides more accurate estimates in comparison with the other models. © 2012 Elsevier B.V.
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.
Ranji A.,Islamic Azad University at Urmia
Journal of Midwifery and Women's Health | Year: 2012
Introduction: The aims of this descriptive study were to determine the prevalence of illegal induced abortion among participants, the factors that influence decision making to have an abortion, and the health consequences of abortion in Iran. Methods: Women who attended health centers or an antenatal clinic in Iran were interviewed to complete a questionnaire. Results: Among the 2705 participants, 17% had experienced at least 1 illegal induced abortion. Education level, family income, religion, ethnicity, number of children, and age at marriage are associated with having an induced abortion. One-third of abortions (33%) were performed by nonmedical providers. The desire to stop or postpone childbearing and family economic problems were the most common reasons for having an abortion. Most women (84%) experienced a complication of abortion that required hospitalization. Discussion: Strategies to prevent abortion complications are needed and could include training midwives and general physicians to perform abortions and promoting the availability of post-abortion care. © 2012 by the American College of Nurse-Midwives.