Faculty of Shahreza Pardis The Shahreza Campus of University of Isfahan, established in 2007, stands as a beacon of academic excellence in central Iran, offering a comprehensive range of programs across three main faculties: Engineering, Basic Sciences, and Humanities. With state-of-the-art research facilities including advanced materials testing labs, robotics centers, and a newly established AI research hub, the campus fosters innovation and cutting-edge research.
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Scientia Iranica (23453605) 14(6)pp. 631-640
In this paper, reinforcement learning is used in order to model the reputation of buying and selling agents. Two important factors, quality and price, are considered in the proposed model. Each selling agent learns to evaluate the reputation of buying agents, based on their profits for that seller and uses this reputation to dedicate a discount for reputable buying agents. Also, selling agents learn to maximize their expected profits by using reinforcement learning to adjust the quality and price of the products, in order to satisfy the buying agents' preferences. In contrast, buying agents evaluate the reputation of selling agents based on two different factors: Reputation based on quality and price. Therefore, buying agents avoid interacting with disreputable selling agents. In addition, the fact that buying agents can have different priorities on the quality and price of their goods is taken into account. The proposed model has been implemented with Aglet and tested in a large-sized marketplace. The results show that selling/ buying agents that use the proposed algorithms in this paper obtain more satisfaction than the other selling/buying agents. © Sharif University of Technology, December 2007.
Journal of Theoretical and Applied Electronic Commerce Research (07181876) 2(1)pp. 1-17
In this paper, we propose a market model which Is based on reputation and reinforcement learning algorithms for buying and selling agents. Three important factors: quality, price and delivery-time are considered in the model. We take into account the fact that buying agents can have different priorities on quality, price and delivery-time of their goods and selling agents adjust their bids according to buying agents preferences. Also we have assumed that multiple selling agents may offer the same goods with different qualities, prices and delivery-times. In our model, selling agents learn to maximize their expected profits by using reinforcement learning to adjust product quality, price and delivery-time. Also each selling agent models the reputation of buying agents based on their profits for that seller and uses this reputation to consider discount for reputable buying agents. Buying agents learn to model the reputation of selling agents based on different features of goods: reputation on quality, reputation on price and reputation on delivery-time to avoid interaction with disreputable selling agents. The model has been implemented with Aglet and tested in a large-sized marketplace. The results show that selling/buying agents that model the reputation of buying/selling agents obtain more satisfaction rather than selling/buying agents who only use the reinforcement learning. © 2007 Universidad de Talca.
Jannati, M. ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Baghaee h.r., pp. 203-207
Almost 70-90% of faults in extra high voltage (EHV) transmission lines in modern interconnected power systems are intrinsically transient. The necessity of rapid fault clearing results in fast developing of protection equipments. Morever, need for reliable supplying of loads, lead to improve in single phase auto-reclosing equipments. In this paper, a new method is proposed to reduce dead time of transmission lines. Leads to improve the performance and efficiency of single phase auto-reclosing. In the occurrence of permanent faults, the proposed yardstick is accurate and authentic to diagnose fault's type (transient or permanent). To validate accuracy and authenticity of proposed method, a 765 kV transmission system is simulated in Electromagnetic Transients Program software and results are presented. © 2008 IEEE.
A novel approach for fault detection in high voltage DC transmission systems using neural networks is presented. In the presented method, at first, Harmonics of voltage waveform in rectifier side are derived rapidly by using an adaptive linear neuron. Then, different types of faults including DC line fault, AC system Fault and Converter's faults are detected property using proposed criterion. In the under study voltage DC transmission systems system, rectifier and its controllers and required filters is modeled completely. A proposed criterion is tested on a high voltage DC system by computer simulation performed in MATLAB/Simulink environment. Simulation resultes demonstrates that the proposed approach can be used for online fault detection in high voltage DC systems. © 2008 IEEE.
Jannati, M. ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Baghaee h.r., pp. 215-220
Reducing dead time of high voltage power transmission lines is one of the most important issues in power system protection. Besides, need for reducing the dead time is a matter of grave concern to increase voltage level of power transmission lines and insulation coordination. In this paper, different methods for decreasing the capacitive coupling and consequently reducing the dead time of power transmission lines are compared. This leads to faster quenching of secondary arc and limit the transient over voltage. Moreover, a novel hybrid approach is presented for reducing dead time of power transmission lines and faster quenching of secondary arc current. Simulations performed in electromagnetic transient program are performed for different cases. Simulation results show that dead time is reduced appropriately by proposed method.
Simulation (17413133) 84(12)pp. 601-610
In modern interconnected power systems, almost 70-90% of faults in high voltage Power Transmission Lines (PTLs) are intrinsically transient. The necessity of rapid fault clearing results in fast developing of protection equipments. Moreover, need for reliable supplying of loads, lead to improvements in single-phase autoreclosure (SPAR) equipments. An ADAptive LInear NEuron (ADALINE) is suitable for important applications such as protection of power systems and digital relays. In this paper, a novel simple adaptive SPAR algorithm is introduced. This algorithm is based on learning error function of an ADALINE. It can be distinguished by fault type (transient fault or a permanent fault), and if the fault is permanent, autoreclosure should be blocked. This leads to improve the performance and efficiency of SPAR. Electromagnetic transients program-based simulation results show that the autoreclosure scheme based on learning error function of ADALINE on a typical 400 kV circuit for various system and fault conditions improves the reliability of fault discrimination.© 2008 The Society for Modeling and Simulation International.
Baghaee h.r., ,
Jannati, M. ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Rastegar h., pp. 209-214
Modern power systems are prone to widespread failures. With the increase in power demand, operation and planning of large interconnected power system are becoming more and more complex, so power system will become less secure. Operating environment, conventional planning and operating methods can leave power system exposed to instabilities. Voltage instability is one of the phenomena which have result in a major blackout. Moreover, with the fast development of restructuring, the problem of voltage stability has become a major concern in deregulated power systems. To maintain security of such systems, it is desirable to plan suitable measures to improve power system security and increase voltage stability margins. FACTS devices can regulate the active and reactive power control as well as adaptive to voltage-magnitude control simultaneously because of their flexibility and fast control characteristics. Placement of these devices in suitable location can lead to control in line flow and maintain bus voltages in desired level and so improve voltage stability margins. This paper presents a Genetic Algorithm (GA) based allocation algorithm for FACTS devices considering Cost function of FACTS devices and power system losses. Proposed algorithm is tested on IEEE 30 bus power system for optimal allocation of multi-type FACTS devices and results are presented.
Baghaee h.r., ,
Jannati, M. ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Jazebi s., pp. 162-166
as power transfer increases, operation of power system become gradually more complex. Short circuit level increases and so power system will become less secure. Moreover, the problem of power system, security has become a mater of grave concern in the deregulated power industry. FACTS devices can control power flow because of their flexibility and fast control characteristics. Placement of these devices in suitable location can lead to control in line flow and maintain bus voltages in desired level and so improve power system security. This paper presents a novel algorithm for allocation of FACTS devices based on Genetic Algorithm (GA). Cost function of FACTS devices and power system losses are considered in this algorithm. Proposed algorithm is tested on IEEE 30 bus power system for optimal allocation of multi-type FACTS devices and results are presented © 2008 IEEE.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (03029743) 5097pp. 681-692
In this paper, we propose a flexible parallel ant colony algorithm for classification rule discovery in the large databases. We call this algorithm Parallel Ant-Miner2. This model relies on the extension of real behavior of ants and data mining concepts. The artificial ants are firstly generated and separated into several groups. Each group is assigned a class label which is the consequent parts of the rules it should discover. Ants try to discover rules in parallel and then communicate with each other to update the pheromones in different paths. The communication methods help ants not to gather irrelevant terms of the rule. The parallel executions of ants reduce the speed of convergence and consequently make it possible to extract more new high quality rules by exploring all search space. Our experimental results show that the proposed model is more accurate than the other versions of Ant-Miner. © 2008 Springer-Verlag Berlin Heidelberg.
Energy Conversion and Management (01968904) 49(10)pp. 2629-2641
The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, which is an important subset of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for New England and IEEE68 bus test systems. © 2008 Elsevier Ltd. All rights reserved.
Loading of today power systems continuously increases especially in the developed countries and liberalized electricity markets. On the other hand, operating points of a power system are acceptable in the feasible region usually surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, a major concern of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for two bus, New England and IEEE 68 bus test systems. ©2008 IEEE.
International Review of Electrical Engineering (25332244) 4(5)pp. 985-993
Nearly 80% of faults in extra high voltage transmission lines are intrinsically transient. The necessity of rapid fault clearing has resulted in fast development of protection equipments. Moreover, need for reliable supply of loads has led to improvements in single phase auto-reclosing equipments. The success of the single phase auto-reclosing depends on the extinction of the secondary arc. In this paper, a novel adaptive single phase auto-reclosure is introduced. This auto-reclosure is based on the faulted phase voltage fundamental harmonic to discriminate between transient and permanent faults and also detect the extinguishing time of secondary arc.Validation of the proposed algorithm is verified via various simulations in EMTP/ATP software and experimental test. © 2009 Praise Worthy Prize S.r.l.
International Journal of Hydrogen Energy (03603199) 34(5)pp. 2396-2407
This paper presents exergy analysis of a hybrid solid oxide fuel cell and gas turbine (SOFC/GT) system in comparison with retrofitted system with steam injection. It is proposed to use hot gas turbine exhaust gases heat in a heat recovery steam generator to produce steam and inject it into gas turbine. Based on a steady-state model of the processes, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. The components with the highest proportion of irreversibility in the hybrid systems are identified and compared. It is shown that steam injection decreases the wasted exergy from the system exhaust and boosts the exergetic efficiency by 12.11%. Also, 17.87% and 12.31% increase in exergy output and the thermal efficiency, respectively, is demonstrated. A parametric study is also performed for different values of compression pressure ratio, current density and pinch point temperature difference. © 2008 International Association for Hydrogen Energy.
Applied Mathematics Letters (18735452) 22(10)pp. 1571-1576
In this work we show that among all n-vertex graphs with edge or vertex connectivity k, the graph G = Kk ∨ (K1 + Kn - k - 1), the join of Kk, the complete graph on k vertices, with the disjoint union of K1 and Kn - k - 1, is the unique graph with maximum sum of squares of vertex degrees. This graph is also the unique n-vertex graph with edge or vertex connectivity k whose hyper-Wiener index is minimum. © 2009 Elsevier Ltd. All rights reserved.
The correct use of constraints within relational DBMSs is essential for one to take full advantage of the significant benefits offered by the relational model. The use of formal descriptions to capture constraints early in the process may be appropriate in this regard. The theory of relational databases has much in common with the mathematical structures central to the Z notation. In this position paper, we describe how create suitable tables and sql code for Z specifications that have been made according to UML diagrams by Robert's methods[5].Here We use the Z notation as our specification language, and SQL as our implementation language. © 2009 IEEE.
In this paper, a shape reconstruction method for electromagnetic tomography based on contour deformations exploiting level set method is proposed. The algorithm is able to reconstruct the shape of multiple perfect conducting objects in two-dimensions. Incident waves are assumed to be TM (Transverse Magnetic) plane waves. The fast marching method is used in reinitialization process which has drastically improved the velocity of the reconstruction. The numerical results clearly shows that this inversion algorithm provides accurate reconstructions of objects from initial guess. ©2009 IEEE.
Discrete Applied Mathematics (0166218X) 158(3)pp. 219-221
A block graph is a graph whose blocks are cliques. For each edge e = u v of a graph G, let Ne (u) denote the set of all vertices in G which are closer to u than v. In this paper we prove that a graph G is a block graph if and only if it satisfies two conditions: (a) The shortest path between any two vertices of G is unique; and (b) For each edge e = u v ∈ E (G), if x ∈ Ne (u) and y ∈ Ne (v), then, and only then, the shortest path between x and y contains the edge e. This confirms a conjecture of Dobrynin and Gutman [A.A. Dobrynin, I. Gutman, On a graph invariant related to the sum of all distances in a graph, Publ. Inst. Math., Beograd. 56 (1994) 18-22]. © 2009 Elsevier B.V. All rights reserved.
Osinga, S.A. ,
Kramer, M.R. ,
Hofstede, G.J. ,
Roozmand, O. ,
Beulens, A.J. Lecture Notes in Economics and Mathematical Systems (00758442) 645pp. 177-188
This paper investigates the effect of a selected top-down measure (whatif scenario) on actual agent behaviour and total system behaviour by means of an agent-based simulation model, when agents' behaviour cannot fully be managed because the agents are autonomous. The Chinese pork sector serves as case. A multilevel perspective is adopted: the top-down information management measures for improving pork quality, the variation in individual farmer behaviour, and the interaction structures with supply chain partners, governmental representatives and peer farmers. To improve quality, farmers need information, which they can obtain from peers, suppliers and government. Satisfaction or dissatisfaction with their personal situation initiates change of behaviour. Aspects of personality and culture affect the agents' evaluations, decisions and actions. Results indicate that both incentive (demand) and the possibility to move (quality level within reach) on farmer level are requirements for an increase of total system quality. A more informative governmental representative enhances this effect. © Springer-Verlag Berlin Heidelberg 2010.
International Journal Of Thermodynamics (13019724) 13(4)pp. 153-160
In this paper, an exergetic performance analysis of unglazed transpired collectors (UTC), as well as an exergetic optimization of a typical UTC is performed. A steady-state model is used to calculate heat transfers and pressure drop through the perforated plate and back wall. In order to maximize the exergy efficiency, the optimization procedure is carried out for some important parameters including plate hole diameter and hole pitch. A maximum efficieny of 2.28% is obtained. In spite of all the thermal performance advantages, the exergetic efficiency of the UTC is significantly lower than its energetic efficiency. Other parameters such as incident solar radiation, approach velocity, plate hole diameter and pitch are examined in the parametric study.
Inverse Problems (13616420) 26(9)
A shape reconstruction method for microwave imaging of perfect electric conductor objects based on contour deformations exploiting the level set method is presented. The calculation of the method of moments impedance matrix in the direct scattering part is done in a single step using the relation of the original and adjoint systems. In the inverse scattering part the fast marching method is used in the re-initialization process which has drastically improved the velocity of the reconstruction. Based on the simulation results the inverse scattering method presented in this paper has proved to be efficient and accurate, giving highly accurate reconstructions in relatively short computational times for single or multiple objects and also in the presence of noise. The accuracy and efficiency of the method suggest that it could usefully be extended to the three-dimensional case. © 2010 IOP Publishing Ltd.
In this paper, a shape reconstruction method for electromagnetic tomography based on contour deformations exploiting level set method is proposed. The algorithm is able to reconstruct the shape of multiple perfect conducting objects in two-dimensions. Incident waves are assumed to be TM (Transverse Magnetic) plane waves. The fast marching method is used in reinitialization process which has drastically improved the velocity of the reconstruction. The numerical results clearly shows that this inversion algorithm provides accurate reconstructions of objects from initial guess. ©2010 IEEE.
Bulletin of the Korean Mathematical Society (10158634) (4)pp. 663-673
This work was intended as an attempt to introduce and investigate the Connes-amenability of module extension of dual Banach algebras. It is natural to try to study the weak*-continuous derivations on the module extension of dual Banach algebras and also the weak Connesamenability of such Banach algebras. © 2010 The Korean Mathematical Society.
Asia-Pacific Power and Energy Engineering Conference, APPEEC (21574847)
Various studies have showed that about 70 to 90% of single line to ground faults occurred on High voltage transmission lines have transient nature. This type of faults is cleared by temporary outage (by the single phase auto-reclosure). The interval between opening and reclosing of the faulted phase circuit breakers is named "Dead Time" that is varying about several hundred milliseconds. For adjustment of traditional single phase auto-reclosures that usually are not intelligent, it is necessary to calculate the dead time in the off-line condition precisely. If the dead time used in adjustment of single phase auto-reclosure is less than the real dead time, the reclosing of circuit breakers threats the power systems seriously. So in this paper a novel approach for precise calculation of dead time in power transmission lines based on the network equivalencing in time domain is presented. This approach has extremely higher precision in comparison with the traditional method based on Thevenin equivalent circuit. For comparison between the proposed approach in this paper and the traditional method, a comprehensive simulation by EMTP-ATP is performed on an extensive power network. ©2010 IEEE.
Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearings, and shock absorbers to tires. Rubber has good properties and is thermal and electrical resistant. We used carbon nanotube in rubber and modeled this composite with ABAQUS software. Because of hyperelastic behavior of rubber we had to use a strain energy function for nanocomposites modeling. We tested a sample of rubber and gained uniaxial, biaxial and planar test data and then used this data to get a good strain energy function. Mooney-Rivlin form, Neo-Hookean form, Ogden form, Polynomial form, reduced polynomial form, Van der Waals form and etc, are some methods to get strain function energy. Modulus of elasticity and Poisson ratio and some other mechanical properties gained for a representative volume element (RVE) of composite in this work. We also considered rubber as an elastic material and gained mechanical properties of composite and then compared result for elastic and hyperelastic rubber matrix together.
Journal of Solid Mechanics (discontinued) (20087683) 2(1)pp. 43-49
An elastomer is a polymer with the property of viscoelasticity, generally having notably low Young's modulus and high yield strain compared with other materials. Elastomers, in particular rubbers, are used in a wide variety of products ranging from rubber hoses, isolation bearings, and shock absorbers to tires. Rubber has good properties and is thermal and electrical resistant. We used carbon nanotube in rubber and modeled this composite with ABAQUS software. Because of hyperelastic behavior of rubber we had to use a strain energy function for nanocomposites modeling. A sample of rubber was tested and gained uniaxial, biaxial and planar test data and then the data used to get a good strain energy function. Mooney-Rivlin form, Neo-Hookean form, Ogden form, Polynomial form, reduced polynomial form, Van der Waals form etc, are some methods to get strain function energy. Modulus of elasticity and Poisson ratio and some other mechanical properties gained for a representative volume element (RVE) of composite in this work. We also considered rubber as an elastic material and gained mechanical properties of composite and then compared result for elastic and hyperelastic rubber matrix together. © 2010 IAU, Arak Branch.
International Review on Modelling and Simulations (19749821) 3(6)pp. 1483-1491
Modeling of transient states is one of the important part of power system analysis. Also, the EMTP/ATP is the standard software widely used universally accepted program by the electrical engineers for digital simulation of Electromagnetic Transient phenomena, as well as electromechanically behaviors of electrical power systems. In this paper, a new method has been introduced to teach the Ms Students of electrical engineering as a part of power system transient course. Simulation of fault arc by EMTP/ATP has been presented in order to teach the principles of fault arc modeling in power systems and to analyze the simulation results of transient states. As the first part of this paper, the fault arc model in power systems and its distinction in TACS has been clarified. At the second part, the step by step simulation of arc model in TACS has been presented. The effectiveness of this method has been shown in several semesters with more than 20 students and it can improve the understanding of TACS capabilities and fault arc model. © 2010 Praise Worthy Prize S.r.l.-All rights reserved.
Jannati, M. ,
Jazebi s., ,
Vahidi, B. ,
Hosseinian s.h., S.H. Journal of Electrical Engineering and Technology (19750102) 6(6)pp. 742-749
Power transmission lines are one of the most important components of electric power system. Failures in the operation of power transmission lines can result in serious power system problems. Hence, fault diagnosis (transient or permanent) in power transmission lines is very important to ensure the reliable operation of the power system. A hidden Markov model (HMM), a powerful pattern recognizer, classifies events in a probabilistic manner based on fault signal waveform and characteristics. This paper presents application of HMM to classify faults in overhead power transmission lines. The algorithm uses voltage samples of one-fourth cycle from the inception of the fault. The simulation performed in EMTPWorks and MATLAB environments validates the fast response of the classifier, which provides fast and accurate protection scheme for power transmission lines.
Energy Conversion and Management (01968904) 52(2)pp. 1354-1363
A novel differential protection approach is introduced in the present paper. The proposed scheme is a combination of Support Vector Machine (SVM) and wavelet transform theories. Two common transients such as magnetizing inrush current and internal fault are considered. A new wavelet feature is extracted which reduces the computational cost and enhances the discrimination accuracy of SVM. Particle swarm optimization technique (PSO) has been applied to tune SVM parameters. The suitable performance of this method is demonstrated by simulation of different faults and switching conditions on a power transformer in PSCAD/EMTDC software. The method has the advantages of high accuracy and low computational burden (less than a quarter of a cycle). The other advantage is that the method is not dependent on a specific threshold. Sympathetic and recovery inrush currents also have been simulated and investigated. Results show that the proposed method could remain stable even in noisy environments. © 2010 Elsevier Ltd. All rights reserved.
Jannati, M. ,
Vahidi, B. ,
Hosseinian s.h., S.H. ,
Ahadi s.m., International Journal of Electrical Power and Energy Systems (01420615) 33(3)pp. 639-646
In modern interconnected power systems, nearly 80% of faults in high voltage transmission lines are intrinsically transient. The necessity of rapid fault clearing has resulted in fast development of protection equipments. Moreover, need for reliable supply of loads has led to improvements in single phase auto-reclosing equipments. In this paper, a novel and efficient method is proposed that leading to improved performance and efficiency of single phase auto-reclosing. In the case of occurrence of permanent faults, the proposed yardstick is accurate and authentic to diagnose fault type (transient or permanent). To validate accuracy and authenticity of the proposed method, a 400 kV transmission system is simulated using EMTP software and results are presented. © 2010 Elsevier Ltd. All rights reserved.
Roozmand, O. ,
Ghasem-aghaee, N. ,
Hofstede, G.J. ,
Nematbakhsh, M.A. ,
Baraani, A. ,
Verwaart, T. Knowledge-Based Systems (09507051) 24(7)pp. 1075-1095
Simulating consumer decision making processes involves different disciplines such as: sociology, social psychology, marketing, and computer science. In this paper, we propose an agent-based conceptual and computational model of consumer decision-making based on culture, personality and human needs. It serves as a model for individual behavior in models that investigate system-level resulting behavior. Theoretical concepts operationalized in the model are the Power Distance dimension of Hofstede's model of national culture; Extroversion, Agreeableness and Openness of Costa and McCrae's five-factor model of personality, and social status and social responsibility needs. These factors are used to formulate the utility function, process and update the agent state, need recognition and action estimation modules of the consumer decision process. The model was validated against data on culture, personality, wealth and car purchasing from eleven European countries. It produces believable results for the differences of consumer purchasing across eleven European countries. © 2011 Elsevier B.V. All rights reserved.
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