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Security Improvement of Key Management Protocols in Hierarchical Wireless Sensor Network

, M.Sc. Thesis Sharif University of Technology Mokhtari Ardakani, Ehsan (Author) ; Salmasizadeh, Mahmood (Supervisor) ; Mohajeri, Javad (Supervisor)

Abstract

Wireless sensor networks (WSNs) use many tiny sensors to monitor phenomena such as temperature, humidity, brightness and traffic, and then transmit this information to a base station using wireless channels. WSNs find applications in military, ecological, urban and health related areas. Hierarchical wireless sensor networks are kind of sensor networks that use communication entities with different capabilities in terms of energy, processing power, bandwidth, communication range and etc. In this thesis, an introduction to WSNs and their applications, characteristics and designing factors is expressed. It continues on studying the infrastructures and the role of cryptography in enhancing...

Establishment, Characterization and Evaluation of a Reference Field in a MNSR Reactor for Calibration Neutron Dosimeters

, Ph.D. Dissertation Sharif University of Technology Asgari, Afrouz (Author) ; Hosseini, Abolfazl (Supervisor) ; Choopan Dastjerdi, Mohammad Hossein (Co-Supervisor) ; Mokhtari, Javad (Co-Supervisor)

Abstract

The purpose of this research is to establish a neutron reference field for the calibration of neutron dosimeters based on the beam of the neutron radiography system in the Isfahan miniature neutron source reactor (MNSR). The aim is to address the several limitations, including the inability to achieve a wide range of dosimetry, high uncertainty due to variations in distance from the source, significant scattering, and non-uniformity. To overcome these issues, a linear, stable, and wide-range dosimetry field based on MNSR have been established, characterized and evaluated by using the variations of the reactor power. In the first step of establishing the calibration field, the linear and...

A fuzzy random minimum cost network flow programming problem [electronic resource]

, Article Journal of Industrial and Systems Engineering (JISE)-Iranian Institute of Industrial Engineering ; Article 3, Volume 6, Issue 1, Spring 2012, Page 34-47 Nematian, J. (Javad) ; Eshghi, Kourosh ; Sharif University of Technology

Abstract

In this paper, a fuzzy random minimum cost flow problem is presented. In this problem, cost parameters and decision variables are fuzzy random variables and fuzzy numbers respectively. The object of the problem is to find optimal flows of a capacitated network. Then, two algorithms are developed to solve the problem based on Er-expected value of fuzzy random variables and chance-constrained programming. Furthermore, the results of two algorithms will be compared. An illustrative example is also provided to clarify the concept

Special classes of mathematical programming models with fuzzy random variables [electronic resource]

, Article Journal of Intelligent and Fuzzy Systems, Published In: IOS Press ; Volume 19, Number 2, 2008 Eshghi, K. (Kourosh) ; Nematian, Javad ; Sharif University of Technology

Abstract

In this paper, we will discuss two special classes of mathematical programming models with fuzzy random variables. In the first model, a linear programming problem with fuzzy decision variables and fuzzy random coefficients is introduced. Then an algorithm is developed to solve the model based on fuzzy optimization method and fuzzy ranking method. In the second model, a fuzzy random quadratic spanning tree problem is presented. Then the proposed problem is formulated and solved by using the scalar expected value of fuzzy random variables. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper

A special class of fuzzy integer programming model with all different constraints [electronic resource]

, Article Scientia Iranica ; Vol. 16, No. 1, pp. 1-10, 2009 Eshghi, K. (Kourosh) ; Nematian, Javad ; Sharif University Of Technology

Abstract

In this paper, a fuzzy approach is applied to special classes of integer programming problems with all diierent constraints. In the rst model, a fuzzy integer programming model is developed to represent the all-diierent constraints in mathematical programming. In order to solve the proposed model, a new branching scheme for the Branch and Bound algorithm is also presented. In the second model, a special class of large-scale multi-objective fuzzy integer programming problems with all-diierent constraints is introduced. A solution method for the proposed model is also developed by using the decomposition technique, weighting method and Branch and Bound algorithm. An illustrative numerical...

Fuzzy random minimum cost network problem [electronic resource]

, Article Journal of Industrial and Systems Engineering ; Vol. 6, No. 1, pp 34-47, 2012 Nematian, J. (Javad) ; Eshghi, Kourosh ; Sharif University of Technology

Abstract

In this paper, a fuzzy random minimum cost flow problem is presented. In this problem, cost parameters and decision variables are fuzzy random variables and fuzzy numbers respectively. The object of the problem is to find optimal flows of a capacitated network. Then, two algorithms are developed to solve the problem based on Er-expected value of fuzzy random variables and chance-constrained programming. Furthermore, the results of two algorithms will be compared. An illustrative example is also provided to clarify the concept

Performance evaluation of thyristor-based static transfer switch with respect to cross current

, Article IEEE/PES Transmission and Distribution Conference and Exhibition 2002 : Asia Pacific, Yokahama, 6 October 2002 through 10 October 2002 ; Volume 2, Issue ASIA PACIFIC , 2002 , Pages 1326-1331 Mokhtari, H ; Sharif University of Technology

2002

Abstract

Providing clean, continuous and reliable power to many industrial customers has become a necessity. Where possible, sensitive customers are supplied by two medium-voltage utility feeders one of which is used as back up. Thyristor-based Static Transfer Switches (STSs) are able to provide the loads with a fast transfer to the back up feeder when the main one fails. In addition to being fast, the transfer must be performed with no source paralleling which creates a cross current flowing between the main feeder and the back up one. Due to practical limitations, however, in some cases, cross current cannot be avoided. This paper investigates the performance of thyristor-based STSs with respect to...

, M.Sc. Thesis Sharif University of Technology Zadkhast, Sajad (Author) ; Mokhtari, Hosain (Supervisor)

Abstract

By taking a new sight into the system dynamic equations, the controllers are designed based on the simplification and converting higher order dynamics to the first order systems. This issue not only simplifies controller design but also stabilize system in all operational points. Moreover, proposed controllers are applied to the parallel Active Power Filters (APFs) because of the new trends in modularizing of APFs. On the other hand, the IEEE-1459 standard has proposed new definitions for the power in unbalanced and non-sinusoidal conditions and it stimulated researchers to use this standard for controlling APF directly. However, the proposed definitions are based on RMS values and...

Design of a Smart Algorithm Based on Two Dimensional Wavelet Transformation for Detection and Classification of Power Quality Disturbances

, M.Sc. Thesis Sharif University of Technology Mollayi, Nader (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

Power Quality can be simply defined as the quality of voltage at electrical loads. Detection and classification of voltage and current disturbances is of high importance in power system protection and monitoring. This procedure cannot be implemented by operators because of the high volume of the data which must be processed. So, it is needed to automate this procedure. Systems designed for this purpose usually contain three main parts: feature generation, feature selection and classifier design. The algorithms used for feature generation for power quality disturbances are mainly based on discrete Fourier transformation or discrete wavelet transformation. These approaches have shown some...

Expansion of Power Definition in IEEE-1459 in Order to Apply to Shunt Active Power Filters

, M.Sc. Thesis Sharif University of Technology Ahmadi, Meysam (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

Increase of nonlinear loads has led rise of harmonic currents, voltage distortion and imbalance in power system. Those polluted nonsinusuidal environments have made electrical engineer and researchers to define new and more compelet definition of electrical power quantities such as power factor, apparent power, THD and … . The new definitions have resulted in new methods of power quality enhancement technique. IEEE-1459 Std. proposes definitions for electric power in sinusoidal, nonsinusoidal, balanced and unbalanced conditions which can be used for compensation of nonsinusoidal and unbalanced systems. This reaserch introduces a new method to obtain shunt active filter reference signal. This...

Modeling of Atmospheric Toxic Release and Dispersion Using CFD

, M.Sc. Thesis Sharif University of Technology Mokhtari, Mojtaba (Author) ; Rashtchian, Davood (Supervisor)

Abstract

In this project, ammonia dispersion in the environment have been investigated and the experimental data have been used in order to show accuracy of calculations. Also, the results of CFD have been compared with the results of PHAST software. The results show that when there is no obstacle in the way of gas release, dispersion models will get good results, but due to existence of the obstacle, their error will be increased to 300%. However, the error resulting from CFD is less than 24% even if there are obstacle there. The effects of obstacle’s distance and height on the dispersion of ammonia gas are investigated. This study showed that the concentration of ammonia increase, when the distance...

Control of Multi Inverter Microgrid Considering Hybrid Distributed Generation Systems and Renewable Energy Sources in Island Mode

, M.Sc. Thesis Sharif University of Technology Ghazanfari, Amin (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

Nowdays, distributed generation (DG) systems based on renewable energy sources have significantly increased around the world as an alternative solution to enhance the power quality and reliability and reduce the need for extensive transmission system as well. An evolved recent concept called microgrid is developed by grouping a cluster of loads and DG units in a common local area which increases the integaration of sustainable energy generation systems. This thesis presents control of a medium voltage (MV) microgrid considering multi-hybrid distributed generation systems (MHGS) and renewable energy resources in island mode. The first part is focused on the development a control strategy for...

Call Admission Control Schemes in WiMAX Networks

, M.Sc. Thesis Sharif University of Technology Mokhtari, Zeinab (Author) ; Beigy, Hamid (Supervisor)

Abstract

The rapid growth of broadband wireless access (BWA) has increased the demand of new application such as VoIP, video conferencing, online gaming each of which has different requirement for quality of service. Due to limited bandwidth provided for these networks, one of the most important issues is how effective we manage bandwidth in order to support requests. The quality of service is an important indicator of the effective management of bandwidth. Using mechanisms of call admission control is a commonly accepted method for balance between quality of service and increase of utilization resource in cellular mobile networks. In fact, ...

Reliability Optimization of Series-Parallel System with Redundancy Allocation and Stochastic Failure Rate

, M.Sc. Thesis Sharif University of Technology Mokhtari, Zahra (Author) ; Mahlooji, Hashem (Supervisor)

Abstract

This thesis presents a method to solve a redundancy allocation problem for the series-parallel system. The modeling formulation deals with the choice of the best redundancy strategy, component and redundancy level for each subsystem in order to maximize the system reliability under system-level constraints. Majority of the solution methods for the general redundancy allocation problems assume that the failure rate of components is determined. However, in practice variable failure rate may be used. The complexity of this problem is known as NP-hard and therefore the optimal solution is not accessible in the normal course of events. It is demonstrated in this thesis that genetic algorithm is...

Harmonic Source Detection and Determination of Customer and Utility Harmonic Contributions at the PCC

, M.Sc. Thesis Sharif University of Technology Shojaie, Mehdi (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

Harmonics are of the most important issues associated with electric power quality. Non-linear loads such as power electronic converters are harmonic-producing devices in a network. Due to negative impacts of harmonics such as increased losses and reduced life of network equipment, harmonic analysis of a polluted network, is an essential task. Furthermore, harmonic source identification in order to trace harmonics in a network and adequate implementation of harmonic mitigation techniques is also important. Harmonic contribution determination of a customer at a point of common coupling (PCC) is subjected to difficulties such as harmonic voltage and current interactions, unknown customer and...

Lead Time Quotation and Lot Sizing in Production Systems

, Ph.D. Dissertation Sharif University of Technology Mokhtari, Ghasem (Author) ; Kianfar, Farhad (Supervisor)

Abstract

Due date assignment for customer orders has been studied in various production environments. In this thesis a production system is considered in which the orders of several customers are produced in a single lot because of the economy of scale. If a lot is completed before receiving customer orders, inventory carrying cost is incurred. On shortages, a due date is quoted to customers and lead time quotation cost is incurred. The due date may not be met because of (lead-time) uncertainty in production system. Hence if the order is delivered after its due date, tardiness cost is charged. The literature reviews show that such a model is not considered by other researchers. Two different problems...

Hybrid Modeling and Control of Voltage Source Inverters

, M.Sc. Thesis Sharif University of Technology Mazaheri, Behnam (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

Modeling and control of power electronic converters, due to their non-linear nature, are from important research subjects in power electronics. Power electronic systems contain both continuous-time dynamics and discrete-time inputs, and therefore, are categorized as hybrid systems. Conventionally, modeling and control of hybrid systems is done by linearizing and state-space averaging. However, these methods do not guaranty well operation of the system over a wide range of load or input variation. In this project, by employingMLD modeling method, a model for an inverter which is connected to a three-phase RL load through an LC filter, is derived. Then, this model is used in an optimization...

A Single-Phase to Three-Phase Matrix Converter to Control Three-Phase Induction Motor

, M.Sc. Thesis Sharif University of Technology Najmi, Vahid (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

converters, the different configurations for matrix converters are proposed. In this thesis, a one-phase to three-phase matrix converter is used to control in three-phase induction motor. Different control methods are proposed to control the induction motor. The novel control methods include close loop speed and converter output current controls of induction motor are proposed based on SPWM. The structure of indirect matrix converter for the mentioned application also investigated. Moreover, three usual method of control of induction motor: DTC (Direct Torque Control), FOC (Field Oriented Control) and Space Vector Modulation are applied to the single to three- phase matrix converter. Each of...

Harmonic Modelling of Residential Loads and Their Effects on Distribution Network

, M.Sc. Thesis Sharif University of Technology Karimi, Elham (Author) ; Mokhtari, Hossein (Supervisor)

Abstract

In recent years, there has been an increasing concern about harmonic distortion and the effects of harmonics on power systems. Nonlinear loads such as electronic power supplies, battery chargers, motor drives, UPS systems and … are the primary source of harmonic currents. Harmonic currents generated by nonlinear loads flow from the load into the power system due to the network low path of impedance Harmonic currents cause additional heat and losses in power system components and results in voltage distortion as well.To deal with the problems associated with harmonics and to reduce their effects on power networks, study of the effects of non-linear loads on distribution networks is essential....

Simulating Sediment Transportation (Scour) Under Pipelines

, M.Sc. Thesis Sharif University of Technology Mokhtari, Hossein (Author) ; Abbaspour, Madjid (Supervisor)

Abstract

Regarding to significant role of marine pipelines in transferring oil, water and other products, a research was carried out to study the sediment transportation (Scouring) under pipelines which threaten pipelines. Interaction between fluid phase (flow field), structure phase (pipe) and sediment, determine scour profile shape and specifications of each phase which can change scour depth. In this research Flow-3D software was used to simulate scouring process under cylinder. First the flow field around cylinder near wall was studied and the scour depth under direct and oscillating flow was simulated. In addition, in next pace, the number of pipes and their distance were varied to measure...