Loading...
Search for:
mokhtari--ali
0.131 seconds
Total 2517 records
Designing a Robot Head for Studying Social Interaction with the Ability to Express Emotions Using a Projector
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor) ; Shariati, Azadeh (Supervisor)
Abstract
The most crucial physical component in human-robot interaction is the head of the robot, which may have the potential to interact via representing facial expressions. There are several different types of robotic heads. This thesis presents the design process and realization of a retro-projected social robotic head, “Taban”. Taban is a cost-effective portable robot with a lifelike robotic face which can produce different facial expressions, different 3D face animation avatars (ranging from different ages, races, and gender) with the help of rear-projector in its head to projects animations onto a translucent 3D printout mask. It has a neck system with two degrees of freedom, a camera in the...
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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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
;
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...
Optimal Placement of Active Filters in a Power System
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
The extensive use of nonlinear loads such as motor drives and new generation of home appliances has caused a deterioration of power quality in power systems. The use of active power filters due to the fast variation of the loads has been recommended by power engineering. In this method, the harmonic profiles are controlled by applying active filters in a distribution feeder. Optimal placement of active filters in a distribution system due to the increase of harmonic generation loads has attracted researchers. However placement of each filter is the major concern that researchers face. In this paper, a new objective function is introduced to determine the optimal number and location of active...
Optimal Distributed Generation Allocation Considering Power Qaulity Indices
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
The demand for independent power generation has been increased in recent years due to the growing demand in distributed networks, losses and power qaulity in power systems. These losses occur in transmission to distribution networks from the generation sites to the end-user loads which have harmonic losses besides fundamental losses.. The non-linear load makes the harmonics flow in the line and create the harmonic losses. However, in a distributed network with several DGs of different types and with all kinds of variable nature loads, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of time,...
Optimal Distributed Generation Allocation and Sizing Considering Operation Indices
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
The need for independent power generation has been increased in recent years with the growing demand in micro grid systems. Losses in power systems are unavoidable. These losses occur in transmission to distributionnetworks from the generation sites to the end-user loads. Reduction of power losses has been one of the reasons for engineers to be attracted by micro grid systems which include small size independent power generation units. However, in a micro grid with several DGs of different types and with all kinds of loads of variable nature, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of...
Improvement of Power Sharing In Microgrids Consist of Synchronous Generators and Converter Based Distributed Generation Units
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
This dissertation studies the operation of the power sharing system in a micro-grid (MG) which includes a synchronous generator and the converter based distributed generation (DG) units. Increasing advent of MGs and the huge penetration of DGs to the existing power systems require comprehensive studies on the interactions between synchronous generators and converter based DGs for the sharing of power during and after the occurrence of different disturbances such as load changing. Thus, this project discusses existing control methods which can be used to share the power between a synchronous generator and converter based DGs. Then, a new control strategy is proposed in order to enhance the...
Investigation of Causes of Increased 5th Harmonic in Azarbayjan Regional Electricity Grid and Subject to Provide Practical Solutions to Reduce it
,
M.Sc. Thesis
Sharif University of Technology
;
Mokhtari, Hossein
(Supervisor)
Abstract
Iran's electrical grid is connected to the Eastern Turkey grid via Khoy-Basqale 400KV transmission line. Harmonic mesurements indicate high level of the 5th harmonic voltage in Azarbayjan grid which is magnified in Van substation. According to Iran international obligations and economic losses caused by the high level of harmonics in Azerbaijan regional electricity grid, a comprehensive study is required. Early studies showed that this unprecedented increase in the 5th harmonic voltage is due to the small harmonic loads scattered throughout the network. The aim of this thesis is to perform a comprehensive harmonic analysis of Azerbaijan network due to scattered harmonic loads. In this...