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hemmat--zahra
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Modeling and Simulation of a High Power Photoconductive Semiconductor Switch (PCSS)
, M.Sc. Thesis Sharif University of Technology ; Faez, Rahim (Supervisor)
Abstract
There are a wide variety of light-triggered switches. Photoconductive semiconductor switches (PCSSs) have been investigated intensively for many applications owing to their unique advantages over other switches. The advantages of PCSSs make them a perfect choice for many important applications where high switching accuracy and high-power capability are required. Photoconductive switches are fabricated from a variety of semiconductors, including silicon carbide (SiC), gallium arsenide (GaAs) and gallium nitride (GaN). In Photoconductive semiconductor switches (PCSSs) the switching mechanism is initiated by optical illumination and laser source controls the flow of current. In the off or...
Simulation and investigation of a back-triggered 6H-SiC high power photoconductive switch
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 253-256 ; 9781479976539 (ISBN) ; Faez, R ; Amiri, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This paper has investigated the performance of a linear, 6H-SiC high power photoconductive semiconductor switch. A three-dimensional device modeling with SILVACO ATLAS tools was used to model the optically initiated 6H-SiC switch. The 6H-SiC PCSS device is designed in a rear-illuminated, radial switch structure. The material properties of vanadium compensated 6H-SiC PSCC have been analyzed for breakdown, photocurrent profile such as rise and fall time in terms of their applications as a photoconductive switch at high bias conditions. This structure and also new type of illumination extends the blocking voltage by reducing the peak electric field near electrodes. In this presentation the...
Evaluation of Granularity of Reconfigurable Architectures for Wireless Communication Applications
, M.Sc. Thesis Sharif University of Technology ; Hemmat yar, Afshin (Supervisor)
Abstract
Wireless communication applications need high computing power, flexibility and scalability. Although ASICs have the ability of high computing power but they are not flexible to changing or completing of communication protocols. On the other hand, general purpose microprocessors or DSPs are flexible, but do not provide sufficient computing power. Thus devices with reconfigurable architecture have been proposed as a compromise between ASICs and microperocessors. One of the main features of reconfigurable devices is the granularity. The granularity of a reconfigurable devices shows the amount of computing power incorporate in a processing element. In this thesis we have evaluated different...
Optimal Method in Cognitive Radio Networks Routing
, M.Sc. Thesis Sharif University of Technology ; Hemmat Yar, Afshin (Supervisor)
Abstract
Cognitive radio (CR) technology is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. CR networks, however, impose unique challenges due to the high fluctuation in the available spectrum as well as diverse quality-of-service (QoS) requirements. Specifically, in cognitive radio ad hoc networks (CRAHNs), the distributed multi-hop architecture, the dynamic network topology, and the time and location varying spectrum availability are some of the key distinguishing factors. In this literature, we propose a new routing algorithm that tries to...
Futuristic Greedy Algorithm on some NP-complete Problems
, Ph.D. Dissertation Sharif University of Technology ; Izadi, Mohammad (Supervisor)
Abstract
Many problems in the field of 0-1 integer programming are NP-Complete. Execution time for exact solving these problems is very high due to many constraints and decision variables. Hence, scientists use Fast algorithms, for example, the Greedy algorithms, in the approximated solution of these problems.A classic greedy approach may not search the whole solution space for better choices. However, other methods with a greedy approach, such as meta heuristic and hyper heuristic, in addition to local search, consider the more search space. These methods search randomly, so it does not provide a good guarantee for finding the proper solutions. Finding suitable solutions in this category of...
Developing BIM Vision and BIM Strategic Plan for Municipalities
, M.Sc. Thesis Sharif University of Technology ; Alvanchi, Amin (Supervisor)
Abstract
The municipality is an administrative, public and non-state institution that falls into the city district of the most countries’ administrative divisions. This institution has relatively autonomy and independent power. Municipalities are trying to apply the best approaches (Such as Building Information Modeling (BIM) as a procedure contributing the project management) to save time and money, as well as to satisfy the citizens in the implementation of civil projects. This study examines and evaluates the readiness of municipalities to modify the construction projects based on BIM. In addition, a pattern for identifying BIM applications, evaluating the organization readiness and the needs of...
Nanofluid flooding in a randomized heterogeneous porous media and investigating the effect of capillary pressure and diffusion on oil recovery factor
, Article Journal of Molecular Liquids ; Volume 320 , December , 2020 ; Esfandeh, S ; Hosseinizadeh, E ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In the initial recovery stage, only 5 to 15% of hydrocarbons can be extracted from oil reservoirs, so it is necessary to supply energy from an external reservoir or to use advanced solutions to increase oil recovery. By using secondary recovery method and flooding, greater amount of oil can be extracted. In this study, a new procedure of flooding using nanofluid was simulated. The nanofluid and source rock were modeled as a single phase and heterogeneous porous media, respectively. The geometry was considered as a two-dimensional rectangular area. Two phase Darcy equations and mass transfer equations were utilized to simulate this process. Moreover, the effects of different volume fractions...
Investigation on nanofluid flooding effect on enhancement oil recovery process in a random pore distribution incomplete cone
, Article International Communications in Heat and Mass Transfer ; Volume 117 , October , 2020 ; Hosseinizadeh, E ; Mosaferi, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
By reducing the exploration of new oil reservoirs, enhanced oil recovery from previous oil reservoirs is a solution to supply energy demand. In order to develop the production, various technologies and methods have been proposed such as steaming, direct heating, flooding by nano-fluid, chemical injection, polymer injection and etc. In the present study, nanofluid flooding has been attempted on a rock reservoir with incomplete cone geometry and its performance has been evaluated on oil recovery. The porous media is considered heterogeneous in simulation in accordance with oil reservoirs. The heterogeneous geometry considered in this study is incomplete cone that is heterogeneous in a random...
Flooding numerical simulation of heterogeneous oil reservoir using different nanoscale colloidal solutions
, Article Journal of Molecular Liquids ; Volume 302 , 15 March , 2020 ; Hosseinizadeh, E ; Esfandeh, S ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this study, flooding of oil reservoir by implementing Nanoscale colloidal solutions as a working fluid is simulated. All oil reservoirs are heterogeneous porous media; therefore, in this investigation for more accurate prediction of the problem, the porous media is considered heterogeneous. The governing equations of this problem are solved by finite element method (FEM). Moreover two-phase equations of Darcy and mass transfer equations are used. In this paper, the effect of temperature and volume fractions of nanoparticles on the rate of oil recovery is investigated. The SiO2, Al2O3, and CuO nanoparticles are used in the enhanced oil recovery (EOR) process. Also, in order to solve the...
Nanofluid flooding for enhanced oil recovery in a heterogeneous two-dimensional anticline geometry
, Article International Communications in Heat and Mass Transfer ; Volume 118 , November , 2020 ; Esfandeh, S ; Hosseinizadeh, E ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In the present study, we try to numerically simulate the nanofluid flooding method, which is one of the newest methods in this field. For this purpose, the nanofluid is considered as a single phase fluid that enters the porous petroleum reservoir containing oil. Since all porous petroleum reservoirs are heterogeneous, the porous grid is also considered heterogeneous and is solved using the finite element numerical method. The geometry considered in this study is a two-dimensional anticline medium that is heterogeneous. In this study, the effect of using different volume fractions of nanoparticles in nanofluid is studied. Capillary pressure or diffusion are considered in simulation and their...
Effect of radial structure on the performance of lateral high-power GaAs photoconductive switch
, Article IEEE International Conference on Electro Information Technology, 21 May 2015 through 23 May 2015 ; Volume 2015-June , 2015 , Pages 436-439 ; 21540357 (ISSN) ; 9781479988020 (ISBN) ; Moreno, E ; Rasouli, F ; Alizad, S. H ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
In this paper, the effect of radial structure on the performance of a linear-lateral GaAs high power photoconductive semiconductor switch (PCSS) is investigated. For this purpose a three-dimensional device modeling is used to model the optically initiated GaAs switch. In this simulation a p-type device with carbon as shallow acceptor is compensated by deep donor EL2 level as a trap level. The PCSS device is designed in a back-triggered, radially symmetric switch structure which extends the blocking voltage by reducing the peak electric field near the electrodes. Device modeling was performed and the effect of different trap concentrations on dark I-V characteristics has been investigated. In...
Mesoporous silica nanoparticles (MCM-41) coated PEGylated chitosan as a pH-Responsive nanocarrier for triggered release of erythromycin [electronic resource]
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; 2014, Volume 63, Issue 13, Pages 692-697 ; Mazaheri Tehrani, Zahra ; Sharif University of Technology
Abstract
A pH-responsive drug delivery system based on core shell structure of mesoporous silica nanoparticle (MSN) and chitosan-PEG copolymer was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM) techniques. In order to improve compatibility MSN and drug, mesoporous nanosilica was modified by 3-aminopropyl triethoxysilane. The release of erythromycin (a macrolide antibiotic) as a model drug was investigated in two pHs, 7.4 and 5.5
Distributed Publisher-Subscriber Pattern for Content-Based Routing in Software Defined Networks
, M.Sc. Thesis Sharif University of Technology ; Hemmat Yar, Ali Mohammad Afshin (Supervisor)
Abstract
Content-based routing, as provided by publisher/subscriber systems,has evolved as a key paradigm for interactions between loosely coupled application components (content publishers and subscribers). Content-based routing aims to increase the efficiency of forwarding by utilizing the diversity of information exchanged between application components. Using content-based forwarding rules (also called content filters) installed on content-based routers (also termed brokers), bandwidth-efficiency is increased by only forwarding content to the subset of subscribers who are actually interested in the published content. Many middle-ware implementations for content-based publish/subscribe have been...
Theoretical and Computational Investigation of Quantum Plasmonic Properties of Nanocluster Dimers
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Zahra (Supervisor)
Abstract
In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon...
Theoretical Investigation of Ab-initio MD Approach to Increase the Efficiency and Accuracy of VCD Spectrum Calculation
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Zahra (Supervisor)
Abstract
Understanding of the Molecules is the main purpose of the chemistry. Ab-initio molecular dynamics (AIMD) as a branch of the computational chemistry, tries to give us a deep comprehension of the molecule, and its chemical, physical and optical activities. This comprehension, relies on the accuracy of quantum mechanics, in addition to the speed of the classical mechanics. The mixing of the quantum mechanics and the classical mechanics could simulate activities of the atoms in the time-domain, provided the mixing is done with precaution. This, in turn, helps us to forecast the response of a molecule in different situations, and also translating the macroscopic phenomena in a nanoscopic...
Investigation of Plasmonic Excitation in Carbonic Nanostructures Within Near-IR
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Zahra (Supervisor)
Abstract
To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have...
Using Nonlinear Effects of Light for Optical Signal Processing
, M.Sc. Thesis Sharif University of Technology ; Kavehvash, Zahra (Supervisor)
Abstract
Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the...
Using Simulation-Optimization Approach for Fire Station Location and Vehicle Assignment Problem: a Case Study in Tehran, Iran
, M.Sc. Thesis Sharif University of Technology ; Amini, Zahra (Supervisor)
Abstract
In this research, the problem of locating fire stations and allocating equipment has been studied and a simulation-optimization approach has been presented to solve the problem. The mathematical models of this research were developed based on the idea of the randomness of the covered demand and the maximum expected coverage model. In these models, the issue of non-availability of equipment to cover accidents, the random nature of accidents, various fire incidents and the equipment needed to cover them are considered. Two mathematical models with deterministic and non-deterministic approach with different scenarios for demand are proposed. The non-deterministic model is developed with the aim...
Introducing An Integrated Framework For Solving The Fleet Planning Problem Using A Simulation-Optimization Approach
, M.Sc. Thesis Sharif University of Technology ; Amini, Zahra (Supervisor)
Abstract
One of the main concerns of industrial companies’ managers is providing an efficient logistics system. To achieve an efficient logistics system, the fleet planning problem is studied by many researchers in recent years. This problem consists of multiple sub-problems at three levels: operational, tactical, and strategic. These sub-problems are closely related to each other and need to be studied and addressed in an integrated manner. In this research, an attempt is made to provide an integrated framework to solve the vehicle routing problem (operational), outsourcing problem (tactical), and fleet composition problem (strategic). These problems have various uncertainties, including customer...
Transient and steady state study of a rear-illuminated 6H-SiC photoconductive semiconductor switch
, Article Optik ; Volume 127, Issue 11 , 2016 , Pages 4615-4620 ; 00304026 (ISSN) ; Faez, R ; Moreno, E ; Rasouli, F ; Radfar, F ; Zaimbashi, M ; Sharif University of Technology
Elsevier GmbH
2016
Abstract
In this paper characteristics of a linear, 6H-SiC photoconductive semiconductor switch are presented. The vanadium-doped semi-insulated 6H-SiC PCSS device is designed in a back-triggered, radial switch structure. For this purpose, three-dimensional (3D) device modeling tool was used to model and test the optically initiated 6H-SiC switch. Dark I-V characteristic results show that newly proposed rear-illuminated radial switch structure extends the blocking voltage by reducing the peak electric fields near electrodes. Also this radial structure has higher dark resistance as compared to the previous 6H-SiC PCSS experimental results. The ON-state characteristics of vanadium compensated 6H-SiC...