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ale-ahmad--haleh-sadat
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Design and Implementation of an Internet-Based Survey on Route Choice Characteristics
, M.Sc. Thesis Sharif University of Technology ; Zokaei Aashtiani, Hedayat (Supervisor)
Abstract
It is assumed in many traffic assignment models that people choose their path based on shortest travel time. Few empirical studies of revealed route characteristics have been reported in the literature. In this study, first, an innovative internet-based survey using Google map has been designed and implemented. The sample includes the people who commute to Sharif University of Technology in the morning peak hours. Next, observed routes in 134 valid questionnaires have been analyzed by using Tehran network database and VBA programming. Besides the length and travel time of each path, other characteristics of the observed route such as the number of right, left, and U-turns, number of...
A new variable frequency zero voltage switching control method for boost converter operating in boundary conduction mode
, Article International Journal of Engineering, Transactions B: Applications ; Volume 33, Issue 11 , 2020 , Pages 2222-2232 ; Ghoreishy, H ; Ale Ahmad, A ; Tahami, F ; Sharif University of Technology
Materials and Energy Research Center
2020
Abstract
This paper proposes a new variable frequency zero voltage switching (ZVS) control method for boost converter operating in boundary conduction mode (BCM). The intended method keeps the converter in BCM despide of the load and input voltage variations. This is done by changing switching frequency in a certain specified range. The proposed method can guarantee circuit performance in BCM via zero-crossing detection of the inductor current and changing the switching frequency. In addition, with a slight modification in control structure, it is possible to achieve a fully ZVS in all cases. This converter control is carried out in analog form without using microprocessors which, compared with the...
Stability analysis of variable frequency control method of soft switching for boost converter with wide bandgap semiconductors
, Article 2023 14th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2023 ; 2023 ; 979-835033664-1 (ISBN) ; Ghoreishy, H ; Ale Ahmad, A ; Tahami, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
As a means of achieving soft switching in a boost converter without altering the converter's structure or its variable frequency control, the quasi-resonance method is proposed. The method enables the boost converter to operate in Boundary Conduction Mode (BCM) regardless of variations in input voltage or load by adjusting the switching frequency within a defined range. This high-frequency approach is implemented in analog form, which is a more cost-effective option than digital implementation. Simulation tests using LTspice and stability analysis applied to a bidirectional boost converter demonstrate the effectiveness of the proposed technique. © 2023 IEEE
Investigation on Conductivity and Piezoelectric Effects on Biological Properties of Conductive Nerve Regenerating Scaffolds by Nano Composite of Gelatin/Polyvinyl Fluoride/Graphene
, M.Sc. Thesis Sharif University of Technology ; Ramazani Saadat Abadi, Ahmad (Supervisor) ; Bakhshandeh Abkenar, Haleh (Supervisor) ; Atyabi, Mohammad (Co-Supervisor)
Abstract
Neural system in human body due to limitated cell proliferation requires high care, because the damage causes serious hurts and disables different tissues. Limit regeneration in central neural system can cause different neural diseases including brain exhaustions specially in old people, but the peripheral neural system may have been disabled and intrupt some other tissue beacuase of possible external injuries before aging. So that while some damages like neural fibers severing, some new medical care methods are required. Some of these methods are outograft, allograft and xenograft which implants neural tissues either between other patient's tissues or from somebody else's; however these...
Bi-objective optimization of a job shop with two types of failures for the operating machines that use automated guided vehicles
, Article Reliability Engineering and System Safety ; Volume 175 , July , 2018 , Pages 92-104 ; 09518320 (ISSN) ; Akhavan Niaki, S. T ; Haleh, H ; Naderi, B ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Reliability of machinery and equipment in flexible manufacturing systems are among the most important issues to reduce production costs and to increase efficiency. This paper investigates the reliability of machinery in job shop production systems, where materials, parts, and other production needs are handled by automated guided vehicles (AGV). The failures time of the parallel machines in a given shop follow either an exponential or a Weibull distribution. As there is no closed-form equation to calculate the reliability of the shop in the Weibull case, a simulation approach is taken in this paper to estimate the reliability. Then, a bi-objective nonlinear optimization model is developed...
Reliability optimization of tools with increasing failure rates in a flexible manufacturing system
, Article Arabian Journal for Science and Engineering ; Volume 44, Issue 3 , 2019 , Pages 2579-2596 ; 2193567X (ISSN) ; Akhavan Niaki, S. T ; Haleh, H ; Naderi, B ; Sharif University of Technology
Springer Verlag
2019
Abstract
Tool reliability is one of the most important issues in a flexible manufacturing system. If a tool fails to operate correctly, the performance of the manufacturing system is reduced, the due date may be violated, or the product quality falls behind the standards. This paper develops a bi-objective mathematical model for tool selection in a flexible manufacturing system in order to optimize both reliability and cost. The tools in these environments are considered to have increasing failure rates as they are used over time; a case closer to reality. This paper aims to evaluate the availability of different tools used in a production system, in which the reliability of a tool is dependent on...
Cluster-based adaptive SVM: a latent subdomains discovery method for domain adaptation problems
, Article Computer Vision and Image Understanding ; Volume 162 , 2017 , Pages 116-134 ; 10773142 (ISSN) ; Jamzad, M ; Sharif University of Technology
2017
Abstract
Machine learning algorithms often suffer from good generalization in testing domains especially when the training (source) and test (target) domains do not have similar distributions. To address this problem, several domain adaptation techniques have been proposed to improve the performance of the learning algorithms when they face accuracy degradation caused by the domain shift problem. In this paper, we focus on the non-homogeneous distributed target domains and propose a new latent subdomain discovery model to divide the target domain into subdomains while adapting them. It is expected that applying adaptation on subdomains increase the rate of detection in comparing with the situation...
Indoor Noise Pollution Modeling: A Case Study on Resalat Tunnel
, M.Sc. Thesis Sharif University of Technology ; Vaziri, Manouchehr (Supervisor)
Abstract
Noise or noise pollution, is defined as an unwanted sound, produced mostly by motor vehicles in urban areas. If the noise exceeds its limit, adverse effects on users and citizens are expected. Thus the assessment of the noise level and its comparison with allowable values is mandatory. Traffic induced noise depends upon different factors such as traffic, weather, and, sound barriers. Noise pollution study has a long history all over the world. Many studies, mostly representing the outdoor noise pollution models, have been done in recent years. This paper presents an assessment of traffic-induced noise in a heavily traveled tunnel, locally referred to as Resalat tunnel, which is located in...
The Effect of Travel Time Reliability on Morning Peak Travellers route choice in Large Metropolitan Area
, M.Sc. Thesis Sharif University of Technology ; Poorzahedy, Hossein (Supervisor)
Abstract
Data collected from street networks show that travel time in urban street networks is a stochastic variable, whose range of variation increases with the congestion level. Work and school trips comprise the major part of morning peak volumes, whose common characteristic is that they need to be made on time. For this reason, these travelers are pessimistic in their route choice, and try to choose routes which are more reliable. Travel time standard deviation is one of the common measures for estimating travel time reliability that is related to properties of day-to-day travel time distribution on a particular route. Based on the empirical data collected from Tehran street network, this paper...
Design and Implementation of a FlexRay Transceiver
, M.Sc. Thesis Sharif University of Technology ; Atarodi, Mojtaba (Supervisor)
Abstract
With the advancement of automotive industry, the number of electronic systems that need to communicate with each other has increased. An effective strategy to meet these growing demands is using bus-based protocols, which can establish safe communication among numerous nodes with reasonable cost, weight, and space requirements. The objective of this thesis is the design and implementation of a transceiver based on the FlexRay protocol. The significance of this protocol lies in its ability to provide higher data transmission rates compared to other protocols like CAN and LIN, and its role as the foundational communication medium among various domains in modern vehicle architectures. In this...
Using Information Beyond Text to Generate Language Embedding Vectors
, M.Sc. Thesis Sharif University of Technology ; Sameti, Hossein (Supervisor)
Abstract
In this thesis, we introduce a novel Artificial Intelligence (AI) system inspired by the philosophical and psychoanalytical concept of imagination as a ``Re-construction of Experiences". Our AI system is equipped with an imagination-inspired module that bridges the gap between textual inputs and other modalities, enriching the derived information based on previously learned experiences. A unique feature of our system is its ability to formulate independent perceptions of inputs. This leads to unique interpretations of a concept that may differ from human interpretations but are equally valid, a phenomenon we term as ``Interpretable Misunderstanding". We employ large-scale models,...
Entanglement Distillation for Weakly Entangled States
, M.Sc. Thesis Sharif University of Technology ; Mirkamali, Maryam Sadat (Supervisor)
Abstract
Quantum entanglement is an essential resource in quantum information processing, such as quantum communication and quantum computing. Although entanglement is critical for practical implementations in these fields, creating and transmitting entanglement without altering the states is challenging. External noise may destroy or weaken the entanglement. Consequently, there is a need for methods to improve entanglement. Entanglement distillation is an effort to address this issue. It is a process where, probabilistically, a smaller number of strongly entangled states are created from a fixed number of noisy entangled states. This process is carried out using only local operations and classical...
Deformation and Annealing Behavior of an Austenitic Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor)
Abstract
In this research, non-isothermal annealing process at temperatures ranging between 400°C to 830 °C was investigated in warm and cold-rolled austenitic stainless steel 304L. First, the wide variety of austenitic to martensitic structure was produced by the multi-pass rolling process at room temperature -8 °C, 200 °C, and 280°C. The n exponent in Olson-Cohen equation was governed 2.83 after non-linear curve fitting to assess the fraction of deformation-induced martensite as a function of strain. Afterward, Abaqus/Explicit method was utilized to achieve the stored energy and plastic strains distribution through the thickness. Then, Cellular automata and Galerkin-finite element models were...
Utilizing network coding for file dessimination in peer-to-peer systems
, Article 3rd International Conference on New Technologies, Mobility and Security, NTMS 2009, 20 December 2009 through 23 December 2009, Cairo ; 2009 ; 9781424462735 (ISBN) ; Movaghar, A ; Sadat Bathaee, N ; Sharif University of Technology
2009
Abstract
Network coding was first introduced in information theory for increasing the multicast rate in the networks with directed links. We can model many of the content distribution networks and overlay networks with such a network. Therefore, the solutions introduced in information theory can be used in these networks. In this paper, we analyze using of network coding in uncoordinated cooperative content distribution systems. Reaching the optimum performance in an uncoordinated system needs blocks of the system to be "equally important". In that case, we can retrieve the whole data without need of central controller or complex algorithms. In part of this paper, we exactly define the concept of...
Controlling longitudinal safe distance between vehicles
, Article Promet - Traffic - Traffico ; Volume 21, Issue 5 , 2009 , Pages 303-310 ; 03535320 (ISSN) ; Fathi, M ; Vaziri, M ; Sharif University of Technology
2009
Abstract
Controlling the safe distances between vehicles on freeways can be used to prevent many accidents. In this research, image-processing techniques have been used to develop an online system that calculates the longitudinal distances between vehicles. This system facilitates controlling safe distances between vehicles without the need for high technology devices. Our approach is real-time and simple, but efficient operations have been used to reduce the image occlusion problem. The main concept of this system is using simple, quick, and effective algorithms for calculating the position of each vehicle in each image. In this way, traffic parameters like speed and distances between vehicles can...
A novel structure of dithered nested digital delta sigma modulator with low-complexity low-spur for fractional frequency synthesizers
, Article COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering ; Volume 35, Issue 1 , 2016 , Pages 157-171 ; 03321649 (ISSN) ; Farshidi, E ; Sadoughi, S ; Sharif University of Technology
Emerald Group Publishing Ltd
2016
Abstract
Purpose - Digital Delta Sigma Modulator (DDSM) is used widely in electronic circuits including Radars, class-D power amplifiers and fractional frequency synthesizers. The purpose of this paper is to propose an implementation for MASH DDSMs named as Multi Modulus Reduced Complexity (MMRC) architecture. Design/methodology/approach - This architecture will use a very simple pseudorandom Linear Feedback Shift Register (LFSR) dither signal with period N-d to randomize the digital MMRC modulator used for fractional frequency synthesizers. Using error masking methodology, the MMRC modulator can decrease the hardware consumption and increase accuracy of the fractional frequency synthesizer. Rules...
Entropy-based video steganalysis of motion vectors
, Article Entropy ; Volume 20, Issue 4 , 2018 ; 10994300 (ISSN) ; Faez, K ; Saffari Pour, M ; Sharif University of Technology
MDPI AG
2018
Abstract
In this paper, a new method is proposed for motion vector steganalysis using the entropy value and its combination with the features of the optimized motion vector. In this method, the entropy of blocks is calculated to determine their texture and the precision of their motion vectors. Then, by using a fuzzy cluster, the blocks are clustered into the blocks with high and low texture, while the membership function of each block to a high texture class indicates the texture of that block. These membership functions are used to weight the effective features that are extracted by reconstructing the motion estimation equations. Characteristics of the results indicate that the use of entropy and...
Analysis of Launch Time in New Product Development With Risk Considerations
,
M.Sc. Thesis
Sharif University of Technology
;
Sheikhzadeh, Mehdi
(Supervisor)
Abstract
The importance of New Product Development (NPD) projects has been realized more and more in recent years. Among different decisions to be made in NPD process, one of the most critical decisions is about the best time to launch new product(s). Due to existence of many internal and external influential factors, determining the optimal launch time is often too complicated and it is quite hard to systematically analyze it. Despite risky nature of NPD, risk considerations in determining the optimal launch time have not been addressed in literature due to the mentioned complexity. In this research, we developed a model that takes in to account risk considerations while systematically determining...
Integration Frameworks for Assimilating Satellite Remote Sensing Observations with Hydrological Model Outputs
, Ph.D. Dissertation Sharif University of Technology ; Ataie Ashtiani, Behzad (Supervisor)
Abstract
Global climate change and anthropogenic impacts lead to alterations in the water cycle, water resource availability and the frequency and intensity of floods and droughts. As a result, developing effective techniques such as hydrological modeling is essential to monitor and predict water storage changes. However, inaccuracies and uncertainties in different aspects of modeling, due to simplification of meteorological physical processes, data limitations and inaccurate climate forcing data limit the reliability of hydrological models. Assimilation of new observations constrains the dynamics of the model based on uncertainties associated with model and data, which can introduce missing water...
Synthesis of Heterogeneous Catalysts Based on Metal-Organic Framework and Investigation of Their Applications to Promote Oxidative Carbon-Carbon Cross Coupling Reactions
, M.Sc. Thesis Sharif University of Technology ; Matloubi Moghaddam, Firouz (Supervisor)
Abstract
The magnetic MOF-based catalytic system has been reported here to be an efficient catalyst for running CDC reactions and synthesis of Triazole rings under optimal conditions. The robust MOF catalyst was built based on magnetic nanoparticles and HKUST-1 which further modified with thioacetamide and carbonization. The catalyst structure was confirmed by various techniques. Furthermore, the products’ yields were obtained in good to excellent for all reactions under mild conditions which result from superior activity of the synthesized heterogeneous catalyst containing Cupper. Also, the magnetic property of the MOF-based catalyst makes it easy to separate from reaction mediums and reuse in the...