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ahmadi-boroujeni--mehdi
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Numerical Modeling of Pile Bearing Capacity and Group Efficiency under Axial Loading
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
Bearing capacity of piles depends on many factors among which geometrical properties of piles, soil type, and strength properties of soil are of great importance. Based on these parameters, several approaches have been developed in order to overcome the uncertainty in the prediction of pile bearing capacity. Studies carried out in this area or research can be divided into two main categories: first, laboratory based approaches, and second, numerically based approaches. The research followed in the present study is based on numerical modeling. In this study, a single pile is initially modeled in the axisymmetric configuration and its bearing capacity is determined. The results of the model...
A Numerical-Analytical Solution for Determining the In-situ Horizontal Stress according to the CPT Measurements
, Ph.D. Dissertation Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor)
Abstract
Separation of the effects of the initial horizontal stress and relative density on the cone tip resistance in the sandy soils has been a complicated issue for many years. On the other hand, there is no reliable method for determining the in-situ horizontal effective stress based on the piezocone measurements in the cohesive soils, and the empirical correlations suggested in the literature produce no more than a rough estimation.Considering the aforesaid issues, an attempt is made in this thesis to provide a new innovative solution for determining the in-situ horizontal (effective) stress in the sandy and clayey soils according to the CPT measurements. In this regard, at first, numerical...
Theoretical and Numerical Analysis of Shock Waves Propagation in Porous Medium
, Ph.D. Dissertation Sharif University of Technology ; Ahmadi, Mohammad Mehdi (Supervisor) ; Mohammadi, Soheil ($item.subfieldsMap.e)
Abstract
Particulate porous mateials have always been of interest in terms of reducing shock waves effects in different protective applications. Therefore, the physics governing the flow in porous media is especially significant for which different models have been presented by the researchers. The complexities of these media have caused many existing models to be unable to properly predict the behavior of granular media under shock loadings. On the other hand, the complexity of the equations makes the numerical solution of them cumbersome and costly in a way that many researchers do not solve the whole coupled equations and reduce their number. In addition, current high-resolution TVD solutions of...
Millimeter-Wave response of all metal-organic deposited YBCO transition edge bolometer
, Article IEEE Transactions on Applied Superconductivity ; Volume 31, Issue 1 , 2021 ; 10518223 (ISSN) ; Mohajeri, R ; Alipour, Z ; Mirzaei, S. I ; Ahmadi Boroujeni, M ; Vesaghi, M. A ; Grivel, J. C ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We report on the response of a monolithic high Tc transition-edge bolometer to about 3 mmWave for the first time. The detector structure consisting of 400-nm YBa2Cu3O7-x(YBCO) film on buffered yttria stabilized zirconia substrate without any coupled antenna, shows bolometric type responsivity to the 3-mmWave radiation at its transition temperature. The YBCO thin film Ce0.9La0.1O2 buffer layer are both fabricated by the metal-organic deposition method. The meander line pattern of the bolometer is designed for obtaining maximum absorption and responsivity possible when the polarized radiation of the source is aligned with the pattern. Meander lines are 50 micrometers wide and 1.5-mm long. We...
Improved MPC algorithms for edit distance and ulam distance
, Article 31st ACM Symposium on Parallelism in Algorithms and Architectures, SPAA 2019, 22 June 2019 through 24 June 2019 ; 2019 , Pages 31-40 ; 9781450361842 (ISBN) ; Seddighin, S ; Sharif University of Technology
Association for Computing Machinery
2019
Abstract
Edit distance is one of the most fundamental problems in combinatorial optimization. Ulam distance is a special case of edit distance where no character is allowed to appear more than once in a string. Recent developments have been very fruitful for obtaining fast and parallel algorithms for both edit distance and Ulam distance. In this work, we present an almost optimal MPC algorithm for Ulam distance and improve MPC algorithms for edit distance. Our algorithm for Ulam distance is optimal in the sense that (1) the approximation factor of our algorithm is 1 + ϵ, (2) the round complexity of our algorithm is constant, (3) the total memory of our algorithm is almost linear (OH(n)), and (4)] the...
Haptic device application in persian calligraphy
, Article Proceedings - 2009 International Conference on Computer and Automation Engineering, ICCAE 2009, 8 March 2009 through 10 March 2009, Bangkok ; 2009 , Pages 160-164 ; 9780769535692 (ISBN) ; Meghdari, A ; Sharif University of Technology
2009
Abstract
The Haptic device is capable of interacting dynamically with the operator by the forces it can exert on human's hand. Controlling the haptic device and constraining it through the desired trajectory is the common task in the most of the training systems. Haptic interface application in virtual Persian handwriting learning system is investigated in this paper. Two different modes of learning is investigated: The full guidance mode, guides the user to follow a prerecorded trajectory by applying proper force to operator's hand; whereas in partial guidance, combination of haptics andvisual feedback guides the operator and prevents deviation from the desired trajectory. © 2009 IEEE
Improving the efficiency and directivity of THz photoconductive antennas by using a defective photonic crystal substrate
, Article Optics Communications ; Volume 412 , April , 2018 , Pages 74-79 ; 00304018 (ISSN) ; Ahmadi Boroujeni, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
One of the shortcomings of photoconductive (PC) antennas in terahertz (THz) generation is low effective radiated power in the desirable direction. In this paper, we propose a defective photonic crystal (DPC) substrate consisting of a customized 2D array of air holes drilled into a solid substrate in order to improve the radiation characteristics of THz PC antennas. The effect of the proposed structure on the performance of a conventional THz PC antenna has been examined from several aspects including radiation efficiency, directivity, and field distribution. By comparing the radiation performance of the THz antenna on the proposed DPC substrate to that of the conventional solid substrate, it...
Design of terahertz photoconductive antenna arrays based on defective photonic crystal substrates
, Article Optics and Laser Technology ; Volume 114 , 2019 , Pages 89-94 ; 00303992 (ISSN) ; Ahmadi Boroujeni, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna...
Haptic Device Application in Virtual Training
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor)
Abstract
Haptic Interfaces have been used as cooperative systems to reproduce and simulate human actions. The Haptic Interface (HI) can be used as a tool capable of interacting dynamically with the operator using haptic technology. By controlling the haptic interface and constraining it to move through the desired trajectory which is required for most of the training systems such as Hand Writing Learning System, Minimally Invasive Surgical Simulation, virtual welding training and gaming applications the users can easily interact with virtual environment through the sense of touch. Haptic device application in virtual handwriting training was investigated in this thesis. Two different modes of...
The Productivity Effects of Privatization: The Islamic Republic of Iran
, M.Sc. Thesis Sharif University of Technology ; Manzoor, Davood (Supervisor)
Abstract
One of the major aims of privatization is increasing the productivity by transferring ownership to private sector. We would like to estimate this effect in selected state –owned firms. Analysis the productivity effect of privatization of Iranian firms that were initially state-owned will show the requirement of needy policies in management field of privatization to ratify and run the privatization policy faster base on academic estimate. We analyze the productivity effect of privatization using time series and cross search data (panel data) for 21 selected initially state-owned firms that are privatized in different industry with several observations pre and post privatization. Our goal is...
Game Theory in Computational Biology
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
In recent years, game theory passed from areas of economics and socials to other fields such as computational biology and bioinformatics. Several evolutionary games and cooperative games have been defined to predict the behavior of nonrational agents in interaction situations arising from computational biology.One of the these main applications is using Shapley value. Shapley value allocates a fair value to each player, in games that each coalition has a profit.But in many cases the computation of Shapley value is #P-complete. Thus,the goal is to optimally find Shapley value or to approximate it in each game.Another option is Banzhaf index.One of the essential games on genes is Pathway game....
Integration of a Cyclic Three-Stage Supply Chain for Fast Moving Consumer Goods
, Ph.D. Dissertation Sharif University of Technology ; Shadrokh, Shahram (Supervisor)
Abstract
This research deals with a realistic cyclic three-stage supply chin consisting of one supplier, one manufacturer and one or more retailers, in FMCG environment. Orders from retailers are supposed to iterate over cycles and parallel machines are available to process perishable jobs with given release dates, due dates and deadlines. To start process of he jobs, perishable raw material, supplied by an external supplier, is required. Jobs are subject to post-production shelf life limitation and must be delivered to retailers during the corresponding time window bounded by due dates and deadlines. Both early and tardy jobs are penalized by partial weighted earliness/tardiness functions and the...
Modeling of Cancer Progression by Using Evolutionary Game Theory
, M.Sc. Thesis Sharif University of Technology ; Habibi, Jafar (Supervisor)
Abstract
Mathematical modeling and computer simulation are powerful tools to help cancer research because they provide a good insight of cancer progression and an efficient framework to test biological hypothesis. Most of the previous studies ignored many intracellular communication between tumor cells. Gap junction is one of the interaction ways between tumor cells which plays a crucial role in cancer progression. In the first phase of this thesis, a model of intracellular communication through gap junction using evolutionary game theory scoring is proposed. In the second phase of this thesis, cancer is modeled by Markov decision process (MDP). Given that considering nutrient level constant is one...
Processing Queries with Mathematical Expressions on Encrypted Outsourced Databases
, M.Sc. Thesis Sharif University of Technology ; Jalil, Rasool (Supervisor)
Abstract
The ever-increasing volume of data and the lack of computational and storage facilities have caused a managerial challenge to organizations. The existence of these challenges on the one hand and the increase of storage services on the other hand have compelled the organizations to delegate their storage and management of data to the server providers of cloud storage services. The outsourcing of data to servers obviates the need for purchasing exorbitant storage equipment and recruiting professional workforce in the organization. Since the organization’s data will be kept outside the organization’s ambience in case of using such services in form of outsourcing, and the data will not be under...
Development of Heuristic Algorithms for Real-Time Model Predictive Control of Nonlinear Parameter Varying Systems with Uncertainty
, Ph.D. Dissertation Sharif University of Technology ; Nobahari, Hadi (Supervisor)
Abstract
In this study, novel algorithms are presented for nonlinear parameter varying systems with uncertainty in the model predictive control using heuristic algorithms. To this end, some algorithms are developed which provide the possibility of estimating simultaneously states and control signal of the stochastic nonlinear systems. Then, the model predictive control algorithm is presented for stochastic nonlinear systems with uncertainty to estimate uncertainty and compensate it using ant colony optimization. Next, the model predictive control algorithm is developed for nonlinear system with matched bounded uncertainty using particle swarm optimization. Performance of the developed controllers is...
Using Artificail Neural Networks for Solving Assignment Problems in WorldWide Webs Optimization
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
In this thesis the capacity and flow assignment problems in worldwide webs is considered in order to minimize the total cost of networks and delays in network links. The main result of this problem is increasing the speed of message transmission and providing better quality of service delivery for network users. For pursuing these goals, Recursive Artificial Neural Networks is proposed for solving the problem and because of their high power and accuracy in reaching optimal solutions, they are convergent to optimal solutions very well. The method is tested on four different topologies and the results show that Recursive Artificial Neural Networks have high efficiency to reach optimal...
Approximating Edit Distance
, Ph.D. Dissertation Sharif University of Technology ; Ghodsi, Mohammd (Supervisor)
Abstract
Edit distance or Levenshtein distance is one of the most fundamental problems in computer science and engineering to measure the dissimilarity between strings.This problem is solvable in O(n^2) time using dynamic programming and in 2015 it was conditionally proven that no truly subquadratic time algorithm (\textit{i.e.}, O(n^{2-ε})) exists for edit distance.Since 2001, approximating edit distance within a constant factor was recognized as one of the biggest unsolved problems in the field of combinatorial pattern matching.This thesis designs seven approximation algorithms for edit distance and its related problems.Firstly, two quantum approximation algorithms are designed with constant...
Improved MPC algorithms for Edit distance and Ulam distance
, Article IEEE Transactions on Parallel and Distributed Systems ; Volume 32, Issue 11 , 2021 , Pages 2764-2776 ; 10459219 (ISSN) ; Ghodsi, M ; Seddighin, S ; Sharif University of Technology
IEEE Computer Society
2021
Abstract
Edit distance is one of the most fundamental problems in combinatorial optimization to measure the similarity between strings. Ulam distance is a special case of edit distance where no character is allowed to appear more than once in a string. Recent developments have been very fruitful for obtaining fast and parallel algorithms for both edit distance and Ulam distance. In this work, we present an almost optimal MPC (massively parallel computation) algorithm for Ulam distance and improve MPC algorithms for edit distance. Our algorithm for Ulam distance is almost optimal in the sense that (1) the approximation factor of our algorithm is $1+epsilon$1+ϵ, (2) the round complexity of our...
Fatigue Life Assessment of the Joints in Offshore Structures:Considering Residual Stress Caused By Welding Process and Elliptical Crack
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholam Hossein (Supervisor)
Abstract
Offshore structures are valuable structures used in the offshore petroleum and gas fields for the purpose of hydrocarbon production operation. These structures are influenced by wave loads. Sea waves are inherently alternative and for this reason fatigue failure is considered as one of the most important modes of failure in these structures. Joints in these structures are made by tubes and they are called tubular joints. The joining process in manufacturing of these joints is welding. Welding process induces residual stresses, mostly tensional, in the substructure of materials. This tensional residual stress has a destructive effect on fatigue life of the joint and increases probability of...
Design of a hybrid spoof plasmonic sub-terahertz waveguide with low bending loss in a broad frequency band
, Article Optics Express ; Volume 25, Issue 6 , 2017 , Pages 6860-6873 ; 10944087 (ISSN) ; Ahmadi Boroujeni, M ; Sharif University of Technology
OSA - The Optical Society
2017
Abstract
The effect of dielectric cladding on the waveguiding characteristics of an array of metallic pillars on a metal plane in the sub-terahertz band is explored. Firstly, a 2D structure made up of a metallic grating of infinite lateral width with various dielectric overlays is analytically studied to get more insight into the problem. Then the ideas inferred from the 2D structure are applied to the realistic 3D structure that has a finite lateral width. It is shown that by proper design of the dielectric medium surrounding the metallic structure the modal field confinement can be enhanced in a broad frequency band resulting in a low bending loss. Especially, by integrating the pillars into a...