Axisymmetric Response of a Transversely Isotropic Half-space Stiffened by a Thin Plate Considering Refined Interaction Theory

, M.Sc. Thesis Sharif University of Technology Shanesaz Zadeh, Pouya (Author) ; Eskandari, Morteza (Supervisor)

Abstract

In this paper, the elastic response of a surface-stiffened transversely isotropic half-space subjected to a surface normal load is addressed. The half-space is reinforced by a Kirchhoff thin plate bonded to its surface. Two different boundary conditions are considered across the plate-half-space interface: (i) the classic approach in which the plate in-plane deformation is neglected by writing the interfacial boundary conditions across the plate mid-plane, and (ii) the refined approach that considers the in-plane deformation of plate due to bending by writing the boundary conditions across the bottom face of plate. By virtue of appropriate displacement potentials, the complete set of elastic...

Autonomous runway alignment of fixed-wing unmanned aerial vehicles in landing phase

, Article 5th International Conference on Autonomic and Autonomous Systems, ICAS 2009, Valencia, 20 April 2009 through 25 April 2009 ; 2009 , Pages 208-213 ; 9780769535845 (ISBN) Pouya, S ; Saghafi, F ; Sharif University of Technology

2009

Abstract

In this paper, the development of a controller for autonomous lateral alignment of fixed-wing Unmanned Aerial Vehicles (UAVs) with runway centerline in landing phase is presented. Fuzzy Logic Control (FLC) is used in order to enable the vehicle to mimic the decision making procedure that a pilot follow in the same situation. Also, for longitudinal motion controller design for the UAV to follow a pre-defined trajectory, the pole-placement technique is used. It is assumed that the runway relative position and orientation are provided by a built in vision system and its associated image processing unit. The performance of the controller in the presence of the Gaussian noises is investigated by...

Improved optimal control technique for control of parallel three- phase inverters

, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, Sharjah, 10 November 2009 through 12 November 2009 ; 2009 ; 9789948427155 (ISBN) pouya, H. R. N ; Mokhtari, H ; Sharif University of Technology

2009

Abstract

This paper proposes a high performance voltage tracking and current sharing among parallel connected inverters by applying optimal control and minimizing the cost function. The control system forces the voltage of load to track the voltage reference, and the current of all inverters becomes equal. Therefore, both current sharing and voltage tracking are obtained. In addition, the smallest input energy and simplicity in control circuit are the other advantages of the suggested method. To show the performance of the proposed control scheme, the simulations with two-modular practical systems are performed and the results are provided. The results indicate that the control objectives are...

Seismic Response of “Karroon III” DAM to Non-Uniform Ground Motions

, M.Sc. Thesis Sharif University of Technology Pouya, Mohammad Reza (Author) ; Ghaemian, Mohsen (Supervisor)

Abstract

Usually in analysis of arch dams, applied seismic motions on dam-foundation interface are assumed to be uniform. This is while that recorded motions show non-uniform accelerations in dam-foundation interface. Analyzing of the dam under this non-uniform accelerations we can find the importance of this assumption in analysis of arch dams. Two earthquakes were excited “KAROON III” dam at 20.11.2007 and 21.11.2007. The respective motions were recorded by the array of accelerometers that has been installed on the dam. The recorded motions, indicated non-uniformity of excitations in accelerometers were installed near the dam-foundation interface. Therefore this data provided an opportunity to...

The effect of non-uniformity in ground motions on the seismic response of arch dams

, Article SN Applied Sciences ; Volume 3, Issue 3 , 2021 ; 25233971 (ISSN) Pouya, M. R ; Sohrabi Gilani, M ; Ghaemian, M ; Sharif University of Technology

Springer Nature 2021

Abstract

Recorded ground accelerations at various locations of Karun III Dam during November 20, 2007, were recorded by an array of accelerometers located on the dam. In terms of amplitude and phase, these accelerations show non-uniformities in different elevations. In this paper, the effect of these non-uniform ground motions on the seismic response of the dam taking dam-reservoir-foundation interaction into account is investigated. The EACD-3D-2008 finite element program and ABAQUS Software are used for carrying out the seismic analyses. For this purpose, time histories of the earthquake accelerations are interpolated at nodal points located on the dam foundation interface. The analysis has been...

Thermal analysis of RCC dams during construction considering different ambient boundary conditions at the upstream and downstream faces

, Article Journal of Civil Structural Health Monitoring ; Volume 12, Issue 3 , 2022 , Pages 487-500 ; 21905452 (ISSN) Pouya, M. R ; Sohrabi Gilani, M ; Ghaemian, M ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2022

Abstract

Thermal analysis of Roller Compacted Concrete (RCC) dams is generally carried out considering identical ambient boundary conditions at upstream and downstream faces. For the case of Shahri-Kor Dam (an RCC dam with a height of 57 m), recorded thermal data depicts a considerable difference between upstream and downstream ambient temperatures, especially during cold months. This paper investigates how taking this difference into account can affect the thermal response of the dam. For this purpose, two thermal analyses are carried out with and without consideration of these different ambient boundary conditions (DABC). Consequently, the computed temperatures at representative points are compared...

Design of a Control System Based on the Permanent Magnet for Control of a Magnetic Catheter

, M.Sc. Thesis Sharif University of Technology Hatami Pouya, Mohammad (Author) ; Nejat Pishkenari, Hossein (Supervisor)

Abstract

Currently, the use of robots and microrobots in medical applications has significantly increased due to their extensive and unique capabilities. One such application involves the utilization of magnetic continuum robots controlled by an external magnetic field in minimally invasive surgeries. This research focuses on discussing methods for effectively controlling magnetic-continuum robots and applying external magnetic fields. Two primary methods for applying the external magnetic field are explored: the use of electromagnetic coils and permanent magnets. Based on these methods, systems for applying the field and controlling the magnetic continuum robot have been constructed and...

The maximum disjoint routing problem

, Article 22nd International Conference on Computing and Combinatorics, COCOON 2016, 2 August 2016 through 4 August 2016 ; Volume 9797 , 2016 , Pages 319-329 ; 03029743 (ISSN); 9783319426334 (ISBN) Shahmohammadi, F ; Sharif Zadeh, A. S ; Zarrabi Zadeh, H ; Sharif University of Technology

Springer Verlag 2016

Abstract

Motivated by the bus escape routing problem in printed circuit boards, we revisit the following problem: given a set of n axis-parallel rectangles inside a rectangular region R, find the maximum number of rectangles that can be extended toward the boundary of R, without overlapping each other. We provide an efficient algorithm for solving this problem in O(n2 log3 n log log n) time, improving over the current best O(n3)-time algorithm available for the problem

Learning overcomplete dictionaries from markovian data

, Article 10th IEEE Sensor Array and Multichannel Signal Processing Workshop, SAM 2018, 8 July 2018 through 11 July 2018 ; Volume 2018-July , 2018 , Pages 218-222 ; 2151870X (ISSN); 9781538647523 (ISBN) Akhavan, S ; Esmaeili, S ; Babaie Zadeh, M ; Soltanian Zadeh, H ; Sharif University of Technology

IEEE Computer Society 2018

Abstract

We explore the dictionary learning problem for sparse representation when the signals are dependent. In this paper, a first-order Markovian model is considered for dependency of the signals, that has many applications especially in medical signals. It is shown that the considered dependency among the signals can degrade the performance of the existing dictionary learning algorithms. Hence, we propose a method using the Maximum Log-likelihood Estimator (MLE) and the Expectation Minimization (EM) algorithm to learn the dictionary from the signals generated under the first-order Markovian model. Simulation results show the efficiency of the proposed method in comparison with the...

Direction and Range Assignment for Directional Antennae in Wireless Networks

, M.Sc. Thesis Sharif University of Technology Kharrati-Zadeh, Mohammad Mehdi (Author) ; Zarrabi-Zadeh, Hamid (Supervisor)

Abstract

In recent years, significant interest has been attracted towards using directional antennae in wireless and sensor networks due to it’s decreased energy consumption, increased security and decreased radio wave overlapping. Substituting omni-directional antennae with directional antennae should be performed in a way that not only guarantees connectivity, but also minimizes radius and latency in network nodes. The problem is not polynomially solvable in general and effort has been made in recent years to present approximation algorithms to solve this problem. The approximation algorithms have been made possible using unit disk
graphs, Euclidean minimum spanning trees, grouping of...

Experimental study on macro segregation behavior in short and wide range solidification of different aluminum alloys

, Article Materials Science and Technology Conference and Exhibition 2013, MS and T 2013 ; Volume 2 , 2013 , Pages 822-829 ; 9781629933092 (ISBN) Shafiei Zadeh, B ; Mohammad Salehi, E ; Hassan Nejad, H ; Shafiei Zadeh, S ; Sharif University of Technology

2013

Abstract

Data are presented on the solidification of aluminum alloys and their macro segregation behavior. Three alloys with different solidification ranges were prepared in two temperatures. Two types of molds were also prepared by sand and metallic materials. The solidification of Al alloys were studied and the effects of four parameters were determined, including cooling rate, casting temperature, degassing and nucleation effects on solidification and a comparison was conducted to Scheil model performance. Three types of aluminum alloys (Al-12.1%Si, Al-6.9%Si and Al-4.4% Cu) with short, medium and wide solidification ranges were studied and the results showed that degassing, nucleation, increasing...

On the rectangle escape problem

, Article Theoretical Computer Science ; Volume 689 , 2017 , Pages 126-136 ; 03043975 (ISSN) Ahmadinejad, A ; Assadi, S ; Emamjomeh Zadeh, E ; Yazdanbod, S ; Zarrabi Zadeh, H ; Sharif University of Technology

2017

Abstract

Motivated by the bus escape routing problem in printed circuit boards, we study the following rectangle escape problem: given a set S of n axis-aligned rectangles inside an axis-aligned rectangular region R, extend each rectangle in S toward one of the four borders of R so that the maximum density over the region R is minimized. The density of each point p∈R is defined as the number of extended rectangles containing p. We show that the problem is hard to approximate to within a factor better than 3/2 in general. When the optimal density is sufficiently large, we provide a randomized algorithm that achieves an approximation factor of 1+ε with high probability improving over the current best...

A higher index theorem for foliated manifolds with boundary

, Article Bulletin des Sciences Mathematiques ; Volume 136, Issue 2 , 2012 , Pages 201-238 ; 00074497 (ISSN) Esfahani Zadeh, M ; Sharif University of Technology

2012

Abstract

Following Gorokhovsky and Lott and using an extension of the b-pseudodifferential calculus of Melrose, we give a formula for the Chern character of the Dirac index class of a longitudinal Dirac type operators on a foliated manifold with boundary. For this purpose we use the Bismut local index formula in the context of noncommutative geometry. This paper uses heavily the methods and technical results developed by E. Leichtnam and P. Piazza

A note on some classical results of Gromov-Lawson

, Article Proceedings of the American Mathematical Society ; Volume 140, Issue 10 , 2012 , Pages 3663-3672 ; 00029939 (ISSN) Zadeh, M. E ; Sharif University of Technology

2012

Abstract

In this paper we show how the higher index theory can be used to prove results concerning the non-existence of a complete Riemannian metric with uniformly positive scalar curvature at infinity. By improving some classical results due to M. Gromov and B. Lawson we show the efficiency of these methods to prove such non-existence theorems

Delocalized betti numbers and morse type inequalities

, Article Rocky Mountain Journal of Mathematics ; Volume 41, Issue 4 , August , 2011 , Pages 1361-1374 ; 00357596 (ISSN) Zadeh, M. E ; Sharif University of Technology

2011

Abstract

In this paper we state and prove delocalized Morse type inequalities for Morse functions as well as for closed differential 1-forms. These inequalities involve delocalized Betti numbers. As an immediate consequence, we prove the vanishing of delocalized Betti numbers of manifolds fibering over the circle under a vanishing condition on the delocalizing conjugacy class

Parallel in-vitro and in-vivo techniques for optimizing cellular microenvironments by implementing biochemical, biomechanical and electromagnetic stimulations

, Article Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS ; 2012 , Pages 1397-1400 ; 1557170X (ISSN) ; 9781424441198 (ISBN) Shamloo, A ; Heibatollahi, M ; Ghafar Zadeh, E

2012

Abstract

Development of novel engineering techniques that can promote new clinical treatments requires implementing multidisciplinary in-vitro and in-vivo approaches. In this study, we have implemented microfluidic devices and in-vivorat model to study the mechanism of neural stem cell migration and differentiation.These studies can result in the treatment of damages to the neuronal system. In this research, we have shown that by applying appropriate ranges of biochemical and biomechanical factors as well as by exposing the cells to electromagnetic fields, it is possible to improve viability, proliferation, directional migration and differentiation of neural stem cells. The results of this study can...

On vanishing of low-degree higher Â-genera

, Article Differential Geometry and its Application ; Volume 43 , 2015 , Pages 56-59 ; 09262245 (ISSN) Esfahani Zadeh, M ; Sharif University of Technology

2015

Abstract

In this short note we apply methods introduced by B. Hanke and T. Schick to prove the vanishing of (low degree) higher Â-genera for spin manifolds admitting a positive scalar curvature metric. Our aim is to provide a short proof for this beautiful result

The Minimum vulnerability problem

, Article Algorithmica ; Volume 70, Issue 4 , 2014 , pp 718-731 ; ISSN: 14320541 Assadi, S ; Emamjomeh-Zadeh, E ; Norouzi-Fard, A ; Yazdanbod, S ; Zarrabi-Zadeh, H ; Sharif University of Technology

2014

Abstract

We revisit the problem of finding (Formula presented.) paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the (Formula presented.) paths. We provide a (Formula presented.)-approximation algorithm for this problem, improving the best previous approximation factor of (Formula presented.). We also provide the first approximation algorithm for the problem with a sublinear approximation factor of (Formula presented.), where (Formula presented.) is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be...

The minimum vulnerability problem

, Article Algorithmica ; Volume 7676 LNCS , 2012 , Pages 382-391 ; 14320541(ISSN) ; 9783642352607 (ISBN) Assadi, S ; Emamjomeh Zadeh, E ; Norouzi Fard, A ; Yazdanbod, S ; Zarrabi Zadeh, H ; Sharif University of Technology

2012

Abstract

We revisit the problem of finding k paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the k paths. We provide a ⌊k/2⌋-approximation algorithm for this problem, improving the best previous approximation factor of k - 1. We also provide the first approximation algorithm for the problem with a sublinear approximation factor of O(n3/4), where n is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be improved to O(√n). While the problem is NP-hard, and even hard to approximate to within an O(log n)...

MR artifact reduction in the simultaneous acquisition of EEG and fMRI of epileptic patients

, Article 16th European Signal Processing Conference, EUSIPCO 2008, Lausanne, 25 August 2008 through 29 August 2008 ; 2008 ; 22195491 (ISSN) Amini, L ; Sameni, R ; Jutten, C ; Hossein Zadeh, G. A ; Soltanian Zadeh, H ; Sharif University of Technology

2008

Abstract

Integrating high spatial resolution of functional magnetic resonance imaging (fMRI) and high temporal resolution of electroencephalogram (EEG) is promising in simultaneous EEG and fMRI analysis, especially for epileptic patients. The EEG recorded inside an MR scanner is interfered with MR artifacts. In this article, we propose new artifact reduction approaches and compare them with the conventional artifact reduction methods. Our proposed approaches are based on generalized eigenvalue decomposition (GEVD) and median filtering. The proposed methods are applied on experimental simultaneous EEG and fMRI recordings of an epileptic patient. The results show significant improvement over...