Efficient Visibility Computation and Simplification in Different Environments

, Ph.D. Dissertation Sharif University of Technology Zarei, Alireza (Author) ; Ghodsi, Mohammad (Supervisor)

Abstract

In this thesis, we considered several types of the visibility problem. These problems include computing the visibility polygon of a point observer inside a polygonal domain, maintaining visibility polygon of a moving point observer, visibility coherence in space, maintaining visibility polygon of a moving segment observer and visibility dependent simplification. Furthermore, we considered these problems in both offline and streaming settings. These problems arise in different practical areas, such as computer graphics, machine vision, robotics, motion planning, geographic information systems (GIS) and computational geometry. We obtained effective theoretical results as well as superior...

Investigation of Modeling and Implementation of Systolic Arrays on Accelerators

, M.Sc. Thesis Sharif University of Technology Zarei, Parisa (Author) ; Ghodsi, Mohammad (Supervisor)

Abstract

The ever-increasing volume of data and calculations has caused a noticeable increase in the importance of computer processing speed. Therefore, topics related to parallel processing as an effective solution in increasing the speed of calculations have been specially investigated and studied. Systolic computing is a powerful approach to parallelize data and perform concurrent computations. Systolic arrays fulfill the goals of the algorithm by directing data flow among different processors and performing minor calculations on them. The slowness and limitations of processors compatible with these arrays, such as FPGAs, have faced many challenges in applying and using their capacities. These...

Valuation of Emerging Companies by Taking into Account the Rate of Discounting of the Variable and Volatility Changes Using the New Valuation Approaches

, M.Sc. Thesis Sharif University of Technology Zarei, Hashem (Author) ; Modarres, Mohammad (Supervisor)

Abstract

Nowadays the evaluation startups has been difficult and this problem increases the likelihood of misunderstanding price of company's stock. Companies need precise evaluation in different steps of their development. during fund-raising, To make the investors’ share determine, the value of companies should be calculated because the investors’ share equals the ratio of new investment to the value of company after investment. Besides, during the merge or possession of a company, to determine the value of the deal or the share of the dealers, we need to evaluate value of the company. to evaluate the Intrinsic value of company, we need to know potential revenue streams, financial statements, the...

, M.Sc. Thesis Sharif University of Technology Zarei, Mohammad Jafar (Author) ; Hooshmand, Mahmoud (Supervisor)

Abstract

Telecommunication Company of Iran (TCI), as a government owned company that provides fixed, mobile and Internet services. It is in the process of privatization. In order to be survived in competitive environment, it is required to be an agile and dynamic organization. Also it should be seriously sensitive in profit margin. To be a dynamic company, the management of the company is expecting to introduce a new and modern service named Advanced Communication Services (ACS). This service consists of Video on Demand (VOD), live and archive television programs, tell-learning and e- shopping. For TCI, it's crucial to find a right and precise answer to the challenging question "Will ACS be a...

Conflict-free Chromatic Art Gallery Covering with Vertex Guards

, M.Sc. Thesis Sharif University of Technology Zarei Moradi, Somayeh (Author) ; Ghodsi, Mohammad (Supervisor)

Abstract

The visibility is one of the most important problems in computational geometry. Two points are said to be visible to each other, if the line segment that joins them does not intersect any obstacles. The art gallery problem is a well-studied visibility problem in computational geometry. It originates from a real-world problem of guarding an art gallery with the minimum number of guards who together can observe the whole gallery. In many of applications, the “guards” are “landmarks” deployed in an environment to help provide navigation and localization service to mobile robots. The mobile device communicates with these landmarks through wireless, or other “line-of-sight” signaling...

Clustering Massive Data Streams

, M.Sc. Thesis Sharif University of Technology Bahrami, Mohammad Saleh (Author) ; Zarei, Alireza (Supervisor)

Abstract

With the advancement of technologies such as the Internet of Things the number of devices that are connected to the Internet are increasing rapidly and they continuously generate data that is increasing day by day. Data generation rate in these devices can be so large that practically the existing hardware has not the ability to store and process all information related to that data in appropriate way. In this situation, streaming models become more important. In the stream computing models, online processing of these data are implemented with memory complexity of O(1) . Stream algorithms refers to algorithms that input data is in the form of streams. Data appear and are removed from the...

Minimum Link Navigation

, M.Sc. Thesis Sharif University of Technology Davari, Mohammad Javad (Author) ; Zarei, Ali Reza (Supervisor)

Abstract

Finding a path between two specified points is one of the most common problem in computational geometry. The minimum-link path problem is in this category. The minimum-link path between two points is the path between these points with the minimum number of segments. Minimum-link paths have application in areas such as computer graphic, geographic information systems, robotics, image processing, cryptography and VLSI.In this thesis we study variations of the minimum link path problem. Specifically we consider the constrained minimum-link paths in which the path must passes through some given
regions. We detected a flaw in a previously presented algorithm and propose a method to fix this...

The Completeness in Statistical Mechanics

, M.Sc. Thesis Sharif University of Technology Zarei, Mohammad Hossein (Author) ; Karimipour, Vahid (Supervisor)

Abstract

Ising model. It means that the partition function of each lattice model is equal to the partition function of 2D Ising model. This completeness is proved by using concepts and techniques from quantum information theory and is based on the universality of cluster states. We have now proved this important result, by using independent and general concepts and methods which are accessible to a wide audience of researchers across many disciplines. Furthermore, our method has the advantage of eing algorithmic in nature so that, by following a set of simple graphical transformations, one is able to transform any discrete lattice model to an Ising model defined on a (polynomially) larger 2D...

An Analitical Model for Grid Stiffened Structures of Various Patterns

, M.Sc. Thesis Sharif University of Technology Zarei, Mohsen (Author) ; Kouchakzadeh, Mohammad Ali (Supervisor)

Abstract

Structural efficiency is a primary concern in today’s aerospace and aircraft industries. This brings about the need for strong and light weight structures. To increase the strength of a panel without considerable increase in its weight, we may use a lattice of stiffeners which may have shells connected to one side of the lattice or both sides of it. These structures are usually called grid stiffened structures. Aircraft fuselage and launch vehicle fuel tanks are some of the many applications of these structures in aerospace and aircraft industries. These structures include two major groups; isogrids (grid stiffened structures with equivalent isotropic properties) and orthogrids (grid...

Graph Signal Processing-Based Resource Allocation in Fiber-Optic Networks

, M.Sc. Thesis Sharif University of Technology Zarei Ardestani, Mohammad Hossein (Author) ; Hadi, Mohammad (Supervisor) ; Pakravan, Mohammad Reza (Supervisor)

Abstract

With the advancement of technology, the volume of network traﬀic has also increased dramatically. The optical network, as the main part of the backbone communication system, plays a significant role in the transmission of network traﬀic. Due to the limited network resources, an eﬀicient resource allocation in optical networks is required to increase network performance and reduce costs. To solve resource allocation optimization problems, an effective tool is needed to provide a suitable solution in a reasonable time. Resource allocation problems are usually developed on a graph, which is derived from network topology or other properties of the network. As a result, graph-based tools seem to...

Effect of the Chemical Coagulant and Oxidizer on the Membrane Fouling During the Treatment of Wastewater Using a Membrane Bioreactor

, M.Sc. Thesis Sharif University of Technology Zarei Baygi, Ali (Author) ; Moslemi, Mohammad Reza (Supervisor)

Abstract

Membrane bioreactor (MBR) is a combination of conventional activated sludge (CAS) and membrane filtration which owing to its advantages such as high quality effluent and low excess sludge production, has gained increasing application in wastewater treatment. The major drawback of a MBR is the membrane fouling that reduces the permeate flux, which in turn increases the overall operational costs due to high energy requirements. In existing study, the combination of sludge oxidation and coagulation/flocculation addition was investigated for mitigation of membrane fouling in a membrane bioreactor. Oxidation can facilitate sludge flocculation and hence improve the properties of mixed liquor. The...

Robust Vision-Based Pose and Parameter Estimation of Unknown Space Objects in the Cluttered Orbits

, Ph.D. Dissertation Sharif University of Technology Zarei Jalalabadi, Mahboubeh (Author) ; Malaek, Mohammad Bagher (Supervisor)

Abstract

To provide a safe environment for space equipments and infrastructures in addition to managing the role of hazardous objects that are known as space debris, the presented thesis describes a new robust technique to estimate the dynamic states and inertial parameters of Uncooperative Space Objects (USO) with uncertain dynamics in the cluttered orbits. The prescribed method is especially effective to capture stray objects, capture and servicing of the satellites, rendezvous and collision avoidance maneuvers, space explorations as well as Actrive Debris Removal (ADR) missions. Such missions call for high degree of precision and reliable estimation methods. The proposed estimation architecture...

Optimum Camera Position for UAV Vertical Plane Maneuvers

, M.Sc. Thesis Sharif University of Technology Zarei Jalal Abadi, Mahboube (Author) ; Malaek, Mohammad Bagher (Supervisor)

Abstract

This work presents the methodology to investigate Optimum Camera Installation Angle (OCIA)while employing the so called?Vision Based Navigation (VBN)? in urban areas.The approach is suitable for future general aviation aircraft as envisioned in Small Air Transportation System (SATS) as well as Unmanned Aerial Vehicles (UAV).Due to practical constraints, the work is limited to the maneuvers in the vertical plane while conducting Simultaneous Localization and Mapping (SLAM) technique.This technique was originated in robotics and is commonly used to guide both ground based and low speed aerial robots in unknown environments involving different types of obstacles. A variety of camera...

Probabilistic Evaluation of Steel Moment Frames with Partially Restrained Connections

, M.Sc. Thesis Sharif University of Technology Zarei Rahmat Abadi, Davood (Author) ; Kazemi, Mohammad Taghi (Supervisor)

Abstract

Considering connections as ideally rigid or pinned is a common assumption during design and analysis of steel moment frames. However, in real world, steel connections show a non-linear behavior between these two ideal states. The aim of this research is to investigate the effect of partially restrained connections on the design and performance of two-dimensional steel moment frames under vertical and horizontal loads that are applied statically. For this aim, nonlinear finite element modeling is used in probabilistic evaluation process to assess the performance of existing structures. To capture the real behavior of structure in models, geometric and material sources of nonlinearity are...

Introducing a Comprehensive Framework to Measure Spike-LFP Coupling

, Ph.D. Dissertation Sharif University of Technology Zarei, Mohammad (Author) ; Jahed, Mehran (Supervisor) ; Daliri, Mohammad Reza (Co-Supervisor)

Abstract

LFP characteristics have been shown to be informative of sensory stimuli and influenced by attention. We show the gamma power in area MT is selective to motion direction showing a Gaussian tuning curve. Here we show for the first time, some evidence based on a single monkey’s data that spatial attention enhances the tuning curve based on gamma power.The synchronization of activity across neurons has been a focus in many recent studies of information processing in networks of cortical cells and areas. One aspect of such inter-neuronal synchrony is the locking of spiking activity to local field potentials (LFPs). Such an interaction has been observed between the timing of individual action...

What drives mergers and acquisitions waves in developing countries? Evidences from Iranian banking industry

, Article Iranian Economic Review ; Volume 19, Issue 2 , 2015 , Pages 123-137 ; 10266542 (ISSN) Zarei, M ; Alambeigi, A ; Karimi, P ; Zarei, B ; Sharif University of Technology

2015

Abstract

Many Middle-East countries, like Iran, have dynamic banking industries and have observed merger and acquisitions (M&A) waves. M&A waves are usually defined in the developed world context and some of their main drivers were identified as: market timing, environment's shocks, merger manias, government regulation and regulatory, and technological changes. It has been discussed that merger waves and their reasons are among the ten most important unsolved mysteries in the field of finance (Brealey and Myers, 1991, p. 923), and as a result of this, it was not possible to completely clarify the reasons behind emerging M&A waves, especially in developing countries; for this reason in these...

The effects of mergers and acquisitions (M&As) on bank performance and entrepreneurial orientation (EO)

, Article Iranian Entrepreneurship: Deciphering the Entrepreneurial Ecosystem in Iran and in the Iranian Diaspora ; 2017 , Pages 361-375 ; 9783319506395 (ISBN); 9783319506388 (ISBN) Zarei, M ; Alambeigi, A ; Zarei, B ; Karimi, P ; Sharif University of Technology

Springer International Publishing 2017

Abstract

This chapter aims at pointing out that how mergers and acquisitions (M&As) as popular strategies which they are based on external growth approach have affected the performance of banks and entrepreneurial orientation (EO) in the context of Iranian financial sector. In this regard, it has been tried to investigate in what way EO moderates the relationships between the performance of banks in one hand, and M&As on the other hand. For this goal, 114 participants including the top and middle managers of the Iranian banks were chosen to be closely considered. The research is an applied research and a cross-correlation methodology has been used to spotlight on the probable relationships between EO...

Capturing Co2 of the Atmosphere by Molten Carbonates and Transforming to Carbon Nanofiber

, M.Sc. Thesis Sharif University of Technology Zarei, Mohammad Mahdi (Author) ; Moosavi, Ali (Supervisor) ; Nouri Borujerdi, Ali (Supervisor)

Abstract

Capturing the atmospheric CO2 and turning it into value added products is a topic that has been extensively studied in recent years. One of the methods through which CO2 is valorized is via converting it into carbon nanofiber, CNFs. CNFs can be an important material in future human activities due to its valuable properties such as wide range of electrical conductivity, their superior flexibility and strength, But it is currently obstructed in use due to the high cost of manufacturing and the complexity of the synthesis. Furthermore, in today's world, human life is heavily influenced by greenhouse gases, and avoiding emitting gases like CO2, is almost infeasible. This thesis provides an...

Visualization of Pool Boiling Heat Transfer of Magnetic Nano-Fluid

, M.Sc. Thesis Sharif University of Technology Zarei Salehabad, Mostafa (Author) ; Shafiee, Mohammad Behshad (Supervisor) ; Moosavi, Ali (Co-Supervisor)

Abstract

The use of nano-fluid, which is a stable solid liquid mixture, has been proposed as a new strategy for heat transfer operations. Much research has been done on heat transfer of nano-fluids until now, whereas the study of phenomena associated with phase change, such as boiling where there is heat transfer in larger scales is very necessary. The boiling process based on its potential for transferring high amounts of heat at low temperatures is a very effective and common mechanism, and it occurs in many engineering systems, including boilers at plants, evaporators in refrigeration systems and nuclear reactors. Also, a considerable amount of research was done recently in the field of...

Efficient Observer-Dependent Simplification in Polygonal Domains

, Article Algorithmica (New York) ; April , 2011 , Pages 1-21 ; 01784617 (ISSN) Zarei, A ; Ghodsi, M ; Sharif University of Technology

2011

Abstract

In this paper, we consider a special version of the well-known line-simplification problem for simplifying the boundary of a region illuminated by a point light source q, or its visibility polygon VP(q). In this simplification approach, we should take the position of q as an essential factor into account to determine the quality of the resulting simplification. For this purpose, we redefine the known distance- and area-distortion error criteria as the main simplification criteria to take into account the distance between the observer q and the boundary of VP(q). Based on this, we propose algorithms for simplifying VP(q). More precisely, we propose simplification algorithms of O(n2) and...