Sharif Digital Repository

The increasing growth of composite materials in various industries and the use of these materials in the production of the main structures, recognized study and simulation of accurate behavior of these materials at different scales. On the other hand, the appearance of Nano-scale materials with amazing physical and mechanical properties and the use of these nanoparticles as reinforcement in the structure of polymer composites, further highlights the importance of simulating the behavior of polymer nanoparticles at different scales. One of the issues that is considered in various industries, especially in the airspace industry, is the phenomenon of fatigue. The complexity of the fatigue... 

A metal cylinder tank with composite coating is a pressure vessel which is made of a thin metal layer and a composite layer; like Graphite, and most of the loading is carried by the composite layer. In this study the penny-shaped cracks in cylindrical pressure vessels with composite coating is studied. These kinds of cracks are mostly initiated in manufacturing processes and they have crucial rule in fatigue life and load carrying of the structure. Although there are numerous analytical and numerical methods, they have shortcomings in the case of penny-shaped cracks problems. The strain discontinuity in the interfaces of materials along with discontinuity and singularity due to the crack are... 

Rotating shafts are widely used in various industries, especially aerospace industries such as engines, compressors and turbines. Due to the sensitivity of these shafts, considerable efforts have been made by researchers to investigate their dynamic behavior. In this thesis, the finite element numerical method has been used to analyze and investigate rotating shafts using a pipe elbow element. This element has four nodes and six degrees of freedom in each node, that is, three degrees for translation and three degrees for rotation relative to the general coordinate system and has a circular cross section. In the linear part of the dynamic formulation of the finite element for rotating axes... 

In this research, the reliability of time domain modal identification methods is studied. First three different MIMO time domain method are studied which are EITD, PRCE and ERA. The effectiveness and accuracy of the methods are evaluated for simulated mass-spring system and numerical cantilever beam in EMA (using time history data of impulse response directly) and OMA (using correlation function of random response of the structure) cases. Based on the results achived in this section, the most qualified method is identified (which was ERA) to continue the research. In order to evaluate the reliability of time domain OMA technique in case of repeated modes, first a numerical plate is studied... 

Euthanasia is one of the most controversial topics in medical ethics and in the areas of religion, law and ethics are studied .Different approaches to the authorities in case of euthanasia on the ballot, specifically rooted in the philosophical approach, to their beliefs and culture. According to the above description. The main objective of this paper is to study the philosophical approach of euthanasia. Therefore, this text answer three main questions. The first question will be discussed in the first chapter is that "How general philosophical issues applied to specific cases such as euthanasia?" The second question is about the definition and types of euthanasia .This question will be... 

A semi-analytical solution for rotating axisymmetric disks made of functionally graded materials was previously proposed by Hosseini Kordkheili and Naghdabadi [10]. In the present work the solution is employed to study thermoelastic creep behavior of the functionally graded rotating disks with variable thickness in to the time domain. The rate type governing differential equations for the considered structure are derived and analytically solved in terms of rate of stress and strain as a reduced to a set of linear algebraic equations. The advantage of this method is to avoid simplifications and restrictions which are normally associated with other creep solution techniques in the literature.... 

The world's freshwater resources are rapidly decreasing due to population growth, industrial and technological progress, successive droughts, climate changes, increased food demand, and poor management of water resources. Using desalination methods is one of the ways to produce the required freshwater. Several methods have been developed for desalination. The most widely used method is reverse osmosis (RO). In this thesis, an electrodialysis (ED) desalination system was designed and modeled using up-to-date and reliable articles. This modeling was done in EES software and after validating that, the effect of considering Donnan's potential was investigated. At the 60 ppt concentration of the... 

In this work, we consider the problem of secure multi-party computation (MPC). This system includes Γ sources, N processing nodes or workers and one data collector or master. Each node has a constraint on its storage,such that it can store 1/m fraction of size of each input matrices from each node. In addition, up to t of these workers are adversary and may collude to gain information about the private inputs or can do malicious actions to make the final result incorrect. The objective is to calculate an arbitrary polynomial of some massive private matrices as inputs while the privacy is preserved. The main concern in these kind of systems is to reduce the minimum number of workers needed... 

Multiple-input multiple-output (MIMO) systems have been considered a lot in the recent decade. Use of these systems results in higher data rate and higher reliability in communication systems. Use of intermediate nodes which are called relay in cooperative networks result in higher reliability and higher coverage range in wireless networks. Finally use of multiple antennas in cooperative networks results in higher data rate, higher reliability and higher coverage range in wireless networks. A drawback of multi-antenna systems is that more antennas require more RF chains. More RF chains result in higher computational complexity and higher hardware cost. A remedy for this drawback is the... 

After restructuring in power systems, Independent System Operators (ISO's) are looked for an appropriate auction mechanism to find the market operation point. In deregulated electricity markets, Offer Cost Minimization (OCM) auction is used to minimize the total bid cost for selecting offer and demand bids. But a uniform market clearing price (MCP) or Locational Marginal Price (LMP) is used for consumer payments. Hence, the minimized bid cost is different from settlement cost. The used mechanisms are for manufactures offer and their cost functions optimization. The Payment Cost Minimization (PCM) is one of the mechanims that affect directly on the consumers payment and lead to reduction of... 

Global collapse in earthquake engineering refers to the inability of a structural system to sustain gravity loads when subjected to seismic excitation. Dynamic instability phenomena in exist buildings have a key position and for this reason strict criteria in structural seismic assessing codes presented for avoiding this phenomena. At this study, dynamic instability of five designed concrete buildings with moment frame system, mixed up 3, 6, 9, 12 and 15 story building, are investigated. P-delta effects, deterioration in strength and stiffness and cyclic deterioration in structural components considered in this investigation. For modeling nonlinear behavior of elements, experimental results... 

With increasing number of processors on a chip, the role of interconnections becomes more important in both power consumption and bandwidth. As a result, in MultiProcessor System-on-Chip architectures, the design constraints will shift from "Computational Constraints" to "Communicational Constraints". Nowadays, optical information transfer is introduced as a suitable substitution for electrical interconnections in chips, which can eliminate their problems. Many different optical networks have been presented so far. These networks can be divided into two subcategories. Networks of the first category use an electrical infrastructure as well as optical one. Hence, the scalability of scheme is... 

In the first description if we describe technology as a tool, Communication technologies or media should be consider as the most important element of today's technological world. This research is going to cover reconsidering and recreating the mean of media based on the Ideas of JacquesDerrida. In this regard, two major dichotomy is evident in the public understanding of media. meanwhile "media versus message" and on the other hand opposition between "media and audience". So deconstruction in the face of these binary oppositions, want to read out the notion that message is superior to media, and on the other hand to deconstruction of the hegemony of the media on the audience