Sharif Digital Repository

Integrated SOFC plants, because of the high efficiency and optimum energy consumption, are important processes that have many applications. According to the importance of these plants, their optimum operability and favorable operations are also very important. One of the ways to optimize the process performance is the suitable selection of the control structures. The objective of this project is to analyze the operability or inherent controllability of integrated SOFC plants in the absence of any controller. In this work, the controllability of the process have been investigated with using the output controllability index and the other indexes such as relative gain array, singular value and... 

This thesis discusses design and, simulation procedure of a mono-injector combustion chamber, in order to study and, analyze the ignition and, stable combustion characteristics, for Kerosene and, liquid Oxygen cryogenic propellants. Accordingly, the design and, simulation for the combustion chamber, for Kerosene and, liquid Oxygen propellants is performed. Also, effective parameters on the flame taking place are studied, and finally an algorithm for design and, properties study of cryogenic propellant ignition is presented  

Increasing in social communication via electronic ways has been made social network analysis of these communications more important each day. One of the most important aspects in social network analysis is community detection in such networks. There are many different ways to extract communities from social graph structure which in some of them the content of communication between actors has been noticed in community extraction algorithm. In this thesis after a short survey over advantages and disadvantages of existing methods for community detection, a new method for extracting communities from social networks has been suggested which in addition to streaming property of data it spot the... 

Studying the performance of flow meters is of great importance in order to improve their quality. In this study, we are looking for an optimal design for a turbine flow meter in which the measurement accuracy, pressure drop and response speed indices are improved. For this purpose, a turbine flow meter with a diameter of 2 inches has been selected and its performance has been numerically modeled using computational fluid dynamics in a steady and transient state. By modeling the steady state, the measurement accuracy and pressure drop indices are obtained, and by modeling the transient state, the response time of the flow meter is obtained. In order to increase the accuracy of numerical... 

This thesis describes a robust algorithm in speech recognition system based on phoneme recognition. Automatic speech recognition systems (ASR) can be divided into two main types: speaker-dependent continuous speech PC-based systems and speaker-independent continuous-speech server based systems. In speaker- independent systems, there is no need to have knowledge about the speaker(s) before using the system, on the other hand, in speaker dependent systems it is essential to have voice training by the speaker(s) supposed to work with the system. In this thesis, a speaker-independent continuous speech PC-based system has been chosen to work with. Acoustic-phonetic approach has been chosen among... 

One way to increase the efficiency and improve the performance of a gas turbine is to increase the inlet gas temperature. On the other hand, the inlet temperature has an allowable operating range, and increasing it beyond the tolerance of the alloys used in turbine blades causes structural defects and significantly reduces the blade life. Therefore, to increase the blade life, various cooling methods such as internal and layer cooling are used. Considering the blade geometry and cooling paths, accuracy in the manufacturing process is doubly important in the production of these blades. The importance of this issue is that if the cooling channels produced are inconsistent with the design... 

In this research, among the levels of the blood supply chain, hospital is chosen for study because of its importance. A model of inventory management of hospital blood bank is presented. In this case, we consider some assumptions which are more realistic. These assumptions include two types of emergency and ordinary demands, young blood demand, and finally, a cross-match process. In the existing articles, although blood groups considered in mathematical models, the priority of allocation of blood groups is not considered in these articles. In this study, three mathematical models are developed with deterministic parameters. In the first model, the assumption of ordinary and emergency demand,... 

The purpose of this study is to apply the governing equations of the theory of porous media with the concept of volume fractions to calculate the isotropic half-space responses subjected to a surface and asymmetric loading and to compare the responses with Biot’s theory. For this purpose, each of the components is first considered continuous and the equilibrium equations of mass and momentum for the solid and fluid phases based on the mixture theory are expressed. The concept of volume fractions and the effect of interaction between the two phases, distinguish these equations from the equations of the continuum theory. Thus, the governing coupled partial differential equations of the theory... 

The standard model of Cosmology (SM), based on Einstein’s theory of general relativity (GR), is the best model in describing the cosmic-scale observations. In galactic scales, however, galactic dynamics show a discrepancy between the observed luminous mass and the predicted value from the theory. Two approaches are suggested to eliminate this inconsistency: assuming the existence of dark matter within the context of GR, or modifying the theory of gravity in galactic scales, like MOND or MOG. In this thesis, we study the spherical collapse and the formation of shell galaxies in MOG, in comparison with SM. We introduce the action and the field equations of MOG and the equation of motion of a... 

Localization of radio sources has various applications in civil and military communications. Some of important localization methods consist of Angle of Arrival (AoA) estimation of the illuminated signals from the interested sources. Between various Direction Finding (DF) methods, subspace based methods are of special importance, because of their high resolution and accuracy. And from beginning of invention, because of new challenges, have been focus of numerous researches. In this thesis, first we explain the most important subspace based DF methods called MUSIC and root-MUSIC. Then a novel modification for root-MUSIC is introduced. In our new method the computational complexity of... 

In spite of succesfull achievements of standard quantum mechanics in describing variety of physical phenomenons, this theory has some conceptual problems in some areas. One of the important problems is the behavior of macroscopic objects and their interaction with microscopic systems, which is called “measurement problem”. Actually because the standard quantum mechanic is linear, it anticipates the occurrence of superposition of macroscopic states which is in contrast with our understanding of macroscopic objects. The standard theory answers this problem by using the wave function reduction principle.
There has been various proposals about the mechanism of wave function reduction,... 

Water-gas shift reaction (CO(g) + H2O(g) ↔ CO2(g) + H2(g)) is performed as the key step in the hydrogen and ammonia industrial plant. In this work, Fe/Cr/Cu high temperature water gas shift catalysts were synthesized by coprecipitation method, using sulfate precursors, in order to improve the catalytic performance and particular emphasis is placed on the catalytic activity affected by aging time, precipitating agent and ways of increasing the mechanical strength. Finally the prepared and industrial catalysts were compared when they were situated in the operating conditions (at 360oC and 2 bar) and were characterized by BET, XRD, TPR, TEM and crushing strength analysis. Catalysts being made... 

Numerical simulation of combustion in turbulent flow regimes is of high importance. The accuracy of numerical predictions depends on the quality of turbulence modeling and its interaction with combustion processes. In order to more accurately represent turbulent structures and mixing, the use of Large Eddy Simulation (LES) turbulence models is desirable, despite their relatively high computational cost. Premixed combustion at low equivalence ratios has gained widespread attention in recent years due to its high efficiency and reduced emissions. In this field, a significant portion of turbulent combustion simulations have focused on Flamelet-based models. Although these models have been... 

Apatite-coated Ag/AgBr/TiO2 was prepared by deposition of Ag as noble metal to generate electron-hole pairs by extending the excitation wavelength to visible light region, AgBr as photo-sensitizer to increasing yield of photo catalyst, and apatite as adsorption bio ceramic for adsorbing pollutants and micro organisms respectively. The bactericidal experiments in dark media indicated that only novel catalyst show inhibiting growth of bacteria. In this case Transmission electron microscopy image illustrated that catalyst nano particles adhere to the outer membrane of the cell and acts as inhibitor to nourish of bacteria from around media. The mechanism for deactivation E-Coli and B.Sub in the... 

Strongly Rayleigh measures are an important class of negatively dependent (repulsive) probability measures. These measures are defined via a geometric condition, called “real stability”, on their generating polynomials, and have interesting probabilistic properties. On one important property of negatively dependent measures is their rigid dependence structure. In other words, the it is impossible for these measures to have strong overall dependencies. In this thesis, we study two manifestations if this phenomenon: (1) paving property and (2) tail triviality. Informally, the paving property states that it is possible to partition the set of the components of every strongly Rayleigh random... 

Most of current the MAC protocols for Wireless Sensor Networks (WSNs) concern about energy efficiency rather than low latency. The main source of energy consumption in the MAC layer is idle listening, and most of these protocols use duty cycling for reducing energy consumption. But duty cycling method increases packet delivery latency. This problem is very critical in real time applications where packets should meet their deadline. There are some solutions for this problem. For example a node forwards data packets multi hop away instead of one hop in a single cycle. In this research, an efficient cross layer MAC protocol for real time applications is proposed. In this protocol multi hop... 

Human eye is one of the most important organs of the human body. Performance of the eye may be decreased by some anomalies such as myopia, hyperopia, astigmatism, cataract, glaucoma, etc. There are variety of techniques to treat eye anomalies including surgery, using optical elements and training methods.The easiest way of treating refractive errors of the eye, is to use optical elements such as contact lenses, intraocular lenses and glasses. In the case of cataract, Crystalline lens loses its opacity and should be replaced by artificial lens. The best choice is Fresnel lens which has lower weight and thickness than refractive lenses.Fresnel lens is a diffractive optical element which uses... 

In the current study, shape-memory alloys are analysed analytically under mechanical loading. Due to the special properties of these materials, their usage in various applications is rapidly increasing. However, mostly, the numerical methods such as finite-elements methods are employed to model the thermo-mechanical behavior of these materials. Also, due to the complexity of their behavior, there are few analytical solutions for them in the literature. In this research, an analytical approach is proposed to investigate the response of these materials under mechanical loading using a fundamental model which is suitable for modelling their crystalline structure. Given the impact of multiple... 

A thermo-mechanical multi-scale framework is presented in this study for simulating the compaction process of aluminum nanopowders coated with a surface oxide layer. The primary objective is to link atomistic-scale information with continuum-scale models in order to improve the accuracy of predictions of material response under varied mechanical loading and thermal conditions. This approach enables analysis of the role of atomic-scale mechanisms in the overall material response and aims to achieve improvements in both predictive accuracy and computational efficiency relative to conventional methods. In the first step, the mechanical properties of the nanopowders were extracted at 300, 400,... 

In this thesis, consider three important questions in the Iranian Wholesale Electricity Market (IWEM) and answer its. The first one is whether the bidding behavior of the firms in the IWEM has been ex-post optimal? The results of the research show that, on average, the firm’s bidding behavior didn’t optimal in the IWEM, and therefore the bidding strategy of them could be improved. This issue is importance from the regulatory viewpoint in terms of assessing market efficiency and market power of firms, as well as from the firm’s point of view to improve the bidding strategy and increase its profits. The second issue is the assessment of the firm’s ability to exercise unilateral market power by...