Sharif Digital Repository

Considering the daily growth of industries in international market competition and the necessity of investment in related infrastructure development, determining the priority of industries in order to strengthen or support of these industries, seems as an inevitable issue, so for the purpose of making proper decisions in an optimum way, we must use scientific decision making methods. This study evaluates the priority of industries in Iran and comparison of them. Therefore, according to the international standard classification of economic activities (ISIC), two-digit and four-digit codes are specified for each industry. In addition, based on major economic indicators, the status of these... 

The main objective of all managers of the economic organizations, manufacturing and industrial companies and service providers is to take steps toward improvement and effective use of different resources like workforce, capital, materials, energy and information. To attain the desired productivity, managers have to observe requirements such as establishment of a working organizational structure, effective implementation methods, safe equipment and tools, balanced working atmosphere and qualified human force as the most important factor. Therefore productivity culture should be publicized throughout the organization, and human force should be considered as the main component of this process.... 

Our problem is to evaluation state and form of a tracer passing through the vessel. Using this method, we can identify the effect of during used in some defected parts of body. This evaluation leads to in solving a Laplace equation with mixed boundary condition. Separating that problem, we reach to a collection of algebraic and linear equations. Solving this system, we approximate coefficients of the solution with a series the existence and uniqueness of and analytic solution has been proved using the Eigen functions finally, using numerical algorithms, we have interpreted the analytical solutions.
 

In this thesis, which is based on an article of Claus Scheiderer (Reference [21]), the relation between positive semi-definite elements of a semilocal ring, called psd, and elements of the ring which can be written as a sum of square elements of the ring and are called sos will be evaluated. In Chapter One, the concepts of prime cones, real spectrum of a ring and real ideals will be defined and then the relation between psd and sos elements in the total rings of quotients will be assessed. The Krull Valuation of an element which is a sum of squares will also be determined. In Chapter Two, the concept of totally positive elements in a ring will be defined and their properties will be... 

Obtaining the exact elastic response of composite systems to externally applied stresses is thought to be the most important way for predicting the mechanical behavior and tailoring the properties of composites. Over the past few decades, a variety of analytical models has been developed to investigate different stress transfer mechanisms in fiber composites. Although 2-D analytical model is still highly desired. So in present research a modified analytical model is developed for 2-D elastic stress field distribution in short fiber composites in plain strain for overlapping fibers subjected to an applied axial load . Two sets of exact displacement solutions for the matrix and fiber derived... 

In this study, electrochemical oxygen reduction reaction (ORR) was studied on Cu, Pd, Rh, Pd-Cu and Rh-Cu alloys in alkaline solution. Pd-Cu and Rh-Cu alloys were prepared by electrochemical methods. On copper electrode it is found that direct oxygen reduction is accompanied by the electrochemical reductions of copper oxides. Also, mechanism and kinetics of reaction change as the amount of copper oxides increase on the surface. For electrodeposited alloys, it is indicated that the reactivity of Pd-Cu and Rh-Cu alloys toward oxygen reduction is higher than pure Pd and pure Rh. The maximum reactivity among Pd-Cu alloys is related to the sample with 24.5% copper content while the maximum... 

Hydrocarbon reservoirs may be classified on the basis of their drive mechanisms. In the reservoirs adjoined by water aquifers, waterdrive may be the primary production mechanism. The invasion of reservoir rock by aquifer water may have a significant impact on reservoir performance. Therefore, water influx into hydrocarbon reservoirs must be predicted accurately as a function of time, pressure history at the reservoir/aquifer interface, reservoir/aquifer size ratio, and aquifer characteristics.To forecast the performance in a waterdrive reservoir, an aquifer model simulating the fluid flow in the aquifer and flow from the aquifer into the reservoir is needed. Robust techniques for analysis of... 

There are different approaches in modifications of General Relativity as the theory of gravity. The modified theories of gravity are important cases in this context, which mostly start by modifying the Einstein-Hilbert action, while keeping the general covariance. Within the modified theories of gravity, we consider two cases. The first is the f(R) theories of gravity, and the second is curvature squared theories of gravity with an action like S = ∫d4x pg( 116GR + (R)2 + R2 +(R)2). Curvature squared theories of gravity have interesting feautures, most important of which is renormalizability, in contrast with General Relativity. But this advantage, as noted by K.S. Stelle in 1977 comes at... 

In this thesis, we consider the motion of a stretched string coupled with a rigid body at one end and we study the existence of periodic solution when a periodic force acts on the body. In this hybrid system, there is a weak dissipation that characterizes. The main difficulty of the study is related to the weak dissipation which does not ensure a uniform decay rate of the energy. In this thesis, firstly, under the condition of 0 1 0 , we prove there exists a periodic solution. Then, we change the conditions on , Indeed, we restrict ourselves to solve the problem. In this case, under the condition of 0 2 0 , we show there is a periodic solution for rational periods. In the last part, by... 

Let (X; d) be a metric space and (X;) be a partially ordered Space. Let F, g be measurable mappings such that F has g-monotone property and satisfying in a contraction condition. Firstly, some extentions of Banach fixed point theorem was investigated in particular way that lead to random coupled and random fixed point for mentioned mappings. Then, linear stochastic evolution equation and semilinear dissipitive stochastic evolution equation driven by infinite dimentional fractional Brownian noise was evaluated. It has been shown these equations define random dynamical systems with exponentially attracting random fixed points that are stationary solution for them  

Graphene is one of the most attractive subjects for scientists in the last decade. Its unique properties has been probed by many research groups and innumerable projects have been developed to investigate applications of graphene in electronics, mechanics, biophysics etc. Due to high surface to volume ratio and magnificent electron mobility in graphene, it is a suitable candidate for gas sensing. This has been proved by several theoretical and experimental researches for various gases such as CO, NH3 and NO2 etc. In present thesis, graphene has been prepared chemically and transferred to silicone substrates that are previously coated with a 300 nanometer silicone dioxide layer, by dip... 

In this study, some of robust and exact tuning methods for fractional order PD and PI controllers are investigated in order to extract their solution existence conditions. Using aforementioned methods needs solving a set of nonlinear equations to obtain desired controller parameters which satisfy the control objectives. Hence, one of the aims of this study is to find necessary and sufficient condition on tuning specifications which guarantee the applicability of the aforementioned methods. The achievable performance region of the methods is obtained through the extracted necessary and sufficient conditions. The other aim of this work is to investigate the uniqueness of the methods... 

Improvement of numerical solutions and application of them is very important section of engineering researches. So, there are several numerical methods and procedures for solution of equations or problems. All of them have advantages and disadvantages for selection best method. The efficiency of a method is a function of Limitation parameter like time, software and hardware. One of the recent numerical methods for engineering problems is Direct Discrete Method (DDM). This method prepares modern theory for balance equations; also this method combines some advantages of the other numerical methods like finite element and finite difference. DDM uses a double set of mesh structures namely primal... 

In this thesis, two kind of Kirchhoff type equations are investigated. for each of them we prove existence and uniqueness of weak solution by letting hypothesizes on problems functions and initial conditions and using Faedo-Galerkin method and some theorems in functional analysis. It is should be mentioned that one of the problems has unique strong solution according to compactness theorems. In the nest step stability of these equations are investigated. for this purpose it is showed that total energy of systems will tend to zero as time goes to infinity. Furthermore at the end of each chapter numerical results are presented to illustrate accuracy of obtained theoretical results. Finally we... 

In this work we investigate the propagattion of light in inhomogenous cosmic spacetime within general relativity framework. We use Lemaitr-Tolaman-Bondi metric for modeling inhomogenous spacetime. For investigation of gravitational lensing we need to solve geodesic equaions in this model. Beacuse of nonlinearity and complexity of these equations we should apply numerical methods. At first we used Runge-Kutta method with adaptive step size, but beacuse of stiffness of these equaions, the results of this method did not match to approximation methods for low deflection angles. So we try semi-implicit Rosenbrock method. Then for inspection of thin lens approximation for the first time; we... 

Direct reduction of iron is a process to reduce iron in solid phase. The output of this procedure is direct reduced iron (DRI) that can be used in electric arc furnacewithout further changes. Midrex technology, which is the most important one among direct reduction of iron processes, provides 60% of DRI.
Required synthesis gas for reduction process is gained from reforming of the natural gas,with the major proportion of methane, with water steam and carbon dioxide in a piece of equipment called “reformer”. As a matter of fact, reformer is a type of plug chemical reactors. Input materials (natural gas, water steam and carbon dioxide) enter from the bottom section to the prepared pipes in... 

The aquatic canopy areas such as wetlands play an important role in ecology of these area. The exchange flow between open water and vegetated area occurs due to sunlight and surface cooling. Wind also causes surface evaporation and create a cold layer at the surface of water. The creation of exchange flow and its magnitude depends on parameters like solid volume fraction and thermal gradient. In this thesis, the goal is to determine the effects of floating vegetation on the hydrodynamic characteristics of exchange flowas a result of surface cooling experimentally. In this research, the PIV method was used to measure velocity profiles. In the experiments, solid volume fraction, depth of... 

The object of this research is modeling, simulation and control of a crystallization process. Population balance equation (PBE) has been used for modeling of such processes. Most of the existing numerical methods cannot solve the general form of PBE in presence of the breakage and agglomeration terms and some others are not suitable for control objectives, because of their intractable CPU time. In this work a new developed numerical method called conservation element and solution element (CE/SE) has been used for solving general form of multidimensional population balance equations. The accuracy and effectiveness of the scheme is demonstrated through computer simulation. According to the...