Sharif Digital Repository

The Weil group WF is assigne to every local field F. Langlands Correspondence is a bijetion between semisimple two-dimensional Deligne representations of Weil Group WF and irreducible representations of GL2(F) which fixes assigned L-functions and local constants. In this thesis we have classified an important class of irreducible representations of GL(2) over local fields called Principal Series. We also tried to give a taste of Langlands Correspondence to the reader. First we explain preliminaries and introduce locally profinite groups and their smooth representations. Then we classify representations of GL2(F) when F is finite. Then we study GL2(F) when F is a local field. Finally we... 

Nematic liquid crystal shells (droplets) containing cores have attracted considerable attention in recent years. Defect structures that form in such systems do not emerge in the bulk.These shells which could be created using double emulsion techniques in the laboratory have provided applications in microscale optical structures.In the past just boundary conditions and bulk parameters were noticed but recently the geometry of the core is considered likewise.In this work oblate ellipsoid cores are examined numerically using finite-element method. The boundary conditions in studied systems are perpendicular in outer surface of droplet and planar in the vicinity of the core. First by minimizing... 

The advent and advancement of technology through the conversion of Gas-Synthesis (a mixture of CO and H) into liquid hydrocarbons, by Fischer- Tropsch synthesis (FTS) gives more promising future in this field. Metals such as cobalt, nickel, zinc and iron are used as catalysts for FTS. Studies have shown that the surface structure of metal catalyst has a great influence on the process, and leads to different products and transition states. Iron has been known the most used and the most cost-effective metal catalyst in FTS. Different surfaces of Iron have different catalytic roles. In our work, Fe(100) -that is the most stable after Fe(110) and is known as the most active iron’s surface in... 

In the present thesis we will design and study some rendezvous algorithms for cognitive radio networks. In cognitive radio networks, secondary users try to access the spectrum of primary users in an opportunistic manner. Each secondary user constructs a channel list of accessible resources by channel sensing. These resources are not necessarily the same for different users; therefore, in order to make a connection in absence of a fixed control channel, different secondary users should find each other properly and quickly after entering the network. This is known as the blind rendezvous problem. We will develop and examine a new sequence based algorithm for blind rendezvous. Moreover, some... 

Generally, virtual loads is used to test all AC power and energy meters and are usually passive. To prevent possible damage of this heat and to control the temperature, cooling blowers are used which increases the volume and weight. So, recycling the power delivered from the grid causes a small amount of power to be converted to heat in proportion to the load efficiency. The purpose of this study is design, predictive controller model for programmable electronic regenerative AC load. The structure used is a back-to-back converter consisting of an AC-DC converter and a DC-AC converter, which according to existence of capacitance between these two structures, two converters can be controlled... 

In this study, the numerical investigation of the plasma actuator has been discussed on the combustion within a channel by FLUENT software. For this purpose, the empirical and analytical force is applied as a source term in the momentum equations in a certain area of the channel. The empirical force is obtained from experimental data and the analytical force is obtained by simplification of Maxwell equations. These equations include electrical potential and density of charge particle equations. In order to validation of UDF code, the analytical force is applied to air flow and the results are compared with other numerical simulation. Then, we discussed the results of combustion without... 

This project shows the flow of implementing a 5s Program into a factory. From it’s first step by studying current situation until the last step implementing and monitoring the results. Manufacturing companies have a growing, market-driven need to adopt World Class operating technologies, including lean manufacturing 5S principles. Understanding the program's importance and knowing how to get started are the most important steps. In Iranian economic environment it is always hard to convince any top management to invest on methodologies like TPM. The reason behind this is that there are very few examples of companies with successful implementation of these methodologies. Since management... 

Machining of Aluminum Metal Matrix Composites faces different problems including adhesive wear, large machining forces, chatter, poor surface quality and therefore low geometric accuracy etc. due to the fact that a ductile matrix is supporting brittle particles. On of the methods used to reduce such difficulties is vibration assisted machining in which a 10 to 20 micron displacement stimulation is applied to the workpiece or tool during machining process. The effect of this method on the milling of the Al/Sic composite is studied through two separate experiments including one and two dimentional vibration assisted milling respectively. Milling forces, tool wear and surface quality are... 

Tin Oxide Nanoparticle (SnO2) with the band gap of around 3.6 eV is one of the promising materials in various fields such as photocatalysis water splitting, pollutant removal and also biotechnology. Inorder to use this material in a visible-light rang, some promotions should be conducted.By combining SnO2 nanoparticles with the non-metalic graphitic carbon nitride (g-C3N4), a proper nanocomposite with wide range of application can be obtained. But, in order to industrialize this material, the cost of the final product is an imperative issue to consider.Here we have introduced a novel and low-cost method for synthesis of g-C3N4/SnO2 nanocomposite by using urea as a precursor for g-C3N4 and... 

Best way to extinguish one kind of species is targeting their habitat instead targeting the species directly. Targeting tumor microenvironment is source of several methods of cancer immunotherapy attending to the effective factor at microenvironment appears as main spot in designing immunotherapy protocols. Cells compete in an atmosphere in which they create different mechanisms in tumor microinvronment. Now, we can make abstract models of these cellular mechanism using accurate mathematical instruments, this is theoretical biology which is as subset in the field of mathematical biology. In these models, we can identify parameters that has more therapeutic value in the microenvironment.... 

We study colorings of quasiordered sets (qosets) with a least element 0. To any qoset Q with 0 we assign a graph (called a zerodivisor graph) whose vertices are labelled by the elements of Q with two vertices x; y adjacent if the only elements lying below x and y are those lying below 0. We prove that for such graphs, the chromatic number and the clique number coincide  

Asdefined by Nicholson [W. K. Nicholson. (1977). Lifting idempotents and exchange rings. Trans. Amer. Math. soc. 229: 269-278] an element of a ring is clean if it is the sum of a unit and an idempotent, and a subset of is clean if every element of is clean. In this thesis some like-cleanness properties are introduced and relations between them are investigated.Many equivalent conditions for cleanness of reduced, semiprimitive Gelfand and functional rings are obtained,and finally these results are applied in the rings of continuous functions  

Grobner bases were introduced by Bruno Buchberger in 1965. The terminology acknowledges the influence of Wolfgang Grobner on Buchberger’s work. He introduced a specific generator for ideals in the ring of polynomials over a field and then gave an algorithm for computing of that generator. It leads to solutions to a large number of algorithmic problems that are related to polynomials in several variables. Most notably, algorithms that involve Grobner basis computations allow exact conclusions on the solutions of systems of nonlinear equations, such as the (geometric) dimension of the solution set,the exact number of solutions in case there are finitely many, and their actual computation with... 

Given a simple graph G on n vertices, we prove that it is possible to reconstruct several algebraic properties of the edge ideal from the deck of G, that is, from the collection of subgraphs obtained by removing a vertex from G. These properties include the Krull dimension, the Hilbert function, and all the graded Betti numbers. We also state many further questions that arise from our study  

In this thesis, we study the properties of simplicial complexes Δ with the equality I(m) Δ = Im Δ for a given m _>2. The main results are combinatorial characterizations of such complexes in the two-dimensional case  

We study Beck-like coloring of partially ordered sets (posets) with a least element 0. To any poset P with 0 we assign a graph (called a zero-divisor graph) whose vertices are labelled by the elements of P with two vertices x, y adjacent if 0 is the only element lying below x and y. We prove that for such graphs, the chromatic number and the clique number coincide.Also, we give a condition under which posets are not finitely colorable