Sharif Digital Repository

Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion.... 

The fiber-reinforced composite materials possess advantage for structural purpose in various industries. Delamination is recognized as one of the major causes of damage during drilling of fiber reinforced composites, which not only reduces the structural integrity, but also has the potential for long-term performance deterioration. It is difficult to produce precise quality holes with high efficiency by conventional drilling method. Drilling is frequently applied in production cycle while the anisotropy and nonhomogeneity of composite materials affect the chip deformation and machining behavior during drilling. In this thesis, a new non-traditional drilling technology is presented for solve... 

Let G be a graph with adjacency matrix A and Δ be a diagonal matrix whose diagonal entries are the degree sequence of G. Then the matrices L = Δ− A and Q = Δ+A are called Laplacian matrix and signless Laplacian matrix of G, respectively. The eigenvalues of A, L, and Q are arranged decreasingly and denoted by λ1 ≥ · · · ≥ λn, μ1 ≥ · · · ≥ μn ≥ 0, and q1 ≥ · · · ≥ qn ≥ 0, respectively. The energy of a graph G is defined as E(G) :=
n
i=1
|λi|.
Furthermore, the incidence energy, the signed incidence energy, and the H¨uckel energy of G are
defined as
IE(G) :=
n
i=1
√
qi, LE(G) :=
n
i=1
√
μi, HE(G) :=

2
r
i=1 λi, n=... 

Internet video networks have already attracted millions of Internet users, and Internet video is one of the fast growing Internet services. The peer-to-peer (P2P) network is an efficient solution to supporting large scale video streaming on the Internet. P2P networks can deliver live multimedia content to millions of users with low cost at any time, and at anywhere they want. In this thesis, we investigate solutions to enhancing the performance of the unstructured mesh-based. Locality awareness or network proximity is one of the essential characteristics of P2P networks. In live P2P video streaming we face to some challenges like bandwidth heterogeneity of peers, and peer churn. In the P2P... 

Graph Theory and Combinatorial Analysis like the other branches of science use the probability for solving their problems. At the first , we will introduce the most common tools from probability used in Discrete Mathematics, such as “The Lovasz Local Lemma”. Most of them are based on Linearity of Expectation, Concentration Theorems and some other innovative methods such as Deletation Method. We will present different examples for these techniques. Also we will introduce “Random Graphs” and their importance. Specially we will explain how to use “Threshold Functions” to obtain different properties about the majority of graphs. Rainbow Connection, is a natural and interesting quantifiable way... 

Let R be a ring with unity, M be a unitary left R-module and I(M)* be the set of all non-trivial submodules of M. The intersection graph of submodules of M, denoted by G(M), is a graph with the vertex set I(M)* and two distinct vertices N and K are adjacent if and only if N\K ̸= 0. We investigate the interplay between the module-theoretic properties of M and the graph-theoretic properties of G(M). We characterize all modules for which the intersection graph of submodules is connected. Also the diameter and the girth of G(M) are determined. We study the clique number and the chromatic number of G(M). Among other results, it is shown that if G(M) is a bipartite graph, then G(M) is a star... 

One of the most applicable fields in data mining is customer relationship management (CRM). CRM process includes four aspects: Customer identification, Customer attraction, Customer retention, and Customer development. Data mining can be a supportive tool for decision making in each of these CRM aspects. Huge volume of data and information corresponding to CRM that exists in companies' databases, has made sufficient potential for data mining process and discovering hidden knowledge. Importance of concepts like customer needs identification, customer retention, and increasing customer value for companies has made the need to use of data mining techniques more valuable. Saipa Yadak Co., as a... 

The purpose of the study was four-fold: first to investigate the predictive adequacy of the Task-Induced Involvement Load Hypothesis which contends that higher-load inducing tasks yield better retention rates in incidental learning situations, second, to examine whether type of dictionary search could affect vocabulary retention, third, to investigate the effect of translation direction on retention rate, and finally to determine the most effective tasks. To meet these ends, six groups of EFL learners - all male, aging 19-25, majoring in various fields of engineering sciences were assigned to the study. Each one of the groups performed distinct tasks which were as follow: reading... 

Let X = fx1; : : : ; xng be the set of vertices of a hypergraph H and E = fe1; : : : ; emg be the set of its edges. The incidence matrix of hypergraph H is an n m and (0; 1)-matrix, N, such that nij = 1 if xi 2 ej and nij = 0, otherwise. A zero-sum flow for H is a vector with non-zero entries that is in the null space of N. A zero-sum k-flow is a flow with non-zero integer entries that absolue value of each entry is at
most k 1. In this thesis we study the existence of zero-sum flows for designs and hypergraphs. Also we consider zero-sum 3-flows in 2-Steiner designs  

Superalloys are widely used in aerospace and power industries due to the good performance at high temperatures for examples gas turbines, steam turbines and aircraft components. In addition to the turbines cobalt-base superalloys are used in medical implants such as knee and hip joints. The main strengths of the superalloys are heat-resistant, retaining their high mechanical and chemical properties at high temperatures, high melting temperatures, high corrosion resistance, resistance to thermal fatigue, thermal shock, creep, and erosion. Because of difficult to machine properties of superalloys, grinding is one of the effective methods for machining superalloys. The surface integrity of the... 

U-shaped assembly lines usually are more effective than straight lines. Therefore special attention has been paid to u-shaped line balancing problem in recent years. On the other hand most articles on the line balancing problems are investigated for the first time. However, within the lifetime of an ALB, the balancing problems do not occur only once prior to its construction, but rather continuously as rebalancing. For example whenever the demand structure or production technology changes or producing seasonal products, the ALB needs to be reconfigured. So many balancing issues in the real world are related to re-balancing of production lines.
Therefore in this study, U-shaped assembly... 

Due to the growing oil price and environmental considerations, tendency to use local and environmentally friendly energy sources has increased.Bidirectional transmission can be one of the key features of the smart grid,so the use of car battery connected to the grid as local energy sources makes sense. This can provide network stability, especially during peak load times. Vehicles connected to grid (V2G) is an electric vehicle or a plug-in hybrid electric vehicles can delivered the electricity to the grid. These systems require either two separate power electronic converters can be used for transmission in either directions or a two-way transfer charger. The aim of this project is to design... 

In this thesis, we study some connections between the graph-theoretic and algebraic properties of co-maximal graph of algebraic structures. We follow two purposes. First, what properties of algebraic structures can be found from co-maximal graph of algebraic structures. Second, what geometric or graph theoretical properties of co-maximal graph of algebraic structures can be found from specefic algebraic structures. Let G be a group and I(G)∗be the set of all non-trivial sub-groups of G. The co-maximal graph of subgroups of G, denoted byΓ(G), is a graph with the vertex set I(G)∗and two distinct vertices H and K are adjacent if and only if HK=G. We char-acterize all groups whose co-maximal...