Sharif Digital Repository

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to... 

In the beginning of the 90’s a new type of robot was introduced by Fukuda. The brachiation is a type of mobile robot that moves from branch to branch like a long-armed ape. Here, as a new innovation, optimal control is used to obtain the optimal trajectories for two different problems. The first problem is “Brachiation between fixed branches with different distance and height” and the second is “Brachiating and catching the moving target branch”. Theoretical results show that the control effort in the proposed method is reduced by 25% in comparison with the “Target Dynamics” method which was proposed in prior articles for this robot. The obtained optimal trajectory also minimizes the... 

In recent years, various nanocars have been synthesized to provide controlled mechanical function, transport other nanoparticles, or enable bottom-up assembly capability. In this research, using molecular dynamics and quantum mechanics, the motion of nanoworm on the gold substrate was investigated. The incorporation of the azobenzene chromophore at the middle of the chassis allows for the potential motion of nanoworm by light as a source of external stimuli. The creators claimed that nanoworm could achieve controlled wormlike movement on gold substrate, which should be validated as the purpose of this research. In the first section, the movement of the p-carborane wheel on the gold surface... 

After the discovery of integer and fractional quantum Hall effects, a comprehensive effort started to understand the physics behind these findings thoroughly. At the end, these efforts resulted in the introduction of topological phases of matter and the notion of topological phase transition. With the recent developments in this field, as the introduction and synthesis of 3D topological insulators, many researchers began inspecting the effects of disorders and impurities in the lattice structure on the topological phases, As these imperfections are inevitable in the lab-created instances. Since, in the previous works only on-site disorders was studied, the concentration of this thesis is on... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

In the first chapter of this thesis we consider the simplest problem of calculus of variation with mixed boundary conditions and we obtain the Euler-Lagrange equation. We will see that the work here is very similar to the work for Dirichlet boundary conditions. In chapter two we investigate the sufficient condition for the existence of solution. Here we will see the work is really different from the work for Dirichlet condition. In fact this result is published in a credible journal. The main work of this thesis will begin in chapter three and will end in chapter five. In these chapters we will investigate a necessary condition for existence of solution for a calculus of variation problem... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without... 

The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction... 

Zero knowledge proofs allow a person (prover) to convince another person (verifier) that he has performed a specific computation on a secret data correctly, and has obtained a true answer, without having to disclose the secret data. QAP (Quadratic Arithmetic Program) based zkSNARKs (zero knowledge Succinct Non-interactive Argument of Knowledge) are a type of zero knowledge proof. They have several properties that make them attractive in practice, e.g. verifier's work is very easy. So they are used in many areas such as Blockchain and cloud computing. But yet prover's work in QAP based zkSNARKs is heavy, therefore, it may not be possible for a prover with limited processing resource to run... 

Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the... 

Enzymes are biological catalysts that carry out chemical reactions in a stereoselective manner. Fumarate hydratase (abbreviated as fumarase) is a metabolic enzyme found in both mitochondrial and cytosolic isoforms. Its mitochondrial form functions in the Krebs cycle (TCA) and specifically converts fumarate into L-malate. In recent studies, the role of the cytosolic form of this enzyme in the repair of DNA double-strand breaks has been elucidated. Fumarase and its precursors are indirectly related to many metabolic pathways, including phenylalanine and tyrosine metabolism, urea cycle, etc. As a result, it is very important to know the factors affecting this enzyme and its activity. In this... 

Nowadays, we are forced to use distributed computing due to the growth of data, the challenge of storing and processing it, as well as the emergence of new problems in machine learning and the complexity of the models. In distributed computing, the computation is per- formed by a distributed system consisting of several worker nodes such that, the main task is divided into several smaller tasks and assigned to each worker node. Then, different worker nodes will cooperate to accomplish the main task. Although distributed systems are efficient in solving problems and dealing with the mentioned challenges, they are vulnerable to the presence of stragglers, adversarial worker nodes, high... 

Payment channel networks (PCNs) are a promising technology to improve the scalability of cryptocurrencies. Users can send instant and almost free transactions via payment channel networks and, at the same time, enjoy the security guarantees of Blockchains. In order to open a mutual payment channel, two users should send a ``channel creation" transaction to the underlying Blockchain. Through this transaction, two parties deposit some money on the Blockchain. This money, which we call the channel's capacity, can be used to send off-chain transactions between the two users. After the channel creation, the channel-holders can send each other off-chain transactions by forwarding the money back...