Sharif Digital Repository

In a distributed system, each solution for the problem of Byzantine Agreement requires that some of correct processes reach a common decision value from a set of proposed values while Byzantine processes may behave arbitrary. This problem is one of the most fundamental problems in the theory of distributed systems. While the problem has been widely studied in fully-connected fixed networks, few studies have been carried out in the context of self-organizing mobile networks such as Mobile Ad-Hoc Networks.
This research presents a randomized consensus protocol with three additional modules for the case of dynamic networks: Participant Detectors, Failure Detectors and Maintainer. We assume... 

Use of renewable energy has already increased significantly. One of the renewable and suitable sources for replacement with fossil fuels is wind energy, especially wind turbines. But the design, construction, installation maintenance and operation of wind turbines are relatively expensive. One of the most expensive parts of a wind turbine is its gearbox. Wind turbines gearbox due to fluctuating loads unexpected is likely to suffer a premature fatigue. The purpose of this project is to calculate some of the oscillating loads applied to the gearbox and then to investigate the effect of these loads on the service life of the gearbox components. Tower shadow effect and wind shear effect are the... 

Pipe freezing has become well established in industry as a method of short-termisolation in order to carry out maintenance or repairs. It is often necessary to repair system components without plant shutdown or drainage of system having many piping structures which may have hazardous or expensive fluid. Therefore, a series of tests has been arranged to investigate the ice plug formation in two standard pipes with different diameter size. The freeze zone on the pipe has been created by means of an aluminum jacket which liquid nitrogen flows in it. In the tests the freezing time, amount of liquid nitrogen usage andthe pressure tolerance of ice plug have been determined. Moreover, the numerical... 

In positioning and navigation, Sonar with utilization of sound waves in water environments is similar to the role of Radar in not watered (irrigated) environments. In the Sonar field, modeling and simulation of propagation of sound waves in the undersea environment is a fundamental and very important topic. Nowadays simulation is significant tool that allow to the researchers to predict the quality of Sonar function respect to the experimental conditions. For simulation and modeling of sound wave propagation are used two different methods; Wave theory and Ray theory. In the wave theory, because of the large volume of data, the interpretation of the results is hard. Also in this method cannot... 

Markov chains are memoryless stochastic processes that undergoes transitions from one state to another state on a state space having the property that, given the present,the future is conditionally independent of the past. Under general conditions, the markov chain has a stationary distribution and the probability distribution of the markov chain, independent of the staring state, converges to it’s stationary distribution.
We use this fact to construct markov chain monte carlo, which are a class of algorithms for sampling from probability distributions based on constructing a markov chain that has the desired distribution as its stationary distribution. The state of a chain after a large... 

Partially submerged propellers are new type of propellers which knowledges ragard them is limited. These propellers found a growing market ahead of them and expertsexpect to use these propellers for big vessels at high speeds. This type of propulsors do not lose their efficiences at high speeds and are assumped to be economical. Meanwhile due to continuosus hit to water surface, huge stresses are extered on tha blade witch needs to be fundamentally studied. Several researchers have studied the partially submerged propellers which unfortunately did not publish their results. Undergo less or more thrust and torques which in both cases the efficiency also increases. The use of numerical methods... 

The electrospray technique involves the production of small charged droplets through the application of electrohydrodynamic forces. Under well-defined operating conditions, multiple flow modes can be observed, among which the stable jet-cone mode has received significant attention from the research community. This mode is desirable due to its uniform droplet diameter, reduction in droplet rebound when impacting hot surfaces, and potential for utilizing two-phase heat transfer for cooling purposes. In this study, a comprehensive experimental investigation was conducted to evaluate the cooling of hot surfaces through the use of electrospray in the steady cone-jet mode. The fundamental... 

On May 5, 2014, Iran began the Health Transformation Plan in public hospitals to promote vaginal delivery by increasing physician fees and by freeing payment of natural labor. About five month later part of the plan extended to non-public hospitals, and the fee of vaginal delivery increased there as well. These consequent exogenous policies provide an ideal environment to examine how Ob/Gyn physicians and pregnant mothers respond to financial incentives using difference-in-difference identification. We find that after the first reform caesarean rates declined by 4.92 percent in public hospitals without any health deterioration, a significant but modest drop. Our results suggest that in the... 

TIN (Triangulated Irregular Network) is a Data Structure for storing and manipulating surfaces like maps in GIS applications or 3D models in game engines or Vector Fields . A TIN contains a set of triangulated vertices (which has irregular distribution) and each vertex shows a point in space . We trying to find the smallest possible set (optimal solution) of vertices from input surface (which given as a TIN) to approximate input surface with epsilon error which is given as input. also, surface simplification problem is a member of NP-Hard class. The hardness of problem makes it infeasible to find an optimal solution in polynomial time. So we try finding an approximate algorithm for this... 

In this thesis we consider the effect of random locations of users in the capacity analysis of SIR-based power control systems and comparison to the strength-based systems, for the first time. Unlike previous works we do not consider a simple deterministic uniform model for the analysis. We provide simulations and analytical solutions for calculating the interference statistics, based on which, we not only calculate the interference statistics, but also study the effect of locating a user in every location in the network coverage area and its share in the interference. We also calculate each cell’s share in every statistics of the interference. In this thesis, based on the common assumption... 

The microstructures of stainless steels consist of an austenitic matrix with almost continuous network of primery carbides.This class of steel had replaced the traditional super alloys with a reduction in costs and has similar properties under conditions of creep, which is one of the principal degradation mechanisms leading to failure in service at elevated temperaturs , therefore, their mechanical properties such as tensile strength and creep resistance are particularly important in hot deformation. Recently the effects of temperature and aging time on static strain aging in worked stainless steel have been investigated. In this study the deformation behavior of HP-series austenitic... 

Many countries use a single water meter for multiple units within a building. This creates a cost externality where the cost of water consumed is spread over all units. Using administrative data from Tehran Water and Wastewater Co. for 2013 and 2014, we find an increase in the number of units on a communal meter on average increases per unit use by 0.4 percent. Estimation at different levels of units reveals that almost all communal meters have higher per unit water use. The results suggest that the externality is responsible for 2.7 percent of water consumption in our sample.
JEL classification: L9, Q25, Q50, Q58
 

Can economics be a value-free science? The issue of values in science is a topic of discussion in the philosophy of science, and obviously in the social sciences, especially in economics, this issue becomes more controversial. Throughout the history of economics, these controversies have been the source of challenging debates among economists, philosophers, and sociologists. This question is still posed to philosophers and social scientists. Certainly, the answer to this question will have methodological implications. The issue of values has been an issue for economists from the very beginning of the Austrian school of economics. This dissertation deals with a view presented by a group of... 

Moving towards a sustainable energy system in the evolving society requires the utilization of new applications like Electrical Vehicles (EVs) and integration of Renewable Energy Sources (RESs) which will make new challenges for today’s power grids. To address these challenges, it is essential for emerging demand control paradigm to not only adapt the required demand with available supply but also consider the comfort and the level of lifestyle each customer may have in practice. In this research, due to the ever-growing interconnectivity of the grids, a distributed Commodity Market (CM) framework is proposed in which intelligent agents embedded in Demand Control Entity (DCE) units in... 

The research examines the influence of Kant’s practical philosophy on John Rawls’ theory of justice, under the concept of “autonomy”. In the initial chapter, foundational concepts of the study such as “autonomy” and “duty” are discussed in detail within the context of prevailing views in moral philosophy, particularly deontological ethics. The overarching idea of this chapter is to establish a general conceptual framework for posing the main research question. The second chapter of this research specifically and independently elucidates Kant’s practical philosophy and clarifies his interpretation of the concept of “autonomy”. The aim of structuring this chapter is to demonstrate that... 

Social robots that are designed to interact with people in order to fulfill purposes like education, healthcare, etc. have to behave interactively like human. One of the human’s interactive behaviors is eye gaze. Studying the literature, we found out that in previous researches conducted to control the social robots’ gaze behavior, human gaze behavior was investigated in some limited situations such as two- or three-way conversation in order to extract the pattern of this behavior. Therefore, increasing the variety of studied social situations is a way to fill this gap. In this research we intend to propose an empirical motion-time pattern for human gaze behavior in some different social... 

Object tracking is one of the first, most basic and among the topics of interest in the field of computer vision. Nowadays, with the availability of high-quality and inexpensive video cameras and the expansion of neural networks, there has been a great interest in automatic video analysis using object tracking algorithms. However, many of the existing object tracking algorithms do frame-by-frame tracking using videos with high frame rates, which is not suitable for all locations that use surveillance cameras, because due to existing hardware limitations, the recorded videos are either kept for a limited period of time or are forcibly stored with low frame rates, which leads to the loss of a...