Sharif Digital Repository

Rail transport system plays an important role in the development of the economies of the countries. This system is worn out over time by operating and weather conditions and requires maintenance and repair. One of the objectives of maintenance operations is to maintain tracks in an acceptable level and prevent their excessive deviation from the optimal situation. This deviation is called geometric irregular deviation. If these irregularities go away, they can cause traffic accidents and derailment in addition to losing travel convenience. So avoiding the deviation of the tracks is a very important. Maintenance management systems in the past few decades have been considered by the experts in... 

It is of fundamental importance to find algorithms obtaining optimal performance for learning of statistical models in distributed and communication limited systems. In this thesis, we aim at characterizing the best learning strategies over distributed datasets such that the communications between storing machines are minimized. We have addressed two problems in distributed setting: learning of Gaussian processes, and structure learning of Gaussian Graphical Models (GGM). The performance of the proposed methods are analyzed theoritically and verified experimentally. The experimental results show that with spending few bits the proposed distributed methods have close performance to the... 

Nowadays, the explosion of the volume data provides more accuracy in machine learning models. But, Working with a vast amount of data is not easy, especially in a situation that data are distributed over the systems. In such systems, designing distributed learning algorithms that in communication efficient setting demand reliable and more accurate results, are so important. We studied sparse structure learning of Gaussian graphical model in a situation that our data are distributed over the system and each machine has a dimension of data. Each local machine should send its data to a central machine and the central machine is responsible for learning the structure. For reliable learning under... 

Distributed learning has been a popular area of machine learning for researchers according to having access to an unprecedented amount of data distributed over many clients in a network. Moreover, high dimensional learning, when the dimensions of data are high but the effective features are low, has great usage in learning especially in medical science. In this paper, we attempted to develop a method for learning high-dimensional sparse problems in a distributed manner, whit a star shape network. Our main focus in this research is on optimizing the communication flow in the network. The prominent idea of our proposed method is to extract the main feature in the first step, then continuing... 

Control of complex networks is the main topic in this study. In this thesis, we consider the methods to steer the dynamics of a network from an initial state to the desired final state. To achieve this goal, one needs to inject appropriate control signals from some of the network nodes, known as driver nodes. We consider the quadratic sum of control signals as a cost function, to control the dynamics of the network. By minimising the cost function, we obtain the control signals as well as driver nodes for a linear time-invariant system. As an example, we provide the results of an energy minimization strategy to control the second order Kuramoto and Rössler dynamics in Erdos-Renyi and... 

The purpose of this study is to present a suitable model for calculating the costs imposed on society due to deaths and injuries due to infrastructure failure due to earthquakes, which is used in the analysis of community resilience. Much research has been done to date to calculate the economic costs of infrastructure failure. However, no suitable analytical framework has been provided to quantify the costs of deaths and injuries to people due to earthquake failure. Previous research has provided methods such as the value of statistical life to quantify the social costs caused by accidents and environmental pollution. However, the literature review results in the field of seismic resilience... 

Nowadays sharing data between users and organizations can be difficult due to privacy and legal reasons. Therefore, real-world data is not fully exploited by machine learning methods. A novel model training method called Federated Learning was proposed to alleviate the aforementioned problem by enabling users to jointly train learning models without sharing data. Federated learning utilization faces many challenges among which high communication cost, statistical heterogeneity and system heterogeneity are most important. This research deals with these challenges by proposing two methods of Reduced Clustering Federated Learning (RCFL) and Weighted Federated Distillation (WFD). Moreover, we... 

Developments in the field of data storage which is due to computers have led to an extraordinary increase in medical data just like the increase in all other fields. As a result, physicians are faced with the problem of using the stored data. Therefore, the traditional manual data analysis is inadequate due to the large amounts of data. Furthermore, the ability to use this data to extract useful information is critical for the quality of medical care. Therefore, data mining techniques arose so that we will be able to extract knowledge through applying them to the raw data and subsequently help the doctors in making decisions.
In this study, we are pursuing four goals. First, in order to... 

This dissertation proposes a probabilistic framework for optimal calibration of design provisions based on the minimization of lifecycle cost (LCC) and its uncertainty. Subsequently, this framework is utilized to determine the optimal robust design base shear coefficient of building structures, and propose a methodology for codifying it while preserving the current structure of the base shear equation. In the first part of the proposed methodology, various structures are designed with different seismic base shears. Then, at each site, their LCC comprising the construction costs and seismic losses is calculated. Various types of seismic loss considered in this study include the direct... 

Considering the special importance of network flow problems in human life, as well as the complexity of solving these problems in very large scales, there are numerous methods to solve them and the interior point methods are the most important approaches among them. In a number of methods, a preconditioned conjugate gradient solver has been applied for the solution of the Karush-Kuhn-Tucker (KKT) system, in each interior point iteration; therefore, the selection of an appropriate preconditioner is a special issue. In spite of presenting different preconditioners in recent years, discussion and implementation of a particular class of triangulated graph-based preconditioners is our main... 

We examine the economic implications of the SEC disclosure rules for companies doing business with Iran on their riskiness of debt. We exploit Section 219 of the Iran Threat Reduction and Syria Human Rights Act (ITRA), which requires companies listed on U.S exchanges to disclose their activities and transactions with Iranian institutions. We analyze the impact of the first ITRA disclosure on the cost of capital for both American and foreign companies listed on the US exchanges. Using a difference-in-difference approach, we document a negative impact of ITRA disclosures on loan spread and credit rating of foreign companies. Further, using textual analysis, we identify the elements in the... 

Verification of timed systems is concerned by many researchers in the last decades because of using these systems in critical applications. So, several models such as Timed Automat (TA) and Time Petri Nets (TPN) have been proposed for modeling these systems and variety of logics and abstraction methods are defined. One of the significant problems in timed system is cost-optimal reachability problem where, given an initial state and a target state, the task is to comput a path with infimum cost from initial state to the target state. Priced Timed Automat (PTA) introduce for solving cost-optimal reachability problems such as optimal scheduling and planing in timed systems. PTA is defined as an... 

Steganography is method for communicating confidential information through a non-trustworth in way which hides the existence of communication. For improving the security of steganography statistical detectability must decrease as such as possible. Despite the fact, that the quality of the relation between statistical detectability and amount of distortion engendered by embedding is still an open problem, problem of detectability reduces to problem of management of pixel embedding in order to minimization of distortion. As in wet paper coding methods, an optimum (or approximately optimum) algorithm proportioned to Pixel-cost has been offered, the current problem of steganography is to find... 

Family economics consider children either as "goods" in consumption vector of their parents or as agents that have the ability of full economic independency. While the children reach adolescent age, the theory models their role, not only as individuals with their own preferences, but also as agents who can have an impact on family outcomes. Aim of this study is to focus on the fact that if children of certain ages take part in the households’ decisions or not. We use data from Households Income and Expenditures Survey 2011 for urban area and families with three members, parents and child with the age range 15 - 30. For a closer look, households were divided into four groups which include... 

Hayek is one of the most impressive figures of Austrian School of Economics established by Carl Menger. The Thinkers of this school of thought believed that governments should not intervene in the market process. They argued that such interventions would spoil the market performance in resource allocation. Hayek believes that the order which emerges from the market is a spontaneous one; it means no one has designed it, but it has evolutionarily evolved by distinctive agents' actions who had no plan to make it. Hayek's arguments for spontaneous order are based on some epistemological presuppositions such as: "methodological individualism", "methodological subjectivism", "tacit knowledge" and... 

This research solves a Location-Routing model based on the data of Tejarat bank branches in Tehran. The goal of the model is to minimize the cost of building & operating bank treasuries, optimize the cost of money transferring to branches of the bank & reduce the stealing risk. Because of the wide range of definitions for risk, time parameter is used as risk factor for its importance in bank money car stealing. Non-dominated Sorting Genetic Algorithm which is a common algorithm in multi-objective optimization literature with big data, is used to solve the proposed model  

In the process of industrial and economic development and in the competitive environment in the world, reducing the cost of industrial products is an important factor for more customers' satisfaction, more revenue acquisition, and stability and success in the business. Cost engineering is the area of engineering practice concerned with the application of scientific principles and techniques to problems of cost estimating, cost control, business planning, management science, profitability analysis, project management, planning and scheduling. In this research through the studying the structures and models of cost engineering, in addition to consider this dimensions of cost engineering, the... 

Under volatile economic conditions, where inflation is high and market prices of materials, labor, and equipment change unexpectedly, construction cost rise. To avoid the disruption of work, the owner may be required to compensate the contractors in a way that the excess construction cost is partially or completely covered. This compensation should be provided to the contractors in a way that is authorized by the laws and regulations under which the contract is stipulated. Hence it is essential to have the proper mechanism, for sharing the burden of cost overruns caused by unforeseen economic conditions.
In Iran, the payment scheme for the majority of the medium-and large-scale contracts... 

costs of construction of a structure include: initial construction cost, maintanance cost, seismic risk cost and etc., that in this investigation,the seismic risk of multi-span conc. & steel bridges has been compared. the seismic damage is converted to equivalent finincial value by the concept of life-cycle cost, and then is compared with initial construction cost of structure.in this method, assessment of seismic damage based on structure response, in different earthquake intensity and by damage state concept is done. ET method has been used for predicting response of models.in this investigation two conc. & steel models, with similar geometrical specification and different design results,... 

The actual value of structures should not be evaluated only based on initial cost, because failure cost and economical losses due to corrosion and natural hazards can be catastrophic. The aim of this research is Comparative study of life cycle cost of steel and concrete building systems designed based on standard 2800 by Endurance Time Method. These costs include initial cost and life cycle cost Due to the aftermath of the earthquake in the life of the structure. In this research, because it requires a lot nonlinear dynamic time history analysis, Endurance Time Method used which is both good accuracy and also drastically reduces the cost of computing-off. Selected models for the study, four,...