Sharif Digital Repository

Most construction projects contain activities repeated in project units or locations with definite consequence. These kinds of projects are called repetitive projects. One of the fundamental objectives of planning and scheduling of repetitive projects is using resources optimally and without interruption, a concept known as continuous workflow. Traditional planning and scheduling methods like Critical Path Method (CPM) are criticized for their disability to produce a reliable workflow. Ignoring the concept of workflow in project schedule causes time and cost overrun that arise from additional waiting times and also increase the risk of accessibility to resources on time. Therefore in this... 

Limited fossil energy resources and problems with greenhouse gas emissions, has increasingly focused attentions on renewable energy as a solution to this issue. Marine energy due to the the vast amount of wind, current and wave available resources, can play a major role in providing renewable energy and reducing CO2 emissions. However, using one renewable energy, in some cases due to its high volatility and high costs is impractical. Combining different marine renewable energies, can be mentioned as a solution to increase competitiveness with fossil fuels. The aim of the current research, is to introduce a method to select the best location in terms of renewable energy farms wind, current... 

In this thesis, a new hub-and-spoke location problem is investigated in which, the location of spoke nodes should be decided upon, in addition to the location of hub nodes. Three research problems are investigated: In the first problem, the goal is to determine both hub and spoke node locations. In this problem, the objective function considers the following costs, to be minimized: flow transportation costs, lost demand costs, in addition to the hub and spoke location costs. The demand distribution among different nodes follow the gravity rule, and the hub network is considered to be fully connected. Following the gravity rule, the demand among different node is not set a priory and depends... 

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... 

As time has passed, the cost of maintaining expert human resources has been increasing worldwide; as a result, factories and stakeholder has sought ways to exploit the expertise of their human resources as much as possible so they can reduce their costs and, of course, raise their profits. To achieve this, managers decided to assign their human resources to tasks that demands their expertise and knowledge and therefore provides added value for their companies; nevertheless, this decision needs proper alternatives to do routine and predetermined jobs as substitutions for expert human resources.As the technology and the science has been growing day by day, the use of robots has been extremely... 

In this research, we propose a formulated approach to locate and allocate two level of a three-level closed-loop supply chain consist of a number of capable points production facilities, redistribution centers and customer clusters for multiple products in multiple time periods. Also, we consider environmental aspects in this supply chain network by taking into account an objective function, aside from cost objective function, in the template of emitted carbon dioxide. In this research for the first time we consider vehicles’ emitted CO2 different in each period which is a result of gradual depreciation of vehicles. In the end for the sake of validating model’s performance we developed few... 

This thesis presents a variety of methods have been proposed for optimal locating and sizing of Distributed Resource (DR) in restructured power system to reduce congestion and enhance security. Initially three different methodologies, based upon LMP and congestion rent, are presented that form priority list of candidate buses to reduce solution space. For taking into account security, The N−1 contingency criterion is performed and then a priority list of the worst contingencies from congestion rent point of view is organized. Based upon both normal condition and selected contingencies of the network a priority list of buses for optimal placement and for each level of power output of DR is... 

Facility location decisions are critical elements in strategic planning processes for a wide range of private and public firms. High costs associated with facility location and construction make facility location or relocation projects long-term investments. One of the most popular models among facility location models is the covering problem. This is due to its application in real life, especially for service and emergency facilities. Set covering problem (SCP) and the maximal covering location problem (MCLP) are two categories of the covering models. The presented model in this study is based on the maximal covering location problemwhile considering some real¬ life constraintssuch as... 

Opportunistic networks are special ad-hoc networks in which nodes exploit any opportunisty of pairwise contact to forward packets, without requiring any fixed infrastructures. Routing in Opportunistic Networks due to intermittently connected, non-existence an end to end path between source and destination and with a dynamic topology is a challenging issue. There are several different routing approaches in deliver packets from source to destinations. This approaches can be divided into four categories: awareness approaches, Non-Awareness, direct Delivery and coding based. Use of awareness approaches can be more improved routing process. This category consists of two parts: Context-Aware and... 

Five-Level Active-Neutral-Point -Clamped (5L-ANPC) converter is used for medium-voltage and high-power applications. In many of these applications, availability and robustness against fault are the most important issues. On the other hand, this converter is made of a large number of power semiconductor switches, diodes and capacitors which could increase the failure probability. Thus, fault detection of power circuit elements is necessary for fault tolerant operation of the converter. In this thesis, following an introduction to the topology and operation principles of Five-Level Active Neutral point clamped converter, a novel open-circuit fault detection and localization method is... 

Increasing the performance and efficiency of the transportation system is one of the issues that has attracted the attention of many managers and experts in the industrial sector during the last decades, which aims to deliver the product to the customer in the earliest possible time with minimum cost. Therefore, it appears crucial to shed light on two aspects of the issues in this regard. The first one is to create routes functioning as flow transmission interface between many origins and many destinations and to satisfy the allowable time of tours in each route. The other one is the route that vehicles must take within the window time of each destination point. It should be pointed that the... 

In this thesis, a new passive method suitable for Geolocating LPI radars is introduced. The method uses two Electronic Support (ES) receivers placed on a fast moving platform (e.g., an airplane or a satellite). The proposed method has a high processing gain, which makes it highly suitable for very weak LPI signals. The processing gain of the method was analytically derived and illustrated with simulation to determine if the proposed method can detect LPI radars in much lower SNRs compared to regular time-frequency LPI detection methods. Also, the resolution of the proposed method in both range and cross-range direction in radar location finding was analyzed. Furthurmore, the effect of the... 

Nowadays, cleanrooms have a growing application in a broad range of industries, e.g. pharmacy, aerospace, nuclear energy and electronics. So, it seems that numerical modeling of airflow in such spaces becomes more essential. As computational fluid dynamics has become a powerful tool for indoor airflow studies, in this research, influence of effective parameters on the flow and concentration distribution in cleanrooms has been investigated by the use of CFD. To do so, aerosol flow in a 3-D cleanroom has been numerically modeled by Fluent 6.3, using Euler-Euler approach and standard k- turbulence model. Comparison between numerical results and experimental data shows a considerably good... 

In recent years, there have been many studies aimed at finding program defect using information of previous ones. These studies, by using the program text, previous bugs, and information related to version control and project management systems create an defect prediction model to find other defect prone areas in the program. The output of defect prediction methods is part of the program’s text, which is likely to have defects. Considering that the result of this method is just the text of the program and does not provide any extra information for finding defects to the user, these methods have not yet been applied to the software industry. On the other hand, by spreading the use of Q & A... 

In this research, an integrated location-inventory-transportation problem with uncertainty in the parameters is analyzed using Robust Optimization techniques. Unknown demand distribution is the underlying assumption, which relates better to the reality. The model’s main purpose is to determine the number and locations of the Distribution Centers (DC) that connect the supplier to the retailers, and then to assign retailers to them. The problem’s mathematical model is developed on the basis of Robust Optimization techniques and the solution space is explored by Tabu Search. The results show that the Tabu Search method achieves optimality in small-scale cases, while providing desirable... 

Plants, distribution centers, and other facilities generally function for years or decades, during which time the environment in which they operate may change substantially. Costs, demands, travel times, and other inputs to classical facility location models may be highly uncertain. So when making decisions of location considering the factors that may change is beneficial. In this thesis a version of covering location model under uncertainty in a congested system is proposed. The aim is to locate m facilities to maximize the captured customer utility, having in mind that there may be up to q facilities established in future; the only information at hand about the number of the new facilities... 

We propose a range-free localization framework in which a network of randomly deployed acoustic sensors can passively use natural acoustic phenomena within its environment to localize itself. We introduce a novel approach for registration of sensors observations which takes advantage of a clustering technique on triplets of associated observations. A Bayesian filtering method is employed to incrementally improve system state estimation as more observations become available. To the best of our knowledge this is the first work done on range-free passive acoustic localization. Furthermore, we have proposed a simple but effective and efficient acoustic detection method which can be used to... 

Control and managing of fuel consumption is one of the most important issues facing man kind today. Locating gas stations has a great effect on fuel consumption. The gas station locating problem consists of selecting the optimal choice between the candidate nodes for constructing gas stations in such a way that minimizes the excess travel time that results from the gas station not being located on daily travel paths. The gas station locating model is presented for two conditions of either considering and not considering the gas station capacity. In the case of not considering the gas station capacity, a compact model is presented, too. Softwares for medium sized networks and the Simulated... 

Facility layout is one of the most important problems in industrial engineering and Operation Research. Facility layout problem is concerned with the determination of the most effective arrangement and configuration of physical facilities. The most successful heuristic approaches are based on graph theoretic concepts. solving facility layout problem by graph theory consists of two stages. In the first stage a planar graph which specifies desired adjacencies is obtained and in the second stage a Block layout is achieved from the planar graph which satisfies adjacency and area requirements. In this Research, a branch and bound algorithm will be suggested for WMPG Problem. The algorithm can... 

Sensor Localization is a crucial part of many location‐dependent applications that utilize wireless sensor networks (WSNs). Several approaches, including range‐based and range‐free, have been proposed to calculate the position of randomly deployed sensor nodes. With specific hardware, the range‐based schemes typically achieve high accuracy based on either node‐to-node distances or angles. On the other hand, the range‐free mechanisms support less positioning accuracy with less expense. The proposed scheme is based on range‐free localization, which utilizes the received signal strength (RSS) from the anchor nodes. In this work, genetic fuzzy and neuro-fuzzy systems are used to yield more...