Sharif Digital Repository

Dams are one of the vital infrastructures of the country and their correct use can have a significant impact on reducing costs and increasing their productivity. Due to the fact that dams are mainly large structures with a large number of components and with many complications of operation and maintenance, their operation and maintenance require spending a lot of money. On the other hand, the depth and volume of water behind the dams and the entanglement of the connection between the dams and the surrounding environment make the operation and maintenance of dams face many risks. The use of new technologies that can reduce the costs and risks of operating and maintaining dams can greatly help... 

Software defect prediction is a significant and growing field in software development that focuses on identifying software modules prone to defects before the testing phase. The challenge of lacking historical data has shifted software defect prediction towards a cross-project approach. In this method, identifying defective software modules in a project (target project) is done using historical data collected from other projects (source project). The difference in data distribution between source and target projects is a major challenge in cross-project defect prediction. One way to overcome this challenge is the appropriate selection of the source project, which most existing studies... 

This dissertation deals with nonwandering (e.g. area-preserving) homeomorphisms of the torus which are homotopic to the identity and strictly toral, in the sense that they exhibit dynamical properties that are not present in homeomorphisms of the annulus or the plane. This includes all homeomorphisms which have a rotation set with nonempty interior. There are two types of points: inessential and essential. It is known that the set of inessential points Ine(f ) is a disjoint union of periodic topological disks ("elliptic islands"), while the set of essential points Ess(f ) is an essential continuum, with typically rich dynamics ("the chaotic region"). One of the key results in this context is... 

In 1917 Einstein used Λ as a cosmological constant in his theory of general relativity, but after a while he receded for some reasons. This constant has been reconsidered again recently. But using it in general relativity has caused some problems. In this thesis, after a short review of important elements in studying cosmological constant problem, like a short introduction to general relativity and cosmology in the first chapter as well as a short review of quantum field theory and supersymmetry in the second chapter, we will study the history and introduction of the problem in the third chapter.in the third chapter , different solutions to this problem ,like supersymmetry,anthropic... 

Neutron fluctuations in both low and high power reactors provide important information about the system. The origins of these fluctuations are different in both regimes. In low power the branching process is the reason of these fluctuations. But the random nature of technological processes such as boiling in the reactors cooling and mechanical structure vibrating such as control rod and fuel rod created the neutron noise. Mathematical descriptions and applications of neutron noise for each mode are different. In common mode, fluctuations in the neutron detection system, determine some parameters and determin the start abnormality in system. In this study the spatial dependence of the cross... 

The airport terminal is difficult to plan and design due to the different components and the intricate complexity of its parts. At the airport terminal, we face a queue system which simulation is always a good way to analyze. In addition, computer simulation using modern softwares with the capability to model different types of systems, including the airport terminal, while being less realistic than analytical models, is less costly than operational Exercise.In this study, a supportive approach for better and specific management of Iranian airport terminal buildings with discrete-event simulation is proposed, considering the need for managing the airport terminals building in the country and... 

Left-turn operation is a critical component in the safe and efficient operation of a signalized intersection. The proper type of left-turn phasing results in reduction of traffic delay and number of accidents. A review of the literature indicates that different warrants have been proposed for the installation of the protected left-turn phase; however, there is not a consensus to implement a specific warrant up to the present. In general, the warrants fall into four categories: traffic volume, operational characteristics of traffic, intersection geometrics and accident experiences. Considering the high rate of accidents resulting from left-turn movements at signalized intersections in Iran,... 

High number of traffic accidents in Iran and its rate which is well above the world's average is a major issue of concern. The results of recent researches show a direct relation between survival rate of traffic accidents' injuries and the Emergency Response Time (ERT). The main objective of this research is to analyze different aspects of ERT in Tehran, Iran and to compare these results with the International standards. This study intends to compare the selected routes by ambulance drivers with the shortest paths recommended by EMME/2. Results of analysis show that when the travel time between accident scene and the emergency dispatch center is less than 8 minutes, the possibility of... 

Identification of hazardous locations and improvement of these locations are the basis of most highway safety inspection programs. In most cases, performance of successful highway safety management programs requires accurate accident data, and availability of these data. Unfortunately, in Iran, there is some uncertainty about the accuracy and completeness of these data to be used in a safety management program.The main purpose of this study is to identify and compare highway accident hazard index for a two-lane rural highway in Iran using two different methods. In the first method, traffic and alignment characteristics of the highway were recorded through roadway auditing technique, GPS... 

For any country, the road system is an important part of its infrastructure which can affect economic development. A good level of service for a road system requires implementation of work zone projects to maintain it which usually close one or more of the lanes available for traffic. Lane reductions could cause a disturbance to normal traffic flow and speed reductions, further resulting in a reduction of road capacity and an increase of traffic delay. In addition, work zone capacity and traffic delay are the two critical indices to determine whether the effectiveness of traffic control systems is acceptable or not. Hence, the accurate estimation of capacity and traffic delay in work zones is of... 

Estimation of travel time in transportation engineering has always been an important issue. So far, most of travel time studies have focused on freeways and highways, and very few research have been done on travel time estimation for arterials. In this study, by using shock wave concept, a probabilistic model is developed for estimating the travel time of a signalized arterials consisting of two pre-timed signalized intersections. This model can be used in both coordinated and non-coordinated signals. In this study, travel time and traffic volume data were collected for Fatemi Ave. in Tehran, Iran. By using these data, some parameters of VISSIM simulation package were calibrated to reflect... 

Nowadays, there are three factors in traffic issues, which are very important. These factors are delay time, fuel consumption and environmental pollution. A good choice of the type of traffic nodes (intersection and roundabout) can play an important role in reducing some of the traffic problems such as: the amount of vehicles' delay time, energy consumption and pollution due to the transport system. In this study, we try to identify factors that influence delay time, fuel consumption and air pollution in different types of intersections and roundabout. According to previous studies, these factors were such as: variables of each route volume, distribution of through, right turn and left turn... 

Traffic accidents, is an inevitable event. There are various reasons for accidents and almost not possible to identify all of them, but a careful study of these phenomena can identify the main causes of this phenomenon. This study estimates Multi-Vehicle severity in terms of different weather. Accidents data the Including 2,949 accidents recorded during 1388 to 1392 in six axes of the East Azerbaijan roads in three levels of accident severity: damage, injury and death. For modeling, sequential Logit model was selected because accidents severity have Sequential nature. This model used the Stata software, version 12, for evaluation and sensitivity analysis. The obtained model consists of... 

Natural disasters, earthquakes in particular, claim many human lives and damage major lifelines such as transportation networks. Transportation networks play an important role in various stages of response to disasters, such as evacuation, search, rescue and reconstruction missions. Hence, special attention must be paid to transportation networks in any disaster management system. Hence, in order to reduce the impacts of earthquakes on denser cities and metropolitan areas, analysis of the resiliency and vulnerability of critical infrastructures such as transportation network, can be used as an effective strategy.The resiliency and vulnerability of transportation network have attract a lot...