Sharif Digital Repository

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... 

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,... 

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... 

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... 

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... 

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... 

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... 

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... 

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... 

The lack of road safety imposes heavy costs on society. The cost of treatment, disability, travel time and mental disorders are examples of costs caused by unsafe roads in a country. One of the most effective manners to improve road safety over the last decade is to use safe driving incentives and in particular usage-based insurance. Usage-based insurance reduces road accidents by internalizing the cost of driving violations and the cost of vehicle usage.Risky behaviors and driving violations, especially speed limits violations, have a significant effect on increasing unsafe road traffics. Accordingly, in this Ph.D. dissertation, a new scheme of usage-based insurance was introduced to reduce... 

The road authorities of a city have the responsibility of constantly assessing how well their city performs when traffic conditions are taken into account. In many metropolises around the world, if not taken preventive measures, there will be observed a density above the network capacity and a noticeable decrease in the level of service, especially in the morning and evening peak hours. Also, the dynamic congestion pricing of certain areas based on the traffic condition has always been considered significant by urban planning officials. Since this is not possible except by constantly assessing the current traffic state, a variety of methods have been used to predict the future traffic... 

Road casualty is the fourth leading cause of death in Iran after cardiovascular disease, cancer, and respiratory disease. Moreover, up to 7% of Iran’s Gross Domestic Product (- GDP) is spent annually on motor vehicle crashes’(MVCs) adverse outcomes. Recent studies have highlighted the role of anger and aggressive behaviors, while driving as two main predicters of MVCs. On the other hand, bus drivers and passengers, compared with the small number of registered buses in Iran, are more prone to fatal crashes than occupants of any other vehicles, based on the last WHO’s report. The aim of current research was to evaluate the influence of aggressive thoughts and behaviors on the road, driver’s... 

Human error is one of the most important causes of accidents. Distraction and lack of attention to driving, fatigue, poor vision, speeding, and other such errors by drivers can cause accidents. With the rapid advancement of technology, transportation planners also thought of making cars as smart as possible to reduce human error. In this study, the effect of self-driving cars on the number of accidents at two unsignalized intersections is investigated using traffic microsimulation. For conventional vehicles, the factor considered for the simulation and calibration is driver distraction, which may be caused by reading or writing a text message on a cellphone or other items. This factor can be...