Sharif Digital Repository

Airline scheduling is a dynamic process in nature such that it changes not only during one year period but also in smaller intervals due to the economic, political, religious, and social factors. Basically, airlines schedule planners through using mathematical models decide which flights are to be served in what periods of time and at what costs. This has to be done considering a set of constraints of different nature, from airspace and airport congestion up to climatic conditions or even crews working conditions. Such a complex problem requires different methods for an efficient solution. In this study by using network optimization method and applying different operational constraints on... 

Shortest path computation is one the fundamental problems in computer science. Triangulated Irregular Networks (TINs) are used in computational geometry to represent terrians and geometric surfaces. One of the most efficient mothods to solve the shortest path problem on a TIN is reducing it to shortest path problem on a graph. This reduction from continuous space to discrete space results in approximate solutions, but acceptable in real applications. In real applications we still encounter a large graph and using the simple Dijkstra algorithm consumes a lot of times. Memory shortage is another issue. Parallel processing could be a solution in this case. Multicore industry caused a... 

We consider two variations of shortest paths problem inside a poly-gon. In the first variation, we want to find a shortest path from asource to view a destination inside a polygon with holes. We pro-pose two algorithms for this problem with the time complexity of O (hn log n) and O(n log n) in which the second one is optimal. In the second variation, we want to place a center policeman inside a sim-ple polygon so that the longer of the two shortest paths from two existing guards to the visibility polygon of the center policeman is minimized. We propose an algorithm for this problem with the time complexity of O(n 3)  

Nonstop growth of environmental concerns regarding ordinary vehicles detrimental effects have led to increasing use of Electrical Vehicles which require more researches in different fields of study. The main purpose of this study is solving the problem of Electrical Vehicles' traffic assignment considering recharging time as a function of amount of charge. Existing EVs have limited driving range, and these cars' drivers usually have to spend a considerable amount of time on recharging in order to complete a path. As a result, their corresponding optimum route choice differs from that of gasoline-based vehicles' drivers. In more detail, this study proposes an algorithm to solve the shortest... 

Nowadays, the necessity of management tools for controlling the ever increasing congestions in transportation networks has been increased. Pricing is one of these tools for mitigating congestions in transportation networks. In this regard, different pricing models have been developed for transportation networks. By considering the advancement in technologies and possibility of recording the vehicles’ traveled distance in the tolling areas, the amount of toll each user pays could be a nonlinear function of the distance traveled inside tolling areas. As a result, the generalized travel cost of each path may not be link-wise additive; therefore, the resulting shortest path problem cannot be... 

Knowing the trip information such as paths that travelers prefer to choose is useful for practice in developing certain transportation planning step. There are different methods such as using GPS and conducting survey for volunteer travelers in order to understand actual paths. Obviously, all of these methods have some deficiencies. This research suggests and examines a method for estimating travelers’ path by using cell phone data. The main advantage of using these kinds of data is enabling the process of collecting information without any active interference of the users. A big data set consisting of 300,000 cell phone users’ information in the city of Shiraz is studied to achieve this... 

In minimum cut problem we aim at finding a set of edges with minimum overall cost possible, such that removing them would separate two specific vertices, source and sink. This problem has been studied thoroughly, however the available algorithms were not proven to be time-wise optimal. Nowadays, planar graphs have attracted more attention because of their applications in cities and countries map. Moreover,their characteristics and properties, make some problems easier to solve in planar case. In this thesis, we will have a survey on algorithms for minimum cut on planar graphs. Our motivation to choose these algorithms is the balance between how easily they could be implemented and how fast... 

The goal of this research is to solve the traffic assignment of electric vehicles with considering trip chains. Limited driving range of electric vehicles is considered as one the most important obstacles for the development of these cars. The worry that the battery will run out of power before the destination is an important issue regarding the electric cars and people usually experience it more in trip chains. In this research, a complementary model and a linearization method is used for traffic assignment. In determining shortest paths in the traffic assignment, in addition to considering the travel time and the distance limit, the constraint of passing through activity nodes is... 

During the past decade the ever increasing volume of greenhouse gases due to fossil fuels consumption have made humans to seek for alternative, non-polluting fuels as an effective strategy to reduce pollution and prevent environmental issues thereof. Electric cars are today known as one of the most effective solutions for this purpose. Of course, transition from gasoline-powered cars to electric cars in a wide scale is not technically possible in short term due to technological and infrastructural limitations. As a result, this lengthy process would lead to emergence of a combinational transportation system including both gas and electric-powered vehicles. The major differences between these... 

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... 

Natural hazards such as earthquake take many lives each year and cause significant damages to infrastructures such as transportation networks. Whether after occurrence of a natural disaster like storm in order to evacuate, or after an abrupt event such as earthquake in order to provide emergency measures, a transportation network should maintain its functionality and performance in an acceptable degree and should recover in an effectively short period of time. In this study, the link or the set of links which their removal causes significant damage to the transportation network are identified. A specific index (N-Q index) has been used to describe the performance of the network. In addition,... 

Computing shortest paths and minimum spanning trees are basic and well-known problems in computer science and graph theory; also they have been considered as basic subroutines for many practical algorithms. There exists optimal algorithms for solving these problems when information about the basic graph is certain and specified. But, in real applications when the graph is obtained by using measurement tools which have limited computing precision, practically we are facing a graph in which locations of vertices or weights of edges are estimated.In such cases determining upper bounds or lower bounds for solutions of the shortest path and the minimum spanning tree are estimations of the... 

The Steiner forest problem is one of the most fundamental issues in network design that emerges in various contexts, such as the design of communication networks,transportation networks, VLSI circuits and phylogenetic network reconstruction. In this problem, we are given a connected weighted undirected graph and a special subset of vertices that are partitioned in pairs. The goal is to fnd a minimum-cost sub-graph in which each special vertex is connected to its mate. In this thesis we review a set of selected solutions for this problem and a few other related problems.For example, we study modeling and solving the s-t shortest path problem in order to gain insight into current Steiner... 

In today's life, we look at each other, seeing different networks, such as power networks, telecommunication networks, transportation networks (freeways, roads, streets), rail networks, air service networks, shipping networks, Logistics networks (networks of construction and distribution), computer networks, Internet networks (e-commerce, banking networks), airline reservation networks, social networks and so on. In all of these networks, an entity such as man, product, car, electricity, message, information, aircraft, etc. from one source into a destination is moved according to the network's purposes and objectives.This thesis analyzes the sensitivity analysis and optimization of... 

Due to increasing quality of satellite images, volume of stored data significantly increased, so speed of statistical and computational processing decreased. For solving this problem, simplification
problem has been suggested. Surface simplification problem is a fundamental problem in computational geometry and it has many applications in other fields such as GIS, computer graphics, and image processing. Major goal of simplification problems is reducing stored information in any surface, Because it improves speed of processes. One of common types in this field is 3D terrain simplification while error of simplified surface be acceptable. Simplification is NP-Hard problem. In this project,... 

In respect of increasing expanse public urban transport, road network complexity as well optimized route planning is necessary in transport network more than ever. Multi-modal network is a transport network which has various means of transportation modes. In that network the presentation a sequence transport mode is essential apart from determining the optimal route. Although choosing the shortest viable path has some limitation the user chooses that. In this paper a modal path planning in multi-modal network has been expressed which two objective functions in addition to minimize the number of change modes have been designed the first is cost and the second is time. Moreover, in this... 

Routers play a key role in transferring information between various Networks. It is very important to make sure about the compatibility of OSPF in a router with its standard description. In this regard, before presenting or applying a router and also evaluating its performance, it is necessary to carry out conformance test with the help of network equipment testers Tester designers extract test cases from protocol standard description through non-formal ways and exam them on network equipment.
In this thesis, a part of OSFP protocol has been modeled through colored Petri nets. In this regard, two sections of OSPF RFC have been model checked: neighbor state machine and data base... 

Complex networks represent a wide diversity of systems in nature and human interactions. Networks are graphs that describe the structures of interacting systems and give significant information about the patterns of connections between the nodes in a particular system. In turn, having knowledge about the structure of networks and their arrangements enables one to make certain types of predictions about their behavior of network.Network methods have had profound influence in many domains and fields in the past decade. Centrality measures are very important tool for analysis complex networks, in real-world complex networks are heterogeneous structures, all their components such as nodes... 

In the context of differential privacy, a data holder has confidential information about users. The goal is to provide a randomized algorithm that takes this information as input and outputs an aggregation of the input. The algorithm must have the property that for any neighboring input pairs, the output distribution of the algorithm is close. One problem in differential privacy research is the release of shortest distances in a weighted graph. This model, first studied by Adam Sealfon, involves an edge-weighted graph G=(V, E) with weights w : E → R, where the topology of the graph is public and the private information is the weight of the edges. The aim is to provide an (ϵ, δ)-DP algorithm... 

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...