Sharif Digital Repository

One important problem in all, particularly in developing countries, is shortage of funds to invest in infrastructure projects. One way to lessen this difficulty is to benefit from the private sector participation in this respect. Build-Operate-Own-Transfer (BOT) is a Public-Private-Partnership (PPP), in which the private sector invests and builds a (e.g. road) project, operates it for a specified period of time to collect the tolls to return the investment cost plus the specified attractive rate on it, and then transfer it to the public sector. This research, which is a continuation of previous endeavors in this area, formulates the problem, discusses the multiplicity of the solutions, and... 

Pricing users of the network in the congested Central Business District (CBD) will cause change in the travel behavior of the different sectors of these users . The problem of optimal pricing of CBD is formulated in this study as a bilevel optimization . The lower level problem is a joint trip production-distribution-mode choice-assignment problem , which identifies three groups of the users , namely shoppers , retailers and basic employees . The upper level problem maximizes total long-run benefit and minimizes air pollution and changes in attractions of the zones . The demand for shoppers and retailers is elastic , but that of the basic employees is assumed inelastic . The decision... 

Pavement maintenance and rehabilitation is an important problem in road pavement programming. Pavements experience significant distress over its life due to passage of vehicle (particularly heavy trucks), as well as abrupt variation in temperature (freeze and thaw). This would deteriorate pavements and reduces their serviceability. Rise of pavement maintenance costs places higher importance upon the need for maintenance programming. This study employs an evolutionary model to optimize the long-run benefit of the maintenance program. The model is stochastic in nature, and imbeds a Markovian decision procedure in the model to take into account such variabilities. The model is applied on... 

Transportation networks are considered as complex systems, and in many cases they behave in such an irregular and unexpected manner. Such complexities cause problems in studying the behavior of these systems. An example of such complexities is chaos in the network flows. On the other hand, the behavior of these networks is highly affected by the incidents like accidents and bad weather. Such events affect the level of service and travel time reliability of the networks. In this research, a dynamical approach to traffic assignment has been chosen to model chaos and uncertainties in the network. By using this approach for modeling flow evolution, edge of chaos and uncertainty in supply and... 

Two significant features of a transportation network, uncertainty and complexity, might cause some irregular behaviors. One example of such behaviors is chaotic flow in which the transportation system fails to reach equilibrium and people experience different daily travel times. These uncertainties are not controllable in any transportation system and, if not taken into consideration, will result to low levels of service and poor reliability. In this study, an evolutionary traffic assignmet model is used to illustrate when the network reaches bifurcation and chaos. Later, the effects of uncertainty in the parameters of supply and demand is tested on the evolutionary traffic assignment model.... 

One effective way to reduce air pollution created by automobiles is to tax/toll the unfavorable characteristics of the automobiles. This study is an extension of the current literature on taxing visible and measurable aspects of automobile ownership and use, namely engine size, age, fuel used, and technology level. A three sided model, comprising the operator (government), consumers, and automobile producers, has been constructed to control emission by proper taxation. Engine size tax is one-time, age-tax is yearly, and fuel use is usage-based. The model has been built and experimented based on a sample population and the results have been shown to be in the direction of the management... 

There is a two-way relationship between land use and transportation. So each of them can be used to manage and control the other one. Land use can be Auto-Oriented, or Transit-Oriented. Auto-Oriented Development leads to urban sprawl, causing longer trips and increasing use of private cars. Problems related to this type of development appeared by the end of the 20th century. On the other hand, Transit-Oriented Development may lead to higher density areas, and higher transit use, providing better space for pedestrians and cyclists, as well as increasing environmental pollutions. Land use-transportation relationship hs been the subject of many recent studies. One of the previous models... 

Estimation of demand, for example, for transportation is an important issue for the planning and programming of various systems. Thus, enhancing the predictability power of such models is of high value. Demand stems from choices of individuals, and choice is subject to uncertainty and fuzziness. Uncertainty comes from many factors including incomplete information of decision-maker, and fuzziness comes from many other factors including personal perception regarding the value of the variables affecting choice. This study tries to introduce a new approach in building choice models, in which variables are transformed into another variable by the help of a global wisdom. This wisdom shows the... 

Natural disasters have been with the earth, and felt critical as far back as human history. These incidents are inevitable, but their effects may be controlled. One important problem after a disastrous earthquake is the management of people’s vehicular movements in a chaotic situation. This study is an endeavor to envisage what would possibly happen after such an incident, and how could we possibly control or manage the traffic in such an occasion. We start with the analysis of the online reports of similar past incidents, and try to picture how people react to these events. We try to identify the trip purposes that have been shown to be pursued, and the respective origins and destinations.... 

Transportation systems are dynamic and complex systems due to the interaction between human and non-human factors. In certain circumstances, the dynamics of traffic flow causes the transportation system fail to reach equilibrium and chaos will occur. In such cases, travel times vary daily and travel time reliability decreases. Moreover, these systems are continuously exposed to incidents that cause a high degree of uncertainty. So, it is necessary to enter such dynamics and uncertainty in the decision making models, such as network design. In this study a bilevel network design problem is defined with chaos and uncertainty taken into account. At the higher level problem, the optimization... 

Land-use and transportation are inter-related, such that land-use may be used to control transportation. This study aims to design a suitable combination of the residential and service land-use on one side, and the transportation system on the other side. The model presented in this study has two external and internal levels, and its objective is to minimize the cost of residence, receiving goods and services, and transportation. The performance of any combination of spatial allocation of population and employment, as well as transportation, is evaluated by the internal level of the model which determines the interaction between population, employment, and transportation. This is done by a... 

Natural phenomena, such as earthquakes, floods, and hurricanes, have been, and will be, one major source of mankind disastrous problems. Mankindinterventions to relieve this heavy pressure on humanity have been divided into four categories: mitigation, preparedness, response, and recovery. This study is in the response phase, and aims to find an optimal network to help people in the devastated part of a city, hit by a major earthquake. Such earthquakes demolish buildings over the people inside, causing them fatal harm and serious injuries. At the same time, they ruin the city infrastructures (life lines), including transportation networks, preventing flow of relief supply to reach to the... 

This research deals with the joint problem of reopening the roads closed after a disastrous natural event and the damaged area relief programming. While these two problems are connected to each other by the joint resources of ruins and debris removal, they are usually treated separately in the literature, and their solutions are sought in practice by the art of experienced authorities. This study formulates a dynamic tri-level integer programming problem to represent the two problems of Road Reopening and Relief, in which the crisis manager has the objective of minimizing the death tolls over a planning time interval. It identifies the roads for reopening at the first level; and the second... 

Governments are concurrently faced with two problems in Network Development Problem (NDP): limited resources to invest, and the economic justification of the candidate projects. Public- Private Participation (PPP) is a solution for the first problem, in which Build- Operate- Transfer (BOT) is a scheme to implement this partnership.This study formulates a NDP, in which two sources of funds back projects’ construction: that of the private investor and the public budget for this purpose. The problem is seen as bi-level optimization, with the upper level dealing with the government decisions on the level of participation (from 0 to 100 percent of the project costs), and the lower level being a... 

Earthquake is one of the deadliest natural hazards that has taken more than 400 thousand lives, only in the last decade. Iran is one of the countries that are at high risk of potential death toll resulting from such hazards, firstly because it is located in a potentially high-risk zone, the so-called earthquake belt and, secondly because of its problems in the management of disastrous situations (especially, pre-disaster management). Bam 2003 earthquake is one of the most painful experiences in this context. So, in this research, emphasizing on the practical use of optimization models, an existing model is applied on the damaged area of the Bam earthquake. The mentioned model considers the... 

Relaxing the underlying assumptions of transportation networks analysis and approaching to more realistic behavioral assumptions in route choice modeling, allows more precise predictions for equilibrium traffic pattern. Furthermore, enhancing the degree of sensitivity in modeling traffic equilibrium is crucial from planning perspective in the sense that it can make transportation analyst capable to evaluate and predict the impacts of a broad spectrum of supply and demand management policies. This research has concentrated on proposing some generalizations in route choice behavior modeling and relaxing some restrictive assumptions of the previous approaches in this area. Formally speaking, in... 

Variations in supply and demand of transportation, as well as those in the related environment, would cause daily variations in user travel time of transportation networks. This phenomenon particularly happen in morning travel time peaks, and make estimation of travel time highly unreliable. Morning peak passengers, whose timely presence at the destinations are highly important to them, prefer to choose paths that have minimum travel time and maximum reliability. Thus, the look at travel time pessimistically, and based on their experience, they put a margin of reliability to reach at timely at their destinations.
This study analysis such reliability margins based on the standard... 

Increasing demand for Gold in electronic devices and catalysts, and its high cost, makes it crucial to recover the Gold from waste electronic devices such as Printed Circuit Boards. In this research, recovery of Gold by hydrometallurgical process based on heating the scraps along with a strong oxidizing agent, Potassium Persulphate, which is “eco-friendly” or “green”process is concerned. Recovery of Gold achieved by simple filtration process following by washing with water and nitric acid in order to dissolve impurities such as Al and Sn. The systematical and analytical evaluation method of Taguchi quality engineering has been applied for the leaching to evaluate the optimal experimental... 

One of the main challenges construction industry face is the shortage of skilled labor. It is also one of the main reason of project’s delay. Many strategies including compensation payment, longer hiring duration and increase in wages has been proposed. Conventional scheduling assumes unlimited amount of resources or if consider the resource, is restricted to single-skilled resource. This is in contrast with real-world where workers may not be available at any time or they may possess a range of skills. Multiskilling is a workforce strategy that has been shown to reduce indirect labor cost, improve productivity and make the planning more realistic. Past researches proposed algorithms using...