Sharif Digital Repository

Hydrophilic polymers are widely used in enhanced oil recovery (EOR) processes to increase water viscosity during polymer flooding. However, these polymers increase the viscosity of injected water in undesirable strands, before reaching considerable positions that make some problems in polymer flooding process such as thermal, mechanical, bacterial degradation, surface absorption and undesirable plugging. In this study, a novel core-shell structure of polyacrylamide as an active polymer and nanoscale coating polystyrene as a shell polymer was designed and prepared to intelligently control mobility ratio in oil reservoirs and overcome weakness and limitations of classical polymer flooding.... 

One of the fundamental constraints that should have been in mind in flight scheduling is aircraft maintenance scheduling. Based on the accepted rules, regulations and flight safety, in a given period of time or after definite number of flight hours each aircraft should be sent to maintenance site. This influences the flight schedule. This research provides a comprehensive model for the flight scheduling. Given the flight schedule, number of the flights and aircrafts, maintenance center's capacity and other parameters such as each check's time, allowable flight days and allowable flight hours this model could determine each season's flight schedule and solve the aircraft routing problem.... 

Airlines spend considerable time, effort and financial resources on planning. It is essential to create a competitive timetable and construct a fleet and a crew schedule that utilizes these resources to maximum. Unfortunately, it is all too common that an airline is faced with the necessity of reconstructing their schedule due to some unforeseen event such as an aircraft breakdown or unsuitable weather condition. Rescheduling flight in such conditions is inevitable. In this article, first, a mathematical model is presented to minimize the expense caused by aircraft breakdown, flight delay and airport closure with considering crew constraints. Cancellation, delay, aircraft swaps and replacing... 

Decreasing travel time is one of the main goals of passengers in urban areas for which transportation operators use various policies. Among these policies, expanding public transportation facilities is one of the urban planner major purposes. Considering the fact that making these facilities needs great investment, optimize use of the current facilities is valuable. Waiting time in transit station has influence on increasing passengers’ travel time and inconsistency, so coordination between different transit lines is necessary. In this thesis, creating coordination among different transit lines in a transit network by the use of integer programming is studied in the form of two models. In... 

A basic highway design problem is to find the most economical alignment connecting two given end points based on topography, soil conditions, socioeconomic factors and environmental impacts, while satisfying a set of design and operational constraints. The cost function complexity and numerous limitations such as highway design criteria have made this problem a NP-hard one. In this study, a swarm based searching algorithm has been applied to a three dimensional highway alignment optimization model. The spatial data has been exploited from a GIS databases using a heuristic swift approach. In addition, the majority of cost items that depend on highway design have been extended in a practical... 

Knowledge about travel demand patterns is an important requirement for strategic planning and management of urban transportation networks. Use of theoretical trip distribution models such as growth, gravity or intervening opportunities, estimation with the help of questionnaire surveys and development of volume- based O-D estimation methods have been major fields of scientific efforts in recent years.Rapid changes in land use and transportation networks especially in developing countries has raised the importance level of knowledge about changes in travel demand.Traditional approaches are costly, time consuming and suffer from inaccuracies, so,... 

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... 

There has been growing interest in exploiting cellular network data for transportation planning purposes in recent years. In this thesis, we utilize these data for determining mode of travel in the city of Shiraz, Iran. Cellular data records -including location updates in 5minute time intervals- of 300,000 users from the city of Shiraz has been collected for 40 hours in three consecutive days in a cooperation with the major telecommunications service provider of the country. Depending on the density of mobile BTS’s in different zones of the city, the user location can be located within an average of 200 meters. Considering data filtering and smoothing, data preparation and converting them to... 

The tendency towards using activity-based models to predict trip demand has increased dramatically over recent years, but these models have suffered insufficient data for calibration and the intrinsic problems of traditional methods imposes the need to search for better alternatives. This paper discusses ways to process the cellphone spatio-temporal data in a manner that makes it comprehensible for traffic interpretations and proposes methods on how to infer urban mobility and activity patterns from the aforementioned data. Movements of each subscriber is described by a sequence of stays and trips and each stay is labelled by an activity. The type of activities are estimated using features... 

Origin-destination (OD) matrix is one of the most important sources of information used in planning and management of transportation networks. Estimation of a precise OD matrix is a fundamental component for enabling the administrative authorities to optimize the use of their transportation network. Traditionally, urban planners use direct approaches including household questionnaires to estimate OD matrices. These methods are time-consuming and costly. Strategies that are more recent like Bluetooth, Wi-Fi, and RFID scanners and detectors include deficient precision and the additional cost of accessories. Exploiting GPS technology in spite of its high locating accuracy, due to user... 

Origin-Destination (OD) table is an important input for managing and controling processes of transportation systems. OD flow estimation based on the observations of traffic sensors is a famous way of attaining this table. Technology developments in recent years reduce the cost and improve the quality of the results for this method. This research explores the methods for applying one of these technologies, vehicle identification systems, with the purpose of OD flow estimation.In this research several location models for vehicle identification systems are presented. These models have better performances comparing to the existing models in the literature. Furthermore, location models for some... 

The process of urbanization and the dramatic increase in residential population lead to significant development in urban area, especially in metropolitan areas, and cause unpredicted challenges for transportation planning and the mobility of dwellers and products. One of the most heated discussions in urban transportation planning during the last decades is devoted to the nexus among urban spatial development, sprawl and poly-centricity phenomena, and urban transportation system parameters. Definitely, the drivers' behaviors have also altered rapidly during this process. Besides, the complicity of the nature of transportation models for predicting the travel demand of system is inevitable.... 

Activity bases models of travel demand considers travel demand as a derived demand to fulfill activities. Development of these models cause better understanding of the mechanism of travel through Integrity, interdependencies, higher temporal and spatial aggregation, and behavioral basis. Although these models requires of spatial and temporal data with high resolution of huge number of peoples. Gathering this data through surveys require great labor and time. Mobile phone data of cellular network have high spatial-temporal resolution used for billing purposes and can be used as a supplementary source of data to develop activity based models. This research uses mobility patterns called motifs... 

This research presents a model to adjust origin-destination (OD) matrix using split ratios of network nodes. Conventional direct methods for OD estimation are resource intensive and time consuming therefore developing indirect methods which are less costly is important. Split ratios of network nodes can be obtained from nowadays technologies such as Bluetooth sensors with acceptable accuracy. An iterative bilevel estimation framework is presented that uses split ratios and link flows as observations. The upper level problem is to minimize a weighted objective function of the deviation between observed and estimated data. In the lower level the OD matrix is assigned to the network. This model... 

Route information and link traffic volume are among the most important means that are used for analyzing transportation networks. In the past, data from Traffic Counters and Automatic Number Plate Recognition were common ways for estimating route volumes. However, the estimation of these information has improved significantly and can be done cheaper with the development of new technologies and emergence of powerful tools. One of the cheapest and highly available tools is the use of wireless networks. The most popular of such these networks are Bluetooth and Wi-Fi technologies. The use of data generated from these technologies in engineering sciences has increased due to the popularity of... 

Rail transport system plays an important role in the development of the economies of the countries. This system is worn out over time by operating and weather conditions and requires maintenance and repair. One of the objectives of maintenance operations is to maintain tracks in an acceptable level and prevent their excessive deviation from the optimal situation. This deviation is called geometric irregular deviation. If these irregularities go away, they can cause traffic accidents and derailment in addition to losing travel convenience. So avoiding the deviation of the tracks is a very important. Maintenance management systems in the past few decades have been considered by the experts in... 

Trip distribution is the second step of the four-step travel demand modeling. Like other travel demand models, the most important objective of trip distribution models generation is forecasting the travel data of a year in the future. On the one hand, extensive changes in cities’ urban structures and people’s travel behavior during the years brings up the essential question of how temporally stable and transferable trip distribution models are? This question becomes even more important when the more complex structure of trip distribution models compared to models such as trip generation is considered. On the other hand, it is logical to assume that the consideration of the effects of urban... 

The costly and time-consuming methods of traditional data collection through interviews or questionnaires have led researchers to use new methods, including mobile networks, to obtain the information they need. Information obtained from the mobile network has been widely used in recent studies due to features such as passive information generation, extensive coverage and low cost of data collection, and attempts have been made to use this information to model citizens activities and urban travel demand. However, extracting information such as travel patterns and mode share of transportation has been challenging given the nature of this type of data. This research pursues two goals separately... 

In the development of intelligent transportation systems for customer use and resource management, accurate prediction of traffic volume on links across urban road network is critical. Since road traffic is the result of a complex interplay between traffic demand and traffic supply features, traffic volume prediction is a complex non-linear operation that has been the subject of much research over the past few decades. The two popular methods to trace people’s location during a day are the Global Positioning System (GPS) technology and commuters voluntary surveys. The two approaches bring significant benefits, yet hold limitations in their applications. In this research, a new method is... 

Autonomous vehicles will have a major impact on parking demands in urban areas in the future. Compared to conventional vehicles that should park near the destination of the passengers, autonomous vehicles can drop off the travelers at their destinations and then drive to the parking spaces by themselves. However, choosing a parking space in a far zone from the destination could lead to more travel demand in the network. We investigate traffic network equilibrium for traveling and parking with autonomous vehicles under a fully automated traffic environment. We introduce a Bi-level model, considering parking choices in the upper level and route choices in the lower level. The upper-level...