Sharif Digital Repository

Mobile Broadband Wireless Access technologies provide mobile users with broadband services, for example music downloading, online games and etc. IEEE 802.20 standard is one of the Mobile Broadband Wireless Access technologies , which has been published to support mobile users with high vehicular speed up to 250(km/h). The issue studied in this research is enhancement of MAC layer in IEEE 802.20 standard.
By having this intention in mind we firstly developed a simulator for IEEE 802.20 MAC layer implementation , then we tried implementing 3 different approaches for connecting mobile users to a new network in order to analyze their performance. Then we provided a method for decreasing... 

Machine-to-machine communication (M2M) can be considered as one of the most important types of high-density communication in the Internet of Things (IoT). Therefore, how to send data using the cooperation of machines with each other and selecting the appropriate relay can play an effective role in improving the quality of network communication, especially when communication between sources and their destinations is weak. Since in the real world some of the applications used on a set of IoT machines require the similar bandwidth, we also followed this assumption. For this purpose, we went through three steps in this thesis. First, two new relay selection algorithms with static RF interface... 

This study is an endeavor to model the interaction between transportation and land use, as a constituent of a joint land use-network design problem defined in the context of transit oriented development (TOD). Population and employment follow a Garin-Lowry model; the endogenously determined transportation demand is administered by a joint mode choice-assignment model; and mode choice is governed by a logit model. Equilibrium of population choice of place of residence, employment choice of place of retailing, and passenger choice of mode and path, are all governed by a maximum utility principle. An algorithm is devised to reach these equilibrium states by an evolutionary process, whose engine... 

This thesis presents a new approach to feedback active noise cancellation. The problem of Reducing the noise level in the environment has been the focus of research over the years. Active Noise Cancellation (ANC) is one such approach that has been proposed to eliminate Noise. ANC refers to an electro acoustic approach of canceling acoustic disturbance to Produce a quieter environment. The basic principle of ANC is to introduce a canceling “anti Noise” signal that has the same amplitude but the exact opposite phase, thus resulting in Reducing the remainder noise signal. We use neural networks based on system identification And predict control to cancel acoustic noise. Canceling acoustic... 

Improvement of public transportation systems through attention to service quality of these systems, is important in order to increase the use of these systems. Various quantitative and qualitative attributes of travel are known effective on service quality of public transportation. The investigated factors in this research, with refrence to regular bus system of the city of Tehran, are: in-vehicle time, fare, crowding and headway. For this purpose, the stated preference data of the respondents who travel to work by regular bus, collected. The survey was conducted during the last month of spring and 360 questionnaires were completed. Stated preference scenarios relating to aforementioned... 

Chemical industries are associated with hazardous chemicals and extreme operating conditions. Unsafe events can incur dramatic costs in terms of the loss of life, financial penalties and damages to the environment. Therefore, design of industrial processes which can be operated safely over a wide range of operating conditions is vital. Nevertheless, operation of industrial processes is a strong function of their design. If the process is initially poorly designed, ensuring its safe operation, if not impossible, would require costly modifications at the operational phases. This observation is due to the fact that process design decisions (e.g. design of process equipment) often have a... 

Genetic significant dose to the Iranian population from diagnostic radiology procedures has been measured. A survey of 26500 radiology patients has radiological tests, age and sex distribution. A second survey has produced the radiological operational parameters, including kV, mAs, FTD, field size, filtration, film number & body orientation. Statistical demographic data have been obtained and from which child expectancy number have been calculated. A Rando phantom has been used for dosimetry phase of the gonad doses using TLD. Combining all of the above data a new GSD of 10.5 mrem/year has been calculated which is 14% higher than the previous number measured in 1980  

By developing composites, difficulties of modeling of degradation of properties as stiffness is most considered. The recent advances in the modeling of degradations in stratified composites have led to improved models on all scales. Macro scales methods are good to estimate fracture but not to estimate the failure in micro scale (as microcrack) and moreover, they need many experimental data. Therefore by considering a stratified structure which contains fiber, matrix and intermediate area, mesoscale modeling method is most suitable. In this research Micromechanical Progressive Algorithm (MPA) is used. The method employed is Micromechanic Method of Fracture (MMF). In this work by developing a... 

Today due to increasing demand of using energy and petroleum products, finding optimum ways to produce more oil and gas in a way which petroleum reservoirs faces less pressure drop is very necessary. Therefore, petroleum engineers face multiphase flow proportionally more than other issues. So, they have to comprehend this issue in a complete manner in order to discover the best practical ways for maximum utilization. Researchers in different ways tried to model multiphase flow, but many of provided models are so complicated and sometimes have low accuracy. In this project we tried to present a model that in simplicity has high accuracy and works in a way that apperceiving it, is very... 

The purpose of this project is to design and build a motorized walker with sit to stand ability, by means of which the user can get up from a chair or the edge of the bed and stand with complete independence; Relying on it, the patient could walk easily and finally sit down on the chair, the edge of the bed, or the toilet seat. For this purpose, the conducted researches and previously built devices were studied and the strengths and weaknesses of each were examined. The stages of conceptual design including the design of the sit to stand mechanism, the design of the structure and finally the control algorithm were completed, then the detailed design of the mentioned topics was carried out.... 

Air pollution caused by industrialization is the problem which adversely affects human life. Among air pollutants suspended particles, especially particles smaller than 10 microns (PM10), for their high concentration in air in large cities are the major index as air pollutant. Due to their small size, PM10 can penetrate into the aspiration organs causing harmful effects. The objective of this work is to develop an Artificial Neural Network (ANN) model for prediction of short-term concentration of PM10 in the city of Tehran. Complex mechanism of reactions, numerous types of pollutant materials produced from transportation and industrial activities, variety of sources, difficulties in data...