Sharif Digital Repository

This researⅽh investigates the perforⅿanⅽe of epiⅾeⅿiⅽ routing، in ⅿobiⅼe soⅽiaⅼ net−works (ⅯSNs)، whiⅽh ⅿakes use of the store−ⅽarry−forwarⅾ paraⅾigⅿ for ⅽoⅿⅿuni−ⅽation. Reaⅼ−ⅼife ⅿobiⅼity traⅽes show that peopⅼe have skeweⅾ ⅼoⅽation visiting pref−erenⅽes، with soⅿe pⅼaⅽes visiteⅾfrequentⅼy anⅾ soⅿe others infrequentⅼy. In orⅾer to ⅿoⅾeⅼ epiⅾeⅿiⅽ routing in ⅯSNs، we first anaⅼyze the tiⅿe taken for a noⅾe to ⅿeet the first noⅾe beⅼonging to a set of noⅾes restriⅽteⅾ to ⅿove in a speⅽifiⅽ subarea. Af−terwarⅾs، two networks are ⅽonsiⅾereⅾ. For eaⅽh network، a ⅿonoⅼithiⅽ stoⅽhastiⅽ re−warⅾ net (SRN) is proposeⅾ to evaⅼuate the ⅾeⅼivery ⅾeⅼay anⅾ the average nuⅿber of transⅿissions unⅾer... 

In this thesis we will present some aspects of discrete chaos and their usage in cryptography.We discuss a couple of regular attacks to chaotic cryptosystems. We will use this information to analyze the chaotic part of the CPSS cryptosystem(Daneshgar, Farzad, Khadem) and will show that the system has weak keys. Finally, we will show that how these weak keys can be generated in an algorithmic way  

The purpose of this study is to introduce a new indicator to estimate the amount of irrigation water in excess of the need and also to determine the optimal irrigation pattern to reduce water loss in agriculture. According to the Food and Agriculture Organization of the United Nations, the major loss of fresh water takes place in agriculture, and the reduction of water resources is more significant in developing countries that do not have advanced agricultural equipment. One of the challenges in the studies related to reducing the amount of water used in agriculture is a lack of knowledge on the spatial distribution and temporal changes in water loss in a region. Although estimation of... 

This study evaluates the impact of fuel price increase on urban and interstate travel demands via the linear regression model. Indeed this study has two aims. First, analyze the effect of fuel price increase on travel demands of two modes of transit ridership (Subway and Bus Rapid Transit), and determine the cross elasticity of demands. To achieve the demands, the origin-destination matrix of each mode was obtained using automated fare collection data and the trip-chaining method. Second, examine the impact of fuel price increase on interstate travel demands and provide the elasticity of vehicle-kilometer traveled with respect to fuel price. The ordinary least-square method was used to... 

Human blood is a valuable and scarce product which is only produced by human body. There is no replaceable material for our blood and there has always been a constant need to donors and blood products in societies. Like every other product, blood has to be transfused to patients after it is donated and this process requires a complete and effective blood supply chain. Considering all properties, complexities and uncertainties of a blood supply chain, we need to develop stable methodologies in order to simplify decision making in blood supply chain. In this research, we develop a novel blood distribution system from a regional blood center (RBC) to its nearby hospitals. It helps RBCs plan the... 

Here we study on-design and off-design analysis of twin spool turbofan engines and also we present scaling methods to produce the characteristics performance maps of compressors and fans. Mathematical modeling of engine performance has been performed by serial nested loops algorithm. Performance of components have been modeled by performance maps, thermodynamic snd gas dynamic equations. The working fluid supposed to be a perfect gas and the effects of water vapor existing in atmosphere are neglected. In hot and cold sections of the engine, different thermo-physical properties are used. Mathematical modeling procedure of a turbofan engine, is complex. Therefor, initially, the off-design... 

Recent years have seen the development of various remote sensing-based methods for river streamflow estimation. Among them, the C/M approach estimates streamflow by analyzing surface reflectance at two benchmark pixels, namely dry and wet. However, its efficiency heavily depends on the expert-selected dry and wet pixels, which cannot be chosen randomly. In this study, we introduced the Normalized Difference Streamflow Index (NDQI) as a novel proxy for streamflow estimation. This index, which utilizes the spectral bands of the Sentinel-2 satellite, is sensitive both to soil moisture changes along riverbanks and turbidity variations during high-flow events. Unlike the C/M approach, NDQI does... 

This thesis targets the multidisciplinary area of time-variant seismic risk analysis of transportation networks. For this purpose, a new methodology and a library of probabilistic models are developed. Risk, in this context, denotes the probability of exceeding the sum of direct and indirect losses due to seismic events. Direct economic losses are due to the repair cost of the physical damage in the components of the network, such as bridges. The indirect losses are due to the reduced capacity of the components for traffic flow, which results in increased travel times in the network. This leads to socioeconomic losses. In this research, a reliability-based approach is adopted to carry out... 

This research concerns investigating the behavior of two-phase flow in the inlet and outlet of the microchannels.Both the droplet based and the continuous microfluidics are considered. For the continuous system whenthe minor fluid enters the microchannel, due to ratio of viscosity of two fluids, viscous folding occurs.Viscous folding phenomena is similar to the buckling phenomena in solids.This means that the viscosity of the fluid, which is applied to two sides of the fluid layer, causes folding the fluid layer and changing the shape of it. For the study we employ a VOF based numerical routine. In order to verify numerical results, the grid and the time step independenciesare checked. In... 

Trip demand analysis is among the most important parts in comprehensive transportation studies. Developing four stage models including trip generation, trip distribution, mode choice, and assignment are so common in demand analyzing. In this study, trip generation models have been studied and to analyze data, two different methods including OLR and GWR are utilized. This study aims to examine relationship between aggregate zones in order to forecast future trips. Moreover, results of modeling trip generation with two different methods, OLR and GWR, are compared. Comparing different levels of aggregation reveals that as the number of zones decreases, the results get better. Decreasing number...