Sharif Digital Repository

Nowadays recommender systems are one of the most important parts of big websites. These systems help users to find their intended items among enormous amounts of data. Traditionally, recommender systems are designed and implemented using different methods such as content based, collaborative and demographic filtering. Each of these methods had some problems that lead to emergence of a new kind of recommender systems called hybrid recommender systems. This kind of recommender systems try to combine the other methods and make them better. In this thesis, we have selected some previous recommender systems and then, we have made a new system by combining and reforming them. The resulted... 

With the daily increase in the volume of information and due to the growth and pervasiveness of wireless networks, the structures and the way of connection of intermediate nodes have become very important in terms of energy, communication speed and communication overhead. In this thesis, we examine the structure of directionless wireless networks assuming nodes are selfish. In these networks, nodes seek to minimize their costs while being required to access all nodes with limited path length. Due to the selfishness of nodes, we used game theory to analyze the structure and behavior of nodes by calculating the Nash equilibrium state and to compare these networks with networks that are managed... 

In this dissertation, we will attempt a discussion of some ethical implications of genetic enhancement and present an argument against certain group of enhancements. We will demonstrate that this discussion requires a distinction between therapy and enhancement, therefore the arguments for and againt this distinction will be examined but it will be adopted in the end based on its merits. We will also show how genetic enhancement is a real possibility that will be available for consumers in the near future; and how probing the ethical issues surrounding the technology is quite necessary. We will then turn our focus to different theories of normative ethics and an examination of their merits... 

Plasma Electrolytic Oxidation is a new and promising method for synthesis of oxide layers and coatings on light metals such as titanium and aluminum. This method is a fast, easy and economicalway to produce TiO2 layers on Ti substrate. Photocatalytic properties of TiO2 can be improved with doping of other elements such as metals and non-metals by expanding its band gap which is in UV area of light spectrum in to visible area.Photocatalytic properties of TiO2 is also dependent on surface area and grain size, oxide layers which has been produced with PEO process has a high surface area due to its porosity. Voltage, electrolyte and additives concentration are among parameters which can affect... 

Video encryption algorithms have become an important field of research nowadays. As the increasing rate of employing videos in commerce and other visual applications , the security of video data is becoming more vital. A digital media can be transmitted easily in real time everywhere at any time due to the advanced development of communications, Internet and multimedia technology. As a result information availability has increased naturally with the introduction of mobile devices. However, this availability faces with the problem of maintaining the security of information that is transmitted in public channels.
The new version of video coding standard that is... 

The most fundamental concept in considering electrical properties of reservoir rocks are formation Resistivity factor and Resistivity index which are defined by Archie and are useful in interpretation of well logging, evaluation of porosity and saturation. A theory on the relationship between formation resistivity factor and porosity, also resistivity index and saturation are presented by use of parameters Cementation factor and Saturation exponent. The Archie equation is valid only when the rock is strongly water-wet and clay free, which is not the case in carbonate rocks. Therefore the Archie equation cannot be generalized over the entire carbonate reservoirs. On the other hand influence... 

By considering the effect of surface/interface stress, classical problems of the interaction between dislocations and inhomogeneities are addressed. Especifically two distinct problems are solved, the first one is consisted of an edge dislocation located near an elliptical nano-inhomogeneity and the second one hasa screw dislocation laid in the core-shell nanowire. The stress field as well as the image force on the dislocation are calculated and discussed in detail. Results show that by decreasing the dimension of the problem to nano-scale, the differences between classical elasticity and surface approachincrease rapidly. By considering the effect of the surface/interface stress, new... 

Quantum computing is an emerging and promising computational paradigm that pro- vides substantial speedup for important applications such as integer factorization, database search, and machine learning. Since practical quantum computers remain in their infancy, researchers must rely on classical machines to model quantum behav- ior and design algorithms—simulations that impose exponentially escalating demands on both memory and processing power. In this study, we propose a novel method for distributing the computation load (based on Dynamic Load Partitioning (DLP)) of the simulation among CPUs and GPUs in a hybrid computer system to reduce the required memory and computation time. Our...