Sharif Digital Repository

Social networks and the shared data in these networks are always considered as good opportunities in hands of the attackers. To evaluate the privacy risks in these networks and challenge the anonymization techniques, several de-anonymization attacks have been introduced so far. In this thesis, we propose a technique to improve the success rate of passive seed based de-anonymization attacks. Our proposed technique is simple and can be applied in combination with different types of de-anonymization attacks. We show that it can achieve high success rates with low number of seeds compared to similar attacks. Our technique can also be used for applying partial attacks on graphs which results in... 

We study the general nonlinear integer programming problem. We consider two general classes of this problem: nonlinear integer programming problem and mixed integer nonlinear programming problem (MINLP). We explain the basic concepts for solving these problems and describe common methods for solving them, including branch and bound, Benders decomposition and outer approximation. Furthermore, we introduce two methods based on using penalty methods. Penalty based methods, by using appropriate penalty functions, convert a general nonlinear integer programming problem into a sequence of nonlinear programming problems and these problems are solved by a global optimization algorithm. Computational... 

Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

Superalloys are widely used in aerospace and power industries due to the good performance at high temperatures for examples gas turbines, steam turbines and aircraft components. In addition to the turbines cobalt-base superalloys are used in medical implants such as knee and hip joints. The main strengths of the superalloys are heat-resistant, retaining their high mechanical and chemical properties at high temperatures, high melting temperatures, high corrosion resistance, resistance to thermal fatigue, thermal shock, creep, and erosion. Because of difficult to machine properties of superalloys, grinding is one of the effective methods for machining superalloys. The surface integrity of the... 

Drilling super alloys with a good hole quality and acceptable surface finish is a constant challenge in modern industries dealing with such materials. Ultrasonic assisted drilling is a modern and nonconventional method of drilling which has attracted many researchers attention recently. In this study deep drilling on Inconel 738 LC is done using ultrasonic assisted drilling technique and the results are compared with those of Electro Discharge Machininng or EDM method. The results show that Ultrasonic Assisted Drilling or UAD is an appropriate alternative for EDM of Inconel. The whole process time is decrease dimensional accuracy is improved and surface roughness is decreased significantly.... 

Due to popularity of mobile wireless devices, security of mobile ad hoc networks (MANETs) being more important than before. Traditional key management schemes based on symmetric key cryptography are became ineffective because of dynamic and infrastructureless nature of these networks.Recent studies are mainly based on traditional public key cryptography schemes and ID-based cryptography schemes. On the other hand, Contributory schemes seem suitable for MANETs because of their inherent self-organize property. Key update and Key revocation are the fundamental issues of key management schemes in mobile ad hoc networks. Certificateless public key cryptography, in addition to solve those issues,... 

International trade arrangements have been considerably developed in recent decadees. Especially, one can note the role of these factors in economic development and improvement of life standards in member countries. In the meantime, Economic Cooperation Organization (ECO) was established in 1985, by Iran, Pakistan and Turkey and then extended by seven other countries: Afghanistan, Azerbaijan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan. Improving economic development and intra-group trade of member countries is one of the main objectives for the group. The purpose of this research is to estimate the ex-post effects of ECO on the intra-group trade of member countries.... 

Establishing an efficient free trade agreement (FTA) requires some conditions in both trading partners. The median voter approach insists on the direction of general interests (identified by the utility of a median voter) to explain how two countries may agree to sign an FTA. At the other side, lobbying approach emphasizes on the role of interest groups (groups with a large influence on the public decisions) in forming FTAs. Taking into account the theoretically based and empirically robust foundation of the median voter approach, we rely on it to investigate the major determinants of free trade agreements in the case of ECO countries besides all their main trade partners. The database... 

During the two last decades, Iranians have faced with a wide and substantial increase in housing prices, especially in great metropolitans such as Tehran, Mashhad, Isfahan and Shiraz. This easily could be refered to a hyperinflation which significantly impeded the access of low and medium income families to housing. This study uses a structure model to recognize the responsible factors of such a rise in housing prices and to show whether there is any price bubble in market. The model consists of both supply and demand side determinants to explain the price changes across Iranian provinces over 1375-1390, in a panel data context. In particular, we use a longer and larger database which also... 

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, point angle and ultrasonic vibration amplitude as control factors. The results show that applying...