Sharif Digital Repository

Nuclear energy is one of the most important sources of energy from the economical point of view and also in terms of cleanliness and safety. Hence, strategically, uranium is one of the most basic elements of the earth and nowadays, the importance of this element is more marked due to the nuclear industry developement. Therefore, uranium recovery from the wastes generated during nuclear fuel production in Isfahan’s uranium conversion plant- in which yellow cake is converted to uranium hexafluoride- is quite pivotal. In this experimental research, uranium is extracted from the sludge of evaporation lagoons of Isfahan’s UCF plant via solvent extraction method. Execution of this project in an... 

With increasing number of processors on a chip, the role of interconnections becomes more important in both power consumption and bandwidth. As a result, in MultiProcessor System-on-Chip architectures, the design constraints will shift from "Computational Constraints" to "Communicational Constraints". Nowadays, optical information transfer is introduced as a suitable substitution for electrical interconnections in chips, which can eliminate their problems. Many different optical networks have been presented so far. These networks can be divided into two subcategories. Networks of the first category use an electrical infrastructure as well as optical one. Hence, the scalability of scheme is... 

Considering the advantages of heterogeneous catalysts for the easy work up procedure, being eco-friendly, and the reusability, herein, two projects are carried out by metal-supported SBA-15 catalysts. The first one is the oxidative deprotection of trimethylsilyl ethers catalyzed Cr (VI) in the presence of TBHP as oxidant. In this project, trimethylsylil ethers are oxidized in good to high yields. The second project is the oxidative coupling of thiols to disulfides catalyzed by Fe (III) in the presence of hydrogenperoxide. This catalyst/oxidant system convets different aromatic thiols to corresponding disulfides efficiently  

Hadron therapy is one of the cancer treatment methods using the targeted dose distributhion. In hadron therapy, the prompt gamma is produced from excited nucleas of target in the following of non-elastic nuclear interactions between the target and the incident proton within few nano-seconds and with energy less than 10 MeV. The excited energy level depends on incident particle energy and the target materials. Since the Spatial distribution of prompt gamma rays depends on incident particles energy, it can be useful for determinding the incident particle range. Also, the prompt gamma energy spectrum of each element is an individual feature, thereby targets with different composition of... 

Molecular Dynamics as a powerful method in the field of Nano-simulation has been widely used in recent years. Different contact processes such as Nano-manipulation, AFM Imaging, and Nano-indentation can be simulated using this method. There have been numerous researches done on calculating techniques of simulation of different phenomena in Nano-technology. Specifically, friction and Nano-indentation which are parts of Nano-contact processes have been simulated by different investigators. However, on some other parts, e.g. Nano-manipulation and AFM Imaging, there are few studies done up to now. Thus, a simulation and computational software seems necessary in this field. The main goal of... 

The ternary 122-type AeFe2As2 (Ae=Ba,Sr,Ca) compounds are antiferromagnetic metals with the orthorhombic lattice structure at ambient pressure and low temperature. By applying mechanical pressure, structural, magnetic and superconducting transitions occur in these compounds. The isovalent doping of Ba with Sr and Ca elements induces chemical pressure and reduces the onset pressure of these transitions. The main purpose of this thesis is to investigate and compare the effects of mechanical and chemical pressures on the structural and magnetic phase transition in the 122 compounds. To achieve this purpose, we have done first-principle calculations for many properties such as the structural... 

The human brain is the most sensitive and important human organ and surgery must be done with high precision and without risk. During surgery, brain tissue deform continuously due to gravity, out of the cerebrospinal fluid and the changing pressure of the cerebrospinal fluid and the surgical maneuvers. Because the surgeon has no direct view on brain internal, the ways to solve this problem is to pay attention. This method makes it possible to the surgeon see in the brain and the brain tissue deformation. This thesis method is based on biomechanical modeling. After forming finite element model from the pre-operative MRI, brain surface and volume datasets during surgery as a load, apply to the... 

Recently, demand for using variant applications in distributed networks has been increased largely. Most of these applications are based on group communication.In distributed group communication, two important factors need to be considered, group construction, and Group Key Management (GKM). The group construction specifies the process of constructing a new group by cooperation between distributed users. As well, GKM ensures re-freshness of the group key after each join/leave operation. Both of these tasks must be done by collaboration between members. This leads to imposing complexity and communication overhead to the system.This thesis proposes efficient methods for group construction and... 

Recently, the number of requests for multicast services through the wireless networks has increased. However, for successful deployment of these services, security and efficiency of content delivery must be provided at first. This thesis presents a new approach for secure multicast in wireless networks. This approach, CRAW (Combination of Re-keying and Authentication in Wireless networks) combines member authentication procedure with group key management protocol together to provide efficient re-keying. One-time password is proposed for member authentication and CKC (Code for Key Calculation) is suggested for group key management in wireless networks. In fact, the combination of...