Sharif Digital Repository

Boundary conditions on a background field can change structure of quantum vacuum such that cause the attraction force between two parallel ideal metal plates. This is known as the Casimir effect, and it has dynamic aspect that seen by changes in the position of the boundary conditions imposed at the time. In the static case, creation and annihilation of virtual particles leads to system pressure that can be negative (attraction) or positive (repulsive) with respect to parameters such as the shape and topology, the materials used in and temperature. In the dynamical case, particles are real and emits as radiation and pumps energy from vacuum. In this thesis, our first attempt isto recognize... 

In this survey we explore the black hole information problem, one of the most challenging issues in theoretical physics over the past few decades. According to the theory of general relativity, black holes can form through gravitational collapse of matter. At semiclassical level, however, black holes emit thermal Hawking-radiation and eventually completely evaporate. After evaporation the radiation state cannot retain all the information about the initial matter that underwent gravitational collapse, contradicting the principles of quantum mechanics. Various approaches have been proposed to address this issue. One such approach is the black hole complementarity principle, introduced by... 

In this study, two conventional methods for controlling flexible two-link robots based on artificial neural networks is improved. The first method is implemented by combining fuzzy logic and reinforcement learning in the form of a neural network. This method is modified in two steps. In the first step, the system feedback is changed and in the second step, the system Jacobin is used. This Jacobin can be the result of system identification. In the second method, an optimal controller is proposed for the system, which is also implemented in the form of a neural network. The performance of the neural-optimal controller is further improved by redefining the Bellman's principle of optimality.... 

This thesis discusses cosmic particles. Cosmic particles are originated by stars and black holes that could live in the Milky Way or other galaxies. These energetic particles can be protons, carbon, iron, gamma, electrons and positrons, and so on. After reaching the earth, these particles collide with atmospheric atoms to make the first interaction, which leads to the production of secondary particles. The number of secondary particles produced also increases steadily due to successive collisions with atmospheric atoms. The set of secondary particles that originate from the cosmic primary particle is called the extensive air shower. The aim of this paper is to investigate the properties of... 

technologies for cooling of electronic devices, have high efficiency due to the heat transfer in two-phase state. In this project, experimental effects of asymmetric triangle groove has been studied on the boiling fluid and effect of the motion on the boiling and heat pipe. Therefore, the experiment has been done by 3 heat pipes and each with 3 plates. The plates consist of a smooth plate, a plate with triangle groove and a plate with rectangle groove. Each heat pipe was filled by methanol in volumetric percentage from 10 to 60. The results show that 20 percent methanol is the optimum for all kind of heat pipe, which has been used. In addition, it is shown that heat pipe with triangle groove... 

To understand the impact of predation by different types of predators on the vole population dynamics,we formulate a three differential equation model describing the population dynamics of voles, the “specialist predator”and the “generalist predator.” First we perform a local stability study of the different steady states of the basic model and deduce that the predation rates of the “specialist” as well as the “generalist” predator are the main parameters controlling the existence/extinction criteria of the concerned populations. Next we analyze the model from a thermodynamic perspective and study the thermodynamic stability of the different equilibria. The analysis revealsthat when the... 

Increasing demand in power systems necessitates the Generation Expansion Planning (GEP) which is to determine the type, size, and location of new generating units in a planning horizon. The final solution of GEP is based on the minimum cost and/or optimum reliability taking into account various constraints such as capacity of units and lines, operating constraints, and budget restrictions. This paper presents a model based on scenarios for generation expansion planning and units retirement decision. The proposed model could be used by vertically integrated utilities as well as the ISOs in electricity markets to obtain generation expansion schemes. In this approach, uncertainty of units are... 

The current restructuring trend in power industry emplaces the owners and managers under a great pressure to not only reduce the associated investment costs, but also reasonably cut the operation and maintenance expenses as much as possible, while keeping both the power quality and reliability requirements met. Reliability-Centered Maintenance (RCM) has been proved to be in response to this dilemma in power systems since it has been yet successfully applied in various engineering contexts worldwide. This process is more challenging when it comes to the power transmission systems because of its bulkiness and complex structure. On the other hand, market involvement and its intricate behavior... 

Current trend of energy consumption and aging infrastructure of electricity grids mandates high amounts of investment in transmission and distribution networks. On the other hand, with increased awareness about environmental issues, share of renewable energy resources in power generation portfolio has risen in recent years. Microgrids, as one of the most promising solutions to tackle these issues, are able to accommodate high penetration levels of renewable energy sources and distributed generation in distribution systems. However, microgrids sizes are limited due to some operational considerations and as a result, efficient management of distribution systems with high penetration of...