Sharif Digital Repository

In this project, in general, we have studied the particle production during and after the Inflation.Today, the Inflation is considered as a part of the standard model of cosmology and it solves so-called two cosmological problems: flatness and horizon problem. According to it,the universe after the inflation becomes supercool; however, the thing we observe today is in contradiction with this theory. The Reheating era is a time period in which the inflationary field gets to its minimum of potential and starts to socialite. Actually, here is the place in which the phenomenon of the particle production occurs. This period is called the Reheating era. therefore, it seems all particles which we... 

We consider a special class of Congestion Games enhanced with a notion of time.Network Routing problems, such as road traffic networks, computer neworks, and evacuation problems are some applications of this class of games. Two subclasses of these games, namely atomic and non-atomic is considered in this article, both of them introduced in 2009. Some of the existing results are Nash equilibria existence proof for “single-source single-sink” case, and a mechanism for improving price of anarchy in the non-atomic subclass. There are also some results in the atomic subclass of this game.We extend both models of atomic and non-atomic subclasses to “multi-source,multi-sink” configurations. We call... 

In the last decade, magnesium alloy has been developed owing to it’s low density, high specific strength, good castability and damping property. AZ91 alloy is proved to be the most common and most important magnesium casting alloy. It is shown that, rheocasting process is a proper way which increases the mechanical properties of the products. Since 28 years, so many new methods for preparing Semi-Solid alloy slurry and rheoforming process have been suggested. Electromagnetic Stirring ( EMS ) method was used for making globular structures. In this research, the semi-solid slurry of AZ91 magnesium alloy was prepared by electromagnetic stirrer under different conditions of stirring current and... 

Acidizing is one of the widely used practices of formation damage remediation. The success of this rather expensive job depends on the precise design and operation. Though, improper execution of an acid job, not only does not improve the formation damage but also can contribute to even more damage itself. For this purpose, it is critically important to thoroughly design an acidizing job conducting extensive lab experiments and utilizing numerical tools before operation in order for a successful acidizing. Unlike, carbonate acidizing, the chemistry of sandstone acidizing is very complex and challenging because of the wide variety of minerals and aqueous species present in the system. Hence, a... 

Wildfire in natural habitats is a common natural disaster that can have natural or human origins. With the increasing global temperature and consecutive droughts, the number and intensity of these fires are increasing. In our country, due to a lack of natural resources and recent droughts, the importance of preventive measures in starting and effectively extinguishing fires is increasingly felt. Nowadays, with the increase in computational power, numerical methods have come as the aid of physical models to predict the spread of fire and have become a worthy replacement for experimental tests due to the destructive nature of fire. In this research, we have investigated the effect of main...