Sharif Digital Repository

In this research, a comprehensive examination on hot and cold deformation of Al-Mg6 alloy has been performed. In order to find out hot deformation behavior of Al-Mg6, hot compression tests at 350, 450, and 550 oC and at strain rates of 0.001, 0.1, and 1 s-1 have been carried out. After the correction of the curves due to friction and adiabatic heating effects, constitutive equation of this alloy has been derived. Corrected curves show the occurrence of dynamic recovery. A new method for developing strain dependent constitutive equation has been employed using normalized stress and strain curve. After normalization, the curves at all deformation conditions follow a similar behavior.Rolling of... 

Severe plastic deformation (SPD) can refine microstructure of steel and increase its strain energy. Ultra-rapid annealing (URA) influences on the temperature and kinetics of recrystallization and transformation, and causes to improve the mechanical properties of steel. In this research, low-carbon steel with the average grain size of 80 μm was subjected to SPD using 2 passes of constrained groove pressing (CGP) method and its grains size is reduced to 30 μm. Ultra-rapid annealing with the reference heating rate of 200 oC/s was performed on SPDed steel up to subcritical and intercritical temperature ranges. Other heating rates of 75 oC/s to 1800 oC/s were performed for further examinations.... 

One of the most important aspects in the stability of arch dams which have been encountered, are the stability of the abutment. In order to assess the stability of wedge, Londe Method has been considered by simple assumption. Displacement and velocity of the wedge were calculated by Newmark beta method. In this study stability of abutment of Luzzone dam due to static and seismic loading was investigated. After modeling a finite element of dam-foundation-reservoir of Luzzone dam, the horizontal and vertical earthquake was applied to the model and the thrust force was recorded. By using a software stability safety factor of wedge was studied.it was found that the wedge is unstable and will... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

Ionization probability of Cl2 molecule is studied by irradiation of 800 nm Ti: Sapphire laser pulses at intensities of 1014 Wcm-2 to 1016 Wcm-2 with the Gaussian package. Molecular orbital symmetry and orientation of the molecule dipole moment with laser field polarization axis are very effective in ionization probability. The results show that the most ionization probability for the intensity of 1014 wcm-2 is at 900 and also 50 at intensity of 1016 wcm-2. Due to the lack of intrinsic dipole moment, variation of dipole moment with the intensity, bond length and time evolution of dipole moment are investigated. It is found that there is a linear dependance of these parameters with ionization... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without... 

The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction... 

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to...