Sharif Digital Repository

The process of energy transfer in quantum systems is an interesting phenomenon due to the emergence of quantum effects . This phenomena can be studied in one of two possible spaces : real space and energy space of the system . In addition , to evaluate how this process is successful , one can define an efficiency as the population of a target state . Finding the approaches to increase this quantity takes into account one of the main objectives of the current researches . On the other hand , isolating the quantum systems from the surrounding environment (bath) in practice is impossible and then interaction between them is inevitable . In this research , we provide a comprehensive... 

It has been five years since the new education system was started, according to which fundamental changes have been applied to school text books. The mentioned changes in the text books are based on “the fundamental transformation document” and “Iran’s national educational curriculum”. In “Iran’s national educational curriculum”, eleven fields concerning pedagogy and learning are explicitly mentioned; one of these eleven fields is “training and learning work and technology”. One of the merits which has been stressed in this field, is “technological thinking”. Nowadays, methods of extending and reinforcing the technological thinking have come to be the subject of investigations in many... 

Diverse methods of producing semi-solid metal have been the subject of extensive study for the past 40 years. Among all these methods, electromagnetic stirring (EMS) and gas induced semi solid (GISS) have been used on a commercial scale. Considering the fact that in previous studies the intensity of electromagnetic field in the central part of the stirring chamber was negligible, a hollow cylinder with an almost pure iron core was utilized in the central part of the chamber in order to intensify the electromagnetic field in the center and to introduce gas bubbles into the melt. Aluminum A356 alloy was stirred by a three phase electromagnetic stirrer and introduction of gas bubbles under... 

In this thesis we study the strongly correlated electron systems and investigate the interply between electron-electron and electron-phonon interactions using a non-perturbative method, known as Dy- namical Mean Field Theory (DMFT). This method is capable of going beyond standard perturbation techniques. DMFT is by construction a local theory which neglects spatial correlations. In a first step, we approach the problem of interplay between these two interactions in the normal state of cuprate materials using the Holstein-Hubbard model. We then introduce orbital degrees of freedom, and study the polaron crossover and the pairing transition for a two-orbital model with Jahn-Teller coupling to a... 

In this study, SiO2-CaO-MgO galsses and glass-ceramic powder doped with Nd3+ were synthesized with sol-gel method. Tetraethylorthosilicate (TEOS), Ca(NO3)2.4H2O, Mg(NO3)2.6H2O, Nd(NO3)3.6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with STA, XRD, DRS, PL, FTIR and SEM analysis. From XRD patterns of glass samples, the role of dopant was introduced as intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that the bredigite and akermanite crystals were formed in glass matrix. The band gap energy of samples were calculated from DRS analysis and were seen with increasing the dopant... 

In this project we tried to examine the effective variables on rent to price ratio and how the variations in R/P influence households’ decisions. Using rent to price ratio, the efficiency of Housing market has been inspected. However, the results for Tehran are in contrast to efficiency assumptions. Moreover, having access to unique database which remarkably increase the accuracy of our estimation, the relation between rent risks and House price has been examined. The results show that rent fluctuations has positive impact on house price. Rent to Price ratio has different applications and we tried to determine the variables that can explain this ratio. Literature review demonstrate that... 

Pragmatic assessment and consistency in rating are among the subject matters which are still in need of more in-depth investigations. The significance of the issue is highlighted when remembering that inconsistency in ratings would surely damage the test fairness issue in assessment and lead to much diversity in ratings. The purpose of this study was investigating the criteria that native (American) and non-native (Iranian) English speaking teachers considered while rating the pragmatic productions of Iranian EFL learners regarding the two speech acts of compliment and compliment response. Overall, a hundred and twenty teachers (sixty native and sixty non-native raters) participated in this... 

This thesis deals with a theoretical and experimental investigation of different approaches for reduction of electronic recombination in the semiconductor/Dye interface of dye sensitized solar cells (DSSC) including dye coverage, core-shell structures and energy level distributions. Interface of ZnO/TiO2 in the core-shell structure have been studied by density functional theory and the energy level distribution of surface atoms, recombination and Fermi level changes, open circuit voltage and surface dipole distributions have been discussed.
The presence of TiO2 shell increases the ZnO surface dipole moment, and shifts the ZnO conduction and valence bands to higher energies. Also, it...