Sharif Digital Repository

Needs analysis is the key step to designing relevant and useful courses in English for Specific Purposes (ESP), but finding ways to deliver needs in a motivating and interesting way is also paramount. Therefore, investigating students’ motivation to learn ESP is central in needs analysis. Few studies have investigated needs from the perspective of ESP learners’ motivation. Focussing on engineering fields at three Iranian state universities, this study aimed to identify factors that affect engineering students’ motivation for learning technical English in ESP courses. Using a mixed method design, this study was conducted in two phases. In the first phase, semi-structured interviews with 40... 

Needs analysis is the key step to designing relevant and useful courses in English for Specific Purposes (ESP), but finding ways to deliver needs in a motivating and interesting way is also paramount. Therefore, investigating students’ motivation to learn ESP is central in needs analysis. Few studies have investigated needs from the perspective of ESP learners’ motivation. Focussing on engineering fields at three Iranian state universities, this study aimed to identify factors that affect engineering students’ motivation for learning technical English in ESP courses. Using a mixed method design, this study was conducted in two phases. In the first phase, semi-structured interviews with 40... 

This study examined Iranian EFL learners’ preferences regarding oral Corrective Feedback (CF) in a TOEFL speaking course. A 30-item questionnaire was administered to 32 participants in a TOEFL preparation course to elicit EFL learners’ views concerning their CF expectations. The results showed that based on the nature and objective of the course, students cared about their accuracy while fluency for these students was of secondary importance. Therefore, CF was regarded as crucial and necessary by the participants and they considered their grammatical errors as the most important one to be corrected followed by vocabulary and pronunciation errors. In terms of CF type, explicit and delayed... 

Core/shell structure of ZnO nanowires coated with a monolayer of TiO 2 is investigated using Density Functional Theory (DFT). The electronic states of the semiconductor is calculated and compared before and after coating of the TiO2 monolayer on a ZnO [101 0] surface. The effect of TiO2 coating induce surface states changes and shifts the conduction and valence band edges to higher energies. Our results, in qualitative agreement with the experimental work of Matt Law et al. (J. Phys. Chem. B, 110, 22652), show an increase in open circuit voltage and a decrease in short circuit current in ZnO/TiO2 core shell dye sensitized solar cells. Regarding the semiconductor density of states (DOS), TiO2... 

Light scattering, porosity, surface area, and morphology of TiO2 working electrode can affect the power conversion efficiency of dye -sensitized solar cells dramatically. Here mesoporous TiO2 microbeads were tested as working electrode in dye-sensitized solar cells based on cobalt tris-bipyridine electrolyte. Power conversion efficiencies up to 6.4% were obtained with D35 dye adsorbed onto the light-scattering microbeads. Electron transport, studied using small light perturbation methods, was found to be significantly faster in the microbead films than in standard mesoporous TiO 2 films. This was attributed to the favorable assembly of nanocrystals in the microbeads, which can increase the... 

One of the drawbacks of typical dye-sensitized solar cells (DSCs) is their high cost and the high electrical resistance of the transparent conducting substrate. In conventional sandwich-type DSCs, only one of the FTO substrates can be replaced by a metal substrate. We investigated an all-metal-electrode single-sided DSC in which interpenetrated bracken-like Cr electrodes were created using photolithography; mesoporous TiO2 and Pt films were deposited on the laterally separated electrodes. Thermal Pt deposition and electrodeposition methods were investigated and it was found that a cyclic electrodeposition method resulted in selective Pt deposition at room temperature with a higher device... 

Herein, the one-pot tandem synthesis of β-ketoallylic methylsulfones has been achieved from readily available dimethyl sulfoxide and acetophenones as coupling partners in one step. In this procedure, dimethyl sulfoxide serves as a triple role including solvent, dual synthon and as an oxidant agent. The use of magnetic Ag–Cu MOF as a bimetallic catalyst is the key to the progress of the reaction due to its accessible active sites. It provides facile access to various β-ketoallylic methylsulfone derivatives from direct C(sp 3)–H bond activation and functionalization of aromatic methyl ketones especially acetophenones with electron-rich and electron-poor groups. Moreover, the present work... 

The low temperature thermoelectric properties of hydrogen-passivated graphene-based antidot lattices are theoretically investigated. Calculations are performed using density functional theory in conjunction with the Landauer formula to obtain the ballistic transport coefficients. Antidot lattices with hexagonal, triangular and rectangular antidot shapes are studied. Methods to reduce the thermal conductance and to increase the thermoelectric power factor of such structures are studied. Our results indicate that triangular antidot lattices have the smallest thermal conductance due to longer boundaries, the smallest distance between the neighboring antidots, and the armchair edges. This... 

The effect of dye coverage of the mesoporous TiO2 electrode on the performance of dye-sensitized solar cells based on the cobalt tris(bipyridine) electrolyte and the D35 dye was studied in detail. The dye coverage was controlled by using a dye bath with different dye concentrations and containing an inert salt, LiClO4, which was found to promote equilibrium conditions in the dye adsorption process. The amount of adsorbed D35 dye on mesoporous TiO2 was reasonably fit using the Langmuir adsorption isotherm, with a binding constant of 55 000 M-1. Upon increasing the dye coverage on the TiO2 electrode, the electron lifetime in the dye-sensitized solar cell increased remarkably, demonstrating the... 

In this paper the effect of strain and impurity on the quantum conductance of semiconducting carbon nanotubes (CNTs) have been studied by ab-initio calculations. The effect of strain and impurity on the CNT conducting behavior and physical characteristics, like density of states (DOS), band structure, and atomic local density of state (LDOS), is considered and discussed separately and simultaneously. Our results show that the quantum conductance of semiconductor CNTs is increased by compression strain, elongation strain, and replacing nitrogen and boron doping in its structure. The amount of increasing in the conductance depends on the type of strain and impurity. Conductance of CNT can be...