Sharif Digital Repository

Textbooks play major roles in education and incorporation of textbooks into the courses can better the outcome of the learning (McGrath, 2006; Sheldon, 1988). Considering the role of textbooks, it seems crucial to examine and evaluate textbooks to select the best material for the educational courses (Tomlinson, 2001). This study focused on the evaluation of the EFL textbook, Prospect 1, which is currently taught at secondary schools of Iran. The researcher intended to evaluate the textbook from the perspectives of both teachers and learners based on the evaluation model proposed by Litz (2005). The participants of the study were 173 learners and 102 teachers who filled out the questionnaires... 

Resistance spot welding is one of the fabrication processes of gas turbines. Due to few published works about using RSW for joining participation hardened nickel base super alloys like Nimonic C263 and solid solution hardened ones like Hastelloy X, this work tries to investigate the microstructure and mechanical properties of RSW joints of these super alloys. In phase one, effect of welding current on structural properties of welds, hardness profile from the center of the weld to the edge of it, failure mod and failure energy were investigated. In phase two, effect of standard heat treatment of Nimonic C263 and the initial microstructure of the base metal on the micro-structure and... 

In this research, using a hydrochemical model alongside three dominant instabilities of shape, Bjerknes and diffusion, the effect of ambient parameters on the single bubble sonoluminescence (SBSL) in Sulfuric Acid (SA) is studied. The phase diagrams of the bubble in the (R0 − Pa) space are presented, and the parametric dependence of the light intensity is discussed. In a part of this research a hot plasma core is considered at the center of the bubble. The study of ambient temperature shows that in contrast to water, the calculated thermalbremsstrahlung mechanism of light emission at the fixed degassing condition of high SA concentrations shows that with increasing the temperature of aqueous... 

Millimeter-wave (mmWave) communication systems exhibit large bandwidth and severe channel attenuations. To maintain the received signal-to-noise ratio on an acceptable level, mmWave systems use large antenna arrays and directional beamforming at both transmitter and receiver. The existence of many antenna elements, however, challenges traditional approaches for pilot transmission and channel estimation wherein the number of pilots linearly scales up with the total number of transmit antennas. For instance, for the uplink channel estimation with a constant coherence interval, adding more antennas to the users comes at the expense of a linear penalty on the number of users, which can...