Sharif Digital Repository

Darrieus turbines are one of the most widely used turbines in extracting energy from tidal currents. This study aimed to investigate the effect of utilizing helical blades and variable solidity ratio on the efficiency of Darrieus tidal turbines. For this purpose, three types of helical turbines with different solidity ratios have been designed, and computer simulation has been used to investigate the effect of the mentioned parameters on the efficiency of the Darrieus turbines. According to the simulation results, the helical turbine has less efficiency than the straight blade Darrieus turbine. The maximum hydrodynamic efficiency of the Darrieus turbine with straighted blades is 38.5,... 

Theanine is a non-protein amino acid which was first isolated from tea plant leaves (Camellia sinensis) and also found in a mushroom named Xerocomus badius and some other Camellia species such as C.japonica and C.sasanqua. Theanine comprises about 50% of amino acids in tea and 1-2% of dry weight of tea leaves. It contributes to the umami taste and unique flavor to tea infusion and has many physiological and pharmaceutical effects such as anti-tumor and anti-cancer activity, neuroprotection, antihypertensive, relaxation, increased focus and anti-obesity effects. So this compound is essential for human body but is not synthesized in it and should be administrated orally. In recent years, study... 

Schiff bases are used as prevalent ligands in coordination chemistry and are prepared easily. Their application as mild inhibitory agents for prevention of various steel’s corrosion in acidic solution has been proved. When their structure is altered, multi-purpose application for them is found. This property has led to a motive for research and study. In this study, electronic properties of a group of Schiff bases are investigated. The goal of this study is using quantum mechanics (QM) as a tool for specifying electronic properties of some of these bases. With respect to QM calculation which is done by density functional theory (DFT), their properties as inhibitory agents are studied. First,... 

Among different subfields of pragmatics some have been analyzed meticulously and some seem to be in a more stringent need of investigation. ILP rating is a novel branch of pragmatics studies through which various aspects and process of rating the L2 learners’ pragmatics knowledge are analyzed. Unfortunately, despite its great impact on learning and teaching second language, investigation of L2 raters’ behaviors and criteria has not been explored much. Problems in the process of ILP rating are very critical, as they can easily undermine the fairness of the test. Therefore, this study attempted to analyze overall 100 EFL teachers’ rating criteria (50 Iranian nonnative and 50 American native)... 

Conveying a successful message within a language profoundly stems from not only a linguistically appropriate utterance, but also a pragmatically appropriate discourse too. Broadly considering various facets of pragmatics, pragmatic assessment has not been potentially brought into perspective, and, as a result, the literature deserves more comprehensive attention. This study, guided by the principles of mixed methods design, pursued three purposes: to inspect the matches and mismatches, to explore rating variations, and to assess the rater consistency between the holistic and analytic rating methods of agreement and disagreement speech acts in L2 by non-native English teachers. To address... 

Vocabulary knowledge is one of the main building blocks in the process of learning a new language and presents many challenges to language learners. Using computer software and online programs is suggested as possible approaches for overcoming some of these challenges. In the present study, the researcher attempted to study the effect of creating and sharing different sets of online flash cards on the use of vocabulary items among Iranian English for Academic Purposes (EAP) students. Thirty-nine university students in two groups participated in this study (29 males, 10 females). One group were instructed to create online flash cards containing the definitions of words and their synonyms and... 

By new advancements in vehicle manufacturing; vehicle quality evaluation and assurance has become a more critical issue. Today noise and vibration generated inside and outside a vehicle are more important factors than before. In present work, the vibration transfer path analysis and vibration path ranking of a car interior has been performed. The method is similar to classical multilevel TPA methods but has distinct differences. The method is named VIVS which stands for Vehicle Interior Vibration Simulation. Performance of some tests like chassis dyno test, virtual mass function test and body transfer function test are required in this approach. The accelerations on both sides of the engine... 

In this millennium there has been a thought-provoking dispute over the inclusion of Critical Thinking (CT) programs into teaching syllabi; this inspiring challenge of change has led researcher to investigate the teachability and transferability of Critical Thinking. Thus, this study investigated whether explicit critical thinking instruction can foster critical thinking skills of in-service EFL teachers and enhance their disposition, perception and attitude. To fulfill the purposes of this study, California Critical Thinking Skill Tests (CCTST), EMI Critical Thinking Disposition Inventory, as well as perception and attitude questionnaires were utilized. The participants of this research were... 

In the past few decades the use of textbooks has increased dramatically in ELT due to the growing need for English both as a foreign and second language all over the world. Along with this growth in textbook application in ELT, textbook evaluation as a comparably new line of esearch has gained significant attention from both researchers and ELT specialists. As an attempt to contribute to this growing body of research, the present study was conducted to evaluate eight most popular global and local textbooks which are taught in Iranian ELT institutes in order to investigate the realization of environmental and human rights issues as well as other various topics in ELT textbooks in Iranian... 

Developing ESP knowledge of a specific academic discipline is not only a privilege but a prerequisite for successful performance in related academic and occupational settings. English for Specific Purposes (ESP) courses at undergraduate level in Iranian universities are designed to serve this purpose. Needs analysis is the foremost step to design relevant and useful ESP courses, but how to approach needs in a motivating and interesting way is still a question pending further research. Accordingly, focusing on engineering fields in three Iranian state universities, this study aimed at identifying factors that affect engineering students’ motivation for learning technical English in ESP... 

It is generally observed that the textbooks employed in the classrooms play a crucial role in the process of teaching and learning a second/foreign language. As a result, a number of studies have been carried out to evaluate English Language Teaching (ELT) materials. Trying to contribute to this growing body of literature, the present study was conducted to evaluate the eight most popular global textbooks which are taught in Iranian ELT institutes in terms of their task types according to Nunan’s (1999) classification of the tasks. Nunan (1999) classified tasks into different groups according to the strategies underpinning them. He divided tasks into five major groups each one consisting... 

No-one likes being confined to a hospital bed. Children particularly can feel lonely, bored or frightened in these conditions. Hours feel like days, and they may not be able to fully comprehend why they are there. Among kids hospitalized because of distinct diseases, children with cancer have incomparable status and needs. They experience physical and mental problems caused by cancer and medications. Cancer treatment may cause distress which can lessen the effectiveness of the treatment. Utilizing social robots to interact with children in clinical environments has been verified to both diminish their distress level and enhance the effectiveness of the treatment process. To improve the... 

In this thesis, the purpose of the research was to develop a four-wheeled Mobile platform (Lower body) with three degrees of freedom for a humanoid robot upper body which is called RASA. RASA robot was designed and constructed for helping kids who have speech and hearing impairments. The objective was to develop a low-cost and affordable robot as compared to its international models to be used at home or school as a teacher assistant. RASA can help kids to learn signs as fast as possible due to the game-based and entertaining education system. The wheeled base platform consists of a new mechanism with 6 bar linkage for bending robot from the hip to about 60 degrees from a vertical position...