Sharif Digital Repository

Small Permanent Magnet Synchronous Generators (PMSGs) are widely used in small rooftop wind turbines. In order to inject the electric power generated by the PMSG, into the grid, a back-to-back AC/DC/AC converter is required. In this paper, a low cost with high efficiency converter is proposed for the rectifier stage to obtain the maximum power per ampere of PMSG. This structure based on Discontinuous Conduction Mode Single-Ended Primary Inductor Converter (DCM SEPIC) with a single power electronic switch, proposes a converter which is cost-effective and suitable for the small wind turbine used in residential applications. Furthermore, other advantages of the proposed converter include... 

Small Permanent Magnet Synchronous Generators (PMSGs) are widely used in small rooftop wind turbines. In order to inject the electric power generated by the PMSG, into the grid, a back-to-back AC/DC/AC converter is required. In this paper, a low cost with high efficiency converter is proposed for the rectifier stage to obtain the maximum power per ampere of PMSG. This structure based on Discontinuous Conduction Mode Single-Ended Primary Inductor Converter (DCM SEPIC) with a single power electronic switch, proposes a converter which is cost-effective and suitable for the small wind turbine used in residential applications. Furthermore, other advantages of the proposed converter include... 

The present work aimed to investigate the frequency of occurrences and proportions of speech acts of complaints and compliments in the four volumes of the course book English Result (Elementary, Pre-intermediate, Intermediate, and Upper-intermediate), by Mark Hancock and Annie McDonald (2009), published by Oxford University Press. Investigation of the two speech act strategies was based on complaints strategies (Olshtain and Weinbach, 1987) and compliment strategies (Wolfson and Manes, 1981). It was found that the books were rich in terms of the number of the two speech acts, but in presenting them, there were one or two dominant strategies in both cases. Chi-square analysis demonstrated... 

The present paper is an attempt to evaluate Pacesetter Series (Strange and Hall, 2005), an EFL course book series, in four levels of starter, elementary, pre-intermediate, and intermediate, being currently instructed at several language institutes in Iran. The purpose of this study is to determine the appropriateness of the series in Iranian EFL contexts. Litz (2000) questionnaire was exploited to examine the series thoroughly in all essential aspects. Sixty four EFL teachers rated the series. The results of descriptive statistics indicated that there is an overall consensus among the teachers that Pacesetter rightly addresses the needs of the learners in a communicative curriculum. However,... 

Teachers' self-efficacy beliefs within a foreign language context are helpful in terms of their own conceptualization of effective language teaching. While Foreign Language (FL) literature has established a modest presence in EFL classrooms, the teachers' self-perceptions of efficacy in literature instruction strategies have gone rather unnoticed. The objectives of this study were to discover the impact of EFL teachers' gender and teaching experience on their perceived capabilities as literature instructors. To this end, 61 EFL teachers completed Teacher Sense of Efficacy Scale in Literature (Mills, 2011) and background questionnaire indicating their ability in the pedagogy of literature.... 

The analysis of raters' comments on pragmatic assessment of L2 learners is among new and understudied concepts in second language studies. To shed light on this issue, the present investigation targeted important variables such as raters' criteria and rating patterns by analyzing the interlanguage pragmatic assessment process of the Iranian non-native English speaking raters (NNESRs) regarding the request speech act, while considering important factors such as raters' gender and background teaching experiences. For this purpose, 62 raters' rating scores and comments on Iranian EFL learners' requests based on six situations of specified video prompts were analyzed. The results of the content... 

Technology, as a source of instruction, has fulfilled various purposes in foreign language learning environments. During the last decade, Robot-Assisted Language Learning (RALL) has attracted teachers' and researchers' attention due to the look and feel of humanoid robots. However, in the field of pragmatics, studies highlighting the role of RALL have gone relatively unnoticed. To bridge this gap, this study sought to explore the effect of RALL on pragmatic features, including request and thanking speech acts by young Persian-speaking EFL learners. For this aim, 38 preschool children (3 to 6 year-old boys and girls) with no English learning experience were randomly assigned to the RALL (19... 

This paper presents the design process and construction of a mobile social robot companion "Arash" for educational and therapeutic intervention for children with chronic diseases; one which is based on their interests and needs. This study concentrates on children with cancer who suffer from physical pain caused by both the disease and its treatment. Moreover, cancer treatment causes emotional distress, which can reduce the efficiency of medications. Using social robots to interact with ill children in a hospital environment could decrease their distress, thereby improving the efficiency of the treatment. Arash is a 15 degrees-of-freedom cost effective humanoid mobile robot companion,... 

Virtual Reality (VR) technology is a growing technology that has been used in various fields of psychology, education, and therapy. One group of potential users of VR are children with autism who need education and have poor social interactions; this technology could help them improve their social skills through real-world simulation. In this study, we evaluated the feasibility of conducting virtual music education programs with automatic assessment system for children with autism at treatment/research centers without the need to purchase a robot, resulting in the possibility of offering schedules on a larger scale and at a lower cost. Intervention sessions were conducted for five children... 

Virtual Reality (VR) technology is a growing technology that has been used in various fields of psychology, education, and therapy. One group of potential users of VR are children with autism who need education and have poor social interactions; this technology could help them improve their social skills through real-world simulation. In this study, we evaluated the feasibility of conducting virtual music education programs with automatic assessment system for children with autism at treatment/research centers without the need to purchase a robot, resulting in the possibility of offering schedules on a larger scale and at a lower cost. Intervention sessions were conducted for five children... 

This study explores the effect of RALL (Robot Assisted Language Learning) on instructing greeting to young EFL (English as Foreign Language) students in Tehran, Iran. To this end, 38 preschool EFL children ranging from 3 to 6 years old were randomly assigned to the RALL (19 students) and game-based (19 students) groups, and the greeting sentences were extracted from the Functional Communication in English book [1] and ESL library website scenarios. In addition, the robot for the RALL group was used as an assistant to the teacher while for the game-based group the instruction was based on gaming methods such as command, mystery bag, and pass the ball. The instructional duration for both... 

In this paper, the whale optimization algorithm is proposed for harmonics elimination in a cascaded multilevel inverter. In selective harmonic elimination pulse width modulation, the selected low-order harmonics are eliminated by solving nonlinear equations, while the fundamental of output waveform is adjusted to a desired value. In this paper, whale optimization algorithm is applied to a 7-level cascaded H-bridge inverter to solve the equations. Also, it was validated by experimental results, since this algorithm has an ability to search in entire solution space, the probability of catching a global best solution is very high. This method has higher accuracy and probability of convergence... 

In this paper, the whale optimization algorithm is proposed for harmonics elimination in a cascaded multilevel inverter. In selective harmonic elimination pulse width modulation, the selected low-order harmonics are eliminated by solving nonlinear equations, while the fundamental of output waveform is adjusted to a desired value. In this paper, whale optimization algorithm is applied to a 7-level cascaded H-bridge inverter to solve the equations. Also, it was validated by experimental results, since this algorithm has an ability to search in entire solution space, the probability of catching a global best solution is very high. This method has higher accuracy and probability of convergence...