We numerically study the dynamics of meandering spiral waves in the excitable system subjected to a feedback signal coming from two measuring points located on a straight line together with the initial spiral core. Th...We numerically study the dynamics of meandering spiral waves in the excitable system subjected to a feedback signal coming from two measuring points located on a straight line together with the initial spiral core. The core location and size radius of the final attractors are computed, and they change with the position of the moving measuring point in a unique way. By the Fourier Spectral analysis, we find the frequency-locked behaviors different from the driving scheme of the external periodic force. It when the moving measuring point approaches closely is also found that the meandering spiral wave can be eliminated the boundary and its feedback gain is large enough. This offers an effective and convenient method for eliminating meandering spiral waves.展开更多
Pulse width modulation （ PWM） drive control digitalization is the key for the full digital invert power supply. New ideas are proposed, which are based on field programmable gate array （ FPGA ）. First, digital PWM...Pulse width modulation （ PWM） drive control digitalization is the key for the full digital invert power supply. New ideas are proposed, which are based on field programmable gate array （ FPGA ）. First, digital PWM principles are discussed. The primary and secondary current characteristics are analyzed when the transformer is in both normal and magnetic bias conditions. Second, two digitalization methods are put forward after the research on PWM adjustment principles, which are based on the primary current feedback. Though the two methods could restrain magnetic bias, their realization is difficult. A new method is researched on double close-loops to overcome the above shortcomings, which uses the secondary current as the feedback signal and the primary current as the protection signal. Finally, the secondary current control made is discussed and realized. Welding experimental results show that the method has strong flexibility and adaptability, which can be used to realize the full digital welding power supply.展开更多
The overarching aim of this study is to find out the effects of peer feedback on Turkish EFL learners at pre-intermediate level. More specifically, the researcher sought to probe the strategies most suitable to these...The overarching aim of this study is to find out the effects of peer feedback on Turkish EFL learners at pre-intermediate level. More specifically, the researcher sought to probe the strategies most suitable to these students by motivating them to scrutinize each other’s writings and develop their own perceptions of the advantages of becoming more critical of their writing. By addressing these aims and objectives, the researcher hoped to discover the advantages and effects of peer feedback in improving the writing skills of these students. A mixture of both quantitative and qualitative methods was considered appropriate to meet the needs of research. A questionnaire on attitudes and writing tests were used to collect primary data for the study in order to gain information about the needs of the students and the suitable strategies required for peer reading, examining, and giving feedback. Semi-structured interviews were also conducted to examine the students’ perceptions of peer feedback. Results of this study revealed that the peer feedback process helped learners in improving their writing performance as a result of which the students had a positive attitude towards using peer feedback in EFL classrooms. Based on the findings, implications for foreign language （FL） writing classes and suggestions for future studies are presented.展开更多
Hossein Nassaji&Eva Kartchava(eds.),2017.Corrective Feedback in Second Language Teaching and Learning.New York:Routledge.①引言纠正性反馈(corrective feedback,CF)是指"为提示学习者二语产出中不恰当用法所提供的...Hossein Nassaji&Eva Kartchava(eds.),2017.Corrective Feedback in Second Language Teaching and Learning.New York:Routledge.①引言纠正性反馈(corrective feedback,CF)是指"为提示学习者二语产出中不恰当用法所提供的反馈信息"(Chaudron,1988:150)。作为教师和学生互动的一种重要体现形式,纠正性反馈一直是二语习得领域的研究热点(Sheen&Ellis,2011)。近二十年,纠正性反馈研究取得了丰厚成果,为保持良性发展、持续繁荣的态势,交流和整合反馈研究显得尤为重要;另一方面,反馈研究与教学实践呈现脱节迹象,如何有效利用研究成果改进课堂教学,成为二语研究者和教师面临的重要挑战。展开更多
As the number of Chinese international students studying in the U.S. has grown dramatically in recent years, there has been increasing attention to how English Composition instructors approach these students＇ writing...As the number of Chinese international students studying in the U.S. has grown dramatically in recent years, there has been increasing attention to how English Composition instructors approach these students＇ writings. Using a dialogue format representing ＂narratives of classroom life＂ （Nelson, 2011a）, this paper demonstrates two polemic views held by teachers and researchers： one view sees students＇ language use as problematic as it differs from the expected standards required for academic success in the U.S., while the other calls for more tolerance of the students＇ linguistic and cultural diversity and accordingly, more strategic ways to give ＂error feedback.＂ By opening up the debate, the paper explores possibilities for teachers in the U.S. and around the world to help their students address the gap between academic expectations, and what they are currently capable of.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No. 11005030Science Foundations of Hebei Education Department under Grant No. 2009135+1 种基金Science Foundations of Inner Mongolia Education Department under Grant No. NJ09178Science Foundation of Hebei Normal University
文摘We numerically study the dynamics of meandering spiral waves in the excitable system subjected to a feedback signal coming from two measuring points located on a straight line together with the initial spiral core. The core location and size radius of the final attractors are computed, and they change with the position of the moving measuring point in a unique way. By the Fourier Spectral analysis, we find the frequency-locked behaviors different from the driving scheme of the external periodic force. It when the moving measuring point approaches closely is also found that the meandering spiral wave can be eliminated the boundary and its feedback gain is large enough. This offers an effective and convenient method for eliminating meandering spiral waves.
文摘Pulse width modulation （ PWM） drive control digitalization is the key for the full digital invert power supply. New ideas are proposed, which are based on field programmable gate array （ FPGA ）. First, digital PWM principles are discussed. The primary and secondary current characteristics are analyzed when the transformer is in both normal and magnetic bias conditions. Second, two digitalization methods are put forward after the research on PWM adjustment principles, which are based on the primary current feedback. Though the two methods could restrain magnetic bias, their realization is difficult. A new method is researched on double close-loops to overcome the above shortcomings, which uses the secondary current as the feedback signal and the primary current as the protection signal. Finally, the secondary current control made is discussed and realized. Welding experimental results show that the method has strong flexibility and adaptability, which can be used to realize the full digital welding power supply.
文摘The overarching aim of this study is to find out the effects of peer feedback on Turkish EFL learners at pre-intermediate level. More specifically, the researcher sought to probe the strategies most suitable to these students by motivating them to scrutinize each other’s writings and develop their own perceptions of the advantages of becoming more critical of their writing. By addressing these aims and objectives, the researcher hoped to discover the advantages and effects of peer feedback in improving the writing skills of these students. A mixture of both quantitative and qualitative methods was considered appropriate to meet the needs of research. A questionnaire on attitudes and writing tests were used to collect primary data for the study in order to gain information about the needs of the students and the suitable strategies required for peer reading, examining, and giving feedback. Semi-structured interviews were also conducted to examine the students’ perceptions of peer feedback. Results of this study revealed that the peer feedback process helped learners in improving their writing performance as a result of which the students had a positive attitude towards using peer feedback in EFL classrooms. Based on the findings, implications for foreign language （FL） writing classes and suggestions for future studies are presented.
文摘Hossein Nassaji&Eva Kartchava(eds.),2017.Corrective Feedback in Second Language Teaching and Learning.New York:Routledge.①引言纠正性反馈(corrective feedback,CF)是指"为提示学习者二语产出中不恰当用法所提供的反馈信息"(Chaudron,1988:150)。作为教师和学生互动的一种重要体现形式,纠正性反馈一直是二语习得领域的研究热点(Sheen&Ellis,2011)。近二十年,纠正性反馈研究取得了丰厚成果,为保持良性发展、持续繁荣的态势,交流和整合反馈研究显得尤为重要;另一方面,反馈研究与教学实践呈现脱节迹象,如何有效利用研究成果改进课堂教学,成为二语研究者和教师面临的重要挑战。
文摘As the number of Chinese international students studying in the U.S. has grown dramatically in recent years, there has been increasing attention to how English Composition instructors approach these students＇ writings. Using a dialogue format representing ＂narratives of classroom life＂ （Nelson, 2011a）, this paper demonstrates two polemic views held by teachers and researchers： one view sees students＇ language use as problematic as it differs from the expected standards required for academic success in the U.S., while the other calls for more tolerance of the students＇ linguistic and cultural diversity and accordingly, more strategic ways to give ＂error feedback.＂ By opening up the debate, the paper explores possibilities for teachers in the U.S. and around the world to help their students address the gap between academic expectations, and what they are currently capable of.
