基于自适应预测算法的APF无差拍控制方法

有源电力滤波器（active power filter, APF）补偿电流跟踪控制要求具有较高的稳态精度和较快的动态响应速度。文章将自适应预测滤波算法应用于无差拍控制,实现APF补偿电流精确控制。根据APF时域数学模型,推导滤波系统的无差拍控制离散方程;通过自适应(finite impulse response filter, FIR)预测滤波算法实现基波电流预测,消除控制系统的计算延迟,给无差拍控制提供所需的指令电流预测值。对预测算法进行MATLAB仿真,验证预测算法的稳态精度和动态跟踪快速性;实验室样机验证控制实验结果证明所提出的控制策略有效的,具有一定的实用性。     

Reflective practicum in higher education: the influence of the learning environment on the quality of learning

Sustaining students in becoming reflective practitioners is considered as a valued outcome of higher education. The paper aims to evaluate the impact of the learning environment conditions inspired by Schön’s theory of reflective practicum, by discussing a case study of a master’s degree class. The learning environment was designed to sustain reflective practice and meaningful engagement through professional practice simulation, problem-based learning and reflective writing. Unlike much of the research into reflective learning, the quality of learning was evaluated by assessing the use of reflective practice in students’ weekly journaling, rather than measuring students’ satisfaction or perceptions of effectiveness. Two hundred and six journal entries of 23 students were assessed and used in a quantitative analysis based on a linear mixed-effects model. Findings indicated that the reflective practicum has an incremental effect on students’ reflective practices and that reflective practice is dynamic and sensitive to specific learning environment conditions. In conclusion, students’ co-responsibility of the learning environment allowed by the professional practice simulation appears to foster meaningful and reflective learning. Conversely, conditions that stimulate only cognitive engagement have little impact or even inhibit reflective practices. Practical implications of the use of reflective journal are discussed.     

Teaching geographical databases at the engineering master level: learner-centred approach vs. teacher-centred approach

This paper reports numbers about the author’s experience, spanning over 13 academic years, of teaching an introductory course about geographical databases to students of the Master degree in Information Engineering at L’Aquila University (Italy). The first eight editions of the course were delivered according to the teacher-centred approach, while the successive five editions have been delivered according to the student-centred approach. The large student engagement which characterised the last five editions of the course was vital in enhancing the student experience and encouraging deeper learning. Two preconditions that explain the results achieved in terms of classroom attendance and students’ performance.     

Classroom Debates: Using Speed Rounds To Encourage Greater Participation

The primary obstacle that can derail the effectiveness of a debate is one in which few students are involved and all of the energy and learning is limited to a few students. This leaves the majority of students passively absorbing information and does not encourage participation among those students that typically do not talk in class. This quick fix proposes a technique to increase the involvement of all students in the debate.     

Contribution of uncertainty in estimation of active drag using assisted towing method in front crawl swimming

Active drag force in swimming can be calculated from a function of five different variables: swim velocity, tow velocity, belt force, power output and exponent of velocity. The accuracy of the drag force value is dependent on the accuracy of each variable, and on the contribution of each variable to drag estimation. To calculate uncertainty in drag value, first the derivatives of the active drag equation with respect to each variable were obtained. Second, these were multiplied by the uncertainty of that variable. Twelve national age and open level swimmers were recruited to complete four free swimming and five active drag trials. The uncertainties for the free and the tow swim velocities, and for the belt force, contributed approximately 5–6% and 2–3% error, respectively, in calculation of drag. The result of the uncertainty of the velocity exponent (1.8–2.6) indicated a contribution of about 6% error in active drag. The contribution of unequal power output showed that if a power changed 7.5% between conditions, it would lead to about 30% error in calculated drag. Consequently, if a swimmer did not maintain constant power output between conditions, there would be substantial errors in the calculation of active drag.     

Exploring the values of writing collaboratively through a digital storytelling platform: a mixed-methods analysis of users’ participation,perspectives and practices

Digital technologies allow teachers and students to experience new pedagogical approaches leveraging on interactivity and collaboration. Among the available techniques, digital storytelling (DST) has been usually regarded as an activity that can both enrich the teaching practices and foster students’ active behaviour. This paper aims at analysing to what extent a DST platform proposing the collaborative writing of a fictional story and leveraging on an active learning technique such as role-play can affect a variety of dimensions, namely students’ performance, commitment, creativity and social skills. Combining the analysis of the data-log automatically collected by the system with the evaluations given by teachers before and after the activity, this article shows that the use of a DST tool in the teaching practice can have positive effects on students, including the ones that usually manifest moderate scores for the previously mentioned dimensions. Additionally, semi-structured interviews and direct observations provide an insight on how the benefits stemming from the use of a DST tool in the classroom can especially lie on the collaborative process that is activated.     

Large Lecture Halls: Whiteboards,Not Bored Students

Large lecture halls are a common feature of many undergraduate mathematics programs. However, teaching effectively in a large lecture hall can be challenging. This paper discusses the use of personal whiteboards for students as a way to make large lecture halls a more productive learning environment. I discuss the logistics of using whiteboards, setting up norms, and provide examples of supporting instructional techniques. These techniques are: warmup problems, think-pair-share, group work, and student presentations. To support this exposition, I draw on personal reflections as an instructor and report from a brief student survey on their experiences using the whiteboards.     

图书情报学领域高产研究机构的合作网络指标分析

[目的/意义]当前有关论文合著的研究大多以主题或学科为研究对象,很少从整个研究机构的角度去探讨各个机构之间的学术合著情况。[方法/过程]本研究选取2007-2016年在Web of Science发表的图书情报学方面的期刊文章,利用书目计量及社会网络分析两种工具,对其论文合著情况进行分析。[结果/结论]研究显示M大学在图书情报学领域的学术合著已经成为普遍趋势,同时论文合著活跃度分别与学术生产力和学术影响力轻度正相关。本文的研究结果为后续研究机构分析学术研究网络提供参考。     

色散条纹传感技术用于拼接镜面位移探测的仿真研究

根据色散条纹传感技术的基本原理,从物理光学的角度对色散条纹传感器(DFS)进行了模拟研究,仿真出理论干涉图形,并从中采集能量信号,拟合光强分布曲线,得出测量结果.通过比较在不同波段的采样,提出在CCD上开出窗口采集有效信号的2种方法,借以提高检测精度.色散条纹传感器的检测范围为±50μm,检测精度可以达到几十nm.     

基于双频控制技术的有源电力滤波器分析及应用研究

有源电力滤波器作为对治理电力谐波很有前途的方法,因其功率器件水平限制了APF单元的容量、投入电网运行后的的稳定性问题、以及初装成本高等三个方面啄因限制了APF的大量运用特别是在大功率等级的运用。以后的研究方向是提高补偿容量、降低APF的成本以及解决有源电力滤波器的稳定性问题。为了解决这三个方面的问题,本文提出双频控制有源电力滤波器的新解决方案,用一个低频APF与一个高频APF组合运行。双频控制APF采用低频APF来主要输出功率,可以用低频器件GTO等,这样就可以提高功率等级,提高在现有器件水平下的容量。同时因为低频单元处理功率,系统效率可以大为提高,可靠性也将进一步提高。相对于多重化等拓扑结构而言,系统成本也将大大降低。而高频APF不主要承担处理功率的任务,可以采用IGBT工作在高频,这样就可以提高系统的补偿性能。