Low-cost sensorless control of four-switch, brushless DC motor drive with direct back-EMF detection

We propose a position sensorless control scheme for a four-switch, three-phase brushless DC motor drive, based on the zero crossing point detection of phase back-EMF voltages using newly defined error functions （EFs）. The commutation instants are 30° after detected zero crossing points of the EFs. Developed EFs have greater magnitude rather than phase or line voltages so that the sensorless control can work at a lower speed range. Moreover, EFs have smooth transitions around zero voltage level that reduces the commutation errors. EFs are derived from the filtered terminal voltages Vao and Vbo of two low-pass filters, which are used to eliminate high frequency noises for calculation of the average terminal voltages. The feasibility of the proposed sensorless control is demonstrated by simulation and experimental results.     

Investigating substantive and consequential validity of student ratings of instruction

This study aimed at exploring faculty and student perspectives on student evaluations, as well as identifying their perceptions of the usefulness and appropriateness of the ratings for evaluating teaching effectiveness. More specifically, the study aimed at identifying the consequences, both intended and unintended, of using the evaluations, in addition to better understanding the process students used in responding to evaluations and what use faculty members made of them. Two surveys were developed and placed on the website of the Office of Institutional Research and Assessment. Emails were sent to all students and faculty participating in evaluations soliciting their cooperation and requesting their input. Faculty and student perceptions were compared qualitatively and statistically. Results revealed that students and faculty believe in the effectiveness and usefulness of the system with the need to overcome some negative consequences and biases inherent in its application at the University. Recommendations for system improvement are provided.     

An optimal Fuzzy-logic based frequency control strategy in a high wind penetrated power system

This paper introduces a new load frequency control (LFC) model in the presence of high wind power penetration level. The main issue in a wind-penetrated power system is to maintain the system frequency in a normal operating band which is specified by the given system grid codes. Essentially, the power system equilibrium point changes following a contingency, and in this case, the high penetration of wind farms makes it harder to regain an acceptable system equilibrium points through conventional control applications. In order to overcome the aforesaid problem, a new Fuzzy-logic controller is designed optimally in this paper using the artificial bee colony (ABC) algorithm. In this approach, the ABC algorithm tunes the membership function parameters of the Fuzzy controller to acquire a good-enough performace of the proposed strategy. More importantly, the proposed Fuzzy-logic controller is blessed with robustness, simplicity, and reliability in order to ameliorate the frequency deviation. It is worth saying that the stability analysis is presented in this paper as well as the noise analysis of the proposed method. The research results indicates how effectively wind farm could participate in the system frequency control through inertial control, primary frequency control, and supplementary frequency control.     

Evaluation of tactical training in team handball by means of artificial neural networks

While tactical performance in competition has been analysed extensively, the assessment of training processes of tactical behaviour has rather been neglected in the literature. Therefore, the purpose of this study is to provide a methodology to assess the acquisition and implementation of offensive tactical behaviour in team handball. The use of game analysis software combined with an artificial neural network (ANN) software enabled identifying tactical target patterns from high level junior players based on their positions during offensive actions. These patterns were then trained by an amateur junior handball team (n = 14, 17 (0.5) years)). Following 6 weeks of tactical training an exhibition game was performed where the players were advised to use the target patterns as often as possible. Subsequently, the position data of the game was analysed with an ANN. The test revealed that 58% of the played patterns could be related to the trained target patterns. The similarity between executed patterns and target patterns was assessed by calculating the mean distance between key positions of the players in the game and the target pattern which was 0.49 (0.20) m. In summary, the presented method appears to be a valid instrument to assess tactical training.     

MRI and PET images fusion based on human retina model

The diagnostic potential of brain positron emission tomography (PET) imaging is limited by low spatial resolution. For solving this problem we propose a technique for the fusion of PET and MRI images. This fusion is a trade-off between the spectral information extracted from PET images and the spatial information extracted from high spatial resolution MRI. The proposed method can control this trade-off. To achieve this goal, it is necessary to build a multiscale fusion model, based on the retinal cell photoreceptors model. This paper introduces general prospects of this model, and its application in multispectral medical image fusion. Results showed that the proposed method preserves more spectral features with less spatial distortion. Comparing with hue-intensity-saturation (HIS), discrete wavelet transform (DWT), wavelet-based sharpening and wavelet-à trous transform methods, the best spectral and spatial quality is only achieved simultaneously with the proposed feature-based data fusion method. This method does not require resampling images, which is an advantage over the other methods, and can perform in any aspect ratio between the pixels of MRI and PET images.     

未来的巴基斯坦地质公园——盐岭

盐岭包括六个峡谷,具有出露充分的地质学和古生物学特征,并且交通便利。这些特点吸引了研究者对这个独特地区的地质时代测定方面的浓厚兴趣,开始对寒武纪三叶虫、二叠纪腕足类、三叠系下统菊石、下第三系大型有孔虫和上第三系及第四纪脊椎动物产生的古地理进行了研究调查。在地质学家眼中,这些盐岭峡谷充满着如此美妙的地质遗址,堪称为世界上独特的野外自然历史博物馆,同时也可能被建设为巴基斯坦的一个地质公园。     

Still as divided as ever? Northern Ireland,football and identity 20 years after the Good Friday Agreement

ABSTRACT

The signing of the Belfast-Good Friday Agreement in 1998 was widely welcomed by those that interpreted it as offering Northern Ireland the prospect of a fresh start, free from inter-ethnic violence that had blighted the country for almost 80 years. Soon it began to be seen by some observers as the genesis too of a ‘Northern Irish’ identity, as the community at large came to reconcile themselves to their common lives in Northern Ireland. Sport was also viewed as offering the prospect of adding weight to this sense of a shared journey and governing bodies of sport unquestionably played their parts in supporting a settled political environment where division had previously existed. This article examines the still contested concept of a ‘Northern Irish’ identity and critically reviews its real currency in a divided society, even if sport and, specifically, association football offers renewed hope for something better in the time ahead.     

The effect of content representation design principles on users’ intuitive beliefs and use of e-learning systems

A model is proposed to assess the effect of different content representation design principles on learners’ intuitive beliefs about using e-learning. We hypothesized that the impact of the representation of course contents is mediated by the design principles of alignment, quantity, clarity, simplicity, and affordance, which influence the learner’s intuitive beliefs about using e-learning systems. The model was empirically validated using data collected from a survey administered to university students. This study demonstrates that these design principles are essential predictors of learners’ intuitive beliefs, which in turn directly influence their decisions about using e-learning systems. The findings provide system designers with quasi-quantitative managerial insights into how to motivate users to continue using e-learning systems.     

The alignment between the fourth grade Lebanese science curriculum and classroom assessments

The purpose of this study was to investigate the alignment between the fourth-grade summative classroom assessments and the ‘Matter and Energy’ unit in the Lebanese science curriculum using: content and cognitive levels. Summative assessments were collected from a sample of 17 schools. The alignment between the classroom assessments and the Lebanese science curriculum were examined using three instruments: Curriculum Coding Sheet, Items Coding Sheet, and Item Analysis Sheet. The curricular learning objectives were used for matching the test items to the learning objectives in terms of content. Findings showed moderate content alignment; further analysis revealed that public schools had higher content alignment, and they covered a wider range of topics. In terms of cognitive level, there was a low alignment between the assessments collected and the curriculum; however, there were items that had higher cognitive level. Recommendations for curriculum developers and future research are discussed in light of these findings.     

Search systems and their features: What college students use to find and save information

College students have often been surveyed about their general information seeking behaviors. However, little has been done to explore what specific system features they use to find and save information when they are working on their real-life tasks. In this study, 32 college students were invited to an information interaction lab for a session in which they recalled a recently finished task and worked on a to-be-finished task using a computer in the lab. They were asked to complete questionnaires regarding what systems they used to finish their tasks and what features were helpful for searching and for saving information. Results showed that college students rely more heavily on the Internet sources than on library sources, even for their course related work. The study identified fourteen categories of system features helpful for information search and eight categories helpful for information saving. The findings have implications for designing systems that will better help people accomplish their tasks.