Real-time dynamic modeling of hydrogen PEMFCs     

Y.H. Hung  C.W. Hong 《Journal of The Franklin Institute》2008,345(2):182-203

A control-oriented dynamic model of proton exchange membrane fuel cells (PEMFCs) has been developed in this paper. It aims to generate system dynamics with real-time performance for the micro-chip controller design. A unified bond graph approach was employed that integrates physical and chemical domains in the fuel cell operation, including fluid dynamics, heat transfer, and electrochemistry effects. In this paper, two major bond graphs, one for thermofluids, the other for the electrochemical system, were constructed. They are inter-connected to interpret the highly nonlinear transport and reaction system dynamics. The nonlinear simulation on a personal computer (PC) is about four times faster than the realistic operation. A step response test shows that the start-up time of an example PEMFC is about 5 s from ambient conditions. Further frequency-response test in the operation region shows that the bandwidth is near 2 rad/s.  相似文献   

Recurrence of maltreatment: an application of the National Child Abuse and Neglect Data System (NCANDS).     

J D Fluke  Y Y Yuan  M Edwards 《Child abuse & neglect》1999,23(7):633-650

OBJECTIVE: The research describes and compares patterns of maltreatment recurrence across multiple states using large samples, confirms the patterns of recurrence found in the literature, and explores unreported patterns of recurrence. METHOD: A recurrence data set for calendar years 1994 and 1995 was constructed from the multi-state case level data from the National Child Abuse and Neglect Data System. These data were available for 10 states and included a range from 2,419 to 99,288 substantiated or indicated report-child pairs per state. A common set of data constructs lent consistency to data construction and analysis, while preserving differences in policy. Event History Analysis (survival) techniques were used. RESULTS: Single site studies were confirmed across the 10 states. These include the pattern where neglect is most likely to recur, followed by physical abuse and then sexual abuse. Similarly, younger children are more likely to recur. A finding of the analysis is that the likelihood of recurrence increases in a systematic and consistent fashion based upon the sequential ordering of recurrent maltreatment events. Also, the likelihood of recurrence is associated with the provision of postinvestigative services. CONCLUSION: Highly consistent patterns of recurrence were observed across states. Children experiencing multiple recurrences compared to no recurrence or one recurrence may represent a special at risk population requiring additional research. Adequate baselines and an understanding of recurrence is needed when considering recurrence as an outcome indicator or in developing risk assessment tools. Important recurrence patterns may be difficult to detect reliably with relatively small samples.  相似文献   

The Subject Matter Knowledge in Physics Related Topics of Hong Kong Junior Secondary Science Teachers     

Yip  D. Y.  Chung  C. M.  Mak  S. Y. 《Journal of Science Education and Technology》1998,7(4):319-328

The subject matter competence in physics related topics of 147 inservice junior secondary science teachers in Hong Kong was identified using a true-or-false instrument based on a framework conceptualized by the authors. The findings of this study showed that teachers are weak both in factual knowledge and conceptions in these topics. Although physics majors outperform nonphysics majors significantly in the test, their own performance is by no means satisfactory on criterion referenced terms. Items incorrectly answered by over 40% of the teachers are listed with corrections given. The sources of conceptual mistakes and specific remedial measures were elaborated for items incorrectly answered by more than 60% of the teachers. General implications and possibilities for improvement in tertiary education, science teaching, and teacher education were discussed.  相似文献   

The impact of pictorial stimulus on written expression output of adolescents and adults     

Jason C. Cole  Tracy A. Muenz  Bryan Y. Ouchi  Nadeen L. Kaufman  Alan S. Kaufman 《Psychology in the schools》1997,34(1):1-9

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Political and Legal Prerequisites for the Formation of the Modern Policy of the Republic of Kazakhstan in the Field of Higher Education     

Khvedelidze  Teimuraz B.  Toleubekova  Bakhitzhan Kh.  Sailibayeva  Zhanel Y.  Tynybekova  Zulfiyat K. 《Interchange》2021,52(3):377-391

Interchange - This research is relevant, as higher professional education has a large-scale impact on civilisation, the level of social, socio-economic, technological development and has a powerful...  相似文献   

Building a World-class Comprehensive,Innovative, Intelligent and Benchmarking Academic Library in an All-round Way: Summari- zing the Effectiveness of Peking University Library 2019-2022 Ac- tion Platform北大核心     

陈建龙  刘素清  刘宇初 《中国图书馆学报》2023,49(5):14-25

2018年，北京大学图书馆于建馆120周年之际研究制定了面向2035年愿景的《北京大学图书馆2019—2022年行动纲领》。在《行动纲领》引领下，北京大学图书馆牢固树立“用户导向、服务至上”基本理念，坚持“固本应变、服务转型、综合改革、立杆引领”等重要方针，持续完善文献保障和信息服务体系，扎实推进图书馆治理体系和治理能力现代化，创新驱动图书馆事业现代化转型发展，开创了发展根基更坚实、新型服务更有效、综合改革更深入、引领作用更突出的崭新局面，基本建成了世界一流的综合性、创新型、智能化、标杆位大学图书馆。本文从固本培元、服务创新、人本改革、标杆引领四个方面对《行动纲领》实施以来的工作实绩和用户效用进行总结和述评，以期为业界提供借鉴和参考。参考文献4。  相似文献   

Evaluation of the Role of Routine Laboratory Biomarkers in COVID-19 Patients: Perspective from a Tertiary Care Hospital in India     

Barnali Das  Seema Y. Bhatia  Poonam M. Pal 《Indian journal of clinical biochemistry : IJCB》2021,36(4):473

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Happiness and counterfactual thinking at the 2016 Summer Olympic Games     

Mark S. Allen  Sarah J. Knipler  Amy Y. C. Chan 《Journal of sports sciences》2019,37(15):1762-1769

The purpose of this study was to investigate potential differences in emotional expression and counterfactual thought between bronze and silver Olympic medallists. In Study 1, 468 photographs (156 gold medallists, 156 silver medallists, 156 bronze medallists) were obtained of Olympic medal winners standing on the podium at the 2016 Summer Olympic Games, and 20 students rated the level of expressed happiness in each photograph. The students were blind to the outcome of the event and an average score for each photograph was used in data analysis. Results showed that gold medallists displayed greater levels of happiness than silver medallists but that silver and bronze medallists showed little difference in their expressed happiness. In Study 2, 192 quotations from bronze and silver medallists were obtained from news outlets, and 20 students rated the expression of counterfactual thought in each quotation. Results showed that compared to bronze medallists, silver medallists had more counterfactual thoughts overall, more counterfactual thoughts about how things could have gone better, and more counterfactual thoughts about their opponents’ behaviour. Overall, findings indicate that counterfactual thoughts differ between bronze and silver medallists, but that differences in expressed emotion are likely to be trivial or negligible.  相似文献   

Development and validation of perceptions of online interaction scale     

Ayşe Bağrıacık Yılmaz 《Interactive Learning Environments》2018,26(3):337-354

The aim of this study was to develop a measurement instrument which is compatible with literature, of which validity and reliability are proved with the aim of determining interaction perceived by learners in online learning environments. Accordingly, literature review was made, and outline form of the scale was formed with item pool by taking 14 expert opinions. As a result of exploratory factor analysis of data obtained from participation of 177 learners from eight different universities, it was seen that the scale consisted of 30 items and 3 dimensions. These dimensions are learner–content interaction, learner–instructor interaction and learner–learner interaction. Cronbach Alpha reliability coefficient of the whole scale was .95. Confirmatory factor analysis showed that fit indexes of the structure provided a good and acceptable fit. Based on these findings, Perceptions of Online Interaction Scale is a valid and reliable tool that may be used in measuring interaction occurring in online learning environments.  相似文献   

“We (Tong) Chinese”: Contemporary identity positioning through health management among Cantonese Chinese Americans     

Genevieve Leung  Evelyn Y. Ho  Han-Lin Chi  Siyuan Huang  Isabelle K. Ting  Donald Chan 《Journal of International and Intercultural Communication》2018,11(4):271-285

This paper explores discursive ways Chinese American older adults with type 2 diabetes mellitus (T2DM) take ownership of their health management. Fifteen patient stakeholders with T2DM took part in four focus group interviews. We used qualitiative discourse analysis to examine how participants used the phrase, “We (Tong) Chinese,” and variants, to index models of Chinese-living-in-the-U.S. personhoods, to incorporate “Chinese” and “western” ways of doing health management, to be Chinese American, and to interact with medical practitioners. We show how terms like “Tong” distinguish transnational boundaries and position participants in claiming “Chinese-in-America-ness” in relevant ways. Findings have implications for healthcare providers, health education, and intercultural communication.  相似文献