Failure analysis of a kind of low power connector     

ZHOU Yi-lin ZENG Ning XU Liang-jun JORGENS Stefan 《浙江大学学报(A卷英文版)》2007,8(3):384-392

A kind of low power connector used e.g. in household appliances was partly burned in routine experiment. The heat sources were four paralleled contacts constructed by springs (Sn/CuSn-alloy) in socket and a plug sheet (Ni/Steel) while mating. The contact interfaces were detected by scanning electronic microscope (SEM) and X-ray energy dispersive spectros- copy (XEDS), obvious wear tracks and various contaminants, including element Si, Al, Na, K, S, Cl, O, etc., were found. The contamination degrees on the four paralleled contacts were different, so that the ratio of average contact resistance on the four contacts was about 5:8:3:1. The maximum contact resistance on contacts of the plug sheet reached 28 ?. The main failure rea- sons were fretting and contamination between the contact interfaces. Fretting simulation showed that connection resistance of connectors was raised up, even to ohms level. When the current increased to 5 A, the socket housing was heated and decom- posed. By the thermal analysis, it was estimated that the connector would be burned under the lower current if the current was not evenly distributed on the four paralleled contacts caused by uneven contamination. Improvement methods for connector failure are also discussed.  相似文献   

Using action research to enhance learning on end-use energy demand: lessons from reflective practice     

Saska Petrova  Miguel Torres Garcia  Stefan Bouzarovski 《Environmental Education Research》2017,23(6):812-831

This paper responds to the need for a greater integration of energy and environment themes in the higher education curriculum. We explore the practical implications of empowering students towards the implementation of individual action research projects focused on investigating and addressing insufficient or wasteful energy consumption among households and businesses. The paper scrutinizes a series of teaching and assessment activities within this domain, undertaken during 6 consecutive academic years – between 2008 and 2013 – within a third-level undergraduate course unit at the University of Birmingham in the United Kingdom. Using questionnaire surveys, assessed projects and interviews with the students, we have found evidence to suggest that the action research projects contributed to the emergence of constructive alignment in the entire teaching process, while opening the space for informal action learning ‘sets’ leading to the generation of new problem-solving skills useful in the job market.  相似文献   

Kompetenzniveaus in der ingenieurwissenschaftlichen akademischen Grundbildung – Analysen im Fach Technische Mechanik     

Elmar Dammann  Stefan Behrendt  Florina Ştefănică  Reinhold Nickolaus 《Zeitschrift für Erziehungswissenschaft》2016,19(2):351-374

This paper examines subject-specific structures and the levels achieved by students of Mechanical and Construction Engineering in the subject of Engineering Mechanics (EM). EM presents a major obstacle for students in the two courses of study mentioned. Until now, researchers have not examined which characteristics of the requirements in EM cause this obstacle. Initial efforts to address this research gap were made in the research project KoM@ING. Competence structure modelling confirms three dimensions of EM: statics, elastostatics and dynamics. This paper presents results on proficiency scaling for statics and dynamics. We found that the subject-specific mathematical requirements primarily explain the item difficulties. Moreover, the following features are relevant for item difficulty: the number of solution steps (for statics), the number of EM-specific terms and the content-specific features of complexity (for dynamics). The mathematical requirements and the content-specific features of complexity are revealed as important didactic elements in this higher education context.  相似文献   

Central Europe-South Eastern Europe: Inter-regional Relations in Education,Science, Culture,and Communication     

Stefan Messmann  Leland Conley Barrows 《Higher Education in Europe》2001,26(2):153-164

The central premise in the holding of the Symposium was that there is a long tradition of co-operation among the countries of the sub-regions concerned in the domains of education, science, culture, and communication. Given the perspective of accession of most of these countries to EU membership, this co-operation will develop and expand. As such, it is worth studying so as to better understand and promote it. Thus, the Symposium examined the following topics: (i) Looking Ahead: Links and Co-operation in the Central and South Eastern Europe; (ii) Science and the Application of Science for Technology Development: Towards Enhancement of Endogenous Capacities; (iii) Co-operation through Culture Interactions: Lessons from the Past and Agenda for the Future; (iv) Enhancing the Quality of Communication for and through Better Co-operation. The conclusion is that co-operation of all sorts among the countries of the sub-regions is stronger than co-operation between them but that they should pursue their EU accession efforts, enhancing them through sub-regional co-operation in all domains.  相似文献   

为什么引入COO     

Stefan Stern 《现代企业教育》2006,(15):3

你可能不会对这样的事情很吃惊:一位猎头与他人合著了一本书,详细探讨了企业应该着手创造COO(首席运营官)这一新角色的方法和原因.你也许会说,别管组织结构,先算算这么做的成本吧.……  相似文献   

Factor structure of the WISC‐V in four standardization age groups: Exploratory and hierarchical factor analyses with the 16 primary and secondary subtests          下载免费PDF全文

Gary L. Canivez  Stefan C. Dombrowski  Marley W. Watkins 《Psychology in the schools》2018,55(7):741-769

This study examined the factor structure of the Wechsler Intelligence Scale for Children‐Fifth Edition (WISC‐V) with four standardization sample age groups (6–8, 9–11, 12–14, 15–16 years) using exploratory factor analysis (EFA), multiple factor extraction criteria, and hierarchical EFA not included in the WISC‐V Technical and Interpretation Manual. Factor extraction criteria suggested that one to four factors might be sufficient despite the publisher‐promoted, five‐factor solution. Forced extraction of five factors resulted in only one WISC‐V subtest obtaining a salient pattern coefficient on the fifth factor in all four groups, rendering it inadequate. Evidence did not support the publisher's desire to split Perceptual Reasoning into separate Visual Spatial and Fluid Reasoning dimensions. Results indicated that most WISC‐V subtests were properly associated with the four theoretically oriented first‐order factors resembling the WISC‐IV, the g factor accounted for large portions of total and common variance, and the four first‐order group factors accounted for small portions of total and common variance. Results were consistent with EFA of the WISC‐V total standardization sample.  相似文献   

Solutions in global software engineering: A systematic literature review     

Stefan Schneider  Richard Torkar  Tony Gorschek 《International Journal of Information Management》2013

Global software engineering (GSE) has received increased attention, as globalization enables and encourages increased distribution of product development. Many empirical studies and systematic literature reviews (SLRs) focus on the identification of challenges, this paper however presents the first SLR collecting and analyzing solutions associated with GSE, while also evaluating the level of empirical validation of said solutions. As a starting point the paper presents a GSE model, designed to categorize solutions into process areas, useful for the analysis of the research community's contributions to state-of-the-art and identifying fundamental gaps in research. In addition, the model categorizing the solutions is populated with references and good-examples, useful for practitioners, which can use the model to find solutions to overall challenges in various process areas. The overall results of the systematic review revealed more than 330 papers containing 127 solutions that were then identified and mapped to the model. The process areas of project management are highly populated, while other areas like product integration have received surprisingly little attention. In addition, selected process area is elaborated upon in terms of contents and deficiencies.  相似文献   

A Portable System for the Rapid Calculation of Metabolic Data     

Stefan H. Constable  Gary S. Krahenbuhl  Keith D. Ruppert 《Research quarterly for exercise and sport》2013,84(3):559-561

  相似文献   

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing     

Thomas Stöggl  Erich Müller  Stefan Lindinger 《Journal of sports sciences》2013,31(11):1225-1233

Abstract

The aims of the study were to: (1) adapt the “double-push” technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional “V2” skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 ± 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 ± 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.  相似文献   

Academic Procrastination: The Perspective of University Counsellors     

Justine Patrzek  Carola Grunschel  Stefan Fries 《International journal for the advancement of counseling》2012,34(3):185-201

The purpose of this study was to investigate the antecedents and consequences of academic procrastination in students who frequent university counselling in regard to this issue. To undertake this, semi-structured interviews with 12 experienced university counsellors in German universities were conducted. A qualitative content analysis resulted in two category systems—antecedents and consequences. Whereas the antecedents were differentiated into nine categories and 30 themes, the consequences were differentiated into 10 categories and 20 themes. The findings indicated that the antecedents and consequences were largely a reflection of the students’ characteristics, their personal and learning situations, and the university environment. A layer model is discussed as a heuristic model for future research and for university counselling services.  相似文献