Failure analysis of a kind of low power connector

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.     

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

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.     

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

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.     

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

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.     

为什么引入COO

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.……     

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

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.     

Exploring teaching concerns and characteristics of graduate teaching assistants

The purpose of the study was to explore a conceptual structure of graduate teaching assistant (GTA) teaching concerns. Results indicated that GTAs experience five distinct, inter-related types of concerns: class control, external evaluation, task, impact and role/time/communication. These ‘teaching concerns’ were further analysed by examining their relationship with the value placed on them by the GTAs and the confidence in dealing with the teaching-related issues of concern. The results revealed that GTAs tend to have concerns about self, task or role/time/communication-related issues when the nature of the concerned issues is perceived as being valuable but challenging. On the other hand, GTAs are more likely to have concerns with impact-related issues when the nature of the issues is perceived as both being valuable and manageable. Several GTA characteristics, such as teaching experience, teacher efficacy, participation in professional development and values on teaching practices, were examined as predictors of GTA teaching concerns.     

Solutions in global software engineering: A systematic literature review

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.     

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

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.