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关键词： 电抗器   电容器   补偿装置   氧化锌避雷器  

摘要： 由于系统谐波的存在或限制涌流,目前攀钢不接地系统大多采用串联电抗器的静止电容器无功补偿装置。但在工程实践中,由于装置元件参数设计选取的不恰当或接线方式的不合理,造成设备无法投运或在运行中出现问题。本文结合曾出现过的问题,对不接地系统并联电力电容器补偿系统各元件的参数选取及整个补偿装置的接线方式进行了分析,提出了合理的参数选取方法及正确的接线方式,实施后,取得了明显成效,确保整个补偿系统的安全可靠运行。

关键词： Refrigeration system   Process control   Global optimization   Controllability study   Model predictive control  

摘要： This work is focused on optimal control of mechanical compression refrigeration systems. A reduced order state-space model based on the moving boundary approach is proposed for the canonical cycle, which eases the controller design. The optimal cycle (that satisfying the cooling demand while maximizing efficiency) is defined by three variables, but only two inputs are available, therefore the controllability of the proposed model is studied. It is shown through optimization simulations how optimal cycles for a range of the cooling demand turn out not to be achieved by keeping the degree of superheating to a minimum. The Practical NMPC and a well-known feedback-plus-feedforward strategy from the literature are compared in simulation, both showing trouble in reaching the optimal cycle, which agrees with the controllability study. (C) 2020 ISA. Published by Elsevier Ltd. All rights reserved.

关键词： 物理   网络开放课程   课程设计   自主学习   探索与实践  

摘要： 有效实施网络开放课程已经成为各校教学改革面临的重要课题。为弥足传统物理教学中的不足,需要教师利用信息技术设计出符合学生学习规律的物理网络开放课程,来有效地促进学生全面发展。本文对物理网络开放课程设计中存在的问题进行总结反思,并提出建设性建议:更新物理网络开放课程内容,提高物理网络开放课程的制作水平,提高教师职业素养等等。希望我们的研究能为提高物理网络开放课程的质量提供有力的帮助。

关键词： FUNDAMENTAL MOVEMENT SKILLS   PHYSICAL SELF-CONCEPT   ENHANCING PERFORMANCE EXPECTANCIES   HEALTH-RELATED FITNESS   PERCEPTION PROFILE   ELEMENTARY-SCHOOL   DECISION-MAKING   ASSOCIATIONS   COORDINATION   VALIDATION  

摘要： Background Actual and perceived motor competence are important correlates of various health-related behaviors. As such, numerous studies have examined the association between both constructs in children and adolescents. Objectives The first aim of this review and meta-analysis was to systematically examine, analyze and summarize the scientific evidence on the relationship between actual and perceived motor competence (and by extension more general physical self-perception) in children, adolescents and young adults with typical and atypical development. The second aim was to examine several a priori determined potential moderators (i.e., age, sex, and developmental status of study participants, as well as level of alignment between measurement instruments) of the relationship between actual motor competence and perceived motor competence/physical self-perception. Design This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement and was registered with PROSPERO on August 21st 2017. Data Sources A systematic literature search of five electronic databases (i.e., MEDLINE, SPORTDiscus, Web of Science, PsycINFO and EMBASE) with no date restrictions was conducted. Eligibility Criteria for Selecting Studies Eligibility criteria included (1) a study sample of youth aged 3-24 years, (2) an assessment of actual motor competence and perceived motor competence/physical self-perception, and (3) a report of the association between both, using a cross-sectional, longitudinal, or experimental design. Only original articles published in peer-reviewed journals with at least the title and abstract in English were considered. Analyses Meta-analyses were conducted by type of actual motor competence (i.e., overall motor competence, locomotor, object control, stability/balance and sport-specific competence) through univariate and multivariable random-effects meta-regression and clustered random-effects met

关键词： 绥德水文站   铅鱼测流系统   流量测验   应用分析  

摘要： 简述绥德水文站新的铅鱼测流系统的构成、原理及工作流程,通过与该站以前的测流方式进行对比,分析该测流系统的稳定性、安全性、适用范围等,总结其在实际使用过程中的优缺点,为其他将使用铅鱼测流系统的相似站点提供参考。

关键词： 近代物理实验   线上教学   创新教学方法  

摘要： 2020年春季学期,受新冠肺炎疫情影响,清华近代物理实验课程开展了线上实验教学。近代物理实验课程以前沿的课题为载体,精密的实验和数据分析为特色。教学中,内容上注重前沿性、精密性、研究性、拓展性,教学思路上注重自由乐学、引领志趣、因材施教。为把这些课程特点有机的融入线上教学环节,课程教研组全体教员一起,开展讨论,尝试革新,细致实践,着手开展了各种有利于线上实验课程品质提升的探索性工作,并取得良好效果。本文就这段时间,线上教学中,课程在教学规划、内容设计、授课模式革新、教学方法创新、教学成效评估等方面进行描述,开展探讨;并总结经验,归纳不足,展望未来。

关键词： 城乡规划   人才培养   课程体系  

摘要： 高等学校是专业人才培养的重要基地,由培养目标和课程体系组成的培养体系不仅决定着人才培养方向,也深刻影响着人才培养质量。以美国奥尔巴尼大学地理与规划学系城乡规划专业为例,从办学层次、培养目标、课程体系、教学管理等方面系统分析了其培养体系构建,从培养目标设定、知识体系构建、思维方法训练及职业道德培养等方面对其办学经验进行了梳理总结。

关键词： Statistics   Sample size   Statistical power   In vitro testing   Spine biomechanics   DISC DEGENERATION   LUMBAR SPINE   BIOMECHANICAL EVALUATION   DYNAMIC STABILIZATION   FLEXIBILITY   IMPLANT   LEVEL  

摘要： Proper statistical analysis is essential in the research studies. In particular, as regards the in vitro testing of the lumbar spine, the criteria for the standardization have been extensively discussed but the use of statistics has not been reviewed. Unfortunately, cadaveric testing is a very difficult and complex experimental field, in which many factors such as collection times, costs, funding, personnel and logistic issues, availability of implant components, can determinate low sample sizes, with impacts on the statistical evaluation. Moreover, as in any other field, some errors can be commonly made in the choice of the most appropriate statistical tests. The present tutorial article provides a comprehensive overview of the theoretical basics of the statistical approach, focusing on the experimental testing of the lumbar spine. Reference values about adequate sample size and statistical power were provided. The use of statistics was reviewed in a selection of 20 papers, chosen among the most cited and representative contributions for the in vitro study of the lumbar spine. Overall, only 7 in 20 papers applied fully corrected procedures. The achieved power, calculated for the medium conventional level of the effect size, ranged from 0.13 to 0.99 but overall was found rather poor, below 0.6. The study also revealed that applying incorrect statistical tests and having low sample size can impact p-value and power, respectively, with consequences on the identification of the significant outcomes. We emphasize that this review is not intended as a mere critical analysis from a statistical perspective, but as a constructive investigation aimed to support the researchers in the challenging field of cadaveric testing. It is worth noting that the provided recommendations and reference values can be also accounted for experimental scenarios testing the other spine regions, either in human or in animal models.

关键词： 线上教学   数学   新冠疫情  

摘要： 新冠肺炎全球暴发,唐山学院广大教师积极响应"停课不停教,停课不停学"的要求,展开线上授课,使得教学顺利进行,并取得了积极成效。笔者作为一线教师,结合实际,从教学准备、在线课堂教学过程、在线教学注意的问题三个方面进行了实践总结。