4MW斩波串级调速系统的应用研究     

毕天昊  王钦若  张卓  王永昌 《环球赛鸽科技》2015,(17)

本文主要讲述的是将状态空间平均法应用于4MW电动机斩波串级调速系统,解决了4MW电机斩波串级调速的控制系统的设计问题。利用状态空间平均法,将绝缘栅双极型晶体管（IGBT）和续流二极管（FWD）考虑为非理想元器件。实验表明,相比于传统串级调速系统,该控制系统可靠稳定,静态特性和动态特性更好,功率因数也更高。工业生产中,采用这种控制系统的设备运行良好,节能效果显著。  相似文献   

自然速度裸足跑足底压力特征与慢跑鞋设计研究     

刘卫国  高晗  欧瑜枫  李强 《北京体育大学学报》2015,38(1):74-79

摘要：目的：以探索自然速度裸足跑单步足支撑时间与负荷结构的部位分布规律为基础,并依据功能设计2要素（位置选择与频率设置）的特征研究慢跑鞋能量回输功能设计的策略与方法。方法：研究主要利用RSscan系统对91名大学生自然速度裸足跑进行了足底压力测试。首先采用独立样本T检验、单因素方差分析与卡方构成比检验等方法分析自然速度裸足跑足支撑的时间与负荷特征, 然后利用聚类分析与判别分析对慢跑鞋设计进行了量化研究。结果：自然速度裸足跑单步支撑时间先短后长、负荷空间分布不均集中作用于后足与前足,但时间与负荷分布均无性别差异;大众慢跑鞋后跟与前掌回弹频率的类别设计具有小中大频3类确定标准,个体慢跑鞋类别选择具有确定方法。结论：1）自然速度裸足跑个体单步足支撑先快后慢、节奏鲜明,负荷集中作用于后跟与前掌,但节奏与负荷均无性别差异。2）获得了小中大频3类大众慢跑鞋频率设计标准,并给出了个体慢跑鞋类别选择标准与方法。3）提出了有利于能量回输的个性化专业慢跑鞋设计思路与策略。  相似文献   

Increasing plantarflexion angle during landing reduces vertical ground reaction forces,loading rates and the hip’s contribution to support moment within participants     

K. Michael Rowley  James G. Richards 《Journal of sports sciences》2015,33(18):1922-1931

The ankle joint’s role in shock absorption during landing has been researched in many studies, which have found that landing with higher amounts of plantarflexion (PF) results in lower peak vertical ground reaction forces and loading rates. However, there has not yet been a study that compares drop landings within participants along a quantitative continuum of PF angles. Using a custom-written real-time feedback program, participants adjusted their ankles to an instructed PF angle and dropped onto two force platforms. For increasing PF, peak ground reaction force and peak loading rate during weight acceptance decreased significantly. The hip’s contribution to peak support moment decreased as PF at initial contact increased up to 30°. The ankle and knee contributions increased over this same continuum of PF angles. There appears to be no optimal PF angle based on peak ground reaction force and loading rate measurements, but there may be an optimum where joint contributions to peak support moment converge and the hip moment’s contribution is minimised.  相似文献   

速度滑冰项目的专门性训练     

赛娜  熊铮 《冰雪运动》2015,(3):1-4

通过多年对沈阳体育学院竞技体校速滑队运动员16人(健将6人,国家一级运动员10人)的非冰期训练的研究,并根据研究需要,查阅了大量的相关书籍和文献,通过访谈几名速滑专业教练员对本研究的意见,认识并发现陆上专门性所存在速滑技术是一个相对不稳定的因素、技术训练上存在差距等问题.把采用的专门性训练方法和手段进行比较和分析,重点探析陆地专门性训练中不同的问题采用针对性较强的训练方法和动作对冰上技术和运动成绩的影响,为陆地专门性训练提供有效的训练方法.  相似文献   

滑冰课程教学对大学生综合素质的促进作用     

吕宏宁  李斌 《冰雪运动》2015,(5):62-65

高校冬季体育教学对促进大学生身体素质的全面发展,培养大学生形成健全的人格具有重要的意义。高校冬季体育中的滑冰课程教学实践表明,通过滑冰课程教学能有效地发展大学生的身体素质,促进其运动技能能力的提高,对建立乐观的情绪与积极健康的心理状态、培养良好的意志品质、提高社会竞争意识、培养适应客观环境变化的能力,以及提升思想道德品质等综合素质具有不可替代的作用。  相似文献   

目标设置教学模式在冰上课中的实验研究     

王贺 《冰雪运动》2015,(3):73-76

目标设置教学模式是将冰上课的总体教学目标分解、细化成每一节冰上课的课时目标,学生们在教学中目标明确,热情高涨,会较为顺利地掌握冰上技能.对绥化学院的学生在冰上课中进行目标设置教学模式的教学实验,结果显示教学效果显著.总结出激发学生学习兴趣和自觉性、利于学生获得成功体验和促进学生运动技能的形成等积极效应;并提出目标设置要明确、适度、合理,教师要及时监督、反馈,教学中要合理评价、适时激励等目标设置教学模式中应注意的问题,为冰上课教学改革提供参考依据.  相似文献   

速度轮滑在高校体育教学中的地位与作用     

吕慧鹏 《冰雪运动》2015,(4):34-37

速度轮滑作为一种体育竞技项目,深受广大青少年的喜爱,由于其具有一定的危险性影响了其在高校体育教学中应有的教学地位.教学实践表明,速度轮滑教学对大学生身心健康具有积极的影响,能增强体魄、活跃业余生活,缓解了大学生的心理压力,提高思维的灵活性,提高竞争的意识;高校开设速度轮滑课程能增加体育教学的场地,促进体育教师一专多能,提高体育教学的器材多样化,丰富体育教学内容,对高校体育教学模式、内容、方法和手段具有优化的促进作用.  相似文献   

Exploring mechanisms of rapid automatized naming to arithmetic skills in Chinese primary schoolers     

Yiji Wang  Xiaolin Ye  Ciping Deng 《Psychology in the schools》2020,57(4):556-571

Rapid automatized naming (RAN) is associated with children's arithmetic performance, which is multifactorial by nature and consists of arithmetic fluency, arithmetic procedure, and word problems. Yet, it is unclear whether RAN can predict all key aspects of arithmetic skills independently and what cognitive mechanisms may explain this relation. Using a sample of Chinese primary school students (N = 170), results showed that while RAN was associated with all key aspects of arithmetic skills, the relations of RAN–arithmetic procedure and RAN–word problems may be dependent on that of RAN–arithmetic fluency. Supporting the processing speed hypothesis, results further suggested that processing speed may underlie the relation between RAN and arithmetic performance. Findings made unique contribution to understanding the effect of RAN on arithmetic performance and cognitive mechanisms that may underpin this association in the context of Chinese culture.  相似文献   

基于单向流固耦合的不同风速下帆板帆翼空气动力性能仿真     

雷晓珊  马勇  蔺世杰 《武汉体育学院学报》2019,53(11):95-100

目的：探究不同风速对帆板帆翼结构以及周围流场的影响。方法：以奥运女子级别的Neil Pryde RS：X帆板帆翼为研究对象，考虑空气动力与结构的流固耦合效应，利用ANSYS Workbench进行单向流固耦合分析。结果：Realizable模型适合计算帆翼周围的流场湍流度，在风速为2m/s时帆翼升阻比最大；随着风速的增大，帆翼面发生变形和振动会导致风激振现象、背风面产生明显的涡脱现象，且帆翼表面应力区增大，全帆的应变逐步增加。结论：不同风速下的帆翼迎风面和背风面的压力分布、帆翼整体空气动力有一定差异，运动员比赛中应该根据当时风况调整帆翼参数。  相似文献   

Key somatic variables associated with,and differences between the 4 swimming strokes     

Alan M. Nevill  Yassine Negra  Tony D. Myers  Senda Sammoud  Helmi Chaabene 《Journal of sports sciences》2020,38(7):787-794

ABSTRACT

This study identified key somatic and demographic characteristics that benefit all swimmers and, at the same time, identified further characteristics that benefit only specific swimming strokes. Three hundred sixty-three competitive-level swimmers (male [n = 202]; female [n = 161]) participated in the study. We adopted a multiplicative, allometric regression model to identify the key characteristics associated with 100 m swimming speeds (controlling for age). The model was refined using backward elimination. Characteristics that benefited some but not all strokes were identified by introducing stroke-by-predictor variable interactions. The regression analysis revealed 7 “common” characteristics that benefited all swimmers suggesting that all swimmers benefit from having less body fat, broad shoulders and hips, a greater arm span (but shorter lower arms) and greater forearm girths with smaller relaxed arm girths. The 4 stroke-specific characteristics reveal that backstroke swimmers benefit from longer backs, a finding that can be likened to boats with longer hulls also travel faster through the water. Other stroke-by-predictor variable interactions (taken together) identified that butterfly swimmers are characterized by greater muscularity in the lower legs. These results highlight the importance of considering somatic and demographic characteristics of young swimmers for talent identification purposes (i.e., to ensure that swimmers realize their most appropriate strokes).  相似文献