网球正、反手切削球"拍臂角"讨论及其教学辅助控制装置设计研究   总被引：1，自引：0，他引：1  

段文义 《首都体育学院学报》2006,18(1):79-81

采用图像(片)资料分析对比、文献资料研究、实验验证、数理统计等方法,对网球正、反手切削球技术进行分析。结果发现,网球运动切削球技术对“球拍控制”具有非常显著的特征。依据“运动学习过程”理论,探索性的提出“拍臂角”概念,并进一步探讨切削球“拍臂角”变化规律,构思设计了简便实用的“拍臂角”教学辅助控制装置。  相似文献   

光电耦合器及其应用     

唐红 《贵阳金筑大学学报》2006,(4)

半导体光电耦合器现已发展成为一类特殊的半导体隔离器件。它体积小、寿命长、无触点、抗干扰、能隔离,并具有单向信号传输等特点。本文介绍了光电耦合器的特点、典型结构及应用,以及简易测试方法。  相似文献   

肌肉力量连续统一体理论及其在力量训练中的应用研究   总被引：2，自引：0，他引：2  

臧秋华 《沈阳体育学院学报》2005,24(4):76-78

通过对肌肉力量中主动张力和被动张力的关系所作的深入探讨,认为肌肉在不同收缩形式和收缩速度下,肌力的组成以及各组成成分之间既相互区别又相互联系,形成一个连续统一体。这为力量训练理论与实践研究开辟了新的思路。  相似文献   

Environmentally-induced stone decay: the cumulative effects of crystallization–hydration cycles on a Lincolnshire oopelsparite limestone     

Belinda J. Colston  David S. Watt  Helen L. Munro   《Journal of Cultural Heritage》2001,2(4)

An investigation has been undertaken at St Andrew’s church, Walpole St Andrew, Norfolk, to establish the underlying causes of the observed stone decay to the upper parts of the six stone piers. The stone decay was first recorded in the early 1930s. The salt-contaminated masonry within the church has been shown to undergo severe salt decay during the summer, with little damage occurring over the winter months. The south aisle piers have been shown to decay 2.5 times faster than the north aisle piers. Although crystallization–hydration cycles have been identified, the rate of decay is at its greatest when the cycling is relatively infrequent. This was not the expected trend. Furthermore, it has been shown that during extended periods where the ambient relative humidity is less than 75%, the rate of decay reaches a maximum. It is the length of this ‘drying’ period that apparently has the greatest influence on the rate of decay and could explain the significant difference in the rate of decay between the south and north aisle piers. The results have serious implications for passive conservation, where it is often recommended to lower the ambient relative humidity to well below the equilibrium relative humidity of the salt contaminant, to avoid crystallization–hydration cycles. Since, at the time of building, the church was situated on the coast, it is possible that the sodium chloride contamination occurred during the building process (1440–1520), particularly since the area was prone to sea-flooding at this time. Alternatively, the salt could have been applied as a treatment during the general restoration of 1897. Whatever the source of the salt, it seems likely that the ambient environment was changed by the insertion of a sealed floor in 1897, which could account for the onset of the salt decay.  相似文献   

社交媒体用户消极使用行为：多源数据融合视角     

范春竹  邓小昭  韩毅 《图书情报工作》2022,66(15):76-85

[目的/意义]通过融合不同来源数据的方式探索社交媒体用户消极使用行为影响因素,为用户健康合理地可持续使用社交媒体提供理论支撑,并为平台改进服务提供参考信息。[方法/过程]对访谈数据进行三级编码,结合爬虫获取的包含部分受访者数据的用户行为轨迹数据分析社交媒体用户消极使用原因,构建社交媒体用户消极使用行为影响因素模型。[结果/结论]通过多源数据融合能够解决单一来源数据有效性不足问题。研究发现外部环境因素(任务情境、信息过载、社交过载、不良言论)和平台因素(系统功能、品牌形象、付费服务)通过内部个人因素(信息需求、认知差异、负面情绪、使用成本、使用习惯、隐私关注)影响用户使用社交媒体,产生潜水、屏蔽、间歇使用、转移、退出和抵制等不同程度的消极使用行为,一定程度上反映了用户作为弱势对象在技术环境下的自我保护。  相似文献   

检索工具功能的延伸与扩展   总被引：1，自引：0，他引：1  

陈大辉 《图书馆杂志》2006,25(9):49-50,76

文章对实现检索工具衍生功能的操作过程进行了描述，并据此探讨了它们的基本特征及其影响。  相似文献   

工程服务中心:构建工程创新实践教育的支撑体系——上海交通大学国家双创示范基地案例分析     

付宇卓  李翠超  董德礼  田夏 《高等工程教育研究》2018,(6):39-46

在高等工程教育中学生自主实践创新教学活动极为重要,而当前高校普遍缺乏创新支撑服务平台及灵活的实践服务模式,学生在自主开展实践教学活动时常常需耗费大量的时间和成本去完成创新项目所需资源的准备;一轮轮的教学实践环境建设,由于多围绕课程、学科的培养体系投入,造成设备利用率低,与学生强烈的创新实践需求形成尖锐矛盾。本文基于当前国家双创示范基地中学生创新中心建设,创造性提出以工具借出、设备借用、远程加工、设计IP撮合等为特点的特色服务模式,持续大量地为学生提供基本器具资源使用和加工服务。围绕学生需求提供"创新实践图书馆"式的服务,为学生创造创新实践的服务环境。本文就设备借出、3D打印等具体工程服务分中心建设的内容、目标和服务模式,阐述了这类创新实践服务中心的建设模式,需要解决的问题和实施思路。实践证明,建设工程服务中心能有效解决设备利用率问题,更好地培养大规模勇于投身实践的创新人才,为高校创新人才培养模式开辟新途径。  相似文献   

Seeking Nettle Textiles – Utilizing a Combination of Microscopic Methods for Fibre Identification     

Jenni A. Suomela  Krista Vajanto  Riikka Räisänen 《文物保护研究》2018,63(7):412-422

Bast fibres have been commonly used as a textile material in Northern Europe since Neolithic times. However, the process of identifying the different species has been problematic, and many important questions related to their cultural history are still unanswered. For example, a modified Herzog test and the presence of calcium oxalate crystals have both been used in identification. In order to generate more reliable results, further research and advancement in multi-methodological methods is required. This paper introduces a combination of methods which can be used to identify and distinguish flax (Linum usitatissimum), hemp (Cannabis sativa), and stinging nettle (Urtica dioica). The research material consisted of reference fibres and 25 fibre samples obtained from 12 textiles assumed to be made of nettle. The textiles were from the Finno-Ugric and Historical Collections of The National Museum of Finland. The fibre samples were studied by observing the surface characteristics and cross sections with transmitted light microscopy, and by using a modified Herzog test with polarized light, in order to identify the distinguishable features in their morphological structures. The study showed that five out of 25 samples were cotton, 16 nettle, one flax, and one hemp. Findings from two samples were inconsistent. The results show that it is possible to distinguish common north European bast fibres from each other by using a combination of microscopic methods. Furthermore, by utilizing these combined methods, new and more reliable information could be obtained from historical ethnographic textiles, which creates new vistas for the interpretation of their cultural history.  相似文献   

教师职业研究的新视角——情绪工作研究探析     

王艳华 《桂林师范高等专科学校学报》2011,25(2):107-110

首先从情绪工作的定义、特征出发分析教师是属于高情绪工作者,之后阐述情绪工作的调节策略以及影响调节策略的相关因素,以期为研究教师职业提供一个新视角。  相似文献   

Wearable skin-like optoelectronic systems with suppression of motion artifacts for cuff-less continuous blood pressure monitor     

Haicheng Li  Yinji Ma  Ziwei Liang  Zhouheng Wang  Yu Cao  Yuan Xu  Hua Zhou  Bingwei Lu  Ying Chen  Zhiyuan Han  Shisheng Cai  Xue Feng 《国家科学评论(英文版)》2020,7(5):849

According to the statistics of the World Health Organization, an estimated 17.9 million people die from cardiovascular diseases each year, representing 31% of all global deaths. Continuous non-invasive arterial pressure (CNAP) is essential for the management of cardiovascular diseases. However, it is difficult to achieve long-term CNAP monitoring with the daily use of current devices due to irritation of the skin as well as the lack of motion artifacts suppression. Here, we report a high-performance skin-like optoelectronic system integrated with ultra-thin flexible circuits to monitor CNAP. We introduce a theoretical model via the virtual work principle for predicting the precise blood pressure and suppressing motion artifacts, and propose optical difference in the frequency domain for stable optical measurements in terms of skin-like devices. We compare the results with the blood pressure acquired by invasive (intra-arterial) blood pressure monitoring for >1500 min in total on 44 subjects in an intensive care unit. The maximum absolute errors of diastolic and systolic blood pressure were ±7/±10 mm Hg, respectively, in immobilized, and ±10/±14 mm Hg, respectively, in walking scenarios. These strategies provide advanced blood pressure monitoring techniques, which would directly address an unmet clinical need or daily use for a highly vulnerable population.  相似文献