中低氮呋喃树脂的合成   总被引：3，自引：0，他引：3  

刘荣王锐  汪爱军 《大连大学学报》1999,20(6):44-45,57

根据实际生产的需要研究合成了含氮3％以下的脲醛改性呋喃树脂,确定了工艺条件,经筛选加入的添加剂不仅降低树脂中游离甲醇的含量,而且使树脂的强度有所增加．  相似文献   

Collegiate baseball players with more optimal functional movement patterns demonstrate better athletic performance in speed and agility     

Yu-Pin Liang  Yi-Liang Kuo  Hsiang-Chin Hsu  Yen-Ysung Hsia  Ya-Wen Hsu 《Journal of sports sciences》2019,37(5):544-552

Sports injuries are common among baseball players and may result in abnormal movement patterns, increased risks of future injury, and unsatisfactory performance. The Functional Movement Screen (FMS?) has been developed to detect abnormal functional movement patterns and can be used for predicting risks of sports injury. However, whether FMS? scores are associated with athletic performance remains unclear. The goal of this study was to determine the association between functional movements and athletic performance in elite baseball players. Core stability, muscular strength and flexibility of the lower extremities, and FMS?, as well as athletic performance in sprinting, agility, and balance tests were assessed in 52 male collegiate Division I baseball players placed into two groups based on FMS? scores. The high-scoring group demonstrated better athletic performance than the low-scoring group, with a shorter duration of the agility test. No group differences were found in core stability, muscular strength, or muscle flexibility, except for rectus femoris flexibility. Thus, the FMS? score is associated with sprinting and agility performance in elite baseball players. These findings indicate that the FMS? may have a role in predicting athletic performance and thereby help determine the goals of training regimens or return-to-play strategies.  相似文献   

A preliminary evaluation of the associations among functional performance tasks and quality of life in obese and healthy weight youth     

Matthew S. Briggs  Sharon Bout-Tabaku  Jackie Buell  Susan White  Patricia F. Rosenstein 《Journal of sports sciences》2019,37(1):20-28

The associations among lower extremity functional performance and quality of life in obese youth are unknown. The aims of this study were to compare lower extremity strength, lower extremity functional performance, and health related quality of life between obese and healthy-weight youth and evaluate the relationships between lower extremity performance and health related quality of life in obese youth. Twenty obese and 20 age and sex matched healthy-weight youth were recruited. Peak torque of the major lower extremity muscles were measured. Functional performance was measured with single leg hop and single leg balance tests. The Paediatric Quality of Life questionnaire's physical and psychosocial health subscales were used. Paired t-tests and multiple regression analyses were performed. Obese youth demonstrated decreased peak torque in all muscles measured (P < 0.05), poorer functional performance (P < 0.05), and worse physical health related quality of life (P < 0.05) compared to healthy-weight youth. Lower extremity functional performance was associated with aspects of quality of life in the obese group (P = 0.002), but not in the healthy-weight group (P < 0.05). These results may assist in encouraging best practices in the promotion of exercise, physical activity, and quality of life in obese youth.  相似文献   

氯化钠侵蚀环境下固化疏浚土宏微观力学特性试验     

史旦达  汪存石  刘文白  邵伟 《上海海事大学学报》2019,40(4):111-117

为研究固化疏浚土在氯化钠侵蚀环境下的工程特性,以上海市南汇东滩某吹填场地的黏质粉土为试验土料,掺入自制固化剂制备固化疏浚土试块,进行氯化钠浸泡试验,研究氯化钠初始质量浓度和浸泡龄期对试块抗压强度的影响。采用扫描电镜拍摄试块表面微观结构照片;采用Image-Pro Plus (IPP)图像处理技术结合MATLAB分析程序得到与颗粒和孔隙相关的微观结构参数;基于分形理论,研究氯化钠初始质量浓度、分形维数和抗压强度三者之间的宏微观关联。结果表明:试块的抗压强度随着氯化钠初始质量浓度和浸泡龄期的增长而增长;氯化钠初始质量浓度的增加会引起分形维数的变化,进一步影响试块的宏观抗压强度,三者之间存在内在的定量关联。  相似文献   

Multi-joint rate of force development testing protocol affects reliability and the smallest detectible difference     

David Drake  Rodney A. Kennedy  Eric S. Wallace 《Journal of sports sciences》2019,37(14):1570-1581

Isometric tests have been used to assess rate of force development (RFD), however variation in testing methodologies are known to affect performance outcomes. The aim of this study was to assess the RFD in the isometric squat (ISqT) using two test protocols and two testing angles. Eleven participants (age: 26.8 ± 4.5 years, strength training experience: 7.1 ± 3.03 years) completed test and retest sessions one week apart, whereby two test protocols with respect to duration and instructions were compared. Isometric peak force (ISqT^peak) and isometric explosive force (ISqT^exp) tests were assessed at two joint angles (knee flexion angle 100° and 125°). Force-time traces were sampled and subsequently analysed for RFD measures. Average and instantaneous RFD variables did not meet reliability minimum criteria in ISqT^peak at 100° or 125°. The ISqT^exp test at 100° met reliability criteria in the RFD 0–200 and 0–250ms variables. The ISqT^exp test at 125° met reliability criteria in the RFD 0–150, 0–200 and 0–250ms variables. Force-time characteristics were optimized at the higher knee joint angle. Average and instantaneous RFD measures obtained using a traditional peak force test do not meet basic reliability criteria. Researchers assessing multi-joint RFD should employ the explosive RFD test protocol as opposed to the traditional isometric peak force protocol.  相似文献   

Acute effects of aerobic exercise performed with different volumes on strength performance and neuromuscular parameters     

Natalia Ribeiro  Carlos Ugrinowitsch  Valéria Leme Gonçalves Panissa  Valmor Tricoli 《European Journal of Sport Science》2019,19(3):287-294

The aim of the present study was to investigate the acute effect of the aerobic exercise volume on maximum strength and strength-endurance performance; and possible causes of strength decrements (i.e. central and peripheral fatigue). Twenty-one moderately trained men were submitted to a maximal incremental test to determine anaerobic threshold (AnT) and maximum dynamic strength (1RM) and strength-endurance (i.e. total volume load [TV]) tests to determine their baseline strength performance. Following, subjects performed six experimental sessions: aerobic exercise sessions (continuous running at 90% AnT) with different volumes (3?km, 5?km or 7?km) followed by 1RM or strength-endurance test in the 45° leg press exercise. Maximum voluntary isometric contraction (MVIC), voluntary activation (VA) level, contractile properties, and electromyographic activity (root mean square [RMS]) of the knee extensor muscles were assessed before and after aerobic exercises and after strength tests. TV was lower after 5?km and 7?km runs than in the control condition (12% and 22%, respectively). Additionally, TV was lower after 7?km than 3?km (14%) and 5?km (12%) runs. MVIC, VA, RMS, and contractile properties were reduced after all aerobic exercise volumes (～8%, ～5%, ～11% and ～6–14%, respectively). Additionally, MVIC, VA, and contractile properties were lower after strength tests (～15%, ～6%, ～9–26%, respectively). In conclusion, strength-endurance performance is impaired when performed after aerobic exercise and the magnitude of this interference is dependent on the aerobic exercise volume; and peripheral and central fatigue indices could not explain the different TV observed.  相似文献   

职业需求视角下体能训练的理论探讨     

李文娟 《体育科技文献通报》2020,(1):8-9

随着近几年来我国经济社会的进一步发展,我国各个行业和各个领域的发展速度也在进一步加快,企业的数量在逐年增多,而这产生的直接影响就是社会上的用工量不断增加。特别是随着近几年来,我国社会分工愈发多样化和细化,传统的人才就业和招聘形势已经发生了很大的变化,岗位对人才的要求也愈发细致,对员工专业化素质的要求越来越高。我国经济社会不断发展带来的影响除了经济愈发繁荣之外,还会给人们的就业和工作带来影响,员工的工作压力越来越大,近几年来由于长期工作压力过大而导致的事故频频发生,甚至曾经发生过此现象,该问题的一个重要原因就是员工的个人体能和身体素质不达标,无法适应高强度的工作需要。所以在我国的人才培养工作中,需要考虑到人才未来的工作需求,对其开展体能训练,本文就从职业需求的角度出发,探究人才体能训练的模式和方法,促进人才素养的提升。  相似文献   

力量训练对高中100米项目特长生专项成绩的影响分析——以滕州二中为例     

马伟 《体育科技文献通报》2020,(2):148-149

高中生现阶段正处于身体的发育期,如何在这一阶段强化百米项目特长生的整体训练,提升整体成绩,成为高中短距离跑步项目教练员不断思考的问题。现阶段,在百米特长生专项训练中,整体过于关注成绩本身,忽视了专项力量训练对于特长生的意义。基于此,本文以滕州市第二中学30名体育特长生做为实验对象,以专项力量训练对100M跑中对成绩的影响因素为研究内容,将其分成实验组和对照组,每组各15人,进行为期10周内训练的成果进行测试,对测试的结果进行分析,发现力量训练与高中100米项目特长生专项成绩之间的关系。  相似文献   

基于100米跑突破10秒运动员时空分布的100米跑发展格局分析     

孙民康  龚丽景 《体育科技文献通报》2020,(4):71-77

目的:了解100米跑突破10秒运动员时空分布特征,探究世界100米跑发展趋势及实力格局演变。方法:利用国际田联官方网站、维基百科整理突破100米跑10秒运动员的突破时间、人数、所属国家、所属大洲及运动员跑进10秒的次数。基于空间和时间两个维度进行描述性统计和回归分析。结论:(1)截止2018年12月31日,共有分布于5个大洲27个国家的136名运动员完成100米跑突破10秒。(2)100米跑突破10秒运动员空间分布极不均衡,最多的北美洲,突破10秒屏障的运动员有92名,最少的南美洲人突破人数为0,美国、牙买加突破人数分别为55、20、10、8、6,合计占比72.79%。(3)20世纪80年代之前只有个别运动员突破10秒,人数上没有取得大突破,20世纪80年代之后,新增突破人数不断增加,且增加速度逐渐加快。(4)北美洲100米跑的综合实力和未来潜力均领先其他大洲,其霸主地位短期内无法撼动;21世纪10年代之前,非洲综合实力仅次于美国,处于第二集团,欧洲处于第三集团;21世纪10年代,欧洲实力超越非洲,与非洲共同跻身第二集团;同时,亚洲稳步提升,进入第三集团,大洋洲和南美洲实力最弱。(5)2005年之前,美国"一枝独秀",特立尼安达和多巴哥、尼日利亚实力较强;2005-2016年,牙买加和美国"二超争霸",遥遥领先其他国家;2016-2018年,100米最高水平竞争进入"一超(美国)多强(牙买加、英、法、南非)"时代,新时期,各100米强国实力层级越来越分化,层级变多,中间集团竞争异常激烈,格局变化速度越来越快。  相似文献   

21世纪以来中日青少年 体力促进政策比较分析及启示          下载免费PDF全文

李晓晨 《河北体育学院学报》2020,34(4):39-44

青少年的健康水平关乎国家的未来,面对我国青少年体力不足、体质持续下滑的现实问题,日本经验或可借鉴。首先,梳理了21世纪以来中日两国发布的青少年体力促进政策,并通过比较发现：中日两国都重视学校、家庭、社会等多元主体参与,都建立了完善的青少年体力评估制度,但日本更注重饮食教育,且课外体育活动方式更多样。认为,我国应该提高对青少年体育教育的重视程度,加大政策法规的制定和落实力度,在实践层面进一步完善家庭、学校、社会、政府四方联动,加强青少年科学饮食教育和青少年体育参与的社会支持。旨在为提高我国青少年健康水平提供依据。  相似文献