水泥粉煤灰固化滩涂淤泥的强度与固化机理研究     

金裕民  郑旭卫  蔡纯阳  王国才  沙玲 《科技通报》2015,(5)

为进一步揭示滩涂淤泥固化土的强度特性及其影响因素,对以沿海滩涂淤泥为原料土、水泥-粉煤灰作为主固化剂配置固化而成的滩涂淤泥固化土的强度特性与固化机理进行了试验研究。通过无侧限抗压强度试验,详细探讨了水泥、粉煤灰、减水剂、石灰、石膏、三乙醇胺、硫酸钠、氯化钠等主固化剂和外掺剂对滩涂淤泥固化土强度特性的影响,分析了固化剂和外掺剂对提高固化土强度的机理。结果表明:龄期以及水泥、减水剂、石灰、石膏、粉煤灰、三乙醇胺、硫酸钠和氯化钠等的掺量均对固化土的强度有影响。水泥和粉煤灰掺量越多,固化土的强度越高,而外掺剂,如减水剂、石灰、石膏、三乙醇胺、硫酸钠和氯化钠的掺量存在临界值。在临界值内,固化土的强度随外掺剂的掺量的增加而增加,超过该值后,则随外掺剂掺量的增加而减小。龄期对固化土的强度有较大影响,7 d龄期下的固化土的强度要远小于28 d时的强度。  相似文献   

提升陕西民办高等教育办学水平和综合实力的若干思考     

苟灵生  王兴亮 《佳木斯教育学院学报》2015,(1)

文章对陕西民办高等教育目前存在的问题进行了深入分析,并从培养目标、培养方案、培养体系、培养条件、市场导向的角度提出了提升陕西民办高等教育办学水平和综合实力的对策思考。  相似文献   

Physiological responses in different intensities of resistance exercise – Critical load and the effects of aging process     

Vivian Maria Arakelian  Cássia da Luz Goulart  Renata Gonçalves Mendes  Nuno Manoel de Sousa  Renata Trimer  Solange Guizilini 《Journal of sports sciences》2019,37(12):1420-1428

Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO₂) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La^?]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males.  相似文献   

短跑专项力量训练手段训练效应的实证研究——以拖重物跑为例     

王蓓  谢慧松  刘少飞 《武汉体育学院学报》2019,53(8):82-88

研究目的：探究拖重物跑训练手段对短跑运动员的身体素质、途中跑阶段的技术特征及下肢环节肌肉力量的影响，深入认识其对短跑途中跑技术和专项力量的作用机制。研究方法：对14名男子二级左右水平短跑运动员进行为期8周每周3次6%~10% BM负荷的拖重物跑训练，采用高速摄像分析法、等动肌力测试法分析运动员身体素质；支撑阶段髋、膝、踝关节运动学参数和下肢各环节肌肉力量实验前后的变化情况。结果：（1）实验后运动员30m、60m、立定跳远、立定三级跳远等身体素质及专项成绩显著提高；（2）步长、重心水平速度显著性提高，两大腿剪绞平均速度提高、单步时间减少；支撑阶段最小膝、踝角显著降低，角速度提高；（3）髋、膝关节伸/屈肌群PT/BW、AP除膝关节60°/sPT/BW值未见统计学意义，其余各角速度下PT/BW、AP均呈显著性差异，踝关节跖屈肌群各角速度下PT/BW值显著提高，跖屈肌群60°/s速度下AP提高，背屈肌群AP略降低。结论：适宜负荷的拖重物跑训练可显著改善短跑运动员运动素质、提高运动成绩；有利于提高髋关节剪绞-制动力量，使膝、踝关节处于低位超等长"屈蹬"状态；提高了髋、膝关节屈伸肌群快速主动收缩能力及踝关节跖屈肌群退让性快速收缩能力。  相似文献   

上肢康复机器人主动康复训练控制策略     

刘鹏  葛小青  李宇  赵佳欣 《中国科学院大学学报》2019,36(4):570-576

近年来，脑卒中和交通事故造成上肢损伤的人数逐年上升，医疗领域对康复器械的需求越来越大。为满足实际需求，开发以气动人工肌肉为驱动器的4自由度（肩关节外收/内展（被动）、前驱/后伸、肘关节屈曲、腕关节屈曲）可穿戴上肢康复机器人。首先设计上肢康复机器人的结构，并采用气动人工肌肉作为肘关节与腕关节的驱动器。然后针对该上肢康复机器人，研究主动康复训练控制策略，设计两种控制策略。通过穿戴实验验证控制策略的有效性和实际应用价值。  相似文献   

我国男生引体向上“零”分探因:基于三角互证的研究策略     

何素艳  石岩 《武汉体育学院学报》2019,53(10):81-87

我国多数男生引体向上得"零"分，使上肢力量测评出现"地板效应"。采用量化研究和质性研究两种范式提高研究效度。量化研究对学生体质与健康调研数据和监测数据进行方差分析、多重比较和回归分析，结果表明：（1）每5~10年，男生的握力、体重、身高、BMI、引体向上均值差异显著；（2）年龄、握力、体重、身高、BMI分别显著预测引体向上成绩，体重和握力是影响我国男生引体向上成绩的主要影响因素。质性研究结果表明，引体向上"零"分主要有四个方面的原因：体重增长难挡，力量增长受限，个体认知偏差，社会支持薄弱。结论：我国男生引体向上"零"分的首要原因是体重增长较快，其次，主要肌群绝对力量和耐力增长不足，男生对引体向上的认知有偏差，学校、家长、社会支持较弱；借助政策控制体重、发展肌力、完善测评标准、促进男生积极练习引体向上十分重要。  相似文献   

竞技武术套路运动员力量素质的训练措施分析     

安志超  何英 《中华武术(研究)》2020,(4):109-112

在现代竞技武术比赛中,超强的力量素质对创造优异的运动成绩起着重要作用。本文通过文献资料法、逻辑分析法等方法,针对竞技武术套路的运动特点指导和制定科学合理的力量素质训练方法,旨在使竞技武术套路训练走向更加科学化和规范化的道路,以期促进我国武术事业的发展。  相似文献   

Physical activity and nutrition guidelines to help with the fight against COVID-19     

Kayvan Khoramipour  Aref Basereh  Amirhoseein Ahmadi Hekmatikar  Lindy Castell  Ruheea Taskin Ruhee 《Journal of sports sciences》2021,39(1):101-107

ABSTRACT

As the world is witnessing the epidemic of coronavirus disease 2019, emerging genetics and clinical pieces of evidence suggest a similar immunopathology to those of severe acute respiratory syndrome and Middle East respiratory syndrome. Staying at home to prevent the spread of the virus and consequently being largely inactive is associated with unintended consequences. These can actually enhance the infection risk and exacerbate poor health conditions including impaired immune function. Physical activity is a feasible way of improving health, particularly physical and mental health in a time of social isolation. However, people with certain health conditions in these circumstances may need a special physical activity programme in addition to any exercise they may already be performing via online programmes. This review aims to provide practical guidelines during the COVID-19 quarantine period. We suggest performing aerobic, resistance training, respiratory muscle training and yoga in the healthy, and in those with upper respiratory tract illness, patients with lower respiratory tract illness should be restricted to respiratory muscle training and yoga. In addition, vitamins D and C, omega-3 fatty acids, and regular consumption of fruit and vegetables might be considered as nutritional aids to support the immune system in those affected by COVID-19.  相似文献   

Fatigue increases ankle sprain risk in badminton players: A biomechanical study     

Alexis Herbaut  Julien Delannoy 《Journal of sports sciences》2020,38(13):1560-1565

ABSTRACT

Ankle sprains are the most common injury in regular badminton players and usually occur at the end of a match or training. The purpose of the present study was to examine the influence of fatigue produced by badminton practice on the lower limb biomechanics of badminton players. It was hypothesized that fatigue induces ankle kinematic and lower leg muscle activity changes which may increase the risk of ankle sprain. Ankle kinematics, ankle kinetics and muscles activities of 17 regular badminton players were recorded during lateral jumps before and after an intense badminton practice session. Post-fatigue, ankle inversion at foot strike and peak ankle inversion increased (+2.6°, p = 0.003 and +2.5°, p = 0.005, respectively). EMG pre-activation within 100 ms before foot landing significantly decreased after fatigue for soleus (?23.4%, p = 0.031), gastrocnemius lateralis (?12.2%, p = 0.035), gastrocnemius medialis (?23.3%, p = 0.047) and peroneus brevis (?17.4%, p = 0.036). These results demonstrate impaired biomechanics of badminton players when fatigue increases, which may cause a greater risk of experiencing an ankle sprain injury.  相似文献   

The relative age effect on physical fitness in preschool children     

Rocío Cupeiro  Miguel A. Rojo-Tirado  Cristina Cadenas-Sanchez  Enrique G. Artero  Ana B. Peinado  Idoia Labayen 《Journal of sports sciences》2020,38(13):1506-1515

ABSTRACT

The aim of the present study was to investigate the existence of a relative age effect (RAE) on physical fitness of preschoolers. Anthropometry and physical fitness were assessed in 3147 children (3–5 years old) using the PREFIT battery. Based on the birth year, participants were divided into 3year groups (3-, 4- and 5-years). Within each year group, 4quarter groups were created: quarter 1, preschoolers born from January to March; quarter 2, from April to June; quarter 3, from July to September; quarter 4, from October to December. The MANCOVA analysis revealed a main effect of year group (Wilks’ λ = 0.383; F_10,5996 = 369.64; p < 0.001, η_p ² = 0.381) and of quarter (Wilks’ λ = 0.874; F_15,8276.6 = 27.67; p < 0.001; η_p ² = 0.044) over the whole battery of tests. To the best of our knowledge, this is the first study to report the existence of RAE at the preschool stage. In general, performance improved as the relative age increased (i.e., those born in quarter 1 performed better than those in the other quarters). Individualization strategies should be addressed within the same academic year not only in elementary or secondary years but also in preschoolers.  相似文献