山地森林—干旱河谷交错带表层土壤侵蚀率与土壤物理性质的关系   总被引：1，自引：0，他引：1  

何淑勤  宫渊波  郑子成  王玲 《资源科学》2013,35(4):824-830

采用野外调查与室内分析相结合的方法,研究了山地森林-干旱河谷交错带表层土壤侵蚀率及其与土壤物理性质的关系.结果表明:岷江上游干旱河谷区不同植被条件下表层土壤侵蚀较为严重,平均土壤侵蚀率为27.58％.土壤侵蚀率与土壤结构破坏率(SPBR)极显著正相关;与土壤有机质含量、＞0.25mm水稳性团聚体含量(WSA)、湿筛后团聚体平均重量直径(MWD)和几何平均直径(GMD)显著负相关.土壤侵蚀率分别与土壤有机质含量、结构破坏率、湿筛后团聚体MWD和GMW、＞0.25mm水稳性团聚体含量建立的回归方程预测效果相对较好.  相似文献   

黄河上中游降水正态性与稳定性分析   总被引：1，自引：0，他引：1  

夏权  马敏劲  李艳  张永泽 《资源科学》2013,35(7):1455-1462

基于1961-2011年黄河上中游45站年、月降水量资料,利用偏态(峰度)系数、变差系数、皮尔逊Ⅲ型分布等统计方法,对该区降水量进行正态性和稳定性分析,并拟合不同保证率下的年降水量及百年重现期.结果表明:年降水量有33.3％的台站未通过正态性检验.月降水量冬季各月几乎所有台站均不服从正态分布,夏季各月降水量正态性略好,但未通过正态性检验站数也在60％以上.对降水量进行非线性变换后的正态化效率达95.4％,其中1月、2月、3月平方根法优于立方根法,11月、12月反之,其余月份基本相同.降水稳定性冬季最差,春季次之,夏、秋季最好,从区域看,青海高原东部降水稳定性最好,河套北部最差.P=50％和P=80％保证率下的降水量自东南向西北递减,前者接近平均值,后者远低于平均值.有21个台站年降水量历史极大值突破了百年一遇,与年降水量未通过正态性检验的台站基本对应,主要集中在陇中-陇东-宁夏南部地区,该区域属于气候变化的敏感区和极端降水事件的多发区.  相似文献   

零借阅率的SPSS Statistics分析——以南昌大学图书馆为例     

夏勍 《情报探索》2013,(12):115-118

采用SPSS Statistics软件中的聚类分析法,对南昌大学图书馆流通书库2009-2011年零借阅的图书品种进行分析,以年均入藏量和零借阅率为统计变量,以中图类目（共35类,包含T大类下二级类目）为标注个案,进行系统聚类和OLAP立方体分析,据此提出了读者热衷型、读者关注型和读者漠视型图书的概念,并探讨了降低零借阅率的方法.  相似文献   

瑞士球核心稳定性训练对心肺及其调节功能影响的实验研究     

王艳霞  赵敬国 《吉林体育学院学报》2013,(2):87-90

观察为期四周瑞士球核心稳定性训练（球上跪姿抬臂）对普通女大学生心率变异性和最大吸氧量的影响规律。利用芬兰产的POLAR S810i遥测心率表及瑞典产的MONARK 839E有氧功率车为工具,测量比较了四周瑞士球核心稳定性训练前后18名普通女大学生（实验组10人,对照组8人）心率变异性指标、最大吸氧量以及血压、心率的变化。经过四周锻炼,实验组的10名受试者均能在瑞士球上维持跪姿抬臂标准姿势5min。实验组最大吸氧量绝对值呈现极显著性增加（P〈0.01）,相对值呈现显著性增加（P〈0.05）、舒张压、心率则出现了显著性降低（P〈0.05）;SD、RMSSD以及HF都出现了显著性增加（P〈0.05）。对照组各项指标均未出现显著性差异（P〉0.05）。四周瑞士球核心稳定性训练可显著提高心肺功能,降低安静时交感神经的紧张性,增加副交感神经的紧张性。提示该训练方法对强身健体、缓解压力可能有显著性作用。  相似文献   

Physiological efficiency of constant power output at varying pedal rates     

E.G. Merrill  J.A. White 《Journal of sports sciences》2013,31(1):25-34

Abstract

The study investigated the absolute and relative (% maximal) physiological demands of constant power output at three pedal rates chosen to incorporate the range used by racing cyclists. Following the assessment of maximal exercise capabilities utilizing a recently developed racing cycle ergometry system, ten highly trained racing cyclists undertook a randomized sequence of work bouts at low (70.0 ± 1.1), medium (94.8 ± 0.8) and high (126.5 ± 1.1) pedal rates per minute at constant power output under an unloaded (free wheel) condition and under a loaded (196.2 ± 8.0 W) condition which demanded approximately 75% VO₂ max. In both the unloaded and loaded conditions absolute cardiorespiratory demands of work at the highest pedal rate were significantly higher than those at the low and medium pedal rates (P<0.05). Similarly, the relative (% max) cardiorespiratory demands of unloaded work at the highest pedalling rate were significantly greater that at low and medium pedal rates (P < 0.05). There were clear, but nonsignificant trends of elevated relative cardiorespiratory demands during loaded work at the highest pedal rate, compared with low and medium pedal rates. Furthermore, net muscular efficiency demonstrated a significant decline (P<0.01) at the highest pedalling rate (21.2%) compared with the medium (24.0%) and low (25.6%) pedalling rates, confirming that metabolic economy of constant power output declined with increased pedalling rate under simulated racing cycling conditions.  相似文献   

Validation of a single-stage submaximal treadmill walking test     

Lindsey Waddoups  Jennifer Fallon  Edward Heath 《Journal of sports sciences》2013,31(5):491-497

Abstract

The single-stage treadmill walking test of Ebbeling et al. is commonly used to predict maximal oxygen consumption ([Vdot]O_2max) from a submaximal effort between 50% and 70% of the participant's age-predicted maximum heart rate. The purpose of this study was to determine if this submaximal test correctly predicts [Vdot]O_2max at the low (50% of maximum heart rate) and high (70% of maximum heart rate) ends of the specified heart rate range for males and females aged 18 – 55 years. Each of the 34 participants completed one low-intensity and one high-intensity trial. The two trials resulted in significantly different estimates of [Vdot]O_2max (low-intensity trial: mean 40.5 ml · kg^?1 · min^?1, s = 9.3; high-intensity trial: 47.5 ml · kg^?1 · min^?1, s = 8.8; P < 0.01). A subset of 22 participants concluded their second trial with a [Vdot]O_2max test (mean 47.9 ml · kg^?1 · min^?1, s = 8.9). The low-intensity trial underestimated (mean difference = ?3.5 ml · kg^?1 · min^?1; 95% CI = ?6.4 to ?0.6 ml · kg^?1 · min^?1; P = 0.02) and the high-intensity trial overestimated (mean difference = 3.5 ml · kg^?1 · min^?1; 95% CI = 1.1 to 6.0 ml · kg^?1 · min^?1; P = 0.01) the measured [Vdot]O_2max. The predictive validity of Ebbeling and colleagues' single-stage submaximal treadmill walking test is diminished when performed at the extremes of the specified heart rate range.  相似文献   

Energy Cost of Rebound-Running     

Victor L. Katch  John F. Villanacci  Stanley P. Sady 《Research quarterly for exercise and sport》2013,84(2):269-272

Using Sonstroem, Harlow, and Josephs' (1994) expanded version of the Exercise and Self-Esteem Model (EXSEM; Sonstroem &; Morgan, 1989), we explored how 9 older adults (6 women and 3 men, aged 65–72 years) involved in a resistance training program experienced and perceived changes in physical self-worth (i.e., improved strength, functional competency, physical condition, and body satisfaction). We conducted three in-depth interviews with each participant over the course of the program. In individual log books, participants recorded the weight lifted and the number of repetitions for each exercise. Our findings showed the course of changes in physical self-perceptions in these older adults and how actual individual changes in strength performance related to perceived changes in important psychological outcomes.  相似文献   

Peripheral Narrowing among Experienced and Inexperienced Rifle Shooters under Low- and High-Stress Conditions     

Daniel M. Landers  Wang Min Qi  Patricia Courtet 《Research quarterly for exercise and sport》2013,84(2):122-130

Abstract

This study examined Easterbrook's (1959) hypothesis that performance on a primary task would improve or at least be maintained with increased levels of arousal, while performance on a secondary task would decrease. To test this hypothesis, the performance of 20 collegiate rifle shooters (10 experienced, 10 inexperienced) on a primary target shooting task and a secondary auditory task were compared while shooting under low- and high-time stress conditions. Heart rate results, but not a self-report anxiety measure, provided evidence for the effectiveness of the stress manipulation. The results primarily supported Easterbrook's hypothesis. There were no differences in secondary task performance between experienced and inexperienced shooters. However, subjects who first underwent high time stress followed by low (H-L) shot better than those given the reverse order (L-H). These findings are discussed in relation to the attention demands of self-paced sports as well as the transfer effects of stress.  相似文献   

Cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children 6–8 years of age     

Niina Lintu  Tuomo Tompuri  Anna Viitasalo  Sonja Soininen  Tomi Laitinen  Kai Savonen 《Journal of sports sciences》2013,31(7):652-659

Abstract

We investigated cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children. The participants were a population sample of 425 children (204 girls, 221 boys) aged 6–8 years. Heart rate (HR) and systolic blood pressure (SBP) were measured from the beginning of pre-exercise rest to the end of recovery period. We provided reference values for peak workload and changes in HR and SBP during and after maximal exercise test in girls and boys. Girls had a lower cardiovascular fitness, indicated by peak workload per body weight [mean (2 s) 2.7 (0.9) vs. 3.1 (1.0) W · kg^–1, P < 0.001] and lean mass [mean (2 s) 3.5 (0.9) vs. 3.8 (1.0) W· kg^–1, P < 0.001] than boys. Plateau or decline in SBP close to the end of the test was found in about third of children and was considered a normal SBP response. Girls had a slower HR decrease within 2 min after the test than boys [mean (2 s) 53 (18) vs. 59 (22) beats · min^–1, P < 0.001]. The results are useful for physicians and exercise physiologists to evaluate cardiovascular fitness and haemodynamic responses to exercise in children and to detect children with low exercise tolerance or abnormal haemodynamic responses to exercise.  相似文献   

Reliability and validity of the Yo-Yo intermittent recovery test level 1 in young soccer players     

Dieter Deprez  Aaron James Coutts  Matthieu Lenoir  Job Fransen  Johan Pion  Renaat Philippaerts 《Journal of sports sciences》2013,31(10):903-910

Abstract

The present study investigated the test-retest reliability from the Yo-Yo IR1 (distance and heart rate responses), and the ability of the Yo-Yo IR1 to differentiate between elite and non-elite youth soccer players. A total of 228 youth soccer players (11–17 years) participated: 78 non-elite players to examine the test-retest reliability within 1 week, added with 150 elite players to investigate the construct validity. The main finding was that the distance covered was adequately reproducible in the youngest age groups (U13 and U15) and highly reproducible in the oldest age group (U17). Also, the physiological responses were highly reproducible in all age groups. Moreover, the Yo-Yo IR1 test had a high-discriminative ability to distinguish between elite and non-elite young soccer players. Furthermore, age-related standards for the Yo-Yo IR1 established for elite and non-elite groups in this study may be used for comparison of other young soccer players.  相似文献