Effect of swimming velocity on arm coordination in the front crawl: a dynamic analysis

We examined the preferred mode of arm coordination in 14 elite male front-crawl swimmers. Each swimmer performed eight successive swim trials in which target velocity increased from the swimmer's usual 3000-m velocity to his maximal velocity. Actual swim velocity, stroke rate, stroke length and the different arm stroke phases were then calculated from video analysis. Arm coordination was quantified by an index of coordination based on the lag time between the propulsive phases of each arm. The index expressed the three coordination modes in the front crawl: opposition, catch-up and superposition. First, in line with the dynamic approach to movement coordination, the index of coordination could be considered as an order parameter that qualitatively captured arm coordination. Second, two coordination modes were observed: a catch-up pattern (index of coordination?=??8.43%) consisting of a lag time between the propulsive phases of each arm, and a relative opposition pattern (index of coordination?=?0.89%) in which the propulsive phase of one arm ended when the propulsive phase of the other arm began. An abrupt change in the coordination pattern occurred at the critical velocity of 1.8?m?·?s^?1, which corresponded to the 100-m pace: the swimmers switched from catch-up to relative opposition. This change in coordination resulted in a reorganization of the arm phases: the duration of the entry and catch phase decreased, while the duration of the pull and push phases increased in relation to the whole stroke. Third, these changes were coupled to increased stroke rate and decreased stroke length, indicating that stroke rate, stroke length, the stroke rate/stroke length ratio, as well as velocity, could be considered as control parameters. The control parameters can be manipulated to facilitate the emergence of specific coordination modes, which is highly relevant to training and learning. By adjusting the control and order parameters within the context of a specific race distance, both coach and swimmer will be able to detect the best adapted pattern for a given race pace and follow how arm coordination changes over the course of training.     

Short-Term Memory Trace Decay in Kinesthetically Monitored Force Reproduction

Abstract

The decay of the memory trace for intervals of 1/2 min., 1 1/2 min., and 4 min. between the test stimulus and the reproduction trial was studied for a force reproduction task in which the amount of movement was very small, .13 in. The subject pushed against a handle attached to the top of a steel bar with the preferred hand. Sixty-three women volunteers from college physical education classes performed the experiment. For Part A all subjects first had four trials in which the reproduction was immediate (the control condition). Then they were divided randomly into three subgroups of 21, and each subgroup was assigned to one of the three retention intervals (experimental conditions) for four more trials. In Part B the whole experiment was repeated. For both absolute and algebraic error, analysis of covariance indicated no significant differences at the .05 level among the experimental conditons. Also, no significant differences were found comparing a condition in Part A with its respective condition in Part B. While there were no significant differences between control and experimental conditions for absolute error, significant differences were found for algebraic error. The algebraic error changed from considerable overestimation upon immediate reproduction to only slight overestimation after a 1/2-min. retention interval.     

Frequency Distributions and Standards of Anthropometric and Physical Performance Measures for College Women

Abstract

Frequency distributions of the records of a random selection of 200 college women in a nonmajor required program on anthropometric and physical performance measures commonly employed in physical education were compared with best-fitting normal curves for the same data. A table of random numbers was used to secure the sample. A percentile table for the various measurements was constructed. It was concluded that various measurements commonly employed by physical educators give a non-normal distribution. Hence, the obtained distribution as found on various measurements in this study does not warrant treating these data as normal.     

基于专利的北京新一代信息技术产业SWOT分析

本文以北京新一代信息技术产业为对象,在传统专利地图的基础上,结合专利授权率、研发能力、专利技术价值、技术机会、技术优势等分析方法,采用国内专利和国际专利数据,对北京发展新一代信息技术产业的优势、劣势、机会、威胁进行了定量与微观层面的分析,在与国内外地区专利情况的对比中明确了发展方向。在此基础上提出了北京发展新一代新兴技术产业的对策。研究结果表明,上述思路和分析方法对于分析我国战略性新兴产业现状与对策也具有指导意义。     

Value transfer in concurrent-schedule discriminations by pigeons

When pigeons are trained on a discrete-trial simultaneous discrimination, some of the value associated with the positive stimulus appears to transfer to the negative stimulus (Zentall & Sherburne, 1994). Pigeons preferred a negative stimulus that had been discriminated from an always-positive stimulus (S+) over a negative stimulus that had been discriminated from a sometimes-positive stimulus (S±). A very different finding (suggestive of transitivity of preference or contrast) was reported by Belke (1992). On concurrent probe tests of stimuli associated with equal variable interval (VI) schedules but originally trained in alternative concurrent pairs (one with a richer schedule, the other with a poorer schedule—VI 20 sec vs. VI 40 sec and VI 40 sec vs. VI 80 sec), the stimulus originally paired with the poorer schedule was preferred. But Belke’s results may have been obtained because the pigeons had been trained to peck the VI 40 sec paired with the poorer schedule and they had been trained not to peck the VI 40 sec paired with the richer schedule. In the present experiment, we avoided this bias by training pigeons on two concurrent schedules in which the tested stimuli both had been associated with the poorer schedule of the pair [A(VI 20 sec) vs. B(VI 80 sec) and C(VI 40 sec) vs. D(VI 80 sec)]. Evidence for value transfer was demonstrated when on probe trials pigeons preferred B over D.     

隋末骁果兵浅探

骁果兵是由隋炀帝在全国范围内招募的勇武豪侠之士组成的一支精锐部队.其最初的目的是为了征辽战争的需要,"雁门之围"之后发展成为一支完全由隋炀帝控制的亲军部队.从骁果兵的待遇、管理及使用等方面来看,它是与原有府兵完全不同的募兵."江都之变"之时,江都的主要军事力量是骁果兵.骁果的发展是隋炀帝加强中央集权的重要措施之一.     

高校实验室安全事故应急管理体系研究

通过对高校实验室安全管理现状的分析,指出目前高校在实验室安全管理应急预案建设中存在的问题。结合浙江工业大学的实际,提出实验室安全事故应急管理体系由应急工作组织系统、预测预警系统、信息报送系统、应急响应系统和后期处置系统组成,同时彰明建立、推广一套科学的实验室安全事故应急管理体系的必要性,以实现高校实验室安全管理。     

江西省企业创新信息服务发展对策

江西省企业对科技政策不了解,与高校和科研机构联系不紧密,严重影响了企业创新能力。而这些问题可以通过适当的信息服务来解决。文章在分析了江西省企业创新信息服务现状的基础上,提出了相应的发展对策。     

图书馆关联数据孵化小组使命、活动及成果分析

梳理图书馆关联数据孵化小组的使命、活动内容及活动成果,以关联数据用例分析为基础,围绕《图书馆关联数据孵化小组最终报告》,深入分析关联数据技术应用面临的挑战、对利益相关者的影响及目前可用的关联资源情况,最后探讨实现关联数据的相关技术以及关联数据未来的发展。