城市化与社区教育的关系初探

长期以来,我国“城乡二元制经济结构”已成为影响国家经济发展与社会和谐的一个重要因素。十五大以来,党中央出台一系列战略性的重要举措“千方百计遏制日益扩大的城乡收入差距”,其中,最引人注目的是推进城市化战略。从世界一些发达国家的城市化情况看,城市化决不是简单地把农村变成城市,把农民变成城市居民,而是在大力发展第二、三产业,加快农业产业化步伐的同时,努力提高农村居民的文化素质,使农村的生产生活方式和物质文化生活以及农民的文化教育程度,达到城市的水平。因为人口素质的高低决定了一个城市发展的空间和规模限度,因此,城市…     

略论抗日战争的历史地位和作用

抗日战争是近代中国人民反抗外敌入侵第一次取得胜利的民族解放战争;是弱国战胜强国的光辉典范;中国人民的抗日战争是世界反法西斯战争重要组成部分.中华民族为世界反法西斯战争作出了巨大的民族牺牲和历史贡献.伟大的抗日战争,提高了中国的国际地位,振奋了中华民族的自尊心和自信心,是中华民族重新奋起的新起点.     

Correspondence

Abstract

Selected kinematic variables of the foot segments and the metatarsophalangeal (MTP) joint were investigated in relation to sprinting performance among 100 m sprint athletes at the 2000 Summer Olympic Games. It was hypothesized that the kinematics of the MTP joint, and forefoot and rearfoot segments, are related to sprint performance for both male and female athletes. Kinematic sagittal plane data were collected using two digital video cameras recording at 120 fields per second. It was determined that faster male sprinters experienced higher maximal rates of MTP extension, and faster female sprinters touch down with higher posterior sole angles and take off with lower posterior sole angles.     

The conceptual process of skill progression development in artistic gymnastics

In this study, we examined the methods used and knowledge required by 16 elite men's gymnastic coaches in the development of skill progressions. Following in-depth interviews, a conceptual model representing the process of skill progression development was generated. We found that: (1) elite gymnastic coaches developed skill progressions through experimental practice, reflection and critical inquiry; (2) the development of skill progressions was underpinned by the coaches acquiring a mindset based on four further sub-components (i.e. skill progression refinement, current coaching knowledge, mental imagery and biomechanical understanding); and (3) coaches identified the importance of replication of the spatial and temporal characteristics of the final skill. The results are consistent with task analysis, reflective practice and the principle of specificity. Practically, these findings suggest the need to develop coaches with a more objective approach to skill progression development and a greater understanding of the controlling mechanisms inherent in such practices.     

The influence of the vaulting table on the handspring front somersault

The traditional “horse” was replaced by a new vaulting “table” in artistic gymnastics competitions in 2001.The aim of this study was to determine whether the table led to a change in vaulting technique. This was achieved by comparing three-dimensional video-based analyses (50 Hz) of selected biomechanical discrete and continuous variables across four elite male gymnasts performing a series of handspring front somersault vaults on the traditional horse and the new table. Individual joint and inter-segment coupling (continuous relative phase) were used to quantify techniques used on the two apparatuses. Differences were attributed in part to the design and construction of the new table. No differences were observed for the approach and take-off from the board. Significant differences in hip flexion at board take-off and strike angle on the table were observed. One of the effects of the latter was an increase in vertical take-off velocity compared with the horse. Individual strategies were observed in hip and shoulder coordination patterns that were obscured when group data were considered. Close monitoring of the evolution of skill on this new apparatus is paramount for gymnastics coaching, and further studies of current elite competitive vaulting techniques are required.     

Influence of longswing technique on the kinematics and key release parameters of the straddle Tkachev on uneven bars

Tkachev on uneven bars is a release and re-grasp skill performed using variations of preparatory longswing techniques; the reasons why different techniques are chosen remains unclear. This study examined kinematic and key release parameters specific to three distinct techniques with the aim of understanding the relative benefits of each. During two international artistic gymnastics competitions six arch, straddle and pike longswings preceding the straddle Tkachev were recorded using twin video cameras. Calibration and movement images were digitised and reconstructed using 3D DLT. Shoulder and hip angular kinematics, angular momentum and key release parameters were compared between techniques. In the arch longswing, the first and second hip functional phases began significantly earlier than the straddle or pike. No significant differences were established for release parameters although large effect sizes for horizontal release velocity and angular momenta about the mass centre and bar were reported between the arch and other two variants. Therefore, the arch variant may provide the opportunity to develop more complex combinations following the Tkachev. Providing insight into mechanical advantages of specific longswing techniques, and highlighting those that elicit desirable characteristics offers the potential to provide coaches with objective data on technique selection and ultimately skill development.     

Implications of intra-limb variability on asymmetry analyses

The aim of this study was to investigate the effect of intra-limb variability on the calculation of asymmetry with the purpose of informing future analyses. Asymmetry has previously been quantified for discrete kinematic and kinetic variables; however, intra-limb variability has not been routinely included in these analyses. Synchronized lower-limb kinematic and kinetic data were collected from eight trained athletes (age 22 ± 5 years, mass 74.0 ± 8.7 kg, stature 1.79 ± 0.07 m) during maximal velocity sprint running. Asymmetry was quantified using a modified version of the symmetry angle for selected kinematic and kinetic variables. Significant differences (P < 0.05) between left and right values for each variable were calculated to indicate intra-limb variability relative to between-limb differences. Significant asymmetry was present in only 39% of kinematic variables and 23% of kinetic variables analysed. Large kinetic asymmetry values (>90%) were calculated for some athletes that were not significant, due to large intra-limb variability. Variables that displayed significant asymmetry were athlete-specific. Findings highlight the potential for misleading results if intra-limb variability is not included in asymmetry analyses. The exclusion of asymmetry scores for variables not displaying significant asymmetry will be useful when calculating overall asymmetry for different participants and could be applied to future running gait analyses.     

权力、政绩与职位关系之探析

政治体制改革的核心问题就是权力问题。权力、政绩、职位三者间的交互关系在实践中左右着我国政治体制的有效运转,而职位的存在为权力与政绩的交互作用提供了最佳的场域。全文从权力、政绩、职位三者间的交互关系的视野对腐败问题的成因进行分析、探究。     

技术创新专用性投资与治理机制

资产专用性理论把企业契约的不完全性作为逻辑分析的起点,把专用性资严投资当成逻辑的核心变量,把治理机制安排看成是逻辑的结果,整个理论在契约不完全一资产专用性一企业所有权安排这一分析框架中来运行.运用资产专用性理论分析框架,分析技术创新专用性投资不足的本质原因,提出技术生命周期不同阶段技术创新投资的专用性与其治理机制应该相互匹配.     

Biomechanical similarities of progressions for the longswing on high bar

Based on specificity of training and biomechanical analysis, the aim of this study was to develop a method to rank selected progressions for learning the longswing on high bar. Four members of the Men's National Gymnastics Squad were recorded (50 Hz) performing three series of five longswings and eight progressions. Real world co-ordinates from the digitized data were determined using two-dimensional direct linear transformation. Biomechanical similarity between the functional phases of the longswing and the corresponding phases of the progressions were calculated. The functional phases were described as a hyperextension to flexion of the hip and hyperflexion to extension of the shoulder joints as the gymnast passed underneath the bar. Using a combined score of 'Difference' and movement 'Variability' a 'Specificity score' was calculated for hip and shoulder angular displacements and velocities. An overall score based on the average of the four scores provided a ranked list of progressions based on their similarity to the target skill. The progression that showed the greatest similarity to the biomechanics of the longswing, and was therefore ranked first, was the chalked bar pendulum swing. The least similar progression, and, therefore, eighth ranked, was the chalked bar bent knee longswing. The hip kinematics were found to contribute most to the overall differences because the performance requirements of these progressions emphasize an increase in hip flexion during the ascending phase. The method described provides a means to quantify and rank progressions based on their kinematic similarity to the longswing.