基于系统动力学的移动电子商务产业演化研究

近年来我国移动电子商务产业规模迅速扩大。从系统的角度出发,移动电子商务产业可看作由经济、政策、移动技术和产业链4个相互关联的子系统构成,根据各子系统的内在因果关系,运用Vensim软件构建移动电子商务产业的系统动力学模型;在检验模型有效性的基础上,对我国移动电子商务产业的演化趋势进行仿真,并在政策和技术的不同投入力度场景下分析系统行为的变化。仿真结果表明,在适度的政策引导下,协同移动技术和产业链的发展能有效促进我国移动电子商务产业健康、可持续发展。     

Interpersonal coordination tendencies supporting the creation/prevention of goal scoring opportunities in futsal

Abstract

Research on 1vs1 sub-phases in team sports has shown how one player coordinates his/her actions with his/her opponent and the location of a target/goal to attain performance objectives. In this study, we extended this approach to analysis of 5vs5 competitive performance in the team sport of futsal to provide a performance analysis framework that explains how players coordinate their actions to create/prevent opportunities to score goals. For this purpose, we recorded all 10 futsal matches of the 2009 Lusophony Games held in Lisbon. We analysed the displacement trajectories of a shooting attacker and marking defender in plays ending in a goal, a goalkeeper's save, and a defender's interception, at four specific moments during performance: (1) assisting attacker's ball reception and (2) moment of passing, (3) shooter's ball reception, and (4), shot on goal. Statistical analysis showed that when a goal was scored, the defender's angle to the goal and to the attacker tended to decrease, the attacker was able to move to the same distance to the goal alongside the defender, and the attacker was closer to the defender and moving at the same velocity (at least) as the defender. This study identified emergent patterns of coordination between attackers and defenders under key competitive task constraints, such as the location of the goal, which supported successful performance in futsal.     

Teamwork in sport: a theoretical and integrative review

A commonly held belief in sports is the need for team members to be able to work well together in order for that team to be successful. Despite this assumption, research in the field of sport psychology has yet to formally or sufficiently conceptualize what is meant by teamwork. In this theoretical and integrative review, we draw from the extant organizational psychology and team development literature to present a multidimensional conceptual framework of teamwork in sport. We provide a working definition of teamwork in sport and discuss how teamwork sits within a broader model of team effectiveness. We conclude by providing an overview of salient research avenues on teamwork and team effectiveness in sport, which have potential implications for guiding interventions with sports teams.     

Dynamics of the basketball shot with application to the free throw

Abstract

A completely general three-dimensional dynamic model is presented for the motion of basketball shots that may contact the rim, the backboard, the bridge between the rim and board, and possibly the board and the bridge simultaneously. Non-linear ordinary differential equations with six degrees of freedom describe the ball angular velocity and ball centre position. The model includes radial ball compliance and damping and contains five sub-models: purely gravitational flight, and ball – rim, ball – bridge, ball – board, and ball – bridge – board contact. Each contact sub-model has both slipping and non-slipping motions. Switching between the sub-models depends on the reaction force at, and velocity of, the contact point. Although the model can be used to study shots from any point on the court, we here use it to study the sets of free throw release angle, velocity, angular velocity, and lateral deviation angle that result in success (capture), as well as underhand free throws and those using an under-inflated ball. Free throw shots with larger backspin, lower inflation pressures, and underhand release conditions are shown to result in larger capture percentages.     

基于SD的船舶敏捷制造项目进度管理模型研究

针对传统项目管理方法的不足,提出利用系统动力学方法来研究船舶敏捷制造项目的进度管理问题.通过传统项目管理方法与系统动力学方法的比较,证明利用系统动力学研究船舶敏捷制造项目进度管理的可行性和必要性,然后确定建模边界,构建因果关系图,对其中的反馈关系进行详细分析,得到四种反馈回路,进而对系统做进一步分析,建立船舶敏捷制造项目进度管理系统的系统动力学模型,最后通过实例仿真对模型进行有效性验证.     

创新资源视角的创新型城市内在成长动力研究

选取上海市1995～2010年的时间序列数据,综合运用因子分析、单位根检验、协整检验、Granger因果关系检验、脉冲响应函数进行深入研究。研究发现,创新型城市成长的内在驱动因素主要靠创新财力资源,其次是创新知识资源,最后是创新人力资源;创新型城市成长有利于创新资源的积聚。提出了保持创新型城市持久成长动力的政策建议。     

Analysis of lower limb internal kinetics and electromyography in elite race walking

Abstract

The aim of this study was to analyse lower limb joint moments, powers and electromyography patterns in elite race walking. Twenty international male and female race walkers performed at their competitive pace in a laboratory setting. The collection of ground reaction forces (1000 Hz) was synchronised with two-dimensional high-speed videography (100 Hz) and electromyography of seven lower limb muscles (1000 Hz). As well as measuring key performance variables such as speed and stride length, normalised joint moments and powers were calculated. The rule in race walking which requires the knee to be extended from initial contact to midstance effectively made the knee redundant during stance with regard to energy generation. Instead, the leg functioned as a rigid lever which affected the role of the hip and ankle joints. The main contributors to energy generation were the hip extensors during late swing and early stance, and the ankle plantarflexors during late stance. The restricted functioning of the knee during stance meant that the importance of the swing leg in contributing to forward momentum was increased. The knee flexors underwent a phase of great energy absorption during the swing phase and this could increase the risk of injury to the hamstring muscles.     

珠江三角洲农田黄毛鼠种群动态分析

根据1987～1990年和1992～1993年虎门镇农田调查的数据为依据．全面系统地研究和分析了黄毛鼠种群动态的基本特征，包括性比、年龄组成、繁殖强度等．同时，研究了种群季节迁移和季节变化．研究表明．黄毛鼠种群每年有两个繁殖高峰期和一个数量高峰期．     

基于群体动力学理论的基础教育数字资源USGC四方联动共建共享模式的构建与实现

在前期研究构建“基于资源分类的基础教育数字资源共享机制”的基础上,文章采用行动研究法,进一步深入分析现实问题,以群体动力学为理论基础,构建基础教育数字资源USGC四方联动共建共享模式。在该模式中,高校(U)、中小学(S)、政府(G)、企业(C)这四大主体各司其职而又互联互动。高校的主要职能为师资培训、政策建议、促进联动、实践推进,中小学的主要职能为质量审核、评价反馈、资源建设、创新生成,政府的主要职能为系统规划、政策驱动、经费保障、评估激励,企业的主要职能为资源(软硬件)供给、标准化共享平台、技术保障、管理服务。研究选取三所学校分别开展持续四年的基于校情的分阶段、分层次、有步骤的USGC四方联动共建共享模式的实践:A中学基于电子书包开展校内数字资源共建共享、B中学开展校际数字资源共建共享、C中学依托河南省“互联网+教育”精准扶贫计划开展区域数字资源共建共享。结果表明,此模式切实可行,对实践具有一定的指导意义。