Kinetic analysis of the lower limbs in baseball tee batting

The purpose of this study was to investigate effects of the ground reaction forces on the rotation of the body as a whole and on the joint torques of the lower limbs associated with trunk and pelvic rotation in baseball tee batting. A total of 22 male collegiate baseball players participated in this study. Three-dimensional coordinate data were acquired by a motion capture system (250 Hz), and ground reaction forces of both legs were measured with three force platforms (1,000 Hz). Kinetic data were used to calculate the moment about the vertical axis through the body’s centre of mass resulting from ground reaction forces, as well as to calculate the torque and mechanical work in the lower limb joints. The lateral/medial ground reaction force generated by both legs resulted in the large whole body moment about its vertical axis. The joint torques of flexion/extension of both hips, adduction of the stride hip and extension of the stride knee produced significantly larger mechanical work than did the other joint torques. To obtain high bat-head speed, the batter should push both legs in the lateral/medial direction by utilising both hips and stride knee torques so as to increase the whole body rotation.     

细胞色素c与氧化石墨烯的吸附研究

通过分子动力学模拟,研究细胞色素c在氧化石墨烯表面的吸附行为.结果表明,细胞色素c和氧化石墨烯之间有较强的结合趋势.均方根涨落及回转半径分析表明,部分体系的吸附构象与原始构象比较接近,但P3系统有着较大的偏离.这些结果表明,在某些构象中,氧化石墨烯可能将细胞色素c结构破坏.     

非惯性系动力学的第一积分

现行理论力学教材[1-4]在质点的非惯性系动力学中一般只讨论其相对运动微分方程,没有对其进行时,空的全部积分．本文首先积分出动量、动能定理．然后对其第一积分进行了分析讨论,指出了第一积分在应用方面的困难．最后举例说明了动能定理在应用方面是具有其优势的．     

基于VB的材料力学仿真实验系统

本文提出了如何在Windows XP环境下,借助Visual Basic6.0可视化高级程序设计语言,利用大型有限元分析软件ANSYS10.0开发材料力学仿真实验软件的设计思路,并给出了相应的具体开发方案,为今后材料力学仿真实验软件的开发探索出一种新方法,对材料力学仿真实验教学进行了有益尝试.     

露地和温室栽培模式下西兰花中3种农药的残留动态与风险评估

西兰花是中国典型的出口兼内销蔬菜品种。毒死蜱、辛硫磷和茚虫威是中国蔬菜生产中的常用农药。通过田间试验,对比这3种农药在露地和温室栽培模式下,按照推荐剂量和1.5倍推荐剂量用药,在西兰花花球、叶片和土壤中的残留动态。样品采用QuEChERS方法处理和液相色谱-质谱（LC-MS/MS）多残留检测。验证结果表明：在质量比分别为0.02、0.2和1 mg/kg时,毒死蜱、辛硫磷和茚虫威的添加回收率分别为85.8%~101.0%、90.8%~105.3%和86.1%~107.5%。3种农药的最低检出限（LOD）为0.006 mg/kg,最低定量限（LOQ）为0.01 mg/kg,满足方法要求。残留动态结果表明：在西兰花花球上,毒死蜱的半衰期为5.53~7.20 d,辛硫磷为3.55~3.92 d,茚虫威为6.11~7.73 d;在西兰花叶片上,毒死蜱的半衰期为4.33~6.93 d,辛硫磷为3.85~5.77 d,茚虫威为3.85~5.33 d;在土壤中,毒死蜱的半衰期为23.1~34.6 d,辛硫磷为23.1~34.6 d,茚虫威为17.3~23.1 d。最终残留对比表明,3种农药在西兰花叶片的残留量高于花蕾的残留量。在试验剂量施用量条件下,茚虫威和毒死蜱的限量标准不会超过现有欧盟、日本、CAC标准;在高剂量使用条件下,辛硫磷会出现超标现象。     

吸附在Au(100)、Au(110)和Au(111)表面的CTAB双分子层的结构和动力学性质的分子模拟

金纳米棒的各向异性生长常被认为是由于金表面吸附溴化十六烷基三甲基铵（CTAB）双分子层导致的。利用密度泛函理论（DFT）研究溴离子在（100）、（110）和（111）3种金表面上可能的吸附位点,根据它构建金表面CTAB双分子层模型,再利用分子动力学模拟方法研究这种烷基链互相交错排布的双分子层的结构。此外,动力学性质研究表明外层CTAB有着明显的横向扩散现象,而在法向上则出现上下起伏振动。相比较而言,在（111）表面上的双分子层结构的横向扩散和法向涨落更加显著。用外层单个CTA⁺脱离双分子层所需要的能量表征金表面CTAB双分子层的稳定性。结果表明（111）表面的CTAB双分子层的稳定性弱于其他两种金表面上的CTAB双分子层。认为这是因为（111）表面上的CTAB双分子层的排布密度相对较低,导致它相对于其他两种表面的双分子层有更高的扩散性和较低的稳定性。这可能是金纳米颗粒倾向于沿（111）表面生长的原因。     

Examining social identity and intrateam moral behaviours in competitive youth ice hockey using stimulated recall

Social identity – identity formed through membership in groups – may play an important role in regulating intrateam moral behaviour in youth sport (Bruner, M. W., Boardley, I., & Côté, J. (2014). Social identity and prosocial and antisocial behavior in youth sport. Psychology of Sport and Exercise, 15(1), 56–64. doi:10.1016/j.psychsport.2013.09.003). The aim of this study was to qualitatively examine this potential role through stimulated recall interviews with competitive youth-ice-hockey players. Twenty-three players (M_age = 13.27 years, SD = 1.79) who reported engaging in high, median or low frequency of antisocial teammate behaviour (determined through pre-screening with the Prosocial and Antisocial Behaviour in Sport Scale [Kavussanu, M., & Boardley, I. D. (2009). The prosocial and antisocial behavior in sport scale. Journal of Sport and Exercise Psychology, 31(1), 97–117. doi:10.1123/jsep.31.1.97]) were recruited from eight youth-ice-hockey teams in Canada. Interviews involved participants recalling their thoughts during prosocial/antisocial interactions with teammates, prompted by previously recorded video sequences of such incidents. Thematic analysis of interview data revealed all athletes – regardless of reported frequency of intrateam antisocial behaviour – felt prosocial interactions with teammates enhanced social identity. In contrast, the perceived influence of antisocial teammate behaviour on social identity differed depending on athletes’ reported frequency of intrateam antisocial behaviour; those reporting low and median frequencies described how such behaviour undermines social identity, whereas athletes reporting high frequency did not perceive this effect. The study findings highlight the potential importance of intrateam moral behaviour and social identity for youth-sport team functioning.     

系统动力学建模的知识转移演化模型与仿真

基于系统与控制理论,通过分析组织间知识转移过程及知识转移对各主体知识存量的影响,运用系统动力学的方法分析组织间知识转移的因果关系和行为演化特性,在此基础上构建知识转移演化的系统动力学模型,并采用Vensim PLE软件对模型进行仿真。通过对仿真模型的有效性和灵敏度的验证分析,表明该模型能够较好的对组织间的知识转移演化过程进行拟合,揭示组织间知识转移的特性及机理,为组织制定知识转移策略提供理论依据和指导。计算机仿真模型的构建与运行为研究组织间知识转移机制提供一种有效的手段和方法。     

Altered trends in carbon uptake in China's terrestrial ecosystems under the enhanced summer monsoon and warming hiatus

The carbon budgets in terrestrial ecosystems in China are strongly coupled with climate changes. Over the past decade, China has experienced dramatic climate changes characterized by enhanced summer monsoon and decelerated warming. However, the changes in the trends of terrestrial net ecosystem production (NEP) in China under climate changes are not well documented. Here, we used three ecosystem models to simulate the spatiotemporal variations in China''s NEP during 1982–2010 and quantify the contribution of the strengthened summer monsoon and warming hiatus to the NEP variations in four distinct climatic regions of the country. Our results revealed a decadal-scale shift in NEP from a downtrend of –5.95 Tg C/yr² (reduced sink) during 1982–2000 to an uptrend of 14.22 Tg C/yr² (enhanced sink) during 2000–10. This shift was essentially induced by the strengthened summer monsoon, which stimulated carbon uptake, and the warming hiatus, which lessened the decrease in the NEP trend. Compared to the contribution of 56.3% by the climate effect, atmospheric CO₂ concentration and nitrogen deposition had relatively small contributions (8.6 and 11.3%, respectively) to the shift. In conclusion, within the context of the global-warming hiatus, the strengthening of the summer monsoon is a critical climate factor that enhances carbon uptake in China due to the asymmetric response of photosynthesis and respiration. Our study not only revealed the shift in ecosystem carbon sequestration in China in recent decades, but also provides some insight for understanding ecosystem carbon dynamics in other monsoonal areas.     

政府干预下技术风险传播机制与控制决策——基于系统动力学的数理论证与实证仿真

当前我国快速发展的现代技术为推动社会进步作出了巨大贡献,但是可能存在的技术不足也会带来一定的社会风险,并随着企业间技术和产品的输入输出而不断转移使影响范围越来越大,所以政府就有必要进行干预。本文创新性地将复杂网络上的传染病模型引用到技术风险传播中,构建了政府干预下技术风险传播SEIR模型。首先通过数理论证研究模型的平衡点和稳定性,初步得出政府对于技术风险传播的干预机制,然后调查了云南省50家科技类企业并结合系统动力学原理构建STELLA实证仿真模型,分析政府干预对于技术风险传播的影响,给出政府风险管控的最优策略。