Elementary Magnet School Students' Interracial Interaction Choices

ABSTRACT

The authors investigated children's self-reported high-calorie food intake in Grade 5 and its relationship to trends in obesity status and academic achievement over the first 6 years of school. They used 3-level hierarchical linear models in the large-scale database (the Early Childhood Longitudinal Study–Kindergarten Cohort). Findings indicated that frequency of eating fast food in Grade 5 was negatively related to mathematics and reading scores at Grade 5 and to the grow rate in both subjects. Frequency of obtaining salty snacks at school was moderately and negatively related to mathematics performance at Grade 5. School vending machines were not significantly associated with academic achievement patterns or obesity status. These results are informative of trends worth further investigation through prospective models.     

An examination of slo-pitch pitching trajectories

Many slo-pitch coaches and players believe that generating spin on a ball can affect its trajectory. The influence of air resistance on a ball that is thrown at a moderate speed and spin is unclear. The aim of this study was to examine the influence of spin on the ball's trajectory in slo-pitch pitching using both experimental results and ball flight simulations. Fourteen pitchers participated in the study, each of whom threw five backspin and topspin pitches each. Data were collected using standard three-dimensional videography. The horizontal velocity, vertical velocity, angular velocity, release height, and horizontal displacement of the backspin pitches were significantly higher than those of the topspin pitches. The ball flight simulations were developed to examine the influence of the ball spin, and it was concluded that the spin of the ball had a significant effect on the ball's vertical and horizontal displacements. Furthermore, our results suggest that a backspin pitch that reaches the maximum height allowable and lands in the front edge of the strike zone has the steepest slope. The present results add to our understanding of projectile motion and aerodynamics.     

Characteristic of drop coalescence resting on liquid-liquid interface

The trajectory model of dispersed phase drops and the model of basic flow for drop motion between two inclined parallel plates are derived with the optimized calculation. The analytical results of direct numerical simulation indicate that the basic flow plays an important role in the drop coalescence on liquid-liquid interface. In the stratified two-phase flow field, the smaller droplets are difficult to drain the thin continuous film between the approaching droplets and bulk interfaces and eventually immerse into the trickling film to yield coalescence. They almost attain the velocity of their local surroundings. Moreover, the basic flow exerts a dominant influence on the motion of smaller droplet. The smaller droplets are easily entrained by the basic flow. On the contrary, the larger drop presents advantageous characteristics of coalescence due to its high velocity. The range of 0.3 mm δR≤ 0.75 mm is the advantageous drop coalescence condition since the rapidly varied velocity and its first derivative theoretically cause the forces acting on a drop to become imbalanced. On the other hand, the thin layer of the continuous phase drained from the interval between the drops and trickling film should not be neglected in the calculation of shearing force since it is important for drop rotation. The drop rotation is an indispensable factor in coalescence.     

浅谈绘画中线条的美感

绘画中线条是点的运动轨迹,是一个可视的行动轨迹。线本身也不断的运动,表现不同的生命。没有线的前进、转向、曲缩和变化,就不可能有美的形式。线作为一种表现手段,是人类最初艺术才华的流露,也是人类几千年智慧的结晶,不同的画家,不同的思维方式,不同的文化积累,便会产生不同的绘画作品,可以说,线是艺术处理中表达感受最直接了当的语言,是人们认识和反映自然形态时最简明的表现形式。     

隐性知识外显案例之多案例诱导型适配研究

[目的/意义]知识经济时代知识成为核心资源,隐性知识是组织创造价值的源泉。文章设计了一套隐性知识外显案例的多案例诱导型适配方法,对知识用户提供过程辅助,以此提高组织隐性知识的应用效益。[方法/过程]采用熵权法确定案例条件方面权重,利用向量相似度算法计算待解问题与案例库中既有历史案例之间的视图相似度,从而确定待解问题的多案例适配集;针对适配案例集中存在的冗余方面不利于挖掘出案例条件空间对决策空间的决定关系问题,采用遗传算法简化待解问题的适配案例集,并基于简化的适配案例集,利用C4. 5决策树算法求解待解问题诱导型适配的解轨迹。[结果/结论]算例表明,与业内既有适配方法相比,文章提出的多案例诱导型适配方法合理、有效,具有相对优势。     

新中国成立以来《孙子兵法》研究述略

从学术史的视角,梳理总结了新中国成立以来的《孙子兵法》研究状况及相关成果。重点阐释了这一时期孙子生平与著作背景研究、《孙子兵法》文献研究、《孙子兵法》理论研究、《孙子兵法》普及应用研究等方面的新成就,并揭示了这一时期《孙子兵法》研究的发展轨迹、总体特点及发展趋势。     

A regression discontinuity analysis of graduation standards and their impact on students’ academic trajectories

In 2006, North Carolina put in place high school exit standards requiring students to pass a series of high-stakes exams across several years. I use a regression discontinuity (RD) approach to analyze whether passing or failing one of these exams (Algebra I) impacts a student's decision between choosing a more rigorous college-preparatory math curriculum and an easier ‘career’ track math curriculum. I find a 5 percentage point gap in the probability of selecting the rigorous curriculum between 9th grade students who just passed and those who just failed the exam. RD results across two years (one year in which the graduation standards were not in place) suggest that the discontinuity arose due to fewer students opting into the college track as a result of the exam results.     

从《红高粱》到《英雄》再到《归来》--论张艺谋电影的艺术变迁与文化轨迹

张艺谋的电影创作贯穿了从上个世纪80年代到新世纪以来的当下,常常处于时代文化潮头,具有某种文化编年的意味。更准确地说,是当下的时代、社会、文化创造了张艺谋,制造了一种独特的“张艺谋现象”。在张艺谋电影创作的表象背后,我们可以发现文化、社会、时代变迁的轨迹。划分了张艺谋电影的几个主要阶段,分析了各个阶段具有代表性意义的影片的艺术与文化特点,进而探析张艺谋电影的美学风格变迁、文化流变及文化价值或文化缺失。     

基于MATLAB/SimMechanics模块六自由度串联机器人的运动分析与控制

以KR5ARC型机器人为研究对象,建立机器人杆件坐标系,获得相应的结构参数和运动参数;利用MATLAB/SimMechanics模块建立机器人的仿真模型,并进行了一定的运动学分析;设定机器人的运行轨迹,并在MATLAB环境下编程,通过MATLAB程序的循环求解,自行求得机器人各关节转动角度的最优解,并对机器人轨迹规划进行仿真。通过仿真模型末端的传感器模块和轨迹模块,获得末端执行器和各关节运动的各种数据,为工程人员控制分析机器人提供一种有效的手段。     

基于灰色靶关联的智能体任意球轨迹修正方法

无论是在实体足球比赛还是智能体机器人足球比赛中,近距离的任意球破门收益率较高。研究智能体足球机器人比赛的任意球轨迹修正和优化控制问题,进而指导足球训练提高任意球得分率。提出一种基于灰色靶关联分析的智能体任意球轨迹修正方法,首先对整个机器人足球的环境态势和球员行为体选择进行模型构建,然后给出了灰色靶关联分析的任意球轨迹修正算法,进行球体着力点和应力点的适应值分析,构建基于灰色靶关联分析的任意球应力衰减特性分析模型,指导任意球轨迹修正,最后在智能体足球世界杯3D仿真平台进行实验验证了算法的优越性能。实验结果得出,采用该算法能有效指导任意球发球着力点控制,优化任意球的攻击轨迹,提高智能体机器人足球的任意球进球成功率,预测和控制精度提高。