Analysis of the distance covered by Brazilian professional futsal players during official matches

The purpose of this study was to measure and characterise the distances covered by Brazilian professional futsal players. The trajectories of 93 players during five matches were obtained using an automatic tracking method. The distances covered were analysed for different game conditions: over the entire game and during the times when the ball was out of play and in play separately. When the entire game was considered, the results showed that there was a reduction in the total distance covered per minute from the first [median ± IQR (interquartile range): 97.9 ± 16.2 m/min] to the second half (median = 90.3 m/min; IQR = 12.0), and when only the in-play time was considered (first half: 136.6 ± 17.2 m/min; second half: 129.2 ± 16.7 m/min). The percentage of distance covered in the standing and walking velocity range was higher in the second half than in the first when considering the entire game (30.8% and 28.0%, respectively) and during the in-play time (19.3% and 16.2%, respectively). In conclusion, this study verified that futsal players reduced the physical performance during the second half.     

两级式单相光伏并网系统的最大功率点跟踪控制策略

为在光伏并网发电系统中通过应用最大功率点跟踪(Maximum Power Point Tracking,MPPT)技术提高光伏电池的利用率,针对两级式单相光伏并网发电系统,选取基于前级变换器的MPPT控制策略.该控制策略中,前级采用改进的变步长扰动观察法实现MPPT;后级通过直流母线电压反馈构成电压电流双闭环控制,实现母线稳压.运用PSIM 9.0进行建模仿真,结果表明,该控制策略能够很好地实现MPPT和直流母线稳压,系统的动态响应速度较快,稳定性较好.     

乒乓球机器人视觉系统的实时跟踪

针对乒乓球机器人视觉系统中的实时跟踪问题,分别在高速和低速2种摄影条件下设计完全不同的算法对乒乓球进行跟踪识别研究。在高速摄影条件下主要利用乒乓球的5大特征信息(圆度、周长、面积、X距和Y距)设置阈值进行识别;在低速摄影条件下将机器学习和图像匹配的方法进行代入,实现对带拖影乒乓球的识别。采用基于注意力的图像分割算法对图片进行预处理,可有效解决因环境干扰等造成的像素失真问题。提出规划感兴趣区(ROI)的算法,利用乒乓球的运动特征提前确定下一帧图像中乒乓球的可能位置,从而降低计算量,缩短计算时间,实现跟踪的实时性。     

Eye Movement Modeling Examples guide viewer eye movements but do not improve learning

Recent research has tested whether Eye Movement Modeling Examples (EMMEs) can effectively cue attention and improve learning. However, the effects of EMMEs are variable, and the degree to which viewers follow these cues remains unclear. In the current paper, we compared screen-captured instructional videos that included an EMME in the form of a transparent circular overlay depicting the instructor's gaze location with identical videos that lacked this cue. We observed that EMMEs drove viewer saccades to cued locations and resulted in shorter distances between viewer gaze and the EMME, but learning performance and video preference were unaffected by the presence of an EMME. We argue that EMMEs can effectively guide attention, but the range of circumstances under which they improve learning may be limited.     

The achievement gap: The impact of between-class attainment grouping on pupil attainment and educational equity over time

Despite extensive research on attainment grouping, the impact of attainment grouping on pupil attainment remains poorly understood and contested. This paper presents evidence from a study conducted with 2944 12–13 year olds, from 76 schools in England, who were allocated to between-class attainment groups (‘setting’) in English and mathematics over the first 2 years of secondary schooling. After controlling for prior attainment, pupils in the top set performed significantly better than pupils in the middle and bottom sets in both English and mathematics. The findings indicate a widening gap in attainment, especially in the case of English. Findings, especially in the case of mathematics, provide more evidence of a relative benefit for pupils placed in top sets than a relative detriment for those in bottom sets.     

国家高新区政策机制演进研究——一个基于政策过程的分析框架

国家高新区发展变迁史也是一部政策机制演进史。本文将通过国家高新区政策机制的“D-A-T-P”理论分析模型，分析政策机制演进的逻辑和规律。研究表明，国家高新区政策机制演进呈现规律性特征:需求触发机制从国家战略向个体创新需求转变；目标导向机制从点上改革突破向面上辐射带动转变；工具实现机制从单型工具向多型工具转变；绩效跟踪机制从经济单一向度向高质量综合向度转变。本文结合国家高新区政策机制演进经验，从促进政策供求匹配、形成政策目标共识、优化政策工具结构、畅通政策绩效链路四个方面提出对策建议。