K_(2,r)-单路图谱半径的极限和上界

研究一种直径趋于无穷大的图类K2,r-单路图,利用图谱理论和高等数学求极限的方法,求得当点数n趋于无穷时,K2,r-单路图的谱半径有极限,并且求出了该极限值.进一步验证了该极限值即为K2,r-单路图的一个上界.     

Improving mathematics results: does teachers’ academic optimism matter? A study of lower secondary schools

Educational effectiveness research has provided evidence about the importance of teacher beliefs and attitudes for teaching and learning. This study builds on the concept of academic optimism, which combines 3 aspects of a teacher’s professional creed: self-efficacy, trust, and academic emphasis. The study explores the functioning of the collective and individual measures of academic optimism in the Czech environment and studies its impact on students’ outcomes. The analyses are based on pilot data from 39 schools, 325 teachers, and 1,316 Grade 9 students and on the data from the Czech Longitudinal Study in Education (CLoSE), covering 163 schools, 1,469 teachers, and 4,798 students. The individual measure was selected for further studies based on 2-level confirmatory factor analysis. Two-level structural equation modelling showed a significant impact of a school’s academic optimism on students’ achievement even after controlling for prior achievement and socioeconomic status at both the student and the school level.     

Lower leg and foot contributions to turnout in female pre-professional dancers: A 3D kinematic analysis

Turnout is a central element of classical ballet which involves sustained external rotation of the lower limbs during dance movements. Lower leg and foot compensation mechanisms which are often used to increase turnout have been attributed to the high incidence of lower limb injury in dancers. Evaluation of dancers’ leg posture is needed to provide insight into the lower limb kinematic strategies used to achieve turnout. The primary purpose of this study was to use 3D kinematic analyses to determine the lower leg and foot compensations that are incorporated by female university dancers to accentuate their turnout. Active and passive external tibiofemoral rotation (TFR) was also measured. A moderate-strong negative relationship was observed between hip external rotation (HER) and foot abduction in the three first position conditions. A moderate negative relationship was found between passive TFR and foot abduction in all first position conditions. Our findings suggest dancers are more likely to pronate, than rotate the knee to compensate for limited HER. Dancers with a limited capacity to pronate may force additional rotation via the knee. Ongoing research would benefit from more in-depth analyses of the foot/ankle complex using a multi-segment foot model.     

汉江中下游水文测验方式发展方向初探

在满足社会对水文信息精度需求的前提下,水文测验方式方法技术创新迫在眉睫。文章分析了汉江中下游各控制站的测站特性和洪峰变化特征,并对皇庄、沙洋两站的中低水水位流量关系,概化为单一曲线等问题进行了探讨。     

含时滞反应扩散方程周期解的存在唯一性

应用上下解和迭代方法研究了一类含多个离散时滞的单种群模型,得到了该方程周期解的存在唯一的一个充分条件。     

国家优秀女子速滑运动员直道滑行中下肢功率情况分析

为了有效评价运动员下肢各环节在蹬冰过程中的贡献情况,借助爱捷三维录像解析系统和CY-BEXNORM等动测试装置获得国家健将级女子速滑运动员的运动学和动力学数据,并采用牛顿差值计算方法计算出与实际运动学数据相对应的关节力矩,在此基础上计算出下肢各环节在蹬冰时功率输出值。研究结果表明:髋关节在单支撑阶段适当伸展,有利于增加整个蹬冰阶段的大腿功率输出;高速度、大角度伸膝肌群肌力差,引起两人小腿峰值功率过早出现,减少双支撑蹬冰阶段功率输出;踝关节肌力不足,刻意展踝,加重了伸小腿肌力不足现象,减少小腿在整个蹬冰过程中的作用。     

对脚斗士运动员下肢关节慢性损伤的研究

目的：研究长期进行脚斗士运动训练和比赛的人群下肢关节慢性运动损伤的情况。方法：以90名参加脚斗士运动训练四年以上不同专业学生为研究对象,通过问卷调查、访谈、X线、CT、核磁共振检查等方法对训练者下肢关节的慢性损伤情况进行调查并与未参加该项运动的学生对照组对比。结果：长时间从事脚斗士运动下肢关节的损伤情况与对照组存在差异,慢性损伤的发生率为：骶髂关节5.6%、髋关节3.3%、膝关节27.8%、踝关节34.4%、足关节16.7%,均高于对照组。结论：角斗士比赛及训练过程中存在慢性损伤的风险。训练时间过长、训练场地不规范、训练方式不合理、对运动损伤的认识不够是造成这些慢性损伤的主要原因,需要进一步加强管理及改进训练方法。     

一种抽取多数类边界样本的入侵检测算法

针对传统网络入侵检测方法在实时性响应和入侵行为识别率上存在的不足,本文提出了一种抽取多数类边界样本的入侵检测算法。该算法首先根据中心距离确定网络链接行为中多数类样本的边界样本,然后将多数类样本的边界样本与少数类样本合并构成新的训练集合,最后进行分类学习。该算法有效地降低了类别之间的不平衡度和减少了训练样本数目,具有更好的入侵检测性能。在KDD CUP 99数据集上的仿真实验,充分验证了该算法的有效性。     

Effects of leg dominance on performance of ballet turns (pirouettes) by experienced and novice dancers

Turns (pirouettes) are an important movement in ballet and may be affected by “lateral bias”. This study investigated physiological differences exhibited by experienced and novice dancers, respectively, when performing pirouette with dominant and non-dominant leg supports, respectively. Thirteen novice and 13 experienced dancers performed turns on dominant or non-dominant legs. The maximum ankle plantarflexion, knee extension and hip extension were measured during the single-leg support phase. The inclination angle of rotation axis is the angle between instantaneous rotation axis and global vertical axis in the early single-leg support phase. Both groups exhibited a greater hip extension, knee extension, and ankle plantarflexion when performing a turn on the non-dominant leg. For experienced dancers, the inclination angle of rotation axis during the pre-swing phase was generally smaller for dominant leg support than non-dominant leg. However, no significant difference was found in inclination angle of rotation axis of novice dancers. For experienced dancers, an improved performance is obtained when using the dominant leg for support. By contrast, for novice dancers, the performance is independent of choice of support leg. The significant lateral bias in experienced dancers indicates the possible influence of training. That is, repetitive rehearsal on the preferred leg strengthens the impact of side dominance in experienced dancers.     

线性不等式约束优化问题的强信赖域算法

对一类带有非负边界约束的线性不等式约束优化问题进行了研究，提出了一种新的信赖域算法．该算法在内点法的基础上，把非负边界约束从一般的不等式约束中分离出来，化为信赖域约束的一部分，得到一个简单易解的子问题．在一定的条件下证明了该算法具有强收敛性，并给出了数值结果．