Does local dynamic stability of kayak paddling technique affect the sports performance? A pilot study

During competition, kayak athletes must optimally adapt to environmental factors (e.g. wind, waves) to achieve peak performance. However, the ability to adapt to such perturbations has never been assessed in kayak paddling. Therefore, the aim of the current study was to evaluate the local dynamic stability in sports technique of youth sprint kayak athletes. In a cross-sectional study, 14 healthy male athletes were recruited from an elite youth sprint kayak squad. During an incremental kayak ergometer test, mean power, heart rates and local dynamic technique stability of hands, arms, trunk and paddle were registered and the association with the athletes 2000?m free-water times were estimated using mixed models. The 2000?m free-water performance significantly predicted the paddles (p?=?.037) local dynamic stability whereas no association was found for the trunk or the upper extremity kinematics. In conclusion, kayak athletes with high-performance capability over 2000?m paddling depict high local dynamic technique stability. This emphasizes the importance of a stable technique for advanced kayak skills, especially regarding paddling movements.     

矩阵方程组异类约束解的MCG1-3-5算法

借鉴求线性矩阵方程组同类约束解的MCG算法（修正共轭梯度法）,建立了求多个未知矩阵的线性矩阵方程组的一种异类约束解的MCG1-3-5算法,证明了该算法的收敛性。该算法不仅可以判断矩阵方程组的异类约束解是否存在,而且在有异类约束解,且不考虑舍入误差时,可在有限步计算后求得矩阵方程组的一组异类约束解;选取特殊初始矩阵时,求得矩阵方程组的极小范数异类约束解。同时还能求取指定矩阵在该矩阵方程组异类约束解集合中的最佳逼近。算例表明,该算法有效。     

带Hardy-Sobolev临界指数和权函数的半线性椭圆问题的非平凡解

借助环绕定理和非线性分析技巧,研究如下一类带Hardy-Sobolev临界指数和权函数的半线性椭圆方程 - Δ u-μ u |x|² =λu+K(x) |u|^2*(s)-2u |x|^s , x∈Ω; u=0, x∈Ω, 解的存在性,其中Ω是 R ^<em>N具有光滑边界的有界开区域,0∈Ω,N≥5,0≤s≤2, 0≤μ≤ N-2 2 ², λ>０,K(x)是 上有界正函数.     

指数函数模型线性化后的误差问题

基于一元线性回归,对指数函数模型线性化后的随机误差存在的问题进行分析。引入对数正态分布,比较线性化前后误差的期望。     

基于竞争力择优的产业联盟知识转移网络动态演化模型

针对BA网络模型模拟现实世界的局限性,综合考虑产业联盟复杂网络的动态演化特性、竞争性等特点,构建了竞争力择优动态演化模型.该模型在考虑节点增加的同时,包含了节点的删除、旧节点之间竞争力择优的再生连接和反择优的删除连接.运用连续介质理论和平均场理论建立起与之对应的演化方程,导出该模型的度分布仍然具有无标度网络的一般性质,BA无标度网络是它的一种特殊情形.数值仿真的模拟结果验证了理论分析的正确性.研究结果表明,通过调节参数可以与现实中许多复杂网络的幂率指数相吻合,因此,改进的模型更具有适应性和真实性.     

星型网络中的混沌同步

Using an example,it was analytically proved that the dynamical systems constructed on a star coupled network is more easy to be synchronized than that in coupled map lattices(CML).The result shows that the synchronization in small-world networks may be realized more easily.     

关于朗道相变理论的一个修正

由单轴铁磁体对自发磁化强度M的对称性,对朗道相变理论中自由能的表达式作了一个修正,并运用卡尔丹公式得到其临界指数β=1/3,与实验值一致。     

Armijo型线搜索下一个修正Hestenes-Stiefel共轭梯度法的全局收敛性

提出一个新的修正Hestenes-Stiefel(HS)非线性共轭梯度法(MHSCG算法).在精确线搜索下MH-SCG算法化归为标准的HS共轭梯度算法.该算法产生的搜索方向不依赖于线搜索准则而具有充分下降性.新方法在一个修正Armijo型线搜索下具有全局收敛性.数值试验表明,对于多数算例新算法比PRP、HS、LS算法具有更好的计算结果.     

可对角化矩阵的矩阵指数计算

以常系数齐次线性微分方程组x’=Ax的基解矩阵expAt的计算为应用背景,运用线性代数中矩阵的对角化方法,将可对角化的矩阵A对角化,再计算矩阵指数expA,从而为基解矩阵expAt的计算提供更有针对性的方法.     

加工表面多重分形谱权重因子的估算方法

多重分形谱能精细全面地描述工件表面图像特征,而采用配分的方法获得多重分形谱,并对具体的算法进行了描述,将多重分形谱和奇异指数对权重因子求取一阶导数,确定了权重因子的取值范围。