基于微分方程系统的混沌控制

针对微分方程所表征的系统,对其状态方程进行了平衡点的稳定性分析。数值模拟了该系统的混沌行为,并对该系统加入棒棒控制方法进行控制。利用数值仿真分析系统的周期行为和混沌行为。通过调整适当的控制参数,将系统的混沌行为有效地控制到稳定的周期轨道。     

Simplified method of designing FIR filter with controllable center frequency

A novel simplified method is presented to design FIR filter with controllable center frequency. The properties of transfer curves for all-phase filters are illustrated under 3 windowing conditions. By combining single-window all-phase filter design steps and double phase-shift combination, a series of design formulas for point-pass filter, notch filter, band-pass filter and band-stop filter are derived, thus the design computation complexity is greatly reduced. Experiments prove that the center frequency of all the filters can be accurately specified at arbitrary position by adjusting frequency parameters m and λ.     

自由偶极子运动规律研究

讨论了由正负离子实组成的自由偶极子的相互作用能,分析了仅在该作用下偶极子的运动,求解其运动方程,得出自由偶极子的运动为匀速直线运动和简谐振动的叠加,其质心作匀速直线运动,在质心系中,两离子分别在其平衡位置附近作简谐振动.     

Examining the influence of grip type on wrist and club head kinematics during the golf swing: Benefits of a local co-ordinate system

Wrist movements have been identified as an important factor in producing a successful golf swing, with their complex motion influencing both club head velocity and orientation. However, a detailed analysis of wrist angles is lacking in the literature. The purpose of this study was to determine kinematics across wrists and club head characteristics during the golf swing under weak, neutral and strong grip conditions. Twelve professional male golfers executed 24 shots using a driver under three grip conditions. A six degrees of freedom analysis of the hand with respect to the distal forearm was performed using a 10-camera three-dimensional motion capture system. Differences in joint angles were explored using repeated measures ANOVAs at key swing events (onset, top of backswing and impact), in addition club head velocity and clubface angle at impact were also explored. Main findings revealed significant differences in flexion/extension and internal/external rotation for both wrists at all swing events, whereas fewer significant interactions were found in ulnar/radial deviation across grips for both wrists at all events. Clubface angle only differed significantly between the weak and the strong and neural grips, presenting a more ‘open’ clubface to the intended hitting direction. This study is the first to explore tri-planar wrist movement and the effect of different grips, such analysis has implications for coaching knowledge and practice and should inform future research into different aspects of skill, technique analysis and may inform injury mechanisms/prevention.     

Contextual factors on physical demands in professional women’s soccer: Female Athletes in Motion study

The aim of this study was to examine the impact of contextual factors on relative locomotor and metabolic power distances during professional female soccer matches. Twenty-eight players (forwards, n?=?4; midfielders, n?=?12; defenders, n?=?12) that competed in a 90-min home and away match (regular season only). The generalised estimating equations (GEE) was used to evaluate relative locomotor and metabolic power distances for three contextual factors: location (home vs. away), type of turf (natural vs. artificial), and match outcome (win, loss and draw). No differences were observed for home vs. away matches. Moderate-intensity running (20.0?±?1.0?m?min^?1 and 16.4?±?0.9?m?min^?1), high-intensity running (8.6?±?0.4?m?min^?1 and 7.3?±?0.4?m?min^?1) and high-metabolic power (16.3?±?0.5?m?min^?1 and 14.4?±?0.5?m?min^?1) distances were elevated on artificial turf compared to natural grass, respectively. Relative sprint distance was greater during losses compared with draws (4.3?±?0.4?m?min^?1 and 3.4?±?0.3?m?min^?1). Overall physical demands of professional women’s soccer were not impacted by match location. However, the elevation of moderate and high-intensity demands while playing on artificial turf may have implications on match preparations as well as recovery strategies.     

基于多系数保角变换法的船舶垂荡纵摇运动仿真

为给航海模拟器建立实用可靠的船舶在波浪中运动的数学模型,基于二维线性势流理论,采用多系数保角变换法对每个船舶横剖面进行高精度拟合,计算各个横剖面的水动力系数和波浪激励力,利用Visual Studio自主开发出船舶在规则波中的纵向运动数值模拟程序。为验证这个数值模拟程序的可靠性,对S175集装箱船在迎浪中运动的幅值响应因子(response amplitude operator, RAO)进行数值计算。结果表明:当弗劳德数为0.275时,RAO计算结果在大部分频率范围内与试验结果吻合良好。因此,这个数值模拟程序能准确地对船舶在波浪中的运动时历进行仿真。     

乒乓球运动员以预防损伤为主的功能训练

功能训练的理念来源于康复领域,现已逐步应用到运动训练中。由于乒乓球运动的项目特征,乒乓球运动员肩关节、腰椎关节、膝关节、踝关节、腕关节等部位容易出现运动损伤。通过对乒乓球运动员常出现的功能问题进行分析,寻找存在的常见问题,进而提出相应的功能训练建议。乒乓球运动员可根据情况,增加改善肩关节、胸椎关节、髋关节、踝关节的活动范围的训练,提高肩胛骨、核心和下肢稳定性的训练,以及改善肩袖、躯干肌力不平衡的训练,通过针对性的功能训练有效减少乒乓球运动员损伤的发生。     

基于卡尔曼滤波的PS-InSAR地表形变预测方法

PS-InSAR是用于监测大范围地表形变的微波遥感技术,可提供精确地表形变信息,但该技术无法对形变趋势进行预测。现有形变预测方法只能预测少数监测点的形变,不适用于大面积预测。针对这些问题,提出一种基于卡尔曼滤波的PS-InSAR地表形变预测方法。结合PS-InSAR方法的技术流程,从理论上推导设计卡尔曼滤波器,通过真实的多时相SAR数据对该方法进行验证。实验结果表明,该算法可充分利用PS-InSAR形变监测信息,有效预测大面积观测区域的形变趋势。     

Skating start propulsion: three-dimensional kinematic analysis of elite male and female ice hockey players

The forward skating start is a fundamental skill for male and female ice hockey players. However, performance differences by athlete’s sex cannot be fully explained by physiological variables; hence, other factors such as skating technique warrant examination. Therefore, the purpose of this study was to evaluate the body movement kinematics of ice hockey skating starts between elite male and female ice hockey participants. Male (n = 9) and female (n = 10) elite ice hockey players performed five forward skating start accelerations. An 18-camera motion capture system placed on the arena ice surface captured full-body kinematics during the first seven skating start steps within 15 meters. Males’ maximum skating speeds were greater than females. Skating technique sex differences were noted: in particular, females presented ~10° lower hip abduction throughout skating stance as well as ~10° greater knee extension at initial ice stance contact, conspicuously followed by a brief cessation in knee extension at the moment of ice contact, not evident in male skaters. Further study is warranted to explain why these skating technique differences exist in relation to factors such as differences in training, equipment, performance level, and anthropometrics.     

Kinematic analysis of hip and knee rotation and other contributors to ballet turnout

Turnout, or external rotation (ER) of the lower extremities, is essential in ballet. The purpose of this study was to utilise physical examination and a biomechanical method for obtaining functional kinematic data using hip and knee joint centres to identify the relative turnout contributions from hip rotation, femoral anteversion, knee rotation, tibial torsion, and other sources. Ten female dancers received a lower extremity alignment assessment, including passive hip rotation, femoral anteversion, tibial torsion, weightbearing foot alignment, and Beighton hypermobility score. Next, turnout was assessed using plantar pressure plots and three-dimensional motion analysis; participants performed turnout to ballet first position on both a plantar pressure mat and friction-reducing discs. A retro-reflective functional marker motion capture system mapped the lower extremities and hip and knee joint centres. Mean total turnout was 129±15.7° via plantar pressure plots and 135±17.8° via kinematics. Bilateral hip ER during turnout was 49±10.2° (36% of total turnout). Bilateral knee ER during turnout was 41±5.9° (32% of total turnout). Hip ER contribution to total turnout measured kinematically was less than expected compared to other studies, where hip ER was determined without functional kinematic data. Knee ER contributed substantially more turnout than expected or previously reported. This analysis method allows precise assessment of turnout contributors.