能实现垂直缠绕攀爬的蛇形机器人     

孙洪 《苏州市职业大学学报》2020,(2):6-9

垂直缠绕攀爬的蛇形机器人是基于模块化的P_R(pitch_roll)关节,以串行总线舵机作为关节驱动装置,其控制系统采用协调级和执行级配合的二级结构,以空间三连杆组成的蠕动爬行作为基本步态,实现了蛇形机器人具有垂直缠绕攀爬的功能。  相似文献   

全渠道零售场景下配送车辆路径问题     

施天娇  杨斌  朱小林 《上海海事大学学报》2020,41(2):51-57

为研究全渠道零售的配送系统对企业物流成本的影响,综合考虑时间窗、车型选择等因素,以运输成本最低为目标,建立高度协同的全渠道零售场景下的物流配送模型。该模型采用自适应遗传算法求解,利用MATLAB进行算例分析。结果显示:全渠道零售模式下的车辆调度方案能迅速响应消费者需求,与一般配送模式相比可以减少物流成本,优化车辆配置。与粒子群优化算法相比,自适应遗传算法的运行时间更短、优化结果更好,这验证了模型和算法的可行性和有效性。  相似文献   

乒乓球运动员膝关节损伤机制研究——对3种常用步法的膝关节负荷特征分析     

周星栋  肖丹丹  郭文霞  黄习梅  张晓栋 《中国体育科技》2020,(6):62-67

目的:了解不同性别乒乓球运动员完成并步、跳步、跨步3种常用步法时膝关节的负荷特征,并探析乒乓球运动员膝关节的损伤机制。方法:对乒乓球男、女各10名运动员完成3种常用步法动作时的下肢运动学、动力学数据进行采集和处理,并运用方差分析法比较不同性别、不同技术之间的差异。结果:受试者在完成3种步法过程中,膝关节屈角大致范围在20°~60°。当地面反作用力最大时,女运动员比男运动员表现出更小的外展角(P<0.05),跳步比并步和跨步表现出更小的外展角(P<0.05);在三维受力方面,膝关节受到垂直方向上的力最大,水平向后和向左的力次之,未表现出显著的性别差异和技术差异;在三维力矩方面,膝关节受到的伸膝力矩较大,也未表现出显著的性别差异和技术差异。结论:膝关节屈曲状态下,较大的地面反作用力和膝关节外展角易导致乒乓球运动员前交叉韧带损伤,女运动员的损伤风险小于男运动员,跳步的损伤风险小于并步和跨步;水平向后和向左的力易造成乒乓球运动员软骨和半月板损伤;过大的伸膝力矩易导致乒乓球运动员髌腱末端病和髌骨软化。  相似文献   

The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking     

Taeyou Jung  Yumi Kim  Hyosok Lim  Konstantinos Vrongistinos 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(3):297-307

The purpose of this study was to investigate kinematic and spatiotemporal variables of aquatic treadmill walking at three different water depths. A total of 15 healthy individuals completed three two-minute walking trials at three different water depths. The aquatic treadmill walking was conducted at waist-depth, chest-depth and neck-depth, while a customised 3-D underwater motion analysis system captured their walking. Each participant’s self-selected walking speed at the waist level was used as a reference speed, which was applied to the remaining two test conditions. A repeated measures ANOVA showed statistically significant differences among the three walking conditions in stride length, cadence, peak hip extension, hip range of motion (ROM), peak ankle plantar flexion and ankle ROM (All p values < 0.05). The participants walked with increased stride length and decreased cadence during neck level as compared to waist and chest level. They also showed increased ankle ROM and decreased hip ROM as the water depth rose from waist and chest to the neck level. However, our study found no significant difference between waist and chest level water in all variables. Hydrodynamics, such as buoyancy and drag force, in response to changes in water depths, can affect gait patterns during aquatic treadmill walking.  相似文献   

Hip joint kinetics in the table tennis topspin forehand: relationship to racket velocity     

Yoichi Iino 《Journal of sports sciences》2018,36(7):834-842

The purpose of this study was to determine hip joint kinetics during a table tennis topspin forehand, and to investigate the relationship between the relevant kinematic and kinetic variables and the racket horizontal and vertical velocities at ball impact. Eighteen male advanced table tennis players hit cross-court topspin forehands against backspin balls. The hip joint torque and force components around the pelvis coordinate system were determined using inverse dynamics. Furthermore, the work done on the pelvis by these components was also determined. The peak pelvis axial rotation velocity and the work done by the playing side hip pelvis axial rotation torque were positively related to the racket horizontal velocity at impact. The sum of the work done on the pelvis by the backward tilt torques and the upward joint forces was positively related to the racket vertical velocity at impact. The results suggest that the playing side hip pelvis axial rotation torque exertion is important for acquiring a high racket horizontal velocity at impact. The pelvis backward tilt torques and upward joint forces at both hip joints collectively contribute to the generation of the racket vertical velocity, and the mechanism for acquiring the vertical velocity may vary among players.  相似文献   

The effect of sex and localised fatigue on triceps surae musculoarticular stiffness     

Aurélio Faria  Ronaldo Gabriel  Helena Moreira  Tanya Camacho  Rui Brás  Massimiliano Ditroilo 《European Journal of Sport Science》2018,18(4):483-490

Purpose: The main purpose of this study was to investigate the influence of fatigue on musculoarticular stiffness (MAS) of the ankle joint across sexes. Methods: Twenty-seven males and 26 females participated in the study. After baseline assessment of MAS and related variables, localised fatigue was induced in triceps surae using the standing heel-rise test during which the subjects were instructed to lift and drop the heel at a frequency of 0.5?Hz. When subjects were unable to continue due to exhaustion the test was terminated and another MAS test was performed soon after. Results: Significant higher triceps surae MAS was found in men compared to women (p?p??1 and from 14.5 to 13.9?KN?m^?1 in men and women, respectively. Percentage changes revealed, however, that in relative terms the changes in all the variables evaluated were similar (p?>?.01) between sexes, with MAS less than 5%. Conclusion: Despite the sex-related differences at baseline, fatigue seems to affect biomechanical properties of the ankle joint similarly in men and women.  相似文献   

Differences between motion capture and video analysis systems in calculating knee angles in elite-standard race walking     

Brian Hanley  Catherine B. Tucker  Athanassios Bissas 《Journal of sports sciences》2018,36(11):1250-1255

Race walking is an event where the knee must be straightened from first contact with the ground until midstance. The aim of this study was to compare knee angle measurements between 2D videography and 3D optoelectronic systems. Passive retroreflective markers were placed on the right leg of 12 race walkers and 3D marker coordinate data captured (250 Hz), with 2D video data (100 Hz) recorded simultaneously. Knee angle data were first derived based on the markers’ coordinates, and separately by using a 3D model that also incorporated thigh and shank clusters; the video data were analysed using both automatic tracking and manual digitising, creating four conditions overall. Differences were calculated between conditions for stance (using root mean square values), and at discrete events. There were few differences between systems, although the 3D model produced larger angles at midstance than using automatic tracking and marker coordinates (by 3 – 6°, P < 0.05). These differences might have occurred because of how the 3D model locates the hip joint, and because of the addition of marker clusters. 2D videography gave similar results to the 3D model when using manual digitising, as it allowed for errors caused by skin movement to be corrected.  相似文献   

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

Sarah L. Carter  Rebekha Duncan  Andries L. Weidemann  Luke S. Hopper 《Journal of sports sciences》2018,36(19):2217-2225

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.  相似文献   

城市生态交通系统理论与实现途径     

王汉新 《科技管理研究》2016,(1):246-251

生态交通系统以人流物流为核心,讲究车、路、站、能源、管理等要素与人、经济、自然的协调,其目标是生态安全、绿色出行、和谐交通。居民以"慢行+公交"生态出行理念的实现,需从规划、技术上扩充步行、自行车与公共交通的生态位,同时采用限行、收费方式压缩轿车的生态位。效仿公交式的物流配送网络建设,既是对轴辐式配送网络的完善,也是货运从独立经营到共同配送的良性生态演化。客运与货运的生态位重叠,可通过时、空维数的部分分离来减缓竞争。  相似文献   

引导基金联合参股的杠杆效应研究     

杨敏利  焦飞飞  董建卫  姚和浪 《科研管理》2020,41(10):114-124

摘要：本文通过清科旗下私募通数据库搜集数据并利用PSM(倾向得分匹配)方法进行样本的匹配构造，实证检验了引导基金联合参股投资杠杆效应的差异化影响，得出如下结论：一是引导金联合参股低声誉创投机构形成的杠杆效应显著高于联合参股高声誉创投机构，该结论支持认证效应假说。二是引导基金联合参股国有背景创投机构形成的杠杆效应显著高于联合参股非国有背景创投机构，该结论不支持政治关联假说。三是引导基金联合参股创投发展落后区域创投机构形成的杠杆效应显著高于联合参股成熟区域创投机构，该结论支持良性循环假说。  相似文献