排序方式： 共有33条查询结果，搜索用时 26 毫秒
1.
基于ANSA中的Morph功能，在某改款车型的概念设计阶段，对标杆车的有限元模型进行快速的结构调整，通过仿真手段，对改款车的模态刚度进行分析；然后，对原型车白车身结构进行模态实验，获取其模态频率及对应振型，进而与改款车进行对比，提前对改款车结构的合理性做出评价。 相似文献
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尼楣 《大连教育学院学报》2006,22(2):38-39
孙惠芬的小说除了揭示农民“现代化”的渴望与觉醒外,更深入到切实的社会问题,即农民在“城市化”、“现代化”过程中的现实生活与精神情感的苦难和困惑。 相似文献
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本文针对发生的电动葫芦吊物坠落事故,在现场勘查测量和计算的基础上,分析了导致该事故发生的主要原因,最终给出事故调查结论。 相似文献
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Mark P. Moresi Elizabeth J. Bradshaw David A. Greene Geraldine A. Naughton 《Journal of sports sciences》2015,33(2):180-191
Double-leg repeated jumping tasks are commonly used as measures of lower limb stiffness in exercise science research. Within similar stiffness calculations, variation in data-reduction criteria exists. The impact of these varied data-reduction methods on stiffness measures is unknown. Sixteen adolescent female participants from varied physical activity backgrounds performed 15 self-paced, bent-knee continuous jumps (CJb) on two force plates. Leg stiffness was calculated as the ratio of the peak force and the centre of mass displacement for each contact. Using combinations of criteria based on previous literature, 83 data-reduction methods were applied to the raw data. Data reduction suitability was assessed based on intra-trial reliability, the number of participants excluded and the average contacts excluded. Four data-reduction methods were deemed suitable for use with adolescent female populations, with three consecutive contacts within 1 SD of the average jump frequency considered optimal. The average individual stiffness values were not greatly influenced by the data-reduction method; however, for a single participant, a stiffness change of up to 6 kN · m?1 (30%) was observed. The role and potential impact of data-reduction methods used to evaluate measures of lower limb stiffness during repeated jumping tasks warrants consideration. 相似文献
5.
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
6.
The aim of the present study was to examine the effects of viscoelastic properties of human tendon structures during stretch?–?shortening cycle exercise. The elongation of tendon and aponeurosis of the medial gastrocnemius muscle of 26 participants was measured by ultrasonography while they performed ramp isometric plantar flexion up to the voluntary maximum, followed by a ramp relaxation. The relationship between estimated muscle force and tendon elongation during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness. The percentage of the area within the muscle force?–?tendon elongation loop relative to the area beneath the curve during the ascending phase was defined as hysteresis. In addition, maximal voluntary concentric contractions at 2.09 and 3.14 rad?·?s?1 with and without prior eccentric contractions were performed. The difference in the concentric torque at equivalent joint angles with and without prior eccentric contractions (i.e. pre-stretch augmentation) was negatively correlated with stiffness (P <?0.05) and hysteresis (P <?0.05). Furthermore, there was a higher correlation between the pre-stretch augmentation and the viscoelastic properties index – that is, the sum of normalized score values of stiffness and hysteresis (P <?0.01) – than with either stiffness or hysteresis alone. The results of this study suggest that performance during stretch?–?shortening cycle exercise is significantly affected by the viscoelastic properties of the tendon structures. 相似文献
7.
Germán Carretero-Navarro Doménico Cherubini Wolfgang Taube 《European Journal of Sport Science》2019,19(5):595-602
Weighted vests are widely used to improve running economy and performance. However, it is not well-studied how running mechanics are adapted to counteract the higher peak vertical ground reaction forces (Fpeak) while running with such a device. Therefore, the present study aimed to investigate the effects of different loading conditions on running mechanics at different velocities. Thirteen subjects participated in two separate sessions one week apart. In the first session, maximal aerobic speed (MAS) was determined through a maximal incremental running test while in the second session, they were instructed to run during one minute under different loading (0%, +10% and +20% of body mass [BM]) and velocity (60%, 80% and 100% of MAS) conditions in a random order. Spatiotemporal data were recorded and then running mechanics modelled using the spring-mass model. The main results indicated that vertical and leg stiffness (Kvert and Kleg, respectively) were increased (P?P?>?.05) when load was changed. At the same time, alterations of the running kinematics were observed such as longer contact times, reduced flight times, stride frequencies and step lengths, as well as an increase of the centre of mass dynamics. Based on these results it is assumed that runners maintain a certain stiffness level for each velocity despite different loading conditions. As a consequence, Fpeak increases and this probably causes spatiotemporal adjustments in the movement kinematics. 相似文献
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9.
The influence of shaft stiffness on potential energy and puck speed during wrist and slap shots in ice hockey 总被引：1，自引：1，他引：0
The purpose of this study was to explore the relationship between hockey stick shaft stiffness and puck speed with mechanical
energy considerations during stationary wrist and slap shots. Thirty left-handed pro-model composite hockey sticks, submitted
by eleven hockey stick manufacturers, were subjected to a mechanical cantilever bend test to determine the shaft stiffness
of each stick. Eight sticks representing the entire spectrum of stiffnesses were then used by five elite male hockey players
to perform stationary wrist and slap shots in a laboratory setting. Eight infra-red high-speed digital video cameras were
used to capture shaft deformation and puck speed. A second mechanical test then replicated the loading patterns applied to
each stick during shooting. Force-deformation data from this test were used to determine the shaft stiffness and potential
energy storage and return associated with each stick during shooting. The results of this study suggest that shaft stiffness
has an influence on puck speed in wrist but not slap shots. During a wrist shot, a given player should realise higher puck
speeds with a stick in which they store increased elastic potential energy in the shaft. In general, flexible sticks were
found to store the most energy. However, how the athlete loads the stick has as much influence on puck speed as stick construction.
Energy considerations were unable to explain changes in puck speed for the slap shot. For this type of shot it is the athlete
and not the equipment influencing puck speed, but the governing mechanisms have yet to be elucidated. 相似文献
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