排序方式: 共有75条查询结果,搜索用时 31 毫秒
21.
22.
23.
Shigetada Kudo Yoshihisa Sakurai Takahiro Miwa Yuji Matsuda 《Journal of sports sciences》2017,35(10):945-952
This study re-evaluated the magnitude of hand propulsion (HP) in the pull and push phases of the front crawl stroke and investigated the association between the angular velocity of shoulder roll (ωSR) and hand propulsive lift (HPL). ωSR was computed in the plane normal to a forward direction for 16 skilled swimmers performing the front crawl stroke at a maximal sprinting pace. HP, hand propulsive drag (HPD) and HPL were determined by a dynamic pressure approach. HP and HPD in the pull phase were greater than in the push phase (P < 0.05) while HPL in the pull phase was similar to that in the push phase. Eleven swimmers out of the 16 swimmers had a significant within-swimmers correlation between ωSR and HPL in the push phase (P < 0.05). That is, HPL increased in the push phase as the ωSR of rolling back to the neutral position became faster. A swimmer should use more drag for hand propulsion in the pull phase and propulsion from drag and lift equally in the push phase. Based on the relationship between ωSR and HPL in the push phase, a possible stroke technique to enhance HPL using ωSR is discussed. 相似文献
24.
本文探索了共轴直升机气动力参数估算技术,用以确定其疲劳载荷谱。首先给出了气动力计算的主控方程和数值方法,然后,分别建立了共轴直升机机身与旋翼的三维层流和湍流流场模拟的物理模型和计算网格模型,采用计算流体力学(CFD)方法,进行了共轴直升机机身与旋翼的层流和湍流流场数值模拟,估算了其气动力参数曲线,并对计算结果进行了分析对比,以检验建模技术的有效性,分析结果表明:该项技术实用可行,能得到一些与工程实际吻合的现象和结论。 相似文献
25.
杨中 《连云港职业技术学院学报》2005,18(4):29-31
在我国,低保对象还将长期大量地存在,政府应通过不断完善城市居民最低生活保障制度,加大就业帮扶力度,积极发展医疗、教育、住房救助项目,鼓励社会互助和社会慈善捐助等措施帮助低保人群脱贫。 相似文献
26.
王楠 《北京工业职业技术学院学报》2013,12(4):41-45,54
汽车驶入水中导致司乘人员伤亡的事故近年来逐渐增多,尤其是城市中地势低洼排水不畅的地段在大雨后容易积存大量雨水,司机在不知水深的情况下冒然驶入,导致车体没入水中,车门车窗无法打开造成惨剧.针对这一问题,以北京现代伊兰特汽车左前车门车窗升降机构为例,通过计算进行结构模拟和优化,从而减少人员伤亡.结果表明,经过对伊兰特左前车门车窗升降机构改进后,司乘人员能够达到成功逃生的目的,事故伤亡率大大降低. 相似文献
27.
文章主要包括两个结果,一个是关于有限交换群的子群与同态像之间的联系.另一个是关于子群有正规补的一个特征标刻划。 相似文献
28.
设计制作了一个太阳能充电控制器,可实现75 W太阳能电池板对蓄电池的可靠充电。主要采用Cuk电路和光耦电压反馈,并利用TL494实现PWM控制,LM393加互补功放实现驱动。通过MSP430单片机和1602液晶进行电压采样和显示。经实验论证,本方案基本完成了设计预期。 相似文献
29.
道奕光 《六盘水师范高等专科学校学报》2013,(5):57-60
就现阶段国内外研究成果分析,肋片具有减小摩擦阻力及增加流动扰动等特点。平板上采用肋片减阻的效果及肋片参数对减阻的影响已相对清晰,而二维翼型上采用加装肋片后减阻效果如何变化还未可知。文章选取二维翼型S825并使用计算流体力学软件Fluent进行气动性能计算及性能分析,初步发现翼型的表面减阻效果的影响规律,得到升、阻力系数随攻角的变化关系。并用该软件计算带肋片的二维翼型的气动性能,与无肋片的翼型气动性能进行对比分析。结果显示:肋片结构在翼型表面可以产生一定的减阻效果;总阻力的计算公式为压差阻力与粘性阻力之和。由于二维翼型上加装了肋片,改变了压差阻力和粘性阻力,继而改变了总阻力的数值,产生了很好的减阻效果。 相似文献
30.
Deborah L. King Sarah L. Smith Michele R. Brown Jean L. Mccrory Barry A. Munkasy Gary I. Scheirman 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):222-237
In this study, we compared the kinematic variables of the split triple twist with those of the split double twist to help coaches and scientists understand these landmark pair skating skills. High-speed video was taken during the pair short and free programmes at the 2002 Salt Lake City Winter Olympics and the 2003 International Skating Union Grand Prix Finals. Three-dimensional analyses of 14 split double twists and 15 split triple twists from eleven pairs were completed. In spite of considerable variability in the performance variables among the pairs, the main difference between the split double twists and split triple twists was an increase in rotational rate. While eight of the eleven pairs relied primarily on an increased rotational rate to complete the split triple twist, three pairs employed a combined strategy of increased rotational rate and increased flight time due predominantly to delayed or lower catches. These results were similar to observations of jumps in singles skating for which the extra rotation is typically due to an increase in rotational velocity; increases in flight time come primarily from delayed landings as opposed to additional height during flight. Combining an increase in flight time and rotational rate may be a good strategy for completing the split triple twist in pair skating. 相似文献