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排序方式: 共有211条查询结果,搜索用时 9 毫秒
31.
煤矿井巷锚杆支护施工的分析与探讨 总被引:1,自引:0,他引:1
李进 《河北能源职业技术学院学报》2009,9(3):60-61
介绍了锚杆支护的特点、原理、类型、工艺、注意事项、质量要求。 相似文献
32.
We propose a novel kind of compound permanent magnet synchronous machine (CPMSM), which is applicable in low-speed and high-torque situations. We first explain the structure of the CPMSM. Based on theoretically deducing the calculation formulae of the CPMSM electromagnetic parameters, we analyze the operating characteristics of the CPMSM, and obtain the power-angle curves and working curves. The no-load magnetic field distribution and the cogging torque are analyzed by applying the finite element method of three-dimensional (3D) magnetic fields, to determine the no-load leakage coefficient and the wave0form of the cogging torque. Furthermore, the optimal parameters of the permanent magnet for reducing the cogging torque are determined. An important application target of the CPMSM is in direct-drive pumping units. We have installed and tested a directdrive pumping unit in an existing oil well. Test results show that the power consumption of the direct-drive pumping unit driven by CPMSM is 6 1. 1% of that of the beam-pumping unit, and that the floor space and weight are only 50% of those of a beam-pumping unit. The noise output does not exceed 58 dB in a range of 1 m around the machine when the machine is 1.5 m from the ground. 相似文献
33.
Pui W. Kong 《Journal of sports sciences》2013,31(5):537-543
Abstract A modelling approach was used in the present study to investigate the role of the hip muscles during the come-out of forward and inward multiple somersaulting dives in a pike position. A planar two-segment model was used to simulate the somersault and come-out of three commonly performed dives from a 3-m springboard: forward two-and-one-half somersault pike dive (105B), forward three-and-one-half somersault pike dive (107B), and inward two-and-one-half somersault pike dive (405B). Three simulations were run for each dive: (1) hip angle was constrained to be constant, (2) hip torque was removed after 0.1 s, and (3) hip angle was constrained to a typical come-out time history used by elite divers. Simulation results indicated that hip flexion torque was required both to maintain a rigid pike position during somersault (range = 205.5–282.3 Nm) and to control the hip extension movement during the come-out (peak torque range = 355.8–548.1 Nm) in forward and inward multiple somersaulting dives. Coaches and divers should be aware that dry-land exercise drills producing hip extension movement by concentric actions of the hip extensor muscles do not replicate the neuromuscular control during the come-out of fast rotating dives. 相似文献
34.
Gail M. Dummer David H. Clarke Paul Vaccaro Lee Vander Velden Allan H. Goldfarb James M. Sockler 《Research quarterly for exercise and sport》2013,84(2):97-102
Abstract The purpose of this study was to examine age-related differences in muscular strength and muscular endurance among 73 female masters swimmers aged 24 to 71 years. Each subject was assessed on measures of body size, grip strength, peak isokinetic torque of shoulder and knee flexion and extension, and endurance of shoulder and knee movements. Although swim training appears to have resulted in higher strength values for these swimmers than for less active women, an age-related decline in muscular strength values was nevertheless apparent. The results fail to reveal a similar age-related trend for muscular endurance, suggesting that swim training influences muscular endurance more than muscular strength among adult women. 相似文献
35.
Abstract Eighteen male subjects, ages 20–28 years, engaged in three fatigue bouts using an isokinetic dynamometer (Cybex II). Maximum knee extension contractions were given for 100 s at a rate of 30 per minute. The three contraction speeds chosen were 120° · s –1 160° · s –1 and 200° · s –1.Peak torque at 120° · s –1 was significantly greater (p <.05) than at 200° · s –1 for the first 60 s, and 160° · s –1 for the first 50 s. Thereafter, no significant differences existed among conditions. All three curves were found to follow two-component exponential functions as shown by the equation yt =a 2 ek2t – a 1 ek1t + c. The three curves possessed similar rate constants for both components. Time to peak torque was achieved at similar times for testing at 160 and 200° · s –1 (p <.05). It is concluded that peak torque varies inversely with movement speed, and that the pattern of decrement is independent of movement speed. Time to peak torque does not appear to change significantly across trials in isokinetic fatigue. 相似文献
36.
Abstract The purpose of this study was to examine knee extensor/flexor muscle strength and physical activity in healthy males and females approaching retirement. Peak torques of the knee extensor and knee flexor muscle groups were measured bilaterally in 95 individuals (mean age 59.4 years) using an isokinetic dynamometer. Isokinetic concentric contractions were performed at angular velocities of 1.05 and 3.14 rad · s?1. Physical activity, including household, leisure, and sporting activities, was assessed. The results show that the average peak torques exhibited were lower than previously reported in studies using the same methodology with different populations of similar age and body size. Over one-third of the participants were sedentary, with just 13% being active enough to obtain health benefits. The poor muscle strength and low physical activity of this self selecting group of healthy working adults were surprising, and potentially a cause for concern. The combination of retirement being a potential watershed for a decrease in physical activity and the known age-related decline in physical performance indicates that some of these participants are at risk of losing their functional independence fairly early in the retirement stage. We recommend the introduction of effective health promotion interventions for individuals approaching retirement, encouraging them to become more physically active. 相似文献
37.
Abstract In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torquepeak) and peak heart rate peak (HRpeak) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HRpeak), heart rate (HRtrain), torque (Torquetrain), and changes in EMG amplitude (ΔEMGamp) and frequency (ΔEMGfreq) were determined. The markers of training intensity were: Torquetrain relative to the 2min-torquepeak (%2min-torquepeak), EMG relative to EMGpeak (%EMGpeak), HRtrain ΔEMGamp, ΔEMGfreq, and %MVC. Mean systolic (?4.9 mmHg) and arterial blood pressure (?2.7mmHg) reductions correlated with %2min-torquepeak (r = ?0.65, P = 0.02 and r = ?0.59, P = 0.03), ΔEMGamp (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMGfreq (r = ?0.67, P = 0.01 and r = ?0.64, P = 0.02), and %EMGpeak (systolic blood pressure only; r = ?0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training. 相似文献
38.
关于膝损伤患者伸、屈肌群力矩值及修正值的研究 总被引:4,自引:0,他引:4
利用Kin-Com等速测力仪对108名膝关节损伤的男性患者健、患膝关节伸、屈肌群向心性收缩的平均力矩、峰力矩及单位体重下的修正值进行比较研究。实验表明,受伤膝关节的伸肌群与正常膝关节相比在平均力矩和峰力矩方面均有明显下降;而屈肌群的下降并不明显。伸肌群产生最大量的角度大约在60度左右,屈肌群产生最大力量的角度大约为20度左右。患者正常侧膝关节H/Q平均值在80%左右,伤侧H/Q平均值高达90%以上。实验所得平均力矩修正值和峰力矩修正值相对于一般人群膝关节损伤患者具有重要的参考价值。受伤膝关节伸肌群的平均力矩和峰力矩,与对侧正常膝关节相比,低于10%以上,可以作为膝关节损伤诊断和康复评定的有意义指标之一。 相似文献
39.
40.
用有限元法分析径向磁性联轴器的力矩特性 总被引:1,自引:0,他引:1
杨红 《深圳职业技术学院学报》2004,3(2):22-25
从电磁场的基本理论出发,建立了径向磁性联轴器的有限元数学模型,利用磁场的周期性条件来压缩求解区域范围,使计算大为简化。分析了环间转角、磁极数、磁环尺寸、磁环间距等因素对联轴器传动力矩的影响,并总结了径向磁性联轴器力矩特性的变化规律。 相似文献