图书捐赠对藏书建设的作用及其推动措施

从增加藏书数量、提升藏书品位、让藏书有序传承、提高社会利用率几方面阐述捐赠对藏书建设的作用,并从规范接收、表彰奖励、媒体宣传、满足要求、政策支持等方面提出了推动图书捐赠的相应措施。     

社会力量参与图书馆建设途径探讨

图书馆属于公益性社会机构,应当主要依靠国家财政支持其建设和日常运转。但现阶段,要实现我国图书馆事业的快速发展,仅仅依靠政府的力量是难以实现的。调动社会力量参与图书馆事业建设,可弥补政府投资之不足。分析了社会力量参与图书馆建设的可行性,并对社会力量参与图书馆建设的途径进行了探讨。     

讨论式教学法在士官大专《工程力学》课例中合理运用

讨论式教学法能够充分调动学员的学习热情,培养创新思维和多种能力,是一种实用性很强的教学方法,本文针对讨论式教学法在士官大专《工程力学》课程中的试点,结合用微积分关系法绘制剪力图和弯矩图的典型课例,详细论证了讨论式教学法的不同形式在该课例中的灵活运用,不但活跃了课堂气氛,而且取得了良好的教学效果。     

Optimal machining conditions for turning Ti-6AI-4V using response surface methodology

Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force （Fz） and surface roughness （Ra）. In the present work, the performance of PVD/TiA1N coated carbide inserts was investigated using response surface methodology （RSM） for turning Ti-6A1-4V. The effects of process parameters such as speed （v）, feed （/＇）, depth of cut （d） and back rake angle （Ty） on Fz and Ra were investi- gated. The experimental plan used for four factors and three levels was designed based on face centered, central composite design （CCD）. The experimental results indi- cated that Fz increased with the increase in d, f and decreased with the increase in v and yy, whereas Ra decreased with the increase in v and 7y, and increased with d and v. The goodness of fit of the regression equations and model fits （R2） for Fz and Ra were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model.     

带式输送机跑偏现象力学分析

胶带跑偏是带式输送机的常见故障,不仅会造成胶带磨损缩短胶带的使用寿命,而且严重时将导致整个输送机设备无法正常。本文总结了跑偏的各种原因,并从力学的角度对各种跑偏现象进行了分析。     

动力学数学模型下弧圈球运行轨迹的研究

通过建立乒乓球的动力数学模型,对弧圈球在每一种情况下的运动规律及运行轨迹变化曲线进行分析。结果显示：影响弧圈球运行轨迹的主要因素有乒乓球运动方向、运动速度、旋转速率、加速度及Magnus力,其中乒乓球运动方向和Magnus力的变化是改变乒乓球速度变化的重要因素;在运行过程中,球向的不断变化使弧圈球的速度及加速度也不断改变;而影响乒乓球运行轨迹的直接因素是旋转速率,且弧圈球第一弧线和第二弧线在不同旋转速率下存在着明显的区别。     

In vivo behavior of vastus lateralis muscle during dynamic performances

Length changes in vastus lateralis fascicles were measured in vivo using ultrasonography during one-legged squat jumps (SJ), counter movement jumps (CMJ), and drop jumps (DJ) in the sledge apparatus (n = 9). Patellar tendon forces were recorded simultaneously with an optic fiber technique from 4 subjects. Fascicle length changes were compared with muscletendon unit length changes calculated from kinematic recordings. In general, the tendomuscular and fascicle length changes demonstrated similar patterns. During SJ the fascicles showed shortening throughout the action while during CMJ and DJ they underwent stretch-shortening cycle. In DJ greater muscular activity in braking phase.     

Torque–velocity characteristics and contractile rate of force development in elite badminton players

Abstract

Elite badminton requires muscular endurance combined with appropriate maximal and explosive muscle strength. The musculature of the lower extremities is especially important in this context since rapid and forceful movements with the weight of the body are performed repeatedly throughout a match. In the present study, we examined various leg-strength parameters of 35 male elite badminton players who had been performing resistance exercises as part of their physical training for several years. The badminton players were compared with an age-matched reference group, the members of whom were physically active on a recreational basis, and to the same reference group after they had performed resistance training for 14 weeks. Maximal muscle strength of the knee extensor (quadriceps) and flexor muscles (hamstrings) was determined using isokinetic dynamometry. To measure explosive muscle strength, the contractile rate of force development was determined during maximal isometric muscle contractions. In general, the badminton players showed greater maximal muscle strength and contractile rate of force development than the reference group: mean quadriceps peak torque during slow concentric contraction: 3.69 Nm · kg^?1, s=0.08 vs. 3.26 Nm · kg^?1, s=0.8 (P<0.001); mean hamstring peak torque during slow concentric contraction: 1.86 Nm · kg^?1, s=0.04 vs. 1.63 Nm · kg^?1, s=0.04 (P<0.001); mean quadriceps rate of force development at 100 ms: 24.4 Nm · s^?1·kg^?1, s=0.5 vs. 22.1 Nm·s^?1 · kg^?1, s=0.6 (P<0.05); mean hamstring rate of force development at 100 ms: 11.4 Nm · s^?1·kg^?1, s=0.3 vs. 8.9 Nm · s^?1 · kg^?1, s=0.4 (P<0.05). However, after 14 weeks of resistance training the reference group achieved similar isometric and slow concentric muscle strength as the badminton players, although the badminton players still had a higher isometric rate of force development and muscle strength during fast (240° · s^?1) quadriceps contractions. Large volumes of concurrent endurance training could have attenuated the long-term development of maximal muscle strength in the badminton players. The badminton players had a higher contractile rate of force development than the reference group before and after resistance training. Greater explosive muscle strength in the badminton players might be a physiological adaptation to their badminton training.     

Strength,power, and postural control in seniors: Considerations for functional adaptations and for fall prevention

Abstract

The ageing neuromuscular system is affected by structural and functional changes that lead to a general slowing down of neuromuscular performance and an increased risk of falling. As a consequence, the process of ageing results in a reduced ability to develop maximal and explosive force, as well as in deficits in static and dynamic postural control. A decrease in the number and size of type II fibres in particular accounts for the age-related decline in muscle mass (sarcopaenia) and strength performance. Multiple denervation and re-innervation processes of muscle fibres seem to be responsible for the reduced number of muscle fibres. Recently, it has been suggested that it is not the decline in motoneurons that accounts for the loss in number of muscle fibres but the disturbed potential of fibre regeneration and re-innervation. Furthermore, an age-related reduction in the number of satellite cells has also been associated with sarcopaenia. The ability to compensate for platform and gait perturbations deteriorates with ageing as reflected in longer onset latencies and inefficient postural responses. All sites within the somatosensory system are affected by ageing and therefore contribute to postural instability. However, morphological changes of muscle spindles appear primarily to be responsible for the impaired ability to compensate for balance threats in old age. Given these neuromuscular limitations in old age, it is important to apply adequate training interventions that delay or even reverse the onset of these constraints. Strength training has the potential to enhance maximal as well as explosive force production capacity. This is accomplished by neural factors, including an improved recruitment pattern, discharge rate, and synchronization of motor units. Furthermore, an increase in number of satellite cells most likely accounts for training-induced muscle hypertrophy. Recent studies have investigated the impact of balance training in old age on the ability to develop maximal and explosive force. In addition, the effects of balance training on reflex activity during gait perturbations were also examined. Increases in maximal and explosive force production capacity and an improved ability to compensate for gait perturbations were observed. It is evident from the literature that researchers are increasingly studying the effects of more specifically designed training programmes on performance in populations of older adults. Thus, in the near future, strength training could be replaced by high-velocity forms of power training and balance training by perturbation-based training programmes. It is hypothesized that this new approach is more efficient in terms of fall prevention than the traditional approach.