人体小腿肌腱生物材料力学特征实验研究

目的：：人体小腿肌腱损伤后的防治、修复、人工材料替换等需要大量的生物材料力学特征方面的实验数据作为其参考依据。方法：使用德国产Zwick万能材料实验机,对小腿9种72条成人新鲜小腿肌腱进行“一维拉伸破坏试验”,并对实验数据进行统计学处理。结果：(1)当应变为0-5%范围时,形变随拉伸应力改变较小,属于曲线的“坡脚区”;当应变为8%-16%范围时,应力随应变增大而增大,属于曲线的“直线区”;当应变达到20%左右时,拉伸应力则随应变增大而减小。(2)小腿肌腱之间极限应变没有显著性差异;跟腱极限应力明显小于趾长伸肌腱、趾长屈肌腱、拇长伸肌腱与拇长伸肌腱(P<0.05)。(3)部分小腿肌腱之间拉伸刚度与弹性模量有显著性差异(P<0.05)。结论：(1)小腿肌腱与前臂肌腱均是以规则致密结缔组织为主构成,故其“应力—应变曲线”也呈现基本相同的特征。(2)从小腿各肌腱极限应变指标对比结果差异不明显可以推断小腿肌腱抵抗最大负荷的能力基本相同;跟腱由于其截面积大,应力呈现分散现象,故极限应力最小。(3)跟腱的拉伸刚度较大,从生物材料上保证其能够承受踝关节完成高频率、大强度、较大运动幅度的背屈运动。(4)肌腹强大的肌腱主要通过肌肉收缩力使其产生弹性变形,而肌腹较小的肌腱主要通过自身弹性变形满足承担功能的需要。     

存现句语义对谓语动词的制约

存现句是现代汉语中一种很有特点的句式。从20世纪50年代开始,很多学者从结构形式、句法性质、动词特点、语法意义和变换关系的角度对存现句作了多方位的研究。本文试图以存现句的语义特征为研究的出发点,分析存现句语义对谓语动词在语义和句法上的各种制约关系,并重新划分存现句的类别。     

The effects of a unilateral gluteal activation protocol on single leg drop jump performance

Warm-up protocols are commonly used to acutely enhance the performance of dynamic activities. This study examined the acute effect of low-load gluteal exercises on the biomechanics of single-leg drop jumps. Eight men and seven women (18–22 years old) performed 10 single-leg drop jumps on three separate days. The gluteal exercises were performed within the warm-up on day 2. Contact time, flight time, peak vertical ground reaction force (GRF), rate of force development, vertical leg-spring stiffness, and reactive strength index were determined. A repeated measures analysis of variance was used to examine differences on all variables across days. Significant differences were found for contact time, peak GRF, and flight time between days 1 and 2 and for flight time between days 1 and 3 (p ≤ 0.05) with no significant difference in any variables between days 2 and 3. This suggested that the improvements in day 2 were due to practice effects rather than the gluteal activation exercises. In addition, a typical error analysis was used to determine individual responses to the gluteal exercises. The results using this analysis showed no discernible response pattern of enhancement or fatigue for any participant.     

浅谈三维动画中“Stretch IK”的实现方法

在三维动画角色绑定阶段涉及到"弹性"的话题非常多,这里仅对"stretch IK"实现的基本方法做一些讨论.在MAYA中实现"Stretch IK"的思路主要有两种,一种是依靠编写脚本来实现,即依靠MAYA的MEL语言,另一种是依靠MAYA的节点网络来实现.     

伸长法测量金属杨氏模量实验的改进

本文对传统的杨氏模量的测量方法作了改进:用电阻丝替代原来用的钢丝,用电桥替代光杠杆测量金属丝的微小伸长△l,结果使该实验操作简单,仪器调试容易,测量结果精度提高。