非比例循环载荷下的随动强化律

对于４２ＣｒＭｏＡ钢的非比例循环实验，讨论了几个随动强化律的适用性，其中包括Ｐｒａｇｅｒ、Ｚｉｇｌｅｒ、Ｃｈａｂｏｃｈｅ、Ｍｒｏｚ和Ｔｓｅｎｇ－Ｌｅｅ强化律。分析表明与双曲面本构模型相关的Ｍｒｏｚ和Ｔｓｅｎｇ－Ｌｅｅ强化律能给出较好的预测。文中还给出了一个简化的双曲面本构模型     

多轴载荷作用下表面裂纹的疲劳扩展

通过对圆柱体直前缘表面裂纹在循环拉伸与循环扭转载荷共同作用下的扩展规律进行实验研究,分析了不同载荷曲线相位差、以及拉扭应力幅度对表面裂纹扩展路径、疲劳寿命和裂纹扩展速率的影响。结果表明:不同的相位差对裂纹扩展行为有着非常重要的影响。初始阶段的裂纹扩展主要受到剪应力幅度的影响,后继扩展则依赖于轴向应力幅度。拉应力和剪应力的增加均会增加裂纹扩展速率,但轴向应力幅度变化的影响大于剪切应力幅度。     

Layer-layout-based heuristics for loading homogeneous items into a single container

The container loading problem (CLP) is a well-known NP-hard problem. Due to the computation complexity, heuristics is an often-sought approach. This article proposes two heuristics to pack homogeneous rectangular boxes into a single container. Both algorithms adopt the concept of building layers on one face of the container, but the first heuristic determines the layer face once for all, while the second treats the remaining container space as a reduced-sized container after one layer is loaded and, hence, selects the layer face dynamically. To handle the layout design problem at a layer's level, a block-based 2D packing procedure is also developed. Numerical studies demonstrate the efficiency of the heuristics.     

加载速率对玻璃纤维土工格栅断裂强力的影响

对三种玻璃纤维土工格栅在不同的加载速率下的断裂强力进行了大量的试验研究,得到了断裂强力与加载速率的关系曲线。结果表明,加载速率对断裂强力的影响明显,速率越大,断裂强力越高。     

活性炭固载磷钨杂多酸催化合成苯乙酸乙酯

以活性炭固载磷钨杂多酸为催化剂,苯乙酸和乙醇为原料合成苯乙酸乙酯,考察了影响反应的因素。结果表明,反应温度为80～85℃时,n(醇)∶n(酸)=3.5∶1;催化剂用量为1.0g(苯乙酸为0.05mol的情况下);反应时间为4.5h是最适宜的反应条件。酯化率可达92.5%。     

基于VR的火箭炮装填训练模拟器的设计

针对某型火箭炮实装训练噪声大、磨损大、消耗高等缺点,提出了基于VR的火箭炮装填训练模拟器的设计,文中简述了模拟器的设计原则、总体结构,重点展示了模拟器的硬件构成、软件设计及模拟训练功能的实现,经教学试用,该模拟器达到了设计的要求。     

高温气候重载水泥混凝土路面典型结构受力特性研究

为了解高温气候条件下重载水泥混凝土路面结构受力特征,本文以福建省高温气候条件与重载交通特性为研究实体,采用三维有限元程序EverFE2.24计算高温气候下重载交通对路面的影响.研究结果表明,高温气候下重载交通对水泥混凝土路面造成的不利影响,降低了路面寿命.各参数对面板的受力敏感性分析结果表明,增加面板的厚度、提高地基刚度及设置传力杆,均能有效改善面板的受力性能,其中增加面板厚度带来的受力性能改善的效果最显著.此外,增大基层厚度,在减少了车辆荷载应力的同时,也增大了面板的温度应力,因此对于改善面板受力特性不一定有效.     

Effects of vibration and exercise training on bone mineral density and muscle strength in post-menopausal women

Abstract

The purpose of this study was to compare the effects of a specific vibration programme with those of combined aerobic and resistance exercise training on bone mineral density (BMD), body composition, and muscular strength in post-menopausal women, over a period of 6 months. Thirty-two healthy, inactive post-menopausal women aged 46–62 years were divided into exercise (n = 10), vibration (n = 13), and control (n = 9) groups. The exercise group participated in a supervised programme of strength training at 70% of one-repetition maximum (1-RM) 2 days a week, and aerobic exercise at 70–85% of maximum heart rate one day a week. The vibration group performed vibration training 3 days a week (9 sets×45–80 s per session, 35–40 Hz, peak-to-peak amplitude of vertical vibration = 1.5 mm) on a vibration platform (NemesTM LCB, Bosco System). The BMD of the lumbar spine (L2–L4) was assessed using dual-energy X-ray absorptiometry, and muscle strength with the 1-RM method at baseline and after 6 months of intervention. The BMD of L2–L4 increased in the exercise group (P < 0.05), remained steady in the vibration group, and decreased in the control group (P < 0.05). Muscular strength of leg-extension and leg-curl exercise improved by 28% and 25.5% (P < 0.01) in the exercise group and by 13% (P < 0.01) and 20.5% (P < 0.001) in the vibration group, respectively. The results indicate that conventional training contributed to the increase in BMD of L2–L4, while the vibration programme helped to maintain BMD in post-menopausal women. Both training programmes were efficient in improving muscle strength.     

我国高水平女子短距离自行车运动员全程性多年训练不同阶段的专项训练手段及负荷特征

近年来,我国女子短距离自行车运动员在世界大赛中获得了优异的成绩,系统的多年训练是她们成功的重要致因.运用文献资料法、访谈法、调查法、数理统计法以及逻辑分析法等方法,对我国部分高水平女子短距离自行车选手全程性多年训练实践中各阶段的专项训练手段及负荷进行了研究,力求揭示她们在各阶段训练中专项训练手段和负荷安排的一般性规律及某些个性特征,为科学地组织好运动员的多年训练,为我国女子短距离自行车竞技水平的持续发展提供理论依据与实践指导.     

长时间操作电脑静力性损伤状况及体疗方法研究

随着自动化程度的提高和计算机的广泛应用,静力性负荷所致损伤的发病率显著提高,直接影响了长时间从事电脑操作人群的身体健康和正常工作,因此探索这种损伤的预防及治疗措施逐渐成了研究的重点。以长时间静力性工作的教师为研究对象,对他们的颈部、腰部、肩部或腕部等部位疼痛或活动受限情况进行了调查,结果发现：在接受调查的教师中,有86．5％的人保持现在使用电脑工作方式在3年以上;83．8％的人使用鼠标的姿势不正确;87．8％的人自我感觉出现了机体某些部位的疼痛,尤其表现在颈部和肩部;66．2％的人自我感觉疼痛症状在休息后得到减轻。对调查结果进行了深入的分析并提出了简单易行的体疗方法