空间柔性机械臂三维动力学数值仿真

本文应用ｄ＇Ａｌｅｍｂｅｒｔ－Ｌａｇｒａｎｇｅ原理，对由基座、（ｎ－１）个柔性连杆及端部负载组成，相互用柱铰连接的柔性链式多体系统进行建模；对在空间技术中，具有一刚杆，两柔杆加上刚性负载所组成的三维机械臂系统，采用Ｇｅａｒ算法进行数值仿真。仿真结果比较符合实际，从而在柔性多体系统的数学模型为刚性常微分方程的情况下，为解决其数值仿真问题，特别是三维问题的数值仿真取得了进展。     

柔性轧制Q390C和Q420C钢板生产实践

目前市场对中厚板的订单具有个性化和多样化的特点，而对于不同强度级别的钢板，化学成分设计往往是不同的，这样会增加不同钢坯冶炼之间衔接的时间及化学成分控制的难度，导致冶炼成本增加，工序复杂化。结合市场需求与生产实际，采用同一Q390低合金高强度钢板坯，通过不同的控轧控冷工艺，对Q390C和Q420C两种强度级别热轧钢板进行了试制。结果表明，通过控轧控冷技术，可以充分发挥细晶强化作用，采用同一Q390低合金高强度钢板坯实现了Q390C和Q420C两个强度级别热轧钢板的柔性生产。试制生产的两种钢板，强塑性及0 ℃冲击功均满足标准要求，Q420C钢板屈服强度达441 MPa以上，抗拉强度达579 MPa以上。采用柔性轧制技术，降低了Q420C高强钢板的生产成本。     

Computational Schemes for Flexible,Nonlinear Multi-Body Systems

This paper deals with the development of computational schemes for the dynamic analysis of flexible, nonlinear multi-body systems. The focus of the investigation is on the derivation of unconditionally stable time integration schemes for these types of problem. At first, schemes based on Galerkin and time discontinuous Galerkin approximations applied to the equations of motion written in the symmetric hyperbolic form are proposed. Though useful, these schemes require casting the equations of motion in the symmetric hyperbolic form, which is not always possible for multi-body applications. Next, unconditionally stable schemes are proposed that do not rely on the symmetric hyperbolic form. Both energy preserving and energy decaying schemes are derived that both provide unconditionally stable schemes for nonlinear multi-body systems. The formulation of beam and flexible joint elements, as well as of the kinematic constraints associated with universal and revolute joints. An automated time step selection procedure is also developed based on an energy related error measure that provides both local and global error levels. Several examples of simulation of realistic multi-body systems are presented which illustrate the efficiency and accuracy of the proposed schemes, and demonstrate the need for unconditional stability and high frequency numerical dissipation.     

Highly Thermal Stable Polyimides Applied in Flexible Resistive Memory

Flexible memory devices are one of the most crucial elements in the wearable electronics. In this work, polyimides (PIs)-based flexible resistive memory devices with an excellent thermal and mechanical durability are demonstrated. Four kinds of functional PIs are derived from the heterocyclic diamines including 2,6-diaminodibenzo-p-dioxin (OODA) and 2,6-diaminothianthrene, and dianhydrides including 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride. PI with diamine of OODA and dianhydride of 6FDA (PI(OODA_6FDA)) possesses outstanding thermal and mechanical properties with a high glass transition temperature of 352 °C, a low coefficient of thermal expansion of 28.1 ppm K⁻¹, and a high elongation at break of 10%. In addition, PI(OODA_6FDA)-based memory shows write-once-read-many behavior with a high on/off current ratio of 10⁶ and a stable data retention, attributed to the donor–acceptor charge transfer between the polymer chains. The retained current levels at a low resistive state can be observed even with thermal treatment at 200 °C for 24 h or 1000 times cyclic bending at a bending radius of 5 mm. These results demonstrate the potential of heterocyclic PIs for flexible resistive memory.     

柔性结构系统的观测器型鲁棒最优保性能控制

通过简要分析柔性直线系统结构,给出3自由度高阶直线柔性系统的数学模型。根据实际直线柔性控制过程滑动质量块位置状态信息易得、但速度状态信息不易得的特点,构造了速度状态观测器。同时针对柔性结构系统对于干扰激发的振动具有难以迅速稳定的特点,设计了基于观测器的直线柔性系统的鲁棒最优保性能控制。实验结果表明:对于直线柔性系统,所设计的观测器型鲁棒最优保性能控制是有效的。     

高性能纤维的弯曲疲劳断裂研究

在自制弯曲疲劳装置上 ,对 3种高强对位芳纶及超高相对分子质量聚乙烯纤维 (Dyneema SK65 )进行双面弯曲疲劳试验。结果表明 ,Twaron 2 0 0 0弯曲疲劳寿命的自然对数与预加应力、弯曲角度呈线性关系 ,Dyneema SK65弯曲疲劳寿命明显长于对位芳纶 ,Twaron 2 0 0 0 ,Kevlar 12 9相近 ,都比Kevlar 2 9略长 ;高强型对位芳纶的弯曲疲劳断裂断口芯层呈现出“毛笔头”或“拔丝形”原纤化分裂形态 ,超高相对分子质量聚乙烯纤维弯曲疲劳断裂断口有明显的脆性折断形态 ,无原纤出现。     

望远镜专用PVC外装饰皮的开发应用

从生产用原材料、配方、生产工艺及影响因素等方面介绍了软质PVC在望远镜用外装饰皮中的应用,并进行了分析、探讨,提出了软质PVC在望远镜用外装饰皮中研制开发的看法与建议。     

柔性分离盘抑制圆柱涡激振动的风洞试验

该文利用附属柔性分离盘对圆柱涡激振动(VIV)控制问题进行了风洞试验研究。针对弹性支撑的圆柱及不同长度柔性分离盘的试验模型,在雷诺数7 500-40 000情况下,测定不同约化速度(3.5-18.7)下的振动瞬态位移。结果表明:柔性分离盘长度(L)/圆柱直径(D)比为0.6、0.8和1三种圆柱的横向无因次均方根振幅远小于单圆柱,涡激振动抑制效果很好,均在77.6%以上,其中L=0.8D的圆柱抑制效果最佳,几乎无振动;而L=1.2D和1.5D的圆柱反而出现振动增强,约4.5%和9%。对比单圆柱的共振区,附属柔性分离盘的圆柱共振区在约化速度上更靠后且范围更大。     

世界石油化工发展中的问题

１９９６年３月美国休斯顿市德惠特（Ｄｅ Ｗｉｌｔ）石油化工研讨会和化学市场协会集团（ＣＭＡＩ）１１届石化研讨会，先后发表对今后５年石油化工发展展望。要点：（１）石油化工的裂解原料要选用弹性裂解炉，适应原料价格变化。（２）聚烯烃下游产品（含合纤）需求与生产，仍是上升趋势。（３）炼油与石化结合才有高效益。     

基于PLC的船舶机舱监测报警系统的改进方案

针对原机舱监测报警系统的老化以及无法表示监测点的具体数值的问题,利用西门子PLC S7-200作为数据的采集和发送单元,利用西门子触摸屏MP377搭载组态软件WinCC flexible 2010,对数据进行实时的监测与报警,同时PLC将机舱监测报警系统所有测点的实时数据发送到轮机长室,实现对机舱主机及付机的各项参数的实时监测。改进的监测系统已经投入使用,事实证明该系统安全可靠。