Bioinspiration of the vein structure of dragonfly wings on its flight characteristics

Dragonflies have excellent flight characteristics, which are inextricably related to the characteristics of their wings. Their wings not only support a variety of loads during flight but also maintain high-efficiency flight characteristics. In this study, the forewing of a dragonfly (Pantala flavescens (Fabricius)) was used as a research object to explore the microstructure of the surface, cross section, and the vein distribution. Three-dimensional models of three different structures of the forewing vein, including an oval-shaped hollow tube, a circular hollow tube, and a circular solid tube, were established. Fluid dynamics analysis of these three forewing models under different angles of attack during gliding was carried out by FLUENT software, and subsequently, the influence of the dragonfly forewing vein structure on its flight characteristics was analyzed. The numerical simulation results indicated that the vein structure has a considerable influence on the lift, drag, and lift–drag ratio of the P. flavescens forewing. It was indicated that among the tested models, the forewing model with oval-shaped hollow tubular veins has better flight efficiency and aerodynamic characteristics. The results of this study may provide the basis for a novel bionic concept of flapping wing microaircraft design.     

背景相对湿度对滑动弧放电降解正丁烷的影响

通过研究背景相对湿度对滑动弧放电特性的影响，分析正丁烷的降解过程和降解机理.结果表明，增大湿度会减少等离子区域电子数量，降低放电电流强度，抑制臭氧的生成.无论是在空气还是氮气条件下，正丁烷降解率随背景相对湿度的增大而增大(分别由81.9% 和33.8%增至91.2%和54.7%)，提高背景相对湿度可以减少副产物中NO2的生成量.根据实验结果推测，基团诱发的反应在正丁烷的降解过程中起主要作用，在潮湿背景条件下，OH基团对正丁烷的降解起关键作用     

水下滑翔机水动力性能分析及滑翔姿态优化研究

水下滑翔机是一种新型的无人运载器,具有低阻力、长航程、长续航力特点,其独特的设计显示出了极大的优势。文中采用数值模拟方法计算了不同速度不同攻角情况下水下滑翔机的阻力、升力及对于浮心的俯仰力矩,对其周围流场水动力学性能进行了分析,并通过流场的流动结构研究了受力随滑翔姿态变化的规律。从做功的角度提出了滑翔姿态的优化目标函数,得出水下滑翔机模型高效滑翔姿态角的控制规律。     

关于摩擦力做功问题的讨论

通过例题分析，分别说明了滑动摩擦力和静摩擦力均有不做功，做正功和做负功的情况。分析了摩擦力与其反作用力做功的情况，指出了静摩擦力做功与滑动摩擦力做功的主要区别。     

Gull-inspired joint-driven wing morphing allows adaptive longitudinal flight control

Birds dynamically adapt to disparate flight behaviours and unpredictable environments by actively manipulating their skeletal joints to change their wing shape. This in-flight adaptability has inspired many unmanned aerial vehicle (UAV) wings, which predominately morph within a single geometric plane. By contrast, avian joint-driven wing morphing produces a diverse set of non-planar wing shapes. Here, we investigated if joint-driven wing morphing is desirable for UAVs by quantifying the longitudinal aerodynamic characteristics of gull-inspired wing-body configurations. We used a numerical lifting-line algorithm (MachUpX) to determine the aerodynamic loads across the range of motion of the elbow and wrist, which was validated with wind tunnel tests using three-dimensional printed wing-body models. We found that joint-driven wing morphing effectively controls lift, pitching moment and static margin, but other mechanisms are required to trim. Within the range of wing extension capability, specific paths of joint motion (trajectories) permit distinct longitudinal flight control strategies. We identified two unique trajectories that decoupled stability from lift and pitching moment generation. Further, extension along the trajectory inherent to the musculoskeletal linkage system produced the largest changes to the investigated aerodynamic properties. Collectively, our results show that gull-inspired joint-driven wing morphing allows adaptive longitudinal flight control and could promote multifunctional UAV designs.     

基于对数螺旋滑移面的土坡稳定性分析——极向条分极限分析法

鉴于传统极限分析法中协调速度场建立的复杂性。构建了基于对数螺旋滑移面的土坡极向条分破坏模式,解决了协调速度场难以建立的问题。应用塑性力学极限分析原理,采用强度储备安全系数定义法,推导出了基于对数螺旋滑移面的均质土坡稳定性分析——极向条分极限分析法。通过算例验证,该法具有使用简便、可靠性强等优点,对于评价均质土坡的稳定性具有重要的指导意义。     

新型改性氟材料滑动零部件的研制

对新型改性氟材料滑动零部件的组成、加工以及摩擦磨损性能进行了研究，制得具有优异摩擦磨损性能的改性氟材料滑动零部件。     

滑动弧光等离子体技术在化工中应用研究进展

滑动弧光等离子体综合了热平衡等离子体和非平衡等离子体的优点,是一种很有前景的等离子体技术。本文介绍了滑动弧光等离子体的产生过程及反应器结构,并对其在化工领域中的应用进行了综述。     

高压高温处理改色的黄绿色金刚石

继“ＧＥ ＰＯＬ”用高压高温方法将茶色方法将茶色金刚石改成无色之后,同样用此方法将茶色或浅黄色、无色金刚石改成鲜艳的黄绿或绿黄经们没有明显的鉴别特征,无法判别其是天然致色还是人工处理改色。