磁悬挂天平的变结构控制

鉴于磁悬挂天平系统强烈的非线性特性及存在的多种不确定性，针对非匹配不确定性情况设计了变结构控制器。根据对悬浮时模型受力图的分析，及其模型两端电磁力、电流和电压的平衡关系，并以y轴方向受力为例，讨论了磁悬挂天平的非线性变结构设计过程。该设计的目的是使镇定误差趋近于0，其设计步骤包括期望性能到期望力的传递、满足滑动模态可达条件的控制力到控制电压的传递、控制电压的求解。同时对设计的结果进行了仿真分析，仿真结果表明磁悬挂天平的变结构控制系统具有良好的动态性能。     

高空远程滑翔UUV低空突防段弹道运动仿真与分析

高空远程滑翔UUV技术是一种集高空滑翔与水下航行于一体的综合设计研究,低空突防段弹道是高空远程滑翔UUV弹道流程中的重要部分。通过建立高空远程滑翔UUV的六自由度数学模型,对低空突防段弹道进行了运动仿真和详细分析。采用常规等高控制方案控制飞行高度,仿真结果显示产生了掉高过大的现象,甚至在水平面以下,低空突防不能实现。为避免这种现象,选择两种方案解决这一问题,一是在突防段引入极限舵角的方式,一是修改高度控制方程。经仿真分析,两种方案均能改变掉高过大现象,且第二种方案具有较好的适用性,系统相对也较稳定。     

Development and Control of Underwater Gliding Robots: A Review

As one of the most effective vehicles for ocean development and exploration, underwater gliding robots (UGRs) have the unique characteristics of low energy consumption and strong endurance. Moreover, by borrowing the motion principles of current underwater robots, a variety of novel UGRs have emerged with improving their maneuverability, concealment, and environmental friendliness, which significantly broadens the ocean applications. In this paper, we provide a comprehensive review of underwater gliding robots, including prototype design and their key technologies. From the perspective of motion characteristics, we categorize the underwater gliding robots in terms of traditional underwater gliders (UGs), hybrid-driven UGs, bio-inspired UGs, thermal UGs, and others. Correspondingly, their buoyancy driven system, dynamic and energy model, and motion control are concluded with detailed analysis. Finally, we have discussed the current critical issues and future development. This review offers valuable insight into the development of next-generation underwater robots well-suited for various oceanic applications, and aims to gain more attention of researchers and engineers to this growing field.      

重掺硼对直拉单晶硅片上压痕位错运动的影响

对比研究了轻掺硼(1.5×10~(16)cm~(-3))和重掺硼(1.2×10~(20)cm~(-3))直拉硅片上维氏压痕周围的残余应力分布及压痕位错在900℃滑移的情况。研究表明:重掺硼直拉硅片上压痕周围的残余应力及应力场区域显著小于轻掺硼硅片的。在900℃热处理时,轻掺硼硅片上的压痕位错发生显著的滑移,而重掺硼硅片上的压痕位错几乎不发生滑移。一方面,重掺硼降低了单晶硅的压痕断裂韧性,使侧向裂纹尺寸增大而释放更多的应力,从而使压痕的残余应力变小;另一方面,重掺硼对位错具有明显的钉扎作用,使位错的滑移需要更大的应力驱动。可以认为正是上述两方面的效应使得重掺硼硅片的压痕位错几乎不发生滑移。     

Flame versus air atmospheric gliding arc plasma treatment of polypropylene-based automotive bumpers: Physicochemical characterization and investigation of coating properties

In this research, the polypropylene (PP) sheets used for automotive bumper surface were treated using two methods: air atmospheric gliding arc plasma and flame modifications. Atomic force microscopy was applied to study the morphology of surfaces before and after treatment processes. While calculating the surface free energy (SFE), contact angle of the surfaces was measured, and the chemical composition of the PP surface was analyzed using X-ray photoelectron spectroscopy. Surface modifications by gliding arc plasma increased the ratio of the oxygen and nitrogen atoms on the surface by 100%, indicating that polar chemical functionalities form on the surface. The surface morphology was highly affected by gliding arc plasma treatments, which triggered an impact on roughness and etching. It was also found that the SFE was drastically increased by certain modifications. Noticeable improvement was also observed in wettability by the gliding arc plasma technique. In the next stage, polyurethane paints were coated on the treated and untreated PP surfaces. Then, we examined the flame and gliding arc plasma treatments' effect on coating properties of PP bumper, adhesion analysis, water immersion resistance, and sulfuric acid resistance. Finally, high-pressure carwash test and gloss analysis were conducted on the treated and untreated coated sheets, respectively.     

脉冲重复频率对微秒脉冲滑动放电特性影响的实验研究

脉冲滑动放电能够在大气压下产生高能量、高电子密度的低温等离子体,在废水处理、点火助燃、甲烷转化等领域具有广泛的应用前景。为了研究重复频率微秒脉冲电源对滑动放电特性的影响,采用自主研制的重复频率微秒脉冲电源,通过改变电源的脉冲重复频率进行了实验研究。结果表明在大气压空气中滑动放电产生的火花通道能够顺着气流的方向沿刀型电极刃面向上滑动,最大高度和长度可以达到29 mm和43 mm,各火花通道彼此分散。进一步分析脉冲重复频率对滑动放电的影响规律可知,高频时(500~1 500 Hz),随着脉冲重复频率的增大,火花放电通道逐渐向上发展,发生火花放电的最高位置逐渐向刀型电极的刀尖处靠拢。滑动放电的击穿电压逐渐减小,工作电压逐渐分散。这与驻留粒子的记忆效应和电极间隙的变化有关。低频时(1~300 Hz),由于气流的作用,电极间隙内驻留的粒子较少,其记忆效应对滑动放电的影响较弱,火花通道不能沿刀型电极刃面向上滑动。     

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     

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。