表面黏附导致的接触行为转变

应用大规模分子动力学方法, 模拟了具有不同原子级粗糙形貌的两种刚性球形探头与弹性平面基体的黏附接触行为. 研究了载荷与真实接触面积、接触界面排斥力与真实接触面积, 以及黏附力与真实接触面积之间的关系. 分子模拟得到的载荷与真实接触面积的关系, 与连续力学接触理论预测很好地定性一致. 无论是原子级光滑探头还是粗糙探头, 黏附接触下的排斥力与真实接触面积的关系, 都与无黏附接触时的规律相一致, 即黏附力对接触行为的影响作用, 可以等效为附加在真实外载荷基础上的虚拟载荷, 将对黏附接触行为的分析转变为无黏附接触分析. 两种探头的黏附力随真实接触面积都呈幂函数形式的增长, 但是, 原子级光滑探头的幂指数大于1, 而原子级粗糙探头的幂指数小于1. 关键词： 接触行为 表面黏附 分子动力学模拟     

手机、电脑显示屏的发光光谱以及对人眼健康的影响

长时间使用手机、平板电脑、电脑显示屏等设备,已成为当今社会生活中十分普遍的现象.这些设备的发光波段具体是多少?是否会对人们眼部视力造成伤害?这也成为大家十分关注的问题.针对这些问题,本文利用光谱仪测量了不同型号手机、电脑显示屏的发光光谱,以及光谱强度随探测距离的变化,并对不同设备进行了分析和比较,讨论了这些设备对人眼可能造成的危害.     

运动颗粒流中的摩擦起电

绝缘颗粒系统的摩擦带电现象是一种普遍现象,但至今仍未得到很好的认识.月球及火星表面漂浮着大量尘埃颗粒,这将严重影响探测设备的太阳能帆板、散热和观察系统等的正常工作.近年来,电帘除尘方法被认为是在月表进行尘埃防护的有效手段,研究表明颗粒表面摩擦带电对月尘静电来源贡献最大,因此正确理解颗粒摩擦带电的机理对分析尘埃颗粒的运动规律至关重要.本文建立了一个基于高能态电子假定的分析模型来预测颗粒间的摩擦电荷分布.计算了颗粒摩擦生电与颗粒粒度的依赖关系,以及粒度范围对摩擦电荷产生的概率大小的影响.揭示了电荷分布的一个上限,并讨论了可能的原因.对粒子碰撞过程中的电荷转移进行了粒子动力学模拟,验证了理论预测结果.     

月表尘埃颗粒带电的机理及应用研究

研究月尘颗粒在电子束环境下以及紫外源辐照下的带电机理,利用数值方法模拟月尘颗粒在不同背景环境下的充电过程,以探索月表尘埃颗粒的带电机理,进而便于地面月尘环境模拟装置选择合适的月尘带电方式进行空间模拟实验.给出了尘埃在电子束环境下的充电方程,并将紫外辐射带电与具体应用相结合.通过模拟结果可知,在电子束环境下,月尘表面的电荷数随粒径尺寸增大,随电子枪辐照束斑半径减少,随电子枪流强的增加而增多;在紫外源的辐照下,月尘表面电荷数随颗粒尺寸的增大以及紫外线辐照度的增加而增多.由月尘颗粒受太阳紫外辐照带电的数值模拟结果可知,月尘需要在太阳长时间的辐照下才可以带上可观的电荷数,地面模拟该过程需增加辐照源来加速实验.通过模拟结果的分析比较并结合"空间环境模拟装置"中对月尘舱的设计要求,最终优选紫外源辐照带电方式作为月尘颗粒的带电方案.     

材料表面之间黏附过程分析

对两材料表面黏附过程进行了理论分析，得出了跳触距离的计算公式，发现跳触距离与试样的几何尺寸和系统的刚度有关，而且也受到相对湿度的影响. 利用单峰接触模型和幂律流体的本构方程，对材料表面吸附的水膜进行了动力学分析，改进了描述拉开力和停留时间关系的方程. 并利用自制的黏附力测试装置对跳触力和拉开力进行了测试和分析. 关键词： 黏附 范德华力 相对湿度 水膜     

大型液冷机组的振动测试与减振设计

针对大型液冷机组工作时产生的振动对设备和人员健康可能产生的潜在危害,对某300k W制冷量的液冷机组进行了振动测试,并根据测试结果和机组模态仿真情况,对机组进行了被动减振设计。减振后的测试结果表明,经过减振处理可有效降低工作时机组到安装基础的振动传递率,并满足相关标准要求。     

基于MIC总线的军用车载网络故障诊断与测试方法研究

针对军用车辆综合电子系统故障机理复杂这一问题,文章构建了MIC网络主动和被动相结合的在线数据测试方法,从消息传输的完整性和实时性角度系统地提出了网络性能测试及分层故障定位模型,运用在线数据解析技术和实时数据库管理技术进行网络测试设备的开发。通过某型车辆的实车测试,证明了上述测试方法和测试模型的可行性和有效性。     

背景和装甲目标毫米波被动探测统计特性研究

根据背景和装甲目标不同的毫米波辐射机理,采用不同的统计方法得到了背景和装甲目标的不同统计特性。针对背景的不均匀性造成的背景辐射特性的非单一性,提出了采用假设检验的方法得到背景的统计分布;针对装甲目标难以得到统计分布的特点,提出了以目标信号复杂度为特征量的装甲目标辐射特性的统计方法。为毫米波被动探测地物及装甲目标识别方法的研究提供了必要的理论依据,具有切实可行的指导意义。     

星载被动光学遥感大气风场探测技术进展综述

大气风场是表征整个地球大气系统动力学特征的重要参数,也是气象预报、空间天气、气候学等领域业务工作和科学研究必需的基础数据。被动光学遥感是大气风场测量领域的主要技术手段之一。本文综述了基于大气移动目标监测和大气光谱多普勒频移探测的两类天基被动光学大气风场测量技术的研究进展,主要介绍了云导风、红外高光谱水汽示踪、测风干涉仪和多普勒调制气体相关4种风场测量技术的基础物理原理和风速反演基本方法,根据每种星载被动光学测风技术体制分类及特点,介绍了代表性风场探测载荷技术研究进展及应用情况,探讨了星载被动光学大气风场探测技术的未来发展趋势。     

智能型多功能激光防护镜与自动探测告警复合装置

设计研制智能型多功能激光防护镜与自动探测告警一体化复合装置,主要用于各类激光辐射人眼损伤的防护和预警。对防护镜和探测告警系统及智能化复合防护技术进行研究和性能测试,利用防护镜与告警装置的信号互联和联动作用,使防护镜双镜复合,并发出告警信号。结果表明,当激光防护告警复合装置探测到激光入侵时均能以不同方式发出各种告警信号和复合防护响应,包括不同颜色灯光闪烁、音响和振动告警,驱使两个防护镜单元镜组复合,对532 nm、1 064 nm、470 nm、808 nm和700～2 000 nm特定波长激光和超连续谱激光进行有效防护,可通过无线信号互联实现集群联动告警和防护。该激光防护镜与探测告警复合装置具有智能化、模块化、多功能集成的特点,各项性能符合设计要求。     

Mitigation of lunar dust adhered to mechanical parts of equipment used for lunar exploration

A unique cleaning system has been developed utilizing electrostatic force to remove lunar dust adhered to the mechanical parts of equipment used for lunar exploration. A single-phase voltage is applied to parallel electrodes printed on a flexible substrate to remove the dust. More than 90% of adhered dust was repelled from the surface of the slightly inclined device in a vacuum, and the cleaning performance of the system would be further improved in the low-gravity environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.     

Lunar terrain and mineral's abundance automatic analysis

The image is the important data in the lunar exploration. The main objective of this work is to detection lunar craters with the multi-information fuzzy logic method, and to quantify the image's terrain and the abundance of lunar surface minerals based on crater distribution law and soil characterization consortium data set with lunar surface reflectance. We implement image processing to recognize lunar crater and analysis lunar terrain; use lunar reflectance model to solve mineral reflectance question; joint commonly used look-up lunar reflectance tables and least squares to solve lunar surface reflectance questions; and calculate the minerals reflectance, region reflectance, and then estimate abundance of lunar surface soil minerals. An actual lunar image (Apollo 15 landsite, Clementine mission) of Mare region as an example, this method analysis results of the terrain and mineral's abundance are basically same with published literature. In the future, this method can be simple rapid in-time implemented in real-time lunar exploration.     

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ~10^10.4 m^-3 and ~10^11.5 m^-3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.     

Mitigation of lunar dust on solar panels and optical elements utilizing electrostatic traveling-wave

A system for removing lunar dust from the surface of solar panels and optical elements is of great importance for lunar exploration. We have developed a method of removing lunar dust using electrostatic traveling-waves generated by four-phase rectangular voltage applied to a transparent conveyer consisting of parallel ITO (indium tin oxide) electrodes printed on a glass substrate. On the basis of basic investigations, we have demonstrated the removal of actual lunar dust. A numerical investigation predicts that the performance will improve in the low-gravity environment on the Moon.     

Impacts of fast meteoroids and a plasma–dust cloud over the lunar surface

The possibility of the formation of a plasma–dust cloud in the exosphere of the Moon owing to impacts of meteoroids on the lunar surface is discussed. Attention is focused on dust particles at large altitudes of ~10–100 km at which measurements were performed within the NASA LADEE mission. It has been shown that a melted material ejected from the lunar surface owing to the impacts of meteoroids plays an important role in the formation of the plasma–dust cloud. Drops of the melted material acquire velocities in the range between the first and second cosmic velocities for the Moon and can undergo finite motion around it. Rising over the lunar surface, liquid drops are solidified and acquire electric charges, in particular, owing to their interaction with electrons and ions of the solar wind, as well as with solar radiation. It has been shown that the number density of dust particles in the plasma–dust cloud present in the exosphere of the Moon is ?10^?8 cm^?3, which is in agreement with the LADEE measurements.     

Adhesion and peeling of a Fugu coal molecule on a graphene substrate: molecular dynamics simulations

Controlling coal dust produced in the process of underground coal mining is imperative because it can cause serious health problems, such as pneumoconiosis. In the present work, we have conducted a comprehensive investigation of the adhesion and peeling process of a coal molecule on graphene using molecular dynamics(MD) simulation. First, we simulate the adhesion of a coal molecule on a graphene substrate, where the critical adhesion distance and adhesion force are analyzed. Next, the process of a coal molecule peeled from the substrate is simulated, the equilibrium configurations, loading position, peeling force, and peeling angle of which are discussed. After comparing the MD simulation results with those of continuum models, we conclude that they are in excellent agreement. These analyses have deepened our understanding of the interplay between coal molecules and solid surfaces, which may prove beneficial when creating scientific methods of dust control.     

模拟月壤发射率光谱测量实验及精度评定

基于月球样品反射光谱的月表矿物识别和成分反演能力受到月球环境的严重影响,仅限于月球表面5％的成熟度较低的区域。相比之下,包含大量硅酸盐矿物的月球样品发射光谱不仅光谱特征明显,而且受月表大气、温差和真空等环境的影响较小,是研究月表成分和物理特性的新途径。因此,对于嫦娥五号月球探测器采集的月球实地样品的发射光谱测量不仅可用于月表硅酸盐类矿物的成分分析,而且可以作为遥感研究中可见光-近红外光谱的有效补充。但是,实验室发射光谱测量中最大的难题是寻找最佳的实验方法和仪器,以便获得准确可靠的光谱数据。研究以模拟月壤样品为测量对象,分别在实验室大气、氮气冷背景和模拟真空环境中,利用TurboFT 102F和Bruker VERTEX 70V两种仪器,设计和实施了傅里叶光谱法、独立黑体法和反射率法三种发射率测量实验,并利用误差传播定律和已有Apollo样品发射率光谱对实验获得的发射率光谱进行了精度分析与评定。发现在异常复杂和困难的模拟月球真空测量环境构建完成之前,密闭实验室环境中的反射率法发射率光谱特征最明显,测量精度最高,可以作为目前月球样品发射率光谱测量的最佳选择。研究希望能为嫦娥五号采集的月球样品发射率光谱测量实验提供理论基础和技术参数。     

机载红外设备多平台协同探测无源定位方法

随着科学技术的发展日新月异,红外侦察设备已越来越广泛地应用于机载平台。典型机载红外设备红外传感器和激光传感器作用距离存在着明显的不匹配问题,对超远距离目标无法精确定位。为实现距离缺失条件下远距离或超远距离目标的高精度定位,提出了多平台协同探测无源定位方法。仿真结果表明,多平台协同探测无源定位算法可有效实现高精度目标定位,其定位精度约为7%R,优于传统到达时差定位（TDOA）和到达方向定位（DOA）等方法。