月尘测量:从嫦娥三号到嫦娥五号

月尘是月球表面最重要的空间环境因素.月尘容易在太阳辐照、空间带电粒子和碰撞摩擦的作用下带上电荷,并在电场的作用下悬浮和迁移.月尘对探测器敏感表面和宇航员健康安全存在潜在危害,关系着科学探测目标的实现和任务的成败.探测月尘,一方面要获得月尘累积量的时空分布,另一方面要探测它的带电特性,从而全面了解月尘的运动迁移机制,同时...     

食品粉体螺旋输送荷电特性数值模拟

目的 研究食品粉体螺旋输送的荷电特性,为食品粉体除静电技术提供理论基础。方法 基于EDEM中“Tribocharging”摩擦充电模型以及“Hertz-Mindlin(noslip)”接触模型,用SolidWorks软件建立螺旋喂料结构三维模型并导入EDEM软件;以小麦粉为仿真材料,对同一转速、不同粒径或同一粒径、不同转速下的颗粒荷电过程进行模拟仿真。结果 在螺旋轴转速为100r/min等距螺旋输送仿真条件下,粒径为0.1、0.2、0.3mm小麦粉体颗粒的平均荷质比分别为1.43、1.6、2.45nC/g;粒径为0.3mm的小麦粉颗粒,在螺旋转速为80、100、120 r/min仿真条件下,平均荷质比分别为2.68、2.45、2.26 nC/g;带电颗粒主要集中在与料筒和螺旋体接触的区域,出料口中间区域存在带电量较少或不带电的颗粒。结论 小麦粉等距螺旋输送,颗粒的平均荷质比随粒径增大而增大,随螺旋轴转速增加而减小,为粉体除静电技术提供了参考。     

气力输送中PVC粉体静电带电影响因素

为了研究工业中常用的聚氯乙烯(PVC)粉体在气力输送过程中的静电影响因素，以PVC粉体为输送对象，以荷质比为指标，研究PVC粉体的下料质量流量、气流速度、气单位体积的气体中所含粉体的质量和球阀开度对粉体带电的影响。结果表明：当下料质量流量一定时，PVC粉体的荷质比会随气流速度增大而增大，随球阀开度减小而减小；当气流速度一定时，PVC粉体的荷质比会随下料质量流量增大而减小，输送颗粒的荷质比存在临界值为0.2μC/kg;当单位体积的气体中所含粉体的质量一定时，下料质量流量对PVC粉体荷质比影响要大于气流速度对其的影响；当下料质量流量一定时，PVC粉体的荷质比会随球阀开度的减小而减小。     

外加电压对明胶膜液荷电与润湿性能的影响及其预测模型

目的 探究不同荷质比明胶溶液的润湿性能,并建立预测模型。方法 以明胶可食涂膜为研究对象,利用感应荷电施加外源静电场以改善膜液润湿性能,探究电场电压对明胶液滴荷质比与表面张力,以及液滴在疏水表面接触角的影响,并通过机器学习建立荷质比与表面张力/接触角之间预测模型。结果 随着电压升高,明胶液滴荷质比不断增大,且仅以司盘20为表面活性剂（tw0组）时液滴具有最高的荷质比（-50 nC/g）。在0～7 kV内,明胶液滴的表面张力随电压升高从35.99～40.65 mN/m降至31.38～35.65 mN/m,其中tw0组表面张力下降最为明显。明胶液滴在石蜡表面的接触角也随电压升高而减小,在表面活性剂吐温20与司盘20质量比为1∶1时具有最小值,即电压7 kV时接触角为64.99°。深度神经网络预测模型决定系数接近于1,均方误差小于0.08,平均绝对误差小于0.15,具有最好的预测效果。结论 静电喷涂能够有效改善膜液在食品表面的润湿性能,利用深度神经网络能够建立膜液液滴荷质比与表面张力/接触角的良好预测模型。     

基于特征融合的新型电力系统网源荷储协同控制方法

传统的电力系统网源荷储协同控制方法只能获取网源特征信息,导致电力系统运行成本较高,因此本文设计了一种基于特征融合的新型电力系统网源荷储协同控制方法。通过提取和整合网源、负荷和储能等各组成部分的特征信息,准确计算出电力系统的缺电率。将不同特征信息进行融合,设置相应的约束条件,为优化控制策略提供保障。通过分析网源、负荷和储能等各组成部分的特征信息,确定协同控制策略的特性。划分出L1-L5共5种新型电力系统网源荷储协同控制等级。试验结果表明,本文设计的基于特征融合的新型电力系统网源荷储协同控制方法中,各设备运行成本均最小,证明该方法能够节省成本控制,提高新型电力系统网源荷储协同控制的有效性。     

静电相互作用对荷电超滤过程中带电小分子清除的影响

研究了不同荷电量小分子(分子量为1 kD左右)通过表面带同种电荷但荷电量不同的超滤膜(截留分子量为10 kD)时的行为.实验结果表明,荷电超滤膜对带电小分子的截留作用与超滤膜荷电量、小分子带电量以及溶液离子强度密切相关.低离子强度条件下,荷电超滤膜对高荷电小分子的截留率很高,这主要是静电相互作用的结果.随着离子强度的增加,静电屏蔽作用增强,荷电超滤膜对带电小分子的截留作用也相应减小.结果还表明,表观透过率的实验值与基于滞膜模型的理论计算值有较好的吻合.     

一种监测月球尘埃沉积质量的方法

月球探测过程中,由于自然悬浮和人类活动激起的月尘沉积在航天器表面,致使航天器敏感部件性能下降,需要实地监测长期探测过程中月尘的沉积质量,进而对其影响进行预估。通过对月尘遮挡效应的研究,设计利用测量太阳电池短路电流来监测月尘沉积量的方法。     

盘荷波导结构高频特性分析及其在高功率速调管中的应用

以周期边界法、谐振法以及微扰法分别对盘荷波导结构色散特性、耦合阻抗进行分析,研究了不同结构参数下盘荷波导结构高频特性的变化规律.设计了C波段π/2模速调管盘荷波导输出结构,对其注-波互作用开展了PIC粒子模拟.计算结果表明,相对于传统单间隙圆柱输出腔,盘荷波导输出结构可以在获得高效率的同时显著降低输出间隙场强.     

采用塞曼效应仪测定电子荷质比方法研究

依据光源发出光谱线在外磁场作用下分裂为多条谱线的事实,通过采用塞曼效应两种测量方法一拍照法和目测法对电子荷质比进行测定,分析测量方法与测量结果的关系。     

第五章 ZLS—23型氦质谱检漏仪介绍

一、仪器的工作原理本仪器的工作原理同 JLH—1型一样,是利用质谱分析的原理将不同荷质比的气体离子分开后,收集极上只收集荷质比为4的氦离子。这样,当用氦气进行检漏时,氦气一旦遇到漏孔,仪器输出指示便会发生明显变化,从而指示了漏孔的存在。     

Electrostatic collection of tribocharged lunar dust simulants

Levitation and consecutive deposition of naturally charged particles on lunar surface were troublesome in previous NASA explorations. Protecting sensitive surfaces from dust deposition in the limiting condition of the lunar atmosphere is imperative for future space exploration. This study reports experimental investigation of the collection efficiency of an electrostatic lunar dust collector (ELDC). A dual-functional remotely controlled particle charger/dropper was designed for tribocharging 20 μm lunar dust simulants, and a system of Faraday cup connected to an electrometer working in the nC range was used to measure the particle charges. Tribochargeability of two lunar dust simulants was studied, and the process was found to be the most effective with the JSC-1A samples. Aluminum was verified to be a more effective plate material than stainless steel. For the tested range of electrostatic field strength (0.66–2.6 kV/m), the mass-based and charge-based collection efficiencies were in the range of 0.25–1% and 0.45–1.45% for the low vacuum (10⁻¹ Torr), and 8–35% and 12–54% for the high vacuum (10⁻⁵ Torr) conditions. The linear relationship between the applied voltage and ELDC collection efficiency predicted by the theoretical model was confirmed, and the collection pattern of the collected particles over the collection plate was consistent with the previously computed charge distribution on the collection plate. Aside from validating the predictability of the theoretical model, this study offers a novel method of particle charging inside a vacuum chamber with a variety of applications for studying chargeability of particles at different temperatures and pressures.     

尘土颗粒带电特征的研究

使用密立根方法,对尘土颗粒的带电特性进行了研究。结果表明:尘土颗粒所带电荷的变化趋势可用一元三次多项式表示,电荷分布呈现带状区域,其所带的平均正电荷高于所带的负电荷。尘土颗粒的等效表面积和表面形貌是影响尘土带电的重要因素。环境相对湿度影响尘土颗粒的带电量,相对湿度越大,尘土带电荷越少。适当地控制机电元件运行的环境湿度,以及进行防尘处理,可以有效地降低故障率。     

Ion recombination on dust particles in a dense gas plasma excited by a hard ionizing factor

A theoretical model is proposed that describes the main kinetic mechanisms operating in a dust plasma formed upon the bulk ionization of a dense gas by a hard factor. An expression is derived for the ion density distribution around a charged dust particle. It is shown that ions in the plasma recombine with charged dust particles according to the Langevin mechanism. A condition is established under which the dust particles are bearing all the negative charge in the plasma, compensated by the positive charge of ion clouds. A new criterion for manifestation of the collective properties in the dust plasma is formulated.     

Electrically charged filter materials

Filters made from ordinary textile fibres are too coarse to remove micrometre-sized dust particles, which are responsible for much respiratory disease. If, however, an electric charge is applied to the fibres, a filter can provide a very good respiratory protection. Fibres can be charged by triboelectric exchange, by corona or by induction; and charge levels can give rise to electric fields in the interstices of the filter, approaching the breakdown field of the air. Some of the effect of the charge is lost as the filters become loaded with dust, but charge stability during storage is high, with shelf lives of years being attainable. The author discusses the capture of particles by electric forces and electrically charged filter materials and their production methods. The measurement of electric charge on filters, charge stability during storage, filter performance when loaded with dust and the advantages and disadvantages of such filters, are also discussed     

The interaction between charged dust particles calculated in Cassini coordinates

The Poisson-Boltzmann equation for two charged dust particles surrounded by a cloud of charged plasma was numerically solved using the Cassini coordinates. The force of the electric field acting on each particle was determined by integrating the field pressure over the particle surface. It is shown that the dust particles can exhibit attraction at distances on the order of the Debye screening radius and the average spacing between particles. The attraction drops sharply if the particle charge is significantly smaller than the charge of surrounding plasma species.     

Preparation of monodisperse charged droplets via electrohydrodynamic device for the removal of fine dust particles smaller than 10 μm

Electrohydrodynamic (EHD) device is utilized in various applications and could be useful for the suppression of particulate matter in ambient conditions. In this study, we focused on the ejection of charged droplets containing electrolytes in a microdripping mode and with high charge density. Several different electrolytes with different physical and electrical properties were tested for our EHD process in order to produce the charged droplets stably. Results from series images by high-speed camera represented that droplet size and frequency were dependent on the applied voltage and flow rate, and showed different behaviors in various EHD modes such as dripping, microdripping, mixed dripping, and unstable dripping. Consecutive experimental data for charge density showed that 15?wt% KCl solution was proper to obtain highly charged droplets with the size from 50 to 100?μm. For this solution, the suppression of the fine dust particle was tested for the removal of PM10, PM2.5, and PM1 at various applied voltages. The droplet formation in microdripping mode was effective for the removal of smaller dust particles and could be applicable for the air remediation in indoor or domestic environment.     

An upgraded high-velocity dust particle accelerator at Concordia College in Moorhead, Minnesota

In 1975, Concordia College in Moorhead, Minnesota acquired a 2 MeV dust particle accelerator from NASA/GSFC that was used to test the lunar ejecta and micrometeorite (LEAM) experiment flown on Apollo 17. This high-speed dust particle accelerator is still fully functional and is currently being upgraded. Improvements to the electronic detection system have been undertaken including a computer-based, data acquisition system and new particle detection sensor electronics. These sensors have additional amplifiers that extend the range of charge detection to 1×10⁻¹² C allowing for the detection of larger particles. Improvements to the vacuum system have also been made. The accelerator beam line is now pumped with an oil-free, turbomolecular pump reducing possible problems with hydrocarbon contamination. In this work, we describe the facility, and outline some of the recent improvements to the dust particle accelerator and discuss its capabilities and limitations. We also summarize some of the recent experiments conducted using the facility.     

Dusting of Alumina and Electrostatic Charging

The dust content and electrostatic charge of aluminium oxide (alumina) has been measured with the Faraday cup and in an electrostatic deflection apparatus. The dust was made and released from a fluidized bed. After generation, the dust entered the measurement zone where it was separated according to charge. Large differences in the electrostatic charge and the dusting behavior were observed. The charge of the alumina dust is generally relatively neutral, but aluminas with highly charged particles were observed. The dusting profile varies considerably. Some powders released dust only in the beginning of the test, while others constantly released dust.     

Dusting of Alumina and Electrostatic Charging

The dust content and electrostatic charge of aluminium oxide (alumina) has been measured with the Faraday cup and in an electrostatic deflection apparatus. The dust was made and released from a fluidized bed. After generation, the dust entered the measurement zone where it was separated according to charge. Large differences in the electrostatic charge and the dusting behavior were observed. The charge of the alumina dust is generally relatively neutral, but aluminas with highly charged particles were observed. The dusting profile varies considerably. Some powders released dust only in the beginning of the test, while others constantly released dust.