Interplanetary medium – A dusty plasma

The average mass of dust per volume in space equals that of the solar wind so that the interplanetary medium should provide an obvious region to study dust plasma interactions. While dust collective behavior is typically not observed in the interplanetary medium, the dust component rather consists of isolated grains screened by and interacting with the plasma. Space measurements have revealed several phenomena possibly resulting from dust plasma interactions, but most of the dust plasma interactions are at present not quantified. Examples are the production of neutrals and pick-up ions from the dust, dust impact generated field variations at spacecraft and magnetic field variations possibly caused by solar wind interacting with dust trails. Since dust particles carry a surface charge, they are exposed to the Lorentz force in the interplanetary magnetic field and for grains of sub-micrometer sizes acceleration can be substantial.     

韧性材料的冲蚀损伤数值仿真综述

砂尘造成韧性材料的冲蚀损伤现象和损伤演化规律是冲蚀机理研究的重要内容，基于相应冲蚀试验和数值仿真的分析 方法是揭示冲蚀机理的重要手段。回顾了砂尘冲蚀损伤研究的缘起和发展经历，在介绍砂尘冲蚀损伤机理的基础上，总结了当前 数值仿真研究的3种主流方法：有限元方法、无网格方法和计算流体动力学方法。从数值仿真角度针对砂尘对韧性材料造成的破 坏模式、砂尘冲击姿态、砂尘冲击速度和形状、砂尘破碎对材料去除机制的影响等4个方面综述了影响冲蚀损伤机理的主要因素 和当前研究进展。砂尘对韧性材料造成的破坏模式通常分为材料凹陷、滑动、犁削、切削等4种不同机制；砂尘的冲击姿态决定了 材料的损伤模式；砂尘的冲击速度和砂尘的形状决定了材料的损伤严重程度；砂尘破碎现象对材料的去除机制有一定影响。     

The Coma of Comet 9P/Tempel 1

As comet 9P/Tempel 1 approaches the Sun in 2004–2005, a temporary atmosphere, or “coma,” will form, composed of molecules and dust expelled from the nucleus as its component icy volatiles sublimate. Driven mainly by water ice sublimation at surface temperatures T > 200 K, this coma is a gravitationally unbound atmosphere in free adiabatic expansion. Near the nucleus (≤ 10² km), it is in collisional equilibrium, at larger distances (≥10⁴ km) it is in free molecular flow. Ultimately the coma components are swept into the comet’s plasma and dust tails or simply dissipate into interplanetary space. Clues to the nature of the cometary nucleus are contained in the chemistry and physics of the coma, as well as with its variability with time, orbital position, and heliocentric distance. The DI instrument payload includes CCD cameras with broadband filters covering the optical spectrum, allowing for sensitive measurement of dust in the comet’s coma, and a number of narrowband filters for studying the spatial distribution of several gas species. DI also carries the first near-infrared spectrometer to a comet flyby since the VEGA mission to Halley in 1986. This spectrograph will allow detection of gas emission lines from the coma in unprecedented detail. Here we discuss the current state of understanding of the 9P/Tempel 1 coma, our expectations for the measurements DI will obtain, and the predicted hazards that the coma presents for the spacecraft. An erratum to this article is available at .     

RPC-MIP: the Mutual Impedance Probe of the Rosetta Plasma Consortium

The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore, MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature of plasmas at higher Debye lengths than those for which the MIP is originally designed.     

直升机砂尘环境试验风洞的温度控制及仿真

 直升机砂尘环境试验风洞内部的热负荷变化范围较大,高低热负荷工况下需要采取不同的调温措施,为了简便地解决其温度控制难题,在对其温度变化进行动态特性分析与建模的基础上,提出了一种引入风速协调因子的砂尘环境试验风洞温度控制策略,并对其控制效果进行了仿真研究,仿真结果表明这一控制策略能在不同的热负荷条件下有效协调加热与制冷两种作用相反的控制措施,并将风洞内的温度控制在要求范围内。     

Effects of adiabaticity and non-adiabaticity of dust charge fluctuation on the propagation of the dust ion acoustic waves in inhomogeneous dusty plasma

A theoretical investigation has been made for adiabatic positive and negative dust charge fluctuations on the propagation of dust-ion acoustic waves (DIAWs) in a weakly inhomogeneous, collisionless, unmagnetized dusty plasmas consisting of cold positive ions, stationary positively and negatively charged dust particles and isothermal electrons. The reductive perturbation method is employed to reduce the basic set of fluid equations to the variable coefficients Korteweg–de Vries (KdV) equation. Either compressive or rarefactive solitons are shown to exist depending on the critical value of the ion density, which in turn, depends on the inhomogeneous distribution of the ion. The dissipative effects of non-adiabatic dust charge variation has been studied which cause generation of dust ion acoustic shock waves governed by KdV-Burger (KdVB) equation. The results of the present investigation may be applicable to some dusty plasma environments, such as dusty plasma existing in polar mesosphere region.     

着陆作用下月尘激扬的三维离散元分析

基于模拟月尘的细观颗粒形状,采用刚性圆球单元重叠法建立了4种典型不规则模拟月尘颗粒的三维几何模型.根据月尘所处环境和颗粒间接触特性,建立了月尘离散元接触力学模型.通过三轴压缩实验离散元模拟的结果和模拟月尘的实际三轴压缩实验数据的对比,确定模拟月尘颗粒的三维离散元模型参数.采用建立的模型和获得的参数,进行了圆盘模拟体着陆...     

The Ice Survey Opportunity of ISO

The instruments on board the Infrared Space Observatory have for the first time allowed a complete low (PHOT, CVF) to medium resolution (SWS) spectroscopic harvest, from 2.5 to 45 μm, of interstellar dust. Amongst the detected solids present in starless molecular clouds surrounding recently born stellar and still embedded objects or products of the chemistry in some mass loss envelopes, the so-called “ice mantles” are of specific interest. They represent an interface between the very refractory carbonaceous and silicates materials that built the first grains with the rich chemistry taking place in the gas phase. Molecules condense, react on ices, are subjected to UV and cosmic ray irradiation at low temperatures, participating efficiently to the evolution toward more complex molecules, being in constant interaction in an ice layer. They also play an important role in the radiative transfer of molecular clouds and strongly affect the gas phase chemistry. ISO results shed light on many other species than H₂O ice. The detection of these van der Waal's solids is mainly performed in absorption. Each ice feature observed by ISO spectrometer is an important species, with abundance in the 10⁻⁴–10⁻⁷ range with respect to H₂. Such high abundances represent a substantial reservoir of matter that, once released later on, replenishes the gas phase and feeds the ladder of molecular complexity. Medium resolution spectroscopy also offers the opportunity to look at individual line profiles of the ice features, and therefore to progressively reveal the interactions taking place in the mantles. This article will give a view on selected results to avoid to overlap with the numerous reviews the reader is invited to consult (e.g. van Dishoeck, in press; Gibb et al., 2004.). Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA.     

应用组合除尘技术治理手烧炉烟尘

本文介绍了一种集多种湿法除尘技术之长处于一体的新型组合式除尘装置，该装置不仅能有效地消除手烧锅炉燃烧时产生的烟尘，而且实现了除尘水的内循环，消除了其它湿式除尘器所带来的水的二次污染问题。     

火星尘埃与探测

火星表面尘埃与太阳辐射、热辐射的相互作用直接影响火星大气的结构、热平衡和动力学过程,并会产生改变火星表面反照率和火星地貌的长期效应.火星尘埃环境还对登陆于火星表面的着陆器能源系统和光学载荷等系统构成影响.为此需开展火星大气尘埃的直接就位探测.在介绍了火星的尘埃特性与主要探测方法基础上,提出了采用微质量计技术开展火星表面尘埃就位探测的综合探测器方案.探测器包含3种传感器.尘埃累积传感器通过设置其敏感晶体表面朝上,可以探测火星表面尘埃的沉积质量与速率;荷电尘埃传感器通过加置不同极性的偏置电压,可以探测荷正电尘埃和荷负电尘埃的累积特性;磁尘传感器通过在敏感晶体后加设小型永久磁铁,可以探测磁性尘埃的累积特性.传感器感测质量范围为10^-11~10^-4g.火星尘埃综合探测器可应用于未来的火星着陆探测计划.