气体微流量标准装置

介绍了气体微流量标准装置的工作原理，并对其测量不确定度进行了分析与验证。测试结果表明：流量的校准范围为１７．１～１．２２×１０￣（－５）ＰａＬ／ｓ，不确定度为２％。     

对10V直流电压参考标准校准方法的探讨

介绍３种校准１０Ｖ直流电压参考标准的方法，并对３种校准方法进行了详细的误差分析。第１种方法是由美国ＦＬＵＫＥ公司生产的３３５Ａ型直流标准电压源，７２０Ａ型Ｋ－Ｖ分压器，８４５ＡＲ型零值检测器和０．０００２级控温标准电池构成校准系统，其传递误差小于１×１０￣（－６）。在该方法中用英国ＤＡＴＲＯＮ公司的４０００Ａ型直流标准电压源取代３３５Ａ，其传递误差可降低到０．４×１０￣（－６）。第２种方法是由７２０Ａ型Ｋ－Ｖ分压器，８４５ＡＲ型零值检测器和０．０００２级控温电池构成校准系统，其传递误差小于０．３×１０￣（－６）。第３种方法是由３３５Ａ型直流标准电压源，７２０Ａ型Ｋ－Ｖ分压器、８４５ＡＲ型零值检测器，１５５型零值检测器和０．０００２级控温电池构成校准系统，其传递误差小于０．２×１０￣（－６）。在同样的条件下，对上述３种方法进行了比对（３种方法所用的标准电池为同一１０只组电池），比对结果表明，３种方法之间的误差小于０．３×１０￣（－６）。     

气体微流量标准装置的不确定度评定与研究

介绍了气体流是标准装置的不确定度评定与验证。测试结果表明：气体流量的校准范围（１７－１×１０＾５）ＰａＬ／ｓ，不确定度为２％。     

恒压式气体微流量计的设计

恒压式气体微流量计是校准气体微流量的一种装置,校准范围为（１７．１－１＊１０＾－５）Ｐａ．Ｌ／ｓ,不确定度于小于２％,可采用直接测量法和比较测量法对标准漏孔进行校准。文章介绍恒压式气体微流量计的设计方法和结构参数的选择。     

一种高灵敏度无水肼气体传感器

采用Ｌａｎｇｍｕｉｒ－Ｂｌｏｔｇｅｔ（ＬＢ）技术在Ａｌ平面电极上沉积制备了一种有机络合物ＬＢ膜。测试结果说明,这种敏感膜对无水肼（Ｎ２Ｈ４）气体在室温环境下具有很高的探测灵敏度：对无水肼在空气中的探测极限优于５×１０－７,其响应时间和恢复时间均不大于１０ｓ。这种高灵敏度敏感薄膜可用于制备便携式Ｎ２Ｈ４气体监测装置。     

动态比较法校准正压漏孔的漏率

介绍了校准正压漏孔漏率的动态比较法,可以校准的正压漏孔漏率范围为１×１０－４～１×１０－７Ｐａｍ３／ｓ。参考漏孔动态比较法是用一只漏率已知的正压漏孔作参考标准,分别让示漏气体通过参考正压漏孔或被校正压漏孔后,在内充大气的累积容器中累积不同的时间,产生大致相同的示漏气体增量;静态膨胀后,测量它们在动态流量法系统中产生的动态平衡分压力,再进行线性近似比较计算出被校正压漏孔的漏率。定量气体动态比较法是采用定量的示漏气体作参考标准,替代参考漏孔动态比较法中示漏气体通过参考正压漏孔后在累积容器中的累积量。     

气体微流量标准装置的测控系统和实验研究

气体微流量标准装置的测控系统在计算机控制下,采用电容薄膜规、光栅尺、铂电阻温度计等高精度传感器测出变容室内气体的压力、体积变化、温度等参量;并在流量测量的动态过程中将变客室内气体的压力波动控制在±０．０１％之内;工作软件实现了对气体微流量标准装置的计算机自动化控制和管理。气体激流量标准装置可以标准１７．１～１．２２×１０－５ＰａＬ／ｓ范围内的气体流量,校准不确定度小于１．９３％;目前它已用于标准漏孔的标定和实用型气体流量计的校准工作中。     

用标准电池校准固态电压标准

介绍了用１．０１８Ｖ的标准电池,通过分压器校准１０Ｖ固态电压标准的方法,分析并解决了所遇到的问题,对校准不确定度进行了分析。在校准实验室能力测试中,对核查标准—参加过国际比对且经约瑟夫森电压标准校准的７３２Ｂ固态电压标准进行了校准,其校准结果与约瑟夫森电压标准的校准结果相差２×１０－７,验证了该方法的可靠性和实用性。     

Ka波段开腔电介质自动测量系统

介绍了以自行研制的开放式谐振腔为中心的Ｋ＿ａ波段电介质自动测量系统。该系统在计算机控制下，改变频率；采集并读取谐振长度和功率数据；计算Ｑ值，即时算出被测材料的介电常数ε＿ｒ和损耗角正切ｔｇδ。除腔谐振尚需人工调节外，全部实现自动测量。通过测量聚苯乙烯泡沫、聚四氟乙烯、聚乙烯、高压聚乙烯、聚苯乙烯、微晶玻璃、陶瓷基片、复合微波介质基片等材料的电介质参数证实，ε＿ｒ和ｔｇδ在３２～３９ＧＨｚ频率范围内，量程分别达１．２０～２５．０和２．０×１０￣（－５）～２．０×１０￣（－３）。ε＿ｒ和ｔｇδ的测量不确定度分别达±０．５％和±（８％＋３×１０￣（－６））。     

多种示漏气体分析仪的研制

借鉴欧洲空间中心所用检漏仪的原理及主要技术措施，采用分子泵和机械泵的真空获得系统、钛升华泵和旁通阀真空维持系统、高灵敏的质谱分析系统，研制出了一次能检测出多个系统的高灵敏的多种示漏气体分析仪。文章介绍该分析仪的原理、设计方案、设计特点、设计计算。进行了性能测试，结果表明：该分析仪在大气环境条件下，最小可检测Ｈｅ，ＣＦ４的浓度小于５×１０－８，对Ｎｅ小于５×１０－７。     

Learning in an immersive digital theater

The Houston Museum of Natural Science, in collaboration with Rice University has an outreach program taking portable digital theaters to schools and community sites for over five years and has conducted research on student learning in this immersive environment. By using an external independent evaluator, the effectiveness of NASA-funded Education and Public Outreach (EPO) projects can be assessed. This paper documents interactive techniques and learning strategies in full-dome digital theaters. The presentation is divided into Evaluation Strategies and Results and Interactivity Strategies and Results. All learners from grades 3–12 showed statistically significant short-term increase in knowledge of basic Earth science concepts after a single 22-min show. Improvements were more significant on items that were taught using more than one modality of instruction: hearing, seeing, discussion, and immersion. Thus immersive theater can be an effective as well as engaging teaching method for Earth and Space science concepts, particularly those that are intrinsically three-dimensional and thus most effectively taught in an immersive environment. The portable system allows taking the educational experience to rural and tribal sites where the underserved students could not afford the time or expense to travel to museums.     

Scaling analysis and model estimation of solar corona index

A monthly average solar green coronal index time series for the period from January 1939 to December 2008 collected from NOAA (The National Oceanic and Atmospheric Administration) has been analysed in this paper in perspective of scaling analysis and modelling. Smoothed and de-noising have been done using suitable mother wavelet as a pre-requisite. The Finite Variance Scaling Method (FVSM), Higuchi method, rescaled range (R/S) and a generalized method have been applied to calculate the scaling exponents and fractal dimensions of the time series. Autocorrelation function (ACF) is used to find autoregressive (AR) process and Partial autocorrelation function (PACF) has been used to get the order of AR model. Finally a best fit model has been proposed using Yule-Walker Method with supporting results of goodness of fit and wavelet spectrum. The results reveal an anti-persistent, Short Range Dependent (SRD), self-similar property with signatures of non-causality, non-stationarity and nonlinearity in the data series. The model shows the best fit to the data under observation.     

Stochastic particle acceleration by the forced interaction of relativistic current sheets

We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γ^−s dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.     

Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results

In the frame of the 2009 Mars Science Laboratory (MSL) mission a new sample preparation system (SPS) compatible with gas chromatography–mass spectrometry (GC–MS) has been developed for the in situ analysis of complex organic molecules in the Martian soil. The goal is to detect, if they exist, some of the key compounds that play an important role in life on Earth including carboxylic acids, amino acids and nucleobases.     

Concept options for the aerial survey of Titan

Various aerial platforms intended for long endurance survey of the Titan surface are presented. A few novel concepts are introduced, including a heated methane balloon and a balloon with a tethered wind turbine. All the concept options are predicted to have lower scientific payload fractions than the Huygens probe. It is concluded that the selection of the best aerial platform option depends on more accurate mass estimates and a clear decision on whether, or not, in situ surface composition measurements are required in conjunction with aerial remote sensing.     

Heterogeneous solid/gas chemistry of organic compounds related to comets,meteorites, Titan,and Mars: Laboratory and in lower Earth orbit experiments

To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.     

基于LuGre模型的电液加载系统摩擦补偿

为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.      

The ESA scientific programme

The ESA scientific programme has, so far, provided several significant astrophysics experiments and further important missions are scheduled for execution during the next decade. These missions are briefly summarised together with several astrophysics investigations presently under study.     

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

Return to Europa: Overview of the Jupiter Europa orbiter mission

Missions to explore Europa have been imagined ever since the Voyager mission first suggested that Europa was geologically very young. Subsequently, the Galileo spacecraft supplied fascinating new insights into this satellite of Jupiter. Now, an international team is proposing a return to the Jupiter system and Europa with the Europa Jupiter System Mission (EJSM). Currently, NASA and ESA are designing two orbiters that would explore the Jovian system and then each would settle into orbit around one of Jupiter’s icy satellites, Europa and Ganymede. In addition, the Japanese Aerospace eXploration Agency (JAXA) is considering a Jupiter magnetospheric orbiter and the Russian Space Agency is investigating a Europa lander.