PDM技术及其在直升机研制中的作用

本文首先分析了当前直升机在运用CAD/CAE/CAM技术进行研制中存在的一些问题,接着提供了解决的方法,介绍了PDM的概念、构成、主要功能。最后简述了PDM技术在直升机研制中的作用,以及企业在实施PDM当中应注意的一些问题。     

The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research

Energetic Neutral Atom (ENA) imaging has contributed substantially to substorm research. This technique has allowed significant advances in areas such as observation and quantification of injected particle drift as a function of energy, observation of dynamics in the tail that are directly related to the effects of imposed (growth phase) and induced (expansion phase) electric fields on the plasma, the prompt extraction of oxygen from the ionosphere during substorms, the relationship between storms and substorms, and the timing of substorm ENA signatures. We present discussion of the advantages and shortcomings of the ENA technique for studying space plasmas. Although the technique is in its infancy, it is yielding results that enrich our understanding of the substorm process and its effects.     

Microthrusters in silicon for aerospace application

This paper reviews the results of the thermal and static analysis of small motor aerospace technology (SMART) propulsion system, constituted of a microthrusters array realised by MEMS technology on silicon wafers. This system has been studied using FEM (NASTRAN) and the results have been verified by the electro-thermic analogy and the FDM method, using, respectively, SPICE and MATLAB codes. The simulation results demonstrated the feasibility of SMART systems for aerospace applications such as attitude control and deorbiting missions for small satellite station-keeping. A theoretical impulse of 20 mNs has been calculated for the SMART system.     

Elemental and Isotopic Abundances of Carbon and Nitrogen in Meteorites

We have taken an inventory of the elemental and isotopic abundances of major carbon- and nitrogen-bearing components in different groups of meteorites. Primary phases, inherited from the solar nebula, are frequently isotopically heterogeneous, and surprisingly resistant to modification through parent body processing. Even melted and recrystallised meteorites retain primordial carbon and nitrogen isotopic signatures. This revised version was published online in August 2006 with corrections to the Cover Date.     

Isotopes of Volatiles in Pre-Solar Grains

Elements usually considered volatile are key constituents (C, N, O) of the pre-solar grains identified in primitive meteorites and/or key diagnostic elements (noble gases). Their isotopic compositions generally are unlike anything seen in matter of solar-system origin. The large variations are indicative of the various stellar sources and various processes of nucleosynthesis by which they were created. This revised version was published online in August 2006 with corrections to the Cover Date.     

NASDA aquatic animal experiment facilities for Space Shuttle and ISS.

National Space Development Agency of Japan (NASDA) has developed aquatic animal experiment facilities for NASA Space Shuttle use. Vestibular Function Experiment Unit (VFEU) was firstly designed and developed for physiological research using carp in Spacelab-J (SL-J, STS-47) mission. It was modified as Aquatic Animal Experiment Unit (AAEU) to accommodate small aquatic animals, such as medaka and newt, for second International Microgravity Laboratory (IML-2, STS-65) mission. Then, VFEU was improved to accommodate marine fish and to perform neurobiological experiment for Neurolab (STS-90) and STS-95 missions. We have also developed and used water purification system which was adapted to each facility. Based on these experiences of Space Shuttle missions, we are studying to develop advanced aquatic animal experiment facility for both Space Shuttle and International Space Station (ISS).     

Evolution of UV-B regulation and protection in plants.

Plants have evolved under the influence of UV-B radiation and have acquired systems for monitoring it and investing appropriate resources for protection against it, i.e., filters, quenchers of radicals and reactive oxygen species, and repair systems. An hypothesis for how plants monitor radiation has been presented.     

Induction machine based flywheel energy storage system

This study introduces a field oriented controlled (FOC) induction machine based flywheel energy storage (FES) system fed from a 20 kHz high frequency (HF) ac link and pulse density modulated (PDM) Converter. The feasibility of FES system is investigated both in software and hardware and is demonstrated successfully in both cases. The investigated system offers a good potential as a temporary energy storage system for various applications from automobile industry to aerospace applications.