Laser time transfer and its application in the Galileo programme

We are presenting the new instrument, new technology available and new measurement technique proposal for the Galileo programme – optical detector for the laser time transfer and one way laser ranging ground to space.     

多喷口环量控制翼型流动的研究

提出了多喷口环量控制翼型的想法，并进行了数值研究。结果表明，多喷口环量控制方法可以在中、小Ｃμ吹气时提高翼型的升力和减小能耗，并能改善环量控制翼型在较高来流马赫数下的气动性能，避免“压缩性失速”。     

创造具有自身特色的经营策略：———论云南航空公司的经营策略

阐述了在国内外航空市场的竞争压力下航空公司应采取的措施。针对过去和未来一段时期内国际航空市场的变化，结合云南航空公司的实际情况，分析了国内航线和国际航线运营状况，提出了具有其自身特色的发展战略和经营策略。     

基于Gauss-Newton法的L1数据拟合

在数据拟合中，当个别数据存在较大测量误差时，采用Ｌ１准则对数据进行拟合要优于最小二乘准则。本文通过建立Ｌ１准则与最小二乘准则之间的关系，给出了一种基于Ｇａｕｓｓ－Ｎｅｗｔｏｎ法的Ｌ１数据拟合自满。计算结果表明，该方法易于理解，便于编程，具有一定的理论意义和现实意义。     

Sulfur “concrete” for lunar applications – Sublimation concerns

Melting sulfur and mixing it with an aggregate to form “concrete” is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO₂ powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.     

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 .     

Deep Impact Mission Design

The Deep Impact mission is designed to provide the first opportunity to probe below the surface of a comet nucleus by a high-speed impact. This requires finding a suitable comet with launch and encounter conditions that allow a meaningful scientific experiment. The overall design requires the consideration of many factors ranging from environmental characteristics of the comet (nucleus size, dust levels, etc.), to launch dates fitting within the NASA Discovery program opportunities, to launch vehicle capability for a large impactor, to the observational conditions for the two approaching spacecraft and for telescopes on Earth.     

The History and Dynamics of Comet 9P/Tempel 1

Since its discovery in 1867, periodic comet 9P/Tempel 1 has been observed at 10 returns to perihelion, including all its returns since 1967. The observations for the seven apparitions beginning in 1967 have been fit with an orbit that includes only radial and transverse nongravitational accelerations that model the rocket-like thrusting introduced by the outgassing of the cometary nucleus. The successful nongravitational acceleration model did not assume any change in the comet’s ability to outgas from one apparition to the next and the outgassing was assumed to reach a maximum at perihelion. The success of this model over the 1967–2003 interval suggests that the comet’s spin axis is currently stable. Rough calculations suggest that the collision of the impactor released by the Deep Impact spacecraft will not provide a noticeable perturbation on the comet’s orbit nor will any new vent that is opened as a result of the impact provide a noticeable change in the comet’s nongravitational acceleration history. The observing geometries prior to, and during, the impact will allow extensive Earth based observations to complement the in situ observations from the impactor and flyby spacecraft.     

TiC/Al复合材料在锌液中均匀化机理分析

采用自蔓延高温合成（SHS）法制备高TiC颗粒含量的TiC／Al复合材料。利用自制的实验装置研究复合材料中TiC颗粒在静止锌液中的均匀化过程。结果表明：当锌液温度低于铝的熔点时，TiC／Al复合材料置于锌液后，锌向其内部扩散，引起复合材料表层内液相线温度降低，当表层内Al-Zn合金的液相线温度等于或低于锌液温度时，Al-Zn合金便处于熔融状态，TiC颗粒随其一起从TiC／Al复合材料块上脱落，并不断地向锌液内部传输，最终均匀分布在锌液中；而当锌液温度高于铝熔点时，TiC／Al复合材料置入后，锌和铝同时进行扩散，但是当复合材料表面温度达到铝熔点时，铝开始熔化，铝的熔化导致TiC颗粒的脱落，脱落下来的TiC颗粒不断向锌液内部传输，最终均匀分布在锌液中。     

有1的结合环的交换性

本文证明了有１的结合环的两个交换性定理，推广了Ｇｉｒｉ．Ｒ．Ｄ等人在参考文献１中的结果。