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11.
本文用自制的装有 BaF_2探头的高探测效率的正电子湮没寿命谱仪测量了在室温下正电子素 o-Ps 与 p-RPhG 及 m-RPhG(R=NO_2,Cl,H,CH_3,cH_3O)在20%(V/V)二氧六环水溶液中的络合形成速度常数。实验结果表明,这些o-Ps-M 络合形成速度常数 K 值均与作为配位体的 p-RPhG、m-RPhG 的碱性解离常数 K 的负对数 pK_2 呈线性函数。这表明上述瞬态络合反应满足线性自由能关系,由此可推断出上述络合反应的一些重要性质。 相似文献
12.
经营机制创新是中小型外贸企业摆脱困境的必由之路。针对目前面临的主要问题,从外部环境及企业自身经营机制缺陷方面对中小型外贸企业生存环境进行分析,并从实现经营机制创新角度探讨改善现状的方法,力图找出中小型外贸企业经营机制创新的突破点。 相似文献
13.
Astronomy and space science, including their associated basic research activities, enjoy broad popular backing. People generally
support them, and say that they follow their results with interest. This article summarizes some of the detailed results of
public surveys in the United States, focusing on popular opinions and attitudes, and the somewhat paradoxical finding that
despite being interested and supportive, people are often ignorant about the basic facts. I explore some of the reasons for
the popularity of space science, and suggest ways of justifying space science research in the broader context of science research.
I argue that vigorous and innovative education and outreach programs are important, and can be made even more effective.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
周其焕 《中国民航学院学报》2005,23(1):61-64
为减少和消除海峡两岸科技文化交流上的词汇障碍,各学科广泛开展着科技术语的调查研究、交流和讨论。当前做法为两步走,首先是分析两岸用词上相同和差异的词目,共同编订对照本,共建对照和约定;然后逐步地通过对存在差异的个例进行选优汰劣和具体的商榷,过渡到更多的协调和一致。 相似文献
15.
Joris A. D. L. Blommaert Jan Cami Ryszard Szczerba Michael J. Barlow 《Space Science Reviews》2005,119(1-4):215-243
A large fraction of ISO observing time was used to study the late stages of stellar evolution. Many molecular and solid state
features, including crystalline silicates and the rotational lines of water vapour, were detected for the first time in the
spectra of (post-)Asymptotic Giant Branch (AGB) stars. Their analysis has greatly improved our knowledge of stellar atmospheres
and circumstellar environments. A surprising number of objects, particularly young planetary nebulae with Wolf-Rayet (WR)
central stars, were found to exhibit emission features in their ISO spectra that are characteristic of both oxygen-rich and
carbon-rich dust species, while far-IR observations of the PDR around NGC 7027 led to the first detections of the rotational
line spectra of CH and CH+.
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. 相似文献
16.
17.
本文对质量矩控制导弹的动力学方程简化和控制系统的设计进行了研究。详细阐述了所提出的控制方法,介绍了径向基单隐层神经网络进行误差补偿的算法原理,用Lyapunov理论证明了所采用方法的稳定性。在给出了质量矩导弹的六自由度动力学方程和简化后的方程后,用所提出的方法设计控制系统。通过仿真分析,得出了本文所提出的方法具有较好的误差补偿能力的结论。 相似文献
18.
D. Koschny V. Dhiri K. Wirth J. Zender R. Solaz R. Hoofs R. Laureijs T.-M Ho B. Davidsson G. Schwehm 《Space Science Reviews》2007,128(1-4):167-188
ESA’s Rosetta mission was launched in March 2004 and is on its way to comet 67P/Churyumov-Gerasimenko, where it is scheduled
to arrive in summer 2014. It comprises a payload of 12 scientific instruments and a Lander. All instruments are provided by
Principal Investigators, which are responsible for their operations.
As for most ESA science missions, the ground segment of the mission consists of a Mission Operations Centre (MOC) and a Science
Operations Centre (SOC). While the MOC is responsible for all spacecraft-related aspects and the final uplink of all command
timelines to the spacecraft, the scientific operations of the instruments and the collection of the data and ingestion into
the Planetary Science Archive are coordinated by the SOC. This paper focuses on the tasks of the SOC and in particular on
the methodology and constraints to convert the scientific goals of the Rosetta mission to operational timelines. 相似文献
19.
The fastest pulsar and the slowest nova; the oldest galaxies and the youngest stars; the weirdest life forms and the commonest
dwarfs; the highest energy particles and the lowest energy photons. These were some of the extremes of Astrophysics 2006.
We attempt also to bring you updates on things of which there is currently only one (habitable planets, the Sun, and the Universe)
and others of which there are always many, like meteors and molecules, black holes and binaries. 相似文献
20.
The architecture of digital sheet metal manufacturing system is proposed based on the classification of sheet metal manufacturing information.The essence of digital manufacturing is the definition,management and transfer of information,and the key technologies are brought forward and described.It is pointed out that knowledge-based manufacturing elements design is necessary to make digital technology efficient.The management of all kinds of sheet metal manufacturing element information is to build single source of manufacturing data.Multi-state model-based digital transfer and coordination method is designed to provide a foundation for digital manufacturing of aircraft sheet metal part.The application of digital sheet metal manufacturing is exemplified with an aircraft sheet metal part.The application result is compared to that of the traditional analog transfer technology.It is shown that the developed technology can improve part quality,shorten manufacturing time and lower manufacturing cost. 相似文献