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排序方式: 共有272条查询结果,搜索用时 62 毫秒
1.
天气雷达用于抗灾和减灾很重要,本文提出一种人工降雨和驱冰雹软件,给出了程序流图,对编程的关键进行了分析,最后结果表明它能提高人控作业效率。 相似文献
2.
This study employed Slack-based measure (SBM), Meta-frontier analysis, and Malmquist–Luenberger index (MLI) approaches to measure energy efficiency (EE), production technology heterogeneity, and energy productivity variation and its main determinants in developed and developing G20 countries for the period 1995–2020. The study's findings are: (i) Average EE for G20 countries is 0.8577, but still has an improvement potential of 14.23 percent. (ii) Developed countries have a higher average EE than developing (0.8927 > 0.8290). Results further revealed that energy efficiency scores in Argentina, Australia, Brazil, France, Saudi Arabia, South Africa, the US, the UK, and Korea are>1. (iii) Technology gap ratio (TGR) value in developed countries is higher than in developing (0.9869 > 0.6801), indicating that developed countries have advanced energy technologies superiority. The average MLI is less than one, showing a decline in energy productivity mainly due to a decline in technical efficiency, as EC < TC. (iv) Developed G20 countries get 0.64 percent aggregate growth in energy productivity as their MLI score is 1.0064, mainly due to technological growth (TC = 1.0161). Developing G20 countries, on the other hand, witnessed a decline in their energy productivity during 1995–2020, as MLI = 0.9925 > 1, designating that, on average, there is a 0.75 % decline in MLI. 相似文献
3.
选取四川省汶川至马尔康公路线的磨子沟作为试验对象,采用弯道超高法推算其泥石流流速。进而可以计算出该次泥石流的平均流量,为公路的改建工程提供设计依据。经过实地调查,用此方法计算磨子沟2005年8月17日暴发的泥石流流速为4.4m/s。同其他流速方法计算的结果相比较,前者值偏大,且偏向于工程安全值。弯道超高法可以解决泥石流观测的局限性和泥石流发生的不可重复性。此方法简便易行,对泥石流防治工程具有一定的实用价值。 相似文献
4.
The Precambrian massif of Ourika is crosscut by two systems of basic dykes, striking N40°E and N90–120°E. Using incompatible trace elements, the two systems form two distinct chemical groups, displaying a continental tholeiitic affinity. The composition variations between the two defined groups can be due to heterogeneities of mantle sources and to contamination, during the magma ascent, by the continental crust. The emplacement of these basic dykes, before the late-PIII formations, can be related to the Neoproterozoic distension generalised to the Anti-Atlas chain. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 827–833. 相似文献
5.
新疆入境旅游市场竞争态分析 总被引:10,自引:2,他引:10
提出旅游业市场竞争态模型,运用此模型可以定量分析、对比旅游市场的现实竞争状态,在此基础上,进行市场研究,确定本地区在旅游高超中的地位,明确现在和未来市场竞争的优势和劣势,为地区旅游业发展规划提供参考依据。应用这一模型,分析了新疆入境旅游的客源市场竞争态及省内各地区目的地市场竞争态。 相似文献
6.
B. P. Harlamov 《Mathematical Geology》2003,35(4):431-449
Zones of increased concentration formed by a solvent flowing from a source are considered. A matehmatical model for forming such zones is proposed. It takes into account that such a zone is composed of a set of independent particles. Hence the distribution of a substance around the source can be explained by movement of an individual particle. In the model this movement is a continuous semi-Markov process with terminal stopping at some random point in space. Parameters of the process depend on the velocity field of the flow. Forward and backward partial differential equations for the distribution density of a random stopping point of the process are derived. The forward equation is investigated for the centrally symmetric case. Solutions of the equation demonstrate either a maximum or a local minimum at the source location. In the latter case a concentric ring around the source is formed. If different substances vary in their absorption rates, they can form separable concentration zones as a family of concentric rings. 相似文献
7.
综合介绍了信息高速公路及国家空间信息基础设施的基本情况、地理科学的信息化和地理信息系统的发展趋势和特点,并说明了信息高速公路对地理科学信息化及地球科学研究及应用的影响。 相似文献
8.
9.
M. Koch-Müller P. Dera Y. Fei H. Hellwig Z. Liu J. Van Orman R. Wirth 《Physics and Chemistry of Minerals》2005,32(5-6):349-361
We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a
multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction,
Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron
radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures
(down to −180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT
polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional
phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT
polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The
IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure
derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than
the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering
occurs not only at the Mg sites but also at the hydrogen sites. 相似文献
10.