Properties of iron alloys under the Earth's core conditions     

《Comptes Rendus Geoscience》2014,346(5-6):130-139

The Earth's core is constituted of iron and nickel alloyed with lighter elements. In view of their affinity with the metallic phase, their relative high abundance in the solar system and their moderate volatility, a list of potential light elements have been established, including sulfur, silicon and oxygen. We will review the effects of these elements on different aspects of Fe–X high pressure phase diagrams under Earth's core conditions, such as melting temperature depression, solid–liquid partitioning during crystallization, and crystalline structure of the solid phases. Once extrapolated to the inner–outer core boundary, these petrological properties can be used to constrain the Earth's core properties.  相似文献   

国外儿童地理学研究进展与启示     

马倩怡  段玉山  吴蓉 《世界地理研究》2022,31(1):177-188

20世纪70至80年代,在地理学“空间转向”的背景下,国外儿童地理学研究兴起。2003年Children’s Geographies诞生,成为儿童地理学的旗帜性刊物,标志着儿童地理学的发展进入新阶段。借助可视化工具,系统梳理国外儿童地理学研究的核心主题、研究热点以及研究方法。研究发现：（1）国外儿童地理学的科研人员、科研机构以及研究所属区域都呈现高度集中性,欧美国家占据主导地位;（2）核心研究主题包括移民与流动身份、伦理与地区差异、教育与青年志向、童年与多元空间以及游戏与情感体验等;（3）亚洲儿童地理研究成为近期研究热点,聚焦于“跨国儿童移民”以及“亚洲青年教育及就业问题”两部分;（4）研究方法历经探索期、发展期、繁盛期以及信息技术广泛应用时期的演进,技术手段随时代发展不断更新。  相似文献   

Transnational technology transfer network in China: Spatial dynamics and its determinants     

LIU Chengliang  YAN Shanshan 《地理学报(英文版)》2022,32(12):2383-2414

Patent transfer has been regarded as an important channel for the nations and regions to acquire external technology, and also a direct research object to depict the relationship between supply and demand of technology flow. Therefore, based on traceable patent transfer data, this article has established a dual-pipeline theoretical framework of transnational-domestic technology transfer from the interaction of the global and local (glocal) perspective, and combines social networks, GIS spatial analysis as well as spatial econometric model to discover the spatial evolution of China’s transnational technology channels and its determinant factors. It is found that: (1) The spatial heterogeneity of the overall network is significant while gradually weakened over time. (2) The eastward shift of the core cities involved in transnational technology channels is accelerating, from the hubs in North America (New York Bay Area, Silicon Valley, Caribbean offshore financial center, etc.) and West Europe (London offshore financial center etc.) to East Asia (Tokyo and Seoul) and Southeast Asia (Singapore), which illustrates China has decreased reliance on the technology from the USA and West Europe. (3) The four major innovation clusters: Beijing-Tianjin-Hebei region (Beijing as the hub), Yangtze River Delta (Shanghai as the hub), The Greater Bay Area (Shenzhen and Hong Kong as the hubs) and north Taiwan (Taipei and Hsinchu as the hubs), are regarded as global technology innovation hubs and China’s distribution centers in transnational technology flow. Among those, Chinese Hong Kong’s betweenness role of technology is strengthened due to linkage of transnational corporations and their branches, and low tax coverage of offshore finance, thus becoming the top city for technology transfer. Meanwhile, Chinese Taiwan’s core position is diminishing. (4) The breadth, intensity, and closeness of domestic technology transfer are conducive to the expansion of transnational technology import channels. Additionally, local economic level has positive effect on transnational technology transfer channels while technology strength and external economic linkage have multifaceted influences.  相似文献   

A method for averaging the perturbing function in Hill’s problem     

M. A. Vashkov’yak 《Astronomy Letters》2003,29(6):416-423

A modified method for averaging the perturbing function in Hill’s problem is suggested. The averaging is performed in the revolution period of the satellite over the mean anomaly of its motion with a full allowance for a variation in the position of the perturbing body. At its fixed position, the semimajor axis of the satellite orbit during the revolution of the satellite is constant in view of the evolution equations, while the remaining orbital elements undergo secular and long-period perturbations. Therefore, when the motion of the perturbing body is taken into account, the semimajor axis of the satellite orbit undergoes the strongest perturbations. The suggested approach generalizes the averaging method in which only the linear (in time) term is included in the perturbing function. This method requires no expansion in powers of time. The described method is illustrated by calculating the perturbations of the semimajor axes for two distant satellites of Saturn, S/2000 S 1 and S/2000 S5. An approximate analytic solution is compared with the results of numerical integration of the averaged system of equations of motion for these satellites.  相似文献   

NIGHTGLOW: an instrument to measure the Earth’s nighttime ultraviolet glow—results from the first engineering flight     

Louis M. Barbier  Robert Smith  Scott Murphy  Eric R. Christian  Rodger Farley  John F. Krizmanic  John W. Mitchell  Robert E. Streitmatter  Eugene C. Loh  Stephen Stochaj 《Astroparticle Physics》2005,22(5-6):439-449

We have designed and built an instrument to measure and monitor the “nightglow” of the Earth’s atmosphere in the near ultraviolet (NUV). In this paper we describe the design of this instrument, called NIGHTGLOW. NIGHTGLOW is designed to be flown from a high altitude research balloon, and circumnavigate the globe. NIGHTGLOW is a NASA, University of Utah, and New Mexico State University project. A test flight took place from Palestine, Texas on July 5, 2000, lasting about 8 h. The instrument performed well and landed safely in Stiles, Texas with little damage. The resulting measurements of the NUV nightglow are compared with previous measurements from sounding rockets and balloons.  相似文献   

Measuring the flow resistance of submerged grass     

C. A. M. E. Wilson  M. S. Horritt 《水文研究》2002,16(13):2589-2598

Through laboratory experiments conducted in a grass‐lined flume, the hydraulic resistance of grass is measured and quantified. For the grass examined, it is found that Manning's n value is greater than those recommended in well‐established texts such as Chow (1959. Open Channel Flow. McGraw‐Hill: Singapore), relatively lower than those predicted by n‐UR methods, but corresponds well with the value found from calibration studies of two‐ and three‐dimensional numerical models. The assumption of a uniform Manning's n value with flow depth, which is often made in numerical modelling, may be invalid depending on the relative submergence of the vegetation. Drag coefficients are evaluated for a method applicable to three‐dimensional numerical models. Further detailed experimental investigation and application of these approaches within a numerical modelling framework is now recommended. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

角动量守恒定律适用于地球核幔体及其与岩石圈之间的相对运动吗？──与盖保民先生商榷     

于品清 《大地测量与地球动力学》1994,(1)

对《地球演化》一书中的某些重要论点提出质疑。认为运用角动量守恒原理应考虑其适用条件，这一定律不适用于地球核幔体；核幔体与岩石圈之间能否作相对运动尚有待证实；地壳运动的总趋势是逐渐减弱而不是逐步增强。  相似文献   

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a marine ciliate, Pleuronema coronatum (ciliophora, scuticociliatida)     

Qiu Yantao  Song Weibo 《中国海洋大学学报(英文版)》2002,1(2):211-214

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a commonly occurred marine ciliate Pleuronema coronatum (Ciliophora, Scuticociliatida) were measured. Linear regression analysis of the results highlighted the close relationships between doses of the medicines and mortalities of the organisms, thus providing a capability to predict toxicity effects from the dose. Toxic effects of the medicines on the ciliates were described in the present paper, and the median lethal concentrations (LC₅₀ values) were given. Results of measurements indicated that 2 h-LC₅₀ and 12 h-LC₅₀ values of formalin on P. coronatum were 59.00×10⁻⁶ and 43.57×10⁻⁶, while those of Lugol’s solutions were 90.13 and 67.84×10⁻⁶ respectively. The tolerance of P. coronatum to formalin is apparently lower than that to Lugol’s iodine solution and potassium permanganate is a suitable medicine to kill ciliates in short time.  相似文献   

Celestial-mechanical peculiarities of Uranus’s satellite system     

M. A. Vashkov’yak 《Astronomy Letters》2001,27(7):464-469

We consider the structural peculiarities of Uranus’s satellite system associated with its separation into two groups: inner equatorial satellites moving in nearly circular orbits and distant irregular satellites with retrograde motion in highly elliptical orbits. The intermediate region is free from satellites in a wide range of semimajor axes. By analyzing the evolution of satellite orbits under the combined effect of solar attraction and Uranus’s oblateness, we offer a celestial-mechanical explanation for the absence of equatorial satellites in this region. M.L. Lidov’s studies during 1961–1963 have served as a basis for our analysis.  相似文献   

太阳表面米粒结构观测对比度分析     

饶长辉  姜文汉  凌宁 《天文学报》2001,42(2):134-139

分析以观测系统焦面上和探测器测到的太阳表面米粒结构的对比度与观测系统口径，大气湍流相干长度以及系统探测灵敏度的关系，给出了不同口径，不同大气湍流相干长度以及不同系统探测灵敏度时的米粒结构对比值计算结果，此外还给出了实验结果。  相似文献