Ice clathrate as a possible source of the atmospheres of the terrestrial planets     

Godfrey T. Sill  Laurel L. Wilkening 《Icarus》1978,33(1):13-22

The presence and compositions of atmospheres on the terrestrial planets do not follow directly from condensation models which would have Earth accreting near 500°K. No single mechanism yet proposed adequately accounts for the abundances of noble gases and carbon and nitrogen in the atmospheres. We show that the composition of clathrates forming at low temperatures in cold regions of the nebula can be predicted. Addition of about 1 ppm clathrate material to the Earth can explain observed abundances of Ar, Kr, and Xe. Condensation and adsorption processes occuring at 400–500°K are necessary to explain the observed abundances of Ne, H₂O, C, and N. Possible sources of clathrates could be cometary bodies formed in the outer solar system.  相似文献   

Putting Japanese investment in Europe in its place   总被引：1，自引：0，他引：1  

Peter Dicken  Adam Tickell  Henry Yeung 《Area》1997,29(3):200-212

Summary Research on Japanese economic activity in Europe concentrates almost exclusively on investment in manufacturing. However, this paper demonstrates that this emphasis both underestimates the longevity of Japanese direct investment in Europe and also grossly underdefines the importance of services. Not only does Japanese direct investment have a much longer history in Europe than is usually recognized but also—and perhaps more significantly—the bulk of that investment is not in manufacturing production per se but in a variety of circulation services. Using establishment-level data, this paper shows that the spatial manifestation of these circulation services is very different from that of manufacturing production.  相似文献   

Three-dimensional stability of landslides based on local safety factor     

Tao Yang  Man-chu Ronald Yeung  Bing Yang  Yong-jiang Liu  Yan-xin Yang 《山地科学学报》2016,13(9):1515-1526

Unlike the limit equilibrium method (LEM), with which only the global safety factor of the landslide can be calculated, a local safety factor (LSF) method is proposed to evaluate the stability of different sections of a landslide in this paper. Based on three-dimensional (3D) numerical simulation results, the local safety factor is defined as the ratio of the shear strength of the soil at an element on the slip zone to the shear stress parallel to the sliding direction at that element. The global safety factor of the landslide is defined as the weighted average of all local safety factors based on the area of the slip surface. Some example analyses show that the results computed by the LSF method agree well with those calculated by the General Limit Equilibrium (GLE) method in two-dimensional (2D) models and the distribution of the LSF in the 3D slip zone is consistent with that indicated by the observed deformation pattern of an actual landslide in China.  相似文献   

Correlation of spectroscopic properties and substitutional sites of Cr3+ in aluminosilicates: II. Andalusite and sillimanite     

J. Qin  C. Rudowicz  Y. M. Chang  Y. Y. Yeung 《Physics and Chemistry of Minerals》1994,21(8):532-538

This paper is an extension of the earlier one dealing with kyanite in which the best fitting value of the oxygen ligand distance for Cr³⁺ is adopted to study the spectroscopic properties of Cr³⁺ ions doped at the two possible Al sites in the other two polymorphs of the aluminosilicate group (Al₂O₃ · SiO₂), namely, andalusite and sillimanite. The superposition model and the crystal field analysis package recently developed for 3d ions doped at arbitrary low symmetry sites in crystals are used to predict energy levels and statevectors within the whole 3d ³ configuration. Then the values of the ground state zerofield splitting for Cr³⁺ ions at each Al sites in the two crystals are obtained. The splittings of the lower excited states ² E and ⁴ T ₂ as well as the admixture of ⁴ T ₂ into ² E have also been predicted. Comparison of our results with the available experimental data enable us to correlate the optical and EPR Spectroscopic properties with the substitutional Cr³⁺ sites. The conclusion is that in andalusite and sillimanite only the Al sites with nearly-octahedral six-fold coordination seem to be occupied by Cr³⁺ ions.  相似文献   

Petrogenesis of late stage magmatism at Hold with Hope, East Greenland     

Rob M. Ellam  Brian G. J. Upton  J. Godfrey Fitton 《Contributions to Mineralogy and Petrology》1998,133(1-2):51-59

The Myggbukta caldera complex and a swarm of basic dykes constitute the latest Tertiary magmatism in the Hold with Hope region, East Greenland. The Sr and Nd isotope ratios of these rocks show coherent variations which extend to high ⁸⁷Sr/⁸⁶Sr and low ¹⁴³Nd/¹⁴⁴Nd values and require a contribution from continental lithosphere. Broad correlations with major element differentiation indices suggest that the continental component was incorporated during magmatic differentiation thereby favouring a crustal contamination process. Trace element concentrations are strongly correlated with isotopic compositions but display ranges for many incompatible elements which extend beyond likely crustal contaminant compositions. This is readily modelled by AFC processes in which the dominant cause of trace element enrichment is the concentration effect of fractional crystallisation rather than the composition of the contaminant. The simplest such models still require unrealistically high degrees of fractional crystallisation to explain the ten-fold enrichment of some trace elements. This can be overcome if the primary magmas entering the crust already had highly variable trace element compositions. Such variability is readily achieved if melts from different parts of the melting column escape without thorough homogenization. An AFC model which incorporates variability in parental magma composition is then able to simulate the range of compositions observed at Hold with Hope. This carries the implication that the variations observed are more readily attributed to changes in uncontaminated parental magma than to variations in the composition or amount of contaminant. Received: 5 March 1998 / Accepted: 16 June 1998  相似文献   

A physiographic approach to land use planning     

Andrew E. Godfrey 《Environmental Geology》1977,2(1):43-50

Physiography has been studied in the United States for more than 75 years, but only recently has it been applied to land use planning. Advantages of a physiographic approach are that it 1) focuses on the problems at the proper scale and conserves energy, effort, and time by selecting the critical parameters, 2) stresses geologic structure and process as factors which should control land use, and 3) presents data in a form which the non-geologically trained planner can easily understand. In 1928 Fenneman delineated and described the provinces and sections of the United States. This paper proposes a classification of smaller physiographic units and presents two examples of how they can be used for planning purposes. Below the section, the units used in this paper are the subsection, the land type, and the topographic element. Subsections delineate areas of distinct geologic structure or process whereas land types delineate ranges in the intensity of those processes. Topographic elements delineate units with distinct ranges of slopes or shapes of slopes, such as concave or convex.  相似文献   

Using acoustic backscatter from a sidescan sonar to explain fish and invertebrate distributions: a case study in Bristol Bay, Alaska     

Yeung  Cynthia; McConnaughey  Robert A. 《ICES Journal of Marine Science》2008,65(2):242-254

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Models of class II methanol masers based on improved molecular data     

D. M. Cragg  A. M. Sobolev  P. D. Godfrey 《Monthly notices of the Royal Astronomical Society》2005,360(2):533-545

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Model of the W3(OH) Environment Based on Data for Both Maser and “Quasi-Thermal” Methanol Lines     

Andrei M. Sobolev  Edmund C. Sutton  Dinah M. Cragg  Peter D. Godfrey 《Astrophysics and Space Science》2005,295(1-2):189-196

In studies of the environment of massive young stellar objects, recent progress in both observations and theory allows a unified treatment of data for maser and quasi-thermal lines. Interferometric maser images provide information on the distribution and kinematics of masing gas on small spatial scales. Observations of multiple masing transitions provide constraints on the physical parameters.Interferometric data on quasi-thermal molecular lines permits an investigation of the overall distribution and kinematics of the molecular gas in the vicinity of young stellar objects, including those which are deeply embedded. Using multiple transitions of different molecules, one can obtain good constraints on the physical and chemical parameters. Combining these data enables the construction of unified models, which take into account spatial scales differing by orders of magnitude.Here, we present such a combined analysis of the environment around the ultracompact HII region in W3(OH). This includes the structure of the methanol masing region, physical structure of the near vicinity of W3(OH), detection of new masers in the large-scale shock front and embedded sources in the vicinity of the TW young stellar object.  相似文献   

A newly discovered active contact binary in the field of NGC 1348     

Xiang-Song Fang  Sheng-Hong Gu  Ho-Keung Hui  Chi-Tai Kwok  Bill Yeung  Kam-Cheung Leung 《天体物理学报》2012,(1):93-103

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