Generalized non-linear elastic inversion with constraints in model and data spaces     

Philip M. Carrion 《Geophysical Journal International》1989,96(1):151-162

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Radar characteristics of small craters: Implications for Venus     

Ronald Greeley  Philip R. Christensen  John F. McHone 《Earth, Moon, and Planets》1987,37(1):89-111

Shuttle radar images (SIR-A) of volcanic and impact craters were examined to assess their appearance on radar images. Radar characteristics were determined for: (a) 9 maarlike craters in the Pinacate volcanic field, Sonora, Mexico; (b) the caldera of Cerro Volcan Quemado, in the Bolivian Andes; (c) Talemzane impact crater, Algeria; and (d) Al Umchaimin, a possible impact structure in Iraq. SIR-A images were compared with conventional photographs and with results from field studies. Consideration was then given to radar images available for Venus, or anticipated from the Magellan mission. Of the criteria ordinarily used to identify impact craters, some can be assessed with radar images and others cannot be used; planimetric form — expressed as circularity — and ejecta-block distribution can be assessed on radar images, but rim and floor elevations relative to the surrounding plain and disposition of rim strata are difficult or impossible to determine. We conclude that it will be difficult to separate small impact craters from small volcanic craters on Venus using radar images, and suggest that it will be necessary to understand the geological setting of the areas containing in order to determine their origin.Department of Geology.Center for Meteorite Studies, Arizona State University, Tempe, Ariz., U.S.A.  相似文献   

The shapes and surface features of Prometheus and Pandora     

Philip J. Stooke 《Earth, Moon, and Planets》1993,62(3):199-221

Topographic models of Saturn's F-Ring shepherd satellites Prometheus and Pandora were derived from the shapes of limbs and terminators in Voyager images, modified locally to accommodate large craters and ridges. The models are presented here in tabular and graphic form, including the first published maps of the satellites. The shape of Prometheus is approximated by a triaxial ellipsoid with axes of 145, 85 and 60 km. The volume is estimated to be 3.9 ± 1.0 × 10⁵ km³, significantly smaller than previous estimates. A system of prominent ridges and valleys cross the north polar region. Prometheus appears to be less heavily cratered than the other small satellites near the edge of the rings, though this may be an artifact of the low resolution of available images. Pandora is approximated by a triaxial ellipsoid with axes of 114, 84 and 62 km. The volume is estimated to be 3.1 ± 1.0 × 10⁵ km³. Its surface appears to be very heavily cratered.  相似文献   

Triangle based interpolation     

D. F. Watson  G. M. Philip 《Mathematical Geology》1984,16(8):779-795

Triangle based interpolation is introduced by an outline of two classical planar interpolation methods, viz. linear triangular facets and proximal polygons. These are shown to have opposite local bias. By applying cross products of triangles to obtain local gradients, a method designated slant-top proximal polygon interpolation is introduced that is intermediate between linear facets and polygonal interpolation in its local bias. This surface is not continuous, but, by extending and weighting the gradient planes, a C¹ surface can be obtained. The gradients also allow a roughness index to be calculated for each data point in the set. This index is used to control the shape of a blending function that provides a weighted combination of the gradient planes and linear interpolation. This results in a curvilinear, C¹,interpolation of the data set that is bounded by the linear interpolation and the weighted gradient planes and is tangent to the slant-top interpolation at the data points. These procedures may be applied to data with two, three, or four independent variables.  相似文献   

Compositional evidence regarding the influx of interplanetary materials onto the lunar surface     

John T. Wasson  William V. Boynton  Chen-Lin Chou  Philip A. Baedecker 《Earth, Moon, and Planets》1975,13(1-3):121-141

Siderophilic element/Ir ratios are higher in mature lunar soils from highlands sites than in those from mare sites. We infer that the population of materials responsible for the early intense bombardment of the Moon had high ratios, and that the population responsible for the essentially constant flux has low ratios. No group of chondrites has siderophile/Ir ratios identical to those in the mare or highlands soils; CM chondrites are the most similar, and CM-like materials may account for a major fraction of Earth-crossing materials during the past 3.7 b.y.Siderophile/Ir ratios may be used to determine the amount of highlands regolith in soils or breccias from the mare-highlands interface areas (Apollo 15 and 17), and to infer the time of formation of highlands breccias whose sideropbiles originated in mature soils. Arguments are summarized against the viewpoint that the siderophiles in most highlands breccias originated in basin-forming projectiles. Differences in mature soil siderophile concentrations at Apollo 14 and 16 indicate a substantially greater concentration at the latter site immediately following the Imbrium event.Siderophile concentrations are used to estimate mean regolith depths at the landing sites; as relative values these are more precise than estimates based on seismic or crater observations. The longlived flux is calculated to be 2.9 g cm^–2 b.y.^–1 averaged over the past 3.7 b.y. A consideration of the relationship between mass fluence and time indicates that the mass flux decreased with a half-life of about 40 m.y. immediately following the Imbrium event.  相似文献   

Fisheries aid: low in development league     

W.Philip Appleyard 《Marine Policy》1983,7(3):218-220

Fisheries have tended to be a relatively neglected aspect of aid to developing countries. In the article below, Philip Appleyard gives some reasons for this and indicates ways in which future fisheries aid could be usefully employed.  相似文献   

Economics of fisheries development: Rowena Lawson Frances Pinter,London, 1984, 283 pp. £18     

Philip Appleyard 《Marine Policy》1985,9(1):82-84

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The surfaces of Larissa and Proteus     

Philip J. Stooke 《Earth, Moon, and Planets》1994,65(1):31-54

Topographic models of Neptune's small inner satellites Larissa and Proteus were derived from the shapes of limbs and terminators in Voyager images, modified locally to accomodate large craters and ridges. The models are presented here in tabular and graphic form, including the first map of Larissa and the first detailed relief map of Proteus. The shape of Larissa is approximated by a triaxial ellipsoid with axes of 208, 192 and 178 km, but is only weakly constrained by the single available view. The volume is estimated to be 3.5 ± 1.0 × 10⁶ km³. The surface is heavily cratered and may be crossed by one or two poorly seen linear ridges. Proteus is approximated by a triaxial ellipsoid with axes of 424, 390 and 396 km (the latter being the rotation axis dimension). The volume is estimated to be 3.4 ± 0.4 × 10⁷ km³. Its surface appears to be very heavily cratered and extensive evidence for linear fractures is observed despite very low image quality.  相似文献   

The concise Oxford dictionary of earth sciences. A. Allaby and M. Allaby. Publisher Oxford University Press 1990 £20.00 ISBN 0 19 866146 0     

Philip Gibbard 《第四纪科学杂志》1991,6(1):79-80

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Migrants,manufacturing and metropolitan labour markets in Australia     

Philip S. Morrison 《The Australian geographer》1990,21(2):151-163

While the experience of migrants in the Australian labour market has received considerable attention, few researchers have asked how uniform this experience has been across the country's major metropolitan labour markets. This paper shows that migrants employed in the manufacturing sector exhibit noticeable differences in their relative access to jobs in different parts of the country. This evidence raises a number of questions about the appropriate scale within which to consider the labour participation and occupational selection experience of migrant men and women.  相似文献