Small-scale mantle convection system and stress field under the Pacific plate     

Edward S. Chang  George H. Wyatt 《Physics of the Earth and Planetary Interiors》1976,13(3):212-217

The existence of nonhydrostatic high-degree harmonics in the gravitational field of the earth has recently been determined using satellite and gravity observations. In this paper, we have applied the Goddard Space Flight Center GEM-8 gravity field model to calculate the small-scale mantle flow system under the Pacific plate. The resulting tectonic forces or stresses exerted by the flow currents show tensional forces under the Hawaiian Island chain and a system of latitudinal convection rolls under the East Pacific plate and are in agreement with geophysical theories.  相似文献   

Carbonaceous chondrites—II. Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions     

T.E. Bunch  S. Chang 《Geochimica et cosmochimica acta》1980,44(10):1543-1577

Petrographic observations and analyses of CM matrices are consistent with their origin as in situ low temperature (<400°K) aqueous alteration products in a parent body regolith. At least four different phyllosilicates were tentatively characterized in Murray and Murchison meteorites, in addition to Fe- and Mg-serpentines in Nogoya. In comparison with bulk meteorite compositions, all phyllosilicates and bulk matrices show enrichment of K relative to Na. Possible loss of Na and possibly some Cl, with addition of H₂O and CO₂ and water-soluble organic compounds during alteration, indicates a partially open system during alteration. Poorly characterized phases (PCP) are fine-grained (< 1 μm) admixtures of variable proportions of phyllosilicates, carbonaceous matter and opaque oxides of sulfur with high Fe, Ni and Cr contents. Calcite and some magnetite show paragenetic overlap with PCP and phyllosilicates. Carbonaceous matter is largely associated with PCP in altered CM matrices. In the unaltered CV Allende, carbonaceous matter is concentrated on olivine surfaces as a micromounded coating, particularly in the dark haloes that surround some chondrules and aggregates. Precursive alteration material may have been analogous to similarly coated olivine mixed with smaller amounts of metal and sulfides.Synthesis of the water soluble organic compounds found in CM matrices may have occurred prior to or in the same environment as did aqueous alteration of the precursive phases. Preservation or partial preservation of this organic matter may reflect the degree of overlap in episodes of synthesis and alteration.Nogoya is 95% altered and has a bulk carbon content of 5.2 wt%, which is higher than any meteorite. In addition, it has the lowest measured ${}^{13}\text{C}{}^{12}\text{C}$ ratio of any other carbonaceous chondrite, except for Karoonda.  相似文献   

Effect of radiation damping on earthquake response of pile-supported offshore platforms     

Toyoaki Nogami  I. M. Idriss  M. S. Power  C.-Y. Chang 《地震工程与结构动力学》1983,11(3):337-353

An economical approach was developed to examine the effect of radiation damping on earthquake response of pilesupported offshore platforms. Parameteric studies were conducted to evaluate the effects of radiation damping on response. Various features of this effect were found for pile head stiffnesses, and responses of platforms subjected to harmonic and earthquake excitations.  相似文献   

中国南方的二叠-三叠系界线          下载免费PDF全文

范嘉松  孙亦因  张守信 《地质科学》1980,15(2):112-124

海相三叠系广泛发育于中国南方,含有丰富的动物化石:瓣鳃类、菊石、腹足类及介形虫等。在此区内,海相二叠系也极为发育,有许多二叠-三叠系连续沉积剖面。因此,二叠-三叠系的界限剖面,可以在许多地点见到。 二叠-三叠系的界限日益受到国际地层学界的注意。  相似文献   

Calculation of oil concentrations under chemically dispersed slicks     

Donald Mackay  Simon Chang  Peter G. Wells 《Marine pollution bulletin》1982,13(8):278-283

Equations are proposed which describe the diffusion of a plume of oil from chemically dispersed oil slicks into the oceanic water column and which yield estimates of oil concentration as a function of the volume of oil dispersed, time-varying plume area, depth, time, and as a function of a single adjustable parameter, vertical diffusivity. A ‘diffusion floor’ at any desired depth may be included. Experimental data were fitted to the equations to yield an estimate of this diffusivity. It is concluded that oil concentrations can be estimated with a mean error of a factor of three, this high value being attributable to the inherently variable nature of the oceanic diffusion processes. Implications for assessing the toxic effects of dispersed slicks are discussed. It may be possible to calculate acute median lethal water depths and volumes for given organisms subjected to given dispersed oil slicks.  相似文献   

Arma models for earthquake ground motions     

Mark K. Chang  Jan W. Kwiatkowski  Robert F. Nau  Robert M. Oliver  Karl S. Pister 《地震工程与结构动力学》1982,10(5):651-662

This paper outlines the use of discrete, autoregressive/moving-average (ARMA) models for identification and estimation of parameters in models derived from analysis of uniformly digitized earthquake ground motion acceleration data. Such models are of equal generality as compared to continuous-time models and have a number of significant advantages for purposes of digital analysis and simulation. The structure of ARMA models is briefly described, their relation to continuous models noted, and results of their application to a number of recorded accelerograms summarized.  相似文献   

Bioassay of baltimore harbor sediments     

Chu-Fa Tsai  Justine Welch  Kwei-Yang Chang  John Shaeffer  L. Eugene Cronin 《Estuaries and Coasts》1979,2(3):141-153

Baltimore Harbor, a tributary area of the northern Chesapeake Bay, has recelved and is receiving large quantities of chemical pollutants. As part of a cooperative study to explore possible corrective treatment for existing pollution burdens, gross bioassay analyses were performed for sediments from nine representative stations, employing two species of fish, mummichogs (Fundulus heteroclitus) and spot (Leiostomus xanthurus), and one mollusc, the soft-shell clam (Mya arenaria). Acclimated organisms were exposed in static systems to a series of concentrations of suspended sediment from each station, to fuller's earth in suspension, and in control tanks for 48 hours. Parallel analysis of the sediment was performed for the metals, Pb, Cr, Zn, Ca, As, for PCB's and for hexane extracts. The sediments were all substantially polluted with low correlations among components. Twenty-four hour TLm and 48-hour TLm increased proportionately with sediment concentration but display species specificity. The relationships observed permit use of mummichog data to index gross toxicity of sediments throughout the harbor. Further comparison of mummichog 24-hour TLm value with benthie species diversity determined in a previous study permitted zoning of the entire harbor into highly toxic, moderately toxic, low toxic and slightly toxic zones. Gross toxicity of sediments determined by bioassay can therefore be used as an index of the suitability of the sediments for benthic macroinvertebrate communities.  相似文献   

Light element geochemistry of the Apollo 16 site     

J.F Kerridge  I.R Kaplan  C Petrowski  S Chang 《Geochimica et cosmochimica acta》1975,39(2):137-162

Pronounced variations in abundances and isotopic compositions of some light elements in soils from the Apollo 16 site are interpreted in terms of differing degrees of solar wind exposure for an originally, and approximately, homogeneous regolith. Carbon abundances in soils are compatible with a model in which equilibrium is established, after 10⁴-10⁵ yr, between solar wind input and loss by H stripping. However, this model does not explain the observed C isotopic distribution, suggesting that other sources of C or other processes, or both, are also important. Carbon abundances in rocks from Apollo 16 are higher (average 40 ppm) than at other landing sites although their isotopic compositions, ?35 < δ¹³C < ?16%. PDB, are normal. Abundances of N and, to a less extent, He and H in soils correlate with C as does a fraction of metallic Fe attributed to in situ reduction of indigenous Fe²⁺ by solar wind H.Fillet soil 67461 apparently contains solar wind C and N in a relatively unfractionated form, yielding an upper limit to solar wind (δ¹³C of ?16%., PDB and a value of 3.4 for $\text{C}\text{N}$ in the solar wind.Sulfur at the Apollo 16 site represents a paradox in that, although abundances in soils are apparently controlled by local rock S contents, they also correlate, for all but one sample, with δ³⁴S, which itself is apparently controlled by surface exposure age. A complex lunar S cycle is suggested.  相似文献   

A matter of terminology — the ecological approach in geography: a re-examination of basic concepts     

L.W. Senger  S. Chang 《Geoforum》1975,6(2):164-167

Ecology is receiving increased attention as a research focus for geography and other academic disciplines. A consideration of basic concepts and the relationship of such ideas to the organizing frameworks of individual disciplines is needed to define the position of ecology as a substantive field or methodological approach. Geographers are concerned with the identification and explanation of the spatial patterning of earth phenomena. The ecosystem concept, with an emphasis on structure, networks of interaction, and function, is quite useful for conducting such geographical investigations. It acquires enhanced value within the subfields of geography by refining the approach through topical foci. Cultural ecology is one example; in this case a system is studied in terms of how its various cultural and biophysical components relate to a cultural characteristic (s) selected as the focus of investigation. Ecology is thus viewed as a methodological approach with significant applications for geographic research.  相似文献   

On the relationship between mean monthly global radiation and air temperature     

Prof. Dr. Jen-hu Chang  Barry Root 《Theoretical and Applied Climatology》1975,23(1-2):13-30

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