A review of models for predicting the thermomechanical behaviour of soft clays     

H. N. Seneviratne  J. P. Carter  D. W. Airey  J. R. Booker 《国际地质力学数值与分析法杂志》1993,17(10):715-733

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Cosmological constraints from the X-ray gas mass fraction in relaxed lensing clusters observed with Chandra     

S. W. Allen  R. W. Schmidt  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2002,334(2):L11-L15

We present precise measurements of the X-ray gas mass fraction for a sample of luminous, relatively relaxed clusters of galaxies observed with the Chandra observatory, for which independent confirmation of the mass results is available from gravitational lensing studies. Parametrizing the total (luminous plus dark matter) mass profiles using the model of Navarro, Frenk & White, we show that the X-ray gas mass fractions in the clusters asymptote towards an approximately constant value at a radius r ₂₅₀₀, where the mean interior density is 2500 times the critical density of the Universe at the redshifts of the clusters. Combining the Chandra results on the X-ray gas mass fraction and its apparent redshift dependence with recent measurements of the mean baryonic matter density in the Universe and the Hubble constant determined from the Hubble Key Project, we obtain a tight constraint on the mean total matter density of the Universe,     , and measure a positive cosmological constant,     . Our results are in good agreement with recent, independent findings based on analyses of anisotropies in the cosmic microwave background radiation, the properties of distant supernovae, and the large-scale distribution of galaxies.  相似文献   

Sonar acoustic facies and sediment distribution on an area of the deep ocean floor     

Robert B. Kidd  Robert W. Simm  Roger C. Searle 《Marine and Petroleum Geology》1985,2(3):210-221

Long-range sidescan sonar can be used to map sediment distributions over wide expanses of deep ocean floor. Seven acoustic facies that arise from differing sediment or rock types have been mapped over the low-relief Saharan continental rise and Madeira abyssal plain. These have been calibrated with sampling, profiling and camera studies and the facies can be traced confidently on a regional scale using the sidescan data. The mapping of the sediment distribution shows that a complex interplay of turbidity current and debris flow processes can occur at a continental rise/abysaal plain transition over 1000 km from the nearest continental slope.  相似文献   

Preliminary organic petrography of Palaeozoic rocks from the Grand Banks,Newfoundland     

F. Goodarzi  L.R. Snowdon  P.R. Gunther  W.A.M. Jenkins 《Marine and Petroleum Geology》1985,2(3):254-259

Samples of lower Palaeozoic bedrock from the Grand Banks of Newfoundland were examined using reflected light microscopy and Rock-Eval pyrolysis. These samples contained organic material which included bitumen (structureless organic material), acritarchs, chitinozoa, scolecodonts and graptolites. The reflectance of the organic material increased from acritarchs towards graptolites with bitumen showing a wide range of reflectance. Multiple phases of oil migration through one sample were inferred by examination of the bitumens: the lowest reflecting being more recent than the highest reflecting bitumen. Combined reflectance and Rock-Eval analysis indicate that these samples are mature to overmature. The two oldest samples (Arenig-Llanvirn, Ordovician) are assessed as mature and as having potential for generation of liquid hydrocarbons, but must be considered as mainly gas prone.  相似文献   

Readout Techniques for Drift and Low Frequency Noise Rejection in Infrared Arrays     

Gert Finger  Reinhold J. Dorn  Alan W. Hoffman  Hamid Mehrgan  Manfred Meyer  Alan F. M. Moorwood  Joerg Stegmeier 《Experimental Astronomy》2002,14(2):117-127

Three different methods are presented to subtract thermal drifts and low-frequency noise from the signal of infrared array. The first is dead pixels with open Indium bumps, the second is reference output as implemented on the Hawaii2 multiplexer, and the third is dark pixels to emulate reference cells having a capacity connected to the gate of the unit cell field-effect transistor (FET). The third method is the most effective and yields a reduction in readout noise from15.4–9.4 erms. A novel method will be described to extend this readout technique to the Aladdin 1 K × 1 K InSb array. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Analytic result for the properties of gravitational waves emitted by a large class of model sources     

H. Beltrami  W. Y. Chau 《Astrophysics and Space Science》1985,111(2):335-341

Expressions for the mass quadrupole moment tensor in the model for a wide variety of astrophysical objects are shown to be identical in form. This makes it possible to obtain analytical expressions for the gravitational radiation emitted by the sources, as well as the angular distribution, polarization dependence, and the wave forms of the radiation.  相似文献   

Regolith Surface Reflectance: A New Attempt to Model     

Petrova  E. V.  Markiewicz  W. J.  Keller  H. U. 《Solar System Research》2001,35(4):278-290

The reflectance coefficient of the regolith layer of celestial bodies has been studied in relation to the physical properties of regolith particles (size, refractive index, and packing density) on the basis of an accurate numerical radiative-transfer algorithm for a semi-infinite flat layer. Using the geometric-optics approximation, we have found that a shape mixture of randomly oriented spheroids can successfully model the single-scattering phase function of independent soil grains. In order to take into account the effect of packing density in a regolith layer, the concept of the so-called static structure factor was used. The main effect of increasing packing density is to suppress the forward-scattering peak of the phase function and to increase the albedo of the reflecting surface. We also investigated the influence of fine dust on the reflected light. An addition of small particles not only increases the surface albedo, but also changes the brightness profile and enhances the backscattering. Although the problem of unique solution, which is inherent in the retrieval of the properties of a medium from the measurements of the intensity of light scattered by this media, cannot be removed in the proposed model, the procedure used here, in contrast to widely used approximations, allows us to fit observational data with a set of real characteristics of the regolith. Semiempirical approaches are able to fit the measurements well with a small number of free parameters, but they do not explicitly contain crucial physical characteristics of the regolith such as grain sizes or the refractive index. We compared the numerical solution of the radiative-transfer equation with the Hapke approximation, which is most often used by investigators. The errors introduced by the Hapke model are small only for near-isotropic scattering by isolated particles. However, independent regolith grains are known to scatter light mainly in the forward direction.  相似文献   

Baryte and calcite cements in the 'breccias' of Ogmore-by-Sea, South Wales     

CHRIS W. LEE 《Geology Today》1991,7(4):133-136

Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times.  相似文献   

Integral field spectroscopy with the GEMINI multiobject spectrographs     

Jeremy Allington-Smith  Graham Murray  Robert Content  George Dodsworth  Bryan W. Miller  James Turner  Inger Jorgensen  Isobel Hook 《Experimental Astronomy》2002,13(1):1-37

We describe the integral field unit (IFU) which converts the Gemini Multiobject Spectrograph (GMOS) installed on the Gemini-North telescope to an integral field spectrograph,which produces spectra over a contiguous field of view of 7 × 5 arcsec with spatial sampling of 0.2 arcsecover the wavelength range 0.4-1.0 μm.GMOS is converted to this mode by the remote insertion of the IFU into thebeam in place of the masks used for the multiobject mode. A separate fieldof half the area of the main field, but otherwise identical, is alsoprovided to improve background subtraction. The IFU contains 1500lenslet-coupled fibres and was the first facility of any type for integralfield spectroscopy employed on an 8/10 m telescope.We describe the design, construction and testing of the GMOS IFU and present measurements of the throughput both in the laboratory and at the telescope. We compare these with a theoretical prediction made before construction started. All are in good agreement with each other, with the on-telescope throughput exceeding 60% (averaged over wavelength). Finallywe show an example of data obtained during commissioning to illustrate the power of the device.  相似文献   

The determination and analysis of the orbit of NIMBUS 1 ROCKET, 1964-52B: Part 1: The orbits     

W.J. Boulton 《Planetary and Space Science》1985,33(6):721-734

Orbital parameters of the satellite NIMBUS 1 ROCKET (1964-52B) have been determined at 285 epochs using about 14,500 optical and radar observations during the last 2233 days of its life. 1964-52B was in an orbit inclined at about 98.7° to the Equator and it decayed on 13 August 1974. The orbital elements were found using the RAE orbit refinement program PROP 6 giving average orbital accuracies in perigee height and inclination at 110 m and 0.002° respectively.  相似文献