Observations and recommendations of the second un/esa workshop on basic space science     

S. Torres 《Earth, Moon, and Planets》1993,63(2):163-170

Observations and recommendations of the second un/esa workshop on basic space science  相似文献   

Natural resources: allocation, economics and policy: Rees, J. (2nd ed.). London: Routledge, 1990. 528 pp. £19.99 paperback     

Alan S. Pitkethly 《Applied geography (Sevenoaks, England)》1991,11(4)

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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   

On the possible hazard on the major cities caused by asteroid impact in the Pacific ocean     

S. Yabushita  N. Hatta 《Earth, Moon, and Planets》1994,65(1):7-13

Semi-quantitative investigation is made of hazard expected from an asteroidal impact in the Pacific. An impact ofd (diameter) = 200 m asteroid has a probability of hitting somewhere in the Pacific once in 15000 y. By carrying out a Monte Carlo simulation, such an impact, on average, is shown to create a tsunami as high as 16, 14, 15, and 21 m at Japan, Taiwan, Shanghai and Hawaii, respectively. Wooden houses, stone and brick houses, and reinforced concrete buildings are likely to be demolished by tsunamis of height 2, 7 and 20 m respectively. Thus, there is a probability of 1% or so that most of the artificial constructions on the coast lines of the Pacific be destroyed in the next century by an asteroidal impact.  相似文献   

Remote sensing for ocean resources     

S Z Qasim 《Journal of the Indian Society of Remote Sensing》1992,20(4):175-182

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A 20 cm2 CCD mosaic camera for a dark matter search part I : Mechanics,optics and cryogeny     

Arnaud  M.  Aubourg  E.  Bareyre  P.  Br';ehin  S.  Caridroit  R.  de Kat  J.  Dispau  G.  Djidi  K.  Gros  M.  Lachièze-Rey  M.  Laigneau  Y.  Laurent  B.  Lesquoy  E.  Lavocat  Ph.  Magneville  C.  Mazeau  B.  Milsztajn  A.  Moscoso  L.  Pasquaud  J.  Paul  B.  Perrin  P.  Petibon  J.  Piret  Y.  Queinnec  F.  Rich  J.  Spiro  M.  de Trogoff  J.  Vigroux  L.  Zylberajch  S.  Ansari  R.  Cavalier  F.  Moniez  M.  Beaulieu  J. P.  Ferlet  R.  Grison  Ph.  Vidal-Madjar  A.  Adrianzyk  G.  Berger  J. P.  Burnage  R.  Delclite  J. C.  Kohler  D.  Magnan  R.  Richaud  A.  Guibert  J.  Moreau  O.  Tajahmady  F.  Baranne  A.  Maurice  E.  Prévôt  L.  Gry  C. 《Experimental Astronomy》1994,4(3-4):265-278

A 20cm ² CCD mosaic camera has been especially built to search for dark galactic halo objects by the gravitational microlensing effect. The sensitive area is made of 16 edge-buttable CCDs developped by Thomson-CTS, with 23×23 µm ² pixels. The 35 kg camera housing and mechanical equipment is presented. The associated electronics and data acquisition system are described in a separate paper. The camera resides at the focal plane of a 40 cm, f/10, Ferson reflector. The instrument has been in operation since December 1991 at the La Silla Observatory (ESO).  相似文献   

Purana basins of peninsular India: a review     

Vivek S. Kale  V. G. Phansalkar 《Basin Research》1991,3(1):1-36

Seven supracratonic, Proterozoic basins, occupying more than a fifth of the Precambrian exposures in the Indian Peninsula, comprise the Purana basins. A comprehensive review of the current status of knowledge of these voluminous orthoquartzite-carbonate-shale suites in the context of their contemporary lithostratigraphy, depositional environments and structural disposition is presented. Stromatolite biostratigraphy and available geochronological data are compared, to discern their age limits.
These basins contain perhaps one of the most elaborate records of Middle to Late Proterozoic (Riphean-Vendian) sedimentation preserved in an unmetamorphosed and only slightly deformed state. Further sedimentological and structural studies could lead to a better understanding of the Proterozoic craton-margin processes. Their close association with the Middle Proterozoic Mobile Belt of peninsular India is that of two contrasting tectonic regimes, contemporaneously adjoining each other. The existing lithostratigraphic classifications of many of these sequences may not stand the test of process - response considerations as demonstrated by the recent revisions in the stratigraphy of the Cuddapah and Bhima basins. The prolific stromatolitic, micro-organic and trace-fossil communities preserved in them require much more detailed, but cautious study, and may yield information on the Riphean-Vendian biota. However, these studies must be undertaken in association with elaborate geochronological determinations which are sparse at present.
Inadequacy of the existing knowledge of these basins is highlighted, with the view of inviting the attention of the geological community to these unique basins from peninsular India.  相似文献   

The estimation of the shape of an array using a hidden Markov model     

Quinn  B.G. Barrett  R.F. Kootsookos  P.J. Searle  S.J. 《Oceanic Engineering, IEEE Journal of》1993,18(4):557-564

A hidden Markov model (HMM) technique for the estimation of the shape of a towed array is presented. It is assumed that there is a far-field source radiating sound containing possibly weak spectral lines. The technique uses either the Fourier coefficients at a given frequency computed from a single time block or the maximal eigenvector of a sample spectral covariance matrix. The technique is illustrated using several simulations. The results of these simulations indicate that the HMM technique yields shape and bearing estimates more accurate than those provided by a maximum-likelihood array shape estimation technique  相似文献   

Postglacial history of a cedar swamp in southeastern Connecticut     

Robert M. Thorson  Robert S. Webb 《Journal of Paleolimnology》1991,6(1):17-35

Stratigraphic and palynologic analyses of sediment cores from a large mire, combined with geologic and hydrologic studies of its watershed, provide a late Quaternary record of environmental change at Cedar Swamp in southeastern Connecticut. Since deglaciation of the area, the basin has evolved from an open lake characterized by the rapid accumulation of allochthonous inorganic sediments to an ombrotrophic mire with peat accumulation keeping pace with the gradual rise in the water table. Lithostratigraphic, pollen, and chronologic evidence suggest that the long-term trend of basin infilling and paludification was interrupted by two intervals (14 000–13 000 and 8000–4700 yr B.P.) when the water table elevation dropped at least 1 m.  相似文献   

Study of radiative energy losses in the moving envelopes of T Tau stars     

V. P. Grinin  A. S. Mitskevich 《Astrophysics》1990,32(1):41-51

Crimean Astrophysical Observatory. Translated from Astrofizika, Vol. 32, No. 1, pp. 69–83, January–February, 1990.  相似文献