Trend-surface analysis     

G. S. Watson 《Mathematical Geology》1971,3(3):215-226

This paper is largely an exposition of the work of the French geostatistian G. Matheron and his school in English and at a simpler mathematical level. The probability theory on which it is based is essentially all contained in the references cited, most of which will be unfamiliar to mathematical geologists. The important method of universal kriging is explained intuitively. The genuine statistical problems, which have yet to be overcome, are pointed out.Research supported by the Office of Naval Research under contract NONR 4010(09) awarded to the Department of Statistics, The Johns Hopkins University. This paper in whole or in part may be reproduced for any purpose of the United States Government.  相似文献   

Ice in the Southern Coalsack     

R. G.Smith †  R. D.Blum †  D. E.Quinn  K.Sellgren  D. C. B.Whittet † 《Monthly notices of the Royal Astronomical Society》2002,330(4):837-843

To better understand the conditions under which ice mantles form on grains in molecular clouds, three globules in the Southern Coalsack have been searched for the presence of H₂O ice. Given the total lack of star formation in the Coalsack, it is an ideal site for studying unprocessed icy molecular mantles. In our sample of eight field stars lying behind the Coalsack we detect strong H₂O ice absorption in the lines of sight to two stars and possible weak absorption in four others. We estimate H₂O ice column densities or upper limits for these lines of sight. Compared to dark clouds such as Taurus, the Coalsack H₂O ice column densities are lower than expected given the quiescent nature of the Coalsack region. It is possible that the chemical evolution of the Coalsack may simply be at too early a stage for significant ice mantles to appear on the grains, except perhaps in the densest parts of some of the globules. Alternatively, the presence or absence of ice absorption may be related to the distribution of dust along each line of sight, specifically, the relative contributions of dense globules and a more extended diffuse component. For example, our observations are consistent with an ice threshold extinction similar to that observed in the Taurus dark cloud if extinction amounting to   A _V∼5  towards Globules 2 and 3 arises in the extended component. Globule 1 appears to have no extended component.  相似文献   

The role of multipolar magnetic fields in pulsar magnetospheres     

Estelle Asseo  David Khechinashvili 《Monthly notices of the Royal Astronomical Society》2002,334(4):743-759

We explore the role of complex multipolar magnetic fields in determining physical processes near the surface of rotation powered pulsars. We model the actual magnetic field as the sum of global dipolar and star-centred multipolar fields. In configurations involving axisymmetric and uniform multipolar fields, 'neutral points' and 'neutral lines' exist close to the stellar surface. Also, the curvature radii of magnetic field lines near the stellar surface can never be smaller than the stellar radius, even for very high-order multipoles. Consequently, such configurations are unable to provide an efficient pair-creation process above pulsar polar caps, necessary for plasma mechanisms of generation of pulsar radiation. In configurations involving axisymmetric and non-uniform multipoles, the periphery of the pulsar polar cap becomes fragmented into symmetrically distributed narrow subregions where curvature radii of complex magnetic field lines are less than the radius of the star. The pair-production process is only possible just above these 'favourable' subregions. As a result, the pair plasma flow is confined within narrow filaments regularly distributed around the margin of the open magnetic flux tube. Such a magnetic topology allows us to model the system of 20 isolated subbeams observed in PSR B0943+10 by Deshpande & Rankin. We suggest a physical mechanism for the generation of pulsar radio emission in the ensemble of finite subbeams, based on specific instabilities. We propose an explanation for the subpulse drift phenomenon observed in some long-period pulsars.  相似文献   

The origin of spatial intermittency in the galaxy distribution     

PeterColes 《Monthly notices of the Royal Astronomical Society》2002,330(2):421-424

The dynamical equations describing the evolution of a self-gravitating fluid can be rewritten in the form of a Schrödinger equation coupled to a Poisson equation determining the gravitational potential. This approach has a number of interesting features, many of which were pointed out in a seminal paper by Widrow & Kaiser. In particular we show that this approach yields an elegant reformulation of an idea of Jones concerning the origin of lognormal intermittency in the galaxy distribution.  相似文献   

Synchrotron emission from anisotropic disordered magnetic fields     

R.A. Laing 《Monthly notices of the Royal Astronomical Society》2002,329(2):417-422

We derive expressions for the total and linearly polarized synchrotron emissivity of an element of plasma containing relativistic particles and disordered magnetic field that has been sheared or compressed along three independent directions. Our treatment follows that given by Matthews & Scheuer in the special case of a power-law electron energy spectrum. We show that the emissivity integrals depend on a single parameter, making it straightforward to generate one-dimensional look-up tables. We also demonstrate that our formulae give identical results to those in the literature in special cases.  相似文献   

On dust-correlated Galactic emission in the Tenerife data     

P. Mukherjee  A. W. Jones  R. Kneissl  A. N. Lasenby 《Monthly notices of the Royal Astronomical Society》2001,320(2):224-234

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The SZ effect as a probe of non-gravitational entropy in groups and clusters of galaxies     

A. Cavaliere  N. Menci 《Monthly notices of the Royal Astronomical Society》2001,327(2):488-498

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Cracked media, Poisson's ratio and the structure of the upper oceanic crust     

Peter M. Shearer 《Geophysical Journal International》1988,92(2):357-362

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湖北省棉花产量的变化与棉田布局的战略调整^*     

唐文雅 《地理研究》1988,7(3):34-43

本文揭示了湖北省棉花亩产的增长具有北高南低的特点,分析了鄂北地区种植棉花的自然优势和经济效盆大于江汉平原,从而提出湖北省棉花北移的战略调整的设想。  相似文献   

The properties of spiral galaxies: confronting hierarchical galaxy formation models with observations     

Eric F. Bell  Carlton M. Baugh  Shaun Cole  Carlos S. Frenk  Cedric G. Lacey 《Monthly notices of the Royal Astronomical Society》2003,343(2):367-384

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