空间方向关系形式化描述模型研究

空间方向关系形式化描述模型是空间关系研究的难点和重点，目前尚无完善的模型出现，因此进行其模型的研究意义重大。首先论述运用平面目标Voronoi图描述方向关系在理论上的可行性；然后详细阐述基于Voronoi图的空间方向关系形式化描述模型建立；为了验证模型的正确性，给出几个典型的算例；最后指出模型的优、缺点。     

Sorted circles in the maritime Subantarctic,Marion Island

Active sorted circles are quantitatively described for the first time for the maritime Subantarctic. Increasing altitude and hence increasing frost penetration are associated with systematic increases in pattern spacing, cell width, height of the fine centre relative to the border, and depth of sorting (but not the width of coarse margins). These results imply consistent dimensional scaling of circle parameters. It is argued, on the basis of the altitudinal trends in pattern morphology, the dimensional scaling of forms, and the morphology of the patterns, that differential frost heave in association with convection cells is responsible for circle formation. Copyright © 2003 John Wiley & Sons, Ltd.     

Calculated Phase Relations in High-Pressure Metapelites in the System NKFMASH (Na2O-K2O-FeO-MgO-Al2O3-SiO2-H2O)

Using an internally consistent thermodynamic dataset and updatedmodels of activity–composition relation for solid solutions,petrogenetic grids in the system NKFMASH (Na₂O–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O)and the subsystems NKMASH and NKFASH have been calculated withthe software THERMOCALC 3.1 in the P–T range 5–36kbar and 400–810°C, involving garnet, chloritoid,biotite, carpholite, talc, chlorite, kyanite/sillimanite, staurolite,phengite, paragonite, albite, glaucophane, jadeite, with quartz/coesiteand H₂O in excess. These grids, together with calculated AFMcompatibility diagrams and P–T pseudosections, are shownto be powerful tools for delineating the phase equilibria andP–T conditions of Na-bearing pelitic assemblages for avariety of bulk compositions from high-P terranes around theworld. These calculated equilibria are in good agreement withpetrological studies. Moreover, contours of the calculated phengiteSi isopleths in P–T pseudosections for different bulkcompositions confirm that phengite barometry is highly dependenton mineral assemblage. KEY WORDS: phase relations; HP metapelite; NKFMASH; THERMOCALC; phengite geobarometry     

Laboratory simulation of water-resources conservation by means of the layout of a series of ponds along a streambank

 The purpose of this research is to describe a water-storage method that is more reliable than reservoirs, and to study the efficacy of interception and storage of surface runoff in ponds. In this method, a series of ponds is laid out along a streambank so that interception of surface runoff can be increased and more water can be stored in the wet season for use in the dry season. The simulated results show that the structure of a pond, vegetation and the extent of land development, topographic slope, and the degree to which a pond penetrates an aquifer affect the efficacy of interception and storage of surface runoff in ponds. Received, May 1996 Revised, July 1997, March 1998 Accepted, October 1997     

Satellite-derived vegetation index and cover type maps for estimating carbon dioxide flux for arctic tundra regions

The spatial variability and co-variability of two different types of remote sensing derivatives that portray vegetation and geomorphic patterns are analyzed in the context of estimating regional-scale CO₂ flux from land surfaces in the arctic tundra. For a study area encompassing the Kuparuk River watershed of the North Slope of Alaska, we compare satellite-derived maps of the normalized difference vegetation index (NDVI) generated at two different spatial resolutions to a map of vegetation types derived by image classification of data from the Landsat multispectral scanner (MSS). Mean values of NDVI for each cover type stratum are unique (with the exception of moist acidic tundra and shrubland types). Based on analysis of semi-variograms generated for SPOT-NDVI data, most of the vegetation cover and landform features of this arctic tundra landscape have spatial dimensions of less than 1 km. Thaw lakes on the coastal plain and glacial depositional landforms, such as moraines in the foothills, seem to be the largest features, with vegetation units having dimensions no larger than 700 m. Frequency distributions of NDVI and vegetation types extracted for sampling transects flown by an aircraft sensing CO₂ flux, relative to distributions for the entire Kuparuk River watershed, suggest a slight sampling bias towards greater cover of mesic wet sedge tundra and thaw lakes and associated lower NDVI values. The regional pattern of NDVI for the North Slope of Alaska corresponds primarily to differences between the two major physiographic provinces of this region.     

Truncation error formulae for the disturbing gravity vector

Recurrence relations have been derived for truncation error coefficients of the extended Stokes' function and its partial derivatives required in the computation of the disturbing gravity vector at any elevation above the earth's surface. The corresponding formulae, the example of values of the truncation error coefficients for H=30.1 km and ψ₀=30^∘ and the estimations of truncation error are given in this article. Received: 26 January 1996 / Accepted: 11 June 1997     

Justification of the Inertial Dissipation Technique in Anisotropic Mean Flow

The inertial dissipation technique has been successfully employed for many years to measure the wind stress, especially over the open ocean. This method is based on Kolmogorov's theoretical prediction of universality in the inertial wavenumber range. The theory was developed under the assumption of locally isotropic turbulence, and the dissipation technique has been criticized as lacking justification in a boundary-layer shear flow. In this paper, Kolmogorov's theory is explicitly applied to the anisotropic conditions prevailing in the atmosphere. It is shown that the inertial dissipation method relies on the homogeneity and isotropy of the spectrum _ii(k) for k in the inertial range. This is a weaker condition than Kolmogorov's assumption of isotropy of the correlation function B_ij(r). In high-Reynolds-number shear flows, isotropy of _ii(k) is realized to a good approximation, whereas isotropy of B_ij(r) is not. Some consequences for the experimental implementation are discussed; in particular, sampling times (block lengths) not exceeding the order of the eddy life time are recommended in the calculation of spectra.     

模糊对象粗糙表达及其空间关系研究

空间数据的模糊性是当前GIS领域研究的难点之一。现有的GIS数据模型基本上还不具备对模糊性进行描述、处理和分析的功能 ,使得GIS对数据的处理容易造成信息损失。把粗糙集和模糊集对空间数据的模糊性和不确定性处理的优势结合起来表达模糊对象 ,即利用粗糙集处理由于知识的粒度性所造成的模糊性和不精确性 ;利用模糊集处理模糊对象原始数据所具有的不确定性 ,从而扩展了空间数据模型对模糊数据的表达能力 ,并详细研究了模糊面与模糊面以及模糊线与模糊面之间的拓扑关系     

Estimation of the Exchange Coefficient of Heat During Low Wind Convective Conditions

For the first time, the exchange coefficient of heat C_H has been estimated from eddy correlation of velocity and virtual temperature fluctuations using sonic anemometer measurements made at low wind speeds over the monsoon land atJodhpur (26°18' N, 73°04' E), a semi arid station. It shows strong dependence on wind speed, increasing rapidly with decreasing wind speed, and scales according to a power law C_H = 0.025U₁₀ ^-0.7 (where U₁₀ is the mean wind speed at 10-m height). A similar but more rapid increase in the drag coefficient C_Dhas already been reported in an earlier study. Low winds (<4 m s^-1) are associated with both near neutral and strong unstable situations. It is noted that C_H increases with increasing instability. The present observations best describe a low wind convective regime as revealed in the scaling behaviour of drag, sensible heat flux and the non-dimensional temperature gradient. Neutral drag and heat cofficients,corrected using Monin–Obukhov (M–O) theory, show a more uniform behaviour at low wind speeds in convective conditions, when compared with the observed coefficients discussed in a coming paper.At low wind convective conditions, M-O theory is unable to capture the observed linear dependence of drag on wind speed, unlike during forced convections. The non-dimensional shear inferred from the present data shows noticeable deviations from Businger's formulation, a forced convection similarity. Heat flux is insensitive to drag associated with weak winds superposed on true free convection. With heat flux as the primary variable, definition of new velocity scales leads to a new drag parameterization scheme at low wind speeds during convective conditionsdiscussed in a coming paper.