Algebraic approach to spatial reasoning     

TERENCE R. SMITH  KEITH K. PARK 《International journal of geographical information science》2013,27(3):177-192

Abstract

A simple, exemplary system is described that performs reasoning about the spatial relationships between members of a set of spatial objects. The main problem of interest is to make sound and complete inferences about the set of all spatial relationships that hold between the objects, given prior information about a subset of the relationships. The spatial inferences are formalized within the framework of relation algebra and procedurally implemented in terms of constraint satisfaction procedures. Although the approach is general, the particular example employs a new ‘complete’ set of topological relationships that have been published elsewhere. In particular, a relation algebra for these topological relations is developed and a computational implementation of this algebra is described. Systems with such reasoning capabilities have many applications in geographical analysis and could be usefully incorporated into geographical information systems and related systems.  相似文献   

Influences on formation and dissipation of high arctic fogs during summer and autumn and their interaction with aerosol   总被引：1，自引：0，他引：1  

E. DOUGLAS NILSSON  E. KEITH BIGG 《Tellus. Series B, Chemical and physical meteorology》1996,48(2):234-253

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An undulatory discontinuity surface on a gently inclined muddy ramp: possible evidence of secondary helical flow from the geological record     

KEITH B. MILLER 《Sedimentology》1991,38(6):1097-1112

An unusual, somewhat cryptic, undulatory discontinuity has been recognized near the basal contact of the Wanakah Shale Member of the Middle Devonian Ludlowville Formation in western New York. It is in part marked by undulating diagenetic limestone beds and concretionary horizons, but can be traced continuously by subtle surfaces of fossil and pyritic lags. This surface marks the top of parallel, elongate mud ridges trending approximately N-S, perpendicular to the inferred E-W depositional strike of the Appalachian Basin in western New York. These ridges are observed in the field as irregularly spaced mud swells which have up to 1.5 m of relief, and vary from 30 to 50 m or more in width. The intervening, broad, flat‘channel floors’ are characterized by dense concentrations of diminutive brachiopods with gastropods and styliolinids, which are gradually replaced by thin styliolinid horizons with abundant pyrite nodules and pyritized burrows over the tops of the swells. Traceable shelly horizons are observed to pinch out over the swells, suggesting a period of relatively undisturbed sediment-filling following the formation of the channellized surface. The interval of nearly barren shale below this irregular surface, however, contains concretionary horizons and rare styliolinid pavements which are themselves irregular, possibly indicating a changing topography for this surface through time. Previous taphonomic and palaeoecological studies of the lower Wanakah Shale Member have disclosed a well-defined regressive-transgressive cycle with more subtle superimposed subcycles. The undulatory surface described here occurs within the early regressive part of this cycle, and appears to record an accentuated regressive kick of a lower-order subcycle. The formation of this surface is therefore interpreted to be a consequence of regressive submarine erosion and sediment bypass, together with redeposition from suspension. The development of the‘channels’ and parallel longitudinal mud ridges was probably controlled by helical flow cells within offshore-directed bottom currents. They may be the first recorded instance of sedimentary furrows described from the geological record. Taphonomic and biofacies data indicate relative depths below average storm wave-base, suggesting that sediment winnowing and redeposition occurred at depths only rarely affected by the direct impact of storm wave agitation.  相似文献   

A Chemical Study of Serpentinization--Burro Mountain, California   总被引：7，自引：0，他引：7  

COLEMAN  R. G.; KEITH  T. E. 《Journal of Petrology》1971,12(2):311-328

Serpentinized dunites and harzburgites from the Burro Mountainperidotite show no change in the ratio of iron and magnesiato silica when compared with the same ratio for the unserpentinizedequivalents. The mineral assemblage resulting from serpentinizationconsists of lizardite-chrysotile, brucite, and magnetite andis determined by the original bulk composition of the peridotite.The chemical and mineralogical data indicate that serpentinizationproceeded under isochemical conditions except for the introductionof water into the peridotite. Expansion accompanies serpentinizationbecause the serpentine products occupy a greater volume thanthe peridotite protolith. Tectonic emplacement of the BurroMountain peridotite was facilitated by serpentinization andthe attendant expansion.  相似文献   

Petrogenesis of Mesozoic, Peraluminous Granites in the Lamoille Canyon Area, Ruby Mountains, Nevada, USA   总被引：5，自引：0，他引：5  

LEE  SANG-YUN; BARNES  CALVIN G.; SNOKE  ARTHUR W.; HOWARD  KEITH A.; FROST  CAROL D. 《Journal of Petrology》2003,44(4):713-732

Two groups of closely associated, peraluminous, two-mica graniticgneiss were identified in the area. The older, sparsely distributedunit is equigranular (EG) with initial  相似文献   

Late Holocene climatic history of northern Germany and Denmark: peat macrofossil investigations at Dosenmoor, Schleswig-Holstein, and Svanemose, Jutland   总被引：3，自引：0，他引：3  

KEITH E. BARBER  FRANK M. CHAMBERS  DARREL MADDY 《Boreas: An International Journal of Quaternary Research》2004,33(2):132-144

Plant macrofossil remains have been analysed from two raised peat bogs in northern Germany and Denmark. The quantified vegetation reconstructions of each profile were subjected to multivariate analyses to extract records of changing bog surface wetness (BSW), which are interpreted in these rain-fed bogs as being proxy climate signals. Age/depth models were constructed using radiocarbon dates and a number of drier and wetter phases were defined. The records both register cooler/wetter conditions around 2700, 1800 and 1400 cal. yr BP, and at the beginning of the Little Ice Age around AD 1250–1350. These rising bog water tables must have been reflected in poorer conditions for agriculture, and in particular near Dosenmoor where the profile records a catastrophic change to such conditions culminating at 2750–2600 cal. yr BP.  相似文献   

Analytical compensation between DTM grid resolution and effective values of staurated hydraulic conductivity within the TOPMODEL framework     

GEORGES-MARIE SAULNIER  CHARLES OBLED  KEITH BEVEN 《水文研究》1997,11(9):1331-1346

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Modelling the hydrological response of mediterranean catchments,Prades, Catalonia. The use of distributed models as aids to hypothesis formulation     

JOSEP PI OL  KEITH BEVEN  JAMES FREER 《水文研究》1997,11(9):1287-1306

This paper attempts to extend the physical arguments underlying the distributed TOPMODEL concepts in an application to the strongly seasonal contributing area responses in two adjacent small mediterranean catchments in the Prades region of Catalonia, Spain. A perceptual model of hydrological response in these catchments is used to suggest possible modifications of the model in a hypothesis testing framework, including an attempt to modify the topographic index approach to reflect the expansion of the effective area of subsurface flow during the wetting-up sequence. It is found that slight improvements in modelling efficiency are possible but that different model parameter distributions are appropriate for different parts of the record. The model was much more successful for the catchment producing the higher runoff volumes. © 1997 John Wiley & Sons, Ltd.  相似文献   

TOPMODEL: A critique     

KEITH BEVEN 《水文研究》1997,11(9):1069-1085

TOPMODEL (a TOPography based hydrological MODEL) is now 20 years old and has been the subject of numerous applications to a wide variety of catchments. This paper represents a critical review of some of the issues involved in application of the TOPMODEL concepts, including the basic assumptions involved; the derivation of topographic index distributions from digital terrain data; additional model components; meaning and calibration of the model parameters; and issues involved in model validation and predictive uncertainty. The aim is to provoke a thoughtful approach to hydrological modelling and the interaction of modelling and field work. Some recommendations are made for future modelling practice. © 1997 John Wiley & Sons, Ltd.  相似文献   

LINKS BETWEEN PROGLACIAL STREAM SUSPENDED SEDIMENT DYNAMICS,GLACIER HYDROLOGY AND GLACIER MOTION AT MIDTDALSBREEN,NORWAY     

IAN C. WILLIS  KEITH S. RICHARDS  MARTIN J. SHARP 《水文研究》1996,10(4):629-648

Two-hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining Midtdalsbreen, Norway are modelled using multiple regression and time series techniques. Suspended sediment fluctuations are influenced by stream discharge variations, diurnal hysteresis effects, medium-term sediment supply and transport variations and the recent suspended sediment concentration history of the stream. They do not appear to be influenced by seasonal exhaustion or rainfall variations. Possible reasons for this are discussed. Large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations; these sediment flushes correlate with periods of enhanced glacier motion. They cannot be explained by enhanced sediment production by subglacial erosion, but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and/or configuration of the subglacial hydrological system. Seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration.  相似文献