Natural regions for national parks: the Canadian experience     

Ronald A. Foresta 《Applied geography (Sevenoaks, England)》1985,5(3):179-194

This article examines the history and characteristics of the system of natural regions devised by the Canadian federal government as a basis for selecting new national parks and in use since 1971. It begins with an examination of the political and scientific problems faced by those who devised the regional system and of how the system they devised solved these problems. It then examines the system's strengths and weaknesses as an instrument of public policy and evaluates its success as a guide to the selection of new national parks. It concludes by observing that the system's lack of those characteristics commonly considered the hallmarks of a logically satisfying regional system, distinct regions and unambiguous boundaries delineated by an objective process, was unimportant. Far more important to its success as an instrument of policy were other, less formal characteristics such as its overall appearance of reasonableness and the way it led to the selection of sites which were aesthetically, and therefore politically, appealing.  相似文献   

Stochastic analysis of complex lithological successions     

Ronald W. May  Brian Jones 《Mathematical Geology》1982,14(5):405-417

It is difficult to develop stochastic models for complex lithological sequences that are typically associated with intertidal-supratidal depositional environments. A sequence from the Upper Silurian Leopold Formation on eastern Somerset Island is used to demonstrate that a combination of cluster analysis, Markov Chain analysis, and substitutability analysis can give considerable insight into the nature of such complex successions. The high variability of this sequence was created by a combination of (a) variation in the depositional environment, (b) variation in the degree of dolomitization, (c) variation in the clastic influx, (d) random highenergy (possibly storm associated events) and (e) random breaks in the succession of depositional environments.  相似文献   

TERRA BOOKS PALAEOBIOLOGY A SYNTHESIS     

Derek.E.G. Briggs  Peter R. Crowther 《地学学报》1991,3(1):103-105

1990, £89.50 (hbk), 583 pp. Blackwell Scientific Publications, Oxford ISBN 0–632–02525–5  相似文献   

Precision size-frequency distributions of craters for 12 selected areas of the lunar surface     

Ronald Greeley  Donald E. Gault 《Earth, Moon, and Planets》1970,2(1):10-77

Total crater populations in Lunar Orbiter photographs have been counted and measured for 12 selected areas of the lunar surface using precision techniques. Details of the counting procedure are described. Incremental and cumulative frequencies per km² (and their logarithms) are presented in graphical as well as tabular form for general use by other investigators. The data include 333,404 craters in areas totaling 10,833.3 km².  相似文献   

THE EFFECT OF SOCIAL HETEROGENEITY WITHIN URBAN TRAVEL CORRIDORS ON THE TRAVEL BEHAVIOR OF RESIDENTS     

Ronald L. Mitchelson 《The Professional geographer》1982,34(2):185-196

Results from behavioral investigations of urban travel indicate the importance of privacy as a personal construct that significantly affects the manner in which individuals traverse North American urban transportation networks. With an expectation of encountering social heterogeneity in travel, the privacy aspect becomes all the more important to the traveling public. It is hypothesized in this paper that social heterogeneity within urban travel corridors significantly reduces patronage of public transportation by residents of these corridors. A causal analysis of bus patronage in travel corridors of Columbus, Ohio, Louisville, Kentucky, Syracuse, New York, and Hartford, Connecticut results in the acceptance of the hypothesized relationship, and it points out a critical question that must be addressed if public transportation is to meet the desires of consumers of travel services.  相似文献   

Hydrodynamical winds from two-temperature plasma in X-ray binaries     

David J. Lin  R. Misra  Ronald E. Taam 《Monthly notices of the Royal Astronomical Society》2001,324(2):319-324

Hydrodynamical winds from a spherical two-temperature plasma surrounding a compact object are constructed. The mass-loss rate is computed as a function of electron temperature, optical depth and luminosity of the sphere, the values of which can be constrained by the fitting of the spectral energy distributions for known X-ray binary systems. The sensitive dependence of the mass-loss rate with these parameters leads to the identification of two distinct regions in the parameter space separating wind-dominated from non-wind-dominated systems. A critical optical depth ( τ _c) is defined as a function of luminosity and electron temperature, which differentiates these two regions. Systems with optical depths significantly smaller than τ _c are wind-dominated.
The results are applied to black hole candidate X-ray binary systems in the hard spectral state (Cyg X-1, GX 339−4 and Nova Muscae), and it is found that the inferred optical depth ( τ ) is similar to τ _c, suggesting that they are wind-regulated systems. On the other hand, for X-ray binary systems containing a neutron star (e.g., Cyg X-2) τ is much larger than τ _c indicating the absence of significant hydrodynamical winds.  相似文献   

Orbiting the Sun. Planets and satellites of the solar systems: Fred L. Whipple. Harvard Univ. Press,Cambridge, Mass., 1981. 338 pp. $20.00     

F.H. Briggs 《Icarus》1982,50(1):123-124

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The US Geological Survey's national coal resource assessment: the results     

Leslie F. Ruppert  Mark A. Kirschbaum  Peter D. Warwick  Romeo M. Flores  Ronald H. Affolter  Joseph R. Hatch 《International Journal of Coal Geology》2002,50(1-4)

The US Geological Survey and the State geological surveys of many coal-bearing States recently completed a new assessment of the top producing coal beds and coal zones in five major producing coal regions—the Appalachian Basin, Gulf Coast, Illinois Basin, Colorado Plateau, and Northern Rocky Mountains and Great Plains. The assessments, which focused on both coal quality and quantity, utilized geographic information system technology and large databases. Over 1,600,000 million short tons of coal remain in over 60 coal beds and coal zones that were assessed. Given current economic, environmental, and technological restrictions, the majority of US coal production will occur in that portion of the assessed coal resource that is lowest in sulfur content. These resources are concentrated in parts of the central Appalachian Basin, Colorado Plateau, and the Northern Rocky Mountains.  相似文献   

Coal as a source rock for oil: a review   总被引：2，自引：0，他引：2  

Ronald W. T. Wilkins  Simon C. George   《International Journal of Coal Geology》2002,50(1-4)

The geological debate about whether, and to what extent, humic coals have sourced oil is likely to continue for some time, despite some important advances in our knowledge of the processes involved. It is clear that not only liptinites, but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification. Some liptinites, especially alginite, cutinite, and suberinite, contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are, therefore, more oil-prone. It is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed. Review of the distribution of oil-prone coals in time and space reveals that most are Jurassic–Tertiary with key examples from Australia, New Zealand, and Indonesia. Methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals. Results are not entirely consistent among the different approaches, and there is much overlap in the ranges of degradation, but it seems probable that in the natural environment vitrinites begin to generate early, followed by labile liptinites such as suberinite, then cutinite, sporinite, and, finally, alginite.Petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro-techniques, especially fluorescence and infrared (IR) spectroscopy, or bulk techniques such as elemental analysis and ¹³C NMR spectroscopy. The latter three techniques enable a measure of the polymethylene component of the coal, which now appears to be one of the best available approaches for determining petroleum potential. No method of experimental simulation of petroleum generation from coals is without criticism, and comparative results are highly variable. However, hydrous pyrolysis, confined pyrolysis, and forms of open-system hydrous pyrolysis approach acceptable simulations.Whether, and to what degree generated liquid hydrocarbons are expelled, has long been the central problem in ‘oil from coal’ studies. The structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained. Recent studies show the pores are not interconnected. Combined with a dynamic model of pore generation, it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries. The main reason for poor expulsion is the adsorption of oil on the organic macromolecule, which may be overcome (1) if coals are thin and interbedded with clastic sediments, or (2) if the coals are very hydrogen-rich and generate large quantities of oil.The existence of oil in vitrinite is attested to by solvent extractions, fluorescence properties, and by microscopic observations of oil and bitumen. Experimental simulation of expulsion of oil from coals has only recently been attempted. The relative timing of release of generated CO₂ and CH₄ could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear. As it is universally agreed that dispersed organic matter (DOM) in some shales readily generates and expels petroleum, it is curious that few consistent geochemical differences have been found between coal macerals and DOM in interbedded shales.Unambiguous evidence of expulsion from coals is limited, and in particular only a few commercial oil discoveries can be confidently correlated to coals. These include Upper Cretaceous Fruitland Formation coals in the USA, from which oil is produced; New Zealand Tertiary coals; and Middle Jurassic coals from the Danish North Sea. It is likely that coals have at least contributed to significant oil discoveries in the Gippsland Basin, Australia; in the Turpan Basin, China; and in the Kutei and Ardjuna basins in Indonesia, but this remains unproven. Early reports that early Jurassic coals in mid-Norway were a major source of the reservoired oils have been shown to be inaccurate.None of the proposed ‘rules of thumb’ for generation or expulsion of petroleum from coals seem particularly robust. Decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information. The assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain.  相似文献   

气候变化对中国植被可能影响的模拟   总被引：46，自引：0，他引：46  

赵茂盛  延晓冬  董文杰 《地理学报》2002,57(1):28-38

依据我国植被和气候的关系对生物地理模式MAPSS中的某些参数和过程进行了调整。将改进后MAPSS模拟的当前气候状况下潜在植被类型及叶面积指数的分布与我国植被区划图和多年平均的NDVI（NOAA／AVHRR）比较，发现结果有了很大的改进。将大气环流模式HadCM2对未来气候变化的预测结果应用于改进后的MAPSS对我国植被未来的变化进行了模拟。考虑到未来大气升高的CO2浓度对植物水分利用率（WUE）的可能影响，进行了WUE变化和不变化2种预测。结果发现未来气候变化可能导致我国东部森林植被带的北移，尤其是北方的落叶针叶林的面积减少很大，以至可能移出我国境内；华北地区和东北辽河流域未来可能草原化；西部的沙漠和草原可能略有退缩，相应被草原和灌丛取代；高寒草甸的分布可能略有缩小，将被萨瓦纳和常绿针叶林取代。同时模拟的结果表明模型对WUE非常敏感。最后对结果的不确定性进行了讨论。  相似文献