On the Issues of Scale,Resolution, and Fractal Analysis in the Mapping Sciences*   总被引：1，自引：0，他引：1  

Nina Siu-Ngan Lam  Dale A. Quattrochi 《The Professional geographer》1992,44(1):88-98

Scale and resolution have long been key issues in geography. The rapid development of analytical cartography, GIS, and remote sensing (the mapping sciences) in the last decade has forced the issues of scale and resolution to be treated formally and better defined. This paper addresses the problem of scale and resolution in geographical studies, with special reference to the mapping sciences. The fractal concept is introduced, and its use in identifying the scale and resolution problem is discussed. The implications of the scale and resolution problem on studies of global change and modeling are also explored.  相似文献   

Monitoring well placement using conditional simulation of hydraulic head   总被引：1，自引：0，他引：1  

Dale H. Easley  Leon E. Borgman  Dennis Weber 《Mathematical Geology》1991,23(8):1059-1080

A theoretical technique for conditioning simulations in frequency domain is developed and then applied to a hydraulic-head data set from Pittman, Nevada. Frequency-domain simulation rapidly generates simulations while requiring minimal computer memory. This makes it possible by using a personal computer to create large numbers of simulations of a physical parameter field for use in studying stochastic processes. In our application, groundwater flowlines are constructed from the simulations of the hydraulic head field. Then, the crossings of the flowlines at a transect down-stream from a contaminant point source generate histograms for predicting the probability of plume interception by groundwater monitoring wells. The simulation process is discussed in detail for the Pittman study site.  相似文献   

Probability of plume interception using conditional simulation of hydraulic head and inverse modeling     

Dennis Weber  Dale Easley  Evan Englund 《Mathematical Geology》1991,23(2):219-239

A procedure to estimate the probability of intercepting a contaminant groundwater plume for monitoring network design has been developed and demonstrated. The objective of the procedure is to use all available information in a method that accounts for the heterogeneity of the aquifer and the paucity of data. The major components of the procedure are geostatistical conditional simulation and parameter estimation that are used sequentially to generate flow paths from a suspected contaminant source location to a designated monitoring transect. From the flow paths, a histogram is constructed that represents the spatial probability distribution of plume centerlines. With an independent estimate of the plume width, a relationship between the total cost and the probability of detecting a plume can be made. The method uses geostatistical information from hydraulic head measurements and is conditioned by the data and the physics of groundwater flow. This procedure was developed specifically for the design of monitoring systems at sites where very few, if any, hydraulic conductivity data are available.  相似文献   

A study of channel changes in a reach of the North Nashwaaksis stream,New Brunswick,Canada   总被引：1，自引：0，他引：1  

Dale I. Bray 《地球表面变化过程与地形》1987,12(2):151-165

Repeated surveys of a short channelized reach of the North Nashwaaksis Stream near Fredericton, N.B. over the period 1971-1981 provide the basis for evaluating the type and magnitude of some physical and botanical changes in the study reach. In 1967 a 200 m reach of the stream was shortened by about 10 per cent by cutting a new channel through a pasture. The original channel was protected by a dense growth of shrubs along its banks. The average width of the top of the channel in the channelized reach widened from 11 m to 17 m in response to a major flood in 1973. Rough estimates indicate that as much as 78 per cent of the published suspended-sediment load associated with the flood could reasonably have been derived from the banks in this short channelized reach. During the 1973 flood, a mid-channel bar was formed in the portion of the channel which experienced the most widening. Subsequent to the flood, the mid-channel bar was first colonized by sedges, and then by alders. By 1981, the width of the low flow channel in the channelized reach was about the same as that for the unmodified upstream reaches. This case study provides useful information for those planning channelization projects on small to intermediate size streams in humid temperate areas.  相似文献   

Oceanographic studies supporting the assessment of deep-sea disposal of defueled decommissioned nuclear submarines     

G. Ross Heath  David K. Rea  Gordon Ness  R. Dale Pillsbury  Thomas M. Beasley  Carlos Lopez  Daniel M. Talbert 《Environmental Geology》1984,6(4):189-199

Based on criteria developed by the international Atomic Energy Agency (IAEA), potential disposal sites for defueled, decommissioned nuclear submarines appear to exist in deep water south of the Mendocino Fracture Zone within 200 nautical miles of the United States Oceanographic measurements in the water column and at the sea floor in a study area (W-N) at 39 5°N, 127 5°W will allow the operational and radiological consequences of deep-sea disposal to be compared with land burial of old submarines. The W-N studies also are yielding new data that will provide insights to the deposition and early diagenesis of distal hemipelagic sediments Royalty-free reproduction of this article by the U S Government or by the authors for U S. Government purposes is permitted.  相似文献   

The chemistry of sublimates collected directly from lava fountains at Kilauea Volcano,Hawaii     

John J. Naughton  Virginia A. Lewis  Dale Hammond  Daniel Nishimoto 《Geochimica et cosmochimica acta》1974,38(11):1679-1690

During 1970, it was occasionally feasible to collect sublimate from directly above the lava fountain in the crater of Mauna Ulu on the east rift zone of Kilauea Volcano, when the level of the lava pool had dropped within the crater. Collecting equipment was suspended down the steep wall to a position above the fountain. Collections were made on quartz wool held within open-ended quartz tubes and, for silica detection, on stainless steel wool in a stainless steel tube. The main components in the sublimate were, in order of decreasing concentration for the best sample, Na, Ca, Al, Fe, Mg, K, B, Si, Ti, Zn, H⁺, NH₄⁺, Cu, Ni in the form of sulfates, chlorides and fluorides.In order to investigate the forms in which the sublimate ions occur under different conditions of temperature and oxidation, the equilibrium compositions of the compounds most likely to be present were calculated. This was done for those important components for which thermodynamic data are available, using a computer program to calculate the minimum free energy for the mixture. The results indicate that, for primary conditions of high temperature and low oxygen partial pressure, the halides were the most likely form of the metallic compounds. Particulate sulfates appear under increasing oxidizing conditions caused by the access of air. These conclusions were reinforced by collections made from holes drilled through the thin crust of a lava lake formed during the same eruption.  相似文献   

Geomorphic response to minor cyclic climate changes, San Diego County, California     

R. Craig Kochel  Jerry R. Miller  Dale F. Ritter 《Geomorphology》1997,19(3-4)

Short-term episodic cycles of wet and dry patterns of climate are common in southern California. Wet intervals, like the one in 1978-83, are often characterized by more than double the average annual precipitation. The impact of these episodic climatic fluctuations on landforms and surficial processes has not been well documented for areas inland of the coast. The response to these cycles may be significant in the evolution of hillslopes and fluvial landforms, and may have significant implications for geologic hazards in this rapidly developing region.Using aerial photographs and field investigations we found little response to the 1978–1983 wet interval on upland hillslopes, but documented significant response on alluvial fans and in channels in desert piedmont areas. These observations may lend support to the Langbein-Schumm (1958) model relating sediment yield to precipitation. A variety of techniques, including dendrogeomorphology, studies of the weathering of clasts, soil stratigraphy, and aerial photo mapping were used to discern at least six units on alluvial fans ranging from Late Pleistocene to present. Terraces along active fan channels and the San Felipe River record a geomorphic record of the most recent wet intervals (ca. 1940 and 1980) as a significant depositional event. Geomorphic responses to the wet interval along the San Felipe River were complex, varying locally according to controls on sediment storage and downstream transfer through a recently integrated drainage system. Additional complex responses to the wet period were experienced in selected sites where antecedence and response times may be measured in months or even years.  相似文献   

First Images of Impulsive Millimeter Emission and Spectral Analysis of the 1994 August 18 Solar Flare     

Silva  Adriana V. R.  Gary  Dale E.  White  Stephen M.  Lin  R. P.  de Pater  Imke 《Solar physics》1997,175(1):157-173

We present here the first images of impulsive millimeter emission of a flare. The flare on 1994 August 18 was simultaneously observed at millimeter (86 GHz), microwave (1-18 GHz), and soft and hard X-ray wavelengths. Images of millimeter, soft and hard X-ray emission show the same compact ( 8) source. Both the impulsive and the gradual phases are studied in order to determine the emission mechanisms. During the impulsive phase, the radio spectrum was obtained by combining the millimeter with simultaneous microwave emission. Fitting the nonthermal radio spectra as gyrosynchrotron radiation from a homogeneous source model with constant magnetic field yields the physical properties of the flaring source, that is, total number of electrons, power-law index of the electron energy distribution, and the nonthermal source size. These results are compared to those obtained from the hard X-ray spectra. The energy distribution of the energetic electrons inferred from the hard X-ray and radio spectra is found to follow a double power-law with slope 6–8 below 50 keV and 3–4 above those energies. The temporal evolution of the electron energy spectrum and its implication for the acceleration mechanism are discussed. Comparison of millimeter and soft X-ray emissions during the gradual phase implies that the millimeter emission is free-free radiation from the same hot soft X-ray emitting plasma, and further suggests that the flare source contains multiple temperatures.  相似文献   

Mineralogy and mineral chemistry of detrital heavy minerals from the Rhine River in Germany as evidence to their provenance,sedimentary and depositional history: focus on platinum-group minerals and remarks on cassiterite,columbite-group minerals and uraninite     

Thomas Oberthür  Frank Melcher  Simon Goldmann  Hermann Wotruba  Axel Gerdes  Arjan Dijkstra  Christopher W. Dale 《International Journal of Earth Sciences》2016,105(2):637-657

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Modeling of Plume Capture by Continuous, Low-Permeability Barriers     

Kevin P. Garon  P.G.    Dale S. Schultz  Ph.D.  Richard C. Landis 《Ground Water Monitoring & Remediation》1998,18(3):82-87

Modeling was performed to simulate ground water flow through reactive barriers of lower hydraulic conductivity than the surrounding aquifer to determine the plume capture widths. As a plume approaches such a barrier, it spreads laterally. Therefore, to intercept an entire plume, the barrier must be wider than the upgradient width of the undisturbed plume. The results indicate that, for practical values of barrier thickness and plume width, hydraulic conductivities ten-fold less than that of the aquifer can be accommodated by making the width of the barrier approximately 20% greater than the upgradient width of the plume. Barrier hydraulic conductivities one-hundred-fold less than that of the aquifer may require barrier widths up to twice the width of the upgradient plume for plumes 100 feet wide (33 m) and as little as 1.1 times for plumes 1000 feet wide (325 m). The results presented here lend support to the view that novel emplacement methods that create zones of slightly lower hydraulic conductivity than the native aquifer may be viable alternatives to the excavation-and-backfill approaches which have thus far been used for installing permeable reactive barriers.  相似文献