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31.
《The Professional geographer》2013,65(4):471-477
Much science-fiction literature is based upon the creation and exploration of alternative environments. Stanley G. Weinbaum's short story, “Parasite Planet,”introduces an unusual environment that may be wrong in the light of recent evidence on Venus but still stimulates the geographical imagination. 相似文献
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ABSTRACT. This study examines the residential patterns of immigrant newcomers within a relatively new immigrant destination, Washington, D.C. Particular attention is given to how these patterns are shaped by the newcomers' race and ethnicity. Our analysis is based primarily upon data on immigrant flows from the U.S. Immigration and Naturalization Service for the 1990–1998 period. Evidence from our study suggests a racial and ethnic hierarchy to the residential location of Africans, Asians, Europeans, and Latin Americans, providing some support for the pattern expected in the place‐stratification model. When their residential patterns are compared with those of non‐Hispanic blacks, we find that African newcomers are more likely to settle among blacks than are other regional‐origin groups. However, Africans are also found to reside in multiethnic zip codes where large numbers of newcomers are concentrated. The findings suggest that race is an important but not exclusive factor in explaining the residential choices of recent immigrants. 相似文献
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Distribution and sources of phosphorus in tidal river sediments in the Washington, DC, Area 总被引:2,自引:0,他引:2
Sediments in the rivers and basins around Washington, DC, have high concentrations of phosphorus, which, based on geographic
distributions, is largely derived from urban runoff and municipal sewage. Dissolved-particulate phosphate exchange reactions
and biological uptake of dissolved phosphorus from the water column may be an added source of phosphorus to the sediments.
Concentrations of total sedimentary phosphorus ranged from 24 to 56 μm P/g-dw, and were highest in areas near combined sewer
outfalls. As a part of this study, sedimentary phosphorus was fractionated into Fe-P, Ca-P, Al-P, and organic phases using
a selective-sequential leaching procedure. The distribution of the phases in all sediments analyzed follow the order , Fe-P>Ca-P>Al-P.
Spatial variations in the amounts of phosphorus in the different phases is related to the sources of phosphorus to the area.
The proportions of occluded Al-P and organic P are 10–20% of the total P, respectively. This suggests that phosphorus from
natural sources is small compared to anthropogenic inputs in this area. The high leachable Fe-P and Ca-P in these sediments
might contribute a substantial amount of P to the water column under conditions of remobilization.
Received: 20 February 1996 · Accepted: 2 April 1996 相似文献
36.
Nufar Avni 《Urban geography》2019,40(4):488-505
In the last decade, justice has been revived as a primary criterion for the analysis and evaluation of planning policies. This paper continues this line of research by examining a proposed redevelopment project in Washington, D.C. that sets equitable development as its goal . The proposed 11th Street Bridge Park would be a top-notch elevated park, physically and symbolically connecting D.C’s wealthy west with the disadvantaged east. The project is managed by a nonprofit organization and seemingly stands out in its progressive vision: An Equitable Development Plan has been developed in an attempt to secure the future of the local residents in light of the neighborhood's anticipated gentrification. However, preliminary findings show that despite explicit commitment to equity, the planning of the park also resurfaces racial and class tensions . The analysis of procedural and substantive aspects of justice in this case suggests that issues of recognition, power and representation are instrumental to fully understand urban (in)justices. 相似文献
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Increasing wave heights and extreme value projections: The wave climate of the U.S. Pacific Northwest 总被引:1,自引:0,他引:1
Deep-water wave buoy data offshore from the U.S. Pacific Northwest (Oregon and Washington) document that the annual averages of deep-water significant wave heights (SWHs) have increased at a rate of approximately 0.015 m/yr since the mid-1970s, while averages of the five highest SWHs per year have increased at the appreciably greater rate of 0.071 m/yr. Histograms of the hourly-measured SWHs more fully document this shift toward higher values over the decades, demonstrating that both the relatively low waves of the summer and the highest SWHs generated by winter storms have increased. Wave heights associated with higher percentiles in the SWH cumulative distribution function are shown to be increasing at progressively faster rates than those associated with lower percentiles. This property is demonstrated to be a direct result of the probability distributions for annual wave climates having lognormal- or Weibull-like forms in that a moderate increase in the mean SWH produces significantly greater increases in the tail of the distribution. Both the linear regressions of increasing annual averages and the evolving probability distribution of the SWH climate, demonstrating the non-stationarity of the Pacific Northwest wave climate, translate into substantial increases in extreme value projections, important in coastal engineering design and in quantifying coastal hazards. Buoy data have been analyzed to assess this response in the wave climate by employing various time-dependent extreme value models that directly compute the progressive increases in the 25- to 100-year projections. The results depend somewhat on the assumptions made in the statistical procedures, on the numbers of storm-generated SWHs included, and on the threshold value for inclusion in the analyses, but the results are consistent with the linear regressions of annual averages and the observed shifts in the histograms. 相似文献
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In a recent paper, Hedger, R.D., Malthus, T.J., Folkard, A.M., Atkinson, P.M. [2007. Spatial dynamics of estuarine water surface temperature from airborne remote sensing. Estuarine, Coastal and Shelf Science 71, 608–615] demonstrate that airborne thermal remote sensing shows great potential for monitoring estuarine dynamics and surface currents. One aspect needing further attention is the impact of bottom-generated vertical mixing as this can create both stationary thermal features as well as thermal patterns that advect with the flow. This dual effect is illustrated using airborne infrared imagery of a mixing front having an embedded pattern of thermal boils. The boils are several meters in diameter (in water less than 4 m deep) and are ∼0.2 °C cooler than the ambient water surface. Time sequential imagery that captures the movement of individual boils as well as their growth rate can be used to deduce both the near-surface current and the intensity of turbulent mixing. 相似文献
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Soft-sediment clasts composed of silt and clay are contained within glacial outwash sands in the Puget Sound, Washington State, USA. The outwash was deposited during ice retreat of the Cordilleran ice sheet around 17 cal kyr BP. The soft-sediment clasts have a distinctive and consistent morphology and disposition within the sand beds. The sedimentology, sedimentary structures and presence of soft-sediment clasts suggest sand was deposited as proglacial outwash with silts and clays deposited in meltwater pools. Following drying-out of the pools and subaerial cracking, lumps of silt and clay were excavated by meltwater and transported distally as soft-sediment clasts within high-density flows. The most likely final depositional setting is as a Salisbury-type ‘delta’ in which subaqueous outwash grades distally into deeper water. This interpretation shows the power of soft-sediment clasts to inform on past processes and palaeogeography for which there is often little evidence in the geologic record. 相似文献