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Globalization is constituted not only through interurban networks of global city regions, but also by intraurban linkages within city regions. In this article, we use the Madrid city region as a case study to analyze the emergence of new “globalization arenas”—dense agglomeration nodes of knowledge-intensive business services (KIBSs)—on the outskirts of large metropolises (METs). We focus on two distinct types of centers. New employment centers (NECs) are produced by intrametropolitan suburbanization and realignment of preexisting small agglomerations. Historic administrative cities (HACs) are created by suprametropolitan scale processes remaking historically autonomous centers beyond the MET, which are only now being articulated in metropolitan transformation. We use statistical, cartographic, and econometric techniques to analyze proximity and economic base characteristics of NECs and HACs. As KIBSs continue to evolve in patterns of decentralized concentration, HACs are becoming more important KIBS nodes amidst complex landscapes of functional specialization and repositioning.  相似文献   

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《Geomorphology》1988,1(2):161-189
Bank recession at twenty stations along the eastern end of 286 km long Lake Sakakawea, North Dakota, measured regularly between 1983 and 1986, showed a recession range from essentially zero to almost 9 m yr−1 with an average of 1.6 m yr−1. Between 1969 and 1979, rates were greater, the declining rate a normal consequence of the factors affecting bank recession. Rates of recession vary with seasons, with 78% of the annual recession occurring during the warmer season (May–October) as a result of wave erosion. The remaining 22% occurs during thaw failure in spring.Prediction of ultimate (500 yr) bank recessions attempted using historical recession data, the three years of detailed field measurements, and regression analysis of the erosion factors. An equation, presented here, requires field measurement of bank orientation and height, batch width and composition, and slope of the offshore area. Effective fetch must be measured, as well. The resulting equation for the monthly warm season recession rate is: Rs=154.9 −, (18.8 √ A+ 25.1 √ B +10.1 √ c +6.9 √ 0+5.0 √ E + 1.1 √ F) where: A = sine of angle between bank orientation and dominant wind; B = offshore slope angle; C = beach width; D = bank height; E = effective fetch; and F = percentage of coarse beach clasts. The colder season recession percentage is: Rw = Rs [(2.05D = 0.043G) − 2/100] where D is bank height and G the bank orientation with respect to sun. The total yearly predicted recession (cm yr−1) is: Rt = 6 (Rw) + 6 (Rs) 6 being the number of months of “cold” and “warm” weather at Lake Sakakawea.For this rate to be projected into the future, it is necessary to assume a declining rate of recession, employing a parabolic trend. From this, the ultimate bank recession for Lake Sakakawea is predicted to range up to 542 m.  相似文献   

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Saline playas in north-western Nevada, U.S.A., remnants of pluvial periods of the Pleistocene, represent a tremendous source of unconsolidated sediments available for aeolian transport. This study investigated the transport of aqueous-soluble solutes in dust from July 1994 through June 1996 along a transect from a barren salt-encrusted playa surface (elevation=1224 m), to a former pluvial lake beach (elevation=1228 m), to a dune-mantled upland (elevation=1248 m). The content of aqueous-soluble solutes in aeolian dust showed a significant (p≤0·05) interaction with dust trap location (playa, beach, dune) and time of collection. Dust collectors on the playa surface generally contained significantly more aqueous-soluble solutes and had greater total flux of solutes than either the beach or the dune locations. The solute content of aeolian dust was usually higher, in some cases several orders of magnitude, than that in the surface 5 cm of soil. Recent changes in playa hydrology may explain this result. Pulses of nitrate-rich dust, synchronous with spring emergence, and other nutrient additions via aeolian dust may have stimulated invasion of dune-mantled uplands by the weedSalsola paulsenii (barb-wire Russian thistle).  相似文献   

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Observations of hourly wind speeds and directions were taken over a 56-day period in summer 1978, at the 3,000 m ground level near an INSTAAR mountain research site on the east slope of the Front Range, Colorado Rockies. During nearly calm weather, which persisted for longer periods than normal in summer 1978, the pattern of diurnal wind variations resembles results from other mountain studies of wind along high mountain slopes. However, timing of high wind speeds during the daily cycle is not readily explainable, although hypotheses can be offered. Results of this study can assist in interpretations of forest clearing microclimates at high elevations in the mountains and in important air quality questions (e.g., precipitation pH) in the Rocky Mountains.  相似文献   

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《Urban geography》2013,34(1):46-69
This paper examines the geography of institutional stock ownership for 603 major publicly traded companies. Linkages between cities are created using the stockownership levels between headquarters cities of investors and headquarters cities of firms. Both cartographic and statistical methods show that the urban connections describe a highly selective network of high-order urban centers. New York City is the dominant city, followed by Boston, Los Angeles, Philadelphia, and San Francisco. A simple gravity model, used to test the level of the effect of space on market perfection, explains a substantial portion of the investment-defined network. Differences between the levels of investment by different classes of institutional investors also are revealed.  相似文献   

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Military training activities reduce vegetation cover, disturb crusts, and degrade soil aggregates, making the land more vulnerable to wind erosion. The objective of this study was to quantify wind erosion rates for typical conditions at the Marine Corps Air Ground Combat Center, Twentynine Palms, CA, U.S.A. Five Big Spring Number Eight (BSNE) sampler stations were installed at each of five sites. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0·05 m and the highest sampler at 1·0 m above the soil surface. Once a month, sediment was collected from the samplers for analysis. Occurrence of saltating soil aggregates was recorded every hour using Sensits, one at each site. The site with the most erosion had a sediment discharge of 311 kg m−1 over a period of 17 months. Other sites eroded much less because of significant rock cover or the presence of a crust. Hourly sediment discharge was estimated combining hourly Sensit count and monthly sediment discharge measured using BSNE samplers. More simultaneously measured data are needed to better characterize the relationship between these two and reconstruct a detailed time-series of wind erosion. This measured time-series can then be used for comparison with simulation results from process-based wind erosion models such as the Wind Erosion Prediction System (WEPS), once it has been adapted to the unique aspects of military lands.  相似文献   

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Late Quaternary soils in southern New Mexico support previous work that suggested pedogenic gypsum accumulates in successive stages as a function of time, similar to pedogenic carbonate. However, gypsum also occurs as small (0·5–1 mm), powdery spheres that we term snowball morphology. The snowball morphology represents one of the initial stages of pedogenic gypsum development. Scanning electron microscope analyses indicate that soil microorganisms and organic material may play a crucial role in the development of this morphology. However, no trends were found in the crystal habits of gypsum suggesting the snowball morphology forms in a dynamic environment.  相似文献   

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