Land Use Diversification in the Elite Residential Sector of Quito,Ecuador*     

Roy H. Ryder 《The Professional geographer》2004,56(4):488-502

It is generally assumed that older mansions in the elite residential sector of Latin American cities filter down to the middle classes once their residents migrate to modern suburban homes. Five land use maps compiled between 1975 and 1999 show that the elite residential sector of Quito (Mariscal Sucre) experienced a much more complex fate. Diffusion of nonresidential land uses from the city center and its associated spine transformed the residential neighborhood into a vibrant upper‐scale business district. Sophisticated businesses subsequently moved on to modern suburban facilities, but Mariscal Sucre became a major hub for business, nocturnal entertainment, and tourism. Diversification of land use in Mariscal Sucre confirms the Crowley hypothesis of complexity in Latin American urban land use patterns ( Crowley 1995 ).  相似文献   

Removal of Cryptosporidium parvum Oocysts by Rapid Sand Filtration with Ballasted Flocculation‐Filtration and Intermediate Downwashes     

Vitaly Gitis  Viatcheslav Freger  Roy C. Haugth  Robert M. Clark 《洁净——土壤、空气、水》2005,33(4):355-364

A novel and efficient protocol optimising deep‐bed filtration of surface water was developed. The innovation lies in ballasted‐flocculation filtration and an intermediate downwash. The approach is based on the assumption that kaolin particles with a partial positive charge may adsorb onto the surface of C. parvum oocysts and neutralize their negative charge. Application of this technology enhanced removal of inorganic particles and Cryptosporidium parvum oocysts by approximately 30 % and shortened the ripening stage of the filtration process from 1 h to about 10 min.  相似文献   

Effects of model resolution and subgrid-scale physics on the simulation of precipitation in the continental United States   总被引：4，自引：0，他引：4  

J. P. Iorio  P. B. Duffy  B. Govindasamy  S. L. Thompson  M. Khairoutdinov  D. Randall 《Climate Dynamics》2004,23(3-4):243-258

We analyze simulations of the global climate performed at a range of spatial resolutions to assess the effects of horizontal spatial resolution on the ability to simulate precipitation in the continental United States. The model investigated is the CCM3 general circulation model. We also preliminarily assess the effect of replacing cloud and convective parameterizations in a coarse-resolution (T42) model with an embedded cloud-system resolving model (CSRM). We examine both spatial patterns of seasonal-mean precipitation and daily time scale temporal variability of precipitation in the continental United States. For DJF and SON, high-resolution simulations produce spatial patterns of seasonal-mean precipitation that agree more closely with observed precipitation patterns than do results from the same model (CCM3) at coarse resolution. However, in JJA and MAM, there is little improvement in spatial patterns of seasonal-mean precipitation with increasing resolution, particularly in the southeast USA. This is because of the dominance of convective (i.e., parameterized) precipitation in these two seasons. We further find that higher-resolution simulations have more realistic daily precipitation statistics. In particular, the well-known tendency at coarse resolution to have too many days with weak precipitation and not enough intense precipitation is partially eliminated in higher-resolution simulations. However, even at the highest resolution examined here (T239), the simulated intensity of the mean and of high-percentile daily precipitation amounts is too low. This is especially true in the southeast USA, where the most extreme events occur. A new GCM, in which a cloud-resolving model (CSRM) is embedded in each grid cell and replaces convective and stratiform cloud parameterizations, solves this problem, and actually produces too much precipitation in the form of extreme events. However, in contrast to high-resolution versions of CCM3, this model produces little improvement in spatial patterns of seasonal-mean precipitation compared to models at the same resolution using traditional parameterizations.  相似文献   

Analysis of Hawaiian diurnal rainfall patterns     

S. Sen Roy  R. C. Balling Jr. 《Theoretical and Applied Climatology》2004,79(3-4):209-214

Summary We analyzed hourly precipitation data over the period 1965–1998 for 133 stations located throughout the Hawaiian Islands and found distinctive diurnal cycles in the amount and frequency of the rainfall. The diurnal signals were generally strongest on the island of Hawaii and more pronounced in the summer than in the winter. Windward sides of the islands generally showed the time of maximum for frequency or amount to be before sunrise while the leeward sides generally revealed the primary maximum in the afternoon. We conducted the analyses for El Niño years and La Niña years and found the diurnal patterns in rainfall to be unaffected by this Pacific-area oscillation. The results are consistent with others who have argued, based on work on the island of Hawaii, that anabatic and katabatic wind flows are responsible for the observed diurnal rainfall patterns. A semi-diurnal cycle with two maxima and two minima appears to be important in the summer season in the leeward locations. Our results show that processes and patterns described for the island of Hawaii are found throughout the larger islands of the Hawaii chain.  相似文献   

Estimation for rainfall-runoff modeled as a partially observed Markov process     

T. N. Kaseke  M. E. Thompson 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(1):1-16

Abstract: Linear continuous time stochastic Nash cascade conceptual models for runoff are developed. The runoff is modeled as a simple system of linear stochastic differential equations driven by white Gaussian and marked point process noises. In the case of d reservoirs, the outputs of these reservoirs form a d dimensional vector Markov process, of which only the dth coordinate process is observed, usually at a discrete sample of time points. The dth coordinate process is not Markovian. Thus runoff is a partially observed Markov process if it is modeled using the stochastic Nash cascade model. We consider how to estimate the parameters in such models. In principle, maximum likelihood estimation for the complete process parameters can be carried out directly or through some form of the EM (estimation and maximization) algorithm or variation thereof, applied to the observed process data. In this research we consider a direct approximate likelihood approach and a filtering approach to an algorithm of EM type, as developed in Thompson and Kaseke (1994). These two methods are applied to some real life runoff data from a catchment in Wales, England. We also consider a special case of the martingale estimating function approach on the runoff model in the presence of rainfall. Finally, some simulations of the runoff process are given based on the estimated parameters.  相似文献   

Quantifying Macropore Recharge: Examples from a Semi-Arid Area   总被引：6，自引：0，他引：6  

Warren W. Wood  Ken A. Rainwater  David B. Thompson 《Ground water》1997,35(6):1097-1106

  相似文献   

Partial melting of metavolcanics in amphibolite facies regional metamorphism     

Alan Bruce Thompson 《Journal of Earth System Science》2001,110(4):287-291

Metavolcanic rocks containing low-Ca amphiboles (gedrite, cummingtonite) and biotite can undergo substantial dehydration-melting. This is likely to be most prominent in Barrovian Facies Series (kyanite-sillimanite) and occurs at the same time as widespread metapelite dehydrationmelting. In lower pressure facies series, metavolcanics will be represented by granulites rich in orthopyroxene when dehydration occurs at much lower temperatures than melting. In higher pressure facies series it is not well known whether metavolcanic rocks dehydrate or melt at temperatures lower or similar to that of metapelites.  相似文献   

Water requirements for cultivatingSalicornia bigeloviiTorr. with seawater on sand in a coastal desert environment     

Edward Glenn  Seiichi Miyamoto  David Moore  J.Jed Brown  T.Lewis Thompson  Paul Brown 《Journal of Arid Environments》1997,36(4):711-730

The forage and oilseed halophyte,Salicornia bigeloviiTorr., was grown in gravity-drained lysimeters set in open plots of the same crop over two seasons in a coastal desert environment in Sonora, Mexico. The lysimeters were irrigated daily with seawater (40 g l⁻¹salts) at rates ranging from 46–225% of potential evaporation. Biomass and seed yields increased with increasing irrigation depth over the range of treatments. Biomass yields ranged from 13·6–23·1 t DM ha⁻¹, equivalent to conventional forage crops, on seasonal water application depths of 2·3–3·8 m, but were markedly lower at lower irrigation depths. Increasing the irrigation depth lowered the soil solution salinity, resulting in greater growth and water use, and hence leaching fractions that were nearly even over irrigation treatments, averaging 0·5. Evapo-transpiration rose in direct proportion to the irrigation depth. Potential evaporation was estimated by site pan evaporation and by the Blaney-Criddle and Penman models using climatological data; the methods agreed within 15%. The ratio of evapo-transpiration to potential evaporation increased over the growing season and approached 1·5 by pan on the highest irrigation treatment due to the combined effects of high transpiration and high evaporation from the permanently moist soil surface. The best field predictor of biomass yield was the salinity of the soil moisture in the top 15 cm of soil profile, which constitutes the root zone for this crop. Root zone salinity must be kept at 70–75 g l⁻¹for high yields. Although irrigation and drainage requirements were high compared to conventional crops, seawater irrigation appears to be feasible in medium sand and could augment crop production along coastal deserts. The possibility of using this crop for animal production is discussed.  相似文献   

Damping and response measurement on A small-scale model of A cable-stayed bridge     

Mihail A. Garevski  Roy T. Severn 《地震工程与结构动力学》1993,22(1):13-29

A small-scale model of an existing cable-stayed bridge has been designed and built. Hammer, sinusoidal and random signal tests have been performed to determine the dynamic characteristics of the model. An attempt has been made to evaluate the real effect of the vibration of stays upon system damping. Initial measurements have been performed for a model where there was no vibration of the stays because of the absence of appropriately scaled additional mass of these stays. In this way the effect of the cables was eliminated in damping measurement. During the second series of measurements appropriate mass has been added to the stays, causing them to take part in the vibration. The comparison of the measured damping of the model for each case makes possible the estimation of the effect of the stays upon the system damping. By using the shaking table, two types of seismic excitation were applied, with corresponding response quantities in the critical sections being measured. Good agreement between the analytical and the experimental results was achieved.  相似文献   

Constraints on the structure and dynamics of the β-cristobalite polymorphs of SiO2 and AlPO4 from 31P, 27Al and 29Si NMR spectroscopy to 770 K     

Brian L. Phillips  John G. Thompson  Yuehui Xiao  R. James Kirkpatrick 《Physics and Chemistry of Minerals》1993,20(5):341-352

Nuclear magnetic resonance spectroscopic data are presented for the cristobalite polymorphs of AlPO₄ and SiO₂ from RT to 770 K, through their respective α-β transitions. The nuclear magnetic resonance (NMR) data include chemical shifts for ³¹P, ²⁷Al, and ²⁹Si, ²⁷Al quadrupole coupling parameters, and ³¹P and ²⁷Al spin-lattice relaxation rates. Also presented are electron diffraction patterns of β-cristobalite AlPO₄ that show diffuse scattering similar to that reported previously for SiO₂. For the α-phases of both AlPO₄ and SiO₂, the chemical shifts decrease approximately linearly with increasing temperature from RT to T_c and discontinuously by -2 to -3 ppm from α to β. This result is consistent with a small, continuous increase in the mean T-O-T angle (〈θ〉) of the α-phases with increasing T and an increase of 〈θ〉 by about 4° across the α-β transition for both cristobalite and its AlPO₄ analogue. Based on the ²⁹Si chemical shifts, the mean Si-O-Si angle for β-cristobalite is 152.7±1° near T_c. For AlPO₄-cristobalite, the ²⁷Al nuclear quadrupole coupling constant (C_Q) decreases approximately linearly from 1.2 MHz at RT to 0.94 MHz near T_c (493±10 K). At the α-β transition the ²⁷Al C_Q approaches zero, in agreement with the cubic average structure observed by diffraction. The satellite transitions retain a small frequency distribution above the α-β transition from electric field gradients attributed to defects. The short-range cubic symmetry of the Al-site and non-linear Al-O-P angle support a dynamically disordered model of the β-cristobalite structure. Complete averaging of the ²⁷Al quadrupole coupling in the β-phase indicates that the lifetime of any short-range ordered domains must be shorter than about 1 μs.  相似文献