A second-order closure model for flow through vegetation   总被引：2，自引：0，他引：2  

J. D. Wilson 《Boundary-Layer Meteorology》1988,42(4):371-392

By splitting the turbulent kinetic energy into two wavebands and adopting as the turbulence timescale the ratio k/ of the kinetic energy in the low-frequency band to its turnover-rate, the second-order closure scheme of Launder et al. (1975) has been adapted for flow through vegetation. Predictions of the model compare satisfactorily with observations of the mean windspeed and (somewhat less satisfactorily) with the turbulent velocity variances in two very different canopies.  相似文献   

Tropical deforestation: Important processes for climate models   总被引：4，自引：0，他引：4  

A. Henderson-Sellers  R. E. Dickinson  M. F. Wilson 《Climatic change》1988,13(1):43-67

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Modal summation methods for structural dynamic computations     

P. Leger  E. L. Wilson 《地震工程与结构动力学》1988,16(1):23-27

The rate of convergence of the conventional mode superposition method can be significantly improved for systems subjected to relatively low frequency loadings by adding static correction terms to approximate the contribution of higher modes neglected by the use of a truncated eigenbasis. Two computational variants of the classical mode-acceleration method are developed for that purpose. It is recommended that the pseudo-static displacement correction vector should be computed from an expansion of the flexibility matrix in terms of the retained eigenvectors for actual computer implementation.  相似文献   

Editors’ preface     

John E. Moore  Clifford I. Voss  William E. Wilson 《Hydrogeology Journal》1994,2(1):3-5

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The role of bioindicators in estuarine management     

James G. Wilson 《Estuaries and Coasts》1994,17(1):94-101

Estuarine organisms can be considered three ways as bioindicators—first, as indicators of a defined set of environmental conditions, second, as indicators of contaminant loads on the system, and third, as indicators of the overall health of the system. By their very nature, estuarine organisms are eurytolerant and this, along with the various stratagems that have evolved to cope with the problems of life in estuaries results in a confusing picture for the estuarine manager. The recommended bioindicators for estuarine conditions are plankton; for contaminant loads, a range of species with different feeding types; and for system status, a eurytolerant species, such as the musselMytilus edulis for laboratory monitoring or a “target” species such as the clamMacoma balthica for field monitoring. However, it would be unwise to rely on a single indicator, and the recommendation is that the final choice, and preferably choices, be tailored to the desired goal.  相似文献   

Formic and acetic acids in atmospheric condensate in Wilmington,North Carolina     

Joan D. Willey  Carol A. Wilson 《Journal of Atmospheric Chemistry》1993,16(2):123-133

Formic and acetic acids occurred in atmospheric condensate with concentrations similar to rainwater collected in Wilmington, North Carolina, during the sampling period from June to October of 1990. Atmospheric concentrations of these acids (calculated from the condensate concentrations) were higher in continental versus maritime air masses. Concentrations of formic and acetic acids were correlated with each other in both condensate and air. Traffic was a source of acetic acid and of bisulfite to atmospheric condensate in this study.  相似文献   

Mapping the Geographical Diffusion of a Finnish Smallpox Epidemic from Historical Population Records     

James L. Wilson 《The Professional geographer》1993,45(3):276-286

Smallpox mortality from an early 19th century epidemic in Finland is mapped at the parish village level. First, geographically referenced historical materials are used to construct a map showing the spread of smallpox mortality among villages. Next, the diffusion of smallpox morbidity is simulated by computer for the same set of villages. These two maps are then compared. Results indicate that at this scale maps of mortality diffusion can show general trends but have no direct spatial correspondence to the underlying pattern of morbidity diffusion. Mortality maps cannot be used as a surrogate measure of infectious contact behavior at micro scales of analysis.  相似文献   

Comment on “Evidence for long residence times of rhyolitic magma in the Long Valley magmatic system: the isotopic record in precaldera lavas of Glass Mountain” by A.N. Halliday, G.A. Mahood, P. Holden, J.M. Metz, T.J. Dempster and J.P. Davidson     

R.Stephen J. Sparks  Herbert E. Huppert  Colin J.N. Wilson 《Earth and Planetary Science Letters》1990,99(4)

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Chemistry of alkali extraction of brown coals—I. Kinetics, characterisation and implications to coalification     

Louis S.K. Pang  Anthony M. Vassallo  Michael A. Wilson   《Organic Geochemistry》1990,16(4-6)

Three Australian brown coals have been separated into humin and humic acid fractions and studied by high resolution solid state ¹³C NMR spectroscopy and Fourier transform IR spectroscopy. The aromatic rings of the humic acids are highly substituted showing that extensive cross linking must have occurred during formation from wood lignin and tannin. However, the humins contain more aliphatic carbon and hydrogen than the corresponding humic acids. This shows that little cross linking has occurred with other components of the brown coal such as resins, waxes cutin and algal detritus, and cross linking has not rendered the aromatics alkali insoluble. The kinetics of extraction are complex and not simple first order. This is reflected in the chemical composition of the humic acid which is extraction temperature dependent. We also observed that there is a conversion of aromatic carbon to aliphatic carbon and gas during extraction, probably by alkaline oxidation, resulting in ring opening. A range of suitable model compounds have been studied to confirm this finding. Such a mechanism may account for the modification of lignin in oxidising environments such as those occurring in the initial stages of coalification (lignite or brown coal formation) and in soils.  相似文献   

Consequences of explosive eruptions on small Solar System bodies: the case of the missing basalts on the aubrite parent body     

Lionel Wilson  Klaus Keil 《Earth and Planetary Science Letters》1991,104(2-4)

Aubrite meteorites are composed of constituents which are almost certainly of igneous origin. If they were generated by the melting and fractionation of enstatite chondrite-like parental material, as seems very likely, then plagioclase-rich, basaltic complements to the aubrites should have formed. However, such materials are not known as individual meteorites, and the compositions of two plagioclase-silica clasts and one albite-silica-(diopside-anorthite) clast (probably an impact melt) in the Norton County aubrite breccia suggest that they are not the putative enstatite-plagioclase basalts. We propose a new mechanism that explains the absence of these materials, showing that the expansion of even very small amounts of volatiles present in a melt approaching the surface of a small, low-gravity body will be enough to disrupt the melt into a spray of droplets moving faster than the local escape velocity. This explosive volcanic process of melt removal requires larger melt volatile contents on larger bodies, and data on the solubility of volatiles in basaltic melts suggest that the process was limited to bodies smaller than about 100 km in radius.  相似文献