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A new analytical solution for water table fluctuations in coastal aquifers with sloping beaches 总被引：3，自引：0，他引：3
H. T. Teo D. S. Jeng B. R. Seymour D. A. Barry L. Li 《Advances in water resources》2003,26(12):1239-1247
The Boussinesq equation appears as the zeroth-order term in the shallow water flow expansion of the non-linear equation describing the flow of fluid in an unconfined aquifer. One-dimensional models based on the Boussinesq equation have been used to analyse tide-induced water table fluctuations in coastal aquifers. Previous analytical solutions for a sloping beach are based on the perturbation parameter, N=αcotβ (in which β is the beach slope, α is the amplitude parameter and is the shallow water parameter) and are limited to tan−1(α)βπ/2. In this paper, a new higher-order solution to the non-linear boundary value problem is derived. The results demonstrate the significant influence of the higher-order components and beach slope on the water table fluctuations. The relative difference between the linear solution and the present solution increases as and α increase, and reaches 7% of the linear solution. 相似文献
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T.-Y. Koh B. C. Bhatt K. K. W. Cheung C. K. Teo Y. H. Lee Matthias Roth Purnawirman 《Meteorology and Atmospheric Physics》2012,115(1-2):35-45
This study evaluates the spectral scaling of a heavy rainfall event and assesses the performance of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model in terms of the multiscale variability of rainfall in the temporal spectral domain. The event occurred over southern Malay Peninsula on 18 December 2006 and was simulated at high resolutions. 10, 5 and 1?min aggregate rainfall data from rain gauge stations in Singapore and simulated rainfall sampled at different evaluation points on 0.9, 0.3 and 0.1?km grids were utilized. The simulated and observed rain rates were compared via Fourier and wavelet analyses. A scaling regime was noted in the observed rainfall spectra in the timescales between 60?min and 2?min. The scaling exponent obtained from the observed spectra has a value of about 2, which may be indicative of the physics of turbulence and raindrop coalescence and might suggest the predominance of a characteristic raindrop size. At 0.9?km resolution, the model rainfall spectra showed similar scaling to the observed down to about 10?min, below which a fall-off in variance was noted as compared to observations. Higher spatial resolution of up to 0.1?km was crucial to improve the ability of the model to resolve the shorter timescale variability. We suggest that the evaluation of dynamical models in the spectral domain is a crucial step in the validation of quantitative precipitation forecasts and assessing the minimal grid resolution necessary to capture rainfall variability for certain short timescales may be important for hydrological predictions. 相似文献
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Teo P 《GeoJournal》1991,23(2):125-133
The New Economic Policy (NEP) formulated in 1970 in Peninsular Malaysia had a two-fold aim of reducing poverty and redressing ethnic inequalities in wealth. The spatial bias of development on the west coast where the Chinese concentrate in the urban centres was also addressed. Population planning worked in tandem with NEP to reduce Malay to non-Malay differences in fertility. 1980 census data was evaluated to assess the impact of NEP on fertility transition in the country. Socioeconomic data for specific cohorts (15–24; 25–34 and 35–49) were collected and factor analysed to examine poverty conditions. The study found poverty to be differentiated by ethnicity. Malay poverty is high in both absolute (e.g. employment rate and education) and relative terms (as compared to the Chinese). The Chinese dimension is the exact opposite. Unfortunately, regional polarisation of wealth remains unchanged, even a decade after NEP. Poverty was regressed against cohort fertility and found to increase with it, especially for the older cohorts. Although NEP reduced fertility among the youngest cohort, its impact was not exceptionally large. The NEP is currently up for review. The apparent failure of the policy to achieve income equity and fertility transition must therefore be taken seriously. 相似文献
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The mummichog,Fundulus heteroclitus, is one of the most important macrofaunal components of salt marsh surfaces and an important link to subtidal areas of the
adjacent estuary along the east coast of the U.S. We estimated growth, population size, and production of the mummichog in
a restored marsh in order to improve our understanding of the role of this resident fish and to evaluate the success of the
restoration. The restored marsh, covering 234 ha, was a former salt hay farm located in the mesohaline portion of Delaware
Bay that was restored to tidal influence in August 1996. We separated the mummichog population into two components based on
life history stage and summer habitat use patterns. One component, consisting of adults and large young-of-the-year (YOY),
exhibited tidal movements to and from the marsh surface and the subtidal creeks. These were examined with an intensive mark
and recapture program using coded wire tags. Another component, consisting of small YOY, remained on the marsh surface throughout
the tidal cycle. Throw traps were used to sample these small YOY. The mean annual population density of adults and large YOY
for the entire marsh was approximately 1.2 fish m−2 and mean monthly density peaked at 2.9 fish m−2. The mean annual density of small YOY on the marsh surface was 15.1 fish m−2 and mean monthly density peaked at 41.4 fish m−2. Size and season influenced the growth rate of individual fish and instantaneous growth rates ranged from 0.03 to 2.26 mo−1. Total annual mummichog production was estimated to be 8.37 g dw m−2 yr−1, with adults and large YOY contributing 28.4% (2.38 g dw m−2 yr−1) and small YOY on the marsh surface contributing 71.6% (5.99 g dw m−2 yr−1). The seasonal use and population densities were comparable to previous studies in natural marshes while growth and production
of mummichog in this restored marsh appeared to be higher. Coupled with the results of other studies on the feeding, movement,
and habitat use of this species in this restored marsh, the species has responded well to the restoration. 相似文献