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The variation of effective hydraulic conductivity as a function of specific discharge in several 0.2-m and 0.3-m cubes of Key Largo Limestone was investigated. The experimental results closely match the Forchheimer equation. Defining the pore-size length scale in terms of Forchheimer parameters, it is demonstrated that significant deviations from Darcian flow will occur when the Reynolds number exceeds 0.11. A particular threshold model previously proposed for use in karstic formations does not show strong agreement with the data near the onset of nonlinear flow. 相似文献
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Censored (nondetect) values occur when chemical concentrations in water samples are near or below the level that can be measured by an analysis method. It is common to either delete or substitute values for nondetect observations for use in model calibration, but this practice can bias the estimated parameter values and the model predictions. A more realistic representation of the system is obtained from the calibration if we include such observations in a manner reflecting that we know only the value is below the detection limit. Consequently, we propose use of the censored-residual approach to including nondetect values as observations for calibration. In this approach, residuals are calculated as the detection limit minus the simulated value when the simulated value exceeds the detection limit, and the residual is assigned a value of zero when the simulated value is below the detection limit. The new censored-residual approach is particularly advantageous when calibrating transport models to low concentration data. 相似文献
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探地雷达探测地下管线的能力 总被引:21,自引:0,他引:21
这是作者摘编的有关探地雷达探测管线的一些资料.通过细致的实验,从中分析管线的粗细、材质、充填物、缺损情况及天线频率、噪音等对雷达图像的影响,对今后开展城市管线探地雷达调查工作会有所帮助. 相似文献
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Chen Shaohua Sun Mingguang This study is financially supported by National Science Foundation of China Postgraduate Zhongshan University Guangzhou Professor Zhongshan University Guangzhou 《中国海洋工程》1993,(4)
- In this paper, a six-order nonlinear dynamic model with three degrees of freedom is presented for the study of the "fishtail" motion of a Single Point Mooring System. The effect of parameter variations on the equilibrium state of the system is analized. In order to study the stability of the equilibrium state, the mooring-line length / is chosen as a bifurcation parameter, so that all eigenvalues of the Jacobian matrix under different parameters can be worked out, and then the Hopf-bifurcation point can be found . Finally, the Hopf-bifurcation periodic solution of the system is computed. 相似文献
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Experiments on the immiscible displacement of water by air were performed in two horizontal artificial open rough-walled fractures with different correlation structures. The aperture field of the first fracture has a Gaussian variogram with a finite correlation length, while that of the second one has a power-law variogram, for which no finite correlation length can be assigned. We simulated the displacement process using an invasion percolation model, which takes the in-plane curvature of the interface between water and air into account. The correlation structure of the aperture field has no effect on the irregularity of the shape of the air clusters. However, the correlation structure in combination with the in-plane curvature influences the density of the air clusters and thus has an impact on characteristic properties of the flow. We analyze the model parameters and properties with respect to the fracture properties. The stochastic average of the air clusters for models with different curvature numbers and fields with different correlation lengths is then calculated in order to analyze their influence on continuum approach models. 相似文献