MODFLOW 2000 head uncertainty,a first-order second moment method   总被引：1，自引：0，他引：1  

Glasgow HS  Fortney MD  Lee J  Graettinger AJ  Reeves HW 《Ground water》2003,41(3):342-350

A computationally efficient method to estimate the variance and covariance in piezometric head results computed through MODFLOW 2000 using a first-order second moment (FOSM) approach is presented. This methodology employs a first-order Taylor series expansion to combine model sensitivity with uncertainty in geologic data. MODFLOW 2000 is used to calculate both the ground water head and the sensitivity of head to changes in input data. From a limited number of samples, geologic data are extrapolated and their associated uncertainties are computed through a conditional probability calculation. Combining the spatially related sensitivity and input uncertainty produces the variance-covariance matrix, the diagonal of which is used to yield the standard deviation in MODFLOW 2000 head. The variance in piezometric head can be used for calibrating the model, estimating confidence intervals, directing exploration, and evaluating the reliability of a design. A case study illustrates the approach, where aquifer transmissivity is the spatially related uncertain geologic input data. The FOSM methodology is shown to be applicable for calculating output uncertainty for (1) spatially related input and output data, and (2) multiple input parameters (transmissivity and recharge).  相似文献   

The 1786 earthquake-triggered landslide dam and subsequent dam-break flood on the Dadu River, southwestern China   总被引：17，自引：1，他引：17  

F.C. Dai  C.F. Lee  J.H. Deng  L.G. Tham 《Geomorphology》2005,65(3-4):205-221

Chinese historic documents recorded that on June 1, 1786, a strong M=7.75 earthquake occurred in the Kangding-Luding area, Sichuan, southwestern China, resulting in a large landslide that fell into the Dadu River. As a result, a landslide dam blocked the river. Ten days later, the sudden breaching of the dam resulted in catastrophic downstream flooding. Historic records document over 100,000 deaths by the flood. This may be the most disastrous event ever caused by landslide dam failures in the world. Although a lot of work has been carried out to determine the location, magnitude and intensity of the 1786 earthquake, relatively little is known about the occurrence and nature of the landslide dam. In this paper, the dam was reconstructed using historic documents and geomorphic evidence. It was found that the landslide dam was about 70 m high, and it created a lake with a water volume of about 50×10⁶ m³ and an area of about 1.7 km². The landslide dam breached suddenly due to a major aftershock on June 10, 1786. The peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation. The possibility of a future failure of the landslide seems high, particularly due to inherent seismic risk, and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide.  相似文献   

Vector magnetic analysis within the southern Ayu Trough, equatorial western Pacific   总被引：2，自引：1，他引：2  

Sang-Mook Lee  Seung-Sep Kim 《Geophysical Journal International》2004,156(2):213-221

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Small-scale variations in seismic anisotropy near Kimberley, South Africa   总被引：1，自引：0，他引：1  

Matthew J. Fouch  Paul G. Silver  David R. Bell  Jean N. Lee 《Geophysical Journal International》2004,157(2):764-774

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How are storm time injections different from nonstorm time injections?     

D.-Y. Lee  J.A. Hwang  E.S. Lee  K.W. Min  W.Y. Han  U.W. Nam 《Journal of Atmospheric and Solar》2004,66(18):1715

One of the key elements of storms and substorms is the injection of energetic particles into the region of near geosynchronous orbit, that is, the sudden flux enhancement in the energy range of tens to hundreds of keV. This paper reports the observational results on how such injection features during storm times are different from those of nonstorm times. We particularly focus on the difference between proton injections and electron injections. Based on a number of storm time injection events that meet our strict selection criteria, we find a notable difference between proton injections and electron injections in the energy-spectral dependence of the flux enhancement averaged over the first 30 min after the injection onset: The average flux enhancement of many protons injections tends to be bigger at higher energy channels than at lower energy channels, but electron injections exhibit the opposite tendency for the energy-spectral dependence of flux enhancement, i.e., average flux enhancement decreasing with increasing energy. We show that this feature is almost unique only for the injection events during the storm main and early recovery phase. It is suggested that any successful scenario intended to model storm time injections should be able to explain this difference between proton injections and electron injections.  相似文献   

Evaluation of the seismic performance of a three‐story ordinary moment‐resisting concrete frame     

Sang Whan Han  Oh‐Sung Kwon  Li‐Hyung Lee 《地震工程与结构动力学》2004,33(6):669-685

This study focuses on the seismic performance of Ordinary Moment‐Resisting Concrete Frames (OMRCF) designed only for gravity loads. For this purpose, a 3‐story OMRCF was designed in compliance with the minimum design requirements in the American Concrete Institute Building Code ACI 318 (1999). This model frame was a regular structure with flexure‐dominated response. A 1/3‐scale 3‐story model was constructed and tested under quasi‐static reversed cyclic lateral loading. The overall behavior of the OMRCF was quite stable without abrupt strength degradation. The measured base shear strength was larger than the design base shear force for seismic zones 1, 2A and 2B calculated using UBC 1997. Moreover, this study used the capacity spectrum method to evaluate the seismic performance of the frame. The capacity curve was obtained from the experimental results for the specimen and the demand curve was established using the earthquake ground motions recorded at various stations with different soil conditions. Evaluation of the test results shows that the 3‐story OMRCF can resist design seismic loads of zones 1, 2A, 2B, 3 and 4 with soil types S_A and S_B . For soil type S_C , the specimen was satisfactory in seismic zones 1, 2A, 2B and 3. For soil type S_D , the OMRCF was only satisfactory for seismic zones 1 and 2A. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Hybrid seismic protection of cable‐stayed bridges     

H.‐J. Jung  K.‐S. Park  B. F. Spencer  I.‐W. Lee 《地震工程与结构动力学》2004,33(7):795-820

This paper proposes a hybrid control strategy combining passive and semi‐active control systems for seismic protection of cable‐stayed bridges. The efficacy of this control strategy is verified by examining the ASCE first‐generation benchmark problem for a seismically excited cable‐stayed bridge, which employs a three‐dimensional linearized evaluation bridge model as a testbed structure. Herein, conventional lead–rubber bearings are introduced as base isolation devices, and semi‐active dampers (e.g., variable orifice damper, controllable fluid damper, etc.) are considered as supplemental damping devices. For the semi‐active dampers, a clipped‐optimal control algorithm, shown to perform well in previous studies involving controllable dampers, is considered. Because the semi‐active damper is a controllable energy‐dissipation device that cannot add mechanical energy to the structural system, the proposed hybrid control strategy is fail‐safe in that the bounded‐input, bounded‐output stability of the controlled structure is guaranteed. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective in protecting seismically excited cable‐stayed bridges. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Nested lumped‐parameter models for foundation vibrations     

Wen-Hwa Wu  Wen-How Lee 《地震工程与结构动力学》2004,33(9):1051-1058

The concept of polynomial‐fraction approximation is explored in this article to develop a nested type of systematic lumped‐parameter model for unbounded soil. Based on the optimal coefficients determined from the flexibility formulation, the reciprocal of the polynomial‐fraction is first taken to represent the dynamic stiffness function of foundation and then decomposed into a linear polynomial and another polynomial‐fraction. The nested division introduced in this study is operated to generate a nested form for this decomposed polynomial‐fraction, which directly corresponds to a nested discrete‐element model. The nested type of lumped‐parameter model is then easily constructed by connecting this nested discrete‐element model in series with another simple discrete‐element model corresponding to the linear polynomial. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A series solution for surface motion ampli-fication due to underground group cavities: Incident P waves     

梁建文  张浩  Vincent W Lee 《地震学报(英文版)》2004,17(3):296-307

Introduction In recent years some big cities in China commonly build subways in central urban areas to improve crowded surface transportation, and the subways usually are large-scale group cavities composed by two parallel cavities. Construction of large-scale group cavities will certainly affect the design ground motion near the cavities, and further affect seismic safety of the existing build-ings nearby. So it is of significance to estimate this effect on seismic design of the buildings. H…  相似文献   

Advances in meteorological instrumentation for air quality and emergency response     

W. F. Dabberdt  G. L. Frederick  R. M. Hardesty  W.-C. Lee  K. Underwood 《Meteorology and Atmospheric Physics》2004,87(1-3):57-88

Summary Air quality forecasting and emergency response are receiving increasing emphasis in the US and elsewhere; both share similar but not identical needs for advanced meteorological observations. At the same time, there has been a steady increase in the performance characteristics of ground-based remote sensing systems as well as ground-based and airborne in situ measurement systems. The structure of the planetary boundary layer is summarized in the context of implications for transport and diffusion, along with the measurement requirements for dispersion modeling. We then review the current state-of-the-art of operational and quasi-operational measurement systems with a focus on boundary layer measurements. Measurement systems discussed include: meteorological radar, radar wind profilers, radio acoustic sounding systems, lidar, sodar, GPS receivers, microwave radiometers, radiosonde systems, commercial aircraft measurements, and traditional near-surface in situ sensors.  相似文献