珠江口红树林湿地演变与现状的遥感分析   总被引：1，自引：0，他引：1  

黎夏  叶嘉安  刘凯  WANG Shugong 《地理学报(英文版)》2006,16(2):155-164

1 Introduction Half of the mangrove wetlands in China are situated in Guangdong province (Wang and Chen, 1998). The province used to have various types of wild mangrove forests along its coastal areas. The rapid expansion of urban areas and the fast deve…  相似文献   

Designing an optimal multivariate geostatistical groundwater quality monitoring network using factorial kriging and genetic algorithms   总被引：1，自引：0，他引：1  

Ming-Sheng Yeh  Yu-Pin Lin  Liang-Cheng Chang 《Environmental Geology》2006,50(1):101-121

The optimal selection of monitoring wells is a major task in designing an information-effective groundwater quality monitoring network which can provide sufficient and not redundant information of monitoring variables for delineating spatial distribution or variations of monitoring variables. This study develops a design approach for an optimal multivariate geostatistical groundwater quality network by proposing a network system to identify groundwater quality spatial variations by using factorial kriging with genetic algorithm. The proposed approach is applied in designing a groundwater quality monitoring network for nine variables (EC, TDS, Cl⁻, Na, Ca, Mg, SO ₄ ²⁻ , Mn and Fe) in the Pingtung Plain in Taiwan. The spatial structure results show that the variograms and cross-variograms of the nine variables can be modeled in two spatial structures: a Gaussian model with ranges 28.5 km and a spherical model with 40 km for short and long spatial scale variations, respectively. Moreover, the nine variables can be grouped into two major components for both short and long scales. The proposed optimal monitoring design model successfully obtains different optimal network systems for delineating spatial variations of the nine groundwater quality variables by using 20, 25 and 30 monitoring wells in both short scale (28.5 km) and long scale (40 km). Finally, the study confirms that the proposed model can design an optimal groundwater monitoring network that not only considers multiple groundwater quality variables but also monitors variations of monitoring variables at various spatial scales in the study area.  相似文献   

Karst groundwater management by defining protection zones based on regional geological structures and groundwater flow fields   总被引：2，自引：0，他引：2  

Yonghong Hao  Tian-Chyi J. Yeh  Caihong Hu  Yanrong Wang  Xia Li 《Environmental Geology》2006,50(3):415-422

In a semiarid region, the karst aquifer generally forms a large groundwater reservoir that can play an important role in regional water supply. But because of the specific physical properties of karst aquifers, they are vulnerable to pollution and anthropogenic impacts. Karst groundwater management strategies are vital. As representative of karst springs in a semiarid area, Niangziguan Springs is located in the east of Shanxi Province, China with an annual average rate of discharge of 10.34 m³/s (1956–2003) (Y. Liang, unpublished data). The Niangziguan Spring Basin covers an area of 7,394 km² with an annual average precipitation of 535 mm (1958–2003) (Hao et al. in Carsologica Sinica 23(1):43–47, 2004). Over the past three decades, accelerated groundwater exploitation has caused water-table decline in the aquifer, reduction of the spring discharge, and deterioration of water quality. In this study, three protection zones were defined to ensure the quality and capacity of this resource. The confluence of the 11 spring systems and the discharge areas were defined as I protection zone, the recharge basin was II protection zone, and the slack water area where there is little surface recharge was the III protection zone. Management strategies for each zone were suggested and evaluated to provide a scientific foundation for sustainable utilization.  相似文献   

On simulating reactive chemical transport with dominating precipitated species controlling chemical equilibrium     

Hwai‐Ping Cheng  Gour‐Tsyh Yeh 《Computational Geosciences》1998,2(2):151-170

We present an approach developed to compute chemical equilibrium and its corresponding reactive chemical transport when dominating precipitated species (DPS) exist. In computing chemical equilibrium, most models take the concentrations or activities of component species and precipitated species as the master variables. However, when the amount of a precipitated species is much larger than those of other species, small computational errors on this DPS concentration might introduce large errors on the concentrations of other species and would cause non‐mass‐conserved numerical results. To deal with the existence of DPS, we pick as master variables the concentration change, rather than the concentration, of DPS to compute chemical equilibrium. Since the concentration changes of DPS will no longer be much larger than the concentrations of other species in determining equilibrium, our approach is able to provide correct numerical results. We also employ the modified total analytical concentrations, rather than the total analytical concentrations, of aqueous components as the dependent variables in presenting and solving corresponding transport equations. Several examples are given to reveal the numerical problems associated with DPS and to demonstrate the success of our approach. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A parallelizable method for two‐phase flows in naturally‐fractured reservoirs     

Jim Douglas Jr.  Felipe Pereira  Li‐Ming Yeh 《Computational Geosciences》1997,1(3-4):333-368

A parallelizable, semi‐implicit numerical method is proposed for the study of naturally‐fractured reservoir systems. It has proved to be computationally efficient in producing accurate numerical solutions for the dual‐porosity model for immiscible, two‐phase flow in such reservoirs. The method combines hybridized mixed finite elements, a new version of the modified method of characteristics, a sophisticated operator‐splitting procedure for separating the pressure calculation in the fractures from that of the saturation, another operator splitting to handle the interaction of the matrix blocks and the fractures, and domain decomposition iterative procedures for both the pressure and the saturation. It permits moderately long time steps for the pressure and the saturation in the fractures and matrix blocks by using short, inexpensive microsteps to treat the transport portion of the saturation equation in the fractures. This paper is devoted to the formulation of the method and a discussion of numerical results for five‐spot and vertical cross‐section examples.  相似文献   

北京/上海-香港客源潜力研究^*   总被引：2，自引：3，他引：2  

金凤君  叶嘉安 《地理研究》1997,16(4):7-14

文章对内地主要城市与香港间的客源潜力进行了研究,包括居民的赴港愿望、交通方式选择,以及上述决策与收入、职业、费用、旅行时间、安全舒适性等因子的关系。分析得出:内地居民的赴港愿望和交通方式选择具有明显特征,以上海、北京为源地或中转地的居民,作为未来访港的客源,具有较大潜力,并在交通方式选择上有较强倾向性,偏好直达列车、直达飞机等便捷、快速的交通方式,且被访者的职业、收入水平等对其旅行方式选择有重要影响;对北京、上海近期与远期赴港客源潜力作了测算。  相似文献   

Effect of Near-fault Terrain upon Dislocation Modeling     

B.-S. Huang  Y. T. Yeh 《Pure and Applied Geophysics》1997,150(1):1-18

—Coseismic surface deformation provides important information needed to determine source rupture geometry and slip distribution as well as to estimate seismic moment. In this study, numerical experiments were designed to analyze and classify how free-surface topography affects surface deformation. The investigation was performed by 3-D finite element modeling. Results of this study show that crustal deformation induced by near-fault terrain is significant and can be measured with present geodetic survey techniques. The characteristics of the terrain effects show that a hill structure produces more crustal deformation than a half-space model, and that the crustal deformation of a basin structure is less than that of the half-space model. The topographic correction is in the order of five percent of the fault dislocation. On the basis of the relationship between fault offset and earthquake magnitude, it is suggested that the terrain effects on the coseismic crustal deformation of shallow earthquakes with a magnitude greater than 5.6 should be considered as one of the major errors in coseismic deformation modeling which ignored the surface topography on the order of 300 meters.  相似文献   

Linear spatial interpolation: Analysis with an application to San Joaquin Valley     

H. A. Loaiciga  R. H. Shumway  W. W. -G. Yeh 《Stochastic Environmental Research and Risk Assessment (SERRA)》1988,2(2):113-136

The properties of linear spatial interpolators of single realizations and trend components of regionalized variables are examined in this work. In the case of the single realization estimator explicit and exact expressions for the weighting vector and the variances of estimator and estimation error were obtained from a closed-form expression for the inverse of the Lagrangian matrix. The properties of the trend estimator followed directly from the Gauss-Markoff theorem. It was shown that the single realization estimator can be decomposed into two mutually orthogonal random functions of the data, one of which is the trend estimator. The implementation of liear spatial estimation was illustrated with three different methods, i.e., full information maximum likelihood (FIML), restricted maximum likelihood (RML), and Rao's minimum norm invariant quadratic unbiased estimation (MINQUE) for the single realization case and via generalized least squares (GLS) for the trend. The case study involved large correlation length-scale in the covariance of specific yield producing a nested covariance structure that was nearly positive semidefinite. The sensitivity of model parameters, i.e., drift and variance components (local and structured) to the correlation length-scale, choice of covariance model (i.e., exponential and spherical), and estimation method was examined. the same type of sensitivity analysis was conducted for the spatial interpolators. It is interesting that for this case study, characterized by a large correlation length-scale of about 50 mi (80 km), both parameter estimates and linear spatial interpolators were rather insensitive to the choice of covariance model and estimation method within the range of credible values obtained for the correlation length-scale, i.e., 40–60 mi (64–96 km), with alternative estimates falling within ±5% of each other.  相似文献   

Numerical Identification of Parameters in Leaky Aquifers   总被引：2，自引：0，他引：2  

Hund-Der Yeh  Hung-Yuang Han 《Ground water》1989,27(5):655-663

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Attenuation relations of Arias intensity based on the Chi-Chi Taiwan earthquake data   总被引：1，自引：0，他引：1  

H. Hwang  C. K. Lin  Y. T. Yeh  S. N. Cheng  K. C. Chen 《Soil Dynamics and Earthquake Engineering》2004,24(7):509-517

This paper presents a derivation of attenuation relations of Arias intensity for various site conditions based on the strong-motion data recorded in the 1999 Chi-Chi Taiwan earthquake. The data are from the mainshock and three large aftershocks with stations in the footwall area and in the area away from the fault. At each station, Arias intensity is computed from two horizontal acceleration time histories. The Arias intensity data are separated into four groups according to site classes assigned to recording stations. For each site class, the attenuation relation of Arias intensity is derived using a two-step regression analysis method. The attenuation relations established in this study can be used to estimate Arias intensity from a rupture of a thrust fault for sites in the footwall area or in the area away from the fault.  相似文献