How much complexity is needed to simulate watershed streamflow and water quality? A test combining time series and hydrological models          下载免费PDF全文

Huicheng Chien  D. Scott Mackay 《水文研究》2014,28(22):5624-5636

Modelled hydrologic processes are represented in a set of numerical equations; the complexity of which can be measured by the total number of variables needed. A single dominant hydrologic process could control the hydrologic response of a watershed, and so the identification of the corresponding dominant variable(s) would aid in identifying a parsimonious model and in collecting more reliable data. By accounting for both model complexity and serial correlation in the variables, a model is used to identify the dominant variables for representing watershed scale streamflow, sediment transport and phosphorus yields. Long‐term water quantity and quality data were used to show that rainfall and non‐linear soil water storage were the dominant variables for weekly streamflow, suspended sediment and particulate phosphorus. Model accuracy did not consistently improve when other statistically significant variables were included. The results suggest that improved model performance may not justify the added model complexity. As such, identification of dominant variables would be the priority for developing parsimonious hydrologic models, especially at watershed scales. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Modeling crack propagation path of anisotropic rocks using boundary element method     

Chien‐Chung Ke  Chao‐Shi Chen  Cheng‐Yu Ku  Chih‐Hao Chen 《国际地质力学数值与分析法杂志》2009,33(9):1227-1253

In a cracked material, the stress intensity factors (SIFs) at the crack tips, which govern the crack propagation and are associated with the strength of the material, are strongly affected by the crack inclination angle and the orientation with respect to the principal direction of anisotropy. In this paper, a formulation of the boundary element method (BEM), based on the relative displacements of the crack tip, is used to determine the mixed‐mode SIFs of isotropic and anisotropic rocks. Numerical examples of the application of the formulation for different crack inclination angles, crack lengths, and degree of material anisotropy are presented. Furthermore, the BEM formulation combined with the maximum circumferential stress criterion is adopted to predict the crack initiation angles and simulate the crack propagation paths. The propagation path in cracked straight through Brazilian disc specimen is numerically predicted and the results of numerical and experimental data compared with the actual laboratory observations. Good agreement is found between the two approaches. The proposed BEM formulation is therefore suitable to simulate the process of crack propagation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Application of wavelet‐based multi‐model Kalman filters to real‐time flood forecasting     

Chien‐Ming Chou  Ru‐Yih Wang 《水文研究》2004,18(5):987-1008

This paper presents the application of a multimodel method using a wavelet‐based Kalman filter (WKF) bank to simultaneously estimate decomposed state variables and unknown parameters for real‐time flood forecasting. Applying the Haar wavelet transform alters the state vector and input vector of the state space. In this way, an overall detail plus approximation describes each new state vector and input vector, which allows the WKF to simultaneously estimate and decompose state variables. The wavelet‐based multimodel Kalman filter (WMKF) is a multimodel Kalman filter (MKF), in which the Kalman filter has been substituted for a WKF. The WMKF then obtains M estimated state vectors. Next, the M state‐estimates, each of which is weighted by its possibility that is also determined on‐line, are combined to form an optimal estimate. Validations conducted for the Wu‐Tu watershed, a small watershed in Taiwan, have demonstrated that the method is effective because of the decomposition of wavelet transform, the adaptation of the time‐varying Kalman filter and the characteristics of the multimodel method. Validation results also reveal that the resulting method enhances the accuracy of the runoff prediction of the rainfall–runoff process in the Wu‐Tu watershed. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Factors affecting grassland succession retardation in the Juifang area   总被引：1，自引：0，他引：1  

Chao-Yuan Lin  Chin-Wei Chuang  Chang-Hai Chien 《Natural Hazards》2011,59(2):987-1002

This study classifies the vegetation status to determine the factors affecting grassland succession retardation in the Juifang area. Data derived from Land Use Investigation of Taiwan, GIS techniques, multivariate analysis, and on-site investigation was applied in this research. Discriminant analysis shows that forests that have low human disturbance cannot be correctly identified and classified by the topography and soil depth. This indicates that the topography and soil depth in the Juifang area are not the limiting factors of forest growth. Grasslands are usually susceptible to periodic wildfires. This can be used as an environmental index for disturbed and/or polluted soils. Comparing the current vegetation status with the vegetation distribution derived from discriminant analysis, potential wildfire frequency can be estimated. Acid sulfate soils and copper-contaminated soils are the major polluted soils in the Juifang area. Because the Juifang area is an important coal field in northern Taiwan, acid sulfate can be easily found in the spoiled soils of several mining spots due to sulfur oxidation from the soil and/or rock layers dug out during mining operations. Copper-contaminated soils were detected at the sites near the Li-Lo Copper Refining Plant and Taiwan Metal Mining Company. Polluted soils and periodic wildfires inhibiting the invasion of trees are the major factors retarding the succession of grasslands in the Juifang area.  相似文献   

汶川8级地震前后陕西地形变异常特征分析   总被引：1，自引：0，他引：1  

邢西淳  毛娟  邵辉成 《高原地震》2011,23(4):17-23

分析了汶川8.0级地震前后的关中垂直形变及陕西地区地倾斜变化特征。结果表明：震前,跨断层垂直形变表现出阶段性变化特征,南大同、大塬、涧峪口、清河口、口镇等场地的垂直形变出现了明显的趋势转折、加速变化。汉中、宝鸡、乾县、西安台的地倾斜潮汐因子γ存在3个月左右异常变化。  相似文献   

Efficiency of Moso Bamboo Charcoal and Activated Carbon for Adsorbing Radioactive Iodine     

Chuan‐Chi Chien  Ying‐Pin Huang  Wie‐Chieh Wang  Jun‐Hsing Chao  Yuan‐Yao Wei 《洁净——土壤、空气、水》2011,39(2):103-108

Preventing radioactive pollution is a troublesome problem but an urgent concern worldwide because radioactive substances cause serious health‐related hazards to human being. The adsorption method has been used for many years to concentrate and remove radioactive pollutants; selecting an adequate adsorbent is the key to the success of an adsorption‐based pollution abatement system. In Taiwan, all nuclear power plants use activated carbon as the adsorbent to treat radiation‐contaminated air emission. The activated carbon is entirely imported; its price and manufacturing technology are entirely controlled by international companies. Taiwan is rich in bamboo, which is one of the raw materials for high‐quality activated carbon. Thus, a less costly activated carbon with the same or even better adsorptive capability as the imported adsorbent can be made from bamboo. The objective of this research is to confirm the adsorptive characteristics and efficiency of the activated carbon made of Taiwan native bamboo for removing ¹³¹I gas from air in the laboratory. The study was conducted using new activated carbon module assembled for treating ¹³¹I‐contaminated air. The laboratory results reveal that the ¹³¹I removal efficiency for a single‐pass module is as high as 70%, and the overall efficiency is 100% for four single‐pass modules operated in series. The bamboo charcoal and bamboo activated carbon have suitable functional groups for adsorbing ¹³¹I and they have greater adsorption capacities than commercial activated carbons. Main mechanism is for trapping of radioiodine on impregnated charcoal, as a result of surface oxidation. When volatile radioiodine is trapped by potassium iodide‐impregnated bamboo charcoal, the iodo‐compound is first adsorbed on the charcoal surface, and then migrates to iodide ion sites where isotope exchange occurs.  相似文献   

Assessing effects of model complexity and structure on predictions of hydrological responses using serial and parallel model design     

Huicheng Chien  D. Scott Mackay 《水文研究》2020,34(2):404-419

By utilizing functional relationships based on observations at plot or field scales, water quality models first compute surface runoff and then use it as the primary governing variable to estimate sediment and nutrient transport. When these models are applied at watershed scales, this serial model structure, coupling a surface runoff sub-model with a water quality sub-model, may be inappropriate because dominant hydrological processes differ among scales. A parallel modeling approach is proposed to evaluate how best to combine dominant hydrological processes for predicting water quality at watershed scales. In the parallel scheme, dominant variables of water quality models are identified based entirely on their statistical significance using time series analysis. Four surface runoff models of different model complexity were assessed using both the serial and parallel approaches to quantify the uncertainty on forcing variables used to predict water quality. The eight alternative model structures were tested against a 25-year high-resolution data set of streamflow, suspended sediment discharge, and phosphorous discharge at weekly time steps. Models using the parallel approach consistently performed better than serial-based models, by having less error in predictions of watershed scale streamflow, sediment and phosphorus, which suggests model structures of water quantity and quality models at watershed scales should be reformulated by incorporating the dominant variables. The implication is that hydrological models should be constructed in a way that avoids stacking one sub-model with one set of scale assumptions onto the front end of another sub-model with a different set of scale assumptions.  相似文献   

甘肃地区“十五”数字化水温观测及其地震前兆监测效能评估   总被引：1，自引：0，他引：1  

张昱  刘小凤  邵辉成  常千军  陈瑶 《华南地震》2010,30(4):1-9

对甘肃地区已建成的"十五"数字化水温观测点的年、月、日动态特征以及主要影响数字化学温资料的干扰因素进行了分析,结果发现,多数井点的资料比较连续可靠,多数井水温观测年动态正常稳定。数字化水温观测中目前较为突出的问题是,个别井点水温动态中存在较大幅度的脉冲、突变,个别井点还有断记。根据以往的震例总结,多数井点有可能识别出破年变为标志的中期前兆异常,月动态规律清楚的井点,有可能在短期前兆监测中发挥效能。部分井点有可能在阶变和脉冲为特征的短临异常识别中发挥作用。并提出了进一步发挥井水温度观测监测效能的若干建议。  相似文献   

关于1998年1月5日泾阳地震震级研究     

王平  邵辉成  狄秀玲  杜长娥  柯昌安 《高原地震》2010,22(3):30-32

利用陕西省地震台网观测报告及西安数字地震台网、中国地震台网、华北遥测地震台网、陕西邻省部分台站记录的数据资料,对1998年1月5日泾阳地震震级做了对比分析研究。结合泾阳地震的宏观考察数据综合分析,认为泾阳地震震级为ML5.2是合理的。  相似文献   

Seismic retrofit of reinforced concrete frames using buckling‐restrained braces with bearing block load transfer mechanism          下载免费PDF全文

Kuan‐Yu Pan  An‐Chien Wu  Keh‐Chyuan Tsai  Chao‐Hsien Li  Hsen‐Han Khoo 《地震工程与结构动力学》2016,45(14):2303-2326

A new method of retrofitting reinforced concrete (RC) frames with buckling‐restrained braces (BRBs) to improve frame strength, stiffness and energy dissipation is proposed. Instead of typical post‐installed anchors, load is transferred between the BRB and RC frame through compression bearing between an installed steel frame connected to the BRB, and high‐strength mortar blocks constructed at the four corners of the RC frame. This avoids complex on‐site anchor installation, and does not limit the allowable brace force by the anchor strength. Cyclic displacements of increasing amplitudes were imposed on two RC frame specimens retrofitted with different BRB strength capacities. In one of the frames, the bearing blocks were reinforced with wire mesh to mitigate cracking. A third RC frame was also tested as a benchmark to evaluate the retrofit strength and stiffness enhancements. Test results indicate that the proposed method efficiently transferred loads between the BRBs and RC frames, increasing the frame lateral strength while achieving good ductility and energy‐dissipating capacity. When the bearing block was reinforced with wire mesh, the maximum frame lateral strength and stiffness were more than 2.2 and 3.5 times the RC frame without the BRB respectively. The BRB imposes additional shear demands through the bearing blocks to both ends of the RC beam and column member discontinuity regions (D‐regions). The softened strut‐and‐tie model satisfactorily estimated the shear capacities of the D‐regions. A simplified calculation and a detailed PISA3D analysis were shown to effectively predict member demands to within 13.8% difference of the measured test results. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献