A combinatorial optimization scheme for parameter structure identification in ground water modeling   总被引：5，自引：0，他引：5  

Tsai FT  Sun NZ  Yeh WW 《Ground water》2003,41(2):156-169

This research develops a methodology for parameter structure identification in ground water modeling. For a given set of observations, parameter structure identification seeks to identify the parameter dimension, its corresponding parameter pattern and values. Voronoi tessellation is used to parameterize the unknown distributed parameter into a number of zones. Accordingly, the parameter structure identification problem is equivalent to finding the number and locations as well as the values of the basis points associated with the Voronoi tessellation. A genetic algorithm (GA) is allied with a grid search method and a quasi-Newton algorithm to solve the inverse problem. GA is first used to search for the near-optimal parameter pattern and values. Next, a grid search method and a quasi-Newton algorithm iteratively improve the GA's estimates. Sensitivities of state variables to parameters are calculated by the sensitivity-equation method. MODFLOW and MT3DMS are employed to solve the coupled flow and transport model as well as the derived sensitivity equations. The optimal parameter dimension is determined using criteria based on parameter uncertainty and parameter structure discrimination. Numerical experiments are conducted to demonstrate the proposed methodology, in which the true transmissivity field is characterized by either a continuous distribution or a distribution that can be characterized by zones. We conclude that the optimized transmissivity zones capture the trend and distribution of the true transmissivity field.  相似文献   

Experimental evaluation of piecewise exact solution for predicting seismic responses of spherical sliding type isolated structures   总被引：1，自引：0，他引：1  

C. S. Tsai  Tsu‐Cheng Chiang  Bo‐Jen Chen 《地震工程与结构动力学》2005,34(9):1027-1046

The use of base isolation for enhancing seismic resistibility has been proven as an efficient method in experimental and theoretical studies. It is usual to insert a flexible device in the horizontal direction to permit the most of relative deformation of a structure at this level. Because the rigidity of the superstructure is much higher than that of the base isolator underneath the structure, the behavior of the superstructure can be idealized as a rigid body during earthquakes. In general, hundreds of degrees of freedom and a step‐by‐step time history analysis are the basic requirements for calculating the seismic response of a base‐isolated structure under earthquakes. In order to develop a simple tool which can be easily adopted for calculating the seismic responses of the spherical sliding type isolated structures, a piecewise exact solution for predicting the seismic responses of base‐isolated structures has been derived in this study. The comparison between the experimental results conducted at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan and the analytical results obtained from the piecewise exact solution show that the formulation derived in this study can predict the seismic responses of the base‐isolated structure with a very high accuracy. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Analyzing Spatial and Temporal Changes of Aquaculture in Yunlin County,Taiwan*     

Bor‐Wen Tsai  Kang‐Tsung Chang  Chang‐Yi Chang  Chieh‐Ming Chu 《The Professional geographer》2006,58(2):161-171

This article analyzes spatial and temporal changes of aquaculture land use in Yunlin County, Taiwan, and discusses the driving forces for these changes. Digital land‐use maps and satellite imagery for 1982, 1988, 1994, and 2002 were used to extract aquaculture areas. A geographic information system was used to derive changes in aquaculture areas and to compute the spatial clustering statistics over time. A survey of eighty‐seven farmers was conducted to obtain their views and concerns about aquaculture. The results show a rapid expansion in aquaculture during the 1980s, driven mainly by exports to Japan, and a continuous decline since the mid‐1990s because of economic, environmental, and demographic factors.  相似文献   

A numerical simulation of debris flow and its application   总被引：16，自引：0，他引：16  

Cheng-Lun Shieh  Chyan-Deng Jan  Yuan-Fan Tsai 《Natural Hazards》1996,13(1):39-54

Debris flow is the flow of solid-fluid mixture and was treated as the flow of a continuum in routing in this study. A mathematical model was proposed to describe debris flow including deposition process and then solved numerically with suitable boundary conditions. Laboratory experiments were also conducted for comparison and calibration of the numerical results as well as for investigation of debris flow phenomena. The numerical model was also applied to simulate the debris flow caused by heavy rainfall in Tungman village of Hualien County located in the east of Taiwan on 23 June 1990. The simulated bed topographies in alluvial fan were in good agreement with those obtained from laboratory experiments and field observations.  相似文献   

Slip, Stress Drop and Ground Motion of Earthquakes: A View from the Perspective of Fractional Brownian Motion     

C.-C. P. Tsai 《Pure and Applied Geophysics》1997,149(4):689-706

—The characteristics of slip and stress drop distributions accompanying earthquakes are explored from the perspective of fractional Brownian motion (fBm). Slip and stress drop distributions are assumed to be processes of fBm.The Hurst exponent (H), which reveals the roughness of a random process of fBm, is first estimated from ten inferred slip maps for six crustal earthquakes occurring in California. The relationships between the Hurst exponents with respect to static slip (H _u ),stress (H _τ ), static stress drop (H _δσ ) and slip velocity (H _ú ) are then established following Andrews (1980). They are found to be H _δσ = H _τ = H _u -1 = H _ú -0.5. Empirically, H _u is recognized as being about 1 which, according to the theory of fBm, implies that the static slip distribution of an earthquake is just on the margin between being and not being self-similar, depending on the individual case. Cases where H _u is less than 1 (i.e., self-similar) suggest that H _δσ < 0(i.e., the distribution of static stress drop diverges), which is, in light of fBm, invalid. One possible explanation for this paradox is that H _u is less than 1 in crustal earthquake phenomena only over a certain specific bandwidth of wavenumbers, or it could be that the relation H _δσ = H _u -1 is not valid, which implies that static stress drop in the wavenumber domain is not the product of stiffness and slip as described in Andrews (1980). It could be that some different physics apply over this particular bandwidth. In such cases, multi-fractals may be a better way to explore the characteristics of the Hurst exponents of slip. In general, static stress drop and stress distributions are more likely to be self-similar than static slip distribution. H _u ≌ 1 and H _δσ ≌ 0 are good first approxima tions for the slip and stress drop distributions. The spectrum of ground motion displacement falls off as ω ^{-(Hδσ + 2)} with H _δσ ≌ 0, consistent with an ω^-2 model of the earthquake source.  相似文献   

Non-classical damping in dynamic analysis of base-isolated structures with internal equipment     

Hsiang-Chuan Tsai  James M. Kelly 《地震工程与结构动力学》1988,16(1):29-43

It has been shown that the use of base isolation not only attenuates the response of a primary structural system but also reduces the response of a secondary system mounted on or within the main structure. The isolation system, superstructure and equipment may be made of different materials with significantly different energy dissipation characteristics such that the damping matrix for the combined system is non-classical and can only be approximately expressed by modal damping ratios if the classical mode method is used for analysis. The object of this paper is to evaluate the accuracy of this procedure in approximating the responses of base-isolated structures and internal equipment. The complex mode method can provide exact solutions to problems with non-classical damping and is used here to find the exact response of the isolation-superstructure-equipment system. The entire system is assumed to be linear elastic with viscous damping and the superstructure is assumed to be proportionally damped so that the deformation of the superstructure can be expressed in terms of its classical modes. Recognizing that the ratio of the equipment mass to the structural mass and the ratio of the stiffness of the isolation system to the superstructural stiffness are both small, perturbation methods are used to find the response. This study shows that the response of base-isolated structures can be determined by the classical mode method to some degree of accuracy, but the higher frequency content is distorted. The equipment response derived by the classical mode method is much smaller than the exact solution so that the complex mode method should be applied to find equipment response.  相似文献   

Seismic response of the superstructure and attached equipment in a base-isolated building     

Hsiang-Chuan Tsai  James M. Kelly 《地震工程与结构动力学》1989,18(4):551-564

Base isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base-isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base-isolated structure by a different analytical approach—perturbation analysis. Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base-isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base-isolated building. This study shows that the first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. The contribution of higher modes to the response of base-isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small.  相似文献   

Seismotectonics of Taiwan   总被引：3，自引：0，他引：3  

Tsai Yi-Ben 《Tectonophysics》1986,125(1-3)

High-quality seismicity data and focal mechanism solutions obtained during 1973–1983 by the permanent Taiwan Telemetered Seismographic Network and several temporary local seismographic networks are used for a detailed study of the seismotectonics of the Taiwan area. Seismicity distribution in southern Taiwan clearly reveals an east-dipping Benioff zone which has a thickness of about 30 km and begins to deepen along 121°E at a dip angle of 55°–60°. The leading edge of this Benioff zone reaches a depth of about 180 km between 21°N and 22°N, but tapers off to a shallower depth of about 100 km from 22°N to 23°N. The presence of this seismic zone implies that subduction of the South China Sea plate under the Philippine Sea plate extends from Luzon northward to about 23°N. The position of the northern boundary of the South China Sea plate, as tentatively defined according to the seismicity distribution, passes through southern Taiwan from the offshore area in the Taiwan Strait west of Kaohsiung in an east-northeast direction to the Taitung area where a triple junction probably lies. Seismicity is found to disappear abruptly below a certain depth in many parts of Taiwan. This phenomenon may be attributed to the frictional to quasiplastic transition in the crust or upper mantle. Comparison of shallow seismicity with surface faults and fractures shows that all areas of active shallow seismicity are marked by densely-developed faults and fractures. However, the converse is not necessarily true. This may be partly due to the relatively short duration of seismicity data and partly due to excessive weakening of some of the severely faulted and fractured areas. Finally, focal mechanism solutions for west central Taiwan and the Kuangfu-Fuli area in eastern Taiwan predominantly show a maximum horizontal compression in the SE-NW direction which can be related to collision between the Eurasian and Philippine Sea plates. However, focal mechanism solutions for both the Hualien area in eastern Taiwan and the Tainan area in southwestern Taiwan show remarkable irregularities which may result from local tectonic complexities.  相似文献   

Trophic coupling between <Emphasis Type="Italic">Synechococcus</Emphasis> and pigmented nanoflagellates in the coastal waters of Taiwan,western subtropical Pacific     

Lin Yun-Chi  Tsai An-Yi  Chiang Kuo-Ping 《Journal of Oceanography》2009,65(6):781-789

In our attempt to characterize the interaction of trophic coupling between Synechococcus and pigmented nanoflagellates (PNFs), successive size-fraction experiments were performed at a coastal station on the northeast coast of Taiwan from June, 2005 to January, 2006. By estimating the growth rate and grazing rate of Synechococcus in the presence of nanoflagellates of different sizes, we truncated the food web by removing organisms with different body sizes (<2 μm, <5 μm, <10 μm, and <20 μm). The growth rates of Synechococcus ranged from −0.016 to 0.051 h⁻¹ during the experimental period, suggesting that temperature was a primary mechanism controlling Synechococcus growth. In addition to size and relative biomass of pigmented nanoflagellates and Synechococcus, it is suggested that community structures played an important role in trophic link. Furthermore, we conclude that the trophic cascading effect in the northeast coast of Taiwan includes: 1) high grazing rates at night in the warm season; 2) the Synechococcus biomass generally exceeds the grazing threshold (6 × 10⁴ cells mL⁻¹); and 3) the biomass ratio of <5 μm PNFs to >5 μm PNFs should be 1:1 to 2:1.  相似文献   

ISEE: Internet‐based Simulation for Earthquake Engineering—Part I: Database approach     

Yuan‐Sen Yang  Shang‐Hsien Hsieh  Keh‐Chyuan Tsai  Shiang‐Jung Wang  Kung‐Juin Wang  Wei‐Choung Cheng  Chuan‐Wen Hsu 《地震工程与结构动力学》2007,36(15):2291-2306

An Internet‐based framework, named Internet‐based Simulation for Earthquake Engineering (ISEE) was developed to facilitate collaborative earthquake engineering experiments performed by multiple laboratories in a network environment. One of the approaches in the ISEE framework, named Database Approach, offers an easy way to perform multi‐site networked collaborative pseudo‐dynamic experiments. The Database Approach uses the Structured Query Language (SQL), a common and standardized computer language used in database management systems, for inter‐laboratory communications. Using the SQL protocol, it is easy to monitor the experiments' progress, access the data, as well as develop additional programs to expand the functions for a networked experiment. This approach offers consistency and durability of selected experimental data both during and after experiments. Two networked pseudo‐dynamic experiments were conducted to demonstrate the feasibility and expansibility of the Database Approach in ISEE. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献