Kok-Kwang Phoon

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This paper presents a systematic theoretical and numerical evaluation of three common block preconditioners in a Krylov subspace method for solving symmetric indefinite linear systems. The focus is on large-scale real world problems where block approximations are a practical necessity. The main illustration is the performance of the block diagonal,(More)
The difficulties of simulating non-Gaussian stochastic processes to follow arbitrary product–moment covariance models and arbitrary non-Gaussian marginal distributions are well known. This paper proposes to circumvent these difficulties by prescribing a fractile correlation function, rather than the usual product–moment covariance function. This fractile(More)
A copula-based method is presented to investigate the impact of copulas for modeling bivariate distributions on system reliability under incomplete probability information. First, the copula theory for modeling bivariate distributions as well as the tail dependence of copulas are briefly introduced. Then, a general parallel system reliability problem is(More)
Two solution schemes are proposed and compared for large 3D soil consolidation problems with nonassociated plasticity. One solution scheme results in the nonsymmetric linear equations due to the Newton iteration, while the other leads to the symmetric linear systems due to the symmetrized stiffness strategies. To solve the resulting linear systems, the QMR(More)
This paper aims to propose a bootstrap method for characterizing the effect of uncertainty in shear strength parameters on slope reliability. The procedure for a traditional slope reliability analysis with fixed distributions of shear strength parameters is presented first. Then, the variations of the mean and standard deviation of shear strength parameters(More)
In recent years, geotechnical engineers have paid much attention on reliability-based design. The probability density functions (PDFs) of the uncertain soil parameters are required for the reliability-based design. Once these PDFs are obtained, reliability analysis can be conducted, and reliability-based design can be achieved. Among the soil parameters,(More)
Reversed-phase high performance liquid chromatographic methods for the analysis of ointments containing hydrocortisone and clioquinol have been investigated. A successful method using a C18 column and methanol--0.05 M phosphoric acid (80:20) as eluting solvent has been developed which allows both compounds to be determined simultaneously. The(More)
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