• Journal of the Korean Mathematical Society
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• v.60 no.1
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• pp.71-90
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• 2023

We construct generalized Cauchy-Riemann equations of the first order for a pair of two ℝ-valued functions to deform a minimal graph in ℝ³ to the one parameter family of the two dimensional minimal graphs in ℝ⁴. We construct the two parameter family of minimal graphs in ℝ⁴, which include catenoids, helicoids, planes in ℝ³, and complex logarithmic graphs in ℂ². We present higher codimensional generalizations of Scherk's periodic minimal surfaces.

• Journal of the Korean GEO-environmental Society
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• v.16 no.5
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• pp.13-25
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• 2015

This paper proposes an extended model evaluation method that considers not only the model performance but also the model structure and parameter uncertainties in hydrologic modeling. A simple reservoir model (SFM) and distributed kinematic wave models (KWMSS1 and KWMSS2 using topography from 250-m, 500-m, and 1-km digital elevation models) were developed and assessed by three evaluative criteria for model performance, model structural stability, and parameter identifiability. All the models provided acceptable performance in terms of a global response, but the simpler SFM and KWMSS1 could not accurately represent the local behaviors of hydrographs. Moreover, SFM and KWMSS1 were structurally unstable; their performance was sensitive to the applied objective functions. On the other hand, the most sophisticated model, KWMSS2, performed well, satisfying both global and local behaviors. KMSS2 also showed good structural stability, reproducing hydrographs regardless of the applied objective functions; however, superior parameter identifiability was not guaranteed. A number of parameter sets could result in indistinguishable hydrographs. This result indicates that while making hydrologic models complex increases its performance accuracy and reduces its structural uncertainty, the model is likely to suffer from parameter uncertainty.

• Journal of the Korean Chemical Society
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• v.52 no.3
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• pp.281-294
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• 2008

synergistic action caused by iodide ions on the corrosion inhibition of aluminium (Al) in 0.5 M HCl in the presence of Azadirachta Indica (AZI) plant extract has been investigated using potintiodynamic polarization and impedance techniques. It is found that AZI extract inhibits the corrosion of aluminium in 0.5 M HCl. The inhibition efficiency increases with the increase in AZI extract concentration, until 24% v/v of AZI extract, then Inh.% is decreased with father increase in AZI extract concentration. The adsorption of this extract in the studied concentration is found to obey Frewendlish adsorption isotherm. The addition of iodide ions enhances the inhibition efficiency to a considerable extent. The increase in Inh.% values in presence of fixed concentration of iodide ions indicates that AZI extract forms an insoluble complex at lower AZI extract concentrations by undergoing a joint adsorption. But at higher concentrations of AZI extract, competitive adsorption is found between iodide ions and the formed complex leading to less Inh.%.The Inh.% decreased in presence of iodide ions with AZI extract than in presence of AZI extract alone at all studied iodide concentrations. The synergism parameter Sq is defined and calculated from surface coverage values. This parameter in the case of AZI extract is found to be more than unity, indicating that the enhanced inhibition efficiency caused by the addition of iodide ions.

• Geophysics and Geophysical Exploration
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• v.10 no.1
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• pp.60-68
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• 2007

Conventional analysis of spectral induced polarization (SIP) data consists of measuring impedances over a range of frequencies, followed by spectral analysis to estimate spectral parameters. For the quantitative and accurate estimation of subsurface SIP parameter distribution, however, a sophisticated and stable inversion technique is required. In this study, we have developed a two-step inversion approach to obtain the two-dimensional distribution of SIP parameters. In the first inversion step, all the SIP data measured over a range of frequencies are simultaneously inverted, adopting cross regularisation of model complex resistivities at each frequency. The cross regularisation makes it possible to enhance the noise characteristics of the inversion by imposing a strong assumption, that complex resistivities should show similar characteristics over a range of frequencies. In numerical experiments, we could verify that our inversion approach successfully reduced inversion artefacts. As a second step, we have also developed an inversion algorithm to obtain SIP parameters based on the Cole-Cole model, in which frequency-dependent complex resistivities from the first step are inverted to obtain a two-dimensional distribution of SIP parameters. In numerical tests, the SIP parameter images showed a fairly good match with the exact model, which suggests that SIP imaging can provide a very useful subsurface image to complement resistivity.

• Journal of the Korean Mathematical Society
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• v.32 no.3
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• pp.401-413
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• 1995

This paper is concerned with the problem given below $$ (1.1) i\frac{dx}{du_1(x,\lambda)} + q1(x)u_2(x,\lambda) = \lambdau_1(x,\lambda) 0 \leq x < \infty - i\frac{dx}{du_2(x,\lambda)} + q2(x)u_1(x,\lambda) = \lambdau_2(x,\lambda), $$ $$ (2) u_2(0,\lambda) - hu_1(0,\lambda) = 0 $$ where $\lambda$ is a complex parameter and h is a non-zero complex number.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.10a
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• pp.24-30
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• 1993

When modeling a complex system we use an event tree to analyze propagation of failure. An event tree cannot represent the statistical interrelationships among parameters, but it can be represented as a statistically identical influence diagram so that parameter updating can be easily performed. After updating parameters we can calculate posterior distribution of the failure rate for each path. But exact distribution requires considerably complex numerical integration. We propose an approximation method to calculate the posterior and derive the predictive distribution of the time to next failure. Finally we introduce the system which implements our methodology.

• Bulletin of the Korean Mathematical Society
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• v.52 no.3
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• pp.963-975
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• 2015

In this paper, we give a representation formula for an isotropic curve with pseudo arc length parameter and define the structure function of such curves. Using the representation formula and the Frenet formula, the isotropic Bertrand curve and k-type isotropic helices are characterized in the 3-dimensional complex space $\mathbb{C}^3$.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.2
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• pp.303-308
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• 2002

Genetic markers engendered by genome projects drew enormous interest in quantitative genetics, but knowledge on genetic architecture of complex traits is limited. Complexities in genetics will not allow us to easily clarify relationship between genotypes and phenotypes for quantitative traits. Quantitative genetics guides an important way in facing such challenges. It is our exciting task to find genes that affect complex traits. In this paper, landmark research and future prospects are discussed on genetic parameter estimation and quantitative trait locus (QTL) mapping as major subjects of interest.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.301-304
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• 2012

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.1
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• pp.18-23
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• 2006

The complex system synchronization methods improve based on synchronization theory; however, due to deeper level of complexity within complex system compared to that of chaos system, it is difficult to synchronize complex signals from complex system. In this paper, we proposed coupled-synchronization theory in the n-double scroll circuit and new embedding driven-synchronization theory, a method of accomplishing synchronization with only one parameter out of may parameters, in hyper-chaos circuit to apply synchronization in the complex system. By applying proposed synchronization method using computer simulation, we confirmed the accomplishment of superior synchronization in complex system.