• Coupled systems mechanics
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• v.1 no.4
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• pp.325-343
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• 2012

We present different numerical methods for solving the shallow shelf equations with basal drag (SSAB). An alternative approach of splitting the SSAB equation into a Laplacian and diagonal shift operator is discussed with respect to the underlying eigenvalue problem. First, we solve the equations using standard methods. Then, the coupled equations are decomposed into operators for membranes stresses, basal shear stress and driving stress. Applying reasonable parameter values, we demonstrate that the operator of the membrane stresses is much stiffer than the operator of the basal shear stress. Here, we could apply a new splitting method, which alternates between the iteration on the membrane-stress operator and the basal-shear operator, with a more frequent iteration on the operator of the membrane stresses. We show that this splitting accelerates and stabilize the computational performance of the numerical method, although an appropriate choice of the standard method used to solve for all operators in one step speeds up the scheme as well.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2060-2065
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• 2003

Aeolian tone generation from a two dimensional circular cylinder is numerically investigated via direct numerical simulation and hydrodynamic-acoustic splitting method. All governing equation are spatially discretized with the sixth-order compact scheme and fourth-order Runge-Kutta method to avoid excessive numerical dissipations and dispersions of acoustic quantities. Comparisons of two results show that the previous splitting method can not accurately predict the aeroacoustic noise of wall bounded shear flow. In this study, a perturbation viscous term and a new energy equation have been developed. This modified splitting method accurately predicts aeroacoustic noise from wall-bounded shear flow. The present results agree very well with the direct numerical simulation solution.

• Advances in concrete construction
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• v.2 no.4
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• pp.301-308
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• 2014

The present research work is on the effect of sawdust ash (SDA) on the mechanical strengths of self compacting concrete (SCC) using naphthalene sulfonate (NS) as a plasticizer. Experiments on compressive, flexural and splitting tensile strengths are conducted and the data analyzed using the Minitab 15 software. The results showed that SDA can defer the reaction of cement hydration and prolong the setting times of cement paste. This was very much pronounced on the flexural and splitting tensile strengths at 90 days of curing which are 36 % and 33 % higher than the control strengths, respectively. The study has proposed strength relations of mortar compressive strength with the flexural and splitting tensile strengths and these are, 5 and 7 times respectively. The flexural strength is 1.5 times that of the splitting tensile. Finally, linear models were developed on these relationships.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.75-78
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• 1998

1. Introduction : The clean technology using ion exchange membranes have drawn attention increasingly with advancement of the membrane synthesis. Ion exchange membranes have been used for diffusion dialysis, electrodialysis, electrodialytic water splitting and electrodeionization. Bipolar membranes(BPM), consisting of a cation exchange layer and an an_ion exchange layer, can convert a salt to an acid and a base without chemical addition. Using the bipolar membrane, a large quantity of industrial wastes containing salts can be reprocessed to generate acids and bases. Recent development of high performance bipolar membranes enables to further expand the potential use of electrodialysis in the chemical industry. The water-splitting mechanism in the bipolar membrane, however, is a controversial subject yet. In this study bipolar membranes were prepared using commercial ion exchange membranes and hydrophilic polymer as a binder to investigate the effects of the interface hydrophilicity on water-splitting efficiency. In addition, the water splitting mechanism by a metal catalyst was discussed.

• Applied Science and Convergence Technology
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• v.27 no.4
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• pp.61-64
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• 2018

The basic principle and concept for hydrogen production via water-splitting process are introduced. In particular, recent research activities and their progress in the photoelectrochemical water-splitting process are investigated. The material perspectives of semiconducting photocatalysts are considered from metal oxides, including titanium oxides, to carbon compounds and perovskites. Various structural configurations, from conventional photoanodes with metal cathodes to tandem and nanostructures, are also studied. The pros and cons of each are described in terms of light absorption, charge separation/photoexcited electron-hole pair recombinations and further solar-to-hydrogen efficiency. In this research, we attempt to provide a broad view of up-to-date research and development as well as, possibly, future directions in the photoelectrochemical water-splitting field.

• Bulletin of the Korean Mathematical Society
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• v.56 no.1
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• pp.265-276
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• 2019

For a simple implementation, a linear convex splitting scheme was coupled with the Fourier spectral method for the Cahn-Hilliard equation with a logarithmic free energy. However, an inappropriate value of the splitting parameter of the linear scheme may lead to incorrect morphologies in the phase separation process. In order to overcome this problem, we present a nonlinear convex splitting Fourier spectral scheme for the Cahn-Hilliard equation with a logarithmic free energy, which is an appropriate extension of Eyre's idea of convex-concave decomposition of the energy functional. Using the nonlinear scheme, we derive a useful formula for the relation between the gradient energy coefficient and the thickness of the interfacial layer. And we present numerical simulations showing the different evolution of the solution using the linear and nonlinear schemes. The numerical results demonstrate that the nonlinear scheme is more accurate than the linear one.

• The KIPS Transactions:PartD
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• v.12D no.6 s.102
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• pp.829-836
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• 2005

The way to assign a splitting criterion for correct object classification is the main issue in all decisions trees. This paper describes new splitting rules for classification in order to find an optimal split point. Unlike the current splitting rules that are provided by searching all threshold values, this paper proposes the splitting rules that we based on the probabilities of pre assigned intervals. Our methodology provides that user can control the accuracy of tree by adjusting the number of intervals. In addition, we applied the proposed splitting rules to a set of image data that was retrieved by parameterized feature extraction to recognize image objects.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.225-231
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• 2018

In this paper, in order to explain the splitting of cylindrical rock specimen under uniaxial loading, cracks in cylindrical rock specimen are divided into two kinds, the longitudinal crack and the slanting crack. Mechanical behavior of the rock is described by elastic-brittle-plastic model and splitting is assumed to suddenly occur when the uniaxial compressive strength is reached. Expression of the stresses induced by the longitudinal crack in direction perpendicular to the major axis of the crack is deduced by using the Maxwell model. Results show that the induced stress is tensile and can be greater than the tensile strength even before the uniaxial compressive strength is reached. By using the Inglis's formula and simplifying the cracks as slender ellipse, the above conclusions that drawn by using the Maxwell model are confirmed. Compared to shearing fracture, energy consumption of splitting seems to be less, and splitting is most likely to occur when the uniaxial loading is great and quick. Besides, explaining the rock core disking occurred under the fast axial unloading by using the Maxwell model may be helpful for understanding that rock core disking is fundamentally a tensile failure phenomenon.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.709-714
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• 2000

A splitting method for the direct numerical simulation of solid-liquid mixtures is presented, where a symmetric pressure equation is newly proposed. Through numerical experiment, it is found that the newly proposed splitting method works well with a matrix-free formulation fer some bench mark problems avoiding an erroneous pressure field which appears when using the conventional pressure equation of a splitting method. When deriving a typical pressure equation of a splitting method, the motion of a solid particle has to be approximated by the 'intermediate velocity' instead of treating it as unknowns since it is necessary as a boundary condition. Therefore, the motion of a solid particle is treated in such an explicit way that a particle moves by the known form drag (pressure drag) that is calculated from the pressure equation in the previous step. From the numerical experiment, it was shown that this method gives an erroneous pressure field even for the very small time step size as a particle velocity increases. In this paper, coupling the unknowns of particle velocities in the pressure equation is proposed, where the resulting matrix is reduced to the symmetric one by applying the projector of the combined formulation. It has been tested over some bench mark problems and gives reasonable pressure fields.

• Explosives and Blasting
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• v.37 no.2
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• pp.1-13
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• 2019

In this study, Rock deformation on the splitting surface was investigated by using the finite element code relating to the blasting in urban area. The maximum principal strain according to the blasting detonation pattern was analyzed by the modeled blast section, and deformation of the splitting surface formed by the numerical analysis and the real blasting were compared. As a result, it was found that the maximum principal strain was observed a difference according to the blasting detonation pattern on the splitting surface, and the splitting surface was showed a similar waveform both the numerical analysis and the real blasting.