• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.91-91
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• 2013

Imagine a world where we could biomanufacture hybrid nanomaterials having atomic-scale resolution over functionality and architecture. Toward this vision, a fundamental challenge in materials science is how to design and synthesize protein-like material that can be fully self-assembled and exhibit information-specific process. In an ongoing effort to extend the fundamental understanding of protein structure to non-natural systems, we have designed a class of short peptides to fold like proteins and assemble into defined nanostructures. In this talk, I will talk about new strategies to drive the self-assembled structures designing sequence of peptide. I will also discuss about the specific interaction between proteins and inorganics that can be used for the development of new hybrid solar energy devices. Splitting water into hydrogen and oxygen is one of the promising pathways for solar to energy convertsion and storage system. The oxygen evolution reaction (OER) has been regarded as a major bottleneck in the overall water splitting process due to the slow transfer rate of four electrons and the high activation energy barrier for O-O bond formation. In nature, there is a water oxidation complex (WOC) in photosystem II (PSII) comprised of the earthabundant elements Mn and Ca. The WOC in photosystem II, in the form of a cubical CaMn4O5 cluster, efficiently catalyzes water oxidation under neutral conditions with extremely low overpotential (~160 mV) and a high TOF number. The cluster is stabilized by a surrounding redox-active peptide ligand, and undergo successive changes in oxidation state by PCET (proton-coupled electron transfer) reaction with the peptide ligand. It is fundamental challenge to achieve a level of structural complexity and functionality that rivals that seen in the cubane Mn4CaO5 cluster and surrounding peptide in nature. In this presentation, I will present a new strategy to mimic the natural photosystem. The approach is based on the atomically defined assembly based on the short redox-active peptide sequences. Additionally, I will show a newly identified manganese based compound that is very close to manganese clusters in photosystem II.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.171-178
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• 2003

Wing and secondary cracks are unique types of cracks observed in rock masses subjected to uniaxial and biaxial compressive loading conditions. In this study, morphological features of wing and secondary cracks developed in gypsum specimens are investigated in the macro and micro scales. Along the path of wing crack, microtensile cracks are observed. Microtensile cracks coalesce with pores and show branch phenomenon. From the onset of the wing crack, multiple initiations of microtensile cracks are observed. Microtensile cracks show tortuous propagation paths and relatively constant aperture of the cracks during the propagation. It is shown that microtensile cracks propagate by splitting failure. At the micro scale, microfsults are observed in the path of the secondary cracks. Along the path of the secondary cracks, separation of grains and conglomerate grains, oblique microfaults, and irregular aperture of microfault are observed. These features show that the secondary cracks are produced in shear mode. The measured sizes of fracture process zone across the propagation direction near the tip of wing and secondary cracks range from 10$\mu{m}$ to 20$\mu{m}$ far wing cracks and from 100$\mu{m}$ to 200$\mu{m}$ for secondary cracks, respectively.

• Journal of the Korean Mathematical Society
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• v.51 no.1
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• pp.17-53
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• 2014

Let ${\gamma}$ be a hyperbolic closed orbit of a $C^1$ vector field X on a compact boundaryless Riemannian manifold M, and let $C_X({\gamma})$ be the chain component of X which contains ${\gamma}$. We say that $C_X({\gamma})$ is $C^1$ robustly shadowable if there is a $C^1$ neighborhood $\mathcal{U}$ of X such that for any $Y{\in}\mathcal{U}$, $C_Y({\gamma}_Y)$ is shadowable for $Y_t$, where ${\gamma}_Y$ denotes the continuation of ${\gamma}$ with respect to Y. In this paper, we prove that any $C^1$ robustly shadowable chain component $C_X({\gamma})$ does not contain a hyperbolic singularity, and it is hyperbolic if $C_X({\gamma})$ has no non-hyperbolic singularity.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.2
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• pp.159-164
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• 2004

Lot-streaming is the process of splitting a job (lot) into a number of smaller sublots and then scheduling these sublots in order to accelerate the completion of jobs in a multi-stage production system. Anew genetic algorithm (NGA) is proposed for an-job, m-machine, equal-size sublot lot-streaming flow shop scheduling problem with delivery windows in which the objective is to minimize the mean weighted absolute deviation of job completion times from due dates. The performance of NGA is compared with that of an adjacent pairwise interchange (API) method and the results of computational experiments show that NGA works well for this type of problem.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.2
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• pp.63-72
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• 2005

In this study, the physical and mechanical properties of steel fiber reinforced lightweight polymer concrete were investigated experimentally with various steel fiber contents. All tests were performed at room temperature, and stress-strain curve and load-deflection curve were plotted up to failure. The unit weight of steel fiber reinforced lightweight polymer concrete was in the range of $1,020{\sim}1,160\;kg/m^3$, which was approximately $50\%$ of that of the ordinary polymer concrete, The compressive strength, splitting tensile strength, flexural toughness and flexural load-deflection curves after maximum load were shown with increase of steel fiber content. The stress-strain curves of steel fiber reinforced lightweight polymer concrete were bilinear in nature with a small transition zone, Based on these results, steel fiber reinforced lightweight polymer concrete can be widely applied to the polymer composite products.

• Progress in Superconductivity
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• v.6 no.1
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• pp.52-55
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• 2004

The inductive coupling theory in serially stacked $Bi_2$$Sr_2$$CaCu_2$$O_{8+x}$ intrinsic Josephson junctions predicts that the lattice structure of the Josephson vortices along the c axis gradually changes from the triangular to the rectangular lattice with increasing the vortex velocity. This lattice transition appears as voltage jumps or sub-branch splitting in the Josephson vortex-flow region of current-voltage characteristics (IVC). We report the IVC in external magnetic fields from 2 to 4 T. The stack, with the lateral size of 1.4${\times}$15 $u\m^2$, was fabricated by using the double-side cleaving technique. The sub-branches in the Josephson vortex-flow region, corresponding to a plasma propagation mode in serially coupled intrinsic Josephson junctions, were also observed in the range of 2∼4T. Switching from one branch to another in Josephson vortex-flow region suggests the structural transition of the moving Josephson vortex lattice.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.979-982
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• 2002

Compressing image data by using Vector Quantization (VQ)［1］-［3］will compare Training Vectors with Codebook. The result is an index of position with minimum distortion. The implementing Random Codebook will reduce the image quality. This research presents the Splitting solution ［4］,［5］to implement the Codebook, which improves the image quality［6］by the average Training Vectors, then splits the average result to Codebook that has minimum distortion. The result from this presentation will give the better quality of the image than using Random Codebook.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.48-54
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• 1998

Three-dimensional incompressible Navier-Stokes equations have been solved by the node-centered finite volume method with unstructured hybrid grids. The pressure-velocity coupling is handled by the artificial compressibility algorithm and convective fluxes are obtained by Roe's flux difference splitting scheme with linear reconstruction of the solutions. Euler implicit method is used for time-integration. The viscous terms are discretised in a manner to handle any kind of grids such as tetrahedra, prisms, pyramids, hexahedra, or mixed-element grid. The numerical efficiency and accuracy of the present method is critically evaluated for several example problems.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.156-157
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• 2003

A simple method is proposed to split the flux vector of the Euler equations by introducing two artificial wave speeds. The direction of wave propagation can be adjusted by these two wave speeds. This idea greatly simplifies the upwinding, and leads to a new family of upwind schemes. Numerical flux function for multi-dimensional Euler equations is formulated for any grid system, structured or unstructured. A remarkable simplicity of the scheme is that it successfully achieves one-sided approximation for all waves without recourse to any matrix operation. Moreover, its accuracy is comparable with the exact Riemann solver. For 1-D Euler equations, the scheme actually surpasses the exact solver in avoiding expansion shocks without any additional entropy fix. The scheme can exactly resolve stationary contact discontinuities, and it is also freed of the carbuncle problem in multi­dimensional computations.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4392-4396
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• 2011

Porous silicon with a complex network of nanopores is utilized for photoelectrochemical energy conversion. A novel electroless Pt deposition onto porous silicon is investigated in the context of photoelectrochemical hydrogen generation. The electroless Pt deposition is shown to improve the characteristics of the PS photoelectrode toward photoelectrochemical $H^+$ reduction, though excessive Pt deposition leads to decrease of photocurrent. Furthermore, it is found that a thin layer (< 10 ${\mu}m$) of porous silicon can serve as anti-reflection layer for the underlying Si substrate, improving photocurrent by reducing photon reflection at the Si/liquid interface. However, as the thickness of the porous silicon increases, the surface recombination on the dramatically increased interface area of the porous silicon begins to dominate, diminishing the photocurrent.