• Applied Microscopy
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• v.28 no.3
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• pp.329-343
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• 1998

Early wound healing responses in the skin of the Korean fire bellied toad, Bombina orientalis, were examined using histochemical , scanning and transmission electron microscopical techniques. Cutaneous wounds were induced by sharp razor blade , and maintained in special cages for up to 3 days. By this treatment whole parts of epithelium and dermis were profoundly affected. After injury, retraction of damaged surface of the skin was observed. At 3 hours after injury, poly-band was form by mucous substance. The wound skin consisted of mucous gland secreted mucous substance which flows into wound cavity and the wound area was sealed by mucous substance which form thick layer at 6 hours. It appeared that natural disposition showed acid and neutral mucous substance by reaction of PAS and Alcian blue (pH 2.5) staining. After formation of the poly-band, epithelial cells were formed by migration of regenerating epithelial cells. These cells moved over the wound surface by migration at 12 hours after wounding. Poly-band was much increased in thickness and migrating cells were completely formed wound closure at 24 hours post-wounding. After 72 hours regenerated epithelial layer consists of four or five cell layers which are similar to clear, granular, and spinous layer.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.487-492
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• 2007

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchical void element with the integrals of Legend polynomials is used to characterize the fracture behavior of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. The numerical approach is based on the v-version degenerate shell element including the theory of anisotropic laminated composites. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness of materials. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of hierarchical void element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem.

• Journal of Surface Science and Engineering
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• v.49 no.1
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• pp.32-39
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• 2016

In this study, Al and Zn arc thermal spray coatings were carried out onto the substrate of SS400 steel to improve corrosion resistance and durability of hull structural steel for ship in marine environment. Therefore cavitation-erosion test was conducted to evaluate the durability of painted and thermal spray coated specimens. And then the damaged surface morphology and weight loss were obtained to compare with each other, respectively. As a result, the painted specimen was the poorest cavitation resistance characteristics because surface damage behavior appeared to be exfoliated in bulk shape during the cavitation experiment. And Zn thermal spray coating layer presented the significant surface damage depth due to relatively low surface hardness and local cavitation damage tendency. On the other hand, as a result of the weight loss analysis, the painting layer presented the poorest cavitation resistance and the Al thermal spray coating layer relatively showed the best results after cavitation experiment.

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.262-266
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• 2020

In this paper, we investigated the effect of the passivation stack with Al₂O₃, hydrogenated silicon nitride (SiN_x:H) stack and Al₂O₃, silicon oxynitride (SiON_x) stack in the n type bifacial solar cell on monocrystalline silicon. SiNx:H and SiON_x films were deposited by plasma enhanced chemical vapor deposition on the Al₂O₃ thin film deposited by thermal atomic layer deposition. We focus on passivation properties of the two stack structure after laser ablation process in order to improve bifaciality of the cell. Our results showed SiN_x:H with Al₂O₃ stack is 10 mV higher in implied open circuit voltage and 60 ㎲ higher in minority carrier lifetime than SiON_x with Al₂O₃ stack at Ni silicide formation temperature for 1.8% open area ratio. This can be explained by hydrogen passivation at the Al₂O₃/Si interface and Al₂O₃ layer of laser damaged area during annealing.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.384-390
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• 2021

In this paper, durability evaluation and surface damage mechanism were investigated through solid particle erosion (SPE) test after applying hot-dip aluminizing (HDA) technology for the purpose of maintenance of marine economizer tube. Damaged surface shape was analyzed using SEM and 3D microscope. Compositional changes and microstructure of the HDA layer were analyzed through EDS and XRD. Durability was evaluated by analyzing weight loss and surface damage depth after SPE. HDA was confirmed to have a two-layer structure of Al and Al₅Fe₂. HDA+HT was made into a single alloy layer of Al₅Fe₂ by diffusion treatment. In the microstructure of HDA+HT, void and crack defect were induced during the crystal phase transformation process. The SPE damage mechanism depends on material properties. Plastic deformation occurred in the substrate and HDA due to ductility, whereas weight loss due to brittleness occurred significantly in HDA+HT. As a result, the substrate and HDA showed better SPE resistance than HDA+HT.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.209-224
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• 2022

In this study, the numerical analysis model of π-beam explosion is established to compare and analyze the failure modes of the π-beam under the action of explosive loads, thus verifying the accuracy of the numerical model. Then, based on the numerical analysis of different protection forms of π beams under explosive loads, the peak pressure of π beam under different protection conditions, the law of structural energy consumption, the damage pattern of the π beam after protection, and the protection efficiency of different protective layers was studied. The testing results indicate that the pressure peak of π beam is relatively small under the combined protection of steel plate and aluminum foam, and the peak value of pressure decays quickly along the beam longitudinal. Besides, as the longitudinal distance increases, the pressure peak attenuates most heavily on the roof's explosion-facing surface. Meanwhile, the combined protective layer has a strong energy consumption capacity, the energy consumed accounts for 90% of the three parts of the π beam (concrete, steel, and protective layer). The damaged area of π beam is relatively small under the combined protection of steel plate and aluminum foam. We also calculate the protection efficiency of π beams under different protection conditions using the maximum spalling area of concrete. The results show that the protective efficiency of the combined protective layer is 45%, demonstrating a relatively good protective ability.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.297-303
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• 2023

This study aimed to evaluate hydrogen permeation behaviors of pre-strained twinning-induced plasticity steel with or without Zn coating using electrochemical permeation technique. In contrast to un-strained and 30% strained samples, permeation current density was measured in the 60% strained sample. Tensile pre-straining at 60% involved microstructural modifications, including a high level of dislocation density and stacking fault with a semi-coherent twin boundary, which might provide a high diffusion path for hydrogen atoms. However, reproducibility of measurements of hydrogen permeation current was low due to non-uniform deformation and localized stress concentration. On the other hand, the permeation current was not measured in pre-strained TWIP steel with Zn coating. Instead, numerous blisters with some cracks were observed on the surface of the coating layer. In locally damaged Zn coating under tensile straining, hydrogen atoms could relatively easily permeate through the coating layer. However, they were trapped at the interface between the coating layer and the substrate, which might delay hydrogen penetration into the steel substrate.

• Conservation Science in Museum
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• v.15
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• pp.122-137
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• 2014

The National Museum of Korea own a historical document box ^K976 that was once used to store Joseon Wangjo Sillok ^{Annals of the Joseon Dynasty} of the Joseon Dynasty. The rectangular box has a lid, and the entire surface is varnished with black lacquer. The wood of the box had become warped and the upper part of the wooden frame had been damaged. In some areas, the paint was flaking off, exposing the underlying wood, and an iron ring that connected the lid to the body of the box was missing. Thus, in 2013, Conservation Science Department in National Museum of Korea began to repair and restore the Joseon document box. Before the treatment, analyses were conducted to examine the box's structure, damaged parts, species of wood, and lacquering techniques. The wood was found to be that of a linden tree. As for the lacquering technique, the surface of the box was first coated with a layer of lacquer and bone ash, and then covered with Korean traditional paper. Next, the box was painted with a layer of mud and ashes, followed by a layer of black pigment mixed with soot, and then varnished again with lacquer.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.150-168
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• 2017

This study was carried out to compare stand structure in Bihwajin basin Samcheok-si, Gangwon-do, Korea for ten years between 2003 and 2014, in which occurred the east coastal forest fire in 2000. Data were collected from 32 quadrates that followed by the analysis of vegetation classification according to plant sociology, importance value by Mclntosh and Curtise, species diversity and similarity index. In the result of vegetation classification, the vegetation unit decreased from 7 units to 4 units, and the number of species groups changed from 11 to 7. As a result of importance value (IV) changes, IV of Quercus mongolica, Q. serrata and Q. variabilis was increased by 6.8%, 5.2% and 2.9% in the order, respectively. However, that of Pinus densiflora was decreased by 2.8%. That of major planted species such as Castanea crenata, Chionanthus retusa, Prunus armeniaca var. ansu, Acer triflorum and Koelreuteria paniculata was reduced. As a result of species diversity, it was increased from 0.252 to 0.287 in tree layer, from 0.252 to 0.434 in subtree layer, and from 1.293 to 1.333 in shrub layer. But that in herb layer was decreased from 1.745 to 1.646. As a result of similarity index, it was 0.78, 0.65, 0.72 and 0.55 by layers that showed most difference in herb stratum. Considering the results, this study would be applied to the ecosystem diagnose and management of forest fire damaged area similar to the investigated area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.679-685
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• 2014

For the measurements of surface shape milled using FIB (focused ion beam), the silicon bulk, $Si_3N_4/Si$, and Al/Si samples are used and observed the shapes milled from different sputtering rates, incident angles of $Ga^+$ ions bombardment, beam current, and target material. These conditions also can be influenced the sputtering rate, raster image, and milled shape. The fundamental ion-solid interactions of FIB milling are discussed and explained using TRIM programs (SRIM, TC, and T-dyn). The damaged layers caused by bombarding of $Ga^+$ ions were observed on the surface of target materials. The simulated results were shown a little bit deviation with the experimental data due to relatively small sputtering rate on the sample surface. The simulation results showed about 10.6% tolerance from the measured data at 200 pA. On the other hand, the improved analytical model of damaged layer was matched well with experimental XTEM (cross-sectional transmission electron microscopy) data.