• Applied Microscopy
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• v.28 no.3
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• pp.379-390
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• 1998

Dermal wound healing responses in the skin of the toad, Bombina orientalis, were examined using transmission electron microscopy. At 12 hours after wounding, debridement and collagenolysis occurred in damaged dermis. Histocyte has a large nucleus and long cytoplasm process. Phagocytic vesicle and lysosome were observed in the cytoplasm. Damaged blood cells were transformed spindle to irregular shape. Autolysis was observed in their cytoplasm. Histocytes are found in poly-band. The irregularly shaped nucleus is located peripheral region in cytoplasm. At 2 days after wounding, partial aggregation of blood cells is observed. Phagocytic, activity is observed in histocyte and collagenolytic collagen fibers are scattered. Fibroblast is observed in the dermis at 3 days after wounding. Clusters of ribosomes and some short cisternae of rough-surfaced endoplasmic reticulum are found in the cytoplasm. In histocyte at 7 days post wounding, various size granules composed of moderately dense material are found the cytoplasm. In this period histocyte is round to rod in profile, with slender processes projecting from the surface. At 7 day after injury, it was observed that formation of connective tissue fibers and amorphous ground substance in regenerating skin.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.4
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• pp.1134-1139
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• 2004

This study was conducted to investigate the application possibility of leaf and stem extract(LSE) from the mixture of leaf and stem of ginseng radix(Panax Ginseng CA Meyer). This study measured antifatigue effects by rota-rod test and swimming test. Also we examined the cell toxicity in normal liver and kidney cells, and acute toxicity in mice. Dropping times of LSE treated group decreased about 39-83% compared to the control group according to supplementation intake levels. Swimming time in LSE treated group increased compared to the control group at short and long supplementation. Negative effects were not found from the results of the cell toxicity. Also acute toxicity not shown. These results imply that the leaf and stem of ginseng radix could be used as possible food resources and functional food material and feed stuff.

• Journal of Pharmaceutical Investigation
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• v.36 no.3
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• pp.175-184
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• 2006

Poly(D,L-lacic acid)(PLA) microshperes containing loazepam were prepared by a solvent-emulsion evaporation method and their release patterns were investigated in vitro. Various batches of microspheres with different size and drug content were obtained by changing the ratio of lorazepam to PLA, PLA concentration in the dispersed phase and stirring rate. Rod-like lorazepam crystals on microsphere surface, which were released rapidly and could act as a loading dose, were observed with increasing drug content. The release rate was increased with increase in drug contents and decrease in the molecular weight of PLA. The release rate of lorazepam for long-acting injectable delivery system in vitro, which would aid in Predicting in vivo release Profile, could be controlled by properly optimizing various factors affecting characteristics of microspheres.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.605-608
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• 2001

Molybdenum disilicide is widely used for manufacturing high-temperature heating elements owing to its low electrical resistivity, good thermal conductivity, and ability to withstand oxidation at high temperatures. MoSi$_2$heating elements with 4-5wt% of montmorillonite type bentonite as plasticzer and a small amount of Si$_3$N$_4$, ThO$_2$, and B as additives was manufactured. Extruded rods of 3.7mmø and 6.7mmø diameter and 400mm long were fabricated using a vacuum extruder, which were then sinrered for 4-5 hrs. at the max. temperrature of 140$0^{\circ}C$. After 10 minute's oxidation treatment, the diameter of the rod is reduced. The heating elements thus prepared was stable at 1$700^{\circ}C$ and the physical properties such as specific electrical resistivity, hardness, apparent densisty, thermal expansion coefficient, and bending strength were almost identical with thoes of commercial heating elements. In this study we have tried to gain the practical knowledge of manufacturing MoSi$_2$heating elements so that it may be utilized later in a research of pilot scale and eventually be transferred to industry.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.131-133
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• 2000

Single phase simulations were carried out in order to determine a solutive conductor to the aeolian noise which will be locally applied to 765 kV transmission lines Basic solutive conductors have already been proposed including conductors equipped with spiral rod. low noise conductor of a special shape and others. A low aeolian noise conductor, however, should have excellent corona characteristics in addition to aeolian noise reduction function. In this paper, we compared the performances of the audible noises and radio interferences of 6 candidate conductor bundles by using corona cage. We also developed two programs to need for evaluating environmental effects of each conductor bundle. Those are a program to calculate the conductor surface gradient of various special bundles and a conversion program of single phase data to the model of transmission line. The future determination on the final low aeolian noise conductor will be made through a long-term test to verify environmental impacts at the full-scale Kochang 765 kV test line.

• Macromolecular Research
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• v.15 no.4
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• pp.291-301
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• 2007

The rheological behaviors and morphologies of polylactide (PLA) and chemically modified plasticized starch (CMPS) blends were investigated. For this study, oscillatory shear flow measurements of the PLA, CMPS and their blends were performed. A scanning electron microscope (SEM) study was also conducted on the extracted extrudates of the blends. The morphology of the blend changed in relation to the composition: sphere-shaped CMPS disperse/continuous PLA, rod-like deformed CMPS phase/continuous PLA, a co-continuous structure with bridged CMPS long rods and PLA dispersed/continuous CMPS. The composition of the phase inversion could be estimated and closely coincided from the observed morphology experimental results. The rheological behavior of the blends, from oscillatory measurements, was found to vary in relation to the composition, and reflected the morphologies of the blends. PLA showed Newtonian flow behavior, while CMPS showed strong shear thinning behavior. The relationships between the morphology and rheological properties were observed in detail.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.324-331
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• 1998

After the addition of yttrium aluminum garnet of 2, 5, 10 mol% as a sintering aid, $\alpha$-silicon carbides were prepared by a liquid-phase sintering at $1850^{\circ}C$, and the microstructural evolution was investigated during sintering as functions of liquid-phase amount and sintering time. The highest apparent density in each compositions was obtained in specimens sintered for 2 h, and the percentage of weight loss increased with sintering time. By increasing the amount of sintering aid (yttrium aluminum garnet), the rate of grain growth during sintering decreased, but the apparent density of sintered body increased. The phase transformation from 6H-SiC to 4H-SiC was partially observed in specimens sintered for a long time, and so, a few rod-like grains were observed.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.101-106
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• 2003

In order to investigate the mechanical behavior of newly developed materials, the evaluation of mechanical properties using small-size specimen is essential. For those purposes, an instrumented impact testing apparatus, which provides the load-displacement curve under impact loading without oscillations, was devised. To develop the test procedure with the setup, the impact behaviors of various kinds of structural materials such as S45C, SCM4, Ti alloys (Ti-6V-4Al) and Zr-based bulk amorphous metal, were investigated through the instrumented Charpy V-notch impact tests. The calibrations of the dynamic load and displacement that was calculated based on the Newton' second law were carried out through the quasi-static load test and the comparison of a directly measured value using a laser displacement meter. Satisfactory results could be obtained. The crack initiation and propagation processes during impact fracture could be well divided on the curve, depending on the intrinsic characteristic of specimen tested; ductile or brittle. The absorbed impact energy in Zr-basd BAM was largely used for crack initiation not for crack propagation process. The fracture surfaces under impact loading showed different feature when compared with the static cases.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.609-614
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• 2006

Micro-alloyed steels(MA steels) for cold forging was developed to replace the usual quenched and tempered steel. MA steels have several advantages over the conventional quenched and tempered carbon steels. First of all, energy consumption could be lowered due to the elimination of spherodizing annealing and quenching/tempering heat treatment. Also, bending during quenching could be avoided when MA steels are applied for manufacturing of long fastener parts. However, larger amount of load is exerted on the dies compared than in the case of conventional mild steels, which might lead to the earlier fracture of dies, when MA forging steels are applied in forging practice. Therefore, die lift could be a critical factor to determine whether HA forging steels could be widely applied in cold forging practice. In the present study, authors have investigated the forging characteristics of non-heat treated micro-alloyed steel by using a series of experimental and numerical analyses. Firstly, microstructural features and its effect on the deformation behavior have been studied. Numerical analysis has been done on the forging of guide rod pin to investigate for the optimization of forging process and die stress prediction.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1373-1376
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• 2008

A supporting structure for a long tube bundle of a large diameter is considered in this paper. The primary purpose of the present study is to develop a spacer grid structure for a so-called "dual cooled nuclear fuel", which has been being studied for a nuclear power uprate. The outer diameter of the fuel rod increases considerably from the conventional one. So a completely new shape of the supporting structure (spacer grid) needs to be developed. One of the challenges is to insert a supporting tube into the cross points of the grid straps. To meet a supporting performance, the load vs. displacement characteristics should be obtained. So the present study focuses on the finite element analysis technology to evaluate the characteristics through a parametric study. As a result, major influencing parameters are investigated for an optimized spacer grid design.