• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.70-73
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• 2000

A finite element analysis model is suggested for analysis of forming process of milli structure whose size is from a few hundreds ${\mu}m$ to a few mm. In this paper, finite element formulation which assemble crystal plasticity theory considering texture development with damage mechanics is developed, since orientation development and growth of micro voids became the primary factors for deformation aspects in large deformation of milli structure. Applying to, extremely, extrusion process of single crystal and extrusion/drawing process of polycrystal milli-size bar, extrusion force, preferred orientation, and damage evolution are examined to understand the characteristics of deformation of milii-size bar.

• The Journal of Korean Medicine
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• v.21 no.1
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• pp.91-98
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• 2000

The water extract of Seongpungtang(SPT) has commonly been used for treatment of ischemic brain damage in Oriental traditional medicine. However, little is known about the mechanism by which the water extract of SPT rescues brain cells from ischemic damage. To elucidate the protective mechanism of ischemic induced cytotoxicity, the regulation of Lipopolysaccharide (LPS) and PMA (phobol-12-myristate-13-acetate) induced iNOS expression in microglial cells was investigated. LPS and PMA treatment for 48 hr in microglial cells markedly induced nitric oxide (NO), but treatment of the cells with the water extract of SPT decreased nitrite formation. In addition, LPS and PMA treatment for 48 hr induced severe cell death in microglial cells. However treatment of the cells with the water extract of SPT did not induce significant changes compared to the control cells. Furthermore, NO production was markedly decreased by treatment of nuclear factor kappa B(NF-kB) inhibitor, pyrrolidine dithiocarbamate(PDTC). According to the above results, it is suggested that the protective effects of the water extract of SPT against ischemic brain damage may be mediated by regulation of iNOS during ischemic condition.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.2
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• pp.147-151
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• 1998

Primary localized laryngeal amyloidosis is an uncommon disorder of unknown cause that occurs in the absence of systemic amyloidosis or associated disease. There is a risk of either missing concomitant systemic amyloidosis or exhaustively investigating for this when it is not present through failure to appreciate the nature of the disease. We present 2 cases of primary localized laryngeal amyloidosis in supraglottic region. Biopsy of the mass of patients revealed findings consistent with amyloidosis, which were Congo red reaction with a apple green birefringence in polarized light fluorescence microscopy. An extensive workup for systemic amyloidosis was negative. All of two cases were treated by vaporization via $CO_2$ LASER using "Swiftlase Flshscan" for creating a wide, shallow char-free treatment site by precisely controlling ablation depth without causing residual thermal damage to tissue. The postoperative recovery of all cases was uneventful with good vocal quality and no aspiration. At the present time, the patients have no evidence of disease, recurrence and complication.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.2
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• pp.121-127
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• 2000

Intracellular accumulation of bile acids in the hepatocytes during cholestasis is thought to be pathogenic in cholestatic liver diseases. The objective of this study was to determine the role of lipid peroxidation and glutathione on the bile acid-induced hepatic cell death mechanism in primary cultured rat hepatocytes. To induce hepatic cell death, we incubated primary cultured rat hepatocytes with glycochenodeoxycholic acid $(GCDC;\;0{\sim}400\;{\mu}M)$ for 3 hours. In electron microscopic examination and agarose gel electrophoresis, low concentration of GCDC treatment mainly induced apoptotic feature. Whereas $400\;{\mu}M$ GCDC treated cells demonstrated both apoptosis and necrosis. Lipid peroxidation was increased dose-dependently in GCDC treated hepatocyte. And this was also accompanied by decreased glutathione. Therefore, oxygen free radical damage may play a partial role in GCDC-induced hepatic cell death.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.83-91
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• 1998

Cracking problems which high temperature plant components suffer during long-term service, occur very often at welded locations. The crack occurs due to accumulated creep damage near fusion line or at heat affected zone (HAZ). However, most of the studies on creep crack growth behavior have been performed with matrix metal not wit welded metal due to the difficulty of interpreting the test results. In this study, creep crack growth rates were measured with C(T) specimens whose cracks were formed along the fusion line or HAZ. The measured crack growth rates were characterized by {TEX}$C_{t}${/TEX}-parameter derived for elastic-primary-secondary creeping material. Since contribution of primary creep was significant for the tested 1Cr-0.5Mo steel, its effect was carefully studied. Effects of crack tip plasticity and material aging were also discussed.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.1036-1046
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• 2016

We propose a primary water stress corrosion cracking (PWSCC) initiation model of Alloy 600 that considers the stress triaxiality factor to apply to finite element analysis. We investigated the correlation between stress triaxiality effects and PWSCC growth behavior in cold-worked Alloy 600 stream generator tubes, and identified an additional stress triaxiality factor that can be added to Garud's PWSCC initiation model. By applying the proposed PWSCC initiation model considering the stress triaxiality factor, PWSCC growth simulations based on the macroscopic phenomenological damage mechanics approach were carried out on the PWSCC growth tests of various cold-worked Alloy 600 steam generator tubes and compact tension specimens. As a result, PWSCC growth behavior results from the finite element prediction are in good agreement with the experimental results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.269-272
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• 2003

The importance of the improving quality of electric power is being strongly raised, owing to an increasing use of sensitive and small-sized electronic devices and system. The transient overvoltage on low-voltage AC power distribution system are induced by direct or indirect lightning return strokes, and those can cause damage and/or malfunction of the utility system for borne automation, office automation and factory automation as well as medical equipments. The behavior of lightning surge transferred to the primary side from the primary side in distribution transformers were experimentally investigated the protection effect of low voltage SPD installed at the secondary side of distribution transformers was analyzed.

• The Korean Journal of Physiology and Pharmacology
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• v.26 no.2
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• pp.69-75
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• 2022

Chronic pain is induced by tissue or nerve damage and is accompanied by pain hypersensitivity (i.e., allodynia and hyperalgesia). Previous studies using in vivo two-photon microscopy have shown functional and structural changes in the primary somatosensory (S1) cortex at the cellular and synaptic levels in inflammatory and neuropathic chronic pain. Furthermore, alterations in local cortical circuits were revealed during the development of chronic pain. In this review, we summarize recent findings regarding functional and structural plastic changes of the S1 cortex and alteration of the S1 inhibitory network in chronic pain. Finally, we discuss potential neuromodulators driving modified cortical circuits and suggest further studies to understand the cortical mechanisms that induce pain hypersensitivity.

• Archives of Pharmacal Research
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• v.27 no.4
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• pp.454-459
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• 2004

The present study investigated the effects of gossypin, 3,3',4',5,7,8-hexahydroxyflavone 8-glucoside, on the toxicity induced by oxidative stress or $\beta$-amyloid ($A_{\beta}$) in primary cultured rat cortical cells. The antioxidant properties of gossypin were also evaluated by cell-free assays. Gossypin was found to inhibit the oxidative neuronal damage induced by xanthinelxanthine oxidase or by a glutathione depleting agent, D,L-buthionine (S,R)-sulfoximine. In addition, gossypin significantly attenuated the neurotoxicity induced by $A_{{\beta}(25-35)}$. Furthermore, gossypin dramatically inhibited lipid peroxidation initiated by $Fe^{2+}$ and ascorbic acid in rat brain homogenates. It also exhibited potent radical scavenging activity generated from 1 ,1-diphenyl-2-picrylhydrazyl. These results indicate that gossypin exerts neuroprotective effects in the cultured cortical cells by inhibiting oxidative stress- and $A_{\beta}$-induced toxicity, and that the antioxidant properties of gossypin may contribute to its neuroprotective actions.

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.207-216
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• 2014

This paper revisits the Fukushima accident to draw lessons in the aspect of nuclear safety considering the fact that the Fukushima accident resulted in core damage for three nuclear power plants simultaneously and that there is a high possibility of a failure of the integrity of reactor vessel and primary containment vessel. A brief review on the accident progression at Fukushima nuclear power plants is discussed to highlight the nature and characteristic of the event. As the severe accident management measures at the Fukushima Daiich nuclear power plants seem to be not fully effective, limitations of current severe accident management strategy are discussed to identify the areas for the potential improvements including core cooling strategy, containment venting, hydrogen control, depressurization of primary system, and proper indication of event progression. The gap between the Fukushima accident event progression and current understanding of severe accident phenomenology including the core damage, reactor vessel failure, containment failure, and hydrogen explosion are discussed. Adequacy of current safety goals are also discussed in view of the socio-economic impact of the Fukushima accident. As a conclusion, it is suggested that an investigation on a coherent integrated safety principle for the severe accident and development of innovative mitigation features is necessary for robust and resilient nuclear power system.