• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.77-84
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• 1993

Systems with journal bearings generally operate in large scale and under severe loading conditions such as steam generator turbines and internal combustion engines, in contrast to the machineries using rolling element bearings. Failure of the bearings in these machineries can result in the system breakdown. To avoid the time consuming repair and considerable economic loss, the detection of incipient failure in journal bearings becomes very important. In this experimental approach, acoustic emission monitoring is employed to the detection of incipient failure caused by intervention of foreign particles most probable in the journal bearing systems. It has been known that the intervention of foreign materials, insufficient lubrication and misassembly etc. are principal factors to cause bearing failure and distress. The experiment was conducted under such designed conditions as inserting alumina particles to the lubrication layer in the simulated journal bearing system. The results showed that acoustic emission could be an effective tool to detect the incipient failure in journal bearings.

• 전기의세계
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• v.26 no.2
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• pp.57-65
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• 1977

In roder to investigate the influence of treeing on electric breakdown of solid organic insulator the initiation and growing mechanism of tree itself, and the correlation between corona discharge and treeing phenomena in solid orgainc insulating materials, several experiments were carried out by means of needle test on polymethyl-methacrylate. The obtained results showed that the existence of voids in specimen had important effects on initiation voltage of trees and, when the direct voltage was applied, the initiation voltage of trees increased by space charge effect. And also the stagnation phenomena due to the transfer of vacancy cluster or polymekr cage in specimen might beconsidered in process of growth of trees, and corona discharge seemed to be the pre-phenomena of treeing because trees were normally initiated by internal discharge in voids.

• Journal of Korean Foot and Ankle Society
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• v.17 no.4
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• pp.257-263
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• 2013

Open reduction and internal fixation is currently considered as a gold standard of treatment in most of the intra-articular calcaneal fractures. Among various different approaches, extensile lateral approach is the most popular since it provides good exposure to the subtalar joint. However, wide skin incision followed by extensive soft tissue dissection leading to increased risk of wound breakdown is the most serious drawback. Sinus tarsi approach, a minimal invasive technique to approach the subtalar joint and reduce the intra-articular calcaneal fractures, provides good clinical outcome and less wound complications compared to the extensile lateral approach. This article introduces the surgical technique and review of the literature regarding the sinus tarsi approach.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.112-116
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• 2004

On-line monitoring of fault discharge is an important approach for indicating the condition of electrical insulation of stator winding in high voltage motor. In this paper, several key aspects of on-line monitoring system are discussed, involving the characteristics of fault discharge of stator winding in high voltage motor, spectrum analysis of four simulation fault signals, feature extraction of internal fault discharge from apply voltage to breakdown. The study of the partial discharge activities allows to highlight the ageing stage in the winding fault under test. During the life of the winding insulation fault, the shape of PD signal change relating to the ageing stage. The ageing of stator winding insulation fault of high voltage motor is investigated based on the characteristics of partial discharge pulse distribution and statistical parameters, such as maximum, skewness and kurtosis using discrete wavelet transform coefficients.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.1
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• pp.18-24
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• 1982

The Tree phenomenon of the PMMA resin depends on an annex of the inorganic fillers and water. If the internal of an arganic insulating materials exist the fault of inorganic fillers, Void and Projecting part, the high voltage concentrates in this place. It leaves a trace about the partical breakdown and this phenomenon develops into the degration of insulating material. This paper researchses that have an effect on the tree phenomenon by the inorganic fillers and water. The results is as follow. (1) The growth of tree are less the influence of inorganic fillers. Because , the constant of water are more. (2) If the tree branches contact the inorganic filler, the advance are relaxation.

• The Journal of Internal Korean Medicine
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• v.25 no.2
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• pp.202-213
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• 2004

Object : Objective: This study was conducted to investigate the anti-cancer effects of Mylabris phalerata (반모) in some kinds of cancer cells. Materials and Methods: Some kinds of cancer cells lines were treated. We used nine kinds of cancer cell lines, such as stomach cancer cells (Kato), lung cancer cells (Calu-1, NCI-H 1395), urinary bladder cancer cells (HS789T), bone cancer cells (Saos-2), brain cancer cells (SK-N-MC), liver cancer cells (Hep-G2), skin cancer cells (Mo-1) and prostate cancer cells (PC-3) with the water decoction of Mylabris phalerata. The histological changes of all cell lines in the media (RPMI-1640) containing the decoction of Mylabris phalerata were observed and we examined cell death assay by trypan blue exclusion testing was examined. Finally, the change of mitochondrial membrane potential was measurd and the inhibitory effect of Mylabris phalerata on cell increase was examined by analyzing the cell cycle. Results: In histologic change all cancer cell lines showed withdrawn and floating appearance that is typical in cellular impairment. Most of the cell lines showed over 50% death rate after 24 hours in trypan blue exclusion tests. Especially the stomach, urinary bladder. brain and liver cell lines showed over 30% death rate after 12 hours. All cell lines treated with Mylabris phalerata were less stained than the control group and the mitochondrial membrane potential in the Mylabris phalerata treated cell lines was markedly lower than that in the control group. The measurement of DNA quantity in all cell lines showed the disappearance of the peak and the thickened left axis, which suggests that all cellular DNA degraded. Conclusion: Mylabris phalerata had cytotoxicity on various kinds of cancer cell lines and the mechanism of that was the impairment of mitochondria by the breakdown of the mitochondrial cell membrane. We propose that this is in part attributable to the destruction of DNA in cancer cells.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.4
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• pp.1120-1128
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• 2004

Zinc ion has both essential and toxic effects on mammalian cells. The results demonstrated that the ability of zinc to act as an inducer of apoptosis in C6 glial cells. Incubation with 0.2 mM ZnCl₂ caused cell death that was characterized as apoptosis by internucleosomal DNA fragmentation, formation of apoptotic bodies, nuclear fragmentation and breakdown of the mitochondrial membrane potential. ZnCl₂-induced apoptosis of C6 glial cells was prevented by the addition of Sibjeondaebo-Tang and antioxidants including reduced glutathione, N-acetyl-L-cysteine. We further confirmed that ZnCl₂ decreased the intracellular levels of GSH as well as generation of H₂O₂ in C6 glial cells. In 2D-electrophoresis, computer-assisted comparative analysis of the respective silver stained spot patterns revealed 3 groups with strongly decreased intensity by ZnCl₂. Whereas, 3 groups with increasing intensity were recovered by Sibjeondaebo-Tang. These results suggest that Sibjeondaebo-Tang may function as an antioxidant against free radicals and be applicable to the treatment of brain cells against oxidative stress.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.327-337
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• 2016

In this study, laboratory hydraulic fracturing tests are carried out to evaluate the effects of the cleavage anisotropy of Pocheon granite. Breakdown pressure is smaller when cracks are generated to the direction of rift plane in constant pressurization rate condition because of higher microcracks density. Besides not only injection rate changes but also the amount of injection pressure for fracture initiation and crack expansion is detected while testing due to internal deformation. Pressurization rate is higher while hydraulic fracture testing with constant injection rate condition in case of the specimen which has rift plane perpendicular to borehole because there are much flow paths to penetrate compared to the specimen which has hardway plane perpendicular to borehole. Observation by X-ray CT scanning shows that almost all of cracks due to hydraulic fracturing are generated to the direction of plane which has higher microcrack density that is rift plane or grain plane.

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.121-124
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• 2013

The incorporation of 90 nm alumina particles into an epoxy matrix to form a composite microstructure is described in present study. It is shown that the use of ultrafine particles results in a substantial change in the behavior of the composite, which can be traced to the mitigation of internal charges when a comparison is made with conventional $Al_2O_3$ fillers. A variety of diagnostic techniques have been used to augment pulsed electro-acoustic space charge measurement to provide a basis for understanding the underlying physics of the phenomenon. It would appear that, when the size of the inclusions becomes small enough, they act cooperatively with the host structure and cease to exhibit interfacial properties. It is postulated that the $Al_2O_3$ particles are surrounded by high charge concentrations. Since $Al_2O_3$ particles have very high specific areas, these regions allow limited charge percolation through $Al_2O_3$ filled dielectrics. The practical consequences of this have also been explored in terms of the electric strength exhibited. It would appear that there was a window in which real advantages accumulated from the nano-formulated material. An optimum filler loading of about 0.5 wt.% was indicated.

• Horticultural Science & Technology
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• v.19 no.1
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• pp.48-53
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• 2001

The study was conducted to examine the storage potential of recently developed oriental pears, 'Kamchun' and 'Chuhwang'. The content of soluble solids of 'Kamchun' pears was above 13.2% but the acidity was below 0.082% at three harvest dates. Although skin browning disorder did not occur in 'Kamchun', about 40% of fruits were affected by core breakdown especially when harvested after middle of October. In contrast, flesh browning was also observed in early harvested fruit. Flesh firmness of 'Chuhwang' was higher than that of 'Kamchun' at harvest as well as after storage. The acidity of 'Chuhwang' was constantly higher than that of 'Kamchun'. Severe skin browning (approximately 80%) occurred in 'Chuhwang' pears regardless of harvest dates. Also, more flesh browning disorder was found in fruit harvested early in the season. Further research is required to determine the optimum harvest date of both cultivars and postharvest managements to inhibit the physiological disorders.