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CHEMICAL VAPOR DEPOSITION에 依한 炭素/炭素 複合材料의 高密度化
도은성,주혁종 忠南大學校 産業技術硏究所 1990 산업기술연구논문집 Vol.5 No.1
This study was carried out to investigate the effects of the reactor conditions and some structural charactersistics of the substrates on densification of C/C Composites by Chcmical Vapor Deposition, using Isothermal process and propylene as a carbon source gas. With increasing temperature of the reactor, the rate of deposition was also increased, but above some temperature the pyrolytic carbon deposition occured more on the surface of substrates than on the inside of pores. The deposition rate was changed increasingly as the concentration of the source gas diluted with nitrogen was increased, but above some concentration the low density-sooty carbon was formed in the reactor. The effect of the flow rate of diluted gas was similar to that of the concentration. The total mass gain was grown up according as the reaction time used on CVD was grown up, but the mass gain ratio was become smaller. The results affected only by the initial density or initial porosity of the substrates were uncertain. The optimum conditions in this system were as follows: temperature of reactor :800℃ concentration of carbon source gas :20%vol. flow rate of carbon source gas :13.2cc/min
오영상,이은우,정종혁,문승원,김수현,김동한,양혁승,박정환,박경옥,강성수,이영직 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.2
Tracheobronchopathia osteoplastica is a rare disorder of unknown cause characterized by the projection of numerous bony or cartilaginous submucosal nodules into the tracheobronchial lumen with sparing of the posterior membranous portion of tracheobronchial tree. In the past, most of the cases were diagnosed as secondary finding at autopsy. Nowaday, the key component of the evaluation is flexible fiberoptic laryngoscopy and bronchoscopy, which typically demonstrates irregular spicules of subrnucosal bone and cartilage projecting into the tracheobronchial lumen and causing various degrees of airway obstruction. A 45 years old man was visited Sunchon St. Carollo hospital due to discomfort on throat. We saw several nodules just below vocal cord via laryngoscope. The computed tomography revealed multiple small calcified nqdules on trachea and both main bronchi. Pathologic finding of bronchoscopic biopsy showed abnormal proliferation of bony and cartilagious nodules in the tracheal submucosa. These fingdings were consistent with tracheobronchopathia osteoplastica. We report here on a case of tracheobronchopathia osteoplastica with review of literature.
Rifampicin에 의한 것으로 추정되는 위막성 대장염1예
김수현,이은우,정종혁,문승현,김동한,양혁승,오영상,김호동,김도현,박혁,박정환,박경옥,이영직 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.2
Pseudomembranous colitis, caused by altering the normal colonic flora and allowing the multiplication of Clostridium difficile, is an deleterious adverse effect of antibiotics. But it is rarely reported by rifampicin. Rifampicin is one of the first line drug in the treatment of tuberculosis and many patients are exposed to its potential adverse effects. We experienced a patient that had abdominal discomfort and hematochezia due to pseudomembranous colitis after receiving antituberculous medication, and which was probably caused by rifampicin. A 82 years old man was admitted with abdominal discomfort and hematochezia for one week. On the past history he had been diagnosed as endobronchial tuberculosis about 4 months ago. Colonoscopy revealed multiple discrete whitish mucosal lesion on rectosigmoid colon, and histologic findings were consistent with pseudomembranous colitis. The antituberculous agents were discontinued and vancomycin was administered. The patient's symptoms were resolved within several days. There was no recurrence after reinstitution of the antituberculous agents excluding rifampicin. We report here on a case of pseudomembranous colitis probably due to rifampicin.
결정형 규산분진에 폭로된 섬유모세포의 자가증식 : Evaluation by H₂O₂and PDGF-AA 와 TGFβ
안병용,김경아,문제혁,정진숙,김은경,임영 대한산업의학회 2000 대한직업환경의학회지 Vol.12 No.2
Objectives : The aim of this study is to find out the activity of autoproliferation of rat fibroblast exposed to crystalline silica and the role of mediators secreted from rat fibroblast. Methods : The effect of α-quartz on production of growth factor (platelet-derived growth factor-AA and transforming growth factorβ) from rat fibroblasts were evaluated by ELISA and immunocytochemical analysis. Gene expression of these growth factors in rat fibrobast exposed to crystalline silica was evaluated by RT-PCR. Furthermore, fibroblast proliferation by culture supernatant of rat fibroblast was assayed by the neutral red test. Results : The amounts of H2O2 and growth factors synthesized in rat fibroblasts were significantly increased by the stimulation of crystalline silica (α-quartz) , which showed the dose-dependent manner to the concentration of α-quartz with the maximum response at the dosage of 100 ㎍/㎠. The result of RT-PCR demonstrated that α-quartz induced gene expression of PDGF-AA and TGFβ in rat fibroblast. We also found that supernatant of α-quartz-cocultured rat fibroblast induced a significant proliferation of fibroblast. Conclusion : Crystalline silica directly induce functional change In fibroblast such as increased release of reactive oxygen species and growth factors. The products of these functional change promote fibroblast proliferation via autocrine loop.
Low-power CMOS Front-end ROIC using Inverter-feedback RGC TIA for 3-D Flash LADAR Sensor
Eun-Gyu Lee,Jae-Eun Lee,Han-Woong Choi,Kyeong-Hyeok Lee,Bang Chul Jung,Choul-Young Kim 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.1
This work proposes a pixel architecture for a front-end readout integrated circuit (ROIC) using an inverter-feedback regulated-cascode (RGC) trans-impedance amplifier (TIA) for the focal plane array of a three-dimensional flash laser detection and ranging sensor. Although there are various TIA topologies for wideband operation, the inverter-feedback RGC structure is adopted owing to the importance of the small area and low power consumption of the array configuration. A single pixel also consists of an overcurrent protector, comparator, amplitude-to-voltage converter, and time-to-voltage converter to sense the range and intensity information of the remote object. A single pixel dissipates a power of 5.28 mW from a 3-V supply. The receiver achieves an input referred noise current of 7.5 pA/√Hz with a bandwidth of 453 MHz, transimpedance gain of 76 dB · >, and a maximum detection range of 60 m with a 3.8-ns pulse. A single pixel is developed within 100 μm × 100 μm and the total die size, including the I/O pads, is 2200 μm × 2200 μm.
Breakdown Characteristics of SF_6 and Liquefied SF_6 at Decreased Temperature
Eun-Hyeok Choi,김기채,이광식 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.5
SF_6 gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the SF_6 gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of SF_6 gas (SF_6) and SF_6 liquid (LSF_6) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of SF_6 gas. The breakdown characteristics are classified into three stages,namely the gas stage of SF_6 according to Paschen's law, the coexisting stage of SF_6 gas with liquid in considerable deviation at lower temperature, and the stage of LSF_6 and remaining air. The result shows that the ability of the LSF_6 insulation is higher than the high-pressurized SF_6. Moreover, it reveals that the breakdown characteristics of LSF_6 are produced by bubble-formed LSF_6 evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of LSF_6 is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for LSF_6. It provides fundamental data not only for SF_6 gas useless equipment but also for electric insulation design of hightemperature superconductor and cryogenic equipment machinery, which will be developed in future studies.
Breakdown Characteristics of SF6 and Liquefied SF₆ at Decreased Temperature
Eun-Hyeok Choi,Ki-Chai Kim,Kwang-Sik Lee 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.5
SF6 gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the SF6 gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of SF6 gas (SF6) and SF6 liquid (LSF6) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of SF6 gas. The breakdown characteristics are classified into three stages, namely the gas stage of SF6 according to Paschen"s law, the coexisting stage of SF6 gas with liquid in considerable deviation at lower temperature, and the stage of LSF6 and remaining air. The result shows that the ability of the LSF6 insulation is higher than the high-pressurized SF6. Moreover, it reveals that the breakdown characteristics of LSF6 are produced by bubble-formed LSF6 evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of LSF6 is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for LSF6. It provides fundamental data not only for SF6 gas useless equipment but also for electric insulation design of hightemperature superconductor and cryogenic equipment machinery, which will be developed in future studies.