• 한국정보전자통신기술학회논문지
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• 제10권1호
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• pp.31-37
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• 2017

본 논문에서는 고출력 무전극 램프 시스템 개발에서 램프 내에 가스종류, 혼합비, 압력과 방전관 사이즈, 아말감종류 및 혼합비, 페라이트코어의 특성등의 최적화를 통한 램프 설계 부분을 연구하였다. 또한 구동방식에 따른 점등회로의 역율 및 효율개선, 파형이나 인가 주파수에 따른 특성 분석을 통한 점등회로설계 부분 등을 고려하였으며, 최종적으로 주변 환경을 고려 무전극 등기구 설계를 수행 하였다. 고출력 무전극 램프용 점등회로의 설계를 통한 특성분석을 진행하여 개선 보완을 통하여 효울을 향상 시켰으며 점등회로의 구동주파수에 따른 무전극 램프의 광학적 특성 및 시스템 영향을 확인한 결과, $7{\sim}10^{\circ}C$ 정도 낮은 특성의 135kHz로 구동하는 점등회로를 최적화하였다. 실험적으로 Peak Noise 발생으로 인한 FET(Q3,Q4) demage 현상을 개선하였다. 최종적으로 무전극램프용 점등회로 최종 설계도을 통해 약 2~3배 이상의 수명을 확보함으로써 안정기의 신뢰성 및 무전극 램프 시스템의 효율이 높음을 알 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.135-135
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• 2015

Tubes are of extreme importance in industries as for fluid channels or wave guides. Furthermore, some weapon systems such as cannons use the tubes as gun barrels. To increase the service life of such tubes, a protective coating must be applied to the tubes' inner surface. However, the coating methods applicable to the inner surface of the tubes are very limited due to the geometrical restriction. A small-diameter cylindrical magnetron sputtering gun can be used to deposit coating layers on the inner surface of the large-bore tubes. However, for small-bore tubes with the inner diameter of one inch (~25 mm), the magnetron sputtering method can hardly be accommodated due to the space limitation for permanent magnet assembly. In this study, a new approach to coat the inner surface of small-bore tubes with the inside diameter of one inch was developed. Instead of using permanent magnets for magnetron operation, an external electro-magnet assembly was adopted around the tube to confine the plasma and to sustain the discharge. The electro-magnet was operated in pulse mode to provide the strong axial magnetic field for the magnetron operation, which was synchronized with the negative high-voltage pulse applied to the water-cooled coaxial sputtering target installed inside the tube. By moving the electro-magnet assembly along the tube's axial direction, the inner surface of the tube could be uniformly coated. The inner-surface coating system in this study used the tube itself as the vacuum chamber. The SS-304 tube's inner diameter was 22 mm and the length was ~1 m. A water-cooled Cu tube (sputtering target) of the outer diameter of 12 mm was installed inside of the SS tube (substrate) at the axial position. The 50 mm-long electro-magnet assembly was fed by a current pulse of 250 A at the frequency and pulse width of 100 Hz and 100 usec, respectively. The calculated axial magnetic field strength at the center was ~0.6 Tesla. The central Cu tube was synchronously driven by a HiPIMS power supply at the same frequency of 100 Hz as the electro-magnet and the applied pulse voltage was -1200 V with a pulse width of 500 usec. At 150 mTorr of Ar pressure, the Cu deposition rate of ~10 nm/min could be obtained. In this talk, a new method to sputter coat the inner surface of small-bore tubes would be presented and discussed, which might have broad industrial and military application areas.

• 대한전자공학회논문지SD
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• 제38권8호
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• pp.13-19
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• 2001

분자선 결정 성장법을 이용하여 성장된 서로 다른 장벽층의 두께를 갖는 $Al_{0.3}Ga_{0.7}N$ heterojunction field effect transistors (HFETs) 를 제작하여 그 특성을 비교, 관찰하였다. $Al_{0.3}Ga_{0.7}N$층의 두께에 따른 특성의 비교로부터 최적의 2 차원 전자개스 (2 dimensional electron gas) 를 가질 수 있는 $Al_{0.3}Ga_{0.7}N$/GaN HFET 소자 구조를 얻을 수 있었다. $L_g=0.6$ ${\mu}m$ 와 $W_g=34\;{\mu}m$ $Al_{0.3}Ga_{0.7}N$/GaN (20 nm/2 mm) HFET에서 Imax ($V_{gs}=1\;V$) 와 $G_{m,maX}$는 각각 1.155 A/mm 및 250ms/${\mu}m$ 이었으며 $F_t=13$ GHz 와 $F_{max}=48$ GHz의 우수한 고주파 특성을 얻을 수 있었고 2 inch 기판상에서 제작된 소자들은 5% 이하의 매우 균일한 DC 특성을 나타내었다. 이와 더불어 게이트-드레인 간의 간격에 따른 소자의 특성을 관찰함으로서 소자의 항복전압과 고주파 특성과의 상관관계를 고찰하였다.

• Nutrition Research and Practice
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• 제10권5호
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• pp.516-523
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• 2016

BACKGROUND/OBJECTIVES: This study was conducted to examine relationships between dietary habits and intakes of antioxidants and B vitamins and the risk of ischemic stroke, and to compare dietary factors according to the presence of cerebral artery atherosclerosis and stroke subtypes. SUBJECTS/METHODS: A total of 147 patients and 144 control subjects were recruited consecutively in the metropolitan area of Seoul, Korea. Sixty participants each in the case and control groups were included in analyses after 1:1 frequency matching. In addition, 117 acute ischemic stroke patients were classified into subtypes according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) guidelines. Dietary intake was measured using a semi-quantitative food frequency questionnaire composed of 111 food items and plasma lipid and homocysteine levels were analyzed. RESULTS: When compared with control subjects, stroke patients had unfavorable dietary behaviors and lower intakes of fruits ($73.1{\pm}83.2g$ vs. $230.9{\pm}202.1g$, P < 0.001), vegetables ($221.1{\pm}209.0g$ vs. $561.7{\pm}306.6g$, P < 0.001), and antioxidants, including vitamins C, E, $B_6$, ${\beta}$-carotene, and folate. The intakes of fruits, vegetables, vitamin C, and folate were inversely associated with the risk of ischemic stroke after adjusting for confounding factors. Intakes of vegetables, vitamins C, $B_6$, $B_{12}$, and folate per 1,000 kcal were lower in ischemic stroke with cerebral atherosclerosis than in those without. Overall vitamin $B_{12}$ intake per 1,000 kcal differed according to the TOAST classification (P = 0.004), but no differences among groups existed based on the post-hoc test. CONCLUSIONS: When compared with control subjects, ischemic stroke patients, particularly those with cerebral atherosclerosis, had unfavorable dietary intake, which may have contributed to the development of ischemic stroke. These results indicate that proper dietary recommendations are important for the prevention of ischemic stroke.

• Genomics & Informatics
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• 제15권3호
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• pp.87-97
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• 2017

Multiple myeloma (MM) is a malignant disease caused by an abnormal proliferation of plasma cells, of which the prognostic factors include chromosomal abnormality, ${\beta}$-2 microglobulin, and albumin. Recently, the term chromothripsis has emerged, which is the massive but highly localized chromosomal rearrangement in response to a one-step catastrophic event. Many studies have shown an association of chromothripsis with the prognosis in several cancers; however, few studies have investigated it in MM. Here, we studied the association between chromothripsis-like patterns and treatment resistance or prognosis. First, we analyzed nine MM cell lines (U266, MM.1S, RPMI8226, KMS-11, KMS-12-BM, KMS-12-PE, KMS-28-BM, KMS-28-PE, and NCI-H929) and bone marrow samples of four patients who were diagnosed with MM by next-generation sequencing-based copy number variation analysis. The frequency of the chromothripsis-like pattern was observed in seven cell lines. We analyzed the treatment-induced chromothripsis-like patterns in KMS-12-BM and KMS-12-PE cells. As a result, breakpoints and chromothripsis-like patterns were increased after drug treatment in the relatively resistant KMS-12-BM. We further analyzed the patients' results according to the therapeutic response, which was divided into sensitive and resistant, as suggested by the International Myeloma Working Group. The chromothripsis-like pattern was more frequently observed in the resistant group. In the sensitive group, the frequency of the chromothripsis-like pattern decreased after treatment, whereas the resistant group showed increased chromothripsis-like patterns after the treatment. These results suggest that the chromothripsis-like pattern is associated with treatment response in MM.

• 한국광학회지
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• 제21권1호
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• pp.33-37
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• 2010

본 연구에서는 전도성이 매우 높은 탄소나노튜브 박막을 제작하고 테라파 영역에서의 광학상수를 측정하였다. 탄소나노튜브박막은 스핀코팅법 또는 진공여과법을 이용하여 연성플라스틱 기판 위에 증착되었다. 테라파 영역의 전자파 투과율은 박막의 두께조절을 통해 가능하며, 산처리 등의 후속공정을 통해서도 조절이 가능하다. 시분해 테라파 투과파의 진폭과 위상 측정을 통해유전상수를 포함한 광학상수의 스펙트럼을 측정하였다. 이를 통해 탄소나노튜브 박막이 Drude 자유전자 모델에 잘 부합하며, 높은 플라즈마 진동수를 가지는 등, 우수한 금속의 특성을 가지고 있음이 밝혀졌다. 또한 산처리 전후 유전상수가 변화하는 것을 직접확인할 수 있었다. 마지막으로 셀룰로즈 멤브레인에 증착된 CNT 필름의 경우엔 기판의 효과가 제거된 광학계수 측정이 가능함을 보여준다.

• Clinical and Experimental Pediatrics
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• 제52권3호
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• pp.370-375
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• 2009

목 적 : 터너증후군 환자에서 대사증후군과 심혈관 질환의 위험성이 높다. 성인 연령의 터너증후군 환자들에서 대사증후군 관련요인을 분석하고, 인슐린 저항성의 대사위험성을 알아보기 위한 연구를 시행하였다. 방 법 : 43명의 성인 터너증후군 환자에서 대사증후군의 빈도와 관련 요인 값들을 분석하였다. HOMA-IR을 이용하여 인슐린 저항성군과 비저항성군으로 분류한 후 각 집단을 분석하고, HOMA- IR과 대사 증후군 관련요인의 상관관계를 알아보았다. 결 과 : 대사증후군은 터너증후군 환자의 7%에서 보였고 각 항목에 대해서 인슐린 저항성은 16.3%, 복부 비만이 15.4%, 고중성지방이 2.3%, 저HDL 콜레스테롤이 9.3%였고, 고혈압이 36.8 %였다. 체질량지수, 허리둘레, 공복 혈당, HOMA-IR, 수축기 혈압은 인슐린 저항성군에서 의미 있게 높게 나왔으며, HOMA-IR은 체질량지수, 허리둘레, 공복 혈당, 수축기 혈압과 양의 상관관계를 보였다(P<0.05). 결 론 : 터너증후군 성인 환자들에서 대사증후군의 위험성이 있으며, 인슐린 저항성과 대사증후군 관련요인 간에 상관관계를 보인다. 터너증후군 환자들에게서 대사관련 요인을 일정기간 마다 검사하여 대사증후군 또는 인슐린 저항성으로의 진행여부를 감시하고 심혈관 합병증을 예방하는 것이 필요하다.

• 한국자기학회지
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• 제10권6호
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• pp.269-273
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• 2000

Fe-l7Cr-2M(M=Si, Nb, Mo)합금분말을 Electrode Rotating Atomizer로 제조한 후 성형하여 소결한 시편의 첨가원소, 성형 압력 및 소결온도 에 따른 교류자기특성의 변화를 체계적으로 조사하였다 제조된 Fe-l7Cr-2M(M=Si, Nb, Mo) 합금분말의 형상은 구형이며, 포화자화값은 Mo와 Nb을 첨가한 Fe-l7Cr-2Mo과 Fe-l7Cr-Nb의 경우 약 155 emu/g로 Si을 첨가한 경우보다 크다. 성형압력 12 ton/$cm^2$, 소결온도 1200 $^{\circ}C$에서 제조된 Fe-l7Cr-2M(M=Si, Nb, Mo)합금분말 소결체의 진폭비 투자율은 주파수, f=1 kHz에서 3~5 Oe의 인가자장 범위에서 가장 크다. 전력손실은 인가자장 H$_{a}$ =5 Oe, 주파수 f=1 kHz에서 Fe-l7Cr-2Nb 경우 40 mW/cc로 Si이나 Mo를 첨가한 경우 보다 약 1/2값을 나타낸다.

• 한국재료학회지
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• 제2권5호
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• pp.353-359
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• 1992

열산화법과 PECVD법으로 p-type (100) Si 기판위에 T$a_2O_5$ 박막을 형성시킨 후 A1/T$a_2O_5$/p-Si capacitor를 제작하였다. 제작된 시편의 제반 물성은 XRD, AES, high frequency C-V analyzer, I-V meter, TEM 등을 사용하여 분석하였다. XRD 분석을 통해 T$a_2O_5$ 박막은 비정질임이 확인되었으며 65$0^{\circ}C$ 열처리의 경우에는 hexagonal $\delta$-T$a_2O_5$ 상으로 결정화가 일어남을 확인할 수 있었다. AES spectrum의 분석을 통해 T$a_2O_5$ 박막의 조성이 2:5의 stoichiometry에 근접해 있음이 관찰되었다. 열산화법에 의해 제작된 T$a_2O_5$는 산화온도 60$0^{\circ}C$의 조건에서 누설전류 5${ imes}10^{-6}$A/c$m^2와 유전상수 31.5로 가장 좋은 성질을 나타냈으며, PECVD로 제작한 T$a_2O_5$는 RF Power가 0.47W/c$m^2일 때 2.5${ imes}10^{-5}$A c$m^2and 24.0으로 가장 좋은 특성을 나타내었다. TEM 분석을 통해 제조된 박막과 계면을 관찰하였다.

• 생물정신의학
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• 제6권2호
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• pp.209-218
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• 1999

Objectives : The aims of this study were to discriminate the clinical differences, to measure the estrogen and homovanillic acid levels, to evaluate a correlation between estrogen and homovanillic acid, and to identify an association of cognitive deficit with estrogen and homovanillic acid among male and female schizophrenics. Methods : In addition to the structured interviews, the plasma estrogen levels by radioimmunoassay and the homovanillic acid levels by HPLC were measured in 20 male and 21 female schizophrenics as well as 10 healthy male and 9 female controls. Results : 1) The plasma estrogen levels were higher in females than males, and significantly higher in female schizophenics than female controls. The homovanillic acid levels were higher in female schizophrenics than female controls, and were lower in male schizophrenics than male controls. 2) The onset age seemed to be earlier in male schizophrenics, and the frequency of admission, duration of antipsychotic drug administration, dosage of antipsychotics and duration of illnesses were more in males. The estrogen and homovanillic acid levels were significantly higher in female schizophrenics. 3) The estrogen levels had a significant positive correlation with sex, age and onset age, while the homovanillic acid levels did with sex. However, estrogen were not correlated with homovanillic acid levels. 4) The estrogen and homovanillic acid levels were not significantly different between male and female schizophrenics with cognitive deficits. In the schizophrenic patients without cognitive deficits, the estrogen levels were significantly higher in females, while there were no significant sex differences in homovanillic acid. 5) In the male and female schizophrenics predominantly with negative symptoms, there were no significant differences in estrogen and homovanillic acid levels. In those predominantly with positive symptoms, the estrogen levels were significantly higher in females, while there were no sex differences in homovanillic acid levels. 6) In schizophrenics with undifferentiated subtype, the estrogen and homovanillic acid levels were significantly higher in females. In those with paranoid or disorganized subtypes, the estrogen levels were significantly higher in females, while there were no sex differences in the homovanillic acid levels. 7) The mean values of PANSS-negative, PANSS-total, PANSS-CF, MMSE-K and estrogen levels were significantly higher in male schizophrenics with cognitive deficits. The mean values of illness duration, CGI, PANSS-positive, PANSS-negative, PANSS-total, PANSS-CF and MMSE-K were significantly higher in female schizophrenics with cognitive deficits. 8) The variables which showed significant correlation with cognitive deficits were PANSS-negative, PANSS-total, PANSS-CF, MMSE-K and estrogen levels in male schizophrenics. The variables which showed significant correlation with cognitive deficits were subtypes, onset age, illness durataion, CGI, PANSS-positive, PANSS-negative, PANSS-total, PANMSS-CF and MMSE-K in female schizophrenics. The estrogen levels were significantly correlated with admission frequencies, history of antipsychotic administration, duration of antipsychotic administration and cognitive deficits in male schizophrenics, while age were not correlated with in females. The homovanillic acid levels had a significant correlation with subtypes and onset age in male schizophrenics, while there were no correlation among variables in females. Conclusions : Although the plasma concentrations of estrogen and homovanillic acid in female schizophrenics were significantly higher than males, we could not find an association between them. Furthermore, the various factors affecting on the cognitive deficits, estrogen and homovanillic acid levels seemed to be somewhat different according to sex.