GMA 용접 시스템의 시뮬레이션

유중돈,Yoo, Choong-Don 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.6

GMA 용접 시스템을 시뮬레이션 하기 위한 요소 기술과 문제점에 대하여 간단하게 설명하였다. 현재까지의 연구 결과로부터 GMA 용접 시스템을 해석하는데 필요한 원리 및 기본 방정식은 거의 알려진 상태이지만, 이와 같은 시뮬레이션은 이상적인 조건에서 계산한 결과로서 실제와는 차이가 발생한다. 이와 같은 오차는 실험을 통하여 지속적으로 수정 및 보완되어야 시뮬레이션의 정확도를 향상시킬 수 있으며, 향후 시뮬레이션이 용접 생산성과 품질을 향상시키는 도구로 활용될 수 있기를 기대한다.

Association of lamivudine-resistant mutational patterns with the antiviral effect of adefovir in patients with chronic hepatitis B

Cha, Choong Keun,Kwon, Hyeok Choon,Cheong, Jae Youn,Cho, Sung Won,Hong, Sun Pyo,Kim, Soo-Ok,Yoo, Wang Don Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of medical virology Vol.81 No.3

<P>Adefovir has a potent antiviral activity as a rescue treatment against lamivudine-resistant strains. The aim of this study was to assess the patterns of lamivudine-resistant mutations and their influence on the virologic response to adefovir rescue therapy in patients with lamivudine-resistant chronic hepatitis B. Sixty-seven patients with lamivudine-resistant chronic hepatitis B were treated with adefovir monotherapy. Baseline blood samples were analyzed for lamivudine-resistant mutations via restriction fragment mass polymorphism. Virologic responses, ALT normalization and loss of HBeAg were assessed. Serum HBV DNA levels were measured using real-time PCR at baseline and 24 weeks of adefovir therapy. Of the 67 patients with chronic hepatitis B, 65 patients (97%) had lamivudine-resistant mutations in the YMDD motif [27 (41%) rtM204I, 22 (34%) rtM204V, and 16 (25%) rtM204I/V]. In addition to the YMDD mutations, the rtL180M, rtL80I, and rtV173L mutations were also present in 78%, 43%, and 11% of patients, respectively. The rtM204V mutation always accompanied rtL180M, and rtL80I was always observed in conjunction with rtM204I. Decrease in mean serum HBV did not differ between patients carrying the rtM204I versus rtM204V mutant at week 24 (−3.3 vs. −3.3 log<SUB>10</SUB> copies/ml, respectively; P = 0.303). The presence of the rtL180M, rtL80I, and rtV173L did not significantly affect viral load reduction during adefovir administration. These results demonstrate that the rtL80I mutant is co-selected with rtM204I as a compensatory mutation in the same manner as rtL180M with rtM204V, and that adefovir shows similar antiviral efficacy against all of the evaluated patterns of lamivudine-resistant HBV mutations. J. Med. Virol. 81:417–424, 2009. © 2009 Wiley-Liss, Inc.</P>

소음노출수준과 연령이 연차적 청력변동에 미치는 영향 : Annual Follow-up Studies for Seven Years

양승림,유철인,김옥현,김돈균,이지호,이수일,이충렬,조병만 大韓産業醫學會 1999 대한직업환경의학회지 Vol.11 No.2

This study was carried out to evaluate the effect of noise exposure and age on the changes of group mean hearing threshold level(HTL) over 7-year period. For this purpose, consecutive annual audiometric tests were performed from 1991 to 1997, among 718 male employees of a metal product manufacturing factory. The subjects were divided four groups as follows according to noise level category(NLC). NLC-Ⅰ: officer, exposed noise level was under 60 dB(A) of time weighted average(TWA); NLC-Ⅱ: technical assistant or engineer, they exposed to workplace noise occasionally ; NLC-Ⅲ : worker, exposed noise level was below 85 dB(A) of TWA, wore hearing protection device(earmuff or earplug) ; NLC-Ⅳ: worker, exposed noise level was over 85 dB(A) of TWA, wore hearing protection device(earmuff and earplug). The results were as follows: 1. The improvement of group mean HTL was continued until the fifth year, showing the peak at the third year. The magnitudes of this learning effect were 1.5∼4.6dB. 2. The mean HTL of each age group tended to increase after the third year and the tendency was more prominent at 4000Hz. 3. In noise exposed group(NLC-Ⅱ, Ⅲ, and Ⅳ), mean HTL increased from the third year after decreasing, meanwhile, in noise free group(NLC-Ⅰ), it was few changed for the entire period. Among the noise exposure group, the mean HTL OF NLC-Ⅳ was lower than that of NLC-Ⅲ and NLC-Ⅳ. 4. After learning effect, the mean increase of HTL in noise free group (NLC-Ⅰ) was 0.4∼1.7 dB that suggests aging effect, and that in noise exposure group(NLC-Ⅱ, Ⅲ, and Ⅳ) was 0.9∼4.1 dB that suggests noise effect. 5. Statistical analysis of the general linear model implicated that the effect of age was statistically significant at 500, 3000, 4000 and 6000 Hz, and the effect of noise exposure was statistically significant at all frequencies except 6000Hz. However, the age* noise interaction was not significant at all frequencies. From these results, it was concluded that the effect of age and noise exposure seems to affect the mean HTL independently and these two factors contribute to an additive effect for the mean HTL change. Furthermore, more concerns should be needed for hearing conservation of low level exposures without any specific protection.

A laser-induced thermal spray printing process for phosphor layer deposition of PDP

Lee, Jae Hak,Yoo, Choong Don,Kim, Yong-Seok IOP 2007 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.17 No.2

<P>An efficient printing process, called laser-induced thermal spray printing (LITSP), is introduced in this work to deposit the phosphor layer of the plasma display panel. LITSP is a non-contact printing process, which transfers the phosphor paste from the donor plate to the substrate by the bubble pressure induced by laser heating. The mechanism of the LITSP is analysed through numerical calculation and experiments. The temperature distribution of the donor plate is calculated to explain the paste ejection phenomena, and the proper paste composition and laser heating condition are determined experimentally. The entire phosphor paste is ejected successfully from the etched hole of the donor plate when the etched hole bottom is heated.</P>

Nicotine에 의한 자발성고혈압백서(自發性高血壓白鼠)의 혈장 Cholesterol 농도의 변동

류호충,고상돈,신홍기,김기순,Yoo, Ho-Choong,Koh, Sang-Don,Shin, Hong-Kee,Kim, Kee-Soon 대한생리학회 1982 대한생리학회지 Vol.16 No.2

The present study was undertaken to find out fasting total plasma cholesterol levels of SHR at different phases(labile, established and malignant) in the course of hypertension development and also to investigate effect of nicotine on plasma cholesterol levels of these animals. In nicotine administered group, 2.18 mg/kg nicotine was given daily for six weeks. The results obtained are as follows; 1) Mean total plasma cholesterol levels of SHR at labile, established and malignant phases were $104.6{\pm}3.1\;mg/dl$, $120.8{\pm}2.6\;mg/dl$ and $136.6{\pm}2.5\;mg/dl$ respectively. The total plasma cholesterol level generally increased with age of experimental animals. 2) After administration of nicotine (2.18 mg/kg/day) for six weeks, mean total plasma cholesterol levels of SHR at labile, established and malignant phases were $130.2{\pm}3.1\;mg/dl$, $150.4{\pm}3.3\;mg/dl$ and $166.6{\pm}3.2\;mg/dl$, respectively. The result of present study strongly suggests that nicotine has a positive relationship with plasma cholesterol levels in SHR.

급속 열처리시 실리콘 웨이퍼의 온도분포와 슬립 현상의 해석

이혁,유영돈,엄윤용,신현동,김충기,Lee, Hyouk,Yoo, Young-Don,Earmme, Youn-Young,Shin, Hyun-Dong,Kim, Choong-Ki 대한기계학회 1992 대한기계학회논문집 Vol.16 No.4

본 연구에서는 텅스텐 할로겐 램프를 이용한 급속 열처리 장치로 웨이퍼를 가 열할 때 시간에 따라 변하는 웨이퍼의 2차원 온도 분포와 온도 구배에 의해 발생하는 열응력을 실리콘 웨이퍼의 결정방향에 따라 다른 값을 갖는 탄성계수를 고려하여 계산 하고, 슬립의 발생 시기, 웨이퍼의 가열속도와 슬립량의 관계, 그리고 웨이퍼에 발생 한 슬립의 진전 특성에 대하여 살펴보고 실험결과와 비교하였다. A numerical solution of temperature and thermally induced stress in a wafer during rapid thermal processing (R.T.P) is obtained, and an analysis of onset and propagation of slip is performed and compared with experiment. In order to calculate temperature distribution of a wafer in R.T.P system, heat conduction equation that incorporated with radiative and convective heat transfer model is solved, and the solution of the equation is calculated numerically using alternating direction implicit (A.D.I) method. In dealing with radiative heat transfer, a partially transparent body that absorbs the radiation energy is assumed and this transparent body undergoes multiple internal reflections and absorptions. Two dimensional (assuming plane stress) thermoelastic constitutive equation is used to calculate thermal stress induced in a wafer and finite element method is employed to solve the equation numerically. The stress resolved in the slip directions on the slip planes of silicon is compared with the yield stress of silicon in order to predict the slip. The result of the analysis shows that the wafer temperature at which slip occurs is affected by the heating rate of the R.T.P system. It is observed that once slip occurs in the wafer, the slip grows.

Spin-on Glass를 이용한 실리콘과 유리의 저온 접합 공정

이재학,유중돈,Lee Jae-Hak,Yoo Choong-Don 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.6

Low temperature bonding of the silicon and glass using the Spin-on Glass (SOG) has been conducted experimentally to figure out the effects of the SOG solution composition and process variables on bond strength using the Design of Experiment method. In order to achieve the high quality bond interface without rack, sufficient reaction time of the optimal SOG solution composition is needed along with proper pressure and annealing temperature. The shear strength under the optimal SOG solution composition and process condition was higher than that of conventional anodic bonding and similar to that of wafer direct bonding.

힘-변위 모델을 이용한 펄스 GMAW의 해석

이재학,유중돈,Lee, Jae-Hak,Yoo, Choong-Don 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.1

In order to determine the One-Drop One-Pulse(ODOP) condition of the pulsed gas metal arc(GMA) welding, the drop detaching phenomenon during the peak time is investigated using the force-displacement model. The drop detaching criterion is established based on the displacement of the pendant drop, and the forces exerted on the drop are calculated using the Modified Force Balance Model(MFBM). The effects of wire melting on the drop size and force are included in the force-displacement model. While the peak current has most significant effects on the drop detaching time, the initial drop mass prior to the peak time also influences drop transfer. The calculated results show good agreements with the experimental data, which implies that the ODOP condition can be predicted using the force-displacement method.

Force–displacement model for analysis of pulsed-GMAW

Arif, Nabeel,Lee, Jae Hak,Yoo, Choong Don Institute of Physics [etc.] 2009 Journal of physics. D, applied physics Vol.42 No.3

<P>A force–displacement model (FDM) is introduced in this work to analyse pulsed gas metal arc welding (GMAW). The drop detaching criterion is established based on the displacement of the pendant drop instead of the previous force balance criterion. The displacement of the drop is calculated by integrating the acceleration of the drop, and the force exerted on the drop is predicted using the modified force balance model coupled with wire melting. When the peak current, base current and time of pulsed-GMAW are given, the peak time for the one-drop one-pulse condition is determined using the FDM. While the peak current has the most significant effect on drop detachment, the initial drop mass prior to the peak time also influences the drop transfer. The FDM is applied to the dc as well as pulsed-GMAW, and the calculated results show good agreement with the experimental data.</P>

투기 ·기구운동선수들의 스포츠 상해에 관한 조사 연구 : 慶熙大學運動選手를 中心으로

梁幸錫,宋胤碩,金泰運,朴忠緖,宋禹圭,孫斗玉,金斗煥,池男容,方永鎭,金裕賢,禹善弼,朴英震,金熙圭,安德均,金泰勳,全廷祐,金亨燉,崔名鎭 慶熙大學校 體育科學大學 1992 體育科學論叢 Vol.- No.5

The pmrpose of this study was to Collect the date concerning game athller. For the purpose, 144k university athlete were selectel and investigated on the injufunite symton and caused. 1. In was of skin injunier blister was necooded the higkert on the occarion of fregreucy. 2. In was of muscle iujunier bruire was the higleet. 3. In was of bore injunrer brurie was also the higaleet. 4. In was of joint spualrn was the higaleet occasions. 5. In was of nerve-sensatian injunrer werve pain was shoovn as the hihleat occatians. 6. In the study injunrer time most othleiar were injuited during tIne practie time. 7. In was of season mist athletes were injunrer during the wiater time. 8. many athletes (58.3%) wew injuried aftenovn practice. 9. The most important marson for the injurier were beliebed as lack of warimup and after the injuries waches were mostey the person for quint aid. they weed moassgae and physical therapy among the mazy proceduver.