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劉世煥,廉容泰 고려대학교 의과대학 1984 고려대 의대 잡지 Vol.21 No.1
The distribution of ametropia whether refractive or axial in communities is variable according to factors such as ethnicon, age, living environment, and working begavior among others. Among young adults in Korea whose eves are fully matured most ametropia results form myopic refractive errors. It is well known that the prevalence of myopia among college students in Korea is very high, more than 60%. Nevertheless, community based epidemiological research on the causalities of myopia has: not been adequately performed to provide preventive or control measures for myopia for the young in Korea. In view of this, the author attempted an epidemiological study on myopia using the distribution of personal characteristics, and analyzing these factors on a total of 8,555(4,006 in 1981 and 4,549 in 1982) newly enrolled college students of Korea University The summarized results were as follows: 1. A total sample of 115 among 3,337 ametropic cases discovered during screening by visual acuity examination were selected for confirmation by objective refraction tests. One hundred percent of these were discovered to be of the myopic type. Statistical analysis of visual acuity and refraction revealed: R=-3.172+3.407V, r=-0.781, p<0.001 V=0.748+0.179R, r=-0.781, p<0.001 Using simple linear regression; and log(-R)=0.543-1.050V, R^(2)=0.673, F=419.478, p<0.001 logV=-0.042+0.629R, R^(2)=0.760, f=588.559, P<0.001 using logarithmic transformation of exponential curve linear regression, where V= visual acuity, and R=refraction in diopter. 2. The prevalence of ametropia was 65% in 1981 and 73% in 1982. Most of the ametropic cases were predicted to be the myopic type of refractive errors. No significant difference in prevalence by sex was found. However, the rates among males raised in urban areas, and among high economic females found to be significantly higher than other groups. 3. Factors related to causalities of myopia were analysed in terms of work credit, reading behavior, heredity, and food habits as shown in the followings; (1) The correlation between the variables of visual acuity and score on college entrance examinations was V=-0.01S+1.52, r=-0.14, p<0.001(where S=score) Showing a low interpretation capacity but very high reliability. (2) Average distance between the eyes and a book while reading was significantly shorter in myopia than the emetropia group. Distance in the majority of myopia cases were less than 25cm. (3) Attack rate of myopia of siblings born from myopic parents(one or both eyes) was found to be significantly higher(doubled) than that from emetropic parents. This provides substantial evidence that heredity plays an important role in revealing myopia. (4) There were more vegetarians and persons with seriously unbalanced diets in the myopia group. However, rates by visual acuity were too low to be tested for significance. 4. Clinical findings included the relationship between the site of major eye and myopic eye, data on the correction of visual acuity, and onset on visual disturbances. (1) In the majority of the emetropic group the major eye was the right eye, while in persons whose right eyes were myopic the majority had left eyes as the major ones. Similarly, in case where the left eye was myopic the right eye tended to be the major eye. In cases where both eyes were myopic, the pattern followed the emetropic group in that the majority had the right eyes as the major eye. (2) The more severe the myopic status was, the higher the rate of wearing glasses was. About 50% of glasses wearers got their glasses from opticians without an ophthalmologist’s prescription. (3) The onset of visual disturbance in the majority(47%) of myopic cases was during highschool.
유도발열롤의 내부 자속 및 표면 온도 분포의 수치 해석
류세환,원창섭,안형근,한득영 건국대학교 산업기술연구원 2003 건국기술연구논문지 Vol.28 No.-
The induction heating roll is an essential part of calender, which is used for polishing, density increasing, and smoothing of synthetic and natural fibers such as paper, textile, non-woven and artificial leather and has merits of high thermal efficiency and quick response. In this work, internal magnetic flux and temperature distribution on the surface of the induction heating roll were analyzed by using the finite element method. For improving efficiency of the induction heating roll, the structure of internal magnetic flux path was remodeled and we obtained lower temperature differences of the surface of roll.
류세환,김선범,연상원,투르크 아이만,조양희,황방연,안미정,이미경 한국생약학회 2019 생약학회지 Vol.50 No.4
Boehmeria pannosa (Urticaceae) is a perennial herb widely distributed in Korea. In this study, investigation on the constituents of B. pannosa was conducted by chromatographic techniques and spectroscopic analysis. As a result, nine compounds including eight phenolic compounds, 3-hydroxy-1-(4-hydroxyphenyl)propan-1-one (1), b-hydroxypropiovanillone (2), C-veratroylglycol (3), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl)-propan-1-one (4) 2,3-dihydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl) -1-propanone (5), p-coumaric acid (6), 4-hydroxybenzoic acid (7), vanillic acid (8) and one lignan, (-)-(7R,8S)-dihydrodehydrodiconiferyl alcohol (9) were isolated from the EtOAc-soluble fraction of B. pannosa. Among them, compounds 5, 6 and 9 inhibited a-glucosidase inhibitory activity more than 50% at the concentration of 100 μM.
류세환,이호길,안형근,한득영,Ryu, Se-Hwan,Lee, Ho-Kil,Ahn, Hyung-Keun,Han, Deuk-Young 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.1
In this paper, transient characteristics of the Punch Through Insulated Gate Bipolar Transistor (PT-IGBT) have been studied. On the contrary to Non-Punch Through Insulated Gate Bipolar Transistor(NPT-IGBT), it has a buffer layer and reduces switching power loss. It has a simple drive circuit controlled by the gate voltage of the MOSFET and low on-state resistance of the bipolar junction transistor. The transient characteristics of the PT-IGBT have been analyzed analytically. Excess minority carrier and charge distribution in active base region, the rate of anode voltage with time are expressed analytically by adding the influence of buffer layer. The experimental data is obtained from manufacturer. The theoretical predictions of the analysis have been compared with the experimental data obtained from the measurement of a device(600 V, 15 A) and show good agreement.
유한 요소 도구를 이용한 NPT IGBT의 열 특성 해석
류세환(Sehwan Ryu),이명수(Myungsoo Lee),원창섭(Changsub Won),안형근(Hyungkeun Ahn),한득영(Deukyoung Han) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
As the power density and switching frequency increase, thermal analysis of power electronics system becomes imperative. The analysis provides valuable information on the semiconductor rating, long-term reliability. In this paper, thermal distribution of the Non Punchthrough(NPT) Insulated Gate Bipolar Transistor has been studied. For analysis of thermal distribution, we obtained results by using finite element simulator, Ansys and thermal distributions form experiments.