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최충석,김향곤,김동욱 한국안전학회 2004 한국안전학회지 Vol.19 No.1
The PVC insulated flexible cords are used mainly as power supply cords of electric appliance. This electric wire is a stranded wire consisted of dozens of strands. In case stranded wires are disconnected by mechanical stress, it weakens electrically. Finally, the over current flows through stranded wires, and electrical fire occurs. In this study, we analyzed the melting properties of strands by over current, such as melting process, melting current and melting time. And we analyzed that quantity of heat for melting, a cross sectional structure, and surface structure by optical microscope and SEM. As analysis results, melting time decreased as melting current increased. And quantity of heat for melting was low, too. From the cross sectional structure of melted wire, when a melting current low and melting time long, it was found that the dendrite structure grew. However, the dendrite structure is hard to grow because growing time is not enough when a melting current high and melting time short.
김동석,서정호,송승구 한국환경과학회 2000 한국환경과학회지 Vol.9 No.4
The variation of microorganisms (activated sludge, Saccharomyces cerevisiae, Aureobasidium pullulans) caused by the biosorption of Pb^2+ was observed by TEM and microscope. By the TEM observation of S. cerevisiae, the plasmolysis and lysis of cell wall or cell membrane were occurred by the penetration of Pb^2+ into the inner cellular region. However, in the case of A pullulans, the plasmolysis and lysis of cell wall or cell membrane were not occurred because of the prevention of Pb^2+ penetration by the extracelluar polymeric substances (EPS). A flocculation of microorganisms, in the case of A. pullulans, was observed by the Pb^2+ accumulation after 3∼4 h and the color was changed from white to black after 1 day. The flocculation of activated sludge was improved by the accumulation Pb^2+ after 1 h, however, the floc was broken up and the settling efficiency decreased after 1 day.
S. cerevisiae와 A. pullulans를 이용한 수용액 중의 납 제거에서 온도와 pH의 영향
김동석,서정호,우형택,송승구 대구효성가톨릭대학교 응용과학연구소 1997 응용과학연구논문집 Vol.6 No.1
The environmental factors, temperature and pH, were controlled to investigate the effects on the removal of lead in the solution by S. cerevisiae and A. pullulans. The range of experimental temperature was 20℃∼50℃, and that of Ph was 2.5∼6.5 and 2.5∼12, respectively. The optimum temperature of S. cerevisiae and A. pullulans in the removal of lead was 30℃ and 40℃, respectively. And the initial removal rate of lead by, S. cerevisiae was increased according to the increase of temperatue. The variation of the amounts of lead removal by S. cerevisiae according to the variation of temperature was steeper that by A. pullulans. The optimum pH condition was existed on both of the microorganisms, S. cerevisiae and A. pullulans, in our experimental range and that is 4.5 and 9.0, respectively.
정동원,이영석 濟州大學校 産業技術硏究所 2001 산업기술연구소논문집 Vol.12 No.1
This paper presents a semi-analytical method for the prediction of roll force in oval-round (or round-oval) pass rolling sequence most commonly employed in present continuous rod (or bar) mills. Introduced was a concept of a weak plane strain deformation taking into account of the deformation characteristics of workpiece (material) in the roll grooves when the equation for the roll force was formulated. Flow stress (deformation resistance) of the workpiece was characterized by Shidas constitutive equation. Hot rod rolling experiment was conducted to examine the proposed semi-analytical method. Result reveals that using the uvak plane strain deformation condition was found to be appropriate in solving three-dimensional problems. where it was often necessary to reduce the cost of computation by simplification. For low plain carbon steel. the roll forces predicted were in good agreement with those obtained experimentally with the rolling temperature changed (800~ 1100C).
유기용제에 장기간 폭로된 근로자의 정신의학적 기능과 삶의 질
김석재,강순아,유지숙,국승희,윤진상,문재동,이형영 大韓神經精神醫學會 2000 신경정신의학 Vol.39 No.5
연구목적: 본 연구는 Y공단의 제조공정에서 저농도의 유기용제(solvent)에 장기간 노출된 근로자의 정신의학적 기능과 삶의 질을 평가하고자 하였다. 방법: 총 142명의 남성근로자 중 유기용제에 폭로된 군(이하 폭로군) 82명과 폭로되지 않는 군(이하 비폭로군) 60명에게 간이정신진단검사(Symptom Checklist-90-R, SCL-90-R), 인지 및 정신운동성검사 (Critical Flicker Fusion Threshold. CFFT; Choice Reaction Time, CRT;Compensatory Tracking Task, CTT;Digit-Symbol Substitution, DDS) 및 한국판 스미스클라인 비챰 삶의 질 척도(Korean version of the SmithKline Beecham 'Quality of Life' Scale, KvSBQOL) 등을 적용하였다. 두 군간의 비교는 평가치의 평균에 대해 t-검증을 하였고 또한 연령과 학력을 공변인으로한 공변량분석(ANCOVA)을 하였다. 결과: SCL-90-R의 9개 증상 차원과 3개 전체 지표 점수는 두 군이 각각 정상범위였다. 그러나 신체화 (Somatization, SOM), 우울(Depression, DEP), 적대감(Hostility, HOS), 공포불안(Phobic anx-iety, PHOB)의 증상차원과 전체심도지수(Global Severity Index, GSI), 표출증상합계(Positive Symptom Total, PST)의 전체 지표는 폭로군이 비폭로군보다 유의하게 높았다. 인지 및 정신운동성 검사와 삶의 질은 두 군간에 유의한 차이는 없었다. 결론: 이상의 결과는 유기용제가 허용치 이하일지라도 장기간 폭로되는 경우에는 정신의학적 문제를 다소 일으킬 수 있음을 시사하였다. 중심단어:유기용제·근로자·정신건강·정신운동성 기능·삶의 질. Objectives: The aim of this study was to evaluate the psychiatric function and quality of life of the chemical workers who had been exposed to long-term, low-level organic solvents in the Y industrial complex. Method: A total of 144 male workers, of whom 82 were in the exposed group and 60 in the unexposed-control group, were evaluated by using Symptom Checklist-90-R(SCL-90-R), series of neuropsychological tests(critical flicker fusion threshold, CFFT) ; choice reaction time, CRT ; compensatory tracking task, CTT) ; digit symbol substitution test, DSS), and the Korean version of the SmithKline Beecham Quality Of Life scale(KvSBQOL). For the statistical analyses, comparisons of the means of the two groups were performed for each variable with two-tailed t-test as well as ANCOVA including age and education as covariates. Results: For the SCL-90-R, the nine symptom scales and the three global indices were clinically within normal range in both groups. However, the scores on the symptom scales of 'somatization','depression','hostility' and 'phobic anxiety', and those on the global indices of 'global severity index' and 'positive symptom total', were significantly higher in the exposed group than in the unexposed group. In terms of the neuropsychological function and the quality of life, there wes no significant difference between the two groups. Conclusion: These findings suggested that the long-term eposure to mixed organic solvents, even at the low level below the permissible exposure limit, might induce some psychiatric problems. KEY WORDS: Organic solvent·Worker·Mental health·Psychomotor function·Quality of life.