• 한국콘텐츠학회논문지
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• 제9권11호
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• pp.247-253
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• 2009

본 연구는 국소온열요법(Local Hyperthermia)에 사용되는 발열체(Thermo-rod)의 온도에 따른 세포성장률의 변화를 관찰하고자 한다. 연구에 사용된 발열체는 듀플렉스 스테인리스 강(Duplex Stainless Steel)을 이용하여 개발되었다. 세포성장률을 관찰하기 위하여 CPAE세포와 Osteoblast세포를 이용하였다. 각각의 세포를 well에 분주 후 3일, 6일, 9일, 12일, 15일 동안 배양만 한 군을 대조군으로 하고 well에 발열체를 식립 후 세포를 분주하여 3일 간격(3일, 6일, 9일, 12일, 15일)으로 하루 30분 유도가열을 실시하여 15일 간 배양한 군을 시험군으로 하였다. CPAE세포와 Osteoblast세포의 성장률을 관찰한 결과 두세포 모두 3일의 대조군과 시험군 모두 세포 성장률이 급격히 상승하다 6일의 대조군과 시험군 모두 급격히 감소하고 9일과 12일 그리고 15일의 대조군과 시험군의 성장률은 불규칙하게 감소하였다. 이러한 성장률 관찰 결과 두종의 세포 모두 약 $41^{\circ}C$의 온도를 가한 시험군과 온도를 가하지 않은 대조군의 차이가 없다. 따라서 CPAE세포와 Osteoblast세포는 발열체에 의한 온도(약 $41^{\circ}C$)에 영향이 없는 것으로 판단된다.

• 한국패류학회지
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• 제25권2호
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• pp.113-119
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• 2009

본 연구는 2008년 3월 24일에 전남 영광군에서 채취한 말백합 어미 1,200 마리를 확보하여 수온조절 (20, 25, $30^{\circ}C$ 및 자연해수) 에 의한 인위적인 성 성숙을 유도하였으며, 성숙 유도된 어미로부터 생존율, 비만도, 생식소 및 성숙 소요일수를 조사하였다. 말백합 어미의 연체부지수는 사육초기에는 다소 낮아지는 경향이 있었으나, 5월 중순부터 증가하는 경향이 있었으며, 시험 종료 시에는 연체부 지수가 급격히 증가하였으며, 각부용적지수도 유사한 경향을 나타내었다. 말백합의 생식소 발달단계는 비활성기, 초기 활성기, 후기활성기, 완숙기, 방출 및 퇴화기의 5 단계로 구분할 수 있는데, 시험 개시일인 3월 25일경은 전기 활성기였으며, 시험 종료일인 6월 30일에는 수온별로 다양한 생식주기를 나타내었다. 시험 종료 시 성숙 유도율은 $30^{\circ}C$ 실험구에서 46.0%로 가장 높았고, $15^{\circ}C$ 실험구 35.0%, 자연수온 18.0% 및 $20^{\circ}C$ 실험구 12.0%로 순으로 나타났으며, 시험 기간 중 생존율은 전 구간이 90% 이상으로 나타났다. 사육수온을 20, 25, $30^{\circ}C$ 및 자연수온으로 성숙 시험한 결과, 암컷의 경우 $30^{\circ}C$ 실험구가 성숙이 가장 빨랐고, 수온이 낮을수록 늦은 경향이었으며, 수컷도 비슷한 경향을 나타내었다. 말백합의 수온별 어미성숙은 $20^{\circ}C$ 보다는 수온이 높은 실험구인 25, $30^{\circ}C$에서 성숙 유도율이 높게 나타났다.

• 대한의생명과학회지
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• 제11권3호
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• pp.343-347
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• 2005

Bambusae caulis in Liquamen is one of the important herbal medicine produced by heating bamboo indirectly and is used for treatment of stroke, hypertension, and diabetes etc. Recently the mechanism of clinical effects on Bambusae caulis in Liquamen has been studied. This experiment was conducted to confirm the clinical effects of Bambusae caulis in Liquamen on type 1 diabetes and its related mechanism. We divided C57BL/6 mice into 3 groups and induced them to be type 1 diabetes by injection of streptozocin into peritoneum. The dosage of each group was 150 mg/kg once only, 140 mg/kg once only and 40 mg/kg for 5 days respectively. The two groups injected streptozocin for once took orally Bambusae caulis in Liquamen after the induction of diabetes, and the other one group was given Bambusae caulis in Liquamen during the diabetes inducing period. As the result, the two diabetes-induced groups showed blood glucose decreasing effect by Bambusae caulis in Liquamen on an average, but they didn't show the signiftcant differences statistically. But Bambusae caulis in Liquamen showed the anti-diabetic effect suppressing blood sugar rising trend during the diabetes inducing peried (P<0.05). The anti-oxidative effect of Bambusae caulis in Liquamen was measured with the hypoxanthine/xanthine oxidase (HX/XOD) system. The quantity of ROS was measured using DCFDA reagent indirectly. As the result, $10\%$ solution of Bambusae caulis in Liquamen showed anti-oxidative effect by scavenging $93.4\%$ superoxide as compared with control group. It is suspected that the anti-oxidative effect of Bambusae caulis in Liquamen suppressed the increase of blood glucose in the diabetes-inducing group. These results could be useful data to understand the effect of Bambusae caulis in Liquamen on type 1 diabetes and type 1 diabetes developing because ROS were closely connected with the induction and complications of diabetes.

• 한국패류학회지
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• 제20권1호
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• pp.75-84
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• 2004

Reproductive cycle, the condition index, sex ratio of the Pacific oysters, Crassostrea gigas were investigated by histological and morphometric data. The specimens were collected in the two oyster farms of Geoje and Namhae, Gyeongsangnam-do, Korea, from November 1995 to October 1996. Growth of shell length in two regions was similar, but growth of total weight of the oyster in Namhae was faster than that in Geoje oyster farm. The spawning periods in female and male clams were from July to October in Geoje and from June to October in Namhae oyster farm. Ripe oocytes were approximately 50 m in diameter. The reproductive cycle of in females and males in Geoje and Namhae oyster farms can be divided into five successive stages: early developing, late developing, ripe, partially spawned and spent/inactive. Monthly changes in gonad developmental phases showed somewhat different patterns between female and male clams except for the spawning period. On the whole, however, monthly changes in the gonad developmental phases showed a similar pattern in the same sex. The sex ratios of females to males in Geoje and Namhae oyster farms were not significantly different from a 1:1 sex ratio ($x^2$ = 0.55 (p > 0.05) in Geoje and $x^2$ = 0.27 ( p > 0.05) in Namhae). Artificial induction of maturation by heating of adult oysters (two-year-old) was investigated from 17 January to 18 March in 1996. Maturity at the fixed water temperature group of $20^{\circ}C$ was 80%, it showed the highest maturity of experimental groups cultured for five weeks. The survival (%) of Crassostrea gigas in the raised water temperature experimental groups (15, 20, $25^{\circ}C$) were over 98.5%, as similar to the control group (100%). But, the survival of C. gigas in the fixed water temperature experimental groups (15, 20, 25, $30^{\circ}C$) were decreased with the increase of the water temperatures. In the fixed water temperature experimental group of $30^{\circ}C$, the survival was 51.1%. Base on these results, the fixed water temperature of $20^{\circ}C$ was the best condition for artificial induction of sexual maturation.

• 한국패류학회지
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• 제22권2호
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• pp.175-182
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• 2006

본 연구는 2004년 3월 10일 남해 강진 만에서 채취한 피조개 어미 1,200 마리를 확보하여 수온조절에 의한 인위적인 성성숙을 유도하였으며, 성숙 유도된 어미로부터 잔존율, 비만도, 생식소 조직검사, 적산수온 및 성숙소요일수를 조사하였다. 성 성숙유도된 어미의 잔존율은 $20^{\circ}C$가 94.8％로 가장 높았고, $23^{\circ}C$가 90.3％, 대조구(자연수온구)가 84.8％이었고, $26^{\circ}C$가 18.1％로 온도가 높을수록 잔존율이 낮은 경향이 있었다. 42일 째 생식소 조직의 암컷의 완숙기 출현율은 $23^{\circ}C$ 실험 구에서 67%로 가장 높았고, $20^{\circ}C$ 실험구에서 56%, $26^{\circ}C$에서 22%였으며, 자연수온 실험구에서는 성숙이 매우 늦어 완숙기에 이르지 못하였다. 수컷의 경우, $23^{\circ}C$ 실험구에서 완숙기 출현율이 100%로 가장 높았고, $20^{\circ}C$ 실험구에서 87%, $26^{\circ}C$에서 73%였으며, 자연수온 실험구에서는 50% 순으로 나타났다. 성숙소요일수는 $23^{\circ}C$와 $20^{\circ}C$에서 각각 42일 및 49일, 대조구인 자연수온 $(9.5-14.8^{\circ}C)$에서는 79일이였으며, 성 성숙 유도율은 $20^{\circ}C$와 $23^{\circ}C$에서 각각 55.5% 및 60.5%로 타 실험구와는 유의한 차이를 나타내었다 (p < 0.05). 따라서 $20^{\circ}C$ 실험구 (적산수온: $1,295^{\circ}C$) 가 피조개 어미를 인위적으로 성 성숙을 유도하는데 가장 좋은 것으로 판단된다.

• 한국산업보건학회지
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• 제32권4호
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• pp.381-392
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• 2022

Objectives: Objective of this study is to review briefly exposure characteristics, monitoring instruments and threshold limit values for extremely low frequency-magnetic field (ELF-MF) methods. This study was undertaken through brief literature review. We performed a literature search in PubMed to identify ELF-MF studies conducted in workplaces. Initial search keywords such as 'extremely low frequency-magnetic field (ELF-MF)' and 'electromagnetic fields (EMF)' combined or singly. We limited our review to occupational rather than general nonworkplace environmental exposures. Methods: The contents we reviewed: key industry and occupations generating ELF-MF, several direct-reading instruments monitoring ELF-MF and threshold limit values (TLV) preventing health effects may be caused by the exposure to ELF-MF. Results: The industries related to the generation and supply of electricity, electrolytic installations, welding, and induction heating and more were regarded as high ELF-MF exposure industries. All jobs handling or employed performed in power cable lines, electrical wiring, and electrical equipment are found to be exposed to ELF-MF. Threshold or ceiling limit, 1,000 µT, is established to prevent acute effects of exposure to low-frequency EMFs on the nervous system: the direct stimulation of nerve and muscle tissues and the induction of retinal phosphenes. The International Agency for Research on Cancer (IARC) has classified ELF-MF as possibly carcinogenic to humans chiefly based on epidemiological studies on childhood leukemia. However, a causal relationship between magnetic fields and several types of cancer including childhood leukemia has not been established nor has any other long-term effects. Risk management using precautionary measures, has been initiated by the US and EU to prevent chronic health effects related to ELF-MF exposure in workplaces. Conclusion: This study recommends the implementation of various measures such as theestablishment of occupational exposure limit values for ELF-MF and precautionary principle to prevent potential chronic occupational health effects may be caused by ELF-MF in Korea.

• 조명전기설비학회논문지
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• 제14권1호
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• pp.109-117
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• 2000

본 논문은 고주파 유도가열용 전원에 사용되는 인버터에 WVF 기능을 부여한 풀-브릿지형 복공진 고주파 인버터회로를 제시하였다. 제안한 인버터는 직렬공진회로의 전류를 병렬공진회로의 주입전류로 사용하기 때문에 스위치의 전류 분담을 감소시킬 수 있으며, 또한 본 논문은 Phase-shift를 이용하여 스위칭 주파수와는 무관한 독립 출력 제어를 행하였다. 회로의 해석은 정규화 파라메타를 도입하여 범용성 있게 기술하였고, 인버터 특성을 스위칭 주파수, Phase-shift의 위상차각($\phi$) 변화와 제 파라메타에 따라 특성평가를 행하였다. 또한, 이론해석에서 얻은 특성값을 기초로 한 회로 설계 기법의 일 예도 제시하였다. 첨가해서, 실험을 통해 이론 해석의 타당성을 검증하였으며, 향후 유도가열 응용, OC-OC 컨버터 등의 전원 시스템에 웅용 가능성을 보여주고 있다.

• 한국정밀공학회지
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• 제19권2호
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• pp.114-125
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• 2002

As semi-solid forging (SSF) is compared with conventional easting such as gravity die-easting and squeeze casting, the product without inner defects can be obtained from semi-solid forming and globular microstructure as well. Generally speaking. SSF consists of reheating, forging, ejecting precesses. In the reheating process, the materials are heated up to the temperature between the solidus and liquidus line at which the materials exists in the form of liquid-solid mixture. The process variables such as reheating time, reheating temperature, reheating holding time, and induction heating power have much effect on the quality of the reheated billets. It is difficult to consider all the variables at the same time when predicting the quality. In this paper, Taguchi method, regression analysis and neural network were applied to analyze the relationship between processing conditions and solid fraction. A356 alloy was used for the present study, and the learning data were extracted by the reheating experiments. Results by neural network were on good agreement with those by experiment. Polynominal regression analysis was formulated by using the test data from neural network. Optimum processing condition was calculated to minimize the grain size, solid fraction standard deviation, otherwise, to maximize the specimen temperature average. In this time, discussion is liven about reheating process of row material and results are presented with regard to accurate process variables for proper solid fraction, specimen temperature and grain size.

• Tribology and Lubricants
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• 제36권3호
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• pp.124-132
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• 2020

The effect of the stoichiometry on the sliding wear properties of NiAl coatings has been investigated. Three different powder mixtures with the compositions of Ni-50at%Al, Ni-54at%Al and Ni-42at%Al were diepressed respectively, and which were subsequently coated on mild steel through combustion synthesis in an induction heating system. Sliding wear behavior of the coatings was examined against an alloyed tool steel using a pin-on-disc type sliding wear test machine. As results, it could be seen that powder mixture(Ni-54at%Al) with displaying Al-rich deviations from the stoichiometry of NiAl(Ni-50at%Al) was promoted the most the synthetic reactivity. The microstructure of the coating layer with the compositions of Ni-54at%Al exhibits the porous NiAl single phase structure. However, the microstructure of the coating layer of the compositions of Ni-42at%Al exhibits the denser multi-phase structure containing several intermediate phases in addition to NiAl. Densification of the coating layer was enhanced by increasing the reacting temperature. On the other hand, the wear properties of the coating layers showed that the wear mode at speeds of around 1 m/s was severe wear, regardless of the stoichiometry and reacting temperature. However, wear properties of coating layer with the compositions of Ni-42at%Al were superior to those of coating layer with the compositions of Ni-54at%Al. This would be attributed by the fact that coating layer with the compositions of Ni-42at%Al develops little void and much intermediate phases with high strength.

• 조명전기설비학회논문지
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• 제23권1호
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• pp.141-149
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• 2009

본 논문에서는 준정적 FDTD 기법을 FORTRAN 프로그래밍을 통해 직접 구현하고 이를 이용해 중간주파수 대역의 인체유도전류 분포를 해석하였다. 제작된 프로그램의 타당성을 검증하기 위하여 기존 FDTD 기법을 적용하기 어려운 테스트 모델에 대한 계산결과를 이론적 해와 비교하고, 타임스텝이 크게($5.68{\times}10^6$배) 단축되는 것을 확인하였다. 검증된 수치해석 기법을 이용하여 20[kHz] 자기장과 1[MHz] 전기장에 노출된 3차원 고해상도 인체모델에 유기되는 유도전류의 분포를 계산하고, 양 발의 접지조건이 유도전류의 분포와 크기에 미치는 영향을 분석하였다. 본 연구는 인체유도전류의 안전성 평가, 생체전기 응용 진단장치 개발 등을 포함한 다양한 분야에서 활용될 것으로 기대된다.