• Corrosion Science and Technology
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• 제10권6호
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• pp.218-224
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• 2011

The fresh water and sea water in present ships is used as cooling water for marine engine. Therefore, corrosion damage in seawater system is frequently occurred. In particular, in the impeller of pump, the performance and material span due to the corrosion and cavitation erosion has adverse effects. Most of the pump impellers in vessels are used Cu-Al alloy. Cu-Al alloy which having the excellent mechanical properties and corrosion resistance is widely used in marine environments. However, despite the excellent characteristics, the periodic replacement parts due to the cavitation damage in seawater is vulnerable to economic viewpoint. In this study, Cu-Al alloy used with impeller for centrifugal pump were conducted various experiments to evaluate its characteristics in seawater and fresh water solutions. As an electrochemical result, the dynamic conditions that exposed to the cavitation environment presented high corrosion current density with collapse of the cavity compared with the static conditions. Cavitation test results, the weightloss and weightloss rate in fresh water are observed more than those of seawater.

• 해양환경안전학회지
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• 제12권4호
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• pp.253-259
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• 2006

본 논문은 가장 극한 조건(공정모델-2)에서 화학 제염한 경우 원자로 냉각재 펌프용 스테인리스강의 내식성 평가에 관하여 연구하였다. 사이클 경과에 따른 304 스테인리스강의 전기화학적 특성은 다른 스테인리스 강보다 우수한 특성을 나타냈다. 또한 공정모델-1과 공정모델-2의 304 스테인리스강은 가장 낮은 무게 감량을 나타냈다. 공정모델 용액에서 304 스테인리스강, 415 스테인리스강, 431 스테인리스강에 대한 실험 결과 공정모델-1에 대한 공정모델-2의 무게감량비는 각각 2.908, 2.372,그리고 2.370배를 나타냈다. 그 이유는 공정모델-2의 경우가 공정모델-1에 비하여 화학약품 농도나 온도가 높은 가혹한 조건에 기인한 것으로 사료된다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권7호
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• pp.883-889
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• 2014

고속유체 환경에서 압력차에 의한 국부적 비등으로 캐비테이션 침식 손상이 발생한다. 캐비테이션은 유체의 압력, 속도, 온도, pH, 그리고 매질 등의 다양한 환경에 영향을 받는다. 특히 해수 용액에서 캐비테이션 환경에 노출될 경우 염소이온에 의한 부식이 캐비티에 의한 침식 손상을 가속화 시킨다. 따라서 본 연구는 마르텐사이트계 스테인리스강에 대해 천연 해수 용액에서 적용 전류밀도와 캐비테이션 시간에 따른 시편 손상 경향을 규명하였다. 정전류 실험 결과 캐비테이션 조건에서 정적인 조건에 비해 비교적 적은 손상 경향이 나타났다. 또한 캐비테이션 실험 결과 3시간부터 급격하게 무게 감소량, 캐비테이션 손상률, 손상깊이가 증가하였다.

• 한국식품영양학회지
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• 제6권4호
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• pp.255-267
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• 1993

This study was performed to investigate the correlations among physical anthropometric measurement, diet intakes, physical fitness test, and serum lipids in eight sedentary women(control group), and twenty seven exercising women(aerobic groups), aged 35~45 years. The results of the study are as follows : 1) systolic blood pressure(SBP) and diastolic blood pressure(DBP) of aerobic groups were lower than serf entary. Pulse rate was decreased according to the length of aerobic periods. Muscular endurance and jump power of all subjects were stronger than standard range, and those of aerobic exercising groups were stronger than control group. Muscular power of the upper half of the body In all subjects were lower than standard range. 2) Daily calorie intakes of all subjects were in the ring: of recommended dietary allowances (RDA) for Koreans. But daily protein Intakes were higher than RDA. daily cholestrol intakes of all subjects were slightly less than 200~300 mg: which is normal consumption of Koreans. 3) There was a significant positive correlation between serum 7G and daily protein intakes. It was considered that excessive protein intake converted to serum 7G. There was not a significant correlation between serum TC and dietary TC. Therefore, dietary TC seemed to have not much effect on serum TC. Physical fitness was negatively related to serum TG, TC, LDL-C, but positively related to HDL-C, HDL-C /TC. It was found that the serum lipids could be changed better according to improving the physical fitness. There were significant positive correlations between SBP and serum TC, LDL-C. (According to this results), the higher SBP, the higher serum TC, LDL-C tended to be. There was a significant positive correlations between sit up and weightloss nth exercise r=0.7(p<0.001), push ups and weightless with exercise r=0.5(p<0.001). It was considered that muscle strength could be improved according to the weightloss. 4) The purpose of exercise in aerobic groups was rather promoting health than reducing body fatness. Most of al1 subjects (83.2%) drank caffeine-contained beverage therefore, we should concern about that absorption of Fe could be Interrupted and blood pressure could be elevated by caffeine.

• 한국세라믹학회지
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• 제24권2호
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• pp.117-122
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• 1987

Glass forming ranges in the AlF3-(Mg＋Sr＋Ba)F2-P2O5 system are studied and ultraviolet transmission, infrared transmission, coefficient of refractive index, thermal expansion coefficient, density and chemical durability of the glasses are determined. Glass forming range is restricted MgF2 0-10wt%, SrF2 10-50wt%, BaF2 10-40wt% in this system. While BaF2 is substituted by SrF2, density and refractive index are decreased, micro hardness and thermal expansion coefficient are increased according to the increasing of SrF2 at fixed MgF2 contents. These samples represent high transmittance(93%) from 400nm to 3800nm and chemical durability of these samples show less than 0.3mg/$\textrm{cm}^2$$.$hy by weightloss.

• 한국표면공학회지
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• 제40권6호
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• pp.271-278
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• 2007

In this study, applicable possibility in chemical decontamination for reactor coolant pump(RCP) was investigated for the various stainless steels. The stainless steel(STS) 304 showed the best electrochemical properties for corrosion current density and the lowest weight loss ratio in chemical decontamination process model 3-3 than other materials. The weightloss quantity in chemical decontamination process model 3-3 presents the lowest value compare to the other chemical decontamination process model 1, 2, 3-1 and 3-2. In the case of SEM observation, the pitting corrosion was generated in both STS 415 and STS 431 with the increasing numbers of cycle. The intergranular corrosion in STS 431 was sporadically observed. The sizes of their pitting corrosion were also increased with increasing cycle numbers.

• 동국한의학연구소논문집
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• 제5권
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• pp.273-280
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• 1996

This study is to know the relation between the symptom of Vinyl House disease and seo-byung of oriental medical. The results are summarised as follows, 1. One of the pathogenic factors of Vinyl house disease is the environtal of high temperature and humidity,that is coincident with seo-byung's pathogenic factors. 2. The most common symptoms of Vinyl house disease are heaedache, sweating, dizziness, weightloss, fatigue, nausea, vomiting, numbed limb, breathless etc. that are included in seo-byung's symptoms. 3. Vinyl house disease belong to the category of the seo-byung of oriental medical. In concrete term, Vinyl house disease is come under chronic seo-byung or symptomic seo-byung.

• Corrosion Science and Technology
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• 제10권4호
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• pp.136-142
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• 2011

Al alloys have been used widely for commercial and military ships in most ocean countries since mid-1950s, and the value as light metal with high mechanical strength has been proven. As the safety and fuel efficiency of Al ships have improved, she can carry more freight, sail faster and travel longer distances. Furthermore, in the shipbuilding industry, Al alloys are applied as structural materials for ships to various areas including the deck of luxurious cruises, battleships and leisure ships. In addition, Al alloys are being spotlighted as environmental-friendly material as they can be recycled even after end of lifespan. However, Al alloys for ships must be carefully selected after considering corrosion resistance, endurance, strength, and weldability in sea water environment. Al alloys to satisfy these conditions are used widely include 5000 series Al-Mg alloy and 6000 series Al-Mg-Si alloy. Thus, this study selected and evaluated the cavitation characteristics of the 5000 series Al alloys that are used in hulls that directly contact seawater and the 6000 Al alloys that are used in the upper structures of ships. Results of cavitation test with time, weightloss and cavitation rate of 5456-H116 showed the smallest damage among 5052-O, 5456-H116 and 6061-T6.

• 해양환경안전학회지
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• 제18권5호
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• pp.481-487
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• 2012

최근 FRP 선박의 폐선 처리문제, 환경 규제의 강화, 자원 재활용 등의 관점에서 소형 알루미늄 합금 선박의 건조가 증가하는 추세이다. 그러나 알루미늄은 가볍기 때문에 해양에서 고속으로 운행 가능한 알루미늄 선박은 캐비테이션이 발생되어 기포붕괴에 따른 큰 충격압력에 의해 캐비테이션 침식이 일어남으로서 재료의 수명에 있어 문제점을 드러내고 있다. 따라서 본 연구에는 캐비테이션에 의한 손상을 방지하여 내구 수명을 연장시키기 위한 방법으로 워터 캐비테이션 피닝 기술을 선박용 알루미늄 합금에 적용하였다. 이를 위하여 워터 캐비테이션 피닝을 실시하여 내캐비테이션 특성이 가장 우수한 적용 시간을 규명하였다. 선박용 알루미늄 합금 5456-H116, 5083-H321 그리고 5052-O는 워터캐비테이션 피닝을 실시함으로써 내캐비테이션 특성이 워터 캐비테이션 피닝을 하지 않은 시편보다 무게감소량이 각각 42.11 %, 50.0 % 그리고 25.7 % 개선되었다.

• 한국식품영양과학회지
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• 제11권4호
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• pp.53-59
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• 1982

감자의 장기안전저장법(長期安全貯藏法) 개발(開發)을 위하여 적정조사선량(適正照射線量)및 적정조사시기(適正照射時期)를 구명(究明)한 결과(結果)는 아래와 같다. (1) 품종간(品種間)에 차이(差異)는 있으나 수확후 $15{\sim}30$일(日) 사이에 방사선(放射線)을 조사(照射)할때는 12.5krad의 선량(線量)이 적당하고, 수확후 45일(日) 이후에 조사(照射)할때는 15krad 정도의 조사(照射)가 필요(必要)하며, 가급적 수확후 휴면기간(休眠期間)중 빨리 조사(照射)하는 것이 유리하다고 본다. (2) 적정조사선량(適正照射線量)에서의 조사구(調査區)는 무처리구(無處理區)에 비(比)해 물리적성질(物理的性質)이 우수(優秀)하였으며, 방사선조사(放射線照射) 후(後) 자연저온저장고(自然低溫貯藏庫)에 저장(貯藏) 함으로서 무처리구(無處理區)보다 저장기간(貯藏期間)을 4개월이상(個月以上) 연장시킬수 있었다.