세라믹/금속접합재의 고온 열사이클에 따른 잔류응력분포 및 굽힘강도 특성

박영철,허선철,부명환,김현수,강재욱,Park, Young-Chul,Hue, Sun-Chul,Boo, Myoung-Hwan,Kim, Hyun-Su,Kang, Jae-Wook 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.10

Since the ceramic/metal joint material is made at a high temperature, the residual stress develops when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of Si$_3$N$_4$STS304 joints quantitatively and to compare the strength of joints. The difference of residual stress is measured when repeated thermal cycl is loaded, under the conditions of the practical use of the ceramic/metal joint. The residual stress increases at 1 cycle of thermal load but decreases in 3 cycles to 10 cycles of thermal load. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a result, it is known that the stress of joint decreases as the number of thermal cycle increases.

mBHT의 랫드를 이용한 단회경구투여 독성시험

박영철,박용기,Park, Young-Chul,Park, Yong-Ki 동국대학교 한의학연구소 2008 東國韓醫學硏究所論文集 Vol.11 No.-

Objectives: The study was designed to evaluate the single dose toxicity of modified Bo-yang-Hwan-o-Tang (mBHT) in Sprague-Dawley (SD) rats. Methods: The mBHT was once administrated orally to both sexes of rats at dose 2,000 mg/kg body weight which are the recommended maximum limit dose for acute toxicity. We recorded clinical signs of toxicity, body weight, gross and histological changes in target organs for all rats. Results: Neither significant changes of body weight not death was observed during the observation period in mBHT-administrated rats. Neither significant toxic signs not histopathological changes were shown during the observation period. There were not observed significant gross abnormality between the control and mBHT-administrated rats. Conclusions: These results indicated that the toxicity of mBHT is greater than 2,000 mg/kg body weight in SD rats.

생체용 Ti-18Nb-6Zr-XO (X = 0~1.5at%) 합금의 형상기억특성에 미치는 산소 농도의 영향

박영철,옥지면,오정화,박수호,이준희,김재일,Park, Young-Chul,Ock, Ji-Myeon,Oh, Jeong-Hwa,Park, Su-Ho,Lee, Jun-Hee,Kim, Jae-Il 한국재료학회 2011 한국재료학회지 Vol.21 No.11

The effect of oxygen on the shape memory characteristics in Ti-18Nb-6Zr-XO (X = 0-1.5 at%) biomedical alloys was investigated by tensile tests. The alloys were fabricated by an arc melting method at Ar atmosphere. The ingots were cold-rolled to 0.45 mm with a reduction up to 95% in thickness. After severe cold-rolling, the plate was solution-treated at 1173 K for 1.8 ks. The fracture stress of the solution-treated specimens increased from 450 Mpa to 880 MPa with an increasing oxygen content up to 1.5%. The fracture stress increased by 287MPa with 1 at% increase of oxygen content. The critical stress for slip increased from 430 MPa to 695 MPa with an increasing oxygen content up to 1.5 at%. The maximum recovery strain of 4.1% was obtained in the Ti-18Nb-6Zr-0.5O (at%) alloy. The martensitic transformation temperature decreased by 140 K with a 1.0 at% increase in O content, which is lower than that of Ti-22Nb-(0-2.0)O (at%) by 20 K. This may have been caused by the effect of the addition of Zr. This study confirmed that addition of oxygen to the Ti-Nb-Zr alloy increases the critical stress for slip due to solid solution hardening without being detrimental to the maximum recovery strain.

틸트 로터형 무인항공기의 손상허용 설계

박영철,임종빈,박정선,Park, Young Chul,Im, Jong Bin,Park, Jung Sun 항공우주시스템공학회 2007 항공우주시스템공학회지 Vol.1 No.2

The Damage Tolerant Design is developed to help alleviate structural failure and cracking problems in aerospace structures. Recently, the Damage Tolerant Design is required and recommended for most of aircraft design. In this paper, the damage tolerant design is applied to tilt rotor UAV. First of all, the fatigue load spectrum for the tilt rotor UAV is developed and fatigue analysis is performed for the flaperon joint which has FCL (fatigue critical location). Tilt rotor UAV has two modes: helicopter mode when UAV is taking off and landing; fixed wing mode when the tilt rotor UAV is cruising. To make fatigue load spectrum, FELIX is used for helicopter mode. TWIST is used for fixed wing mode. Fatigue analysis of flaperon joint is performed using fatigue load spectrum. E-N curve approach is used for picking crack initiation point. The LEFM(Linear Elastic Fracture Method) is considered for analyzing crack growth or propagation. Finally, including the crack initiation and propagation, the fatigue life is evaluated. Therefore the Damage Tolerant Design can be done.

배양망막색소상피세포에서 젤라틴아제의 발현에 대한 산화스트레스의 영향

박영철,최광주,Young-Chul Park,Gwang-Ju Choi 대한안과학회 2005 대한안과학회지 Vol.46 No.11

Purpose: To evaluate the expression pattern of gelatinases in the human retinal pigment epithelial cell line ARPE-19 in response to oxidative stress. Methods: ARPE-19 cells were exposed to paraquat for 72 hours. The cells were assayed for the mRNA expression of gelatinase A and gelatinase B by reverse transcriptase polymerase chain reaction (RT-PCR). The conditioned media were assayed for the production of gelatinases protein by Western blotting. Also, the inhibitory effect of the antioxidants against oxidative stress to the cells was evaluated. Results: The gelatinase levels in the RPE cells increased under oxidative stress compaired with the control (p〈 0.05). Also, the levels decreased when the cells were incubated with the antioxidant N-acetylcysteine (NAC). Conclusions: Oxidative stress upregulates gelatinase expression in ARPE-19 cells.

웨이블릿을 이용한 QRS complex 검출 알고리즘의 고정 소수점 연산 최적화

박영철,Park, Young-chul 한국정보전자통신기술학회 2014 한국정보전자통신기술학회논문지 Vol.7 No.3

본 논문에서는 웨이블릿 변환을 통하며 QRS complex를 검출 하며, 32비트 고정 소수점 연산이 가능한 프로세서에도 동작하도록 알고리즘 최적화 기법을 제시한다. 먼저 입력 ECG 신호를 밴드 패스 필터를 통과 시키고, 3개의 서로 다른 웨이블릿 함수를 하나로 병합한 웨이블릿 함수를 이용하여 웨이블릿 변환을 하며, 다음으로 시간 평균 함수를 뒤에 마지막으로 QRS complex를 검출 한다. 제안 알고리즘은 MIT-BIH arrhythmia database에 적용하여 검증한다. 모든 과정은 32비트 고정 소수점 연산으로 구현되며, 삼각함수 같은 복잡한 연산은 테이블화 하였다. 검출 알고리즘은 컴퓨터 시뮬레이션을 통해 평가 한다. In this study, QRS complex is detected by Wavelet Transform and it can be worked in 32bit fixed point operation thought optimization. First, ECG signal is passed though band pass filter. Second, it is transformed using one-band combined wavelet function from 3-band wavelet function. Third, it is passed though moving window integral. Finally, QRS complex is detected by decision rule. The proposed algorithm is evaluated using MIT-BIH arrhythmia database. Its all of process make progress 32-bit fixed-point operation and it makes table that high complexity operations like trigonometrical function. The detection algorithm evaluate through computer simulation.

숙지황(Rehmannia glutinosa)의 약리작용과 독성

박영철,이기용,백낙민,손혜영,국윤범,이선동,Park, Yeong-Chul,Lee, Gi-Yong,Baek, Lag-Min,Son, Hye-Young,Kook, Yoon-Boom,Lee, Sun-Dong 대한한의학방제학회 2011 大韓韓醫學方劑學會誌 Vol.19 No.1

Objectives : Rehmannia glutinosa has been used extensively in Korean traditional medicine. Although thorough clinical trials are lacking, Various pharmacological actions for Rehmannia glutinosa has been identified newly using animal models. In addition, it was reported that reactive intermediates, potentially causing toxic effects, was isolated from one of components in Rehmannia glutinosa. In this article, it is purposed for explanation and introduction of new studies for Rehmannia glutinosa in terms of pharmacological action and toxicology. Methods : New studies for Rehmannia glutinosa were reviewed and summarized in terms of pharmacological action and toxicity. Results and Conclusions : Rhmannia glutinosa and its components including iridoids, saccharides, as well as amino acid, showed a variety of pharmacological actions on the blood system, immune system, endocrine system, cardiovascular system and the nervous system. In addition, it was identified that aucubin, one of major components of Rhmannia glutinosa was biotransformed to reactive intermediates by ${\beta}$-glycosidase and acid-hydrolysis, resulting in forming aucubigenin- albumin adduct. Even if a lot of new pharmacological actions has been identified, it should be considered for Rhmannia glutinosa to contain the material producing reactive intermediates which may induce the side effects.

적외선 체열 촬영을 이용한 중풍(中風) 편마비(片痲痺) 환자(患者)의 합곡혈(合谷穴) 일반 자침시(刺針時)와 심자시(深刺時) 피부온도변화(皮膚溫度變化) 관찰(觀察)

박영철,채진석,엄재용,송성세,최익선,Park, Young-chul,Chae, Jin-seok,Eom, Jae-yong,Son, Sung-se,Choe, Ick-seon 대한침구의학회 2003 대한침구의학회지 Vol.20 No.4

Objective : This study designed to find out the effects of deep acupuncture in cerebrovascular hemiplegia. Methods : This study was performed on 30 patients with cerebrovascular hemiplegia to observe difference in temperature of skin surface between general acupuncture and deep acupuncture at Hapkok using digital infrared thermographic imaging(D.I.T.I.) Results : 1. Temperature of paralytic side is sigficantly higer $0.39{\pm}0.78^{\circ}C$ than that of contralateral side. 2. Thermal difference(${\Delta}T$) of paralytic side-contralateral side decreased $0.08{\pm}0.53^{\circ}C$ after general acupuncture, but there is no significant. $0.20{\pm}0.50^{\circ}C$ after deep acupuncture decreased significantly. So deep acupuncture is more effective than general acupuncture. 3. Thermal difference of paralytic side-paralytic side and contralateral side-contralateral side decreased significantly after acupuncture, and thermal difference of deep acupuncture on paralytic side-paralytic side decreased $0.42{\pm}1.07^{\circ}C$ more than that of general acupuncture. So deep acupuncture is more effective than general acupuncture. Conclusions: This study showed that deep acupuncture is more effective than general acupuncture In cerebrovascular hemiplegia, and further study is needed on clinical trials.

겨울철 부산항 주변해역의 수질과 표층퇴적물 환경특성

박영철,양한섭,이필용,김평중,PARK Young-Chul,YANG Han-Soeb,LEE Pil-Yong,KIM Pyoung-Joong 한국수산과학회 1995 한국수산과학회지 Vol.28 No.5

부산항 주변 해역의 이화학적 특성을 파악하기 위하여 1992년 12원에 해수 및 표층 퇴적물중 오염지표 항목들을 측정하였다. 염분과 영양염류, AOU와 영양염류의 상관관계로 보아 겨울철 부산항에서 영양염류의 농도는 주로 도시하수의 유입에 의해 좌우되며, 수주내의 유기물 분해와 같은 생화학적 과정에 의한 영양염 재생에 따른 영향도 다소 나타나고 있다. 부영양화 지수 (TSI)는 평균 33.6 (범위 0.5-258.1)이고, 북외항, 북내항, 남항 및 감천항에서 각각 평균 19, 50, 56 및 5로 남항에서 가장 높은 부영양화 지수를 보인다. 표층퇴적물중의 총강열감량, COD 및 총황화물의 평균 농도는 각각 $12.1\%$, 17.5mg/g.dry 및 1.18mg/g.dry 였으며 북내항에서 가장 높다 그리고, Ro(1975)의 자료에 비해 총강열감량과 COD는 북내항에서 2-3배정도 높은 농도를 보인다. 표층 퇴적물중 총유기탄소와 총유기 질소 및 총인의 평균 농도는 각각 24.9, 1.3 및 0.69mg/g.dry 였으며, 총유기탄소와 총인의 농도는 남항에서 가장 높은 농도를 보인 반면에, 총유기질소의 농도는 북내항에서 가장 높은 농도를 보였다. 특히 부산항 퇴적물중 TOC/TON 비값은 평균 22.5 (범위 10.2-60.2)로서 육상기원 유기물질의 퇴적이 우세하였다. The chemical constituents for the seawater and sediment were measured to evaluate pollution in the sea around Pusan Harbor in winter, n992. The average value of trophic state index (TSI) was 19.4 at the outside of Buk Harbor, 50,4 at the inside of Buk Harbor, 56,3 at the Nam Harbor and 5,0 at the Kamchun Harbor. The high correlation found in salinity-nutrients diagram with AOU suggested that the enrichment of nutrients in Pusan Harbor during winter was mainly due to the influx of terrestrial effluents and partially by regenerated nutrients from suspended organic matters in the water column. The mean values of total ignition loss (TIL), COD and total sulfide in the surface sediments were$12.1\%$, 17.5 mg/g.dry wt. and 1.18 mg/g.dry wt. respectively. The highest level of those parameters was shown mostly at the inside of Buk Harbor. The mean concentration of total organic carbon (TOC), total organic nitrogen (TON), and total phosphorus were 24.9 mg/g.dry wt., 1.3mg/g.dry wt. and 0.69 mg/g. dry wt., respectively, Both of the highest level for TOC and total phosphorus have found at the Nam Harbor. On the other hand, the Highest level for TON was found at the inside of Buk Harbor. The TOC/TON atomic ratio with a range of 10.2-60.2 (mean value of 22.5) strongly indicated the active role of the input from the terrestrial organic pollutants.

잎절편 배양에 의한 제주 자생나리의 재분화

박영철(Young-Chul Park),김정선(Jeong-Seon Kim),송승운(Seung-Woon Song),김용철(Yong Chol Kim),김광호(Kwang-Ho Kim) 한국자원식물학회 2005 한국자원식물학회지 Vol.18 No.3

아그로박테리움을 이용한 형질전환연구에 기초자료로 활용코자 기내배양중인 땅나리, 하늘나리, 대만나리의 잎절편으로부터 식물체를 유도하였다. 땅나리 잎절편으로부터 다수의 배양체를 얻기 위해서는 MS배지에 0.2mg·L-1BA 와 0.5mg·L-1NAA 를 첨가하여 암조건에서 배양하는 것이 효과적이었고, 하늘나리 잎 재분화에는 0.2mg·L-1BA 와 2.0mg·L-1NAA 혼용처리하는 것이 효과적이었으며, 대만나리의 잎 재분화에는 1.0mg·L-1BA 와 1.0mg·L-1NAA 혼용처리가 우수하였다. This study was conducted to examine the effects of plant growth regulators on the plant regeneration from leaf segments of Lilium callosum, L. concolor var. partheneion, and L. formosanum. Leaf segments were sectioned about 5 mm long and cultured on the basal medium (MS medium with 3% sucrose and 0.8% agar) under dark condition, The most effective plant regulators on harvesting more shoots from leaf culture of L. callosum were 0.2mg·L-1BA and 0.5mg·L-1NAA . Culturing in the basal medium with 0.2mg·L-1BA and 2.0mg·L-1NAA was effective for leaf culture of L. concolor var. partheneion. The treatment of 1.0mg·L-1BA and 1.0mg·L-1NAA was the most effective condition for shoot harvest at the leaf culture of L. formosanum.