섬유-금속 적층판의 인장 및 압입 하중에서의 손상감지

양유창(Yoo Chang Yang),한경섭(Kyung Seop Han) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in<br/> damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied<br/> in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix<br/> cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity<br/> impacts. Tensile and indentation test was performed with the measurement of optical signal and acoustic<br/> emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated<br/> by wavelet transform. It was found that damage information of comparable in quality to acoustic emission<br/> data could be obtained from the optical fiber vibration sensor signals.

뇌성 마비 환아에서 뇌 자기공명 영상 소견

유창현(Chang Hyun Yoo),윤대영(Dae Young Yoon),조현상(Hyun Sang Cho),민기식(Ki Sik Min),김종완(Jong Wan Kim),유기양(Ki Yang Ryoo) 대한소아신경학회 1999 대한소아신경학회지 Vol.6 No.2

목적: 뇌성마비 환아의 MRI를 후향적으로 분석하여, 뇌손상 평가지 MRI의 역할, 임신 주수에 따른 MRI 소견의 차이를 알아보았다. 방법: 1994년 1월부터 1998년 7월까지 강동성심병원에서 뇌성마비로 진단받은 66명(만삭아 37명 미숙아 29명)의 MRI를 미숙아군과 만삭아군으로 나누어 비교하였다. 결과: 미숙아군 29례에서 13례가 저산소성 허혈성 뇌손상의 소견을 보였는데 PVL이 12례(41.3%)로 가장 많았고 신경 세로 이주 장애가 6례(20.8%), 기타 선천성 뇌기형 5례(17%), multifocal ischemic necrosis 1례(3.4%), 정상 소견이 5례(17%)에서 관찰되었다. 만삭아군 37례에서 22례가 저산소성 허열성 뇌손상의 소견을 보였으며 selective neuronal necrosis 11례(29.7%), PVL 4례(10.8%), focal and multifocal ischemic necrosis 4례(10.8%), 대리석 상태 3례(8.1%), 신경 세포 이주 장애 4례(10.8%), 기타 선천성 뇌기형 5례(13.5%), 정상 소견이 6례(16.2%)에서 관찰되었다. 결론: MRI를 통해서 뇌성 마비 환아에서 다양한 병변을 관찰할 수 있으며 저산소성 허혈성 뇌손상은 미숙아군과 만삭아군에서 유의한 차이를 보였다. 미숙아군에서는 PVL이 흔하고 만삭아군에서는 selective neuronal necrosis가 통계적으로 많았다. Purpose: We used MRI to retrospectively analyze the brain of patients suffering from cerebral palsy. Our aim is to determine MRI's role in the assessment of brain damage, the relationship of gestational age. Methods: A total of 66 patients(29 preterm group and 37 term group), who visited Kang-Dong Sacred Heart Hospital from January, 1994 to July, 1998, where enrolled in study. Results: Among the 29 in the preterm group, 13 patients showed MR images of hypoxic ischemic injury in which periventricular leukomalacia(PVI) and multifocal ischemic necrosis in 12(41.3%) and 1(3.4%) respectively. Neuronal MR images 5(17%) in this preterm group. Among the 37 in the term group, 22 patients showed MR images of hypoxic ischemic injury in which selective neuronal necrosis were 11(29.7%), PVL 4(10.8%), focal and multifocal ischemic necrosis 4(10.8%) and status marmoratus 3(8.1%). Meuronal migration disorders were 4(10.8%), other congenital malformations 5(13.5%) normal MR images 6(16.2%) in the term group. Conclusion: MRI provided useful information in a majority of children with cerebral palsy. Hypoxic ischemic injury was significantly different in preterm and term groups. PVL was frequent in the preterm group and selective neuronal necrosis was statistically common in the term group.

섬유/입자 혼합보강 금속복합재료의 피로균열 진전거동

오광환(Kwang-Hwan Oh),양유창(Yoo-Chang Yang),한경섭(Kyung-Seop Han) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

The effects of short fiber and particle hybrid reinforcement on fatigue crack propagation behaviors in aluminum matrix composites have been investigated. Single and hybrid reinforced 6061 aluminum containing same 20 Al₂O₃ volume % with four different constituent ratios of short fibers and particles were prepared by squeeze casting method and tested to check the near-threshold and stable crack growth behavior. The fatigue threshold of the composites increased with portion of particle contents and shows the superior crack resistance in low stress intensity range. In stable crack growth region, the slop of Paris' Law which indicating the crack growth rate was independent of microstructure. After allowing for crack closure, the differences in crack propagation rate among the composites were significantly diminished. Observation of the crack path revealed that the fatigue crack propagate mainly to the interfaces and across the hoop direction of short fibers, however crack seldom propagate though the particle for their low aspect ratio. Overall experimental results was shown that Particle reinforcing was enhanced the fracture toughness and fatigue threshold and induced the resistance of crack propagation.

연료전지 차량용 금속분리판 개발

진상문(Jin, Sang-Mun),양유창(Yang, Yoo-Chang),김세훈(Kim, Sae-Hoon) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06

Currently, the bipolar plates are fabricated mainly from graphite materials. However, metal bipolar plate are getting most attractive due to their good feasibility of mass production and low cost. In this study, metal bipolar plates for fuel cell Vehicles were developed with a concept based on the straight flow patterns to minimize the pressure drop and spring back. And molded gasket apply to the bipolar plate for improve sealing performance. Results show that the metal bipolar plate have a high potential to replace for graphite materials in fuel cell application.

“SK텔레콤의 창업지원 활동내용과 성과를” 통한 CSV 사례연구

송윤화(YunHwa Song),양윤재(YunJae Yang),유창조(Chang Jo Yoo) 한국경영학회 2019 Korea Business Review Vol.23 No.1

SK 그룹은 창업초기부터, 기업은 기업활동을 통해 사회적 국가적 발전에 기여해야한다는 확고한 철학을 갖고 있었다. SK 그룹은 이러한 경영철학을 계승하면서 회사만의 고유한 사회공헌활동을 전개해 오고 있다. SK 그룹은 ‘행복경영철학’을 선언하고 실천하면서 전 계열사가 ‘모든 이해관계자들의 행복추구’를 경영이념으로 넣은 혁신적 시도에 동참하고 있다. SK 텔레콤 역시 기업 역량을 사회에 투자하는 방식으로 사회 공헌을 위한 활동을 실천해 오고 있다. 이 회사는 기업의 핵심 역량인 정보통신기술(ICT)을 활용하여 새롭고 창의적인 가치 창출을 위해 노력하고 있다. 특히 SK텔레콤은 2010년 이후 사회공헌활동의 연장선상에서, 그리고 일자리 창출의 하나로 “창업지원”을 꾸준히 실천해오고 있다. 전 세계가 경제 저성장 속에서 한국역시 일자리 창출을 위한 새로운 성장의 동력으로 창업에 대한 지원은 정부 차원에서 이루어지고 있다. 이를 위해 창업 생태계 구축을 위한 대기업 및 민간 지원과 협조는 절대적으로 필요한 상황이다. 그러나, 한국의 창업 생태계를 보면 정부의 지원에도 불구하고 생존율 등은 OECD 국가 중 최하위를 보이고 있다. 이는 정부의 규제, 상생적 이득을 가져올 수 있다는 대기업의 확신 부재, 여기에 창업 지원을 위한 사회 문화적 여건이 마련되지 못하였기 때문이다. 이런 상황적 여건에도 불구하고, SK텔레콤이 2013년 이후 2017년까지 지속해온 창업 지원 및 청년 창업지원을 위한 프로그램을 운영 발전시켜 온 것은 매우 고무적인 일이다. 실제적으로 “브라보! 리스타트(Bravo! Restart)” 등을 통해 SK텔레콤의 창업 지원을 받은 46개 업체는 2016년 3분기 기준으로 250억원 가량의 매출을 기록하고 있다. 이 사례 보고서의 목적은 SK텔레콤의 “창업 지원” CSV 활동의 내용과 그 성과를 소개하는데 있다. 이를 위해 본 연구는 SK텔레콤의 창업지원 및 청년 창업 지원을 위해 세운 프로그램 내용 및 세부적 실천내용과 그 성과를 상세히 기술하였으며, SK텔레콤 및 대기업의 창업지원 활동을 지속 강화하기 위해서 필요한 미래과제를 논의하였다. Jong Hyun Choi, founder of SK group firmly believed that the company have to make contribution to social and national development. SK has inherited founder’s philosophy and developed its unique social contribution programs to date. SK group is implementing the ‘Happiness Management Philosophy’. All affiliated companies are participating in innovative attempts to incorporate ‘all stakeholder’ happiness’ as a management philosophy. SK Telecom is trying to make a better world by investing its corporate capabilities to society. The company has been making efforts to generate new and creative value by utilizing ICT (Information and Communication Technology), which is the core competence of enterprises. Since 2010, SK Telecom has continued to practices its “entrepreneurial support” with social contribution and job creation activities. The world is living in a low growth economy. South Korea is also trying to create jobs to overcome the situation. Support for entrepreneurship as a new growth engine is being implemented at the government level. For this purpose, private support and cooperation are absolutely necessary for the establishment of a new entrepreneurial ecosystem. However, in Korea`s entrepreneurial ecosystem, the substantiality rate after establishment is the lowest among OECD countries, despite the government`s support. This is due to government regulations, lack of confidence that large companies can bring about a win-win benefit and lack of sociocultural conditions to support start-ups. Despite these circumstances, it is highly encouraging that SK Telecom has operated and developed programs to support startup and youth start-ups from 2013 to 2016. During this period, 46 companies received SK Telecom start-up supports through “Bravo! Restart” and have recorded sales of around 25 billion won by the third quarter of 2016. The purpose of this case report is to introduce the content of SK Telecom`s CSV activities, support for entrepreneurship, and its results. For this purpose, this study describes the contents of SK Telecom`s startup support program and its accomplishments. We discussed the future challenges necessary to strengthen support for SK Telecom and its large enterprises.

연료전지 차량용 고출력 분리판 개발

진상문(Sang Mun Jin),양유창(Yoo Chang Yang),금영범(Young Bum Kum),이종현(Jong Hyun Lee),김세훈(Sae Hoon Kim) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The next generation bipolar plates for 100㎾ fuel cell stacks were developed with a concept based on the straight flow patterns to minimize the pressure drop, decrease flooding in the bipolar plate and maximize the stack power simultaneously. Cell performance tests, pressure and temperature distribution measurements were performed for various flow pattern combinations on the air, H2 and coolant sides. Results show that the stack performance and the power are increased by 12% and 400/0, respectively.

피로균열진전에 따른 304강의 음향방출 거동

오광환(Kwang Hwan Oh),정창규(Chang Kyu Jung),양유창(Yoo Chang Yang),한경섭(Kyung Seop Han) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Acoustic emission behavior during fatigue crack growth test was investigated under various loading<br/> condition. To describe the acoustic emission activity, counts rate (dh/dn) was related with SIFR (stress<br/> intensity factor range, DK). Results indicated that SIFR could be divided into two parts according to its<br/> relationship with counts rate. For DK<25MPa m , counts rate was increased as the SIFR increased. However,<br/> for values greater than 25MPa m , decreasing behavior was shown. This behavior of counts rate corresponding<br/> SIFR was keeping the same trend regardless of load range or crack length. Acoustic emission response to the<br/> single overload was sudden drop and slow recovery in counts rate like crack growth retardation. Under<br/> variable loading condition, counts rate of each loading block was same as that of constant amplitude loading.<br/> Overall experimental data was somewhat scattered since sensitive characteristics of acoustic emission method.<br/> However, these empirical relations indicated that counts rate was uniquely correlate with single parameter,<br/> SIFR.

PEMFC용 금속분리판 코팅 기술 개발

윤용식(Yun, Yong-Sik),정경우(Chung, Kyeong-Woo),양유창(Yang, Yoo-Chang),안승균(Ahn, Seung-Gyun),전유택(Jeon, Yoo-Taek),나상묵(Na, Sang-Mook) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

As the stainless steel has good corrosion resistance, mechanical property and ease of manufacture, it has been studied as the candidate material of metallic bipolar plate for automotive PIMFC. But, metal is dissolved under fuel cell operating conditions Dissolved ions contaminate a membrane electrode assembly (MEA) and, decrease the fuel cell performance. In addition, metal oxide formation on the surface of stainless steel increases the contact resistance in the fuel cell. These problems have been acted as an obstacle in the application of stainless steel to bipolar plate. Therefore, many kinds of coating technologies have been examined in order to solve these problems. In this study, stainless steel was coated in order to achieve high conductivity and corrosion resistance by several methods. Contact resistance was measured by using a tensile tester and impedance analyzer Corrosion characteristics of coated stainless steel were examined by Tafel-extrapolation method from the polarization curves in a solution simulating the anodic and cathodic environment of PEMFC. Fuel cell performance was also evaluated by single cell test. We tested various coated metal bipolar plate and conventional and graphite were also tested as comparative samples. In the result, coated stainless steel bipolar plate exhibited better cell performance than graphite to bipolar plate.

PEMFCB금속분리판 코팅 기술 개발

정경우(Chung, Kyeong-Woo),김세융(Kim, Se-Yung),양유창(Yang, Yoo-Chang),안승균(Ahn, Seung-Gyun),전유택(Jeon, Yoo-Taek),나상묵(Na, Sang-Mook) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

Bipolar plate, which forms about 50% of the stack cost, is an important core part with polymer electrolyte membrane in PEMFC. Bipolar plates have been commonly fabricated from graphite meterial having high electrical conductivity and corrosion resistance. Lately, many researchers have concentrated their efforts on the development of metallic bipolar plate and stainless steel has been considered as a potential material for metallic bipolar plate because of its high strength, chemical stability, low gas permeability and applicability to mass production. However, it has been reported that its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions and an increase in contact resistance by the growth of passive film therefore, its corrosion resistance as well as contact resistance must be improved for bipolar plate application. In this work, several types of coating were applied to 316L and their electrical conductivity and corrosion resistance were evaluated In the simulated PEMFC environment. Application of coating gave rise to low interfacial contact resistances below 19m{Omega}cm² under the compress force of 150N/cm². It also made the corrosion potential to shift in the posit ive direct ion by 0.3V or above and decreased the corrosion current from ca. 9{mu}A/cm² to ca. 0.5{mu}A/cm² in the mixed solution of 0.1N;N₂SO₄ and 2ppm HF A coat ing layer under potentiostatic control of 0.6V and 0.75V_{SCE} for 500 hours or longer showed some instabilities, however, no significant change in coat Ing layer were observed from Impedance data. In addition, the corrosion current maintained less than 1{mu}A/cm² for most of time for potentiostatic tests. It indicates that high electrical conductivity and corrosion resistance can be obtained by application of coatings in the present work.

PEMFC용 복합소재 분리판을 위한 2단계 제조공법의 예비성형 조건에 대한 연구

허성일 ( Seong Il Heo ),오경석 ( Kyung Seok Oh ),장준호 ( Jun Ho Jang ),양유창 ( Yoo Chang Yang ),한경섭 ( Kyung Seop Han ) 한국복합재료학회 2007 Composites research Vol.20 No.2