• Korean Chemical Engineering Research
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• 제61권1호
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• pp.26-31
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• 2023

고분자 전해질 연료전지(Polymer electrolyte membrane fuel cell, PEMFC) 고분자막의 내구성 향상을 위해서 빠른 시간에 내구성을 평가할 수 있는 가속 내구 평가법들이 연구 개발되었다. 그러나 트럭, 버스 등 대형 상용차용 연료전지 수명은 승용차보다 3배 이상 요구되어 화학적 가속 내구 평가(Accelerated stress test, AST) 시간도 길어져서 1,500 시간 이상이 되었다. 그래서 본 연구에서는 단 시간내에 고분자막의 화학적 내구성을 평가하기 위한 방법으로 막 초기 특성으로 내구성을 예측할 수 있을지 검토하였다. 초기 특성으로 수소투과전류밀도(Hydrogen crossover current density, HCCD)와 단락 저항(Short resistance, SR)을 그리고 3시간의 셀 밖 실험으로 가능한 Fenton 실험을 통해 AST 시간을 예측하였다. HCCD와 불소 이온 유출 농도가 증가하면 AST 시간이 선형적으로 짧아지는 경향을 보였으나 편차가 있었다(R² ≒0.65). SR이 감소하면 AST 시간이 선형적으로 증가하는 상관관계를 보였으며 정확도가 높아(R² =0.93) 고분 자막 초기 SR로 AST 시간을 예측할 수 있었다.

• Korean Chemical Engineering Research
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• 제62권3호
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• pp.246-252
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• 2024

본 연구에서는 구연산 처리를 통하여 폐흑연의 Li, F 등의 불순물을 제거하였으며, 이에 따른 재생 흑연의 구조적 특성, 용량 및 내구성 변화를 관찰하였다. 질소 분위기에서 전처리를 진행한 재생 흑연은 구연산에서 산처리를 진행하였고 SEM (Scanning Electron Microscope), FT-IR (Fourier Transform Infrared spectroscopy), XRD (X-ray Diffraction), XPS (X-ray Photoelectron Spectroscopy)를 통해 구조와 특성 분석을 진행하였다. 산처리를 진행하지 않은 폐흑연은 70 사이클 이전에서 용량이 급격하게 감소하였으나 구연산 처리를 진행한 흑연은 100 사이클에서 302.9 mAh g^-1의 용량과 93.1%의 용량 유지율을 나타내었다. 또한 Rate performance의 전류 밀도 변화에도 구연산 처리한 샘플은 용량의 변화없이 1.0C에서 340.2 mAh g^-1의 성능을 나타내었다. 결과적으로 구연산 처리는 효과적으로 불순물을 제거하여 높은 용량 유지율을 나타내었을 뿐만 아니라 높은 전류 밀도에서도 안정적인 모습을 나타내는 것으로 확인하였다.

• 유기물자원화
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• 제11권4호
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• pp.120-129
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• 2003

0.3M의 옥살산 용액에서 anodic alumina를 제작하였으며 barrier 층을 제거하기 위하여 20wt% 황산 용액에서 한시간 동안 방치시켰다. 이 anodic alumina를 전극으로 사용하여 수용액에서 $Cd^{2+}$, $Co2^{+}$ 및 $Pb^{2+}$이온들을 환원시켜 제거하였다. XRD와 SBM으로 anodic alumina의 구조를 분석하였고, SEM 결과 anodic alumina에는 60nm의 pore가 존재함을 확인할 수 있었으며, 20wt% 황산 용액으로 처리 후 anodic alumina의 표면이 황산에 약간 녹기 때문에 anodic alumina의 표면의 규칙성이 떨어지는 결과를 보였다. anodic alumina를 음극, 그리고 탄소를 양극으로 각각 사용하여 $Cd(NO_3)_2{\cdot}4H_2O$, $Co(NO_3)_2{\cdot}6H_2O$ 및 $PbSO_4$ 수용액에 24시간동안 직류전류를 흘려주었을 때, 전류를 흘려준 시간에 따라 전압이 각각 4.6, 3.4 및 5.1V 까지 증가하다가 4.2, 2.7 및 2.4V로 일정해지는 결과를 얻었다. 전류를 흘려준 시간이 18시간까지는 시간이 증가할수록 용액내의 금속이온의 농도는 감소하였으며 음극인 anodic alumina의 표면에 각 금속들이 석출되는 것을 확인할 수 있었다. anodic alumina로 금속이온을 제거한 수용액을 retriculate vitreous carbon(RVC)를 작업전극으로 하는 flow cell로 제2차 금속이온 제거를 수행하였다. $Cd^{2+}$ 와 $Co^{2+}$이온의 농도는 용액을 flow cell에 20분간 흘려줄 때까지만 감소하였고 $Pb^{2+}$이온 농도는 30분까지 감소하였다. 이 경우 $Cd^{2+}$, $Co^{2+}$ 및 $Pb^{2+}$이온들 제거효율은 각각 34.78, 28.79 및 86.38% 이었다. 또한 $Cd^{2+}$ 와 $Co^{2+}$이온이 동시에 RVC전극에 흡착 가능한 결과를 보였으며 제거효율은 32.30 및 31.37% 이었다.

• 한국항해학회지
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• 제13권1호
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• pp.21-53
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• 1989

In the past twenty years, there has been a rapid increase in the volume of traffic in Korea due to the Korean great growth of the Korean economy. Since transformation provides an infrastructure vital to economic growth, it becomes more and more an integral part of the Korea economy. The importance of coastal shipping stands out in particular, not only because of the expansion limit on the road network, but also because of saturation in the capacity of rail transportation. In spite of this increase and its importance, coastal shipping is falling behind partly because it is givenless emphasis than ocean-going shipping and other inland transportation systems and partly because of overcompetition due to excessive ship tonnage. Therefore, estimating and planning optimum ship tonnage is the first take to develop Korean coastal shipping. This paper aims to estimate the optimum coastal ship tonnage by computer simulation and finally to draw up plans for the ship tonnage balance according to supply and demand. The estimation of the optimum ship tonnage is peformed by the method of Origin -Destimation and time series analysis. The result are as follows : (1) The optimum ship tonnage in 1987 was 358, 680 DWT, which is 54% of the current ship tonnage (481 ships, 662, 664DWT) that is equal to the optimum ship tonnage in 1998. this overcapacity result is in excessive competition and financial difficulties in Korea coastal shipping. (2) The excessive ship tonnage can be broken down into ship types as follows : oil carrier 250, 926 DWT(350%), cement carrier 9, 977 DWT(119%), iron material/machinery carrier 25, 665 DWT(117%), general cargo carrier 17, 416DWT(112%). (3) the current total ship crew of 5, 079 is more than the verified optimally efficient figure of 3, 808 by 1271. (4) From the viewpoint of management strategy, it is necessary that excessive ship tonnage be reduced and uneconomic outdated vessels be broken up. And its found that the diversion into economically efficient fleets is urgently required in order to meet increasing annual rate in the amounts of cargo(23, 877DWT). (5) The plans for the ship tonnage balance according to supply and demand are as follows 1) The establishment of a legislative system for the arrangement of ship tonnage. This would involve; (a) The announcement of an optimum tonnage which guides the licensing of cargo vessels and ship tonnage supply. (b) The establishment of an organization that substantially arrangement tonnage in Korea coastal shipping. 2) The announcement of an optimum ship tonnage both per year and short-term that guides current tonnage supply plans. 3) The settlement of elastic tariffs resulting in the protect6ion of coastal shipping's share from other tonnage supply plans. 4) The settlement of elastic tariffs resulting in the protection of coastal shipping's share from other transportation systems. 4) Restriction of ocean-going vessels from participating in coastal shipping routes. 5) Business rationalization of coastal shipping company which reduces uneconomic outdated vessels and boosts the national economy. If we are to achieve these ends, the followings are prerequisites; I) Because many non-licensed vessels are actually operating and threatening the safe voyage of the others in Korea coastal routes, it is necessary that those ind of vessels be controlled and punished by the authorities. II) The supply of ship tonnage in Korean coastal routes should be predently monitored because most of the coastal vessels are to small to be diverted into ocean-going routes in case of excessive supply. III) Every ship type which is engaged in coastal shipping should be specialized according to the characteristics of its routes as soon possible.

• 대한방사선기술학회지:방사선기술과학
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• 제19권1호
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• pp.95-120
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• 1996

College level educational training system for the allied health manpower in the country is one of the oldest junior college education programs, and has been developed at very steady phase. Since the school years of the programs limited for 2 to 3 years by the education related law, qualification of the manpower is insufficient to meet the rapidly changing needs in the field of allied health and medicine. The system is comparable with that of developed countries where 4-year baccalaureate degree programs are basically required to be an allied health personnel. Thus, education and training background of allied health program graduates of the country confronts the barriers in competition and cooperation with the graduates of foreign countries at equal basis. Beside, junior college graduates can hardly find the way through advanced courses at 4-year colleges in their specialties except a few programs such as environmental sicience or courses in hygiene. It has long been sought to develop the education and training programs for junior college graduates. Some of them are already materilized and some show remarkable progress while some need to tackle. Wide opening of the opportunity to enroll extensive education program for the junior college graduates of allied health science majors in 4-year colleges with eventual grant of bachelor's degree for those who successfully completed the programs should soon be substantiated. The study was focused to emphasize the necessity of the extensive education and training for the junior college graduate allied health manpower, and to show possibility of the education program development in connection with the 4-year degree granting education programs. The outcome of the study can be summarized as followings. 1. A total number of graduates from eight allied health sciences related programs of junior colleges by the year of 1995 are 109,320. 2. According to the survey report analysed through questionnaires, 99.7% of respondents including administrative deans and professors of junior colleges agreed with the establishment of extensive education and training programs in junior colleges. 53.9% of administrative deans, 52.9% of professors and 47.6% of the graduates expected that it is possible to learn more about their majors, and to earn bachelor's degree through the extensive education programs. Other opinions include that the programs can provide supplementary opportunities to fortify in the area of basic life science, and development of research and technology. 3. It was also found through the survey that 91.2% of the deans, 87.8% of the professors and 68.2% of the graduates responded that the most appropriate organizations to open the extensive education and training programs for allied health manpower are junior colleges where allied health personnel are taught and trained. The majority of the respondents agreed that the acceptable number of credits offered for the previous 2-year junior college graduates are $50\sim60$, and those for the current 3-year graduates are $20\sim30$ units. 4. It was strongly suggested through the survey that baccalaureate degree should be granted for those who successfully completed the extensive courses. The suggestion was claimed by 94.1% of the deans, 89.4% of the professors and 83.4% of the graduates. 5. The model curricula for the extensive education and training programs for the allied health manpower are designed for the purpose of broad capability in practice, enrichment of knowledge and promotion of proficiency for the self access in the major areas. 6. To meet the universal standards of allied health education and training program, it is recommended that opening of the curricula for the extensive, and as well as intensive, courses within junior colleges(continuation education institute) should be materialized. The special baccalaureate degree programs within junior colleges are also recommended to accommodate the junior college graduates and to grant the degree fellowing successful completion of the courses. As a part of the education revolution in progress, the school years at junior college level should be flexible depending upon the nature of course and trend of the universe. For instance, the school years for the allied health manpower should be extended to two to four years from current two to three years.

• Radiation Oncology Journal
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• 제19권1호
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• pp.66-73
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• 2001

목적 : 붕소-중성자 포획치료법(Boron Neutron Capture Therapy, BNCT)을 위해 원자력병원 싸이클로트론에서 발생되는 최대에너지 34.4 MeV의 속중성자(Fast neutron)를 70 cm 파라핀으로 감속시킨 후 선량 특성을 조사하였다. 그 결과를 토대로 열외중성자(Epithermal neutron) 선량 측정법에 대한 프로토콜을 확립하여 원자로에서 방출되는 열외 중성자 선량 특성 평가의 기초를 삼고, 가속기를 이용한 BNCT 연구에 대한 타당성 여부를 조사하고자 한다. 대상 및 방법 : 공기 중 선량 및 물질 내 선량 분포 측정을 위해 Unidos 10005 (PTW, Germany) 전기계와 조직 등가 물질인 A-150 플라스틱으로 제작된 IC-17 (Far West, USA) 및 IC-18, ElC-1 이온함을 사용하였고, 감마선의 측정을 위해서는 마그네슘으로 제작된 IC-l7M 이온함을 이용하였으며 조직등가 기체와 아르곤 기체를 분당 5cc 씩 주입하며 측정하였다. 중성자, 광자, 전자가 혼합된 장의 모의 수송 해석을 위해 이용되는 Monte Carlo N-Particle (MCNP) transport code를 사용하여 2차원적 선량 분포 및 에너지 분포를 계산하였으며 이 결과를 측정값과 비교하였다. 결과 : BNCT에서의 유효 치료 깊이인 물 팬텀 4 cm에서의 선량은 치료기 1 MU 당 $6.47\times10^{-3}\;cGy$로 미세하였으며, 이때 감마 오염도(contamination)는 $65.2{\pm}0.9\%$로 중성자보다는 감마선에 의한 선량 기여분이 우세하였다. 깊이에 따른 선량 분포 특성에서는 중성자 선량은 선형적으로 감쇠 되었고, 감마선량은 지수적으로 보다 급격히 감쇠되는 경향을 보였으며 전체 선량의 $D_{20}/D_{10}$은 0.718 이었다. MCNP에 의한 에너지 분포 전산 계산의 결과 2.87 MeV 이하에서 중성자 피크가 나타났으며, 저에너지 영역에서는 감마선이 연속적으로 분포되는 양상을 보였다. 결론 : 벽 물질이 서로 다른 두 개의 이온함을 사용한 직접 선량 측정과 MCNP 전산 시뮬레이션을 이용한 공간 선량분포 계산으로 미세 속중성자 빔에 대한 선량 특성을 파악할 수 있었으며, 원자로 열외중성자 주(Epithermal neutron column)에 대한 선량 평가 자료로 확보하였다. 아울러 가속기에 대한 연구가 진행되어 고전압, 고전류를 발생시키는 전원 공급장치와 표적핵(Target) 물질이 개발되고 비스무스나 납 등에 의해 감마 오염도를 줄일 경우, 싸이크로트론에 의한 보론-중성자 포획치료도 가능해질 것으로 판단된다.

• 전기화학회지
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• 제2권3호
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• pp.123-129
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• 1999

리튬이온전지용 $LiCoO_2$ 전극의 super s black 도전재료의 함량에 따른 초기 충방전 특성을 1 mol/l $LiPF_6/EC+DEC(1:3\;by\;w/w)$의 전해액에서 리튬기준전극에 대하여 4.3 V에서 2.0 V의 전위 구간에 대하여 C/4 및 C/2율로 충방전하여 측정하였다. 최초의 충전과정에서 high impedance충전 특성을 보였으며, super s black도전재료를 $3\%w/w$ 사용한 경우, $0.5 mA/cm^2$ 전류밀도의 충전에서 high impedance의 해소에 따라 $3.82\;{\Omega}\;{\cdot}\;g-LiCoCo_2$의 저항 감소를 나타내었으며, $0.728\;{\Omega}{\cdot}g-LiCoCo_2$의 전극저항과 비교하여 약 7배 높은 값을 나타내었다. 제2차 충전에의 high impedance해소는 약 $63\;{\Omega}{\cdot}g-LiCoCo_2$으로서 전극저항의 $12\%$ 정도이며, 제1차 충전의 high impedance해소에 비하여 $1.7\%$의 수준으로 감소하였다. 제1차 충전 및 방전 비용량은 C/4방전율에서 각각 160-161 및 $153\~155mAh/g-LiCoO_2$으로, 쿨롱효율은 $95.4\~96.4\%$였으며, 비가역 비용량은 약 6 mAh/g-$LiCoO_2$였다. 충전종료 지점에서 측정한 비저항은 도전재료 함량 $2\~7\%w/w$범위에서 낮은 값을 나타내어 비가역 비용량 특성의 변화와 일치하였다. 도전재료의 함량 증가에 따라 용량밀도가 감소하였으며, C/4율 방전에서 super s black함량 $2\%w/w$와 $2.9\%w/w$의 도전재료를 사용한 전극의 용량밀도는 각각 447mAh/ml 및 431 mAh/ml였다

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 1998년도 제13회 하계학술발표회 논문집
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• pp.116-127
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• 1998

The Necessity of Cyber University. Within the rapidly changing environment of global economics, the environment of higher education in the universities, also, has been, encountering various changes. Popularization on higher education related to 1lifetime education system, putting emphasis on the productivity of education services and the acquisition of competitiveness through the market of open education, the breakdown of the ivory tower and the Multiversitization of universities, importance of obtaining information in the universities, and cooperation between domestic and oversea universities, industry and educational system must be acquired. Therefore, in order to adequately cope wi th these kinds of rapid changes in the education environment, operating Cyber University by utilizing various information technologies and its fixations such as Internet, E-mail, CD-ROMs, Interact ive Video Networks (Video Conferencing, Video on Demand), TV, Cable etc., which has no time or location limitation, is needed. Using informal ion and telecommunication technologies, especially the Internet is expected to Or ing about many changes in the social, economics and educational area. Among the many changes scholars have predicted, the development and fixations of Distant Learning or Cyber University was the most dominant factor. In the case of U. S. A., Cyber University has already been established and in under operation by the Federate Governments of 13 states. Any other universities (around 500 universities has been opened until1 now), with the help of the government and private citizens have been able to partly operate the Cyber University and is planning on enlarging step-by-step in the future. It could be seen not only as U. S. A. trying to elevate its higher education through their leading information technologies, but also could be seen as their objective in putting efforts on subordinating the culture of the education worldwide. UTRA University in U. S. A., for example, is already exporting its class lectures to China, and Indonesia regions. Influenced by the Cyber University current in the U.S., the Universities in Korea is willing .to arrange various forms of Cyber Universities. In line with this, at JUNAM National University, internet based Cyber University, which has set about its work on July of 1997, is in the state of operating about 100 Cyber Universities. Also, in the case of Hanam University, the Distant Learning classes are at its final stage of being established; this is a link in the rapid speed project of setting an example by the Korean Government. In addition, the department of education has selected 5 universities, including Seoul Cyber Design University for experimentation and is in the stage of strategic operation. Over 100 universities in Korea are speeding up its preparation for operating Cyber University. This form of Distant Learning goes beyond the walls of universities and is in the trend of being diffused in business areas or in various training programs of financial organizations and more. Here, in the hope that this material would some what be of help to other Universities which are preparing for Cyber University, I would 1ike to introduce some general concepts of the components forming Cyber University and Open Education System which has been established by JUNAM University. System of Cyber University could be seen as a general solution offered by tile computer technologies for the management on the students, Lectures On Demand, real hour based and satellite classes, media product ion lab for the production of the multimedia Contents, electronic library, the Groupware enabling exchange of information between students and professors. Arranging general concepts of components in the aspect of Cyber University and Open Education, it would be expressed in the form of the establishment of Cyber University and the service of Open Education as can be seen in the diagram below.

• 환경영향평가
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• 제30권1호
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• pp.35-48
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• 2021

본 연구에서는 예산군에 위치한 질산성 질소 오염 지하수 부지를 대상으로 오염지하수의 지중정화현장 적용성 평가를 수행하고자, 영가철/바이오 환경정화소재를 이용한 Injected PRB(Permeable Reactive Barrier)와 관측정을 현장 오염지하수부지에 적용하고 주요 정화지표에 대한 변화를 모니터링하였다. 질산성질소, 아질산성질소, 암모니아성질소, 철 이온, TOC, 탁도 등의 항목 등을 조사하고 미생물 분석을 실시하여 지중정화기술의 현장 적용성을 평가하였다. 연구대상 부지는 농경지역으로 북쪽 경계는 하천이 서쪽에서 동쪽으로 흐르며 하천 경계를 형성하고 남쪽은 불투수 경계로 이루어져 있다. 질산성질소는 전반적으로 지하수 흐름과 유사하게 하천으로 흐르는 것으로 분석되었다. 모델링 결과, 약 3년에서 5년정도 경과 후 안정 상태로 도달하는 것으로 판단되었다. 이는 추가적인 오염원 유입이 없는 현재 상태만 고려한 것으로 지속적 오염이 유입된다면 오염범위 및 안정화 기간이 증가할 수 있다. 모니터링 결과, PRB설치 전, 후 철 이온, TOC, 탁도 값이 큰 차이를 보이지 않아 PRB의 음용수 관정 영향은 없는 것으로 판단되어 해당 지중정화기술의 지중 주입 적합성을 확인하였다. 질산성질소는 PRB 설치 42일 차까지 5 mg/L보다 낮은 농도가 유지되었으나 84일 차부터 PRB 내부의 질산성질소 제거 유효 기간이 끝나 원래의 농도를 회복하였다. PRB 설치 후 아질산성 질소와 암모니아성 질소의 검출은 PRB에 의한 질산성 질소의 환원에 의한 감소를 보여주었으며, 미생물 분석 결과 종 다양성이 증가하고 탈질 미생물을 포함하고 있는 Betaproteobacteria Class 군집이 크게 증가한 결과는 질산성 질소가 생물학적 환원작용에 의한 정화 가능성도 보여주었다.

• Corrosion Science and Technology
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• 제14권2호
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• pp.99-105
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• 2015

The structures of reinforced concrete have been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as seawater, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, specimens having six different coating thickness (W/C:0.5) were prepared and immersed in flowing seawater for five years to evaluate the effect of coating thickness and immersion time on corrosion property. The polarization characteristics of these embedded steel bars were investigated using electrochemical methods such as corrosion potential, anodic polarization curve, and impedance. At the 20-day immersion, the corrosion potentials exhibited increasingly nobler values with coating thickness. However, after 5-yr. immersion their values were shifted in the negative direction, and the relationship between corrosion potential and coating thickness was not shown. Although 5-yr. immersion lowered corrosion potential, 5-yr. immersion did not increase corrosion rate. In addition, after 5-yr. immersion, the thinner cover thickness, corrosion current density was decreased with thinning coating thickness. It is due to the fact that ease incorporation of water, dissolved oxygen and chloride ion into a steel surface caused corrosion and hence, leaded to the formation of corrosion product. The corrosion product plays the role as a corrosion barrier and increases polarization resistance. The corrosion probability evaluated depending on corrosion potential may not be a good method for predicting corrosion probability. Hence, the parameters including cover thickness and passed aged years as well as corrosion potential is suggested to be considered for better assessment of corrosion probability of reinforced steel exposed to partially or fully in marine environment for long years.