• International Journal of Naval Architecture and Ocean Engineering
• /
• 제5권4호
• /
• pp.580-597
• /
• 2013

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low ($-100^{\circ}C$) and cryogenic ($-163^{\circ}C$) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

• 전기학회논문지P
• /
• 제59권4호
• /
• pp.456-461
• /
• 2010

This study compares the criteria of earth leakage breakers (ELB) and analyzes the characteristics of an Igc-free ELB operated by an active component which is not misoperated by capacitive current. Even for the same ELB, the earth leakage current flowing through the human body is estimated to be differ greatly depending on the power source, voltage, location and status of contact, contact time duration, etc. Earth leakage breakers are classified based on the rated voltage, rated sensing current, rated operating time etc. Mounting and demounting of the existing equipment can be performed easily since an $I_{gc}$-free ELB is manufactured with the same structure as a conventional ELB. The rated operating current of a conventional and an $I_{gc}$-free ELB is 30mA, the sensing current is 25mA and the rated non-operating current is 15mA. In the analysis of non-operating current characteristics, the rated non-operating current of 15mA was satisfied up to a 20mA charging current in the conventional ELB, but does not satisfy the rated non-operating current as it operates when the resistive leakage current is lower than 15mA for a charging current exceeding 20mA. Also, the ELB is misoperated without a resistive leakage current when the charging current exceeded 25mA. However, the newly developed $I_{gc}$-free ELB satisfied the rated non-operating current even when the charging current was 60mA. Also, in comparison to the interrupting characteristics, it was confirmed that the charging current satisfying the rated non-operating current of the $I_{gc}$-free ELB was three times higher than that of the conventional ELB.

• 방사성폐기물학회지
• /
• 제20권1호
• /
• pp.43-63
• /
• 2022

The aim of this review is to communicate some essential knowledge of the underlying mechanism of the corrosion of structural containment alloys during molten salt reactor operation in the context of prospective online monitoring in future MSR installations. The formation of metal halide species and the progression of their concentration in the molten salt do reflect containment corrosion, tracing the depletion of alloying metals at the alloy salt interface will assure safe conditions during reactor operation. Even though the progress of alloying metal halides concentrations in the molten salt do strongly understate actual corrosion rates, their prospective 1^st order kinetics followed by near-linearly increase is attributed to homogeneous matrix corrosion. The service life of the structural containment alloy is derived from homogeneous matrix corrosion and near-surface void formation but less so from intergranular cracking (IGC) and pitting corrosion. Online monitoring of corrosion species is of particular interest for molten chloride systems since besides the expected formation of chromium chloride species CrCl₂ and CrCl₃, other metal chloride species such as FeCl₂, FeCl₃, MoCl₂, MnCl₂ and NiCl₂ will form, depending on the selected structural alloy. The metal chloride concentrations should follow, after an incubation period of about 10,000 hours, a linear projection with a positive slope and a steady increase of < 1 ppm per day. During the incubation period, metal concentration show 1^st order kinetics and increasing linearly with time^1/2. Ideally, a linear increase reflects homogeneous matrix corrosion, while a sharp increase in the metal chloride concentration could set a warning flag for potential material failure within the projected service life, e.g. as result of intergranular cracking or pitting corrosion. Continuous monitoring of metal chloride concentrations can therefore provide direct information about the mechanism of the ongoing corrosion scenario and offer valuable information for a timely warning of prospective material failure.

• 대한지리학회지
• /
• 제40권6호
• /
• pp.748-761
• /
• 2005

본 연구는 대한지리학회 60년의 역사를 그 체제, 예산, 간행물, 회원수, 전공, 논문 등을 통해서 그것이 어떻게 변하여 왔는지를 밝히고, 동시에 학회 60년 역사의 시기구분을 시도 한것이다. 한국에 있어서 서구식 근대지리학의 역사는 불과 60년, 대한지리학회가 창립(1945년 9월11일)되면서 비로소 시작된다. 1960년 IGU 스톡홀름 총회 때, 겨우 국제적 회원국으로 가입하였고, 1963년에 대한지리학회 학회지 창간호가 탄생하였다. 이로부터 불과 40여년 만에 한국은 제 29차 국제지리학 대회를 성공적으로 치루면서 새천년을 시작하였으니 대한지리학회는 한국의 경제성장 만큼이나 급성장한 셈이다. 학회의 회원수는 1966년에 불과 116인이었으나 2004년 현재에 약 1000인에 이르고, 박사학위 소지자는 1960년에 단지 2인이었으나 2004년에 388인, 이중에 약$43\%$는 외국에서 받은 학위이다. 전공별 회원수는 경제${\cdot}$사회지리 분야가 가장 많고, 그 다음이 도시${\cdot}$인구지리 분야이다. 최근10년 동안에 생태지리학을 포함한 자연지리와 지리교육, GIS분야의 전공자수가 급증하고 있는데, 이것은 시대의 요구를 잘 반영하는 현상이다 학회지 창간호가 탄생한 것은 1963년이지만 이것이 정기간행물이 된 것은 1966년 부터이고, 1993년부터 영문판을 포함하여 계간 및 격월간으로 간행되고 있다. 학회지에 계재한 논문의 편수를 보면, 1960${\~}$70년대에는 연간 평균7편, 1980년대에 약 11편, 1990년대에 24편, 새천년에 와서 무려 52편으로 급성장하였다. 1990년대 이후 논문을 계재할 기회가 많아졌고, 회원들의 연구활동이 고무되고 있기 때문이다. 학회지에 실린 전공분야의 분포를 보면, 역시 경제${\cdot}$사회지리 분야가 가장 많고 그 다음이 생태학을 포함한 자연지리학 분야, 그리고 도시 인구지리 분야이다. 앞에 지적한 전공 회원수와 함께 논문계재 편수에 있어서도 문화${\cdot}$역사분야, 지리교육 분야, 응용 및 GIS 분야는 최근에 급성장하는 추세이다. 대한지리학회는 회원수나 그 활동으로 보아서 급성장하고 있으며 국제화 되고있다. 그리고 지난 60년의 역사를 시기별로 나누어 성격을 부여한다면 (1)창립과 혼돈기($1945{\~}1959$), (2)재건기($1960{\~}1969$), (3)체제정비기($1970{\~}1989$), (4)약진기($1990{\~}1999$), (5)국제화시기($2000{\~}\;$)로 나눌 수 있다.

• 대한자기공명의과학회:학술대회논문집
• /
• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
• /
• pp.103-105
• /
• 2003

After fifteen years of development, Magnetic Resonance (MR) technology for human imaging and spectroscopy is reaching a refined state with FDA approved 3T clinical products from Siemens, GE, and Philips. Broker has cleared CE approval with a 4T system. Varian supports a 4T system platform as well. Shielded magnets are standard at 3T from GE, Oxford, Magnex, and IGC. A shielded 4T whole body magnet is available from Oxford. Stronger switched gradients and dynamic shim coils, desired at any field, areespecially useful at higher static magnetic fields B0. In addition to the higher currents required for higher resolution slice or volume selection afforded by higher SNR, whole body gradient coils will be driven at increasing slew rates to meet the needs of new cardiac applications and other requirements. For example 3T and 4T systems are now being equipped with 2kV, 500A gradient coils and amplifiers capable of generating 4G/cm in 200msec, over a 67+/-cm bore diameter. High field EPI applications require oscillation rates at 1 kHz and higher. To achieve a benchmark 0.2 ppm shim over a 30cm sphere in a high field magnet, at least four stages of shimming need to be considered. 1) A good high field magnet will be built to a homogeneity spec. falling in the range of 100 to 150 ppm over this 30cm spherical "sweet spot" 2) Most modern high field magnets will also have superconducting shim coils capable of finding 1.5 ppm by their adjustment during system installation. 3) Passive ferro-magnetic shimming combined with 4) active, high order room temperature shim coils (as many as five orders are now being recommended) will accomplish 0.2 ppm over the 30cm sphere, and 0.1 ppm over a human brain in even the highest field magnets for human studies. Safety concerns for strong, fast gradients at any B0 field include acoustic noise and peripheral nerve stimulation. One or more of the mechanical decoupling methods may lead to quieter gradients. Patient positioning relative to asymmetric or short gradient coils may limit peripheral nerve stimulation at higher slew rates. Gradient designs combining a short coil for local speed and strength with a longer coil for coverage are being developed for 3T systems. Local gradients give another approach to maximizing performance over a limited region while keeping within the physiologically imposed dB0/dt performance limits.

• 해양환경안전학회지
• /
• 제27권4호
• /
• pp.529-537
• /
• 2021

LNG 운반선은 선체와 화물창이 일체형인 멤브레인 타입을 적용한 대형선을 중심으로 건조되어 왔으나, 최근 친환경 연료인 LNG의 수요 증가 및 LNG 벙커링 인프라 확대로, 중소형 운반선에 대한 관심이 증가하고 있다. 본 연구에서는 중소형 LNG 운반선에 IMO B 형식 탱크를 적용하고 설계의 안정성 및 적합성을 검증하는 것을 목표로 하였고, B 형식 탱크를 적용하는 경우 필수적으로 수반되는 파괴역학 기반의 균열 진전 해석 및 가스 누출을 대비하여 설치되는 부분 2차 방벽의 크기의 결정을 위한 내용을 소개하였다. LNG 운반선 적용에 적용되는 국제 규정인 IGC 코드를 이용하여 설계 수명동안 균열 진전 해석에 적용될 응력 분포를 산정하는 방법을 제시하였고, Paris 법칙과 British Standard 7910 (BS 79110) 기반의 균열 진전 해석 프로그램을 개발하여 표면 균열 진전 해석을 수행하였다. 다음으로 2차 방벽의 크기를 결정하기 위하여, 초기 관통 균열의 크기를 가정할 수 있는 방법론을 제시하고, 균열 감지 후 회항 가능 기간인 15일 동안의 관통 균열 진전 해석을 수행하여 국제 규정에서 요구하는 B 형식 화물 탱크의 안정성 및 적합성을 검증하였다. 더 정확한 피로 균열 진전 해석을 위하여 코드 기반에 더하여 직접 해석을 통한 해석 절차 개발 및 검증이 필요할 것으로 사료된다.