• 한국안전학회지
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• 제33권3호
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• pp.92-98
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• 2018

The flow of cooling water in a passive containment cooling system (PCCS), used to remove heat released in design basis accidents from a concrete containment of light water nuclear power plant, was conducted in order to investigate the thermo-fluid equilibrium among many parallel tubes of PCCS. Numerical simulations of the subcooled boiling flow within a coolant loop of a PCCS, which will be installed in innovative pressurized-water reactor (PWR), were conducted using the commercially available computational fluid dynamics (CFD) software ANSYS-CFX. Shear stress transport (SST) and the RPI model were used for turbulence closure and subcooled flow boiling, respectively. As the first step, the simplified geometry of PCCS with 36 tubes was modeled in order to reduce computational resource. Even and uneven thermal loading conditions were applied at the outer walls of parallel tubes for the simulation of the coolant flow in the PCCS at the initial phase of accident. It was observed that the natural circulation maintained in single-phase for all even and uneven thermal loading cases. For uneven thermal loading cases, coolant velocity in each tube were increased according to the applied heat flux. However, the flows were mixed well in the header and natural circulation of the whole cooling loop was not affected by uneven thermal loading significantly.

• Journal of Yeungnam Medical Science
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• 제5권1호
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• pp.77-84
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• 1988

환경수로부터 Legionella속 균의 분리를 위해 대구시 내 24개의 대형건물의 냉각탑수를 대상으로 1987년 7월과 9월 2차례에 걸쳐 총 48개의 검수를 채취하여 Legionella속 균의 분리를 시도하였다. 9월에 채취한 냉각탑수 24개중 3개에서만 Legionella가 분리되었으며 동정 결과 이들은 모두 L. pneumophila로 판명되었다. 이들의 serotype, 지속성, 병원성을 밝히기 위해 계속적인 연구가 요망된다. 이상의 결과로 보아 우리 나라의 환경수중에 분포되어 있는 Legionella속 균은 대부분 L. pneumophila인 것으로 추정되며, 우리 나라에서는 계절 변화가 뚜렷하여 겨울철에는 냉각 시설을 가동하지 않는 관계로 냉각탑수 중에서의 Legionella의 검출율은 초 여름보다 늦 여름에 높은 것으로 생각된다.

• 한국자기학회지
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• 제10권1호
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• pp.7-10
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• 2000

Co계 비정질합금을 400~46$0^{\circ}C$에서 열처리 한 후 냉각조건에 따른 자기특성의 변화를 조사하였다 42$0^{\circ}C$에서 30분 열처리 한 뒤 큐리점까지 노냉 후 수냉 시킨 경우 초투자율이 수냉 또는 노냉 했을 때보다 60-100% 정도 증가했다. 냉각속도에 따른 자기적 특성 변화를 내부음력 및 이온쌍의 규칙도(ordering) 관점에서 고찰하였다

• 대한기계학회논문집B
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• 제21권10호
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• pp.1262-1272
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• 1997

An experimental study on the frequency control of an inverter heat pump to get the desired indoor room temperature has been conducted for the performance characteristics during the steady, 4, 8, and 16 step frequency operations. The heat pump model used in this study was operated to meet the experimental conditions of ASHRAE standard. The performance of the system was tested by measuring the temperature and pressure of the refrigerant, and cooling capacity, power consumption, etc. of the system. As the controlling frequency steps increased, the running time of the compressor increased as well as the electric consumption of the system and the cooling energy due to the wall heating load. However, the average cooling COP was improved.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.584-587
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• 2006

An energy generating greenhouse based on fluoropolymer envelope and fresnel lens is proposed. The outstanding properties of the fluoropolymer films make them very suitable for large scale solar applications. Extremely high optical transmission over the whole solar spectrum, combined with mechanical strength, and durability allows us to design a highly optimized greenhouses for both plant growing and energy generation. Systems such as photovoltaic triple junction cells are especially attractive since they have up to 35% efficiency with much less cell material when the sun beam is focused with concentrators such as fresnel lenses. Cooling such devices will enhance the efficiency and provide useful thermal energy that could be further utilized for various applications depending on the local demands. This article introduces the basic ideas and principles of the energy generating greenhouses as a first step towards the actual deployment of such systems under Korean environment.

• Journal of Radiation Protection and Research
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• 제40권2호
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• pp.92-100
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• 2015

경수로 사용후핵연료 건식 중간저장시설의 방사선영향평가 효율성 개선을 목적으로 '선원항 지정방법에 따른 민감도 평가', '2-Step 계산'기법 개발 및 '냉각기간 이득효과' 적용에 따른 방사선 영향평가를 수행하였다. 본 연구에서는 저장건물의 용기배열 순서에 따라 순차적으로 선원항을 지정하여 직접선량에 미치는 민감도를 평가하였으며, 차폐건물 외벽에서의 방사선량은 내벽과 인접한 최근접 2개 열에 의한 영향이 지배적임을 확인하였다. 또한, 저장시설에 차폐 건물이 도입될 경우, 막대한 전산해석 시간을 감소시키기 위해 '2-Step 계산'기법을 수립하여 평가한 결과는 절반가량의 해석시간으로 직접(1-Step) 계산결과와 유사한 결과를 도출하였다. 마지막으로, 저장시설에 순차적으로 저장되는 저장용기의 보관기간을 사용후핵연료의 실제 냉각기간을 적용하면 건물 외벽에서의 방사선량이 냉각기간을 모두 동일하게 설정한 계산값에 비해 40% 정도 낮게 평가됨을 확인하였다. 본 연구는 중간저장시설의 방사선 영향평가를 위한 몬테칼로 차폐해석 방법의 효율성을 향상시키고자 수행되었으며, 좀 더 다양한 사례에 대한 평가를 통하여 신뢰성을 향상시킨다면 저장시설의 설계 및 부지경계 기준설정에 활용할 수 있을 것이다.

• 한국수정란이식학회지
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• 제11권2호
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• pp.125-135
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• 1996

The present study was carried out to investigate the effects of cryoprotectants, equilibration step, freezing rate, culture condition following in vitro fertilization, and age and development stage of embryo by freezing with conventional slow freezing and vitrification on survival of frozen-thawed Korean native cattle(KNC) blastocysts produced in vitro. The KNC blastocysts produced in vitro were equilibrated in 1.8M ethylene glycol or 1.4M glycerol and cooled from -6$^{\circ}C$ to -35$^{\circ}C$ at -0.3$^{\circ}C$ or -O.6$^{\circ}C$ /minute. When equilibrated in 1.8M ethylene glycol, survival rate of fiozen4hawed blastocysts was sarne in both -0. 3$^{\circ}C$ /min and -0.6$^{\circ}C$ /min cooling rate(71.4%). With the equilibration in 1.4M glycerol, survival rate was higher in -0.3$^{\circ}C$ /min(63.6%) than in -0.6$^{\circ}C$ /min cooling rate(53.8%). For vitrification of the KNC blastocysts produced in vitro, they were equilibrated in 2-step or 3-step exposure to vitrification solution(25% ethylene glycol + 25% glycerol). Survival rate was sirilar in both 2-step(45.0%) and 3-step exposure(47.4%). According to culture condition following in vitro fertilization, higher survival rate was obtained for blastocysts co-cultured with bovine oviductal epithelial cell(BOEC, 77.3%) than for those cultured with epidermal growth factor(EGF, 65.7%) or for those co-cultured with BOEG + EGF (54.8%). According to embryo age and development stage, higher survival rate was obtained for 7-day ernbryos(70.0%) than 8-day(56.8%) or 9-day(20.0%) for blastocyst stage and obtained for 8-day embryos(74.3%) than 7-day(62.5%) or 9-day(42.9%) for exponded blastocyst. In surnmary, higher survival rate of frozen4hawed KNC blastocysts produced in vitro were obtained by using ethylene glycol for cryoprotectant and -0.3$^{\circ}C$ /min for cooling rate. And higher survival rate were obtained with co-culture with BOEC for culture condition following in vitro fertilization and with 7-day blastocyst or 8-day expanded blasto cyst for embryo age and development stage.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.169-174
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• 2006

본 연구는 재생냉각형 고압 축소형 연소기 설계에 관한 것으로 이 연소기를 제작하기 전에 열유속측정을 위한 물냉각 고압 축소형 연소기를 제작하였다. 물냉각 고압 축소형 연소기의 연소시험결과 높은 연소성능 및 냉각성능이 검증된 설계 조건을 얻었고 이를 바탕으로 재생냉각형 고압 축소형 연소기의 형상을 설계하였다. 설계된 연소기의 형상은 제작이 완료된 후 연소시험을 수행하여 실용성을 검증 할 예정이다.

• 한국분무공학회지
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• 제19권1호
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• pp.19-24
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• 2014

In this study, the cooling performance of a liquid CPU cooler using the water/propylene glycol(PG)-based $Al_2O_3$ nanofluids is experimentally investigated. Water/PG-based $Al_2O_3$ nanofluids are manufactured by two-step method with ultrasonic energy for 10 hours. The volume fractions of the nanofluids are 0.25% and 0.35%. Thermal conductivity and viscosity of the nanofluids are measured to theoretically predict the thermal performance of the liquid CPU cooler using performance factor. Performance factor results indicate that the cooling performance of the liquid CPU cooler can be improved using the manufactured nanofluids. To evaluate the cooling performance of the liquid CPU cooler experimentally, temperature differences between ambient air and heater are measured for base fluid and nanofluids respectively. Based on the results, it is shown that performance of the liquid CPU cooler using $Al_2O_3$ nanofluids is improved maximum up to 8.6% at 0.25 Vol.%.

• 열처리공학회지
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• 제11권1호
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• pp.46-53
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• 1998

The variation of the mechanical properties, microstructures and the formation of retained austenite with heat treatment conditions in austempered ductile cast iron has been investigated. In the case of austempered ductile cast iron below 25mm diameter, it has been found that a pearlite structure are not obtained under a super cooled condition at range of $0.05^{\circ}C/sec{\sim}10^{\circ}C/sec$, and the matrix is precipitated in graphite, bainite and retained austenite. After austempering treatment the retained austenite is increased with decreasing cooling rate. The elongation increases with decreasing super cooling rate, and the optimum result has been shown to be the elongation of 15.6% at super cooling rate of $0.05^{\circ}C/sec$. The optimum result has been shown to be the tensile strength-elongation balance of $1656kgf/mm^2.%$ and it is more than doubled to as the casting state and continuous cooling condition.