• Ocean and Polar Research
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• 제26권1호
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• pp.65-75
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• 2004

In order to understand the water masses and their distribution in the eastern Yellow Sea from winter to spring, a cluster analysis was applied to the temperature and salinity data of Korea Oceanographic Data Center from 1970 to 1990. From December to April, Yellow Sea Cold Water (YSCW) dominates the eastern Yellow Sea, whereas Eastern Yellow Sea Mixed Water (MW) and Yellow Sea Warm Water (YSWW) are found in the southern part of the eastern Yellow Sea. MW appears at the frontal region around $34^{\circ}N$ between YSCW in the north and YSWW in the south. On the other hand, Tshushima Warm Water (TWW) is found around Jeju Island and the South Sea of Korea. These water masses are relatively well-mixed throughout the water column due to the winter monsoon. However, the water column begins to be stratified in spring due to increased solar heating, the diminishing winds and fresh water discharge, and the water masses in June may be separated into surface, intermediate and bottom layers of the water column. YSWW advances northwestward from December to February and retreats southeastward from February to April. This suggests a periodic movement of water masses in the southern part of the eastern Yellow Sea from winter to spring. YSWW may continue to move eastward with the prevailing eastward current to the South Sea from April to June. Also, the front relaxes in June, but the mixed water advances to the north, increasing salinity. The salinity is also higher in the nearshore region than offshore. This indicates an influx of oceanic water to the north in the nearshore region of the eastern Yellow Sea in spring in the form of mixed water.

• 한국유체기계학회 논문집
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• 제19권3호
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• pp.14-18
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• 2016

The power generation system using cold energy, which evolves in a large amount during the vaporization process of the liquefied natural gas, was designed in favor of the Rankine cycle with a mixed refrigerant as the working fluid. In this study it is intended to identify the allowable limits of the working fluid composition in respect of equipment safety in the Rankine cycle-type power generation system driven by the cold energy. The thermodynamic properties of the working fluid, which is a hydrocarbon mixture, were calculated with the Peng-Robinson model. In the steady state simulation of the power generation system by using a commercial tool Aspen HYSYS, the feed conditions of LNG Test Bed Train No.1 along with some necessary assumptions were incorporated. The results indicated that deterioration of the mechanical performance of the equipment as well as its safety would be brought about if contents of $C_2H_6$ and $C_3H_8$ in the mixture become, respectively, too high or too low.

• 한국초전도ㆍ저온공학회논문지
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• 제15권1호
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• pp.45-50
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• 2013

Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

• 한국염색가공학회지
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• 제28권3호
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• pp.175-182
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• 2016

To investigate dyeing behaviors in accordance with dye structure in cold pad batch dyeing of cotton knit, monochlorotriazine-vinylsulfone bifunctional dyes and monofluorotriazine-vinylsulfone bifunctional dyes were prepared. The spectral property and solubility of the dyes were tested and compared with the imported dyes. In addition, exhaustion behaviors of individual and mixed dye solutions were measured to examine the influence of dye structure on dyeing behavior in cold pad batch dyeing. The substantivity, fixation, migration index and half dyeing time were also calculated for further analysis of dyeing behavior of the prepared dyes. As a result, both dyes exhibited the superior solubilities and satisfactory light absorption properties. Also, monofluorotriazine-vinylsulfone bifunctional dyes showed moderate sensitivity to alkalinity and proper kinetic index values compared with the monochlorotriazine-vinylsulfone bifunctional dyes and the imported dyes. The results indicated monofluorotriazine-vinylsulfone bifunctional structure of the dye is suitable for cold pad batch dyeing.

• 한국건축시공학회지
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• 제13권1호
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• pp.38-47
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• 2013

When building with concrete in cold weather, an insulation method of heat curing must be determined, and a holistic curing plan that considers the characteristics of structures, the heat loss coefficient of a curing sheet, the joint condition of the curing materials and the quantity of heat produced by a heating apparatus is an essential prerequisite for protection against early frost damage. But on a number of national construction sites, there have been serious problems in cold weather concreting due to the unreliability of the information obtained from practical experience. In the construction field in Japan, there is a specification for heat curing prepared by Japanese Architectural Society, which provides an equation for calculating heat quantity. It is also necessary to adopt a detailed specification for a standard heat curing method that is applicable to all national construction sites. In this study, the effect of bubble sheets on the economic feasibility of cold weather concrete is investigated through a comparison with the blue sheets commonly prescribed in national construction sites. In conclusion, this study found that bubble sheets had the effect of reducing the cost of curing materials and the fuel cost consumed by a heating apparatus, compared to the use of blue sheets.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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• pp.300-315
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• 2005

Recently plasma surface-cleaning or surface-etching techniques have been focused in the respect of decontamination of spent or used nuclear parts and equipment. In this study decontamination rate of metallic cobalt surface was experimentally investigated via its surface etching rate with a $CF_4-O_2$ mixed gas plasma and metallic surface wastes of cobalt oxides were simulated and decontaminated with $NF_3$ - Ar mixed gas plasma. Experimental results revealed that a mixed etchant gas with about $80{\%}\;CF_4-20{\%}\;O_2$ gives the highest reaction rate of cobalt disk and the rate reaches with a negative 300 DC bias voltage up to $0.43\;{\mu}m$/min at $380^{\circ}C$ and $20{\%}\;NF_3-80\%$ Ar mixed gas gives $0.2\;{\mu}m$/min of reaction rate of cobalt oxide film.

• Journal of Chest Surgery
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• 제17권4호
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• pp.565-573
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• 1984

The increasing use of cardioplegic solution for the reduction of ischemic tissue injury requires that all cardioplegic solution be carefully assessed for any protective or damaging properties. This study describes functional assessment of the efficiency of steroid in cardioplegic solution by using a Langendorffs perfusion model. Isolated rat heart were subject to a 2 minute period of coronary infusion with the steroid mixed cold cardioplegic solution immediately before and also at the midpoint of a 60 minutes period of hypothermic [10\ulcorner\ulcorner] ischemic arrest. The result of this study were as follows: 1.Spontaneous heart beat after ischemic arrest occurred 14 second later Langendorffs reperfusion in the steroid mixed Young & GIK group and 16 second later in the control group. [Young & GIK without steroid] A good recovery state of spontaneous heart beat was shown in both groups. 2.The percentage of recoveries of heart rate during the 30 minute after postischemic Langendorffs reperfusion was; at first 5 minute 106.3\ulcorner.7% [P<0.05] in the steroid mixed Young & GIK group. This percentage of recovery of steroid mixed Young & GIK group was significantly greater than the control group during the first 5 minute course. 3.The percentage of recovery of coronary flow during the 30 minute after postischemic Langendorffs reperfusion was; at first 5 minute 101\ulcorner.2% in the steroid mixed Young & GI K group. This percentage of recovery of the steroid mixed Young & GIK group was not significantly than the control group during the first 5 minute.

• 한국해양학회지
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• 제9권1_2호
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• pp.10-18
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• 1974

The cold water mass around the southeast coast of the Korean Peninsula is analyzed by using CSK data from 1966 through 1970. It is shown that this water mass flows down from the region offshore of Jukbyun to the area of Youngil Bay along the 100meter contour line of bottom topography. In ordinary summer conditions when the current velocity in the Korea Strait is usually above about 50cm/sec and the wind direction is southwest, the cold water ascends to the surface and makes the surface temperature gradient large, unless disturbed by a tropical cyclon. The bottom water of the Korea Strait is formed by the stratification after the Tsushima intermediate water and the Japan Sea intermediate water have been mixed. In winter the Tsushima intermediate water with high salinity sinks rapidly around the inlet of the Japan Sea and prevents the Japan Sea intemediate water from entering the Korea Strait.

• 산업공학
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• 제25권2호
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• pp.153-162
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• 2012

The reliability is defined as a probability that a system will operate properly for a specified period of time under the design operating conditions without failure and it has been considered as one of the major design parameters in the field of industries. Reliability-Redundancy Optimization Problem(RROP) involves selec tion of components with multiple choices and redundancy levels for maximizing system reliability with constraints such as cost, weight, etc. However, in practice both active and cold standby redundancies may be used within a particular system design. Therefore, a redundancy strategy(active, cold standby) for each subsystem in order to maximize system reliability is considered in this study. Due to the nature of RROP, i.e. NP-hard problem, A Parallel Particle Swarm Optimization(PPSO) algorithm is proposed to solve the mathematical programming model and it gives consistently better quality solutions than existing studies for benchmark problems.

• Journal of Dairy Science and Biotechnology
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• 제35권1호
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• pp.33-38
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• 2017

본 연구는 상업유산균인 단일 균주와 복합 균주를 이용한 산양유의 발효형태와 저장 중 풍미변화를 조사한 결과가 있다. 복합 균주는 단일 균주보다 단시간에 있어서 낮은 pH와 높은 산도를 나타내었다. 또한 복합 균주에서는 유산균 수의 증식 속도도 빠르게 나타내었다. 관능검사는 패널의 숙련도에 따라 느끼는 맛이 다르다. 따라서 수많은 시료를 분석할 경우, 재현성이 있는 객관적인 데이터를 얻기 어려운 단점이 있다. 더욱이 우리는 미각센서를 이용하여 저장 중 풍미변화를 측정하였다. 미각센서는 단일 균주와 복합 균주를 이용한 산양발효유에 대하여 사용 균주별 다양한 풍미의 변화가 측정 가능하였다. 따라서 본 연구는 국내에서 처음으로 발효유에 있어서 미각센서를 이용하여 저온 저장기간 동안 맛 성분의 변화를 측정한 자료로 있다. 이러한 결과는 차후 유제품의 소비기한 유지에 대한 자료로서 이용가치가 크게 기대되고 있다.