• 한국식품과학회지
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• 제21권6호
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• pp.735-741
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• 1989

For the accurate prediction of freezing time, probably the most difficult factor to measure and major error source is the surface heat transfer coefficient. In this work, surface heat transfer coefficient were determined for still air freezing and immersion freezing methods by theory of the transient temperature method and confirmed by using a modification of plank's equation to predict the freezing time of ground lean beef. The results showed the cooling rate of immersion freezing was about 11 times faster than that of still air freezing method. A comparison of surface heat transfer coefficient of copper plate and ground lean beef resulted an difference of 25-30% because the food sample surface is not smooth as copper plate. Also, when h-values measured by ground lean beef were applicated to modified model, the accuracy of its results is very high as difference of about 8%.

• 한국농촌건축학회논문집
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• 제12권4호
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• pp.1-11
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• 2010

This study is a research examining reshaped pattern in the perspective of repairing parts and materials through repairing renovation of registered cultural properties constructed in modern times and results are as followings. Repairing construction of registered cultural properties of Jollanamdo according to parts is shown numerously in the order of roof, walls and windows, and mostly outworn as time passes on and leakage were the main cause of repair. Also when original shape was damaged by previous repair in the past, and this was another reason of repairing. It was surveyed that among the repairing job repair of damage occurred on the part of roofing area including water leakage, corrosion and damage of roofing material, and damage of groove channel were the most main cause of repair. Especially when roof leakage is occurred by outworn of roofing materials, this cause corrosion and damage of materials due to the damage of leakage parts and this cause repeating cycles of worse leakage again and again. Main repairing materials which deform the original shape of registered cultural properties were confirmed as copper plate used on the roof. Copper plate showing high frequency of application which replaces groove slate or cement roofing tile used on the roof before has high durability and anti-corrosion but it is considered improper material to recover original shape.

• 한국재료학회지
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• 제24권7호
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• pp.388-392
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• 2014

$Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.47-51
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• 2002

ECT(eddy currentign testing) is very effective technique to detect a flaw within a conductor. Co-based amorphous wire was used as a sensor head. The wire has almost 0 magneto-striction and high permeability. An uniform magnetic field was applied to 1mm thick copper plate and $25{\mu}m$ thick aluminum sheet conductor using spiral typed coil The size of the coil has $40mm{\times}40mm$ outer width and $8mm{\times}8mm$ inner width. The copper plate and aluminum sheet has 0.5mm and 0.1mm wide gap, respectively. The frequency range of applied field was 100kHz-600kHz. The induced voltage difference of 2.5mV was obtained in the maximum voltage and minimum one measured across the gap of the 1mm thick conductor. In the case of aluminum sheet, 0.4mV was obtained. From this results, the effectiveness of Co-based amorphous wire was confirmed in the ECT technique.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.388-391
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• 1999

Well oriented Bi2212 superconductor thick films were formed successfully on a copper substrate by liquid reaction between a Cu-free precursor and Cu tape method in which Cu-free BSCO powder mixture was' printed on copper plate and heat-treated. And we examined the effect of heat-treatment atmosphere for the superconducting properties and microstructure of Bi2212. The composition of Cu-free BSCO powder mixture was Bi$_2O_3$ : SrCO$_3$ : CaCO$_3$ = 1.2~2 : 1 : 1 and the heat-treatment for the superconducting formation reaction was performed in air, oxygen, nitrogen and low oxygen pressure. At heat-treatment temperature, the printing layer partially melt by reacting with CuO of the oxidizing copper plate, and the nonsuperconducting phases present in the melt are typically Bi-free phases and Cu-free phases. Among the nonsuperconducting phases, it is known that the (Sr,Ca)CuO$_3$ phase restrain the formation of the Bi2212 superconducting phase. Because a kind of the nonsuperconducting phases is controled by the oxygen partial pressure, the optimum condition in which the remnants of the second phases don't leave in the fully processed conductor was determined by XRD and the critical tempera to re (Tc) analysis.

• 한국자기학회지
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• 제24권6호
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• pp.186-190
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• 2014

뫼스바우어 선원 $^{57}Co/Cu$의 제조조건을 도출하기 위하여, 금속 분말 코발트(Co)를 황산에 용해시킨 후 $H_3BO_3$, KOH와 NaCl을 첨가하여 Sulfamate 도금용액을 제조 후 Cu plate 기판에 도금하였다. 도금두께는 $4{\mu}m$로 일정하게 유지하였다. 전류밀도를 $2mA/cm^2$와 $30mA/cm^2$로 유지하면서 pH에 변화를 준 결과 pH가 4 이상으로 증가하면 hcp 결정의 Co 금속 이외의 2차상이 생성되었다. pH가 증가할수록 Co 후막 표면이 거칠어 졌으며 균열된 표면형상을 관찰하였다. pH가 5까지 증가할 경우 평균입도는 54 nmfh 증가함을 확인하였다. 열처리조건을 변화시키면서 Co가 Cu기지 내에 구속되는 온도가 $900^{\circ}C$에서 2 h임을 확인하였다. 열처리는 진공 후 Ar 분위기(1.5 l/min)를 유지하면서 수행하였다.

• 한국항공우주학회지
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• 제31권7호
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• pp.112-117
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• 2003

본 연구에서는 재생 냉각용 연소기에 적용되고 있는 동합금과 2상 스테인리스강의 최적 브레이징 조건을 구하였다. 모재는 C18200 동합금과 S31803 2상 스테인레스강을, 삽입금속으로 두께가 각각 50${\mu}m$, 80${\mu}m$인 AMS4764를 사용하였다. 브레이징한 시제에 대하여 X선 검사, 강도/기밀 및 파괴시험, 파단면 관찰을 한 결과 두께 50${\mu}m$인 삽입금속을 사용한 경우 강도특성과 접합면이 양호함을 확인하였다. 반면 두께 80${\mu}m$인 삽입금속을 사용한 경우는 강도특성은 양호하였으나 냉각유로의 막힘 현상과 유로 확대를 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1219-1224
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• 2004

The objective of this study is to propose an experimental calibration facility in which a heat flux sensor can be calibrated under conductive condition by using helium gas. The heat flux calibration facility was designed, simulated and manufactured for use in a high heat transfer condition. It delivers heat fluxes up to a maximum of 35 KW $m^{-2}$. A copper block heated electrically with 3.5 KW power is designed to produce uniform temperature up to 600 K across its face. High heat fluxes are provided between hot plate and cold plate by 1 mm height helium filled gap. A cold plate is maintained around 300 K through pool boiling using a refrigerant and water-cooled heat exchanger. A simulation was conducted to verify the design of the main test section. To verify the performance of calibration facility, a heat flux sensor was examined. The measured heat fluxes were compared to the calculated one.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권9호
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• pp.443-448
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• 2006

Non-contacting capacitive sensor based on Thompson-Lampard theorem have been fabricated and characterized for measuring of 때 order displacements. To overcome disadvantages of the existed capacitive sensors of parallel plate type with 2-electrodes and 3-electrodes, the developed new sensor was designed to have 4-electrodes with a constant gap of 0.2mm between the electrodes. Two of the electrodes were used as a high potential electrode and a low one, the other two electrodes were used as guard electrodes. These electrodes were made from copper using RF sputtering system on a sapphire plate with diameter 17 mm and thickness 0.7 mm. This sensor can be used for measuring the distance not only between the sensor and metallic target connected to ground potential but also non-metallic target without ground connection.

• 설비공학논문집
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• 제6권3호
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• pp.193-205
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• 1994

A simulation program of the plate finned-tubes condenser widely used in the air conditioning system was developed. The program took into account the variations of the flow properties and fluid friction factor of refrigerant, and the heat transfer coefficients of refrigerant and air sides. The program was applied to a copper tube condenser which has outside diameter of 10.05mm, inside diameter of 9.35mm, length of 5.20m and three rows arraied staggered. Simulation results were such that refrigerant was super-heated state from the entrance to the 0.14m point, two-phase flow from the 0.14m point to the 4.10m point, sub-cooled state from the 4.10m point to the outlet. The degree of sub-cooled was $6.1^{\circ}C$. The variations of refrigerant quality, temperature, pressure, velocity, specific enthalpy, specific volume and air temperature, tube temperature were showed.