• 대한기계학회논문집
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• 제15권2호
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• pp.654-660
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• 1991

Natural convection heat transfer in a horizontal annulus from an inner tube with two vertical fins has been studied for the effects of dimensionless fin length and Rayleigh number. The maximum local Nusselt number of inner tube was obtained at .theta. = 145.deg. and that of outer cylinder at .theta. = 0.deg. for the case of $l_{F}$=0.3 Local Nusselt number distributions for the lower fins show higher values than that of the upper fins. The mean Nusselt number of inner tube was increased with the values of dimensionless fin length. The mean Nusselt number can be represented in an exponential function of Grashof number at various fin lengths. As compared with experimental and numerical results, isotherms and local Nusselt number show good agreement.t.

• 한국공간구조학회논문집
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• 제2권1호
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• pp.67-73
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• 2002

Measurement of fluctuating pressure by tube system is carefully designed due to the organ-pipe resonance. It is necessary to correct the pressure before analysis. The three method for correction the distortion fluctuation pressure short tube length and the frequency response functions and insert a restrictor in the tube to increase the damping. The first method is useful when the tube length is short. In second method, the distorted signal through the tubing transformed into the frequency domain, dividing by transfer function and inverse fourier transforming back into the time domain gives the required pressure signal. In this paper three types of tubing which have different length of 100cm, 150cm, 200cm were experimented the distorted signal and correct the distortion signal

• 연구논문집
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• 통권31호
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• pp.15-21
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• 2001

A thermoacoustic refrigerator has not only considerable feasibility but also commercial usability, because it has high reliability, lower vibration, no moving part. and easy construction. In the present study, the resonant characteristics of a thermoacoustic refrigerator, varying the length of resonant tube from 400mm to 850mm, were investigated to improve performance. In order to determine the optimum position of the stack in the resonant tube and the optimum frequency, the simple open-tube-type thermoacoustic refrigerator was constructed. Air was used as a coolant. In the fifth harmonic, the largest $\DeltaT$ was $52.6^{\circ}C$ at 827Hz, tube length of 400mm, and stack length of 40mm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.527-530
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• 2004

High-temperature Superconductor(HTS) tubes were fabricated in term of different diameter, length and thickness by centrigugal forming method. For powder melting by induction the optimum range of melting temperatures and preheating temperature were $1050^{\circ}C{\sim}1100^{\circ}C\;amd\;550^{\circ}C$ for 30min, respectively. The mould renting speed was 1000rpm. A tube was annealed at $840^{\circ}C$ for 72hours in oxygen atmosphere. The plate-like grains were well developed along the renting direction and typical grain size was about more than $40{\mu}m$. It was found that Ic values increased with increasing the tube diameter while the Ic decreased with increasing tube thickness. Also Ic decreased with increasing the tube length. The measured Ic in $50mm{\times}70mm{\times}25mm$ tube was about 896Amp.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.37-40
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• 2001

A free piston and free displacer (FPFD) Stirling cryocooler for cooling infrared and cryo-sensor is currently under development at Korea Institute of Machinery & Materials. In this study, performance tests of stirling cryocooler with different length of split tube were performed to get characteristics of cryocooler. The Experimental results show the Stirling cryocooler with small volume of split tube has higher cooling power and faster response time.

• Steel and Composite Structures
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• 제28권1호
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• pp.63-71
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• 2018

This paper reports an experimental study that was accomplished to assess the seismic behavior of steel tube reinforced concrete bridge columns (SBCs). The motivation of this study was to verify a supposition that the core steel tube may be terminated at a rational position in the column to minimize the material cost while maintaining the seismic behavior of this composite column. Four SBC specimens were tested under combined constant axial load and cyclic reversed lateral loads. The unique variable in the test matrix was the core steel tube embedment length, which ranged from 1/3 to 3/3 of the column effective height. It is observed that SBCs showed two distinctly different failure patterns, namely brittle shear failure and ductile flexural failure. Tests results indicate that the hysteretic responses of SBCs were susceptible to the core steel tube embedment length. With the increase of this structural parameter, the lateral strength of SBC was progressively improved; the deformability and ductility, however, exhibited a tendency of first increase and then decrease. It is also found that in addition to maintained the rate of stiffness degradation and cumulative energy dissipation basically unchanged, both the ductility and deformability of SBC were significantly improved when the core steel tube was terminated at the mid-height of the column, and these were the most unexpected benefits accompanied with material cost reduction.

• 생물환경조절학회지
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• 제22권1호
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• pp.13-18
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• 2013

본 연구는 참외 개화시의 기온과 상대습도가 화분의 발아에 미치는 영향을 검토하고자 '만리장성', '오복꿀' 및 '조은대'의 3 품종을 재료로 하여 개화 시 온도를 $15^{\circ}C$, $25^{\circ}C$ 및 $35^{\circ}C$, 상대습도를 30%, 60% 및 90%의 처리를 두고 실험하였다. 기온조건에 따른 화분 발아율은 $25^{\circ}C$에서 채취한 것이 가장 높았고 $15^{\circ}C$에서 채취한 것이 가장 낮은 경향이었으며 품종별 화분 발아율은 '만리장성'이 가장 높았고 다음이 '오복꿀'이었으며 '조은대'가 가장 낮은 경향이었다. 화분관 신장길이는 기온조건별로는 $35^{\circ}C$에서 채취한 것이 가장 길었고 다음이 $25^{\circ}C$ 에서 채취한 것이었으며 $15^{\circ}C$에서 채취한 것은 현저히 짧았으며, 품종에 따라서는 '오복꿀'이 가장 길었다. 상대습도 조건에 따른 화분 발아율은 습도조건에 따라 뚜렷한 차이는 없으나 습도가 높을수록 높은 경향이었으며, 품종간에도 큰 차이가 없으나 '만리장성'과 '조은대'에 비해 '오복꿀'에서 낮았다. 그러나 화분관 신장길이는 처리간에 뚜렷한 차이를 나타내어 60%의 상대습도에서 채취한 것이 가장 길었으며, 다음이 30%의 상대습도에서 채취한 것이며 90%의 상대습도에서 채취한 것은 현저히 짧았다. 품종별 화분관 신장길이는 '오복꿀'이 가장 길었고 '조은대'가 가장 짧았다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권5호
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• pp.576-581
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• 2011

본 논문은 $CO_2$ 히트펌프용 모세관의 기초 설계자료를 제공하기 위해서 모세관 길이 예측에 대해서 이론 및 실험적으로 조사하였다. 본 연구에서 고려된 작동변수로는 증발온도, 가스냉각기 냉각압력, 냉매유량, 모세관의 관경 등이다. 몇몇 연구자들의 자료를 바탕으로 $CO_2$ 모세관 길이를 예측할 수 있는 수학적 모델식을 작성하였다. 그리고 단열 모세관 팽창장치내 $CO_2$의 증발온도, 냉매유량, 냉각압력 등에 대해서 실험한 결과, 이들 모두는 식 (3)으로 예측한 값과 0.63~10.9%이내에서 좋은 일치를 보였다. 따라 서 본 연구에서는 $CO_2$ 열펌프 단열 모세관에 대한 기초설계 자료로서, 냉각압력, 증발온도, 모세관 직경, 냉매유량 등의 조건으로부터 모세관 길이를 계산해낼 수 있는 예측 상관식을 제안하였다.

• 대한기계학회논문집B
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• 제29권6호
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• pp.763-771
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• 2005

This paper is an experimental study on the performance according to a capillary tube diameter and length in a domestic small multi refrigerator[kimchi refrigerator]. Pressure drop in a capillary tube is predicted by theoretical analysis and experimental method as the reduction of capillary tube diameter from 0.74 to 0.6 mm. The differences between experimental results and analytical results are mainly caused by friction factor in a capillary tube. Because there are no adequate equations used to calculate pressure drop of capillary tube diameter under 1.0mm. The empirical equations necessary for interpretation of capillary tube were derived from capillary tube test results data using curve fitting method. This study shows that the optimized designs of system, which is capillary tube length and refrigerant charge amount, are 2000mm, 83g at the capillary tube diameter 0.6mm and 3000mm, 73g at the capillary tube diameter 0.74mm. And capillary design tools and system matching techniques necessary for development of the kimchi refrigerator were also developed through this study.

• 대한방사선기술학회지:방사선기술과학
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• 제9권1호
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• pp.73-81
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• 1986

This paper carried out an experiment on the characteristics of time, temperature, electric field and the dependense of electrode materials and gap length by the conduction current of the insulating oil used for x-ray tube housing. The obtained results can be summarized as following: 1. In the x-ray tube housing insulating oil with vacuum condition, conduction current is declined more than the x-ray tube housing insultaing oil with the air, and is held stable states. 2. At the low electric field the higher temperature of the x-ray tube housing insulating oil is increased, the more conduction current. 3. The dependence of electrode material is appeared at the low electric field and the short gap length than the high and the long with Fe> Cu >Al. 4. At the I-E characteristics, the low electric field than 1000 [V/cm] is appeared Ohm's law region, and the high become saturation region. 5. At the same electric field, the longer gap length become, the more conduction current is increased, and the same applied voltage, the longer, the less conduction current is decreased, the less low than high temperature x-ray tube housing insulating oil.