• 한국지반공학회지:지반
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• 제11권4호
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• pp.75-86
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• 1995

내관과 외관으로 구성된 모형 개단 말뚝을 압력 토조속에 상이한 설치방법으로 관입한 후,실제 지진 기록을 이용하여 모델링시킨 유사 지진을 작용시켜 개단 말뚝에서의 지지력 저감 특성을 고찰하였다. 유사 지진 진동에 의한 극한 지지력 감소율은, 타격 관입 말뚝에서 약 20%였으며, 진동 관입 말뚝의 경우 약 40%에 달하였다. 또한,외주변 마찰력의 감소는 극한 지지력 감소의 대부분을 차지하여 약 80%였으며, 선단 강재부 지지력과 관내토 폐색력은 각각 약 10%였으며, 이러한 경향은 말뚝의 설치방법에 따라 크게 달라지지 않았다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.333-336
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• 2006

A new forming method for metal/ other metal two-layer tubes by multi-billet extrusion (MBE) is introduced. The forming possibilities of two-layer tubes CDA 365(inner)/Al 1100(outer) and Al 2014(inner)/Al 1100(outer) by MBE are investigated according to the given frictional condition and die profile. The results show that two-layer tube composed by two types tube as abovementioned can be manufactured by MBE. Some stated variables in the forming process such as effective stress and normalized pressure at welding surface are analyzed by FEM code ($DEFORM^{TM}$-3D)

• 동력기계공학회지
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• 제5권1호
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• pp.104-109
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• 2001

The stress distributions of hydranlic actuator cylinder tube acting in uniform inner pressure were analysed by the boundary element method(BEM). STKM13C tube was utilized for machine structural purposes model, its inner radius was 100 mm and outer radius was 140 mm. Axial length was semi-infinite and the isoparametric element of BEM was used. Radial and tangential stresses are maximum(-20.3 MPa and 52 MPa) at the inner radius and the minimum at the outer radius of the hydraulic actuator cylinders for an industrial systems. Stress diminution ratio was about 0.6 MPa/mm. And then coincidence between the simulation techniques as exact results(Lame' equation) and finite element method(FEM) is found to be fairly good, showing that the proposed analysis by BEM is reliable.

• International Journal of Aeronautical and Space Sciences
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• 제12권3호
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• pp.211-224
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• 2011

This is a written version of an hour-long lecture delivered by the author on June 30, 2011, as Plasmadynamics and Lasers Award Lecture at the AIAA 2011 summer conference in Honolulu, Hawaii. The author proposes that two areas of planetary entry physics be pursued in the future: outer planet aero-capturing and study of aerodynamics of meteoroid entries, both for the purpose of advancing the understanding of the possible extraterrestrial seeding of building blocks of life. For outer planet aero-capturing, the author proposes to develop new shock tube facilities that will produce up to 30 km/s of shock speed without causing photo-ionization of the driven gas by the radiation from the hot driver gas. Regarding meteors, the author proposes to carry out laboratory testing of the Tunguska event and of the seeding of amino acid molecules using a ballistic range which shoots a snowball laden with amino acid molecules toward a water surface.

• 대한기계학회논문집
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• 제18권1호
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• pp.212-222
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• 1994

In the annular Modified Chemical Vapor Deposition process using two concentric tubes, the inner tube is heated to maintain high temperature gradients to have high thermophoretic force which can increase particle deposition efficiency. However, higher axial velocity in a narrow gap between inner and outer tubes can result in a longer tapered entry length. In the present paper, a new concept using an annular jet from the inner tube is presented and shown to significantly reduce the tapered entry length with maintaining high efficiency. Effects of a jet injection on heat transfer, fluid flow and particle deposition have been studied. Of particular interests are the effects of jet velocity, jet location and temperature on the deposition efficiency and tapered length . Torch heating effects from both the previous and present passes are included and the effect of surface radiation between inner and outer tubes is also considered.

• 한국광물학회지
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• 제4권1호
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• pp.51-55
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• 1991

산청 할로이사이트의 전자 회절분석 및 레플리카와 박편을 이용한 형태 연구결과 관산 할로이사이트는 반경이 서로 다른 몇 개의 관들이 중첩되어 있으며 내부의 작은 관은 원형이나 외부의 큰 관은 다각형으로서 두 관 사이에 삼각형의 공극이 형성되어 있음이 관찰되었다. 할로이사이트의 단면은 대체로 직경이 500${\AA}$보다 작으면 원형을 이루고 그보다 크면 다각형을 이룬다. 다각형의 단면을 갖는 할로이사이트의 전자 회절상은 이들이 이층 단사 구조를 갖고 있음을 지시한다.

• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.63-67
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• 2021

Accurate measurements of the heat transfer coefficients of concentric annular space for the test section is important to measure the tube-side heat transfer coefficients of working fluids. This paper presents the annular side heat transfer coefficients of concentric annuli with variation of tube diameter ratios using Wilson plot method. The test facility has a straight, horizontal test section with an active length of 3.0 m. Inner/outer diameters of test tubes are 7.0/7.5 and 8.0/8.56 mm, respectively. An outer diameter of annulus side is 16.0 mm. The test results show that convective heat transfer coefficients in annuli increase with annular diameter ratio. The correlations for convective heat transfer coefficients in annuli are also developed.

• 대한기계학회논문집
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• 제18권5호
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• pp.1264-1274
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• 1994

Heat transfer performance of integral-fin tube which is used in recipro turbo refrigerator or high compact heat exchangers is studied. Eight tubes with trapezoidal shaped integral-fins having fin densities from 748 to 1654 fpm and 10, 30 internal grooves are tested. A plain tube having the same(inner and outer) diameter as the fin tubes is also tested for comparison. Pool boiling heat transfer of R-11 is investigated experimentally and theoretically on single tube arrangement. The refrigerant evaporates at saturation state of 1 bar on the outside tube surface and heat is supplied by not water which circulates inside of the tube. From the result of eight fin tubes and one plain tube tested, a tube having 1299 fpm-30 grooves shows the best performance. A maximum overall heat transfer coefficient of this tube is about 4000 $W/m^{2}K$ at 2.8m/s of water velocity. The maximum heat transfer enhancement (i.e., the ratio of overall heat transfer coefficients of finned to plain tubes)is about 2.1.

• 설비공학논문집
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• 제18권8호
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• pp.656-663
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• 2006

The convective heat transfer on the outer surface of tube arrays perpendicular to the flow direction was experimentally investigated. The test sections which include the aligned and staggered arrangements were made and the local heat transfer coefficients on the outer surface of the tube were measured after the flow has been fully developed. The results showed that the local heat transfer coefficients of the staggered arrangement, which has transverse pitch of 0.075 m and longitudinal pitch of 0.08 m, were about 15% greater than that of the aligned arrangement. Also, the overall mean Nusselt number of the former was greater than that of the latter. It is verified that the results obtained by using the simulation show the same tendency with those of experiment.

• 동력기계공학회지
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• 제13권4호
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• pp.56-61
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• 2009

In recent years, since the continuing increase in the capacity in personal computer such as the optimal performance, high quality and high resolution image, the computer system's components produce large amounts of heat during operation. This study analyzes and investigates the ability and efficiency of a cooling system inside a computer by means of central processing unit (CPU) and power supply cooling fan. This research was conducted to enhancement of efficiency of the cooling system inside the computer by making a structure which produces different air pressures in an air inflow tube. Consequently, when temperatures of the CPU and room inside computer were compared with a general personal computer, temperatures of the tested CPU, the room and the heat sink were as low as $5^{\circ}C$, $2.5^{\circ}C$ and $7^{\circ}C$ respectively. In addition to, revolution per minute (RPM) was shown as low as 250 after 1 hour operation. This research explored the possibility of enhancing the effective cooling of high-performance computer systems.