• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.43-49
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• 2002

Gray-colored materials were synthesized from ball-milled ZnO powders under a thermal annealing at 1380$^{\circ}C$ with an argon carrier gas for 3 hours. The synthesized materials were identified to be wurtzitic hexagonal structured ZnO nanowires by X-ray diffraction and scanning electron microscopy. The ZnO nanowires have the long cylinder-like shape of which cross-section is a circle, and these nanowires are in the range 15∼40 nm width and 10-70 $\mu\textrm{m}$ length, respectively. Transmission electron microscopy revealed that these nanowires are single-crystalline and grow along [110] direction. The optical properties of the ZnO nanowires were investigated with photoluminescence. The analytic results revealed that ZnO nanowires have the singly ionized oxygen vacancies in the surface lattices, as they emit strong green light in room temperature PL. In addition, the growth mechanism of the ZnO nanowires can be described by the vapor-solid procedures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.651-657
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• 2002

Gray-colored materials were synthesized from ball-milled ZnO powders under a thermal annealing at $1380^{\circ}C$ with an argon carrier gas for 3 hours. The synthesized materials were identified to be wurtzitic hexagonal structured ZnO nanowires by X-ray diffraction and scanning electron microscopy. The ZnO nanowires have the long cylinder-like shape of which cross-section is a circle, and these nanowires are in the range 15~40nm width and 10~70 $\mu m$ length, respectively. Transmission electron microscopy revealed that these nanowires are single-crystalline and grow along ［110］ direction. The optical properties of the ZnO nanowires were investigated with photoluminescence. The analytic results revealed that ZnO nanowires have the singly ionized oxygen vacancies in the surface lattices, as they emit strong green light in room temperature PL. In addition, the growth mechanism of the ZnO nanowires can be described by the vapor-solid procedures.

• The Plant Pathology Journal
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• v.19 no.5
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• pp.266-268
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• 2003

In 2002, sooty mold was observed on persimmon (Diopyros kald) from the Jinju Agricultural Products Wholesale Market in Gyeongnam, Korea. The lesion of the sooty mold usually appeared as scars or wounds formed on the surface of the fruits. The symptom started with water soaking lesion, then the fruit softened rapidly. Colony of the causal pathogenic fungus was dark green in color on potato dextrose agar. The diameter of growing hyphae was 1-2 $\mu\textrm{m}$. The mostly one-celled conidia were ovoid, lemon or cylinder in shape, blastophores, and sized 46-132 $\mu\textrm{m}$. Erected conidiophores were long-branched chains and their lengths varied from 24 to 346 $\mu\textrm{m}$ with 2-5 $\mu\textrm{m}$ width. The optimum temperature for mycelial growth was about 2$0^{\circ}C$. Based on their mycological characteristics, the fungus was identified as Cladosporium cladosporioides. This is the first report in Korea of the sooty mold of persimmon caused by the said fungus.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.5
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• pp.553-559
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• 2004

Stratified flow past a three-dimensional obstacle such as a sphere has been a long-lasting subject of geophysical, environmental and engineering fluid dynamics. In order to investigate the effect of the stratification on the near wake, in particular, the unsteady vortex formation behind a sphere, numerical simulations of stratified flows past a sphere are conducted. The time-dependent Navier-Stokes equations are solved using a three-dimensional finite element method and a modified explicit time integration scheme. Laminar flow regime is considered, and linear stratification of density is assumed under Bossiness approximation. The computed results include the characteristics of the near wake and the unsteady vortex shedding. With a strong stratification, the separation on the sphere is suppressed and the wake structure behind the sphere becomes planar, resembling that behind a vertical cylinder.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.241-249
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• 1984

두 개의 긴 수직평판핀을 가진 등온수평원통으로 부터의 자연대류 열전달을 2차원 유한차분법에 의한 수치해석으로 연구하였다. 축방향의 두 수직평판핀을 가진 수평원통으로 부터의 열전달은 Ra=$10^{6}$, Pr=5 및 무차원 $K_{f}$t/KD=0.5인 경우에 보통 원통에서의 열전도보다 5.32% 증가되었다. Ra와 Pr가 증가하면 국소핀 누셀트수는 증가하고 무차원핀 온도는 감소된다. 그 러나 무차원핀 변수가 증가하면 국소핀 누셀트수와 무차원핀 온도분포는 증가된다. 최대국소핀 누셀트수는 Ra=$10^{6}$인 경우에 상향핀과 하향핀의 (r-r$_{0}$)=0.1-0.2에서 존재한다. 수 직핀을 가진 원통주위에서 부력 유도된 유동은 보통 원통에서 보다 더욱 활발하였다. 따라서 Ra=$10^{6}$ , Pr=5인 경우에 핀 근방에서의 무차원 무차원반경 방향 속도는 보통원통의 경 우보다 큰 값을 가진다.다.다.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.97-103
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• 1999

As the noise of ship engine room is too loud, the engineer who works in a ship engine-room has the trouble of hearing. In this paper deals the investigation of the noise of ship engine room and cabins with the internationally allowable noise exposure level and noise exposure time. Recently, the problem of engine-room noise is more serious because of shipowner wants to make small number and larger size of cylinder. Therefore, engineers work in a ship engine-room for a long time have the trouble of hearing when they are exposed the high noise level. In this study, two kinds of vessels were used to investigate the noise of engine room, engine-control room, bridge, offices and cabins. As criteria of sound levels, A-weighted sound pressure level and octave band pressure level were used.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.715-720
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• 2000

Stratified flow past a three-dimensional obstacle such as a sphere has been a long-lasting subject of geophysical, environmental and engineering fluid dynamics. In order to investigate the effect of the stratification on the near wake, in particular, the unsteady vortex formation behind a sphere, numerical simulations of stratified flows past a sphere are conducted. The time-dependent Navier-Stokes equations are solved using a three-dimensional finite element method and a modified explicit time integration scheme. Laminar flow regime is considered and linear stratification of density is assumed under Boussinesq approximation. The computed results include the characteristics of the near wake and the unsteady vortex shedding. With a strong stratification, the separation on the sphere is suppressed and the wake structure behind the sphere becomes planar, resembling that behind a vertical cylinder.

• Wind and Structures
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• v.9 no.5
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• pp.345-356
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• 2006

It is well known that cylinder steel stacks are heavily impacted by vortex-induced vibration. However, the wind-induced vibration behaviors of tower-supported steel stacks are not clarified due to a lack of observation. We studied a stack's response to strong winds over a long period of time by observing the extreme wind-induced vibration of a 200 m-high tower-supported steel stack. This experiment aimed to identify the wind-induced vibration properties of a tower-supported steel stack and assess the validity of the vibration control method used in the experiment. Results revealed a trend in wind-induced vibration behavior. In turn, an effective measure for controlling such vibration was defined by means of increasing the structural damping ratio due to the effects of the tuned mass damper to dramatically decrease the vortex-induced vibration of the stack.

• Bulletin of the Society of Naval Architects of Korea
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• v.20 no.2
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• pp.27-36
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• 1983

This paper presents numerical results of the added mass and damping coefficients of vertical axisymmetric bodies on or under the free surface. Also computed are the excitation forces on these bodies due to an incident regular wave system. The numerical scheme employs a localized finite-element method, which is based on the theory of the calculus of variations. The excitation forces and moments on a submerged half-spheroid lying on the bottom are computed and compared with the results obtained by others. he agreement is good. Several specific types of floating vertical axisymmetric platforms are considered for ten different wave lengths, in connection with the design of an ocean-thermal-energy converter platform. The added mass and damping coefficient, as well as the excitations, are presented. It is shown that simple strip theory gives a good approximation of the sway(and pitch) added mass for a disc platform having a long circular cylinder.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.86-87
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• 2001

Far-ultraviolet IMaging Spectrograph(이하 FIMS)는 2002년에 발사 예정인 과학위성 1호의 주 탑재체이며, 은하 주변에 분포한 고온의 가스에서 방출되는 자외선 영역 (short wavelength band ： 900-1150 $\AA$, long wavelength band ： 1335-1750$\AA$)의 방출선을 약 2$\AA$의 분광 분해능으로 관측하는 천문학적 목표를 가지고 있다 일반적인 망원경을 사용하는 대신 제한된 위성의 크기 내에서, 넓은 지역에 퍼져 있는 가스의 분포와 특성을 관측하는데 적합하도록, 그림 1과 같이 비축 포물 원통 반사경과 타원형의 substrate를 가진 회절 에돌이발 (grating)의 사용을 고안하였다. (중략)