• International Journal of Safety
• /
• 제11권1호
• /
• pp.1-5
• /
• 2012

It has been reported that the plugged steam generator tube of Three Mile Island Unit 1 in America was damaged by growing flaw and then this steam generator tube destroyed the nearby steam generator tubes of normal state. On this account, stabilizer installation is necessary to prevent secondary damage of the steam generator tubes. The flow-induced vibration is one of the major causes of the fluid-elastic instability. To guarantee the structural integrity of steam generator tubes, the flow-induced vibration caused by the fluid-elastic instability is necessary to be suppressed. In this paper, the effective velocity and the critical velocity are calculated to evaluate the fluid-elastic instability. In addition, stability ratio value of the steam generator tubes is evaluated in order to propose one criterion when to determine stabilizer installation.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
• /
• pp.9-13
• /
• 2008

충격파와 같은 moving load가 특별한 속도로 관 안을 전파한다. 이 관 안을 전파하는 moving load 속도는 flexural wave의 활성화의 정도와 큰 변형을 일으키는 공진이 발생할 가능성을 결정한다. 본 연구에서, 우리는 moving load가 관안을 통과하고 있을 때의 변위의 특별해와 공진현상이 일어날 조건을 보일 것이다. 또한 이 이론적 결과를 hydrocode를 이용하여 얻은 수치해석 결과와 비교하여 정당성을 보일 것이다. 이와 같은 결과를 바탕으로 본 연구는 원자력 발전소나 탄화수소 계열의 연료를 사용하는 산업분야에서 공진현상에 의한 대형 사고를 예방하는 목적을 가지고 있다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 춘계 학술발표회
• /
• pp.1376-1381
• /
• 2010

In this study, we dealt with an analysis and development of measurement systems for tunnel and slope structures under a high velocity. Deterioration of tunnel and slope structures becomes a critical issue in regard to both safety and economic concerns. Deterioration itself is inevitable, but condition assessment technology and nondestructive evaluation techniques could provide solutions to ensure public safety by means of detecting damage before serious and expensive degradation consequences occur. We reviewed the existing monitoring and maintenance systems of slopes and tunnels and more advanced directions, especially for highways under high-speed vehicles.

• 천문학논총
• /
• 제9권1호
• /
• pp.39-54
• /
• 1994

We present two codes which estimates virial mass and LTE mass using IMFORT interface within IRAF (Image Reduction and Analysis Facility). It is discussed that threshold value (temperature or CO integrated intensity), which defines a reasonable cloud boundary and size, is the most important parameter determining accurate results. Several virial masses are to be obtained using the vir task, as well as three velocity dispersions including the centroid velocity dispersion, a turbulence indicator. LTE mass is to be estimated by using task lte as well as three by-product images. The $^{13}CO$ abundance and threshold temperature of $^{13}CO$ and $^{12}CO$ peak temperatures are the most critical parameters in LTE technique.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2004년도 추계학술대회 논문집
• /
• pp.48-51
• /
• 2004

Chemical Mechanical Polishing(CMP) is popularly used in production of semiconductor because of large area polishing ability probability of improvement for more integrated circuit. However, present CMP processing causes some non-uniformity errors which can be critical for highly integrated circuit. Previous studies predict that flow-field of slurry during CMP can create non-uniformity, but no quantitative measurement has conducted. In this study, using PIV, slurry velocity flow-field during CMP is measured by changing the ratio of RPM of pad and carrier with tuned PIV system adequate for small room in CMP machine and Cabot's non-groove pad Epad-A100. The result show that velocity of slurry is majorly determined by pad-rpm and the ratio of between carrier and pad rpm make some changes in streamlines.

• 대한기계학회논문집
• /
• 제10권1호
• /
• pp.1-6
• /
• 1986

본 논문에서는 제트유동에 놓인 튜우브 집합체의 진동 발생구조를 깊이 파악하고 일반성 있게 사용할 수 있는 설계 지침을 마련하기 위하여 보다 광법위 하게 수행된 파라미터 연구 내용을 다루었다

• 한국소음진동공학회논문집
• /
• 제22권5호
• /
• pp.407-412
• /
• 2012

The dynamic instability and natural frequency of an axially moving pipe conveying fluid are investigated. Thus, the effects of fluid velocity and moving speed on the stability of the system are studied. The governing equation of motion of the moving pipe conveying fluid is derived from the extended Hamilton's principle. The eigenvalues are investigated for the pipe system via the Galerkin method under the simple support boundary. Numerical examples show the effects of the fluid velocity and moving speed on the stability of system. Moreover, the lowest critical moving speeds for the simply supported ends have been presented.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.304-307
• /
• 2008

Two-dimensional Stokes flow due to the line source and line sink of same strength in semi-infinite flow region with free surface is analysed using complex variable theory and conformal mapping. Surface tension effects are included while gravity is neglected. From the results of analysis, flow pattern and free surface shape are obtained and velocity distribution on the free surface is determined with 2 independent parameters Ca (capillary number) and h (non-dimensionalized distance between source and sink). When the location of the sink is above the source, velocity on the free surface converges and a cusp occurs on the free surface for the value of Ca above some critical capillary number.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권1호
• /
• pp.33-39
• /
• 1999

In this paper an experimenatal investigation of characteristics of developing ransitional steady flows in a square-sectional $180^{\circ}$ curved duct is presented, The experimental study is carried out to measure axial velocity profiles secondary flow velocity profiles and entrance length by using Laser Dopper Velocimeter(LDV) system. The flow development is found to depend upon Dean number and curvature ratio. Of special interest is the secondary flow generated by centrifugal effects in the plane of the cross-section of the duct. The secondary flows becomes strong from $120^{\circ}$ of bended angle on the duct. The entrance length of transitional steady flow is obtained to $120^{\circ}$ of bended angle of the duct in this experimental conditions.

• 대한기계학회논문집B
• /
• 제25권5호
• /
• pp.705-712
• /
• 2001

The flow between two concentric cylinders, with the inner one rotating and with an imposed pressure-driven axial flow, is studied using numerical simulation. The case without the axial flow was investigated in the preceding paper. This study considers the identical flow geometry as in the experiments of Wereley and Lueptow[Phys. Fluid, 11(12), 1999]. They carried out experiments using PIV to measure the velocity fields in a meridional plane of the annulus in detail. When an axial flow is imposed, the critical Taylor number is increased. The axial flow stabilizes the flow field and decreases the torque required to rotate the inner cylinder. The velocity vector fields obtained also show the same flow features found in the experiments of Wereley and Lueptow.