• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.102-103
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• 2004

Simultaneous CH and OH planar laser induced fluorescence(PLIF) and stereoscopic particle image velocimetry(PIV) measurements have been developed to investigate the local flame structure of turbulent premixed flames. The developed simultaneous two radical concentrations and three component velocity measurements on a two-dimensional plane was applied for relatively high Renolds number turbulent premixed flames in a swirl stabilized combustor. All measurements were conducted for methane-air premixed flames in the corrugated flamelets regime. Strong three-dimensional fluctuation implies that misunderstanding of the flame/turbulent interactions would be caused by the analysis of two-component velocity distribution in a cross section. Furthermore, comparisons of CH-OH PLIF and three-component velocity field show that the burned gases not always have high-speed velocity in relatively high Renolds number turbulent premixed flame.

• 한국강구조학회 논문집
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• 제24권6호
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• pp.671-682
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• 2012

박스형 거더나 박공형 철골조 프레임에서 주름웨브보의 사용은 최근 많이 늘어가고 있다. 그 이유는 얇은 주름웨브보를 사용함으로서 압연형강이나 용접을 이용한 조립보에 비해 중량을 크게 줄일 수 있으며, 박판의 좌굴은 주름이 막아줄 수 있기 때문이다. 자동생산기술의 향상으로 인해 주름웨브를 가진 단위 부재를 양산할 수 있게 되어 적용분야가 확장되고 있으며, 주름웨브보의 부재 제원을 고려한 최적설계의 구현이 필요하게 된다. 이를 위해 본 논문에서는 주름웨브보의 생산부재 데이터를 고려한 이산화 최적구조설계 프로그램을 개발하여 집중하중과 등분포하중을 받는 주름웨브 단순보에 대해 적용하였다. 최소중량을 목적함수로, 세장비, 응력 및 처짐을 제약조건으로 채택하고, 전역최소값을 탐색하기 위해서 유전자 알고리즘을 채택하였으며, 생산부재의 번호를 불연속설계변수로 이용하였다. 최종적으로 해석설계의 검증을 위해서 이산화 최적설계 결과를 연속일 때의 결과와 비교하였으며, 최적단면 특성에 대해 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.384-388
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• 2007

Aerodynamic characteristics of Coleoptera species of Epilachna quadricollis and Allomyrina dichotoma are experimentally and numerically investigated. Using digital high speed camera and smoke wire technique, we visualized the continuous wing kinematics and the flight motion of free-flying coleoptera. The experimental visualization shows that the elytra flapped concurrently with the main wing both in the downstroke and upstroke motions. The wing motion of Epilachna quadricollis was captured and analyzed frame by frame to identify the kinematics of the wings and to implement it in the movement of a model wing (thin plate) in the simulation. The two-dimensional simulation of Epilachna quadricollis hovering flight was performed by assuming the wing cross section shape as a thin plate, even though most of insect's wings are made of curved corrugated membrane. The effect of Reynolds number are investigated by the simulation. Meanwhile, in order to investigate the role and effect of elytra, the flow visualization of Allomyrina dichotoma was carried on using smoke wire visualization technique. Here, we confirmed that the vortex generated by elytra due to its movement is strongly influence the vortex dynamic generated by hind wings.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.339-344
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics in wavy ducts of primary surface heat exchanger. Experiments using a naphthalene technique are carried out to determine the local transfer characteristics for flow in the corrugated wall duct. The aspect ratios of the rectangular duct cross-section are 7.3, 4.7 and 1.8 with a corrugation angle of $145^{\circ}$. The Reynolds numbers, based on the duct hydraulic diameter, are ranged from 1000 to 5000. The local heat/mass transfer measurement is conducted in the spanwise directions. The results show that Tayler-Gortler vortices exist on the pressure surface. Flow separation on the suction surface appears at a high Reynolds number resulting in a sharp decrease in the local transfer rates, but relatively high transfer rates are obtained in the reattachment region.

• 한국정밀공학회지
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• 제30권8호
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• pp.790-796
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• 2013

Micro-speaker diaphragms play an important role in generating a desired audio response. The diaphragm is generally a circular membrane, and the cross section is a double dome, with an inner dome and an outer dome. To improve the sound quality of the speaker, a number of corrugations may be included in the outer dome region. In this study, the role of these corrugations is investigated using two kinds of finite element method (FEM) calculations. Structural FEM modeling was carried out to investigate the change in stiffness of the diaphragm when the corrugations were included. Modal FEM modeling was then carried out to compare the natural frequencies and the resulting vibrational modes of the plain and corrugated diaphragms. The effects of the corrugations on the vibration characteristics of the diaphragm are discussed.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1509-1520
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• 1998

An experiment was carried out for the fully developed turbulent flow of water in tube coils on the condition of uniform heat flux. The present work was conducted for various ranges for Dean number(1794~1321), Prandtl number (2.5~4.5), curvature ratio parameters (22~60). Heat transfer to steady viscous flow in coiled tubes of circular cross section was studied for fully developed velocity and temperature fields under the thermal boundary condition of uniform heat flux. The peripherally local Nusselt number correlated as a function of Dean and Prandtl numbers. We studied the flow in heat coiled tubes under the influence of both centrifugal and buoyancy forces in order to gain insight into the flow pattern. In the present study, we obtained three emperical formulas, $Nu_v=0.0231Re^{0.84}Pr^{0.4}(a/R)^{0.13}$ (vertical) $Nu_c=0.0241Re^{0.86}Pr^{0.4}(a/R)^{0.08}$ (corrugated) $Nu_h=0.0227Re^{0.84}Pr^{0.4}(a/R)^{0.09}$ (horizontal).

• Steel and Composite Structures
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• 제42권6호
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• pp.747-764
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• 2022

The design codes and calculation methods related to soil-steel composite bridges and culverts only specify the minimum soil cover depth. This value is connected with the bridge span and shell height. In the case of static and dynamic loads (like passing vehicles), such approach seems to be quite reasonable. However, it is important to know how the soil cover depth affects the behaviour of soil-steel composite bridges under seismic excitation. This paper presents the results of a numerical study of soil-steel bridges with different soil cover depths (1.00, 2.00, 2.40, 3.00, 4.00, 5.00, 6.00 and 7.00 m) under seismic excitation. In addition, the same soil cover depths with different boundary conditions of the soil-steel bridge were analysed. The analysed bridge has two closed pipe-arches in its cross section. The load-carrying structure was constructed as two shells assembled from corrugated steel plate sheets, designed with a depth of 0.05 m, pitch of 0.15 m, and plate thickness of 0.003 m. The shell span is 4.40 m, and the shell height is 2.80 m. Numerical analysis was conducted using the DIANA programme based on the finite element method. A nonlinear model with El Centro records and the time history method was used to analyse the problem.

• 콘크리트학회논문집
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• 제22권3호
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• pp.297-303
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• 2010

현재 개발된 콘크리트 충전 대골형 파형 강판은 아치형 플레이트의 구조로서 그 특징은 구조물이 아치의 형상을 가지므로 모멘트가 작게 발생하는 압축력 지배구조의 구조적 특성을 가지게 되며 이에 따라 강재를 덧대 준공된 공간을 압축력에 유리한 콘크리트를 충전 강재 콘크리트 합성단면을 형성하여 압축력에 대한 강도 발현증대를 목적으로 한다. 이 연구에서는 새로운 개념의 콘크리트 충전 대골형 파형강판(브릿지 플레이트) 부재의 압축 및 휨 시험을 실시하여 평가된 압축력과 콘크리트 충전 브릿지 플레이트 구조물의 설계방법인 캐나다 도로교설계기준(CHBDC)의 방법으로 설계압축력을 산정하여 비교 검토함으로서 새로운 개념의 콘크리트 충전 브릿지 플레이트 부재의 안전율을 평가하였다. 설계압축력과 성능평가 시험을 통하여 얻어진 축력을 비교하여 안전율을 검토한 결과 적정 안전율 2.0이상 과도하게 나타나 CHCBD을 이용한 설계가 매우 보수적으로 평가되고 있으며, 이 연구 결과를 바탕으로 안전율을 설계에 반영한다면, 단면축소 및 시공비용 절감에 따른 경제적인 시공이 가능할 것으로 판단된다.

• 한국항공우주학회지
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• 제34권8호
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• pp.55-62
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• 2006

본 논문에서는 단일층 압전 작동기로 구동되는 곤충 모방 날갯짓 기구의 실험적 평가의 결과를 제시하였다. 변위 증폭기구의 연결막대 길이와 힌지 위치를 조절하여, 말벌류 곤충의 상향 날갯짓 끝에 발생하는 날개 겹침 (clap)을 모방할 수 있도록 하였다. 또한, 실제 곤충 날개의 단면이 지그-재그형인 것을 모방한 날개를 제작하여 부착하였다. 이 두 가지 추가적인 고안으로 인하여 본 날갯짓 기구는 이전 날개에 비하여 면적이 절반 밖에 되지 않음에도 불구하고 더 큰 양력을 발생할 수 있었다. 본 연구에서는 날개의 겹침, 지그-재그형 단면, 인가전압 파형이 양력 발생에 미치는 영향을 조사하였다. 최종적으로는 디지털 고속카메라를 이용하여, 개선된 날갯짓 기구가 상향 날갯짓과 하향 날갯짓에서 와류를 발생함을 확인하였다.