• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.270-275
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• 2001

The characteristics of flow in dividing regions are precise, therefore their classification is very important not only in industry but also in hydrodynamics. By now, many studies of flow in dividing regions have been peformed, but flow characteristics that use visualization In dividing regions have not been studied. The present study of the PIV and the CFD exhibit average velocity distributions, kinetic energy distributions and total pressure distributions etc of the total flow field due to the development of the accurate visualization optical laser and of optical equipment. Also, PIV is accurate with the flows characteristics of the dividing region as continuous analysis is done using input equipment. The study analyzes velocity vector field, turbulence kinetic energy, turbulence viscosity of dividing regions with flow for visualization of the PIV and the CFD measurement in a dividing rectangular ducts.

• Current Optics and Photonics
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• 제6권5호
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• pp.445-452
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• 2022

We developed an adaptive optics test bench using an optical simulator and two rotating phase plates that mimicked the atmospheric turbulence at Bohyunsan Observatory. The observatory was reported to have a Fried parameter with a mean value of 85 mm and standard deviation of 13 mm, often expressed as 85 ± 13 mm. First, we fabricated several phase plates to generate realistic atmospheric-like turbulence. Then, we selected a pair from among the fabricated phase plates to emulate the atmospheric turbulence at the site. The result was 83 ± 11 mm. To address dynamic behavior, we emulated the atmospheric disturbance produced by a wind flow of 8.3 m/s by controlling the rotational speed of the phase plates. Finally, we investigated how closely the atmospheric disturbance simulation emulated reality with an investigation of the measurements on the optical table. The verification confirmed that the simulator showed a Fried parameter of 87 ± 15 mm as designed, but a little slower wind velocity (7.5 ± 2.5 m/s) than expected. This was because of the nonlinear motion of the phase plates. In conclusion, we successfully mimicked the atmospheric disturbance of Bohyunsan Observatory with an error of less than 10% in terms of Fried parameter and wind velocity.

• 수산해양기술연구
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• 제53권4호
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• pp.337-348
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• 2017

The tension of warp from trawler and sea-floor contact can generate tilt and wake turbulence around otter boards. Preliminary measurements of otter board tilt and 3-D flow velocity during bottom trawl operations were taken using a vector instrument to investigate the effects of wake turbulence at the trailing edge of the otter board. Tilt data (i.e., yaw, pitch, and roll) at 1 Hz and flow data (velocities in the towing, lateral, and vertical directions) at 16 Hz were analyzed to determine their periods and amplitudes using global wavelet and peak event analyses. The mean period (${\pm}standard$ deviation) of the tilt from the peak event analysis ($5{\pm}2s$) was longer or double than that of flow velocity ($3{\pm}2s$). The two periods also had a significant linear relationship. The turbulence rate of flow was 30-50% at the trailing edge and was closely related to roll deviation. The frequency of phase difference ratios (i.e., peak time differences between tilts and flow periods) was significantly different from random occurrence in two trials, possibly due to side tidal effects. However, in the other trials, flow peaks were random, as shown by the even peak times between tilts and flows. Future studies should focus on reducing tilt variation, wake turbulence, and bottom contact to stabilize otter board motion.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2174-2181
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• 2011

The purpose of this article is to highlight the relationships among market orientation, environmental turbulence, marketing capabilities, and organizational performance in railway industry(616 participants). Major findings are: 1) market orientation showed a significant effect on marketing capabilities, and organizational performance, 2) environmental turbulence functioned as a moderator not to organizational performance, but to marketing capabilities, 3) and marketing capabilities showed a strong effect on organizational performance. These findings imply that market orientation, as well as marketing capabilities, are so essential for creating a supreme performance in the railway industry.

• 한국전자통신학회논문지
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• 제18권3호
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• pp.387-396
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• 2023

현재 기상관측에 사용되는 대표적인 장비는 기상탑과 윈드라이다가 사용되고 있다. 국제 규정에 의하면 기상탑은 단독 측정이 가능하나 윈드라이다 경우 40m 기상탑 혹은 풍력발전기 블레이드 최하단의 높이에 맞는 기상탑을 필수로 설치하고 측정데이타를 보정하여야 한다. 난류는 특성상 100m 이하의 고도에서 빈번하게 발생하며 기상탑 보다는 윈드라이다가 난류의 영향을 많이 받는다. 그럼에도 불구하고 기상탑에 대한 난류 강도는 국제 규정에 명시되어 있으나 윈드라이다 대해서는 별도로 명시하지 않고 있다. 본 연구는 동일한 조건에서 기상탑과 윈드라이다에서 측정된 데이터를 수집하고 불확도 및 난류 강도 비율을 분석한다. 데이터를 분석한 결과 난류 강도 비율이 3%를 초과하는 구간이 부분적으로 존재한다. 따라서 윈드라이다에 대한 난류강도 오차율을 국제 규정에 명시할 것을 제안한다.

• 무역학회지
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• 제42권4호
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• pp.21-47
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• 2017

본 연구는 중소기업의 기술역량과 국내 마케팅역량이 수출지향성에 미치는 영향을 시장변동성의 조절효과를 중심으로 실증분석하고 있다. 광주·전남 지역에 위치한 206개 중소기업들을 대상으로 실증분석을 실시한 결과는 다음과 같다. 첫째, 중소기업의 기술역량은 수출지향성에 정(+)의 영향을 미치는 것으로 나타났다. 이러한 결과는 선행연구에서 강조하는 바와 같이 중소기업의 기술역량이 규모의 불리함이나 외국인비용 등을 감소시킬 수 있는 유용한 자원으로 활용되어 중소기업의 해외진출의지를 높일 수 있다는 것을 보여준다. 둘째, 중소기업의 국내 마케팅역량은 수출지향성에 정(+)의 영향을 미치는 것으로 나타났다. 이러한 결과 역시 중소기업의 국내 마케팅역량이 해외시장으로 진출하는데 있어 불확실성을 줄여주는 사전지식으로 활용됨으로써 중소기업의 해외진출의지를 높일 수 있다는 것을 보여준다. 셋째, 시장변동성의 조절효과를 검증한 결과, 시장변동성은 기술역량과 수출지향성 간의 관계에서는 조절효과를 보이지 못하는 반면, 국내 마케팅역량과 수출지향성 사이의 관계를 부(-)의 방향으로 조절한다는 증거가 발견되었다. 즉, 시장변동성은 중소기업의 국내 마케팅역량과 수출지향성 간의 긍정적인 관계를 약화시킬 수 있기 때문에 마케팅역량이 중요하게 고려되는 산업에 속해 있거나 제품을 생산하는 중소기업들은 시장변동성을 고려한 전략을 수립할 필요가 있다는 것을 시사한다. 본 연구의 결과는 중소기업의 내부역량과 수출지향성 간 관계에서 시장변동성의 조절효과를 규명함으로써 중소기업의 글로벌화에 있어 의미 있는 이론적·실무적 시사점을 제공할 수 있을 것이다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 추계학술발표논문집
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• pp.92-96
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• 1999

지합에 영향을 미치는 초지공정의 인자로는 펄프섬유의 특성 및 이의 처리조건, Wet-End Chemistry 그리고 Forming부에서의 탈수 Element의 조건 등을 들 수 있다. 본보고는 지합개선을 위하여 Forming부의 탈수에 의한 지료 교란에 초점을 맞추어 초지기 Wire Part의 지료의 움직임과 현 상황을 측정·분석하여 문제점 및 개선점을 도출한 후, 현 초지 조건에 가장 적합하도록 Wire상의 탈수소자를 조정하였다. 그결과 Forming부에서의 Turbulence를 지속적으로 발생시키도록 탈수곡선을 제조정함으로서 조정 전 대비 괄목할 만한 지합 향상효과를 얻어 이를 보고하고자 한다.

• 한국분무공학회지
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• 제16권2호
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• pp.82-89
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• 2011

When pipe components made of carbon steel in nuclear, fossil, and industry plants are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the position of pressure boundary. The aim of this study is to identify the locations at which local wall thinning occurs and to determine the turbulence coefficient related to local wall thinning. Experiment and numerical analyses for the tee sections of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. In order to determine the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components in the main feedwater systems. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• 펄프종이기술
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• 제36권5호
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• pp.1-10
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• 2004

The geometry of headboxes is of great importance in obtaining good formation, even basis weight profile and fiber orientation. Therefore, many attentions have been made to examine the influence of the geometry of headboxes on the flow behavior. In this study, to evaluate flow behavior in headboxes, three types of turbulence generators were examined using pilot headbox. Velocity profiles in MD and CD were measured using a pressure monitoring system and flow in headboxes was visualized by dye injection method. CD velocity profiles at three different locations inside the slice of Type A headbox showed that the velocity increased downstream to slice exit and had a pattern with four humps due to the persisting wall effect of step diffusors. Results from the evaluation of normalized velocity profile and flow visualization showed that L-shaped Type C headbox caused a large pressure drop but it lacked in flow stabilizing ability.

• 동력기계공학회지
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• 제16권6호
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• pp.30-37
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• 2012

Effect of rib heights is found as significant parameter to enhance convective heat transfer performance under laminar and low turbulent regime. Circular ribs with different ribheight to channel height ratios, e/H = 0.05, 0.1, 0.15, are fabricated over the copper substrate respectively in a rectangular duct having 7.5 cross sectional aspect ratio. Only one rib pitch to rib height ratio (P/e = 10) has been chosen for all different height ribs. The result shows that the arithmetic average of turbulence intensity decreases with decreasing roughness height calculated between two ribs under laminar and low turbulent region. It occurs because the area of recirculation and reattachment zone also decreases with decreasing rib height. Optimum thermal enhancement factor is derived by 0.1 rib height to channel height ratio under low turbulent region but 0.15 rib height to channel height ratio gives maximum subjected to laminar flow.