• 한국전산유체공학회지
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• 제19권2호
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• pp.86-92
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• 2014

In this paper, prediction of separation trajectory for Two-stage-To-Orbit space launch vehicle has been numerically simulated by using an aerodynamic database based on steady state analysis. Aerodynamic database were obtained for matrix of longitudinal and vertical positions. The steady flow simulations around the launch vehicle have been made by using a 3-D RANS flow solver based on unstructured meshes. For this purpose, a vertex-centered finite-volume method was adopted to discretize inviscid and viscous fluxes. Roe's finite difference splitting was utilized to discretize the inviscid fluxes, and the viscous fluxes were computed based on central differencing. To validate this flow solver, calculations were made for the wind-tunnel experiment model of the LGBB TSTO vehicle configuration on steady state conditions. Aerodynamic database was constructed by using flow simulations based on test matrix from the wind-tunnel experiment. ANN(Artificial Neural Network) was applied to construct interpolation function among aerodynamic variables. Separation trajectory for TSTO launch vehicle was predicted from 6-DOF equation of motion based on the interpolated function. The result of present separation trajectory calculation was compared with the trajectory using experimental database. The predicted results for the separation trajectory shows fair agreement with reference[4] solution.

• Journal of Biosystems Engineering
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• 제14권4호
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• pp.272-281
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• 1989

It is desirable for the vertical wind tunnel which can build uniform air flow across the vertical duct to be used for the purpose of the investigation of the aerodynamic properties of grains. This study was conducted to examine how the air velocity profile in the vertical duct is influenced by the various alternations of the elements of the wind tunnel, and to prepare design guidance of the vertical wind tunnel which can be used for investigating aerodynamic properties of grains. In addition, several tests were conducted to locate the test section which can be applicable for determining the terminal velocity of grain. The following conclusions were obtained from the study: 1. The size and the location of the outlet of the plenum chamber should be determined such that the outlet air flow is less affected by the air flow and the back pressure by the side wall of the chamber. 2. The honeycomb was not helpful for attaining uniform air flow in case that the air flow profile at the bottom of the vertical duct is serverely different from the ideal one. 3. Even though considerable pressure drop was resulted from the screens installed within the vertical duct, the screens were helpful for attaining uniform air flow in the duct. 4. It is desirable for the test section to be located at the position that not only the air flow of the duct is not disturbed by the distorted back pressure in the plenum chamber, but also less boundary layer is developed.

• Journal of Information Display
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• 제6권2호
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• pp.1-6
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• 2005

We demonstrated stability-enhanced liquid crystal (LC) displays using pixel-isolated LC mode in which LC molecules are isolated in pixel by horizontal polymer layer and vertical polymer wall. The device shows good electro-optic properties against external point or bending pressure due to the polymer structures. The polymer wall acts as supporting structure from mechanical pressure and prevents the cell gap from bending. Moreover, the polymer layer acts as an adhesive to ensure a tight attachment of the two substrates. We present herein various methods for producing polymer structures by using an anisotropic phase separation from LC and polymer composites or patterned micro-structures for stable flexible liquid crystal displays.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.196-201
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• 2004

Aerodynamic characteristics of three-dimensional wings in ground effect for Aero-levitation Electric Vehicle(AEV) are numerically investigated for various ground clearances and wing spans at the Reynolds number of $2\times10^6$. Numerical results show that a sizeable three-dimensional flow separation occurs with formation of an arch vortex at the junction of main and vertical wings, and that this is conjectured a primary cause for the high lift-to-drag(L/D) reduction rate of the main wing, when the wing span is decreased. Improvements on L/D ratios of the wings with small spans are pursued by breaking the coherence of superimposed adverse pressure gradients at the wing junction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.431-433
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• 2006

The goal of this paper is improvement of vision inspection accuracy by using histogram specification operation. The histogram is composed of horizontal axis of image intensity value and vertical axis of pixel number in image. In appearance vision inspection, the histogram of reference image and input image are different because of minutely lighting distinction. The minutely lighting distinction is main reason of vision inspection error in many cases. Therefore we made an effort for elevation of vision inspection accuracy by making the identical histogram of reference image and input image. As a result of this area separation histogram specification algorithm, we could increase the exactness of vision inspection and prevent system error from physical and spirit condition of human. Also this system has been developed only using PC, CCD Camera and Visual C++ for universal workplace.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1685-1686
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• 2008

This paper presents the design and experiment results of a multi-layered microsystem for magnetic bead applications. The magneto-microfluidic device is designed for capable of separating magnetic beads. In the presence of the magnetic field, magnetic beads are attracted and moved to high gradient magnetic fields. A multi-layered microfluidic channel consists of top and bottom layers in order to separate magnetic beads in the vertical direction. Our channel is easily integrated magnetic cell sorter, especially on-chip microelectromagnet or permanent magnet device. Fast separation of magnetic beads in top and bottom channels can be used in high throughput screening to monitor the efficiency of blood and drug compounds.

• 한국동물학회지
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• 제39권3호
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• pp.325-336
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• 1996

제주도 자연림에 서식하는 초파리 군집구조를 파악하기 위하여 19954년 5월부터 10월까지 두 곳의 자연림에서 초파리를 채집하고, 이들의 종 수도와 미수직분포의 계절적 변이를 조사하였다. 전체적으로 우점종은 Drosophila bizonata, D. curviceps, D. lutescens, D. angu leris, D. tsigana and D. immigrans in the annual collections 등 6종이었다. 이들 우점종의 계절적 변화 양상은 두 조사지에서 유사했다. 종다양성의 계절적 변동은 종풍부도(종수)보다는 균등도의 영향을 더 받는 것으로 나타났으며, 모든 우점종의 수도에서 계절적 변동은 단일 장점을 갖는 양상을 보였다. 우점종의 일부는 미수직 분포에서 두 조사지간에 차이를 나타냈다. 이러한 결과들은 수림에 서식하는 우점종들의 생식 시기를 달리함으로써 생태학적 지위의 중복을 피하며, 이드르ㅣ 미수직분포는 계절과 고도 차이에 따른 요인에 많은 영향을 받고 있음을 암시한다.

• Structural Engineering and Mechanics
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• 제76권3호
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• pp.293-310
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• 2020

This study derives the differential equations of free vertical bending and torsional vibrations for two- and three-pylon suspension bridges using d'Alembert's principle. The respective algorithms for natural vibration frequency and vibration mode are established through the separation of variables. In the case of the three-pylon suspension bridge, the effect of the along-bridge bending vibration of the middle pylon on the vertical bending vibration of the entire bridge is considered. The impact of torsional vibration of the middle pylon about the vertical axis on the torsional vibration of the entire bridge is also analyzed in detail. The feasibility of the proposed method is verified by two engineering examples. A comparative analysis of the results obtained via the proposed and more intricate finite element methods confirmed the former feasibility. Finally, the middle pylon stiffness effect on the vibration frequency of the three-pylon suspension bridge is discussed. It is found that the vibration frequencies of the first- and third-order vertical bending and torsional modes both increase with the middle pylon stiffness. However, the increase amplitudes of third-order bending and torsional modes are relatively small with the middle pylon stiffness increase. Moreover, the second-order bending and torsional frequencies do not change with the middle pylon stiffness.

• 한국전문물리치료학회지
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• 제23권2호
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• pp.35-43
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• 2016

Background: The Functional Gait Assessment (FGA) was developed to measure of gait-related activities. The FGA was translated in Korean but only a few psychometric characteristics had been studied. Objects: The purpose of this study was to evaluate the validity and reliability of the Korean version of FGA scale using Rasch analysis. Methods: The study included 120 patients with stroke (age range=30~83 years; mean${\pm}$standard deviation=$58.3{\pm}11.1$). The FGA and Berg Balance Scale were performed, and were analysed for dimensionality of the scale, item difficulty, scale reliability and separation, and item-person map using Rasch analysis. Results: The 4 rating scale categories of FGA were satisfied with optimal rating scale criteria. The most items of the FGA showed sound item psychometric properties except 2 items ('gait with the horizontal head turns', and 'gait with narrow base of support'), and the 2 misfit items were excluded for all further analyses. The 8 items were arranged in order of difficulty. The most difficult item was 'gait with eyes closed', the middle difficult item was 'gait level surface', and the easiest item was 'gait with vertical head turns.' A person separation reliability was .93 and the person separation index was 3.57. Conclusion: This study suggests that the 8-item Korean FGA are valid measure of assess the gait-related balance performance, and to set the goal of rehabilitation plan in patient with stroke.

• Korean Chemical Engineering Research
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• 제51권1호
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• pp.93-97
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• 2013

소형 충전물을 이용한 수평형 증류 장치를 제작하여 실험실 규모의 증류실험을 실시하였다. 직경 6.7 mm Raschig 링 형태의 스테인레스 스틸 충전물을 넣은 40 mm 직경의 유리관을 증류탑으로 사용하였다. 증류관의 길이 방향으로 5개의 독립된 전기가열기를 배열하여 증류관 내부 온도를 분리 조절할 수 있도록 하였다. 증류관 내의 온도가 길이에 따라 연속적으로 변화하도록 조절함으로써 각각의 온도에 상응하는 기-액 평형을 형성하여 분리가 가능하도록 하였다. 증류실험의 결과 증류관의 증류단 상당길이(HETP)가 수직형 증류관에 비해 큰 것을 알았으며, 실용화가 가능한 처리용량과 분리효율을 얻었다.