• 한국유체기계학회 논문집
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• 제16권4호
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• pp.22-27
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• 2013

The purpose of this paper is to perform the structural design of the small scale vertical-axis wind turbine (VAWT) blade using a response surface method(RSM). First, the four design factors that have a strong influence on the structural response of blade were selected. Analysis conditions were calculated by using the central composite design(CCD), which is a typical design of experiment for the response surface method(RSM). Also, the significance of the central composite design(CCD) was verified using analysis of variance(ANOVA). The finite element analysis was performed for the selected analytical conditions for the application of response surface method(RSM). Finally, a optimization problem was solved with a objective function of blade weight and a constraint of allowable stress to achieve a optimal structural design of blade.

• Ocean Systems Engineering
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• 제11권1호
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• 센서학회지
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• 제27권5호
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• pp.275-279
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• 2018

In this study, we introduce a sensing platform based on a plasmonic metasurface absorber (MA) with a vertical nanogap for the ultrasensitive detection of monolayer molecules. The vertical nanogap of the MA, where the extremely high near-field is uniformly distributed and exposed to the external environment, is formed by an under-cut structure between a metallic cross nanoantenna and the mirror layer. The accessible sensing area and the enhanced near-field of the MA further enhance the sensitivity of surface-enhanced infrared absorption for the target molecule of 1-octadecanethiol. To provide strong coupling between the molecular vibrations and plasmonic resonance, the design parameters of the MA with a vertical nanogap are numerically designed.

• 대한치과기공학회지
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• 제3권1호
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• pp.9-16
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• 1981

A comparative study was conducted to evaluate the relationship of investing medium to the amount of vertical occlusal changes and to the differences of surface smoothness during denture construction. Three groups of 20 dentures, 30 sets of upper and lower were fabricated of conventional heatcuring acrylic denture base resin, using silicone-gypsum molding techniques, with or without covering the occlusal surfaces of the teeth by artificial stone and all-gypsum molding techniques. The distance between the two reference points indented by 1/2 round bur on the upper and lower frontal surfaces of each articulator were measured and recorded before processing and again after processing and remounting of each denture on the articulator. The differences between the two recordings indicated the amount of vertical opening during denture processing. The difference of surface smoothness were investigated and determined by 3 observers continual comparing of the two randomly selected dentures with each other, which were seperately selected as pairs from the different two groups of 20. The results obtained were as follows: 1. During resin processing no statistically significant differences of the amount of vertical occlusal changes were detected between any of the two groups of two silicone-gypsum and one allgypsum molding techniques, although the amount of vertical opening was somewhat increased when silicone-gypsum molding technique was used. 2. Surface smoothness of the processed denture was makedly by increased when silicone-gypsum molding technique was used.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.70-86
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• 1996

The purpose of this study was to analyze the stress distribution in mandibular second premolars restored with different post and core techniques. Sixteen two-dimensional finite element model of mandibular second premolars restored with post and core and complete crown were developed according to the diameter, length, and material of post and core. Vertical force, 10N in magnitude, was applied first to the central fossa and then $45^{\circ}$ oblique force of same magnitude was applied to the buccal contact surface of buccal cusp. The obtained results were as follows : 1. Stress distribution within the dentin 1) Regardless of the material of the post and core and the diameter and length of the post, the pattern of stress distribution within the dentin was similar. 2) Maximum dentinal stress was observed on the lingual root surface of alveolar crest level with oblique loading and on lingual side of root dentin at the crown margin on vertical loading. 3) Cast post and cores produced the lowest dentinal stress concentrations and the highest stress concentration was observed in composite resin post and cores. 2. Stress distribution within the post and core 1) Within the amalgam and composite resin post and core, the patterns and maximum values of stress were similar. Maximum stress located at the central fossa of core portion on vertical loading and at the lingual junction of post and core with oblique loading. 2) Among the all post and cores, the cast post and core registered the highest stress concentration and maximum stress value within the post. Maximum stress located at the post apex on vertical loading and at lingual half of the post surface with oblique loading. 3) In case of Para-post and amalgam core, maximum stress located at the central fossa of core portion and lingual tip of the post head on vertical loading. With oblique loading, maximum stress located at the lingual half of the post surface.

• 한국축산식품학회지
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• 제40권6호
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• pp.957-968
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• 2020

The influence of muscle architecture on muscle fiber characteristics and meat quality has not been fully elucidated. In the present study, muscle fiber characteristics on the chop surface of pork loin (M. longissimus thoracis et lumborum, LTL), pennation angle degree, and meat quality were evaluated to understand the pork LTL architecture and its relationship with the loin chop quality. Muscle fiber pennation degree ranged from 51.33° to 69.00°, resulting in an ellipse-shaped muscle fiber on the surface of pork loin chop. The cross-sectional area (CSA) on the sections cut vertical to the muscle length (M-Vertical) was considerably larger (p<0.05) than that on the sections cut vertical to the muscle fiber orientation (F-Vertical) regardless of the fiber type. Pennation angle is positively correlated with CSAs of F-Vertical (p<0.05) and with Warner-Bratzler shear force (r=0.53, p<0.01). Besides the shear force, lightness and pH were positively correlated with the fiber composition and CSA of IIX fiber (p<0.05); however, the redness, yellowness, drip loss, and cooking loss were not correlated with the pennation angle and muscle fiber characteristics on the chop surface (p>0.05). These observations might help us in better understanding pork loin architecture and the relationship between the pennation angle, muscle fiber characteristics, and meat quality of pork loin chop.

• 에너지공학
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• 제23권2호
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• pp.21-27
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• 2014

수직평판의 거칠기에 따른 자연대류 열전달의 변화를 실험적으로 측정하였다. 열전달 실험을 대신하여 유사성에 기초한 물질전달로 모사하여 실험을 수행하였다. 또한 국부적인 열전달률을 알기위해 Piecewise electrode를 채택하였다. Pr수는 2,014 그리고 높이(L)는 0.154m로 고정하고 매끈한 수직평판에 대해 실험을 수행한 결과 Le Fevre의 수직평판 상관식과 거의 일치하였다. 거칠기 정도를 $0.5R_z{\mu}m{\sim}14.1R_z{\mu}m$로 변화시켰을 때 $Nu_L$수는 거칠기 정도가 커지면서 증가하는 경향을 나타내었다. 실험결과는 간단한 상관식으로 정리하였다.

• 설비공학논문집
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• 제12권4호
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• pp.381-387
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• 2000

An experimental study on the stratified fluids was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in the square cavity. The same volume of water and silicon oil was filled in it. The experiments were performed with the variations of initial temperatures and cooling surface temperatures. And the effect of vertical or horizontal cooling surface positions in the square cavity was investigated. When the cooling surface temperatures were $-4^{\circ}C$ , the supercooling phenomena were observed for both cases of cooling surface positions in the full region regardless of the initial temperature of fluid. In the square cavity with horizontal cooling surfaces, the lower the initial temperatures were, the longer the supercooling durations were, and with vertical cooling surface the lower the initial temperatures were, the shorter the supercooling durations were.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.404-413
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• 2013

In the present study, a towed underwater particle image velocimetry (PIV) system was validated in uniform flow and used to investigate the free-surface effects on the turbulent wake of a simple surface-piercing body. The selected test model was a cylindrical geometry formed by extruding the Wigley hull's waterplane shape in the vertical direction. Due to the constraints of the two-dimensional (2D) PIV system used for the present study, the velocity field measurements were done separately for the vertical and horizontal planes. Using the measured data at several different locations, it was possible to identify the free-surface effects on the turbulent wake in terms of the mean velocity components and turbulence quantities. In order to provide an accuracy level of the data, uncertainty assessment was done following the International Towing Tank Conference standard procedure.

• 한국지반공학회논문집
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• 제26권12호
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• pp.51-60
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• 2010

자중에 의한 토압은 일반적으로 깊이에 따라 선형비례하여 증가되지만, 상재하중에 의해 발생되는 토압은 분포형태와 지반상태 및 경계조건에 따라 다르게 분포한다. 본 연구에서는 변위가 구속된 강성벽체에 연직상재하중에 의한 토압분포를 실험적으로 연구하기 위하여 실내모형토조[30 cm(폭) ${\times}$ 110 cm(길이) ${\times}$ 88 cm(높이)]에 각 2개의 로드셀이 배치된 8개의 토압판으로 구성된 강성벽체를 설치하여 연직상재하중의 크기와 위치(벽체에서 이격거리)를 변화시켜 가면서 토압분포와 토압의 영향범위를 관찰하였다. 실험결과, 연직상재하중에 의해 발생되는 수평토압은 일정위치에서 최대값을 보이고 깊어질수록 감소하여 한계깊이를 초과하면 무시할 만큼 작아졌다. 수평토압이 최대가 되는 깊이와 한계깊이는 연직상재하중의 크기와는 무관하게 벽체와의 이격거리에 따라 다르게 나타났다.