• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.439-449
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• 2002

Experimental investigations of the flow structure and heat transfer enhancement in a channel with a built-in circular cylinder and a wing-let type vortex generator are presented. Without any vortex generators, relatively low heat transfer takes place in the downstream of the circular cylinder where is a recirculation region with low velocity fluid is formed. However with a wing-let type longitudinal vortex generator in the wake region behind the cylinder, heat transfer in the region can be enhanced. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from $20^{circ} to 45^{\circ}$, but spacings between the vortex generations are fixed to be 5 mm. The 3-dimensional mean velocity field downstream of the vortex generator is measured by a five-hole pressure probe, and the hue-capturing method using thermochromatic liquid crystals has been used to provide the local distribution of the heat transfer coefficient. The vorticity field and streamwise velocity contour are obtained from the velocity field. Streamwise distributions of averaged Stanton number on the measurement planes show very similar trends for all the experimental cases($\beta=20^{circ}, 30^{circ} and 45^{\circ}$). Circulation strength and heat transfer coefficient have the maximum values when the angle of attack($\beta$) is $30^{\circ}$.

• 한국추진공학회지
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• 제13권4호
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• pp.36-44
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• 2009

광학 선형 패터네이터 및 광학 토모그래피 기법을 사용하여 높은 주위 기체 압력 조건에서 분무단면을 측정하였다. 레이저 직선광이 분무 영역을 지나도록 하여 발생하는 Mie 산란 신호 및 직선광의 투과율을 측정하였으며, 이로부터 Beer-Lambert 법칙 및 수학적 단면 재구성 기법을 이용하여 분무 단면의 감쇠 계수 분포를 재구성하였다. 높은 주위 기체 압력 조건에서 광학적으로 밀한 분무가 발생하며, 그 결과 산란 신호의 감쇠 효과가 크게 증가한다. 따라서 미 산란 신호를 이용하는 광학 선형 패터네이터의 경우 감쇠 효과를 완화하는 데 한계를 보인다. 광학 토모그래피의 경우 분무를 통과하는 레이저광의 투과율 정보만을 이용하여 성공적으로 분무 단면을 재구성하였다.

• The Journal of the Acoustical Society of Korea
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• 제20권1E호
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• pp.20-24
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• 2001

We propose the computation reduction method of real root method that is mainly used in the CELP(Code Excited Linear Prediction) vocoder. The real root method is that if polynomial equations have the real roots, we are able to find those and transform them into LSF[1]. However, this method takes much time to compute, because the root searching is processed sequentially in frequency region. But, the important characteristic of LSF is that most of coefficients are occurred in specific frequency region. So, the searching frequency region is ordered by each coefficient's distribution. And coefficients are searched in ordered frequency region. Transformation time can be reduced by this method than the sequential searching method in frequency region. When we compare this proposed method with the conventional real root method, the experimental result is that the searching time was reduced about 46% in average.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.187-192
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• 2003

The heat (mass) transfer characteristics in the tip-leakage flow region of a high-turning first-stage turbine rotor blade has been investigated by employing the naphthalene sublimation technique. The heat transfer data in the tip-leakage flow area for the tip clearance-to-span ratio, h/s, of 2.0% are compared with those in endwall three-dimensional flow region without tip clearance (h/s = 0.0 %). The result shows that the thermal load in the tip-leakage flow region for h/s = 2.0% is more severe than that in the endwall flow region for h/s = 0.0%. The thermal loads even at the leading and trailing edges for h/s = 2.0% are found larger than those for h/s = 0.0%. The tip-leakage flow results in heat transfer augmentations near the tip on both pressure and suction sides in comparison with the mid-span results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 추계학술대회 논문집
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• pp.21-23
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• 1994

By adding La₂O₃ to optical multicomponent glass composition, after making mother glass and core fiber that enable to enlarge the infrared transmittance region, then surveyed the optical properties. Through thermal analysis of the glass abstained by melt-quenching after selecting stable basic composition on devitrification and replace SiO₂ by 4-12wt% La₂O₃. As La₂O₃ increases up to l2wt% transition temperature, refractive index, density, deformation temperature increased, whereas thermal expansion coefficient decreased. As a result of inspectig transmittance in UV/VIS/IR region, visable region indicated the decrease of transmittance by increasing the La₂O₃ and transmittance region was enlarged by increasing the La₂O₃ in IR region. Also, fabricate core fiber at 820℃ and severy the optical loss we could fact that La₂O₃ composition added 12wt% showed the minimum optical loss.

• 대한원격탐사학회지
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• 제26권6호
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• pp.731-740
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• 2010

A region merging technique is suggested in this paper for the segmentation of high-spatial resolution imagery. It employs a region growing scheme based on the region adjacency graph (RAG). The proposed algorithm uses directional neighbor-line average feature vectors to improve the quality of segmentation. The feature vector consists of 9 components which includes an observation and 8 directional averages. Each directional average is the average of the pixel values along the neighbor line for a given neighbor line length at each direction. The merging coefficients of the segmentation process use a part of the feature components according to a given merging coefficient order. This study performed the extensive experiments using simulation data and a real high-spatial resolution data of IKONOS. The experimental results show that the new approach proposed in this study is quite effective to provide segments of high quality for the object-based analysis of high-spatial resolution images.

• 대한설비공학회지:설비저널
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• 제13권1호
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• pp.14-21
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• 1984

The purpose of this investigation is to study heat transfer characteristics in wall jet region on a flat plate caused by upward impinging water jet. In the wall jet region, heat transfer results by impinging water jet are being compared with the ones with supplementary water. As the radius increases, the heat transfer coefficient in the wall jet region consquently decreases, but decreasing nozzle-heat plate distance, the reduction rate increases. The experimental equation is expressed as follows : $$\frac{N_{ur}}{P_r^{0.4}}{\cdot}\overline{\xi}=m(\overline{\eta}{\codt}Re{\delta})^n,\;m=0.034\~0.056,\;n=1.74\~2.007$$ The optimum height of supplementary water is obtained to improve heat transfer effect of wall jet region.

• 농촌계획
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• 제16권2호
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• pp.57-64
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• 2010

This study aims to understand the degree of inequality of surveyed amenity resources and identify which resource and region have the highest concentration by estimating Lorenz Curve and the Gini's Coefficient. The Lorenz Curve and Gini's Coefficient derived from economics are introduced as tools for investigating and quantifying regional variability of amenity resources concentration. This study describes the concepts underlying the application of the Gini's coefficient to measure the concentration of amenity resources in 11 regions, Chungbuk Province, Korea. The Lorenz Curve presents a graphical view of the cumulative distribution of amenity resources and the Gini's Coefficient provides a single-parameter measure of the distributional concentration of amenity resources. Also the Gini's Coefficient is compared to the number of amenity resource for understanding distributional difference between concentration and quantitative distribution of amenity resources. The results demonstrate significantly different regional variation according to the amenity variables: almost intact nature, interaction between nature and man, man-made.

• 전자공학회논문지D
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• 제36D권5호
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• pp.88-98
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• 1999

레이저의 종축방향으로 회절격자층을 형성하는 위쪽 클래딩 층의 가운데 부분의 굴절률을 양 옆부분과 다르게 하여 유효위상천이 효과를 넓은 영역에서 얻는 refractive index midulated (RIM) DFB 레이저를 제안한다.RIM-DFB 레이저는 SHB 효과를 줄이기 위하여 기존에 제안되었던 회절격자의 주기를 변화시켜 넓은 영역에 걸쳐서 유효 위상 천이를 주는 corrugation pitch modualtion (CPM) 방법과 레이저의 종축 방향으로 결합계수를 달리하여 주는 distributed coupling coefficients (DCC) 방법의 효과를 동시에 얻을 수 있는 실현 가능한 구조이다. 급격한 위상천이가 없기 때문에 광자밀도분포가 균일해져 SHB 효과가 줄어 들게 되며 레이저 공진기 가운데 부분의 결합계수가 양 옆 부분의 결합계수보다 커서 분포결합계수의 효과를 주기 때문에λ/4 위상천이 레이저와 CPM-DFB 레이저에 비해 고출력에서 좋은 단일 모드 특성을 보인다. 그리고, 굴절률이 다른 가운데 부분의 길이가 RIM-DFB 레이저의 동작특성에 미치는 영향에 대하여 연구하였다.

• 대한기계학회논문집
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• 제17권8호
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• pp.1921-1930
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• 1993

In order to evaluate the inlet pressure correctly, the full Navier-Stokes equations are solved numerically for the computational domain which covers the cavity region between pads as well as the bearing film. A nonuiform grid system is adopted to reduce the number of grid points, and the numerical solutions are obtained for a wide range of Reynolds number in laminar regime with various values of the distance between pads. The numerical results show that the inlet pressure is significantly affected by Reynolds number and the distance between pads. An expression for the loss coefficient in terms of Reynolds number and non-dimensional distance between pads is obtained on the basis of the numerical results. It is found that the inlet pressure over the whole range of numerical solutions can be fairly accurately estimated by applying the formula for the loss coefficient to the extended Bernoulli equation.