• Wind and Structures
• /
• 제37권1호
• /
• pp.25-38
• /
• 2023

Due to the complexity and difficulty in meeting the multiphase flow complexity, similarity, and multiscale characteristics, the mechanism of snow drift is so complicated that the snow deposition prediction is still inaccurate and needs to be far improved. Meanwhile, the validation of prediction methods is also limited due to a lack of field-measured data about snow deposition. To this end, a field measurement activity about snow deposition around a cube with time was carried out, and the snow accumulation process was measured under blowing snow conditions in northwest China. The maximum snow depth, snow profile, and variation in snow depth around the cube were discussed and analyzed. The measured results indicated three stages of snow accumulation around the cube. First, snow is deposited in windward, lateral and leeward regions, and then the snow depth in windward and lateral regions increases. Secondly, when the snow in the windward region reaches its maximum, the downwash flow erodes the snow against the front wall. Meanwhile, snow range and depth in lateral regions have a significant increase. Thirdly, a narrow road in the leeward region is formed with the increase in snow range and depth, which results in higher wind speed and reforming snow deposition there. The field measurement study in this paper not only furthers understanding of the snow accumulation process instead of final deposition under complex conditions but also provides an important benchmark for validating prediction methods.

• 한국비블리아학회지
• /
• 제19권1호
• /
• pp.61-87
• /
• 2008

도서관통계와 평가의 관련성이 국제표준안, 업무활동 영역, 항목간의 유사성 면에서 깊고, 불가분의 관계 속에 있음에도 한국 대학도서관의 통계와 평가는 생산단계 및 활용 면에서 전혀 연계되어 있지 않다. 이를 증명하기 위하여 국제표준, 통계데이터를 살펴 두 항목간에 연계적 상관관계를 살펴보아 정량적 데이터의 45%정도의 중복도가 있음을 밝혔다. 반면 기존의 국내 통계 항목과 평가 항목간에는 14-26%의 관계가 있으며, 새로이 연구 개발된 대학도서관통계 실용안에서는 상당히 발전된 관계성을 발견하였으며, 반면 상당한 특정성도 발견되었다. 이제 대학도서관통계 온라인시스템 개발단계에서 통계시스템의 목적 외에 평가시스템정보를 제공한다는 면을 고려하여 항목간의 포괄적 정보가 제공되도록 개발하는 것이 필요하다.

• 한국정보처리학회논문지
• /
• 제5권9호
• /
• pp.2353-2360
• /
• 1998

리엔지니어링에서 기존 소프트웨어 시스템의 환경변화에 따라 대부분 논리적 실행을 중심으로 집단화를 실행해왔으나 본 논문에서는 기존 소스 프로그램을 중심으로 각 모듈간의 정보공유측면에서 효율적으로 집단화할 수 있는 방안을 제안하였다. 정보고유를 이용한 관련 모듈들의 집단화를 위해서 모듈 집단간 휴리스틱 측정방법을 근간으로 본 논문에서 제안한 유사성 및 단일성 알고리즘을 이용한 측정을 한 후 그 결과를 평가하였다. 이를 통해 모듈 및 프로시져의 관련성을 중심으로 관련 모듈 및 프로시져의 정리 및 집단화를 유도할 수 있었다. 소프트웨어 시스템의 환경변화에 따른 기존 시스템을 정보공유를 중심으로 집단화함으로써 과적으로 소프트웨어 시스템을 재구축할 수 있는 방법론을 제시하였으며, 그 구현 가능성을 실제 예를 통해서 보였다.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2009년도 IWAIT
• /
• pp.768-772
• /
• 2009

This paper proposes a method for measurement three-dimensional trajectories of bubbles generated around a swimmer's arms from stereo high-speed camera videos. This method is based on two techniques: two-dimensional trajectory estimation in single-camera images and trajectory pair matching in stereo-camera images. The two-dimensional trajectory is estimated by block matching using similarity of bubble shape and probability of bubble displacement. The trajectory matching is achieved by a consistensy test using epipolar constraint in multiple frames. The experimental results in two-dimensional trajectory estimation showed the estimation accuracy of 47% solely by the general optical flow estimation, whereas 71% taking the bubble displacement into consideration. This concludes bubble displacement is an efficient aspect in this estimation. In three-dimensional trajectory estimation, bubbles were visually captured moving along the flow generated by an arm; which means an efficient material for swimmers to swim faster.

• 한국가시화정보학회지
• /
• 제11권1호
• /
• pp.41-47
• /
• 2013

Turbulence properties of a cylinder wake (d=10 mm) have been investigated with a new volume PTV algorithm. The measurement system consists of two-high-cameras(1 $k{\times}1$ k), a Nd-Yag laser and a host computer. A fitness function representing three-dimensional coherency has been adopted to sort out spurious vectors. A hybrid fitness function representing the relations between the fitness and the three-dimensional shortest distances constructed by the two collinears of the two cameras has been also adopted. The constructed algorithm has been employed for the measurements of the cylinder wakes. The Reynolds numbers tested in this paper are 360, 540, 720, 900, 1080 and 1260. More than 10,000 instantaneous 3D vectors have been obtained by the constructed system. The volumetric distributions of the turbulence intensities (for u', v', w') indicate that clearly different patterns for all Reynolds numbers and imply that a regular pattern (like a similarity rule) for the turbulent properties exists.

• 한국측량학회지
• /
• 제18권2호
• /
• pp.191-198
• /
• 2000

수치사진 측량은 신속한 정보 획득과 갱신을 통하여 지리정보체계의 데이터 베이스 구축에 중요한 역할을 하고 있다. 이러한 수치사진측량의 기본적인 처리과정 중의 하나는 영상정합이다. 그러나 어떠한 영상정합 알고리즘도 인간의 판단과 지적 능력에 의해서 수행되는 것만큼 만족스러운 결과를 산출하지는 못하고 있다. 따라서 본 논문에서는 대상지역이 완만한 경우 정합점이라고 판단되는 점과 그 이웃 점들간에 전체적인 유사성을 관측하여 불량 정합점들을 제거하는 방법(정합 강도의 측정)을 제안하였고, 또한 최종적으로 얻어지는 정합점들의 3차원 좌표를 광속 조정법을 통하여 구하였다 실험결과 제안방법은 불량정합점들을 효과적으로 제거하였고, 계산된 3차원 지상좌표도 허용 오차 범위 이내로 들어왔다.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 추계학술대회
• /
• pp.162-165
• /
• 2017

제안 논문은 x-ray 입력영상에서 관심부위 영역을 추출해 참조이미지와 비교하는 경우가 발생한다. x-ray영상의 모양은 같지만 대상의 크기나 방향 및 위치가 서로 다르게 촬영되어 나타나게 된다. 이와 같이 동일 대상에 대해 서로 다른 영상이 입력될 경우 영상의 유사도 측정법을 이용해 명암의 발기 차이를 측정한다. 또한 거리 측정은 x-ray 데이터의 벡터좌표(x,y,z)를 가지고 두 점간의 거리를 계산한다. 제안 방식은 기존 방식에 비해 관심영역 추출의 정확도 향상과 참조이미지 매칭 수행시간이 효율적임을 실험을 통해 증명하였다.

• 대한기계학회논문집B
• /
• 제21권5호
• /
• pp.700-712
• /
• 1997

The flowfield generated by a 2-D rotating cylinder on a plane moving at freestream velocity was experimentally investigated in a wind tunnel to simulate aerodynamic characteristics of rotating wheels of an automobile. In the flowfield around a rotating cylinder at 3*10$^{3}$ < Re$_{d}$<8*10$^{3}$, unique mean flow and turbulence characteristics were confirmed by hot-wire measurements as well as frequency analysis, which was supported by flow visualization. In the vicinity of a rotating cylinder, a unique turbulence structure on .root.over bar u'$^{2}$ profiles was formed in hump-like shape at 1 < y/d < 3. A peak frequency which characterized the effect of a rotating cylinder had the same value of the rotation rate of a cylinder. In case of cylinder rotation, the depths of mean velocity -defect and turbulent-shear regions were thickened by 20-40% at 0 < x/d < 10 compared with the case of cylinder stationary. Far downstream beyond x/d > 10, the flowfield generated by a rotating cylinder showed self-similarity in the profiles of mean velocity and turbulence quantities. The effect of a rotating cylinder was independent of its rotation rate and Reynolds number in the measurement range.

• 대한원격탐사학회지
• /
• 제22권3호
• /
• pp.175-182
• /
• 2006

Because of the phenological variation of vegetation growth in temperate region, it is often difficult to accurately assess the surface conditions of agricultural croplands, grasslands, and disturbed forests by multi-spectral remote sensor data. In particular, the spectral similarity between soil and dry vegetation has been a primary problem to correctly appraise the surface conditions during the non-growing seasons in temperature region. This study analyzes the spectral characteristics of the mixture of dry vegetation and soil. The reflectance spectra were obtained from laboratory spectroradiometer measurement (GER-2600) and from EO-1 Hyperion image data. The reflectance spectra of several samples having different level of dry vegetation fractions show similar pattern from both lab measurement and hyperspectral image. Red-edge near 700nm and shortwave IR near 2,200nm are more sensitive to the fraction of dry vegetation. The use of hyperspectral data would allow us for better separation between bare soils and other surfaces covered by dry vegetation during the leaf-off season.

• International Journal of Railway
• /
• 제4권2호
• /
• pp.42-49
• /
• 2011

Today, rolling stock has become a fast and convenient mode of transportation and has witnessed increased demand. But the speed improvement has resulted in increased aerodynamic noise and therefore residential districts near the railroad tracks are exposed to ever increasing noise level. A study on methodologies for measuring and appraising rolling stock's environmental noise has therefore become an important area of endeavor. In the case of the environmental noise, there are no changes in tone so prediction can be made by reducing areas around the railway. The present study explores estimation of the noise around the railway using scale model, and the source of the noise has been investigated as well. The scale model of rolling stock will have to be able to measure high frequency noise and it is required to be generated in a short amount of time. Since popping a balloon or firing a gun fits this requirement the present study analyzed the characteristics of these two different noise sources. Measurement was made in a large vacant lot and the reflection due to the ground was also examined. The method proposed here can be used in the future for predicting the environmental noise of railway vehicles.