• 대한기계학회논문집B
• /
• 제26권6호
• /
• pp.893-901
• /
• 2002

Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670 mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer($\delta$=270 mm) was the natural turbulent boundary layer at the test section floor with fairly long developing length(18 m). The thin boundary layer($\delta$=36.5 mm) was generated on the smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity(3 ㎧) and the height of the model(40 mm) was 7.9$\times$10$^3$. The mean velocity vector fields and turbulent kinetic energy distributions were measured and compared. The effect of boundary layer thickness was clearly observed not only in the length of separation bubble but also in the location of reattachment point. The thinner the boundary layer thickness, the higher the turbulent kinetic energy Peak around the model roofbecame. It is strongly recommended that the height ratio between the model and the approaching boundary layer thickness should be encountered as a major parameter.

• 한국항공우주학회지
• /
• 제35권12호
• /
• pp.1135-1142
• /
• 2007

과학기술위성2호는 정밀궤도결정을 위하여 위성레이저반사경을 부착할 예정이다. 위성레이저반사경은 지상으로부터 방사된 레이저가 위성에 부착된 반사경으로부터 되반사되어 돌아오는 광자(Photon)의 이동시간을 측정함으로써 관측소와 위성까지의 거리를 정밀하게 측정하는데 사용된다. 현재 레이저반사경은 준비행모델을 개발하였으며, 환경시험을 수행하였다. 본 논문에서는 레이저반사경의 준비행모델의 개발과정을 소개하고, 환경시험 결과를 보고한다. 준비행모델 레이저반사경의 환경시험은 엔지니어링 모델에서 발생하였던 코너큐브프리즘의 파손없이 성공적으로 수행되었다.

• 소성∙가공
• /
• 제23권1호
• /
• pp.16-22
• /
• 2014

The current study presents a simple setup method for making teeth models using a three-axis CNC milling machine. Physical teeth models can be made by several methods: casting, machining, and three-dimensional printing. Since the shape of a teeth model requires five-axis machining, the machining of a teeth model using a three-axis CNC milling machine requires careful setup operations. In this paper a simple datum shape is designed within the work piece of the teeth model. The datum shape is an n-sided prism with regular n-polygon ends and rectangular sides. In the present study a 12-sided prism is used, which easily makes 30 degree rotations for finish machining. The proposed setup approach does not require any special tools for making the teeth model using a three-axis CNC milling machine. A test was run and the results show that the proposed approach is useful for experimental makings with the limited facilities available.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
• /
• pp.1836-1839
• /
• 1997

This paper presents machine vision technique with a camera modeling that accounts for major sources of camera distortion, namely, radial, decentering, and thin prism distortion. Radial distortion causes an inward or outward displacement of a given image point from its ideal location. Actual optical systems are subject to various degrees of decentering, that is, the optical centers of lens elements are not strictly collinear. It is our purpose to develop the vision system for the pattern recognition and the automatic test of parts and to apply the line of manufacturing.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 춘계학술대회 논문집
• /
• pp.319-324
• /
• 1996

In this paper, radial sheared eletronic shearopgraphy was studied in order to measure vibration characteristics of circular or radial symmetric objects. We calculated amplitude of vibration by using eletro-optic holography theory, and utilized a porror prism for optical arrangement of sheared two images in this experiment. In this case, the data measured by shearing interferometer give us a distribution of the gradient of vibration amplitude. This developed system is applied to symmetical objects such as fans of airconditioner and circular plates to test vibration characteristics.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
• /
• pp.78-81
• /
• 2000

The test specimen proposed in this study, named the bimaterial eccentric compression specimen, is a rectangular prism of two dissimilar materials with a notch at their interface. Normalized energy release rates and phase angles were calibrated with the finite element method. The normalized energy release rate increases with notch ratio but decreases with E2/E2, loading point, and phase angle, Bimaterial specimens consisting of mortar and ploymer as well as mortar and rock were prepared and tested to simulate fracture behavior ar the interface. Test results have confirmed that initial notch has significant effect on the apparent interfacial toughness.

• 한국안광학회지
• /
• 제9권2호
• /
• pp.361-370
• /
• 2004

정확한 사위량 측정을 위한 전제조건이 되는 굴절이상의 완전교정과 광학중심점과 동공중심점의 일치가 선행되지 않을 때 발생할 수 있는 사위량 변동을 알아보기 위해 근시성 굴절이상안 120명을 대상으로 동공중심거리, 장용안경의 광학중심점거리, 안경장용 상태의 사위량을 Von Graefe법을 이용하여 측정하고, 검사대상자의 동공중심과 광학중심점을 정확하게 일치시키고 굴절이상도를 완전교정한 상태에서의 사위량을 각각 측정하여 다음과 같은 결과를 얻을 수 있었다. 1. 굴절이상도가 미교정되고 광학중심점과 동공중심점이 미조정 된 안경을 장용하고 측정한 사위량과 굴절이상도를 완전교정하고 광학중심점과 동공중심이 일치된 상태에서 측정한 사위량은 완전교 정시 정위는 10.0%에서 12.5%로 증가하였고, 외사위는 67.5%에서 62.5%로 감소, 내사위는 22.5%에서 25.0%로 증가하였다. 2. 평균 광학중심점 거리는 31.7024mm, 동공중심점 거리는 평균 31.4881mm로 안경의 Optical Center Distance가 동공중심거리보다 약 0.2143mm 큰 것으로 측정되었다. 3. 동공중심점과 광학중심점이 일치된 안경과 동공중심과 광학중심이 불일치된 안경을 장용한 사람은 각각 37.5%, 62.5%로 조사되었다. 4. 미교정된 근시안 가운데 동공중심과 광학중심이 일치한 사람을 대상으로 근시도를 완전교정하고 사위를 측정한 결과 근시도를 미교정했을 때 보다 외사위량은 53.33%가 감소하였고, 내사위량은 20.0%가 증가하였다. 5. 근시도를 완전교정하고 광학적중심과 동공중심을 정확하게 일치시켜 측정한 외사위량은 구안경 장용시보다 $1.11{\Delta}$ 감소하였고, 내사위량은 $0.39{\Delta}$ 증가한 것으로 나타나 검정결과 매우 유의하였다(p<0.05).

• Structural Engineering and Mechanics
• /
• 제62권1호
• /
• pp.97-106
• /
• 2017

This paper discusses an experimental programme that was carried out to study the effects of specimen size-shape and type of moulds on the compressive strength of concrete. For this purpose, cube specimens with 150 mm dimensions, cylinder specimens with $150{\times}300mm$ dimensions, and prism specimens with $150{\times}150{\times}375mm$ dimensions were prepared. The experimental programme was carried out with several concrete compositions belonging to strength classes C20/25, C25/30, C30/37, C40/50 and C60/75. Furthermore, the test results were curve-fitted using the least squares method to obtain the new parameters for the modified size effect law.

• 한국정밀공학회지
• /
• 제32권2호
• /
• pp.191-198
• /
• 2015

In this paper, six-degree-of-freedom (DoF). Displacement measurement technique using a compact stereo-vision system is proposed. The measuring system consists of a camera, an optical prism, two plane mirrors, and a planar marker on a target. The target was attached on an object so that its six-DoF displacement can be calculated using a proposed coordinates estimating algorithm and stereo images of the marker. A prototype was designed and fabricated for performance test. From the test results, it can be confirmed that the proposed measuring technique can be applied to monitoring and control of various manipulators.

• 한국측량학회지
• /
• 제13권2호
• /
• pp.291-298
• /
• 1995

본 연구에서는 중력장모델링에 있어서 단 파장의 효과인 지형보정량을 계산하고 지오이드의 효과에 미치는 DTM 데이타를 사용하여 계산하였다. 정밀한 지형보정량을 계산하기 위하여 $500\times{500m}$격자 간격의 DTM 데이타를 준비하여 매스프리즘 모델과 매스라인모델을 적용하였다. 적용결과 지형효과가 다소 크게 나타났으며, 이 결과는 정밀한 지오이드의 계산을 위하여는 지형효과가 고려되어야 한다는 것을 알 수 있었다.