• 한국해양공학회지
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• 제24권6호
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• pp.61-70
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• 2010

This study presents free vibration analyses of perforates steel plates with various cutouts. Four different parameters (shape, size, curvature radius ratio, and rotation of cutouts) were considered to investigate the effects of those parameters on the free vibration characteristics, such as natural frequencies of the perforated steel plates. Three different shapes of cutouts are circle, square, and triangle, and the considered sizes are 5, 10, 15, 20, and 25 mm. For the triangular and square cutouts, the characteristic radii of the inscribed circles of those cutouts were defined. In addition, the curvature radius ratio was defined as the ratio of curvature radius of bluntness and the characteristic radius. Then, total seven different curvature radius ratios (0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) were considered. To investigate the rotation effect of the cutouts, it was considered four rotations ($0^{\circ}$, $15^{\circ}$, $30^{\circ}$, and $45^{\circ}$) for the square cutouts and three rotations (0, 15, and 30) for the triangular cutouts. All the free vibration analyses were conducted using a general purpose finite element program. From the analyses we found that the most influential parameter for the free vibration response of the perforated plates is the size of cutout. The other factors such as the shape, curvature radius ratio, and rotation are minors; they mainly change the natural frequency as long as the size effect is accompanied.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.331-336
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• 2002

Recently the critical nozzles with small diameter are being extensively used to measure mass flow in a variety of industrial fields and these have different configurations depending on operation condition and working gas. The curvature radius of the critical nozzle throat is one of the most important configuration factors promising a high reliability of the critical nozzle. In the present study, computations using the axisymmetric, compressible, Navier-Stokes equations are carried out to investigate the effect of the nozzle curvature on critical flows. The diameter of the critical nozzle employed is D=0.3mm and the radius of curvature of the critical nozzle throat is varied in the range from 1D to 3D. It is found that the discharge coefficient is very sensitive to the curvature radius(R) of critical nozzle, leading to the peak discharge coefficient at R = 2.0D and 2.5D, and that the critical pressure ratio increases with the curvature radius.

• 한국정밀공학회지
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• 제14권6호
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• pp.52-63
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• 1997

Non-circular gear has a good velocity ratio in high speed and heavy load without any slip, moreover, it can transmit various motion, using simpler structure than link and cam, automation mechainism. In case of designing and manufacturing non-circular gear. I suggest one of references in applying non-circular gear to industrial plant, and suitable range of application by pressure angle curvature and angle ratio

• 대한안전경영과학회지
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• 제10권2호
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• pp.85-94
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• 2008

The object of this study is to investigate the penetration characteristics according to the change of stacking sequences and curvature radius in the composite laminated shell. They are staked to [02/902]S and [0/902/0]s, their interlaminar number are two and four. We are manufactured to composite laminated shells with various curvature radius. Curvature radius of composite shell is 100, 150, 200mm and ${\infty}$(it's meaning flat-plate). In general, kinetic energy after impact-kinetic energy before impact increased linearly in all specimens. Absorbed energy increased linearly as the curvature increased, and absorbed energy of [02/902]S specimen, which is small interlaminar number, was higher than [0/902/0]s specimen.

• Structural Engineering and Mechanics
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• 제48권4호
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• pp.501-518
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• 2013

Apart from thinning of cortical layers, the local bone curvature, varying along bone periphery, modulates ultrasound waves as well, which is however often underestimated or overlooked in clinical quantitative ultrasound (QUS). A dedicated three-dimensional finite element modelling technique for cortical bones was established, for quantitatively exploring and calibrating the effect of local curvature of cortical bone on ultrasound. Using a correlation-based mode extraction technique, high-velocity group (HVG) and low-velocity group (LVG) wave modes in a human radius were examined. Experimental verification using acrylic cylinders and in vitro testing using a porcine femur were accomplished. Results coherently unravelled the cortical curvature exerts evident influence on bone-guided ultrasound when RoC/${\lambda}$ <1 for HVG mode and RoC/${\lambda}$ <2 for LVG mode (RoC/${\lambda}$: the ratio of local bone curvature radius to wavelength); the sensitivity of LVG mode to bone curvature is higher than HVG mode. It has also been demonstrated the local group velocity of an HVG or LVG mode at a particular skeletal site is equivalent to the velocity when propagating in a uniform cylinder having an outer radius identical to the radius of curvature at that site. This study provides a rule of thumb to compensate for the effect of bone curvature in QUS.

• 한국생산제조학회지
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• 제18권6호
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• pp.681-689
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• 2009

Disk grinding was often applied to deburring process in order to enhance the final product quality. Inherent chamfering capability of the flexible disk grinding process in the early stage was analyzed with respect to various process parameters including workpiece length, wheel speed, depth of cut and feed. Initial chamfered edge defined as arc zone was characterized with local radius of curvature. Averaged radius and arc zone ratio was well evaluated using neural network system. Additional neural network analysis adding workpiece length showed enhance performance in predicting arc zone ratio and curvature radius with reduced error rate. A process condition design parameter was estimated using remaining input and output parameters with the prediction error rate lower than 2.0% depending on the relevant input parameter combination and neural network structure composition.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.91-101
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• 1998

The effect of secondary flow on both methane/air and propane/air premixed flame was investigated experimentally. By changing the radius of curvature, various flame behavior was observed. In the V-bend nozzles, flame surface is deformed from axisymmetry. As the exit velocity increased, flame lifted off partially. When the radius of curvature of the V-bend increased, the region where premixed flame is entirely on the rim increased. Since the axial velocity field is changed due to the secondary flow effect, comparison of V-bend and straight tube with the same diameter shows larger V-bend nozzle exit velocity for both flash back and flame blowout. The flame characteristics are mapped with a equivalence ratio, a velocity, and a nozzle radius of curvature. To identify physical reasoning on the flame surface deformation, numerical calculations are conducted. OH radical distributions in flames are visualized by PLIF technique.

• 한국안광학회지
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• 제17권2호
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• pp.127-133
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• 2012

목적: 각막곡률계를 이용하여 비접촉식으로 안경렌즈의 곡률반경을 측정할 수 있는 방법에 관하여 조사하고자 한다. 방법: 각막곡률계의 전면부에 -9.50 D ~ -11.50 D의 시력검사용 시험렌즈를 부착한 후 안경렌즈를 각막곡률계의 전면부에서 약 25 cm 가량 떨어진 곳에 설치한다. 안경렌즈의 위치를 조금씩 변경시키며 선명한 마이어상을 관찰하여 곡률반경을 측정한 후, 구면계를 이용하여 곡률반경의 보정공식을 만든다. 결과: 전면부에 시험렌즈를 부착한 각막곡률계를 이용하여 곡률반경 측정이 성공적으로 수행되었다. 측정한 곡률반경은 구면계 데이터를 이용하여 보정값으로 변환 되었으며, 보정값을 만드는 직선의 방정식 5가지를 얻었다. 임의의 여러 가지 렌즈들을 전면부에 시험렌즈가 부착된 각막곡률계로 측정한 후 직선의 방정식을 이용하여 계산한 결과 3.5% 미만의 오차로 측정이 가능함을 알았다. 결론: 전면부에 시험렌즈를 부착한 각막곡률계를 이용하여 비접촉식으로 안경렌즈의 곡률반경을 측정하는 것이 가능하며, 그 정확도는 렌즈메져보다 오히려 높은 것으로 나타났다.

• 한국정밀공학회지
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• 제13권8호
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• pp.31-39
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• 1996

In this paper, the error and its sources in manufacturing of bourdon tube pressure gage was studied, and the method to reduce such errors was discussed. In more detail, the effects of parallelism of rollers, spring back, uniformity of radius curvature and the ratio of circumferential speeds of rollers were invesrti- gated. As a reselt, we could find out that the aprallelism of roller affected to the displacement error at the free end of gage and that the amount of spring back was closely related with the ratio of circumferential speeds of rollers. The uniformity of curvature radius was determined by the distance between bending rollers and it was comparatively uniform in the range above 30 .deg. C from the both sides of tube. Also, the ratio of circumfer-ential speeds of rollers was finded out as a very important factor giving severe influence on the creep or the hysteresis of bourdon tube.

• 대한기계학회논문집B
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• 제38권10호
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• pp.797-805
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• 2014

본 연구의 목적은 해수 흡입구를 고려한 초공동 수중운동체 캐비테이터의 항력과 양력특성 및 해수 흡입유로의 입구에서 압력손실에 대해 예측하는 것이다. 흡입구 직경과 유로에서의 속도, 흡입구의 곡률반경 및 캐비테이터의 받음각이 미치는 영향에 대해 유동해석을 수행하였다. 연구 결과 직경비가 커지면, 항력계수와 압력손실계수가 감소하며, 속도비가 증가할 때 항력계수와 양력계수는 감소하고 압력손실계수는 증가한다. 해수 흡입구에 곡률을 주면 항력계수와 양력계수에는 영향을 미치지 않지만, 압력손실계수가 크게 감소한다. 캐비테이터의 받음각은 항력계수와 압력손실계수에 미소한 영향만을 주나, 양력계수를 크게 변화시킨다. 초공동 수중운동체 설계 시 본 연구 결과를 반영할 수 있다.