• 한국분무공학회지
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• 제20권3호
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• pp.175-180
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• 2015

A series of sprinkler discharging tests was conducted to measure the droplet size and its distribution of residential fire sprinkler heads. Droplet sizes in sprinkler spray were measured using a laser diffraction method for the flush, circular and pendent type sprinkler head. In this study, the $D_{v,50}$ of the flush type sprinkler heads were ranged between $530{\sim}1040{\mu}m$ and those of circular and pendent type were $988{\mu}m$ and $916{\mu}m$, respectively. The measured cumulative volume distributions were followed by a combination of the log-normal and Rosin-Rammler distribution which is widely used in the computational fire analysis and the parameters of distribution function were obtained from the best fit line through the measured data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.540-545
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• 2001

An experimental study was conducted to compare the heat transfer characteristics of an impinging slot jet and three kinds of impinging circular jets. Thermochromic liquid crystal with an image processing system was employed to measure the temperature of impinging wall where constant heat flux condition was applied. The distribution of convective heat transfer coefficients were then evaluated for eight nozzle-to-surface distance settings for each jet cases. The cooling effect was linearly proportional to the number of nozzles for circular jet cases at the same nozzle exit speed. However, the heat transfer under constant volume flow rate was the most at single circular jet. It was concluded that the overall convective heat transfer was better at the circular jets than the slot jet.

• 반도체디스플레이기술학회지
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• 제6권4호
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• pp.39-42
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• 2007

Temperature distribution of the circular heat source was studied by analyzing the heat transfer of the environment of the circular source for OLED. Circular nozzle source was used to fabricate thin organic layer as the organic material in it was heated, vaporized and deposited to the large size panel. A modified heater structure of circular source has been suggested. The results of numerical analysis shows that the modified heater structure can use 15% more powder in a batch than the original heater structure does. Moreover, the modified heater structure can improve the uniformity of organic vapor deposition by controlling the temperature.

• 한국음향학회지
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• 제30권6호
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• pp.308-314
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• 2011

본 논문에서는 주기성을 갖는 순환 확률분포를 이용하여 $0^{\circ}{\sim}360^{\circ}$ 범위의 다중 음원의 방향을 추정하는 기법을 제안한다. 음원의 방향 정보를 담고 있는 마이크로폰간의 위상차는 확률분포의 혼합물로 간주될 수 있으며, 음원 방향은 이 확률분포의 혼합물에 적용된 로그-우도함수 (log-likelihood function)를 최대화함으로써 추정된다. 주기성을 갖는 데이터의 분석에 von Mises 확률분포가 널리 활용된다는 사실은 잘 알려져 있지만, 본 논문에서는 기존의 Gaussian이나 Laplacian 확률분포에 $2{\pi}$ 모듈로 (modulo) 연산을 적용함으로써 $0^{\circ}{\sim}360^{\circ}$ 범위의 주기성을 갖는 순환 확률분포를 정의하고 이를 방향 추정에 활용한다. 순환 확률분포의 혼합물에 대한 로그-우도함수를 최대가 되게 하는 음원의 방향은 EM (Expectation-Maximization) 알고리즘을 이용하여 추정된다. 다양한 반향 환경에서의 실험 결과 Laplacian 확률분포가 von Mises나 Gaussian 확률분포보다 우수한 성능을 제공함을 확인할 수 있다.

• 한국정밀공학회지
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• 제16권8호
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• pp.28-37
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• 1999

This investigation is the result of the structural analysis by finite element method and test for considering stress distribution and stress concentration to be generated according to the change of attached shape and method of the bracket to pipe in welding structure. Generally, members that consist structures are subjected to various forces and are jointed each other with a number of bracket. In this case, circular pipe was adapted in order to weld these members easily and to study the optimal design which is used a beam with shape section as main components of the structure, According to attached shape and method, distributed stress on circular pipe is appeared so differently. This may result deeply effects with respect to thickness, material properties. So a study on attaching shape and method of bracket to circular pipe is needed. In this paper, to obtain the maximum equivalent stress or stress concentration was used experimental and F.E.M. analysis. First five parameter was defined with respect to attached a shape and method to circular pipe i.e. the variation of the attached area, the variation of the attached shape, the variation of the attached length, the variation of both directin angles, the variation of the upper angle. Afterward the experimental analysis was practiced as the variation of the both direction angel and the finite element analysis was practiced as each parameters. We can discover stress distribution and stress concentration according to the change of form of bracket. And the result can be referenced for a design of similar structure.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.930-937
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• 2011

The characteristics of mean velocity and turbulence have been analyzed in the circular open channel flow using PIV measurement data for a wide range of water depth. The measured data are fitted to a velocity distribution function over the whole depth of the open channel. Reynolds shear stress and mean velocity in wall unit are compared with the analytic models for fully-developed turbulent boundary layer. Both the mean velocity and Reynolds shear stress have different distributions from the two-dimensional boundary layer flow when the water depth increases over 50% since the influence of the side wall penetrates more deeply into the free surface. The cross-stream Reynolds normal stress also has considerably different distribution in view of its peak value and decreasing rate in the outer region whether the water depth is higher than 50% or not.

• 대한기계학회논문집
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• 제17권5호
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• pp.1218-1226
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• 1993

본 연구에서는 기존의 점진균열법을 개량하여 원판의 잔류응력 분포를 측정하기 위한 새로운 방법을 제시하였으며 이것의 타당성을 입증하기 위한 유한요소 해석(finite element analysis)과 실험을 수행하였다.

• 한국해양공학회지
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• 제25권4호
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• pp.23-27
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• 2011

This experimental study was performed to find rpms of the impeller and the surface flow accelerator to make a uniform velocity vertical distribution in the circular water channel. PIV technique was employed to measure the water velocity profiles into the water depth from the free surface. The number of instantaneous velocity profiles was decomposed into mean and turbulence velocity components, and the distribution of velocity fluctuation and turbulence intensity were computed for each experimental condition. From these results, the velocity uniformity was quantitatively determined to present the flow quality in the measuring section of the circular water channel. It has been shown that the proper operation of the surface flow accelerator would make the uniform velocity profiles and reduce the velocity fluctuation near the free surface.

• 천문학회지
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• 제26권2호
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• pp.103-114
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• 1993

We have analyzed a set of high resolution photographic line profiles of a Zeeman sensitive Fe I $\lambda$ 6302.5 line taken with the Universal Birefringent Filter over a single round sunspot (SPO 5007) at the Sacramento Peak Solar Observatory. The observed spectra recorded on films are traced by PDS and the traced densities are converted to relative intensity by means of IRAF. The Stokes I and V profiles are then constructed by adding together and subtracting from each other the left and right handed circular polarizations, respectively. The reduced I and V profiles are analyzed by means of the coarse analysis(Auer et al.(1977), Skumanich and Lites(1987)) with the use of inversion technique. It is found that the umbral field strength is about 3000 gauss and the field distribution follows closely the emperical model proposed by Wittmann(1974).

• Structural Engineering and Mechanics
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• 제70권1호
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• pp.97-112
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• 2019

Using the classical, first order and third order shear deformation plates theories the motion equations of an undrained porous FG circular plate which is located on visco-Pasternak elastic foundation have been derived and used for free vibration analysis thereof. Strains are related to displacements by Sanders relationship. Fluid has saturated the pores whose distribution varies through the thickness according to three physically probable given functions. The equations are discretized and numerically solved by the generalized differential quadrature method. The effect of porosity, pores distribution, fluid compressibility, viscoelastic foundation and aspect ratio of the plate on its vibration has been considered.