• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.137-145
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• 1997

A two-dimensional program for the analysis of bimaterial inclusion has been developed using the bound- ary element method. In order to study the effects of circular inclusion on the stress field of the crack tip, numerical analysis was performed for the straight crack of finite length around the symmetric circular inclusion whose modulus of elasticity was different from that of the matrix material. In the case of inclusion whose stiffness was smaller than that of the matrix material, the stress intensity factor was found to increase as the crack enamated. The stress intensity factor was uninfluenced from the radial change in inclusion and remained constant for the stiffness equivalent to the matrix materials, where as it decreased for the inclusion with larger stiffness. For the vareation in the distance of the inclusion, a small increase in the stress intensity factor was observed for the case with small or equal stiffness compared with the matrix materials. The inclusion with larger stiffness showed a gradual decrease in the strss intensity factor as the crack emanated.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.4
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• pp.1-10
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• 2006

A computational study was carried out in order to investigate the ground effect of a circular cylinder in the presence of a moving wall at a Reynolds number of 2.0${\times}$104. The viscous-incompressible Navier-Stokes equations and Spalart-Allmaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and the speed of motion was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The numerical results show that there are the differences among the each of the stages in evidence of the vorticity contours and the polar diagrams of $C_l$ vs. $C_d$. The 4 stages of the gap ratio are defined according to the flow features, whose stages are divided into small, intermediate, large and convergence gap ratios, respectively.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.27-34
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• 2018

In this paper, we propose a new method to read the hand of analog gauges to prepare for the smart factory. In addition, we suggest a new and improved method that can apply, in general, diverse analog gauges even if their scale types and ranges are various. Many companies are making great efforts to build smart factories that increase energy efficiency and automation. Managers use a variety of equipment and tools to manage the production process at the factory. In this kind of factory, analog gauges have been often used with many equipment and tools. Analog gauges are mostly circular in shape, and most papers use circular hough transform to find the center and radius of a circle. However, when the object to be found is not of the correct circle type, it takes a long time to recognize the circle using the circular hough transform, and the center and radius of the circle can not be calculated accurately. The proposed method was tested on various circular analog gauges. As a result, we confirmed that our method is outstanding.

• Environmental Engineering Research
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• v.19 no.2
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• pp.151-155
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• 2014

This study compares the effects of flow on oil and suspended solids removal efficiencies in circular enhanced gravity plate separator equipped with coalescence medium. Coalescence medium acts to capture rising oil droplets and settling solid particles and assist in the coalescence of oil and coagulation of solid. The circular separator uses an upflow center-feed perforated-pipe distributor as the inlet. The co-current flow is achieved using 4 increasing sizes of frustum, whereas cross flow uses inclined coalescence plates running along the radius of the separator. The different arrangement gave the cross flow separator a higher coalescence plan area per operational volume, minimal and constant travelling distance for the oil droplets and particles, lower retention time, and higher operational flowrate. The cross flow separator exhibited 6.04% and 13.16% higher oil and total suspended solids removal efficiencies as compared to co-current flow.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.2
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• pp.103-111
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• 2014

The wave power, extracted from a circular array of small power buoys, is investigated under the potential theory. It is assumed that the buoy's radius, the draft, and the separation distance are much smaller than the water depth, the wave length, and the radius of a circular deployment area. The boundary value problem involving the macro-scale boundary condition on the mean surface covered by buoys is solved using the eigenfunction expansion method. The capture width, which is defined as the ratio of the extracted power to the wave power per unit length of the incident wave crest, is assessed for various combinations of packing ratio, radius of a circular array, and PTO damping coefficient. It is found that the circular array deployment is more effective in the viewpoint of efficiency than the single large buoy of the same total displaced volume.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.3
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• pp.269-281
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• 2001

This thesis deals with a novel font-dependent Hangul recognition algorithm invariant to position translation, scaling, and rotation using circular pattern vectors. The proposed algorithm removes noise from input letters using binary morphology and generates the circular pattern vectors. The generated circular pattern vectors represent spatial distributions on several concentric circles from the center of gravity in a given letter. Then the algorithm selects the letter minimizing the distance between the reference vectors and the generated circular pattern vectors. In order to estimate performances of the proposed algorithm, the completed Batang Hangul 2,350 letters were used as test images with scaling and rotational transformations. Experimental results show that the proposed algorithm are better than conventional algorithm using the ring projection in the recognition rates of Hangul letters with scaling and rotational transformation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.103-112
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• 1990

For this study, the full-scale model of Chumsungdae was selected as an object, and various photographs were obtained with metric camera for forming circular strips and blocks. The accuracies were analyzed according to the change of object distance and different configuration of control points by bundle adjustment, and the characteristics of results obtained through combined strips were drawn. This thesis suggests optimal analysis technique of cylindrical structures requiring all-side analysis such as cultural properties. As a result, it is possible to use control points positioned on only any one-side for all-side analysis, and control configuration is more important rather than the number of control points for increasing accuracy. In addition, it is desirable to locate control points in X, Y and Z plane uniformly, and it was shown as object distance was shorten and the number of combined strips increases, the accuracy of results was improved considerably.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2991-3006
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• 1996

An experimental study of jet flow and heat transfer has been carried out for the jet impingement cooling on a semi-circular concave surface. For the jet impingement on the concave surface, three different regions-free jet region, stagnation region, and wall jet flow region-exist, and the distributions of mean velocity and fluctuating velocity for each region have been measured by Laser Doppler Velocimeter. Of particular interests are the effects of jet Reynolds number, the distance between the nozzle exit and cooling surface apex, and the distance from the stagnation point in the circumferential direction. The resulting characteristics of heat transfer at the stagnation point and the variation of heat transfer along the circumferential direction including the existence of secondary peak have been explained in conjunction with measured impinge jet flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.441-449
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• 2002

Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

• Journal of Navigation and Port Research
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• v.47 no.6
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• pp.401-409
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• 2023

This study compared and analyzed the performance of a distributed area search algorithm and a distributed probability search algorithm based on information exchange between ships. The distributed algorithm is a method that can search for an optimal avoidance route based on information exchange between ships. In the distributed area search algorithm, only a ship with the maximum cost reduction among neighboring ships has priority, so the next expected location can be changed. The distributed stochastic search algorithm allows a non-optimal value to be searched with a certain probability so that a new value can be searched. A circular-based ship collision avoidance model was used for the ship-to-ship collision avoidance experiment. The experimental method simulated the distributed area search algorithm and the distributed stochastic search algorithm while increasing the number of ships from 2 to 50 that were the same distance from the center of the circle. The calculation time required for each algorithm, sailing distance, and number of message exchanges were compared and analyzed. As a result of the experiment, the DSSA(Distributed Stochastic Search Algorithm) recorded a 25%calculation time, 88% navigation distance, and 84% of number of message exchange rate compared to DLSA.