• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.753-760
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• 1999

Experiments were conducted to investigate the effect of the initial turbulent intensity on the flow and heat transfer characteristics for a two-dimensional impinging jet. A square rod was installed at the nozzle exit to increase initial turbulent intensity. A hot wire probe and thermochromic liquid crystal technique were used to measure the turbulent intensity and the surface temperature. All measurements were made over a range of nozzle-to-plate distance from 1 to 10 at Re=20,000. When the rod is not installed, the maximum stagnation point Nusselt number is occurred at H/B=9. A higher initial turbulent intensity enhanced the heat transfer on the surface. A correlation between stagnation point Nusselt number and turbulent intensity are presented.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.103-113
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• 1999

Point contact film thickness in elastohydrodynamic lubrication (EHL) is analyzed by the image processing method for the monochromatic incident light. Interference between the reflected lights both on Cr coating of glass disk and on super finished ball makes circular fringes, which are regarded as film thickness together with numbering of fringe order. In this study, we developed technology to measure the film thickness by analyzing dark and bright intensity waves which results from monochrome green light. Two typical fringe patterns only with intensity values 3re examined for the measurement of point contact EHL film thickness. We expect that this technology will give valuable clue to improve color image processing analysis for high resolution of EHL film thickness with white incident light.

• International Journal of CAD/CAM
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• v.7 no.1
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• pp.103-112
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• 2007

This paper presents a practical approach for surface reconstruction from unoriented point clouds. Instead of estimating local surface orientation, we first generate a set of depth images from the input point clouds, and a coarse mesh is then generated based on them by space carving techniques. The resultant mesh is progressively refined by local mesh refinement and optimization according to surface distance measure. A manifold mesh approximating the input points within an given tolerance is finally obtained. Our approach is easy to implement, but has the ability to outputs high quality meshes in different resolutions. We show that the proposed approach is not sensitive to several types of data disfigurement and is able to reconstruct models robustly from variance input data.

• Water Engineering Research
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• v.3 no.3
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• pp.195-202
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• 2002

The mean is generally used as a point estimator in water-quality data. Unfortunately, the nonnormal and skewed distributions of data hinder the direct application of the mean, which is inappropriate statistics in this case. The use of robust statistics such as L, M, and R-estimators are recommended and become more efficient. The median (L-estimator), the biweight (M-estimator), and the Hodges-Lehmann method (R-estimator) are briefly introduced and applied in this paper. From the actual data analyses, it is known that the median does not guarantee robustness for a small number of data sets, and robust measures of location or the arithmetic mean without outliers are highly recommended if the distribution has tails or outliers. Care must be taken to measure the location because water quality level within a water body can change depending on the selected point estimator.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.12a
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• pp.295-299
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• 2002

This paper presents an image contrast enhancement technique for improving low contrast images. We applied fuzzy logic to develop an image contrast enhancement technique in the viewpoint of considering that the low pictorial information of a low contrast image is due to the vaguness or fuzziness of the multivalued levels of brightness rather than randomness. The fuzzy image contrast enhancement technique consists of three main stages, namely, image fuzzification, modification of membership values, and image defuzzification. In the stage of image fuzzification, we need to select a crossover point. To select the crossover point automatically the K-means algorithm is used. The problem of crossover point selection can be considered as the two-category, object and background, classification problem. The proposed method is applied to an experimental image with 256 gray levels and the result of the proposed method is compared with that of the histogram equalization technique. We used the index of fuzziness as a measure of image quality. The result shows that the proposed method is better than the histogram equalization technique.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2000.11a
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• pp.417-426
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• 2000

This study suggests integrated neural network models for Interest rate forecasting using change-point detection, classifiers, and classification functions based on structural change. The proposed model is composed of three phases with tee-staged learning. The first phase is to detect successive and appropriate structural changes in interest rare dataset. The second phase is to forecast change-point group with classifiers (discriminant analysis, logistic regression, and backpropagation neural networks) and their. combined classification functions. The fecal phase is to forecast the interest rate with backpropagation neural networks. We propose some classification functions to overcome the problems of two-staged learning that cannot measure the performance of the first learning. Subsequently, we compare the structured models with a neural network model alone and, in addition, determine which of classifiers and classification functions can perform better. This article then examines the predictability of the proposed classification functions for interest rate forecasting using structural change.

• Journal of the Korea Society for Simulation
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• v.7 no.1
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• pp.27-37
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• 1998

Simulation output is generally stochastic and autocorrelated, and includes the initial condition bias. To exclude the bias, the determination of truncation point has been one of important issues for the steady-state simulation output analysis. In this paper, two methods are presented for detection of truncation point in order to estimate efficiently the steady-state measure of simulation output. They are based on the Euclidean distance equation, and the backpropagation algorithm in Neural Networks. The experimental results obtained by M/M/1 and M/M/2 show that the proposed methods are very promising with respect to coverage and relative bias. The methods could be used for the on-line analysis of simulation outputs.

• Computers and Concrete
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• v.23 no.3
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• pp.171-188
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• 2019

This study proposed a new and efficient 2D damage-plasticity model within the framework of Isogeometric analysis (IGA) for the geometrically nonlinear damage analysis of concrete. Since concrete exhibits complicated material properties, two internal variables are introduced to measure the hardening/softening behavior of concrete in tension and compression, and an implicit gradient-enhanced formulation is adopted to restore the well-posedness of the boundary value problem. The numerical results calculated by the model is compared with the experimental data of three benchmark problems of plain concrete (three-point and four-point bending single-notched beams and four-point bending double-notched beam) to illustrate the geometrical flexibility, accuracy, and robustness of the proposed approach. In addition, the influence of the characteristic length on the numerical results of each problem is investigated.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.49-65
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• 2004

The purpose of this study is development of posture evaluation and Range of Motion(ROM) system by using digital vision analysis method. The results of this study are as follows. First, Scoliosis evaluation through this research measurement system represent 3mm error in 7 cervical point and deepest lumbar point, 0.7mm error in other point. This mean this research measurement system have a reliability for scoliosis evaluation. Second, for spine line evaluation on high fat subject, we need reconstrection spine line after measurement for fat thickness in 7 cervical point and deepest lumbar point. Third, In pedioscope error test, it present 0.01848cm in X axis and 0.01757cm in Y axis. This results mean pedioscope have a reliability foot evaluation. Forth, Posture evaluation and Range of Motion measurement system by using digital vision analysis method can fast measure in range of motion and foot evaluation and posture. therefore we can expect this system application in young people posture clinic center and hospital and so on.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.2
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• pp.47-55
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• 1987

Recently, in precision working, precision is in submicron. Therefore, when we measure various finished goods in superfine measurement, because it is relatively difficult to disregard effect of surroundings, these effect of surroundings must be compensated or canceled. In this study, for roundness measurement, three point method is researched which is able to cancel the effect of rotation accuracy of axis and eccenricity of workpiece. It is difference between this three point method and tradi- tional three point method whose measuring apparatus have three movable pickups posit- ioned with angle and between the pickups. As a results, when rotation accuracy of axis is varied from $0.02\mu\textrm{m}$ to $0.05\mu\textrm{m}$ the width of variation of measured roundness is $0.04\mu\textrm{m}$. And, when eccentricity of workpiece is varied from 0 to $4\mu\textrm{m}$, the width of variation of measured roundness is $0.005\mu\textrm{m}$. These error width are disregardable because they are in 10% of measured roundness. Therefore, by this three point method, the effect of rotation accuracy of axis and the effect of eccentricity of workpiece are canceled. And we are able to select the angle between the pickups ($\phi$ and $\tau$) by means of relation between $F_{k}$ and K.