• Journal of KIISE:Computer Systems and Theory
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• v.33 no.1_2
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• pp.128-136
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• 2006

The stippling techniques, which represent objects with numerous points using pen and ink. The previous stippling techniques for Non-Photorsealistc Rendering(NPR) use single-colored points to represent the tone of gray image ur the material of surface. This paper presents a new stippling technique with various colored points based on the analysis of color information. By using the color information of the input image on HSV model, we define the color weight function that allows to determine automatically the number and size of points. The color jittering based on Munsell's color model can generate stippling drawings using various colored points to represent the image. Our color stippling method is expected to be used in many areas such as animation, digital art, video processing and CG tool.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.3
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• pp.173-180
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• 2007

Oscillating wave amplitude in a bottom-mounted OWC chamber designed for wave energy converter is investigated by applying characteristic wave conditions in Korean coastal water. The effects of shape parameters of OWC chamber in a view of wave energy absorbing capability are analyzed. Both experimental and numerical approaches are adopted and their results are compared to optimize the shape parameters which can result in a maximum power production under given wave distribution. The experiment was carried out in a wave flume under 2-D assumption of OWC chamber. The numerical scheme employed a hybrid Green integral equation which adopts the Rankine Green function inside chamber to take account of fluctuating air pressure, while it uses the Kelvin Green function in outer domain. Air duct diameter, chamber width, and submerged depths of front skirt and back wall of chamber changes the magnitude and peak frequency of wave absorption significantly.

• Journal of the Korea Society of Computer and Information
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• v.13 no.3
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• pp.179-187
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• 2008

In this paper, we apply a set of algorithms to classily normal and cancer nucleus from uterine cervical pap-smear images. First, we use lightening compensation algorithm to restore color images that have defamation through the process of obtaining $1{\times}400$ microscope magnification. Then, we remove the background from images with the histogram distributions of RGB regions. We extract nucleus areas from candidates by applying histogram brightness, Kapur method, and our own 8-direction contour tracing algorithm. Various binarization, cumulative entropy, masking algorithms are used in that process. Then, we are able to recognize normal and cancer nucleus from those areas by using three morphological features - directional information, the size of nucleus, and area ratio - with fuzzy membership functions and deciding rules we devised. The experimental result shows our method has low false recognition rate.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.501-510
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• 2000

Recently, advanced signal analysis which is called "time-frequency analysis" has been used widely in nondestructive evaluation applications. Wavelet transform(WT) and Wigner Distribution are the most advanced techniques for processing signals with time-varying spectra. Wavelet analysis method is an attractive technique for evaluation of material characterization nondestructively. Wavelet transform is applied to the time-frequency analysis of ultrasonic echo waveform obtained by an ultrasonic pulse-echo technique. In this study, the feasibility of noise suppression of ultrasonic flaw signal and frequency-dependent ultrasonic group velocity and attenuation coefficient using wavelet analysis of ultrasonic echo waveform have been verified experimentally. The Gabor function is adopted the analyzing wavelet. The wavelet analysis shows that the variations of ultrasonic group velocity and attenuation coefficient due to the change of material characterization can be evaluated at each frequency. Furthermore, to assure the enhancement of detectability and naw sizing performance, both computer simulated results and experimental measurements using wavelet signal processing are used to demonstrate the effectiveness of the noise suppression of ultrasonic flaw signal obtained from austenitic stainless steel weld including EDM notch.

• Journal of Convergence for Information Technology
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• v.11 no.9
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• pp.130-137
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• 2021

The characteristics of forced vibration by an external excitation force having a frequency were analyzed according to the amplitude and frequency of the excitation force. To obtain displacement, velocity, and acceleration, numerical analysis was performed to obtain the frequency response, and in particular, each FRF(Frequency Response Function) was analyzed to reveal the location of the system natural frequency and excitation frequency in the frequency domain. In the vibration model caused by external excitation, the natural frequency and distribution of the surrounding excitation mode in displacement, velocity and acceleration FRF. The FRF was also shown in the power spectrum and FRF of real and imaginary parts. The external excitation force was approximated with the excitation force of a sine wave by giving the amplitude and frequency, the mode generated by this excitation force could be distinguished. After numerical analysis by changing the equivalent mass, damping and stiffness, the forced vibration response characteristics by external excitation force were systematically analyzed.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.23-33
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• 1987

Plasma arc cutting is a fusion cutting process in which a gas constricted arc is employed to produce high temperature, high velocity jet at the workpiece. Even though the plasma arc cutting has been wid¬ely used in the industry, very little work has been done on the analysis of the process. In this paper, the kerf width was numerically analyzed by soving the temperature distribution in base metal under consideration of the latent heat effect. In modelling the heat flow problem, the heat intensity of the plasma arc was assumed to have a Gaussion distribution in the transverse direction and expone¬ntially decreasing in the thickness direction. The thermal efficiency and the heat input ratio of the top surface were experimentally deterimned for various thickness and cutting conditions, and used in numerical calculation of the kerf width. The experimental results were in eonsiderabely good agreement with the theoretically predicted kerf width.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1129-1133
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• 2004

반도체공정 최적화에 소요되는 시간과 경비를 줄이기 위해 신경망 모델이 개발되고 있다. 주로 역전파 신경망을 이용하여 모델이 개발되고 있으며, 본 연구에서는 Radial Basis Function Network (RBFN)을 이용하여 플라즈마 식각공정 모델을 개발한다. 실험데이터는 유도결합형 플라즈마를 이용한 Silicon Carbide 박막의 식각공정으로부터 수집되었다. 모델개발을 위해 $2^4$ 전인자 (full factorial) 실험계획법이 적용되었으며, 모델에 이용된 식각응답은 식각률과 atomic force microscopy로 측정한 식각표면 거칠기이다. 모델검증을 위해 추가적으로 16번의 실험을 수행하였다. RBFN의 예측성능은 세 학습인자, 즉 뉴런수, width, 초기 웨이트 분포 (initial weight distribution-IWD) 크기에 의해 결정된다. 본 연구에서는 각 학습인자의 영향을 최적화하였으며, IWD의 불규칙성을 고려하여 주어진 학습인자에 대해서 100개의 모델을 발생하고, 이중 최소의 IWD를 갖는 모델을 선택하였다. 최적화한 식각률과 표면거칠기 모델의 RMSE는 각기 26 nm/min과 0.103 nm이었다. 통계적인 회귀모델과 비교하여, 식각률과 표면거칠기 모델은 각기 52%와 24%의 향상된 예측정확도를 보였다. 이로써 RBFN이 플라즈마 공정을 효과적으로 모델링 할 수 있음을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.277-284
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• 1993

Interfacial surface crack perpendicular to the surface, which is imbedded into bonded quarter planes under single anti-plane shear load is analyzed. The problem is formulated using Mellin transform, form which single Wiener-Hopf equation is derived. By solving the equation stress intensity factor is obtained in closed form. This solution can be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.19-24
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• 1998

In this paper, a new closed form expression for the average symbol error rate(SER) of generalized selection combining(SC), whereby the two(three) signals with the two(three) largest amplitudes are combined from the original diversity branches in the channel, for MPSK signals in a frequency-nonselective slowly m-distributed Nakagami fading channel is derived. In order to analyze the error performance for a generalized SC, the Order-Statistics is applied. To derive the SER of MPSK signals with SC, the new expression of pdf is introduced and many other mathematical methods are used. Comparing the derived SER with that of MRC, we find adequate diversity branch number from total Lth-order diversity branches.

• Journal of the Korea Computer Graphics Society
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• v.3 no.1
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• pp.37-47
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• 1997

This paper presents the algorithms for generating ambient traffic in driving simulation. Each ambient car is modeled as an autonomous agent that obeys the traffic rules by sensing the traffic lights, road signs, lanes, and other cars around. The algorithm is localized to the area where the car driven by the participant is currently located. Therefore the complexity of the algorithm does not depend on the size of the road network, allowing a huge environment to be simulated with no extra overhead. To avoid monotony, we produce artificial fluctuations in the behavior by employing various forms of probability distribution functions. The resulting behavior of the ambient cars is quite realistic. Experiments indicate that it is hard to tell whether an ambient car is computer-controlled or human-controlled.