• 대한기계학회논문집B
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• 제23권9호
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• pp.1172-1177
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• 1999

Comparisons of measured turbulence properties in the unburned gas region of turbulent premixed flame stabilized by pilot flame, in cases of combusting and non-combusting flow conditions, are presented. Methane-air premixed jet at fuel equivalence ratio of 0.6 and 1.0 and Reynolds number of 7,000 was diagnosed using two-color laser velocimeter to obtain turbulence statistics. Same set of measurements was repeated at 21 locations within the unburned gas region of both combusting and non-combusting conditions. Velocity data were analyzed to evaluate the spatial distribution of turbulence properties including Reynolds stress, probability densities, joint probability densities and auto correlations. Contrary to assumptions of current theoretical models, significant influence of flame was observed in every property that was studied in the present investigation. The effective viscosity increased ten-fold when flame was on from cold flow values. The effect of mixing on joint probability as well as in turbulence intensity was suppressed by the flame. The measurements suggest that common assumptions of premixed flame model may result in sizable error in prediction of flame length and temperature distribution in near-field.

• 대한의용생체공학회:의공학회지
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• 제36권5호
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• pp.211-220
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• 2015

Recently, model-based iterative reconstruction (MBIR) has played an important role in transmission tomography by significantly improving the quality of reconstructed images for low-dose scans. MBIR is based on the penalized-likelihood (PL) approach, where the penalty term (also known as the regularizer) stabilizes the unstable likelihood term, thereby suppressing the noise. In this work we further improve MBIR by using a more expressive regularizer which can restore the underlying image more accurately. Here we used a spline regularizer derived from a linear combination of the two-dimensional splines with first- and second-order spatial derivatives and applied it to a non-quadratic convex penalty function. To derive a PL algorithm with the spline regularizer, we used a separable paraboloidal surrogates algorithm for convex optimization. The experimental results demonstrate that our regularization method improves reconstruction accuracy in terms of both regional percentage error and contrast recovery coefficient by restoring smooth edges as well as sharp edges more accurately.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.684-687
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• 2006

Airborne imagery must be precisely orthorectified to be used as geographical information data. GPS/INS (Global Positioning System/Inertial Navigation System) and LIDAR (LIght Detection And Ranging) data were employed to automatically orthorectify airborne images. In this study, 154 frame airborne images and LIDAR vector data were acquired. LIDAR vector data were converted to raster image for employing as reference data. To derive images with constant brightness, flat field correction was applied to the whole images. The airborne images were geometrically corrected by calculating internal orientation and external orientation using GPS/INS data and then orthorectified using LIDAR digital elevation model image. The precision of orthorectified images was validated using 50 ground control points collected in arbitrary selected five images and LIDAR intensity image. In validation results, RMSE (Root Mean Square Error) was 0.365 smaller then two times of pixel spatial resolution at the surface. It is possible that the derived mosaicked airborne image by this automatic orthorectification method is employed as geographical information data.

• 대한토목학회논문집
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• 제8권3호
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• pp.85-90
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• 1988

균질토 사면에서 파괴에 대한 확률론적모델이 제시되었다. 사면의 안전은 관례적인 안전을 보다는 파괴확률로써 측정된다. 사면파괴의 Safety Margin은 정규분포라 가정하였다. 어떤 균질한 흙층에 있어서 흙의 특성에 영향을 주는 불확실성의 원인은 본래의 공간적인 가변성, 불충분한 시료에서 오는 판단오차 그리고 실험오차등이 었다. 파괴면을 따라 존재하는 전단강도의 불확실성은 1차원 Random Field Madels로 표현되었다. 파괴aus의 양상은 대수나선 곡선을 따른다고 가정하였다. 파괴면과 그것을 따라 작용하는 힘의 통계적 특성을 유도하여 사면의 파괴확률을 계산하였다. 마지막으로 개발된 절차가 사면의 신뢰성 해석에 대한 하나의 예제 연구에 적용되었다.

• 자원환경지질
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• 제25권1호
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• pp.73-77
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• 1992

본 논문에서는 2차원 전기비저항 모델링에서 후리에역변환을 계산하는 수치구적법을 비교하였다. 지수함수 및 큐빅스프라인 보간을 사용한 구적법을 균질대지 모델에 대하여 검토하였다. 이들 기술적용시, ${\lambda}_{min}$을 최소의 샘플링파수라고 할 때 0에서 ${\lambda}_{min}$까지 간격에 대한 적분은 후리에변환된 포텐샬을 대수 함수로 근사함으로써 계산하였다. 이러한 방법은 ${\lambda}=0$에서의 대수적인 불연속성에 기인한 후리에역변환의 오차를 크게 줄일 수 있다. 수치계산 결과, 샘플링간격이 적당하다면 큐빅스프라인 보간법이 지수함수 보간법보다 더 정확함을 알았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.4170-4188
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• 2014

In this study, we present a denoising algorithm for high-frame-rate videos in an ultra-low illumination environment on the basis of Kalman filtering model and a new motion segmentation scheme. The Kalman filter removes temporal noise from signals by propagating error covariance statistics. Regarded as the process noise for imaging, motion is important in Kalman filtering. We propose a new motion estimation scheme that is suitable for serious noise. This scheme employs the small motion vector characteristic of high-frame-rate videos. Small changing patches are intentionally neglected because distinguishing details from large-scale noise is difficult and unimportant. Finally, a spatial bilateral filter is used to improve denoising capability in the motion area. Experiments are performed on videos with both synthetic and real noises. Results show that the proposed algorithm outperforms other state-of-the-art methods in both peak signal-to-noise ratio objective evaluation and visual quality.

• 한국통신학회논문지
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• 제16권6호
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• pp.545-555
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• 1991

본 논문에서는 단층 퍼센트론 모델의 학습기능과 신경회로망 형성메모리의 오류정정 능력이 서로 보완적으로 결합된 새로운 적응 패턴인식 시스템의 광학적구현을 실현하였다. 여기서, 단층 퍼센트론 모델은 2차원 LCTV 공간 광변조기를 이용하여 편광인코딩방법과 비전형 양자화 방법으로 구현하였으며, Hopfield 연장메모리는 2차원 모델로 황장하고multifocus holoens를 이용하여 광학적으로 구현하였다. 아리비아 숫자 짝.홀수 판별에 고나한 광학적 실험 결과, 오류 및 부분 입력에 대한 정확한 패턴 분류가 됨을 확인함으로서, 본 논문에서 제시한 새로운 적응 광 패턴인식 시스템이 실제로 영상처리, 패턴인식 등의 분야에서 그 응용 가능성을 제시하였다.

• 한국기계가공학회지
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• 제16권5호
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• pp.78-84
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• 2017

Compared to other types of power, hydraulic energy is the most commonly used for heavy vehicles and ships because it has fewer location and space constraints, and its controllability can be maintained even under adverse conditions. Operators have controlled a main control valve of ship winches by pushing or pulling the lever, which is directly connected to the spool. However, because of the spatial arrangement, the importance of remote control valves has emerged. In this paper, experiments of the hysteresis characteristics were performed by analyzing the remote-control valve using a valve tester and RA2300. The validity was verified by comparing with the analytical model using SimulationX as the hydraulic analysis program. This study examined the effects of the spool's notch (Non, End-mill, and Spherical) and the effects of stiffness and pre-load of the spool spring on Spool stroke, open area, and hysteresis characteristics. It is considered possible to reduce the cost and the, trial and error process in designing remote-control valves in the future.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1425-1437
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• 2018

In this paper, a methodology was proposed to reduce the electrical level and spatial size of the smart grid with distributed generations (DGs) to a scale in which the electrical phenomena and control strategies for disturbances on the smart grid could be safely and freely experimented and observed. Based on the design methodology, a micro smart grid simulator with a substation transformer capacity of 190VA, voltage level of 19V, maximum breaking current of 20A and size of $2{\times}2m^2$ was designed by reducing the substation transformer capacity of 45MVA, voltage level of 23kV and area of $2{\times}2km^2$ of the smart grid to over one thousandth, and also reducing the maximum breaking current of 12kA of the smart grid to 1/600. It was verified that the proposed design methodology and designed micro smart grid simulator were very effective by identifying how all of the fault currents are limited to within the maximum breaking current of 20A, and by confirming that the maximum error between the fault currents obtained from the fault analysis method and the simulation method is within 1.8% through the EMTP-RV simulation results to the micro smart grid simulator model.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.576-580
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• 2005

New real-time confocal microscopy using spectral encoding technique and slit confocal aperture is proposed and designed. Spectral encoding technique, which encodes one-dimensional spatial information of a specimen in wavelength, and slit aperture make it possible to obtain two-dimensional lateral image of the specimen simultaneously at standard video rates without expensive scanning units such as polygon mirrors and galvano mirrors. The working principle and the configuration of the system are explained. The variation in axial responses for the simplified model of the system with normalized slit width is numerically analyzed based on the wave optics theory. Slit width that directly affects the depth discrimination of the system is determined by a compromise between axial resolution and signal intensity from the simulation result. On the assumption of the lateral sampling resolution of 50 nm, design variables and governing equations of the system are derived. The system is designed to have the mapping error less than the half pixel size, to be diffraction-limited and to have the maximum illumination efficiency. The designed system has the FOV of $12.8um{\times}9.6um$, the theoretical axial FWHM of 1.1 um and the lateral magnification of-367.8.