• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.182-189
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• 1993

To improve the resolution of complex flow field features, grid adaptation scheme of Anderson has been revised, which was based on the Poisson grid generator of Thompson. Anderson's original scheme adapts the grid to solution automatically, but if flow field is more or less complex, then the adaptivity is weak. So the technique of using threshold which is used in unstructured grid system is adopted. The regions of large variation in the solution are marked by marking function which has the property of total variation of the solution, and these regions have same values of weight but other regions are neglected. This updated method captures shocks clearly and sharpy. Four examples are demonstrated, (1) Hypersonic flow past a blunt body, (2) High speed inlet analysis, (3) Supersonic flow of M=1.4 over a 4% biconvex airfoil in a channel, (4) Hypersonic shock-on-shock interaction at M=8.03.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1305-1315
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• 2000

It is known that a digital image enlargement technique can increase the size of he image but the practical enhancement of resolution is trifle because the frequency bandwidth of the original image is basically limited. To solve this problem, this paper proposes the digital image enlargement technique which interpolates the interpolation points of horizontal and vertical direction by weighting according to the direction of edge information with the component of FOI(First Order Interpolation)and output of the pseudomedian filter for image enlargement and interpolates the interpolation points of diagonal direction by selectively transposing the direction of the subwindows of the pseudomedian filter according to the distribution of neighbored pixels thereto in the extended image. According to the proposed methods, the digital image enlargement which preserves the characteristic of the pseudomedian filter capable of keeping the reconstruction of edge information and reflects the advantage of FOI can be performed. Therefore, visual artifacts could be effectively suppressed, and most characteristics and shape of the original image can be reconstructed as well.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.46-48
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• 2011

기존의 참조 소프트웨어인 MPEG-2, MPEG-4, H.264/AVC에서는 움직임 벡터를 찾을 때 항상 고정된 해상도를 사용하였으며 다른 참조 소프트웨어인 KTA에서는 움직임 벡터를 찾을 때 움직임벡터의 해상도를 슬라이스 단위로 성능이 가장 높은 해상도를 선택해서 사용하였다. 하지만 움직임 벡터의 해상도는 블록마다 서로 다르기 때문에 블록별로 서로 다른 해상도를 적응적으로 사용할 필요가 있다. 적응적인 움직임 벡터 해상도 부호화 방법은 이러한 점을 이용하여 블록 별로 현재 블록의 움직임 벡터가 1/4 해상도인지 1/8 해상도인지에 판단하고 그에 대한 정보를 복호기에 전송해준다. 제안하는 알고리즘은 적응적 움직임 벡터 해상도를 사용하여 부호화 할 때 1/8 해상도 움직임 벡터가 성능이 없다고 판단되는 곳에선 적응적 움직임 벡터 해상도 방식을 사용하지 않고 1/4 해상도로만 움직임 벡터를 찾는다. 이러한 경우 해상도 정보를 복호기에 전송하지 않아 부호화 효율을 높일 수 있고 또한 1/8 해상도에 대한 움직임 예측을 하지 않기 때문에 부호화기 복잡도를 낮출 수 있다. 실험결과 평균 0.2%의 성능을 얻을 수 있었으며 부호화기 복잡도는 4% 감소하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.12
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• pp.1359-1369
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• 2007

This paper describes the technique of satellite direction finding and main beam steering of the adaptive array antenna system which is used for mobile TT&C(Tracking Telemetry&Command) system. To be able to control the satellite on mobile vehicle while moving, the relative directional information of the satellite to the mobile vehicle is necessary to make main beam to the direction of satellite. To do this MUSIC, which is one of the super-resolution algorithm of wave direction finding, is used and then the performance analysis and quantization problem of phase shifter are addressed. This paper is valuable in the respect of showing feasibility of designing the moble TT&C using adative array antenna system.

• The KIPS Transactions:PartB
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• v.9B no.2
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• pp.231-236
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• 2002

The classification of the speech-sound block comes from the multi-resolution analysis property of the discrete wavelet transform, which is used to reduce the computational time for the pre-processing of speech recognition. The merging algorithm is proposed to extract vapid speech-sounds in terms of position and frequency range. It performs unvoiced/voiced classification and denoising. Since the merging algorithm can decide the processing parameters relating to voices only and is independent of system noises, it is useful for extracting valid speech-sounds. The merging algorithm has an adaptive feature for arbitrary system noises and an excellent denoising signal-to-noise ratio and a useful system tuning for the system implementation.

• ETRI Journal
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• v.37 no.4
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• pp.752-765
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• 2015

We propose a novel post-processing algorithm and its very-large-scale integration architecture that simultaneously uses the passive and active stereo vision information to improve the reliability of the three-dimensional disparity in a hybrid stereo vision system. The proposed architecture consists of four steps - left-right consistency checking, semi-2D hole filling, a tiny adaptive variance checking, and a 2D weighted median filter. The experimental results show that the error rate of the proposed algorithm (5.77%) is less than that of a raw disparity (10.12%) for a real-world camera image having a $1,280{\times}720$ resolution and maximum disparity of 256. Moreover, for the famous Middlebury stereo image sets, the proposed algorithm's error rate (8.30%) is also less than that of the raw disparity (13.7%). The proposed architecture is implemented on a single commercial field-programmable gate array using only 13.01% of slice resources, which achieves a rate of 60 fps for $1,280{\times}720$ stereo images with a disparity range of 256.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.1
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• pp.62-68
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• 2014

Recently, MRI(magnetic resonance imager) scanner is continually used for medical diagnosis and many biomedical researches. When it operates, however, intense noise is generated. The SPL(sound pressure level) of the noise approaches 130 dB especially in 3 T(Tesla) MRI. Meanwhile, more than 3 T MRI scanners have been developed to get higher-resolution images, so louder noise is expected in the future. The intense noise makes patients feel nervous and uncomfortable. Moreover, it could possibly cause hearing loss to patient in extreme cases. For this reason, some active noise control systems have been researched. One of them used feedback Filtered-X LMS(FXLMS) algorithm which is able to control only narrowband noises and possible to diverge in severe case. In this paper, we determine the property of MRI noise. Using the property, we applied a method of open-loop and adaptive control for reducing MRI noise at target point inside bore. We verified performance of the method with computer simulation and preliminary experiment. The results demonstrate that the method can effectively reduce MRI noise at target point.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.399-404
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• 2002

To restore image degraded by motion blur and additive noise, it is very difficult. In conventional restoration method, regularization is usually applied to all over the image without considering the local characteristics of image. As a result, ringing artifacts appear in edge regions and the noise amplification is introduced in flat regions. To solve this problem we propose an adaptive restoration method using directional regularization operator considering edges and the regularization operator with no direction for flat regions. We verified that the proposed method showed better results in the resolution. As a result it showed visually better image and improved better ISNR further than the conventional methods.

• Journal of The Korean Astronomical Society
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• v.35 no.3
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• pp.131-141
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• 2002

We present Near-IR photometry of the Arches cluster, a young and massive stellar cluster near the Galactic center. We have analyzed the high resolution (FWHM $\~$ 0.2") Hand K' band images in the Galactic Center Demonstration Science Data Set, which were obtained with the Gemini/Hokupa's adaptive optics (AO) system. We present the color-magnitude diagram, the luminosity function and the initial mass function (IMF) of the stars in the Arches cluster in comparison with the HST/NICMOS data. The IMF slope for the range of 1.0 < log (M/M$\bigodot$) < 2.1 is estimated to be ${\Gamma} = -0.79 {\pm} 0.16$, in good agreements with the earlier result based on the HST/NICMOS data [Figer et al. 1999, ApJ, 525, 750]. These results strengthen the evidence that the IMF of the bright. stars close to the Galactic center is much flatter than that for the solar neighborhood. This is also consistent with a recent finding that the IMFs of the bright stars in young clusters in M33 get flatter as the galactocentric distance decreases [Lee et al. 2001, astro-ph 0109258]. It is found that the power of the Gemini/ AO system is comparable, with some limits, to that of the HST/NICMOS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.3165-3181
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• 2019

Spherical videos, which are also called 360-degree videos, have become increasingly popular due to the rapid development of virtual reality technology. However, the large amount of data in such videos is a huge challenge for existing transmission system. To use the existing encode framework, it should be converted into a 2D image plane by using a specific projection format, e.g. the equi-rectangular projection (ERP) format. The existing high-efficiency video coding standard (HEVC) can effectively compress video content, but its enormous computational complexity makes the time spent on compressing high-frame-rate and high-resolution 360-degree videos disproportionate to the benefits of compression. Focusing on the ERP format characteristics of 360-degree videos, this work develops a fast decision algorithm for predicting the coding unit depth interval and adaptive mode decision for intra prediction mode. The algorithm makes full use of the video characteristics of the ERP format by dealing with pole and equatorial areas separately. It sets different reference blocks and determination conditions according to the degree of stretching, which can reduce the coding time while ensuring the quality. Compared with the original reference software HM-16.16, the proposed algorithm can reduce time consumption by 39.3% in the all-intra configuration, and the BD-rate increases by only 0.84%.