• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.114-116
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• 2000

이동성은 네트웍 계층에서뿐만 아니라, 응용계층에서도 매우 중요하다. 핸드오프는 이동성의 중요한 이슈중의 하나이다. H.323에서의 핸드오프를 위해서, 현재까지의 방법은 새로운 H.323호를 설정하는 것이다. 그러나, 이러한 방법에서는 중첩된 구간에서 새로운 호가 설정되지 않을 경우에 호가 부분적으로 끊길 수 있게 된다. 본 논문에서는 핸드오프를 위해 새로운 호를 만들지 않고, 이동터미널이 간단하게 기존의 논리채널을 닫고 새로운 논리채널을 여는 방법을 제안한다. 제안된 방법은 기존의 H.323 메시지를 변화시킬 필요가 없다. 이러한 방법으로, 지연이 줄어들며, 이동터미널은 MC 기능이 없이도 핸드오프를 수행할 수 있게 된다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.5
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• pp.19-27
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• 2004

A delay dependent fuzzy $H_2/H_{\infty}$ controller design method for delayed fuzzy dynamic systems is considered. Using delay-dependent Lyapunov function, the asymptotical stability and $H_2/H_{\infty}$ performance problem are discussed. A sufficient condition for the existence of fuzzy controller is presented in terms of linear matrix inequalities(LMIs). A simulation example is given to illustrate the design procedures and performances of the proposed methods.

• Journal of the Korean School Mathematics Society
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• v.10 no.4
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• pp.519-533
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• 2007

In this paper we study a equality $\frac{1}{h_a}+\frac{1}{h_b}+\frac{1}{h_c}=\frac{1}{r}$ which contains altitudes and radius of inscribed circle of triangle. We search some paths for proving the equality, and find out 9 proof method of the equality which is related with descriptive geometry, coordinate geometry, and vector geometry.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1998.10a
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• pp.757-764
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• 1998

본 논문에서는 Glover-Doyle의 H$\infty$ 설계기법을 이용하여 H$\infty$ 성능경계를 만족하는 Kalman 필터를 설계하는 방법을 제시한다. 제시한 방법을 사용하면, kalman 필터의 성능 강인성과 안정화 강인성 문제와의 관계를 설계변수의 설정으로 설계자가 적절하게 선택함으로써 구조적 불확실성에 대하여 비교적 강인한 H$\infty$ -norm Kalman 필터를 설계할 수 있도록 한다. 설계의 예를 통하여 H$\infty$ -norm Kalman 필터의 설게방법을 보이고, H2-norm Kalman 필터와 비교함으로써 제시된 방법이 특성을 보인다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.277-280
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• 2009

IPTV, 블루레이 디스크, DMB 등과 같은 멀티미디어 서비스에서 H.264/AVC 비디오 표준기술을 채택하고 있다. 따라서 H.264/AVC 비트스트림을 고속으로 인덱싱하기 위한 썸네일 기술이 요구 된다. 그러나 H.264/AVC는 기존 표준기술과는 다르게 인트라 모드에서도 예측방법을 이용하기 때문에 새로운 썸네일 추출방법이 요구되어 최근에 H.264/AVC 비트스트림 상에서 썸네일을 추출하는 방법이 제안되었다. 그러나 이 방법에서는 인트라 $16{\times}16$ 모드와 연관된 블록에서 심각한 화질의 저하가 발생하며, QP 값이 커질수록 그 증상이 더 심해지는 문제점이 있다. 그리고 공간주파수 영역에서 처리하기 때문에 예측 모드에 따라 연산오류가 발생하여 이 오류가 파급되는 문제가 있다. 따라서 본 논문에서는 공간주파수 영역에서 H.264/AVC 썸네일을 추출할 때 인트라 $16{\times}16$ 예측 모드에서도 오류가 발생하지 않도록 하는 방법과 공간주파수 영역에서 발생하는 연산 오류를 보상하는 방법을 제안한다. 그리고 제안한 방법을 다양한 시험 비디오 시퀀스에 적용하여 이전 썸네일 추출 방법과 비교하여 프레임에 따라 최대 PSNR 약 4dB 증가 및 주관적 화질을 향상시켰다.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.853-867
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• 2010

Recently, thumbnail techniques are required to index a high-performance video at digital convergence-based multimedia service like IPTV and DMB. Therefore a thumbnail extraction method in H.264/AVC bitstreams has been proposed. However, thumbnail quality deterioration problem at converting the general equation of spatial domain to frequency domain which is generated by not considering about H.264/AVC transform and quantization processing and rounding-off operation in intra prediction. In this paper, we propose a new thumbnail extraction method in H.264/AVC bitstreams. The proposed scheme is based on H.264/AVC core-transform for a thumbnail extraction in frequency domain, and probability theory, intra rounding-off error compensation. Through the implementation and performance evaluation, the subjective quality difference between the output of our scheme and the output of reference decoder is negligible and better than the conventional method, and moreover PSNR gain by up to 8.66 dB.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.3
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• pp.187-192
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• 2012

This paper describes efficient H.264/AVC video scrambling methods for digital rights management. The proposed scrambling methods are to scramble level and suffix in entropy encoding and MVD in motion estimation of the H.264 video compression process. Other scrambling methods have been proposed but they degrade the compression efficiency or make it difficult to achieve real-time processing due to the large amount of computational efforts. Since the proposed scrambling methods resolve the drawbacks of other approaches, they do not cause image distortion and the original compression efficiency is maintained. We verified our scrambling methods and evaluated the performance by conducting several experiments with H.264 reference program. Finally, we implemented video player system using USB dongle in order to apply the proposed scrambling/descrambling methods to H.264 video compression.

• Journal of the Korean Society for information Management
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• v.27 no.1
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• pp.249-267
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• 2010

The h-index is a new tool for measuring research outputs based on citation and many variants of h-index have been proposed to improve the weaknesses of h-index. The h-index and its variants can be applied to institutional evaluation in three different ways. We worked out 447 practical cases of professors from 10 business schools and examined h-index and its variants. And then we compared three evaluation methods of research institution based on the h-index and its variants.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.429-437
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• 2006

To establish the efficient treatment technology of chemical cleaning wastewater from power plant, several AOPs($UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton oxidation) were investigated. Treatment efficiencies and the electrical energy requirements based on the EE/O parameter(the electrical energy, required per order of pollutant removal in $1m^3$ wastewater) were evaluated. TOC removal efficiencies of $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton oxidation at the optimum conditions were 95.5%, 92.3%, 91.5%, respectively. The electrical energy requirements of $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton oxidation were $11.26kWh/m^3,\;3.85kWh/m^3,\;0.799kWh/m^3$, respectively. From these results, it could be concluded that all of the three oxidation processes were effective for the degradation of citric acid. Considering the treatment efficiency and economical aspect, photo-Fenton oxidation was the most efficient treatment process among the three processes tested.

• Journal of Broadcast Engineering
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• v.6 no.2
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• pp.187-194
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• 2001

The Advanced Intra Coding(AIC) mode included in the H.263+ which is for video ceding at low bit rates, selects one prediction direction of DCT coefficients among three directions for every intra macroblock. Based ()n the selected direction, It uses a different DCT scanning order, quantization scheme, and VLC table. The use of the AIC mode brings higher compression ratio and improved PSNR than the H.263 baseline. This paper proposes a simplified submode selection method for a direction of the DCT coefficient prediction for advanced ultra coding in H.263. Compared to the conventional method the proposed simplified method can achieve a similar coding Performance at computational complexity reduced to 1/7 and with much less memory requirement. The proposed method will be useful in implementing a simplified H.263 system.