• Journal of KIISE:Computing Practices and Letters
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• v.11 no.2
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• pp.112-123
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• 2005

The latest E-commerce sites provide personalized services to maximize user satisfaction for Internet user The collaborative filtering is an algorithm for personalized item real-time recommendation. Various supplementary methods are provided for improving the accuracy of prediction and performance. It is important to consider these two things simultaneously to implement a useful recommendation system. However, established studies on collaborative filtering technique deal only with the matter of accuracy improvement and overlook the matter of performance. This study considers representative attribute-neighborhood, recommendation textile set, and similarity grouping that are expected to improve performance to the recommendation agent system. Ultimately, this paper suggests empirical applications to verify the adequacy and the validity on this system with the development of Fashion Design Recommendation Agent System (FDRAS ).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.687-692
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• 2006

In a conventional ICA(Independent Component Analysis) based face recognition method, PCA(Principal Component Analysis) first is used for feature extraction, ICA learning method then is applied for feature enhancement in the reduced dimension. It is not considered that a necessary component can be located in the discarded feature space. In the new ICA(NICA), learning extracts features using the magnitude of kurtosis (4-th order central moment or cumulant). But, the pure ICA method can not discard noise effectively. The synergy effect of PCA and ICA can be achieved if PCA is used for noise reduction filter. Namely, PCA does whitening and noise filtering. ICA performs feature extraction. Experiment results show the effectiveness of the new ICA method compared to the conventional ICA approach.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.10a
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• pp.429-434
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• 1997

영상 평활화(Image Smoothing) 작업은 영상 신호 표본화, 정량화, 통신 이동과 같은 과정을 거치면서 잡음 등의 불필요한 신호가 포함된 디지털 영상의 잡음을 감소키는데 많이 이용되고 있다. 이와 같은 영상 평활화 작업에는 대부분 전역적인 공간 영역 혹은 주파수 영역의 전역적인 필터링 기법이 이용되고 있다. 그러나, 기존의 방법들은 왜곡된 잡음 픽셀들의 정보를 그대로 반영하기 때문에 잡음 제거 결과 복원 영상의 선명도는 크게 저해된다. 본 논문에서는 특히나 양자화 과정을 통해 잡음 정보의 변형이 극대화되어지는 압축 영상을 대상으로 하여 적절한 잡음제거 기법을 제안하고자 한다. 특히, 압축 영상의 잡음 추출은 1차 복호화 후의 공간 도메인에서, 추출된 잡음 제거는 주파수 도메인에서 수행함으로써 2차 복호화 후의 잡음제거 결과 영상은 압축 영상의 잡음 제거에 따른 본질적인 문제를 해결하였으며, 실험 결과 역시 다른 기존의 방법에 비해 우수한 성능을 발휘하였다.

• The Journal of Korean Society for Radiation Therapy
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• v.20 no.2
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• pp.123-130
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• 2008

Purpose: To provide practical education, most universities should be equipped with medical appliances in need. As compensatory measures, Gimcheon College has produced in-house dummy linac and dummy accessories, we are going to report efficiency and its usage. Materials and Methods: Dummy linear accelerator (DLINAC-001) has the same mechanical functions as rotation of gantry and collimation in linear accelerator. In addition, to maximize practical education, we have produced and utilized in-house custom blocks, wedge filters, electron cones and head rests. Results: The in-house produced linear accelerator with the same mechanical functions as the linear accelerator, DLINAC-001 can be effectively used in practicing diverse medical instruments. Conclusion: We have produced dummy linear accelerators and dummy accessories and utilized them in practice classes, which can provide the students with clinical training in diverse fields. Consequently, the students exposed to the maximized educational effectiveness can be easily equipped with the practical competence required in real clinical fields.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.236-239
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• 2004

We studied the specular spin valve (SSV) having the spin filter layer (SFL) in contact with the ultrathin free layer composed of Ta3/NiFe2/IrMn7/CoFel/(NOLl)/CoFe2/Cu1.8/CoFe( $t_{F}$)/Cu( $t_{SF}$ )/(NOL2)/Ta3.5 (in nm) by the magnetron sputtering system. For this antiferromagnetic I $r_{22}$M $n_{78}$-pinned spin filter specular spin valve (SFSSV) films, an optimal magnetoresistance (MR) ratio of 11.9% was obtained when both the free layer thickness ( $t_{F}$) and the SFL thickness ( $t_{SF}$ ) were 1.5 nm, and the MR ratio higher than 11% was maintained even when the $t_{F}$ was reduced to 1.0 nm. It was due to increase of specular electron by the nano-oxide layer (NOL) and of current shunting through the SFL. Moreover, the interlayer coupling field ( $H_{int}$) between free layer and pinned layer could be explained by considering the RKKY and magnetostatic coupling. The coercivity of the free layer ( $H_{cf}$ ) was significantly reduced as compared to the traditional spin valve (TSV), and was remained as low as 4 Oe when the $t_{F}$ varied from 1 nm to 4 urn. It was found that the SFL made it possible to reduce the free layer thickness and enhance the MR ratio without degrading the soft magnetic property of the free layer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1155-1163
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• 2011

In this paper, we propose a new pre-processing algorithm applied to depth map to improve the coding efficiency. Now, 3DV/FTV group in the MPEG is working for standard of 3DVC(3D video coding), but compression method for depth map images are not confirmed yet. In the proposed algorithm, after dividing the histogram distribution of a given depth map by EM clustering method based on GMM, we classify the depth map into several layered images. Then, we apply different mean shift filter to each classified image according to the existence of background or foreground in it. In other words, we try to maximize the coding efficiency while keeping the boundary of each object and taking average operation toward inner field of the boundary. The experiments are performed with many test images and the results show that the proposed algorithm achieves bits reduction of 19% ~ 20% and computation time is also reduced.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.175-177
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• 2010

본 논문에서는 MPEG 의 3차원 비디오 시스템의 표준 깊이정보 맵에 대한 효율적인 부호화를 위하여 전처리 방법을 제안한다. 현재 3차원 비디오 부호화(3DVC)에 대한 표준화가 진행 중에 있지만 아직 깊이정보 맵의 부호화 방법에 대한 표준이 확정되지 않은 상태이다. 제안하는 기법에서는 우선, 입력된 깊이정보 맵에 대하여 원래의 히스토그램 분포를 가우시안 혼합모델(GMM)기반의 EM 군집화 기법에 의한 방법으로 분리 후, 분리된 히스토그램을 기반으로 깊이정보 맵을 여러 개의 영상으로 분리한다. 그 후 분리된 각각의 영상을 배경과 객체에 따라 다른 조건의 mean shift filter로 필터링한다. 결과적으로 영상내의 각 영역 경계는 최대한 살리면서 영역내의 화소 값에 대해서는 평균 연산을 취하여 부호화시 효율을 극대화 하고자 하였다. 실험조건은 $1024{\times}768$ 영상에 대해서 50 프레임으로 H.264/AVC base 프로파일로 부호화를 진행하였다. 최종 실험결과 bit rate는 대략 23% ~ 26% 정도 감소하고 부호화 시간도 다소 줄어드는 것을 확인 할 수 있었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.80-85
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• 2010

In this paper, the efficiency of power amplifier has been maximized by the application of EER structure, and the linearity has been improved by using metamaterial structure. This paper has proposed a design of power amplifier in class-F to get the PAE, and to control dynamic power using envelope detector. CRLH structure gets high-linearity by removing harmonics arisen from the mismatching of matching circuit. The PAE and the 3rd order IMD have been improved 5.93 %, 12.83 dB compared with those of conventional Class-F amplifier, respectively.

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.199-210
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• 2000

We present the results from narrow-band spectrophotometry of Comet Hale-Bopp (C/1995 O1) near perihelion obtained at Sobaeksan Optical Astronomy Observatory 61cm telescope equipped with PM 512 CCD camera(512$\times$512, 0.5"/pixel) and narrow-band filter set for the comet on 19 nights from February 21 to May 1, 1997. We discuss molecular emission band morphology and photometric behavior of Comet Hale-Bopp. The morphology of CN band shows more symmetric light distributions than $C_2$ or $C_3$ bands. On other hand, $C_2$ and $C_3$ band have more compact light distributions than CN band. Similar to wide-band image, molecular band morphology shows spiral structures at the core of the comet. The CN surface brightness variation with changing heliocentric distance shows difference from those of $C_2$ and $C_3$. The brightness, however, of these molecular bands near perihelion shows previously known 7day period light variations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.122-128
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• 2016

This paper, proposes a new analysis method for the event detection of an OTDR signal. An OTDR signal was passed through the Hamming filter to remove the high frequency noise included in the signal. The signal was then passed consecutively through a differential filter to detect the events of interest. The terminal position was determined using the fact that there is a large gap between the signal and the trailing noise power beyond the terminal. This study examined the local maxima of the signal up to the terminal position and determined the peak regions. The real events were determined from the peak regions using noise information and peak threshold. Finally, the user events were found by inspecting the user peaks beyond the terminal position. The events of the OTDR signal without users are located at less than 17m compared to the optical fiber link setup. The events of the JDSU device are located less than 25m and their users are less than 5m. For the RadianTech device, the events are detected at less than 19m and the users are found in 5m. The results suggest that the proposed method is sufficiently applicable to an optical fiber link monitoring system.