• Proceedings of the Korea Information Processing Society Conference
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• 2022.05a
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• pp.410-412
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• 2022

협업 필터링은 사용자들간의 집단 지성에 기반한 추천 알고리즘이다. 다양한 시스템에 쓰이고 있는 협업 필터링과 그 장단점에 대해서 알아본다. 그리고 본 논문에서는 기존의 학사 관리 시스템에 협업 필터링을 적용한 새로운 학사관리 시스템을 제안한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.6
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• pp.77-87
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• 2007

It will need a quite long time to replace IPv4 protocol, which currently used, with IPv6 protocol completely, thus we will use both IPv4 and IPv6 together in the Internet during the period. For coexisting protocols, IETF standardized various IPv4/IPv6 transition mechanisms. However, new security problems of IPsec adaptation and IPv6 packet filtering can be raised by tunneling mechanism which mainly used in transition mechanisms. To resolve these problems, we suggested two improved schemes for packet filtering functions, which consists of an inner header filtering scheme and a dedicated filtering scheme for IPv4/IPv6 transition mechanisms. Also we implemented our proposed schemes based on Linux Netfilter framework, and we tested their filtering functions and evaluated experimental performance of our implementation on IPv4/IPv6 transition testbed. These evaluation tests indicated that our improved packet filtering functions can solve packet filtering problems of IPv4/IPv6 transition mechanisms without severely affecting system performance.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.25-28
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• 1999

본 연구에서는 finite impulse response (FIR) 필터에 의해 인식기의 입력 특징벡터가 필터링되는 경우에 hidden Markov model (HMM) 파라미터를 적응시키는 새로운 기법을 제안한다. 제안한 적응 기법은 필터링에 의해 변환된 특징벡터에 대해 HMM 파라미터를 다시 학습시킬 필요가 없으며 주어진 FIR필터 계수만을 사용하여 HMM 파라미터를 적응시킬 수 있다. 개발된 FIR필터링에 대한 HMM 파라미터 적응 기법은 연속 숫자음 인식 실험에서 재학습 방법과 비교 실험한 결과 low-pass 필터의 경우에 재학습 방법과 비슷한 인식 성능을 나타내었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.354-357
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• 2013

The filtering algorithm is used very frequently in the preprocessing stage of many image processing algorithms in computer vision processing. Because video signals are two-dimensional signals, computaional complexity is very high. To reduce the complexity, separable filters and the factorization theorem is applied to the filtering operation. As a result, it is shown that a significant reduction in computational complexity is achieved, although the experimental results could be slightly different depending on the condition of the image.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.270-271
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• 2018

본 논문에서는 새로이 시작된 비디오 압축 표준인 VVC(Versatile Video Coding)의 인-루프(in-loop) 필터링을 위한 CNN 구조를 제안한다. 제안하는 CNN 구조는 복호화된 영상을 입력으로 하고 원본 영상과 복호화된 영상의 오차를 손실함수로 사용하여 학습을 진행한다. 또한, 비디오 부호화에서의 다양한 크기의 CU(Coding Unit)를 고려한 다양한 크기의 컨볼루션 필터를 사용하여 특징을 추출하는 구조에 기반하고 있다. 실험을 통하여 제안한 CNN 기반의 필터링이 VVC 의 시험모델인 VTM(VVC Test Model)의 인-루프 필터링의 성능을 개선할 수 있음을 확인하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.113-122
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• 2016

In this paper, we suggest a approach which comprises fast Fourier transform inversion by wavelet noise attenuation. It represents an inverse filtering by adopting a factor into the Wiener filtering, and the optimal factor is chosen to minimize the overall mean squared error. in order to apply the Wiener filter, we have to compute the power spectrum of original image from the corrupted figure. Since the Wiener filtering contains the inverse filtering process, it expands the noise when the blurring filter is not invertible. To remove the large noises, the best is to remove the noise using wavelet threshold. Wavelet noise attenuation steps are consisted of inverse filtering and noise reduction by Wavelet functions. experimental results have not outperformed the other methods over the overall restoration performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.1-7
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• 2019

In this paper, we propose an approach to design a practical filter and a mathematical modeling for images. In the areas of signal processing, including high-dimensional image processing, the filtering process has been fundamental and crucial in diverse practical applications such as image processing, computer vision, and pattern recognition. In general, the ideal filter is modeled as circular-shaped in the 2D frequency domain as the rectangular shape is ideal for the 1D frequency domain. This paper proposes an approach to modeling practical and efficient image filter in the 2D frequency domain. Instead of employing a circular-shaped filter, this study proposes a polygon-shaped filter inspired by the concept of a hexagon cellular system for frequency reuse in wireless communication systems. By employing the concept of frequency reuse, bandwidth efficiency is also achieved in the frequency domain. To substantiate the proposed approach, quantitative evaluation is performed using PSNR.

• Journal of KIISE:Databases
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• v.34 no.5
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• pp.389-395
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• 2007

Collaborative filtering is a popular technique for information filtering to reduce information overload and widely used in application such as recommender system in the E-commerce domain. Collaborative filtering systems collect human ratings and provide Predictions based on the ratings of other people who share the same tastes. The quality of predictions depends on the number of items which are commonly rated by people. Therefore, it is difficult to apply pure collaborative filtering algorithm directly to dynamic collections where items are constantly added or removed. In this paper we suggest a method for managing dynamic collections. It creates taste space for items using a technique called Singular Vector Decomposition (SVD) and maintains clusters of core items on the space to estimate relevance of past and future items. To evaluate the proposed method, we divide database of user ratings into those of old and new items and analyze predicted ratings of the latter. And we experimentally show our method is efficiently applied to dynamic collections.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.3 s.37
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• pp.3-11
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• 2006

The need for edge detection about topography data from the high resolution satellite imagery is happening with increasing frequency according to many people utilize the its imagery as various fields recently. Many experts is recognizing of other GIS will make use of the road detection from the high resolution satellite imagery, including ITS (Intelligent Transportation Systems) and urban planning. This paper is comparative analysis of LPF (Low Pass Filtering) and HPF (High Pass Filtering) for roads edge detection from high resolution satellite imagery. As a result, LPF and HPF can be highlight selective pixels at edge area about input data. In case or applying to other techniques such as LPF for the same purpose, they aye more effective for wide road width which often cause the slight distortion of boundary or overall change of brightness values on the whole Image. Whereas, HPF has ability to enhance selectively detailed components in a target image.

• The KIPS Transactions:PartD
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• v.11D no.4
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• pp.835-844
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• 2004

Recently, the location-based service for moving customers is becoming one of the most important service in mobile communication area. For moving object applications, there are lots of update operations and such update loads are concentrated on some particular area unevenly. Range queries, whose range can be window or circular, are the most essential query types in LBS. We need to distinguish completely contained cells from partially contained cells in those range queries. Also, it is necessary to consider temporal dimension to filter out qualifying objects correctly. In this paper, we adopt two-level index structures with fixed grid file structures in the second level, which are designed to minimize update operations. We propose a spatial ceil filtering method using VP filtering and a combined spatio-temporal filtering method using time gone concepts. Some experimental results are shown for various window queries and circular queries with different filtering combinations to show the performance tradeoffs of the proposed methods.