• Communications of the Korean Mathematical Society
• /
• v.16 no.1
• /
• pp.25-66
• /
• 2001

복소힐버트 공간상에서 정의된 작용소 중에서 최근 많이 연구되는 분야는 부분정규작용소와 초정규작용소들 들 수 있다. 본 논문에서는 작용소의 부분정규성과 초정규성 사이에 있는 작용소의 여러 성질을 살펴보고 특히 $\textsc{k}$차초정규, 이차약초정규, 삼차약초정규, 다항초정규, 토에플리츠작용소 및 약부분정규작용소에 관한 최근의 연구 결과들을 살펴보며 이와 관련되 미해결 문제들을 제시한다. 마지막으로 틈이론의 응용으로서 작용소이론의 큰 문제인 불변공간문제와의 관련성을 살펴보고 틈이론의 전망과 기타 관련정보를 소개한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2000.10b
• /
• pp.419-421
• /
• 2000

정확한 색 재현(Color Reproduction)을 위해서 영상 입력 장치(Image Input Device)의 조명색(Illuminant Color)에 따른 영상 변화를 분석하는 것은 중요하다. 영상 입력 장치는 피사체(Object)를 비추는 조명의 색 특성에 따라 영상을 생성한다. 이는 인간 시각 시스템(Human Visual System)이 가지는 색 불변성(Color Constancy)과는 다른 특성이며, 정확한 색 재현을 위해 필요한 색 실현 모델(Color Appearance Model)이 영상을 변환하는데 문제점으로 작용한다. 따라서, 영상 입력 장치가 생성하는 영상으로부터 조명 정보를 분석하여 인간 시각 시스템의 색 불변성을 재현할 필요가 있다. 본 논문에서는 영상의 조명 정보를 평가하기 위해 채도(Chroma)가 높은 기준 색 샘플들의 rgb 색도를 이용하여 색도 평면에 색도 다각형(Chromaticity Polygon)을 구성하고 영상의 모든 픽셀들의 rgb 색도 분포와 기준 색 샘플들의 색도 다각형간의 포함 관계에 따라 조명 정보를 평가한다.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.6
• /
• pp.1494-1506
• /
• 1998

본 논문에서는 루프구조의 효율적인 병렬수행을 위한 병렬성 추출에 대하여 불변과 가변 종속거리에 모두적용할 수 있는 통합된 새로운 기법을 제시한다. 이것은 컴파일시간에 순차 루프를 중첩된 DOALL 루프로의 자동 변환에 대한 절차로서, 중첩 루프의 전체적인 병렬화를 하기 위하여 문장들을 반복적으로 수행시키는 것에 의해서 자료 종속을 효과적으로 제거하는 알고리즘이다. 본 논문에 제시된 방법은 성능평가에서도 매우 뛰어난 방법임을 보였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.2
• /
• pp.221-232
• /
• 2012

The double-density discrete wavelet transform(DWT) is an improvement upon the critically sampled DWT with important additional properties. It employs one scaling function and two distinct wavelets, which are designed to be offset from one another by one half. And it is overcomplete by a factor of two. Also, this transformation is nearly shift-invariant. But there is room for improvement because not all of the wavelets are directional. That is, although the double-density DWT utilizes more wavelets, some lack a dominant spatial orientation, which prevents them from being able to isolate those directions. Proposed method is a DWT that combines the double-density DWT and quincunx sampling, each of which has its own characteristics and advantages. Especially, the quincunx sampling treats the different directions more homogeneously. As a result, since proposed method can generate sub-images of multiple degrees rotated versions, this method provides an improved performance in image processing fields.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.5
• /
• pp.972-978
• /
• 2009

In order to achieve color constancy, this paper proposes a method that can detect an invariant direction that affects formation of an intrinsic image significantly, using eigenvector in the $\chi$-chromaticity space. Firstly, image is converted into datum in the $\chi$-chromaticity space which was suggested by Finlayson et al. Secondly, it removes datum, like noises, with low probabilities that may affect an invariant direction. Thirdly, so as to detect the invariant direction that is consistent with a principal direction, the eigenvector corresponding to the largest eigenvalue is calculated from datum extracted above. Finally, an intrinsic image is acquired by recovering datum with the detected invariant direction. Test images were used as parts of the image data presented by Barnard et al., and detection performance of invariant direction was compared with that of entropy minimization method. The results of experiment showed that our method detected constant invariant direction since the proposed method had lower standard deviation than the entropy method, and was over three times faster than the compared method in the aspect of detection speed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.255-258
• /
• 2003

Recently, Digital Watermarking is used to authenticate data and to determine whether the data are distorted or not in medical images which is digitalized. The Fourier Mellin method using the Fourier Transform and the Log-Polar coordinate transform gets an invariant feature for RST distortion in images. But there are several problems in the real materialization. Interpolation of the image value should be considered according to the pixel position and so a watermark loss, original image distortion, numerical approximation is happened. Therefore there should be solved to realization of the Fourier Mellin method. Using the Look up table, there reduce the data loss caused by the conversion between Rectangular and Polar coordinate. After diagnose, medical images are transformed the Polar coordinate and taken the Discrete Fourier transform in the center of ROI region. Maintaining the symmetry in Fourier magnitude coefficient, the gaussian distributed random vectors and binary images are embedded in medical images.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.6
• /
• pp.518-524
• /
• 2018

The cover song refers to live recordings or reproduced albums. This paper studies two-dimensional Fourier transform as a feature-dimension reduction method to search cover song fast. The two-dimensional Fourier transform is conducive in feature-dimension reduction for cover song search due to musical-key invariance. This paper extends the previous work, which only utilize the magnitude of the Fourier transform, by introducing an invariant from phase based on the assumption that adjacent frames have the same musical-key change. We compare the cover song retrieval accuracy of the Fourier-transform based methods over two datasets. The experimental results show that the addition of the invariant from phase improves the cover song retrieval accuracy over the previous magnitude-only method.

• Journal of KIISE:Software and Applications
• /
• v.37 no.2
• /
• pp.148-154
• /
• 2010

In the study of the formal semantics of uncertain databases, we typically take an algebraic approach by mapping an uncertain database to possible worlds which are a set of relational databases. In this paper, we present a new semantics for uncertain databases which takes a logical approach by translating uncertain databases into logical theories. A characteristic feature of our semantics is that it uses linear logic, instead of propositional logic, as its logical foundation. Linear logic is suitable for a logical interpretation of uncertain information because unlike propositional logic, it treats logical formulae not as persistent facts but as consumable resources. As the main result, we show that our semantics is faithful to the operational account of uncertain databases in the algebraic approach.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.8
• /
• pp.1433-1445
• /
• 1994

In this paper, an coherent optical correlator system based on the off-axis projection synthetic discriminant funtion (OA-pSDF) was analyzed and implemented optically. The filter was synthesized by combining conventional pSDF with single reference plane wave multiplexing. Synthesized pSDF were transformed to binary phase only filters (BPOFs) and fabricated as computer generated holograms(CGHs), which was used in the real time optical correlator system instead of using expensive spatial light modulators(SLMs). From the characteristic test, it was found that OA-pSDF showed distortion invariance and good performances in discrminating subset images. The proposed OA-pSDF BPOF could overcome the limitations of conventional BPOFs : that is distortion variance such as acale and rotation, especially out of plane variance.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.186-186
• /
• 2010

개별 블레이드 피치 제어(individual blade pitch control)는 각각의 로터 블레이드의 피치각을 독립적으로 조정함으로써 블레이드에 작용하는 공력을 변화시키는 원리로 풍력 터빈 구조물에 발생하는 동적 피로하중을 저감시키기 위한 제어기법이다. 그러나 개별 피치 제어에 의해 발생하는 각 블레이드의 독립적인 피치 운동은 풍력 터빈 회전자에 비대칭성을 야기하고 구조물의 동적 불안정 현상을 발생시킬 수 있기 때문에 이에 대한 정확한 동적 해석이 선행되어야 한다. 하지만 블레이드의 피치 운동이 반영된 풍력 터빈은 시변계로 간주되어 기존의 시불변계 해석기법을 직접 적용할 수 없기 때문에 동적 해석에 어려움이 있다. 이 논문에서는 각각의 블레이드 피치운동을 주기함수로 근사화 함으로써 풍력 터빈을 주기 시변계로 모형화한다. 그리고 효율적으로 주기 시변계의 근사해를 구하기 위한 변조 좌표 변환(modulated coordinate transformation)기법을 적용하여 블레이드의 피치운동이 반영된 풍력 터빈의 동적 안정성 해석을 수행하였다. 그리고 현재 풍력 터빈의 동적 해석에 활용되는 대표적인 해석 기법인 다중 블레이드 좌표변환(multi-blade coordinate transformation)기법을 이용한 해석보다 정확한 결과를 얻을 수 있음을 보였다.