• Journal of Mechanical Science and Technology
• /
• 제17권3호
• /
• pp.409-421
• /
• 2003

The hierarchical recursive local-correlation PIV algorithm with CBC (correlation based correction) method was employed to increase the spatial resolution of PIV results and to reduce error vectors. The performance of this new PIV algorithm was tested using synthetic images, PIV standard images of Visualization Society of Japan, real flows including ventilation flow inside a vehicle passenger compartment and wake behind a circular cylinder with riblet surface. As a result, most spurious vectors were suppressed by employing the CBC method, the hierarchical recursive correlation algorithm improved the sub-pixel accuracy of PIV results by decreasing the interrogation window size and Increased spatial resolution significantly. However, with recursively decreasing of interrogation window size, the SNR (signal-to-noise ratio) in the correlation plane was decreased and number of spurious vectors was increased. Therefore, compromised determination of optimal interrogation window size is required for given flow images, the performance of recursive algorithm is also discussed from a viewpoint of recovery ratio and error ratio in the paper.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2001년도 Proceedings of 2001 Korea-Japan Joint Seminar on Particle Image Velocimetry
• /
• pp.75-85
• /
• 2001

The hierarchic recursive local-correlation PIV algorithm with CBC(correlation based correction) method was developed to increase the spatial resolution of PIV results and to reduce error vectors. This new algorithm was applied to the single-frame and double-frame cross-correlation PIV techniques. In order to evaluate its performance, the recursive algorithm was tested using synthetic images, PIV standard images from Visualization Society of Japan, real flows including ventilation flow inside a vehicle passenger compartment and wake behind a circular cylinder with rib let surface. As a result, most spurious vectors were suppressed by employing CBC method. In addition, the hierarchical recursive correlation algorithm improved largely the sub-pixel accuracy of PIV results by decreasing the interrogation window size, increasing spatial resolution significantly.

• Smart Structures and Systems
• /
• 제24권4호
• /
• pp.459-474
• /
• 2019

This study develops a novel recursive algorithm to significantly enhance the computation efficiency of a recently proposed stochastic subspace identification (SSI) methodology based on an alternative stabilization diagram. Exemplified by the measurements taken from the two investigated office buildings, it is first demonstrated that merely one sixth of computation time and one fifth of computer memory are required with the new recursive algorithm. Such a progress would enable the realization of on-line and almost real-time monitoring for these two steel framed structures. This recursive SSI algorithm is further applied to analyze 20 months of monitoring data and comprehensively assess the environmental effects. It is certified that the root-mean-square (RMS) response can be utilized as an excellent index to represent most of the environmental effects and its variation strongly correlates with that of the modal frequency. More detailed examination by comparing the monthly correlation coefficient discloses that larger variations in modal frequency induced by greater RMS responses would typically lead to a higher correlation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권7호
• /
• pp.3093-3115
• /
• 2020

Network anomaly detection system plays an essential role in detecting network anomaly and ensuring network security. Anomaly detection system based machine learning has become an increasingly popular solution. However, due to the unbalance and high-dimension characteristics of network traffic, the existing methods unable to achieve the excellent performance of high accuracy and low false alarm rate. To address this problem, a new network anomaly detection method based on data balancing and recursive feature addition is proposed. Firstly, data balancing algorithm based on improved KNN outlier detection is designed to select part respective data on each category. Combination optimization about parameters of improved KNN outlier detection is implemented by genetic algorithm. Next, recursive feature addition algorithm based on correlation analysis is proposed to select effective features, in which a cross contingency test is utilized to analyze correlation and obtain a features subset with a strong correlation. Then, random forests model is as the classification model to detection anomaly. Finally, the proposed algorithm is evaluated on benchmark datasets KDD Cup 1999 and UNSW_NB15. The result illustrates the proposed strategies enhance accuracy and recall, and decrease the false alarm rate. Compared with other algorithms, this algorithm still achieves significant effects, especially recall in the small category.

• 한국산학기술학회논문지
• /
• 제15권5호
• /
• pp.3132-3138
• /
• 2014

많은 통신 시스템에서 심볼간 간섭, 직류성 및 충격성 잡음은 해결하기 어려운 문제로 남아있다. 이러한 간섭신호들을 제거하기 위하여 확률분포 상관도 개념이 블라인드 Equalization에 사용되었다. 그러나 이 알고리듬은 과다한 계산량이 문제로 남아 있다. 이 논문에서는 확률분포 상관도에 기반한 블라인드 알고리듬의 반복적 계산 방법을 제안하였다. 비용함수의 기울기 계산에 쓰이는 합산 계산을 반복적 방식으로 기울기를 계산하도록 바꾸었다. 이 방식은 M 개의 송신 심볼에 대해 N 개의 블록 샘플들을 가지고 계산하는 기존 알고리듬의 계산량 O(NM)으로부터 O(M)으로 그 계산량을 획기적으로 줄인다. 따라서 현실적 구현의 장점을 가지면서 동시에 잡음 및 간섭에 대한 강인성을 그대로 유지한다. 시뮬레이션 결과에서도 제안한 방식은 줄여진 계산량으로 동일한 학습 성능을 보였다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국제학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
• /
• pp.1051-1054
• /
• 1988

In this paper we present initial convergence properties of the Kalman filtering algorithm, we put an arbitrary small positive correlation matrix as an initial condition in the recursive algorithm. This arbitrary small initial condition perturbs the Kalman filtering algorithm and may lead to initial instability. We derive a condition which insures the stable operation of the Kalman filtering algorithm from the stochastic Lyapunov difference equation.

• 전자공학회논문지 IE
• /
• 제48권1호
• /
• pp.7-15
• /
• 2011

본 논문에서는 상관계수를 바탕으로 신호부공간을 추정하는 COPAST(correlation-based projection approximation subspace tracking)의 성능을 향상시키기 위하여 상관계수를 구하는 부분을 순방향 신호 벡터로부터 상관계수를 구하고 동시에 역방향 신호 벡터에서도 상관계수를 구하여 신호 부공간을 추정하는 방법을 제안한다. 또 매번 갱신되는 상관행렬의 안정성을 도모하고자 제곱근 행렬 갱신을 하도록 하였다. 컴퓨터 모의 실험을 통해서 제안된 방법이 기존의 COPAST에 비해서 약 5dB의 신호 부공간 추정 정확도에 향상이 있었음을 확인하였다.

• 대한전자공학회논문지
• /
• 제22권1호
• /
• pp.75-85
• /
• 1985

실시간 설치가 가능한 움직이는 물체를 추적하는 알고리즘에 관하여 연구하였다. 본 논문에서는 연산자 표현과 variation이 알고리즘[10]에 근거하여 fast 알고리즘을 개발하였다. Variational알고리즘에 대한 초기 추정치는 상호 상관 계수가 최대가 되는 위치를 directed search를 통하여 구하였다. 개발한 fast 알고리즘은 먼저 영상을 16개의 작은 부영상으로 분해하고 새로 제시한 움직임 검출 방법과 variational 알고리즘을 각 부영상에 순차적으로 적웅하는 알고리즘이다. 따라서 부영상을 단위로 하는 recursive 알고리즘이다. 개발한 알고리즘은[10]자 비교하여 평균 7대 1 정도의 계산상의 이득을 얻을 수 있다.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2003년도 추계학술대회 논문집
• /
• pp.63-66
• /
• 2003

A new algorithm, CBIR (Correlation Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1778-1782
• /
• 2004

A new algorithm, CBIR (Correlation-Based Image Registration) was proposed to improve the resolution of image registration for PSP (Pressure-Sensitive Paint). The local displacement vectors were obtained by finding the displacement which maximizes the cross-correlation between two interrogation windows of 'wind-off' and 'wind-on' images. A recursive multigrid processing was employed to increase the non-linear spatial resolutions. The variations of image were precisely measured without identifying the control points.