• Smart Structures and Systems
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• 제24권5호
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• pp.597-606
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• 2019

Damage detection based on dynamic characteristics of a structure is one of important roles in structural damage identification. It is difficult to detect local structural damage using traditional dynamic experimental methods due to a limited number of sensors used in an experiment. In this work, a non-contact test stand of fan blades is established, and a full-field noncontact test method, combined with three-dimensional digital image correlation, Bayesian operational modal analysis, and damage indices, is used to detect local damage of a fan blade under ambient excitation without use of baseline information before structural damage. The methodology is applied to detect invisible local damage on the fan blade. Such a method has a seemingly high potential as an alternative to detect local damage of blades with complex high-precision surfaces under extreme working conditions because it is a noncontact test method and can be used under ambient excitation without human participation.

• Journal of Information Processing Systems
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• 제13권5호
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• pp.1372-1381
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• 2017

In this paper, a texture feature extraction method using local energy and local correlation of Gabor transformed images is proposed and applied to an image retrieval system. The Gabor wavelet is known to be similar to the response of the human visual system. The outputs of the Gabor transformation are robust to variants of object size and illumination. Due to such advantages, it has been actively studied in various fields such as image retrieval, classification, analysis, etc. In this paper, in order to fully exploit the superior aspects of Gabor wavelet, local energy and local correlation features are extracted from Gabor transformed images and then applied to an image retrieval system. Some experiments are conducted to compare the performance of the proposed method with those of the conventional Gabor method and the popular rotation-invariant uniform local binary pattern (RULBP) method in terms of precision vs recall. The Mahalanobis distance is used to measure the similarity between a query image and a database (DB) image. Experimental results for Corel DB and VisTex DB show that the proposed method is superior to the conventional Gabor method. The proposed method also yields precision and recall 6.58% and 3.66% higher on average in Corel DB, respectively, and 4.87% and 3.37% higher on average in VisTex DB, respectively, than the popular RULBP method.

• International Journal of Internet, Broadcasting and Communication
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• 제16권1호
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• pp.233-240
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• 2024

We analyzed the effect of local college students' economic activities on the local economy. The analysis method was an industry-related analysis based on data obtained from a survey. As a result of the analysis, local university students were found to be sensitive to price when consuming due to insufficient living infrastructure around local universities. In addition, as a result of analyzing the impact of local college students' consumption expenditures on the local economy, especially local income, using a regional industry correlation table, the total income generated was KRW 130.6 billion (direct and indirect income effects KRW 90.9 billion, induced income effects KRW 39.6 billion), and the number of people induced to be employed was KRW 130.6 billion. It was estimated that there were 2,145 people per year. We examined the effect of local college students' economic activities on the local economy through quantitative analysis. This is a contribution point of the study as evidence supporting the maintenance and necessity of local universities, and suggests that the government and local governments should take active interest and efforts in fostering local universities.

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

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.701-705
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• 2008

Design analysis and computer experiments (DACE) model is widely used to express efficiently the nonlinear responses in the field of engineering design. Kriging model, a DACE model, can approximately replace a simulation model that is very expensive or highly nonlinear. The kriging model is composed of the summation of a global model and a local model representing deviation from global model. The local model is determined by correlation coefficient of the pre-sampled points, where determination of the correct correlation coefficient has an effect on accuracy and robustness of the kriging model. Therefore, robustness of the correlation coefficient is explored with respect to degrees of the global model. Then we propose the range of correlation coefficient to make correct and robust kriging model and the influence of the correlation coefficients on the degrees of global model with respect to the nonlinearity of the pre-sampled responses.

• 한국통신학회논문지
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• 제35권1A호
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• pp.87-94
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• 2010

협력 스펙트럼 감지(cooperative spectrum sensing) 방식은 지역적으로 분산되어 있는 다수의 부 사용자들이 협력하여 스펙트럼 감지를 수행하는 방법으로, 페이딩으로 인한 검파 성능의 손실을 효과적으로 줄일 수 있는 것으로 알려져 있다. 지금까지 협력 스펙트럼 감지에 관해 발표된 대부분의 연구 결과들은 부 사용자들의 스펙트럼 감지 결정이 통계적으로 서로 독립이라는 가정에 기초한 것이다. 그러나 실제 환경에서는 음영 효과(shadowing effect)로 인해 서로 가까이에 위치한 부 사용자들의 감지 결정(decision)들은 상관 관계(correlation)를 가질 수 있다. 이런 요인이 협력 스펙트럼 감지 방식의 성능에 미치는 영향을 평가하기 위하여, 본 논문에서는 주 사용자(primary user)가 활동할 때는 서로 다른 부 사용자 2명의 스펙트럼 감지 결정 사이에 일정한 통계적 상관도(correlation)가 존재하고, 활동하지 않는 경우에는 통계적으로 독립인 것으로 CR 시스템 환경을 설정한 후, 통계적 상관도에 따라 전송 용량(throughput)이 어떻게 변화하는 지를 분석하였다. 분석 결과 부 사용자들의 스펙트럼 감지 결정 사이의 상관 계수가 커질수록 OR 융합 규칙을 사용하는 경우에는 전송 용량이 줄어들은 반면 AND 융합 규칙을 사용하는 경우는 전송 용량이 증가하는 것으로 나타났다.

• Journal of Astronomy and Space Sciences
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• 제30권3호
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• pp.169-174
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• 2013

BOH magnetometer was installed at Mt. Bohyun in 2007 and has provided continuous dataset for 3-axis geomagnetic field over the South Korea. We have calculated real-time K-index based on BOH magnetic field data using well-known FMI method. Local K-index is calculated eight times a day, per every three hours. To calculate K-index, it is critical to get the Quiet Day Curve (QDC). For QDC calculation, we take the previous one month's average of H-component. In this paper, we compared four geomagnetic stations' magnetic field data over South Korea and Japan and K-indices of each stations; Bohyun, Gangneung, Jeju, and Kakioka for two years data, 2011-2012. To investigate the difference depending on the latitude, longitude and local time in more detail, we compare K-index on International Quiet Days (IQDs) and International Disturbed Days (IDDs). As a result, we report the correlation between local K-indices are higher than those between Kp and local K-indices, and the correlation is much better after sunset than after sunrise. As the geomagnetic activity becomes stronger, the correlation between the local K-indices and global Kp-index become higher.

• 한국멀티미디어학회논문지
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• 제19권5호
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• pp.848-855
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• 2016

Face recognition has received a great deal of attention for the wide range of applications in real-world scenario. In this scenario, mismatches (so called heterogeneity) in terms of resolution and illumination between gallery and test face images are inevitable due to the different capturing conditions. In order to deal with the mismatch problem, we propose a local feature learning method using deep canonical correlation analysis (DCCA) for heterogeneous face recognition. By the DCCA, we can effectively reduce the mismatch between the gallery and the test face images. Furthermore, the proposed local feature learned by the DCCA is able to enhance the discriminative power by using facial local structure information. Through the experiments on two different scenarios (i.e., matching near-infrared to visible face images and matching low-resolution to high-resolution face images), we could validate the effectiveness of the proposed method in terms of recognition accuracy using publicly available databases.

• 대한전자공학회논문지
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• 제17권3호
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• pp.52-56
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• 1980

First-order Gauss-Marker신호가 delta변조기에 즉가되어 granular잡음이 발생될 경우에 신호대잡음화의 표시식을 구하고, 또한 근사식에 관하여 고찰하였다. 입력신호의 adjacent correlation값과 local decoder의 prediction coefficient값간의 차에 비하여 adjacent correlation값이 클 경우에는, 입력신호와 오차신호간의 cross covariance값이 징소하므로 간단한 근사식으로 나타내었다. 이 경우에 임의의 adjacent correlation값에 대하여 적용될 수 있는 근사식을 나타내었다.

• 한국통신학회논문지
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• 제38A권5호
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• pp.409-415
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• 2013

본 논문에서는 코사인 위상 이진 옵셋 반송파 (binary offset carrier: BOC) 신호 추적에 알맞은 새로운 비모호 상관함수를 제안한다. 구체적으로는 코사인 위상 BOC 신호를 의사잡음코드의 칩 하나 안에 다수의 부반송파 펄스가 존재하는 형태로 해석하고, 그에 따른 새로운 국소신호들을 설계한다. 이후 새로운 국소신호들과 수신된 코사인 위상 BOC 신호를 상관하여 재조합함으로써 주변 첨두가 없는 새로운 비모호 상관함수를 생성한다. 모의실험을 통해 제안한 상관함수를 이용한 경우 기존의 상관함수들을 이용한 경우들에 비해 더욱 향상된 추적 오차 표준편차를 가지는 것을 확인한다.