• Smart Structures and Systems
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• 제25권2호
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• pp.123-133
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• 2020

Compressive sensing (CS) is a newly developed data acquisition and processing technique that takes advantage of the sparse structure in signals. Normally signals in their primitive space or format are reconstructed from their compressed measurements for further treatments, such as modal analysis for vibration data. This approach causes problems such as leakage, loss of fidelity, etc., and the computation of reconstruction itself is costly as well. Therefore, it is appealing to directly work on the compressed data without prior reconstruction of the original data. In this paper, a direct approach for modal analysis of damped systems is proposed by decomposing the compressed measurements with an appropriate dictionary. The damped free vibration function is adopted to form atoms in the dictionary for the following sparse decomposition. Compared with the normally used Fourier bases, the damped free vibration function spans a space with both the frequency and damping as the control variables. In order to efficiently search the enormous two-dimension dictionary with frequency and damping as variables, a two-step strategy is implemented combined with the Orthogonal Matching Pursuit (OMP) to determine the optimal atom in the dictionary, which greatly reduces the computation of the sparse decomposition. The performance of the proposed method is demonstrated by a numerical and an experimental example, and advantages of the method are revealed by comparison with another such kind method using POD technique.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권6호
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• pp.608-616
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• 2013

This paper presents an adaptive sampling method for electrocardiogram (ECG) signal detection. First, by employing the strings matching process with compression dictionary, we recognize each segment of ECG with different characteristics. Then, based on the non-uniform sampling strategy, the sampling rate is determined adaptively. As the results of simulation indicated, our approach reconstructed the ECG signal at an optimized sampling rate with the guarantee of ECG integrity. Compared with the existing adaptive sampling technique, our approach acquires an ECG signal at a 30% lower sampling rate. Finally, the experiment exhibits its superiority in terms of energy efficiency and memory capacity performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.5015-5038
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• 2018

In this paper, a novel spectral-spatial joint sparse representation algorithm for hyperspectral image classification is proposed based on multi-layer superpixels in various scales. Superpixels of various scales can provide complete yet redundant correlated information of the class attribute for test pixels. Therefore, we design a joint sparse model for a test pixel by sampling similar pixels from its corresponding superpixels combinations. Firstly, multi-layer superpixels are extracted on the false color image of the HSI data by principal components analysis model. Secondly, a group of discriminative sampling pixels are exploited as reconstruction matrix of test pixel which can be jointly represented by the structured dictionary and recovered sparse coefficients. Thirdly, the orthogonal matching pursuit strategy is employed for estimating sparse vector for the test pixel. In each iteration, the approximation can be computed from the dictionary and corresponding sparse vector. Finally, the class label of test pixel can be directly determined with minimum reconstruction error between the reconstruction matrix and its approximation. The advantages of this algorithm lie in the development of complete neighborhood and homogeneous pixels to share a common sparsity pattern, and it is able to achieve more flexible joint sparse coding of spectral-spatial information. Experimental results on three real hyperspectral datasets show that the proposed joint sparse model can achieve better performance than a series of excellent sparse classification methods and superpixels-based classification methods.

• 감성과학
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• 제12권4호
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• pp.433-442
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• 2009

요즈음 인터넷을 통해 물건을 구매하는 경향이 증가하고 있다. 또한 물건을 구매한 소비자는 리뷰, 댓글, 비평 또는 블로그 등의 형식으로 온라인에 그들의 사용 후기를 작성한다. 또한 작성된 사용 후기부터 많은 구매자들은 물건을 구매하기 전에 자신이 구입하고자 하는 물건에 대한 정보를 얻는다. 따라서 회사나 공공기관은 대중이 다른 사람의 의견에 관심을 기울인다는 점 때문에 대중의 의견을 수집하고 분석할 필요성에 직면하였다. 그러나 온라인상에 댓글이 너무 많고, 중복적이면서 짧은 경향이 있다. 이러한 환경 속에서 텍스트 문서의 감성을 인식하는 시스템의 필요성이 대두되었다. 텍스트로부터 작성자의 의견이나 주관적인 생각을 추출할 수 있게 영어에서는 단어에 속성이 주어진 GI와 LKB가 있으나 한글은 아직 속성이 주어진 사전이 존재하지 않는다. 이 논문에서는 한글 품사 중 4개의 품사(명사, 동사, 형용사, 부사)에 속성을 주었다. 그리고 학습 군을 만들어서 감성 단어의 패턴을 구성하고, 문장에서 단어 사이의 공기관계를 구성하여 학습 시켰다. 이 학습을 바탕으로, SO-PMI을 이용하여 문서를 긍정과 부정 2가지 극성을 분류하고, 4개의 품사(명사, 동사, 형용사, 부사)를 각각 조합하여 최상의 조건을 구하였다. 마지막으로 사용자 인터페이스를 통해 새로운 감성 표현, 구성형식, 단어 연관성을 반자동적으로 삽입하고 교정할 수 있는 시스템을 설계하였다.