• 제목/요약/키워드: spectral representation

검색결과 92건 처리시간 0.028초

Simulation of wind process by spectral representation method and application to cooling tower shell

  • Choi, Chang-Koon;Noh, Hyuk-Chun
    • Wind and Structures
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    • 제2권2호
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    • pp.105-117
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    • 1999
  • The various spectral density functions of wind are applied in the wind process simulation by the spectral representation method. In view of the spectral density functions, the characteristics of the simulated processes are compared. The ensemble spectral density functions constructed from the simulated sample processes are revealed to have the similarity not only in global shape but also in the maximum values with the target spectral density functions with a high accuracy. For the correlation structure to be satisfied in the circumferential direction on the cooling tower shell, a new formula is suggested based on the mathematical expression representing the circumferential distribution of the wind pressure on the cooling tower shell. The simulated wind processes are applied in the dynamic analysis of cooling tower shell in the time domain and the fluctuating stochastic behavior of the cooling tower shell is investigated.

Multi-view Clustering by Spectral Structure Fusion and Novel Low-rank Approximation

  • Long, Yin;Liu, Xiaobo;Murphy, Simon
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제16권3호
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    • pp.813-829
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    • 2022
  • In multi-view subspace clustering, how to integrate the complementary information between perspectives to construct a unified representation is a critical problem. In the existing works, the unified representation is usually constructed in the original data space. However, when the data representation in each view is very diverse, the unified representation derived directly in the original data domain may lead to a huge information loss. To address this issue, different to the existing works, inspired by the latest revelation that the data across all perspectives have a very similar or close spectral block structure, we try to construct the unified representation in the spectral embedding domain. In this way, the complementary information across all perspectives can be fused into a unified representation with little information loss, since the spectral block structure from all views shares high consistency. In addition, to capture the global structure of data on each view with high accuracy and robustness both, we propose a novel low-rank approximation via the tight lower bound on the rank function. Finally, experimental results prove that, the proposed method has the effectiveness and robustness at the same time, compared with the state-of-art approaches.

Destripe Hyperspectral Images with Spectral-spatial Adaptive Unidirectional Variation and Sparse Representation

  • Zhou, Dabiao;Wang, Dejiang;Huo, Lijun;Jia, Ping
    • Journal of the Optical Society of Korea
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    • 제20권6호
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    • pp.752-761
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    • 2016
  • Hyperspectral images are often contaminated with stripe noise, which severely degrades the imaging quality and the precision of the subsequent processing. In this paper, a variational model is proposed by employing spectral-spatial adaptive unidirectional variation and a sparse representation. Unlike traditional methods, we exploit the spectral correction and remove stripes in different bands and different regions adaptively, instead of selecting parameters band by band. The regularization strength adapts to the spectrally varying stripe intensities and the spatially varying texture information. Spectral correlation is exploited via dictionary learning in the sparse representation framework to prevent spectral distortion. Moreover, the minimization problem, which contains two unsmooth and inseparable $l_1$-norm terms, is optimized by the split Bregman approach. Experimental results, on datasets from several imaging systems, demonstrate that the proposed method can remove stripe noise effectively and adaptively, as well as preserve original detail information.

Simulation of stationary Gaussian stochastic wind velocity field

  • Ding, Quanshun;Zhu, Ledong;Xiang, Haifan
    • Wind and Structures
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    • 제9권3호
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    • pp.231-243
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    • 2006
  • An improvement to the spectral representation algorithm for the simulation of wind velocity fields on large scale structures is proposed in this paper. The method proposed by Deodatis (1996) serves as the basis of the improved algorithm. Firstly, an interpolation approximation is introduced to simplify the computation of the lower triangular matrix with the Cholesky decomposition of the cross-spectral density (CSD) matrix, since each element of the triangular matrix varies continuously with the wind spectra frequency. Fast Fourier Transform (FFT) technique is used to further enhance the efficiency of computation. Secondly, as an alternative spectral representation, the vectors of the triangular matrix in the Deodatis formula are replaced using an appropriate number of eigenvectors with the spectral decomposition of the CSD matrix. Lastly, a turbulent wind velocity field through a vertical plane on a long-span bridge (span-wise) is simulated to illustrate the proposed schemes. It is noted that the proposed schemes require less computer memory and are more efficiently simulated than that obtained using the existing traditional method. Furthermore, the reliability of the interpolation approximation in the simulation of wind velocity field is confirmed.

A Line Spectrum Frequency Pairs Representation for Spectral Envelop Quantization

  • Park, Youngho;Lee, Won-Cheol;Bae, Myung-Jin
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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    • pp.787-790
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    • 2000
  • This paper introduces a new type of representation of the LSPs as a promising alternative used for transmitting the LPC parameters. Major contribution in this paper is that the vocal track information embedded on the spectral envelope can be represented in terms of the reduced number of LSF compared tn the conventional. Hence, it provides a possibility that LPC parameters could be quantized at a reduced bit rate without causing any major spectral distortion. The simulation result illustrates the capability of the proposed LSPs representation as an efficient quantization method via a proper rejection of the redundant pairs of pole and zero along the unit circle.

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Vector and Scalar Modes in Coherent Mode Representation of Electromagnetic Beams

  • Kim, Ki-Sik
    • Journal of the Optical Society of Korea
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    • 제12권2호
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    • pp.103-106
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    • 2008
  • It is shown that the two mode representations, one with vector modes and the other with scalar modes, for the cross spectral density matrices of electromagnetic beams are equivalent to each other. In particular, we suggest a method to find the vector modes from the scalar modes and formulate the cross spectral density matrix as a correlation matrix.

음성신호의 Sub-Nyquist 비균일 표준화 및 완전 복구에 관한 연구 (Sub-Nyquist Nonuniform Sampling and Perfect Reconstruction of Speech Signals)

  • 이희영
    • 음성과학
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    • 제12권2호
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    • pp.153-170
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    • 2005
  • The sub-Nyquist nonuniform sampling (SNNS) and the perfect reconstruction (PR) formula are proposed for the development of a systematic method to obtain minimal representation of a speech signal. In the proposed method, the instantaneous sampling frequency (ISF) varies, depending on the least upper boundary of spectral support of a speech signal in time-frequency domain (TFD). The definition of the instantaneous bandwidth (IB), which determines the ISF and is used for generating the set of samples that represent continuous-time signals perfectly, is given. Also, the spectral characteristics of the sampled data generated by the sub-Nyquist nonuniform sampling method is analyzed. The proposed method doesn't generate the redundant samples due to the time-varying property of the instantaneous bandwidth of a speech signal.

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ON PREHERMITIAN OPERATORS

  • YOO JONG-KWANG;HAN HYUK
    • 대한수학회논문집
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    • 제21권1호
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    • pp.53-64
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    • 2006
  • In this paper, we are concerned with the algebraic representation of the quasi-nilpotent part for prehermitian operators on Banach spaces. The quasi-nilpotent part of an operator plays a significant role in the spectral theory and Fredholm theory of operators on Banach spaces. Properties of the quasi-nilpotent part are investigated and an application is given to totally paranormal and prehermitian operators.