A simple iterative independent component analysis algorithm for vibration source signal identification of complex structures

ABSTRACT:Independent Component Analysis (ICA), one of the blind source separation methods, can be applied for extracting unknown source signals only from received signals. This is accomplished by finding statistical independence of signal mixtures and has been successfully applied to myriad fields such as medical science, image processing, and numerous others. Nevertheless, there are inherent problems that have been reported when using this technique: insta- bility and invalid ordering of separated signals, particularly when using a conventional ICA technique in vibratory source signal identification of complex structures. In this study, a simple iterative algorithm of the conventional ICA has been proposed to mitigate these problems. The proposed method to extract more stable source signals having valid order includes an iterative and reordering process of extracted mixing matrix to reconstruct finally converged source signals, referring to the magnitudes of correlation coefficients between the intermediately separated signals and the signals measured on or nearby sources. In order to review the problems of the conventional ICA technique and to vali- date the proposed method, numerical analyses have been carried out for a virtual response model and a 30m class submarine model. Moreover, in order to investigate applicability of the proposed method to real problem of complex structure, an experiment has been carried out for a scaled submarine mockup. The results show that the proposed method could resolve the inherent problems of a conventional ICA technique

Numerical Investigation of the Ultimate Strength of D-Ring Devices and Deck Structures

An accurate prediction of the ultimate strength of lashing devices and deck structures is important to ensure the safety of the crews and carrying ships. In this study, finite element analysis using ABAQUS/implicit was performed to investigate the ultimate strength of D-ring devices subjected to various external loads. The resistance of deck plates to which the D-ring devices were clamped was also analyzed numerically, considering the effects of the plate thickness and corrosion wastage. The resultant force-displacement relationship of the devices and the deck plate was investigated from the simulations and the threshold was determined by means of the tangent interaction method. The numerical results were compared with the Cargo Stowage and Securing Code proposed by the International Marine Organization and the results showed that the code predicts conservative ultimate strength of the D-ring devices in most cases. The deck plate with a thickness of 6 mm should have a local stiffener to increase structural strength whereas corrosion wastage has negligible effect on the deck strength. The numerical analysis verified the feasibility of predicting the ultimate strength of D-ring devices and deck structures. Nevertheless, the need for further experimental study is acknowledged to validate the feasibility of the numerical results

Applicability and reliability of an experimental method measuring underwater acoustic radiation efficiency of floating box-type plate structures in a reverberant water tank

This paper aims to investigate the applicability and reliability of an experimental method measuring the underwater acoustic radiation efficiencies of floating plate structures in a reverberant water tank. For the purpose, an experimental method for estimating the acoustic power of a source in a reverberant sound field has been introduced and applied to measure the acoustic radiation efficiencies of two floating box-type plate structures excited by a logarithmic sine sweeping force in a water tank. The validity of the adopted experimental method has been examined by the comparison with numerical results obtained by a fully coupled vibroacoustic analysis with an infinite radiation boundary condition for the structures. From the results, it is confirmed that the experimental method for measuring the underwater acoustic radiation efficiency of floating plate structures in a reverberant water tank is reliably applicable for high-frequency ranges above the Schroeder frequency of the water tank

Measurement of the Ωc0\Omega_c^0 lifetime at Belle II

We report on a measurement of the $\Omega_c^0$ lifetime using $\Omega_c^0 \to \Omega^-\pi^+$ decays reconstructed in $e^+e^-\to c\bar{c}$ data collected by the Belle II experiment and corresponding to $207~{\rm fb^{-1}}$ of integrated luminosity. The result, $\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs$, agrees with recent measurements indicating that the $\Omega_c^0$ is not the shortest-lived weakly decaying charmed baryon