Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
3D temperature distribution measurement in a furnace based on acoustic tomography (AT) calculates temperature field through\nmultipath acoustic time-of-flight (TOF) data. In this paper, a new 3D temperature field reconstruction model based on radial basis\nfunction approximation with polynomial reproduction (RBF-PR) is proposed for solving the ATinverse problem. In addition, the\nmodified reconstruction method that integrates the advantages of the TSVD and Tikhonov regularization methods is presented to\nreduce the sensitivity of noise on perturbations with the ill-posed problems and improve the reconstruction quality (RQ).\nNumerical simulations are implemented to evaluate the effectiveness of the proposed reconstruction method using different 3D\ntemperature distribution models, which include the one-peak symmetry distribution, one-peak asymmetry distribution, and twopeak\nsymmetry distribution. To study the antinoise ability of our method, noises are added to the value of TOF. 3D display of\nreconstructed temperature fields and reconstruction errors is given. The results indicate that our model can reconstruct the\ntemperature distribution with higher accuracy and better antinoise ability compared with the truncated generalized singular value\ndecomposition (TGSVD). Besides that, the proposed method can determine the hot spot position with higher precision, and the\ntemperature error of the hot spot is lower than the other compared methods....
This paper presents a novel scheme for speech dereverberation. The core of our method\nis a two-stage single-channel speech enhancement scheme. Degraded speech obtains a sparser\nrepresentation of the linear prediction residual in the first stage of our proposed scheme by applying\northogonal matching pursuit on overcomplete bases, trained by the K-SVD algorithm. Our method\nincludes an estimation of reverberation and mixing time from a recorded hand clap or a simulated\nroom impulse response, which are used to create a time-domain envelope. Late reverberation is\nsuppressed at the second stage by estimating its energy from the previous envelope and removed with\nspectral subtraction. Further speech enhancement is applied on minimizing the background noise,\nbased on optimal smoothing and minimum statistics. Experimental results indicate favorable quality,\ncompared to two state-of-the-art methods, especially in real reverberant environments with increased\nreverberation and background noise....
Dust plasma is a new field of physics which has developed rapidly in recent decades.The study of dust plasma has received much\nattention due to its importance in the environment of space and the Earth. Dust acoustic waves are generated because of the inertia\nof dustmass while the restoring force is provided by the thermal pressure of electrons and ions. Since dust acoustic waves were first\nreported theoretically in unmagnetized dust plasma by Rao et al., they have become a research hot spot. In this paper, the excitation\nof dust acoustic waves by a gravity field in a dust plasma is analyzed. According to the control equations of dust plasma motion and\nemploying multiscale analysis and perturbation method, we have obtained a (3+1)-dimensional ZK model. Because of the space\nproperty of dust plasma, (3+1)-dimensional ZK equation is more suitable than KdV equation and (2+1)-dimensional ZK equation\nto describe the real dust acoustic waves.Then, the (3+1)-dimensional time-space fractional ZK (TSF-ZK) equation describing the\nfractal process of nonlinear dust acoustic waves is given for the first time. To further explore how dust acoustic waves change energy\nas they travel, we discuss the conservation laws of the newmodel.................
Automatic monitoring of group-housed pigs in real time through porcine acoustic signals has played a crucial role in automated\nfarming. In the process of data collection and transmission, acoustic signals are generally interfered with noise. In this paper, an\neffective porcine acoustic signal denoising technique based on ensemble empirical mode decomposition (EEMD), independent\ncomponent analysis (ICA), and wavelet threshold denoising (WTD) is proposed. Firstly, the porcine acoustic signal is\ndecomposed into intrinsic mode functions (IMFs) by EEMD. In addition, permutation entropy (PE) is adopted to distinguish\nnoise-dominant IMFs from the IMFs. Secondly, ICA is employed to extract the independent components (ICs) of the noisedominant\nIMFs. The correlation coefficients of ICs and the first IMF are calculated to recognize noise ICs. The noise ICs will be\nremoved. Then, WTD is applied to the other ICs. Finally, the porcine acoustic signal is reconstructed by the processed components.\nExperimental results show that the proposed method can effectively improve the denoising performance of porcine\nacoustic signal....
The ear is able to detect low-level acoustic signals by a highly specialized system including\na parametric amplifier in the cochlea. This is verified by a numerical mechanical model of the cochlea,\nwhich reduces the three-dimensional (3D) system to a one-dimensional (1D) approach. A formerly\ndeveloped mechanical model permits the consideration of the fluid and the orthotropic basilar\nmembrane in a 1D fluid-structure coupled system. This model shows the characteristic frequency to\nplace transformation of the traveling wave in the cochlea. The additional inclusion of time and space\ndependent stiffness of outer hair cells and the signal level dependent stiffness of the string enables\nparametric amplification of the input signal. Due to the nonlinear outer hair cell stiffness change,\nnonlinear distortions follow as a byproduct of the parametric amplification at low levels constituting\nthe compressive nonlinearity. More distortions are generated by the saturating displacements of the\nstring at high input levels, which can be distinguished from the low-level distortions by the order of\nadditional harmonics. Amplification factors of 15.5 dB and 24.0 dB are calculated, and a change of the\ntraveling-wave mapping is postulated with parametric amplification representing the healthy state\nof the cochlea....
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