Jointly Tracking and Separating Speech Sources Using Multiple Features and the generalized labeled multi-Bernoulli Framework

This paper proposes a novel joint multi-speaker tracking-and-separation method based on the generalized labeled multi-Bernoulli (GLMB) multi-target tracking filter, using sound mixtures recorded by microphones. Standard multi-speaker tracking algorithms usually only track speaker locations, and ambiguity occurs when speakers are spatially close. The proposed multi-feature GLMB tracking filter treats the set of vectors of associated speaker features (location, pitch and sound) as the multi-target multi-feature observation, characterizes transitioning features with corresponding transition models and overall likelihood function, thus jointly tracks and separates each multi-feature speaker, and addresses the spatial ambiguity problem. Numerical evaluation verifies that the proposed method can correctly track locations of multiple speakers and meanwhile separate speech signals

Acoustic Speaker Localization with Strong Reverberation and Adaptive Feature Filtering with a Bayes RFS Framework

The thesis investigates the challenges of speaker localization in presence of strong reverberation, multi-speaker tracking, and multi-feature multi-speaker state filtering, using sound recordings from microphones. Novel reverberation-robust speaker localization algorithms are derived from the signal and room acoustics models. A multi-speaker tracking filter and a multi-feature multi-speaker state filter are developed based upon the generalized labeled multi-Bernoulli random finite set framework. Experiments and comparative studies have verified and demonstrated the benefits of the proposed methods

An adaptive low-complexity coherence-based beamformer

This paper presents an adaptive coherence-based beamforming algorithm that enhances a target speech signal from an arbitrary direction of arrival (DOA) in the azimuthal plane, while localising and suppressing the interfering speech signal and noise from other directions. In these complex noisy acoustic environments, spatially selective speech enhancement schemes provide significant advantages over single channel enhancement methods. Experimental results demonstrate that the proposed method achieves considerable improvement in Perceptual Evaluation of Speech Quality (PESQ). Moreover, the proposed algorithm is directly suited for real-time implementation

Characterization approach on the extrusion process of bioceramics for the 3D printing of bone tissue engineering scaffolds

The present study proposes a characterization approach for the extrusion process of hydroxyapatite (HA) paste considering the nonlinear characteristics of bioceramics materials with the aim of printing high-resolution ceramic scaffolds using low-temperature extrusion 3D printing technology. A novel method named the three-point experimental extrapolation was executed to analyze the necessary extrusion pressure in relation to the extrusion velocity. This new approach presented a higher analytical accuracy as compared to previous methods. The optimum layout of the 3D printer was obtained by the comparative analysis of four typical topological constructions. On this basis, three main factors affecting the extrusion pressure of bioceramics materials, namely paste formulation (solvent content), nozzle length-to-diameter ratio, and the extrusion velocity, were selected as the control factors, and a series of experiments were performed using the L27 (313) orthogonal array. The results indicate that all the control factors significantly affected the extrusion pressure, of which the length-to-diameter ratio of nozzle exhibited the greatest effect. The scaffold printed using low-temperature extrusion 3D printing technology exhibited a uniform microstructure following the optimization of the printing parameters, which validated the ability of the process to accurately control the microstructure. The results of the study can be considered as a guide for the 3D printing of high-resolution bone tissue engineering scaffolds and can be employed to further compression mold bioactive polyetheretherketone/hydroxyapatite (PEEK/HA) composites

Research on Quadrant Detector Multi-Spot Position Detection Based on Orthogonal Frequency Division Multiplexing

Free space optical communication is developing towards laser communication networking. A novel method of quadrant detector (QD) multi-spot position detection based on orthogonal frequency division multiplexing (OFDM) is proposed for multi-spot laser communication systems. The mathematical model is constructed, and the Monte Carlo method is used to validate it. The position calculation of three beams incident on QD is simulated. The influence of key parameters on the accuracy of position detection is analyzed when the spots are at the same position and a different position. The results show that when the SNR of the system is 31.74 dB, the radius of the Gauss spot is 2 mm, the number of FFT (fast Fourier transform) points is 1024, and the center of the multi-spot is at the same position of the detector target; the accuracy of signal position detection calculated by the equation is 1.433 μm, and the simulation results are 1.351 μm, 1.354 μm, and 1.389 μm, respectively. When the center position of the multi-spot is at different positions of the detector target, the detection accuracy calculated by the formula is 1.438 μm, 1.433 μm, and 1.434 μm, respectively, and the simulation results are 1.419 μm, 1.387 μm, and 1.346 μm, respectively. The experimental results verify the effectiveness of the proposed multi-target simultaneous detection method. This article proposes a new multi-spot position detection method which can not only achieve one-to-multiple node laser communication but also improve the accuracy of point position detection

Direct Selective Laser Sintering and Melting of Ceramics: A review

Purpose: This paper aims to provide a review on the process of additive manufacturing of ceramic materials, focusing on partial and full melting of ceramic powder by a high-energy laser beam without the use of binders. Design/methodology/approach: Selective laser sintering or melting (SLS/SLM) techniques are first introduced, followed by analysis of results from silica (SiO2), zirconia (ZrO2) and ceramic-reinforced metal matrix composites processed by direct laser sintering and melting. Findings: At the current state of technology, it is still a challenge to fabricate dense ceramic components directly using SLS/SLM. Critical challenges encountered during direct laser melting of ceramic will be discussed, including deposition of ceramic powder layer, interaction between laser and powder particles, dynamic melting and consolidation mechanism of the process and the presence of residual stresses in ceramics processed via SLS/SLM. Originality/value: Despite the challenges, SLS/SLM still has the potential in fabrication of ceramics. Additional research is needed to understand and establish the optimal interaction between the laser beam and ceramic powder bed for full density part fabrication. Looking into the future, other melting-based techniques for ceramic and composites are presented, along with their potential applications