Multiple source direction-of-arrival estimation applicable under near-, far-, and mixed-field scenarios.

Traditionally, direction-of-arrival (DOA) estimations under near- and far-field scenarios are treated as independent tasks based on the corresponding acoustic model, hence necessitating a proper soundfield detector as an upstream processing tool, whereas there may not be a distinct boundary between different soundfield types, especially the mixed-field scenarios where both near- and far-field sources coexist simultaneously. To handle this issue, this article investigates a multisource DOA estimator that equally localizes multiple near-, far-, and mixed-field sources, not requiring any specialized adjustments. We (i) define a signal-invariant multichannel feature denoted generalized relative harmonic coefficients in the spherical harmonics domain; (ii) derive the analytical expression of this feature and summarize its unique properties, exhibiting consistence for both near- and far-field sources; (iii) estimate source elevation and azimuth using the magnitude and phase parts of this feature, respectively; (iv) detect single-source dominated periods from the mixed measurements based on an investigated distance measure; and (v) count the number of sources and localize their DOAs by clustering the single-source dominated estimates.

Closed-form multiple source direction-of-arrival estimator under reverberant environments.

Accurate direction-of-arrival (DOA) estimation of multiple sources, simultaneously active in a reverberant environment, remains a challenge, as the multi-path acoustic reflections and overlapped periods dramatically distort the direct-path wave propagation. This article proposes a prominent solution localizing multiple sources in a reverberant environment using closed-form estimates, circumventing any exhaustive search over the two-dimensional directional space. Apart from a low complexity cost, the algorithm has robustness to reverberant, inactive, and overlapped periods and an ease of operation in practice, achieving sufficient accuracy compared to state-of-the-art approaches.

Colorless to Multicolored, Fast Switching, and Highly Stable Electrochromic Devices Based on Thermally Cross-Linking Copolymer.

Transparent-to-colored electrochromic devices exhibit promising application prospects and have gained popularity. Herein, two triphenylamine derivatives TPA-OCH and TPA-CN with styryl moieties and different donor or acceptor units were designed and synthesized to further prepare solvent-resistant thermally cross-linking polymer P(TPA-OCH) and P(TPA-CN) without any additional initiator. P(TPA-OCH) and P(TPA-CN) possess two pairs of redox peaks, and P(TPA-OCH) shows a lower onset oxidation potential compared to P(TPA-CN) because of the pendent donor unit.

An improved non-Cartesian partially parallel imaging by exploiting artificial sparsity.

Purpose: To improve the performance of non-Cartesian partially parallel imaging (PPI) by exploiting artificial sparsity, the generalized autocalibrating partially parallel acquisitions (GRAPPA) operator for wider band lines (GROWL) is taken as a specific example for explanation.

Theory: This work is based on the GRAPPA-like PPI having an improved performance when the to-be-reconstructed image is sparse in the image domain.

Methods: A systematic scheme is proposed to artificially generate the sparse image for non-Cartesian trajectory.

Passive shimming of a superconducting magnet using the L1-norm regularized least square algorithm.

The uniformity of the static magnetic field B0 is of prime importance for an MRI system. The passive shimming technique is usually applied to improve the uniformity of the static field by optimizing the layout of a series of steel shims. The steel pieces are fixed in the drawers in the inner bore of the superconducting magnet, and produce a magnetizing field in the imaging region to compensate for the inhomogeneity of the B0 field.