Statistical analysis of the autoregressive modeling of reverberant speech

Hands-free speech input is required in many modern telecommunication applications that employ autoregressive (AR) techniques such as linear predictive coding. When the hands-free input is obtained in enclosed reverberant spaces such as typical office rooms, the speech signal is distorted by the room transfer function. This paper utilizes theoretical results from statistical room acoustics to analyze the AR modeling of speech under these reverberant conditions. Three cases are considered: (i) AR coefficients calculated from a single observation; (ii) AR coefficients calculated jointly from an M-channel observation (M > 1); and (iii) AR coefficients calculated from the output of a delay-and sum beamformer. The statistical analysis, with supporting simulations, shows that the spatial expectation of the AR coefficients for cases (i) and (ii) are approximately equal to those from the original speech, while for case (iii) there is a discrepancy due to spatial correlation between the microphones which can be significant. It is subsequently demonstrated that at each individual source-microphone position (without spatial expectation), the M-channel AR coefficients from case (ii) provide the best approximation to the clean speech coefficients when microphones are closely spaced (<0.3m).     

Host-guest complexes of carotenoids with beta-glycyrrhizic acid

The structure, stability, and reactivity of the host-guest complexes between a set of carotenoids and the triterpene glycoside, beta-glycyrrhizic acid (GA), were investigated by different physicochemical techniques: high-performance liquid chromatography, optical absorption, and fluorescence spectroscopy. It has been demonstrated recently that the molecular complexes of GA with a number of drugs are characterized by reduced toxicity and increased therapeutic activity of these drugs. In the present work it was found that carotenoids form 1:2 complexes with GA in aqueous solutions as well as in polar organic solvents, methanol, acetonitrile, and dimethylsulfoxide. We assume that the structure of the complex is a cycliclike dimer of GA encapsulating a carotenoid molecule. The stability constants in all solvents are near 10(4) M(-1). In addition, GA forms inclusion complexes with carotenoid radical cations, which results in their stabilization. Complex formation (a) decreases the rate of electron transfer from carotenoids to electron acceptors (Fe3+ or quinone) and (b) considerably increases the lifetime of the carotenoid-quinone charge-transfer complex and the yield of the major product (a carotenoid-quinone adduct). A thermodynamic study shows that hydrophobic interactions are the main driving force of the carotenoid-GA complex formation. These results are important for understanding both the nature of GA complexes and the influence of GA on the therapeutic activity of some drugs. Furthermore, carotenoid-GA complexes could be used for the design of artificial light-harvesting, photoredox, and catalytic systems.     

Superglass phase of 4He

We study different solid phases of 4He, by means of path integral Monte Carlo simulations based on a recently developed worm algorithm. Our study includes simulations that start off from a high- gas phase, which is then "quenched" down to T = 0.2 K. The low-T properties of the system crucially depend on the initial state. While an ideal hcp crystal is a clear-cut insulator, the disordered system freezes into a superglass, i.e., a metastable amorphous solid featuring off-diagonal long-range order and superfluidity.     

Entropy enhancement and black hole microstates

We show that the entropy of fluctuating two-charge supertubes placed in three-charge scaling microstate solutions depends on their "effective" charges, which in strong magnetic fields can be much larger than their charges. This leads to a much larger entropy than one naively would expect. Since fluctuating supertubes source smooth geometries in certain duality frames, we propose that such an entropy enhancement mechanism might lead to a black-hole-like entropy coming entirely from configurations that are smooth and horizonless in the regime of parameters where the classical black hole exists.     

Modified method of simplest equation and its application to nonlinear PDEs

We search for traveling-wave solutions of the class of PDEswhere A_p(Q),B_r(Q),C_s(Q),D_u(Q) and F(Q) are polynomials of Q. The basis of the investigation is a modification of the method of simplest equation. The equations of Bernoulli, Riccati and the extended tanh-function equation are used as simplest equations. The obtained general results are illustrated by obtaining exact solutions of versions of the generalized Kuramoto-Sivashinsky equation, reaction-diffusion equation with density-dependent diffusion, and the reaction-telegraph equation.     

Synthesis and Photophysical Properties of Alkoxysilyl Derivatives of Dibenzoylmethanatoboron Difluoride

Alkoxysilyl derivatives of dibenzoylmethanatoboron difluoride (DBMBF₂) are synthesized by the hydrosilylation reaction of the corresponding O‐allyl derivatives of DBMBF₂ with triethoxysilane. The photophysical properties of the synthesized O‐allyl and alkoxysilyl derivatives are investigated. It is found that the absorption and fluorescence spectra of the DBMBF₂ derivatives essentially depend on the position of the O‐allyl or O‐propyl alkoxysilyl substituent. The highest fluorescence quantum yield is obtained for the para‐position, whereas the substitution at the meta‐position gives the largest bathochromic shift in the fluorescence spectrum. Density functional theory calculations of the structures and time‐dependent density functional theory calculations of the gas‐phase excitation and emission energies of alkoxysilyl derivatives are performed at the PBE0/SVP level of theory. Some spectral features of para‐, ortho‐, and meta‐substituted derivatives can be adequately explained by the overlapping of two absorption bands.     

Local Derivative-Free Approximation of Computationally Expensive Posterior Densities

Bayesian inference using Markov chain Monte Carlo (MCMC) is computationally prohibitive when the posterior density of interest, π, is computationally expensive to evaluate. We develop a derivative-free algorithm GRIMA to accurately approximate π by interpolation over its high-probability density (HPD) region, which is initially unknown. Our local approach reduces the waste of computational budget on approximation of π in the low-probability region, which is inherent in global experimental designs. However, estimation of the HPD region is nontrivial when derivatives of π are not available or are not informative about the shape of the HPD region. Without relying on derivatives, GRIMA iterates (a) sequential knot selection over the estimated HPD region of π to refine the surrogate posterior and (b) re-estimation of the HPD region using an MCMC sample from the updated surrogate density, which is inexpensive to obtain. GRIMA is applicable to approximation of general unnormalized posterior densities. To determine the range of tractable problem dimensions, we conduct simulation experiments on test densities with linear and nonlinear component-wise dependence, skewness, kurtosis and multimodality. Subsequently, we use GRIMA in a case study to calibrate a computationally intensive nonlinear regression model to real data from the Town Brook watershed. Supplemental materials for this article are available online.     

Small Data Scattering for the Nonlinear Schrödinger Equation on Product Spaces

We consider the cubic nonlinear Schrödinger equation, posed on ? ⁿ  × M, where M is a compact Riemannian manifold and n ≥ 2. We prove that under a suitable smallness in Sobolev spaces condition on the data there exists a unique global solution which scatters to a free solution for large times.