Formal degree and existence of stable arithmetic lattices of cuspidal representations ofp-adic reductive groups

Research at MSRI supported in part by NSF Grant DMS-812079-05     

Certain problems of the approximation of functions in two variables by Fourier-Hermite sums in the space L 2(Γ², e -x ² -y ²)

Summary We give an exact estimate of the deviation of the "triangular" partial sums of the double Fourier-Hermite series of functions of the class L^r₂(D) in the space L₂(Γ2, e^-x2-y2).     

Uniqueness of the group topology of some homeomorphism groups

In this paper, we generalize a theorem of Kallman [2, Theorem 1.1] and we resolve the unsettled case there.     

基于超分子结构共掺杂纳米复合薄膜的制备与荧光特性

为改善功能分了的特性,提出一种基于金属纳米粒子-偶氮染料复合物共掺杂超分子结构功能材料的设计新方法.并依照此方法制备出复合材料,观测了其显微结构,测量了其紫外-可见光吸收,研究了该超分子结构复合体系的荧光特性.实验发现,由于金属银纳米粒子的掺杂,使得超分子结构复合体系中功能分子甲基橙在溶液态体系的荧光强度增强近5倍,而在两种不同结构(共混结构和包覆结构)的薄膜态超分子结构体系中,其荧光强度分别被猝灭15%和20%.研究结果表明,复合膜中采用超分子结构完全能够改善功能分子的特性.     

Thickness induced transversal percolation in Pt-Al2O3 nano-composites

Investigations of thickness induced percolation process in Pt_ξ-Al₂O₃ nano-composites were carried out using grazing angle X-ray scattering. It is shown that the morphological characteristics of the nano-scaled Pt particles change significantly within the growth transversal direction. The initially non percolated two phases Pt_ξ-Al₂O₃ nano-composites show a noteworthy tendency to a percolated morphology with a gradual transversal increase of Pt nano-particles' average diameter in addition to the increase of the Pt nano-particles' poly-dispersity. This transversal morphological evolution is followed by a percolation phenomenon of the Pt nano-particles for a thickness of about ∼119.5 nm. This transversal morphological evolution seems to corroborate far too much with a columnar growth process.     

Resonance Raman scattering by excitonic polaritons in CuGaS2

Resonance Raman scattering by exciton polaritons in crystals of CuGaS₂ under excitation with the 4880 and 4765 Å lines of an Ar⁺ laser at 9 K is studied. Lines of one-and two-phonon scattering of excitonic polaritons are found and studied. It is shown that the 1LO and 2LO phonons are arranged in accordance with their energies as the Stokes shifts move farther away from the excitation energy.     

Similarity and the structure of unital matrix quadratic trinomials with pairwise different characteristic roots

The normal form of certain polynomial matrices is found.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademii Nauk SSSR, Vol. 175, pp. 63–68, 1989.     

Envelope expansion methods for speech enhancement

The last decade has seen increasing interest in techniques for the enhancement of digital speech signals. Significant gains have been made in terms of signal-to-noise ratio (SNR) and quality, but few techniques have produced improvements in intelligibility. A method for speech enhancement based on nonlinear expansion of the spectral envelope is presented. The expansion is consistent with both the long-term spectrum of the speech and with the probability that speech is present in a given sample. Objective SNR measures are used to compare this algorithm with the well-known spectral subtraction method, with an alternative expansion scheme, and with limiting SNRs resulting from perfect recovery of the amplitude spectrum. For the purpose of intelligibility assessments, a simplified version of the algorithm has been implemented on a Texas Instruments TMS320-C25 system. Listening trials with this real-time system, conducted using a modified rhyme test, have produced small, but consistent, improvements in articulation scores.