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21.
A single-channel algorithm is proposed for noise reduction in cochlear implants. The proposed algorithm is based on subspace principles and projects the noisy speech vector onto "signal" and "noise" subspaces. An estimate of the clean signal is made by retaining only the components in the signal subspace. The performance of the subspace reduction algorithm is evaluated using 14 subjects wearing the Clarion device. Results indicated that the subspace algorithm produced significant improvements in sentence recognition scores compared to the subjects' daily strategy, at least in stationary noise. Further work is needed to extend the subspace algorithm to nonstationary noise environments. 相似文献
22.
Lobo J Michel EG Bachmann AR Speller S Kuntze J Ortega JE 《Physical review letters》2004,93(13):137602
Stepped Cu nanostripes with varying terrace widths are self-assembled during Ag-induced periodic faceting of vicinal Cu(111). By changing Ag coverage the average terrace size within individual Cu stripes is readily tuned, making it possible to select the one-dimensional or two-dimensional character of surface states. Furthermore, the average terrace size can be smoothly switched from 10 to 30 A, thereby tracking the transition from step-lattice, quasi-two-dimensional umklapp bands to terrace-confined one-dimensional quantum well states. 相似文献
23.
We show that the formation of a vortex lattice in a weakly interacting Bose condensed gas can be modeled with the nonlinear Schr?dinger equation for both T=0 and finite temperatures without the need for an explicit damping term. Applying a weak rotating anisotropic harmonic potential, we find numerically that the turbulent dynamics of the field produces an effective dissipation of the vortex motion and leads to the formation of a lattice. For T=0, this turbulent dynamics is triggered by a rotational dynamic instability of the condensate. For finite temperatures, noise is present at the start of the simulation and allows the formation of a vortex lattice at a lower rotation frequency, the Landau frequency. These two regimes have different vortex dynamics. We show that the multimode interpretation of the classical field is essential. 相似文献
24.
An oil-soluble hexadecyl pyrene (HDP) probe is used to monitor coalescence of hexadecane oil-in-water emulsions, during emulsification, in stirred systems and in a high-pressure homogenizer (microfluidizer), when small molecule surfactants are used as emulsifiers. The effect of sodium dodecyl sulfate concentration and salt concentration on the amount of coalescence and final drop size is studied. The behavior of oil-soluble surfactants and mixtures of oil-soluble and water-soluble surfactants on emulsification performance is also discussed. For high-pressure homogenizers, the drop sizes obtained are found to depend mostly on the ability of surfactants to stabilize the drops against coalescence, rather than their ability to reduce the interfacial tension. Increasing oil phase fractions increase the coalescence rate, because of the increase in collision frequency, which, in turn, impacts the drop size of the homogenized emulsion. 相似文献
25.
Zeolite Na-ETS-10 is studied by the Raman and IR spectroscopy methods. The ethylene polymerization reaction on this zeolite under UV irradiation is studied by IR spectroscopy. It is found that this reaction proceeds at room temperature yielding polyethylene. The experimental data are analyzed using 2D correlation spectroscopy. 相似文献
26.
27.
Lobo AO Corat MA Ramos SC Matsushima JT Granato AE Pacheco-Soares C Corat EJ 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18308-18314
A method for the electrodeposition of hydroxyapatite films on superhydrophilic vertically aligned multiwalled carbon nanotubes is presented. The formation of a thin homogeneous film with high crystallinity was observed without any thermal treatment and with bioactivity properties that accelerate the in vitro biomineralization process and osteoblast adhesion. 相似文献
28.
J. P. Sousa e Silva J. M. Sousa Lobo 《Journal of Thermal Analysis and Calorimetry》2010,102(1):317-321
Study of excipients incompatibility with drugs in an early phase of pharmaceutical development is still a persistent difficulty
within the pharmaceutical industry. We examine here the compatibility between an experimental drug (nebicapone) and common
excipients using differential scanning calorimetry (DSC), high sensitivity DSC (HSDSC) and a conventional heat stress test.
The results obtained indicate that nebicapone may be compatible with lactose monohydrate and sodium croscarmellose but is
incompatible with magnesium stearate. This study concludes that HSDSC, in stepwise isothermal mode, may be used as a potential
tool for detecting excipient incompatibilities. 相似文献
29.
30.
A. Arutyunov V. Dykhta F. Lobo Pereira 《Journal of Optimization Theory and Applications》2005,124(1):55-77
First-order and second-order necessary conditions of optimality for an impulsive control problem that remain informative for abnormal control processes are presented and derived. One of the main features of these conditions is that no a priori normality assumptions are required. This feature follows from the fact that these conditions rely on an extremal principle which is proved for an abstract minimization problem with equality constraints, inequality constraints, and constraints given by an inclusion in a convex cone. Two simple examples illustrate the power of the main result.The first author was partially supported by the Russian Foundation for Basic Research Grant 02-01-00334. The second author was partially supported by the Russian Foundation for Basic Research Grant 00-01-00869. The third author was partially supported by Fundacao para a Ciencia e Tecnologia and by INVOTAN Grant. 相似文献