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101.
102.
Cochlear implants provide users with limited spectral and temporal information. In this study, the amount of spectral and temporal information was systematically varied through simulations of cochlear implant processors using a noise-excited vocoder. Spectral information was controlled by varying the number of channels between 1 and 16, and temporal information was controlled by varying the lowpass cutoff frequencies of the envelope extractors from 1 to 512 Hz. Consonants and vowels processed using those conditions were presented to seven normal-hearing native-English-speaking listeners for identification. The results demonstrated that both spectral and temporal cues were important for consonant and vowel recognition with the spectral cues having a greater effect than the temporal cues for the ranges of numbers of channels and lowpass cutoff frequencies tested. The lowpass cutoff for asymptotic performance in consonant and vowel recognition was 16 and 4 Hz, respectively. The number of channels at which performance plateaued for consonants and vowels was 8 and 12, respectively. Within the above-mentioned ranges of lowpass cutoff frequency and number of channels, the temporal and spectral cues showed a tradeoff for phoneme recognition. Information transfer analyses showed different relative contributions of spectral and temporal cues in the perception of various phonetic/acoustic features. 相似文献
103.
Phase-sensitive optical low-coherence reflectometry technique applied to the characterization of photonic crystal fiber properties 总被引:3,自引:0,他引:3
Palavicini C Jaouën Y Debarge G Kerrinckx E Quiquempois Y Douay M Lepers C Obaton AF Melin G 《Optics letters》2005,30(4):361-363
Localized measurements of group-velocity dispersion and birefringence of photonic crystal fibers are achieved with a phase-sensitive optical low-coherence reflectometry technique. This technique is efficient for fiber samples no longer than 1 m. Theoretical simulations are in good agreement with experimental results. As a result, the stress-induced birefringence proves to be at most 1 order of magnitude below the geometrical-shape birefringence. 相似文献
104.
105.
Lennard?P?NilesEmail author Kristen?J?Armstrong Lyda?M?Rincón Castro Chung?V?Dao Rohita?Sharma Catherine?R?McMillan Laurie?C?Doering David?L?Kirkham 《BMC neuroscience》2004,5(1):41
Background
In order to optimize the potential benefits of neural stem cell (NSC) transplantation for the treatment of neurodegenerative disorders, it is necessary to understand their biological characteristics. Although neurotrophin transduction strategies are promising, alternative approaches such as the modulation of intrinsic neurotrophin expression by NSCs, could also be beneficial. Therefore, utilizing the C17.2 neural stem cell line, we have examined the expression of selected neurotrophic factors under different in vitro conditions. In view of recent evidence suggesting a role for the pineal hormone melatonin in vertebrate development, it was also of interest to determine whether its G protein-coupled MT1 and MT2 receptors are expressed in NSCs. 相似文献106.
A speciation scheme involving the use of flame atomic absorption spectrometry (FAAS) and differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV) techniques was applied to studies of nickel and chromium in wastewater from a nickel-chrome electroplating plant. Dimethylglyoxime (DMG) and diethylenetriaminepentaacetic acid (DTPA) were employed as complexing agents for adsorptive voltammetric determination of Ni and Cr, respectively. Cr(III) and Cr(VI) were determined by exploiting differences in their reactivity towards DTPA at HMDE. Total dissolved metal content was in the range 2906-3141 and 30.7-31.2 mg l−1 for Ni and Cr, respectively. A higher percentage of the metal was present as labile species (mean value of 67.9% for Ni and 79.8% for Cr) suggesting that strongly binding ligands are not ubiquitous in the sample. About 77.8% of Cr was found to exist in the higher oxidization state, Cr(IV). Results on effect of dilution on lability of the metal forms in the sample using DPAdCSV showed slight peak shifts to a more negative (cathodic) value by −0.036 V for Ni and −0.180 V for Cr with a dilution factor of 100, while peak intensity (cathodic current) remained fairly constant. 相似文献
107.
Rainer Buckdahn Marc Quincampoix Catherine Rainer Aurel Răşcanu 《Applied Mathematics and Optimization》2004,49(2):99-112
We study the existence of a
solution of controlled stochastic
differential equations remaining in a given set of constraints
at any time smaller than the exit time of a given open set.
We also investigate the small time attainability of a given closed
set K, i.e., the property that, for all arbitrary small time horizon T
and for all initial condition in a sufficiently small
neighborhood of K,
there exists
a solution to the controlled stochastic
differential equation which reaches K before T. 相似文献
108.
We present a generalized frequency selection method for N-frequency interferometry to form an optimum geometric series at synthetic wavelengths. The absolute range that is measurable is bounded by the number of beat frequency operations, phase noise, and the number of wavelengths used to form the geometric series of synthetic wavelengths. Theoretical predictions are compared with experimental results from a full-field fringe projector. A comparison of this technique with the method of excess fractions shows orders-of-magnitude faster processing with similar measurement reliability. 相似文献
109.
Corriu RJ Mehdi A Reye C Thieuleux C 《Chemical communications (Cambridge, England)》2004,(12):1440-1441
The co-condensation of water soluble sodium silicate and different organotrialkoxysilanes in the presence of non-ionic triblock copolymers under acidic conditions provides a very convenient, general and economic one step synthesis methodology for the preparation of organically functionalised mesostructured silica. 相似文献
110.
We demonstrate that a highly confined plasma inclusion is formed inside a micrometric water droplet that is excited by a femtosecond laser. An 800-nm laser pulse generates a plasma inclusion by laser-induced breakdown that is subsequently probed by the elastic scattering of a second (400-nm) time-delayed ultrashort pulse. For a 25-microm-radius droplet and an incident intensity of 7 x 10(12) W/cm2 the radius of the highly localized plasma is 1.9 +/- 0.4 microm. We probed the plasma formation dynamics on femtosecond time scales by varying the delay between the pump and the probe pulses. Good agreement with numerical simulations of the process was found. 相似文献