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排序方式: 共有419条查询结果,搜索用时 31 毫秒
1.
A new dual-quantisation sigma-delta modulator is proposed, which introduces an additional feedback path in the input of the second integrator. In this way, unlike other dual-quantisation architectures, larger signal-to-noise ratios can be obtained by means of aggressive noise-shaping, like in a conventional multibit modulator. The proposed modulator is also shown to be more robust against non-idealities than other dual-quantisation architectures. 相似文献
2.
M. Delgado-Pinar J. Mora A. Diez J.L. Cruz M.V. Andres 《Photonics Technology Letters, IEEE》2005,17(3):552-554
We report a wavelength-switchable fiber ring laser that includes a Bragg grating-based acoustooptic superlattice modulator. Wavelength switching of the laser emission is achieved by controlling the peak reflectivity of the different reflection bands that appear on both sides of the Bragg wavelength when a longitudinal acoustic wave propagates along the grating. 相似文献
3.
Linares-Barranco B. Serrano-Gotarredona T. Ramos-Martos J. Ceballos-Caceres J. Mora J.M. Linares-Barranco A. 《IEEE transactions on circuits and systems. I, Regular papers》2004,51(4):649-663
We present a very-large-scale integration continuous-time sinusoidal operational transconductance amplifiers quadrature oscillator fabricated in a standard double-poly 0.8-/spl mu/m CMOS process. The oscillator is tunable in the frequency range from 50 to 130 MHz. The two phases produced by the oscillator show a low-quadrature phase error. A novel current-mode amplitude control scheme is developed that allows for very small amplitudes. Stability of the amplitude control loop is studied as well as design considerations for its optimization. Experimental results are provided. 相似文献
4.
Ionic elastomers based on carboxylated nitrile rubber (XNBR) crosslinked with magnesium oxide (OMg) and filled with layered nanoclays have been prepared. Two types of nanofillers were employed: a commercial one (Cloisite 15 A) and the other prepared in our laboratory (BCA-ODA). The properties of raw and vulcanized compounds have been studied in order to elucidate the effect of layered nanoclays. X-ray diffraction analysis shows that during compounding and crosslinking the macromolecular chains of rubber were intercalated in a commercial nanofiller, whilst our nanoclay was exfoliated. However, this fact does not affect the properties of compounds homogeneously. Vulcanization parameters, Mooney viscosity and decay and rheological properties were affected depending on the filler type. Mechanical properties were not significantly varied, but glass transition temperature and ionic transition temperature were shifted in comparison with those of the unfilled compound. 相似文献
5.
Angel L. Esteban Maria P. Galache Francisco Mora Ernesto Diez Jesus San Fabian 《Journal of computational chemistry》1989,10(7):887-895
An equation is formulated on the basis of theoretical INDO/FPT calculations which describes the angular dependence of the propanic long-range coupling constant 4JMeH in substituted HCCCH3 fragments. This equation is a truncated Fourier series in the torsion angle ?, HCCMe, which takes into account the dependence of the Fourier coefficients on the bond angle θ, CCMe. The substituent effects are assumed to be additive. Some parameters in the equation may be obtained from the 4JMeH couplings in propane and neopentane derivatives. The calculated effect upon 4JMeH of changes in the bond angle θ is significant and it seems to be in part the cause of some effects which have been attributed to conformational dependence. 相似文献
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Stephen de Mora Jean-Pierre Villeneuve Eric Wyse 《Accreditation and quality assurance》2007,12(11):587-592
Aspects of the International Atomic Energy Agency (IAEA) Analytical Quality Control Services (AQCS) for marine environmental
studies are discussed, focusing on recent laboratory performance studies (LPS) and the production of reference materials for
trace metals and organic compounds in various marine matrices. The IAEA has organized seventeen global interlaboratory studies
for a range of organic contaminants. Of note has been the inclusion of numerous polychlorinated biphenyl congeners (PCBs)
and some sterols of anthropogenic origin. Concurrently, there have been eleven worldwide intercomparison exercises for trace
metals in the marine environment, most of which included methylmercury. Although such interlaboratory studies can help improve
performance in individual laboratories and regional laboratory networks, the results reveal that problems remain in the determination
of some metals and many organic contaminants. 相似文献