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101.
102.
103.
J. Stankowski 《Applied magnetic resonance》2004,27(1-2):251-258
Microwave nonresonant dissipation observed around zero field makes a powerful method in characterizing superconducting state (to determineT C,H C1,H CJ parameters). This review shows several successful applications of magnetically modulated microwave absorption (MMMA). MMMA enables to study MgB2 superconducting nanoregions embedded in the Mg host structure. Application of MMMA to study intercalation of fullerence enabled the observation of a new superconducting phase. The pressure effect dT C/dp has been studied below the percolation threshold in YBaCuO/PST composites. The local temperature of the Josephson junction measured by the MMMA technique showed that a granular superconductor consists of two phases: host phase and Josephson junction system. MMMA has been applied lately to separate the giant magnetoresistance from the magnetization effect in differential hysteresis loops. 相似文献
104.
Effect of nickel coating on electrochemical performance of graphite anodes for lithium ion batteries
Among the different materials often studied and proposed as negative electrodes for lithium-ion batteries, graphite anodes
are the most used in commercial batteries. For this study, synthetic graphite was tested. During the first discharge 0.2 Li
ions were consumed for the formation of the SEI film and the capacity reaches about 387 mAh/g. But at the end of the first
charge only 72% of the initial charge was recovered (the reversible capacity is about 279 mAh/g). In order to improve this
performance we have deposited metallic nickel on graphite with the intention to obtain a homogeneous thin layer able to modify
the nature of the SEI film, to allow the diffusion of lithium ions through the protective layer, and also to increase the
performance of graphite electrodes. The results show a decrease of the irreversible capacity loss (16% instead of 28% for
pure graphite electrodes) as well as better cycleability for a nickel-deposited graphite electrode with only 11% weight ratio
of nickel. On the other hand, an increase of the nickel content decreases this performance. 相似文献
105.
Fundamentals of the direct measurement of sound intensity and practical applications 总被引:1,自引:0,他引:1
Sound intensity is a measure of the magnitude and direction of the flow of sound energy. Developments in sound intensity measurement capabilities in the last quarter century have occurred because of several reasons. The main ones include the derivation of the cross-spectral formulation for sound intensity and developments in digital signal processing. This paper begins with a brief historical introduction of sound intensity measurements. Then elementary theory for sound intensity is presented. A section on sound intensity measurements is then included. The next section of the paper discusses sources of measurement error; the major sources of error are described in some detail. The paper continues with a discussion of the main applications of sound intensity measurements: sound power determination, noise source identification, and transmission loss measurements. The paper concludes with a discussion of ISO and ANSI intensity related standards and relevant references. 相似文献
106.
107.
Pascher W. Den Besten J. H. Caprioli D. Leijtens X. Smit M. van Dijk R. 《Optical and Quantum Electronics》2003,35(4-5):453-464
Based on a rigorous vectorial analysis, a fast travelling-wave Mach–Zehnder modulator is modelled and designed. The cross-section of the semiconductor layer stack and the lossy electrodes are carefully modelled using the method of lines in order to investigate propagation characteristics, velocity and losses. This yields an accurate microwave and optical field distribution to explain the behaviour of the component. In order to enhance the modulation efficiency, design curves are derived and the cross-sectional dimensions for minimum microwave loss are determined. The loss of the optimized modulator agrees very well with small-signal measurements up to 40 GHz and HFSS simulations. The layerstack of the fabricated device is suitable for integration with InP multi-wavelength lasers. 相似文献
108.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
109.
Mrio J. Edmundo 《Mathematical Logic Quarterly》2005,51(6):639-641
We show that if G is a definably compact, definably connected definable group defined in an arbitrary o‐minimal structure, then G is divisible. Furthermore, if G is defined in an o‐minimal expansion of a field, k ∈ ? and pk : G → G is the definable map given by pk (x ) = xk for all x ∈ G , then we have |(pk )–1(x )| ≥ kr for all x ∈ G , where r > 0 is the maximal dimension of abelian definable subgroups of G . (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
110.
The results of a numerical study are described in which the interactions of a primary shock wave with a secondary diaphragm
in expansion tubes are taken into account. The developing wave pattern in the interacting process of the shock with a secondary
diaphragm are visualized by many kinds of figures (e.g., the time-distance diagrams of the wave phenomena on the axis, the
acoustic impedance contours, and the time histories of the pitot pressure on the axis), and the influences of the shape and
rupture process of the diaphragm on the quality of the test gas are explored. 相似文献