共查询到20条相似文献,搜索用时 15 毫秒
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E.A. Neppiras 《Ultrasonics》1984,22(1):25-28
Acoustic cavitation has been an active area of research for at least 30 years and interest in the subject shows no sign of diminishing. Cavitation may occur whenever high intensity ultrasound is applied to liquids, for example in such important applications as sonar, industrial processing and bio-medical research. Future issues will carry a series of articles reviewing the physics and technology of acoustic cavitation, each contributed by a well-known specialist. The present introductory article is a preface to the series, covering background history, explaining the scope of the subject and defining terms in common use. Also included is a list of the major sources of reference presently available, in the form of books, reviews and collections of papers. 相似文献
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利用基于密度泛函理论的第一性原理,研究了Cu:Fe:Mg:LiNbO3晶体及对比组的电子结构和光学特性.研究显示,单掺铜或铁铌酸锂晶体的杂质能级分别由Cu 3d轨道或Fe 3d轨道贡献,禁带宽度分别为3.45和3.42 eV;铜、铁共掺铌酸锂晶体杂质能级由Cu和Fe的3d轨道共同贡献,禁带宽度为3.24 eV,吸收峰分别在3.01,2.53和1.36 eV处;Cu:Fe:Mg:LiNbO3晶体中Mg^2+浓度低于阈值或高于阈值(阈值约为6.0 mol%)的禁带宽度分别为2.89 eV或3.30 eV,吸收峰分别位于2.45 eV,1.89 eV或2.89 eV,2.59 eV,2.24 eV.Mg^2+浓度高于阈值,会使吸收边较低于阈值情况红移;并使得部分Fe^3+占Nb位,引起晶体场改变,从而改变吸收峰位置和强度.双光存储应用中可选取2.9 eV作为擦除光,2.5 eV作为读取和写入光,选取Mg^2+浓度达到阈值的三掺晶体在增加动态范围和灵敏度等参量以及优化再现图像的质量等方面更具优势. 相似文献
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分别测量了Er YCOB晶体和ErYb YCOB晶体的室温吸收光谱.讨论了Yb3+离子对Er3+离子的敏化作用. 相似文献
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The radiothermoluminescence characteristics have been studied for a number of (ZnS:CdS::Ag:Ni:Co) phosphors, with various cobalt impurity contents, after exposure to90Sr beta-rays at room temperature. Thermoluminescent spectra show a peak wavelength of 7000 Å, which remains unchanged with increase in cobalt concentration. Thermoluminescence curves exhibit a single well-defined peak appearing at temperatures far above room temperature. This peak shifts to lower temperatures with increasing cobalt content. The relation between thermoluminescence response and dose is linear over the dose range of 1 to 500 rads. Thermoluminescence measurements made after storing the irradiated phosphor for 48 hours in dark have revealed an information loss of 4% over this storage period. The radiothermoluminescence characteristics, storage capacity and storage stability of these sulphide phosphors compete reasonably with those of lithium fluoride over the dose range of 1 rad to 500 rads. 相似文献
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Fourier transform profilometry: : a review 总被引:4,自引:0,他引:4
Fourier transform profilometry is one of the popular non-contact 3-D measurement methods, where a Ronchi grating or sinusoidal grating is projected onto a diffuse three-dimensional surface, and the resulting deformed grating image is detected by a CCD camera and processed by a computer. This method requires only one frame (or two frames) of the deformed fringe pattern in some algorithms to retrieve the surface of measured object, so it has obvious advantage for real time data acquisition and 3-D measurement of dynamic process. In this paper, we review some algorithms in FTP, discuss some important problems, including frequency spectra overlapping, phase unwrapping, sampling, and 3-D measurement of dynamic process. With the development of computer hardware and software and availability of high-resolution image grabber, FTP method will be a promising one for acquiring 3-D data of object, and more and more researchers pay attention to it. 相似文献
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Martin Dressel Olivier Klein Steve Donovan George Grüner 《International Journal of Infrared and Millimeter Waves》1993,14(12):2489-2517
The resonant cavity perturbation method as described in the preceding two parts of this series is applied to study the electrodynamical properties of different materials in the microwave and millimeter wave spectral range. We briefly discuss the relevant uncertainties which are asociated with the different measurement techniques and we find that employing the amplitude technique it is possible to measure both the width and frequency to nearly the same precision. We then demonstrate the broad range of applicability of this technique by showing results obtained on several different materials, ranging from an insulator to a superconductor. The performance limitations of this technique are discussed in detail. 相似文献
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Spühler GJ Krainer L Innerhofer E Paschotta R Weingarten KJ Keller U 《Optics letters》2005,30(3):263-265
We report on a simple diode-pumped passively mode-locked Er:Yb:glass laser generating transform-limited 1536-nm solitons of 255-fs duration with a repetition rate of 50 MHz and average power of 58 mW. We also discuss timing jitter and the trade-off between short pulses and high output power in these lasers. 相似文献
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The emission spectra of calcium sulphide phosphors activated with bismuth, thulium, and both together are studied in the spectral range of 4000 Å to 8000 Å. The results indicate resonance transfer of excitation energy from Bi to Tm. Sensitizer to sensitizer transfer also appears to be appreciable. A plausible energy level diagram is proposed to explain the sensitization mechanism. 相似文献
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Olivier Klein Steve Donovan Martin Dressel George Grüner 《International Journal of Infrared and Millimeter Waves》1993,14(12):2423-2457
This report reviews the analysis used to extract the complex conductivity of a compound from a microwave cavity perturbation measurement. We intend to present a generalized treatment valid for any spheroidally shaped sample of arbitrary conductivity which is placed at either the electric or magnetic field antinode of the cavity. To begin with, we establish the relationship between the measured parameters and the conductivity for a spherical sample. Next, we extend these results to the case of spheroids; and for the first time, we cover all different configurations that one can possibly use to study an arbitrary conducting sample inside a cavity: in particular, all possible orientations of the sample with respect to the applied field are solved. 相似文献
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F. R. Ling B. Wang T. Geng S. Q. Fang W. Yuan D. D. Teng C. X. Guan 《Optics & Laser Technology》2004,36(7):541-544
In this paper experimental studies of nonvolatile photorefractive holographic recording in Ce:Cu:LiNbO3 crystals doped with Sc(0,1,2,3 mol%) were carried out. The Sc:Ce:Cu:LiNbO3 crystals were grown by the Czochralski method and oxidized in Nb2O5 powders. The nonvolatile holographic recording in Sc:Ce:Cu:LiNbO3 crystals was realized by the two-photon fixed method. We found that the recording time of Sc:Ce:Cu:LiNbO3 crystal became shorter with the increase of Sc doping concentration, especially doping with Sc(3 mol%), which exceeds the so-called threshold, and there was little loss of nonvolatile diffraction efficiencies between Sc(3 mol%):Ce:Cu:LiNbO3 and Ce:Cu:LiNbO3 crystals. 相似文献
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Tuan Tran-Anh Stefan Hansel Alexander Kirste Hans-Ulrich Mueller Michael von Ortenberg 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):444
Mercury selenide and its ternary and quaternary modifications in the form Hg(A,B)Se with A, B magnetic ions, provide an interesting semiconductor family featuring different kinds of correlation effects. These effects manifest themselves already in three-dimensional, quasi-two-dimensional, and quasi-one-dimensional structures. We have succeeded now in fabricating HgSe:Fe quantum dots using three different growing procedures based on molecular beam epitaxy: (a) Stranski–Krastanov growth; (b) thermally activated surface reorganization; (c) pit filling. The special feature of the HgSe:Fe dots is the intrinsic population of the dot states by electrons, where a large amount of about 50–500 electrons form a many-electron system within a single dot. The formation of the dots was controlled in situ by RHEED. The morphology of the resulting structures was characterized by AFM. Subsequently, the electronic properties of the dots were investigated by megagauss magneto spectroscopy, indicating the presence of strong correlation effects as manifested in a 50% increase of the cyclotron mass in respect to that of structures with a higher dimensionality. 相似文献
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Shahzada Ahmad 《Ionics》2009,15(3):309-321
Polymer electrolytes are an important component of many electrochemical devices. This paper reviews state-of-the-art of the
electrochemical and physical properties of polymer electrolytes. This review mainly encompasses the properties of different
salts, solvents, and polymer hosts, which are encaged in liquid electrolytes. The additions of filler in polymer electrolytes
result in composite polymer electrolytes, having high mechanical integrity and ionic conductivity, that are ideal electrolyte
for these applications. The next generation state-of-the-art room-temperature ionic liquids based electrolytes, which are
far superior to corresponding nonionic solvent-based electrolytes, are also discussed.
An erratum to this article can be found at 相似文献