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951.
Given one or more vibrational modes of a membrane, the free vibration equation can be applied to infer the mass surface density. This paper considers determining the surface density of an inhomogeneous membrane from digitized holographic projections (interferograms) of the modeshapes. Spatially discrete numerical models of the membrane surface are presented, which can be used to solve both forward and inverse vibration problems. The accuracy of the discrete models is examined for exactly solvable free vibration problems involving inhomogeneous membranes. For the solution of the inverse problem, error estimates are given for the mass surface density deduced from modeshape interferograms. The practicability of the method is investigated using simulated experimental data for membranes with composite and continuously inhomogeneous density profiles. Strategies are discussed for reducing errors in the reconstructed densities. 相似文献
952.
S. B. Krupanidhi 《Journal of Chemical Sciences》2003,115(5-6):775-788
Relaxor properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) and non-lead perovskite thin films have been analysed in terms of large frequency dispersion of dielectric response
at low temperatures. A wide spectrum of dielectric relaxation was observed in the frequency-dependent response of the imaginary
part of the dielectric permittivity. Transformation from normal ferroelectric to relaxor behaviour has been observed in the
case of the Ca substituting the BaTiO3 thin films. A number of techniques were exploited to investigate the wide spectrum of relaxation times in pulsed laser ablated
thin films.ac anddc electric field induced complex dielectric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films were studied as function of frequencies at different temperatures. Nonlinear behaviour of dielectric
susceptibility with respect to the amplitude of theac drive was observed at lower temperatures. The frequency dependence of transition temperatureT
m
(temperature of the maximum of dielectric constant) was studied using the Vogel-Fulcher relation.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
953.
A surface-mounted device assembly technique for small optics based on laser reflow soldering 总被引:4,自引:0,他引:4
L. Stauffer A. Würsch B. Gchter K. Siercks I. Verettas S. Rossopoulos R. Clavel 《Optics and Lasers in Engineering》2005,43(3-5):365
The three-dimensional miniaturized optical surface-mounted device (TRIMO-SMD) is a new flexible and automated assembly technique for small optical components (maximum diameter for a lens is 2 mm) based on laser reflow soldering technique. This technology can be compared to the electronic SMD technique but applied to micro-optical devices. We present some recent developments of TRIMO-SMD in its application to industrial products. 相似文献
954.
955.
C. S. Munita L. P. Barroso P. M. S. Oliveira 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):335-338
Summary In general, when characterizing samples, such as ceramic samples or other types of samples, for first time by means of chemical
elements, the analyst measures a large number of variables, many of which may not be very informative. In fact, some may even
be unrelated to the issue at hand and blur the picture instead of making it clearer. In subsequent studies the analyst may
wish to measure fewer variables for several reasons, such as being very time consuming; in cases where measurement time is
important, such as on-line monitoring; in order to reduce cost or effort; etc. Therefore, the hope is to determine those variables
that are most relevant without losing essential information and to remove the less productive information. The problem is
how to perform this in an objective way and to capture crucial information using a multivariate analysis. This paper aims
to describe and illustrate a stopping rule for the identification of redundant variables, and the selection of variable subsets,
preserving multivariate data structure using stepwise discriminant analysis, selecting those variables that are in some senses
adequate for discrimination purposes. One illustrative example using data sets obtained via INAA of ceramic samples from two
archaeological sites is provided. 相似文献
956.
957.
Dinesh Topwal U. Manju Sugata Ray S. Raj D. D. Sarma S. R. Krishnakumar M. Bertolo S. La Rosa G. Cautero 《Journal of Chemical Sciences》2006,118(1):87-92
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function
of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of
such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish
that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is
responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with
composition fluctuations of the type Sr2Fe1+x
Mo1-x
O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献
958.
Golovchenko A. V. Pil'o S. G. Brovarets V. S. Drach B. S. 《Russian Journal of General Chemistry》2003,73(11):1832-1833
Russian Journal of General Chemistry - 相似文献
959.
S Watanabe R R Anderson S Brorson G Dalickas J G Fujimoto T J Flotte 《Photochemistry and photobiology》1991,53(6):757-762
Threshold radiant exposures for grossly apparent immediate whitening and ultrastructural alterations of melanosomes in black guinea pig skin were determined for a series of red visible laser pulses ranging from 4 x 10(-4) to 6.5 x 10(-14) s. Threshold exposures for melanosomal injury were found to be independent of pulsewidth when the pulsewidths were below the estimated thermal relaxation time of melanosomes. Threshold radiant exposures for melanosomal injury were found to increase when the pulsewidths were approximately equal to or above the thermal relaxation time of melanosomes. At longer pulse durations, fracturing of melanosomes was not observed despite the longer exposures necessary for injury. Instead, perimelanosomal vacuoles were noted. These findings are consistent with the theory of selective photothermolysis and provide evidence for the thermal initiation of melanosomal disruption. 相似文献
960.