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21.
This work deals with the mode III fracture problem of a cracked functionally graded piezoelectric surface layer bonded to
a cracked functionally graded piezoelectric substrate. The cracks are normal to the interface and the electro-elastic material
properties are assumed to be varied along the crack direction. Potential and flux types of boundary condition are assigned
on the edge of the surface layer. The problem under the assumptions of impermeable and permeable cracks can be formulated
to the standard singular integral equations, which are solved by using the Gauss–Chebyshev technique. The effects of the boundary
conditions, the material properties and crack interaction on the stress and electric displacement intensity factors are discussed. 相似文献
22.
Humic substances are natural complexed mixtures of organic compounds originated from the decomposition of plant and animal residues. These compounds are ubiquitous in soils, sediments, surface waters and groundwaters. They contain both hydrophobic and hydrophilic moieties, able to interact with hydrophobic organic contaminants and with heavy metals. These sorption interactions play a crucial role in contaminants fate and transport and their understanding and quantification are essential for modeling and predictions. However, sorption analyses frequently suffer from experimental problems. A novel idea presented in this study is to use sol-gel as an inert matrix to immobilize (entrap) specific, well defined, humic molecules which then be used in sorption studies. We developed a successful procedure for the immobilization of humic acid (HA) in a sol-gel matrix. After gelation and drying, the doped gel was crushed and washed several times, yielding a very stable product. It was then used in a series of batch experiments, studying the sorption of several polycyclic aromatic hydrocarbons (PAHs) with Aldrich HA. The sorption coefficients (K
oc) obtained with the immobilized HA were highly correlated with the values expected based on the hydrophobicity of the contaminants. We concluded that the entrapped HA retained its original properties and that it was accessible to the external contaminants through the pore network. 相似文献
23.
Wei-Hung Hsu Ching-Hwei Chue 《International Journal of Solids and Structures》2008,45(25-26):6333-6346
This paper studies the mode III electro-elastic field of a cracked functionally graded piezoelectric strip bonded to a functionally graded piezoelectric half plane. The crack is oriented in arbitrary direction. The material properties along x-axis vary in exponential form. By using the Fourier transform, the problem can be formulated into a system of singular integral equations and solved by applying the Gauss–Chebyshev integration formula. The effects come from the edge, crack orientation and the nonhomogeneous material parameters on intensity factors are discussed graphically. 相似文献
24.
Nhu-An Pham Tim Richardson Jessie Cameron Bruno Chue Brian H Robinson 《Microscopy and microanalysis》2004,10(2):247-260
Using the real time microscope (RTM), a system applying new developments in light microscopy, we documented the spatial and temporal dynamics of mitochondrial behavior in human cultured skin fibroblasts. Without the use of stains or probes, we resolved fibroblast mitochondria as dark slender filaments of approximately 0.2 m wide and up to 10 m long, as well as a few smaller ovoid forms. In the living cell, the three most common mitochondrial movements were: (1) small oscillatory movements; (2) larger movements including filament extension, retraction, and branching as well as combinations of these actions; and (3) whole transit movements of single mitochondrial filaments. Skin fibroblasts from patients with mitochondrial complex I deficiency and normal fibroblasts during incubation with rotenone, or antimycin A, contained higher proportions of mitochondria in the swollen filamentous forms, nodal filaments, and ovoid forms rather than the slender filamentous forms in normal cells. Interestingly, decreased motility was observed with the more ovoid mitochondrial forms compared to the filamentous forms. We conclude that mitochondrial morphology and dynamic motion are strongly associated with changes in mitochondrial energy metabolism. Images documenting our observations are presented both at single time points and as QuickTime videos. 相似文献
25.
This paper considers the solution of the geodetic Doppler multi-stationadjustment, i.e. the problem of computing the positions of severalstations observing the Doppler shift on radio frequencies emittedby several artificial satellites passing over the horizon. Amodification of an algorithm due to Golub and Plemmons, forsolving large linear least-squares problems where the observationmatrix has a block dual angular form, is proposed in this framework.This modification is shown to reduce substantially both datatransfer between the tracking stations and the main computingcentre, and the total computational effort required to obtainthe solution of the problem. Preliminary numerical results arediscussed and some further comments presented. 相似文献
26.
C. Schmitt A. Guessous J.P. Bocquet H.-G. Clerc R. Brissot D. Engelhardt H.R. Faust F. Gönnenwein M. Mutterer H. Nifenecker J. Pannicke CH. Ristori J.P. Theobald 《Nuclear Physics A》1984,430(1):21-60
At the recoil spectrometer “Lohengrin” of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of 239Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct kinetic energies between 93 and 112 MeV. The proton odd-even effect which was measured to be (11.6 ± 0.6)% causes considerable fine structure in the yields. The average kinetic energy of even-Z elements in the light fission-product group is 0.3 ± 0.1 MeV larger than for odd-Z elements. The neutron odd-even effect is (6.5 ± 0.7)%. The comparison with previously published data 1) for thermal-neutron-induced fission of 235U reveals a correlation between the proton odd-even effect in the yield and in the kinetic energy of the elements. The dependence of the proton odd-even effect on the fragmentation is very similar for 235U and 239Pu when it is considered as a function of the nuclear charge of the heavy fission products. The isobaric variances σz2. for thermal-neutron fission of 235U and 239Pu coincide at all kinetic energies if the influence of the proton odd-even effect is averaged out. This supports the hypothesis that the magnitude of σz2 is determined only by quantum-mechanical zero-point fluctuations. The influence of the spherical shells Z = 50 and N = 82 on the fragmentation is discussed. 相似文献
27.
Inhaltsübersicht. Es ist gelungen, ein durch BeO stabilisiertes Bariumoxoiridat der Zusammensetzung BaIr0,67Be0,33O3 in der Kristallform eines kubischen Perowskits mit kleiner Elementarzelle erstmals darzustellen. Raumgruppe O1h–Pm3m, a = 4,1009 Å, Z = 1. Ir5+ und Be2 + besetzen die Oktaederposition des Perowskits statistisch. BaIr0,67Be0,33O3: A Stabilized Cubic Form of BaIrO3 For the first time it was possible to prepare a new barium-oxoiridate of the formula BaIr0,67Be0,33O3, stabilized by BeO. It crystallizes in a small cubic unit cell of the perovskite type. Space group O1h–Pm3m; a = 4.1009 Å; Z = 1. Ir5+ and Be2+ occupy the octahedra positions of the perovskite structure statistically. 相似文献
28.
Shock Waves - In this paper, the effects of boattail junction shaping on aerodynamic drag and stability of supersonic spin-stabilized rounds are investigated using computational fluid dynamics. For... 相似文献
29.
This paper deals with the anti-plane problem of two bonded functionally graded finite strips. Each strip contains an internal crack normal to the interface. The material properties of two strips are assumed to vary along the direction of the crack lines. A system of singular integral equations is derived and then solved numerically by using Gauss–Chebyshev integration formula. The influences of nonhomogeneous parameters, crack interactions and two edge conditions on the mode III stress intensity factors are investigated. 相似文献
30.
KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献