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排序方式: 共有220条查询结果,搜索用时 15 毫秒
1.
A technique for measuring the size and displacement of the disperse phase in two planes of a two-phase flow is presented. Digital image plane holography (DIPH) is used for the simultaneous recording and independent reconstruction of both planes. Each fluid plane is illuminated with two laser sheets propagating in opposite directions. The defocused image fields are holographically recorded at 90°, and can be reconstructed either in a defocused or in the best-focused plane. The analysis of the images in a defocused plane provides the sizes, while the cross-correlation of the focused images provides the velocity field, as in a regular particle image velocimetry (PIV) experiment. For air bubbles freely drifting in glycerine, diameters from 50 m to 400 m and displacements of up to 300 m have been measured. 相似文献
2.
3.
Acetato-bis(pyrazole) complexes [Mo(η3-methallyl)(O2CMe)(CO)2(pz∗H)2], (methallyl = CH2C(CH3)CH2) and fac-[M(O2CMe)(CO)3(pz∗H)2], (pz∗H = pyrazole or 3,5-dimethylpyrazole, dmpzH; M = Mn, Re) are obtained from [Mo(η3-methallyl)Cl(CO)2(NCMe)2] or fac-[MBr(CO)3(NCMe)2] [M = Mn (synthesized in situ), Re], 2 equiv. of pyrazole, and 1 equiv. of sodium acetate for Mo complexes, or silver acetate for Mn or Re complexes. The chlorido-complexes [Mo(η3-methallyl)Cl(CO)2L2] (L = pzH, dmpzH), obtained from the same starting material by substitution of MeCN by pzH or dmpzH, are also described. The crystal structures of the fac-acetato-bis(dimethylpyrazole) complexes present the same pattern of intramolecular hydrogen bonds between the acetate and the dimetylpyrazole ligands, whereas the crystal structures of the fac-acetato-bis(pyrazole) complexes show different hydrogen bonds patterns, with intermolecular interactions. NMR data indicate that these interactions are not maintained in solution. 相似文献
4.
J. Chamón P. C. Gutierrez J. Barrio A. Climent-Font M. Arroyo 《Applied Physics A: Materials Science & Processing》2010,99(2):377-381
A set of fragments of metallic artefacts from the medieval period excavated from Ciudad Real in Spain has been studied. The
objects are gilded copper buckles with a champlevé enamelling decoration. The composition of predominantly blue-coloured enamels has been analysed using three non-destructive
techniques, SEM-EDAX (scanning electron microscopy coupled with energy-dispersive X-ray analysis), X-ray fluorescence (XRF)
and PIXE (particle-induced X-ray emission). Analyses show that Co is responsible for the blue colour. The results of the two
techniques are compared, as well as the main components which constitute the enamel. Analyses suggest that Cu is responsible
for red colour. 相似文献
5.
P.L. Ríos I. Araya-Durán S. Bonardd J.L. Arroyo P. Povea M.B. Camarada 《Materials Today Chemistry》2022
Ferrocene (Fc)-based systems are frequently used as burning rate catalysts in the decomposition of ammonium perchlorate (AP)-based propellants. However, small Fc derivatives migrate to the surface of the propellant resulting in undesirable changes in the designed burning parameters and unstable combustion. To retard the migration and to increase the combustion rate of AP, fourth-generation polyamidoamine (PAMAM) dendrimers modified with Fc (PAMAM generation 4 [G4]-Fc) were synthetized and used as support for the obtention of copper nanoparticles (CuNPs). PAMAM G4 produced smaller nanoparticles (1–2 nm) with lower aggregation than PAMAM G4-Fc (12–14 nm). X-ray photoelectron spectroscopy (XPS) characterization confirmed the superior stabilizing and protecting effect against oxidation of CuNPs by PAMAM G4 in comparison to PAMAM G4-Fc, whereas molecular dynamics simulations have shown less flexibility and lower presence of stabilizing sites for nanoparticles in PAMAM G4-Fc. Antimigration tests confirmed the negligible migration of PAMAM G4-Fc compared with Fc, whereas PAMAM G4-Fc|CuNP affected the high-temperature decomposition of AP positively, decreasing the decomposition temperature in 87 °C owing to a synergistic effect between CuNPs and Fc. PAMAM G4-Fc can act both as an effective antimigration system of Fc and as a stabilizing framework of metal nanoparticles with application as catalysts of AP. 相似文献
6.
Y. Arroyo Gómez J. A. López Sastre J. F. Rodríguez Amo M. A. Sanz Tejedor 《Journal of carbohydrate chemistry》2013,32(7):1051-1058
Abstract The asymmetric oxidation reaction of D-glyceraldehyde diethyl dithioacetal 1 and its di-O-acetyl derivative with a Sharpless reagent to produce the corresponding D-glyceraldehyde diethyl dithioacetal S-oxide derivatives takes place with high stereoselectivity. The configuration of the two new chiral centres formed is deduced. 相似文献
7.
We study non-elastic billiard dynamics in an equilateral triangular table. In such dynamics, collisions with the walls of the table are not elastic, as in standard billiards; rather, the outgoing angle of the trajectory with the normal vector to the boundary at the point of collision is a uniform factor λ < 1 smaller than the incoming angle. This leads to contraction in phase space for the discrete-time dynamics between consecutive collisions, and hence to attractors of zero Lebesgue measure, which are almost always fractal strange attractors with chaotic dynamics, due to the presence of an expansion mechanism. We study the structure of these strange attractors and their evolution as the contraction parameter λ is varied. For λ∈(0,1/3), we prove rigorously that the attractor has the structure of a Cantor set times an interval, whereas for larger values of λ gaps arise in the Cantor structure. For λ close to 1, the attractor splits into three transitive components, whose basins of attraction have fractal boundaries. 相似文献
8.
9.
N. Andrés M. P. Arroyo H. Hinrichs K. Hinsch M. Quintanilla 《Experiments in fluids》2001,30(2):117-122
This paper investigates the feasibility of using holographic interferometry in wind tunnel flows for measuring velocity fields
rather than density or temperature fields. First results were obtained in a vortex street behind a cylinder at Re=190(U
∞=0.7 m/s). The light scattered from an illuminated fluid plane was holographically recorded twice with the same reference
beam. Using a time interval of 10 μs, local fluid displacements smaller than a few microns were recorded. The holographic
plate was placed in front and as close as possible to the fluid plane. The interferograms obtained from the hologram reconstruction
give information about one velocity component, at 45° with the illuminated plane. The alignment of the cylinder axis with
this 45° direction provided definite confirmation about the vortex street having a non-negligible axial velocity. The constant
velocity fluid region has proven to be very useful for quantifying the velocity information contained in the interferogram.
Received: 8 November 1999/Accepted: 14 March 2000 相似文献
10.
Stephen MT Hoke Gaoyang Liang A Irina Mutiu Julie Genereaux Christopher J Brandl 《BMC biochemistry》2007,8(1):16