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31.
Antonio Segalini Ramis Örlü Philipp Schlatter P. Henrik Alfredsson Jean-Daniel Rüedi Alessandro Talamelli 《Experiments in fluids》2011,51(3):693-700
A new approach to evaluate turbulence intensity and transverse Taylor microscale in turbulent flows is presented. The method
is based on a correction scheme that compensates for probe resolution effects and is applied by combining the response of
two single hot-wire sensors with different wire lengths. Even though the technique, when compared to other correction schemes,
requires two independent measurements, it provides, for the same data, an estimate of the spanwise Taylor microscale. The
method is here applied to streamwise turbulence intensity distributions of turbulent boundary layer flows but it is applicable
generally in any turbulent flow. The technique has been firstly validated against spatially averaged DNS data of a zero pressure-gradient
turbulent boundary layer showing a good capacity to reconstruct the actual profiles and to predict a qualitatively correct
and quantitatively agreeing transverse Taylor microscale over the entire height of the boundary layer. Finally, the proposed
method has been applied to available higher Reynolds number data from recent boundary layer experiments where an estimation
of the turbulence intensity and of the Taylor microscale has been performed. 相似文献
32.
Extracts of effluents from two different wastewater treatment plants (WWTP) in Switzerland taken during the application period of pesticides were examined by coupling an HPLC-MS system to a nuclear magnetic resonance spectrometer using a post column peak trapping device. By trapping 1 min portions of the chromatogram onto post column solid phase extraction cartridges (time slice-SPE-NMR) a comprehensive overview of proton carrying constituents could be achieved. Non-supervised statistical analysis of the NMR spectra obtained by this approach revealed NMR resonances pointing to contaminants present in decreasing proton concentration in the extracts. Comparison of exact mass data acquired during the trapping process to these NMR resonances enabled the identification of the pesticides Linuron, Metazachlor, Ethofumesate, Isoproturon, Metamitron, Propazine and Chloridazon. Desaminometamitron, a known transformation product of Metamitron could also be identified together with unexpected highly concentrated C8, C10 and C12 fatty acids and their glycerol mono- and di esters. Other compounds identified were a drug metabolite (3-Carboxymefenamic acid), a sun screen agent (Ensulizole: 2-Phenyl-1H-1,3-benzodiazole-6-sulfonic acid) and industrial chemicals (Benzotriazole, N-Benzyl-indole). In addition, a number of well-resolved proton spectra cannot be attributed to a mass response showing the need of further investigations using 2D-NMR and different ionization techniques. 相似文献
33.
34.
Saliba S Coppel Y Mingotaud C Marty JD Kahn ML 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(26):8084-8091
Branched thermotropic liquid crystals (LCs) were successfully used as stabilizers for the synthesis of isotropic photoluminescent ZnO nanoparticles (NPs) in solution. (1)H?NMR spectroscopy and differential scanning calorimetry experiments demonstrate the existence of specific interactions between the LC and both the ZnO precursor and ZnO NPs. This offers the possibility for some branched molecules to act as structurally ordered hosts for the anisotropic growth of ZnO NPs. 相似文献
35.
Evelyne Grander Grard Leclerc Jean-Daniel Ehrhardt 《Journal of heterocyclic chemistry》1989,26(6):1781-1785
4-Alkyl-2-methyl-3,4-diphenyl-1,2-thiazetidine 1,1-dioxide 5, 6 and 7 were obtained from 2-methyl-3,4-diphenyl-1,2-thiazetidine 1,1-dioxide 1 by reaction of its anion 4 with alkyl halides. cis- and trans-Configuration of the 4-alkylated products were determined by 1H-nmr and NOE difference spectro-scopy studies. 相似文献
36.
G. Andrei Mezincescu Daniel Bessis Jean-Daniel Fournier Giorgio Mantica Francisc D. Aaron 《Journal of statistical physics》1997,86(3-4):675-705
The average density of zeros for monic generalized polynomials,
, with real holomorphic ,f
k
and real Gaussian coefficients is expressed in terms of correlation functions of the values of the polynomial and its derivative. We obtain compact expressions for both the regular component (generated by the complex roots) and the singular one (real roots) of the average density of roots. The density of the regular component goes to zero in the vicinity of the real axis like |lmz|. We present the low- and high-disorder asymptotic behaviors. Then we particularize to the large-n limit of the average density of complex roots of monic algebraic polynomials of the form
with real independent, identically distributed Gaussian coefficients having zero mean and dispersion
. The average density tends to a simple,universal function of =2nlog|z| and in the domain coth(/2)n|sin arg(z)|, where nearly all the roots are located for largen. 相似文献
37.
Boissonnat Jean-Daniel Wintraecken Mathijs 《Foundations of Computational Mathematics》2022,22(4):967-1012
Foundations of Computational Mathematics - Isomanifolds are the generalization of isosurfaces to arbitrary dimension and codimension, i.e. manifolds defined as the zero set of some multivariate... 相似文献
38.
Naloxone 2 was obtained by demethylation of N-allylnoroxycodone 1 with methane sulfonic acid / methionine. This reagent is an excellent substitute for boron tribromide. It was used for the synthesis of analogous derivatives with variable results. 相似文献
39.
E Girard T Tassaing S Camy JS Condoret JD Marty M Destarac 《Journal of the American Chemical Society》2012,134(29):11920-11923
An enhancement of poly(vinyl ester) solubility in supercritical carbon dioxide (sc-CO(2)) can be achieved by decreasing the strength of the polymer-polymer interactions. To demonstrate this, a library of statistical copolymers of vinyl acetate and vinyl trifluoroacetate was synthesized by RAFT/MADIX polymerization with varying compositions at a given number-average molecular weight. These copolymers exhibited unprecedentedly low cloud-point pressures in sc-CO(2) at 40 °C compared with previously reported poly(vinyl esters). Surface tension measurements combined with a computational approach evidenced the prominent role played by polymer-polymer interactions. 相似文献
40.
Sophian Sahnoun Samir Messaoudi Jean-François Peyrat Jean-Daniel Brion Mouad Alami 《Tetrahedron letters》2012,53(23):2860-2863
An efficient hydration reaction of various (hetero)aryl nitriles using Cs2CO3 in pyrrolidinone is described. This new metal-free protocol proved to be highly effective and general to synthesize a variety of (hetero)aryl amides. 相似文献