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1.
The present paper reports an experimental investigation on atomizing liquid flows produced by simplified cavity nozzles. The Weber number being kept low, the sprays produced by these injectors depend on the liquid flow characteristics only, and more precisely, on the non-axial kinetic energy and of the turbulent kinetic energy at the nozzle exit. The investigation reported here concentrates on the characterization of liquid flows during atomization by measuring the spatial variation of the local interface length and of the local interface fractal dimension. Both parameters were found representative of the physics of atomization process: they depend on the characteristics of the flow issuing from the nozzle and they are related to the subsequent drop size distribution. The local interface length is representative of the amount of liquid–gas interface surface area, and is a function of both the non-axial and the turbulent kinetic energies at the nozzle exit. The fractal dimension is representative of the tortuosity of the liquid–gas interface and, as expected, is mainly related to the turbulent kinetic energy at the nozzle exit. As far as the drop size distribution is concerned, it is found that the local interface length at the instant of break-up determines a representative drop diameter of some kind, whereas the fractal dimension at the same instant controls the dispersion of the distribution. 相似文献
2.
DSC measurements indicate that poly(vinyl bromide) (PVB) is miscible with several polyesters [poly(caprolactone), poly(valerolactone), poly(butylene adipate) and poly(hexamethylene sebacate)] but immiscible with others [poly(α-methyl-α-n-propyl-β-propiolactone), poly(α-methyl-α-ethyl-β-propiolactone) and poly(ethylene adipate (PEA)]. However, it is known that poly(vinylchloride) (PVC) is miscible with all these polyesters but PEA. The more limited degree of miscibility of PVB with polyesters, as compared with the case of PVC, is surprising in view of the similar properties of the bromine and chlorine atoms. 相似文献
3.
A concise and convergent route to combretastatin D2 is described together with some preliminary biological data. 相似文献
4.
G. Durry J. S. Li I. Vinogradov A. Titov L. Joly J. Cousin T. Decarpenterie N. Amarouche X. Liu B. Parvitte O. Korablev M. Gerasimov V. Zéninari 《Applied physics. B, Lasers and optics》2010,99(1-2):339-351
A near-infrared tunable diode laser spectrometer called TDLAS has been developed that combines telecommunication-type as well as new-generation antimonide laser diodes to measure C2H2, H2O, CO2 and their isotopologues in the near infrared. This sensor is devoted to the in situ analysis of the soil of the Martian satellite PHOBOS, within the framework of the Russian space mission PHOBOS-GRUNT. In the first part of the paper, we report accurate spectroscopic measurements of C2H2 and 13C12CH2 near 1.533 μm, of H2O and CO2 at 2.682 μm and of the isotopologues 13C16O2 and 16O12C18O near 2.041 μm and H2 17O, H2 18O and HDO near 2.642 μm. The achieved line strengths are thoroughly compared to data from molecular databases or from former experimental determinations. In the second part of the paper, we describe the TDLAS spectrometer for the PHOBOS-GRUNT mission. 相似文献
5.
Oxidation behaviour of SiC coatings 总被引:1,自引:0,他引:1
K. Mergia D. Lafatzis N. Moutis T. Speliotis G. Apostolopoulos F. Cousin 《Applied Physics A: Materials Science & Processing》2008,92(2):387-395
Amorphous silicon carbide (SiC) films were deposited on silicon substrates by radio-frequency magnetron sputtering. The films
were oxidized in air in the temperature range 400–900 °C and for times from 1 to 16 h. Neutron reflectivity measurements provided
information on the thickness, density and roughness of the SiC and on the formed SiO2 layers. Fourier transform infrared spectroscopy was used to determine the bond structure of the formed SiO2 and changes in the bonding of SiC after exposure at the oxidation temperature. The surface morphology of the oxidized films
was characterized by atomic force microscopy measurements. The oxidation kinetics is initially fast and as the SiO2 layer is formed it slows down. The SiC consumption varies linearly with time at all oxidation temperatures. Exposure of the
SiC at the oxidation temperature affects its density and to some degree its bond structure, while the formed SiO2 has density and bond structure as that formed by oxidation of Si under the same conditions.
PACS 66.30.Ny; 68.47.Gh; 68.55.J- 相似文献
6.
Samuel F. Cousin Dr. Pavel Kadeřávek Baptiste Haddou Dr. Cyril Charlier Thorsten Marquardsen Jean‐Max Tyburn Dr. Pierre‐Alain Bovier Dr. Frank Engelke Dr. Werner Maas Prof. Dr. Geoffrey Bodenhausen Dr. Philippe Pelupessy Prof. Dr. Fabien Ferrage 《Angewandte Chemie (International ed. in English)》2016,55(34):9886-9889
Nuclear magnetic resonance (NMR) studies have benefited tremendously from the steady increase in the strength of magnetic fields. Spectacular improvements in both sensitivity and resolution have enabled the investigation of molecular systems of rising complexity. At very high fields, this progress may be jeopardized by line broadening, which is due to chemical exchange or relaxation by chemical shift anisotropy. In this work, we introduce a two‐field NMR spectrometer designed for both excitation and observation of nuclear spins in two distinct magnetic fields in a single experiment. NMR spectra of several small molecules as well as a protein were obtained, with two dimensions acquired at vastly different magnetic fields. Resonances of exchanging groups that are broadened beyond recognition at high field can be sharpened to narrow peaks in the low‐field dimension. Two‐field NMR spectroscopy enables the measurement of chemical shifts at optimal fields and the study of molecular systems that suffer from internal dynamics, and opens new avenues for NMR spectroscopy at very high magnetic fields. 相似文献
7.
J. Cousin W. Chen D. Bigourd M. Fourmentin S. Kassi 《Applied physics. B, Lasers and optics》2009,97(4):919-929
We report on the development of a field deployable compact laser instrument tunable over ∼232 cm−1 from 3.16 to 3.41 μm (2932.5–3164.5 cm−1) for chemical species monitoring at the ppb-level. The laser instrument is based on widely tunable continuous-wave difference-frequency
generation (DFG), pumped by two telecom-grade fiber lasers. DFG power of ∼0.3 mW near 3.3 μm with a spectral purity of ∼3.3
MHz was achieved by using moderate pumping powers: 408 mW at 1062 nm and 636 mW at 1570 nm. Spectroscopic performance of the
developed DFG-based instrument was evaluated with direct absorption spectra of ethylene at 3.23 μm (∼3094.31 cm−1). Absorption spectra of vapor-phase benzene near 3.28 μm (∼3043.82 cm−1) were recorded with Doppler-limited resolution. Line intensities of the most intense absorption lines of the ν
12 band near 3043.8 cm−1 were determined to support development of sensitive mid-infrared trace gas detection of benzene vapor in the atmosphere.
Detection of benzene vapor in air at different concentration levels has been performed for the first time using multi-pass
cell enhanced direct absorption spectroscopy at ∼3.28 μm with a minimum detectable concentration of 50 ppb (1σ). 相似文献
8.
Ultrastructure of the Schistosoma mansoni cercaria. 总被引:1,自引:0,他引:1
9.
Detlef Günther Albrecht v. Quadt Ronny Wirz Herve Cousin Volker J. Dietrich 《Mikrochimica acta》2001,136(3-4):101-107
Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used as a complementary technique to X-ray fluorescence
(XRF), for multi-element analysis of geological samples fused with lithium-tetraborate Li2B4O7). Different calibration strategies using external non-matrix matched reference materials were investigated. Various internal
standards were tested, including the use of Li from the flux, and the use of the naturally occurring internal standards, Si
or Ca. The use of a naturally occurring standard is not as efficient as this required a prior analysis of the samples using
XRF. The obtained values for the analysis of geological reference materials were compared with consensus literature values,
and satisfactory agreement was found. Laser pits, which were formed, had a diameter of 80 μm and 3–5 replicates on each fused
disc were measured. The reproducibility of the method was better than 10% for concentrations above 1 μg/g and better than
15% for lower concentrations. The use of Li as the internal standard offers the possibility of multi-element determinations
in geological samples, which have an unknown composition when the laser ablation analysis is carried out. However, using the
calculated stoichiometric composition of the lithium-tetraborate for the calculation of the Li concentration leads to a constant
deviation from the recommended values. Therefore, it was necessary to determine the Li concentration within each sample batch
using at least one lithium tetraborate fused geological reference material. This resulting Li concentration in the beads was
then used for all subsequent samples in a run. Limits of detection, reproducibility, deviation from reference values indicate
the potential of LA-ICP-MS for such bulk analysis without matrix matched calibration standards. 相似文献
10.
J. Cousin P. Masselin W. Chen D. Boucher S. Kassi D. Romanini P. Szriftgiser 《Applied physics. B, Lasers and optics》2006,83(2):261-266
Development of a continuous-wave tunable fiber laser-based spectrometer for applied spectroscopy is reported. Wide wavelength tunability of an erbium-doped fiber laser (EDFL) was investigated in the near-infrared region of 1543–1601 nm. Continuous mode-hop free fine frequency tuning has been accomplished by temperature tuning in conjunction with mechanical tuning. The overall spectroscopic performance of the EDFL was evaluated in terms of frequency tunability along with its suitability for molecular spectroscopy. High-resolution absorption spectra of acetylene (C2H2) were recorded near 1544 nm with a minimum measurable absorption coefficient of about 3.5×10-7 cm-1/Hz1/2 for direct absorption spectroscopy associated with a 100-m long multipass cell. Detections of C2H2 at different concentration levels were performed as well with high dynamic detection range varying from 100% purity to sub ppmv using cavity ring down spectroscopy. A 3σ-detection-limited minimum detectable concentration (MDC) of 400 ppbv has been obtained by using the transition line Pe(22) of the ν1+ν3+ν5
1(Πg)-ν5
1(Πu) hot band near 1543.92 nm with a detection bandwidth of 2.3 Hz. This corresponds to a minimum detectable absorption coefficient of 6.6×10-11 cm-1/Hz1/2. The sensitivity limit could be further improved by almost one order of magnitude (down to ∼60 ppbv) by use of the Pe(27) line of the ν1+ν3(Σu
+)-0(Σg
+)combination band near 1543.68 nm. PACS 42.55.Wd; 42.62.Fi; 07.57.Ty; 07.88.+y 相似文献