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41.
Gleb I. Pisarev Alex C. HoffmannWeiming Peng Henk A. Dijkstra 《Applied mathematics and computation》2011,217(11):5016-5022
The present work is a study of the gas-flow phenomenon known as the “end of the vortex” (EoV), which spontaneously occurs at the lower end, or under, reverse-flow centrifugal separators such as cyclones or swirl tubes. Different CFD models of swirl tubes have been built to study and analyse this phenomenon in detail. The present numerical work is based on—and compared with—previous experimental observations of this phenomenon. The numerical models were built in complete agreement with the geometrical configurations and operating conditions used in these earlier experimental studies [1]. Two different configurations of swirl tubes were analyzed. One configuration was an in principle long tube with variable length in which the dependence on the vessel length of the behaviour of the vortex core in a simple, well-defined geometry was studied. The other configuration was equipped with a wide “dust collection vessel” at the bottom, the depth of which was varied, to study the behaviour of the vortex core in a widely-used geometry. 3-D LES simulations were carried out using the commercial CFD package Star-CD. The bending of the vortex core to the wall of the vessel and its precessional motion, constituting the phenomenon of the EoV, was seen in both configurations, and the obtained results are in very good agreement, both qualitatively and to an extent quantitatively, with previous experimental results [1]. 相似文献
42.
Kazakova LI Shabarchina LI Sukhorukov GB 《Physical chemistry chemical physics : PCCP》2011,13(23):11110-11117
Enzyme based micron sized sensing system with optical readout was fabricated by co-encapsulation of urease and dextran couple with pH sensitive dye SNARF-1 into polyelectrolyte multilayer capsules. Co-precipitation of calcium carbonate, urease and dextran followed up by multilayer film coating and Ca-extracting by EDTA resulted in the formation of 3.5-4 micron capsules, what enable the calibrated fluorescence response to urea in concentration range from 10(-6) to 10(-1) M. The presence of urea can be monitored on a single capsule level as illustrated by confocal fluorescent microscopy. Variations in urease:dye ratio in capsules, applicability and limits of use of that type multi-component microencapsulated sensors are discussed. 相似文献
43.
Gleb A. Koshevoy 《Journal of multivariate analysis》2002,83(2):360
We prove that if the Tukey depths of two atomic measures are identical, then the measures are also identical. 相似文献
44.
Köhler K Biesheuvel PM Weinkamer R Möhwald H Sukhorukov GB 《Physical review letters》2006,97(18):188301
We study the size of polyelectrolyte multilayer capsules as a function of ionic strength, temperature, and time. A dynamic micromechanical model is developed which successfully describes the experiments. The model includes the polymer-solvent surface tension, an electrostatic force which is strongly ionic strength dependent, and a temperature-dependent mobility parameter. The activation of >50 kT suggests that multiple ion pairs must be broken simultaneously in the process of chain rearrangement. In support of our physical model capsules can repeatedly swell and shrink by varying ionic strength. 相似文献
45.
A detailed study of the role of solution pH and ionic strength on the swelling behavior of capsules composed of the weak polyelectrolytes poly(4-vinylpyridine) (P4VP) and poly(methacrylic acid) (PMA) with different numbers of layers was carried out. The polyelectrolyte layers were assembled onto silicon oxide particles and multilayer formation was followed by zeta-potential measurements. Hollow capsules were investigated by scanning electron microscopy and atomic force microscopy. The pH-dependent behavior of P4VP/PMA capsules was probed in aqueous media using confocal laser scanning microscopy. All systems exhibited a pronounced swelling at the edges of stability, at pHs of 2 and 8.1. The swelling degree increased when more polymer material was adsorbed. The swollen state can be attributed to uncompensated positive and negative charges within the multilayers, and it is stabilized by counteracting hydrophobic interactions. The swelling was related to the electrostatic interactions by infrared spectroscopy and zeta-potential measurements. The stability of the capsules as well as the swelling degree at a given pH could be tuned, when the ionic strength of the medium was altered. 相似文献
46.
Andreeva DV Ip B Gurinov AA Tolstoy PM Denisov GS Shenderovich IG Limbach HH 《The journal of physical chemistry. A》2006,110(37):10872-10879
The ability of strongly sterically hindered pyridines to form hydrogen bonded complexes was inspected using low-temperature 1H and 15N NMR spectroscopy in a liquefied Freon mixture. The proton acceptors were 2,6-di(tert-butyl)-4-methyl- and 2,6-di(tert-butyl)-4-diethylaminopyridine; the proton donors were hydrogen tetrafluoroborate, hydrogen chloride, and hydrogen fluoride. The presence of the tert-butyl groups in the ortho positions dramatically perturbed the geometry of the forming hydrogen bonds. As revealed by experiment, the studied crowded pyridines could form hydrogen bonded complexes with proton donors exclusively through their protonation. Even the strongest small proton acceptor, anion F-, could not be received by the protonated base. Instead, the simplest hydrogen bonded complex involved the [FHF]- anion. This complex was characterized by the shortest possible N...F distance of about 2.8 A. Because the ortho tert-butyl groups did not prevent the hydrogen bond interaction between the protonated center and the anion completely, an increase of the pyridine basicity caused a further shortening of the N-H distance and a weakening of the hydrogen bond to the counterion. 相似文献
47.
In this article we develop a global optimization algorithm for quasiconvex programming where the objective function is a Lipschitz
function which may have “flat parts”. We adapt the Extended Cutting Angle method to quasiconvex functions, which reduces significantly
the number of iterations and objective function evaluations, and consequently the total computing time. Applications of such
an algorithm to mathematical programming problems in which the objective function is derived from economic systems and location
problems are described. Computational results are presented. 相似文献
48.
Lebedenko AN Guralchuk GY Sorokin AV Yefimova SL Malyukin YV 《The journal of physical chemistry. B》2006,110(36):17772-17775
Using fluorescent microscopy and microspectroscopy, optical properties and morphology transformations in individual pseudoisocyanine (PIC) J-aggregates in aqueous electrolyte solutions have been explored. A stringlike structure of J-aggregates with a string diameter much less than 1 microm has been observed. Photodestruction of the strings under short-wavelength excitation has been revealed. Rodlike PIC crystallites, about 1 microm in diameter, have been observed with time. The fluorescence spectrum of rodlike crystallites has been found to differ from that of stringlike J-aggregate and from PIC crystal powder spectra. The crystallites are very stable, and their photodestruction has not been observed under any excitation conditions. It has been found that rodlike crystallites in contrast to stringlike J-aggregates possess optical waveguide properties. The luminescence of crystallites can be observed only at the excitation spot and at butt ends located up to hundreds of micrometers from the excitation spot. 相似文献
49.
Nathan A. Stump Jerry B. Burns Sheng Dai Gleb Mamantov Jack P. Young Joseph R. Peterson 《光谱学快报》2013,46(6):1073-1083
The temperature dependence of the features which arise from the 7F0,1 → 5D3 absorption transitions in EuOCl as seen by diffuse-reflectance spectroscopy has been investigated. The transitions shift linearly to higher energy with increasing temperature. The ratio of the intensities of the transitions arising from the 7F0 state to those arising from the 7F1 state also appears to be a linear function of temperature. 相似文献
50.