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971.
972.
M. V. Buntina V. V. Ostapenko 《Computational Mathematics and Mathematical Physics》2008,48(12):2241-2253
For the shallow water equations in the first approximation (Saint-Venant equations), a TVD scheme is developed for shock-capturing computations of open channel flows with discontinuous waves. The scheme is based on a special nondivergence approximation of the total momentum equation that does not involve integrals related to the cross-section pressure force and the channel wall reaction. In standard divergence difference schemes, most of the CPU time is spent on the computation of these integrals. Test computations demonstrate that the discontinuity relations reproduced by the scheme are accurate enough for actual discontinuous wave propagation to be numerically simulated. All the qualitatively distinct solutions for a dam collapsing in a trapezoidal channel with a contraction in the tailwater area are constructed as an example. 相似文献
973.
Yanfeng Zhang Hao Liu Hefei Dong Changhua Li Shiyong Liu 《Journal of polymer science. Part A, Polymer chemistry》2009,47(6):1636-1650
Amphiphilic ABC miktoarm star terpolymers consisting of polystyrene, poly(ε‐caprolactone), and poly(N‐isopropylacrylamide) arms, PS(‐b‐PNIPAM)‐b‐PCL, were synthesized via a combination of atom transfer radical polymerization, ring‐opening polymerization (ROP), and click chemistry. Difunctional PS bearing an alkynyl and a primary hydroxyl moiety at the chain end, PS‐alknyl‐OH, was prepared by reacting azido‐terminated PS with an excess of 3,5‐bis(propargyloxy)benzyl alcohol (BPBA) under click conditions. The subsequent ROP of ε‐caprolactone using PS‐alknyl‐OH macroinitiator afforded PS(‐alkynyl)‐b‐PCL copolymer bearing an alkynyl moiety at the diblock junction point. Target PS(‐b‐PNIPAM)‐b‐PCL amphiphilic ABC miktoarm star terpolymers were then prepared via click reaction between PS(‐alkynyl)‐b‐PCL and an excess of azido‐terminated PNIPAM (PNIPAM‐N3). The removal of excess PNIPAM‐N3 was accomplished by “clicking” onto alkynyl‐functionalized Wang resin. All the intermediate and final products were characterized by gel permeation chromatography, 1H NMR, and FTIR. In aqueous solution, the obtained amphiphilic ABC miktoarm star terpolymer self‐assembles into micelles possessing mixed PS/PCL cores and thermoresponsive shells, which were further characterized by dynamic laser light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1636–1650, 2009 相似文献
974.
Alexei V. Radchenko Sergei V. Kostjuk Irina V. Vasilenko François Ganachaud Fyodor N. Kaputsky Yohann Guillaneuf 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6928-6939
A kinetic study of the living cationic polymerization of p‐methoxystyrene using 1‐(4‐methoxyphenyl)ethanol ( 1 )/B(C6F5)3 initiating system in a mixture of CH3CN with CH2Cl2 1:1 (v/v) at room temperature was carried out utilizing a wide variety of conditions. The polymerization proceeded in a living fashion even in the presence of a large amount of water ([H2O]/[B(C6F5)3] ratio up to 20) to afford polymers whose Mn increased in direct proportion to monomer conversion with fairly narrow MWDs (Mw/Mn ≤ 1.3). The investigation revealed that the rate of polymerization was first‐order in B(C6F5)3 concentration, while a negative order in H2O concentration close to ?2 was obtained. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decreased concentration in free Lewis acid, the true coinitiator of polymerization. A mechanistic scheme to explain the kinetic behavior of living p‐methoxystyrene polymerization is proposed, which has been validated by PREDICI simulation on multiple‐data curves obtained by 1H NMR in situ polymerization experiment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6928–6939, 2008 相似文献
975.
Quasi‐bubble finite element approximations to the shallow water equations are investigated focusing on implementations of the surface elevation boundary condition. We first demonstrate by numerical results that the conventional implementation of the boundary condition degrades the accuracy of the velocity solution. It is also shown that the degraded velocity leads to a critical instability if the advection term is present in the momentum equation. Then we propose an alternative implementation for the boundary condition. We refer to this alternative implementation as a discontinuous boundary (DB) implementation because it introduces at each boundary node two independent mass–flux values that result in a discontinuity at the boundary. Numerical results show that the proposed DB implementation is consistent, stabilizes the quasi‐bubble scheme, and leads to second‐order accuracy at the surface elevation specified boundary. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
976.
The Langmuir monolayer of sericin protein was studied by means of surface pressure (π)—molecular area (A) isotherms at different pH subphase. The monolayer of sericin exhibits typical phase transition phenomena at pH 2, pH 4.8, pH 7 and pH 11, respectively, including from gas state to gas‐liquid state and finally to condensed solid state. However, the monolayer of sericin on pH 11 subphase appears to be solid state. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
977.
F.-J. Zhang Z. Xu Y.-G. Lv J.-C. Zhang S. L. Zhao J.-Z. Huang Y. Wang G.-C. Yuan D.-W. Zhao X.-R. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):245-248
The organic-inorganic combined structural device (ITO/PVK:Eu/ZnS/Al) is
fabricated based on layered optimization scheme. II–VI semiconductor
material ZnS is acted as an electron function (transporting and
acceleration) layer. The hot electrons which have been accelerated in the
ZnS layer directly impact excitation europium ions through resonant energy
transfer and then recombine with injected holes to form excitons in PVK or
EuTTA2(N-HPA)Phen. Europium (Eu) ions may also be excited by
intramolecular energy transfer from ligands. There are two kinds of
excitation mechanisms: impacted excitation and injected recombination for
the combined structural device. The electroluminescence (EL) intensity of
the combined structural device is strongly improved and reaches up to
381 cd/m2 at 20 V compared with the pure organic structural device. It
may be an effective method to improve the EL intensity of the lanthanide
complex by using electric characteristics of inorganic semiconductor
materials. 相似文献
978.
The bubbles have been widely used in biomedical field, military and chemical industry. The liquid jet generated by the bubble collapse through an orifice is utilized in needle-free injections and inkjet printing. In this paper we devised synchronized triggering equipment, experimentally investigated the mechanism in the interaction of an electric-spark generated a single bubble and a vertical wall with an air-back opening. Detailed observations were recorded and described for bubble oscillation, migration, jetting, as well as the high-speed water spike penetrating through the opening. The results revealed that there was a critical value of the bubble-wall distance, below which the bubble was directed away from the incomplete boundary, while the bubble may tear from the middle for larger distance. As the distance varied, we studied the volume of the water that rushed through the opening, the velocity at the tip of the water spike, and the center of the bubble as well as the migration of the bubble boundary. This work reveals that the high-speed water spike caused by the bubble may be a potential threat to the structures, specifically for cases with a small opening size and short bubble-boundary distance. 相似文献
979.
Kyung Hak Kim Jin Kyoung Park Sang Hyuk Im Bum Jun Park 《Particle & Particle Systems Characterization》2021,38(4):2100006
Waterproof light-emitting perovskite–polymer composite microparticles are synthesized by a continuous one-step microfluidic reactor, which enables in situ production of metal halide perovskite nanoparticles (MHP-NPs) by the ligand-assisted reprecipitation process (LARP) and the encapsulation of MHP-NPs by UV cross-linking polymerization in the microfluidic channel. Successful encapsulation of MHP-NPs in polymer microparticles is attributed to the co-dispersion of an LARP solution and UV polymerizable solution in an aqueous continuous phase within the microfluidic channel, in which N,N-dimethylformamide, in co-dispersion droplets, is continuously extracted to the aqueous medium upon UV polymerization. MHP-NPs–polymer composite microparticles show enhanced stability against air and moisture. 相似文献
980.
A new method for total organic carbon (TOC) measurement was established based on supercritical Fenton oxidation. The organic pollutants in wastewater were oxidized to carbon dioxide in supercritical water by Fenton reagents that was detected using a nondispersive infrared detector. The influence of temperature from 380 to 480°C, oxidant coefficient from 1 to 20, pH from 2.2 to 5.2, and Fe2+ concentration from 0.2 to 0.8?mg?L?1 was characterized; the optimal conditions were at 420°C, an oxidant coefficient n?≥?5, a pH of 4.4, and Fe2+ concentration of 0.8?mg?L?1. Using these parameters, the recovery of potassium hydrogen phthalate exceeded 98.2%. The introduction of Fenton oxidation based on supercritical water lowered the temperature and reduced the oxidant coefficient required for TOC determination. 相似文献