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71.
Yasunori Watanabe Ayumi Saruwatari David M. Ingram 《Journal of computational physics》2008,227(4):2344-2365
A numerical method which fulfils the free-surface boundary conditions and extrapolates the fluid velocity into empty grid cells outside the fluid region on a fixed Cartesian grid system is presented. The complex, three-dimensional, vortex structures formed via surface/vortex interaction and induction between vortices have been computed using the proposed technique implemented within a level-set method for both vertical and oblique droplet impacts in incompressible fluids. The present results have been validated through numerical tests which confirm zero tangential shear at the free-surface and comparisons with experimental observations of cavity and vortex ring formation underneath the impact location. In some cases, transitions from a concentric vortex ring to a fully three-dimensional vortex structure has been confirmed. Whilst the primary vortex ring is initiated at the highly curved contact surface between the droplet and receiving surface, azimuthal instabilities are manifested in the shear layer around the cavity crater developing after the vertical impact, resulting in axial counter-rotating vorticity between the cavity and descending vortex ring. Underlying mechanisms which induce local deformation of the free-surface, creating a so-called scar, due to the sub-surface vortices at the oblique impacts are also discussed. 相似文献
72.
Katsuhiro Yamamoto Youhei Miwa Hiroyuki Tanaka Masato Sakaguchi Shigetaka Shimada 《Journal of polymer science. Part A, Polymer chemistry》2002,40(20):3350-3359
Nickel‐mediated atom transfer radical polymerization (ATRP) and iron‐mediated reverse ATRP were applied to the living radical graft polymerization of methyl methacrylate onto solid high‐density polyethylene (HDPE) films modified with 2,2,2‐tribromoethanol and benzophenone, respectively. The number‐average molecular weight (Mn) of the free poly(methyl methacrylate) (PMMA) produced simultaneously during grafting grew with the monomer conversion. The weight‐average molecular weight/number‐average molecular weight ratio (Mw/Mn) was small (<1.4), indicating a controlled polymerization. The grafting ratio showed a linear relation with Mn of the free PMMA for both reaction systems. With the same characteristics assumed for both free and graft PMMA, the grafting was controlled, and the increase in grafting ratio was ascribed to the growing chain length of the graft PMMA. In fact, Mn and Mw/Mn of the grafted PMMA chains cleaved from the polyethylene substrate were only slightly larger than those of the free PMMA chains, and this was confirmed in the system of nickel‐mediated ATRP. An appropriate period of UV preirradiation controlled the amount of initiation groups introduced to the HDPE film modified with benzophenone. The grafting ratio increased linearly with the preirradiation time. The graft polymerizations for both reaction systems proceeded in a controlled fashion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3350–3359, 2002 相似文献
73.
Regioselective and high-yielding nuclear monobromination of aromatic ethers can be accomplished with a combination of NaClO2, NaBr, and Mn(acac)3 catalyst in dichloromethane under mild and neutral conditions with the aid of Montmorillonite K10. 相似文献
74.
75.
Carbon monoxide reacts with iodine pentoxide at 42°C to produce iodine vapor, which is dtected by a solid-state electrochemical detector, essentially a Pt/AgI/Ag galvanic cell. The response begins to rise steeply 3.7 s after a 1.1-ml gas sample is introduce and reaches a maximum after a further 1.2 s. The response is linearly related to the concentration of carbon monoxide up to 2 ppm from the detection limit of 0.03 ppm. Interferences such as H2S and C2H4 are removed by 5A molecuarl sieve; H2 (1%), CH4 (5%) and C2H4 (5%) are without effect. 相似文献
76.
Shigetaka Fukuda 《Central European Journal of Mathematics》2004,2(3):377-381
Let (X Δ) be a four-dimensional log variety that is projective over the field of complex numbers. Assume that (X, Δ) is not Kawamata log terminal (klt) but divisorial log terminal (dlt). First we introduce the notion of “log quasi-numerically
positive”, by relaxing that of “numerically positive”. Next we prove that, if the log canonical divisorK
X+Δ is log quasi-numerically positive on (X, Δ) then it is semi-ample. 相似文献
77.
2,7-Dimethylpyrrolo[1,2-a]quinoline (1) was synthesized from 2,6-dimethylquinoline and bromoaeetone via a Tsebitsehibabin reaction. The electrophilic substitution reactions of I, namely, nitrosation, acylation, diazonium coupling, formylation, bromination, and nitration were studied. 相似文献
78.
Miyuki Takei Yoshiharu Tsujita Shigetaka Shimada Hisakatsu Ichihara Motohiro Enokida Akira Takizawa Takatoshi Kinoshita 《Journal of Polymer Science.Polymer Physics》1988,26(5):997-1008
The ionic interaction of poly(ethylene-co-methacrylic acid) ionomer neutralized with Mn2+ or Cu2+ was studied by ESR spectroscopy to explore the local structure in the ionic aggregate. ESR spectra of the ethylene ionomer were obtained as functions of degree of neutralization and temperature. The existence of both isolated and aggregated cations in the ionomer was confirmed by ESR. In addition, the formation of a Cu2+?Cu2+ dimer structure similar to the crystal structure of copper acetate monohydrate was found in ethylene ionomer containing the Cu2+. Cation-cation interactions changed markedly around 70°C with increasing temperature, representing the onset of the motion of cations in the aggregated ionic structure. 相似文献
79.
In the flow-injection system reported, the reagent stream is continuously cycled. The circulating chemiluminescence reagents (β-nitrostyrene/NaOH/hexadecyltrimethylammonium bromide sensitized with fluorescein) allowed 0.1–10 ng of copper(II) to be determined in hundreds of successive injections, even with samples of sea water or a solution of zinc dust. 相似文献
80.
The dynamics of crystal water molecules of guanosine dihydrate are investigated in detail by molecular dynamics (MD) simulation. A 2 ns simulation is performed using a periodic boundary box composed of 4 x 5 x 8 crystallographic unit cells and using the particle-mesh Ewald method for calculation of electrostatic energy. The simulated average atomic positions and atomic displacement parameters are remarkably coincident with the experimental values determined by X-ray analysis, confirming the high accuracy of this simulation. The dynamics of crystal water are analyzed in terms of atomic displacement parameters, orientation vectors, order parameters, self-correlation functions of the orientation vectors, time profiles of hydrogen-bonding probability, and translocations. The simulation clarifies that the average structure is composed of various stable and transient structures of the molecules. The simulated guanosine crystal forms a layered structure, with four water sites per asymmetric unit, classified as either interlayer water or intralayer water. From a detailed analysis of the translocations of water molecules in the simulation, columns of intralayer water molecules along the c axis appear to represent a pathway for hydration and dehydration by a kind of molecular valve mechanism. 相似文献