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11.
In this paper, a projection method is presented for solving the flow problems in domains with moving boundaries. In order to track the movement of the domain boundaries, arbitrary‐Lagrangian–Eulerian (ALE) co‐ordinates are used. The unsteady incompressible Navier–Stokes equations on the ALE co‐ordinates are solved by using a projection method developed in this paper. This projection method is based on the Bell's Godunov‐projection method. However, substantial changes are made so that this algorithm is capable of solving the ALE form of incompressible Navier–Stokes equations. Multi‐block structured grids are used to discretize the flow domains. The grid velocity is not explicitly computed; instead the volume change is used to account for the effect of grid movement. A new method is also proposed to compute the freestream capturing metrics so that the geometric conservation law (GCL) can be satisfied exactly in this algorithm. This projection method is also parallelized so that the state of the art high performance computers can be used to match the computation cost associated with the moving grid calculations. Several test cases are solved to verify the performance of this moving‐grid projection method. Copyright © 2004 John Wiley Sons, Ltd. 相似文献
12.
滕志东 《数学物理学报(A辑)》1998,18(2):169-175
该文研究周期二维Lotka-Volterra捕食食饵系统解的有界性,持续生存性以及正周期解的存在性和全局稳定性.并将结果推广到食饵有补充的周期二维Lotka-Volterra竞争系统上去,得到了一系列新的结果,改进和推广了文[1—3]的主要结论. 相似文献
13.
Cheng‐Ho Chen Chih‐Chun Teng Ming‐Shyong Tsai Fu‐Su Yen 《Journal of Polymer Science.Polymer Physics》2006,44(15):2145-2154
A Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na+‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na+‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na+‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na+‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na+‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na+‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006 相似文献
14.
15.
Optical studies of pulsed-laser fragmentation of biliary calculi 总被引:2,自引:0,他引:2
P. Teng N. S. Nishioka R. Rox Anderson T. F. Deutsch 《Applied physics. B, Lasers and optics》1987,42(2):73-78
The fragmentation of gallstones and kidney stones using pulsed visible laser radiation has recently been demonstrated; however, the fragmentation mechanism is not well understood. The temporal and spectral characteristics of the bright flash of light accompanying fragmentation of gallstones were studied using 0.8 and 360-s-long, 690-nm-wavelength, dye-laser pulses. Time-resolved visible emission spectra show a broad continuum upon which line spectra are superimposed. The continuum emission is due to free-free and free-bound electron transitions indicative of a plasma and the line spectra are due to neutral and ionized calcium. Initiation of this plasma is fluence rather than intensity dependent. A model is proposed in which laser energy is coupled to the plasma, which then impulsively expands, generating intense acoustic transients which fracture the stone. 相似文献
16.
Lingjia Xu Liangliang Zhu Shi Wu Xiaopeng Chen Qiwen Teng 《Central European Journal of Chemistry》2006,4(4):732-742
Supermolecular complexes formed by oligophenyleneethynylene derivatives and isophthalic acid were studied using AM1 method
to obtain binding energy. Electronic spectra and IR spectra of the complexes were calculated by INDO/CIS and AM1 methods based
on AM1 geometries. Results indicated that the dimer could be formed by the monomers via hydrogen bonding because of the negative
binding energy. Binding energy of the complexes was affected by electronegativity and steric effects of the substituents.
The first UV absorptions and IR frequencies of N-H bonds of the complexes were both red-shifted compared with those of the
monomers. The complexes could bind small molecules via hydrogen bonds, resulting in the change in UV absorptions and an increase
in IR frequencies of N-H bonds. 相似文献
17.
The use of the reverse atom transfer radical polymerization (RATRP) to end-functionalize poly(methyl methacrylate) (PMMA) with fullerenes, e.g. C60 and C70 was described in this paper. The Cl-terrninated PMMA was prepared via RATRP with designed molecular weight and narrow molecular weight distributions, and then directly used to react with fullerenes to produce C60(C70) terminated PMMA polymers in the presence of CuBr/Cu/bipy or FeCl2/bipy catalysts. The resultant polymers exhibit good solubility in some common organic solvents, e.g. THF, CHCl3 and toluene, and were well structurally characterized by a variety of physical techniques. 相似文献
18.
A series of new 1- and 2-arylmethyl-3,4-dimethylpyrano[2,3-c]pyrazol-6-one derivatives were synthesized and examined for their antiplatelet activities. Some of these compounds showed significant inhibitory activities. Among them, 1-phenylmethyl-3,4-dimethylpyrano[2,3-c]pyrazol-6(1H)-one (4a), 2-(2'-methoxyphenyl)methyl-3,4-dimethylpyrano[2,3-c]pyrazol-6(2H)- one (3e) and 2-(3'-methoxyphenyl)methyl-3,4-dimethylpyrano[2,3-c]pyrazol-6-(2H) - one (3f) were the most effective. These inhibitors acted in a concentration-dependent manner. The antiplatelet effect of compound 3f is due to the inhibition of thromboxane A2 formation and the blockade of thromboxane A2/prostaglandin endoperoxide receptor in washed rabbit platelets. 相似文献
19.
Resolution of freshly prepared and of commercially available (degraded) samples of cardiolipin into 15-30 components has been accomplished by reversed-phase high-performance liquid chromatography using a 3-micron particulate Microsorb C18 column irrigated with linear gradients of acetonitrile--methanol--10 mM phosphate buffer pH 7.4. Selected resolved components were crystallized and characterized by infrared absorption spectra. Saponification of other components and identification of component fatty acids by reversed-phase high-performance liquid chromatography demonstrated the presence of ten fatty acids (14:0, 14:1, 16:0, 16:1, 18:0, 18:1, 18:2, 18:3, 20:0, 20:4), with linoleic acid (18:2) identified in all resolved components. From fatty acid composition data it appears that several resolved fractions consist of single cardiolipin molecular species. 相似文献
20.
Genson KL Hoffman J Teng J Zubarev ER Vaknin D Tsukruk VV 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9044-9052
An amphiphilic heteroarm star polymer containing 12 alternating hydrophobic/hydrophilic arms of polystyrene (PS) and poly(acrylic acid) (PAA) connected to a well-defined rigid aromatic core was studied at the air-water and the air-solid interfaces. At the air-water interface, the molecules spontaneously form pancakelike micellar aggregates which measure up to several microns in diameter and 5 nm in thickness. Upon reduction of the surface area per molecule to 7 nm2, the two-dimensional micelles merged into a dense monolayer. We suggest that confined phase separation of dissimilar polymer arms occurred upon their segregation on the opposite sides of the rigid disklike aromatic core, forcing the rigid cores to adopt a face-on orientation with respect to the interface. Upon transfer onto solid supports the PS chains face the air-film interface making it completely hydrophobic, and the PAA chains were found to collapse and form a thin flattened underlayer. This study points toward new strategies to create large 2D microstructures with facial amphiphilicity and suggests a profound influence of star molecular architecture on the self-assembly of amphiphiles at the air-water interface. 相似文献