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81.
In this paper, we take a different perspective on the derivation of artificial viscosity. Heretofore, the development of artificial viscosity has been based on the paper published in Journal of Applied Physics in 1950 authored by John von Neumann and Robert Richtmyer [1]. Earlier, in 1948, Richtmyer published a report at Los Alamos Scientific Laboratory documenting the original concept [2]. This report was the true origin of shock capturing methods and contains several key ideas that are conceptually different than the 1950 journal article. Unfortunately, this report (LA‐671) was classified until 1993. This has resulted in two issues: the misattribution of the invention of artificial viscosity as primarily being the work of von Neumann and the loss of the structurally different ideas in the original report. We seek to right the record of history here and use the ideas contained in Richtmyer's report to good effect in deriving a new shock viscosity. The focus of previous development has been the Hugoniot curve describing the locus of states connected by a single shock wave. Here we follow a path more focused upon the Rayleigh line, which is strongly guided by Richtmyer's line of development of the original artificial viscosity formulation. We provide an implementation of the method resulting from this perspective and computational results for simple shock problems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
82.
Kontturi M Laurila E Mattsson R Peräniemi S Vepsäläinen JJ Ahlgrén M 《Inorganic chemistry》2005,44(7):2400-2406
Four new zinc and cadmium bisphosphonates [{NaZn(Cl2CP2O6H)(H2O)5}]n (1), [{Cd2(Cl2CP2O6)(H2O)4}.H2O]n (2), [{Zn(Cl2CP2O6Pri2)(H2O)3}.H2O]n (3), and [{Cd2(Cl2CP2O6Pri2)2(MeOH)2(H2O)2}.H2O]2 (4) have been prepared and their crystal structures determined by single-crystal X-ray diffractometry. Two bisphosphonate ligands were used: clodronate, (dichloromethylene)bis(phosphonate) and its symmetrical P,P'-diisopropyl ester derivative. The structure of the Zn complex 1 is three-dimensional, consisting of one-dimensional Zn-clodronate chains connected to the three-dimensional network by Na+ ions. The structure of Cd complex 2 consists of double layers, and a unique bond was found between the Cd2+ cation and a Cl atom of clodronate. Zn complex 3 consists of one-dimensional chains, but the binding of the bisphosphonate ligands is unique: in 3 the bisphosphonate ligand is only bidentate. Compound 4 is a tetramer, and hydrogen bonds hold the tetramers together, forming a layered structure. 相似文献
83.
Birger Scholz Kim Kultima Anna Mattsson Jeanette Axelsson Björn Brunström Krister Halldin Michael Stigson Lennart Dencker 《BMC neuroscience》2006,7(1):12-17
Background
Differentiation of the brain during development leads to sexually dimorphic adult reproductive behavior and other neural sex dimorphisms. Genetic mechanisms independent of steroid hormones produced by the gonads have recently been suggested to partly explain these dimorphisms. 相似文献84.
V. Frishfelds J. G. I. Hellström T. S. Lundström H. Mattsson 《Transport in Porous Media》2011,89(3):441-457
An investigation of the potential to numerically model the no erosion filter test is performed here, where the flow through
a large ensemble of particles is considered by applying minimisation of dissipation rate of energy on the ensemble that is
discretised with modified Voronoi diagrams and Delaunay triangulation. Low-Reynolds number simulations are applied to each
part of the Voronoi diagram using computational fluid dynamics. The mechanical friction between particles is modelled by increasing
the effective viscosity for closely spaced particles. Microscopic mechanisms for successful and unsuccessful sealing of filters
are obtained. The numerical results agree with previously presented experimental observations by Sherard and Dunnigan. A conformity
is that the sealing starts from the end of the channel and continues outwards in the radial direction. The sealing implies
that the permeability can be reduced several orders of magnitude during a test. 相似文献
85.
Sami Hietala Mikael Paronen Svante Holmberg Jan Nsman Jyrki Juhanoja Milja Karjalainen Ritva Serimaa Minna Toivola Tero Lehtinen Katri Parovuori Gran Sundholm Hanna Ericson Britta Mattsson Lena Torell Franciska Sundholm 《Journal of polymer science. Part A, Polymer chemistry》1999,37(12):1741-1753
A series of proton exchange membranes have been prepared by the preirradiation grafting method. Styrene was grafted onto a matrix of poly(vinylidene fluoride) (PVDF) after electron beam irradiation. Part of the samples was crosslinked with divinylbenzene (DVB) or bis(vinylphenyl)ethane (BVPE). Subsequent sulfonation gave membranes grafted with poly(styrene sulfonic acid) and marked PVDF‐g‐PSSA. It was found that the intrinsic crystallinity of the matrix decreased in both the grafting and the sulfonation reaction in all the membranes. The graft penetration and the ion conductivity are influenced strongly by the crosslinker. The ion conductivity is considerably lower in crosslinked membranes than in noncrosslinked ones. Generally, the mechanical strength decreases with crosslinking. The membranes show a regular phase separated structure in which the sulfonated grafts are incorporated in the amorphous parts of the matrix polymer. The phase separated domains are small, of the order of magnitude of 100–250 nm. These were resolved on transmission electron micrographs and on atomic force images but could not be resolved with microprobe Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1741–1753, 1999 相似文献
86.
Thomas Raistrick Matthew Reynolds Helen F. Gleeson Johan Mattsson 《Molecules (Basel, Switzerland)》2021,26(23)
Liquid Crystal Elastomers (LCEs) combine the anisotropic ordering of liquid crystals with the elastic properties of elastomers, providing unique physical properties, such as stimuli responsiveness and a recently discovered molecular auxetic response. Here, we determine how the molecular relaxation dynamics in an acrylate LCE are affected by its phase using broadband dielectric relaxation spectroscopy, calorimetry and rheology. Our LCE is an excellent model system since it exhibits a molecular auxetic response in its nematic state, and chemically identical nematic or isotropic samples can be prepared by cross-linking. We find that the glass transition temperatures () and dynamic fragilities are similar in both phases, and the -dependence of the relaxation shows a crossover at the same for both phases. However, for , the behavior becomes Arrhenius for the nematic LCE, but only more Arrhenius-like for the isotropic sample. We provide evidence that the latter behavior is related to the existence of pre-transitional nematic fluctuations in the isotropic LCE, which are locked in by polymerization. The role of applied strain on the relaxation dynamics and mechanical response of the LCE is investigated; this is particularly important since the molecular auxetic response is linked to a mechanical Fréedericksz transition that is not fully understood. We demonstrate that the complex Young’s modulus and the relaxation time remain relatively unchanged for small deformations, whereas for strains for which the auxetic response is achieved, significant increases are observed. We suggest that the observed molecular auxetic response is coupled to the strain-induced out-of-plane rotation of the mesogen units, in turn driven by the increasing constraints on polymer configurations, as reflected in increasing elastic moduli and relaxation times; this is consistent with our recent results showing that the auxetic response coincides with the emergence of biaxial order. 相似文献
87.
Schwartz G.A. Bergman R. Mattsson J. Swenson J. 《The European physical journal. E, Soft matter》2003,12(1):113-116
The European Physical Journal E - The molecular dynamics of oligomeric poly(propylene glycol) (PPG) liquids ( M w =1200, 2000 and 4000 g/mol) confined in a two-dimensional layer-structured... 相似文献
88.
J. Blomqvist S. A. Hjorth A. Johnson A. Kerek W. Klamra A. Nilsson J. Nyberg S. E. Arnell S. Mattsson H. Roth Ö. Skeppstedt 《Zeitschrift für Physik A Hadrons and Nuclei》1985,322(1):169-170
Yrast levels in the doubly-magic nucleus56Ni have been studied by in-beam gg-spectroscopy with the reaction54Fe(α, 2n)56Ni. A cascade of five γ -transitions is established. A shell model calculation of 2p2h, T=0 states, using empirical matrix elements, suggests the assignments 8+ and 10+ for the two highest levels. 相似文献
89.
90.