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1.
Mueller Eric V. Gallagher Michael R. Skowronski Nicholas Hadden Rory M. 《Transport in Porous Media》2021,138(3):637-660
Transport in Porous Media - Modeling flow in vegetative fuel beds is a key component in any detailed physics-based tool for simulating wildland fire dynamics. Current approaches for drag modeling,... 相似文献
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Chun Y. Chow Hélène Bolvin Victoria E. Campbell Régis Guillot Jeff W. Kampf Wolfgang Wernsdorfer Frédéric Gendron Jochen Autschbach Vincent L. Pecoraro Talal Mallah 《Chemical science》2015,6(7):4148-4159
We report here the synthesis and the investigation of the magnetic properties of a series of binuclear lanthanide complexes belonging to the metallacrown family. The isostructural complexes have a core structure with the general formula [Ga4Ln2(shi3–)4(Hshi2–)2(H2shi–)2(C5H5N)4(CH3OH)x(H2O)x]·xC5H5N·xCH3OH·xH2O (where H3shi = salicylhydroxamic acid and Ln = GdIII1; TbIII2; DyIII3; ErIII4; YIII5; YIII0.9DyIII0.16). Apart from the Er-containing complex, all complexes exhibit an antiferromagnetic exchange coupling leading to a diamagnetic ground state. Magnetic studies, below 2 K, on a single crystal of 3 using a micro-squid array reveal an opening of the magnetic hysteresis cycle at zero field. The dynamic susceptibility studies of 3 and of the diluted DyY 6 complexes reveal the presence of two relaxation processes for 3 that are due to the excited ferromagnetic state and to the uncoupled DyIII ions. The antiferromagnetic coupling in 3 was shown to be mainly due to an exchange mechanism, which accounts for about 2/3 of the energy gap between the antiferro- and the ferromagnetic states. The overlap integrals between the Natural Spin Orbitals (NSOs) of the mononuclear fragments, which are related to the magnitude of the antiferromagnetic exchange, are one order of magnitude larger for the Dy2 than for the Er2 complex. 相似文献
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Rory Campbell Dr. Martin F. Davis Mathew Fazakerley Dr. Peter Portius 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18690-18698
The first charge‐neutral Lewis base adducts of tin(IV) tetraazide, [Sn(N3)4(bpy)], [Sn(N3)4(phen)] and [Sn(N3)4(py)2], and the salt bis{bis(triphenylphosphine)iminium} hexa(azido)stannate [(PPN)2Sn(N3)6] (bpy = 2,2′‐bipyridine; phen = 1,10‐phenanthroline; py = pyridine; PPN = N(PPh3)2) have been prepared using covalent or ionic azide‐transfer reagents and ligand‐exchange reactions. The azides were isolated on the 0.3 to 1 g scale and characterized by IR and NMR spectroscopies, microanalytical and thermal methods and their molecular structures determined by single‐crystal XRD. All complexes have a distorted octahedral Sn[N]6 coordination geometry and possess greater thermal stability than their Si and Ge homologues. The nitrogen content of the adducts of up to 44 % exceed any SnIV compound known hitherto. 相似文献
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S.A. Meguid J.D. Campbell L.E. Malvern 《Journal of the mechanics and physics of solids》1979,27(4):331-343
The elastic-plastic behaviour of a solid circular bar made of a homogeneous, isotropic and nonhardening material but of a rate-dependent type, subjected to different proportional deformation programmes of twist and stretch, is analysed. In this investigation the material is assumed to yield according to the von Mises criterion and then to follow a rate-dependent post-yield constitutive law of the Perzyna type. Four radial paths in the angte-of-twist and axial-stretch plane were investigated. For each deformation path the numerical solution of the governing system of quasi-linear partial differential equations gave the corresponding loading path and the radial variation of the stress field at selected times. This study complements that of S. A. Meguid and J.D. Campbell (1979) which considered mainly nonproportional deformation paths. In this work residual stress profiles were also calculated, based upon instantaneous unloading after various amounts of deformation. Comparison with predictions of a rateindependent theory for a limiting state, where elastic strains are negligible, is made. Over a considerable range, the loading paths beyond the initial yield were nearly straight, at the elastic slope. The load trajectory then bends over and approaches a point on the limit-state locus. The results showed that the approximate procedure of increasing the flow stress by an empirically determined factor corresponding to a mean plastic strain-rate gave a good estimate for the limit-state stresses. 相似文献
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Methods of investigating the plastic flow of materials at high rates are reviewed, and experiments are described in which
thin-walled tubular specimens were subjected to dynamic torsional loading. These experiments were performed using a modified
version of a torsional Hopkinsonbar apparatus used in earlier work. The results show that, at strain rates of order 103 sec−1, the stress-strain curve of the alloy tested does not differ significantly from that found at 10−3 sec−1. In tests involving the propagation of a stress increment, however, it was found that the speed of propagation was that of
elastic shear waves, indicating that the initial response of the material is essentially rate dependent. 相似文献