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61.
The monohydrates of strontium and barium hydroxide have been prepared by decomposition, under vacuum, of the corresponding octahydrates. X-ray powder data for both compounds are reported, together with that for anhydrous strontium hydroxide; the latter is included in order to clarify an apparent anomaly in the literature.
The authors wish to thank Mr. A. Miller for taking the X-ray powder photographs. 相似文献
Zusammenfassung Es wurden die Monohydrate von Strontium und Bariumhydroxid im Vakuum aus den entsprechenden Octahydraten hergestellt. Röntgenographische Daten für beide Verbindungen sowie für wasserfreies Strontiumhydroxid wurden gegeben; für Letzteres, um gewisse Anom alien in der Literatur zu klären.
Résumé Préparation des hydroxydes de strontium et de baryum monohydratés par décomposition dans le vide des octohydrates correspondants. Etude par rayons X de ces composés ainsi que de l'hydroxyde de strontium anhydre, dans le but, pour ce dernier, d'élucider certaines anomalies de la littérature.
, . , ; , .
The authors wish to thank Mr. A. Miller for taking the X-ray powder photographs. 相似文献
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63.
An improved algorithm for in situ adaptive tabulation 总被引:1,自引:0,他引:1
In situ adaptive tabulation (ISAT) is a proven storage/retrieval method which efficiently provides accurate approximations to high-dimensional functions which are computationally expensive to evaluate. Previous applications of ISAT to computations of turbulent combustion have resulted in speed-ups of up to a thousand. In this paper, improvements to the original ISAT algorithm are described and demonstrated using two test problems. The principal improvements are in the table-searching strategies and the addition of an error checking and correction algorithm. Compared to an earlier version of ISAT, reductions in CPU time and storage requirements by factors of 2 and 5, respectively, are observed for the most challenging, 54-dimensional test problem. 相似文献
64.
This paper examines the effects of H2O vapor pressure on the equilibrium conditions of a CuCl2 hydrolysis reactor in the thermochemical Cu–Cl cycle of hydrogen production. A new predictive model is developed to determine the minimum steam requirement in the reactor based on the chemical equilibrium condition, reactor pressure and fraction of gaseous reactant. Experimental data, at three separate vapour pressures of steam, compared well with the new predictive formulation. 相似文献
65.
We consider non-relativistic electrons, each of the same charge to mass ratio, moving in an external magnetic field with an interaction potential depending only on the mutual separations, possibly confined by a harmonic trapping potential. We show that the system admits a “relativity group” which is a one-parameter family of deformations of the standard Galilei group to the Newton–Hooke group which is a Wigner–?nönü contraction of the de Sitter group. This allows a group-theoretic interpretation of Kohn’s theorem and related results. Larmor’s theorem is used to show that the one-parameter family of deformations are all isomorphic. We study the “Eisenhart” or “lightlike” lift of the system, exhibiting it as a pp-wave. In the planar case, the Eisenhart lift is the Brdi?ka–Eardley–Nappi–Witten pp-wave solution of Einstein–Maxwell theory, which may also be regarded as a bi-invariant metric on the Cangemi–Jackiw group. 相似文献
66.
Frontispiece: Lanthanide Tetrazolate Complexes Combining Single‐Molecule Magnet and Luminescence Properties: The Effect of the Replacement of Tetrazolate N3 by β‐Diketonate Ligands on the Anisotropy Energy Barrier
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Comparison of the three-phase oil relative permeability models 总被引:3,自引:0,他引:3
A comparative study of seven different methods for predicting three-phase oil relative permeabilities in the presence of gas and water phases is presented. Predicted oil relative permeabilities from these correlations have been compared with published three-phase experimental data obtained in Berea sandstone core samples. Some of the correlations under study have been recently developed and have never been tested against the laboratory data.The comparison shows that the commonly used models such as Stones' often do not give accurate predictions of the experimental data. It is concluded that the recently developed models fit the experimental data as well as or better than the previously developed and widely used three-phase oil relative permeability models. 相似文献
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70.
Hopper TA Vasilić B Pope JM Jones CE Epstein CL Song HK Wehrli FW 《Magnetic resonance imaging》2006,24(8):1077-1085
Susceptibility artifacts due to metallic prostheses are a major problem in clinical magnetic resonance imaging. We theoretically and experimentally analyze slice distortion arising from susceptibility differences in a phantom consisting of a stainless steel ball bearing embedded in agarose gel. To relate the observed image artifacts to slice distortion, we simulate images produced by 2D and 3D spin-echo (SE) and a view angle tilting (VAT) sequence. Two-dimensional SE sequences suffer from extreme slice distortion when a metal prosthesis is present, unlike 3D SE sequences for which--since slices are phase-encoded--distortion of the slice profile is minimized, provided the selected slab is larger than the region of interest. In a VAT sequence, artifacts are reduced by the application of a gradient along the slice direction during readout. However, VAT does not correct for the excitation slice profile, which results in the excitation of spins outside the desired slice location and can lead to incorrect anatomical information in MR images. We propose that the best sequences for imaging in the presence of a metal prosthesis utilize 3D acquisition, with phase encoding replacing slice selection to minimize slice distortion, combined with excitation and readout gradient strengths at their maximum values. 相似文献