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Radiophysics and Quantum Electronics - Nonlinear acoustic nondestructive evaluation (NA NDE) methods have a higher sensitivity for defect detection than standard methods. These methods use various... 相似文献
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The syntheses, crystal structures determined by single-crystal X-ray diffraction, and characterizations of new Mo(6) cluster chalcobromides and cyano-substituted compounds with 24 valence electrons per Mo(6) cluster (VEC = 24), are presented in this work. The structures of Cs(4)Mo(6)Br(12)S(2) and Cs(4)Mo(6)Br(12)Se(2) prepared by solid state routes are based on the novel [(Mo(6)Br(i)(6)Y(i)(2))Br(a)(6)](4)(-) (Y = S, Se) discrete units in which two chalcogen and six bromine ligands randomly occupy the inner positions, while the six apical ones are fully occupied by bromine atoms. The interaction of these two compounds with aqueous KCN solution results in apical ligand exchange giving the two first Mo(6) cyano-chalcohalides: Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)S(2))(CN)(6)](3).16H(2)O and Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)Se(2))(CN)(6)](3).16H(2)O. Their crystal structures, built from the original [(Mo(6)Br(i)(6)Y(i)(2))(CN)(a)(6)](4)(-) discrete units, will be compared to those of the two solid state precursors and other previously reported Mo(6) cluster compounds. Their redox properties and (77)Se NMR characterizations will be presented. Crystal data: Cs(4)Mo(6)Br(12)S(2), orthorhombic, Pbca (No. 61), a = 11.511(5) A, b = 18.772(5) A, c = 28.381 A (5), Z = 8; Cs(4)Mo(6)Br(12)Se(2), Pbca (No. 61), a = 11.6237(1) A, b = 18.9447(1) A, c = 28.4874(1) A, Z = 8; Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)S(2))(CN)(6)](3).16H(2)O, Pm-3m (No. 221), a = 17.1969(4) A, Z = 1; Cs(0.4)K(0.6)(Et(4)N)(11)[(Mo(6)Br(6)Se(2))(CN)(6)](3).16H(2)O, Pm-3m (No. 221), a = 17.235(5) A, Z = 1. 相似文献
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Salloum D Gautier R Potel M Gougeon P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(33):8513-8517
The Mo(15)S(20) compound was obtained by thermal decomposition of the metastable binary Mo(15)S(19) in sealed silica tube at temperatures above 500 degrees C. Its crystal structure was solved and refined from a two-component composite crystal by X-ray diffraction in the hexagonal space group P6(3)/m and consists of an equal mixture of the original Mo(9)S(27) cluster unit and the classical one Mo(6)S(8)S(6) interconnected through Mo--S bonds. The Mo core of the Mo(9)S(27) unit is totally new and formed a tricapped trigonal prism. Quantum chemical calculations carried out in order to understand these trends as well as magnetic susceptibility measurements are also reported. The title compound becomes superconducting below 5 K. 相似文献
5.
M. Y. Salloum O. S. Grunsky A. A. Man’shina A. S. Tver’yanovich Yu. S. Tver’yanovich 《Russian Chemical Bulletin》2009,58(11):2228-2232
Indirect methods of investigation of composition and defect structures of lithium niobate (LiNbO3) single crystals with different compositions are discussed. The analysis of two methods for the determination of the Li/Nb
ratio in the samples is carried out, viz., the fundamental UV absorption edge and IR vibrational spectra of the OH− group defects. Intrinsic defect concentrations in lithium niobate crystals (lithium vacancies, $
V_{Li^ - }
$
V_{Li^ - }
and defects, $
Nb_{Li^{4 + } }
$
Nb_{Li^{4 + } }
) as a function of the Li/Nb ratio in the samples are given. The results obtained can serve as an effective way of express
non-destructive composition analysis in a mass production of parallel-plane plates. 相似文献
6.
Oliver Heuss Rogério Salloum Dirk Mayer Tobias Melz 《Archive of Applied Mechanics (Ingenieur Archiv)》2016,86(10):1715-1732
In order to reduce structural vibrations in narrow frequency bands, tuned mass absorbers can be an appropriate measure. A quite similar approach which makes use of applied piezoelectric elements, instead of additional oscillating masses, are the well-known resonant shunts, consisting of resistances, inductances, and possibly negative capacitances connected to the piezoelectric element. This paper presents a combined approach, which is based on a conventional tuned mass absorber, but whose characteristics can be strongly influenced by applying shunted piezoceramics. Simulations and experimental analyses are shown to be very effective in predicting the behavior of such electromechanical systems. The vibration level of the absorber can be strongly attenuated by applying different combinations of resistant, resonant, and negative capacitance shunt circuits. The damping characteristics of the absorber can be changed by applying a purely resistive or resonant resistant shunt. Additionally, the tuning frequency of the absorber can be adapted to the excitation frequency, using a negative capacitance shunt circuit, which requires only the energy to supply the electric components. 相似文献
7.
A modified BET apparatus has been developed to measure the surface area of polymer samples in the range 0.2–3.0 m2. The sample holder is designed to permit easy entry for bulky samples, such as polymer shavings, which cannot be loaded through a capillary or exposed to the high temperature required to seal glass. Other apparatus modifications, which allow the accurate measurement of surface area, include the addition of a dibutyl phthalate differential manometer in conjunction with a pressure reservoir. Corrections for the dead volume, nonideality of nitrogen, and the thermal gradient in the sample holder are developed. Calibrations of the equipment with inorganic samples of known areas from 1.81 to 11.8 m2 gave highly accurate values of 1.74 to 11.6 m2. Results on high-density polyethylene shavings showed precision in determinations and very close agreement in the value of 49.7 for C in the BET equation with the published value, 47.7. 相似文献
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Gilmar Mompean Tibisay Coromoto Zambrano Zaynab Salloum 《Comptes Rendus Mecanique》2014,342(8):478-484
This paper presents numerical simulations of Newtonian and viscoelastic flows through a 180° curved duct of square cross section with a long straight outlet region. A particular attention is paid to the development of the flow in the output rectangular region after the curved part. The viscoelastic fluid is modeled using the constitutive equation proposed by Phan–Thien–Tanner (PTT). The numerical results, obtained with a finite-volume method, are shown for three different Dean numbers (125,137,150) and for three Deborah numbers (0.1,0.2,0.3). The necessary outlet length to impose boundary conditions is presented and discussed for these cases. Streamlines and vortex formation are shown to illustrate and analyze the evolution of the secondary flow in this region. 相似文献
9.
Saeid Farhadi Mozhgan Afshari Mansoureh Maleki Zaynab Babazadeh 《Tetrahedron letters》2005,46(49):8483-8486
An efficient, selective and green procedure for the photocatalytic oxidation of primary and secondary benzylic alcohols to the corresponding aldehydes and ketones has been achieved using silica-encapsulated H3PW12O40 as a recyclable heterogeneous photocatalyst in acetonitrile under oxygen gas as the sole reoxidant of the catalyst. 相似文献
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S. Picard D. Salloum P. Gougeon M. Potel 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(11):i112-i114
The crystal structure of hexacaesium heptacosamolybdenum hentriacontasulfide, Cs6Mo27S31, consists of a mixture of Mo9S11S6 and Mo18S20S6 cluster units in a 1:1 ratio. The units are connected through Mo—S bonds. Cs+ cations occupy large voids between the different cluster units. 相似文献