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901.
902.
Fifteen new ternary antimonides T5T' 1‐xSb2+x were synthesized by reaction of the elemental components in an arc‐melting furnace. They crystallize with a tetragonal structure first reported for Nb5SiSn2 (space group I4/mcm, Z = 4.) A structure refinement from four‐circle X‐ray diffractometer data of Hf5Fe1‐xSb2+x (a = 1086.0(1) pm, c = 550.1(1) pm, R = 0.033 for 270 structure factors and 18 variable parameters) showed deviations from the ideal occupancy for two atomic sites, resulting in the composition Hf4.929(3)Fe0.67(1)Sb2.33(1). Structure refinements from X‐ray powder data resulted in the formula Ti5Ni0.45(2)Sb2.55(2), while no deviation from the ideal composition was observed for Ti5RhSb2. The crystal structures of these compounds are discussed together with those of related binary and ternary compounds. 相似文献
903.
Anton Hammerl Gerhard Holl Manfred Kaiser Thomas M. Klaptke Rainer Krnzle Martin Vogt 《无机化学与普通化学杂志》2002,628(1):322-325
1,2‐Diorganylsubstituted derivatives of hydrazinium azide were examined in order to investigate their higher volatility and higher sensitivity to initiation compared to 1,1‐diorganylsubstituted hydrazinium azide derivatives. The compounds were synthesized from the respective hydrazines by reaction with HN3 and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N). Their sensitivity to friction, shock, electrostatic impact and heat was examined and the explosion products were investigated. The crystal structure of pyrazolidinium azide was determined. 相似文献
904.
Pseudo‐Isomerism by Different Jahn‐Teller Ordering: Crystal Structures of the Hemihydrate and the Monohydrate of (pyH)[MnF(H2PO4)(HPO4)] With pyridinium counter cations (pyH+) the MnIII fluoride phosphate anion [MnF(H2PO4)(HPO4)]— can be stabilized. It forms a chain structure with Mn3+ ions bridged by a fluoride ion and two bidentate phosphate groups. Under sleightly differing conditions either the hemihydrate (pyH)[MnF(H2PO4)(HPO4)]·0.5H2O ( 1 ) or the monohydrate (pyH)[MnF(H2PO4)(HPO4)]·H2O ( 2 ) is formed. The hemihydrate 1 crystallizes monoclinic in space group P21/n, Z = 8, a = 7.295(1), b = 17.052(2), c = 18.512(3) Å, β = 100.78(1)°, R = 0.033, the monohydrate triclinic in space group P1¯, Z = 2, a = 7.374(1), b = 8.628(1), c = 10.329(1) Å, α = 83.658(8)°, β = 77.833(9)°, γ = 68.544(8)°, R = 0.025. Whereas the topology of the chain anions is identical in both structures, the Jahn‐Teller effect is expressed in different ordering patterns: in 1 antiferrodistortive ordering of [MnF2O4] octahedra is observed, with alternating elongation of an F—Mn—F‐axis or a O—Mn—O‐axis, respectively. This leads to asymmetrical Mn—F—Mn‐bridges. In 2 ferrodistortive ordering is found, with elongation of all octahedra along the F—Mn—F‐axis. Thus, symmetrical bridges are formed with long Mn—F distances. This unusual pseudo‐isomerism is attributed to the differing influence of inter‐chain hydrogen bonds. 相似文献
905.
906.
907.
Ronald K. Castellano Colin Nuckolls S. Holger Eichhorn Malcolm R. Wood Andrew J. Lovinger Julius Rebek Jr. 《Angewandte Chemie (International ed. in English)》1999,38(17):2603-2606
When outfitted with long alkyl chains , polycaps, capsules along a polymer chain, spontaneously organize themselves into a two-dimensional liquid crystalline phase. Further organization results from shearing or pulling the liquid crystalline samples, producing three-dimensional assemblies of micrometer-wide, infinitely long fibers (see schematic representation). 相似文献
908.
Summary A functionf C (),
is called monotone on if for anyx, y the relation x – y
+
s
impliesf(x)f(y). Given a domain
with a continuous boundary and given any monotone functionf on we are concerned with the existence and regularity ofmonotone extensions i.e., of functionsF which are monotone on all of and agree withf on . In particular, we show that there is no linear mapping that is capable of producing a monotone extension to arbitrarily given monotone boundary data. Three nonlinear methods for constructing monotone extensions are then presented. Two of these constructions, however, have the common drawback that regardless of how smooth the boundary data may be, the resulting extensions will, in general, only be Lipschitz continuous. This leads us to consider a third and more involved monotonicity preserving extension scheme to prove that, when is the unit square [0, 1]2 in 2, strictly monotone analytic boundary data admit a monotone analytic extension.Research supported by NSF Grant 8922154Research supported by DARPA: AFOSR #90-0323 相似文献
909.
Xing Chao Guofeng Shen Kai Sun Zhenhai Wang Qinghui Meng Shengkai Wang Ronald K. Hanson 《Proceedings of the Combustion Institute》2019,37(2):1345-1353
Cavity-enhanced absorption spectroscopy (CEAS) has generated much interest in shocktube kinetics studies because of its recent success in achieving improved sensitivity and high time resolution with robust optical alignment. While recent progress demonstrated experimental schemes including off-axis scanned-wavelength approach and on-axis ps-pulsed laser approach, that both successfully suppressed the laser-cavity coupling noise, this paper develops a theoretical model to predict the CEAS sensor performance that can be used as a design tool applicable to more generalized cases. The method models the optical field in the cavity based on the decentered Gaussian beam model, from which the cavity transmission spectrum and the laser-cavity coupling noise can be numerically calculated. The simulation results predict sensor performance for different cavity configurations and laser characteristics, including various degrees of laser-cavity mode-matching, laser linewidths, scanning rates, and cavity filling conditions. Simulation with example wavelengths in the ultraviolet, near-infrared, and mid-infrared showed increasing mode-matched beam waist size for increasing wavelengths. An off-axis alignment scheme was found to be capable of suppressing the coupling noise by two orders-of-magnitude at a moderate laser linewidth of 1?GHz. Coupling noise level on the order of 1e-5 for scanned-wavelength off-axis alignment case with a narrowband mid-infrared laser was obtained by model calculation and agreed with experimental results within acceptable uncertainty range. The developed method can serve to guide future design and optimization of CEAS system in shocktube studies. 相似文献
910.
Karsten Gröger Max Kaiser Friedrich Dinkelacker 《Proceedings of the Combustion Institute》2019,37(3):3271-3278
For diesel sprays, the primary breakup processes are only rarely understood due to the high optical density and the resulting difficulties to measure them with extremely high spatial and sufficient temporal resolution. The Optical Connectivity Method (OCM) has been proposed in the last years to allow the determination of the breakup length of the connected liquid core, thus giving a measurement quantity of the primary breakup. In this work, an improved optical setup of the OCM is applied to a three-hole test injector nozzle where several measurement techniques are compared currently under well-defined conditions up to 100?MPa injection pressure. In this work, the direct comparison with X-Ray measurements done at the Advanced Photon Source of the Argonne National Laboratory will be described. This allows an evaluation of the OCM technique and a comparison of the different measurement quantities in the first 500?µm range of the spray. The structure of the spray is measured by X-Ray phase contrast imaging and the fuel mass distribution is measured by X-Ray absorption imaging. A detailed comparison of the two X-Ray techniques and the OCM technique has been possible for the first time. It is found that the measurement data of the spray near field are very congruent with all three methods. Due to this comparison, the measurement of the non-perturbed length, which describes the distance from the nozzle orifice up to the point where the formation of surface disturbances is starting, by the OCM is validated for the first time. Within this non-perturbed length of the spray, the OCM signal is weak before it starts to illuminate from the scattering of the perturbed surface. Thus, the OCM technique can deliver two characteristic length scales, the non-perturbed length and the breakup length, characterizing the primary spray breakup. 相似文献