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991.
Harmonic balance and Volterra-based analysis methods are well known, but the capabilities of these methods have been limited by significant issues of complexity which either constrain their application to relatively simple cases, or limit the accuracy of analysis in more complex cases. This study briefly summarizes recent results which effectively extend the capabilities of both harmonic balance and Volterra-based analysis by making complex analyses much more feasible. The new capabilities and performance of the two approaches are then evaluated and compared using benchmark case studies of a Duffing oscillator and a nonlinear automotive damper. The results offer new insights and lead to different conclusions on the relative merits of harmonic balance versus Volterra-based analysis relative to prior studies and similar benchmark analyses. 相似文献
992.
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994.
W.C. Chen R. Erwin J.W. McIver III S. Watson C.B. Fu T.R. Gentile J.A. Borchers J.W. Lynn G.L. Jones 《Physica B: Condensed Matter》2009,404(17):2663-2666
At the NIST Center for Neutron Research (NCNR), we have applied 3He neutron spin filters (NSFs) to the instruments where 3He NSFs are advantageous, such as thermal triple-axis spectrometry, small-angle neutron scattering, and diffuse reflectometry. We present the status of our development and application of this method, including polarized gas production by spin-exchange optical pumping, magnetostatic cavities for storage of the polarized gas on the beam line, and nuclear magnetic resonance (NMR)-based, on-line monitoring and reversal of the 3He polarization. We present the status of developing user-friendly interfaces incorporated into the instrument software to handle these 3He neutron spin filters while taking data and performing data analysis. Finally we discuss the status of development of a polarization capability on the multi-axis crystal spectrometer, which requires polarization analysis over a 220° angular range. 相似文献
995.
T. William Bentley Robert O. Jones Dae Ho Kang In Sun Koo 《Journal of Physical Organic Chemistry》2009,22(9):799-806
Rate constants for a wide range of binary aqueous mixtures and product selectivities (S) in ethanol–water (EW) and methanol–water (MW) mixtures, are reported at 25 °C for solvolyses of benzenesulfonyl chloride and the 4‐chloro‐derivative. S is defined as follows using molar concentrations: S = ([ester product]/[acid product]) × ([water solvent]/[alcohol solvent]). Additional selectivity data are reported for solvolyses of 4‐Z‐substituted sulfonyl chlorides (Z = OMe, Me, H, Cl and NO2) in 2,2,2‐trifluoroethanol–water. To explain these results and previously published data on kinetic solvent isotope effects (KSIEs) and on other solvolyses of 4‐nitro and 4‐methoxybenzenesulfonyl chloride, a mechanistic spectrum involving a change from third order to second order is proposed. The molecularity of these reactions is discussed, along with new term ‘SN3–SN2 spectrum’ and its connection with the better established term ‘SN2–SN1 spectrum’. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
Double-emulsion droplets may be assembled into highly concentric shells using a uniform AC electric field to induce dipole/dipole interactions. The resulting force centers the inner droplet with respect to the outer shell if the outer droplet has a higher dielectric constant than the ambient, suspending liquid. The dielectric constant of the inner droplet does not influence this condition. Applying an electric field >104 Vrms/m achieves centering of approximately 3–6 mm diameter droplets suspended in ~10 centipoise liquids within ~60 s. If the outer shell is electrically conductive, the effect depends strongly on frequency. In the case of the monomer-containing liquids requisite to forming foam shells for laser target fabrication, the electrical field frequency must be ~10 MHz or higher. Because of very stringent requirements imposed on the concentricity and sphericity of laser targets, electric field induced droplet distortion must be minimized. Consequently, the liquid constituents must be matched in density to ~0.1%. 相似文献
997.
998.
Virginia Lozano Peter G. Jones 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o653-o655
The title compounds, C7H8Cl2N+·Cl− and C7H8Br2N+·Br−, are isomorphous. In the crystal packing, layers parallel to the ac plane are formed by a classical N+—H⋯X− hydrogen bond (X = halogen) and two X⋯X contacts. A third X⋯X contact links the layers, and a fourth, which is however very long, completes a ladder‐like motif of halogen atoms. Hydrogen bonds of the form C—H⋯X play at best a subordinate role in the packing. 相似文献
999.
J. M. Schwantes R. S. Addleman J. D. Davidson M. Douglas D. Meier O. D. Mullen M. Myjak M. E. Jones M. L. Woodring B. Johnson P. H. Santschi 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):889-895
We are developing a medium-resolution autonomous in situ gamma detection system for marine and coastal waters. The system is designed to extract and preconcentrate isotopes of interest from natural waters prior to detection in order to eliminate signal attenuation of the gamma rays traveling through water and lower the overall background from the presence of naturally occurring radioactive isotopes (40K and U–Th series radionuclides). Filtration is used to preconcentrate target isotopes residing on suspended particles, while chemosorption is employed to preferentially extract truly dissolved components from the water column. Used filter and chemosorbent media will be counted autonomously using two LaBr3 detectors in a near 4-π configuration around the samples. A compact digital pulse processing system, developed in-house and capable of running in coincidence mode, is used to process the signal from the detectors to a small on-board computer. The entire system is extremely compact (9″ dia. × 30″ len.) and platform independent, but designed for initial deployment on a research buoy. A variety of commercial and in-house nano-porous chemosorbents have been selected, procured or produced, and these and filter and detector components have been tested. 相似文献
1000.
Josiane Arnaud Robert L. Jones Alain LeBlanc Mi-Young Lee Olav Mazarrasa Patrick Parsons Marina Patriarca Andrew Taylor Jean-Philippe Weber Cas Weykamp 《Accreditation and quality assurance》2009,14(8-9):427-430
A critical issue in the organisation of Proficiency Testing/External Quality Assessment Schemes is the definition of the criteria against which the performance of individual laboratories should be evaluated. Organisers of EQAS in Occupational and Environmental Laboratory Medicine (http://www.occupational-environmental-laboratory.com) collaborate to define common acceptable levels of performance. The aim of this study was to compare the Horwitz function to the Fraser’s approach. Sets of results obtained from the distribution of test materials in the Network schemes (for the measurands: copper, selenium or zinc in serum) were used to calculate Z-scores according to both approaches. Quality specifications derived from both approaches were also compared to the standard deviations obtained. Except for selenium, Horwitz criteria suggests a more stringent evaluation than Fraser criteria, the latter being very stringent as regard the participant analytical variability. 相似文献