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111.
G.W. SWENSON JR 《Journal of sound and vibration》2002,255(3):519-529
A directional microphone system for field recording of sounds in the air often involves a parabolic reflector to focus the sound waves on the microphone (transducer) element. Some deficiencies of such a system are noted with respect to reproduction of spectra. The reflector system, involving as it does a structure comparable to a wavelength in linear dimension, is not susceptible to traditional high- or low-frequency approximate methods of computation. Modern numerical techniques now permit precise calculation of the directional responses of small reflectors of various shapes. One result is a proposal for a very economical and effective system involving a plane reflector. Other baffle shapes are also investigated, which may be of interest in special applications. 相似文献
112.
Bunsen und Kirchhoff 《Fresenius' Journal of Analytical Chemistry》1862,1(1):62-63
Ohne Zusammenfassung 相似文献
113.
G. Kirchhoff und R. Bunsen 《Fresenius' Journal of Analytical Chemistry》1862,1(1):139-140
Ohne Zusammenfassung 相似文献
114.
H. E. Marsh JR. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):1397-1418
Abstract The complex and important role of the propellant binder in solid-propellant rockets is described. The severe weight problems of space exploratrion cause high propellant performance to be of major concern in a highly competitive field. Binders contribute to performance, not only in terms of fuel value, but by being compatible with energetic components and by providing good mechanical properties. Both sterilization required for planetary landings and compatibility problems of new energetic oxidizers generate new requirements too stringent for existing binders; only binders composed essentially of saturated aliphatic hydrocarbon are predicted to be suitable. Several saturated-binder developments are in progress. The achievements of one of these programs, based on free-radical synthesis, are evaluated against the goals of the new binder. 相似文献
115.
Paul D. Kirchhoff Rob Brown Scott Kahn Marvin Waldman C. M. Venkatachalam 《Journal of computational chemistry》2001,22(10):993-1003
We present the Cerius2 Structure‐Based Focusing (SBF) application. This application was applied to the estrogen receptor. A series of three‐dimensional queries were generated for the binding site of the receptor. The queries consist of combinations of hydrogen bond donors and acceptors, and lipophilic features for the binding site along with excluded volume regions occupied by the receptor atoms. A database of 31 ligands with known relative binding affinities for the estrogen receptor was used to examine the selectivity of the queries. The objective of the study was to determine if queries generated by the Cerius2 SBF method could differentiate between the more and less active ligands of the training set. Results are promising, with the generated queries showing greater selectivity toward the more active ligands. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 993–1003, 2001 相似文献
116.
Gunther Wittstock Hendrik Emons Matthias Kummer Jon R. Kirchhoff William R. Heineman 《Fresenius' Journal of Analytical Chemistry》1994,348(11):712-718
Different gold surfaces modified by carbon-spray have been investigated by scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM). A transformation of the SECM image to a distance-location profile is proposed which assists the correlation of both images. The structures found in the transformed SECM images of carbon-spray layers on gold substrates can be explained by the topographic features visible in the SEM pictures. Tempering the carbon spray results in an increased density of electrochemically reactive carbon particles which could be confirmed by cyclic voltammetric investigations. Gold minigrids modified with carbon spray expose some areas of especially large currents which could not be predicted from their SEM images. This effect may result from particles located at the edge of a wire intersection having relatively large active surfaces per particle. They contribute significantly to the total current of the minigrid. 相似文献
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119.
This paper is concerned with the construction and analysis ofcompact finite difference approximations to the model linearsource problem (pu')' + qu = f where the functions p,q, and f can have jump discontinuities at a finite number ofpoints. Explicit formulae that give O(h2) O(h3) and O(h4) accuracyare derived, and a procedure for computing three-point schemesof any prescribed order of accuracy is presented. A rigoroustruncation and discretization error analysis is offered. Numericalresults are also given. 相似文献
120.
INTRODUCTION In this third part of a review on chemometrics in spectroscopy we will describe a recent methodology that has attracted increasing interest in spectroscopy. namely multi-way analysis. The application of multi-way analysis in spectroscopy is still relatively new. hence many methodological improvements are being investigated currently. Part of thls review will also be used to describe the algorithmic improvements gained the last decade. 相似文献