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971.
The problem of a linear viscoelastic body, containing a penny-shaped crack subjected to the shear parallel to the edge of the crack is considered in this paper. Closed form expressions for the displacements over the surface of the crack, the shear components in the plane of the crack and the stress intensity factors are determined. The various expressions are then specialized for two particular linear viscoelastic materials and the effect of viscoelasticity, wherever possible, is pointed out. 相似文献
972.
973.
974.
Jerald K. Rasmussen Steven M. Heilmann Larry R. Krepski Howell K. Smith Alan R. Katritzky Kumars Sakizadeh 《Journal of polymer science. Part A, Polymer chemistry》1986,24(11):2739-2747
The reaction of bisazlactones (2-oxazolin-5-ones) with primary diamines containing additional secondary or tertiary amine functionality (e.g., diethylenetriamine, triethylenetetramine, or N-methyliminobispropylamine) readily produces polyamides which serve as precursors to a new class of heterocyclic polymers. Thermal cyclodehydration takes place under relatively mild conditions (180–200°C) to produce water-soluble polymers containing the 2-imidazolin-5-one heterocycle. Model reactions have been studied to verify this mode of cyclization and confirm the proposed polymer structure. 相似文献
975.
E. D. Minor T. A. Armstrong R. Bishop V. Harris R. A. Lewis G. A. Smith 《Zeitschrift für Physik A Hadrons and Nuclei》1990,336(4):461-468
The momentum spectra of charged pions following antiproton annihilation at rest in carbon and uranium have been measured. This information complements our previous measurement of the neutral pion spectra. The total charged pion multiplicity is 2.84±0.10 and 2.47±0.09 for carbon and uranium, respectively, in good agreement with recent INC model predictions of 2.96 and 2.48 for the same quantities. However, structures predicted by the model near 200 MeV/c and 300 MeV/c related to delta-resonance production are not seen in the data. The total energy transfers to the nucleus are calculated to be 119±59 MeV(carbon) and 455±50 MeV(uranium). The possibility of exciting multifragmentation with a¯p beam impinging on heavy nuclei is discussed. 相似文献
976.
An earlier paper has put forward a methodology for measuring the ‘need to spend’ on education by local authorities. This paper examines the economic principles underlying the measurement of the need to spend, and finds some problems inherent in the earlier work. The measurement of spending need would nevertheless seem an essential step in the pursuit of territorial equity, particularly in the light of policy developments in the United Kingdom concerning local management of schools. The paper therefore identifies the areas where further clarification of key issues is required. 相似文献
977.
978.
This article summarizes the basic concepts of multiplication and provides some evidence that the traditional third‐grade curriculum and instruction emphasizing memorization of multiplication facts produces much less understanding of the basic concepts of multiplication than a standards‐based curriculum and instruction emphasizing construction of number sense and meaning for operations. This study also describes a collection of assessment tasks that provided meaningful evidence of children's understandings of basic multiplication concepts, including understandings of the relationships between multiplication and addition. 相似文献
979.
Filip Cuyckens Rob Hurkmans Jose M. Castro‐Perez Laurent Leclercq Russell J. Mortishire‐Smith 《Rapid communications in mass spectrometry : RCM》2009,23(2):327-332
Mass defect, neutral loss and isotope filtration techniques were applied to electrospray ionization mass spectrometry (ESI‐MS) data obtained for in vivo and in vitro samples of drug metabolism studies. A combination of these post‐acquisition processing techniques was shown to be more powerful than the use of one of these tools alone for the detection in complex matrices of metabolites of candidate drugs with a characteristic isotope pattern (e.g. containing bromine, chlorine, or a high proportion of radiolabeled drug (12C/14C)) or characteristic neutral losses. In combination with ‘all‐in‐one’ data acquisition this methodology is able to perform software‐driven constant neutral loss scanning for an unlimited number of mass differences at any time after analysis. Highly selective MS chromatograms were obtained with excellent correlation with their corresponding radiochromatograms. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
980.