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One-dimensional linear stability analysis was performed for single-phase lead–bismuth eutectic (LBE) natural circulation. The Nyquist criterion and a root search method were employed to find the linear stability boundary of both forward and backward circulations. It was found that the natural circulations could be linearly unstable in a high Reynolds number region. Increasing loop friction makes a forward circulation more stable, but destabilizes the corresponding backward circulation under the same heating/cooling conditions. The characteristic wavelength of an unstable disturbance is roughly equal to the entire loop length. 相似文献
134.
Mathematical models for chemical reaction and mass transfer occurring in the manufacture of high-viscosity condensation polymers are considered. A preliminary study indicates that several diverse models can be represented using a single formula based upon an effectiveness factor. The effectiveness factor is shown to depend upon a ratio of time scales of mixing and reaction. The formula giving the effectiveness factor in terms of the time scales ratio is shown to depend upon mixing assumptions only. Starting with a mixing-cell model, a new modeling framework is developed and shown to include the previous models as special cases. The framework is free of inherent mixing assumptions and can be applied to a wide variety of situations once the mixing characteristics are specified. © 1993 John Wiley & Sons, Inc. 相似文献
135.
E Galanis J Buckner D Kimmel R Jenkins B Alderete J O''Fallon CH Wang BW Scheithauer CD James 《Canadian Metallurgical Quarterly》1998,13(4):717-724
ND10 are recently characterized nuclear domains that are composed of 0.5 microm sized, precisely circumscribed dots in cultured human cell lines. To investigate the distribution and number of ND10 on various types of normal and neoplastic human tissues, we carried out immunostaining and immunoprecipitation analyses with monoclonal antibodies 138 and 1150. The number of ND10 varied from 1 to 10 or more in various tissues as did their size. ND10 were diffusely located in early embryonic and normal tissues, except for the exocrine and endocrine cells of the pancreas and for hepatocytes. In normal squamous mucosa, basal cells had more ND10 than did differentiated superficial squamous cells. The number and size of ND10 were markedly increased in malignant neoplasms but were similar in benign tumors and corresponding normal tissues. Sex hormone-related normal tissues, such as the endometrium or myometrium, and neoplasms strongly stained for ND10. The distribution pattern of ND10 in human tissues indicates that they are conserved nuclear substructures that are closely associated with cellular differentiation, hormonal stimulation, and oncogenesis. 相似文献
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137.
Two methods are described for obtaining approximate solutions to non-linear random vibration problems. The first method approximates the non-linear system with the linear system whose corresponding probability density function best solves the Fokker-Planck equation associated with the non-linear system. In the second method, a class of non-linear systems with known solutions to the Fokker-Planck equation is used to best approximate the non-linear system of interest. Two illustrative examples are presented and the results are compared with existing methods. 相似文献
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The effect of alumina particulates on a thermoplastic matrix is investigated, in particular the effect altering the alumina particle size and morphology has on the mechanical properties. Different grades of alumina are used and two thermoplastic matrices; namely poly(propylene) and poly(ethylene-co-vinyl acetate). Investigations showed that optimum properties were achieved with the alumina of smallest particle size and lowest aspect ratio. Preliminary work has also been performed on the use of silane coupling agents and they have proved effective in increasing the tensile properties of the composites. 相似文献
140.