排序方式: 共有6条查询结果,搜索用时 0 毫秒
1
1.
2.
In this paper three‐dimensional lubrication flow of grease is analysed numerically. The lubrication flow configuration is formed by two ellipsoid rollers. The load is assumed to be light enough for the lubrication mode to be purely hydrodynamic. The fluid behaviour is modelled using the Herschel–Bulkley model, and a two‐dimensional modified Reynolds equation is derived. The numerical solutions are obtained by using a hybrid spectral/iterative technique and the Galerkin projection scheme. The effects of the material and geometrical parameters on pressure distribution are emphasized in the study. The investigation is conducted for a situation where the two ellipsoids are fully immersed in a grease lubricant. The effect of the geometry on the pressure distribution is determined by varying the ratio of the semi‐axes and the minimum gap of the two rollers, respectively. The effect of the material parameters is examined by varying the power‐law index and yield stress. It is found that the pressure distribution is strongly influenced by the shape of the rollers, the size of the minimum gap of the rollers and the rheological parameters. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
The rate of adsorption of oleate soap onto a Nigerian hematite in an aqueous medium was determined from 29 to 60°C using the differential analysis method. The activation energy and frequency factor were determined at 57.1 kJ mol−1 K−1 and 4.0 × 103 liter mol−1 min−1, respectively, indicating that the chemical processes are the slow, rate-determining step and that the reaction proceeds relatively fast. The adsorption isotherm was the Langmuir type: chemisorption was considered the dominant mode of adsorption. The desorption isotherm indicated a minor contribution of physical adsorption to the overall adsorption process. 相似文献
4.
5.
P. E. Holland Peter T. Woods Chris Brookes I. Uprichard Paul Quincey R. Robinson Hansa D'Souza Martin Milton Brian Goody William Bell Des Alphonso 《Accreditation and quality assurance》2001,6(3):120-129
The National Physical Laboratory (NPL) is involved in the dissemination of nationally traceable standards to which measurements
of air quality, occupational exposure and air pollution source emissions, and natural gas analyses, can be referenced. This
has required the development of national primary gas standards using absolute gravimetric and other techniques, and the development
of dynamic calibration techniques for gaseous species which would be unstable in high-pressure cylinders. The methodology
used for preparing gas standards gravimetrically is described, together with the rigorous quality assurance measurements and
consistency checks which are used to demonstrate their accuracy and stability. The uncertainty budget assigned to these standards
will also be summarised. NPL primary standards are used to certify traceable 'secondary' gas standards which are disseminated
so as to ensure the accuracy of gas analysis measurements. Examples of the applications of these secondary standards are presented.
The gas standards are employed in proficiency testing of industrial stack-testing organisations, and results of the initial
rounds are presented. NPL gas standards are also now being used as the basis of the United Kingdom Environment Agency's new
type-approval and certification scheme for continuous industrial stack-emission analysers. A recent important international
initiative, in the field of gas analyses, is the agreement by national standards laboratories across the world to demonstrate
the equivalence of their calibrations, by means of key comparisons between them. These worldwide key comparisons are complemented
in Europe through the EUROMET initiative which seeks to establish the equivalence and comparability of calibration standards
held at national standards laboratories across Europe. Examples of these intercomparisons are presented.
Received: 23 March 2000 / Accepted: 18 August 2000 相似文献
6.
1