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121.
The flexural fatigue properties were studied for PP injection-molded samples of different molecular weight and well-defined skin-core morphology (see Part I). It can be clearly seen that the crack initiation always occurs in the subskin layer of higher macromolecular orientation, and propagates towards the core. The mechanisms of cracking are discussed on the basis of fatigue kinetic data and analytical measurements on the stressed sections. The important influence of processing conditions, essentially holding pressure on the fatigue behavior is illustrated. 相似文献
122.
A model of catalyst pellet regeneration is presented that accounts for the separate combustion reactions of the hydrogen and the carbon in the coke. The complete structure of the burn-off time with respect to several system parameters is given. It is shown that there are values of initial coke weight fraction and pellet size that give minimum burn-off time. The model indicates that the combustion of the deposited coke is limited by diffusion at higher temperatures than previously thought, and it predicts relatively high temperature differences between the solid particles and the fluid phase at low levels of conversion for some range of the model parameters. 相似文献
123.
124.
A fast process synthesis procedure is developed for generating preliminary separation schemes. The main approach is based on similarity indices obtained from chemical, physical and operating properties between two chemical species in a separation scheme. For the whole set of species, a similarity matrix results. On this basis, algorithms for classifying chemical species and generating separation sequences are developed. A distance between flowsheets is used in order to compare different separation schemes with one another or to some reference cases. The weights of the properties and heuristics are adjusted to account for well-known optimal cases. Changes in the number of considered separation properties and in their hierarchy are also used to improve the procedure. The algorithm requires very little calculation and can even be implemented by hand in the simplest cases. Extensions of the algorithm include the use of actual values of the separation properties instead of boolean ones and the generation of non-sharp flowsheets. 相似文献
125.
The Simulation of Repolarization Events of the Cardiac Purkinje Fiber Action Potential 总被引:1,自引:0,他引:1
Drouhard Jean-Pierre Roberge Fernand A. 《IEEE transactions on bio-medical engineering》1982,(7):481-493
A mathematical model based on the formalism of the Hodgkin-Huxley equations was implemented on a microcomputer system and used to simulate the membrane action potential of cardiac Purkinje fibers. The complete model is a modification of the representation used by McAllister et al. [1], mainly with respect to the outward current components during the late plateau, the repolarization phase, and the slow repolarization phase of the action potential. A new formulation of the potassium conductance was used, involving two distinct types of ionic channels corresponding, respectively, to the experimentally observed inward-going and outward-going rectification properties of the Purkinje fiber membrane. A unified representation of the Purkinje fiber current components was thus obtained which provides a more satisfactory interpretation of experimental results than was possible with the original model of McAllister et al. [1]. The membrane channel for the potassium pacemaker current is characterized by a set of first-order activation?inactivation variables and a constant fully activated conductance. The other channel carries the potassium current involved in the late plateau and repolarization phase of the action potential. 相似文献
126.
127.
Jean-Marc David Jean-Paul Krivine Jean-Pierre Tiarri Benoit Ricard 《Journal of Intelligent and Robotic Systems》1988,1(3):287-298
DIVA is an expert system for turbine generator diagnosis. Its aim is to help a plant operator interpret vibration evolution to diagnose developing faults. Interpretation of vibration evolution is primarily a recognition process which is achieved by a particular model of heuristic classification. DIVA tries to recognize the observed situation among a hierarchy of typical situations.The purpose of this paper is to present the model we used for heuristic classification, based on prototypes. Prototypes represent typical problem situations and may also be seen as experts with special knowledge of what to do in such situations. We argue that this model presents significant advantages to deal with complex problems such as vibration surveillance. 相似文献
128.
Zden k Slanina Filip Uhlí k Jean-Pierre Fran ois Ludwik Adamowicz 《Fullerenes, Nanotubes and Carbon Nanostructures》1993,1(4):537-546
C60O is studied by means of the AM1 quantum-chemical method. Full geometry optimization of its Cs and C2v structures, and harmonic vibrational analysis, are employed in the evaluation of the temperature dependence of their relative stabilities. The C2v structure remains a minor component of the equilibrium gas-phase mixture even at high temperatures. 相似文献
129.
Species-specific composition of free amino acids on the leaf surface of fourSenecio species 总被引:1,自引:1,他引:0
The specificity of the chemical composition of the leaf surface of fourSenecio species was studied in order to understand the host selection ofTyria jacobaeae, a monophagous moth that hasSenecio jacobaea as its principal host plant. Pyrrolizidine alkaloids characteristic forSenecio species were not detected in water and sulfuric acid extracts of the leaf surface ofSenecio jacobaea. Water extracts of the leaf surfaces ofS. jacobaea, S. vulgaris, S. viscosus, andS. sylvaticus contained low concentrations of free amino acids. The proportions of these amino acids were very different from those inside the leaf tissues. In a discriminant analysis, the four species could be completely separated on the basis of the relative proportions of amino acids on the leaf surface. 相似文献
130.
Jean-Pierre Duval 《Theoretical computer science》1979,9(1):17-26
We study the relationship between the global periodicity of a word and its (local) repetitions, that is to say its successive equal factors.Our main result generalizes the theorem of Cesari Vincent according to which the period of a word is the maximum of the minimal repetitions. Our generalization is twofold, it does not take account of any sides to define repetitions (the above result does) and calculates the maximum only on a special set of points. It allows a sharpened version of the solution to a problem settled by Schützenberger in which the theorem of Cesari Vincent originates. 相似文献