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51.
Wide angle (WAXS) and small angle (SAXS) X-ray scattering studies are reported on block copolymers of acrylonitrile with ethylene oxide. A distinct structural similarity between the copolymers and acrylonitrile homopolymer has been found. Considerable porosity of the copolymers has been shown. The porosity very largely governs the scattering power. It was found that the pores are three dimensional “particles” (scattering exponent α = 4), probably with smooth surfaces (surface fractal dimension ds = 2). 相似文献
52.
An original method was proposed for the determination of the mean residence time in a continuous dryer, based on the step-change in the solids feed rate. The method has been validated through experiments performed in a pilot-scale rotary dryer. The effect of the solids flow rate, gas flow rate, dryer rotation speed, and dryer slope was quantified. Several design correlations to predict the residence time in rotary dryers were critically evaluated, and a new, more accurate correlation was derived. 相似文献
53.
Investigations on the conversion of tolylene-2,4-diisocyanate (2,4-TDI or TDI) with heptane-1,4,7-triol 1,4,7-HPT or HPT) at 55–85°C and various molar ratios of starting materials are described. By means of mass spectroscopic analysis and gel permeation chromatography, molecular weights of six oligomers and their percent contents in the products have been estimated. Moreover, a scheme of the formation of all prepared isocyanate prepolymers has been proposed. It has been shown, that apart from oligomers having the structures resulting from the reaction of 1,4,7-HPT with the isocyanate group in the position “4”, reaction products contained oligomers, which confirmed the reactivity of isocyanate group in the position “2”, too. 相似文献
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We report here a correlated X-ray diffraction and freeze-fracture electron microscope study of the effects of several cryofixation procedures upon human serum low density lipoprotein (LDL2) structure. Only when the LDL2 solutions contained 75%, by weight, glycerol were the room temperature and post cryofixation low temperature LDL2 X-ray scattering curves indistinguishable from one another. Other cryofixation procedures, slow or rapid, with or without glycerol, resulted in differences between the room temperature and low temperature LDL2 X-ray scattering curves, in part due to the effect of quenching upon the solvent. Freezeetching electron microscopy of the slowly cryofixed LDL2 showed marked aggregation of the particles and an unusual morphological appearance. In contrast, after rapid cryofixation or cryofixation in the presence of glycerol, freeze-etch electron microscopy revealed well-isolated particles which had a knobby morphology. The results demonstrate that under certain conditions (in the presence of 75% glycerol) cryofixation results in minimal, if any, structural alteration of, at least, the LDL2 lipid moiety. Further, this study underlines the more general conclusion that any high resolution structural study employing a cryofixation step must be interpreted with caution and the effect of cryofixation upon the sample structure need be evaluated by independent means. 相似文献
56.
The possibility of determination of copper in natural waters was tested by direct potentiometry with chalcocite copper sensitive ion selective electrode. This can be carried out for the copper concentration down to 6 μg l−1 when the standard additions procedure is used. The electrode characteristics was investigated and as a medium was proposed a TFB solution containing Tris, potassium fluoride and potassium nitrate. However at the extreme low concentrations of copper the water samples after addition of TFB should be heated to boiling. In these conditions the accuracy of determination for the average of five measurements is not worse than 25%, and precision is of the order of 20%. 相似文献
57.
A simple model of image formation in a Newtonian telescope was used for calculating an analytical formula, that describes the geometric compression form factors of coaxial and biaxial lidars. Calculations were successfully validated by comparison with real measurements, confirming the accuracy of our approach. The need for different alignment of coaxial and biaxial systems to increase the overlap between the lidar emitter and receiver is also discussed. 相似文献
58.
Interrelation between H-bond and Pi-electron delocalization 总被引:1,自引:0,他引:1
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Prof. Dr.-Ing. Tadeusz Sliwiński 《Electrical Engineering (Archiv fur Elektrotechnik)》1977,59(3):171-181
Übersicht Es werden die von der Eisensättingung stammenden Oberwellen des Luftspaltfeldes, des Magnetisierungsstromes und der Strangspannung analysiert. Nach der Vorstellung des physikalischen Bildes dieser Oberwellen bei Stern- und Dreieckschaltung der Ständerwicklung werden die Ergebnisse der Messungen an speziell gebauten Käfigläufermotoren mit hoher Sättigung entweder der Ständerzähne oder des Ständerjoches berichtet.
Contents Saturation harmonics of magnetic field in the air-gap, of the magnetizing current and of the phase voltage in three-phase induction motors are analysed. The physical picture of these harmonics is presented and the results of tests executed on specially manufactured squirrel-cage motors with highly saturated stator teeth or stator yoke are reported.相似文献