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71.
The notion of n-fold Čech derived functors is introduced and studied. This is illustrated using the n-fold Čech derived functors of the nilization functors Zk. This gives a new purely algebraic method for the investigation of the Brown–Ellis generalised Hopf formula for the higher
integral group homology and for its further generalisation. The paper ends with an application to algebraic K-theory.
(Received: December 2004) 相似文献
72.
73.
Summary A conventional push-rod dilatometer is modified in order to accurately correlate the measured density to the predicted sample
temperature of alloys in the phase-change regime. This new configuration makes use of a standard furnace assembly; however,
the specimen is now symmetrically encased in a well-instrumented, graphite cylindrical shell. The combination of system geometry
and high-conductivity sample holder material promotes the development of a simplified heat transfer model. The solution of
this model properly correlates the measured density to that of the actual sample temperature based on using remote, sample-holder
temperature measurements. Preliminary results using aluminum A356 provide insight into the proposed configuration. 相似文献
74.
Substrate-free thin film of Nylon 13,13 has been prepared continuously by casting the polymer on a water surface from m-cresol solution. The uniform thickness of film is ca. 500 A, as measured with a Profilometer. Film morphology and properties have been characterized by transmission electronic microscopy (TEM), x-ray photoelectron spectroscopy, wide-angle x-ray scattering, differential scanning calorimetry and by contact angle measurements. Results show that there is no preferential accumulation of the amide group toward the water surface. A spherulite structure exists in this film with a crystallinity of 26% by DSC. Fibers were drawn from the films which had a tensile modulus of 5 GPa, stiffer than reported for this nylon as prepared by other means. Other members of the nylon series, such as Nylon 6, Nylon 12, have also been prepared in films by the same casting method under modified conditions. © 1995 John Wiley & Sons, Inc. 相似文献
75.
Semicrystalline polymers generally exhibit moduli well below their theoretical limit due to chain folding and to lack of crystal alignment. Modulus increases attainable through standard drawing procedures are limited by sample fracture before large draw ratios are reached. Using an Instron capillary rheometer which allowed a draw ratio of > 300, transparent polyethylene strands of unusually high c-axis orientation have been produced by a combination of pressure and shear. The virtually perfect crystalline orientation and evidence for extended chains confirm that a significant improvement in modulus can be realized by this technique. The dynamic tensile storage modulus was measured by Vibron over the temperature range ?160°C to +120°C. Room-temperature moduli were 7 × 1011 dyne/cm2, higher than any reported values for drawn polyethylene. Values also remained above 1011 dyne/cm2 even at 120°C. The moduli and morphological data have been related by a model consisting of an extended-chain component in paralled with a conventional drawn morphology. Experimental and calculated moduli are compared and related to available theory. 相似文献
76.
A. Duane Porter 《Annali di Matematica Pura ed Applicata》1965,68(1):21-29
Summary An explicit formula is found for the number of solutions in a finite field of the system of polynomial equations(11), when the coefficients satisfy certain conditions. 相似文献
77.
The course of mercuric-ion catalyzed cyclization of lipid hydroperoxides and the demercuration of the resulting cyclic peroxides is reported. The cyclization products depend on the mercuric ion utilized and the course of demercuration can be altered by conditions of reduction and oxygenation. 相似文献
78.
The transverse momentum dependence of the parton distribution function and the Drell-Yan cross section is studied in detail in the asymptotically free scalar field theory in six dimensions. In the context of the renormalization group approach of Collins, particular attention is devoted to the transition between the small qT formula (due to multe-quanta effects) and the large qT formula (due to single hard-quantum emission). The calculation represents a case study of the application of the renormalization group method and provides a guide to the corresponding study in QCD. 相似文献
79.
80.