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81.
Viscosities of solutions of polystyrene in toluene were measured for concentrations up to 400 kg m?3 at 298 K. Polymers of molecular weights ranging from 8.7 × 103 to 2.4 × 106 were used. It is observed that viscosity of the polymer solution increases with increasing concentration and molecular weight; the rate of increase is greater at higher values of the two parameters. A master curve for the system is constructed by using the experimental data for viscosity, concentration and molecular weight of the polymer. Regions of various polymer interactions in solution are identified. 相似文献
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Ong Chong Pin 《Advances in Mathematics》1975,15(3):269-311
Classical or Newtonian Mechanics is put in the setting of Riemannian Geometry as a simple mechanical system (M, K, V), where M is a manifold which represents a configuration space, K and V are the kinetic and potential energies respectively of the system. To study the geometry of a simple mechanical system, we study the curvatures of the mechanical manifold (Mh, gh) relative to a total energy value h, where Mh is an admissible configuration space and gh the Jacobi metric relative to the energy value h. We call these curvatures h-mechanical curvatures of the simple mechanical system.Results are obtained on the signs of h-mechanical curvature for a general simple mechanical system in a neighborhood of the boundary ?Mh = {xεM: V(x) = h} and in a neighborhood of a critical point of the potential function V. Also we construct functions defined globally on Mh, called curvature functions which characterize the sign of the h-mechanical curvature. Applications are made to the Kepler problem and the three-body problem. 相似文献
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Nonstationary phase processes are defined and a surrogate distribution approximation (SDA) method for analyzing transient and nonstationary queueing systems with nonstationary phase arrival processes is presented. Regardless of system capacityc, the SDA method requires the numerical solution of only 6K differential equations, whereK is the number of phases in the arrival process, compared to theK(c+1) Kolmogorov forward equations required for the classical method of solution. Time-dependent approximations of mean and variance of the number of entities in the system and the number of busy servers are obtained. Empirical test results over a wide range of systems indicate the SDA is quite accurate.This research was partially funded by National Science Foundation grant ECS-8404409. 相似文献
86.
The thermal conductivity, κ, of NbSe3 has been measured by novel self-heating techniques that allowed the electric field dependence of κ to also be measured. Measurements were made from 35 K to room temperature. Above the charge density wave transitions, the phonon thermal conductivity is 4–7 times the electron thermal conductivity, and it rises smoothly below the transitions, indicating that phonon-phonon scattering predominates. Phonon mean free parths have been estimated at 187 A° at 60 K and 60 A° at 150 K. No clear anomalies were observed at the phase transitions, giving upper limits to changes in the phonon mean free path. No field dependence of κ was observed. 相似文献
87.
Dirac-Fock calculations show dramatic variations of the asymmetry parameter with energy for Cs 6s in contrast to the β = 2 prediction of more approximate theories. 相似文献
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A new methodology utilizing a redox-triggered activation for the facile release of dendrimer end groups is reported. 相似文献
90.