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891.
LIU Hui HOU De-Fu LI Jia-Rong 《理论物理通讯》2008,50(8):429-436
Within the framework of finite temperature field theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential. The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient. The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively. 相似文献
892.
893.
We analyze the dynamics of a two-dimensional system constituted by two masses subjected to elastic, gravitational and viscous forces and constrained by a moving frictional mono-lateral surface. The model exhibits a time-varying dynamics capable of reproducing the hopping phenomenon, an unwanted phenomenon observed in many applications such as the motion of a robotic arm on a surface or that of a wiper on a windscreen. The system dynamics, besides being affected by geometrical non-linearities, has a non-smooth nature due to the impact and friction laws involved in the model. The complexity of the resulting equations and of the transition conditions require the problem to be solved numerically. Various periodic motions are found and the effect of varying the system parameters, in particular the friction coefficient, is investigated. Finally, simulations are used to gain some insight the behavior of the windscreen wiper. 相似文献
894.
The expansion coefficient CD|L| of Coulomb potential 1/r12 of atomic system in hyper‐spherical harmonics is derived and the explicit expression is given. 相似文献
895.
We report the results of our modified distorted wave Born approximation calculation of triple differential cross section in the coplanar symmetric single ionization of potassium atom. We have included correlation-polarization potential as a function of electron density parameter and also studied the effect of post-collision interaction. The present attempt significantly improves the agreement between theoretical and experimental results. 相似文献
896.
W.-Q. Chen 《Archive of Applied Mechanics (Ingenieur Archiv)》1999,69(7):455-464
Summary Utilizing the general solution of transversely isotropic piezoelectricity, the paper analyzes the problem of an inclined
rigid circular flat punch indenting a transversely isotropic piezoelectric half-space. The potential theory method is employed
and generalized to take into account the effect of the electric field in piezoelectric materials. Assuming that the punch
is maintained at a constant electric potential, exact expressions for the elastoelectric field are derived in terms of elementary
functions. It is noted that the solution corresponding to a flat circular punch centrally loaded by a concentrated force can
be obtained as a special case.
Received 15 December 1998; accepted for publication 9 March 1999 相似文献
897.
The chromatographic behaviour of a recombinant human antibody (IgG1-subtype, κ-light chain, MW: 149.5 kD, pI: 9.3) was investigated as a function of the buffer pH and buffer type (HEPES, phosphate, borate) on fluoroapatite and hydroxyapatite stationary phases. HEPES buffer was used at pH 7.0, phosphate buffer at pH 8.2 and borate buffer between pH 8.5 and 11. Elution was by a double gradient method of first a salt gradient from 0 to 1 M NaCl in the corresponding buffer, followed by a step gradient to 0.4 M sodium phosphate. Regardless of the pH and buffer type, the antibody eluted in the NaCl gradient; capacity factors decreased with increasing pH. At pH 11 the antibody eluted in the flow-through. Retention was thus dominated by electrostatic interaction throughout the investigated pH-range. Investigation of antibody fragments obtained by papain digestion (fc- and fab-fragments) and deglycosylated fc-fragments showed that the sugar structures had no influence on the chromatographic behaviour. Instead the chromatographic behaviour was dominated by that of the fab-fragment. ζ-Potential measurements verified that the apatite surface bore a negative surface charge in the investigated pH range, while the antibody net surface charge switched from positive to negative as the pH increased. The corresponding isoionic point was a function of both the buffer concentration and the buffer species. However, above a pH of 8.3 the ζ-potential of the antibody generally was negative. Simulations of the molecular electrostatic potential of the antibody and the two fragments revealed the presence of a positively charged patch within the fab-fragment, which only disappeared above a pH of 10. Most likely this patch was responsible for the observed behaviour. 相似文献
898.
The long-time behaviour of spectral semi-discretisations of weakly non-linear wave equations is analysed. It is shown that
the harmonic actions are approximately conserved for the semi-discretised system as well. This permits to prove that the energy
of the wave equation along the interpolated semi-discrete solution remains well conserved over long times and close to the
Hamiltonian of the semi-discrete equation. Although the momentum is no longer an exact invariant of the semi-discretisation,
it is shown to be approximately conserved. All these results are obtained with the technique of modulated Fourier expansions.
Dedicated to Professor Arieh Iserles on the Occasion of his Sixtieth Birthday. 相似文献
899.
900.