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排序方式: 共有188条查询结果,搜索用时 390 毫秒
91.
The experimental study of plasma spots formation in planar surface barrier discharge system at atmospheric pressure in helium gas is presented. Spatio-temporal patterns of plasma spots are followed by varying the applied voltage and operating gas pressure. These spots melt together at high applied voltage and results in uniform glow discharge. Reduction in operating pressure also results in similar effect. Dynamics of these patterns are discussed in detail. 相似文献
92.
93.
Critical impact velocity (CIV) of oxygen-free high-conductivity (OFHC) copper is experimentally measured with a novel facility in a gas gun system. The results are compared with the theoretical predictions using the typical constitutive relations, and the measured CIV value is much lower than the predictions. The difference of physical mechanisms in experiment and in theoretical calculation is discussed. It is suggested that the reduction of CIV in experiment would be related with the damage evolution in tensile copper that needs to be considered in the computation model. 相似文献
94.
First-principles investigations on elastic and thermodynamic properties of zinc-blende structure BeS
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In this paper the elastic and thermodynamic properties of the cubic
zinc-blende structure BeS at different pressures and temperatures
are investigated by using \textit{ab initio} plane-wave
pseudopotential density functional theory method within the
generalized gradient approximation (GGA). The calculated results are
in excellent agreement with the available experimental data and
other theoretical results. It is found that the zinc-blende
structure BeS should be unstable above 60GPa. The thermodynamic
properties of the zinc-blende structure BeS are predicted by using
the quasi-harmonic Debye model. The pressure-volume-temperature
($P-V-T$) relationship, the variations of the thermal expansion
coefficient $\alpha$ and the heat capacity $C_{V}$ with pressure $P$
and temperature $T$, as well as the Gr\"{u}neisen
parameter-pressure-temperature ($\gamma -P-T$) relationship are
obtained systematically in the ranges of 0--90GPa and 0--2000K. 相似文献
95.
Edward Mosteig Moss Sweedler 《Proceedings of the American Mathematical Society》2004,132(12):3473-3483
Given a valuation on the function field , we examine the set of images of nonzero elements of the underlying polynomial ring under this valuation. For an arbitrary field , a Noetherian power series is a map that has Noetherian (i.e., reverse well-ordered) support. Each Noetherian power series induces a natural valuation on . Although the value groups corresponding to such valuations are well-understood, the restrictions of the valuations to underlying polynomial rings have yet to be characterized. Let denote the images under the valuation of all nonzero polynomials of at most degree in the variable . We construct a bound for the growth of with respect to for arbitrary valuations, and then specialize to valuations that arise from Noetherian power series. We provide a sufficient condition for this bound to be tight.
96.
YunGeXU LongCaiLI 《数学学报(英文版)》2004,20(6):1119-1130
Let C be a finite dimensional directed algebra over an algebraically closed field k and A=A(C) the dual extension of C. The characteristic modules of A are constructed explicitly for a class of directed algebras, which generalizes the results of Xi. Furthermore, it is shown that the characteristic modules of dual extensions of a certain class of directed algebras admit the left Groebner basis theory in the sense of E. L. Green. 相似文献
97.
After surveying the experimental evidence for concentration coupling in the shear banding of wormlike micellar surfactant
systems, we present flow phase diagrams spanned by shear stress Σ (or strain rate ) and concentration, calculated within the two-fluid, non-local Johnson-Segalman (d-JS-φ) model. We also give results for
the macroscopic flow curves Σ(ˉ,ˉφ) for a range of (average) concentrations ˉφ. For any concentration that is high enough
to give shear banding, the flow curve shows the usual non-analytic kink at the onset of banding, followed by a coexistence
“plateau” that slopes upwards, dΣ/dˉ > 0. As the concentration is reduced, the width of the coexistence regime diminishes
and eventually terminates at a non-equilibrium critical point [Σc,ˉφc,ˉc]. We outline the way in which the flow phase diagram can be reconstructed from a family of such flow curves, Σ(ˉ,ˉφ), measured
for several different values of ˉφ. This reconstruction could be used to check new measurements of concentration differences
between the coexisting bands. Our d-JS-φ model contains two different spatial gradient terms that describe the interface between
the shear bands. The first is in the viscoelastic constitutive equation, with a characteristic (mesh) length l. The second is in the (generalised) Cahn-Hilliard equation, with the characteristic length ξ for equilibrium concentration-fluctuations.
We show that the phase diagrams (and so also the flow curves) depend on the ratio r ≡ l /ξ, with loss of unique state selection at r = 0. We also give results for the full shear-banded profiles, and study the divergence of the interfacial width (relative
to l and ξ) at the critical point.
Received: 20 December 2002 / Accepted: 24 April 2003 / Published online: 11 June 2003
RID="a"
ID="a"e-mail: physf@irc.leeds.ac.uk
RID="b"
ID="b"e-mail: p.d.olmsted@leeds.ac.uk 相似文献
98.
99.
根据强电解质水溶液形成的热力学设想,修正了Debye-Hückel离子互吸理论,检验结果表明,它能满意地关联各种价型的强电解质水溶液的离子平均活度因子,使适用的浓度范围扩大到了6mol·kg-1。 相似文献
100.
Théneau C Salmerón Sánchez M Rodríguez Hernández JC Monleón Pradas M Saiter JM Gómez Ribelles JL 《The European physical journal. E, Soft matter》2007,24(1):69-77
The enthalpy relaxation of polymer-silica nanocomposites prepared by simultaneous polymerization of poly(2-hydroxyethyl methacrylate)
(PHEMA) and tetraethyloxysilane, TEOS, a silica precursor, is investigated. Both the glass transition temperature, Tg, and the temperature interval of the glass transition, ΔT
g , increase as the silica content in the sample does. Structural relaxation experiments show that the temperature interval
in which conformational motions take place broadens as the silica content in the hybrid increases. A phenomenological model
based on the evolution of the configurational entropy during the structural relaxation process, the SC model, has been used
for determining the temperature dependence of the relaxation times during the process. The results show an increase of the
fragility of the polymer as the silica content increases, a feature that can be related to the broadening of the distribution
of relaxation times characterized by the β parameter of the stretched exponential distribution. On another hand the silica
content increase produces a significant change of the relaxation times in the glassy state. 相似文献