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31.
Dielectric relaxation study of the binary mixtures of poly(vinyl pyrrolidone) (PVP) (Mw=24000, 40000 and 360000 g mol−1) with ethyl alcohol (EA) and poly(ethylene glycol)s (PEGs) (Mw=200 and 400 g mol−1) in dilute solutions of dioxane were carried out at 10.1 GHz and 35°C. The relaxation time of PVP-EA mixtures was interpreted
by the consideration of a wait-and-switch model in the local structure of self-associated ethyl alcohol molecules and also
the PVP chain length as a geometric constraint for the reorientational motion of ethyl alcohol molecules. The formation of
complexes and effect of PVP chain length on the molecular dynamics, chain flexibility and stretching of PEG molecules in PVP-PEG
mixtures were explored from the comparative values of dielectric relaxation time. Further, relaxation time values in dioxane
and benzene solvent confirm the viscosity independent molecular dynamics in PVP-EA mixtures but the values vary significantly
with the non-polar solvent environment. 相似文献
32.
Speed of sound and densities of the ternary mixture 2-propanol + diethyl ether + n-hexane and also the binary mixtures 2-propanol
+ diethyl ether and 2-propanol + n-hexane have been measured at the entire composition range at 298.15 K. The excess isentropic
compressibilities and the excess speed of the sound have been calculated from experimental densities and speed of sound. These
excess properties of the binary mixtures were fitted to Redlich-Kister equation, while the Cibulka’s equation was used to
fit the values related to the values to the ternary system. These excess properties have been used to discuss the presence
of significant interactions between the component molecules in the binary mixtures and also the ternary mixtures.
Speed of sound of the binary mixtures and the ternary mixture have been compared with calculated values from free length theory
(FLT), collision factor theory (CFT), Nomoto’s relation (NR), Van Deal’s ideal mixing relation (IMR) and Junjie’s relation
(JR). The results are used to compare the relative merits of these theories and relations in terms of the root mean square
deviation relative (RMSDr). 相似文献
33.
The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis 下载免费PDF全文
The electron swarm parameters including the density-normalized effective ionization coefficients(α-η)/N and the electron drift velocities V e are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend(SST) experiment.The overall density-reduced electric field strength is from 100 Td to 1000 Td(1 Td = 10-17V·cm2),while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%.From the variation of(αη)/N with the CF3I mixture ratio k,the limiting field strength(E/N) lim for each CF3I concentration is derived.It is found that for the mixtures with 70% CF3I,the values of(E/N) lim are essentially the same as that for pure SF 6.Additionally,the global warming potential(GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment. 相似文献
34.
35.
Investigations on the phase diagrams of two bi-component mixtures of liquid crystals are presented. Whereas in one of the bi-component systems, smectic A (SmA) phase is seen to be induced, in the other case the so-called nematic “island” has been observed. The dielectric properties of magnetically oriented sample forming nematic phase and induced smectic phase in one of the mixtures, and a nematic “island” and SmA phase in the other mixture, were measured in the frequency range from 1?Hz to 10?MHz at different temperatures. The transition temperatures obtained from the polarizing microscope and differential scanning calorimeter measurements agree well with the dielectric relaxation data. 相似文献
36.
在Na-K混合蒸汽中,利用染料激光器,将基态Na原子双光子激发到5S态。用荧光法测量了过程Na(5S)+K(4S)→Na(3S)+K(8D,10S)的碰撞转移截面,K8D,10S对Na5S的荧光比中,含有K8D10S碰撞转移的影响。第2个实验可以消除这个影响,双光子激发K原子到8D(或10S)探测8D(10S)对10S(8D)的荧光比,Na(5S)→K(8D,10S)碰撞转移截面(10-15cm2)分别是10.5±4.2和9.5±3.8 相似文献
37.
We generalize a variational principle for the mean spherical approximation for a system of charged hard spheres in 3D to arbitrary
dimensions. We first construct a free energy variational trial function from the Debye-Hückel excess charging internal energy
at a finite concentration and an entropy obtained at the zero-concentration limit by thermodynamic integration. In three dimensions
the minimization of this expression with respect to the screening parameter leads to the mean spherical approximation, usually
obtained by solution of the Ornstein-Zernike equation. This procedure, which interpolates naturally between the zero concentration/coupling
limit and the high-concentration/ coupling limit, is extended to arbitrary dimensions. We conjecture that this result is also
equivalent to the MSA as originally defined, although a technical proof of this point is left for the future. The Onsager
limitT ΔS
MSA
/ΔE
MSA
→ 0 for infinite concentration/coupling is satisfied for all d ≠ 2, while ford=2 this limit is 1.
On leave from Department of Physics, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico, 00681. 相似文献
38.
基于高斯混合尺度模型的压缩传感图像重构 总被引:1,自引:0,他引:1
在图像处理领域中,压缩传感重构是稀疏表示下的最重要的病态反问题之一。压缩传感图像重构利用图像可稀疏表示的先验知识,从比奈奎斯特采样率低得多的随机投影观测值中重构原始图像。为了克服传统的压缩传感算法中收敛速度慢和未利用变换系数的邻域统计特性的缺点,提出了基于高斯混合尺度模型的压缩传感图像重构算法,证明了独立的高斯混合尺度分布作为压缩传感重构的稀疏先验知识的可行性,结合全变差调整进一步提高算法的性能。实验结果表明,该算法有效地提高了重构图像的主观视觉效果和峰值信噪比,加快了压缩传感图像重构算法的收敛速度。 相似文献
39.
为研究强冲击状态下混入少量空气的甲烷气体的冲击状态参数,利用二级轻气炮加载技术,使加速到5 km/s的钨合金飞片撞击封装有常态下空气混入量依次为零(纯甲烷气体)、1%、5%、10%的甲烷-空气混合气体铝靶。采用六通道瞬态光学高温计记录冲击压缩气体的光辐射历程曲线,得到了相同初始条件下4种不同比例混合气体的冲击状态参数。结果表明,在强冲击压缩下,混合气体的冲击温度随着空气混入比例的增大而增高,冲击波后混合气体存在非平衡辐射过程。采用Saha电离平衡方程,对空气混入量为10%的混合气体的电离度进行了估算。结果表明,常态下空气含量Cair≤10%的甲烷 空气混合气体具有电探针保护能力。 相似文献
40.