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1.
Summary Thermal field-flow fractionation separates polymers with high selectivity according to their Soret coefficient,S
τ, hence, according to their molar mass, and therefore consitutes an efficeint physicochemical tool for the determination of
the Soret coefficient of a given polymer in the carrier liquid from its retention time. However, the polymer concentration
in the sample influences the retention time and, hence, the value ofS
τ derived from it. An experimental study of the influence of sample concentration on retention,S
τ, and peak shape was performed for the polystyrene-decalin system over a relatively large temperature domain and for various
molar masses.
It is found that the retention time and the value ofS
τ increase with increasing sample concentration, the more so as the cold wall temperature is lower. This appears to be in contradiction
with the general non-equilibrium thermodynamic expression derived for polymer-solvent systems with positive second virial
coefficients, such as the present system over the temperature range investigated. There seems to be a temperature for which
the dependence ofS
τ on sample concentration vanishes. This temperature is about 375 K for the polystyrene-decalin system. As the sample concentration
increases, the peak barycentre and the standard deviation increases. As the peaks are fronting, the skewness is negative and
becomes more negative as the sample concentration increases. The peak skewness appears to be a good indicator of the onset
of sample concentration effects. The threshold concentration, for which these effects begin to become significant, decreases
with increasing molar mass. 相似文献
2.
《Physics and Chemistry of Liquids》2012,50(4):345-349
Abstract Isobaric vapour-liquid equilibrium data are measured at 200, 500 and 707 mm Hg at ten compositions spread evenly over the entire liquid mole fraction range, employing a Swietoslawski type ebulliometer. The liquid phase composition vs. bubble temperature (x-t) data are found to be well represented by Wilson model The optimum Wilson parameters are used to calculate the vapour phase compositions, activity coefficients and the excess Gibbs free energies. 相似文献
3.
To summarize some of the most important findings in the field of ultrasonic (US) testing of early age hydration and formation of structure of different cement based materials (CBMs), a review of literature with focus on US P-wave transmission and S-wave reflection methods is presented in this paper. The review shows a great ability of both US techniques to observe setting phenomena and to determine different milestones during the early age formation of CBM’s microstructure. Clear physical basis, high accuracy, and non-destructive nature of the method indicate that US methods could become standardized in the near future. 相似文献
4.
In this study, both the intersubband optical absorption coefficients and the refractive index changes as dependent on the magnetic field are calculated in square and graded quantum wells. Our results show that the position and the magnitude of the linear and total absorption coefficients and refractive index changes depend on the magnetic field strength and the shape of potential. The incident optical intensity has a great effect on the total absorption and refractive index changes. 相似文献
5.
6.
This study aims at figuring out the crucial topological ingredients which affect the outcomes of the ultimatum game located on different networks,encompassing the regular network,the random network,the small world network,and the scale-free network.With the aid of random interchanging algorithm,we investigate the relations between the outcomes of the ultimatum game and some topological ingredients,including the average range,the clustering coefficient and the heterogeneity,and so forth.It is found that for the regular,random and small-work networks,the average range and the clustering coefficient have evident impacts on the ultimatum game,while for the scale-free network the original degree heterogeneity and the underlying rich-club characterizations are the mainly important topologica ingredients that influence the outcomes of ultimatum game substantially. 相似文献
7.
In this paper, we have investigated the mutual and self coupling characteristics of directional couplers using two individual gain guided and index antiguided fibers, which can deliver robust single mode operation with large mode area, respectively owing to the combined adequately large gain coefficients in the core; Some interesting and distinguishing properties from conventional index guided fiber couplers are obtained that: The variations of coupling coefficients are complex-valued and spatially damping oscillated, but not exponential-like decreasing as conventional index guided couplers. 相似文献
8.
The elastic and thermodynamic characteristics of OsC crystal have been predicted through a method of density functional theory within the generalized gradient approximation (GGA). Compared with WC-type OsC, NaCl-type OsC is not only energy unfavorable but also mechanics unstable. The five independent elastic constants (Cij), bulk modulus (B0), the dependence of bulk modulus on temperature and pressure as well as the thermal expansion coefficient (αV) at various temperatures for WC-type OsC are discussed. According to our calculations, WC-type OsC should be an ultra-incompressible material with high bulk modulus about 381 GPa. In addition, the bulk modulus will increase with increasing pressure while decrease with increasing temperature. The researches on the thermal expansion coefficient indicate that there will be a knee point during the process of thermal expansion coefficient variation versus increasing temperature. Our results may provide useful information for theoretical and experimental investigation of OsC. 相似文献
9.
10.
This paper considers the macroscopic and microscopic statistical features of the top 500 firms in China, the United States and the world, denoted as China 500 (CH500), Fortune 500 (US500) and Fortune Global 500 (FG500). From a macroscopic perspective, the firm size distribution of each category, when measured by revenue, is steadily distributed over the observed period, even during periods of financial crises. As is evidenced by the Gini coefficient, divergences between firm scales are most significant for the CH500. From a microscopic perspective, the underlying micro-dynamics are volatile and often turbulent due to the exit and entry of firms as well as shifts in their revenues and ranks. Such fluctuations, or mobility, are visualized in rank/revenue/share clocks. We also propose a revenue/rank/share mobility index that is a quantitative measurement of mobility. Among these, we find that the share mobility acts as an effective indicator of economic status; where there is a share mobility spike, there is an ailing economy. The share mobility indexes indicate that the 2008 Financial Crisis had little impact on the Chinese economy, while it triggered violent changes in the top 500 firms in the United States and the world. 相似文献