1990年以来,超临界水的PVT实验数据和分子动力学模拟数据已延伸到很高的温度和压力。文中详细评价了这些数据的质量。国际水和水蒸汽性质学会所推出的1995年版的水的状态方程(IAPWS95)被选作评价的可靠基础,同时辅以其适当的外延。分析...1990年以来,超临界水的PVT实验数据和分子动力学模拟数据已延伸到很高的温度和压力。文中详细评价了这些数据的质量。国际水和水蒸汽性质学会所推出的1995年版的水的状态方程(IAPWS95)被选作评价的可靠基础,同时辅以其适当的外延。分析结果表明,Zhang and Duan(2005)的模拟数据和Abramson and Brown(2004)通过声速实验值反演得到的PVT数据与目前最精确的水的PVT数据吻合得很好,但后者有较小的系统偏差。其它几组数据都有较大的系统偏差或不确定度。其中,Belonoshko and Saxena(1991)的模拟数据P-T范围很宽,但不确定度很大,而且有显著的系统偏差。Brdoholt and Wood(1993)的模拟数据也有显著的系统偏差。随着压力的增加,这两组模拟数据的体积偏差都有由正转负的趋势,其中后者尤为显著,而且在高压下离散性很弱,因而易于校正。Withers et al.(2000),Brodholt and Wood(1994)和Frost and Wood(1997)的实验数据都有明显的正偏差,其中前一组的偏差较小,后两组的偏差较大,原则上均可近似地校正。Larrieu and Ayers(1997)的数据总体不确度较大,其中偏差较小的数据仅限于特定的温度和压力,其它数据的偏差没有明显的规律。这些结果应当有助于上述新数据的正确使用和进一步优化。展开更多
We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, a...We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental Tg＇s for cis poly（1,4-butadiene） and found an excellent quantitative agreement.展开更多
文摘1990年以来,超临界水的PVT实验数据和分子动力学模拟数据已延伸到很高的温度和压力。文中详细评价了这些数据的质量。国际水和水蒸汽性质学会所推出的1995年版的水的状态方程(IAPWS95)被选作评价的可靠基础,同时辅以其适当的外延。分析结果表明,Zhang and Duan(2005)的模拟数据和Abramson and Brown(2004)通过声速实验值反演得到的PVT数据与目前最精确的水的PVT数据吻合得很好,但后者有较小的系统偏差。其它几组数据都有较大的系统偏差或不确定度。其中,Belonoshko and Saxena(1991)的模拟数据P-T范围很宽,但不确定度很大,而且有显著的系统偏差。Brdoholt and Wood(1993)的模拟数据也有显著的系统偏差。随着压力的增加,这两组模拟数据的体积偏差都有由正转负的趋势,其中后者尤为显著,而且在高压下离散性很弱,因而易于校正。Withers et al.(2000),Brodholt and Wood(1994)和Frost and Wood(1997)的实验数据都有明显的正偏差,其中前一组的偏差较小,后两组的偏差较大,原则上均可近似地校正。Larrieu and Ayers(1997)的数据总体不确度较大,其中偏差较小的数据仅限于特定的温度和压力,其它数据的偏差没有明显的规律。这些结果应当有助于上述新数据的正确使用和进一步优化。
文摘We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental Tg＇s for cis poly（1,4-butadiene） and found an excellent quantitative agreement.
