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121.
定标粒子理论预测乙醇-水体系汽液平衡盐效应 总被引:6,自引:0,他引:6
测定了70℃下3个1-1型电解质(NaCl、NaBr、KCl)在各种不同浓度的乙醇-水体系中的汽液平衡盐效应参数,并给出用定标粒子理论计算盐效应参数的方法。硬球作用项采用Masterton-Lee方程,软球作用项采用胡英的径向分布函数。分子间力在Lennard-Jones位能函数基础上计入偶极-偶极、偶极-诱导偶极、电荷-偶极、电荷-诱导偶极的贡献,其中离子-分子间的静电作用项仅限于规则排列的第一配位圈之内。将混合溶剂的局部介电常数视为液相浓度的函数,函数关系由实验拟合。在乙醇浓度变化的很大范围内,3个体系的预测与实验结果基本相符。 相似文献
122.
以计量置换吸附理论(SDT A)为基础,从理论上推导出计量吸附模型中表征溶质对固定相亲合势大小的参数βa值与流动相中强置换剂浓度的对数呈线性关系。计量置换模型中的参数n和q(n和q分别代表1摩尔溶剂化溶质被吸附时,从吸附剂表面和从溶质分子表面所释放出的溶剂的物质的量)是计量置换参数Z值的分量,是两个非常有用的参数,可以从这个定量关系中直接获得。推导出的方程用苯的衍生物进行了实验验证,获得了较满意的结果。将这种方法计算得到的分量值与SDT A与计量置换保留模型(SDT R)相结合的方法得到的分量值进行了比较。 相似文献
123.
An attempt has been made to apply Green’s function and partitioning technique to the case of XY2Z (ClO2F) pyramidal type molecule belonging toC, point group. The isotopic rules have been formulated. The force constants, rotation distortion constants and mean amplitude
of vibration have been computed and compared with other observed and calculated values whichever is available. 相似文献
124.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
125.
Xing-Zhi Liu Da-Wei Fang Jia-Zhen Yang Jun Li Shu-Liang Zang 《The Journal of chemical thermodynamics》2004,36(12):1061-1065
The equilibrium molalities In3+ in {In2(SO4)3 + Na2SO4 + HDEHMTPCA + n-C8H18 + water} were measured at ionic strength from (0.1 to 2.0) mol · kg−1 containing Na2SO4 as supporting electrolyte in aqueous phase and at constant molality extractant at temperatures from (278.15 to 303.15) K in organic phase. The standard extraction constants K0 at various temperatures were obtained by methods of extrapolation and polynomial approximation. Thermodynamic quantities for the extraction process were calculated. 相似文献
126.
This paper is concerned with optimal control problems of Mayer and Bolza type for systems governed by a semilinear state equationx(t)=Ax(t) + f(t, x(t), u(t)), u(t) U, whereA is the infinitesimal generator of a strongly continuous semigroup in a Banach spaceX. We prove necessary and sufficient conditions for optimality and then use these conditions to investigate properties of the value function related to superdifferentials. Conversely, we use the value function to obtain criteria for optimality and feedback systems.Work (partially) supported by the Research Project Equazioni di evoluzione e applicazioni fisicomatematiche (M.U.R.S.T.-Italy). 相似文献
127.
Miscibility and phase separation in SAN/PMMA blends have been investigated using DSC, IR spectroscopy and positron lifetime spectroscopy (PLS). Single broad glass transition observed throughout the blend compositions, may be due to overlap of two glass transitions. IR measurements clearly indicate the absence of strong interactions. This supports miscibility is due to intramolecular repulsive forces in the SAN component. On the other hand, free volume data show negative deviation from linear additivity indicating the blends are miscible. The interchain interaction parameter β exhibits a complex behavior and the extent of miscibility is not revealed. Following Wolf’s treatment, we have evaluated the geometry factor γ and hydrodynamic interaction parameter α and found α is a suitable parameter in predicting the miscibility window. The cloud points in SAN/PMMA blends increase with decreasing PMMA content. The change in free volume size correlates well with the observed change in cloud point. 相似文献
128.
M. Hoorfar M.A. Kurz A.W. Neumann 《Colloids and surfaces. A, Physicochemical and engineering aspects》2005,260(1-3):277-285
A quantitative criterion called “shape parameter” to evaluate the quality of surface tension measurement of Axisymmetric Drop Shape Analysis (ADSA) is presented. ADSA is a powerful technique for the measurement of interfacial tensions and contact angles of pendant drops, sessile drops, and bubbles. Despite the general success of ADSA, deficient results may be obtained for drops close to spherical shape. Therefore, the “shape parameter” was used to determine the range of drop shapes in which ADSA succeeds or fails. The “shape parameter” is a dimensionless parameter that expresses quantitatively the difference in shape between a given experimental profile and an inscribed circle. The surface tension measurements of ADSA were evaluated for both pendant drop and constrained sessile drop configurations using the shape parameter. Different shapes of the pendant drop were studied using different sizes and materials of holders. For each drop configuration, a “critical shape parameter” was defined based on the minimum value of the shape parameter that guarantees an error of less than ±0.1 mJ/m2. Furthermore, the effects of the type of liquid and constellation on the “critical shape parameter” were studied. 相似文献
129.
Summary We have fabricated glasses in the Bi-2223 HTc superconductor system with Bi2Sr2Ca2Cu3-xErxO10+ δ nominal composition, where x=0.5 and 1.0, by the glass-ceramic technique. Using an analysis developed for non-isothermal crystallization studies, information on some aspects of crystallization temperature and thermal properties has been obtained. The crystallization studies were made using DTA with several uniform rates. The calculations of crystallization activation energies, Ea, and the Avrami parameters, n, were made based on the non-isothermal kinetic theory of Kissinger and the Ozawa’s equations. The DTA data of the samples showed that the first crystallization temperature, Tx1, increases and the second crystallization temperature, Tx2, decreases by increasing the Er concentration. This suggests that the Er substitution had significant effect on the glassification of the BSCCO material due to change on the surface nucleation and increased ionic activities at high temperature region. The activation energy for crystallization, Ea, of the samples was also showed an increase at high Er concentration case. However, the Avrami parameter, n, decreased from 2.5 to 1.7 for x=0.5 and 1.0 samples, respectively. This suggests that the growth mechanism is diffusion-controlled and three-dimensional parabolic growth takes place near the first crystallization temperature. The oxidization rates and the activation barrier for oxygen out-diffusion process, E, was calculated using the TG data. It was found that the total mass gain in the x=0.5 sample is comparably smaller than that of the x=1.0 sample. This shows that the oxygen absorption of the x=1.0 sample is faster than the x=0.5 sample, leading to increase in the oxidization rate in the x=1.0 material. 相似文献
130.