氨基酸在水溶液中扩散系数的预测

以F ick定律和不可逆过程热力学为基础,结合文献中对扩散系数预测模型的分析,提出了一个氨基酸在水溶液中扩散系数预测的半经验模型。用实验测定的7种氨基酸在水溶液中的扩散系数和一些文献中的扩散系数数据对模型参数进行了拟和。利用该模型对多种氨基酸及尿素在水溶液中的扩散系数进行了计算,计算值与实验值的平均相对误差均小于0.6%。     

On the combined heat transfer of natural convection, radiation and conduction in the non-gray semitransparent thermal fibrous insulation

Non-gray semitransparent fibrous insulation hasbroad application in high-temperature industry, such asthe TPS ( thermal protection systems) of reusablelaunch vehicles. A metallic thermal protection systemgenerally consists of a metallic shell panel partit…     

Thermodynamic and Structural Properties of Sodium Lithium Niobate Solid Solutions

Thermodynamics of the Na_1−xLi _x NbO₃ system is investigated by high-temperature drop-solution calorimetry in molten 3Na₂O–4MoO₃ solvent at 973 K. Standard molar enthalpies of formation are derived. The estimated heats of transition between hypothetical and stable structures, lithium niobate and perovskite for NaNbO₃ and vice versa for LiNbO₃ are −6 kJ/mol and −10 kJ/mol, respectively. X-ray diffraction studies at room temperature showed for 0 ≤ x ≤ 0.14 there are three phases based on different ordering of the perovskite type lattice: orthorhombic with a quadrupled reduced perovskite cell at 0 ≤ x ≤ 0.02, orthorhombic with a doubled reduced perovskite cell at 0.015 ≤ x ≤ 0.14, and rhombohedral at 0.08 ≤ x ≤ 0.13. There are two two-phase (morphotropic) regions with coexistence of the two orthorhombic phases at 0.015 ≤ x ≤ 0.02 and with the second orthorhombic phase coexisting with the rhombohedral phase at 0.08 ≤ x ≤ 0.13. A reproducible anomaly in specific heat at ∼600 K, not reported previously, has been observed in pure NaNbO₃. Heat-capacity measurements confirm a phase transition at 553 K for 0.07 ≤ x ≤ 0.09. With increasing lithium concentration, a gradual disappearance of high-temperature phase transitions associated with tilting of oxygen octahedra has been observed.     

Adsorption Studies of Methylene Blue and Malachite Green From Aqueous Solutions by Pretreated Lignocellulosic Materials

Lignocellullosic materials have been used as low-cost adsorbents for the removal of methylene blue (MB) and malachite green (MG) dyes from aqueous solutions. The organic compounds in the adsorbents that contribute to chemical oxygen demand (COD) have been removed through pretreatment of the adsorbents. The percentage of color removal and COD reduction of both MB and MG dyes were found relatively close in values. The adsorption process followed the Langmuir isotherm as well as the Freundlich isotherm and pseudo-second order kinetic model. The process was found to be endothermic in nature.     

Growth behavior of interfacial compounds in galvanized steel joints with CuSi_3 filler under arc brazing

1Introduction Arc brazing is a relatively new joining technique.The main advantages over existing commercially available joining processes are its low cost and potential for being easily incorporated as a workstation in the production chain.This will sign…     

基于COMSOL Multiphysic的煤层甲烷拟稳态吸附-运移数值模拟

由于煤层甲烷在煤岩体中的运移过程及其复杂，因此用来描述其运移的数学模型常常是高阶非线性的偏微分方程，为了能更好的解决此类问题，本文采用多重物理量数值模拟软件COMSOLMultiphysic对所建的拟稳态运移模型进行了模拟求解的研究，结果表明用该软件模拟的压力和浓度动态曲线更符合实际情况，而且可以用动态可视化模块来模拟压降过程。     

Effect of Non-Equilibrium Condensation of Moist Air on Flow Field in Ludwieg Tube

The time-dependent behavior of non-equilibrium condensation of moist air through a Ludwieg tube with a diaphragm downstream is investigated by using a computational fluid dynamics work. The two-dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. The present computations represent the experimental flows well. The results obtained show that for an initial relative humidity over 40 %, the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to non-equilibrium condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity. Furthermore, the variations of condensation properties are also di     

实际联合动力循环有限时间热力学研究

基于有限时间内传热不可逆情况,用有限时间热力学方法建立了内可逆内燃机循环与斯特林循环相结合的联合动力装置的热力学模型,导出了以压缩比、温度比等循环参数表示的联合循环功率和效率表达式,通过对温度比（斯特林循环吸热温度与内燃机循环初始放热温度的比值）的数值计算分析,验证了温度比对联合循环功率和效率的影响,以及联合循环功率与效率之间的关系。该分析结果对联合循环动力装置的性能研究具有实际指导意义。     

Creep rupture properties of homopolymer,copolymer, and terpolymer based on poly(oxymethylene)

Polyacetal copolymers were prepared by cationic ring‐opening copolymerizations of 1,3,5‐trioxane (TOX) with 1,3‐dioxolane (DOX), and polyacetal terpolymers were prepared by terpolymerizations of TOX, DOX, and 2‐ethylhexyl glycidyl ether (EHGE). Polyacetal polymers with three different structures such as polyacetal homopolymers, polyacetal copolymers, and polyacetal terpolymers were compared in the mechanical properties and the creep characteristics, and discussed from the view point of the polymer structure. The polyacetal copolymers and the polyacetal terpolymers were determined by ¹H‐MNR measurement. About 80 mol % of DOX and EHGE amounts in feed were incorporated randomly into the each polymer. From the plots of the degree of crystallinity (X_c) versus the tensile strength, the tensile strength and crystallintiy of the polyacetal homopoymers are higher than those of the polyacetal copolymers and the polyacetal terpolymers. However, the tensile strength does not decrease linearly with a decrease in the crystallinity among the polyacetal polymers with three different structures, the polyacetal homopolymer, the polyacetal copolymers, and the polyacetal terpolymers. Creep rupture was characterized by the activation volume, υ_c, value in Zhurkov's equation, which can be estimated from the slope in the plots of load versus log (rupture time) at 80°C. The polyacetal polymers with higher molecular weight have larger values of the activation volume than those with lower molecular weight. When the activation volume values are compared among the polyacetal polymers with the same molecular weights, they increase in the following order: the polyacetal homopolymers < the polyacetal copolymers < polyacetal terpolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010