嵌入原子势的分子动力学并行算法研究

针对嵌入原子势,提出了1种新的并行分子动力学算法——作用力分解算法.并与另外2种并行算法进行了比较.作用力分解算法并行代码编写简单,不要求模拟区域具有规则形状.而测试并行后的速度表明,当计算的原子数目小于104数量级时,它是最佳的并行算法.

Experimental study on co-pyrolysis characteristics of typical medical waste compositions

Thermal decomposition of 21 kinds of binary mixtures between typical medical compositions was investigated under nitrogen conditions by dynamic thermogravimetric analysis(TGA) at 25–800 °C. The weighed sum method(WSM) coupled with thermal analysis was applied to study the interaction between components. Then, co-pyrolysis kinetic model of the binary mixtures(tube for transfusion(TFT) and gauze) was established to verify the reliability of conclusions. The results show the follows. 1) Strong or weak interactions are shown between binary mixtures containing polyvinyl chloride(PVC), the main ingredient of TFT. The addition of other medical waste could enhance first stage decomposition of TFT. While, the secondary stage pyrolysis may be suppressed or enhanced or not affected by the addition. 2) There exists no interaction between catheter and other component, the DTG peak temperature representing Ca CO3 decomposition in catheter fraction is obviously lower than that of pure catheter; while,the shape of DTG peak keeps unchanged. 3) No evident reaction occurs between the other mix-samples, it is considered that their co-pyrolysis characteristics are linear superposition of mono-component pyrolysis characteristics.

Dynamic simulation of hydrodynamic model of drum level wave action and sloshing

In order to build the model of the drum level wave action and sloshing, based on the method of modularization modeling, the hydrodynamic model of drum level wave action and sloshing was developed, and dynamic simulation researches were carried out based on the model. The results indicate that both drum level and drum length have functional relations with period of drum level wave action and sloshing. When the drum level decreases or drum length increases, the period of drum level wave action and sloshing increases, density of liquid and number of sub-module division have little influence on the period of drum level wave action and sloshing. The model was validated by the analytical solution theory of liquid’s wave action and sloshing in cuboid container, and the 3D graphics of drum level wave action and sloshing was also obtained. The model can dynamically reflect the rules of wave action and sloshing of water in the container exactly.

Novel Control Structure Design of Differential Pressure Thermally Coupled Reactive Distillation for Methyl Acetate Hydrolysis

In this paper, the novel control structures of differential pressure thermally coupled reactive distillation process for methyl acetate hydrolysis were proposed. The RadFrac module of Aspen Plus was adopted in the steady-state simulation. Sensitive analysis was applied to find the stable intial value and provide a basis for the improved control structure design. The Aspen Dynamics software was adopted to study the process dynamic behaviors, and two novel control structures provided with feed ratio controllers and sensitive tray temperature controllers were proposed. The reflux ratio controllers were applied in the improved novel control structures. Both control structures abandoned the composition controllers that were replaced by simpler controllers with which the product purity could meet the specification requiring under a ± 20% disturbance to the total feed flowrate / MeAc composition.

A combined DFT and molecular dynamics study of U(Ⅵ)/calcite interaction in aqueous solution

Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and solvation effect in U（VI） interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite （104） surface prefers to exist in molecular state rather than dis- sociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U（VI） → Ca（II）. In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U（VI）→ Ca（II）, and the one with UO2（CO3）2（H2O）^2- as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilicability of the （104） surface to different extents, where the UO2（CO3）3Ca2 species contributes to the largest degree of energy changes （ 53 kcal/mol）. Our calcula- tions proved that the （104） surface also has the ability to immobilize U（VI） via either surface complexing or ion exchange mechanisms under different pH values.