A parallel computational method for simulating two‐phase gel dynamics on a staggered grid

We develop a parallel computational algorithm for simulating models of gel dynamics where the gel is described by two phases, a networked polymer and a fluid solvent. The models consist of transport equations for the two phases, two coupled momentum equations, and a volume‐averaged incompressibility constraint. Multigrid with Vanka‐type box‐relaxation scheme is used as preconditioner for the Krylov subspace solver (GMRES) to solve the momentum and incompressibility equations. Through numerical experiments of a model problem, the efficiency, robustness and scalability of the algorithm are illustrated. Copyright © 2008 John Wiley & Sons, Ltd.     

A Fast and Simple Screening Method for m-Nisoldipine and Its Related Substances by MEKC

A rapid and simple method has been developed and validated for the determination of m-nisoldipine and its five related substances using micellar electrokinetic capillary chromatography (MEKC). The key factors, including pH, buffer concentration and buffer additive, sodium dodecyl sulfate (SDS) concentration, applied voltage and temperature were systematically investigated in an uncoated fused silica capillary. The total analysis time was less than 9 min. The forced degradation products of m-nisoldipine, which were induced by hydrogen peroxide, acidic and basic conditions, heat and light, were also tested.

     

On some nonlinear problems induced by an abstract maximal element principle

In this paper, by applying an abstract maximal element principle on quasi-ordered sets established by Lin and Du, we obtain a generalized Brézis–Browder principle, system (vectorial) versions of Ekeland's variational principle and maximal element principle and a vectorial version of Takahashi's nonconvex minimization theorem. Moreover, we investigate the equivalence between scalar versions and vectorial versions of these results.     

Effect of Hydrogen on Catalytic Coupling Reaction of Carbon Monoxide to Diethyl Oxalate

The kinetics of hydrolysis of tetrahydrozoline hydrochloride in aqueous solution at 353, 363 and 368 K in the pH-range from 2.00 to 12.20 has been investigated. The decomposition products have been investigated by HPLC. This revised version was published online in June 2006 with corrections to the Cover Date.     

气相色谱法测定眼药水中琥珀酸钠的含量

用气相色谱法测定眼药水中琥珀酸钠的含量。样品减压蒸干后,经酸化使琥珀酸钠变成琥珀酸,加入丙二酸进行衍生化反应,形成琥珀酸丁二酯和丙二酸丁二酯,以DEGS玻璃填充柱为色谱柱,用FID检测,进行气相色谱分析,结果令人满意。     

Solvent extraction of uranium(VI) by p-tert-butylcalix[n]-arene acetate

The solvent extraction of U(VI) by p-tert-butylcalix[n]-arene acetate (H _n L) (n=4, 6, 8) has been studied. The effects of acidity in aqueous phase and concentration of extractant in organic phase on the distribution ratio were examined. It has been found that the distribution ratio is proportional to [H⁺]⁻² and [H _n L]_(O) and the extracted complex species is UO₂H _n ⁻²L. The equilibrium constants of the extraction reactions have been determined. The reaction mechanism is discussed.     

气相色谱法同时测定塑料食品包装袋中4种有机残留物

食品塑料包装袋中的有机残留物甲苯是一种对人体有害的化合物.包装食品用的塑料制品.其含量为卫生和食品监督部门所严格控制.其中的异丙醇、丁酮和乙酸乙酯虽毒性不大,但它们的大量使用以及在环境中的行为不甚明了,因此建立一种同时测定4种组分的分析方法是十分必要的.有关顶空气相色谱法同时测定食品塑料包装袋中的4种残留组分的研究还未见报道.本文研究了一种简便、快速、准确的静态顶空气相色谱法,可同时测定塑料食品包装袋中的甲苯、异丙醇、丁酮和乙酸乙酯.该法操作简便,灵敏度高,重现性好,结果令人满意.     

Study on the flow resistance of the dispersion system of deformable preformed particle gel in porous media using LBM-DEM-IMB method

After being injected into the porous media, the dispersion system of preformed particle gel (PPG) tends to enter high permeability regions and block water channeling passages, which forces the subsequent water to turn to the low permeability regions and thus increases sweep efficiency and enhances oil recovery. However, it is still unclear about the influence factors and the mechanisms how PPG increases water flow resistance, which limits the application of PPG in more oilfields. Therefore, the paper combines the lattice Boltzmann method (LBM), the discrete element method (DEM) and the improved immersed moving boundary (IMB) method to simulate the migration of deformable PPG in porous media. On the basis, the paper quantitatively analyzes the variation law of displacement pressure across the porous media and discusses the influence factors such as the PPG diameter, elasticity modulus and the number concentration. Results indicate that, because of the friction and retention of PPG in pore-throat, the displacement pressure across the porous media during PPG flooding is much higher than that during water flooding. In other words, the existence of PPG increases the flow resistance of injected water. Besides, the displacement pressure is always fluctuant resulting from the continuous process of PPG migration, retention, deformation and remigration. Influence factor analysis shows that the incremental value and fluctuation degree of flow resistance increase with the PPG diameter, elasticity modulus and the number concentration. The study not only provides useful reference for future PPG flooding, but also benefits the development of deformable particle flow theory.     

Densely continuous forms, pointwise topology and cardinal functions

We consider the space D(X, Y) of densely continuous forms introduced by Hammer and McCoy [5] and investigated also by Holá [6]. We show some additional properties of D(X, Y) and investigate the subspace D*(X) of locally bounded real-valued densely continuous forms equipped with the topology of pointwise convergence τ- _p . The largest part of the paper is devoted to the study of various cardinal functions for (D*(X), τ _p ), in particular: character, pseudocharacter, weight, density, cellularity, diagonal degree, π-weight, π-character, netweight etc. This work was supported by Science and Technology Assistance Agency under the contract No. APVT-51-006904. The authors would like to thank Ľubica Holá for suggestions and comments.