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81.
Henri Berthiaux Antonio Guttierrez Lavin Julio Bueno De Las Heras Marisol Muñiz Alvarez 《加拿大化工杂志》2007,85(2):158-170
Despite of its general use in industry, particle sedimentation is still a not well understood unit operation. Hydrodynamics is complex in essence, mainly because the possible volumes are depending on the operating conditions, which in turn has consequences on the stability of the equipment in unsteady state conditions. 相似文献
82.
G. Nelissen B. Van Den Bossche J. Deconinck A. Van Theemsche C. Dan 《Journal of Applied Electrochemistry》2003,33(10):863-873
Laminar and turbulent mass transfer in a parallel plate reactor at high Schmidt number obtained from numerical simulation is compared with literature data. In a first step, the fluid flow is determined numerically in the reactor by solving the Navier–Stokes equations. For turbulent flow, a low Reynolds number k— model is used to calculate the turbulent viscosity. Using the obtained flow field and turbulent viscosity, the current density distribution is calculated for different flow velocities by solving the equations describing the transport of multiple ions due to diffusion, convection and migration. For the laminar case, a very good agreement with literature data is obtained. For turbulent flow, different numerical models for turbulent mass transfer are proposed in the literature. A detailed study of the behaviour close to the wall of these different turbulence models is presented, together with a comparison of the calculated results with literature correlations. This allows identification of the benefits and disadvantages of each of the turbulence models for the numerical calculation of mass transfer at high Schmidt numbers in a parallel plate reactor. 相似文献
83.
ABSTRACT Cadmium as a highly toxic metal is released into the environment through paper production, metal processing, phosphate fertilizers, insecticides, and treatment of wastewater. Cadmium also inhibits the body activities and is very toxic for kidney and other organisms. In the current study, zinc-based metal–organic framework, zeolitic imidazolate framework (ZIF)-8, was synthesized and modified by dimethylethylenediamine (ZIF-8-mmen) for the removal of cadmium. To optimize the experiments, response surface methodology was applied with three variables including pH, adsorbent dosage, and contact time using central composite design. The optimum conditions for pH, dosage, and time were 2, 0.1 g, and 89 min, respectively, with removal efficiency of 85.38%. The Langmuir isotherm (q m = 1000 mg/g) indicates the monolayer adsorption. The kinetic studies reveal that the Lagergren model was predominant and cadmium was not chemisorbed. Thermodynamic parameters show spontaneous, endothermic, and physisorption processes. 相似文献
84.
高桥地区靖边气田石盒子组盒8段砂岩储层井径扩大严重,引起测井信息失真、地质储量评价不准确等一系列问题.通过优化CaCO3酸溶性封堵剂的复配比例和添加成膜剂及润湿反转剂降低砂岩自吸两种途径提高钻井液的封堵性能,从而实现井壁稳定.改进后钻井液对盒8段的封堵率提高至95.6%,砂岩自吸量降低85%. 相似文献
85.
X是拓扑空间,令&={A:A是X的具有性质&的子集},如果对于X的任意邻域指派φ,都存在A∈&,使得X=U{φ(χ):χ∈A},则称X是与性质&对偶的空间.对于给定的特殊性质&,主要讨论了与性质&对偶的空间的一些基本性质,并给出了X是与性质&对偶空间的充分必要条件.这些结论可应用于多种空间类,作为其中的一推论,得到每个正则弱(8)-加细(离散对偶)-散布空间是离散对偶空间.另外,还讨论了aD-空间的相关结论.Abstract: Let X be a space,and &={A:A is a subset of X,and has property &}.A space X is dual the property & if for any neighborhood assignment φ for X,there is a subset A(X,A∈& such that X=U{φ (χ):χ∈ A}.In this note,we mainly discuss properties of spaces which are dually special &,and also give a necessary and sufficient condition for spaces which are dually special & These conclusions can be heId for many spaces.As a corollary,we have that if X is a regular weak (8)-refinable(dually discrete)-scattered space,then X is dually discrete.We also get some conclusions conserning aD-spaces. 相似文献
86.
The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy
was investigated at 900 and 1 000 °C, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization
of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission
election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating
was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing
treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 °C in air. The former forms
a scale of merely Al2O3, and the latter forms a scale of the mixture of Al2O3 and TiO2. Annealing can improve the formation of TiO2.
Foundation item: Project(2007430028) supported by the Science and Technique Foundation of Henan Educational Committee, China 相似文献
87.
砖墙-钢筋混凝土剪力墙组合结构是从砌体结构的基础上发展起来的一种新结构体系,该种结构在砼墙配置合理的情况下具有良好的抗震性能,在设防烈度为8度地区建造这种结构的房屋是可行的. 相似文献
88.
针对有机电致发光器件发光效率低、稳定性差的问题,设计制备了ITO/NPB/Alq3/LiF/Al多层有机电致发光器件.测试了器件的电流电压特性、器件的亮度电压特性、器件的电致发光光谱.结果表明,当外加电压为16V时,器件的电流达到最大值21.70mA,器件的亮度达到了11 700cd/m2;当外加电压为14 V时,电致发光光谱波峰位于528 nm处,归一化强度最大值为0.522 1a.u.制备的器件电子注入能力、电流和亮度均得到了增强. 相似文献
89.
The catalytic activity and selectivity of heterodonor phosphine rhodium catalysts prepared in situ were tested in the hydroformylation of functional alkenes (ethyl acrylate, methyl methacrylate, styrene, 4-vinyl-1-cyclohexene, dicyclopentadiene and cis-1,2,3,6-tetrahydrophthalic anhydride). Systematic variation of the heterodonor atom in the ortho position of the ligand showed that the heterodonor atom has a significant influence on the activities and selectivities of the reaction. However, the activity seems to depend mainly on the modifying ligand, and the regioselectivity mainly on the substrate (i.e., the structure and functionality of the alkene). Nevertheless, regioselective control is only obtained through synergy between the substrate and the catalyst. Clear regiocontrol was observed in the hydroformylation of ,-unsaturated esters and styrene with an in situ formed o-(thiomethylphenyl)diphenylphosphine rhodium catalyst. 相似文献
90.
Ma Xuedan Guo Daishi Jiang Qizhong Ma Zifeng Ma Zhengfei Ye Weidong Li Chunbo 《Frontiers of Chemical Engineering in China》2007,1(1):45-49
Nanosized solid superacids SO4
2−/TiO2 and S2O8
2−/TiO2, as well as MCM-41-supported SO4
2−/ZrO2, were prepared. Their structures, acidities, and catalytic activities were investigated and compared using XRD, N2 adsorption-desorption, and in situ FTIR-pyridine adsorption, as well as an evaluation reaction with pseudoionone cyclization. The results showed that SO4
2−/TiO2 and S2O8
2−/TiO2 possess not only nanosized particles with diameters < 7.0 nm, a BET surface greater than 140 cm2/g and relatively regular mesostructures with pores around 4.0 nm, but also a pure anatase phase and strong acidity. Different
from the Lewis acid nature of SO4
2−/ZrO2/MCM-41, SO4
2−/TiO2 and S2O8
2−/TiO2 exhibit mainly Bronsted acidities. The strongest Bronsted acid sites were produced on SO4
2−/TiO2 promoted with H2SO4, while Lewis acid sites on S2O8
2−/TiO2 even stronger than those on SO4
2−/ZrO2/MCM-41 were generated when persulfate solution was used as sulfating agent. Because of their distinct acid natures, SO4
2−/TiO2 and S2O8
2−/TiO2 exhibited catalytic activities for the cyclization of pseudoionone that were much higher than that of SO4
2−/ZrO2/MCM-41. It can be concluded that the existence of more Br?nsted acid sites was favorable for proton participation in the
cyclization reaction.
Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(2): 239–244 [译自: 高校化学工程学报] 相似文献