月桂氮草酮研究进展

介绍了月桂氮草酮作为高效皮肤促渗剂的发展概况、合成工艺、研究进展及其应用前景。     

OXYGEN TRANSFER IN HORIZONTAL PIPELINE AERATORS WITH NOZZLES

Horizontal pipeline and tubular loop aerators are of interest for fermentation and waste water treatment and are ideally suited for continuous processing. A major drawback is that these pipeline contactors invariably operate in the “elongated bubble and plug” regime in which the mass transfer rate is low. This article evaluates the performance of a horizontal pipeline aerator fitted with nozzles equispaced along its length to enhance mass transfer rates by promoting turbulence and augmenting effective interfacial area. Such devices can also be advantageously used in long pipe lines as in the case of treating waste while it is being transported. Pressure drop and overall liquid-side mass transfer coefficient data are reported as functions of liquid (water) and gas flow rates and nozzle size and spacing. It is shown that for all the conditions studied, k_La = 0.026(ΔP/L)^1.036 and that the pressure gradient is given by a simple correlation, provided an empirical parameter which characterises a nozzle is known. Preliminary investigations on the effect of surfactant ad the presence of suspended solids (size 75 μm) on mass transfer coefficient are also reported. Very high values of power dissipation can be achieved in such aerators without mechanically moving parts and high values of mass transfer coefficient can be realized.     

MATHEMATICAL MODELING OF THROUGH-HOLE-PLATING IN ELECTROCHEMICAL MICROFABRICATION II. AXISYMMETRIC TWO-DIMENSIONAL CONVECTIVE MASS TRANSFER

Axisymmetrical, two dimensional mass transfer in a tube and a through-hole was studied. The elliptic convective-diffusion equation was solved numerically by taking into account both the axial and radial diffusion in the entrance region of an infinite tube. The whole mass-transfer region in a tube of finite length was also studied by dividing the domain into several regions according to different mass-transfer mechanisms. A similar analysis is then conducted for a through-hole geometry by assuming a modified Hagen-Poiseuille fluid pattern. Results show that mass-transfer rate in a through-hole is larger than that in a tube by approximately 10%. This is due primarily to faster fluid flow within the concentration boundary layer in a through-hole.     

拟稳态法测定气相扩散系数

根据拟稳态一维扩散原理,建立了气相扩散系数的测定装置。在该装置上,测定了8个体系的气相扩散系数,其中CH_2Cl_2-空气,CH_2Cl_2-H_2,CH_3CH_2Br-空气,CH_3Cl_2Br-H_2,CHCl_3-H_2等5个体系的气相扩散系数实验值,迄今尚未见文献报道。实验结果表明,本测试装置稳定性好,实验误差小,实验装置体积小,测试过程较为简便。     

APPLICATION OF LINEARIZED MODELS OF MULTICOMPONENT MASS TRANSFER FOR CALCULATION OF EVAPORATION-CONDENSATION PROCESS IN TERNARY SYSTEMS

Results of calculations based on a linearized multicomponent mass transfer theory developed by Burghardt and Krupiczka are compared with experimental data of Modine for condensation-evaporation process in ternary systems. These data have been obtained for acetone-benzene-nitrogen and acetone-benzene-helium in a welted wall column. Models I and II, which take into account diffusional interactions of components in a mullicomponent mixture show good agreement with the experiments as well as with other calculation methods (Krishna-Standart and Toor-Stewart-Prober). When multicomponent mass transfer occurs in the presence of inert species, a straightforward Model II is recommended. Model I, which is more universal, requires some iterative calculations with respect to the sum of mass fluxes. According to theoretical considerations the latter model is limited to the case of low total mass flux. The results of calculations for the systems studied were reasonably good though the total mass fluxes were not small. The calculation procedure based on the presented linearized models are convergent to the proper solutions in contrast to the Krishna-Standart Model IV which in some cases can be unstable.     

Some novel polymer-supported optically active phase transfer catalysts: 2. Use in displacement,reduction, epoxidation and addition reactions

The performance of 27 novel polymer-supported chiral phase transfer catalysts in a range of phase separated reactions has been studied. The later include a number of displacement reactions, sodium borohydride reductions of prochiral ketones, the epoxidation of chalcone, the addition of nitromethane to chalcone and the addition of thiophenol to cyclohexenone. Some of the reactions were performed under liquid/liquid conditions and others using solid/liquid. No systematic difference emerged between these. In general many of the catalysts provided fast reactions and good chemical yields of products. However, in no case was any significant enantiomeric excess achieved. The latter observation is discussed in the light of the reported behaviour of analogous non-supported catalytic systems, and suggestions proposed to explain these differences.     

光学镜头调制传递函数的测试

为了定量、客观、全面地评价光学镜头的像质,介绍了光学镜头调制传递函数的测试。先简要叙述了测试的原理,并给出计算公式;然后介绍了测试步骤,其中包括固定、穿轴、测试中心视场和测试轴外视场;最后介绍了测试时的注意事项,包括对测试工装的要求、对测试平面的要求和正、负轴外视场测试值相差较大时的处理办法。     

A three-dimensional model for suspension-to-membrane-wall heat transfer in circulating fluidized beds

A three-dimensional model is proposed for both furnace-side and wall-side heat transfer in circulating fluidized beds with membrane walls. Following previous publications (Int. J. Heat Mass Transfer (2003a, b)), a core-annulus flow structure is employed in the model, with consideration of the membrane wall influence on bed hydrodynamics. The model couples radiation, conduction and convection on the furnace side to conduction and convection on the wall side. Radiation in the wall layer is simulated by the moment method. A finite-element method is employed to solve the set of non-linear, partial differential equations. The solution is demonstrated for a typical example. The model gives predictions of suspension-to-wall heat transfer which show satisfactory agreement with published experimental data.     

Prediction of liquid film mass transfer coefficients in packed columns using liquid holdup

A unique characteristic linear dimension (d), defined as the cube root of the specific liquid holdup (h_sp) in the packed column, was used to correlate successfully the liquid film mass transfer coefficient k_La for gas absorption-desorption for sparingly soluble gases in liquids below loading. To produce this simple, dimensionless correlation, k_La data reported in literature were used, covering a wide range of physical properties of liquids, packings and operating conditions. This new approach showed operating holdup as an important factor in gas liquid mass transfer.