Direct Evaluation of Partial Molar Volumes of Binary Solutions of Dimethyl Sulfoxide with Ethyl Acrylate,Butyl Acrylate,Methyl Methacrylate and Styrene

The Tikhonov regularization is applied to convert specific molar volume data of binary solutions of dimethyl sulfoxide with a number of acrylates and with styrene into their second- and first-partial derivatives with respect to mole fraction under constant temperature and pressure. Generalized Cross Validation is used to guide the selection of the regularization parameter that keeps noise amplification under control. The resulting first derivative is then used to compute the partial molar volumes. These are compared against that obtained by the traditional method of least-squares fitting of excess molar volumes. Some of the advantages of the current approach and possible extension to other partial molar quantities are briefly discussed.     

Partial molal volumes and adiabatic compressibilities of dodecylpolyoxyethylene glycol monoethers in water at 5, 25, and 45°C

Density and ultrasonic velocity measurements were made on a series of dilute aqueous solutions ofn-C ₁₂ H ₂₅ O (CH ₂ CH ₂ O) _n H (n=6,7 and 8) at 5, 25, and 45°C. The partial molal volumes (V) and adiabatic compressibilities (K)of the solutes were independent of the concentration in the micellar solutions. This finding suggests that the mode of aggregation does not change over the concentration range studied. Larger V and K were found for the CH ₂ CH ₂ groups in micelles than in water, and the micellar core was shown to be liquidlike. The V and K of the monomeric surfactants could not directly be measured because of the very low c.m.c.'s. The infinite dilution values V^° and (K^°) were, however, estimated from the V^° and K^° for the constituent groups on the basis of additivity. Thus, sharp increases were found in both V and K on micellization, which was interpreted in terms of dehydration effects.     

Sufficient conditions for the regularity of the solutions of the Navier–Stokes equations

In this paper we find sufficient conditions, involving only the pressure, that ensure the regularity of weak solutions to the Navier–Stokes equations. Conditions involving only the pressure were previously obtained in [7,4]. Following a remark in this last reference we improve, in particular, Kaniel's result [7]. Our condition can be seen at the light of the heuristic idea that the pressure behaves similarly to the modulus squared of the velocity. Copyright © 1999 John Wiley & Sons, Ltd.     

青饲大豆主要品质参数的近红外光谱快速分析

饲料是畜牧生产的物质基础,饲草原料和饲料产品营养价值的检测与评估是饲料生产中的重要环节,面对饲草资源中粗蛋白含量低和大量依靠进口饲料的局面,大豆作为优质的高蛋白豆科饲草是畜牧业生产利用的重要资源.不同青饲大豆及其不同刈割期的饲用品质参数可以评价青饲大豆的饲用性能,但目前主要以化学方法进行检测,过程繁琐,试验周期长、易造...     

On Nonlinear Eigen-problems of Quasi-linear Elliptic Operators

In this paper, we study the following Eigen-problem {-\frac{∂}{∂x_i}(a_{ij}(x, u)\frac{∂u}{∂x_j}) + \frac{1}{2}a_{iju}(x,u)\frac{∂u}{∂x_i}\frac{∂u}{∂x_j} + h(x)u = μμ\frac{n+2}{n-2} \quad in Ω \qquad (0.1) u = 0 \quad on ∂Ω u > 0 \quad in Ω ⊂ R^n under some assumptions. First. we minimize I(u) = \frac{1}{2}∫_Ωa_{ij}(x, u)\frac{∂u}{∂x_i}\frac{∂u}{∂x_j} + h(x)u² over E_α = {u ∈ H¹_0(Ω); ∫_Ωu^α = 1} ( 2 < α < N = \frac{2n}{n-2}) to give a H¹_0-solution U_α of the perturbation problems of (0.1). Since I is not differentiable in H¹_0(Ω), the key point is the estimate of U_α. Then, we derive local uniform bounds of (U_α) and give a 'bad' solution of (0.1). Last, we remove the singular points of the 'bad' solution to obtain a solution of (0.1), our result is a extension of that of Brezis & Nirenberg.     

二极管阵列检测—偏最小二乘吸光光度法同时测定铜锌

研究了以２－（５－溴－２－噻唑偶氮）５－二乙氨基苯酚（５－Ｂｒ－ＰＡＤＡＰ）作显色剂,ＣＣＤ（Ｃｈａｒｇｅ Ｃｏｕｐｌｅｄ Ｄｅｖｉｃｅ,电荷耦器件）二极管阵列检测分光光度装置采及收光谱,用偏最小二乘法解析,同时测定了粮食中铜和锌。方法的线性范围锌为０．０５～０．４０μｇ．ｍｌ＾－１,铜为０．０２～０．６０μｇ．ｍｌ＾－１;检出限铜为０．０２μｇ．ｍｌ＾－１,平均加标回收率锌为９３．３％～９５．７     

Simultaneous determination of halide and thiocyanate ions by potentiometric precipitation titration and multivariate calibration

Halide and thiocyanate ions can be determined by a precipitation titration with silver nitrate as the titrant, and the end-point can be evaluated by a potentiometric method, in which generally a silver indicator electrode is used as the indicator electrode and a double-junction Ag–AgCl electrode as the reference electrode. However, when mixtures of halide and thiocyanate are titrated, it is difficult to determine these components individually for there are overlapping steps in the potentiometric titration curves, especially in the case that there are obvious differences between concentrations of the components. In this paper, the linear equation for the potentiometric precipitation titration of a mixture of halide and thiocyanate ions was developed and it was then used for determining the components in the mixtures simultaneously with the aid of multivariate calibration methods. By application of this model, 27 synthetic mixtures with three- and four-component combinations of chloride, bromide, iodide and thiocyanate with low concentration levels from 1.8×10⁻⁴ to 6.2×10⁻⁴ mol l⁻¹ were analyzed and acceptable results were obtained.     

A rigorous solution for the axisymmetrical buckling of simply supported cylindrical sandwich shells under axial load

In this paper,based on ref[1],the axisymmetrical buckling of simply supportedcylindrical sandwich shells under the action of uniform axial load is solved by a rigorousmethod.The classical theory of shells is used for the two face sheets and the core isconsidered as a three-dimensional elastic body.A series of transcendental equations areobtained,from which the critical loads can be calculated by numerical methods.Numericalexamples are given to compare with the solutions of sandwich shell theories.     

Studies on Catalysis in Partial Oxidation of Methane to Syngas(Ⅰ)──Performance and Characterization of Ni-based Catalysts

IntroductionWiththedevelopmentofanewgenerationofhighlyactivecatalysts,therehasbeenrenewedinterestinthecatalyticpartialoxidationofmethane(POM)tosyngasasapotentialcommercialalternativetosteam-reformingofmethaneinthepastfourorfiveyears.lncontrasttosteam~reforming,thecatalyticpartialoxidationofmethanetosyngas,ismildlyexothermicandmorese1ective,andtheoreticallyyieldsaH,/COratioof2,whichislowerthanthat0btainedbysteam-reforming,andthusismoreappli-cabletotheFischer-TropschSynthesis(FTS)ofhigherhyd…