A subdomain boundary element method for high‐Reynolds laminar flow using stream function‐vorticity formulation

The paper presents a new formulation of the integral boundary element method (BEM) using subdomain technique. A continuous approximation of the function and the function derivative in the direction normal to the boundary element (further ‘normal flux’) is introduced for solving the general form of a parabolic diffusion‐convective equation. Double nodes for normal flux approximation are used. The gradient continuity is required at the interior subdomain corners where compatibility and equilibrium interface conditions are prescribed. The obtained system matrix with more equations than unknowns is solved using the fast iterative linear least squares based solver. The robustness and stability of the developed formulation is shown on the cases of a backward‐facing step flow and a square‐driven cavity flow up to the Reynolds number value 50 000. Copyright © 2004 John Wiley & Sons, Ltd.     

Fast algorithms for determining the linear complexities of sequences over GF(pm) with the period 3n

In this paper, for the the primes p such that 3 is a divisor of p − 1, we prove a result which reduces the computation of the linear complexity of a sequence over GF(p ^m) (any positive integer m) with the period 3n (n and p ^m − 1 are coprime) to the computation of the linear complexities of three sequences with the period n. Combined with some known algorithms such as generalized Games-Chan algorithm, Berlekamp-Massey algorithm and Xiao-Wei-Lam-Imamura algorithm, we can determine the linear complexity of any sequence over GF(p ^m) with the period 3n (n and p ^m − 1 are coprime) more efficiently.     

鲤鱼体中鱼腥味物质的提取和鉴定

采用同时蒸馏萃取法提取鲤鱼鱼体中的挥发和半挥发性有机物，用GC／MS从提取物中分析鉴定出鱼腥味和疑是鱼腥味物质16种。包括醛、烯醛、酮和呋喃4类化合物。其中己醛、庚醛和2，4-二烯癸醛被确认为鱼腥味的化合物。研究发现，这些物质总量在鲤鱼体的鱼鳞、鱼鳃和鱼肉的分布呈现下降趋势，且其总量与鱼腥味强度之间具有可比较的对应关系。     

A novel method for automated grid generation of ice shapes for local‐flow analysis

Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading‐edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine–cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness. Copyright © 2004 John Wiley & Sons, Ltd.     

A fourth‐order compact finite difference scheme for the steady stream function–vorticity formulation of the Navier–Stokes/Boussinesq equations

A fourth‐order compact finite difference scheme on the nine‐point 2D stencil is formulated for solving the steady‐state Navier–Stokes/Boussinesq equations for two‐dimensional, incompressible fluid flow and heat transfer using the stream function–vorticity formulation. The main feature of the new fourth‐order compact scheme is that it allows point‐successive overrelaxation (SOR) or point‐successive underrelaxation iteration for all Rayleigh numbers Ra of physical interest and all Prandtl numbers Pr attempted. Numerical solutions are obtained for the model problem of natural convection in a square cavity with benchmark solutions and compared with some of the accurate results available in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

一种自制的蒸馏水器保护装置

本装置由检测、控制、执行、报警和电源五部分组成。检测部分采用了靠正常水位导通的两根信号线。当蒸馏水器在正常运行时遇停水,本装置可立即实现断电保护,同时发出声光报警,有效防止干烧,杜绝事故发生。本装置制作简便,元器件均为市售,成本低廉,性能可靠。     

Supercritical fluid chromatography of industrial paraffins and waxes

Summary The application of capillary SFC for SIMDIST investigations of paraffins and waxes is reported. Pressure, density and temperature of the mobile phase are optimized to obtain high chromatographic resolution of complex mixtures of industrial products. Isothermal linear pressure programming and asymptotic pressure and density programming are used in the range from 15 to 35 MPa in the isothermic mode above 100°C. SFC chromatograms of natural and synthetic paraffins, microcrystalline wax and candle wax are compared. The retention behaviour of paraffin mixtures and waxes has been investigated on methyl/phenyl and biphenyl capillary columns. The polarity of the stationary phases influences the absolute retention time more than it influences the chromatographic resolution.     

重整汽油近红外光谱的稳健偏最小二乘解析

近红外光谱(ＮＩＲ)光谱复杂,组分间光谱重叠严重,目前,多元线性回归(ＭｕｌｔｉｐｌｅＬｉｎｅａｒＲｅ ｇｒｅｓｓｉｏｎ,ＭＬＲ)和偏最小二乘法(ＰａｒｔｉａｌＬｅａｓｔ ｓｑｕａｒｅｓ,ＰＬＳ)是近红外光谱分析中使用最多和效果较好的方法[1]。稳健偏最小二乘(ＲｏｂｕｓｔＰａｒｔｉａｌＬｅａｓｔ Ｓｑｕａｒｅｓ,ＲＰＬＳ)是由稳健统计学构造的具有稳健性能的多元校正方法。当化学测量中引入随机异常点或误差的内在分布偏离正态分布时,它仍能给予接近最优性能的校正,确保分析结果的准确性,是消除奇异点的非常有效的方法[2-4],…     

有机液体化学试剂馏程测定注意事项

对有机液体化学试剂馏程测定过程中应注意的一些问题如加热源选择、蒸馏速度控制、温度计选择、蒸馏收率以及同一样品不同特性测量结果的相关性分析等进行了分析，为正确测定馏程提供经验和依据。     

Spectrophotometric determination of boron in complex matrices by isothermal distillation of borate ester into curcumin

In situ distillation of borate ester into the curcumin solution has been developed for the spectrophotometric determination of boron in a variety of complex matrixes. A polypropylene vessel containing the sample solution was placed inside a vessel (PP) containing 10 ml of curcumin solution and the distillation was carried out at room temperature/on a water bath. The borate ester collected in to the curcumin solution was evaporated to dryness on the water bath, taken in acetone and the absorbance was measured at 550 nm. In situ distillation of borate ester directly into the chromogenic reagent eliminates tedious sample treatment (before and/or after borate separation), use of methanol, complicated quartz set up, possible loss of boron and reduces the analysis time significantly. In situ dehydration of sample solution by ethanolic vapour in the absence of dehydrating acid prevents the formation of fluoborate and co-distillation of potential anionic interferents (nitrate and fluoride). This developed method has been applied for the determination of traces of boric acid in boron powder by the distillation of methyl borate at room temperature. For other matrixes (water, uranium oxide, uranyl nitrate, fluoride salt, etc.) distillation of ethyl borate was carried out on the water bath. LOD (3σ) was 5 ng g⁻¹ for water and 30 ng g⁻¹ for solid samples.