Ultratrace determination of phosphorus in ultrapurified water by a slope comparison method

The analytical method for the determination of phosphorus in ultrapurified water was developed. Ultrapurified water was evaporated to concentrate phosphorus and the final sample volume for analysis was 10 ml. In 0.55 mol l⁻¹ HCl, orthophosphate forms molybdophosphate, and then the molybdophosphate forms ion associate with Malachite Green (MG), which can be collected on a tiny membrane filter (diameter: 5 mm, and effective filtering diameter: 2 mm). After the ion associate on the membrane filter is dissolved together with the membrane filter in 1 ml of methyl cellosolve (MC), the absorbance of MC solution is measured at 627 nm by a flow injection-spectrophotometric detection technique. When 10 ml of the sample solution was used for the procedures and absorbance measurement, the calibration graph is linear up to about 500 ng l⁻¹ of phosphorus and the detection limit was 8 ng l⁻¹ (S/N=3). For the determination of phosphorus in an ultrapurified water, 10-40 ml of sample solutions were transferred into poly(tetrafluoroethylene) (PTFE) beaker and evaporated to 5 ml or to dryness. To them, 0.003 mol l⁻¹ HCl was added to get 10 ml of final solution, which was used as sample. Phosphate is determined by comparing the slope of the varied sample volume after evaporation/concentration with a slope of the standard calibration graph (a slope comparison method: SCM). The SCM enables to evaluate the concentration of phosphate in ultrapurified waters more sensitively and accurately.     

Capillary and slit-die flow of two liquid-crystalline polymers. The effect of pressure on viscosity

Viscosity measurements on two commercial thermotropic liquid crystalline polymers (LCPs) (a copolyester and a polyesteramide) were performed using both capillary and slit die methods. The results are in agreement with those presented in the literature for the same LCPs, when the measurements are carried out with a L/D = 30 die; these results are affected more by Bagley corrections for the polyesteramide than for the copolyester. For both LCPs, viscosities measured in the slit die are lower than those obtained by capillary rheometry. Nevertheless, the difference is much bigger in the case of the polyesteramide, for which a reduction by a factor of 3 is observed. This is not due to the preshear or thermal history, since the same piston-barrel system and thermal treatment were applied in both types of measurements. Depending on the polymer sample and temperature, concave and convex curvatures were observed in the pressure profiles during the slit flow. From these curvatures, the pressure coefficient α of viscosity was evaluated. However, in the case of the polyesteramide the convex curvature leads to a negative coefficient (the viscosity decreases with pressure, instead of increasing). This result may be explained by envisaging a change in the structure of the melt along the slit length. © 1993 John Wiley & Sons, Inc.     

APPROXIMATING ANALYSIS OF A KIND OF REPAIRABLE STANDBY SYSTEMS

ＬＩＷＥＩ（李伟）；ＣＡＯＪＩＮＨＵＡ（曹晋华）（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ｔｈｅＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｂｅｉｊｉｎｇ１０００８０，ＣｈｉｎａａｎｄＡｓｉａ－ＰａｃｉｆｉｃＯｐｅｒａｔｉｏ...     

On the Enskog-Thorne theory for a binary mixture of dissimilar rigid spheres

Thorne's method for obtaining transport coefficients in a binary rigid-sphere mixture is reexamined. First, a close look is taken at the way in which the point where the Enskog functionsx _ij are evaluated is introduced. Second, the calculation of the fluxes in the system and the transport coefficients is given. Thorne's results are found to be correct and independent of the choice of the point where the transfer plane is located. This does not hold true for the diffusion flux. It is shown that a different diffusion force is obtained for each selection and that only those diffusional effects which are of first order in the density are consistent with irreversible thermodynamics.     

视觉极限对比测试仪的研制

叙述视觉极限对比测试仪的原理，介绍该仪器系统的设计过程，给出仪器性能参数的实际测试结果。     

块H－矩阵的进一步推广

对Ｎａｂｂｅｎ［２］提出的块Ｈ－矩阵做进一步推广，使得非对角块矩阵不必是Ｈｅｒｍｉｔｅ矩阵．但仍保留其基本特征不变．对块Ｈ－矩阵提出块Ｈ－分裂及块相容Ｈ－分裂．证明了矩阵的任意块相容Ｈ－分裂都是收敛分裂．对ＪＯＲ迭代法给出松驰参数的上界．