Numerical simulations of a filament in a flowing soap film

Experiments concerning the properties of soap films have recently been carried out and these systems have been proposed as experimental versions of theoretical two‐dimensional liquids. A silk filament introduced into a flowing soap film, was seen to demonstrate various stable modes, and these were, namely, a mode in which the filament oscillates and one in which the filament is stationary and aligns with the flow of the liquid. The system could be forced from the oscillatory mode into the non‐ oscillatory mode by varying the length of the filament. In this article we use numerical and computational techniques in order to simulate the strongly coupled behaviour of the filament and the fluid. Preliminary results are presented for the specific case in which the filament is seen to oscillate continuously for the duration of our simulation. We also find that the filament oscillations are strongly suppressed when we reduce the effective length of the filament. We believe that these results are reminiscent of the different oscillatory and non‐oscillatory modes observed in experiment. The numerical solutions show that, in contrast to experiment, vortices are created at the leading edge of the filament and are preferentially grown in the curvature of the filament and are eventually released from the trailing edge of the filament. In a similar manner to oscillating hydrofoils, it seems that the oscillating filaments are in a minimal energy state, extracting sufficient energy from the fluid to oscillate. In comparing numerical and experimental results it is possible that the soap film does have an effect on the fluid flow especially in the boundary layer where surface tension forces are large. Copyright © 2004 John Wiley & Sons, Ltd.     

Kinetics of oil saponification by lead salts in ancient preparations of pharmaceutical lead plasters and painting lead mediums

Lead soaps can be found in archaeological cosmetics as well as in oil paintings, as product of interactions of lead salts with oil. In this context, a better understanding of the formation of lead soaps allows a follow-up of the historical evolution of preparation recipes and provides new insights into conservation conditions. First, ancient recipes of both pharmaceutical lead plasters and painting lead mediums, mixtures of oil and lead salts, were reconstructed. The ester saponification by lead salts is determined by the preparation parameters which were quantified by FT-IR spectrometry. In particular, ATR/FT-IR spectrometer was calibrated by the standard addition method to quantitatively follow the kinetics of this reaction. The influence of different parameters such as temperature, presence of water and choice of lead salts was assessed: the saponification is clearly accelerated by water and heating. This analysis provides chemical explanations to the historical evolution of cosmetic and painting preparation recipes.     

离子色谱法测定皂粒中葡萄糖酸钠含量

建立了离子色谱检测皂粒中葡萄糖酸钠含量的分析方法。样品经METROSEP CARB 1糖分析色谱柱(150 mm×4.0 mm,5μm)分离,以150 mmol·L~(-1) NaOH+20 mmol·L~(-1)NaAc水溶液为流动相进行等度洗脱,流速1.0 mL·min~(-1),采用瑞士万通850型离子色谱仪,选择脉冲安培检测器进行测定,外标法定量。结果显示:葡萄糖酸钠在0.5～200 mg·L~(-1)质量浓度范围内呈良好的线性,相关系数(r~2)为0.999 6,检出限为0.25 mg·L~(-1),定量下限为0.63 mg·L~(-1)。葡萄糖酸钠在1～20 mg/g加标范围内的回收率为80.7%～104%。该方法无需衍生化处理,操作简单方便,灵敏度高,可用于皂粒产线葡萄糖酸钠含量的监控与测定。     

GIS Web服务结构与实现

针对WebGIS需要解决功能和数据的共享问题,阐述了基于Web Service框架开发GIS Web服务的优点;根据数据和功能分别在网络中的位置不同提出了服务的几种结构,并分别介绍了各服务的优点和缺点;根据现在各种GIS Web服务的实现不同方法概括了GIS Web服务几种实现方法,分别说明了它们的发展情况和优缺点.     

A constructive proof by elementary transformations of Roth's removal theorems in the theory of matrix equations

W. E. Roth gave necessary and sufficient conditions for the existence of solution(s) of certain types of linear matrix equations. Proofs were based on invariant factors and were long and complicated. Other shorter but non-constructive proofs have since been provided by later authors. We present here very brief constructive proofs based on the simplest of mathematical techniques, namely row- and column-reduction of a matrix.     

The standard double bubble is the unique stable double bubble in

We prove that the only equilibrium double bubble in which is stable for fixed areas is the standard double bubble. This uniqueness result also holds for small stable double bubbles in surfaces, where it is new even for perimeter-minimizing double bubbles.

     

流动肥皂膜气体界面及其在柱状汇聚激波作用下演化的实验研究

在Richtmyer-Meshkov(RM)不稳定性实验研究中,形成两种不同密度流体的初始扰动界面是前提和关健.本文提出了一种流动肥皂膜气体界面生成方法,其工作原理是由细丝构成的导流框从激波管实验段穿过,肥皂液从导流框的上端注入并在重力作用下在导流框中形成流动肥皂膜,膜的两测可以分别充入不同密度的气体从而形成稳定的气体...     

液膜气泡法测洗涤溶液的表面张力系数

利用自制装置采用液膜气泡法测定了洗涤溶液的表面张力系数．由医用注射器充气形成球形液泡，通过与之连通的微压计测出液泡内外的压强差，运用杨氏-普拉斯方程计算出洗涤溶液的表面张力系数.     

Facile Soap‐Free Miniemulsion Polymerization of Methyl Methacrylate via Reverse Atom Transfer Radical Polymerization

A facile soap‐free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water‐soluble potassium persulfate (KPS) or 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (V‐50) both as the initiator and the stabilizer, and using an oil‐soluble N,N‐n‐butyldithiocarbamate copper (Cu(S₂CN(C₄H₉)₂)₂) as the catalyst without adding any additional ligand. Polymerization results demonstrated the “living”/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300–700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain‐extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive  S C(S) N(C₄H₉)₂ group in the chain end.