Isolation of the effect of the hairy layer length on the mechanical properties of waterborne coatings

The effect of the acidic hairy layer length on the interdiffusion of polymer between particles and as a consequence on the mechanical properties of the films produced from waterborne coatings has been studied. In order to isolate this effect, latexes with the same particle diameter and molecular weight but stabilized with poly(acrylic acid)-block-poly(butyl acrylate) (PAA-b-PBA) block copolymers of controlled and different lengths were prepared. Tensile strength measurements showed at the macroscopic level that the presence of AA chains in the particle surface reduced the mechanical properties of the films dried at room temperature, being its effect worse the longer the AA chain length. Higher annealing temperatures erased the negative effect of the acidic hairy layer on mechanical properties. The neutralization with NaOH instead of with NH₄OH also led to worse mechanical properties. These macroscopic results were supported by Fluorescence Resonance Energy Transfer (FRET) experiments that showed that at the microscopic level, the extent of interdiffusion occurred slower when the AA chains in the particles surface increased, the annealing temperature was lower and when NaOH was used as neutralizing agent instead of NH₄OH.     

Verhalten von Magnesiumlegierungen für Anwendungen im Fahrzeugbau bei mechanisch‐elektrochemischer Komplexbeanspruchung: Einfluss passivierender Deckschichten und Mechanismen der lokalen Schädigung

Behavior of Magnesium‐Alloys for Automotive Applications under Mechanical and Environmental Loading: Influence of Passivating Films and Mechanisms of Local Breakdown To assure an efficient design of components under cyclic loading, all available data concerning fatigue have to be observed. Therefore the influences of manufacturing on the material condition, the mechanical loads and environmental effects have to be analysed. Magnesium‐alloys are of special interest for lightweight applications because of their excellent strength‐density ratio. The corrosion resistance of magnesium‐alloys depends on the same factors that are critical to other metals. The alloys have a good stability to atmospheric exposure and a good resistance to attack by alkali, chromic and hydrofluoric acids. However, because of the electrochemical activity of magnesium, the relative importance of some factors is greatly amplified. The nature and composition of passive films formed on magnesium‐alloys depend on the prevailing conditions, viz. alloy‐composition, passivation potential, pH, electrolyte composition and temperature. Passive films may be damaged by local breakdown. Because of this, magnesium‐alloys suffer a degradation of their properties when exposed to an aqueous environment. The main topic of the present investigations is the verification of mechanisms of the local breakdown of the protecting film. At least two mechanisms are possible for this localization: mechanical breakdown by slip steps and electrochemical breakdown (for e.g. by the effects of chloride ions). Corrosion and passivation of different high purity alloys have been studied in different solutions (neutral, alkaline with specific anions and cations) using electrochemical techniques. The diecasted alloys were tested as produced and machined. The results clarified that depending on alloy/material and surface condition/corrosion environment different mechanisms for electrochemical breakdown of the protecting films are possible. Hence fatigue life under environmental loading is influenced by surface and testing conditions.     

油藏中分散非连续残余油膜的驱替机理分析

水驱后的残余油膜将贴于孔隙壁面，为壁面边界层流体，处于三相界面的包围和共同作用下。目前的调研结果显示，油膜的组成及力学特性沿孔壁方向上是变化的。在化学驱过程中油膜不仅受到驱油剂的驱替作用。还受驱油剂／油界面张力、油／固体界面张力及驱油剂／固体界面张力的阻碍作用。由于油膜组成、力学特性及相间作用的复杂性．以往对油膜驱替机理的研究都是从微观实验的角度对现象作观察和定性解释。本文根据水驱后残余油膜在油藏孔隙中存在的特点，提出了油膜驱替的简化模型。基于油膜驱替的微观实验，采用数值方法从定量的角度分别计算了不同黏弹性驱油剂在不同的驱油剂／原油界面张力作用下对残余油膜的驱替效率。考察了驱油剂的流变性、驱油剂／油界面张力、驱替速度等因素对驱替不同厚度油膜的影响规律。进一步探讨了驱油剂／原油界面特性和流变性在驱替残余油中的综合作用。研究结果表明，驱油剂对油膜的驱替始于驱油剂／油界面，要同时克服驱油剂／油界面约束力和油膜的屈服应力。降低界面张力、增强驱油剂的黏弹性、增加驱替速度，有利于提高驱替残余油膜的驱替效率。适当增加驱油刑的黏弹性可以放宽驱替薄油膜时对超低界面张力的要求。图13参9。     

Effect of select parameters on the properties of edible film from water-soluble fish proteins in surimi wash-water

Edible film from water-soluble fish proteins were developed by casting film solution on leveled trays and effects of pH (9.5, 10.0 and 10.5), heating temperature (60, 70 and 80 °C), and heating time (10, 20 and 30 min) of the film solution on various film properties were determined using Response Surface Methodology (RSM). The impact of pH and heating temperature of film solution was more significant, overall, on the film's properties than heating time. Contour plots of tensile strength and elongation at break was highest at pH of 10.0 at 70 °C (2.75-3.02 MPa) but low in elongation at break (6.35-9.16%), while water vapor permeability and oxygen permeability were at their lowest (58.55-65.96 g mm/m² d kPa and 351.33-624.18 cm³ μm/m² d kPa). There was a direct correlation between the films’ and proteins’ solubility on one hand, and heating temperature of film solution on the other, which reversed with change in pH of film solution. Film color was darker and more yellowish with increase in the pH of film solution.     

利用静电学和测量数据对碳纳米管膜场致发射规律的定量分析

碳纳米管膜的场致发射电流密度仅由它表面的宏观电场决定，无论其表面形状是平的还是半球状的。对于理想的平行板电极系统，其表面电场强度均匀（UId），发射电流密度、总电流与发射面积成正比：对于半球一平面电极系统半球形的阴极存在一个宏观场增强因子ks，一个与两极距离和球半径之比（d/r）相关的函数，其表面的平均场强为ks U/d。对于d/r=0，ks=1，d≥r的情况，ks接近于常数。对于10〈d／r〈100的情况，存在一个经验的表达式：ks=1＋0．15d/s=0．005（d／r）^2。在引入ks后，不同作者给出的平面电极系统和半球一平面电极系统碳纳米管膜的场致发射电流I与宏观表面电场强度E的关系都可以近似用-经验公式描述：I=a（E-Eo）^b，a，b为常数。该经验公式可为稳定生产的CNT膜片应用产品设计提供方便。     

Influence of Polyalkylmethacrylate VII on Boundary Film Formation,Friction,Wear and Efficiency of Lubricants

1 Influence of PAMAon Boundary Fil mFormation and Friction1.1 Experi mental methodsUltra-thin optical interferometry has been used tostudy thinlubricating fil ms for more than a decade and theexperi mental details of this technique have been reportedpreviously[1].The principle of the test setup is shown inFigure1.A polished steel ball is loaded and rolled againstthe flat surface of a glass disc that is coated with a thinsemi-reflecting chromiumlayer and a silica spacer of about500nmthickne…     

Vapor absorption by LiBr aqueous solution in vertical smooth tubes

Heat and mass transfer in a falling film vertical in-tube absorber was studied experimentally with LiBr aqueous solution. The presented results include the effect of solution flow rate, solution subcooling and cooling water temperature on the absorption in a smooth copper tube 16.05 mm I.D. and 400 mm long. The experimental data in the previous report for a 1200-mm-long tube was also re-examined and compared. It was demonstrated by the observation of the flow in the tube that the break down of the liquid film into rivulets leads to deterioration of heat and mass transfer at lower film Reynolds number or in longer tubes. An attempt to evaluate physically acceptable heat and mass transfer coefficients that are defined with estimated temperature and concentration at the vapor–liquid interface was also presented.     

金刚石膜在真空电子器件输出窗中的应用

综述了金刚石膜的性能和制备方法，着重介绍丁国内外常用的封接工艺，讨论了该材料在mm波器件中的应用前景。     

热声制冷机及其改进实验研究

热声制冷作为一种很有前途的制冷方法，在国内外相关领域引起了极大兴趣。热声制冷机由声发生器、共振管、板叠及高、低温换热器等部分组成。对声驱动器的振动膜及其冷却系统、气体弹簧系统、高、低温换热器进行了初步改进，使制冷机冷端温降从原来的12℃提高到27℃左右，这是目前国内报道的最大温降。     

Nonstationary Simulation Model of Absorber with Falling Film of Suspension

A nonstationary model of SO₂ absorption from a gas phase to a countercurrent falling film of absorbing slurry was developed. Laminar, wavy and turbulent film structures were considered based on published information. Resistances to the mass transfer on the gas and the liquid sides of the interphase were considered, together with chemical reactions in the liquid phase. Relevant chemical equilibria in the liquid phase were modeled. Original experimental data on the neutralization reagent dissolution rate presented as a polydispersed two‐phase system of solids and on the rate of dissolved sulfite oxidation were used. The model was verified with experimental data from a laboratory‐scale falling‐film absorber using a single vertical tube under various geometrical and operating conditions, and a very good agreement was found with the experiment. Parametric sensitivity analysis showed the critical parts of the model.