Dielectric Depression and Dispersion in Electrophoretically Fabricated BaTiO3 Ceramic Films

Dielectric depression and dispersion were observed in BaTiO3 ceramic films fabricated by electrophoretic deposition followed by sintering. The dielectric constants were depressed down to 6800–4600 around the Curie point ( T _C ). The dielectric dispersion occurred above T _C . These dielectric properties are attributable to a surface layer formed during sintering. XRD analysis indicated that the surface layer was a hexagonal-like BaTiO₃ phase. A mixed solvent of acetylacetone and alcohol employed in the present work may have been responsible for the formation of the surface layer.     

Abstracts

Journal of the American Oil Chemists' Society -     

Development of high performance,waterborne coatings. Part II: Factors affecting adhesion performance

A new manufacturing process for high performance, waterborne coatings for can coating application was developed, which includes emulsification of an epoxy resin with or without a hardener by incorporation of an acrylic resin. It is possible by this new process to emulsify a variety of resins with minimum effects of the surfactant. (acrylic resin). The effects of surfactant and neutralizer on adhesion performance were studied. It was found that the effects of the acrylic resin amount were relatively small, and that the effects of the neutralizer were significant. It was confirmed that the usage of ammonia or amines with a branched alkyl group is required to achieve balanced dry and wet adhesion.     

Heterogeneous nucleation of organic vapours on a cold substrate

The heterogeneous phase transition of the organic vapours, cyclohexane and p-xylene, on a cold substrate was observed by cooling the substrate at a slow rate under reduced pressure conditions. Either organic vapour at a vapour pressure lower than 130 Pa formed directly solid crystals but p-xylene vapour at a higher vapour pressure formed liquid condensates with subsequent formation of solid crystals. The dependence of the critical supersaturation ratios on the critical temperatures and the physical properties of the organic vapours has been clarified by the equation derived on the basis of classical nucleation theory.     

《时尚学:时尚研究概述》前言

本文是<时尚学:时尚研究概述>(Fashion-ology:An Introduction to Fashion Studies)一书的前言部分,概括了书中的一些主要观点.作者认为应该将对时尚的研究与对衣着的研究区分开来.时尚无关服饰,它只是一种信仰.她主张应该把时尚研究列入社会科学、人文科学的研究范围内,并介绍了人们在心理学、社会心理学、历史学、艺术史、文化人类学和经济学等领域对时尚的研究.她所提倡的时尚理论认为,对时尚的研究应该从时尚系统入手,研究它整个运作过程中的社会属性.     

Radical polymerization of methyl methacrylate with some 1,2-disubstituted tetraphenylethanes as thermal iniferters

Summary The bulk polymerization of methyl methacrylate (MMA) with 1,2-disubstituted tetraphenylethanes, tetraphenylsuccinodinitrile (TPSN), tetra(p-methoxyphenyl)succinodinitrile (TMPSN), and pentaphenylethane (PPE), was investigated. These compounds were found to serve as thermal iniferters to induce living radical polymerization via a mechanism close to the model proposed previously (see Eq. 2). However, the living nature was not so high, because undesirable side reactions occurred. The oligomer with molecular weight of 2500 was isolated from the reaction mixture of MMA with TPSN, which was found to cause further polymerization of MMA. From the polymerization of styrene (St) with the polymers obtained by these iniferters, the block copolymers were produced.     

Short- and long-term strength characteristics of particulate-filled cast epoxy resin

Particulate-filled thermosetting composites are widely used, yet little systematic work has been done on their long-term strength characteristics. In this study short-term tensile, flexural, and impact tests as well as tensile creep-rupture tests were made for unfilled and filled epoxy to clarify the effects of filler size, filler content, and temperature. Fillers used were silica, alumina particles, and glass beads. Test temperatures were varied from 25 to 110°C. As a result of short-term testing, it was found that the Petch relation held between strength and filler size if brittle fracture occurred, while a strength and filler size if brittle fracture occurred, while a strengthening effect existed when ductile fracture occurred. On creeprupture testing, a strengthening is observed with filler size and content for silica and glass beads. The Arrhenius plot of rupture time for various filler sizes and contents converges to a characteristic point corresponding to the glass transition temperature of the material. Using this relation, a modified Larson-Miller master rupture curve is proposed which can predict the long-term strength of particulate-filled thermosetting composites as functions of rupture time, temperature, filler size, and content.     

Pervaporation via silicon-based membranes: Correlation and prediction of performance in pervaporation and gas permeation

Pervaporation (PV) is a membrane technology that holds great promise for industrial applications. To better understand the PV mechanism, PV dehydrations of various types of organic solvents (methanol, ethanol, iso-propanol, tert-butanol, and acetone) were performed on five types of organosilica and two types of silicon carbide-based membranes, all with different pore sizes. Water permeance was dependent on the types of organic aqueous solutions, which suggested that organic solvents penetrated the pores and hindered the permeation of water. In addition, water permeance of various types of membranes in PV was well correlated with hydrogen permeance in single-gas permeation. Furthermore, a clear correlation was obtained between the permeance ratio in PV and that in single-gas permeation, which was confirmed via the modified-gas translation model. These correlations make it possible to use single-gas permeation properties to predict PV performance.     

Effect of strain rate on compressive behavior of a Pd40Ni40P20 bulk metallic glass

Mechanical deformation of Pd₄₀Ni₄₀P₂₀ was characterized in compression over a wide strain rate range (3.3×10⁻⁵ to 2×10³ s⁻¹) at room temperature. The compression sample fractured with a shear plane inclined 42 degree with respect to the loading axis, in contrast to 56 degree for the case of tension. This suggests the yielding of the material deviates from the classical von Mises yield criterion, but follows the Mohr-Coulomb yield criterion. Fracture stress as well as strain was found to decrease with increasing applied strain rate. The compressive stress (1.74 GPa) was also found to be higher than the tensile fracture stress at a quasi-static strain rate. Close examination of the stress–strain curves revealed that localized shear might have occurred at a compressive stress of about 1.4 GPa, much lower than the “apparent” yield stress of 1.74 GPa. However, the stress of 1.4 GPa for shear band initiation is almost the same as the fracture stress measured at a dynamic strain rate of 5×10² s⁻¹. These results suggested that the fracture of a bulk metallic glass is sensitive to the applied loading rate.     

Generalized measuring-worm algorithm: high-accuracy mapping and movement via cooperating swarm robots

Recently, many extensive studies have been conducted on robot control via self-positioning estimation techniques. In the simultaneous localization and mapping (SLAM) method, which is one approach to self-positioning estimation, robots generally use both autonomous position information from internal sensors and observed information on external landmarks. SLAM can yield higher accuracy positioning estimations depending on the number of landmarks; however, this technique involves a degree of uncertainty and has a high computational cost, because it utilizes image processing to detect and recognize landmarks. To overcome this problem, we propose a state-of-the-art method called a generalized measuring-worm (GMW) algorithm for map creation and position estimation, which uses multiple cooperating robots that serve as moving landmarks for each other. This approach allows problems of uncertainty and computational cost to be overcome, because a robot must find only a simple two-dimensional marker rather than feature-point landmarks. In the GMW method, the robots are given a two-dimensional marker of known shape and size and use a front-positioned camera to determine the marker distance and direction. The robots use this information to estimate each other’s positions and to calibrate their movement. To evaluate the proposed method experimentally, we fabricated two real robots and observed their behavior in an indoor environment. The experimental results revealed that the distance measurement and control error could be reduced to less than 3 %.