Nature of PMMA dissolution process by mixtures of acetonitrile/alcohol (poor solvent/nonsolvent) monitored by FTIR-imaging

The dissolution process of poly(methyl methacrylate), PMMA, in mixtures of the binary systems: acetonitrile/alcohol (methanol, ethanol and 1-propanol), individually poor and nonsolvents respectively for the polymer, was studied at 25 °C using FTIR imaging spectroscopy. To investigate this cosolvency phenomenon and the kinetics of the dissolution process, the spatial resolution and sensitivity of FTIR imaging were used. It has been found that the PMMA dissolution rate anomalously increases almost in a parabolic way independently of the solvent system used in this study. These results were interpreted assuming that the dissolution of a polymer by a mixture of solvents is governed by a complex dependence of the solvent molecules size and their thermodynamic characteristics. The kinetics of the PMMA dissolution by AcN/alcohol solvent mixtures were interpreted using conventional Arrhenius behavior in which the activation energy has a simple dependence on the thermodynamic quality and the molecular weight of the solvent mixture.     

Cellule pour etudes electrochimiques sous pression; application a l''etude de la force electromotrice de la pile Cu(Hg)/CuSO4/Hg2SO4/Hg

For a study of the possible electrochemical processes occurring in the formation of polymetallic marine nodules, a vessel has been adjusted for electrochemical studies which allows to attain a pressure of about 500 atm. In order to test this cell, we have been studying the influence of pressure on the electromotive force of the cell

and we have determined an experimental pressure coefficient (?E/?p)_T,ni = 1,04.10^?5 volt.atm^?1.     

Study of the Interfacial Reaction of Styrene/Maleic Anhydride Copolymerand (Amine)-Terminated Butadiene-Acrylonitrile Copolymer Using FTIR Imaging Techniques

The interfacial reaction between styrene/maleic anhydride copolymer (SMA) and amine-terminated butadiene-acrylonitrile copolymer (ATBA) was observed using Fourier transform infrared (FTIR) imaging spectroscopy. The anhydride and amine reacted to form an imide. Each component was detected using a characteristic wavenumber, which was 1601 cm -1 for SMA, 2237 cm -1 for ATBA, and 1701 cm -1 for the imide. FTIR images were taken as the reaction proceeded at 150, 160, 170, and 180°C. At low temperatures (150 and 160°C), diffusion-controlled kinetics were observed since interdiffusion between the reactants did not appear in the images. On the other hand, both the diffusion front and the reaction front are observed in the images at high reaction temperatures (170 and 180°C), which indicates that the kinetics became reaction-controlled rather than diffusion-controlled. Absorbance profiles were extracted from the images and used for the calculation of the extent of reaction. The data were analyzed using the Frederickson and Milner theory based on the assumption of diffusion-controlled kinetics, and this theory fit the low reaction temperature data.     

Evaluation of alternative evolutionary programming techniques for optimization of an automotive alternator

One of the primary design requirements of automotive generation systems is maximizing power density subject to the constraint of minimizing the overall system cost. However, with the progress made in the reduction of automotive drive train noise, the torque ripple of the generator has been found to be a dominant noise source under idle conditions at high electrical loads. Thus, an added design constraint is the minimization of the torque ripple produced by the machine. In order to evaluate alternative machine designs (and select an optimal), numerical tools are typically applied. In this research, a focus is placed on the creation of numerical tools that can be used to effectively search for an optimal design. A primary tool is an evolutionary algorithm (EA) that has been integrated within a customized magnetic equivalent circuit (MEC) model of the machine. The selection of an EA that is most likely to converge to an optimal solution in the least amount of time is described along with its use in selecting an optimal rotor-pole geometry.     

Fundamental studies on vacuum circuit breaker arc quenching limitswith a synthetic test circuit

The aim of this work is to demonstrate the use of a synthetic test circuit with LC resonant circuits for fundamental experimental work on CB (vacuum circuit breakers). Studies have been performed on a 36 kV-model CB at test currents of 5 and 10 kA r.m.s. aimed at separating the influence of different parameters of the transient recovery voltage such as average rate of rise and peak value on the breaking capability. Furthermore, the effect of the arcing time on the measured arc quenching limit is presented     

Fault arcs effects in cable bundles for space applications invacuum

A multitude of `arc tracking' tests on cables for space applications has been performed to improve the basic understanding of the phenomena responsible for the fault arc behavior. The damage in a cable bundle develops in a complex system consisting of metallic conductors, insulation materials and arc plasma. Considering the degradation effects, vacuum as one of the applied test parameters, has turned out to be an important test environment. The investigations are based on a new test method, developed to assess arc tracking properties of cables for space applications. Tests were conducted with different insulation materials at cables with different AWG at 125 V dc and nominal currents. The tests were focused on the vacuum environment, using air only for the purpose of comparison. For some cable types, vacuum has turned out to be a worst-case environmental condition with respect to fault arc effects, such as the conductor burn-off, degradation of the insulation of adjacent cables and the extension of the fault arc. This paper presents these worst case experiments in detail     

Investigation of Functional Hemispheric Asymmetry of Language in Tinnitus Sufferers.

The authors tested functional hemispheric asymmetry through word dichotic listening and lateralized lexical decision tasks in tinnitus patients and controls stimulated by a continuous tinnitus-like noise to test the influence of a tinnitus-like external stimulation. A classic right-ear advantage was shown in the auditory task for all but right-ear tinnitus patients, who performed as equally badly when the stimuli were presented to the right and left ears. Concerning the visual task, all participants demonstrated the expected right visual field advantage for word stimuli. Moreover, those who submitted to external stimulation demonstrated normal asymmetric patterns. These data suggest a specific effect of tinnitus on central processing and provide evidence for a functional reorganization induced by this auditory phantom perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical reactions occurring at the interface of epoxy matrix and aminosilane coupling agents in fiber-reinforced composites

The chemical reactions at the interface between an anhydride-cured epoxy resin and an aminosilane treated fiber have been investigated using Fourier transform infrared methods (FT-IR). The results indicate that chemical bonds are formed in the interfacial region between the matrix and the coupling agents. The amount of interfacial bonding depends on the composition and the processing conditions.     

PARTICLE-SIZE DISTRIBUTION OF GLAZES*

The particle-size distributions of experimental and commercial stains and glazes and glaze materials were determined by using the Andreasen pipette method. The variation in particle size of two porcelain glazes, raw and fritted, was correlated with the glaze working properties and certain physical properties of the glaze film, such as fluidity, microtexture, scratch-hardness, and glaze stress. The relation of grinding efficiency to length of milling time and different ball size was studied for these two glazes and also for a stain, and the color imparted by the stain at different grain sizes was noted.