Materials Literature
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The technological revolution and busy schedule compel human society to search for better civic amenities. This leads to the use of modern personal care goods such as disposable diapers and sanitary napkins. Presently, all of the goods use microporous polyolefin films. The high-strength microporous polyolefin films als…
Electric stress, voltage waveshape, temperature, contaminants and insulation resistance to oxidation have been analyzed as to their influence on triggering breakdown of a water-treed polymer. The transition from a water tree to an electrical tree is dependent on several factors, including voltage waveshape, and magnit…
A laboratory investigation was undertaken to study the nature of surface charge decay and its mechanism with several synthetic organic materials after both corona and contact charging in different environments. Some results for low-density polyethylene (LDPE) are presented and discussed. The behaviour of the decay sho…
Six kinds of typical oil gaps were designed and tested to simulate partial discharges (PD) in the insulation of power transformers. The frequency spectra of acoustic emission (AE) of PD in those gaps were presented and investigated with a computer-aided measuring system. The attenuation of AE and the variation of its…
Graft copolymerization of 2-Hydroxy ethyl methacrylate (HEMA) on to chitosan was studied using cerium (IV) as the initiator. Optimization of the grafting was worked out by varying the reaction time and monomer concentration. Under controlled conditions, up to 685% grafting with a grafting yield of 92.4% was achieved.…
The authors present a brief assessment of the experience gained with synthetic dielectrics as applied to solid extruded cables and review the up-to-date work carried out on the development of oil-filled commercial cables insulated with polypropylene laminated paper (PPLP). The primary emphasis is placed on the relativ…
New copper(II) toluate complexes with saturated monoheterocyclic bases, substituted piperidines, of the type Cu(OOCR)2L (where R = 2‐, 3‐, or 4‐CH3C6H4 and L = 1‐methyl‐, 1‐ethyl‐ or 2,6‐dimethylpiperidine) have been synthesized and characterized by elemental analyses, IR, electronic reflectance and EPR spectral and m…
Corona charging is a powerful method for studying storage and electric charge transport in dielectric films. The development of this technique for the study of polymer foils is summarized. The improvement achieved with the use of a biased vibrating grid, allowing the measurement of the potential buildup is commented o…
The thermal aging of cross-linked polyethylene (XLPE) cable models has been investigated to obtain information on aging effects and mechanisms. After thermal life tests, XLPE cable models were subjected to chemical, physical, electrical and microstructural characterizations. The results of density, melting point and e…
Measurements carried out on a large wall bushing are described. They show that uneven rain distribution can cause flashovers even at very low pollution levels. A possible mechanism for these rain flashovers is proposed. It is reported that water-repellent surfaces provide an efficient remedy for this type of flashover…
Corona-charging characteristics of a nonwoven polypropylene sheet of 140- mu m thickness are studied with respect to the charging conditions. When the grid voltage, V/sub g/, which controls the surface potential of the film, is -3 kV, the surface potential profile of the charged sheet is nonuniform. The profile is ver…
We introduce here one possible definition of the energy of an infinite non-periodic system of particles. We investigate the minimization of it, and the link with standard definitions of local ground state for such systems. The specific models under study are issued from Quantum Mechanics (namely from Density-Functiona…
Castable particulate-filled epoxy resins exhibiting excellent thermal conductivity have been prepared using hexagonal boron nitride (BN) as filter. The thermal conductivity of BN filled epoxies is influenced by the sample preparation procedures, due to agglomeration effects of the particles in the matrix. The temperat…
Radiation-induced changes in the density and viscosity of 30% TBP–n-dodecane–HNO3 mixtures were examined. The increase in the density becomes significant with increasing nitric acid content of the solvent, [HNO3]TBP, and absorbed radiation dose, which concomitantly leads to a much sharper increase in the viscosity of…
The antiferromagnetic, charge and orbitally ordered (AFCOO) ground state of some manganites like ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ can be efficiently destabilized by slight Mn-site substitutions. Such a weakened AFCOO state and related disorder effects were investigated in ${\mathrm{Pr}}_{0.5}…
The available starting methods are discussed for motors above 3000 hp, focusing on technical and economic aspects. The following schemes are discussed: direct online, reactor start, auto transformer start, capacitor start, capative transformer start, and frequency start. A review of the network conditions which favor…
Abstract The synthesis and photochromic reaction of 1,2‐diphenylperfluorocyclopentenes are reported. Upon UV irradiation, hexane solutions of 1,2‐diphenylperfluorocyclopentenes afforded red solution of dihydrophenanthrenes, which gradually give the initial 1,2‐diphenylperfluorocyclopentenes at room temperature thermal…
Simple far-field emission polarization microscopy reveals that the emission transition dipole of CdSe colloidal quantum dots (QDs) is twofold degenerate at room temperature. We measure, model, and compare polarization anisotropy statistics of CdSe QDs and DiI (a one-dimensional emitter). We find excellent agreement be…
Relaxation of conduction electron spins in a semiconductor owing to the hyperfine interaction with spin-1/2 nuclei, in zero applied magnetic field, is investigated. We calculate the electron spin relaxation time scales, in order to evaluate the importance of this relaxation mechanism. Master equations for the electron…
The anisotropy of low-energy $(0\ensuremath{\sim}5\mathrm{eV})$ optical excitations in strongly correlated transition-metal oxides is closely related to the spin and orbital orderings. The recent successes of $\mathrm{LDA}+U$ method in describing the magnetic and electronic structures enable us to calculate the optica…