Materials Literature
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Group-theoretical methods are used to analyze perovskite structures where both ferroelectric cation displacements and simple tilting of octahedral units are present. This results in a list of 40 different structures, each with a unique space-group symmetry. The list is compared with that of Aleksandrov & Bartolomé [Ph…
The preparation and characterization of highly dispersed metal nanoparticles in mesoporous silica SBA-15 are reported. The functionalization with organosilane to generate a monolayer of charged groups on the pore surface facilitates uniform distribution of ion-exchanged metal precursors in the channels of SBA-15, whic…
Polymerization of beta-butyrolactone (BBL) and beta-valerolactone (BVL) using the zinc alkoxide initiator (BDI-1)ZnO(i)()Pr [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentene] proceeds very rapidly under mild conditions to produce poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyvale…
Imaging of the platinum replica of the porous structure and low-pressure argon adsorption allowed us to elucidate the complicated porous structure of SBA-15. These techniques enabled us to draw a coherent picture of the evolution of the SBA-15 precursor mesophase as a function of the synthesis temperature. TEM of the…
Recent advances in thermal infrared (TIR) detection offer design options for space sensors requiring temperature sensitivity in the 0.1-0.5 K range. A cost vs. performance trade-off is illustrated with two "reference" sensor concepts. Both systems use all reflective front optics designed for low cost "bolt-together" a…
Of interest, is to find a mica paper tape with higher dielectric properties than commercially available tapes. This paper presents the results of a preliminary evaluation of Corona Resistant (CR) Kapton/sup (R)/ backed mica paper tape. These tapes were evaluated for possible use for high voltage coil groundwall insula…
In most of the engineering applications, air is used in conjunction with solid insulation. The interface forms a weak point for the occurrence of partial discharges (PD). Therefore it becomes essential to know the behaviour of the PD in such a system. The work presented in the paper is a study of the PD corona pulse s…
The normal method of operation for a GaAs MQW quantum confined Stark effect (QCSE) reflection modulator is given for a device operating wavelength, taken as 852 nm for the analysis in this paper. Modulation in the intensity of a reference optical beam is achieved by shifting the wavelength to achieve both low reflecti…
In order to investigate partial discharge (PD) degradation in composite insulating systems such as a prefabricated cable joint (PJ), we proposed an electrode system to simulate PD degradation at a solid-solid interface. It was observed that the tree at the EPR-epoxy resin interface tended to propagate into the epoxy r…
Long term aging tests of stator bar end arms were carried out over several months. Six specimens affected by one of three types of defect were studied. Those defects were corona activity, surface tracking and bar-to-bar discharges. All the specimens were submitted to an aging voltage of 20 kV c.a. Phase resolved parti…
The pattern of the lowest-lying energy levels of ${\mathrm{Fe}}_{12},$ a ferric wheel comprising $N=12$ antiferromagnetically coupled spins $s=5/2,$ has been determined by specific-heat measurements between 0.5 and 10 K and in magnetic fields up to 7 T. Within the framework of a semiclassical model, we evaluated the p…
The electrical conductivity of amorphous boron wafers obeys Mott's T/sup -1/4/ rule. BP and B/sub 12/P/sub 2/ show band conduction. The thermoelectric power of polycrystalline B decreases with increasing temperature, while that of amorphous B is almost constant in a wide temperature range. That of BP increases with in…
In response to intense development of hybrid electric vehicles throughout the world spurred by energy and environmental concerns, Ovonic Battery Company has developed a series of high power batteries suitable for a range of vehicle design concepts. We have developed a 60 Ah HEV battery with a power capability of 620 W…
In the literature there are many papers that allude to the endurance of dielectric materials subjected to electrical stress. Generally it is noted that the endurance performance is reduced by stressing in moist conditions. However, it is important to realise that moisture barriers are often incorporated in cable desig…
Ferroelectric nonvolatile memories offer low voltage operation and fast write speeds that makes them attractive for embedded applications. The fundamentals of ferroelectric materials and ferroelectric memory operation are reviewed. Also discussed is the process integration of ferroelectric capacitors into a CMOS flow.…
The Peltier effect was discovered early in the 19th century but has only been seriously exploited during the second half of the 20th century. This was no accident, since the development of materials that would yield worthwhile thermoelectric refrigeration depended on a knowledge of the physics of semiconductors, a dee…
This paper discusses the phenomena of the surface degradation in the early ageing period (EAP) under indoor conditions. The surface hydrophobicity of aromatic epoxy resin with different fillers was investigated. The lifetime of the insulating materials depends on their withstand against combined electric and climatic…
A novel buried Ti-W self-heating layer structure has been proposed to generate a controlled temperature gradient along the metal stripe. The maximum temperature difference between the highest temperature point of two samples is about /spl plusmn/1.08/spl deg/C. A metal line resistance method was utilized to determine…
Semiconductive tapes are applied to the end turn region of high voltage stator coils to reduce corona discharge at the slot exit region. The nonlinear, stress grading tapes are used to even out the voltage stress resulting in a more even distribution which also reduces the maximum stress level. To be able to optimize…
This paper presents a generalized dynamic circuit model of high frequency transformers, which includes all types of core losses and thermal effects on magnetic hysteresis. This transformer model provides accurate core loss prediction and is suitable for the simulation of transformers used in high frequency switching-m…