Materials Literature
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Non-linear field-grading materials are used to avoid stress concentrations in many AC and DC high voltage applications. One way to obtain materials having the desired non-linear characteristics is to use compounds, such as an insulating polymer with a semiconducting filler. A possible filler is silicon carbide (SiC).…
This paper presents a new approach of modeling the dynamic behavior of supercapacitors using impedance spectroscopy. The new Matlab/Simulink model can be used in simulating the voltage response and energy efficiency, e.g. for automotive power systems. The model in the frequency domain, the parameter calculation as wel…
Highly efficient, segmented thermoelectric unicouples incorporating advanced thermoelectric materials with superior thermoelectric figures of merit are currently being developed at the Jet Propulsion Laboratory (JPL). These segmented unicouples include a combination of state-of-the-art thermoelectric materials based o…
Samples of ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{FeO}}_{3\ensuremath{-}\ensuremath{\delta}}$ compounds prepared by quenching in different gaseous environments were studied by x-ray diffraction, neutron diffraction, magnetization measurements, and M\"ossbauer spectroscopy (MS). All materials are single phase…
gamma-alumina is known to transform to theta-alumina and finally to alpha-alumina upon thermal treatment with a catastrophic loss of porosity and catalytic activity. First-principles calculations were performed to investigate the atomic scale mechanism of the gamma- to theta-alumina transformation. The transformation…
We present a self-consistent field theory (SCFT) for dilute solutions of semiflexible (wormlike) diblock copolymers, each consisting of a rigid and a flexible part. The segments of the polymers are otherwise identical, in particular with regard to their interactions, which are taken to be of an Onsager excluded-volume…
This paper summarizes our efforts to develop fast algorithms for density functional theory (DFT) calculations of inhomogeneous fluids. Our goal is to apply DFTs to a variety of problems in nanotechnology and biology. To this end we have developed DFT codes to treat both atomic fluid models and polymeric fluids. We hav…
An improved thermoelectric generator (TEG) for the heavy duty class eight diesel trucks is under development at Hi-Z Technology. The current TEG is equipped with the improved HZ-14 thermoelectric module, which features better mechanical properties as well as higher electric power output. Also, the modules are held in…
Iron perovskites ${\mathrm{CaFeO}}_{3}$ and ${\mathrm{La}}_{0.33}{\mathrm{Sr}}_{0.67}{\mathrm{FeO}}_{3}$ show charge disproportionation, resulting in charge-ordered states with ${\mathrm{Fe}}^{3+}:{\mathrm{Fe}}^{5+}=1:1$ and $=2:1,$ respectively. We have made photoemission and unrestricted Hartree-Fock band-structure…
To meet the increasing world demand for energy, the rate of depletion of non-renewable energy sources must be reduced while developing alternative renewable sources. This can be achieved by increasing the overall thermal efficiency of conventional power plants. One way to do this is by waste heat recovery. Most of the…
A series of CuCoZnAl-multicomponent mixed oxide catalysts with various Cu/Co atomic ratios were prepared by the thermal decomposition of CuCoZnAl-hydrotalcite (HT)-like precursors at 450 °C in static air atmosphere. The XRD of calcined materials revealed the formation of a mixture of CuO and ZnO, Co 3 O 4, and/or ZnCo…
The speed control of ac-electric motors can be carried out efficiently by adjustable speed drives (ASD), which are constituted by an AC/DC conversion block, a DC filter and a DC/AC inverter representing the core of the whole power converter. A new generation of DC/AC converters for adjustable speed drives, the so-call…
Geomagnetically induced currents (GIC) can cause severe transformer half-cycle saturation. This paper introduces a simplified method based on the equivalent magnetizing curve of the transformer to estimate harmonic currents and MVAr with only the given the GIC and nameplate and core design information of the transform…
This paper reports the effect of voltage distortion and imbalance (VDI), on the thermal aging of the insulation of low voltage induction motors. The study is based on a detailed thermal modeling of actual motors in the 2 to 200 HP range. The dollar value of the useful life lost was estimated for different VDI conditio…
Abstract The effects of various types of compatibilizers on the mechanical properties of high‐density polyethylene/wood flour composites were investigated. Functionalized polyolefins, including maleated polyethylenes, polypropylene, and styrene–ethylene/butylene–styrene copolymer, were incorporated to reduce the inter…
This paper deals with the removal of a small sphere initially attached to a liquid interface. The sphere is small enough (0.3−1 mm) for the capillary force to dominate the interaction and large enough for the line tension effect to be negligible. We have measured simultaneously the force and the geometric parameters o…
Thin films of La0.7Sr0.3MnO3 on MgO show a metal insulator transition and colossal magnetoresistance. The shape of this transition can be explained by intrinsic spatial inhomogeneities, which give rise to a domain structure of conducting and insulating domains at the submicrometer scale. These domains then undergo a p…
Using the quantum Monte Carlo method, we investigate the spin dynamics of itinerant electrons in the one-dimensional Hubbard system. Based on the model calculation, we have studied the spin-fluctuations in the quarter-filled metallic Hubbard ring, which is aimed at the vanadium ring or chain defined along corner-shari…
A sensitive polarization modulation technique uses photoelastic modulation and hetrodyne detection to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples. The frequencies measured are in the mid-infrared and correspond to the spectral lines of…
We propose a density functional for anisotropic fluids of hard body particles. It interpolates between the well established geometrically based Rosenfeld functional for hard spheres and the Onsager functional for elongated rods. We test the new approach by calculating the location of the nematic–isotropic transition i…