Challenges of user-driven R&D: BARC model

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A second ceramic age - a new materials frontier

A second ceramic age started in the mid-twentieth century as a new, exciting materials frontier. Electroceramics with phenomenally wide range of electrical resistivity (spread over 30 orders of magnitude) span insulators, semiconductors, metal-like conductors, ionic conductors, and, recently, superconductors. They also include ferroelectrics, piezoelectrics, pyroelectrics and electro-optics beside ferrites. Advances in electroceramics have been fascinating and rapid, leading to unprecedented rates of industrial growth. Age-old limitations of poor mechanical strength and brittleness of ceramics are being overcome by outstanding toughness and strength achieved in zirconia-based ceramics exploiting the martensitic transformation at the tetragonal-monoclinic phase change. The dimensional changes at this transition which prevented the use of zirconia earlier has now been turned into a mechanism for toughening ceramics to significant levels. Ceramics with near-zero overall thermal expansion coefficient offer new opportunities to science and industry

Cation composition effects on oxide conductivity in the Zr_2Y_2O_7-Y_3NbO_7 system

Realistic, first-principles-based interatomic potentials have been used in molecular dynamics simulations to study the effect of cation composition on the ionic conductivity in the Zr2Y2O7-Y3NbO7 system and to link the dynamical properties to the degree of lattice disorder. Across the composition range, this system retains a disordered fluorite crystal structure and the vacancy concentration is constant. The observed trends of decreasing conductivity and increasing disorder with increasing Nb5+ content were reproduced in simulations with the cations randomly assigned to positions on the cation sublattice. The trends were traced to the influences of the cation charges and relative sizes and their effect on vacancy ordering by carrying out additional calculations in which, for example, the charges of the cations were equalised. The simulations did not, however, reproduce all the observed properties, particularly for Y3NbO7. Its conductivity was significantly overestimated and prominent diffuse scattering features observed in small area electron diffraction studies were not always reproduced. Consideration of these deficiencies led to a preliminary attempt to characterise the consequence of partially ordering the cations on their lattice, which significantly affects the propensity for vacancy ordering. The extent and consequences of cation ordering seem to be much less pronounced on the Zr2Y2O7 side of the composition range.Comment: 22 pages, 8 figures, submitted to Journal of Physics: Condensed Matte

АСР процесса горения твердого композиционного топлива при безмазутной растопке парового котла

ВКР предполагает разработку комплекта проектной и конструкторской документации для создания АСР процесса горения твердого композиционного топлива при безмазутной растопке парового котла.The WRC involves the development of a set of design and construction documentation for the creation of an ACR for the combustion of solid composite fuel with oil-free kindling of a steam boiler

The Near-Infrared Number Counts and Luminosity Functions of Local Galaxies

This study presents a wide-field near-infrared (K-band) survey in two fields; SA 68 and Lynx 2. The survey covers an area of 0.6 deg.$^2$, complete to K=16.5. A total of 867 galaxies are detected in this survey of which 175 have available redshifts. The near-infrared number counts to K=16.5 mag. are estimated from the complete photometric survey and are found to be in close agreement with other available studies. The sample is corrected for incompleteness in redshift space, using selection function in the form of a Fermi-Dirac distribution. This is then used to estimate the local near-infrared luminosity function of galaxies. A Schechter fit to the infrared data gives: M$^\ast_K = -25.1 \pm 0.3$, $\alpha = -1.3\pm 0.2$ and $\phi^\ast =(1.5\pm 0.5)\times 10^{-3}$ Mpc$^{-3}$ (for H$_0=50$ Km/sec/Mpc and q$_0=0.5$). When reduced to $\alpha=-1$, this agrees with other available estimates of the local IRLF. We find a steeper slope for the faint-end of the infrared luminosity function when compared to previous studies. This is interpreted as due to the presence of a population of faint but evolved (metal rich) galaxies in the local Universe. However, it is not from the same population as the faint blue galaxies found in the optical surveys. The characteristic magnitude ($M^\ast_K$) of the local IRLF indicates that the bright red galaxies ($M_K\sim -27$ mag.) have a space density of $\le 5\times 10^{-5}$ Mpc$^{-3}$ and hence, are not likely to be local objects.Comment: 24 pages, 8 figures, AASTEX 4.0, published in ApJ 492, 45

Additional Ultracool White Dwarfs Found in the Sloan Digital Sky Survey

We identify seven new ultracool white dwarfs discovered in the Sloan Digital Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are presented, and additional BVRI data are given for these and other previously discovered ultracool white dwarfs. The observed colors span a remarkably wide range, qualitatively similar to colors predicted by models for very cool white dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced absorption (CIA) in its spectra, while the spectra and colors of the other six are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A) is part of a binary system -- its companion is also a cool white dwarf, and other data indicate that the companion exhibits an infrared flux deficiency, making this the first binary system composed of two CIA white dwarfs. A third discovery (SDSS J0310-00) has weak Balmer emission lines. The proper motions of all seven stars are consistent with membership in the disk or thick disk.Comment: Accepted for Astrophysical Journal. 16 pages (includes 3 figures

Electronic Structure and Valence Band Spectra of Bi4Ti3O12

The x-ray photoelectron valence band spectrum and x-ray emission valence-band spectra (Ti K _beta_5, Ti L_alpha, O K_alpha) of Bi4Ti3O12 are presented (analyzed in the common energy scale) and interpreted on the basis of a band-structure calculation for an idealized I4/mmm structure of this material.Comment: 6 pages + 7 PostScript figures, RevTex3.0, to be published in Phys.Rev.B52 (Oct.95). Figures also available via anonymous ftp at ftp://ftp.physik.uni-osnabrueck.de/pub/apostnik/BiTiO

Kinetics of electrophoretic deposition of β-alumina

The equations describing electrophoretic deposition, proposed by Hamakar Avgustinik and coworkers, have been verified in the case of β-alumina suspended in isoamyl alcohol. The variation of electrophoretic yield with (i) concentration of suspension, (ii) extent of grinding the suspension, (iii) temperature of the suspension, and (iv) electrode separation was studied. The effect of addition of glycol monethyl ether was also investigated. The effect of various parameters on the electrical conductivity of the suspension, which in turn influences the yield, was noted

Side-by-Side Thermal Tests of Modular Offices: A Validation Study of the STEM Method

Two modular office units were tested at the National Renewable Energy Laboratory (NREL) to establish each unit's thermal performance. The two units were nearly identical in appearance, but one was built with structural insulating panels (SIP), and the other was built using standard frame construction. The primary objective of these tests was to compare the thermal performance of buildings using SIP and standard frame construction. Both units were tested under carefully controlled steady-state conditions in the NREL large-scale environmental enclosure. They were then moved outdoors where Short-Term Energy Monitoring (STEM) tests were performed, and long-term heating and cooling energy use was measured. A secondary objective was to evaluate the accuracy of the NREL STEM method by comparing the results of outdoor STEM tests to steady-state indoor test results. STEM is a method developed by NREL to determine key thermal parameters of a building in-situ, based on a 3-day test sequence. The indoor test facility also provided the opportunity to investigate the phenomenon of infiltration heat recovery in a real building, under carefully controlled conditions, to evaluate the stability of the concentration decay method of tracer gas-based infiltration monitoring, and to compare the blower-door method with the tracer-gas technique in determining infiltration.This project was a cooperative effort with the Structural Insulated Panel Association, the Modular Building Institute, All-American Modular (AAM, the manufacturer of the units), and GE Capitol (the owner of the units). Richard Harmon, the president of AAM, requested NREL's assistance in exploring the feasibility of converting his manufacturing process to SIP construction. His engineering staff needed to assess which comfort and energy benefits might be associated with this new technology. AAM manufactured the two units, and NREL tested the modules for 8 months