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Ensayos acelerados de resistencia del hormigón
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Aplicaciones prácticas de la espectroscopía de absorción infrarroja en el estudio de los crudos, del clínker y del cemento portland anhidro
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Influencia de la temperatura del clínker sobre su molturabilidad
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The Effects of Crystal Field and Temperature on the Photoluminescence Excitation Efficiency of Ce3+ in YAG
Absorption and luminescence spectra of YAG:Ce 3+ crystals have been measured at various temperatures between 4.2° and 300°K. The high resolution, low temperature spectra show resolved fine structure. Zero‐phonon transitions have been assigned and the phonon replicas correlated with lattice phonon energies. The charact…
Zinc and Copper Solubility as a Function of pH in an Acid Soil
Abstract Studies of the effect of pH and competing cations on Zn 2+ and Cu 2+ solubility in an acid mineral soil indicate the probable involvement of hydrous oxides of iron, aluminum, or manganese in the adsorption process. Adsorption on permanent charge sites of clays, or complexation with organic matter could not ac…
Phase Relations and Reaction Sintering of Transparent Cubic Aluminum Oxynitride Spinel (ALON)
A new isobaric, condensed phase diagram in the region of stability of cubic aluminum oxynitride spinel (ALON) along the pseudobinary AI 2 O 3 ‐AIN composition join is presented, deduced primarily from various analytical measurements and microstructural observations. It is shown that cubic aluminum oxynitride spinel me…
Image Contrast And Localized Signal Selection Techniques
SUMMARY A survey is made of a number of the localized signal selection methods and related techniques which may be used to improve the electron microscope image contrast from small regions of material and thereby bring the specimen resolution actually achieved somewhat closer to the electron‐optical resolution of pres…
Liquid-Crystal Lens-Cells with Variable Focal Length
Liquid-crystal cells shaped like a plano-convex lens or a plano-concave lens are prepared. The focal length can be varied from the value f e for an extraordinary ray, where the liquid-crystal cell takes a homogeneous alignment, to f o for an ordinary ray, where it takes a homeo-tropic alignment, by applying an electri…
Effective-medium theory of conductivity and Hall effect in two dimensions
Symmetrical effective-medium theory is used to find the conductivity and Hall effect of a two-dimensional binary mixture. Results are given in detail in the limit of low applied magnetic field, when the expressions for the Hall coefficients simplify to linear combinations of the corresponding quantities for the compon…
Structure of the Smectic-BPhase and the Nature of the Smectic-Bto -HTransition in the N-(4-n-Alkoxybenzylidene)-4′-Alkylanilines
The phase behavior and structures of several liquid crystals of the $n\mathrm{O}.m$ (${\mathrm{C}}_{n}{\mathrm{H}}_{2n+1}\ensuremath{-}\mathrm{OPhCHNPh}{\mathrm{C}}_{m}{\mathrm{H}}_{2m+1}$) series of compounds have been established by a variety of experiments. The hexagonal close-packed layers of the ${S}_{B}$ phases…
Study of transition metal oxides by photoelectron spectroscopy
Abstract Systematics in the X-ray photoelectron spectra (X. p. e. s.) of Ti, V, Cr, Mn and Nb oxides with the metal ion in different oxidation states as well as of related series of mono-, sesqui- and di-oxides of the first row transition metals have been investigated in detail. Core level binding energies, spin-orbi…
Bulk and Grain Boundary Ionic Conductivity in Polycrystalline β″- Alumina
Measurements of conductance and capacitance are made on polycrystalline β″-alumina over a range of frequencies from 10 to 107 Hz and temperatures from −130 to 400 °C. The results are analyzed using complex impedance plots which exhibited a bulk and grain boundary component. Above 220 °C the resistance of the grains ex…
Dynamic mechanical properties of poly(p-phenyleneterephthalamide) fiber
The dynamic mechanical properties of poly(p-phenyleneterephthalamide) fiber were investigated. Measurements of the dynamic mechanical properties were carried out on samples of low crystallinity and low orientation over a temperature range from −100 to +500°C at a frequency of 110 Hz, at a heating rate of 5°C/min. Five…
Dynamics and ensemble averages for the polarization models of molecular interactions
A family of ’’polarization models’’ has been generated for description of polarizable and deformable molecules in condensed phases. Within these models the intermolecular forces are not pairwise additive, but have a many-body component that generalizes the polarization interactions present in conventional electrostati…
Further developments and applications of the Green’s function method of sensitivity analysis in chemical kinetics
A numerical procedure is presented for implementing the Green’s function method of sensitivity analysis in chemical kinetics. The procedure is applied to three sets of chemical reactions: the Chapman mechanism for ozone kinetics, a mechanism for methane combustion and a model for formaldehyde oxidation in the presence…
Elliptic phase boundaries between smectic and nematic phases
Smectic–nematic phase boundaries that resemble arcs of ellipses can be analyzed by a quadratic expansion in temperature and pressure of the change ΔG of Gibbs function. If the change of entropy or volume is known, ΔG and its first two derivatives can be determined. Data on 8OCB and mixtures of 8OCB and 6OCB and of CB9…
Kinetics of radiative recombination in magnesium oxide
We report time-resolved studies of luminescence excited in nominally pure single-crystal MgO by short pulses of 500-keV electrons at sample temperatures from 10 to 500 K. The principal luminescence bands have peaks at approximately 4.9, 3.3, and 1.7 eV. The decay kinetics and spectral shift of the 4.9-eV luminescence…
Energy position of4flevels in rare-earth metals
The energy position of the occupied and unoccupied $4f$ levels relative to the Fermi energy is studied for the rare-earth metals. This is done by treating the excited state as an impurity in an otherwise perfect crystal. This picture is first considered in the complete screening approximation. In this approximation th…
Effect of pressure on bonding in black phosphorus
The bond lengths and bond angles of orthorhombic black phosphorus have been determined as a function of hydrostatic pressures to 26.6(5) kbar using time-of-flight neutron powder diffraction. We show that the markedly anisotropic compression reported previously results from a large pressure-induced shortening of the va…