Materials Literature
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In the case of a periodic object, the wave amplitude in every point of a Fresnel diffraction pattern may be obtained from the values of the wave amplitude at a finite number of points in the object plane. This results is applied to the case of pure phase objects. A simple condition on the object structure is derived,…
A new method is presented of solving Laplace's equation for equidiameter coaxial cylinders separated by a finite distance. The results are used to obtain the focal lengths, focal points and spherical aberration coefficients of double cylinder electrostatic lenses over a large range of voltage ratios and cylinder separ…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelective catalytic reaction of hydrogen with nitric oxide in the presence of oxygenMordecai Shelef, James H. Jones, Joseph T. Kummer, Klaus Otto, and E. Eugene WeaverCite this: Environ. Sci. Technol. 1971, 5, 9, 790–798Publication Date (Print):September 1, 1971Publication H…
Thirty‐four scleractinian coral samples, including both hermatypic and ahermatypic varieties, have been analyzed for trace elements. Acid leaching has been used to infer the distribution of elements between the coral skeleton (acid‐soluble fraction) and detrital phases (acid‐insoluble). Sr, U, Ba, Cu, B, Li, and Zn ar…
A general technique for the measurement of the solid-liquid interfacial free energy, γSL is proposed, based on a theoretical analysis of the equilibrium shape of a grain boundary groove in an applied temperature gradient. The analysis extends the work of Bolling and Tiller to account for unequal thermal conductivities…
Coastal surface seawater off southern California was enriched with phosphate, silicate, vitamins B 12 , B 1 , and biotin, a chelated trace metal mixture, and with nitrogen as nitrate, ammonium, or urea, and the cultures were incubated on deck in daylight. Natural phytoplankton present in the seawater served as inoculu…
Sintering of Sm-Co magnets was first reported on in 1969. Because of success in sintering, Sm-Co magnets are now enjoying added importance. Many processing parameters are critical in the preparation of high quality permanent magnets of Sm-Co. One of these is the sintering temperature. Varying the sintering temperature…
A mechanism for the 'charging' artifacts which obscure detail on SEM images of high resistivity specimens is described. An interaction equation, relating the properties of specimen and environment, predicts negative charge build-up and large potential fields. Charging effects are traced to the specular deflection of b…
Technical Briefs Fire-Fighting Benefits of Polymeric Friction Reduction Andrew G. Fabula Andrew G. Fabula Fluid Mechanics Branch, Naval Undersea Research and Development Center, Pasadena Laboratory, Pasadena, Calif. Search for other works by this author on: This Site PubMed Google Scholar Author and Article Informatio…
The dislocation aspects of the earlier model of Bishop and Chalmers for the structure of high angle symmetric tilt boundaries in metals is extended to twist and more general boundaries having both tilt and twist components. The expected strain contrast in high angle grain boundaries is discussed. It is concluded that…
The magnetic transitions of the Cr-Te system has not been explained by a suitable model. Therefore, the magnetic properties of the single crystals of Cr 2-δ Te 3 , prepared by the chemical transport method, were investigated. From the measurement of the magnetic susceptibility above room temperature S =3.0 8 /2 per Cr…
Optical absorption and emission spectra of vanadium impurities in Y3Al5O12 crystals are reported. Crystals doped with vanadium only and with vanadium counterdoped with charge-compensating calcium and silicon ions were studied. Possible valence states for vanadium include V2+, V3+, V4+; possible substitutional sites in…
Effects of grain size and grain growth in Nb‐doped BaTiO 3 on temperature and frequency dependencies of the dielectric constant were investigated. When 0.65 μm powder is sintered to an average grain size of 1 μm, two dielectric constant peaks indicate the presence of Nb‐free BaTiO 3 and of Nb‐containing material. Sing…
The extended Poole-Frenkel model presented here includes the variation of the barrier height with electric field in directions both opposite and forward to the electric force on an electron. The equation for the voltage-current characteristics based on this model gives not only the usual Poole-Frenkel equation at extr…
Electrical conduction is studied in polyethylene terephthalate and to a limited extent in polyethylene over a range of fields up to 1·2 × 10 6 V cm −1 . In common with previous investigations, it is found that the current decays with time according to an inverse power law, but this can be obviated by a conditioning pr…
Abstract The dynamic mechanical properties of polyester and polyether urethane block polymers have been investigated at four frequencies (3.5, 11, 35 and 110 Hz) in the temperature range of — 150 to 200°C. The existence of a two phase structure was demonstrated in these systems by the observation of two major transiti…
Electrostatic properties of the point-plane electrode configuration are reviewed in the hyperbolic approximation. Simple expressions for the field in the neighbourhood of the tip are derived under the assumption that space-charge distortion is absent. Current induced by a charge carrier moving along a field line is in…
This paper describes a procedure which optimizes the fitting of a `model' of a protein to an electron density map. The technique seeks to minimize ∫ (Qo−Qm)2dv where Qo is the observed electron density and Qm is a density associated with a model in terms of which the observed densities are interpreted. Qm consists of…
A review of molecular-beam epitaxy of GaAs and the observation of surface structures with high-energy electron diffraction in an ultrahigh-vacuum system is described. The utilization of these surface structures as growth conditions to produce n- and p-type layers when doped with Sn, Ge, and Mg, and the electrical and…
The physical properties of many of the rare-earth intermetallic compounds have been collected together. They are discussed in terms of the role that the magnetic exchange and crystal field interactions play in determining these properties. It is pointed out that in this vast number of materials there is an ideal chanc…