Materials Literature
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MNDO and extended Hückel calculations on the electronic structure of BC3 based on structure (1) and the alternatives (2) and (3) suggest that (1) would be an insulator rather than show metallic conductivity but that structures (2) and (3) could explain its high conductivity.
Moxa was soaked in a mixed solvent of chloroform, methanol and water (5:5:1) at room temperature for 7 days, and the supernatant solution was separated into two layers by the addition of water. Heptatriacontane (C37H76), confirmed by measurements of 1H and 13C-NMR spectra and melting point, was obtained from the chlor…
A treatment which significantly increases the pulsed surface flashover potential of some insulator materials in vacuum is described. The flashover potential is measured by placing a short cylindrical sample between brass electrodes in a vacuum chamber at a pressure of 10/sup -4/ Pa and applying a high-voltage (HV) dou…
Space power requirements for future NASA and other United States missions will range from a few kilowatts to megawatts of electricity. Maximum efficiency is a key goal of any power system in order to minimize weight and size so that the space shuttle may be used a minimum number of times to put the power supply into o…
The various attributes of copper alloys and stainless steels for use in sea water handling systems have been compared. As an outcome of this, a 4-year test program was undertaken to establish the corrosion characteristics of various stainless steel alloys in their cast and wrought forms. To facilitate this work, a ful…
In the anhydrous crystal the discoid amphiphile TP6E02M (1) packs in tilted columns whereas in the more hydrated liquid crystal phases these columns are vertical.
The interface of a nematic 7CB - solid substrate has been studied by optical ellipsometry. The phase difference between 0 and E rays, Δ = δ p - δs, and the angle ψ = tan-1 | r p/rs | are measured as a function of incidence angle and temperature. To fit the experimental data, an exponential interfacial region having a…
After suitable thermomechanical treatment a series of Cu-based and Ni-Ti-alloys can show a reversible shape change during heating and/or cooling over a temperature region of about 40 degrees. Two important conditions for this effect are that a thermoelastic martensitic transformation occurs in this temperature range a…
Résumé.- Le formalisme de la mécanique des milieux continus est discuté pour l’analyse des insta-bilités par striction et par bandes. L’apparition de l’instabilité que l’on prédit dépend forte-ment des caractéristiques des matériaux, pas seulement à travers les propriétés comme le durcisse-ment par écrouissage ou la s…
The passivity of metals is reviewed from the perspective of materials science rather than with the usual electrochemical emphasis. Iron and ferrous alloys are used to illustrate the essentials of the phenomenon of passivity. A discussion of the general and engineering aspects is first given followed by a detailed desc…
Three new pyridoxine-glycosides were isolated from rice bran (10 kg) as colorless powder by various chromatographic techniques: compound A, 53 mg; compound B, 7.8 mg; compound C, 5.8 mg. Compound A was shown to consist of pyridoxine and glucose in a 1:2 molar ratio by beta-glucosidase hydrolysis, and by 1H-NMR and sec…
Combined tension/torsion and compression/torsion tests for sintered silicon nitride specimens were carried out at room temperature to investigate the fracture behavior of ceramics under multiaxial stress states. Tension, torsion and 4-point bending tests have been also carried out in order to estimate Weibull's two pa…
Eight bisdesmosidic pregnane glycosides were isolated from Trachelospermum asiaticum NAKAI (Apocynaceae). The glycosides have a common structure of 3-O-β-D-digitalosyl-3β, 17α, 20α-trihydroxy-5α-pregn-6-ene, and three sugars at most are linked to the 20-hydroxyl group.
A simple emprical expression for temperature dependence of liquid viscosity, which carries two adjustable parameters and includes a glass transition temperature, Tg, and the liquid viscosity ηg at Tg, has been proposed in the form :log(η/ηg)=A[exp{B(Tg-T)/T}-1]This expression has been applied to 14 liquids including p…
A method of calculating the temperature rise in the core, conductors, insulation, and cooling air of the stator and rotor of a salient pole alternator is described, with emphasis on the development of a finite-difference model of sufficiently reduced complexity to allow reasonably economic computation. The electrical…
The limitations of the Jernkontoret (JK) method of assessing inclusions as described in ASTM E 45 are pointed out and two alternative quantitative methods of inclusion assessment presented in detail. Close relationships are demonstrated between the rolling contact fatigue life and the quantitative inclusion assessment…
The principal characteristics of gyromagnetic materials that are useful for microwave applications are reviewed, and both the large-signal and small-signal models that govern wave propagation at microwave frequencies are given. Uniform and nonuniform plane waves in an unbounded ferrite medium are considered from the c…
Abstract Durch Austauschreaktion (Na 2 O mit Li 8 TbO 6 ; Na : Tb = 2,1 : 1; Au‐Rohr; 750°C, 30 d) gelang erstmals die Darstellung von Na 2 TbO 3 in Form gelborangefarbener Einkristalle. Na 2 TbO 3 kristallisiert monoklin in C2/c (Z = 8; a = 576,92(6), b = 1001,27(9), c = 1117,91(14) pm, β = 99,98(1)°). Es liegt der L…
Spalling phenomena of the backup rolls used for hot strip mills and their prevention are discussed. The spalling on the surfaces of backup rolls is classified into two categories: excess rolling contact fatigue resulting from the local wear in roll barrel and propagation of the surface cracks generated by thermal shoc…
Analytical chemistry is one of the chemical areas where ultrasonic radiation has been only infrequently used (namely in sample pretreatment, separations, automatic analytical systems and clinical analysis). This auxiliary technique would constitute a powerful aid in the automation of several steps in analytical proces…