The specific heat capacities of V2O5/P2O5-based glasses

The specific heat capacities of a series of V₂O₅/P₂O₅-based glasses have been measured in the approximate temperature range 3–300 K. The proportions of the host constituents were varied and the effects produced by adding oxides of copper, titanium and sodium were examined. The measurements were extended to investigate the influence of fast neutron irradiation upon the specific heat capacity of pure, initially crystalline V₂O₅.The observations are consistent with a spectrum of background vibrations, the form of which is temperature dependent. At intermediate temperatures the vibrations were consistent with the glasses displaying predominantly chain-like characteristics. With reduction to lower temperatures the vibrational behaviour increasingly resembled that of solids displaying three-dimensional characteristics. The temperature dependence of the specific heat capacity at the lowest temperatures was consistent with the presence of a narrow band of low-frequency modes centred upon 1.67 × 10¹¹ s^?1, the density of which increased with phosphorus content. From observations of the density of these modes in the doped specimens, it was concluded that the role of copper wass largely that of a network former, whereas titanium and sodium were essentially network modifiers.     

Control of holding currents in amorphous threshold switches

It is usually assumed that the holding current of an amorphous semiconductor threshold switch is not strongly dependent on the circuit surrounding the switch. This paper shows that the holding current is in fact controlled by both the series resistance and the parallel capacitance, according to two simple inequalities. In order to obtain low holding currents a large series resistor and minimum parallel capacitance are required, and in this way a holding current of 10 μA has been observed. Data are also presented on the effects of device dimensions and temperature on the on-state I-V curves and holding current.     

Low-cycle fatigue in small turbines

Over the years, great quantities of fatigue data have been accumulated with the major emphasis placed on establishing either a finite endurance limit or fatigue strength within the range of 10,000 to 500,000,000 cycles. In recent years, particularly in areas of engineering where hot, high-speed rotating machines have been developed, the importance of defining fatigue strength from 1/4 to 10,000 cycles has been realized. Low-cycle fatigue, often ignored in the original design concept and frequently appearing in the later phases of product development, is discussed and is the basis for explaining a compressor-rotor failure which occurred during the development of a turbojet engine. The number of centrifugal stress cycles accumulated due to routine starting and stopping of the engine during its normal life was sufficient to cause a failure of the low-cycle fatigue type. The steps taken to investigate and eventually solve this particular problem are included. Based on the above, a correlation between stress history and residual strength of the part is postulated.Paper was presented at 1960 SESA Spring Meeting held in Indianapolis, Ind., on May 18–20.     

Fehlerabschätzungen aus den Defekten bei Randwertaufgaben gewöhnlicher und partieller Differentialgleichungen 2. Ordnung

Ohne Zusammenfassung Vorgelegt von L. Collatz     

Die Anwendung des Quantimet zur Ätzgrubendichtebestimmung an Silizium-Einkristallen

A quantitative estimation of the structure of etched silicon crystals is possible with the microscope Quantimet by a fast counting the number of particles, i.e. etch pits on {111}-planes. Boundary conditions of the measuring technique are the requisite size of the etch pits of from > 3 … 5 μm, a plane specimen surface, the correct optical magnification, threshold and acceptance width. Sources of errors due to the structure result from the overlap of etch pits at dislocation densities > 10⁴ cm⁻² which leads to an underestimation of the number of etch pits because of the reduced signal output. An overestimation is most caused by an unwished contrast in the surface which yields additional signal outputs. The errors will be eliminated by using a calibration curved. Due to the short time which is necessary for counting, the Quantimet is well suitable for routine testings and for quantitative evaluation of the structure defects (etch pit density) in silicon, including consideration of possible errors.