Fundamentals of the oxidation protection of columbium and tantalum Semiannual report, Apr. 1 - Oct. 1, 1967

Oxidation protection of niobium and tantalum by their silicide

Fundamentals of the oxidation protection of columbium and tantalum Semiannual report, 1 Apr. - 1 Oct. 1969

Oxidation protection by silicides of niobium and tantalum, and thermochemical dat

Fundamentals of the oxidation protection of tantalum Final report

Fundamentals of oxidation protection of tantalum by silicide

Estimating and forecasting production and orders in manufacturing industry from business survey data: Evidence from Switzerland 1990-2003

A fundamental issue for policy-oriented business cycle research is access to leading - or at least coincident - and reliable indicators of economic activity in manufacturing industry. Therefore, we analyse how the quickly disposable, qualitative information of the business tendency survey conducted by the Swiss Institute for Business Cycle Research (KOF) is related to the official production and order statistics of Switzerland. Pairs of high cross-correlations were selected for further analyses (Granger causality, pattern of turning points). In the next step, the remaining variables are used as predictors of the official statistics in a bivariate and multivariate approach. The results show a very high and stable relationship between the two data-sets particularly for nowcasts and - though to a somewhat lesser degree - for short term prognostics

MACHOs, White Dwarfs, and the Age of the Universe

(Abridged Abstract) A favored interpretation of recent microlensing measurements towards the Large Magellanic Cloud implies that a large fraction (i.e. 10--50%) of the mass of the galactic halo is composed of white dwarfs. We compare model white dwarf luminosity functions to the data from the observational surveys in order to determine a lower bound on the age of any substantial white dwarf halo population (and hence possibly on the age of the Universe). We compare various theoretical white dwarf luminosity functions, in which we vary hese three parameters, with the abovementioned survey results. From this comparison, we conclude that if white dwarfs do indeed constitute more than 10% of the local halo mass density, then the Universe must be at least 10 Gyr old for our most extreme allowed values of the parameters. When we use cooling curves that account for chemical fractionation and more likely values of the IMF and the bolometric correction, we find tighter limits: a white dwarf MACHO fraction of 10% (30%) requires a minimum age of 14 Gyr (15.5 Gyr). Our analysis also indicates that the halo white dwarfs almost certainly have helium-dominated atmospheres.Comment: Final version accepted for publication, straight TeX formate, 6 figs, 22 page

Power systems research at MSFC

Power systems research reviews at Marshall Space Flight Cente

Wannier-Stark ladders in one-dimensional elastic systems

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this paper we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let

Thermal noise of microcantilevers in viscous fluids

International audienceWe present a simple theoretical framework to describe the thermal noise of a microscopic mechanical beam in a viscous fluid: we use the Sader approach to describe the effect of the surrounding fluid (added mass and viscous drag), and the fluctuation dissipation theorem for each flexural modes of the system to derive a general expression for the power spectrum density of fluctuations. This prediction is compared with an experimental measurement on a commercial atomic force microscopy cantilever in a frequency range covering the two first resonances. A very good agreement is found on the whole spectrum, with no adjustable parameters but the thickness of the cantilever