30,193 research outputs found
Method for the production of strongly adhesive films on titanium and titanium alloys with a metallization process
A process for the spray-application of a strongly adhesive, thick antifriction layer on titanium and titanium alloys is proposed. The titanium/titanium alloy component to be coated is first subjected to cleaning in a pickling bath with reducing additives and sand-blasting, then coated with an intermediate layer of nickel, after which the final layer is applied. The formation of TiNi at the interface ensures strong bonding of the antifriction layer
Mix-and-match compatibility in asymmetric system markets
This paper shows that the private incentive for mix-and-match compatibility in system markets diverges from the social planner's incentive if competing suppliers are asymmetric in production cost or product quality. There can be too much or too little compatibility when the market is served by fully integrated system suppliers. Also, the market outcome involves socially too much incompatibility in the form of exclusive technological alliances when the market is composed of independent component suppliers. These results contrast with the standard one obtained in the symmetric setup and shed new light on public policy towards compatibility, technological alliances, and bundling practices in system markets
Compression failure mechanisms in unidirectional composites
Compression failure mechanisms in unidirectional composites were examined. Possible failure modes of constituent materials are summarized and analytical models for fiber microbuckling are reviewed from a unified viewpoint. Due to deficiencies in available models, a failure model based on nonlinear properties and initial fiber curvature is proposed. The effect of constituent properties on composite compression behavior was experimentally investigated using two different graphite fibers and four different epoxy resins. The predominant microscopic scale failure mode was found to be shear crippling. In a soft resin, shear crippling was in the form of buckling of fibers on a microscopic scale. However, stiff resins failure was characterized by the formation of a kink band. For unidirectional laminates, compressive strength, and compressive modulus to a less extent, were found to increase with increasing magnitude of resin modulus. The change in compressive strength with resin modulus was predicted using the proposed nonlinear model
Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System
Using the Moon to occult the Sun, the Clementine spacecraft used its
navigation cameras to map the inner zodiacal light at optical wavelengths over
elongations of 3-30 degrees from the Sun. This surface brightness map is then
used to infer the spatial distribution of interplanetary dust over heliocentric
distances of about 10 solar radii to the orbit of Venus. We also apply a simple
model that attributes the zodiacal light as being due to three dust populations
having distinct inclination distributions, namely, dust from asteroids and
Jupiter-family comets (JFCs), dust from Halley-type comets, and an isotropic
cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that
asteroids + JFCs are the source of about 45% of the optical dust cross-section
seen in the ecliptic at 1 AU, but that at least 89% of the dust cross-section
enclosed by a 1 AU radius sphere is of a cometary origin. When these results
are extrapolated out to the asteroid belt, we find an upper limit on the mass
of the light-reflecting asteroidal dust that is equivalent to a 12 km asteroid,
and a similar extrapolation of the isotropic dust cloud out to Oort Cloud
distances yields a mass equivalent to a 30 km comet, although the latter mass
is uncertain by orders of magnitude.Comment: To be published in Icaru
The effect of resin toughness and modulus on compressive failure modes of quasi-isotropic graphite/epoxy laminates
Compressive failure mechanisms in quasi-isotropic graphite/epoxy laminates were characterized for both unnotched and notched specimens and also following damage by impact. Two types of fibers (Thornel 300 and 700) and four resin systems (Narmco 5208, American Cyanamid BP907, and Union Carbide 4901/MDA and 4901/mPDA) were studied. For all material combinations, failure of unnotched specimens was initiated by kinking of fibers in the 0-degree plies. A major difference was observed, however, in the mode of failure propagation after the 0-degree ply failure. The strength of quasi-isotropic laminates in general increased with increasing resin tensile modulus. The laminates made with Thornel 700 fibers exhibited slightly lower compressive strengths than did the laminates made with Thornel 300 fibers. The notch sensitivity as measured by the hole strength was lowest for the BP907 resin and highest for the 5208 resin. For the materials studied, however, the type of fiber had no effect on the notch sensitivity
Determination of Strong-Interaction Widths and Shifts of Pionic X-Rays with a Crystal Spectrometer
Pionic 3d-2p atomic transitions in F, Na, and Mg have been studied using a bent crystal spectrometer. The pionic atoms were formed in the production target placed in the external proton beam of the Space Radiation Effects Laboratory synchrocyclotron. The observed energies and widths of the transitions are E=41679(3) eV and Γ=21(8) eV, E=62434(18) eV and Γ=22(80) eV, E=74389(9) eV and Γ=67(35) eV, in F, Na, and Mg, respectively. The results are compared with calculations based on a pion-nucleus optical potential
Permeability measurements of two low-density phenolic-nylon chars Final report
Permeability measurements of low-density phenolic-nylon chars in gaseous nitrogen and heliu
Full O(alpha) corrections to e+e- -> sf_i sf_j
We present a complete precision analysis of the sfermion pair production
process e+e- -> sf_i sf_j (f = t, b, tau, nu_tau) in the Minimal Supersymmetric
Standard Model. Our results extend the previously calculated weak corrections
by including all one-loop corrections together with higher order QED
corrections. We present the details of the analytical calculation and discuss
the renormalization scheme. The numerical analysis shows the results for total
cross-sections, forward-backward and left-right asymmetries. It is based on the
SPS1a' point from the SPA project. The complete corrections are about 10% and
have to be taken into account in a high precision analysis.Comment: 32 pages, 24 figures, RevTeX
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