6,341 research outputs found
Effects of high frequency current in welding aluminum alloy 6061
Uncontrolled high frequency current causes cracking in the heat-affected zone of aluminum alloy 6061 weldments during tungsten inert gas ac welding. Cracking developed when an improperly adjusted superimposed high frequency current was agitating the semimolten metal in the areas of grain boundary
Auditory display for the blind
A system for providing an auditory display of two-dimensional patterns as an aid to the blind is described. It includes a scanning device for producing first and second voltages respectively indicative of the vertical and horizontal positions of the scan and a further voltage indicative of the intensity at each point of the scan and hence of the presence or absence of the pattern at that point. The voltage related to scan intensity controls transmission of the sounds to the subject so that the subject knows that a portion of the pattern is being encountered by the scan when a tone is heard, the subject determining the position of this portion of the pattern in space by the frequency and interaural difference information contained in the tone
Environmental effects of strip mining
There are no author-identified significant results in this report
Fiber-modified polyurethane foam for ballistic protection
Closed-cell, semirigid, fiber-loaded, self-extinguishing polyurethane foam material fills voids around fuel cells in aircraft. Material prevents leakage of fuel and spreading of fire in case of ballistic incendiary impact. It also protects fuel cell in case of exterior fire
A small-scale test for fiber release from carbon composites
A test method was developed to determine relative fiber loss from pyrolyzed composites with different resins and fiber construction. Eleven composites consisting of woven and unwoven carbon fiber reinforcement and different resins were subjected to the burn and impact test device. The composites made with undirectional tape had higher fiber loss than those with woven fabric. Also, the fiber loss was inversely proportional to the char yield of the resin
Lithium abundances in nearby FGK dwarf and subgiant stars: internal destruction, Galactic chemical evolution, and exoplanets
We derive atmospheric parameters and lithium abundances for 671 stars and
include our measurements in a literature compilation of 1381 dwarf and subgiant
stars. First, a "lithium desert" in the effective temperature (Teff) versus
lithium abundance (A_Li) plane is observed such that no stars with Teff~6075 K
and A_Li~1.8 are found. We speculate that most of the stars on the low A_Li
side of the desert have experienced a short-lived period of severe surface
lithium destruction as main-sequence or subgiant stars. Next, we search for
differences in the lithium content of thin-disk and thick-disk stars, but we
find that internal processes have erased from the stellar photospheres their
possibly different histories of lithium enrichment. Nevertheless, we note that
the maximum lithium abundance of thick-disk stars is nearly constant from
[Fe/H]=-1.0 to -0.1, at a value that is similar to that measured in very
metal-poor halo stars (A_Li~2.2). Finally, differences in the lithium abundance
distribution of known planet-host stars relative to otherwise ordinary stars
appear when restricting the samples to narrow ranges of Teff or mass, but they
are fully explained by age and metallicity biases. We confirm the lack of a
connection between low lithium abundance and planets. However, we find that no
low A_Li planet-hosts are found in the desert Teff window. Provided that subtle
sample biases are not responsible for this observation, this suggests that the
presence of gas giant planets inhibit the mechanism responsible for the lithium
desert.Comment: ApJ, in press. Complete Tables 1 and 3 are available upon reques
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