4,040 research outputs found
Small gaps between products of two primes
Let denote the number that is a product of exactly two
distinct primes. We prove that
This sharpens an earlier result of the authors (arXivMath NT/0506067), which
had 26 in place of 6. More generally, we prove that if is any positive
integer, then
We also prove several other results on the representation of numbers with
exactly two prime factors by linear forms.Comment: 11N25 (primary) 11N36 (secondary
Tunable adsorption on carbon nanotubes
We investigated the adsorption of a single atom, hydrogen and aluminum, on
single wall carbon nanotubes from first-principles. The adsorption is
exothermic, and the associated binding energy varies inversely as the radius of
the zigzag tube. We found that the adsorption of a single atom and related
properties can be modified continuously and reversibly by the external radial
deformation. The binding energy on the high curvature site of the deformed tube
increases with increasing radial deformation. The effects of curvature and
radial deformation depend on the chirality of the tube.Comment: To be appear in Physical Review Letter
Misalignment factors to affect the fatigue of welded load-carrying joints
To assess the effects of misalignment on the weld fatigue, we present experimental fatigue test results of load- carrying cruciform joints which are subjected to axial variable amplitude loading. The welds were produced from steel AH36 grade and fatigue strength improved by high-frequently mechanical impact treatment. We identify several misalignment factors affecting the fatigue by considering the real and reference welded joint geometries. Our methodology includes proposals for the empirical calibration functions and local stress analyses by using the Structural Hot Spot Stress, Effective Notch Stress and Peak Stress Method. Additionally, we apply our methodology to other sixteen data sets which are extracted from the literature for load-carrying cruciform and butt welded joints subjected to constant amplitude loading. Finally, we present the resultant calibration functions with respect to corresponding fatigue test data
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