835 research outputs found
Approximate solutions for the skyrmion
We reconsider the Euler-Lagrange equation for the Skyrme model in the
hedgehog ansatz and study the analytical properties of the solitonic solution.
In view of the lack of a closed form solution to the problem, we work on
approximate analytical solutions. We show that Pade approximants are well
suited to continue analytically the asymptotic representation obtained in terms
of a power series expansion near the origin, obtaining explicit approximate
solutions for the Skyrme equations. We improve the approximations by applying
the 2-point Pade approximant procedure whereby the exact behaviour at spatial
infinity is incorporated. An even better convergence to the exact solution is
obtained by introducing a modified form for the approximants. The new
representations share the same analytical properties with the exact solution at
both small and large values of the radial variable r.Comment: 15 pages, 5 figures. 1 Reference adde
Venus Atmosphere Profile from a Maximum Entropy Principle
The variational method with constraints recently developed by Verkley and
Gerkema to describe maximum-entropy atmospheric profiles is generalized to
ideal gases but with temperature-dependent specific heats. In so doing, an
extended and non standard potential temperature is introduced that is well
suited for tackling the problem under consideration. This new formalism is
successfully applied to the atmosphere of Venus. Three well defined regions
emerge in this atmosphere up to a height of from the surface: the
lowest one up to about is adiabatic, a transition layer located at the
height of the cloud deck and finally a third region which is practically
isothermal.Comment: 6 pages, 3 figure
Strategies to enhance the 3T1D-DRAM cell variability robustness beyond 22 nm
3T1D cell has been stated as a valid alternative to be implemented on L1 memory cache to substitute 6T, highly affected by device variability as technology dimensions are reduced. In this work, we have shown that 22 nm 3T1D memory cells present significant tolerance to high levels of device parameter fluctuation. Moreover, we have observed that when variability is considered the write access transistor becomes a significant detrimental element on the 3T1D cell performance. Furthermore, resizing and temperature control have been presented as some valid strategies in order to mitigate the 3T1D cell variability.Peer ReviewedPostprint (author's final draft
Core compressor exit stage study, 2
A total of two three-stage compressors were designed and tested to determine the effects of aspect ratio on compressor performance. The first compressor was designed with an aspect ratio of 0.81; the other, with an aspect ratio of 1.22. Both compressors had a hub-tip ratio of 0.915, representative of the rear stages of a core compressor, and both were designed to achieve a 15.0% surge margin at design pressure ratios of 1.357 and 1.324, respectively, at a mean wheel speed of 167 m/sec. At design speed the 0.81 aspect ratio compressor achieved a pressure ratio of 1.346 at a corrected flow of 4.28 kg/sec and an adiabatic efficiency of 86.1%. The 1.22 aspect ratio design achieved a pressure ratio of 1.314 at 4.35 kg/sec flow and 87.0% adiabatic efficiency. Surge margin to peak efficiency was 24.0% with the lower aspect ratio blading, compared with 12.4% with the higher aspect ratio blading
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