11,495 research outputs found
On the Rational Real Jacobian Conjecture
Jacobian conjectures (that nonsingular implies a global inverse) for rational
everywhere defined maps of real n-space to itself are considered, with no
requirement for a constant Jacobian determinant or a rational inverse. The
birational case is proved and the Galois case clarified. Two known special
cases of the Strong Real Jacobian Conjecture (SRJC) are generalized to the
rational map context. For an invertible map, the associated extension of
rational function fields must be of odd degree and must have no nontrivial
automorphisms. That disqualifies the Pinchuk counter examples to the SRJC as
candidates for invertibility.Comment: 7 pages. arXiv admin note: substantial text overlap with
arXiv:1202.294
Mobile impurities in integrable models
We use a mobile impurity or depleton model to study elementary excitations in
one-dimensional integrable systems. For Lieb-Liniger and bosonic Yang-Gaudin
models we express two phenomenological parameters characterising renormalised
inter- actions of mobile impurities with superfluid background: the number of
depleted particles, and the superfluid phase drop in terms of the
corresponding Bethe Ansatz solution and demonstrate, in the leading order, the
absence of two-phonon scattering resulting in vanishing rates of inelastic
processes such as viscosity experienced by the mobile impuritiesComment: 25 pages, minor corrections made to the manuscrip
Evaluation of gas metal arc welding with alterating shielding gases for use on AA6082T6
Studies have been carried out to determine the effects of implementing alternating shielding gases for 6082T6 aluminium alloy welding. Alternating shielding gases is a newly developed method of supplying shielding gases to the weld area to enhance the efficiency of the standard Gas Metal Arc Welding (GMAW) process. This method involves discretely supplying two different shielding gases to the weld zone at a pre-determined frequency which creates a dynamic action in the weld pool. Several benefits have been identified in relation to supplying shielding gases in this manner including increased travel speed, reduced distortion, reduced porosity and, in the case of specific alternating frequencies, marginal improvements in mechanical properties. All in all, this method of shielding gas delivery presents attractive benefits to the manufacturing community, namely the increased productivity and quality in addition to a reduction in the amount of post-weld straightening required. However, the literature available on this advanced joining process is very scant, especially so for aluminium alloys. For this reason, an evaluation has been carried out on the application of alternating shielding gases for the GMAW process on 6082T6 aluminium alloys
Designing Wind Turbine Condition Monitoring Systems Suitable for Harsh Environments
Research into wind turbine condition monitoring is continually receiving greater attention due to the potential benefits from condition monitoring systems (CMS). These benefits can only be realised with high reliability of the condition monitoring system itself. This paper discusses how CMS reliability can be increased, by introducing four types of robustness and how to design the CMS to meet these requirements. The paper uses a case study CMS installation to illustrate the design requirements, and lessons learned from the installation process
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