6,008 research outputs found
Taming the higher power corrections in semileptonic B decays
We study the effect of dimension 7 and 8 operators on inclusive semileptonic
B decays and the extraction of |Vcb|. Using moments of semileptonic B decay
spectra and information based on the Lowest-Lying State saturation
Approximation (LLSA) we perform a global fit of the nonperturbative parameters
of the heavy quark expansion including for the first time the O(1/mb^{4,5})
contributions. Higher power corrections appear to have a very small effect on
the extraction of |Vcb|, independently of the weight we attribute to the LLSA.Comment: 6 pages, 3 figures, small changes to match accepted publication in
PL
TDAS: The Thermal Expert System (TEXSYS) data acquisition system
As part of the NASA Systems Autonomy Demonstration Project, a thermal expert system (TEXSYS) is being developed. TEXSYS combines a fast real time control system, a sophisticated human interface for the user and several distinct artificial intelligence techniques in one system. TEXSYS is to provide real time control, operations advice and fault detection, isolation and recovery capabilities for the space station Thermal Test Bed (TTB). TEXSYS will be integrated with the TTB and act as an intelligent assistant to thermal engineers conducting TTB tests and experiments. The results are presented from connecting the real time controller to the knowledge based system thereby creating an integrated system. Special attention will be paid to the problem of filtering and interpreting the raw, real time data and placing the important values into the knowledge base of the expert system
The Mullins effect in the wrinkling behavior of highly stretched thin films
Recent work demonstrates that finite-deformation nonlinear elasticity is
essential in the accurate modeling of wrinkling in highly stretched thin films.
Geometrically exact models predict an isola-center bifurcation, indicating that
for a bounded interval of aspect ratios only, stable wrinkles appear and then
disappear as the macroscopic strain is increased. This phenomenon has been
verified in experiments. In addition, recent experiments revealed the following
striking phenomenon: For certain aspect ratios for which no wrinkling occurred
upon the first loading, wrinkles appeared during the first unloading and again
during all subsequent cyclic loading. Our goal here is to present a simple
pseudo-elastic model, capturing the stress softening and residual strain
observed in the experiments, that accurately predicts wrinkling behavior on the
first loading that differs from that under subsequent cyclic loading. In
particular for specific aspect ratios, the model correctly predicts the
scenario of no wrinkling during first loading with wrinkling occurring during
unloading and for all subsequent cyclic loading.Comment: 15 pages, 9 figure
Analytical Redundancy and Fuzzy Inference in AUV Fault Detection and Compensation
Proceedings Oceanology 1998, Brighton, March 11-14, 1998 pp.45-5
An Existence Theorem for a Class of Wrinkling Models for Highly Stretched Elastic Sheets
We consider a class of models motivated by previous numerical studies of
wrinkling in highly stretched, thin rectangular elastomer sheets. The model
used is characterized by a finite-strain hyperelastic membrane energy perturbed
by small bending energy. Without bending energy, the stored-energy density is
not rank-one convex for general spatial deformations but reduces to a
polyconvex function when restricted to the plane, i.e., two-dimensional
hyperelasticity. In addition, it grows unbounded as the local area ratio
approaches zero. The small-bending component of the model is the same as that
in the classical von K\'arm\'an model. Here we prove the existence of energy
minima for a general class of such models
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