1,782,528 research outputs found
Frequency shifts in natural vibrations in pantographic metamaterials under biaxial tests
In this paper a 2D continuum model, thought as the homogenized limit of a microstructured pantographic sheet, is studied. The microstructure is characterized by two families of parallel fibers, whose deformation measures account for bending, elongation and relative rotation of the fibers. The deformation energy density of the homogenized model depends on both first and second gradients of the displacement. Modal analysis is performed in order to assess the peculiarities of the dynamic behavior of higher gradient models, and in particular the difference, with respect to classical laminae, in the dependence of the eigenfrequencies on the stiffness
Cancellation of nonlinear Zeeman shifts with light shifts
Nonlinear Zeeman (NLZ) shifts arising from magnetic-field mixing of the two
hyperfine ground-states in alkali atoms lead to splitting of magnetic-resonance
lines. This is a major source of sensitivity degradation and the so-called
"heading errors" of alkali-vapor atomic magnetometers operating in the
geophysical field range (B approx. 0.2-0.7 G). Here, it is shown theoretically
and experimentally that NLZ shifts can be effectively canceled by light shifts
caused by a laser field of appropriate intensity, polarization and frequency, a
technique that can be readily applied in practical situations.Comment: 5 pages, 5 figures, to be published in PR
Sofic-Dyck shifts
We define the class of sofic-Dyck shifts which extends the class of
Markov-Dyck shifts introduced by Inoue, Krieger and Matsumoto. Sofic-Dyck
shifts are shifts of sequences whose finite factors form unambiguous
context-free languages. We show that they correspond exactly to the class of
shifts of sequences whose sets of factors are visibly pushdown languages. We
give an expression of the zeta function of a sofic-Dyck shift
Homogeneous -shifts
The classification of homogeneous scalar weighted shifts is known. Recently,
Kor\'{a}nyi obtained a large class of inequivalent irreducible homogeneous
bi-lateral -by- block shifts. In this paper, we construct two distinct
classes of examples not in the list of Kor\'{a}nyi. It is then shown that these
new examples of irreducible homogeneous bi-lateral -by- block shifts,
together with the ones found earlier by Kor\'{a}nyi, account for every
unitarily inequivalent irreducible homogeneous bi-lateral -by- block
shift.Comment: 26 page
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