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Shake table testing of a tuned mass damper inerter (Tmdi)-equipped structure and nonlinear dynamic modeling under harmonic excitations
This paper presents preliminary experimental results from a novel shaking table testing campaign investigating the dynamic response of a two-degree-of-freedom (2DOF) physical specimen with a grounded inerter under harmonic base excitation and contributes a nonlinear dynamic model capturing the behavior of the test specimen. The latter consists of a primary mass connected to the ground through a high damping rubber isolator (HDRI) and a secondary mass connected to the primary mass through a second HDRI. Further, a flywheel-based rack-and-pinion inerter prototype device is used to connect the secondary mass to the ground. The resulting specimen resembles the tuned mass damper inerter (TMDI) configuration with grounded inerter analytically defined and numerically assessed by the authors in a number of previous publications. Physical specimens with three different inerter coefficients are tested on the shake table under sine-sweep excitation with three different amplitudes. Experimental frequency response functions (FRFs) are derived manifesting a softening nonlinear behavior of the specimens and enhanced vibration suppression with increased inerter coefficient. Further, a 2DOF parametric nonlinear model of the specimen is established accounting for non-ideal inerter device behavior and its potential to characterize experimental response time-histories, FRFs, and force-displacement relationships of the HDRIs and of the inerter is verified
A large sample study of spin relaxation and magnetometric sensitivity of paraffin-coated Cs vapor cells
We have manufactured more than 250 nominally identical paraffin-coated Cs
vapor cells (30 mm diameter bulbs) for multi-channel atomic magnetometer
applications. We describe our dedicated cell characterization apparatus. For
each cell we have determined the intrinsic longitudinal, \sGamma{01}, and
transverse, \sGamma{02}, relaxation rates. Our best cell shows
\sGamma{01}/2\pi\approx 0.5 Hz, and \sGamma{02}/2\pi\approx 2 Hz. We find a
strong correlation of both relaxation rates which we explain in terms of
reservoir and spin exchange relaxation. For each cell we have determined the
optimal combination of rf and laser powers which yield the highest sensitivity
to magnetic field changes. Out of all produced cells, 90% are found to have
magnetometric sensitivities in the range of 9 to 30 fTHz. Noise analysis shows
that the magnetometers operated with such cells have a sensitivity close to the
fundamental photon shot noise limit
Consistency of Semiclassical Gravity
We discuss some subtleties which arise in the semiclassical approximation to
quantum gravity. We show that integrability conditions prevent the existence of
Tomonaga-Schwinger time functions on the space of three-metrics but admit them
on superspace. The concept of semiclassical time is carefully examined. We
point out that central charges in the matter sector spoil the consistency of
the semiclassical approximation unless the full quantum theory of gravity and
matter is anomaly-free. We finally discuss consequences of these considerations
for quantum field theory in flat spacetime, but with arbitrary foliations.Comment: 12 pages, LATEX, Report Freiburg THEP-94/2
Three-dimensional black holes from deformed anti-de Sitter
We present new exact three-dimensional black-string backgrounds, which
contain both NS--NS and electromagnetic fields, and generalize the BTZ black
holes and the black string studied by Horne and Horowitz. They are obtained as
deformations of the Sl(2,R) WZW model. Black holes resulting from purely
continuous deformations possess true curvature singularities. When discrete
identifications are introduced, extra chronological singularities appear, which
under certain circumstances turn out to be naked. The backgrounds at hand
appear in the moduli space of the Sl(2,R) WZW model. Hence, they provide exact
string backgrounds and allow for a more algebraical CFT description. This makes
possible the determination of the spectrum of primaries.Comment: JHEP style, 33 pages, 1 figur
Strengthening of steel-reinforced concrete structural elements by externally bonded FRP sheets and evaluation of their load carrying capacity to face changed load service conditions
The paper has proposed a limit analysis procedure for a preliminary
design of RC elements strengthened by externally
bonded FRP sheets.
The procedure, based on a multi-yield-criteria limit analysis
approach, has led to a reliable prediction of peak loads and failure
modes of the analyzed elements (slabs) by simultaneously
considering the limit state of the constituent materials, so
resulting very useful in many applications of engineering
interest.
The attention has been focused on hospital applications in
which increment of service loads or realization of openings
can weaken some structural elements that have been strengthened
by FRP sheets
A General Framework for Recursive Decompositions of Unitary Quantum Evolutions
Decompositions of the unitary group U(n) are useful tools in quantum
information theory as they allow one to decompose unitary evolutions into local
evolutions and evolutions causing entanglement. Several recursive
decompositions have been proposed in the literature to express unitary
operators as products of simple operators with properties relevant in
entanglement dynamics. In this paper, using the concept of grading of a Lie
algebra, we cast these decompositions in a unifying scheme and show how new
recursive decompositions can be obtained. In particular, we propose a new
recursive decomposition of the unitary operator on qubits, and we give a
numerical example.Comment: 17 pages. To appear in J. Phys. A: Math. Theor. This article replaces
our earlier preprint "A Recursive Decomposition of Unitary Operators on N
Qubits." The current version provides a general method to generate recursive
decompositions of unitary evolutions. Several decompositions obtained before
are shown to be as a special case of this general procedur
Kaon physics with the KLOE detector
In this paper we discuss the recent finalized analyses by the KLOE experiment
at DANE: the CPT and Lorentz invariance test with entangled pairs, and the precision measurement of the branching fraction of
the decay . We also present the
status of an ongoing analysis aiming to precisely measure the mass
Limits on isotropic Lorentz violation in QED from collider physics
We consider the possibility that Lorentz violation can generate differences
between the limiting velocities of light and charged matter. Such effects would
lead to efficient vacuum Cherenkov radiation or rapid photon decay. The absence
of such effects for 104.5 GeV electrons at the Large Electron Positron collider
and for 300 GeV photons at the Tevatron therefore constrains this type of
Lorentz breakdown. Within the context of the standard-model extension, these
ideas imply an experimental bound at the level of -5.8 x 10^{-12} <=
\tilde{\kappa}_{tr}-(4/3)c_e^{00} <= 1.2 x 10^{-11} tightening existing
laboratory measurements by 3-4 orders of magnitude. Prospects for further
improvements with terrestrial and astrophysical methods are discussed.Comment: Replaced with final version published in PR
Twisted Masses and Enhanced Symmetries: the A&D Series
We study new symmetries between A and D type quiver gauge theories with
different numbers of colors. We realize these gauge theories with twisted
masses via a brane construction that reproduces all the parameters of the
Gauge/Bethe correspondence.Comment: 14 pages, 5 figure
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