362,471 research outputs found
Remarks on strong stabilization and stable H∞ controller design
Cataloged from PDF version of article.A state space based design method is given to find strongly stabilizing controllers for multi-input-multi-output plants (MIMO). A sufficient condition is derived for the existence of suboptimal stable H∞ controller in terms of linear matrix inequalities (LMI) and the controller order is twice that of the plant A new parameterization of strongly stabilizing controllers is determined using linear fractional transformations (LFT)
Hydrogen and vacancy clustering in zirconium
The effect of solute hydrogen on the stability of vacancy clusters in
hexagonal closed packed zirconium is investigated with an ab initio approach,
including contributions of H vibrations. Atomistic simulations within the
density functional theory evidence a strong binding of H to small vacancy
clusters. The hydrogen effect on large vacancy loops is modeled through its
interaction with the stacking faults. A thermodynamic modeling of H segregation
on the various faults, relying on ab initio binding energies, shows that these
faults are enriched in H, leading to a decrease of the stacking fault energies.
This is consistent with the trapping of H by vacancy loops observed
experimentally. The stronger trapping, and thus the stronger stabilization, is
obtained for vacancy loops lying in the basal planes, i.e. the loops
responsible for the breakaway growth observed under high irradiation dose.Comment: submitte
Two-color interference stabilization of atoms
The effect of interference stabilization is shown to exist in a system of two
atomic levels coupled by a strong two-color laser field, the two frequencies of
which are close to a two-photon Raman-type resonance between the chosen levels,
with open channels of one-photon ionization from both of them. We suggest an
experiment, in which a rather significant (up to 90%) suppression of ionization
can take place and which demonstrates explicitly the interference origin of
stabilization. Specific calculations are made for H and He atoms and optimal
parameters of a two-color field are found. The physics of the effect and its
relation with such well-known phenomena as LICS and population trapping in a
three-level system are discussed.Comment: the paper includes 1 TeX file and 16 picture
2-(2-HydroxyÂethyl)-3-[(2-hydroxyÂethyl)imino]isoindolin-1-one
In the crystal structure of the title compound, C12H14N2O3, molÂecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O—H⋯N hydrogen bonds with an R
2
2(10) motif, while strong O—H⋯O hydrogen bonds forming C(10) chains connect molÂecules into a two-dimensional network. Additional stabilization is supplied by weak C—H⋯O hydrogen bonds and weak π–π stacking interÂactions with centroid–centroid distances in the range 3.4220 (7)–3.9616 (7) Å
Active laser frequency stabilization using neutral praseodymium (Pr)
We present a new possibility for the active frequency stabilization of a
laser using transitions in neutral praseodymium. Because of its five outer
electrons, this element shows a high density of energy levels leading to an
extremely line-rich excitation spectrum with more than 25000 known spectral
lines ranging from the UV to the infrared. We demonstrate the active frequency
stabilization of a diode laser on several praseodymium lines between 1105 and
1123 nm. The excitation signals were recorded in a hollow cathode lamp and
observed via laser-induced fluorescence. These signals are strong enough to
lock the diode laser onto most of the lines by using standard laser locking
techniques. In this way, the frequency drifts of the unlocked laser of more
than 30 MHz/h were eliminated and the laser frequency stabilized to within
1.4(1) MHz for averaging times >0.2 s. Frequency quadrupling the stabilized
diode laser can produce frequency-stable UV-light in the range from 276 to 281
nm. In particular, using a strong hyperfine component of the praseodymium
excitation line E = 16 502.616_7/2 cm^-1 -> E' = 25 442.742_9/2 cm^-1 at lambda
= 1118.5397(4) nm makes it possible - after frequency quadruplication - to
produce laser radiation at lambda/4 = 279.6349(1) nm, which can be used to
excite the D2 line in Mg^+.Comment: 10 pages, 14 figure
Amplitude death phenomena in delay--coupled Hamiltonian systems
Hamiltonian systems, when coupled {\it via} time--delayed interactions, do
not remain conservative. In the uncoupled system, the motion can typically be
periodic, quasiperiodic or chaotic. This changes drastically when delay
coupling is introduced since now attractors can be created in the phase space.
In particular for sufficiently strong coupling there can be amplitude death
(AD), namely the stabilization of point attractors and the cessation of
oscillatory motion. The approach to the state of AD or oscillation death is
also accompanied by a phase--flip in the transient dynamics. A discussion and
analysis of the phenomenology is made through an application to the specific
cases of harmonic as well as anharmoniccoupled oscillators, in particular the
H\'enon-Heiles system.Comment: To be appeared in Phys. Rev. E (2013
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