20,613 research outputs found
Інтерактивний контроль при формоутворенні багатогабаритних деталей
Physical phenomenon of warping (springing) can be observed as a technological heritage after large-dimensional articles forming or curing and consequent cooling of composite articles. This phenomenon can be seen as gaps between ready article contour and forming jig contour. Deviation degree of ready article surface from theoretical contour and article dimensions has to be controlled during manufacturing. Application of auxiliary controlling jig leads to expenses and labor-manufacturability increasing. Possibility of application forming jig with inserted jet gages is considered for articles shape controlling. Such gages and realization of acoustic methods allow to control not only final article shape but also geometry on intermediate stages of manufacturing.Після формоутворення багатогабаритних листових деталей з листових механічних заготовок або полімеризації і охолодження деталей з композитних матеріалів проявляється технологічна спадковість у вигляді викривлення (пружнення). Це спостерігається у вигляді неприлягання готової деталі до формозадаючої поверхні технологічного оснащення. При контролі якості формозміни необхідно вимірювати
ступінь порушення форми і розмірів. Застосування контрольної оснастки дорого і складно. Розглянуто можливість використання для контролю формозадаючої оснастки з встановленими в ній повітряними струминними датчиками. Такі датчики і застосування акустичних методів дозволяють контролювати не тільки кінцеву форму заготовки, а й форму заготовки на попередваріантних етапах формозміни
Phonon-dressed Mollow triplet in the regime of cavity-QED
We study the resonance fluorescence spectra of a driven quantum dot placed
inside a high semiconductor cavity and interacting with an acoustic phonon
bath. The dynamics is calculated using a time-convolutionless master equation
obtained in the polaron frame. We demonstrate pronounced spectral broadening of
the Mollow sidebands through cavity-emission which, for small cavity-coupling
rates, increases quadratically with the Rabi frequency. However, for larger
cavity coupling rates, this broadening dependence is found to be more complex.
This field-dependent Mollow triplet broadening is primarily a consequence of
the triplet peaks sampling different parts of the asymmetric phonon bath, and
agrees directly with recent experiments with semiconductor micropillars. The
influence from the detuned cavity photon bath and multi-photon effects is shown
to play a qualitatively important role on the fluorescence spectra.Comment: 4 pages, 4 figure
The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa
The UV spectra of nova-like variables are dominated by emission from the
accretion disk, modified by scattering in a wind emanating from the disk. Here
we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-likes
which have been observed with the Hubble Space Telescope in the
far-ultraviolet, in an attempt to constrain the geometry and the ionization
structure of their winds. Using our Monte Carlo radiative transfer code we
computed spectra for simply-parameterized axisymmetric biconical outflow models
and were able to find plausible models for both systems. These reproduce the
primary UV resonance lines - N V, Si IV, and C IV - in the observed spectra in
and out of eclipse. The distribution of these ions in the wind models is
similar in both cases as is the extent of the primary scattering regions in
which these lines are formed. The inferred mass loss rates are 6% to 8% of the
mass accretion rates for the systems. We discuss the implication of our point
models for our understanding of accretion disk winds in cataclysmic variables.Comment: 13 pages, 15 figures and 4 tables. Published in Ap
Dephasing of Mollow Triplet Sideband Emission of a Resonantly Driven Quantum Dot in a Microcavity
Detailed properties of resonance fluorescence from a single quantum dot in a
micropillar cavity are investigated, with particular focus on emission
coherence in dependence on optical driving field power and detuning.
Power-dependent series over a wide range could trace characteristic Mollow
triplet spectra with large Rabi splittings of GHz. In
particular, the effect of dephasing in terms of systematic spectral broadening
of the Mollow sidebands is observed as a strong fingerprint
of excitation-induced dephasing. Our results are in excellent agreement with
predictions of a recently presented model on phonon-dressed QD Mollow triplet
emission in the cavity-QED regime
Phonon-Assisted Incoherent Excitation of a Quantum Dot and its Emission Properties
We present a detailed study of a phonon-assisted incoherent excitation
mechanism of single quantum dots. A spectrally-detuned laser couples to a
quantum dot transition by mediation of acoustic phonons, whereby excitation
efficiencies up to 20 % with respect to strictly resonant excitation can be
achieved at T = 9 K. Laser frequency-dependent analysis of the quantum dot
intensity distinctly maps the underlying acoustic phonon bath and shows good
agreement with our polaron master equation theory. An analytical solution for
the photoluminescence is introduced which predicts a broadband incoherent
coupling process when electron-phonon scattering is in the strong phonon
coupling (polaronic) regime. Additionally, we investigate the coherence
properties of the emitted light and study the impact of the relevant pump and
phonon bath parameters
Brane Universes and the Cosmological Constant
The cosmological constant problem and brane universes are reviewed briefly.
We discuss how the cosmological constant problem manifests itself in various
scenarios for brane universes. We review attempts - and their difficulties -
that aim at a solution of the cosmological constant problem.Comment: corrected typos, added references, 13 pages, accepted by MPLA as
brief revie
Indistinguishable photons from the resonance fluorescence of a single quantum dot in a microcavity
We demonstrate purely resonant continuous-wave optical laser excitation to
coherently prepare an excitonic state of a single semiconductor quantum dot
(QDs) inside a high quality pillar microcavity. As a direct proof of QD
resonance fluorescence, the evolution from a single emission line to the
characteristic Mollow triplet10 is observed under increasing pump power. By
controlled utilization of weak coupling between the emitter and the fundamental
cavity mode through Purcell-enhancement of the radiative decay, a strong
suppression of pure dephasing is achieved, which reflects in close to Fourier
transform-limited and highly indistinguishable photons with a visibility
contrast of 90%. Our experiments reveal the model-like character of the coupled
QD-microcavity system as a promising source for the generation of ideal photons
at the quantum limit. From a technological perspective, the vertical cavity
symmetry -- with optional dynamic tunability -- provides strongly directed
light emission which appears very desirable for future integrated emitter
devices.Comment: 24 pages, 6 figure
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