816 research outputs found
Phase-locking in Multi-Frequency Brillouin Oscillator via Four Wave Mixing
Stimulated Brillouin scattering (SBS) and Kerr-nonlinear four wave-mixing
(FWM) are among the most important and widely studied nonlinear effects in
optical fibres. At high powers SBS can be cascaded producing multiple Stokes
waves spaced by the Brillouin frequency shift. Here, we investigate the complex
nonlinear interaction of the cascade of Stokes waves, generated in a
Fabry-Perot chalcogenide fibre resonator through the combined action of SBS and
FWM. We demonstrate the existence of parameter regimes, in which pump and
Stokes waves attain a phase-locked steady state. Real-time measurements of 40ps
pulses with 8GHz repetition rate are presented, confirming short-and long-term
stability. Numerical simulations qualitatively agree with experiments and show
the significance of FWM in phase-locking of pump and Stokes waves. Our findings
can be applied for the design of novel picosecond pulse sources with GHz
repetition rate for optical communication systems
A novel sampling theorem on the rotation group
We develop a novel sampling theorem for functions defined on the
three-dimensional rotation group SO(3) by connecting the rotation group to the
three-torus through a periodic extension. Our sampling theorem requires
samples to capture all of the information content of a signal band-limited at
, reducing the number of required samples by a factor of two compared to
other equiangular sampling theorems. We present fast algorithms to compute the
associated Fourier transform on the rotation group, the so-called Wigner
transform, which scale as , compared to the naive scaling of .
For the common case of a low directional band-limit , complexity is reduced
to . Our fast algorithms will be of direct use in speeding up the
computation of directional wavelet transforms on the sphere. We make our SO3
code implementing these algorithms publicly available.Comment: 5 pages, 2 figures, minor changes to match version accepted for
publication. Code available at http://www.sothree.or
Progress in Developing Hybrid RPCs: GEM-like Detectors with Resistive Electrodes
We have recently developed an innovative detector of photons and charged
particles: a GEM-like gaseous amplification structure with resistive electrodes
instead of commonly used metallic ones. This novel detector combines the best
property of GEMs- the capability to operate in a cascaded mode and in poorly
quenched gases - and of RPC: the protection against sparks. In this paper will
shortly review our latest achievements in this direction, however the main
focus will be given on a new advanced design that allows to build large area
detectors manufactured by a screen printing technology. The proposed detector,
depending on the applications, can operate either in a GEM mode (electron
multiplications through holes only) or as a hybrid RPC with simultaneous
amplifications in the drift region and in the holes. The possible applications
of this new detector will be discussed
Stable Magnetostatic Solitons in Yttrium Iron Garnet Film Waveguides for Tilted in-Plane Magnetic Fields
The possibility of nonlinear pulses generation in Yttrium Iron Garnet thin
films for arbitrary direction between waveguide and applied static in-plane
magnetic field is considered. Up to now only the cases of in-plane magnetic
fields either perpendicular or parallel to waveguide direction have been
studied both experimentally and theoretically. In the present paper it is shown
that also for other angles (besides 0 or 90 degrees) between a waveguide and
static in-plane magnetic field the stable bright or dark (depending on
magnitude of magnetic field) solitons could be created.Comment: Phys. Rev. B (accepted, April 1, 2002
Entwicklung von Populationen bei Mais (Zea mays L.) Selektionseffizienz und Leistungsfähigkeit
Maize is one of the most important crops around the world. Global players in seed production offer more than hundreds of different varieties. All of them are hybrids whereas open pollinated varieties (OPVs) are rare or extinct. In Germany (and many other European countries) no new OPVs are registered; efforts to do so failed in the past. The main advantage of OPVs is their phenotypic and genetic heterogeneity and thus their ability to adapt to different environmental conditions. This could be of utmost
interest facing the complex challenge of climate change. Populations based on new breeding material were developed and tested in comparison to actual hybrids and
landraces. While the new populations achieved about 80 % of the hybrid yield, landraces failed with only 65 %. The efficiency of selection methods needs to be improved
Indulge or Reduce? A cross-country investigation of consumption patterns following pandemic lockdowns
Pandemic lockdowns in early 2020 disrupted daily lifestyles worldwide and opened a window of opportunity for self-reflection and consumption paradigm shifts. However, consumption patterns might take different directions and opposing views exist about whether consumers (1) prolong consumption-oriented lifestyles post-lockdown, or (2) compensate for lockdown consumption restrictions through self-indulgence. Drawing from self-determination theory and individual-cultural values frameworks, this paper develops a conceptual model of post-lockdown consumption patterns related to three factors: consumers’ fulfilment of basic psychological needs during lockdowns, individual consumer values, and country-level cultural orientations. Consumer surveys conducted after the first lockdowns in three culturally different European countries (UK, Germany, Romania) show that both satisfaction and dissatisfaction of psychological needs during lockdown impact consumption patterns, at least at a short-term level. The direction of consumption patterns is driven by hedonism and universalism values at an individual level and differences in post-materialism and indulgence at a country-level. The results provide implications for international marketers and policymakers in post-pandemic marketplaces
Phase diagram of the -spin-interacting spin glass with ferromagnetic bias and a transverse field in the infinite- limit
The phase diagram of the -spin-interacting spin glass model in a
transverse field is investigated in the limit under the presence
of ferromagnetic bias. Using the replica method and the static approximation,
we show that the phase diagram consists of four phases: Quantum paramagnetic,
classical paramagnetic, ferromagnetic, and spin-glass phases. We also show that
the static approximation is valid in the ferromagnetic phase in the limit by using the large- expansion. Since the same approximation is
already known to be valid in other phases, we conclude that the obtained phase
diagram is exact.Comment: 16 pages, 4 figures. another additional author, some amendment
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