420 research outputs found
Phase Controlled All-Optical Switching In Rocking Filter Fibers
We demonstrate experimentally that all-optical switching of a strong beam can be controlled by the phase of a weak beam in a rocking rotator fiber
A Rapid Approach to Modeling Species-Habitat Relationships
A growing number of species require conservation or management efforts. Success of these activities requires knowledge of the species' occurrence pattern. Species-habitat models developed from GIS data sources are commonly used to predict species occurrence but commonly used data sources are often developed for purposes other than predicting species occurrence and are of inappropriate scale and the techniques used to extract predictor variables are often time consuming and cannot be repeated easily and thus cannot efficiently reflect changing conditions. We used digital orthophotographs and a grid cell classification scheme to develop an efficient technique to extract predictor variables. We combined our classification scheme with a priori hypothesis development using expert knowledge and a previously published habitat suitability index and used an objective model selection procedure to choose candidate models. We were able to classify a large area (57,000 ha) in a fraction of the time that would be required to map vegetation and were able to test models at varying scales using a windowing process. Interpretation of the selected models confirmed existing knowledge of factors important to Florida scrub-jay habitat occupancy. The potential uses and advantages of using a grid cell classification scheme in conjunction with expert knowledge or an habitat suitability index (HSI) and an objective model selection procedure are discussed
Coupled Nonlinear Schr\"{o}dinger equation and Toda equation (the Root of Integrability)
We consider the relation between the discrete coupled nonlinear
Schr\"{o}dinger equation and Toda equation. Introducing complex times we can
show the intergability of the discrete coupled nonlinear Schr\"{o}dinger
equation. In the same way we can show the integrability in coupled case of dark
and bright equations. Using this method we obtain several integrable equations.Comment: 11 pages, LateX, to apper in J. Phys. Soc. Jpn. Vol. 66, No
Scalar and vector modulation instabilities induced by vacuum fluctuations in fibers: numerical study
We study scalar and vector modulation instabilities induced by the vacuum
fluctuations in birefringent optical fibers. To this end, stochastic coupled
nonlinear Schrodinger equations are derived. The stochastic model is equivalent
to the quantum field operators equations and allow for dispersion,
nonlinearity, and arbitrary level of birefringence. Numerical integration of
the stochastic equations is compared to analytical formulas in the case of
scalar modulation instability and non depleted pump approximation. The effect
of classical noise and its competition with vacuum fluctuations for inducing
modulation instability is also addressed.Comment: 33 pages, 5 figure
Control of the Onset of Filamentation in Condensed Media
Propagation of intense, ultrashort laser pulses through condensed media like
crystals of BaF and sapphire results in the formation of filaments. We
demonstrate that the onset of filamentation may be controlled by rotating the
plane of polarization of incident light. We directly visualize filamentation in
BaF_2 via six-photon absorption-induced fluorescence and, concomitantly, by
probing the spectral and spatial properties of white light that is generated.Comment: To appear in Phys. Rev.
Many-body quantum dynamics of polarisation squeezing in optical fibre
We report new experiments that test quantum dynamical predictions of
polarization squeezing for ultrashort photonic pulses in a birefringent fibre,
including all relevant dissipative effects. This exponentially complex
many-body problem is solved by means of a stochastic phase-space method. The
squeezing is calculated and compared to experimental data, resulting in
excellent quantitative agreement. From the simulations, we identify the
physical limits to quantum noise reduction in optical fibres. The research
represents a significant experimental test of first-principles time-domain
quantum dynamics in a one-dimensional interacting Bose gas coupled to
dissipative reservoirs.Comment: 4 pages, 4 figure
Reproductive Ecology Of The Florida Scrub-Jay (Aphelocoma Coerulescens) On John F. Kennedy Space Center/Merritt Island National Wildlife Refuge: A Long-Term Study
From 1988 to 2002 we studied the breeding ecology of Florida Scrub-Jays (Aphelocoma coerulescens) on John F. Kennedy Space Center/Merritt Island National Wildlife Refuge. We examined phenology, clutch size, hatching failure rates, fledgling production, nest success, predation rates, sources egg and nestling mortality, and the effects of helpers on these measures. Nesting phenology was similar among sites. Mean clutch size at Titan was significantly larger than at HC or T4. Pairs with helpers did not produce larger clutches than pairs without helpers. Fledgling production at T4 was significantly greater than at HC and similar to Titan. Pairs with helpers at HC produced significantly more fledglings than pairs without helpers; helpers did not influence fledgling production at the other sites. Nest success at HC and Titan was low, 19% and 32% respectively. Nest success at T4 was 48% and was significantly greater than at HC. Average predation rates at all sites increased with season progression. Predation rates at all sight rose sharply by early June. The main cause of nest failure at all sites was predation, 93%
Quantum many-body simulations using Gaussian phase-space representations
Phase-space representations are of increasing importance as a viable and
successful means to study exponentially complex quantum many-body systems from
first principles. This review traces the background of these methods, starting
from the early work of Wigner, Glauber and Sudarshan. We focus on modern
phase-space approaches using non-classical phase-space representations. These
lead to the Gaussian representation, which unifies bosonic and fermionic
phase-space. Examples treated include quantum solitons in optical fibers,
colliding Bose-Einstein condensates, and strongly correlated fermions on
lattices.Comment: Short Review (10 pages); Corrected typo in eq (14); Added a few more
reference
Suppression and Enhancement of Soliton Switching During Interaction in Periodically Twisted Birefringent Fiber
Soliton interaction in periodically twisted birefringent optical fibers has
been analysed analytically with refernce to soliton switching. For this purpose
we construct the exact general two-soliton solution of the associated coupled
system and investigate its asymptotic behaviour. Using the results of our
analytical approach we point out that the interaction can be used as a switch
to suppress or to enhance soliton switching dynamics, if one injects
multi-soliton as an input pulse in the periodically twisted birefringent fiber.Comment: 10 pages, 4 figures, Latex, submitted to Phys. Rev.
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