2,062 research outputs found
Orthogonal chirp division multiplexing for coherent optical fiber communications
In this paper, we propose an orthogonal chirp division multiplexing (OCDM) technique for coherent optical communication. OCDM is the principle of orthogonally multiplexing a group of linear chirped waveforms for high-speed data communication, achieving the maximum spectral efficiency (SE) for chirp spread spectrum, in a similar way as the orthogonal frequency division multiplexing (OFDM) does for frequency division multiplexing. In the coherent optical (CO)-OCDM, Fresnel transform formulates the synthesis of the orthogonal chirps; discrete Fresnel transform (DFnT) realizes the CO-OCDM in the digital domain. As both the Fresnel and Fourier transforms are trigonometric transforms, the CO-OCDM can be easily integrated into the existing CO-OFDM systems. Analyses and numerical results are provided to investigate the transmission of CO-OCDM signals over optical fibers. Moreover, experiments of 36-Gbit/s CO-OCDM signal are carried out to validate the feasibility and confirm the analyses. It is shown that the CO-OCDM can effectively compensate the dispersion and is more resilient to fading and noise impairment than OFDM
The brief introduction of different laser diagnostics methods used in aeroengine combustion research
Combustion test diagnosis has always been one of the most important technologies for the development of aerospace engineering. The traditional methods of measurement have been unable to meet the requirements of accurate capture of the flow field in the development process of the aeroengine combustor. Therefore, the development of high-precision measurement and diagnostic techniques to meet the needs of the aeroengine combustor design is imperative. Laser diagnostics techniques developed quickly in the past several years. They are used to measure the parameters of the combustion flow field such as velocity, temperature, and
components concentration with high space and time resolution and brought no disturbance. Planar laser-induced fluorescence, coherent anti-Stokes Raman scattering, tunable diode laser absorption spectroscopy, and Raman scattering were introduced systemically in this paper. After analysis of their own advantages and disadvantages, the authors considered validated Raman scattering system and Tunable Diode Laser Absorption Tomography are more suitable for research activities on aeroengine combustion systems
The extended BLMSSM with a 125 GeV Higgs boson and dark matter
To extend the BLMSSM, we not only add exotic Higgs superfields
to make the exotic lepton heavy, but also introduce
the superfields(,) having couplings with lepton and exotic lepton
at tree level. The obtained model is called as EBLMSSM, which has difference
from BLMSSM especially for the exotic slepton(lepton) and exotic
sneutrino(neutrino). We deduce the mass matrices and the needed couplings in
this model. To confine the parameter space, the Higgs boson mass and
the processes , are
studied in the EBLMSSM. With the assumed parameter space, we obtain reasonable
numerical results according to data on Higgs from ATLAS and CMS. As a cold dark
mater candidate, the relic density for the lightest mass eigenstate of and
mixing is also studied
Spectroscopic localization of atomic sample plane for precise digital holography
In digital holography, the coherent scattered light fields can be
reconstructed volumetrically. By refocusing the fields to the sample planes,
absorption and phase-shift profiles of sparsely distributed samples can be
simultaneously inferred in 3D. This holographic advantage is highly useful for
spectroscopic imaging of cold atomic samples. However, unlike {\it e.g.}
biological samples or solid particles, the quasi-thermal atomic gases under
laser-cooling are typically featureless without sharp boundaries, invalidating
a class of standard numerical refocusing methods. Here, we extend the
refocusing protocol based on the Gouy phase anomaly for small phase objects to
free atomic samples. With a prior knowledge on a coherent spectral phase angle
relation for cold atoms that is robust against probe condition variations, an
``out-of-phase'' response of the atomic sample can be reliably identified,
which flips the sign during the numeric back-propagation across the sample
plane to serve as the refocus criterion. Experimentally, we determine the
sample plane of a laser-cooled K gas released from a microscopic dipole
trap, with a axial
resolution, with a NA=0.3 holographic microscope at nm probe
wavelength.Comment: 18 pages, 7 figures, substantial revision with a few mistakes fixe
Electron-Angular-Distribution Reshaping in Quantum Radiation-Dominated Regime
Dynamics of an electron beam head-on colliding with an ultraintense focused
ultrashort circularly-polarized laser pulse are investigated in the quantum
radiation-dominated regime. Generally, the ponderomotive force of the laser
fields may deflect the electrons transversely, to form a ring structure on the
cross-section of the electron beam. However, we find that when the Lorentz
factor of the electron is approximately one order of magnitude larger
than the invariant laser field parameter , the stochastic nature of the
photon emission leads to electron aggregation abnormally inwards to the
propagation axis of the laser pulse. Consequently, the electron angular
distribution after the interaction exhibits a peak structure in the beam
propagation direction, which is apparently distinguished from the
"ring"-structure of the distribution in the classical regime, and therefore,
can be recognized as a proof of the fundamental quantum stochastic nature of
radiation. The stochasticity signature is robust with respect to the laser and
electron parameters and observable with current experimental techniques
UniParser: Multi-Human Parsing with Unified Correlation Representation Learning
Multi-human parsing is an image segmentation task necessitating both
instance-level and fine-grained category-level information. However, prior
research has typically processed these two types of information through
separate branches and distinct output formats, leading to inefficient and
redundant frameworks. This paper introduces UniParser, which integrates
instance-level and category-level representations in three key aspects: 1) we
propose a unified correlation representation learning approach, allowing our
network to learn instance and category features within the cosine space; 2) we
unify the form of outputs of each modules as pixel-level segmentation results
while supervising instance and category features using a homogeneous label
accompanied by an auxiliary loss; and 3) we design a joint optimization
procedure to fuse instance and category representations. By virtual of unifying
instance-level and category-level output, UniParser circumvents manually
designed post-processing techniques and surpasses state-of-the-art methods,
achieving 49.3% AP on MHPv2.0 and 60.4% AP on CIHP. We will release our source
code, pretrained models, and online demos to facilitate future studies
Enzymes and genes involved in the betalain biosynthesis in higher plants
Betalains, a class of water-soluble nitrogen-containing pigments, replace anthocyanins and serve the analogous functions in 13 families of the order, caryophyllales. They modulate the attractive appearance of plants and protect them against destructive oxidative damage. Their antioxidant roles, radicalscavenging properties in human health and their potential uses in food and pharmaceutical industries have made significant progress achieved in the detection, purification, quantification, structure elucidation of betalains, and in particular in the understanding of biosynthetic pathways of the pigments,the enzymes and their genes involved in the pathways. In this paper, major progress in betalain biosynthesis and the enzymes and genes involved in the biosynthetic pathways in higher plant are reviewed, and the perspectives discussed
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