549 research outputs found
Simulation for the Polygonal Coil Magnetic Field
Based on the study of Helmholtz coils, the intensity distribution of polygons coil magnetic field and characteristics of intensity of that magnetic field is given, this lay the foundation for some industrial application is showed here
Regge-like relation and a universal description of heavy-light systems
Using the Regge-like formula between hadron mass
and angular momentum with a heavy quark mass and a string tension
, we analyze all the heavy-light systems, i.e., mesons
and charmed and bottom baryons.Numerical plots are obtained for all the
heavy-light mesons of experimental data whose slope becomes nearly equal to 1/2
of that for light hadrons. Assuming that charmed and bottom baryons consist of
one heavy quark and one light cluster of two light quarks (diquark), we apply
the formula to all the heavy-light baryons including recently discovered
's and find that these baryons experimentally measured satisfy the
above formula. We predict the average mass values of , , ,
, , and with as 6.01, 6.13, 6.15, 3.05, 3.07,
and 3.34 GeV, respectively. Our results on baryons suggest that these baryons
can be safely regarded as heavy quark-light cluster configuration. We also find
a universal description for all the heavy-light mesons as well as baryons,
i.e., one unique line is enough to describe both of charmed and bottom
heavy-light systems. Our results suggest that instead of mass itself, gluon
flux energy is essential to obtain a linear trajectory.Comment: 10 pages, 8 figures, 5 table
A Comprehensive Analysis of Fermi Gamma-Ray Burst Data. IV. Spectral Lag and its Relation to E p Evolution
The spectral evolution and spectral lag behavior of 92 bright pulses from 84 gamma-ray bursts observed by the Fermi Gamma-ray Burst Monitor (GBM) telescope are studied. These pulses can be classified into hard-to-soft pulses (H2S; 64/92), H2S-dominated-tracking pulses (21/92), and other tracking pulses (7/92). We focus on the relationship between spectral evolution and spectral lags of H2S and H2S-dominated-tracking pulses. The main trend of spectral evolution (lag behavior) is estimated with ( ), where E p is the peak photon energy in the radiation spectrum, t + t 0 is the observer time relative to the beginning of pulse −t 0, and is the spectral lag of photons with energy E with respect to the energy band 8–25 keV. For H2S and H2S-dominated-tracking pulses, a weak correlation between and k E is found, where W is the pulse width. We also study the spectral lag behavior with peak time of pulses for 30 well-shaped pulses and estimate the main trend of the spectral lag behavior with . It is found that is correlated with k E . We perform simulations under a phenomenological model of spectral evolution, and find that these correlations are reproduced. We then conclude that spectral lags are closely related to spectral evolution within the pulse. The most natural explanation of these observations is that the emission is from the electrons in the same fluid unit at an emission site moving away from the central engine, as expected in the models invoking magnetic dissipation in a moderately high-σ outflow
catena-Poly[[diaquanickel(II)]-bis(μ-pyridine-4-sulfinato)-κ2 N,O;κ2 O,N]
In the title coordination polymer, [Ni(C5H4NO2S)2(H2O)2]n, the NiII ion is located on an inversion centre and is octahedrally coordinated by two N and two O atoms of four symmetry-related and deprotonated pyridine-4-sulfinate (ps) ligands together with two water molecules in axial positions. The ps− anions, acting as μ2-bridging ligands, link neighbouring NiII ions into a chain structure along the c axis. These polymeric chains are extended into a three-dimensional framework via intermolecular O—H⋯O hydrogen bonds with participation of the water molecules
3D Object Detection Algorithm Based on the Reconstruction of Sparse Point Clouds in the Viewing Frustum
In response to the problem that the detection precision of the current 3D object detection algorithm is low when the object is severely occluded, this study proposes an object detection algorithm based on the reconstruction of sparse point clouds in the viewing frustum. The algorithm obtains more local feature information of the sparse point clouds in the viewing frustum through dimensional expansion, performs the fusion of local and global feature information of the point cloud data to obtain point cloud data with more complete semantic information, and then applies the obtained data to the 3D object detection task. The experimental results show that the precision of object detection in both 3D view and BEV (Bird’s Eye View) can be improved effectively through the algorithm, especially object detection of moderate and hard levels when the object is severely occluded. In the 3D view, the average precision of the 3D detection of cars, pedestrians, and cyclists at a moderate level can be increased by 7.1p.p., 16.39p.p., and 5.42p.p., respectively; in BEV, the average precision of the 3D detection of car, pedestrians, and cyclists at hard level can be increased by 6.51p.p., 16.57p.p., and 7.18p.p., respectively, thus indicating the effectiveness of the algorithm.© 2022 Xing Xu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.fi=vertaisarvioitu|en=peerReviewed
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Effective group dispersion of terahertz quantum-cascade lasers
Terahertz (THz) quantum-cascade lasers (QCLs) are based on complex semiconductor heterostructures, in which the optical gain is generated by intersubband transitions. Using the spacing of the laser modes in the emission spectra, we have determined the effective group refractive index for more than one hundred THz QCLs of the hybrid design with Fabry-Pérot resonators based on single-plasmon waveguides. The experimentally obtained values of for emission frequencies between 2.5 and 5.6 THz generally follow the trend of derived from electromagnetic simulations. However, for a certain number of QCLs, the experimental values of exhibit a rather large deviation from the general trend and the simulation results. From a thorough analysis, we conclude that differences in the optical gain/loss spectra are responsible for this deviation, which lead to a modification of the dispersion in the active region and consequently to altered values of. The analysis also provides evidence that these differences in the gain/loss spectra originate from both, the details of the design and the gain broadening due to interface roughness. © 2020 The Author(s). Published by IOP Publishing Ltd
Spin and orbital angular momentum in gauge theories (II): QCD and nucleon spin structure
Parallel to the construction of gauge invariant spin and orbital angular
momentum for QED in paper (I) of this series, we present here an analogous but
non-trivial solution for QCD. Explicitly gauge invariant spin and orbital
angular momentum operators of quarks and gluons are obtained. This was
previously thought to be an impossible task, and opens a more promising avenue
towards the understanding of the nucleon spin structure.Comment: 3 pages, no figure; presented by F. Wang at NSTAR200
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Terahertz quantum-cascade lasers as high-power and wideband, gapless sources for spectroscopy
Terahertz (THz) quantum-cascade lasers (QCLs) are powerful radiation sources for high-resolution and high-sensitivity spectroscopy with a discrete spectrum between 2 and 5 THz as well as a continuous coverage of several GHz. However, for many applications, a radiation source with a continuous coverage of a substantially larger frequency range is required. We employed a multi-mode THz QCL operated with a fast ramped injection current, which leads to a collective tuning of equally-spaced Fabry-Pérot laser modes exceeding their separation. A continuous coverage over 72 GHz at about 4.7 THz was achieved. We demonstrate that the QCL is superior to conventional sources used in Fourier transform infrared spectroscopy in terms of the signal-to-noise ratio as well as the dynamic range by one to two orders of magnitude. Our results pave the way for versatile THz spectroscopic systems with unprecedented resolution and sensitivity across a wide frequency range
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