2,494 research outputs found
A convenient basis for the Izergin-Korepin model
We propose a convenient orthogonal basis of the Hilbert space for the
Izergin-Korepin model (or the quantum spin chain associated with the
algebra). It is shown that the monodromy-matrix elements acting
on the basis take relatively simple forms (c.f. acting on the original basis ),
which is quite similar as that in the so-called F-basis for the quantum spin
chains associated with -type (super)algebras. As an application, we present
the recursive expressions of Bethe states in the basis for the Izergin-Korepin
model.Comment: 24 pages, no figure
Electrocardiogram Baseline Wander Suppression Based on the Combination of Morphological and Wavelet Transformation Based Filtering
One of the major noise components in electrocardiogram (ECG) is the baseline wander (BW). Effective methods for suppressing BW include the wavelet-based (WT) and the mathematical morphological filtering-based (MMF)algorithms. However, the T waveform distortions introduced by the WTand the rectangular/trapezoidal distortions introduced by MMF degrade the quality of the output signal. Hence, in this study, we introduce a method by combining the MMF and WTto overcome the shortcomings of both existing methods. To demonstrate the effectiveness of the proposed method, artificial ECG signals containing a clinicalBW are used for numerical simulation, and we also create a realistic model of baseline wander to compare the proposed method with
other state-of-the-art methods commonly used in the literature. /e results show that the BW suppression effect of the proposed method is better than that of the others. Also, the new method is capable of preserving the outline of the BW and avoiding waveform distortions caused by the morphology filter, thereby obtaining an enhanced quality of ECG
Spectral Features of the Solar Transition Region and Chromospheric Lines at Flare Ribbons Observed with IRIS
We report on the spectral features of the Si IV 1402.77 \AA, C II 1334.53
\AA, and Mg II h or k lines, formed in the layers from the transition region to
the chromosphere, in three two-ribbon flares (with X-, M-, and C-class)
observed with IRIS. All the three lines show significant redshifts within the
main flare ribbons, which mainly originate from the chromospheric condensation
during the flares. The average redshift velocities of the Si IV line within the
main ribbons are 56.6, 25.6, and 10.5 km s for the X-, M-, and C-class
flares, respectively, which show a decreasing tendency with the flare class.
The C II and Mg II lines show a similar tendency but with smaller velocities
compared to the Si IV line. Additionally, the Mg II h or k line shows a
blue-wing enhancement in the three flares in particular at the flare ribbon
fronts, which is supposed to be caused by an upflow in the upper chromosphere
due to the heating of the atmosphere. Moreover, the Mg II h or k line exhibits
a central reversal at the flare ribbons, but turns to pure emission shortly
after 1--4 minutes. Correspondingly, the C II line also shows a central
reversal but in a smaller region. However, for the Si IV line, the central
reversal is only found in the X-class flare, but not in the other two flares.
As usual, the central reversal of these lines can be caused by the opacity
effect. This implies that in addition to the optically thick lines (C II and Mg
II lines), the Si IV line can become optically thick in a strong flare, which
is likely related to the nonthermal electron beam heating.Comment: 26 pages, 13 figures, accepted for publication in ApJ
Determining layer number of two dimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrate
Transition-metal dichalcogenide (TMD) semiconductors have been widely studied
due to their distinctive electronic and optical properties. The property of TMD
flakes is a function of its thickness, or layer number (N). How to determine N
of ultrathin TMDs materials is of primary importance for fundamental study and
practical applications. Raman mode intensity from substrates has been used to
identify N of intrinsic and defective multilayer graphenes up to N=100.
However, such analysis is not applicable for ultrathin TMD flakes due to the
lack of a unified complex refractive index () from monolayer to bulk
TMDs. Here, we discuss the N identification of TMD flakes on the SiO/Si
substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm)
SiO/Si substrates underneath TMD flakes and that from bare SiO/Si
substrates. We assume the real part of of TMD flakes as that of
monolayer TMD and treat the imaginary part of as a fitting
parameter to fit the experimental intensity ratio. An empirical ,
namely, , of ultrathin MoS, WS and WSe
flakes from monolayer to multilayer is obtained for typical laser excitations
(2.54 eV, 2.34 eV, or 2.09 eV). The fitted of MoS has
been used to identify N of MoS flakes deposited on 302-nm SiO/Si
substrate, which agrees well with that determined from their shear and
layer-breathing modes. This technique by measuring Raman intensity from the
substrate can be extended to identify N of ultrathin 2D flakes with N-dependent
. For the application purpose, the intensity ratio excited by
specific laser excitations has been provided for MoS, WS and
WSe flakes and multilayer graphene flakes deposited on Si substrates
covered by 80-110 nm or 280-310 nm SiO layer.Comment: 10 pages, 4 figures. Accepted by Nanotechnolog
- …