3,400 research outputs found
Type I superconductivity in the Dirac semimetal PdTe2
The superconductor PdTe was recently classified as a Type II Dirac
semimetal, and advocated to be an improved platform for topological
superconductivity. Here we report magnetic and transport measurements conducted
to determine the nature of the superconducting phase. Surprisingly, we find
that PdTe is a Type I superconductor with K and a critical
field mT. Our crystals also exhibit the intermediate
state as demonstrated by the differential paramagnetic effect. For we
observe superconductivity of the surface sheath. This calls for a close
examination of superconductivity in PdTe in view of the presence of
topological surface states.Comment: 5 page
Muon spin rotation study of the topological superconductor SrxBi2Se3
We report transverse-field (TF) muon spin rotation experiments on single
crystals of the topological superconductor SrBiSe with nominal
concentrations and ( K). The TF spectra (
mT), measured after cooling to below in field, did not show any
additional damping of the muon precession signal due to the flux line lattice
within the experimental uncertainty. This puts a lower bound on the magnetic
penetration depth m. However, when we induce disorder in
the vortex lattice by changing the magnetic field below a sizeable
damping rate is obtained for . The data provide microscopic
evidence for a superconducting volume fraction of in the
crystal and thus bulk superconductivity.Comment: 6 pages, includes 4 figure
Kinetic modeling of electro-Fenton reaction in aqueous solution
Author name used in this publication: H. LiuAuthor name used in this publication: X. Z. LiAuthor name used in this publication: Y. J. LengAuthor name used in this publication: C. Wang2006-2007 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe
Superconductivity under pressure in the Dirac semimetal PdTe2
The Dirac semimetal PdTe was recently reported to be a type-I
superconductor (1.64 K, mT) with unusual
superconductivity of the surface sheath. We here report a high-pressure study,
GPa, of the superconducting phase diagram extracted from
ac-susceptibility and transport measurements on single crystalline samples.
shows a pronounced non-monotonous variation with a maximum 1.91 K around 0.91 GPa, followed by a gradual decrease to 1.27 K at 2.5 GPa.
The critical field of bulk superconductivity in the limit ,
, follows a similar trend and consequently the -curves
under pressure collapse on a single curve: .
Surface superconductivity is robust under pressure as demonstrated by the large
superconducting screening signal that persists for applied dc-fields . Surprisingly, for GPa the superconducting transition
temperature at the surface is larger than of the bulk. Therefore
surface superconductivity may possibly have a non-trivial nature and is
connected to the topological surface states detected by ARPES. We compare the
measured pressure variation of with recent results from band structure
calculations and discuss the importance of a Van Hove singularity.Comment: manuscript 9 pages with 8 figures + supplemental material 3 pages
with 6 figure
Classification of Overlapped Audio Events Based on AT, PLSA, and the Combination of Them
Audio event classification, as an important part of Computational Auditory Scene Analysis, has attracted much attention. Currently, the classification technology is mature enough to classify isolated audio events accurately, but for overlapped audio events, it performs much worse. While in real life, most audio documents would have certain percentage of overlaps, and so the overlap classification problem is an important part of audio classification. Nowadays, the work on overlapped audio event classification is still scarce, and most existing overlap classification systems can only recognize one audio event for an overlap. In this paper, in order to deal with overlaps, we innovatively introduce the author-topic (AT) model which was first proposed for text analysis into audio classification, and innovatively combine it with PLSA (Probabilistic Latent Semantic Analysis). We propose 4 systems, i.e. AT, PLSA, AT-PLSA and PLSA-AT, to classify overlaps. The 4 proposed systems have the ability to recognize two or more audio events for an overlap. The experimental results show that the 4 systems perform well in classifying overlapped audio events, whether it is the overlap in training set or the overlap out of training set. Also they perform well in classifying isolated audio events
Penetration depth study of the type-I superconductor PdTe2
Superconductivity in the topological non-trivial Dirac semimetal PdTe was
recently shown to be type-I. We here report measurements of the relative
magnetic penetration depth, , on several single crystals using
a high precision tunnel diode oscillator technique. The temperature variation
follows an exponential function for ,
consistent with a fully-gapped superconducting state and weak or moderately
coupling superconductivity. By fitting the data we extract a -value of ~nm. The normalized superfluid density is in good
agreement with the computed curve for a type-I superconductor with nonlocal
electrodynamics. Small steps are observed in , which
possibly relates to a locally lower due to defects in the single
crystalline sample. single crystalline sample.Comment: 13 pages, including 5 figure
Finger vein biometric identification using discretization method
Over the past years, finger vein identification has gaining increasing attention in biometrics. It has many advantages as compared to other biometrics such as living-body identification, difficult to counterfeit because it resides underneath the finger skin and noninvasiveness. Finger vein feature extraction plays an important role in finger vein identification. The performance of finger vein identification is highly depending on the meaningful extracted features from feature extraction process. However, most of the works focus on how to extract the individual features and not presenting the individual characteristic of finger vein patterns with systematic representation. This paper proposed an improved scheme of finger vein feature extraction method by adopting discretization method. The extracted features will be represented systematically way in order to make classification task easier and increase the identification accuracy rate. The experimental result shows that the accuracy rate of identification of the proposed framework using Discretization is above 98.0%
Effect of Na doping on flux pinning of YBa1.9Na0.1Cu3O7-d
We have prepared Na-doped YBa2Cu3Oy (YBa1.9Na0.1Cu3Oy +40mol%Y211) (YBNCO)
and Na-free YBa2Cu3Oy (YBCO) samples by the Melt-Textured Growth (MTG) method
to study the effect of doped Na ion on flux pinning. The ac susceptibility
curves (acs) as well as the hysteresis loops were measured for the samples.
Then the effective pinning energy (U(T,Hdc,J)), irreversibility line (Hirr(T))
and critical current density (jc(Hdc)) were determined, where T, Hdc and J are
temperature, dc magnetic field and current density, respectively. We found
that, with Na doping, the Hirr(T) line shifted to lower temperature while the
Jc(Hdc) and U(T,Hdc,J) became smaller. It indicates that the Na ions play a
negative role in the flux pinning of YBCO. The appearance of the second peak in
the Jc(Hdc) curves and the enhancement of anisotropy in YBNCO further support
this finding.Comment: 7 pages, 7figures. Submited to Physica.
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