28,683 research outputs found
Nodeless superconductivity in IrPtTe with strong spin-orbital coupling
The thermal conductivity of superconductor IrPtTe
( = 0.05) single crystal with strong spin-orbital coupling was measured down
to 50 mK. The residual linear term is negligible in zero magnetic
field. In low magnetic field, shows a slow field dependence. These
results demonstrate that the superconducting gap of IrPtTe is
nodeless, and the pairing symmetry is likely conventional s-wave, despite the
existence of strong spin-orbital coupling and a quantum critical point.Comment: 5 pages, 4 figure
Magnification relations of quad lenses and applications on Einstein crosses
In this work, we mainly study the magnification relations of quad lens models
for cusp, fold and cross configurations. By dividing and ray-tracing in
different image regions, we numerically derive the positions and magnifications
of the four images for a point source lying inside of the astroid caustic.
Then, based on the magnifications, we calculate the signed cusp and fold
relations for the singular isothermal elliptical lenses. The signed fold
relation map has positive and negative regions, and the positive region is
usually larger than the negative region as has been confirmed before. It can
also explain that for many observed fold image pairs, the fluxes of the Fermat
minimum images are apt to be larger than those of the saddle images. We define
a new quantity cross relation which describes the magnification discrepancy
between two minimum images and two saddle images. Distance ratio is also
defined as the ratio of the distance of two saddle images to that of two
minimum images. We calculate the cross relations and distance ratios for nine
observed Einstein crosses. In theory, for most of the quad lens models, the
cross relations decrease as the distance ratios increase. In observation, the
cross relations of the nine samples do not agree with the quad lens models very
well, nevertheless, the cross relations of the nine samples do not give obvious
evidence for anomalous flux ratio as the cusp and fold types do. Then, we
discuss several reasons for the disagreement, and expect good consistencies for
more precise observations and better lens models in the future.Comment: 12 pages, 11 figures, accepted for publication in MNRA
Superconducting screening on different length scales in high-quality bulk MgB2 superconductor
High quality bulk MgB2 exhibit a structure of voids and agglomeration of
crystals on different length-scales. Because of this, the superconducting
currents percolate between the voids in the ensuing structure. Magnetic
measurements reveal that the superconducting currents circulate on at least
three different length-scales, of ~1 micrometre, ~10 micrometre and whole of
the sample (~millimetre). Each of these screenings contributes to the measured
irreversible magnetic moment (Dm). The analysis of the field dependence of Dm
for samples of subsequently decreasing size showed that the critical current
obtained using the simple critical state model is erroneous. This leads to the
artefact of the sample size-dependent critical current and irreversibility
field. Our data analysis enables the separation of the contribution of each of
the screening currents to Dm. The field dependence of each of the currents
follows a stretched exponential form. The currents flowing around whole of the
sample give a dominant contribution to Dm in the intermediate fields (1T < H <
4T at 20K) and they can be used to obtain the value of Jc from critical state
model, which corresponds to the transport Jc
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Microwave-Induced Interfacial Nanobubbles
A new method for generating nanobubbles via microwave irradiation was verified and quantified. AFM measurement showed that nanobubbles with diameters ranging in 200 - 600 nm were generated at water-HOPG surface by applying microwave to aqueous solutions with 9.0 - 30.0 mg/L of dissolved oxygen. Graphite displays strong microwave absorption and transmits high thermal energy to surface. Due to high dielectric constant (20 °C, 80 F/m) and dielectric loss factor, water molecule has strong absorption ability for microwave. The thermal and non-thermal effects of microwave both had contributions to decrease gas solubility and that facilitated nanobubble nucleation. The yield of nanobubbles increased about ten times when irradiation time increased from 60 s to 120 s at 200 W microwave. The nanobubbles density increased from 0.8 to 15 numbers/μm2 by improving working power from 200 to 600 W. An apparent improvement of nanobubbles yield was obtained between 300 and 400 W, and the resulting temperature was 34 - 52 °C. When the initial dissolved oxygen increased from 11.3 to 30.0 mg/L, the density of nanobubbles increased from 1.2 to 13 numbers/μm2. The generation of nanobubbles could be well controlled by adjusting gas concentration, microwave power or irradiation time. The method maybe valuable in preparing surface nanobubbles quickly and conveniently for various applications, such as catalysis, hypoxia/anoxia remediation or as templates to prepare nanoscale materials
Various Correlations in Anisotropic Heisenberg XYZ Model with Dzyaloshinski-Moriya Interaction
Various thermal correlations as well as the effect of intrinsic decoherence
on the correlations are studied in a two-qubit Heisenberg XYZ spin chain with
the Dzyaloshinski--Moriya (DM) interaction along the z direction, i.e. Dz. It
is found that tunable parameter Dz may play a constructive role on the
concurrence (C), classical correlation (CC) and quantum discord (QD) in thermal
equilibrium while it plays a destructive role on the correlations in the
intrinsic decoherence case. The entanglement and quantum discord exhibit
collapse and revival under the phase decoherence. With a proper combination of
the system parameters, the correlations can effectively be kept at high steady
state values despite the intrinsic decoherence.Comment: 4 pages, 4 figure
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Fault Inductance Based Protection for DC Distribution Systems
The fault protection is a critical element to ensure the reliable and secure operation of DC distribution systems. Most DC distribution systems are tightly coupled systems with low line impedances which may result in fast current increase during a fault. Thus, it is challenging to develop a fast and reliable DC fault protection method. This paper proposes and develops a novel fault inductance based DC protection method without communication between protection units at different locations. The performance of the developed protection algorithm was validated in a Real-Time Hardware-In-the-Loop (RTHIL) test platform. The testing results indicate that the developed inductance based fault location algorithm detects and locates faults with fast speed and high accuracy. Preliminary sensitivity analysis on measurement errors are also conducted to study impacts on accuracy of estimated fault inductance.Center for Electromechanic
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