25 research outputs found
Infinite series models of flux relaxation and vortex penetration constructed at critical points and their unification
The information about the current-carrying ability of a type-II
superconductor can be obtained by studying the flux relaxation and vortex
penetration phenomena in the superconductor. In early studies, the infinite
series models of the flux relaxation and vortex penetration phenomena were
constructed at a vanishing current density and vanishing internal field,
respectively. However, this is not the only possibility. Here it is shown that
one can reconstruct the theoretical models at the critical points. The new
polynomial model of the flux relaxation (vortex penetration) phenomenon was
constructed by expanding the vortex activation energy as an infinite series of
the current density (internal field) about the critical current density
(equilibrium internal field). The unification of the polynomial models was
proposed. The inverse model of the flux relaxation (vortex penetration)
phenomenon was also constructed by expanding the vortex activation energy as an
infinite series of the inverse current density (inverse internal field) about
the critical current density (equilibrium internal field).Comment: 10 pages, 2 figure
Vortex penetration and flux relaxation with arbitrary initial conditions in non-ideal and ideal superconductors
Vortex penetration and flux relaxation phenomenon carry the information about
the pinning ability, and consequently current-carrying ability, of a type-II
superconductor. However, the theoretical descriptions to these phenomena are
currently limited to the cases with special initial conditions. A
generalization to the recently developed infinite series models is presented
here. It is shown that one can convert a vortex penetration process with a
non-zero initial internal field into a process with a zero initial internal
field by introducing some time parameters. Similarly, one can also convert a
flux relaxation process starting with an arbitrary internal field into a
process starting with a melting internal field by introducing a virtual time
interval. Therefore, one can predict the melting internal field (or critical
current density) from a flux relaxation process starting with a lower internal
field. Finally, it is shown that the vortex penetration process in an ideal
superconductor is strongly time dependent because of the surface barrier and
internal field repulsive force. But the flux relaxation process does not occur
in the ideal superconductor.Comment: 9 pages, 3 figure
Erasing and Correction of Liquid Metal Printed Electronics Made of Gallium Alloy Ink from the Substrate
Gallium-based liquid metals have recently been found important in a variety
of newly emerging applications such as room temperature metal 3D printing,
direct writing of electronics and biomedicine etc. In all these practices, one
frequently encounters the situations that a printed circuit or track needs to
be corrected or the unwanted parts of the device should be removed as desired.
However, few appropriate strategies are currently available to tackle such
important issues at this stage. Here we have identified several low cost ways
toward this goal by comparatively investigating three typical strategies
spanning from mechanical, chemical, to electrochemical principles, for removing
the gallium-based liquid metal circuits or thin films. Regarding the mechanical
approach, we constructed an eraser for removing the liquid metal thin films. It
was shown that ethanol (CH3CH2OH) could serve as a good candidacy material for
the mechanical eraser. In the chemical category, we adopted alkalis and acids
to remove the finely printed liquid metal circuits and sodium hydroxide (NaOH)
solution was particularly revealed to be rather efficient in making a chemical
eraser. In the electrochemical strategy, we applied a 15 V voltage to a liquid
metal thin film (covered with water) and successfully removed the target metal
part. These methods were comparatively evaluated with each of the merits and
shortcomings preliminarily clarified in the end. The present work is expected
to be important for the increasing applications of the liquid metal enabled
additive manufactures.Comment: 16 pages, 4 figure
Preparation and Application of Starch/Polyvinyl Alcohol/Citric Acid Ternary Blend Antimicrobial Functional Food Packaging Films
Ternary blend films were prepared with different ratios of starch/polyvinyl alcohol (PVA)/citric acid. The films were characterized by field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis, as well as Fourier transform infrared (FTIR) analysis. The influence of different ratios of starch/polyvinyl alcohol (PVA)/citric acid and different drying times on the performance properties, transparency, tensile strength (TS), water vapor permeability (WVP), water solubility (WS), color difference (ΔE), and antimicrobial activity of the ternary blends films were investigated. The starch/polyvinyl alcohol/citric acid (S/P/C1:1:0, S/P/C3:1:0.08, and S/P/C3:3:0.08) films were all highly transparent. The S/P/C3:3:0.08 had a 54.31 times water-holding capacity of its own weight and its mechanical tensile strength was 46.45 MPa. In addition, its surface had good uniformity and compactness. The S/P/C3:1:0.08 and S/P/C3:3:0.08 showed strong antimicrobial activity to Listeria monocytogenes and Escherichia coli, which were the food-borne pathogenic bacteria used. The freshness test results of fresh figs showed that all of the blends prevented the formation of condensed water on the surface of the film, and the S/P/C3:1:0.08 and S/P/C3:3:0.08 prevented the deterioration of figs during storage. The films can be used as an active food packaging system due to their strong antibacterial effect