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P2-type Na2/3Ni1/3Mn2/3O2 Cathode Material with Excellent Rate and Cycling Performance for Sodium-Ion Batteries
P2-type Na2/3Ni1/3Mn2/3O2 is an air-stable cathode material for sodium-ion batteries. However, it suffers irreversible P2-O2 phase transition in 4.2-V plateau and shows poor cycling stability and rate capability within this plateau. To evaluate the practicability of this material in 2.3–4.1 V voltage range, single-crystal micro-sized P2-type Na2/3Ni1/3Mn2/3O2 with high rate capability and cycling stability is synthesized via polyvinylpyrrolidone (PVP)-combustion method. The electrochemical performance is evaluated by galvanostatic charge-discharge tests. The kinetics of Na+ intercalation/deintercalation is studied detailly with potential intermittent titration technique (PITT), galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV). The discharge capacity at 0.1 C in 2.3–4.1 V is 87.6 mAh g−1. It can deliver 91.5% capacity at 40 C rate and keep 89% after 650 cycles at 5C. The calculated theoretical energy density of full cell with hard carbon anode is 210 Wh kg−1. The moderate energy density associated with high power density and long cycle life is acceptable for load adjustment of new-energy power, showing the prospect of practical application
Gravitational Thermodynamics of Space-time Foam in One-loop Approximation
We show from one-loop quantum gravity and statistical thermodynamics that the
thermodynamics of quantum foam in flat space-time and Schwarzschild space-time
is exactly the same as that of Hawking-Unruh radiation in thermal equilibrium.
This means we show unambiguously that Hawking-Unruh thermal radiation should
contain thermal gravitons or the contribution of quantum space-time foam. As a
by-product, we give also the quantum gravity correction in one-loop
approximation to the classical black hole thermodynamics.Comment: 7 pages, revte
Detecting -phase superfluids with -wave symmetry in a quasi-1D optical lattice
We propose an experimental protocol to study -wave superfluidity in a
spin-polarized cold Fermi gas tuned by an -wave Feshbach resonance. A
crucial ingredient is to add a quasi-1D optical lattice and tune the fillings
of two spins to the and band, respectively. The pairing order parameter
is confirmed to inherit -wave symmetry in its center-of-mass motion. We find
that it can further develop into a state of unexpected -phase modulation
in a broad parameter regime. Measurable quantities are calculated, including
time-of-flight distributions, radio-frequency spectra, and in situ
phase-contrast imaging in an external trap. The -phase -wave superfluid
is reminiscent of the -state in superconductor-ferromagnet
heterostructures but differs in symmetry and origin. If observed, it would
represent another example of -wave pairing, first discovered in He-3
liquids.Comment: 5 pages, 5 figure
On length spectrum metrics and weak metrics on Teichmüller spaces of surfaces with boundary
We define and study metrics and weak metrics on the Teichmüller space of a surface of topologically finite type with boundary. These metrics and weak metrics are associated to the hyperbolic length spectrum of simple closed curves and of properly embedded arcs in the surface. We give a comparison between the defined metrics on regions of Teichmüller space which we call -relative -thick parts} for and
Length spectra and the Teichmüller metric for surfaces with boundary
International audienceWe consider some metrics and weak metrics defined on the Teichmmüller space of a surface of finite type with nonempty boundary, that are defined using the hyperbolic length spectrum of simple closed curves and of properly embedded arcs, and we compare these metrics and weak metrics with the Teichmüller metric. The comparison is on subsets of Teichmüller space which we call ''-relative -thick parts", and whose definition depends on the choice of some positive constants and . Meanwhile, we give a formula for the Teichmüller metric of a surface with boundary in terms of extremal lengths of families of arcs
Phase diagram of two-species Bose-Einstein condensates in an optical lattice
The exact macroscopic wave functions of two-species Bose-Einstein condensates
in an optical lattice beyond the tight-binding approximation are studied by
solving the coupled nonlinear Schrodinger equations. The phase diagram for
superfluid and insulator phases of the condensates is determined analytically
according to the macroscopic wave functions of the condensates, which are seen
to be traveling matter waves.Comment: 13 pages, 2 figure
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