2,862 research outputs found
Direct Observation of Long-Term Durability of Superconductivity in YBaCuO-AgO Composites
We report direct observation of long-term durability of superconductivity of
several YBaCuO-AgO composites that were first prepared and
studied almost 14 years ago [J. J. Lin {\it et al}., Jpn. J. Appl. Phys. {\bf
29}, 497 (1990)]. Remeasurements performed recently on both resistances and
magnetizations indicate a sharp critical transition temperature at 91 K. We
also find that such long-term environmental stability of high-temperature
superconductivity can only be achieved in YBaCuO with AgO
addition, but not with pure Ag addition.Comment: to be published in Jpn. J. Appl. Phy
Unextendible Maximally Entangled Bases in
The construction of unextendible maximally entangled bases is tightly related
to quantum information processing like local state discrimination. We put
forward two constructions of UMEBs in () based on the constructions of UMEBs in and in , which generalizes the results in [Phys. Rev. A. 94, 052302 (2016)] by
two approaches. Two different 48-member UMEBs in have been constructed in detail
Investigation of a New Flux-Modulated Permanent Magnet Brushless Motor for EVs
This paper presents a flux-modulated direct drive (FMDD) motor. The key is to integrate the magnetic gear with the PM motor while removing the gear inner-rotor. Hence, the proposed FMDD motor can achieve the low-speed high-torque output and high-speed compact design requirements as well as high-torque density with a simple structure. The output power equation is analytically derived. By using finite element analysis (FEA), the static characteristics of the proposed motor are obtained. Based on these characteristics, the system mathematical model can be established. Hence, the evaluation of system performances is conducted by computer simulation using the Matlab/Simulink. A prototype is designed and built for experimentation. Experimental results are given to verify the theoretical analysis and simulation
Experiments and simulations of MEMS thermal sensors for wall shear-stress measurements in aerodynamic control applications
MEMS thermal shear-stress sensors exploit heat-transfer effects to measure the shear stress exerted by an air flow on its solid boundary, and have promising applications in aerodynamic control. Classical theory for conventional, macroscale thermal shear-stress sensors states that the rate of heat removed by the flow from the sensor is proportional to the 1/3-power of the shear stress. However, we have observed that this theory is inconsistent with experimental data from MEMS sensors. This paper seeks to develop an understanding of MEMS thermal shear-stress sensors through a study including both experimental and theoretical investigations. We first obtain experimental data that confirm the inadequacy of the classical theory by wind-tunnel testing of prototype MEMS shear-stress sensors with different dimensions and materials. A theoretical analysis is performed to identify that this inadequacy is due to the lack of a thin thermal boundary layer in the fluid flow at the sensor surface, and then a two-dimensional MEMS shear-stress sensor theory is presented. This theory incorporates important heat-transfer effects that are ignored by the classical theory, and consistently explains the experimental data obtained from prototype MEMS sensors. Moreover, the prototype MEMS sensors are studied with three-dimensional simulations, yielding results that quantitatively agree with experimental data. This work demonstrates that classical assumptions made for conventional thermal devices should be carefully examined for miniature MEMS devices
Identifying the Riemann zeros by periodically driving a single qubit
The Riemann hypothesis, one of the most important open problems in pure
mathematics, implies the most profound secret of prime numbers. One of the most
interesting approaches to solve this hypothesis is to connect the problem with
the spectrum of the physical Hamiltonian of a quantum system. However, none of
the proposed quantum Hamiltonians have been experimentally feasible.Here, we
report the first experiment to identify the first non-trivial zeros of the
Riemann zeta function and the first two zeros of P\'olya's fake zeta function,
using a novel Floquet method, through properly designed periodically driving
functions. According to this method, the zeros of these functions are
characterized by the occurrence of crossings of quasi-energies when the
dynamics of the system are frozen. The experimentally obtained zeros are in
excellent agreement with their exact values. Our study provides the first
experimental realization of the Riemann zeros, which may provide new insights
into this fundamental mathematical problem.Comment: 5 pages, 7 figure
2,3,4,6-Tetra-O-acetyl-β-d-galactopyranosyl butyrate
The title compound, C18H26O11, was synthesized by a condensation reaction of 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide and butyric acid. The acetoxymethyl and butyrate groups are located on the same side of the pyran ring, showing the β configuration for the d-glycosyl ester; the butyl group adopts an extend conformation, the C—C—C—C torsion angle being 179.1 (7)°. In the crystal, the molecules are linked by weak C—H⋯O hydrogen bonds
GW25-e4419 Polymer-free dual drug-eluting stents improve endothelialization of stenting coronary artery in a porcine model and the mechanism
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