927 research outputs found
Moving particle simulation for free surface and multi-phase flows
This document provides particle simulation for free surface and multi-phase flows using the MPS (Moving Particle Simulation) method
Microstructures of ramp-edge YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox Josephson junctions on different substrates
Ramp-edge YBa2Cu3/PrBa2Cu3Ox/YBa2Cu3Ox Josephson junctions with PrBa2Cu3Ox (PrBCO) or SrTiO3 as a separating layer on different kinds of substrate have been studied by high-resolution electron microscopy. The bottom YBa2Cu3Ox (YBCO) layer and the separating layer (PrBCO or SrTiO3) were epitaxially c oriented, irrespective of the substrate (yttria stabilized zirconia (YSZ), SrTiO3 or NdGaO3, all in (001) orientation). The use of ion milling in the manufacturing of Josephson junctions was found to yield smooth slopes with an angle of about 20°. The Josephson junction was facing away from the beam direction was found to have a dimple in the substrate near the base of the junction. The barrier layers were observed to have a homogeneous thickness. These layers were as the top YBCO layers were oriented with their c-axis perpendicular to (001) plane of the substrate for perovskite substrates and perpendicular to the surface for YSZ substrates. In the case of a YSZ substrate, the dimple in the substrate as well as the slope of the substrate close to the base of the junction were found to lead to small angle grain boundaries in the YBCO film as well as randomly oriented YBCO grains, which results in a poor ramp-edge junction. In the case of SrTiO3 or NdGaO3 substrate, all components of the device were fully epitaxial, thus resulting in good ramp-edge junctions
Comparative study of flux pinning, creep and critical currents between YBaCuO crystals with and without Y2BaCuO5 inclusions
In the Y-Ba-Cu-O system, YBa2Cu3O(x) phase is produced by the following peritectic reaction: Y2BaCuO5 + liquid yields 2YBa2Cu3O(x). Through the control of processing conditions and starting compositions, it becomes possible to fabricate large crystals containing fine Y2BaCuO5(211) inclusions. Such crystals exhibit Jc values exceeding 10000 A/sq cm at 77 K and 1T. Recently, researchers developed a novel process which can control the volume fraction of 211 inclusions. Elimination of 211 inclusions is also possible. In this study, researchers prepared YBaCuO crystals with and without 211 inclusions using the novel process, and compared flux pinning, flux creep and critical currents. Magnetic field dependence of Jc for YBaCuO crystals with and with 211 inclusions is shown. It is clear that fine 211 inclusions can contribute to flux pinning. It was also found that flux creep rate could be reduced by increasing flux pinning force. Critical current density estimates based on the conventional flux pinning theory were in good agreement with experimental results
Efficient Compressed Ratio Estimation using Online Sequential Learning for Edge Computing
Owing to the widespread adoption of the Internet of Things, a vast amount of
sensor information is being acquired in real time. Accordingly, the
communication cost of data from edge devices is increasing. Compressed sensing
(CS), a data compression method that can be used on edge devices, has been
attracting attention as a method to reduce communication costs. In CS,
estimating the appropriate compression ratio is important. There is a method to
adaptively estimate the compression ratio for the acquired data using
reinforcement learning. However, the computational costs associated with
existing reinforcement learning methods that can be utilized on edges are
expensive. In this study, we developed an efficient reinforcement learning
method for edge devices, referred to as the actor--critic online sequential
extreme learning machine (AC-OSELM), and a system to compress data by
estimating an appropriate compression ratio on the edge using AC-OSELM. The
performance of the proposed method in estimating the compression ratio is
evaluated by comparing it with other reinforcement learning methods for edge
devices. The experimental results show that AC-OSELM achieved the same or
better compression performance and faster compression ratio estimation than the
existing methods.Comment: 7 pages, 7 figures, Submitted to IEEE ICC 202
Initialization Bias of Fourier Neural Operator: Revisiting the Edge of Chaos
This paper investigates the initialization bias of the Fourier neural
operator (FNO). A mean-field theory for FNO is established, analyzing the
behavior of the random FNO from an ``edge of chaos'' perspective. We uncover
that the forward and backward propagation behaviors exhibit characteristics
unique to FNO, induced by mode truncation, while also showcasing similarities
to those of densely connected networks. Building upon this observation, we also
propose a FNO version of the He initialization scheme to mitigate the negative
initialization bias leading to training instability. Experimental results
demonstrate the effectiveness of our initialization scheme, enabling stable
training of a 32-layer FNO without the need for additional techniques or
significant performance degradation
Re-appearance of antiferromagnetic ordering with Zn and Ni substitution in La_{2-x}Sr_xCuO_4
The effects of nonmagnetic Zn and magnetic Ni substitution for Cu site on
magnetism are studied by measurements of uniform magnetic susceptibility for
lightly doped La_{2-x}Sr_xCu_{1-z}M_zO_4 (M=Zn or Ni) polycrystalline samples.
For the parent x=0, Zn doping suppresses the N\'{e}el temperature T_N whereas
Ni doping hardly changes T_N up to z=0.3. For the lightly doped samples with
T_N~0, the Ni doping recovers T_N. For the superconducting samples, the Ni
doping induces the superconductivity-to-antiferromagnetic transition (or
crossover). All the heavily Ni doped samples indicate a spin glass behavior at
\~15 K.Comment: 2 pages including 3 figures, to be published in Physica C (LT23,
Hiroshima 2002
Processing conditions for (Nd, Eu, Gd)-Ba-Cu-O ternary bulk superconductors
Abstract(Nd, Eu, Gd)-Ba-Cu-O ternary bulk superconductors have high potential for practical applications since they exhibit very high critical current densities and thus high field trapping capabilities. (Nd, Eu, Gd)-Ba-Cu-O superconductors are synthesized in a reduced oxygen atmosphere, which requires a control of oxygen partial pressure and needs a special device for hot seeding. In the present study, for simplicity, we employed Ar gas flow into the furnace to control oxygen partial pressure instead of flowing oxygen-controlled gas. Hence, it was necessary to modify the melt processing conditions to produce a single domain. Through the optimization of seeding temperature and cooling rate, we obtained the processing conditions, in which a single domain bulk (Nd, Eu, Gd)-Ba-Cu-O of 20mm diameter could be synthesized
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