151,485 research outputs found
A concentrator for static magnetic field
We propose a compact passive device as a super-concentrator to create an
extremely high uniform static magnetic field over 50T in a large
two-dimensional free space from a weak background magnetic field. Such an
amazing thing becomes possible for the first time, thanks to space-folded
transformation and metamaterials for static magnetic fields. Finite element
method (FEM) is utilized to verify the performance of the proposed device
Transforming magnets
Based on the form-invariant of Maxwell's equations under coordinate
transformations, we extend the theory of transformation optics to
transformation magneto-statics, which can design magnets through coordinate
transformations. Some novel DC magnetic field illusions created by magnets
(e.g. shirking magnets, cancelling magnets and overlapping magnets) are
designed and verified by numerical simulations. Our research will open a new
door to designing magnets and controlling DC magnetic fields
Multi-view Regularized Gaussian Processes
Gaussian processes (GPs) have been proven to be powerful tools in various
areas of machine learning. However, there are very few applications of GPs in
the scenario of multi-view learning. In this paper, we present a new GP model
for multi-view learning. Unlike existing methods, it combines multiple views by
regularizing marginal likelihood with the consistency among the posterior
distributions of latent functions from different views. Moreover, we give a
general point selection scheme for multi-view learning and improve the proposed
model by this criterion. Experimental results on multiple real world data sets
have verified the effectiveness of the proposed model and witnessed the
performance improvement through employing this novel point selection scheme
Observing collapse in two colliding dipolar Bose-Einstein condensates
We study the collision of two Bose-Einstein condensates with pure dipolar
interaction. A stationary pure dipolar condensate is known to be stable when
the atom number is below a critical value. However, collapse can occur during
the collision between two condensates due to local density fluctuations even if
the total atom number is only a fraction of the critical value. Using full
three-dimensional numerical simulations, we observe the collapse induced by
local density fluctuations. For the purpose of future experiments, we present
the time dependence of the density distribution, energy per particle and the
maximal density of the condensate. We also discuss the collapse time as a
function of the relative phase between the two condensates.Comment: 6 pages, 7 figure
Dynamics of a two-species Bose-Einstein condensate in a double well
We study the dynamics of a two-species Bose-Einstein condensate in a double
well. Such a system is characterized by the intraspecies and interspecies
s-wave scattering as well as the Josephson tunneling between the two wells and
the population transfer between the two species. We investigate the dynamics
for some interesting regimes and present numerical results to support our
conclusions. In the case of vanishing intraspecies scattering lengths and a
weak interspecies scattering length, we find collapses and revivals in the
population dynamics. A possible experimental implementation of our proposal is
briefly discussed.Comment: 7 pages, 5 figure
Millimeter Wave MIMO Channel Estimation Based on Adaptive Compressed Sensing
Multiple-input multiple-output (MIMO) systems are well suited for
millimeter-wave (mmWave) wireless communications where large antenna arrays can
be integrated in small form factors due to tiny wavelengths, thereby providing
high array gains while supporting spatial multiplexing, beamforming, or antenna
diversity. It has been shown that mmWave channels exhibit sparsity due to the
limited number of dominant propagation paths, thus compressed sensing
techniques can be leveraged to conduct channel estimation at mmWave
frequencies. This paper presents a novel approach of constructing beamforming
dictionary matrices for sparse channel estimation using the continuous basis
pursuit (CBP) concept, and proposes two novel low-complexity algorithms to
exploit channel sparsity for adaptively estimating multipath channel parameters
in mmWave channels. We verify the performance of the proposed CBP-based
beamforming dictionary and the two algorithms using a simulator built upon a
three-dimensional mmWave statistical spatial channel model, NYUSIM, that is
based on real-world propagation measurements. Simulation results show that the
CBP-based dictionary offers substantially higher estimation accuracy and
greater spectral efficiency than the grid-based counterpart introduced by
previous researchers, and the algorithms proposed here render better
performance but require less computational effort compared with existing
algorithms.Comment: 7 pages, 5 figures, in 2017 IEEE International Conference on
Communications Workshop (ICCW), Paris, May 201
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Precision Extrusion Deposition of Polycaprolactone/Hydroxyapatite Tissue Scaffolds
Freeform fabrication provides an effective process tool to manufacture advanced tissue scaffolds
with specific designed properties. Our research focuses on using a novel Precision Extrusion
Deposition (PED) process technique to directly fabricate Polycaprolactone (PCL) and composite
PCL/ Hydroxyapatite (HA) tissue scaffolds. The scaffold morphology and the mechanical
properties were evaluated using SEM and mechanical testing. In vitro biological studies were
conducted to investigate the cellular responses of the composite scaffolds. Results and
characterizations demonstrate the viability of the PED process as well as the good mechanical
property, structural integrity, controlled pore size, pore interconnectivity, and the biological
compatibility of the fabricated scaffolds.Mechanical Engineerin
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