918 research outputs found
Learning from Minimum Entropy Queries in a Large Committee Machine
In supervised learning, the redundancy contained in random examples can be
avoided by learning from queries. Using statistical mechanics, we study
learning from minimum entropy queries in a large tree-committee machine. The
generalization error decreases exponentially with the number of training
examples, providing a significant improvement over the algebraic decay for
random examples. The connection between entropy and generalization error in
multi-layer networks is discussed, and a computationally cheap algorithm for
constructing queries is suggested and analysed.Comment: 4 pages, REVTeX, multicol, epsf, two postscript figures. To appear in
Physical Review E (Rapid Communications
On-Line Monitoring of Environment-Assisted Cracking in Nuclear Piping Using Array Probe Direct Current Potential Drop
A direct current potential drop method utilizing array probes with measurement ends maintaining an equalized potential designated as equi-potential switching array probe direct current potential drop (ESAP-DCPD) technique has been developed earlier at Seoul National University. This paper validates ESAP-DCPD technique by showing consistency among experimental measurements, analytical solution and numerical predictions using finite element analysis (FEA) of electric field changes with crack growth in metals. In order to examine its viability as an on-line monitoring of environment assisted crack growth at the inner surface of piping welds, artificial inner surface cracks were introduced in a full-scale weldment mockup pipe and stainless steel metal mockup pipe. The weldment was joined by low alloy steel and stainless steel pipes. The pipes were monitored by using ESAP-DCPD in laboratory environments. Optimization of electrical wiring configuration has produced results with significantly reduced noise for adequately long period of time. Then optimized experimental results were compared with the FEA prediction results for the mockup to show a good agreement. Also a round-robin measurement has been made at three laboratories. It has been found that the developed ESAP-DCPD can detect circumferential cracks with a depth of 40Â % of wall thickness in stainless steel with a good detectability for further growth behaviors. For axial cracks, however, the measurements showed poor detectability. Hence the developed ESAP-DCPD system can be used to monitor large circumferential cracks that existing non-destructive examination techniques often fail to detect until leakage takes place.Korea (South). Ministry of Trade, Industry and Energy. Korea Institute of Energy Technology Evaluation and Plannin
Nanoscale structuring of tungsten tip yields most coherent electron point-source
This report demonstrates the most spatially-coherent electron source ever
reported. A coherence angle of 14.3 +/- 0.5 degrees was measured, indicating a
virtual source size of 1.7 +/-0.6 Angstrom using an extraction voltage of 89.5
V. The nanotips under study were crafted using a spatially-confined,
field-assisted nitrogen etch which removes material from the periphery of the
tip apex resulting in a sharp, tungsten-nitride stabilized, high-aspect ratio
source. The coherence properties are deduced from holographic measurements in a
low-energy electron point source microscope with a carbon nanotube bundle as
sample. Using the virtual source size and emission current the brightness
normalized to 100 kV is found to be 7.9x10^8 A/sr cm^2
Parametric amplification of metric fluctuations through a bouncing phase
We clarify the properties of the behavior of classical cosmological
perturbations when the Universe experiences a bounce. This is done in the
simplest possible case for which gravity is described by general relativity and
the matter content has a single component, namely a scalar field in a closed
geometry. We show in particular that the spectrum of scalar perturbations can
be affected by the bounce in a way that may depend on the wave number, even in
the large scale limit. This may have important implications for string
motivated models of the early Universe.Comment: 17 pages, 12 figures, LaTeX-ReVTeX format, version to match Phys.
Rev.
Plasmon-phonon coupling in large-area graphene dot and antidot arrays
Nanostructured graphene on SiO2 substrates pave the way for enhanced
light-matter interactions and explorations of strong plasmon-phonon
hybridization in the mid-infrared regime. Unprecedented large-area graphene
nanodot and antidot optical arrays are fabricated by nanosphere lithography,
with structural control down to the sub-100 nanometer regime. The interaction
between graphene plasmon modes and the substrate phonons is experimentally
demonstrated and structural control is used to map out the hybridization of
plasmons and phonons, showing coupling energies of the order 20 meV. Our
findings are further supported by theoretical calculations and numerical
simulations.Comment: 7 pages including 6 figures. Supporting information is available upon
request to author
Study of a Class of Four Dimensional Nonsingular Cosmological Bounces
We study a novel class of nonsingular time-symmetric cosmological bounces. In
this class of four dimensional models the bounce is induced by a perfect fluid
with a negative energy density. Metric perturbations are solved in an analytic
way all through the bounce. The conditions for generating a scale invariant
spectrum of tensor and scalar metric perturbations are discussed.Comment: 16 pages, 10 figure
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Safety and efficacy of endoscopic submucosal dissection for rectal neoplasia: a multicenter North American experience.
Background and aims âRectal lesions traditionally represent the first lesions approached during endoscopic submucosal dissection (ESD) training in the West. We evaluated the safety and efficacy of rectal ESD in North America. Methods âThis is a multicenter retrospective analysis of rectal ESD between January 2010 and September 2018 in 15 centers. End points included: rates of en bloc resection, R0 resection, adverse events, comparison of pre- and post-ESD histology, and factors associated with failed resection. Results âIn total, 171 patients (median age 63 years; 56â% men) underwent rectal ESD (median size 43âmm). En bloc resection was achieved in 141 cases (82.5â%; 95â%CI 76.8-88.2), including 24 of 27 (88.9â%) with prior failed endoscopic mucosal resection (EMR). R0 resection rate was 74.9â% (95â%CI 68.4-81.4). Post-ESD bleeding and perforation occurred in 4 (2.3â%) and 7 (4.1â%), respectively. Covert submucosal invasive cancer (SMIC) was identified in 8.6â% of post-ESD specimens. There was one case (1/120; 0.8â%) of recurrence at a median follow-up of 31 weeks; IQR: 19-76 weeks). Older age and higher body mass index (BMI) were predictors of failed R0 resection, whereas submucosal fibrosis was associated with a higher likelihood of both failed en bloc and R0 resection. Conclusion âRectal ESD in North America is safe and is associated with high en bloc and R0 resection rates. The presence of submucosal fibrosis was the main predictor of failed en bloc and R0 resection. ESD can be considered for select rectal lesions, and serves not only to establish a definitive tissue diagnosis but also to provide curative resection for lesions with covert advanced disease
AMiBA Wideband Analog Correlator
A wideband analog correlator has been constructed for the Yuan-Tseh Lee Array
for Microwave Background Anisotropy. Lag correlators using analog multipliers
provide large bandwidth and moderate frequency resolution. Broadband IF
distribution, backend signal processing and control are described. Operating
conditions for optimum sensitivity and linearity are discussed. From
observations, a large effective bandwidth of around 10 GHz has been shown to
provide sufficient sensitivity for detecting cosmic microwave background
variations.Comment: 28 pages, 23 figures, ApJ in press
Impact of the timing of hepatitis B virus identification and antiĂą hepatitis B virus therapy initiation on the risk of adverse liver outcomes for patients receiving cancer therapy
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138209/1/cncr30729_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138209/2/cncr30729.pd
The Yuan-Tseh Lee Array for Microwave Background Anisotropy
The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the
first interferometer dedicated to studying the cosmic microwave background
(CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the
contributions from foreground synchrotron radiation and Galactic dust emission.
The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod
platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific
operations began with the detection of a number of clusters of galaxies via the
thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing
data in order to study the structure of dark matter. We also compare our data
with X-ray data in order to derive the Hubble constant.Comment: accepted for publication in ApJ (13 pages, 7 figures); a version with
high resolution figures available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/pho_highreso.pd
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