29,098 research outputs found
Creep fatigue life prediction for engine hot section materials (isotropic)
The first two years of a two-phase program aimed at improving the high temperature crack initiation life prediction technology for gas turbine hot section components are discussed. In Phase 1 (baseline) effort, low cycle fatigue (LCF) models, using a data base generated for a cast nickel base gas turbine hot section alloy (B1900+Hf), were evaluated for their ability to predict the crack initiation life for relevant creep-fatigue loading conditions and to define data required for determination of model constants. The variables included strain range and rate, mean strain, strain hold times and temperature. None of the models predicted all of the life trends within reasonable data requirements. A Cycle Damage Accumulation (CDA) was therefore developed which follows an exhaustion of material ductility approach. Material ductility is estimated based on observed similarities of deformation structure between fatigue, tensile and creep tests. The cycle damage function is based on total strain range, maximum stress and stress amplitude and includes both time independent and time dependent components. The CDA model accurately predicts all of the trends in creep-fatigue life with loading conditions. In addition, all of the CDA model constants are determinable from rapid cycle, fully reversed fatigue tests and monotonic tensile and/or creep data
Application of the multiple-scattering method to analysis of systems with semi-infinite photonic waveguides
We propose a technique of compensating the spurious reflections implied by
the multiple-scattering (MS) method, commonly used for analyzing finite
photonic crystal (PC) systems, to obtain exact values of characteristic
parameters, such as reflection and transmission coefficients, of PC functional
elements. Rather than a modification of the MS computational algorithm, our
approach involves postprocessing of results obtained by the MS method. We
derive analytical formulas for the fields excited in a finite system, taking
explicitly into account the spurious reflections occurring at the artificial
system boundaries. The intrinsic parameters of the investigated functional
element are found by fitting the results of MS simulations to those obtained
from the formulas derived. Devices linked with one and two semi-infinite
waveguides are analyzed explicitly; possible extensions of the formalism to
more complex circuits are discussed as well. The accuracy of the proposed
method is tested in a number of systems; the results of our calculations prove
to be in good agreement with those obtained independently by other authors.Comment: 8 pages, 5 figure
Uniform synchronous criticality of diversely random complex networks
We investigate collective synchronous behaviors in random complex networks of
limit-cycle oscillators with the non-identical asymmetric coupling scheme, and
find a uniform coupling criticality of collective synchronization which is
independent of complexity of network topologies. Numerically simulations on
categories of random complex networks have verified this conclusion.Comment: 8 pages, 4 figure
Attention-Based Models for Text-Dependent Speaker Verification
Attention-based models have recently shown great performance on a range of
tasks, such as speech recognition, machine translation, and image captioning
due to their ability to summarize relevant information that expands through the
entire length of an input sequence. In this paper, we analyze the usage of
attention mechanisms to the problem of sequence summarization in our end-to-end
text-dependent speaker recognition system. We explore different topologies and
their variants of the attention layer, and compare different pooling methods on
the attention weights. Ultimately, we show that attention-based models can
improves the Equal Error Rate (EER) of our speaker verification system by
relatively 14% compared to our non-attention LSTM baseline model.Comment: Submitted to ICASSP 201
Periodic Anderson model with Holstein phonons for the description of the Cerium volume collapse
Recent experiments have suggested that the electron-phonon coupling may play
an important role in the volume collapse transition
in Cerium. A minimal model for the description of such transition is the
periodic Anderson model. In order to better understand the effect of the
electron-phonon interaction on the volume collapse transition, we study the
periodic Anderson model with coupling between Holstein phonons and electrons in
the conduction band. We find that the electron-phonon coupling enhances the
volume collapse, which is consistent with experiments in Cerium. While we start
with the Kondo Volume Collapse scenario in mind, our results capture some
interesting features of the Mott scenario, such as a gap in the conduction
electron spectra which grows with the effective electron-phonon coupling.Comment: 8 pages, 6 figure
Multilingual Speech Recognition With A Single End-To-End Model
Training a conventional automatic speech recognition (ASR) system to support
multiple languages is challenging because the sub-word unit, lexicon and word
inventories are typically language specific. In contrast, sequence-to-sequence
models are well suited for multilingual ASR because they encapsulate an
acoustic, pronunciation and language model jointly in a single network. In this
work we present a single sequence-to-sequence ASR model trained on 9 different
Indian languages, which have very little overlap in their scripts.
Specifically, we take a union of language-specific grapheme sets and train a
grapheme-based sequence-to-sequence model jointly on data from all languages.
We find that this model, which is not explicitly given any information about
language identity, improves recognition performance by 21% relative compared to
analogous sequence-to-sequence models trained on each language individually. By
modifying the model to accept a language identifier as an additional input
feature, we further improve performance by an additional 7% relative and
eliminate confusion between different languages.Comment: Accepted in ICASSP 201
The X-ray binary 2S0114+650=LSI+65 010:A slow pulsar or tidally-induced pulsations?
The X-ray source 2S0114+650=LSI+65 010 is a binary system containing a B-type
primary and a low mass companion believed to be a neutron star. The system has
three reported periodicities: the orbital period, P{orb}~11.6 d, X-ray flaring
with P{flare}~2.7 hr, and a "superorbital" X-ray periodicity P{super}~30.7 d.
The objective of this paper is to show that the puzzling periodicities in the
system may be explained in the context of scenarios in which tidal interactions
drive oscillations in the B-supergiant star. We calculate the solution of the
equations of motion for one layer of small surface elements distributed along
the equator of the star, as they respond to the forces due to gas pressure,
centrifugal, coriolis, viscous forces, and the gravitational forces of both
stars. This calculation provides variability timescales that can be compared
with the observations. In addition, we use observational data obtained at the
Observatorio Astron\'omico Nacional en San Pedro M\'artir (OAN/SPM) between
1993-2004 to determine which of the periodicities may be present in the optical
region. We suggest that the tidal oscillations lead to a structured stellar
wind which, when fed to the neutron star, produces the X-ray modulations. The
connection between the stellar oscillations and the modulation of the mass
ejection may lie in the shear energy dissipation generated by the tangential
motions that are produced by the tidal interaction, particularly in the tidal
bulge region. The tidal oscillation scenario weakens the case for 2S0114+650
containing a magnetar descendent.Comment: 12 pages, 14 figure
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