79,445 research outputs found
Understanding Task Design Trade-offs in Crowdsourced Paraphrase Collection
Linguistically diverse datasets are critical for training and evaluating
robust machine learning systems, but data collection is a costly process that
often requires experts. Crowdsourcing the process of paraphrase generation is
an effective means of expanding natural language datasets, but there has been
limited analysis of the trade-offs that arise when designing tasks. In this
paper, we present the first systematic study of the key factors in
crowdsourcing paraphrase collection. We consider variations in instructions,
incentives, data domains, and workflows. We manually analyzed paraphrases for
correctness, grammaticality, and linguistic diversity. Our observations provide
new insight into the trade-offs between accuracy and diversity in crowd
responses that arise as a result of task design, providing guidance for future
paraphrase generation procedures.Comment: Published at ACL 201
Possible TeV Source Candidates In The Unidentified EGRET Sources
We study the -ray emission from the pulsar magnetosphere based on
outer gap models, and the TeV radiation from pulsar wind nebulae (PWNe) through
inverse Compton scattering using a one-zone model. We showed previously that
GeV radiation from the magnetosphere of mature pulsars with ages of years old can contribute to the high latitude unidentified EGRET
sources. We carry out Monte Carlo simulations of -ray pulsars in the
Galaxy and the Gould Belt, assuming the pulsar birth rate, initial position,
proper motion velocity, period, and magnetic field distribution and evolution
based on observational statistics. We select from the simulation a sample of
mature pulsars in the Galactic plane () and in the high
latitude () which could be detected by EGRET. The TeV flux from
the pulsar wind nebulae of our simulated sample through the inverse Compton
scattering by relativistic electrons on the microwave cosmic background and
synchrotron seed photons are calculated. The predicted fluxes are consistent
with the present observational constraints. We suggest that strong EGRET
sources can be potential TeV source candidates for present and future
ground-based TeV telescopes.Comment: Minor changes, MNRAS in pres
Characterization Of Thermal Stresses And Plasticity In Through-Silicon Via Structures For Three-Dimensional Integration
Through-silicon via (TSV) is a critical element connecting stacked dies in three-dimensional (3D) integration. The mismatch of thermal expansion coefficients between the Cu via and Si can generate significant stresses in the TSV structure to cause reliability problems. In this study, the thermal stress in the TSV structure was measured by the wafer curvature method and its unique stress characteristics were compared to that of a Cu thin film structure. The thermo-mechanical characteristics of the Cu TSV structure were correlated to microstructure evolution during thermal cycling and the local plasticity in Cu in a triaxial stress state. These findings were confirmed by microstructure analysis of the Cu vias and finite element analysis (FEA) of the stress characteristics. In addition, the local plasticity and deformation in and around individual TSVs were measured by synchrotron x-ray microdiffraction to supplement the wafer curvature measurements. The importance and implication of the local plasticity and residual stress on TSV reliabilities are discussed for TSV extrusion and device keep-out zone (KOZ).Microelectronics Research Cente
Modelling total solar irradiance since 1878 from simulated magnetograms
We present a new model of total solar irradiance (TSI) based on magnetograms
simulated with a surface flux transport model (SFTM) and the SATIRE (Spectral
And Total Irradiance REconstructions) model. Our model provides daily maps of
the distribution of the photospheric field and the TSI starting from 1878. We
first calculate the magnetic flux on the solar surface emerging in active and
ephemeral regions. The evolution of the magnetic flux in active regions is
computed using a surface flux transport model fed with the observed record of
sunspot group areas and positions. The magnetic flux in ephemeral regions is
treated separately using the concept of overlapping cycles. To model the
ephemeral region cycles, we assume that their length and amplitude are related
to that of the sunspot cycles. We then use a version of the SATIRE model to
compute the TSI. The area coverage and the distribution of different magnetic
features as a function of time, which are required by SATIRE, are extracted
from the simulated magnetograms and the modelled ephemeral region magnetic
flux. Previously computed intensity spectra of the various types of magnetic
features are employed. Our model reproduces the PMOD composite of TSI
measurements starting from 1978 at daily and rotational timescales more
accurately than the previous version of the SATIRE model computing TSI over
this period of time. The simulated magnetograms provide a more realistic
representation of the evolution of the magnetic field on the photosphere and
also allow us to make use of information on the spatial distribution of the
magnetic fields before the times when observed magnetograms were available. We
find that the secular increase in TSI since 1878 is fairly stable to
modifications of the treatment of the ephemeral region magnetic flux
Some symmetry properties of spin currents and spin polarizations in multi-terminal mesoscopic spin-orbit coupled systems
We study theoretically some symmetry properties of spin currents and spin
polarizations in multi-terminal mesoscopic spin-orbit coupled systems. Based on
a scattering wave function approach, we show rigorously that in the equilibrium
state no finite spin polarizations can exist in a multi-terminal mesoscopic
spin-orbit coupled system (both in the leads and in the spin-orbit coupled
region) and also no finite equilibrium terminal spin currents can exist. By use
of a typical two-terminal mesoscopic spin-orbit coupled system as the example,
we show explicitly that the nonequilibrium terminal spin currents in a
multi-terminal mesoscopic spin-orbit coupled system are non-conservative in
general. This non-conservation of terminal spin currents is not caused by the
use of an improper definition of spin current but is intrinsic to
spin-dependent transports in mesoscopic spin-orbit coupled systems. We also
show that the nonequilibrium lateral edge spin accumulation induced by a
longitudinal charge current in a thin strip of \textit{finite} length of a
two-dimensional electronic system with intrinsic spin-orbit coupling may be
non-antisymmetric in general, which implies that some cautions may need to be
taken when attributing the occurrence of nonequilibrium lateral edge spin
accumulation induced by a longitudinal charge current in such a system to an
intrinsic spin Hall effect.Comment: 11 pages, 6 figure
Magnetization Losses in Multifilament Coated Superconductors
We report the results of a study of the magnetization losses in experimental
multifilament, as well as control (uniform), coated superconductors exposed to
time-varying magnetic field of various frequencies. Both the hysteresis loss,
proportional to the sweep rate of the applied magnetic field, and the coupling
loss, proportional to the square of the sweep rate, have been observed. A
scaling is found that allows us to quantify each of these contributions and
extrapolate the results of the experiment beyond the envelope of accessible
field amplitude and frequency. The combined loss in the multifilament conductor
is reduced by about 90% in comparison with the uniform conductor at full field
penetration at sweep rate as high as 3T/s
Effect of Diethylenetriamine and Triethylamine sensitization on the critical diameter of Nitromethane
In this work, the critical diameter for detonation was measured for Nitromethane (NM) sensitized with two different amines: Diethylenetriamine (DETA) and Triethylamine (TEA). The critical diameter in glass and polyvinylchloride tubes is found to decrease rapidly as the amount of sensitizer is increased, then increase past a critical amount of sensitizer. Thus the critical diameter reaches a minimum at a critical concentration of sensitizer. It was also found that the critical diameter is lower with DETA than with TEA
Thermomechanical Characterization And Modeling For TSV Structures
Continual scaling of devices and on-chip wiring has brought significant challenges for materials and processes beyond the 32-nm technology node in microelectronics. Recently, three-dimensional (3-D) integration with through-silicon vias (TSVs) has emerged as an effective solution to meet the future technology requirements. Among others, thermo-mechanical reliability is a key concern for the development of TSV structures used in die stacking as 3-D interconnects. This paper presents experimental measurements of the thermal stresses in TSV structures and analyses of interfacial reliability. The micro-Raman measurements were made to characterize the local distribution of the near-surface stresses in Si around TSVs. On the other hand, the precision wafer curvature technique was employed to measure the average stress and deformation in the TSV structures subject to thermal cycling. To understand the elastic and plastic behavior of TSVs, the microstructural evolution of the Cu vias was analyzed using focused ion beam (FIB) and electron backscattering diffraction (EBSD) techniques. Furthermore, the impact of thermal stresses on interfacial reliability of TSV structures was investigated by a shear-lag cohesive zone model that predicts the critical temperatures and critical via diameters.Microelectronics Research Cente
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