5,260 research outputs found
Adapting Visual Question Answering Models for Enhancing Multimodal Community Q&A Platforms
Question categorization and expert retrieval methods have been crucial for
information organization and accessibility in community question & answering
(CQA) platforms. Research in this area, however, has dealt with only the text
modality. With the increasing multimodal nature of web content, we focus on
extending these methods for CQA questions accompanied by images. Specifically,
we leverage the success of representation learning for text and images in the
visual question answering (VQA) domain, and adapt the underlying concept and
architecture for automated category classification and expert retrieval on
image-based questions posted on Yahoo! Chiebukuro, the Japanese counterpart of
Yahoo! Answers.
To the best of our knowledge, this is the first work to tackle the
multimodality challenge in CQA, and to adapt VQA models for tasks on a more
ecologically valid source of visual questions. Our analysis of the differences
between visual QA and community QA data drives our proposal of novel
augmentations of an attention method tailored for CQA, and use of auxiliary
tasks for learning better grounding features. Our final model markedly
outperforms the text-only and VQA model baselines for both tasks of
classification and expert retrieval on real-world multimodal CQA data.Comment: Submitted for review at CIKM 201
Electrical current distribution across a metal-insulator-metal structure during bistable switching
Combining scanning electron microscopy (SEM) and electron-beam-induced
current (EBIC) imaging with transport measurements, it is shown that the
current flowing across a two-terminal oxide-based capacitor-like structure is
preferentially confined in areas localized at defects. As the thin-film device
switches between two different resistance states, the distribution and
intensity of the current paths, appearing as bright spots, change. This implies
that switching and memory effects are mainly determined by the conducting
properties along such paths. A model based on the storage and release of charge
carriers within the insulator seems adequate to explain the observed memory
effect.Comment: 8 pages, 7 figures, submitted to J. Appl. Phy
Optimising Spectroscopic and Photometric Galaxy Surveys: Efficient Target Selection and Survey Strategy
The next generation of spectroscopic surveys will have a wealth of
photometric data available for use in target selection. Selecting the best
targets is likely to be one of the most important hurdles in making these
spectroscopic campaigns as successful as possible. Our ability to measure dark
energy depends strongly on the types of targets that we are able to select with
a given photometric data set. We show in this paper that we will be able to
successfully select the targets needed for the next generation of spectroscopic
surveys. We also investigate the details of this selection, including
optimisation of instrument design and survey strategy in order to measure dark
energy. We use color-color selection as well as neural networks to select the
best possible emission line galaxies and luminous red galaxies for a
cosmological survey. Using the Fisher matrix formalism we forecast the
efficiency of each target selection scenario. We show how the dark energy
figures of merit change in each target selection regime as a function of target
type, survey time, survey density and other survey parameters. We outline the
optimal target selection scenarios and survey strategy choices which will be
available to the next generation of spectroscopic surveys.Comment: 16 pages, 22 figures, accepted to MNRAS in dec 201
The number of maximum matchings in a tree
We determine upper and lower bounds for the number of maximum matchings
(i.e., matchings of maximum cardinality) of a tree of given order.
While the trees that attain the lower bound are easily characterised, the trees
with largest number of maximum matchings show a very subtle structure. We give
a complete characterisation of these trees and derive that the number of
maximum matchings in a tree of order is at most (the
precise constant being an algebraic number of degree 14). As a corollary, we
improve on a recent result by G\'orska and Skupie\'n on the number of maximal
matchings (maximal with respect to set inclusion).Comment: 38 page
Mechanism and Control of HighâIntensityâLaserâDriven Proton Acceleration
We discuss the optimization and control of laserâdriven proton beams. Specifically, we report on the dependence of highâintensity laser accelerated proton beams on the material properties of various thinâfilm targets. Evidence of starâlike filaments and beam hollowing (predicted from the electrothermal instability theory) is observed on Radiochromic Film (RCF) and CRâ39 nuclear track detectors. The proton beam spatial profile is found to depend on initial target conductivity and target thickness. For resistive target materials, these structured profiles are explained by the inhibition of current, due to the lack of a return current. The conductors, however, can support large propagating currents due to the substantial cold return current which is composed of free charge carriers in the conduction band to neutralize the plasma from the interaction. The empirical plot shows relationship between the maximum proton energy and the target thickness also supports the return current and target normal sheath acceleration (TNSA) theory. We have also observed filamentary structures in the proton beam like those expected from the Weibel instability in the electron beam. Along with the ion acceleration, a clear electron beam is detected by the RCF along the tangent to the target, which is also the surface direction of target plate. © 2004 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87542/2/595_1.pd
Imaging microvascular dynamics noninvasively with realtime photoacoustic microscopy
A realtime photoacoustic microscopy system consisting of a high-repetition rate pulsed laser, high-frequency (30 MHz) ultrasound array transducer, and realtime receiving system was used to visualize microvessels pulsations over a cardiac cycle. The system offers 100 Όm lateral spatial resolution, 25 ”m axial spatial resolution, and can image at a rate of 83 frames per second. The system shows promise for visualizing time-varying processes in the microvasculature
UHECRs from magnetic reconnection in relativistic jets
Ultra-high energy cosmic rays (UHECRs) may be produced in active galactic
nuclei (AGN) or gamma-ray burst (GRB) jets. I argue that magnetic reconnection
in jets can accelerate UHECRs rather independently of physical processes in the
magnetic dissipation region. First order Fermi acceleration can efficiently
take place in the region where the unreconnected (upstream) magnetized fluid
converges into the reconnection layer. I find that protons can reach energies
up to E~10^{20} eV in GRB and powerful AGN jets while iron nuclei can reach
similar energies in AGN jets of more moderate luminosity.Comment: 5 pages, 2 figures, MNRAS Letters, in press, Sect. 3.3 added to match
the published versio
Magnetic Susceptibility: Solutions, Emulsions, and Cells
Differences in magnetic susceptibility between various compartments in
heterogeneous samples can introduce unanticipated complications to NMR spectra.
On the other hand, an understanding of these effects at the level of the
underlying physical principles has led to the development of several
experimental techniques that provide data on cellular function that are unique
to NMR spectroscopy. To illustrate some key features of susceptibility effects
we present, among a more general overview, results obtained with red blood
cells and a recently described model system involving diethyl phthalate in
water. This substance forms a relatively stable emulsion in water and yet it
has a significant solubility of 5 mmol/L at room temperature; thus, the NMR
spectrum has twice as many resonances as would be expected for a simple
solution. What determines the relative intensities of the two families of peaks
and can their frequencies be manipulated experimentally in a predictable way?
The theory used to interpret the NMR spectra from the model system and cells
was first developed in the context of electrostatics nearly a century ago, and
yet some of its underlying assumptions now warrant closer scrutiny. While this
insight is used in a practical way in this article, the accompanying article
deals with the mathematics and physics behind this new analysis.Comment: 15 pages, 9 figures, v2: updated to resemble the published versio
Photoacoustic imaging of the microvasculature with a high-frequency ultrasound array transducer
Visualization of microvascular networks could provide new information about function and disease. We demonstrate the capabilities of a 30-MHz ultrasound array system for photoacoustic microscopy of small (â€300ÎŒm) vessels in a rat. 3D images obtained by translating the array in the elevation direction are compared with photographs of excised skin. The system is shown to have 100-ÎŒm lateral resolution, 25-ÎŒm axial resolution, and 3-mm imaging depth. To our knowledge this is the first report on photoacoustic microscopy of the microvasculature with a high-frequency array transducer. It is anticipated that the system can be used for studying and diagnosing a number of diseases including cancer, atherosclerosis, dermatological disorders, and peripheral microvascular complications in diabetes
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