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Electrical capacitance tomography for flow imaging: System model for development of image reconstruction algorithms and design of primary sensors
A software tool that facilitates the development of image reconstruction algorithms, and the design of optimal capacitance sensors for a capacitance-based 12-electrode tomographic flow imaging system are described. The core of this software tool is the finite element (FE) model of the sensor, which is implemented in OCCAM-2 language and run on the Inmos T800 transputers. Using the system model, the in-depth study of the capacitance sensing fields and the generation of flow model data are made possible, which assists, in a systematic approach, the design of an improved image-reconstruction algorithm. This algorithm is implemented on a network of transputers to achieve a real-time performance. It is found that the selection of the geometric parameters of a 12-electrode sensor has significant effects on the sensitivity distributions of the capacitance fields and on the linearity of the capacitance data. As a consequence, the fidelity of the reconstructed images are affected. Optimal sensor designs can, therefore, be provided, by accommodating these effect
What and how: doing good research with young people, digital intimacies, and relationships and sex education
© 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. As part of a project funded by the Wellcome Trust, we held a one-day symposium, bringing together researchers, practitioners, and policymakers, to discuss priorities for research on relationships and sex education (RSE) in a world where young people increasingly live, experience, and augment their relationships (whether sexual or not) within digital spaces. The introduction of statutory RSE in schools in England highlights the need to focus on improving understandings of young people and digital intimacies for its own sake, and to inform the development of learning resources. We call for more research that puts young people at its centre; foregrounds inclusivity; and allows a nuanced discussion of pleasures, harms, risks, and rewards, which can be used by those working with young people and those developing policy. Generating such research is likely to be facilitated by participation, collaboration, and communication with beneficiaries, between disciplines and across sectors. Taking such an approach, academic researchers, practitioners, and policymakers agree that we need a better understanding of RSE’s place in lifelong learning, which seeks to understand the needs of particular groups, is concerned with non-sexual relationships, and does not see digital intimacies as disconnected from offline everyday ‘reality’
Astrophysical implications of hypothetical stable TeV-scale black holes
We analyze macroscopic effects of TeV-scale black holes, such as could
possibly be produced at the LHC, in what is regarded as an extremely
hypothetical scenario in which they are stable and, if trapped inside Earth,
begin to accrete matter. We examine a wide variety of TeV-scale gravity
scenarios, basing the resulting accretion models on first-principles, basic,
and well-tested physical laws. These scenarios fall into two classes, depending
on whether accretion could have any macroscopic effect on the Earth at times
shorter than the Sun's natural lifetime. We argue that cases with such effect
at shorter times than the solar lifetime are ruled out, since in these
scenarios black holes produced by cosmic rays impinging on much denser white
dwarfs and neutron stars would then catalyze their decay on timescales
incompatible with their known lifetimes. We also comment on relevant lifetimes
for astronomical objects that capture primordial black holes. In short, this
study finds no basis for concerns that TeV-scale black holes from the LHC could
pose a risk to Earth on time scales shorter than the Earth's natural lifetime.
Indeed, conservative arguments based on detailed calculations and the
best-available scientific knowledge, including solid astronomical data,
conclude, from multiple perspectives, that there is no risk of any significance
whatsoever from such black holes.Comment: Version2: Minor corrections/fixed typos; updated reference
Testing extra dimensions with boundaries using Newton's law modifications
Extra dimensions with boundaries are often used in the literature, to provide
phenomenological models that mimic the standard model. In this context, we
explore possible modifications to Newton's law due to the existence of an
extra-dimensional space, at the boundary of which the gravitational field obeys
Dirichlet, Neumann or mixed boundary conditions. We focus on two types of extra
space, namely, the disk and the interval. As we prove, in order to have a
consistent Newton's law modification (i.e., of the Yukawa-type), some of the
extra-dimensional spaces that have been used in the literature, must be ruled
out.Comment: Published version, title changed, 6 figure
How Protostellar Outflows Help Massive Stars Form
We consider the effects of an outflow on radiation escaping from the
infalling envelope around a massive protostar. Using numerical radiative
transfer calculations, we show that outflows with properties comparable to
those observed around massive stars lead to significant anisotropy in the
stellar radiation field, which greatly reduces the radiation pressure
experienced by gas in the infalling envelope. This means that radiation
pressure is a much less significant barrier to massive star formation than has
previously been thought.Comment: 4 pages, 2 figures, emulateapj, accepted for publication in ApJ
Letter
Improved Torsion Pendulum for Ground Testing of LISA Displacement Sensors
We discuss a new torsion pendulum design for ground testing of prototype LISA
(Laser Interferometer Space Antenna) displacement sensors. This new design is
directly sensitive to net forces and therefore provides a more representative
test of the noisy forces and parasitic stiffnesses acting on the test mass as
compared to previous ground-based experiments. We also discuss a specific
application to the measurement of thermal gradient effects.Comment: 4 pages 1 figure, to appear in the Proceedings of the 10th Marcel
Grossmann Meeting on General Relativit
Tests of the Gravitational Inverse-Square Law below the Dark-Energy Length Scale
We conducted three torsion-balance experiments to test the gravitational
inverse-square law at separations between 9.53 mm and 55 micrometers, probing
distances less than the dark-energy length scale m. We find with 95% confidence
that the inverse-square law holds () down to a length scale
m and that an extra dimension must have a size m.Comment: 4 pages, 6 figure
Galactic Center Extinction: Evidence for Metallic Needles in the General Interstellar Medium
The extinction curve derived from ISO mid-infrared (IR) observations of the
Galactic center (GC) exhibits a surprisingly flat behavior in the ~ 3 to 8
micron region, contrary to the deep minimum expected from standard interstellar
dust models consisting of bare silicate and graphite dust particles. We show
that this extinction is likely caused by the presence of metallic needles in
the interstellar medium (ISM) towards the Galactic center. If the needles
contribute only to the 3 - 8 micron extinction, they must have a long
wavelength cutoff at ~ 8 microns, and therefore a typical length over radius
ratio of about 600, smaller than the 3000 aspect ratio determined for the
needles in Cas A. Homogeneously distributed throughout the ISM, they comprise
only a minor mass fraction of the ISM, with a needle-to-H mass ratio of
\~5x10^{-6}, which is equivalent to 0.14% of the silicate dust mass. Their
total ISM abundance can then be readily explained by the combined production in
SNe and O-rich stellar outflows. It is currently unclear how universal the GC
extinction law is. Local 2 - 5 micron extinction measurements seem to be
consistent with the standard extinction law, suggesting a non uniform
distribution of needles in the ISM. The GC observations show that metallic
needles, in spite of their low abundance or non uniform distribution, can be
the dominant source of opacity in the 3 - 8 micron wavelength region. However,
expelled into the intergalactic medium, their abundance is too low to cause any
dimming of cosmological sources, and their length is too short to make them a
significant source of submillimeter emission.Comment: 9 pages, 1 figure, to appear in the ApJ Letter
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