3,354 research outputs found
Statistically Motivated Second Order Pooling
Second-order pooling, a.k.a.~bilinear pooling, has proven effective for deep
learning based visual recognition. However, the resulting second-order networks
yield a final representation that is orders of magnitude larger than that of
standard, first-order ones, making them memory-intensive and cumbersome to
deploy. Here, we introduce a general, parametric compression strategy that can
produce more compact representations than existing compression techniques, yet
outperform both compressed and uncompressed second-order models. Our approach
is motivated by a statistical analysis of the network's activations, relying on
operations that lead to a Gaussian-distributed final representation, as
inherently used by first-order deep networks. As evidenced by our experiments,
this lets us outperform the state-of-the-art first-order and second-order
models on several benchmark recognition datasets.Comment: Accepted to ECCV 2018. Camera ready version. 14 page, 5 figures, 3
table
Educational Effectiveness Function: An Algorithmic Methodology Uniting Instruments, Stakeholders, and Weighings into Numerical Effectiveness Indices
This study is based on effectiveness data collected from beginning or new vocational education teachers. The report illustrates multiattribute utility technology applied to 31 indicator items first reported in a publication of the Association for Supervision and Curriculum Development. Nineteen of the 31 items were aggregated into a teaching effectiveness component and 12 into a component for school effectiveness. The teaching and school effectiveness components then were aggregated into 5 educational effectiveness functions based on as many different weighings (0, 10. 0.25, 0.50, 0.75. and 0.90) of the teaching effectiveness component. Properties of the resulting distributions were presented. Finally, a more general model of educational effectiveness based on multiattribute utility technology was explored
Flow through a circular tube with a permeable Navier slip boundary
For Newtonian fluid flow in a right circular tube, with a linear Navier slip boundary, we show that a second flow field arises which is different to conventional Poiseuille flow in the sense that the corresponding pressure is quadratic in its dependence on the length along the tube, rather than a linear dependence which applies for conventional Poiseuille flow. However, assuming that the quadratic pressure is determined, say from known experimental data, then the new solution only exists for a precisely prescribed permeability along the boundary. While this cannot occur for conventional pipe flow, for fluid flow through carbon nanotubes embedded in a porous matrix, it may well be an entirely realistic possibility, and could well explain some of the high flow rates which have been reported in the literature. Alternatively, if the radial boundary flow is prescribed, then the new flow field exists only for a given quadratic pressure. Our primary purpose here is to demonstrate the existence of a new pipe flow field for a permeable Navier slip boundary and to present a numerical solution and two approximate analytical solutions. The maximum flow rate possible for the new solution is precisely twice that for the conventional Poiseuille flow, which occurs for constant inward directed flow across the boundary
Hazy Blue Worlds:A Holistic Aerosol Model for Uranus and Neptune, Including Dark Spots
We present a reanalysis (using the Minnaert limb-darkening approximation) of
visible/near-infrared (0.3 - 2.5 micron) observations of Uranus and Neptune
made by several instruments. We find a common model of the vertical aerosol
distribution that is consistent with the observed reflectivity spectra of both
planets, consisting of: 1) a deep aerosol layer with a base pressure > 5-7 bar,
assumed to be composed of a mixture of H2S ice and photochemical haze; 2) a
layer of photochemical haze/ice, coincident with a layer of high static
stability at the methane condensation level at 1-2 bar; and 3) an extended
layer of photochemical haze, likely mostly of the same composition as the
1-2-bar layer, extending from this level up through to the stratosphere, where
the photochemical haze particles are thought to be produced. For Neptune, we
find that we also need to add a thin layer of micron-sized methane ice
particles at ~0.2 bar to explain the enhanced reflection at longer
methane-absorbing wavelengths. We suggest that methane condensing onto the haze
particles at the base of the 1-2-bar aerosol layer forms ice/haze particles
that grow very quickly to large size and immediately 'snow out' (as predicted
by Carlson et al. 1988), re-evaporating at deeper levels to release their core
haze particles to act as condensation nuclei for H2S ice formation. In
addition, we find that the spectral characteristics of 'dark spots', such as
the Voyager-2/ISS Great Dark Spot and the HST/WFC3 NDS-2018, are well modelled
by a darkening or possibly clearing of the deep aerosol layer only.Comment: 58 pages, 23 figures, 4 table
Hazy Blue Worlds:A Holistic Aerosol Model for Uranus and Neptune, Including Dark Spots
We present a reanalysis (using the Minnaert limb-darkening approximation) of
visible/near-infrared (0.3 - 2.5 micron) observations of Uranus and Neptune
made by several instruments. We find a common model of the vertical aerosol
distribution that is consistent with the observed reflectivity spectra of both
planets, consisting of: 1) a deep aerosol layer with a base pressure > 5-7 bar,
assumed to be composed of a mixture of H2S ice and photochemical haze; 2) a
layer of photochemical haze/ice, coincident with a layer of high static
stability at the methane condensation level at 1-2 bar; and 3) an extended
layer of photochemical haze, likely mostly of the same composition as the
1-2-bar layer, extending from this level up through to the stratosphere, where
the photochemical haze particles are thought to be produced. For Neptune, we
find that we also need to add a thin layer of micron-sized methane ice
particles at ~0.2 bar to explain the enhanced reflection at longer
methane-absorbing wavelengths. We suggest that methane condensing onto the haze
particles at the base of the 1-2-bar aerosol layer forms ice/haze particles
that grow very quickly to large size and immediately 'snow out' (as predicted
by Carlson et al. 1988), re-evaporating at deeper levels to release their core
haze particles to act as condensation nuclei for H2S ice formation. In
addition, we find that the spectral characteristics of 'dark spots', such as
the Voyager-2/ISS Great Dark Spot and the HST/WFC3 NDS-2018, are well modelled
by a darkening or possibly clearing of the deep aerosol layer only.Comment: 58 pages, 23 figures, 4 table
Understanding the role of growth factors in modulating stem cell tenogenesis
Current treatments for tendon injuries often fail to fully restore joint biomechanics leading to the recurrence of symptoms, and thus resulting in a significant health problem with a relevant social impact worldwide. Cell-based approaches involving the use of stem cells might enable tailoring a successful tendon regeneration outcome. As growth factors (GFs) powerfully regulate the cell biological response, their exogenous addition can further stimulate stem cells into the tenogenic lineage, which might eventually depend on stem cells source. In the present study we investigate the tenogenic differentiation potential of human- amniotic fluid stem cells (hAFSCs) and adipose-derived stem cells (hASCs) with several GFs associated to tendon development and healing; namely, EGF, bFGF, PDGF-BB and TGF-β1. Stem cells response to biochemical stimuli was studied by screening of tendon-related genes (collagen type I, III, decorin, tenascin C and scleraxis) and proteins found in tendon extracellular matrix (ECM) (Collagen I, III, and Tenascin C). Despite the fact that GFs did not seem to influence the synthesis of tendon ECM proteins, EGF and bFGF influenced the expression of tendon-related genes in hAFSCs, while EGF and PDGF-BB stimulated the genetic expression in hASCs. Overall results on cellular alignment morphology, immunolocalization and PCR analysis indicated that both stem cell source can be biochemically induced towards tenogenic commitment, validating the potential of hASCs and hAFSCs for tendon regeneration strategies.Authors thank the Portuguese Foundation for Science and Technology (FCT) for the research project BIBS (PTDC/CVT/102972/2008) and for the post-doc fellowship grant: SFRH/BPD/86775/2012. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Electric Field-Tuned Topological Phase Transition in Ultra-Thin Na3Bi - Towards a Topological Transistor
The electric field induced quantum phase transition from topological to
conventional insulator has been proposed as the basis of a topological field
effect transistor [1-4]. In this scheme an electric field can switch 'on' the
ballistic flow of charge and spin along dissipationless edges of the
two-dimensional (2D) quantum spin Hall insulator [5-9], and when 'off' is a
conventional insulator with no conductive channels. Such as topological
transistor is promising for low-energy logic circuits [4], which would
necessitate electric field-switched materials with conventional and topological
bandgaps much greater than room temperature, significantly greater than
proposed to date [6-8]. Topological Dirac semimetals(TDS) are promising systems
in which to look for topological field-effect switching, as they lie at the
boundary between conventional and topological phases [3,10-16]. Here we use
scanning probe microscopy/spectroscopy (STM/STS) and angle-resolved
photoelectron spectroscopy (ARPES) to show that mono- and bilayer films of TDS
Na3Bi [3,17] are 2D topological insulators with bulk bandgaps >400 meV in the
absence of electric field. Upon application of electric field by doping with
potassium or by close approach of the STM tip, the bandgap can be completely
closed then re-opened with conventional gap greater than 100 meV. The large
bandgaps in both the conventional and quantum spin Hall phases, much greater
than the thermal energy kT = 25 meV at room temperature, suggest that ultrathin
Na3Bi is suitable for room temperature topological transistor operation
Two-step stabilization of orbital order and the dynamical frustration of spin in the model charge-transfer insulator KCuF3
We report a combined experimental and theoretical study of KCuF3, which
offers - because of this material's relatively simple lattice structure and
valence configuration (d9, i.e., one hole in the d-shell) - a particularly
clear view of the essential role of the orbital degree of freedom in governing
the dynamical coupling between the spin and lattice degrees of freedom. We
present Raman and x-ray scattering evidence that the phase behaviour of KCuF3
is dominated above the Neel temperature (T_N = 40 K) by coupled orbital/lattice
fluctuations that are likely associated with rotations of the CuF6 octahedra,
and we show that these orbital fluctuations are interrupted by a static
structural distortion that occurs just above T_N. A detailed model of the
orbital and magnetic phases of KCuF3 reveals that these orbital fluctuations -
and the related frustration of in-plane spin-order-are associated with the
presence of nearly degenerate low-energy spin-orbital states that are highly
susceptible to thermal fluctuations over a wide range of temperatures. A
striking implication of these results is that the ground state of KCuF3 at
ambient pressure lies near a quantum critical point associated with an
orbital/spin liquid phase that is obscured by emergent Neel ordering of the
spins; this exotic liquid phase might be accessible via pressure studies.Comment: 13 pages, 3 figure
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