1,531 research outputs found
Free bianalytic maps between spectrahedra and spectraballs in a generic setting
Given a tuple of matrices, the collection of
those tuples of matrices (of the same size) such that is called a spectraball . Likewise,
given a tuple of matrices the collection of
tuples of matrices (of the same size) such that is a free spectrahedron
. Assuming and are irreducible, plus an additional mild
hypothesis, there is a free bianalytic map
normalized by and if and only if
and spans an algebra. Moreover is unique, rational and has an elegant
algebraic representation.Comment: 19 page
A Comparison of the Financial Characteristics of NAFTA and Latin American Manufacturing Firms
Comparing the financial characteristics of firms in different countries and different regions has been a popular research topic in finance. However, NAFTA and Latin American manufacturing firms have never been compared. In this paper, we undertake such a study with the MANOVA (Multivariate Analysis of Variance) method and with data drawn from the Research Insight/Global Vintage database in October 2015. Our findings indicate that NAFTA manufacturing firms have less liquidity risk, but more financial risk, compared with Latin American Manufacturing firms. NAFTA manufacturing firms have significantly higher returns on equity due to achieving higher returns on assets and using more financial leverage. Latin American manufacturing firms have more efficient inventory management. However, NAFTA manufacturing firms have more efficient accounts receivable management and total assets management
Graphene field-effect transistors based on boron nitride gate dielectrics
Graphene field-effect transistors are fabricated utilizing single-crystal
hexagonal boron nitride (h-BN), an insulating isomorph of graphene, as the gate
dielectric. The devices exhibit mobility values exceeding 10,000 cm2/V-sec and
current saturation down to 500 nm channel lengths with intrinsic
transconductance values above 400 mS/mm. The work demonstrates the favorable
properties of using h-BN as a gate dielectric for graphene FETs.Comment: 4 pages, 8 figure
Improved GNSS-R bi-static altimetry and independent digital elevation models of Greenland and Antarctica from TechDemoSat-1
Improved digital elevation models (DEMs) of the Antarctic and Greenland ice sheets are presented, which have been derived from Global Navigation Satellite Systems-Reflectometry (GNSS-R). This builds on a previous study (Cartwright et al., 2018) using GNSS-R to derive an Antarctic DEM but uses improved processing and an additional 13 months of measurements, totalling 46 months of data from the UK TechDemoSat-1 satellite. A median bias of under 10 m and root-mean-square errors (RMSEs) of under 53 m for the Antarctic and 166 m for Greenland are obtained, as compared to existing DEMs. The results represent, compared to the earlier study, a halving of the median bias to 9 m, an improvement in coverage of 18 %, and a 4 times higher spatial resolution (now gridded at 25 km). In addition, these are the first published satellite altimetry measurements of the region surrounding the South Pole. Comparisons south of 88∘ S yield RMSEs of less than 33 m when compared to NASA's Operation IceBridge measurements. Differences between DEMs are explored, the limitations of the technique are noted, and the future potential of GNSS-R for glacial ice studies is discussed
Effect of herbicide concentrations on centimetre-scale vertical variability of metabolic and cometabolic mineralization potentials around the groundwater table
Electronic compressibility of layer polarized bilayer graphene
We report on a capacitance study of dual gated bilayer graphene. The measured
capacitance allows us to probe the electronic compressibility as a function of
carrier density, temperature, and applied perpendicular electrical displacement
D. As a band gap is induced with increasing D, the compressibility minimum at
charge neutrality becomes deeper but remains finite, suggesting the presence of
localized states within the energy gap. Temperature dependent capacitance
measurements show that compressibility is sensitive to the intrinsic band gap.
For large displacements, an additional peak appears in the compressibility as a
function of density, corresponding to the presence of a 1-dimensional van Hove
singularity (vHs) at the band edge arising from the quartic bilayer graphene
band structure. For D > 0, the additional peak is observed only for electrons,
while D < 0 the peak appears only for holes. This asymmetry that can be
understood in terms of the finite interlayer separation and may be useful as a
direct probe of the layer polarization
Graphene microwave transistors on sapphire substrates
We have developed metal-oxide graphene field-effect transistors (MOGFETs) on
sapphire substrates working at microwave frequencies. For monolayers, we obtain
a transit frequency up to ~ 80 GHz for a gate length of 200 nm, and a power
gain maximum frequency of about ~ 3 GHz for this specific sample. Given the
strongly reduced charge noise for nanostructures on sapphire, the high
stability and high performance of this material at low temperature, our MOGFETs
on sapphire are well suited for a cryogenic broadband low-noise amplifier
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