27,386 research outputs found
Comparative analysis of VDMOS/LDMOS power transistors for RF amplifiers
A comparison between the RF performance of vertical and lateral power MOSFETs is presented. The role of each parasitic parameter in the assessment of the power gain, 1-dB compression point, efficiency, stability, and output matching is evaluated quantitatively using new analytical expressions derived from a ten-element model. This study reveals that the contribution of the parasitic parameter on degradation of performance depends upon the specific technology and generic perceptions of source inductance and feedback capacitance in VDMOS degradation may not always hold. This conclusion is supported by a detailed analysis of three devices of the same power rating from three different commercial vendors. A methodology for optimizing a device technology, specifically for RF performance and power amplifier performance is demonstrated
Discrete and finite Genral Relativity
We develop the General Theory of Relativity in a formalism with extended
causality that describes physical interaction through discrete, transversal and
localized pointlike fields. The homogeneous field equations are then solved for
a finite, singularity-free, point-like field that we associate to a ``classical
graviton". The standard Einstein's continuous formalism is retrieved by means
of an averaging process, and its continuous solutions are determined by the
chosen imposed symetry. The Schwarzschild metric is obtained by the imposition
of spherical symmetry on the averaged field.Comment: Modified conform the version to appear in Classical and Quantum
Gravit
Going Deeper with Semantics: Video Activity Interpretation using Semantic Contextualization
A deeper understanding of video activities extends beyond recognition of
underlying concepts such as actions and objects: constructing deep semantic
representations requires reasoning about the semantic relationships among these
concepts, often beyond what is directly observed in the data. To this end, we
propose an energy minimization framework that leverages large-scale commonsense
knowledge bases, such as ConceptNet, to provide contextual cues to establish
semantic relationships among entities directly hypothesized from video signal.
We mathematically express this using the language of Grenander's canonical
pattern generator theory. We show that the use of prior encoded commonsense
knowledge alleviate the need for large annotated training datasets and help
tackle imbalance in training through prior knowledge. Using three different
publicly available datasets - Charades, Microsoft Visual Description Corpus and
Breakfast Actions datasets, we show that the proposed model can generate video
interpretations whose quality is better than those reported by state-of-the-art
approaches, which have substantial training needs. Through extensive
experiments, we show that the use of commonsense knowledge from ConceptNet
allows the proposed approach to handle various challenges such as training data
imbalance, weak features, and complex semantic relationships and visual scenes.Comment: Accepted to WACV 201
Medical education on fitness to drive : a survey of all UK medical schools
Aim: To identify the extent to which medical aspects of fitness to drive (FTD) are taught within UK medical schools.
Methods: A survey of all 32 UK medical schools. In-depth interviews with a range of staff at two medical schools; telephone survey of 30 schools.
Results: Two thirds of schools reported specific teaching on medical aspects of FTD but few covered it in any depth or in relation to specific medical conditions. Only one school taught FTD in relation to elderly medicine. FTD was an examination topic at only 12 schools.
Conclusion: Teaching on FTD is inconsistent across UK medical schools. Many new doctors will graduate with limited knowledge of medical aspects of FTD
Including food systems, biodiversity, nutrition and health in the Post-2020 Global Biodiversity Framework: a submission from the Alliance of Bioversity International and the International Center for Tropical Agriculture.
A Compound model for the origin of Earth's water
One of the most important subjects of debate in the formation of the solar
system is the origin of Earth's water. Comets have long been considered as the
most likely source of the delivery of water to Earth. However, elemental and
isotopic arguments suggest a very small contribution from these objects. Other
sources have also been proposed, among which, local adsorption of water vapor
onto dust grains in the primordial nebula and delivery through planetesimals
and planetary embryos have become more prominent. However, no sole source of
water provides a satisfactory explanation for Earth's water as a whole. In view
of that, using numerical simulations, we have developed a compound model
incorporating both the principal endogenous and exogenous theories, and
investigating their implications for terrestrial planet formation and
water-delivery. Comets are also considered in the final analysis, as it is
likely that at least some of Earth's water has cometary origin. We analyze our
results comparing two different water distribution models, and complement our
study using D/H ratio, finding possible relative contributions from each
source, focusing on planets formed in the habitable zone. We find that the
compound model play an important role by showing more advantage in the amount
and time of water-delivery in Earth-like planets.Comment: Accepted for publication in The Astrophysical Journa
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