45,105 research outputs found
A ball trunnion capture latch
The Ball Trunnion Capture Latch described was developed and designed to restrain a spacecraft deployable appendage in three translational directions. The latch is capable of supporting an appendage during STS ascent and landing events and is capable of releasing and restowing an appendage distorted in three translational directions by thermal growth. The requirements, design, analyses, and tests conducted on a development unit of the latch are discussed
High stability amplifier
An electrical RF signal amplifier for providing high temperature stability and RF isolation and comprised of an integrated circuit voltage regulator, a single transistor, and an integrated circuit operational amplifier mounted on a circuit board such that passive circuit elements are located on side of the circuit board while the active circuit elements are located on the other side is described. The active circuit elements are embedded in a common heat sink so that a common temperature reference is provided for changes in ambient temperature. The single transistor and operational amplifier are connected together to form a feedback amplifier powered from the voltage regulator with transistor implementing primarily the desired signal gain while the operational amplifier implements signal isolation. Further RF isolation is provided by the voltage regulator which inhibits cross-talk from other like amplifiers powered from a common power supply. Input and output terminals consisting of coaxial connectors are located on the sides of a housing in which all the circuit components and heat sink are located
Vocational education and economic environments : conflict or convergence?
A better understanding of the relationship between economic policies and human capital formation through vocational education and training (VET) will help both development strategists and education planners. With this in mind, the paper begins with a social systems model to trace the impact of the economic environment and policies on the internal and external efficiency of VET. It continues with a discussion of how specific economic policies can shape efforts to improve the internal and external efficiency of VET. Some evidence of this relationship is provided in a review of the VET experience in selected countries. The paper concludes with some tentative lessons for VET lending and sector work as drawn from this review and offers an agenda for the further study and validation of the economic environment thesis.Economic Theory&Research,Vocational&Technical Education,Teaching and Learning,Environmental Economics&Policies,Banks&Banking Reform
Sensitivity of a proposed space-based Cerenkov astrophysical-neutrino telescope (CHANT)
Neutrinos with energies in the PeV to EeV range produce upgoing extensive air
showers when they interact underground close enough to the surface of the
Earth. We study the possibility for detection of such showers with a system of
very wide field-of-view imaging atmospheric Cherenkov telescopes, named CHANT
for CHerenkov from Astrophysical Neutrinos Telescope, pointing down to a strip
below the Earth's horizon from space. We find that CHANT provides sufficient
sensitivity for the study of the astrophysical neutrino flux in a wide energy
range, from 10 PeV to 10 EeV. A space-based CHANT system can discover and study
in detail the cosmogenic neutrino flux originating from interactions of
ultra-high-energy cosmic rays in the intergalactic medium.Comment: 15 pages, 8 figures, accepted to Phys. Rev.
Learning to Skim Text
Recurrent Neural Networks are showing much promise in many sub-areas of
natural language processing, ranging from document classification to machine
translation to automatic question answering. Despite their promise, many
recurrent models have to read the whole text word by word, making it slow to
handle long documents. For example, it is difficult to use a recurrent network
to read a book and answer questions about it. In this paper, we present an
approach of reading text while skipping irrelevant information if needed. The
underlying model is a recurrent network that learns how far to jump after
reading a few words of the input text. We employ a standard policy gradient
method to train the model to make discrete jumping decisions. In our benchmarks
on four different tasks, including number prediction, sentiment analysis, news
article classification and automatic Q\&A, our proposed model, a modified LSTM
with jumping, is up to 6 times faster than the standard sequential LSTM, while
maintaining the same or even better accuracy
Coulomb Gap: How a Metal Film Becomes an Insulator
Electron tunneling measurements of the density of states (DOS) in ultra-thin
Be films reveal that a correlation gap mediates their insulating behavior. In
films with sheet resistance the correlation singularity appears
as the usual perturbative zero bias anomaly (ZBA) in the DOS. As R is
increased further, however, the ZBA grows and begins to dominate the DOS
spectrum. This evolution continues until a non-perturbative
Efros-Shklovskii Coulomb gap spectrum finally emerges in the highest R films.
Transport measurements of films which display this gap are well described by a
universal variable range hopping law .Comment: 4 figure
Superluminality in the Fierz--Pauli massive gravity
We study the propagation of helicity-1 gravitons in the Fierz--Pauli massive
gravity in nearly Minkowski backgrounds. We show that, generically, there exist
backgrounds consistent with field equations, in which the propagation is
superluminal. The relevant distances are much longer than the ultraviolet
cutoff length inherent in the Fierz--Pauli gravity, so superluminality occurs
within the domain of validity of the effective low energy theory. There remains
a possibility that one may get rid of this property by imposing fine tuning
relations between the coefficients in the non-linear generalization of the
Fierz--Pauli mass term, order by order in non-linearity; however, these
relations are not protected by any obvious symmetry. Thus, among others,
superluminality is a problematic property to worry about when attempting to
construct infrared modifications of General Relativity.Comment: 11 pages, no figure
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