38,502 research outputs found
Digital automatic gain amplifier
A circuit is described for adjusting the amplitude of a reference signal to a predetermined level so as to permit subsequent data signals to be interpreted correctly. The circuit includes an operational amplifier having a feedback circuit connected between an output terminal and an input terminal; a bank of relays operably connected to a plurality of resistors; and a comparator comparing an output voltage of the amplifier with a reference voltage and generating a compared signal responsive thereto. Means is provided for selectively energizing the relays according to the compared signal from the comparator until the output signal from the amplifier equals to the reference signal. A second comparator is provided for comparing the output of the amplifier with a second voltage source so as to illuminate a lamp when the output signal from the amplifier exceeds the second voltage
Motor drivers for dc brushless motors
Nondestructive tests of motor drivers for delta wound dc brushless motor
Enhanced and directional single photon emission in hyperbolic metamaterials
We propose an approach to enhance and direct the spontaneous emission from
isolated emitters embedded inside hyperbolic metamaterials into single photon
beams. The approach rests on collective plasmonic Bloch modes of hyperbolic
metamaterials which propagate in highly directional beams called quantum
resonance cones. We propose a pumping scheme using the transparency window of
the hyperbolic metamaterial that occurs near the topological transition.
Finally, we address the challenge of outcoupling these broadband resonance
cones into vacuum using a dielectric bullseye grating. We give a detailed
analysis of quenching and design the metamaterial to have a huge Purcell factor
in a broad bandwidth inspite of the losses in the metal. Our work should help
motivate experiments in the development of single photon sources for broadband
emitters such as nitrogen vacancy centers in diamond.Comment: 29 pages, 9 figure
Estimates of Radiation by Superluminal Neutrinos
We show that the more energetic superluminal neutrinos with quadratically
dispersed superluminalities \delta=\beta^2-1, for \beta=v/c where v is the
neutrino velocity, also lose significant energy to radiation to the \nu+e^-+e^+
final state in travelling from CERN to Gran Sasso as has been shown to occur
for those with constant superluminality by Cohen and Glashow if indeed \delta
\simeq 5\times 10^{-5}. In addition, we clarify the dependence of such
radiative processes on the size of the superluminality.Comment: 6 pages, no figures; text re-arranged for journal purposes; improved
references; published version(title changed by Editors
Massive Elementary Particles and Black Holes
An outstanding problem posed by Einstein's general theory of relativity to
the quantum theory of point particle fields is the fate of a massive point
particle; for, in the classical solutions of Einstein's theory, such a system
should be a black hole. We use exact results in a new approach to quantum
gravity to show that this conclusion is obviated by quantum loop effects.
Phenomenological implications are discussedComment: 11 pages; 1 figure; improved text relating to asymptotic safet
Quantum Corrections to Newton's Law
We present a new approach to quantum gravity starting from Feynman's
formulation for the simplest example, that of a scalar field as the
representative matter. We show that we extend his treatment to a calculable
framework using resummation techniques already well-tested in other problems.
Phenomenological consequences for Newton's law are described.Comment: 7 pages, 1 figure; improved fig., refs;improved discussion;more
discussion; proo
Generic approach for deriving reliability and maintenance requirements through consideration of in-context customer objectives
Not all implementations of reliability are equally effective at providing customer and user benefit. Random system failure with no prior warning or failure accommodation will have an immediate, usually adverse impact on operation. Nevertheless, this approach to reliability, implicit in measurements such as ‘failure rate’ and ‘MTBF’, is widely assumed without consideration of potential benefits of pro-active maintenance. Similarly, it is easy to assume that improved maintainability is always a good thing. However, maintainability is only one option available to reduce cost of ownership and reduce the impact of failure. This paper discusses a process for deriving optimised reliability and maintenance requirements through consideration of in-context
customer objectives rather than a product in isolation
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