13,086 research outputs found
Toward the assessment of the susceptibility of a digital system to lightning upset
Accomplishments and directions for further research aimed at developing methods for assessing a candidate design of an avionic computer with respect to susceptability to lightning upset are reported. Emphasis is on fault tolerant computers. Both lightning stress and shielding are covered in a review of the electromagnetic environment. Stress characterization, system characterization, upset detection, and positive and negative design features are considered. A first cut theory of comparing candidate designs is presented including tests of comparative susceptability as well as its analysis and simulation. An approach to lightning induced transient fault effects is included
How efficient is an integrative approach in archaeological geophysics? Comparative case studies from Neolithic settlements in Thessaly (Central Greece)
The geophysical prospection of Neolithic tells imposes specific challenges due to the preservation and nature of the architectural context and the multiple, usually disturbed, soil strata. Contrary to the usual application of a single method, this paper deals with the advantages of using an integrated geophysical approach through the employment of various methodologies to map the Neolithic cul-tural and environmental landscape of Thessalian tells (magoules) in Central Greece. The success and failure of each method in resolving the various features of the magoules are discussed in detail, and as a whole, they demonstrate the benefits of a manifold geophysical prospection of the sites
A monitor for the laboratory evaluation of control integrity in digital control systems operating in harsh electromagnetic environments
This paper presents a strategy for dynamically monitoring digital controllers in the laboratory for susceptibility to electromagnetic disturbances that compromise control integrity. The integrity of digital control systems operating in harsh electromagnetic environments can be compromised by upsets caused by induced transient electrical signals. Digital system upset is a functional error mode that involves no component damage, can occur simultaneously in all channels of a redundant control computer, and is software dependent. The motivation for this work is the need to develop tools and techniques that can be used in the laboratory to validate and/or certify critical aircraft controllers operating in electromagnetically adverse environments that result from lightning, high-intensity radiated fields (HIRF), and nuclear electromagnetic pulses (NEMP). The detection strategy presented in this paper provides dynamic monitoring of a given control computer for degraded functional integrity resulting from redundancy management errors, control calculation errors, and control correctness/effectiveness errors. In particular, this paper discusses the use of Kalman filtering, data fusion, and statistical decision theory in monitoring a given digital controller for control calculation errors
Quantum Langevin equations for optomechanical systems
We provide a fully quantum description of a mechanical oscillator in the
presence of thermal environmental noise by means of a quantum Langevin
formulation based on quantum stochastic calculus. The system dynamics is
determined by symmetry requirements and equipartition at equilibrium, while the
environment is described by quantum Bose fields in a suitable non-Fock
representation which allows for the introduction of temperature. A generic
spectral density of the environment can be described by introducing its state
trough a suitable P-representation. Including interaction of the mechanical
oscillator with a cavity mode via radiation pressure we obtain a description of
a simple optomechanical system in which, besides the Langevin equations for the
system, one has the exact input-output relations for the quantum noises. The
whole theory is valid at arbitrarily low temperature. This allows the exact
calculation of the stationary value of the mean energy of the mechanical
oscillator, as well as both homodyne and heterodyne spectra. The present
analysis allows in particular to study possible cooling scenarios and to obtain
the exact connection between observed spectra and fluctuation spectra of the
position of the mechanical oscillator.Comment: 37 pages, 2 figures. Major revisions; new reference
Aircraft electromagnetic compatibility
Illustrated are aircraft architecture, electromagnetic interference environments, electromagnetic compatibility protection techniques, program specifications, tasks, and verification and validation procedures. The environment of 400 Hz power, electrical transients, and radio frequency fields are portrayed and related to thresholds of avionics electronics. Five layers of protection for avionics are defined. Recognition is given to some present day electromagnetic compatibility weaknesses and issues which serve to reemphasize the importance of EMC verification of equipment and parts, and their ultimate EMC validation on the aircraft. Proven standards of grounding, bonding, shielding, wiring, and packaging are laid out to help provide a foundation for a comprehensive approach to successful future aircraft design and an understanding of cost effective EMC in an aircraft setting
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Preparing for the future: A reappraisal of archaeo-geophysical surveying on Irish National Road Schemes 2001-2010
yesThis document reviews Legacy Data generated from 10 years’ worth of road scheme activity in
Ireland to determine how archaeological geophysical surveys could be carried out on national
roads in the future. The geophysical surveys were carried out by several different contractors
across a range of challenging field conditions, geologies, weather and seasons. The research is
based upon the results of linear schemes but also has validity for wider approaches. The
findings of this research are based upon the compilation of all terrestrial archaeological
geophysical surveys carried out on behalf of the National Roads Authority (NRA), a review of
the success or otherwise of those surveys in comparison with ground-observed excavations and
in combination with experimental surveys that tested previously held assumptions or
knowledge to determine best practice methods for the future.
The use and success of geophysical surveys in Ireland differ quite significantly from those in the
UK, from where many of the methods of assessment were derived or adapted. Many of these
differences can be attributed to geology. Ireland has a very high percentage of Carboniferous
limestone geology, overlain mostly by tills and frequent occurrences of peat. These soils can
reduce, to some extent, the effectiveness of magnetometer surveys; the most frequently used
geophysical technique in Ireland. However, magnetometer data can be maximised in these
cases by increasing the spatial resolution to produce effective results. An increase in spatial
resolution is also effective generally, for enhancing the chances of identifying archaeological
features by discriminating between archaeological and geological anomalies as well as
increasing anomaly definition and visualisation of small and subtle archaeological features.
Seasonal tests have determined that Irish soils are generally suitable for year round earth
resistance assessments although some counties in the southeast of the country may experience
very dry soils at the surface during some periods of the year.
A variety of sampling strategies were used in the past, however it is now apparent that detailed
assessments across the full length and width of a proposed road corridor are the most
appropriate form of geophysical investigation. Magnetometer surveys are generally suitable for
most Irish soils and geologies, although exceptions apply in areas of near-surface igneous
deposits, deep peat and alluvial soils; however magnetometer surveys are not capable of
identifying all types of archaeological features and other methods will be required for a full
evaluation.
Analysis of the Legacy Data has determined that in general the NRA archaeological geophysical surveys were historically used in a very positive way on road schemes. The range of features
assessed or identified account for most types of archaeological sites in Ireland. These have
provided a significant archive of case studies that will be of benefit to future archaeological
geophysical research and will help to protect the globally dwindling archaeological resource
that is threatened by development-led or commercially driven projects
Communication system for a tooth-mounted RF sensor used for continuous monitoring of nutrient intake
In this Thesis, the communication system of a wearable device that monitors the user’s diet is studied. Based in a novel RF metamaterial-based mouth sensor, different decisions have to be made concerning the system’s technologies, such as the power source options for the device, the wireless technology used for communications and the method to obtain data from the sensor. These issues, along with other safety rules and regulations, are reviewed, as the first stage of development of the Food-Intake Monitoring projectOutgoin
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