32,851 research outputs found
Channel and active component abstractions for WSN programming - a language model with operating system support
To support the programming of Wireless Sensor Networks, a number of unconventional programming models have evolved, in particular the event-based model. These models are non-intuitive to programmers due to the introduction of unnecessary, non-intrinsic complexity. Component-based languages like Insense can eliminate much of this unnecessary complexity via the use of active components and synchronous channels. However, simply layering an Insense implementation over an existing event-based system, like TinyOS, while proving efficacy, is insufficiently space and time efficient for production use. The design and implementation of a new language-specific OS, InceOS, enables both space and time efficient programming of sensor networks using component-based languages like Insense
Dissociation dynamics of fluorinated ethene cations:\ud from time bombs on a molecular level to double-regime dissociators\ud
The dissociative photoionization mechanism of internal energy selected CHF, 1,1-CHF, CHF and CF cations have been studied in the 13â20 eV photon energy range using imaging photoelectron photoion coincidence spectroscopy. Five predominant channels have been found; HF loss, statistical and non-statistical F loss, cleavage of the CâC bond post H or F-atom migration, and cleavage of the C=C bond. By modelling the breakdown diagrams and ion time-of-flight distributions using statistical theory, experimental 0 K appearance energies, E, of the daughter ions have been determined. Both CHF and 1,1-CHF are veritable time bombs with respect to dissociation via HF loss, where slow dissociation over a reverse barrier is followed by an explosion with large kinetic energy release. The first dissociative ionization pathway for CHF and CF involves an atom migration across the C=C bond, giving CFâCHF and CFâCF, respectively, which then dissociate to form CHF and CF. The nature of the F-loss pathway has been found to be bimodal for CHF and 1,1-CHF, switching from statistical to non-statistical behaviour as the photon energy increases. The dissociative ionization of CF is found to be comprised of two regimes. At high internal energies, a long-lived excited electronic state is formed, which loses an F atom in a non-statistical process and undergoes statistical redistribution of energy among the nuclear degrees of freedom. This is followed by a subsequent dissociation. In other words only the ground electronic state phase space stays inaccessible. The accurate E of CF and CF formation from CF together with the now well established âHÂș of CF yield self-consistent enthalpies of formation for the CF, CF, CF, and CF species
Standard and Non-standard Extensions of Lie algebras
We study the problem of quadruple extensions of simple Lie algebras. We find
that, adding a new simple root , it is not possible to have an
extended Kac-Moody algebra described by a Dynkin-Kac diagram with simple links
and no loops between the dots, while it is possible if is a
Borcherds imaginary simple root. We also comment on the root lattices of these
new algebras. The folding procedure is applied to the simply-laced triple
extended Lie algebras, obtaining all the non-simply laced ones. Non- standard
extension procedures for a class of Lie algebras are proposed. It is shown that
the 2-extensions of , with a dot simply linked to the Dynkin-Kac diagram
of , are rank 10 subalgebras of . Finally the simple root
systems of a set of rank 11 subalgebras of , containing as sub-algebra
, are explicitly written.Comment: Revised version. Inaccurate statements corrected. Expanded version
with added reference
Design-for-test structure to facilitate test vector application with low performance loss in non-test mode.
A switching based circuit is described which allows application of voltage test vectors to internal nodes of a chip without the problem of backdriving. The new circuit has low impact on the performance of an analogue circuit in terms of loss of bandwidth and allows simple application of analogue test voltages into internal nodes. The circuit described facilitates implementation of the forthcoming IEEE 1149.4 DfT philosophy [1]
Noncommutative Solitons and Intersecting D-Branes
We construct intersecting D-branes as noncommutative solitons in bosonic and
type II string theory. ``Defect'' branes which are D-branes containing bubbles
of the closed string vacuum play an important role in the construction.Comment: 17 pages, harvmac; published version with added clarification
Development of polyisocyanurate pour foam formulation for space shuttle external tank thermal protection system
Four commercially available polyisocyanurate polyurethane spray-foam insulation formulations are used to coat the external tank of the space shuttle. There are several problems associated with these formulations. For example, some do not perform well as pourable closeout/repair systems. Some do not perform well at cryogenic temperatures (poor adhesion to aluminum at liquid nitrogen temperatures). Their thermal stability at elevated temperatures is not adequate. A major defect in all the systems is the lack of detailed chemical information. The formulations are simply supplied to NASA and Martin Marietta, the primary contractor, as components; Part A (isocyanate) and Part B (poly(s) and additives). Because of the lack of chemical information the performance behavior data for the current system, NASA sought the development of a non-proprietary room temperature curable foam insulation. Requirements for the developed system were that it should exhibit equal or better thermal stability both at elevated and cryogenic temperatures with better adhesion to aluminum as compared to the current system. Several formulations were developed that met these requirements, i.e., thermal stability, good pourability, and good bonding to aluminum
Total focussing method for volumetric imaging in immersion non destructive evaluation
This paper describes the use of a 550 (25x22) element 2MHz 2D piezoelectric composite array in immersion mode to image an aluminum test block containing a collection of artificial defects. The defects included a 1mm diameter side-drilled hole, a collection of 1mm slot defects with varying degrees of skew to the normal and a flat bottomed hole. The data collection was carried out using the full matrix capture; a scanning procedure was developed to allow the operation of the large element count array through a conventional 64-channel phased array controller. A 3D TFM algorithm capable of imaging in a dual media environment was implemented in MATLAB for the offline processing the raw scan data. This algorithm facilitates the creation of 3D images of defects while accounting for refraction effects at material boundaries. In each of the test samples interrogated the defects, and their spatial position, are readily identified using TFM. Defect directional information has been characterized using VTFM for defect exhibiting angles up to and including 45o of skew
Boundary fermion currents and subleading order chiral anomaly in the AdS/CFT correspondence
We construct a wave-functional whose argument couples to boundary fermion
currents in the AdS/CFT correspondence. Using this we calculate the
contributions from bulk fermions to the chiral anomaly that give the subleading
order term in the exact -dependence of the chiral anomaly of
SYM. The result agrees with the calculation of Bilal & Chu.Comment: 6 page
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