1,244 research outputs found
ESA measurements using the hybrid fibre-optic reflection measurement system
No full textTo be presented at Loughborough Antennas & Propagation Conference, Loughborough, 16th - 17th November 2009Since the introduction of the Wheeler Cap method to measure
the radiation efficiency of an Electrically Small Antenna (ESA), there have
been several techniques presented in literature that have either enhanced
on the method or provided an alternative technique. This paper presents
measurements of the radiation efficiency of an electrically small monopole
using the Hybrid Fibre-Optic RF Reflection Measurement System (HRS)
integrated into the Wheeler Cap. The HRS isolates the ESA from the measurement
system [1]. The ESA’s reflection coefficient can then be measured
with the isolated ESA inside the Wheeler Cap and in freespace to determine
its efficiency. The HRS is also integrated into a far-field measurement
range to measure the far-field radiation pattern of the ESA
Anisotropic phase-field model: interfaces and junctions
No full textn this paper we bring together and extend two recent developments in phase-field models, namely, a phase-field model of a multiphase system [I. Steinbach et al., Physica D 94, 135 (1996)] and the extension of the Cahn-Hoffman ?-vector theory of anisotropic sharp interfaces to phase-field models [A. A. Wheeler and G. B. McFadden, Eur. J. Appl. Math. 7, 369 (1996); Proc. R. Soc. London, Ser. A 453, 1611 (1997)]. We develop the phase-field model of a multiphase system proposed by Steinbach et al. to include both surface energy and interfacial kinetic anisotropy. We show that this model may be compactly expressed in terms of generalized Cahn-Hoffman ? vectors. This generalized Cahn-Hoffman ?-vector formalism is subsequently developed to include the notion of a stress tensor, which is used to succinctly derive the leading-order conditions at both moving interfaces and stationary multijunctions in the sharp interface limit
Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations (I): Catastrophic APS, APS nephropathy and heart valve lesions
No full textThe objectives of the 'Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations' were to assess the clinical utility of the international consensus statement on classification criteria and treatment guidelines for the catastrophic APS, to identify and grade the studies that analyse the relationship between the antiphospholipid antibodies and the non-criteria APS manifestations and to present the current evidence regarding the accuracy of these non-criteria APS manifestations for the detection of patients with APS. This article summarizes the studies analysed on the catastrophic APS, APS nephropathy and heart valve lesions, and presents the recommendations elaborated by the Task Force after this analysis. © The Author(s), 2011
Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations (II): Thrombocytopenia and skin manifestations
No full textThe objectives of the 'Task Force on Catastrophic Antiphospholipid Syndrome (APS) and Non-criteria APS Manifestations' were to assess the clinical utility of the international consensus statement on classification criteria and treatment guidelines for the catastrophic APS, to identify and grade the studies that analyze the relationship between the antiphospholipid antibodies and the non-criteria APS manifestations, and to present the current evidence regarding the accuracy of these non-criteria APS manifestations for the detection of patients with APS. This article summarizes the studies analyzed on thrombocytopenia and skin manifestations, and presents the recommendations elaborated by the Task Force after this analysis. © The Author(s), 2011
All-optical nonlinear Breit-Wheeler pair production with γ-flash photons
No full textHigh-power laser facilities give experimental access to fundamental strong-field quantum electrodynamics processes. A key effect to be explored is the nonlinear Breit-Wheeler process: the conversion of high-energy photons into electron-positron pairs through the interaction with a strong electromagnetic field. A major challenge to observing nonlinear Breit-Wheeler pair production experimentally is first having a suitable source of high-energy photons. In this paper we outline a simple all-optical setup which efficiently generates photons through the so-called
γ-flash mechanism by irradiating a solid target with a high-power laser. We consider the collision of these photons with a secondary laser and systematically discuss the prospects for exploring the nonlinear Breit-Wheeler process at current and next-generation high-power laser facilities.journal articl
Author Citations
No full textAuthor citation graphs for 6 field of studies: Management, Psychology, Economics, Physics(APS), Political Science, Computer Scienc
Ad Hoc Positioning System (APS)
No full textMany ad ho network protools and appliations assume the knowledge of geographi loation of nodes. The absolute loation of eah networked node is an assumed fat by most sensor networks whih an then present the sensed information on a geographial map. Finding loation without the aid of GPS in eah node of an ad ho network is important in ases where GPS is either not aessible, or not pratial to use due to power, form fator or line of sight onditions. Loation would also enable routing in suÆiently isotropi large networks, without the use of large routing tables. We are proposing APS { a distributed, hop by hop positioning algorithm, that works as an extension of both distane vetor routing and GPS positioning in order to provide approximate loation for all nodes in a network where only a limited fration of nodes have self loation apability.Technical report DCS-TR-43
Author Citations
No full textAuthor citation graphs for 6 field of studies: Management, Psychology, Economics, Physics(APS), Political Science, Computer Scienc
Author Citations
No full textAuthor citation graphs for 6 field of studies: Management, Psychology, Economics, Physics(APS), Political Science, Computer Scienc
Consistent probabilities in Wheeler-DeWitt quantum cosmology
No full textWe give an explicit, rigorous framework for calculating quantum probabilities in a model theory of quantum gravity. Specifically, we construct the decoherence functional for the Wheeler-DeWitt quantization of a flat Friedmann-Robertson-Walker cosmology with a free, massless, minimally coupled scalar field, thus providing a complete decoherent histories formulation for this quantum cosmological model. The decoherence functional is applied to study predictions concerning the model\u27s Dirac (relational) observables; the behavior of semiclassical states and superpositions of such states; and to study the singular behavior of quantum Wheeler-DeWitt universes. Within this framework, rigorous formulas are given for calculating the corresponding probabilities from the wave function when those probabilities may be consistently defined, thus replacing earlier heuristics for interpreting the wave function of the universe with explicit constructions. It is shown according to a rigorously formulated standard, and in a quantum-mechanically consistent way, that in this quantization these models are generically singular. Independent of the choice of state we show that the probability for these Wheeler-DeWitt quantum universes to ever encounter a singularity is unity. In addition, the relation between histories formulations of quantum theory and relational Dirac observables is clarified. © 2010 The American Physical Society
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