6,052 research outputs found
Evidence cross-validation and Bayesian inference of MAST plasma equilibria
In this paper, current profiles for plasma discharges on the Mega-Ampere
Spherical Tokamak (MAST) are directly calculated from pickup coil, flux loop
and Motional-Stark Effect (MSE) observations via methods based in the
statistical theory of Bayesian analysis. By representing toroidal plasma
current as a series of axisymmetric current beams with rectangular
cross-section and inferring the current for each one of these beams,
flux-surface geometry and q-profiles are subsequently calculated by elementary
application of Biot-Savart's law. The use of this plasma model in the context
of Bayesian analysis was pioneered by Svensson and Werner on the Joint-European
Tokamak (JET) [J. Svensson and A. Werner. Current tomography for axisymmetric
plasmas. Plasma Physics and Controlled Fusion, 50(8):085002, 2008]. In
this framework, linear forward models are used to generate diagnostic
predictions, and the probability distribution for the currents in the
collection of plasma beams was subsequently calculated directly via application
of Bayes' formula. In this work, we introduce a new diagnostic technique to
identify and remove outlier observations associated with diagnostics falling
out of calibration or suffering from an unidentified malfunction. These
modifications enable good agreement between Bayesian inference of the last
closed flux-surface (LCFS) with other corroborating data, such as such as that
from force balance considerations using EFIT++ [L. Appel et al., Proc. 33rd EPS
Conf., Rome, Italy, 2006]. In addition, this analysis also yields errors on the
plasma current profile and flux-surface geometry, as well as directly
predicting the Shafranov shift of the plasma core.This work was jointly funded by the Australian Government
through International Science Linkages Grant No.
CG130047, the Australian National University, the United
Kingdom Engineering and Physical Sciences Research
Council under Grant No. EP/G003955, and by the European
Communities under the contract of Association between EURATOM and CCFE
Iridium-coated rhenium thrusters by CVD
Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the meltimg temperature of iridium, 2400 C (4350 F)
Fullerene graphs have exponentially many perfect matchings
A fullerene graph is a planar cubic 3-connected graph with only pentagonal
and hexagonal faces. We show that fullerene graphs have exponentially many
perfect matchings.Comment: 7 pages, 3 figure
Coloring random graphs
We study the graph coloring problem over random graphs of finite average
connectivity . Given a number of available colors, we find that graphs
with low connectivity admit almost always a proper coloring whereas graphs with
high connectivity are uncolorable. Depending on , we find the precise value
of the critical average connectivity . Moreover, we show that below
there exist a clustering phase in which ground states
spontaneously divide into an exponential number of clusters and where the
proliferation of metastable states is responsible for the onset of complexity
in local search algorithms.Comment: 4 pages, 1 figure, version to app. in PR
Sustainable Commerce: Public Health Law and Environmental Law Provide Tools for Industry and Government to Construct Globally-Competitive Green Economies
This Article examines the legal mechanics underlying the sustainable commerce private/public governance paradigm whereby industry and government create sustainable commerce initiatives which coordinately grow local/state economies and employment, enhance local/state competitiveness in the global marketplace, and at the same time substantially improve local/state public health and environmental infrastructure. This includes an examination of the legal foundation for state/local sustainable commerce initiatives drawn from existing public health and environmental law and a review of two specific local/state sustainable commerce initiatives which have followed this paradigm with impressive results over a two-to-four year timeframe. Part II of this Article examines how public health and environmental law bases provide legal authority and policy rationales upon which to construct local/state sustainable commerce initiatives. Part III examines how a small Georgia town, Ringgold—the county seat for Catoosa County, GA—recently implemented sustainable commerce initiatives, allowing this North Georgia community to actively participate in market-based low-carbon sustainable commerce initiatives which not only address legacy environmental and public health issues, but which create economic opportunities into the future. Part IV outlines how global industry now fulfills its own sustainable commerce programs requiring U.S. manufacturers to meet detailed environmental and public health metrics for both corporate operations and product life cycle analysis as a condition of purchasing their goods and services. Part IV also details how one U.S. manufacturer, the Murray Corporation, created management systems based on the ISO standard series to address customer environmental and public health metrics for their operations and products in order to qualify as an approved vendor for sales overseas. Part V then concludes with a continued discussion of ISO standard-based management systems as a key legal and regulatory tool by which local government and industry can coordinately construct sustainable commerce initiatives which ensure government and industry will successfully attain defined sustainable commerce goals. The example is drawn from the experience of the U.S. public health system. This discussion includes a review of how ISO-based third party assurance systems complement existing common and statutory law to achieve aggressive sustainable commerce timelines and goals over the immediate future (2–4 year timeframe)
A low-loss, broadband antenna for efficient photon collection from a coherent spin in diamond
We report the creation of a low-loss, broadband optical antenna giving highly
directed output from a coherent single spin in the solid-state. The device, the
first solid-state realization of a dielectric antenna, is engineered for
individual nitrogen vacancy (NV) electronic spins in diamond. We demonstrate a
directionality close to 10. The photonic structure preserves the high spin
coherence of single crystal diamond (T2>100us). The single photon count rate
approaches a MHz facilitating efficient spin readout. We thus demonstrate a key
enabling technology for quantum applications such as high-sensitivity
magnetometry and long-distance spin entanglement.Comment: 5 pages, 4 figures and supplementary information (5 pages, 8
figures). Comments welcome. Further information under
http://www.quantum-sensing.physik.unibas.c
Excitations in time-dependent density-functional theory
An approximate solution to the time-dependent density functional theory
(TDDFT) response equations for finite systems is developed, yielding
corrections to the single-pole approximation. These explain why allowed
Kohn-Sham transition frequencies and oscillator strengths are usually good
approximations to the true values, and why sometimes they are not. The
approximation yields simple expressions for G\"orling-Levy perturbation theory
results, and a method for estimating expectation values of the unknown
exchange-correlation kernel.Comment: 4 pages, 1 tabl
Mobile Resource Guarantees for Smart Devices
Abstract. We present the Mobile Resource Guarantees framework: a system for ensuring that downloaded programs are free from run-time violations of resource bounds. Certificates are attached to code in the form of efficiently checkable proofs of resource bounds; in contrast to cryptographic certificates of code origin, these are independent of trust networks. A novel programming language with resource constraints encoded in function types is used to streamline the generation of proofs of resource usage.
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