102,065 research outputs found
Irreversible energy flow in forced Vlasov dynamics
No full textThe recent paper of Plunk [G.G. Plunk, Phys. Plasmas 20, 032304 (2013)]
considered the forced linear Vlasov equation as a model for the quasi-steady state of a
single stable plasma wavenumber interacting with a bath of turbulent fluctuations. This
approach gives some insight into possible energy flows without solving for nonlinear
dynamics. The central result of the present work is that the forced linear Vlasov equation
exhibits asymptotically zero (irreversible) dissipation to all orders under a detuning of
the forcing frequency and the characteristic frequency associated with particle streaming.
We first prove this by direct calculation, tracking energy flow in terms of certain exact
conservation laws of the linear (collisionless) Vlasov equation. Then we analyze the
steady-state solutions in detail using a weakly collisional Hermite-moment formulation,
and compare with numerical solution. This leads to a detailed description of the Hermite
energy spectrum, and a proof of no dissipation at all orders, complementing the
collisionless Vlasov result
Direct construction of stellarator-symmetric quasi-isodynamic magnetic configurations
No full textWe develop the formalism of the first order near-axis expansion of the MHD
equilibrium equations described in Garren & Boozer (1991), Plunk et al. (2019)
and Plunk et al. (2021), for the case of a quasi-isodynamic, N-field period,
stellarator symmetric, single-well magnetic field equilibrium. The importance
of the magnetic axis shape is investigated, and we conclude that control of the
curvature and torsion is crucial to obtain omnigenous configurations with
finite aspect ratio and low effective ripple, especially for a higher number of
field periods. For this reason a method is derived to construct classes of axis
shapes with favourable curvature and torsion. Solutions are presented,
including a three-field-period configuration constructed at an aspect ratio of
A=20, with a maximum elongation of e=3.2 and an effective ripple under 1%,
which demonstrates that high elongation is not a necessary feature of QI
stellarators.Comment: 28 pages, 19 figure
Irreversible energy flow in forced Vlasov dynamics
No full text© EDP Sciences, Società Italiana di Fisica, Springer-Verlag. The recent paper of Plunk [G.G. Plunk, Phys. Plasmas 20, 032304 (2013)] considered the forced linear Vlasov equation as a model for the quasi-steady state of a single stable plasma wavenumber interacting with a bath of turbulent fluctuations. This approach gives some insight into possible energy flows without solving for nonlinear dynamics. The central result of the present work is that the forced linear Vlasov equation exhibits asymptotically zero (irreversible) dissipation to all orders under a detuning of the forcing frequency and the characteristic frequency associated with particle streaming. We first prove this by direct calculation, tracking energy flow in terms of certain exact conservation laws of the linear (collisionless) Vlasov equation. Then we analyze the steady-state solutions in detail using a weakly collisional Hermite-moment formulation, and compare with numerical solution. This leads to a detailed description of the Hermite energy spectrum, and a proof of no dissipation at all orders, complementing the collisionless Vlasov result.This work was supported by the UK Engineering and Phys-ical Sciences Research Council through a Doctoral TrainingGrant award to J.T.P., with additional support from AwardNo KUK-C1-013-04 made by King Abdullah University of Sci-ence and Technology (KAUST). G.G.P. acknowledges supportfrom the Max-Planck/Princeton Research Center for PlasmaPhysics. This project has received funding from the EuropeanUnion’s Horizon 2020 research and innovation programme un-der Grant agreement No. 633053. The views and opinions ex-pressed herein do not necessarily reflect those of the EuropeanCommission
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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3346: Samuel G. Freedman, author, 2013
No full textPhotograph of author Samuel G. Freedman, at NT Daily Slash meeting in the Mayborn School of Journalism at UNT
The Right to Strike under the United States Constitution: Theory, Practice, and Possible Implications for Canada
No full textAnswering critics of the Canadian Supreme Court's judgment in B.C. Health, the author argues that the Court laid the foundation for a principled and durable doctrine protecting constitutional labour rights, one that goes directly to the heart of the matter — the inequality of workers’ power in the employment relation. In the author’s view, two paths could lead from B.C. Health to the recognition of Charter protec- tion for a right to strike: one that treats the right as an accessory to col- lective bargaining, and one that upholds the right directly on the basis of the Charter values of equality and participation. The author supports the latter approach, contending that constitutional rights should be defined in relation to fundamental values, in a way that is not contingent on time-bound or fact-sensitive assessments about the role of strikes within a particular collective bargaining regime. Although a Charter right to strike may involve the courts in difficult choices about when to defer to legislative policy decisions, and courts may lack the institutional capac- ity to deal effectively with labour law issues, the author points out that judges can look to ILO standards for expert guidance. Noting that the U.S. experience in this area might be of considerable use to Canadians, the author concludes by providing an overview of American case law concerning a constitutional right to strike.Peer reviewe
Perturbing an axisymmetric magnetic equilibrium to obtain a quasi-axisymmetric stellarator
No full textIt is demonstrated that finite-pressure, approximately quasi-axisymmetric
stellarator equilibria can be directly constructed (without numerical
optimization) via perturbations of given axisymmetric equilibria. The size of
such perturbations is measured in two ways, via the fractional external
rotation and, alternatively, via the relative magnetic field strength, i.e. the
average size of the perturbed magnetic field, divided by the unperturbed field
strength. It is found that significant fractional external rotational transform
can be generated by quasi-axisymmetric perturbations, with a similar value of
the relative field strength, despite the fact that the former scales more
weakly with the perturbation size. High mode number perturbations are
identified as a candidate for generating such transform with local current
distributions. Implications for the development of a general non-perturbative
solver for optimal stellarator equilibria is discussed
G-Rank: Unsupervised Continuous Learn-to-Rank for Edge Devices in a P2P Network
No full textRanking algorithms in traditional search engines are powered by enormous training data sets that are meticulously engineered and curated by a centralized entity. Decentralized peer-to-peer (p2p) networks such as torrenting applications and Web3 protocols deliberately eschew centralized databases and computational architectures when designing services and features. As such, robust search-and-rank algorithms designed for such domains must be engineered specifically for decentralized networks, and must be lightweight enough to operate on consumer-grade personal devices such as a smartphone or laptop computer. We introduce G-Rank, an unsupervised ranking algorithm designed exclusively for decentralized networks. We demonstrate that accurate, relevant ranking results can be achieved in fully decentralized networks without any centralized data aggregation, feature engineering, or model training. Furthermore, we show that such results are obtainable with minimal data preprocessing and computational overhead, and can still return highly relevant results even when a user’s device is disconnected from the network. G-Rank is highly modular in design, is not limited to categorical data, and can be implemented in a variety of domains with minimal modification. The results herein show that unsupervised ranking models designed for decentralized p2p networks are not only viable, but worthy of further research.https://github.com/awrgold/G-RankComputer Scienc
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