8,717 research outputs found

    Cumulative effect of Weibel-type instabilities in counterstreaming plasmas with non-Maxwellian anisotropies

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    Counterstreaming plasma structures are widely present in laboratory experiments and astrophysical systems, and they are investigated either to prevent unstable modes arising in beam-plasma experiments or to prove the existence of large scale magnetic fields in astrophysical objects. Filamentation instability arises in a counterstreaming plasma and is responsible for the magnetization of the plasma. Filamentationally unstable mode is described by assuming that each of the counterstreaming plasmas has an isotropic Lorentzian (kappa) distribution. In this case, the filamentation instability growth rate can reach a maximum value markedly larger than that for a a plasma with a Maxwellian distribution function. This behaviour is opposite to what was observed for the Weibel instability growth rate in a bi-kappa plasma, which is always smaller than that obtained for a bi-Maxwellian plasma. The approach is further generalized for a counterstreaming plasma with a bi-kappa temperature anisotropy. In this case, the filamentation instability growth rate is enhanced by the Weibel effect when the plasma is hotter in the streaming direction, and the growth rate becomes even larger. These effects improve significantly the efficiency of the magnetic field generation, and provide further support for the potential role of the Weibel-type instabilities in the fast magnetization scenarios

    The propagation of a vortex ring through multiple liquid interfaces in microgravity

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76118/1/AIAA-1996-593-666.pd

    Velocity field measurements during drop formation by vortical flows in microgravity

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76261/1/AIAA-1998-734-638.pd

    A3 thinking approach to support knowledge-driven design

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    Problem solving is a crucial skill in product development. Any lack of effective decision making at an early design stage will affect productivity and increase costs and the lead time for the other stages of the product development life cycle. This could be improved by the use of a simple and informative approach which allows the designers and engineers to make decisions in product design by providing useful knowledge. This paper presents a novel A3 thinking approach to problem solving in product design, and provides a new A3 template which is structured from a combination of customised elements (e.g. the 8 Disciplines approach) and reflection practice. This approach was validated using a case study in the Electromagnetic Compatibility (EMC) design issue for an automotive electrical sub-assembly product. The main advantage of the developed approach is to create and capture the useful knowledge in a simple manner. Moreover, the approach provides a reflection section allowing the designers to turn their experience of design problem solving into proper learning and to represent their understanding of the design solution. These will be systematically structured (e.g. as a design checklist) to be circulated and shared as a reference for future design projects. Thus, the recurrence of similar design problems will be prevented and will aid the designers in adopting the expected EMC test results

    Demonstrating Universal Scaling in Quench Dynamics of a Yukawa One-Component Plasma

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    The Yukawa one-component plasma (OCP) is a paradigm model for describing plasmas that contain one component of interest and one or more other components that can be treated as a neutralizing, screening background. In appropriately scaled units, interactions are characterized entirely by a screening parameter, κ\kappa. As a result, systems of similar κ\kappa show the same dynamics, regardless of the underlying parameters (e.g., density and temperature). We demonstrate this behavior using ultracold neutral plasmas (UNP) created by photoionizing a cold (T10T\le10 mK) gas. The ions in UNP systems are well described by the Yukawa model, with the electrons providing the screening. Creation of the plasma through photoionization can be thought of as a rapid quench from κ0=\kappa_{0}=\infty to a final κ\kappa value set by the electron density and temperature. We demonstrate experimentally that the post-quench dynamics are universal in κ\kappa over a factor of 30 in density and an order of magnitude in temperature. Results are compared with molecular dynamics simulations. We also demonstrate that features of the post-quench kinetic energy evolution, such as disorder-induced heating and kinetic-energy oscillations, can be used to determine the plasma density and the electron temperature.Comment: 10 pages, 12 figures, to be submitted to Physical Review

    Towards logic-based verification of javascript programs

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    In this position paper, we argue for what we believe is a correct pathway to achieving scalable symbolic verification of JavaScript based on separation logic. We highlight the difficulties imposed by the language, the current state-of-the-art in the literature, and the sequence of steps that needs to be taken. We briefly describe JaVerT, our semiautomatic toolchain for JavaScript verification

    Investigation of Drop Formation by a Vortex Ring in Microgravity

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    An investigation of drop formation by a vortex ring propagating through one or more fluid interfaces in microgravity is described. The main goal of the research is to determine the dynamics of drop formation by vortical flows in the capillary limit with large density change across the intel-face. Dimensional analysis shows that in microgravity experiments the capillary limit can be studied using a relatively large vortex ring diameter to facilitate experimental characterization of the interaction. Results obtained in density matched systems are reviewed to illustrate the complex nature of these interactions

    A trusted infrastructure for symbolic analysis of event-driven web applications

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    We introduce a trusted infrastructure for the symbolic analysis of modern event-driven Web applica-tions. This infrastructure consists of reference implementations of the DOM Core Level 1, DOM UIEvents, JavaScript Promises and the JavaScriptasync/awaitAPIs, all underpinned by a simpleCore Event Semantics which is sufficiently expressive to describe the event models underlying theseAPIs. Our reference implementations are trustworthy in that three follow the appropriate standardsline-by-line and all are thoroughly tested against the official test-suites, passing all the applicabletests. Using the Core Event Semantics and the reference implementations, we develop JaVerT.Click,a symbolic execution tool for JavaScript that, for the first time, supports reasoning about JavaScriptprograms that use multiple event-related APIs. We demonstrate the viability of JaVerT.Click byproving both the presence and absence of bugs in real-world JavaScript code

    An experimental and numerical investigation of drop formation by vortical flows in microgravity

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76442/1/AIAA-1994-244-592.pd
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