2,852 research outputs found

    Method for determining properties of microinstabilities of a magnetized plasma

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    Study comprises a determination of the plasma density at which absolute density becomes predominant by using the dielectric properties at this incipient unstable state. Relationships between wavelength, frequency, and density microinstabilities are used to derive the spatial dielectric function

    The Atmosphere Explorer power subsystem

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    The design and operation of the power subsystem for the Atmospheric Explorer spacecraft are discussed. The additional functional redundancy which was added in several component areas to improve the overall subsystem reliability is analyzed. The battery charging technique has been modified to include third electrode overcharge control. The automatic removal of all battery charge is provided to correct abnormally high battery voltages. An undervoltage detector has been added which removes all nonessential spacecraft loads when the battery voltage falls below a given level. All automatic functions can be over-ridden by ground command

    The diocotron instability in a quasi-toroidal geometry

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    Slipstream instability of low density electron beams in crossed electric and magnetic field

    A laser scanner for 35mm film

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    The design, construction, and testing of a laser scanning system is described. The scanner was designed to deliver a scanned beam over a 2.54 cm by 2.54 cm or a 5.08 cm by 5.08 cm format. In order to achieve a scan resolution and rate comparable to that of standard television, an acousto-optic deflector was used for one axis of the scan, and a light deflecting galvanometer for deflection along the other axis. The acoustic optic deflector has the capability of random access scan controlled by a digital computer

    Rheology of Granular Materials: Dynamics in a Stress Landscape

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    We present a framework for analyzing the rheology of dense driven granular materials, based on a recent proposal of a stress-based ensemble. In this ensemble fluctuations in a granular system near jamming are controlled by a temperature-like parameter, the angoricity, which is conjugate to the stress of the system. In this paper, we develop a model for slowly driven granular materials based on the stress ensemble and the idea of a landscape in stress space. The idea of an activated process driven by the angoricity has been shown by Behringer et al (2008) to describe the logarithmic strengthening of granular materials. Just as in the Soft Glassy Rheology (SGR) picture, our model represents the evolution of a small patch of granular material (a mesoscopic region) in a stress-based trap landscape. The angoricity plays the role of the fluctuation temperature in SGR. We determine (a) the constitutive equation, (b) the yield stress, and (c) the distribution of stress dissipated during granular shearing experiments, and compare these predictions to experiments of Hartley & Behringer (2003).Comment: 17 pages, 4 figure

    Thermodynamic consistency of liquid-gas lattice Boltzmann simulations

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    Lattice Boltzmann simulations have been very successful in simulating liquid-gas and other multi-phase fluid systems. However, the underlying second order analysis of the equation of motion has long been known to be insufficient to consistently derive the fourth order terms that are necessary to represent an extended interface. These same terms are also responsible for thermodynamic consistency, i.e. to obtain a true equilibrium solution with both a constant chemical potential and a constant pressure. In this article we present an equilibrium analysis of non-ideal lattice Boltzmann methods of sufficient order to identify those higher order terms that lead to a lack of thermodynamic consistency. We then introduce a thermodynamically consistent forcing method.Comment: 12 pages, 8 figure

    Lessons Learned in Protection of the Public for the Accident at the Fukushima Daiichi Nuclear Power Plant

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    What insights can the accident at the Fukushima Daiichi nuclear power plant provide in the reality of decision making on actions to protect the public during a severe reactor and spent fuel pool emergency? In order to answer this question, and with the goal of limiting the consequences of any future emergencies at a nuclear power plant due to severe conditions, this article presents the main actions taken in response to the emergency in the form of a timeline. The focus of this paper are those insights concerning the progression of an accident due to severe conditions at a light water reactor nuclear power plant that must be understood in order to protect the public

    Saving Lives and Preventing Injuries from Unjustified Protective Actions - Method for Developing a Comprehensive Public Protective Action Strategy for a Severe NPP Emergency

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    During the response to the Fukushima Daiichi nuclear power plant (FDNPP) emergency about 50 patients died during or shortly after an evacuation when they were not provided with the needed medical support. In addition, during the FDNPP emergency it has been shown that there were increases in mortality rates among the elderly due to long term dislocation as a result of evacuation and relocation orders and an inability to stay in areas advised to shelter for extended periods. These deaths occurred even though the possible radiation exposure to the public was too low to result in radiation induced deaths, injuries or a meaningful increase in the cancer rate, even if no protective actions had been taken. These problems are not unique to the FDNPP emergency and would be expected if the recommendations of many organizations were followed. Neither the International Atomic Energy Agency (IAEA), the International Commission on Radiological Protection (ICRP), the U.S. Nuclear Regulatory Commission (NRC) nor the U.S Environmental Protection Agency (EPA) adequately take into consideration in their recommendations and analysis the non-radiological health impact, such as deaths and injuries, that could result from protective actions. Furthermore, ICRP, NRC, EPA and the Department of Homeland Security (DHS) call for taking protective actions at doses lower than those resulting in meaningful adverse radiation induced health effects and do not state the doses at which such effects would be seen. Consequently, it would be impossible for decision makers and the public to balance all the hazards both from radiation exposure and protective actions when deciding whether a protective action is justified. What is needed, as is presented in this paper, is a method for developing a comprehensive protective action strategy that allows the public, decision makers and others who must work together to balance the radiological with the non-radiological health hazards posed by protective actions, and to counter the exaggerated fear of radiation exposure that could lead to taking unjustified protective actions and adverse psychological, sociological and other effects

    Quantum fluctuation driven first order phase transition in weak ferromagnetic metals

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    In a local Fermi liquid (LFL), we show that there is a line of weak first order phase transitions between the ferromagnetic and paramagnetic phases due to purely quantum fluctuations. We predict that an instability towards superconductivity is only possible in the ferromagnetic state. At T=0 we find a point on the phase diagram where all three phases meet and we call this a quantum triple point (QTP). A simple application of the Gibbs phase rule shows that only these three phases can meet at the QTP. This provides a natural explanation of the absence of superconductivity at this point coming from the paramagnetic side of the phase diagram, as observed in the recently discovered ferromagnetic superconductor, UGe2UGe_{2}.Comment: 5 pages, 5 figure

    Absolute and convective microinstabilities of a magnetized plasma

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    Absolute and convective microinstabilities of hot, fully ionized, collisionless magnetized plasm
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