Global electric field determination in the Earth's outer magnetosphere using charged particles

Although many properties of the Earth's magnetosphere have been measured and quantified in the past 30 years since it was discovered, one fundamental (for a zeroeth order magnetohydrodynamic (MHD) equilibrium) measurement was made infrequently and with poor spatial coverage: the global electric field. This oversight is in part due to the difficulty of measuring a plasma electric field, and in part due to the difficulty of measuring a plasma electric field, and in part due to the neglect of theorists. However, there is renewed interest in the convection electric field, since it has been realized that it is vital for understanding many aspects of the magnetosphere: the global MHD equilibrium, reconnection rates, Region 2 Birkeland currents, magnetosphere-ionosphere coupling, ring current and radiation belt transport, substorm injections, acceleration mechanisms, etc. Unfortunately the standard experimental methods have not been able to synthesize a global field (excepting the pioneering work of McIlwain's geostationary models), and we are left with an overly simplistic theoretical field, the Volland-Stern electric field mode. Again, single point measurements of the plasma pause were used to infer the appropriate amplitudes of the model, parameterized by Kp (Maynard & Chen, JGR 1975). Although this result was never intended to be the definitive electric field model, it has gone nearly unchanged for 15 years. However, the data sets being taken today require a great deal more accuracy than can be provided by the Volland-Stern model. Nor has the variability of the electric field shielding been properly addressed, although effects of penetrating magnetospheric electric fields has been seen in mid- and low-latitude ionospheric data sets. The growing interests in substorm dynamics also requires a much better assessment of the electric fields responsible for particle injections. Thus, we proposed and developed algorithms for extracting electric fields from particle data taken in the earth's magnetosphere. As a test of the effectiveness of these techniques, we analyzed data taken by the AMPTE/CCE spacecraft in equatorial orbit between 1984-1988. Some analytic tools had to be developed before construction of computer algorithms, and they are discussed

Peter Artedi

n/

Report on Screw Fastened Sheet Steel Connections for Canadian Steel Industries Construction Council, Volume I

Ultimate load data is presented from more than 1600 tests on sample connections made with different thicknesses of zinc-coated sheet steel and a variety of commonly used thread forming and self-drilling fasteners. The three fundamental loading conditions examined were pull-over, pull-out and single lap shear. Empirical relationships have been developed which allow interpolation of the data within the range of sheet steel thicknesses tested. Type AB and type A thread forming fasteners, and a number of different self-drilling fasteners were tested, in sizes from #14 (.250 in.) to #8 (.164 in.) diameter. Flat metal washers and a variety of sealing washers were also used in combination with the different fastener types and head styles. The thicknesses of steel sheets ranged from .022 in. to .060 in. depending on the particular loading condition being tested. The sheet material was ductile and of medium strength and hardness. All fastener connections tested under all loading conditions achieved higher failure loads with thicker steel sheets. The #14 (.250 in.) diameter fasteners of each type gave significantly higher connection failure loads in most sheet thicknesses than the other fastener sizes. Connections with #12 (.216 in.), #10 (.190 in.) and #8 (.164 in.) diameter fasteners showed only marginal differences in ultimate load

Controlling chaos in the quantum regime using adaptive measurements

The continuous monitoring of a quantum system strongly influences the emergence of chaotic dynamics near the transition from the quantum regime to the classical regime. Here we present a feedback control scheme that uses adaptive measurement techniques to control the degree of chaos in the driven-damped quantum Duffing oscillator. This control relies purely on the measurement backaction on the system, making it a uniquely quantum control, and is only possible due to the sensitivity of chaos to measurement. We quantify the effectiveness of our control by numerically computing the quantum Lyapunov exponent over a wide range of parameters. We demonstrate that adaptive measurement techniques can control the onset of chaos in the system, pushing the quantum-classical boundary further into the quantum regime

Theophrastus Redivivus

n/