1,834 research outputs found
Power control circuit
Power control switching circuit using low voltage semiconductor controlled rectifiers for high voltage isolatio
The 30-cm ion thruster power processor
A power processor unit for powering and controlling the 30 cm Mercury Electron-Bombardment Ion Thruster was designed, fabricated, and tested. The unit uses a unique and highly efficient transistor bridge inverter power stage in its implementation. The system operated from a 200 to 400 V dc input power bus, provides 12 independently controllable and closely regulated dc power outputs, and has an overall power conditioning capacity of 3.5 kW. Protective circuitry was incorporated as an integral part of the design to assure failure-free operation during transient and steady-state load faults. The implemented unit demonstrated an electrical efficiency between 91.5 and 91.9 at its nominal rated load over the 200 to 400 V dc input bus range
Ion engine thrust vector study Quarterly report
Thrust stand and thruster designs for ion engine
Engineering model 8-cm thruster subsystem
An Engineering Model (EM) 8 cm Ion Thruster Propulsion Subsystem was developed for operation at a thrust level 5 mN (1.1 mlb) at a specific impulse 1 sub sp = 2667 sec with a total system input power P sub in = 165 W. The system dry mass is 15 kg with a mercury-propellant-reservoir capacity of 8.75 kg permitting uninterrupted operation for about 12,500 hr. The subsystem can be started from a dormant condition in a time less than or equal to 15 min. The thruster has a design lifetime of 20,000 hr with 10,000 startup cycles. A gimbal unit is included to provide a thrust vector deflection capability of + or - 10 degrees in any direction from the zero position. The EM subsystem development program included thruster optimization, power-supply circuit optimization and flight packaging, subsystem integration, and subsystem acceptance testing including a cyclic test of the total propulsion package
Advanced Diagnostics for the Study of Linearly Polarized Emission. II: Application to Diffuse Interstellar Radio Synchrotron Emission
Diagnostics of polarized emission provide us with valuable information on the
Galactic magnetic field and the state of turbulence in the interstellar medium,
which cannot be obtained from synchrotron intensity alone. In Paper I (Herron
et al. 2017b), we derived polarization diagnostics that are rotationally and
translationally invariant in the - plane, similar to the polarization
gradient. In this paper, we apply these diagnostics to simulations of ideal
magnetohydrodynamic turbulence that have a range of sonic and Alfv\'enic Mach
numbers. We generate synthetic images of Stokes and for these
simulations, for the cases where the turbulence is illuminated from behind by
uniform polarized emission, and where the polarized emission originates from
within the turbulent volume. From these simulated images we calculate the
polarization diagnostics derived in Paper I, for different lines of sight
relative to the mean magnetic field, and for a range of frequencies. For all of
our simulations, we find that the polarization gradient is very similar to the
generalized polarization gradient, and that both trace spatial variations in
the magnetoionic medium for the case where emission originates within the
turbulent volume, provided that the medium is not supersonic. We propose a
method for distinguishing the cases of emission coming from behind or within a
turbulent, Faraday rotating medium, and a method to partly map the rotation
measure of the observed region. We also speculate on statistics of these
diagnostics that may allow us to constrain the physical properties of an
observed turbulent region.Comment: 34 pages, 25 figures, accepted for publication in Ap
Partisan impacts on the economy: evidence from prediction markets and close elections
Analyses of the effects of election outcomes on the economy have been hampered by the problem that economic outcomes also influence elections. We sidestep these problems by analyzing movements in economic indicators caused by clearly exogenous changes in expectations about the likely winner during election day. Analyzing high frequency financial fluctuations following the release of flawed exit poll data on election day 2004, and then during the vote count we find that markets anticipated higher equity prices, interest rates and oil prices, and a stronger dollar under a George W. Bush presidency than under John Kerry. A similar Republican–Democrat differential was also observed for the 2000 Bush–Gore contest. Prediction market based analyses of all presidential elections since 1880 also reveal a similar pattern of partisan impacts, suggesting that electing a Republican president raises equity valuations by 2–3 percent, and that since Ronald Reagan, Republican presidents have tended to raise bond yields
Redefining the research hospital
Introduction
All medicine was innovation, once. Yet the contemporary notion of medical research is remarkably narrow. While every clinician is encouraged to be aware of the latest advances, only a few are expected to contribute to them. Anyone may be a patient, yet clinical practice is determined by the minority included in research studies. The aim of medicine is to improve the lives of patients, yet knowledge of disease is arbitrarily prioritised as its primary means. The agents of medicine are clinicians, yet new interventions are mostly created by others, within corporate enterprise deliberately kept at arm’s length. We treat the specific, individual patient in front of us, now, yet most research is addressed to faceless, generic groups, to be realised deep into an ill-defined, hypothetical future
Polarization Gradient Study of Interstellar Medium Turbulence Using The Canadian Galactic Plane Survey
We have investigated the magneto-ionic turbulence in the interstellar medium
through spatial gradients of the complex radio polarization vector in the
Canadian Galactic Plane Survey (CGPS). The CGPS data cover 1300 square-degrees,
over the range ,
with an extension to
in the range , and arcminute
resolution at 1420 MHz. Previous studies found a correlation between the
skewness and kurtosis of the polarization gradient and the Mach number of the
turbulence, or assumed this correlation to deduce the Mach number of an
observed turbulent region. We present polarization gradient images of the
entire CGPS dataset, and analyze the dependence of these images on angular
resolution. The polarization gradients are filamentary, and the length of these
filaments is largest towards the Galactic anti-center, and smallest towards the
inner Galaxy. This may imply that small-scale turbulence is stronger in the
inner Galaxy, or that we observe more distant features at low Galactic
longitudes. For every resolution studied, the skewness of the polarization
gradient is influenced by the edges of bright polarization gradient regions,
which are not related to the turbulence revealed by the polarization gradients.
We also find that the skewness of the polarization gradient is sensitive to the
size of the box used to calculate the skewness, but insensitive to Galactic
longitude, implying that the skewness only probes the number and magnitude of
the inhomogeneities within the box. We conclude that the skewness and kurtosis
of the polarization gradient are not ideal statistics for probing natural
magneto-ionic turbulence.Comment: 21 pages, 15 figures, accepted by Ap
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