6,374 research outputs found
SPECIFICATION OF SUPPLIES AND DEMANDS FOR SUBSECTOR AND SUBMARKET STUDIES
Demand and Price Analysis,
INCOME AND WEALTH ISSUES IN COMMERCIAL FARM AND AGRICULTURAL POLICY
Agricultural and Food Policy,
Calibrating and Stabilizing Spectropolarimeters with Charge Shuffling and Daytime Sky Measurements
Well-calibrated spectropolarimetry studies at resolutions of 10,000 with
signal-to-noise ratios (SNRs) better than 0.01\% across individual line
profiles, are becoming common with larger aperture telescopes.
Spectropolarimetric studies require high SNR observations and are often limited
by instrument systematic errors. As an example, fiber-fed spectropolarimeters
combined with advanced line-combination algorithms can reach statistical error
limits of 0.001\% in measurements of spectral line profiles referenced to the
continuum. Calibration of such observations is often required both for
cross-talk and for continuum polarization. This is not straightforward since
telescope cross-talk errors are rarely less than 1\%. In solar
instruments like the Daniel K. Inouye Solar Telescope (DKIST), much more
stringent calibration is required and the telescope optical design contains
substantial intrinsic polarization artifacts. This paper describes some
generally useful techniques we have applied to the HiVIS spectropolarimeter at
the 3.7m AEOS telescope on Haleakala. HiVIS now yields accurate polarized
spectral line profiles that are shot-noise limited to 0.01\% SNR levels at our
full spectral resolution of 10,000 at spectral sampling of 100,000. We
show line profiles with absolute spectropolarimetric calibration for cross-talk
and continuum polarization in a system with polarization cross-talk levels of
essentially 100\%. In these data the continuum polarization can be recovered to
one percent accuracy because of synchronized charge-shuffling model now working
with our CCD detector. These techniques can be applied to other
spectropolarimeters on other telescopes for both night and day-time
applications such as DKIST, TMT and ELT which have folded non-axially symmetric
foci.Comment: Accepted to A&
Human liver flukes
Liver fluke infections occur in people worldwide. In some low-income regions, a combination of ecological, agricultural, and culinary factors leads to a very high prevalence of infection but, in higher-income regions, infections are uncommon. Infection is associated with substantial morbidity and several liver fluke species are recognised as biological carcinogens. Here, we review the epidemiology, clinical significance, and diagnostic and treatment strategies of human infection with these pathogens
Design of a device to remove lunar dust from space suits for the proposed lunar base
The National Aeronautics and Space Administration plans to begin construction of a lunar base soon after the turn of the century. During the Apollo missions, lunar dust proved to be a problem because the dust adhered to all exposed material surfaces. Since lunar dust will be a problem during the establishment and operation of this base, the need exists for a device to remove the dust from space suits before the astronauts enter clean environments. The physical properties of lunar dust were characterized and energy methods for removing the dust were identified. Eight alternate designs were developed to remove the dust. The final design uses a brush and gas jet to remove the dust. The brush bristles are made from Kevlar fibers and the gas jet uses pressurized carbon dioxide from a portable tank. A throttling valve allows variable gas flow. Also, the tank is insulated with Kapton and electrically heated to prevent condensation of the carbon dioxide when the tank is exposed to the cold (- 240 F) lunar night
STRUCTURAL CHANGE: FARM AND FINANCIAL DIMENSIONS
Industrial Organization,
Attitude Determination and Control System (ADCS) and Maintenance and Diagnostic System (MDS): A maintenance and diagnostic system for Space Station Freedom
The Maintenance and Diagnostic System (MDS) that is being developed at Honeywell to enhance the Fault Detection Isolation and Recovery system (FDIR) for the Attitude Determination and Control System on Space Station Freedom is described. The MDS demonstrates ways that AI-based techniques can be used to improve the maintainability and safety of the Station by helping to resolve fault anomalies that cannot be fully determined by built-in-test, by providing predictive maintenance capabilities, and by providing expert maintenance assistance. The MDS will address the problems associated with reasoning about dynamic, continuous information versus only about static data, the concerns of porting software based on AI techniques to embedded targets, and the difficulties associated with real-time response. An initial prototype was built of the MDS. The prototype executes on Sun and IBM PS/2 hardware and is implemented in the Common Lisp; further work will evaluate its functionality and develop mechanisms to port the code to Ada
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