215,582 research outputs found
New analytic results for electroweak baryon number violation
Real-time anomalous fermion number violation has been investigated for
massless chiral fermions in spherically symmetric SU(2) Yang-Mills gauge field
backgrounds which can be weakly dissipative or even nondissipative. Restricting
consideration to spherically symmetric fermion fields, a relation has been
found between the spectral flow of the Dirac Hamiltonian and two
characteristics of the background gauge field. This new result may be relevant
to electroweak baryon number violation in the early universe.Comment: 7 pages with jhep3.cls, based on a talk at the International
Europhysics Conference on High Energy Physics, Budapest, 200
Fully automatic telemetry data processor
Satellite Telemetry Automatic Reduction System /STARS 2/, a fully automatic computer-controlled telemetry data processor, maximizes data recovery, reduces turnaround time, increases flexibility, and improves operational efficiency. The system incorporates a CDC 3200 computer as its central element
Transverse Mercator with an accuracy of a few nanometers
Implementations of two algorithms for the transverse Mercator projection are
described; these achieve accuracies close to machine precision. One is based on
the exact equations of Thompson and Lee and the other uses an extension of
Krueger's series for the projection to higher order. The exact method provides
an accuracy of 9 nm over the entire ellipsoid, while the errors in the series
method are less than 5 nm within 3900 km of the central meridian. In each case,
the meridian convergence and scale are also computed with similar accuracy. The
speed of the series method is competitive with other less accurate algorithms
and the exact method is about 5 times slower.Comment: LaTeX, 10 pages, 3 figures. Includes some revisions. Supplementary
material is available at http://geographiclib.sourceforge.net/tm.htm
Micro-electroforming metallic bipolar electrodes for mini-DMFC stacks
This paper describes the development of metallic bipolar plate fabrication
using micro-electroforming process for mini-DMFC (direct methanol fuel cell)
stacks. Ultraviolet (UV) lithography was used to define micro-fluidic channels
using a photomask and exposure process. Micro-fluidic channels mold with 300
micrometers thick and 500 micrometers wide were firstly fabricated in a
negative photoresist onto a stainless steel plate. Copper micro-electroforming
was used to replicate the micro-fluidic channels mold. Following by sputtering
silver (Ag) with 1.2 micrometers thick, the metallic bipolar plates were
completed. The silver layer is used for corrosive resistance. The completed
mini-DMFC stack is a 2x2 cm2 fuel cell stack including a 1.5x1.5 cm2 MEA
(membrane electrode assembly). Several MEAs were assembly into mini-DMFC stacks
using the completed metallic bipolar plates. All test results showed the
metallic bipolar plates suitable for mini-DMFC stacks. The maximum output power
density is 9.3mW/cm2 and current density is 100 mA/cm2 when using 8 vol. %
methanol as fuel and operated at temperature 30 degrees C. The output power
result is similar to other reports by using conventional graphite bipolar
plates. However, conventional graphite bipolar plates have certain difficulty
to be machined to such micro-fluidic channels. The proposed
micro-electroforming metallic bipolar plates are feasible to miniaturize DMFC
stacks for further portable 3C applications.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Image data compression application to imaging spectrometers
The potential of image data compression techniques to satisfy the anticipated requirements of imaging spectrometer missions is discussed. Noiseless coding, rate controlled compression, cluster compression, and error protection are addressed
Solar pumped laser
A solar pumped laser is described in which the lasant is a gas that will photodissociate and lase when subjected to sunrays. Sunrays are collected and directed onto the gas lasant to cause it to lase. Applications to laser propulsion and laser power transmission are discussed
TRANSPORTATION DEREGULATION AND INTERREGIONAL COMPETITION IN THE NORTHEASTERN FEED ECONOMY
The effects of rail deregulation on feed transportation in the Northeast are examined through construction of a spatial equilibrium model of the Northeastern feed industry. Short-run and long-run effects of deregulation are analyzed through incorporation of rail rate structures for 1981 and 1984, respectively, into model simulations and comparison with pre-deregulation base year results (1980). The results show that the Northeast feed economy has generally benefited from rail deregulation which has led to lower transportation costs, lower feed costs and an enhanced competitive position relative to the Southeastern U.S.Public Economics,
Some practical universal noiseless coding techniques, part 2
This report is an extension of earlier work (Part 1) which provided practical adaptive techniques for the efficient noiseless coding of a broad class of data sources characterized by only partially known and varying statistics (JPL Publication 79-22). The results here, while still claiming such general applicability, focus primarily on the noiseless coding of image data. A fairly complete and self-contained treatment is provided. Particular emphasis is given to the requirements of the forthcoming Voyager II encounters of Uranus and Neptune. Performance evaluations are supported both graphically and pictorially. Expanded definitions of the algorithms in Part 1 yield a computationally improved set of options for applications requiring efficient performance at entropies above 4 bits/sample. These expanded definitions include as an important subset, a somewhat less efficient but extremely simple "FAST' compressor which will be used at the Voyager Uranus encounter. Additionally, options are provided which enhance performance when atypical data spikes may be present
A dual frequency microstrip antenna for Ka band
For fixed satellite communication systems at Ka band with downlink at 17.7 to 20.2 GHz and uplink at 27.5 to 30.0 GHz, the focused optics and the unfocused optics configurations with monolithic phased array feeds have often been used to provide multiple fixed and multiple scanning spot beam coverages. It appears that a dual frequency microstrip antenna capable of transmitting and receiving simultaneously is highly desirable as an array feed element. This paper describes some early efforts on the development and experimental testing of a dual frequency annular microstrip antenna. The antenna has potential application for use in conjunction with a monolithic microwave integrated circuit device as an active radiating element in a phased array of phased array feeds. The antenna is designed to resonate at TM sub 12 and TM sub 13 modes and tuned with a circumferential microstrip ring to vary the frequency ratio. Radiation characteristics at both the high and low frequencies are examined. Experimental results including radiating patterns and swept frequency measurements are presented
Thunderstorm Persistence at Cape Kennedy, Florida
Probabilities of thunderstorm persistence at Cape Kennedy, Florid
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