25,328 research outputs found
Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes
Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black
hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the
Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as
the Ruppeiner scalar curvature and find that the singular points are not the
same with the ones obtained using the heat capacity. Legendre-invariant metric
proposed by Quevedo and the metric obtained by using the free energy as the
thermodynamic potential are obtained and the corresponding scalar curvatures
diverge at the Davies points.Comment: Latex,19 pages,14 figure
Application of Remote Sensing Techniques for Appraising Changes in Wildlife Habitat
An attempt was made to investigate the potential of airborne, multispectral, line scanner data acquisition and computer-implemented automatic recognition techniques for providing useful information about waterfowl breeding habitat in North Dakota. The spectral characteristics of the components of a landscape containing waterfowl habitat can be detected with airborne scanners. By analyzing these spectral characteristics it is possible to identify and map the landscape components through analog and digital processing methods. At the present stage of development multispectral remote sensing techniques are not ready for operational application to surveys of migratory bird habitat and other such resources. Further developments are needed to: (1) increase accuracy; (2) decrease retrieval and processing time; and (3) reduce costs
Automated data acquisition and reduction system for torsional braid analyzer
Automated Data Acquisition and Reduction System (ADAR) evaluates damping coefficient and relative rigidity by storing four successive peaks of waveform and time period between two successive peaks. Damping coefficient and relative rigidity are then calculated and plotted against temperature or time in real time
AMTV headway sensor and safety design
A headway sensing system for an automated mixed traffic vehicle (AMTV) employing an array of optical proximity sensor elements is described, and its performance is presented in terms of object detection profiles. The problem of sensing in turns is explored experimentally and requirements for future turn sensors are discussed. A recommended headway sensor configuration, employing multiple source elements in the focal plane of one lens operating together with a similar detector unit, is described. Alternative concepts including laser radar, ultrasonic sensing, imaging techniques, and radar are compared to the present proximity sensor approach. Design concepts for an AMTV body which will minimize the probability of injury to pedestrians or passengers in the event of a collision are presented
Power system applications of fiber optics
Power system applications of optical systems, primarily using fiber optics, are reviewed. The first section reviews fibers as components of communication systems. The second section deals with fiber sensors for power systems, reviewing the many ways light sources and fibers can be combined to make measurements. Methods of measuring electric field gradient are discussed. Optical data processing is the subject of the third section, which begins by reviewing some widely different examples and concludes by outlining some potential applications in power systems: fault location in transformers, optical switching for light fired thyristors and fault detection based on the inherent symmetry of most power apparatus. The fourth and final section is concerned with using optical fibers to transmit power to electric equipment in a high voltage situation, potentially replacing expensive high voltage low power transformers. JPL has designed small photodiodes specifically for this purpose, and fabricated and tested several samples. This work is described
Discovery of Five Recycled Pulsars in a High Galactic Latitude Survey
We present five recycled pulsars discovered during a 21-cm survey of
approximately 4,150 deg^2 between 15 deg and 30 deg from the galactic plane
using the Parkes radio telescope. One new pulsar, PSR J1528-3146, has a 61 ms
spin period and a massive white dwarf companion. Like many recycled pulsars
with heavy companions, the orbital eccentricity is relatively high (~0.0002),
consistent with evolutionary models that predict less time for circularization.
The four remaining pulsars have short spin periods (3 ms < P < 6 ms); three of
these have probable white dwarf binary companions and one (PSR J2010-1323) is
isolated. PSR J1600-3053 is relatively bright for its dispersion measure of
52.3 pc cm^-3 and promises good timing precision thanks to an intrinsically
narrow feature in its pulse profile, resolvable through coherent dedispersion.
In this survey, the recycled pulsar discovery rate was one per four days of
telescope time or one per 600 deg^2 of sky. The variability of these sources
implies that there are more millisecond pulsars that might be found by
repeating this survey.Comment: 15 pages, 3 figures, accepted for publication in Ap
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