65,485 research outputs found
Matched-Filter Detection of Mode-Locked Laser Signals
The passive Fabry-Perot cavity is shown to be a good practical approach to the match-filter optimization for the sensitive detection of mode-locked laser signals. Doppler measurements of relative motion over a wide range of velocities are possible simply by measuring the cavity length for a peak output
Low-frequency GMRT observations of the magnetic Bp star HR Lup (HD 133880)
We present radio observations of the magnetic chemically peculiar Bp star HR
Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the
source is not detected but we are able to determine upper limits to the
emission. The 647 MHz limits are particularly useful, with a 5\sigma\ value of
0.45 mJy. Also, no large enhancements of the emission were seen. The
non-detections, along with previously published higher frequency detections,
provide evidence that an optically thick gyrosynchrotron model is the correct
mechanism for the radio emission of HR Lup.Comment: 7 pages, accepted for publication in the Bulletin of the Astronomical
Society of India, to appear in the June issu
Unemployment and the UK Labour Market Before, During and After the Golden Age
During the ‘golden age’ of the 1950s and 1960s unemployment in Britain averaged 2 per cent. This was far lower than ever before or since and a number of hypotheses have been put forward to account for this unique period in labour market history. But there has been little attempt to isolate precisely how the determinants of wage setting and unemployment differed before, during and after the golden age. We estimate a two-equation model over the whole period from 1872 to 1999 using a newly constructed set of long-run labour market data. We find that the structure of real wage setting was different in the golden age, consistent with notions about the postwar consensus, but it did not result in wages that were significantly lower relative to productivity than during other eras. Rapid growth in productivity and world trade together with low interest rates did keep unemployment lower during the golden age than after the 1970s. But the key difference between the golden age and the periods before and after was shifts in labour demand that are not accounted for by any of the variables that are usually thought to determine the equilibrium unemployment rate
GMRT Low Frequency Observations of Extrasolar Planetary Systems
Extrasolar planets are expected to emit detectable low frequency radio
emission. In this paper we present results from new low frequency observations
of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at
150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have
been chosen because the stars are young (with ages < 1 Gyr) and are likely to
have strong stellar winds, which will increase the expected radio flux. The
planets are massive (presumably) gas giant planets in longer period orbits, and
hence will not be tidally locked to their host star (as is likely to be the
case for short period planets) and we would expect them to have a strong
planetary dynamo and magnetic field. We do not detect either system, but are
able to place tight upper limits on their low frequency radio emission, at
levels comparable to the theoretical predictions for these systems. From these
observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy
for HD 128311. In addition, these upper limits also provide limits on the low
frequency radio emission from the stars themselves. These results are discussed
and also the prospects for the future detection of radio emission from
extrasolar planets.Comment: 6 pages, 2 figures, accepted for publication in MNRA
INCIDENTAL AND JOINT CONSUMPTION IN RECREATION DEMAND
A theory for analyzing incidental consumption in a single site recreation demand model is presented. We show that incidental consumption on a recreation trip, such as a visit to see friends or a visit to a second recreation site, can be treated as a complementary good and analyzed using conventional theory. We also show that the analysis applies whether the side trips are incidental or joint. In a simple application we find that failing to account for incidental consumption appears to create little bias in valuing recreation sites.Resource /Energy Economics and Policy,
Handling qualities requirements for control configured vehicles
The potential effects of fly by wire and control configured vehicle concepts on flying qualities are considered. Failure mode probabilities and consequences, controllability, and dynamics of highly augmented aircraft are among the factors discussed in terms of design criteria
Analysis of a unidirectional composite containing broken fibers and matrix damage
An analytical solution is developed for the determination of the stresses and displacements in a unidirectional fiber-reinforced composite containing an arbitrary number of broken fibers as well as longitudinal yielding and splitting of the matrix. The solution is developed using a materials-modeling approach which is based on a shear-lag stress transfer mechanism. The equilibrium equation in the axial direction gives a pair of integral equations which are solved numerically. Excellent agreement is shown to exist between the solution and experimental results for notched unidirectional boron/aluminum laminates without splitting. For brittle matrix composites (i.e. epoxy) equally good results are indicated for both matrix yielding and splitting. For yielding without splitting the fracture strength depends on crack length while for large splitting it is crack length independent
Design study of large area 8 cm x 8 cm wrapthrough cells for space station
The design of large area silicon solar cells for the projected NASA space station is discussed. It is based on the NASA specification for the cells which calls for an 8 cm by 8 cm cell of wrapthrough type with gridded back contacts. The beginning of life (BOL) power must be 1.039 watts per cell or larger and maximum end of life (EOL) after 10 years in the prescribed orbit under an equivalent 1MeV electron radiation damage fluence of 5 times 10 to the 13th power e/square cm. On orbit efficiency is to be optimized by a low thermal absorptance goal (thermal alpha) of .63
A Prehispanic Maya Pit Oven? Microanalysis of Fired Clay Balls from the Puuc Region, Yucatán, Mexico
This is a postprint (author's final draft) version of an article published in Journal of Archaeological Science in 2013. The final version of this article may be found at http://dx.doi.org/10.1016/j.jas.2012.10.014 (login may be required). The version made available in OpenBU was supplied by the author.Excavations of a kitchen at Escalera al Cielo in the Puuc Maya region of Yucatán, Mexico
uncovered a concentration of fired clay balls (ca. 3–5 cm in diameter), in addition to other de facto domestic refuse. The kitchen pertains to an intensively excavated elite residential group that was rapidly abandoned sometime near the end of the Terminal Classic period (A.D. 800–950), resulting in floor assemblages that provide an opportunity to explore the types and distribution of daily household activities. The results of experimental replications and a suite of analyses comprising modal analysis, ceramic petrography, Fourier transform infrared spectroscopy (FTIR), and microbotanical residue analysis reveal aspects of clay preparation, firing temperatures, repeated use of the balls, firing conditions, and specific plant food or fuel residues adhering to them. We show that the fired clay balls were manufactured with local, clay-rich soil and employed by the inhabitants of Escalera al Cielo as heating elements; relatively high concentrations of microbotanical residues from edible plants adhering to them support the hypothesis that they were involved in kitchen activities related to food processing
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