9,161 research outputs found
Recent progress in tidal modeling
Recent contributions to tidal theory during the last five years are reviewed. Specific areas where recent progress has occurred include: the action of mean wind and dissipation on tides, interactions of other waves with tides, the use of TGCM in tidal studies. Furthermore, attention is put on the nonlinear interaction between semidiurnal and diurnal tides. Finally, more realistic thermal excitation and background wind and temperature models have been developed in the past few years. This has led to new month-to-month numerical simulations of the semidiurnal tide. Some results using these models are presented and compared with ATMAP tidal climatologies
Advanced electric propulsion system concept for electric vehicles. Addendum 1: Voltage considerations
The two electric vehicle propulsion systems that best met cost and performance goals were examined to assess the effect of battery pack voltage on system performance and cost. A voltage range of 54 to 540 V was considered for a typical battery pack capacity of 24 k W-hr. The highest battery specific energy (W-hr/kg) and the lowest cost (0.057/km and for the flywheel system was $0.037/km
A program of astronomical infrared spectroscopy from aircraft
Astronomical infrared spectroscopy from aircraf
Orbiting astronomical observatory Final report /including status reports for 1 Dec. 1967 - 30 Jun. 1968 and 1 Jul. 1968 - 31 Mar. 1969/
Research activities of Lunar and Planetary Laborator
The optical and near-infrared properties of nearby groups of galaxies
We present a study of the optical (BRI) and near-infrared (JHK) luminosity
fuctions (LFs) of the GEMS sample of 60 nearby groups of galaxies between
0<z<0.04, with our optical CCD photometry and near-IR photometry from the 2MASS
survey. The LFs in all filters show a depletion of galaxies of intermediate
luminosity, two magnitudes fainter than L*, within 0.3 R{500} from the centres
of X-ray faint groups. This feature is not as pronounced in X-ray bright
gropus, and vanishes when LFs are found out to R{500}, even in the X-ray dim
groups. We argue that this feature arises due to the enhanced merging of
intermediate-mass galaxies in the dynamically sluggish environment of low
velocity-dispersion groups, indicating that merging is important in galaxy
evolution even at z~0.Comment: to appear in the proceedings of the ESO workshop "Groups of Galaxies
in the Nearby Universe", Santiago, Dec 5-9, 2005. Eds. I. Saviane, V. Ivanov,
& J. Borissova (Springer Verlag); 5 page
Physics-based derivation of a formula for the mutual depolarization of two post-like field emitters
Recent analyses of the field enhancement factor (FEF) from multiple emitters
have revealed that the depolarization effect is more persistent with respect to
the separation between the emitters than originally assumed. It has been shown
that, at sufficiently large separations, the fractional reduction of the FEF
decays with the inverse cube power of separation, rather than exponentially.
The behavior of the fractional reduction of the FEF encompassing both the range
of technological interest ( being the separation and is
the height of the emitters) and , has not been predicted by
the existing formulas in field emission literature, for post-like emitters of
any shape. In this letter, we use first principles to derive a simple
two-parameter formula for fractional reduction that can be of interest for
experimentalists to modeling and interpret the FEF from small clusters of
emitters or arrays in small and large separations. For the structures tested,
the agreement between numerical and analytical data is
Dust and ionized gas in active radio elliptical galaxies
The authors present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large H alpha + (NII) luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and the authors are currently investigating possible excitation mechanisms (Sparks et al. 1990)
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