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111.
J. L. Casse 《New Astronomy Reviews》1999,43(8-10)
This document describes in broad terms the EVN MkIV Data Processor at JIVE which was officially opened on 22 October 1998. 相似文献
112.
Alan F. M. Moorwood 《Experimental Astronomy》1994,3(1-4):301-304
The four infrared instruments currently planned for the ESO VLT are briefly described and their collective infrared array requirements are summarized and discussed in the light of recent advances in this area. 相似文献
113.
Liu Yangang 《大气科学进展》1997,14(3):369-388
As the second attempt at unifying treatment of atmospheric particle systems, this paper further examines shape characterization of atmospheric particles. First, to support the theoretical framework developed in Part I, methods for studying non-spherical particles are reviewed. It is argued that these different methods can be unified under fractal geometry through the generalized power laws given in Part I. Empirical power-laws for hydrometeors scat-tered in literature since 1935 are summarized and reevaluated in terms of fractals. Second, generalization from self-similar to self-affine particles is discussed. Self-affinity of atmospheric particles is exemplified by examining the exponents in the power laws between the length along a- and c-axis of ice crystals. It is argued that unlike Euclidean and self-similar particles, self-affine particles do not have a simple dimensional relation between original particles and their projections; the relation for projection of self-similar particles and Mandelbrot’ thumb rules for intersection respectively set the lower and upper bound. Using published data, self-affine particles are shown to exist in the at-mosphere. The existence of self-affine particles in turn calls for instruments that can simultaneously measure mass, area and maximum diameter (or their equivalents). 相似文献
114.
Sai K. Vanapalli Vinod K. Garga Patrick Brisson 《Geotechnical and Geological Engineering》2007,25(2):191-202
The design details of a modified permeameter used for determining the unsaturated coefficient of permeability of tailings
are presented in this Paper. This permeameter can accommodate a large tailings specimen, 200 × 200 × 400 mm high, and uses
the Instantaneous Profile Method (IPM) to determine the variation of unsaturated coefficient of permeability with respect
to soil suction using a single specimen. The soil-water characteristic curve data can also be simultaneously determined from
the modified permeameter. The key design features in comparison to a conventional permeameter include the provision of adjustable
sensors that move along with the tailings as it settles due to desaturation during the testing period. The advantages of using
a modified permeameter in the determination of the coefficient of permeability of unsaturated tailings are also discussed
in this paper. Tests were carried out by providing suction using hanging column technique in the suction range of 0–10 kPa.
Such an apparatus can easily be modified to accommodate higher suction values. 相似文献
115.
We present a new speckle camera designed and built at Observatoire Midi-Pyrénées. This focal instrument has been used for four years with the 2-meter Bernard Lyot Telescope of Pic du Midi observatory. It can be set in various operating modes: full pupil imaging, masked-pupil imaging, spectroscopy, wave-front sensor and stellar coronagraphy, hence its name 'PISCO' ('Pupil Interferometry Speckle COronagraph'). Restored images of double and triple stars have demonstrated its capabilities in providing close to diffraction limited images (0.06 in V). PISCO has been fully tested and is now ready to be used by the whole astronomical community. 相似文献
116.
117.
V. Formisano F. Angrilli S. Atreya D. Biondi M.I. Blecka L. Colangeli F. Esposito M. Giuranna V. Gnedykh G. Hansen I. Khatuntsev N. Ignatiev A. Jurewicz J. Lopez Moreno A. Mattana E. Mencarelli V. Moroz F. Nespoli R. Orfei V. Orofino D. Patsaev M. Rataj J. Rodriguez B. Saggin L. Zasova 《Planetary and Space Science》2005,53(10):963-974
The Planetary Fourier Spectrometer (PFS) for the Mars Express mission is an infrared spectrometer optimised for atmospheric studies. This instrument has a short wave (SW) channel that covers the spectral range from 1700 to (1.2-) and a long-wave (LW) channel that covers 250- (5.5-). Both channels have a uniform spectral resolution of . The instrument field of view FOV is about 1.6° (FWHM) for the Short Wavelength channel (SW) and 2.8° (FWHM) for the Long Wavelength channel (LW) which corresponds to a spatial resolution of 7 and 12 km when Mars is observed from an height of 250 km. PFS can provide unique data necessary to improve our knowledge not only of the atmosphere properties but also about mineralogical composition of the surface and the surface-atmosphere interaction.The SW channel uses a PbSe detector cooled to 200-220 K while the LW channel is based on a pyroelectric (LiTaO3) detector working at room temperature. The intensity of the interferogram is measured every 150 nm of physical mirrors displacement, corresponding to 600 nm optical path difference, by using a laser diode monochromatic light interferogram (a sine wave), whose zero crossings control the double pendulum motion. PFS works primarily around the pericentre of the orbit, only occasionally observing Mars from large distances. Each measurements take 4 s, with a repetition time of 8.5 s. By working roughly 0.6 h around pericentre, a total of 330 measurements per orbit will be acquired 270 looking at Mars and 60 for calibrations. PFS is able to take measurements at all local times, facilitating the retrieval of surface temperatures and atmospheric vertical temperature profiles on both the day and the night side. 相似文献
118.
Kevin R. Healy 《Astrophysics and Space Science》1995,227(1-2):83-91
For nearly two decades, the aperature synthesis telescope known as the Very Large Array (VLA) has been providing a wealth of data on all types of astronomical objects. This telescope fills the need for more powerful and more sensitive instruments to gather data on a vast range of plasma phenomena in astrophysical settings. Currently the VLA is capable of observing at eight radio frequency bands (four corresponding to important spectral lines) with sensitivities on the order of 10–29
Wm
–2
Hz
–1, or 10–3 Jansky (1 mJy), and noise levels ten times lower. This paper describes the VLA and its capabilities, and describes how researchers interested in plasma astrophysics can use the instrument. 相似文献
119.
120.
Once completed, the Atacama Large Millimeter Array (ALMA) will be the most powerful (sub)millimeter interferometer in terms of sensitivity, spatial resolution and imaging. This paper presents the capabilities of ALMA applied to the observation of Centaurs and Trans-Neptunian Objects, and their possible output in terms of physical properties. Realistic simulations were performed to explore the performances of the different frequency bands and array configurations, and several projects are detailed along with their feasibility, their limitations and their possible targets. Determination of diameters and albedos via the radiometric method appears to be possible on ∼500 objects, while sampling of the thermal lightcurve to derive the bodies’ ellipticity could be performed at least 30 bodies that display a significant optical lightcurve. On a limited number of objects, the spatial resolution allows for direct measurement of the size or even surface mapping with a resolution down to 13 milliarcsec. Finally, ALMA could separate members of multiple systems with a separation power comparable to that of the HST. The overall performance of ALMA will make it an invaluable instrument to explore the outer Solar System, complementary to space-based telescopes and spacecrafts. 相似文献