共查询到20条相似文献，搜索用时 46 毫秒
1.
This chapter introduces the chronological and interdisciplinary “frieze” which presents the main events relevant (in our opinion) to the problem of the emergence of life on Earth. This selection of events is directly connected to the previous chapters of this book.The frieze may be found in print as an insert at the back of the print publication. This supplementary material is also available in the online version of this article at and is accesssible for authorized users. 相似文献
2.
In this paper we present a new symbolic processor specially suited for the Earth rotation theory. This processor works with a more general kind of Poisson series called Kinoshita series, which has resulted to be very useful in the Earth rotation theory. Its structure is adapted for dealing with the more general analytical expressions that appear in the Earth rotation theory. This new algebraic processor has been successfully used for computing different contributions to the nutation series of the rigid Earth.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
3.
K. S. Dwarakanath A. A. Deshpande N. Udaya Shankar 《Journal of Astrophysics and Astronomy》1990,11(3):311-322
A simple but effective modification to the conventional CLEAN algorithm is suggested. This modification ensures both stability
and speed when CLEAN is applied to maps containing a mixture of point sources and extended structures. The method has been
successfully applied to the recently-completed sky survey at 34.5 MHz (Dwarakanath & Udaya Shankar 1990). This survey was
made using the Gauribidanur T array (GEETEE)1 in 1-D aperture synthesis mode. Since in this case the ‘dirty beam’ (point spread
function) cannot be directly computed, a method to obtain this is discussed in detail. The results of this deconvolution procedure
have been encouraging in terms of reduced computing time and improved dynamic range in our maps. This algorithm should find
wider application in deconvolving maps which have both extended structures and point sources
This telescope is jointly operated by the Indian Institute of Astrophysics, Bangalore & the Raman Research Institute, Bangalore. 相似文献
4.
We present two case studies of cluster encounters with foreshock cavities. For one event, we are able, for the first time, to accurately relate the observation of a foreshock cavity to the measured position of the bow shock. This allows us to compute the shock angle, a vital parameter in models of foreshock cavity formation, with greater confidence than any previous study. This cavity appears to be elongated along the magnetic field and we use the multispacecraft nature of the Cluster mission to constrain its field-parallel and -perpendicular extent. We show that this event is embedded within a region of field-aligned ion beams. This is the first time a foreshock cavity has been shown to be surrounded by foreshock ion beams. A second foreshock cavity is associated with a small rotation in the interplanetary magnetic field (IMF). We show that this event appears on the boundary between an interval when the spacecraft were inside the ion foreshock, and an excursion upstream. This is the first report of a foreshock cavity observed during the traversal of the global foreshock. This second event has some features expected from the new Sibeck et al. (2008) model of cavities as brief encounters with a spatial boundary in the global foreshock. 相似文献
5.
Barbara Cunow 《Astrophysics and Space Science》2003,284(2):743-746
Near-infrared and optical colour gradients of the discs of non-active and active spiral galaxies are investigated by using
disc scalelengths. The measurements indicate that the colour gradients for JHK′ are small and no significant differences exist between the non-active and the active galaxies. This result is different from
what is found for the optical wavelength regions, where significant colour gradients are observed in the discs of the non-active
galaxies, but not in the discs of the active ones. This indicates that the differences between non-active and active galaxies
found in the optical do not exist in the near-infrared.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
S.YA. Braude S.L. Rashkovsky K.M. Sidorchuk M.A. Sidorchuk K.P. Sokolov N.K. Sharykin S.M. Zakharenko 《Astrophysics and Space Science》2002,280(3):235-300
This paper presents results and describes the improved data processing algorithm of the low frequency sky survey of discrete
sources carried out with the UTR-2 radio telescope. The measurements were conducted within the frequency range 10 to25 MHz.
Coordinates and flux densities of the sources detected were obtained. Identification with sources from the 4C survey has been
done. The resulting catalogue contains parameter estimates for 483 sources on a set of frequencies within the UTR-2 range.
This revised version was published online in July 2006 with corrections to the Cover Date.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
A.J. Lim 《Astrophysics and Space Science》2003,285(3-4):745-759
This article describes some of the techniques used to include various micro-processes in numerical gas-dynamic simulations.
These techniques are then used in simulations of photo-evaporating clumps, H2 level populations and time dependent shocks/jets.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Efi Meletlidou Galina Stagika Simos Ichtiaroglou 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):323-335
The structure of the resonance zone in nearly integrable Hamiltonian systems is studied by a more general method than the
pendulum approximation. This method applies to the case of a non-degenerate integrable part in the Hamiltonian. This problem
may be overcome in a class of galactic-type polynomial potentials, in the case where the higher-order term is by itself integrable.
An illustrative example is worked out. 相似文献
9.
Jayant V. Narlikar 《Journal of Astrophysics and Astronomy》1997,18(4):353-362
This paper summarises the recent work on the quasi-steady state cosmology. This includes, the theoretical formulation and
simple exact solutions of the basic equations, their relationship to observations, the stability of solutions and the toy
model for understanding the growth of structures in the universe. 相似文献
10.
M.J. Rees 《Astrophysics and Space Science》2003,285(2):375-388
Fred Hoyle famously drew attention to the significance of apparent coincidences in the energy levels of the carbon and oxygen
nucleus. This paper addresses the possible implications of other coincidences in cosmology.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
Albert Bosma 《Celestial Mechanics and Dynamical Astronomy》1998,72(1-2):69-90
In these notes I will briefly summarize our knowledge about the dark matter problem, and emphasize the corresponding dynamical
aspects. This covers a wide area of research, so I have been selective, and have concentrated on the subject of dark matter
in nearby galaxies, in particular spirals.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
This article uses fractal and correlation analysis of solar radio emission for determining the solar coronal rotation. It
is clear from this analysis that radio emissions are modulated by the solar rotation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Jacques Henrard 《Celestial Mechanics and Dynamical Astronomy》2000,76(4):283-289
This note describes briefly a technique, easily implemented with most computer algebra systems, for the purpose of computing
the two-body expansions (in powers of the eccentricity and in Fourier series of the mean-anomaly) of a large class of functions
of the distance, the true anomaly and/or the eccentric anomaly.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
D. J. Scheeres 《Celestial Mechanics and Dynamical Astronomy》2004,89(2):127-140
Constraints on the final rotation rates of a Hill unstable binary in the full 2-body problem are derived and analyzed. Application
of these constraints are made to the problem of a constant density body spun to disruption. This analysis has relevance to
the evolution of asteroid spin rates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
This paper describes a wide-field survey made at 34.5 MHz using GEETEE,1 the low frequency telescope at Gauribidanur (latitude
13°36′12′′N). This telescope was used in the transit mode and by per forming 1-D synthesis along the north-south direction
the entire observable sky was mapped in a single day. This minimized the problems that hinder wide-field low-frequency mapping.
This survey covers the declination range of-50° to + 70° (- 33° to +61° without aliasing) and the complete 24 hours of right
ascension. The synthesized beam has a resolution of 26′ x 42′ sec (δ- 14°. 1). The sensitivity of the survey is 5 Jy/beam (1σ). Special care has been taken to ensure that the antenna responds
to all angular scale structures and is suitable for studies of both point sources and extended objects
This telescope is jointly operated by the Indian Institute of Astrophysics, Bangalore and the Roman Research Institute, Bangalore. 相似文献
16.
P. Jablonka 《Astrophysics and Space Science》1999,265(1-4):523-529
This review reports on recent results obtained from HST/WFPC2 high resolution observations of field stars and star clusters
in the bulge and the halo of the nearby galaxy M31.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
One of the main limitations to the sensitivity of the infrared camera ISOCAM on-board the Infrared Space Observatory (ISO)
comes from responsivity variations and glitches caused by the impacts of charged particles in photo-detectors. Glitch rate
measurements, glitch properties and removal methods have already been addressed during the first ISO detector workshop(Madrid,
1998) and published in a special issue of Experimental Astronomy. It appeared that glitch rate and most of glitch properties
could be reproduced by Monte-Carlo simulations. This is very interesting in order to predict before launch the effect of charged
particles in photo-detectors operated in space. This paper presents results of Monte-Carlo simulations of radiation effects
on ISOCAM detectors. Glitch rates, spatial and energetic properties of glitches have been computed and are compared with measured
values.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
薛祝和 《中国科学院上海天文台年刊》2011,(0)
介绍了FS软件的基本特征和ES控制标准硬件的详细工作流程。还具体介绍了在FS软件下控制观测站各种特有硬件的方法、步骤。本文可供中国VLBI网观测站程序员参考。 相似文献
19.
Recent claims of small icy comets disintegrating in the high atmosphere point to a component of comets in the form of loose
aggregates of dust. This could be understood in terms of Lyttleton;'s theory of comet formation by accretion of interstellar
grains.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
The polarization distribution of the inner coma of comet Hale-Bopp was measured by CCD imaging around perihelion. The dust
shell positions correlate well with relative maxima of polarization. The images taken in the I-band identify different shell
systems, each showing individual polarization properties. This could be related to differences in the dust properties of the
associated jets.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献