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41.
42.
Preliminary data are presented on seven “special” objects found in low-dispersion spectral plates of the FBS survey. The first
object, FBS 0250+167, is found to be a class M7 dwarf with a high proper motion (∼5.130 arcsec/year) lying about 3 pc from
the sun. Three of the objects, with spectra of classes M8–M9, are suspected of being long-period Mirids with large mass losses
and surrounded by dense clouds. The three remaining objects have very short low-dispersion spectra on the FBS survey plates
(clearly they are non stellar objects) and are of interest for later detailed study.
__________
Translated from Astrofizika, Vol. 50, No. 1, pp. 73–85 (February 2007). 相似文献
43.
V. G. Demin Y. G. Markov I. S. Minyaev 《Celestial Mechanics and Dynamical Astronomy》1990,50(3):231-249
In the restricted three-body problem we consider the motion of a viscously elastic sphere (planet) with its centre of mass moving in a conditionally-periodic orbit. The approximate equations describing the rotational motion of the sphere in terms of the Andoyer variables are obtained by the method of the separation of motion and averaging; the evolution of the motion is also analysed. 相似文献
44.
Efficient control of ships in a designed trajectory is always a significant charge for ship maneuverings. The purpose of this paper is to design a robust H∞ controller and a reliability analysis for a container ship in a way-point tracking. First, the H∞ controller is designed for a container ship because of model parameters’ uncertainties and external disturbances such as waves, winds and ocean currents. Then, to evaluate the reliability of the designed controller, a well-known reliability analysis technique is employed to achieve the predefined heading angle overshoot (that is less than 20%) in way-point tracking. To do this, three random variables including wind speed, wind direction and wave direction are considered as the inputs due to their significant effect on overshoot, compared to other variables. The results demonstrate the capability of the designed H∞ controller against modeling uncertainties and external disturbances in way point tracking control. 相似文献
45.
南海北部陆架区两个台风过境时近惯性运动的若干特征 总被引:2,自引:1,他引:1
Features of near-inertial motions on the shelf(60 m deep) of the northern South China Sea were observed under the passage of two typhoons during the summer of 2009. There are two peaks in spectra at both sub-inertial and super-inertial frequencies. The super-inertial energy maximizes near the surface, while the sub-inertial energy maximizes at a deeper layer of 15 m. The sub-inertial shift of frequency is induced by the negative background vorticity. The super-inertial shift is probably attributed to the near-inertial wave propagating from higher latitudes. The near-inertial currents exhibit a two-layer pattern being separated at mid-depth(25–30 m), with the phase in the upper layer being nearly opposite to that in the lower layer. The vertical propagation of phase implies that the near-inertial energy is not dominantly downward. The upward flux of the near-inertial energy is more evident at the surface layer(17 m). There exist two boundaries at 17 and 40 m, where the near-inertial energy is reflected upward and downward. The near-inertial motion is intermittent and can reach a peak of as much as 30 cm/s. The passage of Typhoon Nangka generates an intensive near-inertial event, but Typhoon Linfa does not. This difference is attributed to the relative mooring locations, which is on the right hand side of Nangka's path(leading to a wind pattern rotating clockwise with time) and is on the left hand side of Linfa's path(leading to a wind pattern rotating anti-clockwise with time). 相似文献
46.
E. A. Perdios 《Celestial Mechanics and Dynamical Astronomy》2007,99(2):85-104
This paper deals with the Sitnikov family of straight-line motions of the circular restricted three-body problem, viewed as
generator of families of three-dimensional periodic orbits. We study the linear stability of the family, determine several
new critical orbits at which families of three dimensional periodic orbits of the same or double period bifurcate and present
an extensive numerical exploration of the bifurcating families. In the case of the same period bifurcations, 44 families are
determined. All these families are computed for equal as well as for nearly equal primaries (μ = 0.5, μ = 0.4995). Some of the bifurcating families are determined for all values of the mass parameter μ for which they exist. Examples of families of three dimensional periodic orbits bifurcating from the Sitnikov family at double
period bifurcations are also given. These are the only families of three-dimensional periodic orbits presented in the paper
which do not terminate with coplanar orbits and some of them contain stable parts. By contrast, all families bifurcating at
single-period bifurcations consist entirely of unstable orbits and terminate with coplanar orbits. 相似文献
47.
We use a new expanded and partially modified sample of 1501 thin edge-on spiral galaxies from the RFGC catalog to analyze the non-Hubble bulk motions of galaxies on the basis of a generalized multiparameter Tully-Fisher relation. The results obtained have confirmed and refined our previous conclusions (Parnovsky et al. 2001), in particular, the statistical significance of the quadrupole and octupole components of the galaxy bulk velocity field. The quadrupole component, which is probably produced by tidal forces from overdense regions, leads to a difference in the recession velocities of galaxies on scales of 8000–10000 km s?1 up to 6% of their Hubble velocity. On Local Supercluster scales (3000 km s?1), its contribution increases to about 20%. Including the octupole components in the model causes the dipole component to decrease to the 1σ level. In contrast, in the dipole model, the galaxy bulk velocity relative to the frame of reference of the cosmic microwave background is 310±75 km s?1 toward the apex with l=311° and b=12°. We also consider a sample of 1493 galaxies that was drawn using a more stringent galaxy selection criterion. The difference between the results of our data analysis for this sample and for the sample of 1501 galaxies is primarily attributable to a decrease in the dipole velocity component (290±75 km s?1 toward the apex with l=310° and b=12°) and a decrease in σ by about 2%. 相似文献
48.
3mm多普勒云雷达测量反演云内空气垂直速度的研究 总被引:7,自引:4,他引:3
垂直指向的W-波段大气云雷达(WACR)不仅测量云粒子的反射率因子Z, 而且测量多普勒速度谱。本文利用寿县气象站WACR在2008年11月1日一个时段的测量, 进行云内空气垂直速度反演试验。首先讨论个例中反射率、 Doppler平均速度及谱宽的分布特征及原因, 然后利用小粒子示踪法和改进的以小粒子示踪法为基础的粒子下降速度w0—反射率因子 (w0-Z) 关系法反演了云内空气垂直速度, 进而结合Doppler谱数据分析反演结果。结果显示: 小粒子示踪法在湍流较弱时能比较精确地反演空气垂直速度, 而湍流较强时, 湍流造成的误差不可忽略; 改进算法在湍流较强时能够减少湍流对反演结果的影响。 相似文献
49.
We apply vector spherical functions to problems of stellar kinematics. Using these functions allows all of the systematic components in the stellar velocity field to be revealed without being attached to a specific physical model. Comparison of the theoretical decomposition coefficients of the equations for a particular kinematical model with observational data can provide precise information about whether the model is compatible with the observations and can reveal systematic components that are not described by this model. The formalism of vector spherical functions is particularly well suited for analyzing the present and future (e.g., GAIA) catalogs containing all three velocity vector components: the propermotions in both coordinates and the radial velocity. We show that there are systematic components in the proper motions of Hipparcos stars that cannot be interpreted in terms of the linear Ogorodnikov-Milne model. The same result is also confirmed by an analysis of the radial velocities for these stars. 相似文献
50.
This paper is a follow-up to a previous paper on the subject of liquefaction potential index (LPI), a parameter that is often used to characterize the potential for surface manifestation of liquefaction at a given site subjected to a given shaking level (represented by a pair of peak ground surface acceleration amax and moment magnitude Mw). In the previous paper by Juang and his coworkers, the LPI was re-calibrated for a piezocone penetration test (CPTU) model, and a simplified model based on LPI was created for computing the conditional probability of surface manifestation of liquefaction (PG). In this paper, the model for this conditional probability PG is extended into a complete framework for assessing the probability of surface manifestation of liquefaction in a given exposure time at a given site subjected to all possible ground motions at all seismic hazard levels. This new framework is formulated and demonstrated with an example site in 10 different seismic regions in the United States. 相似文献