大射电望远镜索牵引并联机构索力优化分析

为对大射电望远镜馈源支撑系统索牵引并联机构实施控制、获得准确的索长信息,采用精确的悬链线方程建立舱体非线性静平衡方程组来求解索力,进而获得大跨度下刚索索长。提出了线性简化模型——赝曲线模型,该模型保证了解算精度,大大提高了解算效率,为实时控制及进一步大规模计算提供了便利。在给定位置下,利用赝曲线模型对姿态角进行搜索,得到满足索力约束条件的姿态角集合。在此基础上,以索力均匀分布为优化目标对索力进行优化,从而保证系统良好的力特性,避免钢索之间的干扰。数值计算说明了赝曲线模型的精确性和快速性,最后利用赝曲线模型得到了优化后精确的索力、姿态角与索长。     

论彗晕的形状

关于彗晕的形状，没有一致的意见和结论．利用何种曲线描述彗晕，对于彗晕模型的建立以及彗晕动力学的理解具有重要的意义．借助于流体力学中一个修正的牛顿公式，指出彗晕的形状接近悬链线．还指出彗晕并不像Eddington所讨论那样，是尘埃颗粒轨道的抛物线包络．     

Hale-BOPP彗星的壳层结构

在紫金山天文台全自动密度扫描仪（PDS）上测量了1997年3月4日（UT）拍摄的Hale-Bopp彗星的壳层结构。对测量的数据用优选法分析后给出：（1）从彗核喷发出的喷流（壳层结构的第一层亦即最靠近彗核的那一层）呈阿基米德螺线形状，喷流喷出物质的速度为1.6公里/秒；（2）壳层结构的第二，三，四层呈抛物线形状，亦与悬链线相近。     

计时观测测量脉冲星参数的数学模型与精度估计

脉冲星计时观测能够精确测量脉冲星自转参数和天体测量参数.概述了脉冲星计时模型和利用最小二乘拟合测量脉冲星各个参数并估计其方差的数学方法.在黄道坐标系导出了脉冲星各个参数误差与计时残差之间关系的数学表达式.给出了脉冲星黄经、黄纬和周年视差测量精度与脉冲星黄纬绝对值之间的关系曲线.讨论了脉冲星各个天体测量参数测量精度与脉冲星纬向参数本身的关系.     

太阳黑子磁场方位角随深度的变化

为了建立三维的太阳黑子磁场模型，必须确定横向磁场的方位角（x)及其随深度的可能变化。本文提出一种探测x随深度变化的方法，即对黑子的一定点依次用磁敏谱线的不同部分测量代表线偏振的两个斯托克斯参数Q和U，然后按由牧田提出并经我们改进的方法，给出磁场方位角图。如果x随深度呈现出扭曲结构，则方位角图上的曲线含有圆圈形，否则可是类似抛物线的较为简单的曲线。在测量仪器的灵敏度足够的情况下，本方法对黑子外面的日面弱磁场区域也可以使用。     

氢线的振子强度

本文给出了氢线振子强度依赖热动平衡偏离的形式表达式,提出了一种由日珥发射线光谱分析确定日珥氢原子次能态热动平衡偏离的方法,并给出了对十个日珥的计算结果。最后,对氢原子2p态布居较2s态相对偏少的可能意义做了讨论。     

星际空间中宇宙线重新加速的研究

本文从能量空间中具有加速的宇宙线传播方程出发,给出了泄漏箱模型图象中高能原初谱及次级与原初核之比的数学表达式,我们的结果表明星际空间中宇宙线的重新加速可能是存在的,没有必要考虑次级和原初的不同空间分布的概念。     

射电天线指向改正模型中轴系误差的完全表达式

为了提高射电天线的目标跟踪精度,采用直接法推导了射电天线轴系误差对指向的影响,并给出轴系误差指向改正模型的完全表达式,明确了指向改正模型中各轴系参数的定义,传统分项以及球谐函数所推导的轴系误差项为该模型的简化形式.基于此,评估得出基本参数改正模型中,因忽略轴系误差高次谐项而引起的指向精度损失可能达到1′′量级,具体需结合轴系误差大小而定;同时明确了基本参数改正模型(如22项指向模型)中与轴系误差有关的部分高次谐项系数的物理意义.为高精度轴系误差指向改正模型的建立提供了理论依据.     

日珥的生长曲线

一、前言自从20世纪30年代以来,生长曲线方法在天体物理学中广泛使用,取得了许多有价值的成果.在日珥的光谱研究中,闵纳尔特(M.Minnaert)和斯洛布(C.Slob)首先用H_a 和 HeD_3两条谱线的强度画出生长曲线.布鲁克(H.A.Brück)和摩斯(W.Moss)重复了他们的工作.不久前,麦耳尼科夫和茹拉甫列夫用两条巴耳未(Balmer)线的强度决定生长曲线.这三项工作的共同点是仅根据两条谱线观测强度的比较,得出日珥的生长曲线.在这篇文章中,我们考虑日珥     

磁星能量注入模型拟合伽玛射线暴X射线余辉光变曲线

某些伽玛射线暴(简称伽玛暴)的中心致密天体可能是一颗具有强磁场的毫秒脉冲星,它通过磁偶极辐射可对伽玛暴外激波注入能量,从而导致早期余辉光变曲线的变平.近年来,从Swift卫星观测到的大量伽玛暴X射线余辉中发现,很多X射线余辉光变曲线在暴后10~2～10~4s期间的确存在明显的变平现象.利用周期为毫秒量级的磁星能量注入模型对11个加玛暴的X射线余辉光变曲线进行了拟合,显示该模型在解释余辉变平现象上的有效性和广泛性,通过对余辉光变曲线的拟合,同时也给出了相关中心磁星的磁场强度和旋转周期.     

Study of a Particular Model of Encounter Between a Comet and a Planet

The objective of this paper is to develop a simple model of an encounter between a comet and a planet, with a subsequent capture or an escape, and to study the potential consequences. The hypothetical scenario is as follows: a comet with a conic orbit meets close to one of its vertices (located near the ecliptic plane), a jovian planet, and transforms its orbit. There are two hypotheses which are made for the shock: this vertex becomes one of the final vertices and the orbital plane of the comet is unchanged during the encounter as it was the case for Brooks 2 in 1886. In this model, it was able to find an equation which was then used to obtain the pre‐ and post‐encounter orbits elements and the kind of orbit (ellipse, hyperbola, parabola) with respect to the initial inclination. The numerical experiments with the observed comets often provide pre‐encounter orbits with an aphelion point located near another jovian planet farther from the Sun, and so on with sometimes several planets, or with an aphelion point located beyond the Pluto orbit. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of a particle in a gravitational field of a homogeneous annulus disk

We formulate the problem of an infinitesimal particle moving in the space under the influence of the gravitational force induced by a homogeneous annulus disk fixed on a plane. We compute using different coordinates and in terms of an elliptic integral the potential associated to this problem. Also we study the symmetries of the associated potential. After that, we look at the dynamics in some particular cases, namely: in the line perpendicular to the plane that contains the annulus disk and passes through the center of the ring and on the plane that contains the massive annulus.      

Evolution of a binary system consisting of a helium star and a white dwarf

Results of evolutionary calculations for a close binary system with a central helium burning He-star filling its Roche lobe and an accreting white dwarf are presented. Values for the mass of the components and the degree of central helium exhaustion before the filling of the Roche lobe are varied. It is shown that in such a system the mass accretion rate will remain for a long time (2–4) Ö 10^–8 yr^–1 ifq<1 (q=M _He,2/M _CO,1). The obtained results are discussed in connection with pre-supernova I phenomenon.     

The formation of a ring galaxy during a head-on collision between a disk and a spherical galaxy

The tidal force effects of a spherical galaxy passing head-on through a disk galaxy have been studied at various regions of the disk galaxy and for various orientations of the disk galaxy with respect to the direction of relative motion of the two galaxies. The density distribution of the disk galaxy is taken to be, (r)=_ce^–4r/R , where _c is the central density andR is the radius of the disk. The density distribution of the spherical galaxy is taken to be that of a oolytrope of indexn=4. It is found that as a result of the collision, through the central parts and the outer parts of the disk galaxy remain intact, the region in between these two regions disrupts. Thus a ring galaxy with a nucleus embedded in the ring-i.e., a ring galaxy of the RN-type, is formed.     

Structure of the clusters of galaxies a 999, a 1016, and a 1142

The hierarchical structure of the clusters of galaxies A 999, A 1016, and A 1142, which are part of one supercluster, is investigated. The HTree method is used to determine that A 999 and A 1016 are a single, dynamically bound system consisting of two “cores” and a common field of galaxies. The composition of the “cores” includes almost all the E and S0 galaxies, the luminosity function of which is very nearly Gaussian. It is also established that the cluster A 1142 has a nonuniform structure, both in density distribution and in radial velocity distribution. The location of the maxima in density and in the radial velocity distribution correlates with the galaxies that are sources of radio and x-ray emission. Translated from Astrofizika, Vol. 43, No. 1, pp. 45-54, January–March, 2000.     

制冷接收机低温杜瓦温度监测系统的研制

从设计、制作和测试方法方面介绍了一种制冷接收机低温杜瓦温度监测系统.主要阐述了低温杜瓦对温度监测系统的要求,根据要求合理设计,涉及到各种器件参数的选择以及布局制板等问题,为高精度温度采集系统的硬件设计提供了理论依据.设计采用多路模拟输入通道即集中采集方式,根据系统的需要划分不同的功能区块进行电路设计.制作完成的温度监测系统先后经调试校准、实验室模拟测试以及安装在乌鲁木齐25m射电望远镜18cm制冷双极化接收机上测试,各项设计功能都能很好地实现,并且运行可靠.     

Production of a short-lived filament by a surge

A large surge was observed on September 17, 1971, part of which, after travelling 200 000 km through the corona, returned to the surface to form a filament. The filament lasted about 30 min, then rose up and returned to the source of the surge. We interpret this as the filling of a semi-stable magnetic trap.The energetics of radio, X-ray, and surge expulsion are estimated. The radio spectrum and flux correspond to a thermal source of area 4 (arcmin)², T 190 000 K, N _e ² V 7 × 10⁴⁸, which is optically deep at 8800 MHz.The soft X-ray source has T 12 × 10⁶ K, N _e ² V 3 × 10⁴⁸; and if an equal mass is expelled in the surge, the kinetic energy of the surge is similar to the thermal energy of the X-ray source.     

Toward a model of a two-component solar cycle

In a two-component cycle, the generation of the dipole field by a separate mechanism as well as the strong link occurring, with a 5–6-yr delay, between the sunspot cycle and the preceding dipole cycle, sets in new terms the problem of the mechanisms at the origin of the solar cycle. In this paper, from various series of synoptic solar data, we identify some of the mechanisms to incorporate in a model of a two-component solar cycle. The first one concerns the dipole field which is not a surface phenomenon. We establish the cyclic behaviour and the various properties of the dipole-field sources which are deep-seated in the solar interior and have a rigid rotation of about 27 days. We identify two cyclic phenomena which, in each hemisphere, link with a 5–6-yr delay, the dipole field generation which occurs at high latitudes, to the bipolar field emergence occurring at sunspot latitudes. They are the signatures of a coupling mechanism taking place deep in the solar interior. Then we study the constraints imposed on the mechanisms of the sunspot field generation both by a two-component cycle and by new observational results. These last ones concern the links occurring between the birth of new sunspot groups and the occurrence of pre-existing features of the photospheric field and of pivot-points in rigid rotation at 27.3 days.Our final discussion is devoted to a first sketch of the distribution of the relevant mechanisms among separate regions of the convective zone. Unfortunately neither the helioseismology, nor our data analysis has yet supplied us with appropriate pieces of information for building a physical model of this two-component cycle.