步进电机步距角的正余弦细分原理

步进电机的步距角由于受到机械结构和经典细分驱动电路的限制，只能适量的减小，但对于许多精度设备的控制及高精度的定位系统，其步距角的分辨率还应提高，正余弦细分驱动电路很好地解决了这一问题，它的主要特点是计算机或单片机的接口简单、转速连续可调；增减ＥＰＲＯＭ的地址线可灵活改变细分数；电机运行平稳，振动小，噪声低。     

定天镜的伺服驱动原理

主要介绍恒星光干涉仪实验系统的定天镜伺服驱动原理．采用电细分和逐级升、降速的方法来减小定天镜在转动时的振动，提高定位、跟踪精度．由于应用了４００的电细分和１０００倍的传速比，步进电机的步距角达到０．００６４８°．     

测定度盘分划改正的新方法──组合固定角距法

本文分析了国外用于测定度盘分划改正的几种方法，并分析了固定角距法的优点和不足之处；详细叙述了组合固定角距法测定对径改正的原理和计算公式；并且讨论了两对显微镜之间夹角变化以及显微镜比例尺变化对对径改正的影响，给出了相应的修正方法。用固定角距法所测的对径改正精度可达±０″．００９。     

多波段太阳光谱仪的高精度扫描回转台

为云南天文台多波段太阳光谱仪改造而专门研制的高精度、小步距角扫描回转台能实现对太阳像的自动扫描。扫描时,竖轴的晃动角小于1″,扫描步距角为0.01°或0.005°,扫描精度为0.001°。     

1.2m望远镜激光测距系统同步旋转快门的设计与实现

介绍了一种对2台步进电机相互间采取等差角同步旋转的控制方案.根据这个方案设计和制作的机电控制电路实现了同步旋转快门功能,最终的同步精度控制在步进电机的性能1.8度/步的范围内,应用在激光测距系统中起到了安全保护单光子探测器的作用.     

机场远距离目标望远镜监控系统的初步设计

望远镜监控系统可以用来监控诸如机场上空的鸟群、低空云层以及跑道和停机坪上的异常物体等机场远距离目标。整个系统的设计分为光学与机械、望远镜控制、以及监控成像与图像处理三个子系统。在光学与机械部分，着重论述望远镜的光学特性和电机驱动方式下的机械结构改进；在望远镜控制部分，分析了控制电机的选择、单片机的控制方式、以及计算机控制软件的功能设计；最后概述了监控成像与图像处理部分的初步实现方式。     

地球场的广义相对论效应对人造卫星轨道的影响

从计及J2项的地球重力场度规出发，我们导出在这样的度规场中人造卫星的摄动加速度及在径向、横向和轨道面法向等方面的摄动函数，进而计算了轨道一阶导数的平均值，讨论了在这种重力场中卫星的轨道特性。其主要结论是：1、球形地球的广义相对论摄动仅对近地点角距ω和平近点角τ产生长期项，而地球J2项的广义相对论效应不仅对这两个根数有长期摄动，而且对升效点角距Ω出有长期摄动。值得注意的是这两种广义相对论效应对半长轴a，偏心率e及倾角i都没有长期摄动；2、球形地球的广义相对论效应对倾角i和升交点角距Ω仅有短周期摄动，但地球J2项的广义相对论效应除了对它们有短周期摄动外，还有长周期摄动，对Ω甚至还有长期摄动。     

哈雷彗星主尾流的研究

哈雷彗星在日彗距较大时出现长而直的主彗尾（尾流），这是很有趣的。尾流一般是指等离子体尾流；但是，当地球接近彗星轨道面时，尘埃尾流可能叠加到主彗尾上。在一般感光波段宽的彗星底片上很难区分这两种尾流。本文选取哈雷彗星在不同日彗距的5条主尾流，作了光度测量和比较分析。得出沿各尾轴及其垂直方向几个截面的亮度分布、亮度半极大全宽、尾轴的视风差角和真风差角及彗尾长度。在所分析的蓝敏底片上，过近日点前的2个尾流肯定是等离子体尾流，而5个尾流的相似性以及其他证据说明它们主要都是等离子体尾流，尘埃彗尾的污染是次要的。     

北京天文台施密特望远镜驱动系统的改进设计

介绍了北京天文台 60 0 / 90 0mm施密特望远镜驱动系统的改进设计 ,即用 2只步进电机 ,取代了原望远镜由 4只变速箱、 7只电机驱动的复杂的赤经 ,赤纬驱动系统 ,最终实现了计算机控制。     

1.2m地平式望远镜驱动系统设计与多电机同步控制策略

对于大型光电望远镜,多电机摩擦轮驱动方案较单力矩电机直接驱动方案在电机的研制和低速平稳跟踪上有明显的优势,但其关键点和难点在于多电机的同步控制上。在云南天文台1.2m望远镜的方位改造中,通过采用合理的多电机驱动方案和设计同步补偿装置,克服多电机在运行时的相互影响,将稳态运行的转速差控制在一个较小的范围,并为校正参数的设计奠定了良好的基础,保证系统在以最大速度3°/s运行时对目标的高精度跟踪。     

丽江2.4米望远镜检偏器控制系统设计

偏振测量是天文四大测量(光谱,光度,偏振,图像)手段之一,而检偏器是进行天体偏振测量的有力工具之一。通过TCP/IP协议控制步进电机驱动检偏器旋转一定的角度值,通过RS485串行通讯实时读取光电绝对编码器的读数作为检偏器绝对位置的反馈量,从而构成一个闭环控制系统。最终实现了转动误差0.42°,步进角度22.5°,转动范围0°～360°的偏振闭环控制系统,完全满足天体偏振测量的基本要求。     

Distribution of ejecta from small impact craters

The present study focuses both on the influence of impact scale on ejecta expansion and on specific features of ejecta deposits around relatively small craters (i.e., those a few kilometers in width). The numerical model is based on the SOVA multimaterial multidimensional hydrocode, considering subaerial vertical impacts only, applying a 2‐D version of the code to projectiles of 100, 300, and 1000 m diameter. Ejecta can roughly be divided into two categories: “ballistic” ejecta and “convective” ejecta; the ballistic ejecta are the ejecta with which the air interacts only slightly, while the convective ejecta motion is entirely defined by the air flow. The degree of particle/air interaction can be defined by the time/length of particle travel before deceleration. Ejecta size‐distributions for the impacts modeled can be described by the same power law, but the size of maximum fragment increases with scale. There is no qualitative difference between the 100 m diameter projectile case and the 300 m diameter projectile impact. In both cases, fine ejecta decelerate in the air at a small distance from launching point and then rise to the stratosphere by air flows induced by the impacts. In the 1000 m‐scale impact, the mass of ejecta is so large that it moves the atmosphere itself to high altitudes. Thus, the atmosphere cannot decelerate even the fine ejecta and they consequently expand to the rarefied upper atmosphere. In the upper atmosphere, even fine ejecta move more or less ballistically and therefore may travel to high altitudes.     

一种可编程逻辑器件在原子钟频率综合电路中的应用

针对被动型铷原子频标电路模块中由三极管等数量众多的分立元件搭建的9倍选频放大模拟电路和种类繁多的集成电路搭建的5.3125 MHz综合器电路,给出了数字化电路解决方案。在此新方案中,通过使用一种复杂可编程逻辑器件对锁相环进行编程控制,可以实现对10 MHz参考信号18倍频的精确控制;同时,利用该复杂可编程逻辑器件内部"虚拟"的集成电路对10MHz参考信号进行分频变换可以得到5.3125MHz信号。实际使用证明,这种设计方案具备易于集成、调试简单的优点,在替换原有模拟倍频、综合器功能电路后,成功实现整机锁定,各项性能指标均达到或优于原有水平,使整机向数字化、小型化迈出重要的一步。     

一种液晶显示系统的单片机接口设计

液晶显示器（LCD）工作电压低、功耗小、能与CMOS电路匹配；且显示柔和、字迹清晰、重量轻、可靠性高、寿命长，自问世以来其发展速度之快，用途之广远远超过了其它发光器件。在自动化仪表及自动控制系统中，越来越多的设计者采用液晶显示与仪器对接，尽管其接口电路较传统的LED显示器复杂，由于其独特的优点，正得到广泛地应用。现介绍一种单片机LCD显示器接口的设计。在使用步进电机进行精密自动控制的系统中，利用8031单片机作为控制器，加之使用8255并行接口，可实现移位显示，也可适时显示转角信息和检测信息。该设计自动化程度高、可控性强，可用于天文仪器的精密定位、扫描以及其它自控监示系统。     

云南天文台四波段太阳射电望远镜群天线伺服系统数控化自动化工程

本文详细介绍了云南天文台四波段射电望远镜天线群伺服控制系统的改造和更新技术。采用TP—801A型单板机和步进电机数控系统代替了原来的机械系统,从而实现了数控化和自动化。     

The 10-μm profile of molecular-cloud and diffuse ISM silicate dust

High signal-to-noise ratio spectra are presented of the 10-μm silicate absorption feature in lines of sight towards Elias 16 and 18 in the Taurus dark cloud, and towards the heavily reddened supergiant Cyg OB2 no. 12. The observations are fitted with laboratory and astronomical spectra to produce intrinsic absorption profiles. These features, which represent molecular-cloud and diffuse ISM dust respectively, are better fitted with emissivity spectra of the Trapezium and μ Cephei than they are with those of laboratory, terrestrial, or other observations of circumstellar silicates. The difference in width between the silicate band in the two environments can be almost entirely ascribed to a broad excess absorption in the long-wavelength wing of the profiles, which is much stronger in the molecular-cloud lines of sight, and possibly reflects grain growth in the denser environment. Limits are placed on the strength of fine spectral structure; if there is a crystalline silicate component in these spectra, it is most likely to be serpentine. Column-density upper limits for methanol and the photolysis product hexamethylenetetramine (HMT) are less than a few per cent of those of water ice and silicates.     

The fibril structure of prominences

In this paper we present several magneto-hydrostatic equilibrium models for prominences with fibril-like fine structure. For all the models ad hoc temperature profiles are used without discussing the energetics. For our models we assume fine structure to occur either across the prominence axis or along it. This approach is intended as a first step towards more realistic models based upon a series of vertical fibril structures.     

Unusual Zebra Patterns in the Decimeter Wave Band

An analysis of new observations showing fine structures consisting of narrowband fiber bursts as substructures of large-scale zebra-pattern stripes is carried out. We study four events using spectral observations taken with a newly built spectrometer located at the Huairou station, China, in the frequency range of 1.1 – 2.0 GHz with extremely high frequency and time resolutions (5 MHz and 1.25 ms). All the radio events were analyzed by using the available satellite data (SOHO LASCO, EIT, and MDI, TRACE, and RHESSI). Small-scale fibers always drift to lower frequencies. They may belong to a family of ropelike fibers and can also be regarded as fine structures of type III bursts and broadband pulsations. The radio emission was moderately or strongly polarized in the ordinary wave mode. In three main events fiber structure appeared as a forerunner of the entire event. All four events were small decimeter bursts. We assume that for small-scale fiber bursts the usual mechanism of coalescence of whistler waves with plasma waves can be applied, and the large-scale zebra pattern can be explained in the conventional double plasma resonance (DPR) model. The appearance of an uncommon fine structure is connected with the following special features of the plasma wave excitation in the radio source: Both whistler and plasma wave instabilities are too weak at the very beginning of the events (i.e., the continuum was absent), and the fine structure is almost invisible. Then, whistlers generated directly at DPR levels “highlight” the radio emission only from these levels owing to their interaction with plasma waves.     

Spatio-temporal fluctuations in HeI 10830 Å line parameters: Evidence for spicule formation

The equivalent width, line depth, line width, and Doppler shift of the He i 10830 Å line were extracted from two time series of spectra. Scatter plots of time-averaged line depth, line width, and Doppler shifts, as well as the root mean square temporal fluctuation of these quantities against the time-averaged equivalent width at a few hundred spatial locations were obtained. The statistical behaviour of these line parameters and their fluctuations was used to infer plausible reasons for the fluctuations. Examination of these results showed that the line parameter fluctuations could be caused by fluctuations in the coronal UV radiation (which could drive the spicules) or by the appearance of density inhomogeneities such as spicules within the line forming domain. In either case, the data can be interpreted as representing the initial phases of spicules.