用一般脉宽调制器构造的变频式脉宽调制器

提出为直流变换器增加一个控制变量的概念,以弥补现行直流变换器只有一个调节变量引起的一些缺陷.本文选定的控制变量是直流变换器的运行频率f,将它与一次电源电压V联系起来,使f随V上升按预设的规律下降,以解决直流变换器以固定频率运行时这种情况下出现的许多问题,如开关管发热加剧等.实现这一设想的主要问题是将一般脉宽调制器构造成变频式脉宽调制器.现以脉宽调制器1842/3/4/5(简记为184X)和1842A/3A/4A/5A(简记为184XA)为例,给出了将它构造成变频式脉宽调制器的方法,示出了可实现的变频特性.设计了两个将一次电源电压转换为变频式脉宽调制器输入电压的线性转换电路,推导了计算这些电路中各元件参数的表达式.实验结果与设计一致.     

玫瑰扫描光学系统头罩气动热建模与仿真

在导弹高速飞行过程中，光学头罩的温度受气动热效应作用而急剧升高，会产生严重的气动热辐射效应。为研究头罩气动热对玫瑰扫描光学系统的影响，建立了基于CFD流体仿真软件的头罩温度场模型。在仿真软件对光学系统结构进行三维建模后，通过光学软件对头罩热辐射对探测器的影响进行了仿真和计算。仿真结果表明：玫瑰扫描光学系统对头罩的温度梯度较为敏感，当头罩温度非均匀分布时，探测器会接收到气动热辐射干扰信号，对弱小目标的正常探测和提取产生干扰，气动热辐射效应不容忽视。     

倾斜摇摆试验台校准技术研究

介绍了倾斜摇摆试验台的倾斜、摇摆及振荡等参数的校准原理及现状,提出了采用具有零频响应的高灵敏度加速度计对倾斜摇摆试验台进行校准的原理和方法,构建了相应的校准装置,进行了不确定度评定。实践表明,使用加速度计可完成倾斜摇摆试验台大部分参数的校准,操作简单方便,并可溯源至国家振动基准。     

卫星星座优化设计的分布式遗传算法

遗传算法在区域卫星星座的优化设计中可以得到很好的结果。但使用遗传算法时，往往计算量很大，星座规模较大时会带来计算上的困难。充分利用计算机网络的空闲计算资源进行分布式计算可以解决这一问题，文章提出了相应的分布式计算模型，给出了实现方法，算例表明分布式遗传算法效率很高，该分布式计算方法也可以推广到其他应用领域。     

深空组合导航中天文测速观测研究

深空天文测速导航方法以空间中的某颗恒星为目标,利用航天器自身携带的光谱仪测量相对于恒星的移动速度来实时调整自行速度和路线。太阳是主要的测速导航源之一,利用目前运行的空间卫星的光谱观测资料,分析和研究了太阳相对于卫星的视线速度和速度误差变化情况,为本项目中自主导航光谱提供实测证据。选取了太阳表面5个位置的光谱观测,持续时间在一个小时左右,通过高斯谱线轮廓拟合观测数据,得到了太阳表面5个位置的亮度变化、谱线宽度和速度,其中主要参数速度平均值大约在10 km/s,和速度变化在3 km/s。这是由太阳表面存在大量的微观尺度上的物质运动所导致的。     

Rocket observation of the ultraviolet spectrum of comet Halley

An ultraviolet sounding rocket telescope/spectrograph experiment observed Comet Halley on 26 February 1986, 17 days after perihelion. From the long-slit spectra, the production rates of O, C, and CO are calculated. The derived water production rate is a lower limit of 5.0 × 10²⁹ s⁻¹ and the volume mixing ratio of CO to H₂O is 21%. The predicted brightness distribution from a radial outflow model with H₂O and CO as parent molecules are in accordance with the measured spatial profiles of OI and CO emissions. The ratio of the production rates of CO to C is 2.7 which is consistent with the carbon source being the photodissociation of CO. However, the radial outflow model which best fits the CO data predicts significantly weaker CI emissions than was observed. A better fit to the carbon data is found when an inner coma source of C at a rate of 3% of the water production rate is included in the model.     

REM/ROSS: a powerful tool for monitoring the prompt afterglow of γ-ray bursts

Observations of the prompt afterglow of γ-ray burst events are unanimously considered of paramount importance for GRB science and cosmology. Such observations at NIR wavelengths are even more promising allowing the monitoring of high-z Ly- absorbed bursts as well as events occurring in dusty star-forming regions. In these pages we present rapid eye mount (REM), a fully robotized fast slewing telescope equipped with a high throughput NIR (Z, J, H, K) camera dedicated to detecting the prompt IR afterglow. REM can discover objects at extremely high redshift and trigger large telescopes to observe them. The REM telescope will simultaneously feed REM optical slitless spectrograph (ROSS) via a dichroic. ROSS will intensively monitor the prompt optical continuum of GRB afterglows. The synergy between the REM-IR camera and the ROSS spectrograph makes REM a powerful observing tool for any kind of fast transient phenomena. Beside its ambitious scientific goals, REM is also technically challenging since it represent the first attempt to locate a NIR camera on a small telescope providing, with ROSS, unprecedented simultaneous wavelength coverage on a telescope of this size.     

Effects of large-scale magnetic fields in the Venus ionosphere

Theoretical models of the ionosphere of Venus have been constructed in the past without due consideration of the fact that the ionosphere is sometimes magnetized. This paper examines some differences between the magnetized and unmagnetized dayside Venus ionosphere using the Pioneer Venus Orbiter Langmuir probe and magnetometer data. Particular attention is given to the evaluation of the altitude profiles of the thermal electron heating and comparison of the magnitude of the magnetic force(¯vׯB) ׯB with other forces in the ionosphere. Several examples illustrate how heating profiles are different in the magnetized ionosphere with effective heating below ～200 km altitude reduced by orders of magnitude compared to the field-free ionosphere. The force associated with the magnetic field is comparable to other forces in the magnetized ionosphere. The measured plasma density, electron temperature and magnetic field thus suggest that large-scale magnetic fields should be included in future ionosphere models.     

基于电离层加热的人工沿场散射RCS估计

在电离层加热理论研究和试验研究的基础上, 根据F层散射体的特征和不均匀体散射理论, 建立了人工沿场散射(AFAS)中散射体的散射截面积数学模型. 通过与国际上理论结果对比, 证明了模型的适用性. 利用模型估算了中国人工沿场散射通信中, 通信频段在20~100 MHz时散射体的散射截面积, 结果显示, 甚高频率(VHF)的低端可达80 dB•m2. 另外, 通过计算验证了雷达波束垂直地磁场方向时可获得最大散射截面积的理论.      

Energy deposition in the polar ionosphere as determined by measurements aboard ‘INTERCOSMOS-BULGARIA-1300’ satellite

Data were obtained from the measurements of optical emissions, ion drift, DC magnetic field and energetic particles, on board INTERCOSMOS - BULGARIA - 1300 satellite. In two cases of night-time passes through auroral oval, an estimate has been made of the energy input by particle precipitation and Joule heating. In order to determine the Joule heating, the Pedersen currents flowing in the lower ionosphere were determined. In orbits 231 and 203 Pedersen currents of 0.94 Am^?1 and 0.71 am^?1 were observed. From these values estimates of Joule heating rates of2 × 10^?7Wm^?3 and8 × 10^?7Wm^?3 were obtained. The integral energy deposited by the precipitated particles was also estimated in the current systems regions. The possibility for identification of the auroral electrojet based only on satellite data is pointed out.     

红外加热笼模拟航天器瞬变外热流的方法研究

以某型号航天器热平衡试验为工程应用背景，采用理论分析、仿真研究和实验研究相结合的方法，建立了红外加热笼和热流计的动态数学模型；在此基础上，讨论了利用红外加热笼作为热流模拟航天器在轨飞行时表面到达热流密度瞬态变化的方法和技术。     

Reevaluation of thermosphere heating by auroral electrons

This paper presents a new calculation of neutral gas heating by precipitating auroral electrons. It is found that the heating rate of the neutral gas is significantly lower than previous determinations below 200 km altitude. The neutral gas heating arises from the many exothermic chemical reactions that take place from the ions and excited species created by the energetic electrons. The calculations show that less than half the energy initially deposited ends up heating the neutral gases. The rest is radiated or lost in the dissociation of O₂ because the O atoms do not recombine in the thermosphere. This paper also presents a new way of calculating the heating rate per ionization that can be used for efficient determination of the overall neutral gas heating for global thermosphere models. The heating rates are relatively insensitive to the neutral atmosphere when plotted against pressure rather than altitude coordinates. At high altitudes, the heating rates are sensitive to the thermal electron density and long-lived species. The calculations were performed with the Field Line Interhemispheric Plasma (FLIP) model using a 2-stream auroral electron precipitation model. The heating rate calculations in this paper differ from previous heating rate calculations in the treatment of backscattered electrons to produce better agreement with observed flux spectra. This paper shows that more realistic model auroral electron spectra can be obtained by reflecting the up going flux back to the ionosphere at the upper boundary of the model. In this case, the neutral gas heating rates are 20%–25% higher than when the backscattered flux escapes from the ionosphere.     

航天飞机气动加热计算

介绍了国内外预测航天飞机气动加热的工程计算方法.给出了轴对称、非轴对称和机翼前缘等各种外形驻点热流密度的计算,分析和比较了平板、锥体的层流和湍流热流密度计算的各种方法,概述了航天飞机迎风面中心线和离开中心线横向热流密度的计算.计算结果表明,本文方法用在航天飞机气动热环境初步设计中比较简单并且有足够精度.     

Catalysis of peptide formation by inorganic oxides: high efficiency of alumina under mild conditions on the Earth-like planets.

Amino acid condensation catalyzed by inorganic oxides is a widely recognized way for prebiotic peptide formation. Silica and alumina are widely distributed in the Earth-like planets' crust as minerals of different complexity, and thus are attractive model catalysts for the studies of abiotic peptide synthesis. Experiments performed in other laboratories have shown that this process can be efficient at > 80 degrees C, which is not easy to find on the planetary surface in combination with sufficient concentrations of amino acids and necessary catalysts. In the present work we tested catalytic activity of three forms of alumina (which proved to be an efficient catalyst for this process) in the intermolecular condensation of L-alanine. We expanded the temperature interval down to 55 degrees C and used the simplest permanent heating procedure, without employing fluctuating drying/wetting conditions. The most important finding is that even under the lowest temperature considered (i.e. 55 degrees C), short peptide formation can be detected already after 10-30 days of heating. This fact implies that the abiotic peptide formation might occur in a wide variety of planetary environments, without need for high temperatures, given the presence of amino acid building blocks and alumina-containing minerals.     

甚低频电磁波变态低电离层的数值模拟

利用由波对电离层加热的模型和适合于夜间低电离层的离子化学模型构成的综合模型，对甚低频波射入低电离层时变态电离层的程度受中性成分参数变化及低电离层离子化学反应参数的影响进行了模拟计算．计算结果表明，中性成分的浓度与温度及电离层离子化学反应参数密切地影响着加热的效果．     

信号传输中的驻波处理

给出了驻波处理的简便方法,考察了有关的理论,给出了新的计算公式。     

基于多最小支持度的加权关联规则挖掘算法

针对交易数据库中数据项重要性不同的现象,提出了新的加权关联规则模型,并基于该模型设计了一个基于多最小支持度的加权关联规则挖掘新算法,允许用户设定多个最小支持度,为数据项设置不同的权重,从而解决数据项的重要性各不相同且出现频率不均匀的问题,发现更多有趣的规则.理论证明了相关性质,并实验验证了算法的有效性.      

改进（DSP）模型运用于货运中心信息系统规划

货运中心信息系统规划,是围绕着公路货物运输网络的信息系统布局,对货运中心适站量的信息输送方式,信息作业规模、以及信息系统的建设水平进行规划。在货物运输过程中,该信息系统需要处理有关物品运输、中转换装、车辆调度、运输代理等多方面的信息流,使之密切配合物流系统的管理,提高货物运输服务水平、工作效率及经济效益。该信息系统群的作业过程,是由一组与物流组织相关的成对信息系统,对每对O—D流进行作业。在满足运输网络流需求的条件下,信息系统的布局应要求以最低的系统费用或最好的效益来安排建设序列。DSP模型是送货系统问题规划模型,本文对该模型进行了适当的改造,首次将之运用到货运中心信息系统规划问题中。主要变化是:(1)一个货运中心为一个节点,所覆盖的运输区内的用户端点都合并到该节点中;(2)成本系数为决策变量的直接相关的函数。本方法已成功地应用于甘肃省货运中心运输网络规划,取得了满意的结果。     

一种负极性直流高压线性电源设计

本文提出了一种基于光耦反馈调整的负极性高压线性电源解决方案，使用NPN型三极管作为功率调整管的前提下，实现了负1200V直流电压输出。本文对提出的电源方案建立了小信号传递函数模型，在传递函数模型的基础上论证了所提出的电源系统具有稳定性高、噪声低等优点。