喷管流场数值仿真CFD／Nozzle软件包设计

ＣＦＤ／Ｎｏｚｚｌｅ软件包是一套专门的二维轴对称跨音速喷管流场计算机辅助设计分析工具。它采用高度集成化的操作环境，将网格生成、数值计算、图形显示全部过程集于一体。具有西文环境下的全中文用户界面，操作环境同时提供详尽的彩色图文方式下的中文提示。数值方法稳健，兼具源程序开放与编译连接自动化特点。叙述了ＣＦＤ／Ｎｏｚｚｌｅ软件包设计思想和实现方式，并给出了流场计算、参数分析、功能扩充几方面的应用实例。     

Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan

The magnetospheric imaging instrument (MIMI) is a neutral and charged particle detection system on the Cassini orbiter spacecraft designed to perform both global imaging and in-situ measurements to study the overall configuration and dynamics of Saturn’s magnetosphere and its interactions with the solar wind, Saturn’s atmosphere, Titan, and the icy satellites. The processes responsible for Saturn’s aurora will be investigated; a search will be performed for substorms at Saturn; and the origins of magnetospheric hot plasmas will be determined. Further, the Jovian magnetosphere and Io torus will be imaged during Jupiter flyby. The investigative approach is twofold. (1) Perform remote sensing of the magnetospheric energetic (E > 7 keV) ion plasmas by detecting and imaging charge-exchange neutrals, created when magnetospheric ions capture electrons from ambient neutral gas. Such escaping neutrals were detected by the Voyager l spacecraft outside Saturn’s magnetosphere and can be used like photons to form images of the emitting regions, as has been demonstrated at Earth. (2) Determine through in-situ measurements the 3-D particle distribution functions including ion composition and charge states (E > 3 keV/e). The combination of in-situ measurements with global images, together with analysis and interpretation techniques that include direct “forward modeling’’ and deconvolution by tomography, is expected to yield a global assessment of magnetospheric structure and dynamics, including (a) magnetospheric ring currents and hot plasma populations, (b) magnetic field distortions, (c) electric field configuration, (d) particle injection boundaries associated with magnetic storms and substorms, and (e) the connection of the magnetosphere to ionospheric altitudes. Titan and its torus will stand out in energetic neutral images throughout the Cassini orbit, and thus serve as a continuous remote probe of ion flux variations near 20R _S (e.g., magnetopause crossings and substorm plasma injections). The Titan exosphere and its cometary interaction with magnetospheric plasmas will be imaged in detail on each flyby. The three principal sensors of MIMI consists of an ion and neutral camera (INCA), a charge–energy–mass-spectrometer (CHEMS) essentially identical to our instrument flown on the ISTP/Geotail spacecraft, and the low energy magnetospheric measurements system (LEMMS), an advanced design of one of our sensors flown on the Galileo spacecraft. The INCA head is a large geometry factor (G ∼ 2.4 cm² sr) foil time-of-flight (TOF) camera that separately registers the incident direction of either energetic neutral atoms (ENA) or ion species (≥5^∘ full width half maximum) over the range 7 keV/nuc < E < 3 MeV/nuc. CHEMS uses electrostatic deflection, TOF, and energy measurement to determine ion energy, charge state, mass, and 3-D anisotropy in the range 3 ≤ E ≤ 220 keV/e with good (∼0.05 cm² sr) sensitivity. LEMMS is a two-ended telescope that measures ions in the range 0.03 ≤ E ≤ 18 MeV and electrons 0.015 ≤ E≤ 0.884 MeV in the forward direction (G ∼ 0.02 cm² sr), while high energy electrons (0.1–5 MeV) and ions (1.6–160 MeV) are measured from the back direction (G ∼ 0.4 cm² sr). The latter are relevant to inner magnetosphere studies of diffusion processes and satellite microsignatures as well as cosmic ray albedo neutron decay (CRAND). Our analyses of Voyager energetic neutral particle and Lyman-α measurements show that INCA will provide statistically significant global magnetospheric images from a distance of ∼60 R _S every 2–3 h (every ∼10 min from ∼20 R _S). Moreover, during Titan flybys, INCA will provide images of the interaction of the Titan exosphere with the Saturn magnetosphere every 1.5 min. Time resolution for charged particle measurements can be < 0.1 s, which is more than adequate for microsignature studies. Data obtained during Venus-2 flyby and Earth swingby in June and August 1999, respectively, and Jupiter flyby in December 2000 to January 2001 show that the instrument is performing well, has made important and heretofore unobtainable measurements in interplanetary space at Jupiter, and will likely obtain high-quality data throughout each orbit of the Cassini mission at Saturn. Sample data from each of the three sensors during the August 18 Earth swingby are shown, including the first ENA image of part of the ring current obtained by an instrument specifically designed for this purpose. Similarily, measurements in cis-Jovian space include the first detailed charge state determination of Iogenic ions and several ENA images of that planet’s magnetosphere.This revised version was published online in July 2005 with a corrected cover date.     

彩色三维激光快速成型技术的研究

目前逆向工程采用线结构激光和一个彩色面阵CCD摄像机构成三维彩色扫描系统,彩色CCD摄像机分两次对被测物体成像,首先摄取物体的彩色图片,然后加用滤光片再摄取激光光平面上的三维信息.最后将两次获取的信息重叠,便可得到三维彩色信息.提出了激光光平面方程式三维测量方法,建立了相应的数学模型.研制成一套适用于彩色逆向工程流程,并进行了实验研究,给出了实验结果.     

建立腔体热释电探测器相对光谱响应度标尺的研究

由于腔体热释电探测器在宽光谱范围内具有相对平坦的光谱响应度,因此经常被用作标定探测器相对光谱响应度的工作基准。但是在标定过程中通常认为腔体热释电探测器是无光谱选择性的,即R(λ)为常数。这样就会使测量结果不够准确,因此建立腔体热释电探测器相对光谱响应度的标尺是非常重要的。本文主要介绍了建立腔体热释电探测器相对光谱响应度标尺的原理和方法,并通过实验利用该方法建立了腔体热释电探测器相对光谱响应度的标尺,从而使该腔体热释电探测器成为红外光谱响应度测量装置的工作基准。     

New multifrequency measurements of the spectrum of the cosmic background radiation

New measurements of the Cosmic Background Radiation temperature at 12 cm, 6.3 cm, 3 cm, 0.9 cm and 0.3 cm have made in July 1982 from the White Mountain High Altitude Research Station. The results are presented and the existence of spectral distortions discussed.     

Study of GNSS-measured ionospheric total electron content variations generated by powerful HF-heating

The purpose of this work is to report the experimental evidences for the influence of perturbations in the electron density in the dayside mid-latitude ionosphere, that are caused by high-frequency heating of the F2 layer, on the GNSS signals. The experiments were carried out at the Sura heater (Radio Physical Research Institute, N. Novgorod). During the sessions of ionospheric heating with different time modulations of the radiated power the rays linking the navigational satellites with the ground receiver intersected the heated region. Variations in the total electron content (TEC) were studied; these variations are proportional to the reduced phases of navigational signals. It is shown that with the square-wave modulation of the radiated power (with periods of 1, 6, 10 and 15 min), perturbations with periods of the main modulation of heating and its harmonics appear in the spectrum of TEC variations. Examples are presented of identification of the heating-induced variations in TEC, including determination of the amplitudes and time characteristics of these variations.     

总线通讯实验系统中矢量字的处理方法

研究了在1553B总线通讯实验系统远程终端（RT）仿真中矢量字的处理方法。设计了矢量字的手动单个设置、自动更新和使能RT中断更新三种处理方法。详细分析了各种方法中数据传输的执行过程。由于实验系统中能够灵活地设置矢量字,因此可以实现对采用更新机制传输消息的通讯过程的仿真。     

A time-frequency analysis of the thermal radiation background anomalies caused by large earthquakes: A case study of the Wenchuan 8.0 earthquake

Strong earthquakes have an impact on the regional thermal radiation background, which has been both observed and confirmed. This effect produces anomalies in the thermal radiation background (TRBA) and increases the difficulty of extracting a thermal radiation anomaly (TRA) that is associated with an earthquake occurring during the same time period. The extraction and identification of such anomalies has been ignored by previous studies. In this study, we investigate the time-frequency analysis (TFA) method, together with the wavelet filtering of the Daubechies method and the relative power spectrum analysis of the Fourier Welch method to extract and analyse the TRBA caused by the 2008 Wenchuan Ms 8.0 earthquake and the TRA of the 2013 Minxian-Zhangxian Ms 6.6 earthquake using data concerning the brightness temperature of a black body (TBB) from the Fengyun-2 series of geostationary meteorological satellites developed by China. The result showed that this method can effectively extract and analyse the TRBA caused by the Wenchuan earthquake and the TRA of the Minxian-Zhangxian earthquake form a complex background environment. Furthermore, we discussed the impact of the earthquake on the TRBA and segmented the process. The impact is mainly reflected by three aspects; the characteristic period of the TRBA changes, the TRBA occurs at the same time every year, which is identical to the time at which the earthquake anomaly occurred, and the impact process is in stages. We also summarized the correlation between the characteristic parameters of a TRA and the regional thermal radiation background, geography, and climatic factors.     

An Artificial Neural Network based approach for estimation of rain intensity from spectral moments of a Doppler Weather Radar

By using a Doppler Weather Radar (DWR) at Shriharikota (13.66°N & 80.23°E), an Artificial Neural Network (ANN) based technique is proposed to improve the accuracy of rain intensity estimation. Three spectral moments of a Doppler spectra are utilized as an input data to an ANN. Rain intensity, as measured by the tipping bucket rain gauges around the DWR station, are considered as a target values for the given inputs. Rain intensity as estimated by the developed ANN model is validated by the rain gauges measurements. With the help of a developed technique, reasonable improvement in the estimation of rain intensity is observed. By using the developed technique, root mean square error and bias are reduced in the range of 34–18% and 17–3% respectively, compared to Z–R approach.     

风扇/压气机周向模态识别中传感器角度偏差的影响

基于任意角度压缩感知(CS)方法分析了传感器安装角度偏差对风扇/压气机周向模态识别重构的影响,设计了一套自适应角度优化程序修正重构误差。利用数值试验探究了传感器角度偏差和数量对周向模态重构结果的影响,研究表明:当角度偏差等级为2.5%时,平均重构误差达到10%以上,若保证重构误差基本不变,将传感器数量从7个增加至25个,仅可以将角度偏差等级放宽至4%。而采用小生境微种群遗传算法进行自适应角度优化,在20 dB信噪比下,通过自适应角度优化可将角度偏差等级从2.5%放宽至10%,降低了传感器安装的精度要求。成功优化了一款冷却风扇在前三阶叶片通过频率下的主要周向声模态重构幅值。自适应角度优化算法有效提升了基于压缩感知的风扇/压气机周向模态重构可靠性。