Augmenting the Linear Variance Equation

A technique is developed to convert the covariance analysis ofcertain time-varying linear systems into time-invariant form, thusallowing an arbitrary time step for the solution of the differentialequations. The result is accomplished by augmenting the linearvariance equation and augmenting the state vector if necessary. Themethod is illustrated with an example showing the covariancepropagation of ring laser gyro errors in a strapdown inertial systeminto navigation errors during turns.     

Residual stresses and endurance strength under tension-compression in the conditions of stress concentration

Residual stresses and endurance strength of specimens with stress concentrators are considered. The results obtained make it possible to predict the fatigue limit of strengthened parts with concentrators in the case of tension-compression.     

An Optimally Integrated Track Recovery System for Aerial Bathymetry

An airborne system has been developed for charting shallow coastal and inland waters. The primary components of this system are an aerial survey camera, a profiling laser radar, an analytical stereo plotter, and a multisensor track recovery system (TRS). The TRS comprises a gimbaled inertial navigation system and a number of auxiliary sensors which acquire redundant position and attitude information. The sensor data are combined postmission using a U-D factorized Kalman filter and modified Bryson-Frazier smoother to compute accurate estimates of the orientation parameters of the survey camera at the times of film exposure. These parameters are used to position each overlapping pair of photographs on the analytical plotter to form a stereo image and corresonding analytical stereomodel from which water depth measurements are made. Flight trial results demonstrate that the TRS can achieve radial position and attitude accuracies which exceed 1 m and 2 arcmin root mean square (rms), respectively, and that this level of performance is sufficient to enable water depth measurements to be made to an accuracy of better than 0.65 m (rms).     

Matter streams in Algol-like systems

Simulations of the Algol-like binary CX Draconis, combined with IUE observations of the stream of material escaping the system can place limits on the inclination of the system and give estimates, via line profile synthesis, of the mass-loss rate at the L1 point.     

日球层内外能量中性原子的探测

能量中性原子(Energetic Neutral Atoms, ENA, 简称能原子)是指在日球层内外空间, 拥有>0.1keV动能的原子.在此空间领域并没有温度>106K的中性气体, 但却充满动能>0.1keV的正离子.因此能原子A应该是A+离子与原地稀薄气体B原子或分子交换电荷所产生的, 即A++B→A+B+. 电荷交换涉及极小的动能变化, 新生的能原子A和离子B+基本上各自保持原有动能. 离子B+随即被当地磁场俘获, 能原子A则脱离磁场约束并携带其原属离子群的成分和能量信息而直线运动, 成为遥测空间等离子体的有效媒介. 美国人造卫星 IBEX (Interstellar Boundary Explorer) 直接探测得到来自日球层以外星际空间的能原子, 大幅延伸了利用能原子遥测空间等离子体的领域. 本文据此论述了空间能原子的发现, 综述了探测空间能原子的基本概念与实例、取得的主要成果、仪器设计和研制进展以及未来空间利用能原子遥测的发展趋势.      

The Martian and extraterrestrial UV radiation environment--1. Biological and closed-loop ecosystem considerations

The Martian surface is exposed to both UVC radiation (<280 nm) and higher doses of UVB (280-315 nm) compared to the surface of the Earth. Terrestrial organisms have not evolved to cope with such high levels of UVC and UVB and thus any attempts to introduce organisms to Mars, particularly in closed-loop life support systems that use ambient sunlight, must address this problem. Here we examine the UV radiation environment of Mars with respect to biological systems. Action spectra and UV surface fluxes are used to estimate the UV stress that both DNA and chloroplasts would experience. From this vantage point it is possible to consider appropriate measures to address the problem of the Martian UV environment for future long term human exploration and settlement strategies. Some prospects for improving the UV tolerance of organisms are also discussed. Existing artificial ecosystems such as Biosphere 2 can provide some insights into design strategies pertinent to high UV environments. Some prospects for improving the UV tolerance of organisms are also discussed. The data also have implications for the establishment of closed-loop ecosystems using natural sunlight on the lunar surface and elsewhere in the Solar System.     

中心进气转静系转盘风阻扭矩数值模拟

采用计算流体力学(CFD)商业软件CFX从流动参数及几何结构两个方面对中心进气转静系盘腔内转盘风阻扭矩特性进行了数值模拟研究,同时搭建一个转盘风阻扭矩实验台测量自由盘风阻扭矩.中心进气转静系转盘风阻扭矩与经典经验公式进行了对比,结果表明:利用数值模拟方法,得到的无量纲扭矩系数与经典经验关系式计算得到的数据总体相差小于10%,利用湍流参数来表征转盘转速以及叠加流流量,对于分析转盘风阻扭矩非常便利.利用湍流参数定量分析时需注意叠加流以及转速的量级同样影响着风阻扭矩的数值.几何结构对于风阻扭矩也有影响,但相比流动参数影响较小.      

The FAST Satellite Fields Instrument

We describe the electric field sensors and electric and magnetic field signal processing on the FAST (Fast Auroral SnapshoT) satellite. The FAST satellite was designed to make high time resolution observations of particles and electromagnetic fields in the auroral zone to study small-scale plasma interactions in the auroral acceleration region. The DC and AC electric fields are measured with three-axis dipole antennas with 56 m, 8 m, and 5 m baselines. A three-axis flux-gate magnetometer measures the DC magnetic field and a three-axis search coil measures the AC magnetic field. A central signal processing system receives all signals from the electric and magnetic field sensors. Spectral coverage is from DC to 4 MHz. There are several types of processed data. Survey data are continuous over the auroral zone and have full-orbit coverage for fluxgate magnetometer data. Burst data include a few minutes of a selected region of the auroral zone at the highest time resolution. A subset of the burst data, high speed burst memory data, are waveform data at 2×10⁶ sample s^–1. Electric field and magnetic field data are primarily waveforms and power spectral density as a function of frequency and time. There are also various types of focused data processing, including cross-spectral analysis, fine-frequency plasma wave tracking, high-frequency polarity measurement, and wave-particle correlations.     

Crossarray Beamforming with a Parametric Receiving Array and a Line Array

A beamforming technique involving cross correlation of the outputs of two directional arrays is investigated. The performance characteristics of the crossarray system are determined and related to the characteristics of the two individual arrays. It is found that the crossarray beam pattern is the average (in decibels) of the beam patterns of the individual arrays, and that the crossarray gain (rejection of spatially distributed noise) is 1.5 dB greater than the average (in decibels) of the individual array gains. The most interesting applications for this system may be those where the two arrays are quite different, as in the case of a parametric acoustic receiving array (PARRAY) and a broadside line array.