SETI education programs in Australia

This paper discusses and evaluates two innovative SETI education programs conducted at the University of Western Sydney, viz: the SETI Pathways Program and the Life in the Universe Curriculum Project.     

Distributed decision fusion using empirical estimation

The problem of optimal data fusion in multiple detection systems is studied in the case where training examples are available, but no a priori information is available about the probability distributions of errors committed by the individual detectors. Earlier solutions to this problem require some knowledge of the error distributions of the detectors, for example, either in a parametric form or in a closed analytical form. Here we show that, given a sufficiently large training sample, an optimal fusion rule can be implemented with an arbitrary level of confidence. We first consider the classical cases of Bayesian rule and Neyman-Pearson test for a system of independent detectors. Then we show a general result that any test function with a suitable Lipschitz property can be implemented with arbitrary precision, based on a training sample whose size is a function of the Lipschitz constant, number of parameters, and empirical measures. The general case subsumes the cases of nonindependent and correlated detectors.     

An experimental investigation of three eigen DF techniques

The comparative direction-finding (DF) performance of multiple signal classification (MUSIC), ROOT-MUSIC, and estimation of signal parameters via rotational invariance techniques (ESPRIT) is considered. Data were collected from two target transmitters operating simultaneously. The objective of the experiment was to evaluate multipath resolution capability using measurement precision equivalent to that found in modern radio direction-finding systems     

An experiment with an S-band radar using pulse compression andrange sidelobe suppression for meteorological measurements

A major technology barrier to the application of pulse compression for the meteorological functions required by a next generation ATC radar is range/time sidelobes which mask and corrupt observations of weak phenomena occurring near areas of strong extended meteorological scatterers. Techniques for suppressing range sidelobes are well known but without prior knowledge of the scattering medium's velocity distribution their performance degrades rapidly in the presence of Doppler. Recent investigations have presented a “doppler tolerant” range sidelobe suppression technique. The thrust of the work described herein is the extension of previous simulations to actual transmitted dispersed/coded waveforms using the S-band surveillance radar located at Rome Laboratory Surveillance Facility. The objectives of the experiment are: 1) to extend the verification of the simulation of the Doppler tolerant technique; and 2) to demonstrate that the radar transmitter, waveform generator, and receiver imperfections do not significantly degrade resolution, performance or reliability of meteorological spectral moment estimates     

CC—高阶通信系统的并发演算

并发演算CC(Concurrent Calculus)是高阶并发通信系统的数学模型,它把λ-演算作为子理论并包含一阶通信系统演算CCS、活动进程演算CMP、和高阶通信系统演算CHOCS的主要特征。在CC中,通信端口可为任意表达式并且进程和通信端口都可以作为在通信中传递的一等对象(First-class Objects)。从而CC不仅可以描述一阶通信行为而且可以刻划通信网络的动态自修改行为。另外,由于CC把λ-演算和进程演算纳入同一形式系统,故CC可以作为并发函数式程序设计的核心语言和理论模型。本文首先给出CC的语法、语义和例子,然后研究CC的高阶双向模拟等价关系以及CC的代数定律。最后简单讨论了相关的工作和今后的研究方向。     

Application of Gram-Schmidt algorithm to fully adaptive arrays

The Gram-Schmidt orthogonalization (GSO) algorithm has excellent numerical performance and is readily applicable to systolic implementations such as in a field of adaptive cancellation systems. A modified GSO algorithm for a fully adaptive array is proposed and computer simulations show that the proposed algorithm gives superior performance. A systolic implementation of the proposed GSO algorithm for fully adaptive array is presented. A feedback mode GSO algorithm for use with analog weights is also presented and has been shown to have excellent performance in the presence of weight errors     

含有任意多个椭圆孔弹性板的应力场计算

本文应用弹性力学的复变函数理论,用多保角变换的方法,导出了含有任意多个椭圆孔的无限大弹性板多复变量应力函数的表达式。每个孔的大小、位置和孔边作用的载荷均为任意指定。板的无限远处作用有和坐标轴方向一致的均匀拉压载荷P_x,P_y和均匀剪切载荷P_(xy)。并在孔边进行复Fourier级数展开,用待定系数法确定应力函数的未知系数,从而计算弹性板的应力场。编制了相应的FORTRAN77标准化程序,进行了考题和算例分析,给出了级数的收敛状况和孔边周向应力的分布图。     

ERS-1 radial position refinement by dual crossover analysis with TOPEX/Poseidon

Achieving orbital accuracies in the radial direction for ERS-1 commensurate with those for TOPEX/Poseidon is of utmost importance for the integration of the two altimeter data sets. This paper outlines a procedure whereby the radial orbit error for ERS-1 is recovered as a time series expansion in the form of a finite Fourier series with additional terms for atmospheric drag, solar radiation pressure, and initial state vector mismodelling. Using a least squares collocation method with constraints derived from the JGM2 gravity field co-variance matrix, the radial error is recovered using both dual crossovers and ERS-1 single satellite crossovers. Aggregate arcs are then used to derive the ERS-1 orbit error over the repeat period of 35 days. The results are presented in the improvement of fit in the dual crossover, ERS-1 crossover and altimetry data sets as well as the recovery of an altimeter bias for the two satellites.     

Stability of resonance rotation of a satellite with respect to its center of mass in the orbit plane

The stability of resonance oscillations and rotations of a satellite in the plane of its orbit in the case when the difference of the moments of inertia with respect to the principal axes lying in the orbit plane is small is determined at a given rotation number m by the sign of function Φ_m(e), introduced by F.L. Chernous’ko in 1963. In this paper, convenient analytical representations of functions Φ_m(e) are described in the form of integrals and series of Bessel functions regular at e → 1^?. Values of Φ_m(1) are calculated in explicit form. A theorem about the double asymptotic form of functions Φ_m(e) at m → ∞ and e → 1^? is proved by the saddlepoint method.     

Public Attitudes Towards Space Science

Astronomy and space science, including their associated basic research activities, enjoy broad popular backing. People generally support them, and say that they follow their results with interest. This article summarizes some of the detailed results of public surveys in the United States, focusing on popular opinions and attitudes, and the somewhat paradoxical finding that despite being interested and supportive, people are often ignorant about the basic facts. I explore some of the reasons for the popularity of space science, and suggest ways of justifying space science research in the broader context of science research. I argue that vigorous and innovative education and outreach programs are important, and can be made even more effective. This revised version was published online in June 2006 with corrections to the Cover Date.