多输出相关免疫逻辑函数的等价刻划及其应用

该文对多输出逻辑函数相关免疫性的两种刻划进行了讨论,在利用Walsh变换理论导出二元随机向量概率分布分解式的基础上,证明了两种刻划的等价性,并利用多输出相关免疫逻辑函数构造了一类不具有输入输出线性组合符合优势的密钥流生成器。     

相关免疫置换的构造和计数

该文引入了相关免疫置换的概念,并给出了相关免疫置换的一个构造方法,解决了该方法构造的相关免疫置换的计数问题。     

ENUMERATING CORRELATION-IMMUNE BOOLEAN FUNCTIONS OF ORDER ONE

A large class of linear structural functions(LSF) satisfying the condition of correlational immunity of order one are constructed by studying the linear structural Boolean functions. With these new founded functions, the known enumeration bounds of correlation-immune functions of order one are greatly improved. In fact, the best, up to now, lower bound is found.     

Accurate spectral characterization of polarization-dependent loss

Building on previous work, a rapid automated nonmechanical measurement system for spectral characterization of polarization-dependent loss (PDL) has been developed. A deterministic fixed-states Mueller-Stokes method in conjunction with realtime calibrated spectral information is used to derive wavelength-dependent Mueller matrix elements. Voltage-modulated liquid-crystal variable retarders set the input polarization states. A narrow voltage-tuned filter provides a wavelength sweep following a broadband source; the sweep wavelength is calibrated in realtime by hydrogen cyanide reference lines. This rapid measurement system can measure PDL over a wavelength range of 15 nm in 5 s. A complete uncertainty analysis has been conducted for PDL in the range of 0.05 to 0.3 dB with an expanded uncertainty of 0.0098 dB over the range of 1535 to 1560 nm. Performance was verified using a Fresnel reference. Finally, design and performance results from all-fiber artifact calibration standards are presented.     

新的一阶相关免疫布尔函数计数下界

研究了一阶相关免疫函数构造、计数问题,提出了两种新的一阶相关免疫函数的构造方法,并通过这两种构造方法给出了一个目前最好的一阶相关免疫函数个数下界。     

计数一阶相关免疫布尔函数的可计算公式

研究了在分组密码和序列密码中有重要应用的相关免疫布尔函数的计数问题。依据布尔函数的定序特征矩阵，利用组合数学中的波利亚计数理论，给出基于整数分拆表示的一阶相关免疫布尔函数的计数公式。     

Terra MODIS on-orbit spectral characterization and performance

The Moderate Resolution Imaging Spectroradiometer (MODIS) protoflight model onboard the National Aeronautics and Space Administration's Earth Observing System Terra spacecraft has been in operation for over five years since its launch in December 1999. It makes measurements using 36 spectral bands with wavelengths from 0.41 to 14.5 /spl mu/m. Bands 1-19 and 26 with wavelengths below 2.2 /spl mu/m, the reflective solar bands (RSBs), collect daytime reflected solar radiance at three nadir spatial resolutions: 0.25 km (bands 1-2), 0.5 km (bands 3-7), and 1 km (bands 8-19 and 26). Bands 20-25 and 27-36, the thermal emissive bands, collect both daytime and nighttime thermal emissions, at 1-km nadir spatial resolution. The MODIS spectral characterization was performed prelaunch at the system level. One of the MODIS onboard calibrators, the Spectroradiometric Calibration Assembly (SRCA), was designed to perform on-orbit spectral characterization of the MODIS RSB. This paper provides a brief overview of MODIS prelaunch spectral characterization, but focuses primarily on the algorithms and results of using the SRCA for on-orbit spectral characterization. Discussions are provided on the RSB center wavelength measurements and their relative spectral response retrievals, comparisons of on-orbit results with those from prelaunch measurements, and the dependence of center wavelength shifts on instrument temperature. For Terra MODIS, the center wavelength shifts over the past five years are less than 0.5 nm for most RSBs, indicating excellent stability of the instrument's spectral characteristics. Similar spectral performance has also been obtained from the Aqua MODIS (launched in May 2002) SRCA measurements.     

一阶相关免疫布尔函数的构造和计数

给出了一阶相关免疫布尔函数的新的构造方法,并通过该方法改进了一阶相关免疫布尔函数的计数下界。     

Optical arbitrary waveform generation and characterization using spectral line-by-line control

This paper demonstrates optical arbitrary waveform generation (O-AWG) and its characterization using spectral line-by-line control with high-resolution grating-based pulse shapers. Such integrated capabilities are the enabling techniques for high-fidelity O-AWG.     

A spectral frequency synthesizer

The spectral digital frequency synthesizer has extremely low battery power consumption. A model, providing two ×460 radio channels in the VHF range, was developed and packaged.     

Temporal characterization of myoelectric spectral moments changes:analysis of common parameters

To investigate the validity of common spectral shift parameterizations, two closely related studies were conducted. Simple linear and exponential regression models were applied to the time-series myoelectric mean power frequency and median power frequency data of two normal subjects as well as a single subject over multiple trials. Statistical analyses were applied to test the hypothesis that no significant differences in extracted features (measurands) exist between different epochs of spectral parameter data. Statistically significant differences were found to exist in both studies, implying that the trial duration can significantly influence the obtained measurement values, and that neither linear nor simple exponential regression models adequately characterize the time-dependent changes. It is concluded that parameterization techniques based on statistical curve-fitting strategies should be supplemented with physiologic models to gain insight into the functional nature of the time dependency. Results are discussed in this context     

光子晶体光纤中四波混频光谱增益特性的研究

采用脉冲宽度为5 ps、峰值功率为5 W的可调谐钛宝石激光器泵浦长度为4.8 m,零色散点在810 nm的光子晶体光纤(PCF),观察到四波混频(FWM)3 dB的信号光增益,信号光和闲频光的间距为20 nm.通过调谐泵浦光的入射中心波长,研究了不同泵浦波长对FWM信号增益的影响,并与理论结果进行了对比,结果表明了很好的一致性.     

General intracavity method for laser transition characterization byrelaxation oscillations spectral analysis

Monitoring the transient buildup of laser emission is proposed as a simple method for spectro-temporal intracavity diagnostics of laser transitions and materials. Using this method, we determined the absolute magnitude of both laser emission and absorption cross sections for a line-narrowed tunable Er³⁺-fiber laser     

On surface EMG spectral characterization and its application to diagnostic classification

Surface EMG was recorded from the biceps with fixed muscle length at S0 percent maximal voluntary contraction. The signal bandpass was 10-230 Hz where most of the surface EMG energy is located. The signal sampled at 500 Hz was found to have a changing spectrum. Stationary segments of 500 ms were subject to linear prediction mathematics to model the system.     

Frequency selective surfaces: spectral characterization and application to multifrequency antenna systems

Frequency Selective Surfaces (fss), used as quasioptical diplexers in reflector antenna systems for telecommunication satellites are attracting much interest, since they allow multifrequency illumination of the main reflector, with consequent mass saving. In this paper the spectral characterization of these surfaces is discussed, and the solution of the scattering problem via the Moment Method is described. The general characteristics of the frequency response of fss are reviewed, when the incident field is a plane wave. Then a method is presented to analyse the behaviour offss in their actual operating environment, even in the near field region of the feeds.     

A spectral matching approach for parameter and spectral estimationof nonstationary rational processes

The parameter and spectral estimation problems of nonstationary signals are considered. The nonstationary signals are modeled as rational processes with time-varying parameters. The spectral matching approach, which was introduced by Friedlander and Porat (1984), is generalized to the nonstationary case and two new estimators, namely, the time-varying spectral matching estimator (TVSME) and the time-frequency spectral matching estimator (TFSME) are proposed. The proposed methods estimate the parameters of the time-varying rational model by fitting the parametric spectrum expression to an estimated time-frequency distribution of the signal. An approximate statistical analysis is given for both methods along with computer simulation results, illustrating the performance of the proposed estimators     

A two-dimensional maximum entropy spectral estimator

Using ideas from one-dimensional maximum entropy spectral estimation a two-dimensional spectral estimator is derived by extrapolating the two-dimensional sampled autocorrelation (or covariance) function. The method used maximizes the entropy of a set of random variables. The extrapolation (or prediction) process under this maximum entropy condition is shown to correspond to the most random extension or equivalently to the maximization of the mean-square prediction error when the optimum predictor is used. The two-dimensional extrapolation must he terminated by the investigator. The Fourier transform of the extrapolated autocorrelation function is the two-dimensional spectral estimator. Using this method one can apply windowing prior to calculating the spectral estimate. A specific algorithm for estimating the two-dimensional spectrum is presented, and its computational complexity is estimated. The algorithm has been programmed and computer examples are presented.     

A note on spectral shaping of minimum-shift-keying-type signals

Recently proposed minimum-shift-keying (MSK)-type modulation schemes are shown to be members of a previously suggested of offset quadrature-carrier modulation techniques called continuous-shift-keying (CSK).