Precision in differential field-flow fractionation: a chemometric study

In the present paper, the capabilities of differential field-flow fractionation, i. e., the determination of an incremental quantity of a colloidal species, e. g., an uptake adsorbed mass, determined by the joint use of two independent FFF measurements, over a species and the same modified species respectively, are considered. The different error types, those related to the retention time determinations and those coming from the operating parameter fluctuations were considered. The different components were computed with reference to SdFFF determinations of bare polystyrene (PS) submicronic particles and the same PS particles covered by IgG. Comparison was made between theoretically computed precision and experiments. The error coming from the experimental measurement of retention times was identified to be the main source of errors. Accordingly, it was possible to make explicit the detection limits and the confidence intervals of the adsorbed mass uptake, as a function of experimental quantities such as the retention ratio, the detector calibration ratio, the injected quantity, the baseline noise, and the void time relative error. An experimentally determined and theoretically foreseen dependence of both the experimental detection and confidence limits (approximately +/- 10(-17) g) on the square root of the injected concentration, for constant injected volume, was found.     

三通道偏振成像系统及系统误差校正方法

为了解决现有偏振成像系统难以满足目标检测和跟踪等实时图像处理领域的要求,提出一种实时三通道偏振成像系统,并对该系统存在的视场差异和非一致性误差提出了校正方法.该系统采用三个独立通道采集0°、60°和120°方向上的偏振图像,针对三个独立通道之间存在的视场差异提出了采用尺度不变特征转换配准法进行校正的方法;同时针对三个独立通道之间的灰度响应非一致性现象,根据积分球的退偏特性和探测器的线性响应模型,利用积分球产生完全非偏振光对灰度响应非一致性误差进行了校正.对比实验证明:1)本文提出的三通道偏振成像系统进行校正后的成像效果能够接近单通道偏振成像系统的水平;2)该系统能够在实时采集图像的同时,克服了多通道带来的偏振图像质量下降问题,提高了实用性.     

星载激光测高系统的大气折射延迟改正模型研究

星载激光测高仪通过测量从卫星平台发射的激光脉冲在卫星与地面激光脚点之间的渡越时间计算两者之间的距离。由于光束经过大气层时发生的折射,导致卫星激光测高系统典型的与大气延迟相关的测距误差在数米量级。讨论了大气折射延迟修正的理论与方法,分析比较了各种大气折射率模型,以全球首个对地观测星栽激光测高仪系统GLAS系统为例,给出了各种折射率模型的计算偏差,发现在常见温度和湿度范围内Owens375模型是一种精度较高的简化折射率模型;计算了GLAS系统高度角偏离天顶方向不超过10°的情况下,使用简单映射函数与CfA2．2映射函数模型的值,发现其差异不超过0．5mm。     

RS码仿真与基于RiBM算法的硬件实现

分析了里德-所罗门码（RS码）的误码率性能,提出了一种基于RiBM算法的RS（15,9）译码器。该译码器采用流水线结构,通过RiBM算法求解关键方程,在此基础上将高斯加性白噪声（AWGN）引入光纤模拟大气激光通信系统,并在现场可编程门阵列（FPGA）平台上完成了测试。测试结果表明：提出的译码器译码速率达到1.11 Gbit/s,为Altera IP核的3.54倍。RiBM算法具有硬件复杂度低、关键路径延时短的优点,能满足系统译码的要求。     

强噪声下三轴磁力计正交及增益误差校正及其测量实验

提出了适用于强测量噪声情况下的三轴磁力计正交及增益误差建模及校正方法,详细推导了磁力计测量误差模型,给出了误差参量辨识及校正算法,仿真证明了在强噪声情况下算法仍具有良好的收敛性,给出了不同信噪比条件下误差校正精度与采样点个数的关系,证实了算法能应用在磁力计测量噪声较强场合,并将其实现地磁场强度测量实验,获得了令人满意的结果。     

Analyse of Corrections during Measurements of Charge of a Semiconductor Detector

The amplitude of signals coming from a semiconductor detector depends on the a amplifier system filter networks, detector physical properties and energy of particles measured. The absolute measuring of detector charge requires an analysis of the influence of the mentioned parameters upon the measuring system reaction. The paper gives the theoretical concepts and correction diagrams for the optimum filter networks of CR-RC and CR-(RC)² tapes taking into consideration the existence of an undesirable integrating constant of the charge sensitive preamplifier. The application of the presented diagrams increases the accuracy and helps checking the obtained results by a pulse generator.     

INVESTIGATION ON COMPLIANCE ROTATION CORRECTION FOR COMPACT TENSILE SPECIMEN IN UNLOADING COMPLIANCE METHOD

The rotation correction method of unloading compliance for a compact tensile (CT) specimen in the current Jintegral resistance curves or critical Jintegral test standards was under suspicion by tracing to its source, and a new rotation correction method was proposed. The rotation center of the specimen is close to the crack tip, and the material constitutive relationship has little effect on the rotational radius R. If the formula for rotation correction recommended in current standards is used to measure the crack length of CT specimen, it will lead to larger error. A new formula with better accuracy for the crack length measurement of the CT specimen was presented.     

基于光照区太阳敏感器和陀螺辅助修正的微小卫星磁测技术

微小卫星经常用磁强计作为姿态测量的主要部件,磁强计的测量精度是影响微小卫星定姿性能的重要指标。为提高磁场估计精度,采用太阳敏感器和陀螺对磁强计误差进行辅助测量与修正,推导了磁强计误差估计方法,在光照区以太阳敏感器与陀螺输出作为俯仰滤波器观测量,估计出卫星俯仰角度和角速度。再采用最小二乘方法,利用滤波输出量对磁强计误差进行估计,估计的结果进入滤波器对磁场输出进行测量修正。仿真表明该方法简单易行,姿态角精度提高了1°左右,角速度精度最高提高了0.003(°)/s左右,并增强了卫星稳定性,有利于成像等任务的完成,有效提高了微小卫星导航系统性能。     

A field theoretical approach to the quasi-continuum method

The quasi-continuum method has provided many insights into the behavior of lattice defects in the past decade. However, recent numerical analysis suggests that the approximations introduced in various formulations of the quasi-continuum method lead to inconsistencies—namely, appearance of ghost forces or residual forces, non-conservative nature of approximate forces, etc.—which affect the numerical accuracy and stability of the method. In this work, we identify the source of these errors to be the incompatibility of using quadrature rules, which is a local notion, on a non-local representation of energy. We eliminate these errors by first reformulating the extended interatomic interactions into a local variational problem that describes the energy of a system via potential fields. We subsequently introduce the quasi-continuum reduction of these potential fields using an adaptive finite-element discretization of the formulation. We demonstrate that the present formulation resolves the inconsistencies present in previous formulations of the quasi-continuum method, and show using numerical examples the remarkable improvement in the accuracy of solutions. Further, this field theoretic formulation of quasi-continuum method makes mathematical analysis of the method more amenable using functional analysis and homogenization theories.