基于经验模式分解的混沌干扰下谐波信号的提取方法

由混沌信号和谐波信号组合而成的复杂信号的分离方法一直受到关注.利用经验模式分解方法,依据任何信号由不同的固有简单振动模态组成的概念,将由混沌信号和谐波信号组合而成的复杂信号分离为不同的内在模态函数,并从中分解出谐波信号.通过利用Duffing方程产生的混沌信号进行的仿真实验,结果都表明该方法在一定参数范围内非常有效. 关键词： 经验模式分解 混沌 信号处理     

Metric entropies of sets in abstract Wiener space

Let (X,H,μ) be an abstract Wiener space, E(?,K) denote the metric entropy of a set K⊂X. If K is not a slim set, then we prove that

     

Stochastic frequency-domain tissue characterization: application to human spleens ‘in vivo’

Ultrasonic waveforms backscattered from normal and pathologic human spleens were recorded in vivo using a high-speed digital data acquisition system. A frequency-domain analysis was performed for 50 digitized waveforms from each spleen, in which auto-correlations of frequency spectra were employed to measure the mean spacing among adjacent tissue scatterers. Mean scatterer spacing for normal spleens averaged 1.10 ± 0.14 mm, whereas abnormal, diffusely enlarged spleens had mean scatterer spacings averaging 1.52 ± 0.14 mm. The results of these measurements are in accord with those expected from splenic histology. The techniques described may be valuable in ultrasonic diagnosis of the spleen and other organs.     

固体浸没透镜光存储的信号探测技术

信号探测是固体浸没透镜成为实用存储技术的一个必需的组成部分。对在该项研究中获得的理论和实验成果进行了介绍。总结了针对固体浸没透镜机理的三维矢量理论 ,对影响信号探测的因素 ,例如头盘间距、盘片结构和光的偏振态等进行了讨论。介绍了基于固体浸没透镜光存储中信号探测的新技术和重要的实验结果。     

激光测距中的几种虚警抑制措施

激光测距的关键在于光电微弱信号的检测，如何调和可靠性和灵敏度之间的矛盾是弱检问题的关键。激光测距系统包括主控电路、发射电路、接收电路、计时电路以及其他一些功能电路，其中与虚警的产生和抑制密切相关的部分主要是接收电路和主控电路。从硬件设计和主控电路软件算法两方面，对测距机虚警抑制方法进行了分析，其虚警抑制方法对其他激光测距系统具有普遍意义。     

Stochastic filtering of multiphase transport phenomena

Whether or not a multiphase mixture is to be considered heterogeneous is a function of scale and hence also a function of the measurement process. Heterogeneities manifested through the measurement process and sampling frequency (extrinsic heterogeneity) are discussed in relationship to the intrinsic heterogeneity associated with the true physical environment. The question of whether or not a multiphase environment may be scaled is partially a function of the scale of the extrinsic heterogeneity of interest. Thus, it is also a function of the instrumental apparatus, which implies that the instrument must also be scaled. We review restrictive scaling constraints in frequency space that an instrument must satisfy for proper scaling of an experiment. Cushman (1984 Water Resour. Res. and 1985 Acta Appl. Math) developed a theory that incorporates the scale and measurement process directly into the multiphase transport equations and which in turn allows for correlation of field properties over scales of motion. We discuss a generalization of this theory which accounts for integral representations of distributional stochastic processes as a function of the scale of the instrument used in the measurement of the field variables. This allows us to solve the stochastic transport equations in an operational setting, i.e., in terms of measurable quantities. Throughout the article examples are presented to illustrate the concepts.     

A small angle neutron scattering and electrochemical impedance spectroscopy study of the nanostructure of the iron chalcogenide glass ion-selective electrode

This paper presents a preliminary structural and interfacial study of the iron chalcogenide glass [i.e., Fe_x(Ge₂₈Sb₁₂Se₆₀)_100−x] ion-selective electrode (ISE) using small angle neutron scattering (SANS) and electrochemical impedance spectroscopy (EIS). SANS detected variations in the neutron scattering as a function of iron content in the chalcogenide glass. Furthermore, a change in the chalcogenide glass structure was observed at elevated iron dopant levels. Conversely, EIS was used to show that the iron chalcogenide membrane comprises various time constants, and the interfacial charge transfer reaction depends on the membrane iron content. Equivalent circuit modeling revealed that the charge transfer resistance decreases at elevated iron levels, and this may be related to the presence of iron defects in the glass. It is proposed that the iron chalcogenide membrane comprises an iron nanostructural network embedded in the amorphous matrix, and this directly influences the electrical conductivity and concomitant electrochemical reactivity of the glass.     

Scanning electrochemical microscopy (SECM) of nanolitre droplets using an integrated working/reference electrode assembly

Scanning electrochemical microscopy (SECM) has been performed in the restricted space of nanolitre droplets with a robust and easy-to-handle coaxial electrode assembly centring a Pt microdisk in a circular Ag electrode. Straightforward and reproducible fabrication of the specially designed probe tips was achieved by using Tollens reaction to chemically deposit a uniform and well-adhering layer of silver on the body of a glass-insulated Pt microdisk electrode. The suitability of the novel dual-electrode SECM tip for measurement in small volumes was evaluated by imaging an array of four Pt band microelectrodes in 500 nL electrolyte.     

Asymptotic analysis via Mellin transforms for small deviations in L 2-norm of integrated Brownian sheets

We use Mellin transforms to compute a full asymptotic expansion for the tail of the Laplace transform of the squared L²-norm of any multiply-integrated Brownian sheet. Through reversion we obtain corresponding strong small-deviation estimates.Research supported by NSF grant DMS–0104167, and by The Johns Hopkins Universitys Acheson J. Duncan Fund for the Advancement of Research in Statistics.Mathematics Subject Classification (2000):Primary 60G15, 41A60; secondary 60E10, 44A15, 41A27