Logistic映射多尺度熵分析

为Logistic映射的理论分析和保密通信应用提供理论支撑,结合Logistic映射系统特性随参数μ变化的关系,以及多尺度熵能够反映混沌系统远离平衡状态程度的特点,提出了一种运用多尺度熵分析Logistic映射非线性动力学特性的方法。从仿真结果得到,多尺度熵能够区分出Logistic混沌系统不同状态,并且能够作为量化Logistic映射非线性动力学行为的指标。     

Adaptive multiscale entropy analysis of multivariate neural data

Multiscale entropy (MSE) has been widely used to quantify a system's complexity by taking into account the multiple time scales inherent in physiologic time series. The method, however, is biased toward the coarse scale, i.e., low-frequency components due to the progressive smoothing operations. In addition, the algorithm for extracting the different scales is not well adapted to nonlinear/nonstationary signals. In this letter, we introduce adaptive multiscale entropy (AME) measures in which the scales are adaptively derived directly from the data by virtue of recently developed multivariate empirical mode decomposition. Depending on the consecutive removal of low-frequency or high-frequency components, our AME can be estimated at either coarse-to-fine or fine-to-coarse scales over which the sample entropy is performed. Computer simulations are performed to verify the effectiveness of AME for analysis of the highly nonstationary data. Local field potentials collected from the visual cortex of macaque monkey while performing a generalized flash suppression task are used as an example to demonstrate the usefulness of our AME approach to reveal the underlying dynamics in complex neural data.     

Supercontinuum generation at 1.55 µm in an all-normal dispersion photonic crystal fiber with high-repetition-rate picosecond pulses

In order to measure the axial flowing velocity of carbon particle suspension with particle diameter of tens of micrometers, the photoacoustic Doppler（PAD） frequency shift is calculated based on a series of individual A scans using an autocorrelation method. A 532 nm pulsed laser with repetition rate of 20 Hz is used as a pumping source to generate photoacoustic signal. The photoacoustic signals are detected using a focused piezoelectric（PZT） ultrasound transducer with central frequency of 5 MHz. The suspension of carbon particles is driven by a syringe pump. The complex photoacoustic signal is calculated by the Hilbert transformation from time-domain photoacoustic signal, and then it is autocorrelated to calculate the Doppler frequency shift. The photoacoustic Doppler frequency shift is calculated by averaging the autocorrelation results of some individual A scans. The advantage of the autocorrelation method is that the time delay in autocorrelation can be defined by user, and the requirement of high pulse repetition rate is avoided. The feasibility of the proposed autocorrelation method is preliminarily demonstrated by quantifying the motion of a carbon particle suspension with flow velocity from 5 mm/s to 60 mm/s. The experimental results show that there is an approximately linear relation between the autocorrelation result and the setting velocity.     

Photoacoustic Doppler flowmetry of carbon particles flow using an autocorrelation method

The potential capability of low coherence backscattering（LBS） is explored to determine the anisotropy factor based on azimuthal light backscattering map. The scattering intensity signal measured at azimuthal angle φ=0° is extracted for analysis. By performing nonlinear regression fitting on the experimental signal to the Henyey-Greenstein phase function, the anisotropy factor is determined. The experiments with tissue phantom consisting of the aqueous suspension of polystyrene microspheres are carried out. The results show that the measured anisotropy factor is well described by Mie theory.     

激光多普勒血流仪对人体经穴皮肤血流灌注量的观察

本文介绍了激光多普勒频移及激光多普勒血流仪的工作原理,并利用激光多普勒血流仪检测了人体经穴皮肤血流灌注情况,同时对各经穴血流灌注量的变化规律及特点进行了讨论.     

Complex time series from a modulated semiconductor laser: itsdeterminism exploration

A singular value decomposition (SVD) eigenvalue spectrum is employed to explore the deterministic nature of the complex time series from a modulated semiconductor laser. With this method, the signature of chaos can be quickly identified and the noise contamination ratio can also be estimated. Relations between the supplied modulation of laser diode and the noise level are illustrated. The connection between relative intensity noise and the noise floor in the SVD spectrum has also been clarified     

Signal processing methodology to study the cutaneous vasodilator response to a local external pressure application detected by laser Doppler flowmetry

The existence of a cutaneous pressure-induced vasodilation (PIV) has recently been reported. This paper proposes a signal processing methodology to improve PIV knowledge. Temporal variations of laser Doppler signals rhythmic activities are first analyzed on anesthetized rats. The results lead to a method that provides a better PIV understanding.     

皮肤三层模型的Monte Carlo法模拟激光多普勒血流测量

本文提出了用Monte Carlo法模拟光子流在表皮、真皮及皮下组织中的传播。经过对模拟结果的分析,提出通过改变环状探测器与入射光束的距离来探测不同深度血流层的血流速度;发现频谱的指数下降规律;指出在血球浓度较小时,平均频移反映红血球的平均速率,在浓度较高时反映红血球的均方根速率;本文还给出了不同血球浓度下光子的穿透深度。     

Bayesian analysis of blood glucose time series from diabetes home monitoring

This paper describes the application of a novel Bayesian estimation technique to extract the structural components, i.e., trend and daily patterns, from blood glucose level time series coming from home monitoring of insulin dependent diabetes mellitus patients. The problem is formulated through a set of stochastic equations, and is solved in a Bayesian framework by using a Markov chain Monte Carlo technique. The potential of the method is illustrated by analyzing data coming from the home monitoring of a 14-year old male patient.     

8C2--Fluid flow measurements with a laser Doppler velocimeter

The basic principles of the laser Doppler velocimeter, a new instrument for measurement of localized flow velocities in gases and liquids, are discussed in detail. Velocity measurements are made by detecting the Doppler shift in monochromatic laser light which is scattered from small contaminant particles in the fluid. ACWgas laser serves as the light source, and the Doppler shift is detected by optical heterodyne techniques. The latest fluid flow measurements obtained with the laser Doppler velocimeter are presented.     

LTI models for 3-iodothyronamine time dynamics: a multiscale view

3-Iodothyronamine (T(1)AM) is a novel relative of thyroid hormone that plays a role in critical body regulatory processes such as glucose metabolism, thermal regulation, and heart beating. This paper was aimed at characterizing time dynamics of T(1)AM and its catabolite 3-iodothyroacetic acid (TA(1)) in different biological scales with linear time-invariant models. Culture medium samples coming from culture of H9c2 murine cells and perfusion liquid samples from perfused rat heart were collected after the injection of a T(1)AM bolus. T(1)AM and TA(1) concentrations in the samples were assayed with high-performance liquid chromatography coupled to tandem mass spectrometry. Kinetic constants relative to T(1)AM transport and conversion were estimated with weighted least-squares method. We found that these constants can be related with an allometric power law depending on mass, with a negative exponent of -0.27 ± 0.19, implying that the velocity of conversion and internalization of T(1)AM decreases with increasing of system mass.     

Volterra series analysis of semiconductor laser diode

Theoretical models for laser nonlinearities are analyzed. Volterra transfer function G/sub n/ are calculated from the laser rate equations using an output-to-input approach. Nonlinear models for second-harmonic, third-harmonic, and two-tone third-order intermodulation distortions are calculated from G/sub n/. The transfer function-based models are simplified and a new equation for intermodulation distortion is developed. Comparisons with previous results are presented. It is suggested that this analytical technique offers a valuable tool for the performance analysis of future broadband optical communication systems.<>     

基于激光多普勒测速的流场测试技术

激光多普勒测速技术,作为一种非接触式测速技术,具有测速精度高,测速范围广,空间分辨率高,不影响流场分布、可测远距离速度场等优点。因此多普勒测速技术已经在众多领域中得到广泛的应用。本文主要从理论上对激光多普勒测速技术进行分析,从实验角度阐述了激光多普勒测速技术的工作机理。并对激光多普勒测速技术在内燃机中流场测试应用的可行性进行分析,最后介绍了多普勒测速技术在内燃机流场测试中的应用和国内外发展情况。     

网络威胁时序的自相似性分析

为了验证网络威胁时序混沌预测模型的可行性和适用性,提出一种基于R/S分析的网络威胁时序分形自相似性分析方法,通过计算并检验3个威胁数据集中选出的典型威胁时序样本的Hurst指数,验证了连续和间断的网络威胁时序具有统计自相似性,因此可预测性较好,而稀疏的威胁时序不具有统计自相似性,可预测性较差.为利用分形和混沌等复杂非线性系统方法进行信息安全风险评估与威胁频率预测奠定了理论基础.     

Modern spectral analysis techniques for blood flow velocity andspectral measurements with pulsed Doppler ultrasound

Four spectral analysis techniques were applied to pulsed Doppler ultrasonic quadrature signals to compare the relative merits of each technique for estimation of flow velocity and Doppler spectra. The four techniques were 1) the fast Fourier transform method, 2) the maximum likelihood method, 3) the Burg autoregressive algorithm, and 4) the modified covariance approach to autoregressive modeling. Both simulated signals and signals obtained from an in vitro flow system were studied. Optimal parameter values (e.g., model orders) were determined for each method, and the effects of signal-to-noise ratio and signal bandwidth were investigated. The modern spectral analysis techniques were shown to be superior to Fourier techniques in most circumstances, provided the model order was chosen appropriately. Robustness considerations tended to recommend the maximum likelihood method for both velocity and spectral estimation. Despite the restrictions of steady laminar flow, the results provide important basic information concerning the applicability of modern spectral analysis techniques to Doppler ultrasonic evaluation of arterial disease.     

Multiscale entropy analysis of pulse wave velocity for assessing atherosclerosis in the aged and diabetic

This study proposed a dynamic pulse wave velocity (PWV)-based biomedical parameter in assessing the degree of atherosclerosis for the aged and diabetic populations. Totally, 91 subjects were recruited from a single medical institution between July 2009 and October 2010. The subjects were divided into four groups: young healthy adults (Group 1, n = 22), healthy upper middle-aged adults (Group 2, n = 28), type 2 diabetics with satisfactory blood sugar control (Group 3, n = 21), and unsatisfactory blood sugar control (Group 4, n = 20). A self-developed six-channel electrocardiography (ECG)-PWV-based equipment was used to acquire 1000 successive recordings of PWV(foot) values within 30 min. The data, thus, obtained were analyzed with multiscale entropy (MSE). Large-scale MSE index (MEI(LS)) was chosen as the assessment parameter. Not only did MEI(LS) successfully differentiate between subjects in Groups 1 and 2, but it also showed a significant difference between Groups 3 and 4. Compared with the conventional parameter of PWV(foot) and MEI on R-R interval [i.e., MEI(RRI)] in evaluating the degree of atherosclerotic change, the dynamic parameter, MEI(LS) (PWV), could better reflect the impact of age and blood sugar control on the progression of atherosclerosis.     

基于激光多普勒血流仪与灵敏电流计对人体皮肤穴位电位的观察

考虑人体皮肤穴位多普勒血流灌注,用灵敏电流计观察了相应穴位的皮肤电流与电位,通过对其分布特性的研究,发现了劳宫与涌泉穴之间电压变化的奇异现象。     

浑水流速的激光测量

实验获得了激光穿过浑水的功率衰减系数和相干性变化。动态下测量了浑水流动速度和多普勒信号特性。得出激光测速的浑水最佳浓度和极限浓度。并用一简化模型对动态实验进行分析,所得结果与实验一致。     

激光多普勒细水雾雾场特性实验研究

结合细水雾的特点和粒子的光散射理论,对三维APV(adaptivephase/Dopplervelocimeter)的光路系统设计了合适的参数,并进行了合理地布局。对细水雾雾场进行了实验研究,细水雾的速度分布、滴径分布以及雾通量的测量等都得到了合理的实验结果。