基于脉搏波相位差的无创连续血压测量方法

无创连续血压测量技术对医疗保健、临床监护、临床研究有重要意义.首次提出利用人体脉搏波的相位差来测量血压的新方法.介绍了桡动脉相位差和指端相位差与血压的关系,设计了实验测量不同血压条件下的人体多点脉搏波相位差,结果表明:多点脉搏波相位差与血压存在很强的相关性,且便携性与稳定性要优于传统的基于脉搏波传输时间(PTT)测量血压.     

A comparative analysis of principal component and independent component techniques for electrocardiograms

Principal component analysis (PCA) is used for ECG data compression, denoising and decorrelation of noisy and useful ECG components or signals. In this study, a comparative analysis of independent component analysis (ICA) and PCA for correction of ECG signals is carried out by removing noise and artifacts from various raw ECG data sets. PCA and ICA scatter plots of various chest and augmented ECG leads and their combinations are plotted to examine the varying orientations of the heart signal. In order to qualitatively illustrate the recovery of the shape of the ECG signals with high fidelity using ICA, corrected source signals and extracted independent components are plotted. In this analysis, it is also investigated if difference between the two kurtosis coefficients is positive than on each of the respective channels and if we get a super-Gaussian signal, or a sub-Gaussian signal. The efficacy of the combined PCA–ICA algorithm is verified on six channels V1, V3, V6, AF, AR and AL of 12-channel ECG data. ICA has been utilized for identifying and for removing noise and artifacts from the ECG signals. ECG signals are further corrected by using statistical measures after ICA processing. PCA scatter plots of various ECG leads give different orientations of the same heart information when considered for different combinations of leads by quadrant analysis. The PCA results have been also obtained for different combinations of ECG leads to find correlations between them and demonstrate that there is significant improvement in signal quality, i.e., signal-to-noise ratio is improved. In this paper, the noise sensitivity, specificity and accuracy of the PCA method is evaluated by examining the effect of noise, base-line wander and their combinations on the characteristics of ECG for classification of true and false peaks.     

近红外动脉血液检测中压力对脉搏波的影响

近红外血液检测技术中,透射式光电容积脉搏传感器具有携带有效信息量大的优点,可为动态光谱检测理论提供有效采样数据,但实际应用受到个体差异性的限制.为了克服不同手指端厚度给传感器带来的检测难题,分析了检测结果中压力与直流分量及交流分量之间的关系,通过不同厚度的手指测试实验,指出了存在一个最佳检测区域使得检测到的脉搏波处在最理想状态.     

Algorithms for the detection of events in electrocardiograms

The detection of events in electrocardiograms (ECGs) and vectorcardiograms (VCGs) is an essential processing step in systems for computer-assisted ECG/VCG interpretation. This paper describes various algorithms for the detection of QRS complexes, atrial activity and artefacts. These algorithms have been used in various versions of the TNO Modular ECG/VCG Interpretation System including its latest version, MEANS. Evaluation results are presented.     

Biological consequences of stress: conflicting findings on the association between job strain and blood pressure

The primary objective is to verify the relation between job strain and clinic blood pressure in a working population from the Milan municipality (1,909 men, 3,786 women) enrolled from 1992 to 1996. Job strain was investigated through the Karasek model. Clinic blood pressure was evaluated using standard procedures from the MONICA project. The association between the two was calculated controlling for age, education, smoking, body mass index, total and high-density lipoprotein (HDL) cholesterol. Significantly, associations were found for systolic blood pressure in men and for both systolic and diastolic blood pressure in women. However, these results do not reflect biological plausibility. The relationship between job strain and blood pressure is an unfinished business: sample characteristics and measurement methods should be carefully considered.     

基于相位差的转矩转速测量原理与设计

详细介绍了以相位差为原理的转矩转速仪原理与设计。通过对转矩转速测量原理的分析,得出转矩转速测量传感器的输出信号是具有相位差的正弦信号。信号经过调理转换电路送入单片机,由单片机对信号进行处理并转换为转速和转矩数据,然后送显示单元显示。系统具有RS-485通信接口和键盘输入接口,可根据用户需求规定传输规约,也可通过键盘输入用户参数,使得转矩转速仪具有良好的适用性,可单独使用,也适合主从式多机通信或分布式远程通信要求。     

科氏质量流量计相位差的一种高精度估计方法

科氏质量流量计是一种用于直接测量质量流量的流量计,其测量精度易受环境噪声的影响。为提高其精度,提出了一种高斯噪声背景下的科氏质量流量计相位差估计新方法。当传感器信号频率在较小范围内缓慢波动时,通过锁相环实现整周期采样。采用离散傅里叶变换计算两路传感器信号的相位差,并实现了219点离散傅里叶变换,以获得精确的相位估计值。与快速傅里叶变换相比,所提出方法具有计算量小、计算速度快等优点,大大降低了数据处理容量。仿真结果表明:当信噪比高于0dB时,该方法的相位估计误差小于0.12°。     

Relationship between activity and three phase boundary in the ternary phase diagram

Theoretical formulae have been derived for determining the activity along a three-phase boundary in a three component system. The activities can be calculated from ternary phase diagrams from the partial thermodynamic properties and the use of a single integration constant. The latter is calculated from the binary phase diagrams. The formulae are rigorous and no assumption is made.     

DFT变换法在科氏质量流量计相位差检测中的应用研究

提出了一种新的采用DFT(离散付利叶变换)实现科氏质量流量计的相位检测方法.该算法首先从理论上分析存在非整周期采样引起的误差随时间的变化规律,提出通过相位变化修正计算DFT的采样点数,使计算DFT的点数接近整周期,最终获得较好的相位计算结果.仿真试验结果表明,这种方法还能够实现频率跟踪,克服频率变化引起的相位计算误差,提高跟踪精度.     

New method to improve the dynamic parameters of liquid crystals: Surface wave treatment of the interface between solid phase and mesophase

Abstract— As a new method to enhance the speed of liquid‐crystal‐display elements, the surface electromagnetic‐wave treatment of the conducting layers has been used. The procedure indicated above improves the control of nematic liquid crystals, decreases the number of layers in a sandwiched structure, decreases the magnitude of the supply voltage, and drastically decrease the relaxation time of the mesophase. The re‐orientation of the liquid‐crystal dipoles under field action can be observed with high speed. Thus, a new method of speed enhancement of pure or nano‐objects‐doped nematic liquid crystal has been demonstrated.     

负压波定位理论在输油管道泄漏监测系统中应用

本文主要讲述了负压波理论在输油管道泄漏监测系统的具体应用情况，分析了采用同压波理论进行泄漏定位的过程中时间差的求解问题，提出了三种求取时间差的方法，通过负压滤理论的定位公式以及时间差对泄漏点进行定位。     

双模态语音识别中乘积HMM权重系数与瞬时SNR的关系研究

在有噪声污染等复杂情况下,为了能够得到更高的语音识别率,提出了一种新的乘积隐马尔可夫模型(HMM)用于双模态语音识别,研究并确定了模型中权重系数与瞬时信噪比(SNR)之间的关系.该模型在独立训练音频和视频HMM的基础上,建立二雏训练模型,并使用重估策略保证更高的准确性.同时引入广义几率递减(GPD)算法,调整音视频特征的权重系数.实验结果表明,提出的方法在噪声环境下体现出了良好稳定的识别性能.     

Electromagnetic wave scattering from the sea surface in the presence of wind wave patterns

The study is concerned with electromagnetic wave (EM) scattering by a random sea surface in the presence of coherent wave patterns. The coherent patterns are understood in a broad sense as the existence of certain dynamical coupling between linear Fourier components of the water wave field. We show that the presence of weakly nonlinear wave patterns can significantly change the EM scattering compared to the case of a completely random wave field. Generalizing the Random Phase Approximation (RPA) we suggest a new paradigm for EM scattering by a random sea surface.

The specific analysis carried out in the paper synthesizes the small perturbation method for EM scattering and a weakly nonlinear approach for wind wave dynamics. By investigating, in detail, two examples of a random sea surface composed of either Stokes waves or horse-shoe (‘crescent-shaped’) patterns the mechanism of the pattern effect on scattering is revealed. Each Fourier harmonic of the scattered EM field is found to be a sum of contributions due to different combinations of wave field harmonics. Among these ‘partial scatterings’ there are phase-dependent ones and, therefore, the intensity of the resulting EM harmonic is sensitive to the phase relations between the wind wave harmonics. The effect can be interpreted as interference of partial scatterings due to the co-existence of several phase-related periodic scattering grids. A straightforward generalization of these results enables us to obtain, for a given wind wave field and an incident EM field, an a priori estimate of whether the effects due to the patterns are significant and the commonly used RPA is inapplicable. When the RPA is inapplicable, we suggest its natural generalization by re-defining the statistical ensemble for water surface. First, EM scattering by an ‘elementary’ constituent pattern should be considered. Each such scattering is affected by the interference because the harmonics comprising the pattern are dynamically linked. Then, ensemble averaging, which takes into account the distribution of the pattern parameters (based on the assumption that the phases between the patterns are random), should be carried out. It is shown that, generally, this interference does not vanish for any statistical ensemble due to dynamical coupling between water wave harmonics. The suggested RPA generalization takes into account weak non-Gaussianity of water wave field m contrast to the traditional RPA which ignores it.     

超声波流量计静水时差温度漂移的解决方法

时差式超声流量计广泛应用于工业生产和日常生活各个领域,其中超声信号在流体中顺、逆流传播时间差的测量精度很大程度上决定了流量的测量精度,由于实际测量中“零点误差”和“温度漂移”的存在,使得消除或抑制这两者的影响成为提高流量测量精度的重要环节。依据电声互易定理,改善测量系统电路的互易性可以有效抑制“零点误差”和“温度漂移”,而发射电路与接收电路阻抗的对称性和测量系统的互易性存在很强的联系,通过匹配激励和接收电路等效阻抗可以改善测量系统的互易性。依据互易电路设计对现有测量系统进行了改进,并搭建实验平台进行了实际测量。实验表明：此电路设计能够非常有效的抑制“零点误差”和“温度漂移”。     

Age-related difference in perceptual responses and interface pressure requirements for driver seat design

Due to typical physiological changes with age, older individuals are likely to have different perceptual responses to and different needs for driver–seat interface design. To assess this, a study was conducted in which a total of 22 younger and older participants completed six short-term driving sessions. Three subjective ratings (comfort, discomfort and overall) were obtained, along with 36 driver–seat interface pressure measures, and were used to assess differences and similarities between the two age groups. For both age groups, localised comfort ratings were more effective at distinguishing between driver seats and workspaces. Older individuals appeared to be less sensitive to discomfort than younger individuals. Across age groups, two distinct processes were used in determining whole-body comfort and discomfort perceptions based on localised comfort/discomfort perceptions. Whole-body discomfort levels were largely affected by lower back discomfort in the younger group versus upper back discomfort in the older group. Four specific pressure measures at several body regions differed between the age groups, suggesting distinct contract pressure requirements and loading patterns among these groups.     

A difference in expressive power between flowcharts and recursion schemes

We show the existence of a single interpretation for which no flowchart produces the same results as a particular recursion scheme.Partially supported by NSF Grant MCS77-15628.Partially supported by NSF Grant DCR75-02373.     

Conservation of the law of phase modulation for UWB pulse signals in the first principal component

This paper considers the possibility to employ the first principal component (Kahrunen-Loeve transform) to reveal the law of reflected signal phase modulation. The processing of modeled and real signals representing ultrawideband impulses reflected from a simple target and from a model imitating human breath was taken as an example. It is experimentally shown that, for small movements of the target, the first principal component??s movement trajectory follows the original law of reflected signal phase modulation with precision of not less than 20%.