基于小波变换的心电图QRS波群检测方法研究

本文就心电图信号的QRS波群检测提出了一种基于小波变换的信号特征提取方法,此方法对心电信号中QRS波群的时变特性及几种常见的心电干扰具有较强的鲁棒性.文中我们采用两种不同性质的小波为母小波对含有噪声污染的心电信号进行多尺度的小波分解,在没有预先消噪处理的情况下,较为准确、快速地检测出QRS波群的信息,并且以国际上广泛承认的心电数据库MIT-BIH中的记录对算法进行检验.     

基于复值小波分解的QRS波群检测算法

心电信号特征参数的提取和识别是心电图分析和诊断的基础。在心电信号的分析中,QRS波群快速准确的检测非常重要,它是相关参数计算和诊断的前提。本文对心电信号进行复值小波分解后,利用分解结果的模值来检测QRS波。由于心电信号的形态和幅值因人而异,所以用自学习算法来调整阈值以适应信号的变化。用MIT-BIH心电数据库中的数据对以上方法进行验证,QRS波群的检测率高达99.81%以上。最后,在检测出QRS波群特征点的基础上,利用相类似的方法检测出P、T波。     

基于变分模态分解的心电信号QRS波检测

为了解决含噪心电信号QRS波的提取问题,本研究提出了一种基于变分模态分解(variation mode decomposition,VMD)的心电信号QRS波群检测和定位的方法。首先确定合适的分解层数,利用变分模态分解将心电信号分解为一系列模态分量。对每层模态分量进行分析,选取含有QRS波的模态分量层。通过小波变换的奇异值检测原理,确定心电信号的奇异值,定位心电信号R波的峰值位置,再检测QRS波的波形宽度。实验证明了该方法对含噪的QRS波检测准确度在96%以上,能够准确的检测和定位心电信号QRS波。     

基于子波多尺度分辨的心电QRS波分类方法的研究

本文分析了心电QRS波的子波多尺度分辨特征,探讨了曲线非线性分开维数的计算方法,提出了一种新的QRS波的分类方法：对心电QRS复合波进行子波多尺度分解,在尺度为4的情况下,根据局部正负极大值对检测出它们前后两个零点Zp1,Zp2,计算出局部正负极大值对位于┃Zp1,Zp┃之间的曲线段的分形维数。根据局部正负极大值对的幅度和分开维数能很好地检出正常心电信号的QRS波及早搏信号;该方法具有很强的抗噪能力,提高了QRS波的正确检出率。     

基于小波变换的QRS波群实时检测算法

本文研究了基于小波变换方法的心电信号QRS波群检测算法,通过对心电信号进行低通滤波、小波变换、差分平滑、阈值检测和修正策略等技术,提高了QRS波群的检测率.经MIT-BIH心律失常心电数据库全部48例数据的检验,QRS波检测灵敏度达99.82%,真阳性率达99.52%.在Windows环境下可实时实现.     

基于数学形态学方法的心电图波形分离技术

讨论了一种基于数学形态学的心电图波形分离方法。使用这种方法,无须检测QRS波群,利用一系列形态学运算,便可以直接去除心电信号中的QRS波群,检出P波和T波的起止点,实现波形的定性和定量分离。定性分离效果甚佳,定量分离结果的方差较小。此外,心电信号的滤波、基线矫正等处理,也完全由类似的形态学算法实现。     

基于提升小波变换和多种策略的QRS波检测算法

目的：为了提高计算机处理心电信号的速率和精度,提出了一种基于提升小波变换,结合多种策略的QRS波检测算法。方法：首先采用基于阀值的提升小波去噪方法去除心电信号中的高频白噪声和低频基线漂移;再对处理后的心电信号进行提升小波分解,得出各层逼近信号和细节信号,在第3尺度上采用模极大值阀值法对R波进行检测．找出备选的R波,同时采用几何的方法定位Q波和S波及QRS波起点和终点;最后采用补偿法、波宽法及QRS波时长法对QRS波群进行纠正。结果：本文算法在时域心电图上实现了QRS波的准确定位．提取了心电图的QRS波段。通过MIT—BIH数据库验证,本算法具有很好的表现。结论：实验结果表明,相比传统的算法,本文采用的提升小波和多种策略的检测算法．能有效的检测QRS波,为心电信号的自动识别奠定了基础。     

基于小波变换的心电信号中QRS复合波内异常高频分量的检测

提出利用小波变换方法提取心电信号中异常QRS复合波内的高频分量，并定义了残余信号的QRS，作为衡量指标，为检测QRS复合波内的异常高频分量提供了有效的定量检测方法。     

一种使用关联积分进行QRS波检测的新方法

使用计算机对ECG信号进行分析和处理能够减少医生的工作量,提高医生的工作效率.在ECG自动诊断系统中,对QRS波进行准确检测非常重要.目前,QRS波的检测方法已经有很多种,如使用差分和滤波器组、小波变换、神经网络等方法等,但还没有一种方法的适应性和准确性得到广泛的认同.关联积分的方法是从混沌学理论中推导出来,是一种全新的检测QRS波方法.使用关联积分的方法对心电信号QRS波进行分析,得到了很好的效果,而且这种分析方法具有较好的鲁棒性.本文利用MIT/BIH Arrhythmia Database库中的数据测试了上述方法,结果证实其对QRS波的正确检出率为99.1%.     

心电信号零相位数字滤波

分析了零相位数字滤波的原理 ,通过对实测心电信号中 5 0Hz工频干扰的抑制结果表明 ,该方法对心电信号的滤波性能优于普通数字滤波方法 ,特别是对心电信号中QRS波群具有更好的滤波效果 ,在心电信号的处理、分析和自动识别中具有很高的应用价值     

Cobalt-induced polycythaemia causing right ventricular hypertrophy and ascites in meat-type chickens

Cobalt increases the red cell mass in both man and animals by increasing the production of erythropoietin. Since meat-type chickens can develop pulmonary hypertension from increased erythropoiesis and polycythaemia, two trials were conducted to investigate the role of cobalt on broiler chicken erythropoiesis and pulmonary hypertension. The results showed that feeding cobaltous chloride at 500 parts/10(6) to meat-type chickens from 1-day-old for 42 days significantly increased haemoglobin content and, to a lesser extent red blood cell count, and haematocrit. No effect was observed on mean corpuscular volume. Increased haemoglobin content was linearly correlated with pulmonary hypertension as measured by the right ventricle weight to total ventricle weight ratio (RV:TV). Levels of malondialde-hyde in cardiac tissue were also correlated with the RV:TV ratio, suggesting that peroxidative damage may be related to ventricular hypertrophy. Chickens fed cobalt showed a significantly higher incidence of right ventricular hypertrophy and right ventricular failure and 18.3% developed ascites.     

Partial potentials of selected cardiac muscle regions and heart activity model based on single fibres

We present single fibre heart activity model (SFHAM) based on the current flow through the five bunches of fibres of the cardiac muscle (CM). The five effective fibres are identified and assigned to the appropriate segments of CM. Analytical functions describing ionic flows along the fibres are derived and proposed. The parameters determining the shapes and amplitudes of the functions proposed are obtained on the basis of standard 12-lead ECG measurements after numerical fitting procedures concentrating on the QRS-waves. As a consequence, five independent courses of partial, transient potentials are obtained representing: anterior, inferior, lateral, posterior walls, and interventricular septum activities, respectively. Moreover, to check our theoretical results we compare the potentials calculated with those from physical measurements performed on the patient’s body surface. We expect that SFHAM will permit detection of pathological changes in particular fragments of CM.     

声衰减与非线性对双频聚焦声焦域的影响

目的：探讨声衰减与非线性对双频聚焦超声声焦域的影响。方法：利用瑞利积分的线性叠加算法数值模拟计算。并在辐照离体生物组织中进行实验验证。结果：随着声衰减系数的增大与非线性的增强．双频声焦域从“椭球形”变成“蝌蚪形”,并且焦域向着换能器方向移动,但声衰减的影响较非线性大。结论：声衰减与非线性对焦域影响较大,在实际应用中应予考虑。本文在利用瑞利积分的线性叠加算法,研究了媒介声衰减与高声强引起的非线性对差频相干模式下的双频聚焦声场焦域的影响。结果表明,随着声衰减系数的增大与非线性的增加。双频声焦域从“椭球形”变为“蝌蚪形”．并且焦域向着换能器方向移动．但声衰减的影响较非线性大。并在离体牛肝的损伤实验中得到初步验证。     

经食管超声评价微创外科房间隔缺损封堵术中患者心功能及血流动力学

目的运用经食管超声对微创外科房间隔缺损封堵术中患者心功能及血流动力学的变化进行评价,探讨超声在微创外科房间隔缺损封堵术中的应用价值。方法门诊筛查选择适合经微创外科封堵术治疗的房间隔缺损患者50例,于术中及手术前后对患者进行经食管超声和经胸超声心动图检查,分别测量左、右室心功能及血流动力学指标,并对手术前后结果进行对照比较。结果术后左、右房室腔的径线与术前比较明显减小（P〈0．05）,右心室舒张末期容积（RVEDV）、右心室每搏输出量（RVSV）、右心排血量（CO）均较封堵前明显减小,左心室舒张末期容积（LVEDV）、每搏输出量（LVSV）及排血量（CO）均较封堵前增加,两者具有显著差异（P〈0．05）。而左心室收缩末期容积（LVESV）和右心室收缩末期容积（RVESV）以及左室和右室射血分数无显著变化。术后肺动脉瓣上最大血流速度、三尖瓣口E峰流速、三尖瓣反流最大流速及肺动脉收缩压与术前比较均显著减小（P〈0．05）,二尖瓣口E峰流速显著增大（P〈0．05）。结论经食管超声可及时反映微创外科房间隔缺损封堵术前后患者心功能及血流动力学变化,为临床评价手术效果提供参考。     

Comparisons of the nonlinear dynamics of electroencephalograms under various task loading conditions: a preliminary report

Comparison of the characteristics of electroencephalogram (EEG) records treated as realizations from a nonlinear process were compared under four different conditions: eyes shut resting, and three silent observation instructions to predict the patterns of randomly generated lights which illuminated every 10 seconds. The correlation dimension of the EEG was calculated by a method involving finding the correlation integral in m-dimensional space, and found to show some variations within time series. The degree and directions of changes in the dimensionality of the process varied between observers and did not clearly confirm some earlier reported findings, but it is demonstrable that the measures of nonlinear brain dynamics can be correlated with psychological variables. Reasons for this are discussed.     

Tracer experiment design for unique identification of nonlinear physiological systems.

The design of tracer kinetic experiments, the purpose of which is to elucidate uniquely the internal couplings of a nonlinear dynamic system, is considered for a practical class of models of physiological systems. The extent of information about the real system contained in tracer kinetic data is a central issue. Criteria for determining whether nonlinear model parameters can be estimated from small-signal, "linearizing" tracer experiments are developed and illustrated by examples. The concept of "structural identifiability" is employed in this analysis to determine which model parameters can be and which cannot be determined "uniquely" from given input-output data; a step-by-step procedure based on an extension of this concept is presented for adapting the overall approach to the experimental design problem. Estimation of unmeasurable endogenous inputs and system state variables, problems that are intimately related to parameter estimation for physiological systems, are also considered.     

Human electroencephalograms seen as fractal time series: mathematical analysis and visualization

The paper presents a novel technique of nonlinear spectral analysis, which has been used for processing encephalograms of humans. This technique is based on the concept of generalized entropy of a given probability distribution, known as the Rényi entropy that allows defining the set of generalized fractal dimensions of encephalogram (EEG) and determining fractal spectra of encephalographic signals. Unlike the Fourier spectra, the spectra of fractal dimensions contain information of both frequency and amplitude characteristics of EEG and can be used together with well-accepted techniques of EEG analysis as an enhancement of the latter. Powered by volume visualization of the brain activity, the method provides new clues for understanding the mental processes in humans.     

Fracture toughness estimation for the TMJ disc

J contour integral fracture toughness of the temporomandibular (TMJ) disc was estimated from a computational model based on fracture load data derived from experimental tests. The computational model involved a stress analysis of TMJ disc specimens with cracks oriented parallel and perpendicular to the primary collagen fiber axis within the intermediate zone of the disc. The results demonstrated differences occurred between crack orientations when an orthotropic model was used. Fracture toughness was much lower for a crack oriented parallel to the collagen fiber direction than that for a crack oriented perpendicularly. Thickness, crack size, and anisotropy ratio were observed as additional variables affecting the fracture toughness of the TMJ disc. Future model enhancements may be achieved by considering the poroviscoelastic nature of the TMJ disc.     

无支架心包二尖瓣的有限元分析

目的　通过无支架心包二尖瓣与有架三叶生物瓣对比，利用有限元法计算，观察在左心室舒张期瞬时跨瓣压差作用下的瓣叶静态应力分布。方法　采用八节点曲线薄壳单元，考虑大应变以及瓣叶闭合过程的接触，应用Newton-Raphson方法求解有限元非线性方程。结果　瓣膜开启状态下两种瓣膜应力水平均不高。在峰值跨瓣压差15.96 kPa作用下，无架心包二尖瓣第一主应力分布均匀，无明显应力集中、平均第一主应力为0.040~0.149 MPa；有架三叶瓣在临床上易发生撕裂的部位明显应力集中，最大第一主应力为2.352 MPa，平均第一主应力为0.223~0.724 MPa，明显高于无架心包二尖瓣。结论　(2)对于几何曲面形状不规则，高度接触的无支架心包二尖瓣，首次采用有限元方法进行应力计算是有效可行的；(2)本研究的有支架心包三叶瓣有限元模型得到的应力分布与临床结果一致；(3)无架心包二尖瓣较有架心包三叶瓣应力分布明显合理，有益于防止瓣叶撕裂和钙化、延长寿命。     

Evaluation of the impression technique by measuring interstitial oedema in rat testis

The impression method for assessment of subcutaneous oedema was evaluated in a rat testis model where the testicular interstitial fluid volume was changed both artificially by infusion of rat plasma and pharmacologically by administration of human chorionic gonadotrophin. Both the integral value and the impression force value, as measured with the impression method, changed with infused volume, and changes as small as 16,μl (approximately 7% of the total interstitial fluid volume in a testis) could be detected. Rats were treated with a single injection of 100 i. u. human chorionic gonadotrophin in order to induce changes in the volume of interstitial fluid in the testis. Both the integral value and the impression force value seemed to reveal information on testicular interstitial fluid volume in rats treated with human chorionic gonadotrophin that was similar to data revealed by measuring the actual fluid content in the testis. Interstitial fluid volume measured morphometrically in the contralateral testis in human chorionic gonadotrophin-treated rats was significantly correlated to the impression force value (r= 0.75) and the integral value (r= 0.52). This rat testis model proved to be an interesting experimental set-up for evaluation of the impression technique.