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1.
对水平管密相气力输送系统的混沌动力学行为进行了分析,对煤粉浓度信号时间序列的最大Lyapunov指数和关联维数进行了计算。结果表明,系统的最大Lyapunov指数均大于零,这充分说明煤粉在水平管中的密相气力输送存在混沌特征。从密相移动床流区到沉积层流区,混沌吸引子由大变小,关联维数从1.5359减小到1.0764。说明从密相移动床流区到沉积层流区,流体系统运动的混沌程度逐渐减弱。 相似文献
2.
INTRODUCTION The significant information of a signal is often carried by singular characteristics or irregular struc-tures of the signal, for example, the most important information of ECG(electrocardiogram) or EEG isoften presented at the transient points of a signal, such as those points near peaks. The singular charac-teristics of these transient points are more obvious than the smooth parts of signals. Therefore,to studythe singularity of a signal is a meaningful work. Those analysi… 相似文献
3.
基于Lyapnuov泛函方法,研究了满足匹配条件的不确定性时滞系统的鲁棒稳定性及具有稳定度β〉0鲁棒稳定性,给出了已有结果不能推出的新判据。这些新判据对已有结果难以使用的情况下也可有是有效的,或有时减少了已有结果的保守性。 相似文献
4.
Riyanto T. Bambang Etsujiro Shimemura Kenko Uchida 《Optimal control applications & methods.》1994,15(3):151-173
The problem of mixed H2/H∞ control with pole placement is considered for linear time-invariant systems. This is the problem of determining a controller for linear time-invariant systems which minimizes the H2-norm of a certain closed-loop transfor function subject to an H∞-norm constraint on another closed-loop transfer function and an additional constraint on the location of the closed-loop poles in the complex plane. An optimization problem is posed for the pole-constrained H2/H∞, problem in such a way that the objective function is expressed as a weighted sum of the actual H2 cost and its upper bound. A necessary condition for the optimization problem is derived via the Lagrange multiplier technique. The condition involves a set of highly coupled equations. By sacrificing the H2 performance, an alternative optimization problem is posed in order to simplify the necessary condition. An iterative algorithm for solving the coupled equations arising in the necessary conditions is proposed and numerical examples are presented. 相似文献
5.
To provide better transient performance in controlling robots, a mixed minimum time and quadratic performance index is used. For known and uncertain revolute robot manipulators a conventional optimal control and a robust guaranteed cost control are proposed respectively. Asymptotic stability is also discussed based on the Lyapunov direct method. The proposed robust control is continuous and requires no knowledge of the uncertain system except for bounding functions. 相似文献
6.
对心率变异性(HRV)进行了研究,比较了心率正常者与心率失常者HRV之间的最大李雅普诺夫指数上的差别。人在正常状态和病理状态下的HRV信号最大李雅普诺夫指数是不同的,当出现病理心血管事件时,指数α减少,因此李雅普诺夫指数可作为人体是否异常或处于何种异常状态的特征刻画指标,本文心率正常者HRV信号的最大李雅普诺夫指数为0.45907,心率不齐者的最大李雅普诺夫指数是0.41472。它们均为混沌信号,但是处于心率不齐状态的节律混沌程度明显比处于心率正常状态的节律混沌程度低。 相似文献
7.
Salman Nazary-Moghadam Mahyar Salavati Ali Esteki Behnam Akhbari Sohrab Keyhani Afsaneh Zeinalzadeh 《The Knee》2019,26(1):88-96
Background
Several investigations have studied gait variability of individuals with anterior cruciate ligament (ACL) deficiency; however, the effect of dual-tasking on the gait variability of these individuals remained unclear. The aim of the present study was to determine the effect of gait speed and dual-tasking on knee flexion–extension variability in subjects with and without ACL deficiency.Methods
The knee flexion–extension Lyapunov exponent (LyE) was measured in 22 ACL-deficient (Mean±SD) (25.95?±?4.69?years) and 22 healthy subjects (24.18?±?3.32?years). They walked at three levels of gait speed in isolation or concurrently with a cognitive task.Results
Repeated-measure analyses of variance (ANOVAs) demonstrated that the interaction of group by gait speed was statistically significant. As the gait speed increased from low to high, the knee flexion–extension LyE significantly decreased for the subjects with ACL deficiency (effect size: 0.57, P?=?0.01). The interaction of group by cognitive load was not statistically significant (P?=?0.07). In addition, the ACL-deficient subjects had statistically slower reaction times than healthy subjects during the dual-task compared with the single-task condition.Conclusions
The ACL-deficient and healthy individuals had a tendency to maintain safe gait. It seems that the ACL-deficient subjects sacrificed the cognitive task more than the healthy individuals to pay more attention toward gait. Additionally, it seems that the gait speed was more challenging than cognitive load on the stride-to-stride variability in the individuals with ACL deficiency. 相似文献8.
Armoundas AA Ju K Iyengar N Kanters JK Saul PJ Cohen RJ Chon KH 《Annals of biomedical engineering》2002,30(2):192-201
Current methods for detecting nonlinear determinism in a time series require long and stationary data records, as most of them assume that the observed dynamics arise only from the internal, deterministic workings of the system, and the stochastic portion of the signal (the noise component) is assumed to be negligible. To explicitly account for the stochastic portion of the data we recently developed a method based on a stochastic nonlinear autoregressive (SNAR) algorithm. The method iteratively estimates nonlinear autoregressive models for both the deterministic and stochastic portions of the signal. Subsequently, the Lyapunov exponents (LE) are calculated for the estimated models in order to examine if nonlinear determinism is present in the deterministic portion of the fitted model. To determine if nonlinear dynamic analysis of heart-rate fluctuations can be used to assess arrhythmia susceptibility by predicting the outcome of invasive cardiac electrophysiologic study (EPS), we applied the SNAR algorithm to noninvasively measured resting sinus-rhythm heart-rate signals obtained from 16 patients. Our analysis revealed that a positive LE was highly correlated to a patient with a positive outcome of EPS. We found that the statistical accuracy of the SNAR algorithm in predicting the outcome of EPS was 88% (sensitivity=100%, specificity=75%, positive predictive value=80%, negative predictive value=100%, p=0.0019). Our results suggest that the SNAR algorithm may serve as a noninvasive probe for screening high-risk populations for malignant cardiac arrhythmias. © 2002 Biomedical Engineering Society.
PAC2002: 8719Hh, 0545Tp, 8710+e 相似文献
9.
证明了可约布尔矩阵幂敛指数的一个一般性上界k(A)≤(n-i)2 i,并给出了幂敛指数达到此上界矩阵的完全刻划,进一步讨论了可约布尔矩阵的一般幂敛指数中缺数段的存在性。 相似文献
10.
Background: Body mass index (BMI) is often criticised since it doesn’t consider sex, age and ethnicity, which may affect the height scaling exponent of the equation.Aims: First, to identify specific height scaling exponents (α) based on sex, age and ethnicity. Second, to assess the performance of the current vs the proposed BMI equations (1) to predict total fat mass (TFM) and metabolic syndrome (MetS) severity and (2) to correctly identify obese individuals and those having MetS.Methods: In total, 41,403 individuals aged 20–80?years (NHANES, 1999–2014) were studied. Specific “α” were identified using the Benn formula. Various statistical approaches were performed to assess performances of the current vs the proposed-BMIs.Results: The proposed “α” varies from 1.2 to 2.5, after considering sex, age and ethnicity. BMIs calculated using the proposed “α” showed a similar capacity to predict TFM and MetS severity and to correctly identify obese individuals and those having MetS compared to the current BMI.Conclusions: Despite sex, age and ethnicity modulating the height scaling exponent of the BMI equation, using these proposed exponents in the BMI equation didn’t improve the capacity to predict TFM and MetS severity, suggesting that the current BMI remains a valid clinical tool. 相似文献