approximate entropy
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Entropy ◽  
2022 ◽  
Vol 24 (1) ◽  
pp. 80
Author(s):  
Alberto Porta ◽  
Francesca Gelpi ◽  
Vlasta Bari ◽  
Beatrice Cairo ◽  
Beatrice De De Maria ◽  
...  

Cerebrovascular control is carried out by multiple nonlinear mechanisms imposing a certain degree of coupling between mean arterial pressure (MAP) and mean cerebral blood flow (MCBF). We explored the ability of two nonlinear tools in the information domain, namely cross-approximate entropy (CApEn) and cross-sample entropy (CSampEn), to assess the degree of asynchrony between the spontaneous fluctuations of MAP and MCBF. CApEn and CSampEn were computed as a function of the translation time. The analysis was carried out in 23 subjects undergoing recordings at rest in supine position (REST) and during active standing (STAND), before and after surgical aortic valve replacement (SAVR). We found that at REST the degree of asynchrony raised, and the rate of increase in asynchrony with the translation time decreased after SAVR. These results are likely the consequence of the limited variability of MAP observed after surgery at REST, more than the consequence of a modified cerebrovascular control, given that the observed differences disappeared during STAND. CApEn and CSampEn can be utilized fruitfully in the context of the evaluation of cerebrovascular control via the noninvasive acquisition of the spontaneous MAP and MCBF variability.


Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 73
Author(s):  
Dragana Bajić ◽  
Nina Japundžić-Žigon

Approximate and sample entropies are acclaimed tools for quantifying the regularity and unpredictability of time series. This paper analyses the causes of their inconsistencies. It is shown that the major problem is a coarse quantization of matching probabilities, causing a large error between their estimated and true values. Error distribution is symmetric, so in sample entropy, where matching probabilities are directly summed, errors cancel each other. In approximate entropy, errors are accumulating, as sums involve logarithms of matching probabilities. Increasing the time series length increases the number of quantization levels, and errors in entropy disappear both in approximate and in sample entropies. The distribution of time series also affects the errors. If it is asymmetric, the matching probabilities are asymmetric as well, so the matching probability errors cease to be mutually canceled and cause a persistent entropy error. Despite the accepted opinion, the influence of self-matching is marginal as it just shifts the error distribution along the error axis by the matching probability quant. Artificial lengthening the time series by interpolation, on the other hand, induces large error as interpolated samples are statistically dependent and destroy the level of unpredictability that is inherent to the original signal.


2021 ◽  
Vol 7 (3) ◽  
pp. 426
Author(s):  
Nuryani Nuryani ◽  
Iftita Ida Sofia ◽  
Mohtar Yunianto

Sistem neuromuscular terdiri dari saraf motorik dan otot rangka yang menghasilkan aktivitas kelistrikan pada otot dan menyebabkan otot dapat berkontraksi dan menghasilkan gerak tubuh. Gangguan neuromuscular dapat terjadi pada sel saraf yang dinamakan Neuropathy dan pada sel otot yang dinamakan Myopathy. Aktivitas kelistrikan pada otot direkam melalui suatu alat yang dinamakan Electromiography (EMG). Pada penelitian ini dilakukan identifikasi sinyal EMG pasien sehat, myopathy dan neuropathy. Neuropathy merupakan gangguan yang disebabkan oleh kerusakan sel saraf. Myopathy merupakan gangguan yang disebabkan oleh kerusakan sel otot. Penanganan dan pengobatan myopathy dan neuropathy berbeda, sehingga diperlukan suatu metode yang dapat mendiagnosis dengan tepat jenis gangguan yang dialami. Analisis karakteristik sinyal EMG dilakukan menggunakan metode dekomposisi Wavelet Discrete Dyadic dan variasi fitur Root Mean Square (RMS), approximate entropy, spectral entropy dan Singular Value Decompotition (SVD) entropy. Sinyal karakteristik yang diperoleh di identifikasi menggunakan metode klasifikasi Adaptive Neuro Fuzzy Inference System (ANFIS). Performa ANFIS dalam mengidentifikasi karakteristik sinyal EMG pada masing-masing koefisien dekomposisi, menghasilkan performa terbaik pada koefisien aproksimasi ke-5 (cA5), dengan akurasi 100%, sensitivitas 100% dan spesivitas 100%.


2021 ◽  
Vol 8 ◽  
Author(s):  
Meseret N. Teferra ◽  
David A. Hobbs ◽  
Robyn A. Clark ◽  
Karen J. Reynolds

Background: With cardiovascular disease continuing to be the leading cause of death and the primary reason for hospitalization worldwide, there is an increased burden on healthcare facilities. Electronic-textile (e-textile)-based cardiac monitoring offers a viable option to allow cardiac rehabilitation programs to be conducted outside of the hospital.Objectives: This study aimed to determine whether signals produced by an e-textile ECG monitor with textile electrodes in an EASI configuration are of sufficient quality to be used for cardiac monitoring. Specific objectives were to investigate the effect of the textile electrode characteristics, placement, and condition on signal quality, and finally to compare results to a reference ECG obtained from a current clinical standard the Holter monitor.Methods: ECGs during different body movements (yawning, deep-breathing, coughing, sideways, and up movement) and activities of daily living (sitting, sitting/standing from a chair, and climbing stairs) were collected from a baseline standard of normal healthy adult male using a novel e-textile ECG and a reference Holter monitor. Each movement or activity was recorded for 5 min with 2-min intervals between each recording. Three different textile area electrodes (40, 60, and 70 mm2) and electrode thicknesses (3, 5, and 10 mm) were considered in the experiment. The effect of electrode placement within the EASI configuration was also studied. Different signal quality parameters, including signal to noise ratio, approximate entropy, baseline power signal quality index, and QRS duration and QT intervals, were used to evaluate the accuracy and reliability of the textile-based ECG monitor.Results: The overall signal quality from the 70 mm2 textile electrodes was higher compared to the smaller area electrodes. Results showed that the ECGs from 3 and 5 mm textile electrodes showed good quality. Regarding location, placing the “A” and “I” electrodes on the left and right anterior axillary points, respectively, showed higher signal quality compared to the standard EASI electrode placement. Wet textile electrodes showed better signal quality compared to their dry counterparts. When compared to the traditional Holter monitor, there was no significant difference in signal quality, which indicated textile monitoring was as good as current clinical standards (non-inferior).Conclusion: The e-textile EASI ECG monitor could be a viable option for real-time monitoring of cardiac activities. A clinical trial in a larger sample is recommended to validate the results in a clinical population.


2021 ◽  
pp. 155005942110640
Author(s):  
Fatih Hilmi Çetin ◽  
Miraç Barış Usta ◽  
Serap Aydın ◽  
Ahmet Sami Güven

Objective: Complexity analysis is a method employed to understand the activity of the brain. The effect of methylphenidate (MPH) treatment on neuro-cortical complexity changes is still unknown. This study aimed to reveal how MPH treatment affects the brain complexity of children with attention deficit hyperactivity disorder (ADHD) using entropy-based quantitative EEG analysis. Three embedding entropy approaches were applied to short segments of both pre- and post- medication EEG series. EEG signals were recorded for 25 boys with combined type ADHD prior to the administration of MPH and at the end of the first month of the treatment. Results: In comparison to Approximate Entropy (ApEn) and Sample Entropy (SampEn), Permutation Entropy (PermEn) provided the most sensitive estimations in investigating the impact of MPH treatment. In detail, the considerable decrease in EEG complexity levels were observed at six cortical regions (F3, F4, P4, T3, T6, O2) with statistically significant level ( p < .05). As well, PermEn provided the most meaningful associations at central lobes as follows: 1) The largeness of EEG complexity levels was moderately related to the severity of ADHD symptom detected at pre-treatment stage. 2) The percentage change in the severity of opposition as the symptom cluster was moderately reduced by the change in entropy. Conclusion: A significant decrease in entropy levels in the frontal region was detected in boys with combined type ADHD undergoing MPH treatment at resting-state mode. The changes in entropy correlated with pre-treatment general symptom severity of ADHD and conduct disorder symptom cluster severity.


Entropy ◽  
2021 ◽  
Vol 23 (12) ◽  
pp. 1669
Author(s):  
Zeming Liu ◽  
Tian Chen ◽  
Keming Wei ◽  
Guanzheng Liu ◽  
Bin Liu

Congestive heart failure (CHF) is a chronic cardiovascular condition associated with dysfunction of the autonomic nervous system (ANS). Heart rate variability (HRV) has been widely used to assess ANS. This paper proposes a new HRV analysis method, which uses information-based similarity (IBS) transformation and fuzzy approximate entropy (fApEn) algorithm to obtain the fApEn_IBS index, which is used to observe the complexity of autonomic fluctuations in CHF within 24 h. We used 98 ECG records (54 health records and 44 CHF records) from the PhysioNet database. The fApEn_IBS index was statistically significant between the control and CHF groups (p < 0.001). Compared with the classical indices low-to-high frequency power ratio (LF/HF) and IBS, the fApEn_IBS index further utilizes the changes in the rhythm of heart rate (HR) fluctuations between RR intervals to fully extract relevant information between adjacent time intervals and significantly improves the performance of CHF screening. The CHF classification accuracy of fApEn_IBS was 84.69%, higher than LF/HF (77.55%) and IBS (83.67%). Moreover, the combination of IBS, fApEn_IBS, and LF/HF reached the highest CHF screening accuracy (98.98%) with the random forest (RF) classifier, indicating that the IBS and LF/HF had good complementarity. Therefore, fApEn_IBS effusively reflects the complexity of autonomic nerves in CHF and is a valuable CHF assessment tool.


Author(s):  
Bo Yang

The subjective factors of sports majors play a critical role in the improvement of their cultural quality. Based on data mining, the valuable information about learning motivation and learning behavior can be obtained from the massive data. Therefore, this paper explores the learning motivations and learning behaviors of sports majors based on big data. Firstly, this paper analyzed the features of the learning behaviors of sports majors, and measured the complexity of their learning behaviors with information entropy, approximate entropy, and change-complexity function. Next, a dataset was established based on the students’ use of campus access network and online learning platforms. After that, a time domain convolutional capsule network model of multiple semantic features was established to recognize and classify the learning motivations of sports majors. The proposed model was proved effective through experiments.


Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2317
Author(s):  
Qing Lu ◽  
Linlan Yu ◽  
Congxu Zhu

In the current paper, a new conservative hyperchaotic system is proposed. We make a quantitative analysis of the complexity of the conservative hyperchaotic system from several different aspects, such as phase diagrams, bifurcation diagrams, Lyapunov exponents, and Kaplan–Yorke dimension. The complexity of chaotic time series is tested with various measurement tools, such as the scale index, the multiscale sample entropy and approximate entropy, TESTU01, and NIST test. In addition, a novel hyperchao-based image encryption scheme with dynamic DNA coding is proposed. The encryption algorithm consists of line-by-line scrambling and diffusion of DNA encoding characters. The dynamic DNA coding mechanism is introduced by using the chaotic sequence. The generation of the intermediate secret keys is related to the sum of the image DNA code, and the ciphertext feedback mechanism of the DNA encoding image is introduced in the diffusion procedure. Simulation experiments and various security analyses show that this algorithm has a good effect on encryption, high time efficiency, and can effectively resist brute force attacks, statistical attacks, chosen-plaintext attacks, and differential attacks.


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