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1.
Eur Phys J Spec Top ; : 1-8, 2021 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-34815830

RESUMO

The COVID-19 pandemic creates a worldwide threat to human health, medical practitioners, social structures, and finance sectors. The coronavirus epidemic has a significant impact on people's health, survival, employment, and financial crises; while also having noticeable harmful effects on our environment in a short span of time. In this context, the complexity of the Corona Virus transmission is estimated and analyzed by the measure of non-linearity called the Generalized Fractal Dimensions (GFD) on the chest X-Ray images. Grayscale image is considered as the most important suitable tool in the medical image processing. Particularly, COVID-19 affects the human lungs vigorously within a few days. It is a very challenging task to differentiate the COVID-19 infections from the various respiratory diseases represented in this study. The multifractal dimension measure is calculated for the original, noisy and denoised images to estimate the robustness of COVID-19 and other noticeable diseases. Also the comparison of COVID-19 X-Ray images is performed graphically with the images of healthy and other diseases to state the level of complexity of diseases in terms of GFD curves. In addition, the Mean Absolute Error (MAE) and the Peak Signal-to-Noise Ratio (PSNR) are used to evaluate the performance of the denoising process involved in the proposed comparative analysis of the representative grayscale images.

2.
Chaos ; 31(8): 083132, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34470247

RESUMO

We propose herein a novel discrete hyperchaotic map based on the mathematical model of a cycloid, which produces multistability and infinite equilibrium points. Numerical analysis is carried out by means of attractors, bifurcation diagrams, Lyapunov exponents, and spectral entropy complexity. Experimental results show that this cycloid map has rich dynamical characteristics including hyperchaos, various bifurcation types, and high complexity. Furthermore, the attractor topology of this map is extremely sensitive to the parameters of the map. The x--y plane of the attractor produces diverse shapes with the variation of parameters, and both the x--z and y--z planes produce a full map with good ergodicity. Moreover, the cycloid map has good resistance to parameter estimation, and digital signal processing implementation confirms its feasibility in digital circuits, indicating that the cycloid map may be used in potential applications.

3.
Entropy (Basel) ; 23(8)2021 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-34441071

RESUMO

Properly measuring the complexity of time series is an important issue. The permutation entropy (PE) is a widely used as an effective complexity measurement algorithm, but it is not suitable for the complexity description of multi-dimensional data. In this paper, in order to better measure the complexity of multi-dimensional time series, we proposed a modified multivariable PE (MMPE) algorithm with principal component analysis (PCA) dimensionality reduction, which is a new multi-dimensional time series complexity measurement algorithm. The analysis results of different chaotic systems verify that MMPE is effective. Moreover, we applied it to the comlexity analysis of EEG data. It shows that the person during mental arithmetic task has higher complexity comparing with the state before mental arithmetic task. In addition, we also discussed the necessity of the PCA dimensionality reduction.

4.
Chaos ; 31(5): 053131, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34240920

RESUMO

Network performance of neurons plays a vital role in determining the behavior of many physiological systems. In this paper, we discuss the wave propagation phenomenon in a network of neurons considering obstacles in the network. Numerous studies have shown the disastrous effects caused by the heterogeneity induced by the obstacles, but these studies have been mainly discussing the orientation effects. Hence, we are interested in investigating the effects of both the size and orientation of the obstacles in the wave re-entry and spiral wave formation in the network. For this analysis, we have considered two types of neuron models and a pancreatic beta cell model. In the first neuron model, we use the well-known differential equation-based neuron models, and in the second type, we used the hybrid neuron models with the resetting phenomenon. We have shown that the size of the obstacle decides the spiral wave formation in the network and horizontally placed obstacles will have a lesser impact on the wave re-entry than the vertically placed obstacles.


Assuntos
Neurônios
5.
Entropy (Basel) ; 22(3)2020 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-33286045

RESUMO

In this paper, dynamical behavior and synchronization of a non-equilibrium four-dimensional chaotic system are studied. The system only includes one constant term and has hidden attractors. Some dynamical features of the governing system, such as invariance and symmetry, the existence of attractors and dissipativity, chaotic flow with a plane of equilibria, and offset boosting of the chaotic attractor, are stated and discussed and a new disturbance-observer-based adaptive terminal sliding mode control (ATSMC) method with input saturation is proposed for the control and synchronization of the chaotic system. To deal with unexpected noises, an extended Kalman filter (EKF) is implemented along with the designed controller. Through the concept of Lyapunov stability, the proposed control technique guarantees the finite time convergence of the uncertain system in the presence of disturbances and control input limits. Furthermore, to decrease the chattering phenomena, a genetic algorithm is used to optimize the controller parameters. Finally, numerical simulations are presented to demonstrate the performance of the designed control scheme in the presence of noise, disturbances, and control input saturation.

6.
Nonlinear Dyn ; : 1-14, 2020 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-32836803

RESUMO

In this paper, a SEIR epidemic model for the COVID-19 is built according to some general control strategies, such as hospital, quarantine and external input. Based on the data of Hubei province, the particle swarm optimization (PSO) algorithm is applied to estimate the parameters of the system. We found that the parameters of the proposed SEIR model are different for different scenarios. Then, the model is employed to show the evolution of the epidemic in Hubei province, which shows that it can be used to forecast COVID-19 epidemic situation. Moreover, by introducing the seasonality and stochastic infection the parameters, nonlinear dynamics including chaos are found in the system. Finally, we discussed the control strategies of the COVID-19 based on the structure and parameters of the proposed model.

7.
Entropy (Basel) ; 21(1)2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33266743

RESUMO

Research on fractional-order discrete chaotic systems has grown in recent years, and chaos synchronization of such systems is a new topic. To address the deficiencies of the extant chaos synchronization methods for fractional-order discrete chaotic systems, we proposed an improved particle swarm optimization algorithm for the parameter identification. Numerical simulations are carried out for the Hénon map, the Cat map, and their fractional-order form, as well as the fractional-order standard iterated map with hidden attractors. The problem of choosing the most appropriate sample size is discussed, and the parameter identification with noise interference is also considered. The experimental results demonstrate that the proposed algorithm has the best performance among the six existing algorithms and that it is effective even with random noise interference. In addition, using two samples offers the most efficient performance for the fractional-order discrete chaotic system, while the integer-order discrete chaotic system only needs one sample.

8.
PLoS One ; 13(9): e0202558, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30180194

RESUMO

There is considerable interest in analyzing the complexity of electroencephalography (EEG) signals. However, some traditional complexity measure algorithms only quantify the complexities of signals, but cannot discriminate different signals very well. To analyze the complexity of epileptic EEG signals better, a new multiscale permutation Rényi entropy (MPEr) algorithm is proposed. In this algorithm, the coarse-grained procedure is introduced by using weighting-averaging method, and the weighted factors are determined by analyzing nonlinear signals. We apply the new algorithm to analyze epileptic EEG signals. The experimental results show that MPEr algorithm has good performance for discriminating different EEG signals. Compared with permutation Rényi entropy (PEr) and multiscale permutation entropy (MPE), MPEr distinguishes different EEG signals successfully. The proposed MPEr algorithm is effective and has good applications prospects in EEG signals analysis.


Assuntos
Algoritmos , Eletroencefalografia , Epilepsia/fisiopatologia , Análise de Variância , Interpretação Estatística de Dados , Entropia , Humanos , Análise de Sistemas
9.
Entropy (Basel) ; 20(8)2018 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-33265645

RESUMO

Designing a chaotic system with infinitely many attractors is a hot topic. In this paper, multiscale multivariate permutation entropy (MMPE) and multiscale multivariate Lempel-Ziv complexity (MMLZC) are employed to analyze the complexity of those self-reproducing chaotic systems with one-directional and two-directional infinitely many chaotic attractors. The analysis results show that complexity of this class of chaotic systems is determined by the initial conditions. Meanwhile, the values of MMPE are independent of the scale factor, which is different from the algorithm of MMLZC. The analysis proposed here is helpful as a reference for the application of the self-reproducing systems.

10.
J Environ Sci (China) ; 38: 103-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26702973

RESUMO

In recent years, engineered nanoparticles, as a new group of contaminants emerging in natural water, have been given more attention. In order to understand the behavior of nanoparticles in the conventional water treatment process, three kinds of nanoparticle suspensions, namely multi-walled carbon nanotube-humic acid (MWCNT-HA), multi-walled carbon nanotube-N,N-dimethylformamide (MWCNT-DMF) and nanoTiO2-humic acid (TiO2-HA) were employed to investigate their coagulation removal efficiencies with varying aluminum chloride (AlCl3) concentrations. Results showed that nanoparticle removal rate curves had a reverse "U" shape with increasing concentration of aluminum ion (Al(3+)). More than 90% of nanoparticles could be effectively removed by an appropriate Al(3+) concentration. At higher Al(3+) concentration, nanoparticles would be restabilized. The hydrodynamic particle size of nanoparticles was found to be the crucial factor influencing the effective concentration range (ECR) of Al(3+) for nanoparticle removal. The ECR of Al(3+) followed the order MWCNT-DMF>MWCNT-HA>TiO2-HA, which is the reverse of the nanoparticle size trend. At a given concentration, smaller nanoparticles carry more surface charges, and thus consume more coagulants for neutralization. Therefore, over-saturation occurred at relatively higher Al(3+) concentration and a wider ECR was obtained. The ECR became broader with increasing pH because of the smaller hydrodynamic particle size of nanoparticles at higher pH values. A high ionic strength of NaCl can also widen the ECR due to its strong potential to compress the electric double layer. It was concluded that it is important to adjust the dose of Al(3+) in the ECR for nanoparticle removal in water treatment.


Assuntos
Compostos de Alumínio/química , Cloretos/química , Nanopartículas/química , Cloreto de Alumínio , Hidróxido de Alumínio/química , Concentração de Íons de Hidrogênio , Nanotubos de Carbono/química , Titânio/química
11.
Zhonghua Yi Xue Za Zhi ; 87(9): 585-9, 2007 Mar 06.
Artigo em Chinês | MEDLINE | ID: mdl-17550723

RESUMO

OBJECTIVE: To evaluate the clinical feasibility and safety of percutaneous screw fixation in the management of vertically unstable pelvic fractures. METHODS: Forty S1 CT films of orthopedic patients aged 18 - 73, were analyzed so as to provide the best screw entrance point and angle for screw entrance. The data thus obtained were used on 14 patients with unequivocally vertical unstable pelvic fractures, 11 cases being of Tile C(1) type, 2 of C(2) type, and 1 of C type, 9 males and 5 females, aged 19 to 68. All the patients received heavy traction to reduce displacement before the surgery. Percutaneous pelvic screw fixation of the disrupted pelvic ring was performed when the patients were in the supine position, and then fixation of sacroiliac joint was performed when the patients were in the prone position. RESULTS: S1 CT scanning showed an average distance from the standard screw entrance point to the backbone of 10.78 cm (9.80 - 12.00 cm), and a standard screw entrance angle of 61.24 degrees (52.18 - 68.20 degrees). Anatomic reduction was achieved in all 14 patients. One patient had neurological deficit due to the screw penetrating into 1/2 of the intervertebral foramen, but the side-effect was released when the screw was removed 21 days after operation. A 6-24 months postoperative follow-up revealed that all the patients had recovered from fracture and resumed their previous work. CONCLUSION: With advantages including simple procedures, better bony stability, minimal invasion of compromised soft tissue and limited blood loss, percutaneous screw fixation is a practical technique which can be widely used to treat vertical unstable pelvic fracture.


Assuntos
Parafusos Ósseos , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Ossos Pélvicos/lesões , Adolescente , Adulto , Idoso , Feminino , Seguimentos , Fixação Interna de Fraturas/instrumentação , Fraturas Ósseas/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X
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