Entropy

1057 KiB

Open AccessArticle

Distribution Entropy Boosted VLAD for Image Retrieval

by Qiuzhan Zhou, Cheng Wang, Pingping Liu, Qingliang Li, Yeran Wang and Shuozhang Chen

Entropy 2016, 18(8), 311; https://doi.org/10.3390/e18080311 - 24 Aug 2016

Cited by 11 | Viewed by 4822

Several recent works have shown that aggregating local descriptors to generate global image representation results in great efficiency for retrieval and classification tasks. The most popular method following this approach is VLAD (Vector of Locally Aggregated Descriptors). We present a novel image presentation [...] Read more.

Several recent works have shown that aggregating local descriptors to generate global image representation results in great efficiency for retrieval and classification tasks. The most popular method following this approach is VLAD (Vector of Locally Aggregated Descriptors). We present a novel image presentation called Distribution Entropy Boosted VLAD (EVLAD), which extends the original vector of locally aggregated descriptors. The original VLAD adopts only residuals to depict the distribution information of every visual word and neglects other statistical clues, so its discriminative power is limited. To address this issue, this paper proposes the use of the distribution entropy of each cluster as supplementary information to enhance the search accuracy. To fuse two feature sources organically, two fusion methods after a new normalization stage meeting power law are also investigated, which generate identically sized and double-sized vectors as the original VLAD. We validate our approach in image retrieval and image classification experiments. Experimental results demonstrate the effectiveness of our algorithm. Full article

(This article belongs to the Special Issue Machine Learning and Entropy: Discover Unknown Unknowns in Complex Data Sets)

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1649 KiB

Open AccessArticle

Exploring the Key Risk Factors for Application of Cloud Computing in Auditing

by Kuang-Hua Hu, Fu-Hsiang Chen and Wei-Jhou We

Entropy 2016, 18(8), 401; https://doi.org/10.3390/e18080401 - 22 Aug 2016

Cited by 7 | Viewed by 5904

Abstract

In the cloud computing information technology environment, cloud computing has some advantages such as lower cost, immediate access to hardware resources, lower IT barriers to innovation, higher scalability, etc., but for the financial audit information flow and processing in the cloud system, CPA [...] Read more.

In the cloud computing information technology environment, cloud computing has some advantages such as lower cost, immediate access to hardware resources, lower IT barriers to innovation, higher scalability, etc., but for the financial audit information flow and processing in the cloud system, CPA (Certified Public Accountant) firms need special considerations, for example: system problems, information security and other related issues. Auditing cloud computing applications is the future trend in the CPA firms, given this issue is an important factor for them and very few studies have been conducted to investigate this issue; hence this study seeks to explore the key risk factors for the cloud computing and audit considerations. The dimensions/perspectives of the application of cloud computing audit considerations are huge and cover many criteria/factors. These risk factors are becoming increasingly complex, and interdependent. If the dimensions could be established, the mutually influential relations of the dimensions and criteria determined, and the current execution performance established; a prioritized improvement strategy designed could be constructed to use as a reference for CPA firm management decision making; as well as provide CPA firms with a reference for build auditing cloud computing systems. Empirical results show that key risk factors to consider when using cloud computing in auditing are, in order of priority for improvement: Operations (D), Automating user provisioning (C), Technology Risk (B) and Protection system (A). Full article

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1274 KiB

Open AccessArticle

Weighted-Permutation Entropy Analysis of Resting State EEG from Diabetics with Amnestic Mild Cognitive Impairment

by Zhijie Bian, Gaoxiang Ouyang, Zheng Li, Qiuli Li, Lei Wang and Xiaoli Li

Entropy 2016, 18(8), 307; https://doi.org/10.3390/e18080307 - 22 Aug 2016

Cited by 9 | Viewed by 5462

Abstract

Diabetes is a significant public health issue as it increases the risk for dementia and Alzheimer’s disease (AD). In this study, we aim to investigate whether weighted-permutation entropy (WPE) and permutation entropy (PE) of resting-state EEG (rsEEG) could be applied as potential objective [...] Read more.

Diabetes is a significant public health issue as it increases the risk for dementia and Alzheimer’s disease (AD). In this study, we aim to investigate whether weighted-permutation entropy (WPE) and permutation entropy (PE) of resting-state EEG (rsEEG) could be applied as potential objective biomarkers to distinguish type 2 diabetes patients with amnestic mild cognitive impairment (aMCI) from those with normal cognitive function. rsEEG series were acquired from 28 patients with type 2 diabetes (16 aMCI patients and 12 controls), and neuropsychological assessments were performed. The rsEEG signals were analysed using WPE and PE methods. The correlations between the PE or WPE of the rsEEG and the neuropsychological assessments were analysed as well. The WPE in the right temporal (RT) region of the aMCI diabetics was lower than the controls, and the WPE was significantly positively correlated to the scores of the Auditory Verbal Learning Test (AVLT) (AVLT-Immediate recall, AVLT-Delayed recall, AVLT-Delayed recognition) and the Wechsler Adult Intelligence Scale Digit Span Test (WAIS-DST). These findings were not obtained with PE. We concluded that the WPE of rsEEG recordings could distinguish aMCI diabetics from normal cognitive function diabetic controls among the current sample of diabetic patients. Thus, the WPE could be a potential index for assisting diagnosis of aMCI in type 2 diabetes. Full article

(This article belongs to the Special Issue Entropy and Electroencephalography II)

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1181 KiB

Open AccessArticle

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

by Fritz Körmann and Marcel H.F. Sluiter

Entropy 2016, 18(8), 403; https://doi.org/10.3390/e18080403 - 20 Aug 2016

Cited by 63 | Viewed by 10334

Abstract

Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions. For BCC NbMoTaW, recent computational studies revealed, [...] Read more.

Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions. For BCC NbMoTaW, recent computational studies revealed, however, a B2(Mo,W;Nb,Ta)-ordering at ambient temperature. This ordering could impact many materials properties, such as thermodynamic, mechanical, or diffusion properties, and hence be of relevance for practical applications. In this work, we theoretically address how the B2-ordering impacts thermodynamic properties of BCC NbMoTaW and how the predicted ordering temperature itself is affected by vibrations, electronic excitations, lattice distortions, and relaxation energies. Full article

(This article belongs to the Special Issue High-Entropy Alloys and High-Entropy-Related Materials)

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572 KiB

Open AccessArticle

Analytical Solutions of the Electrical RLC Circuit via Liouville–Caputo Operators with Local and Non-Local Kernels

by José Francisco Gómez-Aguilar, Victor Fabian Morales-Delgado, Marco Antonio Taneco-Hernández, Dumitru Baleanu, Ricardo Fabricio Escobar-Jiménez and Maysaa Mohamed Al Qurashi

Entropy 2016, 18(8), 402; https://doi.org/10.3390/e18080402 - 20 Aug 2016

Cited by 99 | Viewed by 9993

Abstract

In this work we obtain analytical solutions for the electrical RLC circuit model defined with Liouville–Caputo, Caputo–Fabrizio and the new fractional derivative based in the Mittag-Leffler function. Numerical simulations of alternative models are presented for evaluating the effectiveness of these representations. Different source [...] Read more.

In this work we obtain analytical solutions for the electrical RLC circuit model defined with Liouville–Caputo, Caputo–Fabrizio and the new fractional derivative based in the Mittag-Leffler function. Numerical simulations of alternative models are presented for evaluating the effectiveness of these representations. Different source terms are considered in the fractional differential equations. The classical behaviors are recovered when the fractional order α is equal to 1. Full article

(This article belongs to the Special Issue Wavelets, Fractals and Information Theory II)

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958 KiB

Open AccessArticle

Optimal Noise Benefit in Composite Hypothesis Testing under Different Criteria

by Shujun Liu, Ting Yang, Mingchun Tang, Hongqing Liu, Kui Zhang and Xinzheng Zhang

Entropy 2016, 18(8), 400; https://doi.org/10.3390/e18080400 - 19 Aug 2016

Viewed by 3930

Abstract

The detectability for a noise-enhanced composite hypothesis testing problem according to different criteria is studied. In this work, the noise-enhanced detection problem is formulated as a noise-enhanced classical Neyman–Pearson (NP), Max–min, or restricted NP problem when the prior information is completely known, completely [...] Read more.

The detectability for a noise-enhanced composite hypothesis testing problem according to different criteria is studied. In this work, the noise-enhanced detection problem is formulated as a noise-enhanced classical Neyman–Pearson (NP), Max–min, or restricted NP problem when the prior information is completely known, completely unknown, or partially known, respectively. Next, the detection performances are compared and the feasible range of the constraint on the minimum detection probability is discussed. Under certain conditions, the noise-enhanced restricted NP problem is equivalent to a noise-enhanced classical NP problem with modified prior distribution. Furthermore, the corresponding theorems and algorithms are given to search the optimal additive noise in the restricted NP framework. In addition, the relationship between the optimal noise-enhanced average detection probability and the constraint on the minimum detection probability is explored. Finally, numerical examples and simulations are provided to illustrate the theoretical results. Full article

(This article belongs to the Special Issue Statistical Significance and the Logic of Hypothesis Testing)

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797 KiB

Open AccessArticle

Potential of Entropic Force in Markov Systems with Nonequilibrium Steady State, Generalized Gibbs Function and Criticality

by Lowell F. Thompson and Hong Qian

Entropy 2016, 18(8), 309; https://doi.org/10.3390/e18080309 - 18 Aug 2016

Cited by 6 | Viewed by 4840

Abstract

In this paper, we revisit the notion of the “minus logarithm of stationary probability” as a generalized potential in nonequilibrium systems and attempt to illustrate its central role in an axiomatic approach to stochastic nonequilibrium thermodynamics of complex systems. It is demonstrated that [...] Read more.

In this paper, we revisit the notion of the “minus logarithm of stationary probability” as a generalized potential in nonequilibrium systems and attempt to illustrate its central role in an axiomatic approach to stochastic nonequilibrium thermodynamics of complex systems. It is demonstrated that this quantity arises naturally through both monotonicity results of Markov processes and as the rate function when a stochastic process approaches a deterministic limit. We then undertake a more detailed mathematical analysis of the consequences of this quantity, culminating in a necessary and sufficient condition for the criticality of stochastic systems. This condition is then discussed in the context of recent results about criticality in biological systems. Full article

(This article belongs to the Special Issue Information and Self-Organization)

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Open AccessArticle

Soft Magnetic Properties of High-Entropy Fe-Co-Ni-Cr-Al-Si Thin Films

by Pei-Chung Lin, Chun-Yang Cheng, Jien-Wei Yeh and Tsung-Shune Chin

Entropy 2016, 18(8), 308; https://doi.org/10.3390/e18080308 - 18 Aug 2016

Cited by 28 | Viewed by 7595

Abstract

Soft magnetic properties of Fe-Co-Ni-Al-Cr-Si thin films were studied. As-deposited Fe-Co-Ni-Al-Cr-Si nano-grained thin films showing no magnetic anisotropy were subjected to field-annealing at different temperatures to induce magnetic anisotropy. Optimized magnetic and electrical properties of Fe-Co-Ni-Al-Cr-Si films annealed at 200 °C are saturation [...] Read more.

Soft magnetic properties of Fe-Co-Ni-Al-Cr-Si thin films were studied. As-deposited Fe-Co-Ni-Al-Cr-Si nano-grained thin films showing no magnetic anisotropy were subjected to field-annealing at different temperatures to induce magnetic anisotropy. Optimized magnetic and electrical properties of Fe-Co-Ni-Al-Cr-Si films annealed at 200 °C are saturation magnetization 9.13 × 10⁵ A/m, coercivity 79.6 A/m, out-of-plane uniaxial anisotropy field 1.59 × 10³ A/m, and electrical resistivity 3.75 μΩ·m. Based on these excellent properties, we employed such films to fabricate magnetic thin film inductor. The performance of the high entropy alloy thin film inductors is superior to that of air core inductor. Full article

(This article belongs to the Special Issue High-Entropy Alloys and High-Entropy-Related Materials)

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Open AccessArticle

Contact-Free Detection of Obstructive Sleep Apnea Based on Wavelet Information Entropy Spectrum Using Bio-Radar

by Fugui Qi, Chuantao Li, Shuaijie Wang, Hua Zhang, Jianqi Wang and Guohua Lu

Entropy 2016, 18(8), 306; https://doi.org/10.3390/e18080306 - 18 Aug 2016

Cited by 24 | Viewed by 6354

Abstract

Judgment and early danger warning of obstructive sleep apnea (OSA) is meaningful to the diagnosis of sleep illness. This paper proposed a novel method based on wavelet information entropy spectrum to make an apnea judgment of the OSA respiratory signal detected by bio-radar [...] Read more.

Judgment and early danger warning of obstructive sleep apnea (OSA) is meaningful to the diagnosis of sleep illness. This paper proposed a novel method based on wavelet information entropy spectrum to make an apnea judgment of the OSA respiratory signal detected by bio-radar in wavelet domain. It makes full use of the features of strong irregularity and disorder of respiratory signal resulting from the brain stimulation by real, low airflow during apnea. The experimental results demonstrated that the proposed method is effective for detecting the occurrence of sleep apnea and is also able to detect some apnea cases that the energy spectrum method cannot. Ultimately, the comprehensive judgment accuracy resulting from 10 groups of OSA data is 93.1%, which is promising for the non-contact aided-diagnosis of the OSA. Full article

(This article belongs to the Special Issue Entropy on Biosignals and Intelligent Systems)

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439 KiB

Open AccessArticle

An Efficient Method to Construct Parity-Check Matrices for Recursively Encoding Spatially Coupled LDPC Codes †

by Zhongwei Si, Sijie Wang and Junyang Ma

Entropy 2016, 18(8), 305; https://doi.org/10.3390/e18080305 - 17 Aug 2016

Cited by 1 | Viewed by 4692

Abstract

Spatially coupled low-density parity-check (LDPC) codes have attracted considerable attention due to their promising performance. Recursive encoding of the codes with low delay and low complexity has been proposed in the literature but with constraints or restrictions. In this manuscript we propose an [...] Read more.

Spatially coupled low-density parity-check (LDPC) codes have attracted considerable attention due to their promising performance. Recursive encoding of the codes with low delay and low complexity has been proposed in the literature but with constraints or restrictions. In this manuscript we propose an efficient method to construct parity-check matrices for recursively encoding spatially coupled LDPC codes with arbitrarily chosen node degrees. A general principle is proposed, which provides feasible and practical guidance for the construction of parity-check matrices. According to the specific structure of the matrix, each parity bit at a coupling position is jointly determined by the information bits at the current position and the encoded bits at former positions. Performance analysis in terms of design rate and density evolution has been presented. It can be observed that, in addition to the feature of recursive encoding, selected code structures constructed by the newly proposed method may lead to better belief-propagation thresholds than the conventional structures. Finite-length simulation results are provided as well, which verify the theoretical analysis. Full article

(This article belongs to the Section Information Theory, Probability and Statistics)

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937 KiB

Open AccessReview

Entropy as a Metric Generator of Dissipation in Complete Metriplectic Systems

by Massimo Materassi

Entropy 2016, 18(8), 304; https://doi.org/10.3390/e18080304 - 16 Aug 2016

Cited by 9 | Viewed by 4010

Abstract

This lecture is a short review on the role entropy plays in those classical dissipative systems whose equations of motion may be expressed via a Leibniz Bracket Algebra (LBA). This means that the time derivative of any physical observable f of the system [...] Read more.

This lecture is a short review on the role entropy plays in those classical dissipative systems whose equations of motion may be expressed via a Leibniz Bracket Algebra (LBA). This means that the time derivative of any physical observable f of the system is calculated by putting this f in a “bracket” together with a “special observable” F, referred to as a Leibniz generator of the dynamics. While conservative dynamics is given an LBA formulation in the Hamiltonian framework, so that F is the Hamiltonian H of the system that generates the motion via classical Poisson brackets or quantum commutation brackets, an LBA formulation can be given to classical dissipative dynamics through the Metriplectic Bracket Algebra (MBA): the conservative component of the dynamics is still generated via Poisson algebra by the total energy H, while S, the entropy of the degrees of freedom statistically encoded in friction, generates dissipation via a metric bracket. The motivation of expressing through a bracket algebra and a motion-generating function F is to endow the theory of the system at hand with all the powerful machinery of Hamiltonian systems in terms of symmetries that become evident and readable. Here a (necessarily partial) overview of the types of systems subject to MBA formulation is presented, and the physical meaning of the quantity S involved in each is discussed. Here the aim is to review the different MBAs for isolated systems in a synoptic way. At the end of this collection of examples, the fact that dissipative dynamics may be constructed also in the absence of friction with microscopic degrees of freedom is stressed. This reasoning is a hint to introduce dissipation at a more fundamental level. Full article

(This article belongs to the Special Issue Selected Papers from 2nd International Electronic Conference on Entropy and Its Applications)

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1217 KiB

Open AccessArticle

A Geographically Temporal Weighted Regression Approach with Travel Distance for House Price Estimation

by Jiping Liu, Yi Yang, Shenghua Xu, Yangyang Zhao, Yong Wang and Fuhao Zhang

Entropy 2016, 18(8), 303; https://doi.org/10.3390/e18080303 - 16 Aug 2016

Cited by 22 | Viewed by 7168

Abstract

Previous studies have demonstrated that non-Euclidean distance metrics can improve model fit in the geographically weighted regression (GWR) model. However, the GWR model often considers spatial nonstationarity and does not address variations in local temporal issues. Therefore, this paper explores a geographically temporal [...] Read more.

Previous studies have demonstrated that non-Euclidean distance metrics can improve model fit in the geographically weighted regression (GWR) model. However, the GWR model often considers spatial nonstationarity and does not address variations in local temporal issues. Therefore, this paper explores a geographically temporal weighted regression (GTWR) approach that accounts for both spatial and temporal nonstationarity simultaneously to estimate house prices based on travel time distance metrics. Using house price data collected between 1980 and 2016, the house price response and explanatory variables are then modeled using both the GWR and the GTWR approaches. Comparing the GWR model with Euclidean and travel distance metrics, the GTWR model with travel distance obtains the highest value for the coefficient of determination (

R^{2}

) and the lowest values for the Akaike information criterion (AIC). The results show that the GTWR model provides a relatively high goodness of fit and sufficient space-time explanatory power with non-Euclidean distance metrics. The results of this study can be used to formulate more effective policies for real estate management. Full article

(This article belongs to the Special Issue Applications of Information Theory in the Geosciences)

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1852 KiB

Open AccessArticle

Thermal Analysis of Shell-and-Tube Thermoacoustic Heat Exchangers

by Mohammad Gholamrezaei and Kaveh Ghorbanian

Entropy 2016, 18(8), 301; https://doi.org/10.3390/e18080301 - 16 Aug 2016

Cited by 5 | Viewed by 3858

Abstract

Heat exchangers are of key importance in overall performance and commercialization of thermoacoustic devices. The main goal in designing efficient thermoacoustic heat exchangers (TAHXs) is the achievement of the required heat transfer rate in conjunction with low acoustic energy dissipation. A numerical investigation [...] Read more.

Heat exchangers are of key importance in overall performance and commercialization of thermoacoustic devices. The main goal in designing efficient thermoacoustic heat exchangers (TAHXs) is the achievement of the required heat transfer rate in conjunction with low acoustic energy dissipation. A numerical investigation is performed to examine the effects of geometry on both the viscous and thermal-relaxation losses of shell-and-tube TAHXs. Further, the impact of the drive ratio as well as the temperature difference between the oscillating gas and the TAHX tube wall on acoustic energy dissipation are explored. While viscous losses decrease with

d_{i} / δ_{κ}

, thermal-relaxation losses increase; however, thermal relaxation effects mainly determine the acoustic power dissipated in TAHXs. The results indicate the existence of an optimal configuration for which the acoustic energy dissipation minimizes depending on both the TAHX metal temperature and the drive ratio. Full article

(This article belongs to the Section Thermodynamics)

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1262 KiB

Open AccessArticle

Assessing the Exergy Costs of a 332-MW Pulverized Coal-Fired Boiler

by Victor H. Rangel-Hernandez, Cesar Damian-Ascencio, Juan M. Belman-Flores and Alejandro Zaleta-Aguilar

Entropy 2016, 18(8), 300; https://doi.org/10.3390/e18080300 - 15 Aug 2016

Cited by 5 | Viewed by 5824

Abstract

In this paper, we analyze the exergy costs of a real large industrial boiler with the aim of improving efficiency. Specifically, the 350-MW front-fired, natural circulation, single reheat and balanced draft coal-fired boiler forms part of a 1050-MW conventional power plant located in [...] Read more.

In this paper, we analyze the exergy costs of a real large industrial boiler with the aim of improving efficiency. Specifically, the 350-MW front-fired, natural circulation, single reheat and balanced draft coal-fired boiler forms part of a 1050-MW conventional power plant located in Spain. We start with a diagram of the power plant, followed by a formulation of the exergy cost allocation problem to determine the exergy cost of the product of the boiler as a whole and the expenses of the individual components and energy streams. We also define a productive structure of the system. Furthermore, a proposal for including the exergy of radiation is provided in this study. Our results show that the unit exergy cost of the product of the boiler goes from 2.352 to 2.5, and that the maximum values are located in the ancillary electrical devices, such as induced-draft fans and coil heaters. Finally, radiation does not have an effect on the electricity cost, but affects at least 30% of the unit exergy cost of the boiler’s product. Full article

(This article belongs to the Special Issue Thermoeconomics for Energy Efficiency)

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Open AccessArticle

Determining the Entropic Index q of Tsallis Entropy in Images through Redundancy

by Abdiel Ramírez-Reyes, Alejandro Raúl Hernández-Montoya, Gerardo Herrera-Corral and Ismael Domínguez-Jiménez

Entropy 2016, 18(8), 299; https://doi.org/10.3390/e18080299 - 15 Aug 2016

Cited by 39 | Viewed by 7349

Abstract

The Boltzmann–Gibbs and Tsallis entropies are essential concepts in statistical physics, which have found multiple applications in many engineering and science areas. In particular, we focus our interest on their applications to image processing through information theory. We present in this article a [...] Read more.

The Boltzmann–Gibbs and Tsallis entropies are essential concepts in statistical physics, which have found multiple applications in many engineering and science areas. In particular, we focus our interest on their applications to image processing through information theory. We present in this article a novel numeric method to calculate the Tsallis entropic index q characteristic to a given image, considering the image as a non-extensive system. The entropic index q is calculated through q-redundancy maximization, which is a methodology that comes from information theory. We find better results in the image processing in the grayscale by using the Tsallis entropy and thresholding q instead of the Shannon entropy. Full article

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Open AccessArticle

Heat Transfer and Entropy Generation of Non-Newtonian Laminar Flow in Microchannels with Four Flow Control Structures

by Ke Yang, Di Zhang, Yonghui Xie and Gongnan Xie

Entropy 2016, 18(8), 302; https://doi.org/10.3390/e18080302 - 12 Aug 2016

Cited by 6 | Viewed by 5000

Abstract

Flow characteristics and heat transfer performances of carboxymethyl cellulose (CMC) aqueous solutions in the microchannels with flow control structures were investigated in this study. The researches were carried out with various flow rates and concentrations of the CMC aqueous solutions. The results reveal [...] Read more.

Flow characteristics and heat transfer performances of carboxymethyl cellulose (CMC) aqueous solutions in the microchannels with flow control structures were investigated in this study. The researches were carried out with various flow rates and concentrations of the CMC aqueous solutions. The results reveal that the pin-finned microchannel has the most uniform temperature distribution on the structured walls, and the average temperature on the structured wall reaches the minimum value in cylinder-ribbed microchannels at the same flow rate and CMC concentration. Moreover, the protruded microchannel obtains the minimum relative Fanning friction factor f/f₀, while, the maximum f/f₀ is observed in the cylinder-ribbed microchannel. Furthermore, the minimum f/f₀ is reached at the cases with CMC2000, and also, the relative Nusselt number Nu/Nu₀ of CMC2000 cases is larger than that of other cases in the four structured microchannels. Therefore, 2000 ppm is the recommended concentration of CMC aqueous solutions in all the cases with different flow rates and flow control structures. Pin-finned microchannels are preferred in low flow rate cases, while, V-grooved microchannels have the minimum relative entropy generation S’/S₀’ and best thermal performance TP at CMC2000 in high flow rates. Full article

(This article belongs to the Special Issue Advances in Applied Thermodynamics II)

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Open AccessArticle

Voice Activity Detection Using Fuzzy Entropy and Support Vector Machine

by R. Johny Elton, P. Vasuki and J. Mohanalin

Entropy 2016, 18(8), 298; https://doi.org/10.3390/e18080298 - 12 Aug 2016

Cited by 20 | Viewed by 6881

Abstract

This paper proposes support vector machine (SVM) based voice activity detection using FuzzyEn to improve detection performance under noisy conditions. The proposed voice activity detection (VAD) uses fuzzy entropy (FuzzyEn) as a feature extracted from noise-reduced speech signals to train an SVM model [...] Read more.

This paper proposes support vector machine (SVM) based voice activity detection using FuzzyEn to improve detection performance under noisy conditions. The proposed voice activity detection (VAD) uses fuzzy entropy (FuzzyEn) as a feature extracted from noise-reduced speech signals to train an SVM model for speech/non-speech classification. The proposed VAD method was tested by conducting various experiments by adding real background noises of different signal-to-noise ratios (SNR) ranging from −10 dB to 10 dB to actual speech signals collected from the TIMIT database. The analysis proves that FuzzyEn feature shows better results in discriminating noise and corrupted noisy speech. The efficacy of the SVM classifier was validated using 10-fold cross validation. Furthermore, the results obtained by the proposed method was compared with those of previous standardized VAD algorithms as well as recently developed methods. Performance comparison suggests that the proposed method is proven to be more efficient in detecting speech under various noisy environments with an accuracy of 93.29%, and the FuzzyEn feature detects speech efficiently even at low SNR levels. Full article

(This article belongs to the Special Issue Machine Learning and Entropy: Discover Unknown Unknowns in Complex Data Sets)

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Open AccessArticle

Temporal Predictability of Online Behavior in Foursquare

by Wang Chen, Qiang Gao and Huagang Xiong

Entropy 2016, 18(8), 296; https://doi.org/10.3390/e18080296 - 12 Aug 2016

Cited by 10 | Viewed by 3500

Abstract

With the widespread use of Internet technologies, online behaviors play a more and more important role in humans’ daily lives. Knowing the times when humans perform their next online activities can be quite valuable for developing better online services, which prompts us to [...] Read more.

With the widespread use of Internet technologies, online behaviors play a more and more important role in humans’ daily lives. Knowing the times when humans perform their next online activities can be quite valuable for developing better online services, which prompts us to wonder whether the times of users’ next online activities are predictable. In this paper, we investigate the temporal predictability in human online activities through exploiting the dataset from the social network Foursquare. Through discretizing the inter-event times of users’ Foursquare activities into symbols, we map each user’s inter-event time sequence to a sequence of inter-event time symbols. By applying the information-theoretic method to the sequences of inter-event time symbols, we show that for a user’s Foursquare activities, knowing the time interval between the current activity and the previous activity decreases the entropy of the time interval between the next activity and current activity, i.e., the time of the user’s next Foursquare activity is predictable. Much of the predictability is explained by the equal-interval repeat; that is, users perform consecutive Foursquare activities with approximately equal time intervals. On the other hand, the unequal-interval preference, i.e., the preference of performing Foursquare activities with a fixed time interval after another given time interval, is also an origin for predictability. Furthermore, our results reveal that the Foursquare activities on weekdays have a higher temporal predictability than those on weekends and that users’ Foursquare activity is more temporally predictable if his/her previous activity is performed in a location that he/she visits more frequently. Full article

(This article belongs to the Section Information Theory, Probability and Statistics)

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Open AccessArticle

Information Theoretical Measures for Achieving Robust Learning Machines

by Pablo Zegers, B. Roy Frieden, Carlos Alarcón and Alexis Fuentes

Entropy 2016, 18(8), 295; https://doi.org/10.3390/e18080295 - 12 Aug 2016

Cited by 1 | Viewed by 4090

Abstract

Information theoretical measures are used to design, from first principles, an objective function that can drive a learning machine process to a solution that is robust to perturbations in parameters. Full analytic derivations are given and tested with computational examples showing that indeed [...] Read more.

Information theoretical measures are used to design, from first principles, an objective function that can drive a learning machine process to a solution that is robust to perturbations in parameters. Full analytic derivations are given and tested with computational examples showing that indeed the procedure is successful. The final solution, implemented by a robust learning machine, expresses a balance between Shannon differential entropy and Fisher information. This is also surprising in being an analytical relation, given the purely numerical operations of the learning machine. Full article

(This article belongs to the Special Issue Information Theoretic Learning)

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756 KiB

Open AccessArticle

Understanding Gating Operations in Recurrent Neural Networks through Opinion Expression Extraction

by Xin Wang, Yuanchao Liu, Ming Liu, Chengjie Sun and Xiaolong Wang

Entropy 2016, 18(8), 294; https://doi.org/10.3390/e18080294 - 11 Aug 2016

Cited by 4 | Viewed by 4539

Abstract

Extracting opinion expressions from text is an essential task of sentiment analysis, which is usually treated as one of the word-level sequence labeling problems. In such problems, compositional models with multiplicative gating operations provide efficient ways to encode the contexts, as well as [...] Read more.

Extracting opinion expressions from text is an essential task of sentiment analysis, which is usually treated as one of the word-level sequence labeling problems. In such problems, compositional models with multiplicative gating operations provide efficient ways to encode the contexts, as well as to choose critical information. Thus, in this paper, we adopt Long Short-Term Memory (LSTM) recurrent neural networks to address the task of opinion expression extraction and explore the internal mechanisms of the model. The proposed approach is evaluated on the Multi-Perspective Question Answering (MPQA) opinion corpus. The experimental results demonstrate improvement over previous approaches, including the state-of-the-art method based on simple recurrent neural networks. We also provide a novel micro perspective to analyze the run-time processes and gain new insights into the advantages of LSTM selecting the source of information with its flexible connections and multiplicative gating operations. Full article

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Open AccessArticle

Characterization of Seepage Velocity beneath a Complex Rock Mass Dam Based on Entropy Theory

by Xixi Chen, Jiansheng Chen, Tao Wang, Huaidong Zhou and Linghua Liu

Entropy 2016, 18(8), 293; https://doi.org/10.3390/e18080293 - 11 Aug 2016

Cited by 4 | Viewed by 4963

Abstract

Owing to the randomness in the fracture flow system, the seepage system beneath a complex rock mass dam is inherently complex and highly uncertain, an investigation of the dam leakage by estimating the spatial distribution of the seepage field by conventional methods is [...] Read more.

Owing to the randomness in the fracture flow system, the seepage system beneath a complex rock mass dam is inherently complex and highly uncertain, an investigation of the dam leakage by estimating the spatial distribution of the seepage field by conventional methods is quite difficult. In this paper, the entropy theory, as a relation between the definiteness and probability, is used to probabilistically analyze the characteristics of the seepage system in a complex rock mass dam. Based on the principle of maximum entropy, an equation for the vertical distribution of the seepage velocity in a dam borehole is derived. The achieved distribution is tested and compared with actual field data, and the results show good agreement. According to the entropy of flow velocity in boreholes, the rupture degree of a dam bedrock has been successfully estimated. Moreover, a new sampling scheme is presented. The sampling frequency has a negative correlation with the distance to the site of the minimum velocity, which is preferable to the traditional one. This paper demonstrates the significant advantage of applying the entropy theory for seepage velocity analysis in a complex rock mass dam. Full article

(This article belongs to the Special Issue Applications of Information Theory in the Geosciences)

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2970 KiB

Open AccessArticle

On Multi-Scale Entropy Analysis of Order-Tracking Measurement for Bearing Fault Diagnosis under Variable Speed

by Tian-Yau Wu, Chang-Ling Yu and Da-Chun Liu

Entropy 2016, 18(8), 292; https://doi.org/10.3390/e18080292 - 10 Aug 2016

Cited by 14 | Viewed by 4482

Abstract

The research objective in this paper is to investigate the feasibility and effectiveness of utilizing envelope extraction combining the multi-scale entropy (MSE) analysis for identifying different roller bearing faults. The features were extracted from the angle-domain vibration signals that were measured through the [...] Read more.

The research objective in this paper is to investigate the feasibility and effectiveness of utilizing envelope extraction combining the multi-scale entropy (MSE) analysis for identifying different roller bearing faults. The features were extracted from the angle-domain vibration signals that were measured through the hardware-implemented order-tracking technique, so that the characteristics of bearing defects are not affected by the rotating speed. The envelope analysis was employed to the vibration measurements as well as the selected intrinsic mode function (IMF) that was separated by the empirical mode decomposition (EMD) method. By using the coarse-grain process, the entropy of the envelope signals in the different scales was calculated to form the MSE distributions that represent the complexity of the signals. The decision tree was used to distinguish the entropy-related features which reveal the different classes of bearing faults. Full article

(This article belongs to the Section Complexity)

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806 KiB

Open AccessArticle

Indicators of Evidence for Bioequivalence

by Stephan Morgenthaler and Robert Staudte

Entropy 2016, 18(8), 291; https://doi.org/10.3390/e18080291 - 09 Aug 2016

Cited by 2 | Viewed by 4534

Abstract

Some equivalence tests are based on two one-sided tests, where in many applications the test statistics are approximately normal. We define and find evidence for equivalence in Z-tests and then one- and two-sample binomial tests as well as for t-tests. Multivariate [...] Read more.

Some equivalence tests are based on two one-sided tests, where in many applications the test statistics are approximately normal. We define and find evidence for equivalence in Z-tests and then one- and two-sample binomial tests as well as for t-tests. Multivariate equivalence tests are typically based on statistics with non-central chi-squared or non-central F distributions in which the non-centrality parameter λ is a measure of heterogeneity of several groups. Classical tests of the null

λ \geq λ_{0}

versus the equivalence alternative

λ < λ_{0}

are available, but simple formulae for power functions are not. In these tests, the equivalence limit

λ_{0}

is typically chosen by context. We provide extensions of classical variance stabilizing transformations for the non-central chi-squared and F distributions that are easy to implement and which lead to indicators of evidence for equivalence. Approximate power functions are also obtained via simple expressions for the expected evidence in these equivalence tests. Full article

(This article belongs to the Special Issue Statistical Significance and the Logic of Hypothesis Testing)

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4061 KiB

Open AccessArticle

Control of Self-Organized Criticality through Adaptive Behavior of Nano-Structured Thin Film Coatings

by German Fox-Rabinovich, Jose M. Paiva, Iosif Gershman, Maryam Aramesh, Danielle Cavelli, Kenji Yamamoto, Goulnara Dosbaeva and Stephen Veldhuis

Entropy 2016, 18(8), 290; https://doi.org/10.3390/e18080290 - 09 Aug 2016

Cited by 15 | Viewed by 5037

Abstract

In this paper, we will develop a strategy for controlling the self-organized critical process using the example of extreme tribological conditions caused by intensive build-up edge (BUE) formation that take place during machining of hard-to-cut austentic superduplex stainless steel SDSS UNS32750. From a [...] Read more.

In this paper, we will develop a strategy for controlling the self-organized critical process using the example of extreme tribological conditions caused by intensive build-up edge (BUE) formation that take place during machining of hard-to-cut austentic superduplex stainless steel SDSS UNS32750. From a tribological viewpoint, machining of this material involves intensive seizure and build-up edge formation at the tool/chip interface, which can result in catastrophic tool failure. Built-up edge is considered to be a very damaging process in the system. The periodical breakage of the build-ups may eventually result in tool tip breakage and, thereby, lead to a catastrophe (complete loss of workability) in the system. The dynamic process of build-up edge formation is similar to an avalanche. It is governed by stick-slip phenomenon during friction and associated with the self-organized critical process. Investigation of wear patterns on the frictional surfaces of cutting tools using Scanning Electron Microscope (SEM), combined with chip undersurface characterization and frictional (cutting) force analyses, confirms this hypothesis. The control of self-organized criticality is accomplished through application of a nano-multilayer TiAl60CrSiYN/TiAlCrN thin film Physical Vapor Deposition (PVD) coating containing elevated aluminum content on a cemented carbide tool. The suggested coating enhanced the formation of protective nano-scale tribo-films on the friction surface under operation. Moreover, machining process optimization contributed to further enhancement of this beneficial process, as evidenced by X-ray Photoelectron Spectroscopy (XPS) studies of tribo-films. This resulted in a reduction of the scale of the build ups leading to overall wear performance improvement. A new thermodynamic analysis is proposed concerning entropy production during friction in machining with buildup edge formation. This model is able to predict various phenomena and shows a good agreement with experimental results. In the presented research we demonstrated a novel experimental approach for controlling self-organized criticality using an example of the machining with buildup edge formation, which is similar to avalanches. This was done through enhanced adaptive performance of the surface engineered tribo-system, in the aim of reducing the scale and frequency of the avalanches. Full article

(This article belongs to the Special Issue Entropy Application in Tribology)

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153 KiB

Open AccessCorrection

Correction to Yao, H.; Qiao, J.-W.; Gao, M.C.; Hawk, J.A.; Ma, S.-G.; Zhou, H. MoNbTaV Medium-Entropy Alloy. Entropy 2016, 18, 189

by Hongwei Yao, Jun-Wei Qiao, Michael C. Gao, Jeffrey A. Hawk, Sheng-Guo Ma and Hefeng Zhou

Entropy 2016, 18(8), 289; https://doi.org/10.3390/e18080289 - 09 Aug 2016

Cited by 3 | Viewed by 3864

Abstract

The authors wish to make the following correction to their paper [1].[...] Full article

(This article belongs to the Special Issue High-Entropy Alloys and High-Entropy-Related Materials)

17050 KiB

Open AccessArticle

Microstructures of Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ High-Entropy Alloy and Its Polarization Behaviors in Sulfuric Acid, Nitric Acid and Hydrochloric Acid Solutions

by Chun-Huei Tsau and Po-Yen Lee

Entropy 2016, 18(8), 288; https://doi.org/10.3390/e18080288 - 08 Aug 2016

Cited by 6 | Viewed by 6241

Abstract

This paper investigates the microstructures and the polarization behaviors of Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ high-entropy alloy in 1M (1 mol/L) deaerated sulfuric acid (H₂SO₄), nitric acid (HNO₃), and hydrochloric acid (HCl) [...] Read more.

This paper investigates the microstructures and the polarization behaviors of Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ high-entropy alloy in 1M (1 mol/L) deaerated sulfuric acid (H₂SO₄), nitric acid (HNO₃), and hydrochloric acid (HCl) solutions at temperatures of 30–60 °C. The three phases of the Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ high-entropy alloy are body-centered cubic (BCC) dendrites, face-centered cubic (FCC) interdendrites, and ordered BCC precipitates uniformly dispersed in the BCC dendrites. The different phases were corroded in different acidic solutions. The passivation regions of the Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ alloy are divided into three and two sub-regions in the solutions of H₂SO₄ and HNO₃ at 30–60 °C, respectively. The passivation region of the Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ alloy is also divided into two sub-domains in 1M deaerated HCl solution at 30 °C. The Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ alloy has almost equal corrosion resistance in comparison with 304 stainless steel (304SS) in both the 1M H₂SO₄ and 1M HCl solutions. The polarization behaviors indicated that the Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ alloy possessed much better corrosion resistance than 304SS in 1M HNO₃ solution. However, in 1M NaCl solution, the corrosion resistance of the Al_7.5Cr_22.5Fe₃₅Mn₂₀Ni₁₅ alloy was less than 304SS. Full article

(This article belongs to the Special Issue High-Entropy Alloys and High-Entropy-Related Materials)

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273 KiB

Open AccessArticle

Hawking-Like Radiation from the Trapping Horizon of Both Homogeneous and Inhomogeneous Spherically Symmetric Spacetime Model of the Universe

by Subenoy Chakraborty, Subhajit Saha and Christian Corda

Entropy 2016, 18(8), 287; https://doi.org/10.3390/e18080287 - 08 Aug 2016

Cited by 5 | Viewed by 3577

Abstract

The present work deals with the semi-classical tunnelling approach and the Hamilton–Jacobi method to study Hawking radiation from the dynamical horizon of both the homogeneous Friedmann–Robertson–Walker (FRW) model and the inhomogeneous Lemaitre–Tolman–Bondi (LTB) model of the Universe. In the tunnelling prescription, radial null [...] Read more.

The present work deals with the semi-classical tunnelling approach and the Hamilton–Jacobi method to study Hawking radiation from the dynamical horizon of both the homogeneous Friedmann–Robertson–Walker (FRW) model and the inhomogeneous Lemaitre–Tolman–Bondi (LTB) model of the Universe. In the tunnelling prescription, radial null geodesics are used to visualize particles from behind the trapping horizon and the Hawking-like temperature has been calculated. On the other hand, in the Hamilton–Jacobi formulation, quantum corrections have been incorporated by solving the Klein–Gordon wave equation. In both the approaches, the temperature agrees at the semiclassical level. Full article

(This article belongs to the Special Issue Entropy in Quantum Systems and Quantum Field Theory (QFT))

2091 KiB

Open AccessArticle

A Five Species Cyclically Dominant Evolutionary Game with Fixed Direction: A New Way to Produce Self-Organized Spatial Patterns

by Yibin Kang, Qiuhui Pan, Xueting Wang and Mingfeng He

Entropy 2016, 18(8), 284; https://doi.org/10.3390/e18080284 - 08 Aug 2016

Cited by 8 | Viewed by 3928

Abstract

Cyclically dominant systems are hot issues in academia, and they play an important role in explaining biodiversity in Nature. In this paper, we construct a five-strategy cyclically dominant system. Each individual in our system changes its strategy along a fixed direction. The dominant [...] Read more.

Cyclically dominant systems are hot issues in academia, and they play an important role in explaining biodiversity in Nature. In this paper, we construct a five-strategy cyclically dominant system. Each individual in our system changes its strategy along a fixed direction. The dominant strategy can promote a change in the dominated strategy, and the dominated strategy can block a change in the dominant strategy. We use mean-field theory and cellular automaton simulation to discuss the evolving characters of the system. In the cellular automaton simulation, we find the emergence of spiral waves on spatial patterns without a migration rate, which suggests a new way to produce self-organized spatial patterns. Full article

(This article belongs to the Section Statistical Physics)

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3430 KiB

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Parametric Analysis of the Exergoeconomic Operation Costs, Environmental and Human Toxicity Indexes of the MF501F3 Gas Turbine

by Edgar Vicente Torres-González, Raul Lugo-Leyte, Helen Denise Lugo-Méndez, Martin Salazar-Pereyra and Alejandro Torres-Aldaco

Entropy 2016, 18(8), 286; https://doi.org/10.3390/e18080286 - 06 Aug 2016

Cited by 4 | Viewed by 5151

Abstract

This work presents an energetic, exergoeconomic, environmental, and toxicity analysis of the simple gas turbine M501F3 based on a parametric analysis of energetic (thermal efficiency, fuel and air flow rates, and specific work output), exergoeconomic (exergetic efficiency and exergoeconomic operation costs), environmental (global [...] Read more.

This work presents an energetic, exergoeconomic, environmental, and toxicity analysis of the simple gas turbine M501F3 based on a parametric analysis of energetic (thermal efficiency, fuel and air flow rates, and specific work output), exergoeconomic (exergetic efficiency and exergoeconomic operation costs), environmental (global warming, smog formation, acid rain indexes), and human toxicity indexes, by taking the compressor pressure ratio and the turbine inlet temperature as the operating parameters. The aim of this paper is to provide an integral, systematic, and powerful diagnostic tool to establish possible operation and maintenance actions to improve the gas turbine’s exergoeconomic, environmental, and human toxicity indexes. Despite the continuous changes in the price of natural gas, the compressor, combustion chamber, and turbine always contribute 18.96%, 53.02%, and 28%, respectively, to the gas turbine’s exergoeconomic operation costs. The application of this methodology can be extended to other simple gas turbines using the pressure drops and isentropic efficiencies, among others, as the degradation parameters, as well as to other energetic systems, without loss of generality. Full article

(This article belongs to the Section Thermodynamics)

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800 KiB

Open AccessArticle

ECG Classification Using Wavelet Packet Entropy and Random Forests

by Taiyong Li and Min Zhou

Entropy 2016, 18(8), 285; https://doi.org/10.3390/e18080285 - 05 Aug 2016

Cited by 369 | Viewed by 16557

Abstract

The electrocardiogram (ECG) is one of the most important techniques for heart disease diagnosis. Many traditional methodologies of feature extraction and classification have been widely applied to ECG analysis. However, the effectiveness and efficiency of such methodologies remain to be improved, and much [...] Read more.

The electrocardiogram (ECG) is one of the most important techniques for heart disease diagnosis. Many traditional methodologies of feature extraction and classification have been widely applied to ECG analysis. However, the effectiveness and efficiency of such methodologies remain to be improved, and much existing research did not consider the separation of training and testing samples from the same set of patients (so called inter-patient scheme). To cope with these issues, in this paper, we propose a method to classify ECG signals using wavelet packet entropy (WPE) and random forests (RF) following the Association for the Advancement of Medical Instrumentation (AAMI) recommendations and the inter-patient scheme. Specifically, we firstly decompose the ECG signals by wavelet packet decomposition (WPD), and then calculate entropy from the decomposed coefficients as representative features, and finally use RF to build an ECG classification model. To the best of our knowledge, it is the first time that WPE and RF are used to classify ECG following the AAMI recommendations and the inter-patient scheme. Extensive experiments are conducted on the publicly available MIT–BIH Arrhythmia database and influence of mother wavelets and level of decomposition for WPD, type of entropy and the number of base learners in RF on the performance are also discussed. The experimental results are superior to those by several state-of-the-art competing methods, showing that WPE and RF is promising for ECG classification. Full article

(This article belongs to the Special Issue Entropy on Biosignals and Intelligent Systems)

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