Symmetry

17 pages, 1281 KiB

Open AccessArticle

A Kinetic Theory Model of the Dynamics of Liquidity Profiles on Interbank Networks

by Marina Dolfin, Leone Leonida and Eleonora Muzzupappa

Symmetry 2021, 13(2), 363; https://doi.org/10.3390/sym13020363 - 23 Feb 2021

Cited by 3 | Viewed by 1970

This paper adopts the Kinetic Theory for Active Particles (KTAP) approach to model the dynamics of liquidity profiles on a complex adaptive network system that mimic a stylized financial market. Individual incentives of investors to form or delete a link is driven, in [...] Read more.

This paper adopts the Kinetic Theory for Active Particles (KTAP) approach to model the dynamics of liquidity profiles on a complex adaptive network system that mimic a stylized financial market. Individual incentives of investors to form or delete a link is driven, in our modelling framework, by stochastic game-type interactions modelling the phenomenology related to policy rules implemented under Basel III, and it is exogeneously and dynamically influenced by a measure of overnight interest rate. The strategic network formation dynamics that emerges from the introduced transition probabilities modelling individual incentives of investors to form or delete links, provides a wide range of measures using which networks might be considered “best” from the point of view of the overall welfare of the system. We use the time evolution of the aggregate degree of connectivity to measure the time evolving network efficiency in two different scenarios, suggesting a first analysis of the stability of the arising and evolving network structures. Full article

(This article belongs to the Special Issue Complexity and Symmetry in the Science of Living Systems: Active Particle Methods)

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20 pages, 3148 KiB

Open AccessArticle

GLM-Based Flexible Monitoring Methods: An Application to Real-Time Highway Safety Surveillance

by Arshad Jamal, Tahir Mahmood, Muhamad Riaz and Hassan M. Al-Ahmadi

Symmetry 2021, 13(2), 362; https://doi.org/10.3390/sym13020362 - 23 Feb 2021

Cited by 34 | Viewed by 3371

Abstract

Statistical modeling of historical crash data can provide essential insights to safety managers for proactive highway safety management. While numerous studies have contributed to the advancement from the statistical methodological front, minimal research efforts have been dedicated to real-time monitoring of highway safety [...] Read more.

Statistical modeling of historical crash data can provide essential insights to safety managers for proactive highway safety management. While numerous studies have contributed to the advancement from the statistical methodological front, minimal research efforts have been dedicated to real-time monitoring of highway safety situations. This study advocates the use of statistical monitoring methods for real-time highway safety surveillance using three years of crash data for rural highways in Saudi Arabia. First, three well-known count data models (Poisson, negative binomial, and Conway–Maxwell–Poisson) are applied to identify the best fit model for the number of crashes. Conway–Maxwell–Poisson was identified as the best fit model, which was used to find the significant explanatory variables for the number of crashes. The results revealed that the road type and road surface conditions significantly contribute to the number of crashes. From the perspective of real-time highway safety monitoring, generalized linear model (GLM)-based exponentially weighted moving average (EWMA) and cumulative sum (CUSUM) control charts are proposed using the randomized quantile residuals and deviance residuals of Conway–Maxwell (COM)–Poisson regression. A detailed simulation-based study is designed for predictive performance evaluation of the proposed control charts with existing counterparts (i.e., Shewhart charts) in terms of the run-length properties. The study results showed that the EWMA type control charts have better detection ability compared with the CUSUM type and Shewhart control charts under small and/or moderate shift sizes. Finally, the proposed monitoring methods are successfully implemented on actual traffic crash data to highlight the efficacy of the proposed methods. The outcome of this study could provide the analysts with insights to plan sound policy recommendations for achieving desired safety goals. Full article

(This article belongs to the Special Issue New Advances and Applications in Statistical Quality Control)

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6 pages, 1048 KiB

Open AccessCommunication

Isolation and Structure Elucidation of a Novel Symmetrical Macrocyclic Phthalate Hexaester

by Michiya Kamio, Weina Jiang, Hiroki Osada, Masayuki Fukuoka, Hajime Uchida, Ryuichi Watanabe, Toshiyuki Suzuki and Hiroshi Nagai

Symmetry 2021, 13(2), 361; https://doi.org/10.3390/sym13020361 - 23 Feb 2021

Cited by 1 | Viewed by 1902

Abstract

A novel symmetrical macrocyclic phthalate hexaester (1) and a known macrocyclic phthalate tetraester (2) were isolated during a natural product-exploring program on the cyanobacterium Moorea producens. Their structures were elucidated based on spectroscopic data, including nuclear magnetic resonance [...] Read more.

A novel symmetrical macrocyclic phthalate hexaester (1) and a known macrocyclic phthalate tetraester (2) were isolated during a natural product-exploring program on the cyanobacterium Moorea producens. Their structures were elucidated based on spectroscopic data, including nuclear magnetic resonance and high-resolution mass spectra. In the antibacterial activity test, compounds 1 and 2 showed no bioactivity at the concentrations tested. Full article

(This article belongs to the Special Issue Recent Advances in the Analysis, Distribution and Functions of Enantiomers and Regioisomers of Biomolecules)

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21 pages, 4443 KiB

Open AccessArticle

On the Development of Triple Homogeneously Weighted Moving Average Control Chart

by Muhammad Riaz, Zameer Abbas, Hafiz Zafar Nazir and Muhammad Abid

Symmetry 2021, 13(2), 360; https://doi.org/10.3390/sym13020360 - 23 Feb 2021

Cited by 16 | Viewed by 1960

Abstract

To detect sustainable changes in the manufacturing processes, memory-type charting schemes are frequently functioning. The recently designed, homogenously weighted moving average (HWMA) technique is effective for identifying substantial changes in the processes. To make the HWMA chart more effective for persistent shifts in [...] Read more.

To detect sustainable changes in the manufacturing processes, memory-type charting schemes are frequently functioning. The recently designed, homogenously weighted moving average (HWMA) technique is effective for identifying substantial changes in the processes. To make the HWMA chart more effective for persistent shifts in the industrial processes, a double HWMA (DHWMA) chart has been proposed recently. This study intends to develop a triple HWMA (THWMA) chart for efficient monitoring of the process mean under zero- and steady-state scenarios. The non-normal effects of monitoring characteristics under in-control situations for heavy-tailed highly skewed and contaminated normal environments are computed under both states. The relative efficiency of the proposed structure is compared with HWMA, DHWMA, exponentially weighted moving average (EWMA), double EWMA, and the more effective triple EWMA control charting schemes. The relative analysis reveals that the proposed THWMA design performs more efficiently than the existing counterparts. An illustrative application related to substrate manufacturing is also incorporated to demonstrate the proposal. Full article

(This article belongs to the Special Issue New Advances and Applications in Statistical Quality Control)

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12 pages, 288 KiB

Open AccessArticle

Two-Dimensional Divisor Problems Related to Symmetric L-Functions

by Jing Huang, Huafeng Liu and Fuxia Xu

Symmetry 2021, 13(2), 359; https://doi.org/10.3390/sym13020359 - 22 Feb 2021

Cited by 8 | Viewed by 1537

Abstract

In this paper, we study two-dimensional divisor problems of the Fourier coefficients of some automorphic product L-functions attached to the primitive holomorphic cusp form

f (z)

with weight k for the full modular group

S L_{2} (Z)

[...] Read more.

In this paper, we study two-dimensional divisor problems of the Fourier coefficients of some automorphic product L-functions attached to the primitive holomorphic cusp form

f (z)

with weight k for the full modular group

S L_{2} (Z)

. Additionally, we establish the upper bound and the asymptotic formula for these divisor problems on average, respectively. Full article

(This article belongs to the Section Mathematics)

8 pages, 260 KiB

Open AccessArticle

Bootstrapped Newtonian Cosmology and the Cosmological Constant Problem

by Roberto Casadio and Andrea Giusti

Symmetry 2021, 13(2), 358; https://doi.org/10.3390/sym13020358 - 22 Feb 2021

Cited by 4 | Viewed by 1457

Abstract

Bootstrapped Newtonian gravity was developed with the purpose of estimating the impact of quantum physics in the nonlinear regime of the gravitational interaction, akin to corpuscular models of black holes and inflation. In this work, we set the ground for extending the bootstrapped [...] Read more.

Bootstrapped Newtonian gravity was developed with the purpose of estimating the impact of quantum physics in the nonlinear regime of the gravitational interaction, akin to corpuscular models of black holes and inflation. In this work, we set the ground for extending the bootstrapped Newtonian picture to cosmological spaces. We further discuss how such models of quantum cosmology can lead to a natural solution to the cosmological constant problem. Full article

(This article belongs to the Special Issue Recent Advances in Quantum Gravity)

28 pages, 1447 KiB

Open AccessArticle

Health Monitoring System for Elderly Patients Using Intelligent Task Mapping Mechanism in Closed Loop Healthcare Environment

by Imran, Naeem Iqbal, Shabir Ahmad and Do Hyeun Kim

Symmetry 2021, 13(2), 357; https://doi.org/10.3390/sym13020357 - 22 Feb 2021

Cited by 39 | Viewed by 7860

Abstract

The ageing population’s problems directly impact countries’ socio-economic structure, as more resources are required to monitor the aged population’s health. The growth in human life expectancy is increasing due to medical technologies and nutritional science innovations. The Internet of Things (IoT) is the [...] Read more.

The ageing population’s problems directly impact countries’ socio-economic structure, as more resources are required to monitor the aged population’s health. The growth in human life expectancy is increasing due to medical technologies and nutritional science innovations. The Internet of Things (IoT) is the connectivity of physical objects called things to the Internet. IoT has a wide range of health monitoring applications based on biomedical sensing devices to monitor health conditions. This paper proposes elderly patients’ health monitoring architecture based on an intelligent task mapping approach for a closed-loop IoT healthcare environment. As a case study, a health monitoring system was developed based on the proposed architecture for elderly patients’ health monitoring in the home, ambulance, and hospital environment. The system detects and notifies deteriorating conditions to the authorities based on biomedical sensors for faster interventions. Wearable biomedical sensors are used for monitoring body temperature, heart rate, blood glucose level, and patient body position. Threshold and machine learning-based approaches were used to detect anomalies in the health sensing data. The proposed architecture’s performance analysis is evaluated in terms of round trip time, reliability, task drop rate, and latency performance metrics. Performance results show that the proposed architecture of the elderly patient health monitoring can provide reliable solutions for critical tasks in IoT environments. Full article

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16 pages, 14942 KiB

Open AccessArticle

Plant Recognition Using Morphological Feature Extraction and Transfer Learning over SVM and AdaBoost

by Shubham Mahajan, Akshay Raina, Xiao-Zhi Gao and Amit Kant Pandit

Symmetry 2021, 13(2), 356; https://doi.org/10.3390/sym13020356 - 22 Feb 2021

Cited by 26 | Viewed by 3550

Abstract

Plant species recognition from visual data has always been a challenging task for Artificial Intelligence (AI) researchers, due to a number of complications in the task, such as the enormous data to be processed due to vast number of floral species. There are [...] Read more.

Plant species recognition from visual data has always been a challenging task for Artificial Intelligence (AI) researchers, due to a number of complications in the task, such as the enormous data to be processed due to vast number of floral species. There are many sources from a plant that can be used as feature aspects for an AI-based model, but features related to parts like leaves are considered as more significant for the task, primarily due to easy accessibility, than other parts like flowers, stems, etc. With this notion, we propose a plant species recognition model based on morphological features extracted from corresponding leaves’ images using the support vector machine (SVM) with adaptive boosting technique. This proposed framework includes the pre-processing, extraction of features and classification into one of the species. Various morphological features like centroid, major axis length, minor axis length, solidity, perimeter, and orientation are extracted from the digital images of various categories of leaves. In addition to this, transfer learning, as suggested by some previous studies, has also been used in the feature extraction process. Various classifiers like the kNN, decision trees, and multilayer perceptron (with and without AdaBoost) are employed on the opensource dataset, FLAVIA, to certify our study in its robustness, in contrast to other classifier frameworks. With this, our study also signifies the additional advantage of 10-fold cross validation over other dataset partitioning strategies, thereby achieving a precision rate of 95.85%. Full article

(This article belongs to the Section Computer)

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15 pages, 1881 KiB

Open AccessArticle

Feature Extraction of Marine Water Pollution Based on Data Mining

by Haixia Lin, Jianhong Cui and Xiangwei Bai

Symmetry 2021, 13(2), 355; https://doi.org/10.3390/sym13020355 - 22 Feb 2021

Cited by 2 | Viewed by 1975

Abstract

The ocean occupies more than two-thirds of the earth’s area, providing a lot of oxygen and materials for human survival and development. However, with human activities, a large number of sewage, plastic bags, and other wastes are discharged into the ocean, and the [...] Read more.

The ocean occupies more than two-thirds of the earth’s area, providing a lot of oxygen and materials for human survival and development. However, with human activities, a large number of sewage, plastic bags, and other wastes are discharged into the ocean, and the problem of marine water pollution has become a hot topic in the world. In order to extract the characteristics of marine water pollution, this study proposed K-means clustering technology based on cosine distance and discrimination to study the polluted water. In this study, the polygonal area method combined with six parameters of water quality is used to analyze the marine water body anomalies, so as to realize the rapid and real-time monitoring of marine water body anomalies. At the same time, the cosine distance method and discrimination are used to classify marine water pollutants, so as to improve the classification accuracy. The results show that the detection rate of water quality anomalies is more than 88.2%, and the overall classification accuracy of water pollution is 96.3%, which proves the effectiveness of the method. It is hoped that this study can provide timely and effective data support for the detection of marine water bodies. Full article

(This article belongs to the Special Issue Mathematical Modeling and Computational Methods in Science and Engineering III)

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15 pages, 400 KiB

Open AccessFeature PaperArticle

Application of the Efros Theorem to the Function Represented by the Inverse Laplace Transform of s^−μ exp(−s^ν)

by Alexander Apelblat and Francesco Mainardi

Symmetry 2021, 13(2), 354; https://doi.org/10.3390/sym13020354 - 22 Feb 2021

Cited by 9 | Viewed by 2071

Abstract

Using a special case of the Efros theorem which was derived by Wlodarski, and operational calculus, it was possible to derive many infinite integrals, finite integrals and integral identities for the function represented by the inverse Laplace transform. The integral identities are mainly [...] Read more.

Using a special case of the Efros theorem which was derived by Wlodarski, and operational calculus, it was possible to derive many infinite integrals, finite integrals and integral identities for the function represented by the inverse Laplace transform. The integral identities are mainly in terms of convolution integrals with the Mittag–Leffler and Volterra functions. The integrands of determined integrals include elementary functions (power, exponential, logarithmic, trigonometric and hyperbolic functions) and the error functions, the Mittag–Leffler functions and the Volterra functions. Some properties of the inverse Laplace transform of

s^{- μ} \exp (- s^{ν})

with

μ \geq 0

and

0 < ν < 1

are presented. Full article

(This article belongs to the Special Issue Special Functions and Polynomials)

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9 pages, 1428 KiB

Open AccessArticle

Sliding Mode Control and Geometrization Conjecture in Seismic Response

by Ligia Munteanu, Dan Dumitriu, Cornel Brisan, Mircea Bara, Veturia Chiroiu, Nicoleta Nedelcu and Cristian Rugina

Symmetry 2021, 13(2), 353; https://doi.org/10.3390/sym13020353 - 22 Feb 2021

Cited by 1 | Viewed by 1536

Abstract

The purpose of this paper is to study the sliding mode control as a Ricci flow process in the context of a three-story building structure subjected to seismic waves. The stability conditions result from two Lyapunov functions, the first associated with slipping in [...] Read more.

The purpose of this paper is to study the sliding mode control as a Ricci flow process in the context of a three-story building structure subjected to seismic waves. The stability conditions result from two Lyapunov functions, the first associated with slipping in a finite period of time and the second with convergence of trajectories to the desired state. Simulation results show that the Ricci flow control leads to minimization of the displacements of the floors. Full article

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11 pages, 605 KiB

Open AccessArticle

Quantum Fisher Information and Bures Distance Correlations of Coupled Two Charge-Qubits Inside a Coherent Cavity with the Intrinsic Decoherence

by Abdel-Baset A. Mohamed, Eied. M. Khalil, Mahmoud M. Selim and Hichem Eleuch

Symmetry 2021, 13(2), 352; https://doi.org/10.3390/sym13020352 - 22 Feb 2021

Cited by 9 | Viewed by 2098

Abstract

The dynamics of two charged qubits containing Josephson Junctions inside a cavity are investigated under the intrinsic decoherence effect. New types of quantum correlations via local quantum Fisher information and Bures distance norm are explored. We show that we can control the quantum [...] Read more.

The dynamics of two charged qubits containing Josephson Junctions inside a cavity are investigated under the intrinsic decoherence effect. New types of quantum correlations via local quantum Fisher information and Bures distance norm are explored. We show that we can control the quantum correlations robustness by the intrinsic decoherence rate, the qubit-qubit coupling as well as by the initial coherent states superposition. The phenomenon of sudden changes and the freezing behavior for the local quantum Fisher information are sensitive to the initial coherent state superposition and the intrinsic decoherence. Full article

(This article belongs to the Special Issue Quantum Information and Condensed Matter Physics)

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16 pages, 276 KiB

Open AccessArticle

A Hilbert-Type Integral Inequality in the Whole Plane Related to the Arc Tangent Function

by Michael Th. Rassias, Bicheng Yang and Andrei Raigorodskii

Symmetry 2021, 13(2), 351; https://doi.org/10.3390/sym13020351 - 21 Feb 2021

Cited by 3 | Viewed by 1600

Abstract

In this work we establish a few equivalent statements of a Hilbert-type integral inequality in the whole plane related to the kernel of the arc tangent function. We prove that the constant factor, which is associated with the cosine function, is optimal. Some [...] Read more.

In this work we establish a few equivalent statements of a Hilbert-type integral inequality in the whole plane related to the kernel of the arc tangent function. We prove that the constant factor, which is associated with the cosine function, is optimal. Some special cases as well as some operator expressions are also presented. Full article

(This article belongs to the Special Issue Functional Equations and Analytic Inequalities)

19 pages, 3538 KiB

Open AccessArticle

Supersymmetric Partners of the One-Dimensional Infinite Square Well Hamiltonian

by Manuel Gadella, José Hernández-Muñoz, Luis Miguel Nieto and Carlos San Millán

Symmetry 2021, 13(2), 350; https://doi.org/10.3390/sym13020350 - 21 Feb 2021

Cited by 3 | Viewed by 2305

Abstract

We find supersymmetric partners of a family of self-adjoint operators which are self-adjoint extensions of the differential operator

- d^{2} / d x^{2}

on

L^{2} [- a, a]

,

a > 0

, that is, the one [...] Read more.

We find supersymmetric partners of a family of self-adjoint operators which are self-adjoint extensions of the differential operator

- d^{2} / d x^{2}

on

L^{2} [- a, a]

,

a > 0

, that is, the one dimensional infinite square well. First of all, we classify these self-adjoint extensions in terms of several choices of the parameters determining each of the extensions. There are essentially two big groups of extensions. In one, the ground state has strictly positive energy. On the other, either the ground state has zero or negative energy. In the present paper, we show that each of the extensions belonging to the first group (energy of ground state strictly positive) has an infinite sequence of supersymmetric partners, such that the ℓ-th order partner differs in one energy level from both the

(ℓ - 1)

-th and the

(ℓ + 1)

-th order partners. In general, the eigenvalues for each of the self-adjoint extensions of

- d^{2} / d x^{2}

come from a transcendental equation and are all infinite. For the case under our study, we determine the eigenvalues, which are also infinite, all the extensions have a purely discrete spectrum, and their respective eigenfunctions for all of its ℓ-th supersymmetric partners of each extension. Full article

(This article belongs to the Special Issue Symmetries in Quantum Mechanics and Statistical Physics)

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11 pages, 2082 KiB

Open AccessArticle

Gait Symmetry Analysis in Patients after Treatment of Pilon Fractures by the Ilizarov Method

by Łukasz Pawik, Paweł Wietecki, Artur Leśkow, Andżelika Pajchert Kozłowska, Sławomir Żarek, Radosław Górski, Malwina Pawik, Felicja Fink-Lwow, Wiktor Urbański and Piotr Morasiewicz

Symmetry 2021, 13(2), 349; https://doi.org/10.3390/sym13020349 - 21 Feb 2021

Cited by 4 | Viewed by 1747

Abstract

The aim of this study was to comprehensively assess the gait parameters in patients who had undergone treatment of pilon fractures by the Ilizarov method. We analyzed gait parameters in patients who had undergone treatment for pilon fractures by the Ilizarov method; 20 [...] Read more.

The aim of this study was to comprehensively assess the gait parameters in patients who had undergone treatment of pilon fractures by the Ilizarov method. We analyzed gait parameters in patients who had undergone treatment for pilon fractures by the Ilizarov method; 20 patients aged 47.0 years (25.2–78.6) were included in the study. The control group consisted of 32 healthy volunteers. Gait examination was performed using the pedobarographic platform. Statistically significant differences in the following gait parameters: maximum forefoot force (%), step length (cm), and step time (s) were found between the study group and the control group, between the nonoperated leg, and both the operated leg and the dominant limb. Statistically significant differences in the study group between the treated lower limb and the healthy lower limb were only observed in the case of the maximum forefoot force parameter (%). Healthy subjects from the control group obtained significantly higher values during locomotion for stride time, cadence step, and velocity than the patients, with stride time being statistically significantly shorter and the velocity and the cadence step higher. We observed symmetry in the gait parameters after treating pilon fractures by the Ilizarov method. This method of stabilization allows the restoration of gait parameters, with results similar to those obtained after the treatment of other motor organ pathologies described in the literature, although different from those observed in healthy subjects. In particular, the biomechanics of the lower limbs remain disturbed. Full article

(This article belongs to the Special Issue Symmetry and Biomechanics)

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38 pages, 447 KiB

Open AccessArticle

Off-Shell Noether Currents and Potentials for First-Order General Relativity

by Merced Montesinos, Diego Gonzalez, Rodrigo Romero and Mariano Celada

Symmetry 2021, 13(2), 348; https://doi.org/10.3390/sym13020348 - 20 Feb 2021

Cited by 2 | Viewed by 1664

Abstract

We report off-shell Noether currents obtained from off-shell Noether potentials for first-order general relativity described by n-dimensional Palatini and Holst Lagrangians including the cosmological constant. These off-shell currents and potentials are achieved by using the corresponding Lagrangian and the off-shell Noether identities [...] Read more.

We report off-shell Noether currents obtained from off-shell Noether potentials for first-order general relativity described by n-dimensional Palatini and Holst Lagrangians including the cosmological constant. These off-shell currents and potentials are achieved by using the corresponding Lagrangian and the off-shell Noether identities satisfied by diffeomorphisms generated by arbitrary vector fields, local

S O (n)

or

S O (n - 1, 1)

transformations, ‘improved diffeomorphisms’, and the ‘generalization of local translations’ of the orthonormal frame and the connection. A remarkable aspect of our approach is that we do not use Noether’s theorem in its direct form. By construction, the currents are off-shell conserved and lead naturally to the definition of off-shell Noether charges. We also study what we call the ‘half off-shell’ case for both Palatini and Holst Lagrangians. In particular, we find that the resulting diffeomorphism and local

S O (3, 1)

or

S O (4)

off-shell Noether currents and potentials for the Holst Lagrangian generically depend on the Immirzi parameter, which holds even in the ‘half off-shell’ and on-shell cases. We also study Killing vector fields in the ‘half off-shell’ and on-shell cases. The current theoretical framework is illustrated for the ‘half off-shell’ case in static spherically symmetric and Friedmann–Lemaitre–Robertson–Walker spacetimes in four dimensions. Full article

(This article belongs to the Section Physics)

17 pages, 1282 KiB

Open AccessArticle

A Model Free Adaptive Scheme for Integrated Control of Civil Aircraft Trajectory and Attitude

by Gaoyang Jiang, Genfeng Liu and Hansong Yu

Symmetry 2021, 13(2), 347; https://doi.org/10.3390/sym13020347 - 20 Feb 2021

Cited by 4 | Viewed by 1463

Abstract

The adaptive trajectory and attitude control is essential for the four-dimensional (4D) trajectory operation of civil aircraft in symmetric thrust flight. In this work, an integrated trajectory and attitude control scheme is proposed based on the =multi-input multi-output (MIMO) model free adaptive control [...] Read more.

The adaptive trajectory and attitude control is essential for the four-dimensional (4D) trajectory operation of civil aircraft in symmetric thrust flight. In this work, an integrated trajectory and attitude control scheme is proposed based on the =multi-input multi-output (MIMO) model free adaptive control (MFAC) method. First, the full-form dynamic linearization technique is adopted to build the equivalent data model of aircraft. Also, the MIMO MFAC scheme with saturation constraint is designed to achieve an accurate tracking control for a given 4D trajectory and attitude. Besides, the performance limitations of aircraft are taken into consideration, and the MIMO MFAC scheme with hard constraints is designed. In addition, to improve the simulation efficiency, a control scheme with mixed constraints, i.e., saturation and hard constraints, is further proposed. It can be seen from the simulation results that the proposed method can perform an integrated control of the aircraft 4D trajectory and attitude without precise modeling, and the control performance is better than that of the model-based control method in terms of flight altitude and yaw angle control. The integrated data-driven control scheme proposed in this paper provides a theoretical solution for the precise operation of aircraft under 4D trajectory. Full article

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19 pages, 1084 KiB

Open AccessArticle

A Reduction of Peak-to-Average Power Ratio Based Faster-Than-Nyquist Quadrature Signals for Satellite Communication

by Sergey B. Makarov, Mingxin Liu, Anna S. Ovsyannikova, Sergey V. Zavjalov, ILya Lavrenyuk, Wei Xue and Yidong Xu

Symmetry 2021, 13(2), 346; https://doi.org/10.3390/sym13020346 - 20 Feb 2021

Cited by 10 | Viewed by 2274

Abstract

The increase in the throughput of digital television and radio broadcasting (DVB) channels can be achieved due to application of signals with a compact spectrum and a relatively small peak-to-average power ratio (PAPR). The reason is the usage of traveling wave tubes (TWT) [...] Read more.

The increase in the throughput of digital television and radio broadcasting (DVB) channels can be achieved due to application of signals with a compact spectrum and a relatively small peak-to-average power ratio (PAPR). The reason is the usage of traveling wave tubes (TWT) for amplifying and transmitting signals from a satellite repeater in DVB-S2X systems. At the same time, given that the bandwidth allocated for transmission should be used as efficiently as possible, a high reduction rate of out-of-band emissions level is required. The most effective solution in this direction is the transition to spectrum-economic signals, such as optimal Faster-Than-Nyquist (FTN) signals, which can provide a certain reduction rate of the out-of-band emissions level and minimum acceptable PAPR. This article proposes a method for obtaining optimal FTN pulses, which have symmetry in time domain, with specified PAPR and reduction rate of out-of-band emissions for the quadrature phase shift keying (QPSK) and offset quadrature phase shift keying (OQPSK). The possibility of synthesizing signals with OQPSK modulation is presented theoretically for the first time. Optimal FTN signals can provide PAPR reduction by at most 3 dB and outperform known root raised cosine (RRC) pulses. The simulation model adopts an architecture for quadrature generation of optimal FTN signals with OQPSK modulation with blocks for adjustable pre-amplification, clipping, and power amplification. The proposed signals can be used to increase the spectral and energy efficiencies of satellite broadcasting systems, such as DVB-S2/S2X, as well as low-rate return channels of interactive broadcasting systems with a frequency resource shortage. Full article

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17 pages, 2504 KiB

Open AccessArticle

A Dimensionality Reduction Algorithm for Unstructured Campus Big Data Fusion

by Zhenfei Wang, Yan Wang, Liying Zhang, Chuchu Zhang and Xingjin Zhang

Symmetry 2021, 13(2), 345; https://doi.org/10.3390/sym13020345 - 20 Feb 2021

Cited by 2 | Viewed by 1901

Abstract

Data modeling and dimensionality reduction are important research points in the field of big data. At present, there is no effective model to realize the consistent representation and fusion of different types of data of students in unstructured campus big data. In addition, [...] Read more.

Data modeling and dimensionality reduction are important research points in the field of big data. At present, there is no effective model to realize the consistent representation and fusion of different types of data of students in unstructured campus big data. In addition, in the process of big data processing, the amount of data is too large and the intermediate results are too complex, which seriously affects the efficiency of big data dimension reduction. To solve the above problems, this paper proposes an incremental high order singular value decomposition dimensionality (icHOSVD) reduction algorithm for unstructured campus big data. In this algorithm, the characteristics of audio, video, image and text data in unstructured campus student data are tensioned to form a sub-tensor model, and the semi-tensor product is used to fuse the sub-tensor model into a unified model as the individual student tensor model. On the basis of individual model fusion, the campus big data fusion model was segmented, and each segmented small tensor model was dimensioned by icHOSVD reduction to obtain an approximate tensor as the symmetric tensor that could replace the original tensor, so as to solve the problem of large volume of tensor fusion model and repeated calculation of intermediate results in data processing. The experimental results show that the proposed algorithm can effectively reduce the computational complexity and improve the performance compared with traditional data dimension reduction algorithms. The research results can be applied to campus big data analysis and decision-making. Full article

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13 pages, 6519 KiB

Open AccessArticle

Assessing a Multi-Objective Genetic Algorithm with a Simulated Environment for Energy-Saving of Air Conditioning Systems with User Preferences

by Alejandro Humberto García Ruiz, Salvador Ibarra Martínez, José Antonio Castán Rocha, Jesús David Terán Villanueva, Julio Laria Menchaca, Mayra Guadalupe Treviño Berrones, Mirna Patricia Ponce Flores and Aurelio Alejandro Santiago Pineda

Symmetry 2021, 13(2), 344; https://doi.org/10.3390/sym13020344 - 20 Feb 2021

Cited by 1 | Viewed by 1939

Abstract

Electricity is one of the most important resources for the growth and sustainability of the population. This paper assesses the energy consumption and user satisfaction of a simulated air conditioning system controlled with two different optimization algorithms. The algorithms are a genetic algorithm [...] Read more.

Electricity is one of the most important resources for the growth and sustainability of the population. This paper assesses the energy consumption and user satisfaction of a simulated air conditioning system controlled with two different optimization algorithms. The algorithms are a genetic algorithm (GA), implemented from the state of the art, and a non-dominated sorting genetic algorithm II (NSGA II) proposed in this paper; these algorithms control an air conditioning system considering user preferences. It is worth noting that we made several modifications to the objective function’s definition to make it more robust. The energy-saving optimization is essential to reduce CO2 emissions and economic costs; on the other hand, it is desirable for the user to feel comfortable, yet it will entail a higher energy consumption. Thus, we integrate user preferences with energy-saving on a single weighted function and a Pareto bi-objective problem to increase user satisfaction and decrease electrical energy consumption. To assess the experimentation, we constructed a simulator by training a backpropagation neural network with real data from a laboratory’s air conditioning system. According to the results, we conclude that NSGA II provides better results than the state of the art (GA) regarding user preferences and energy-saving. Full article

(This article belongs to the Special Issue Computational Intelligence and Soft Computing: Recent Applications)

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13 pages, 1366 KiB

Open AccessArticle

Preference for Complexity and Asymmetry Contributes to an Ability to Overcome Structured Imagination: Implications for Creative Perception Paradigm

by Anatoliy V. Kharkhurin and Morteza Charkhabi

Symmetry 2021, 13(2), 343; https://doi.org/10.3390/sym13020343 - 20 Feb 2021

Cited by 5 | Viewed by 2599

Abstract

The study is a part of a research project, which explores the role of creative perception in creative behavior. We operationalized creative behavior as an ability to overcome structured imagination, as measured by the Invented Alien Creature test, and operationalized creative perception as [...] Read more.

The study is a part of a research project, which explores the role of creative perception in creative behavior. We operationalized creative behavior as an ability to overcome structured imagination, as measured by the Invented Alien Creature test, and operationalized creative perception as a preference for complexity and asymmetry, which we assessed using a standard Barron–Welsh Art Scale. Our group of participants was composed of ninety-three undergraduate students from the United Arab Emirates. The degree to which one preferred complexity and asymmetry measurably contributed to their ability to overcome structured imagination. This finding adds another brick to the rising seventh pillar of the creativity construct, namely, creative perception. The article provides a first sketch of the creative perception paradigm. Full article

(This article belongs to the Special Issue Symmetry of Perception and Behaviour)

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18 pages, 627 KiB

Open AccessArticle

Three-Complex Numbers and Related Algebraic Structures

by Wolf-Dieter Richter

Symmetry 2021, 13(2), 342; https://doi.org/10.3390/sym13020342 - 20 Feb 2021

Cited by 6 | Viewed by 1902

Abstract

Three-complex numbers are introduced for using a geometric vector product in the three-dimensional Euclidean vector space

R^{3}

and proving its equivalence with a spherical coordinate product. Based upon the definitions of the geometric power and geometric exponential functions, some Euler-type trigonometric representations [...] Read more.

Three-complex numbers are introduced for using a geometric vector product in the three-dimensional Euclidean vector space

R^{3}

and proving its equivalence with a spherical coordinate product. Based upon the definitions of the geometric power and geometric exponential functions, some Euler-type trigonometric representations of three-complex numbers are derived. Further, a general

l_{2}^{3} -

complex algebraic structure together with its matrix, polynomial and variable basis vector representations are considered. Then, the classes of

l_{p}^{3}

-complex numbers are introduced. As an application, Euler-type formulas are used to construct directional probability laws on the Euclidean unit sphere in

R^{3}

. Full article

(This article belongs to the Section Mathematics)

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14 pages, 5879 KiB

Open AccessArticle

Complexity and Chimera States in a Network of Fractional-Order Laser Systems

by Shaobo He, Hayder Natiq, Santo Banerjee and Kehui Sun

Symmetry 2021, 13(2), 341; https://doi.org/10.3390/sym13020341 - 20 Feb 2021

Cited by 11 | Viewed by 1778

Abstract

By applying the Adams-Bashforth-Moulton method (ABM), this paper explores the complexity and synchronization of a fractional-order laser dynamical model. The dynamics under the variance of derivative order q and parameters of the system have examined using the multiscale complexity algorithm and the bifurcation [...] Read more.

By applying the Adams-Bashforth-Moulton method (ABM), this paper explores the complexity and synchronization of a fractional-order laser dynamical model. The dynamics under the variance of derivative order q and parameters of the system have examined using the multiscale complexity algorithm and the bifurcation diagram. Numerical simulation outcomes demonstrate that the system generates chaos with the decreasing of q. Moreover, this paper designs the coupled fractional-order network of laser systems and subsequently obtains its numerical solution using ABM. These solutions have demonstrated chimera states of the proposed fractional-order laser network. Full article

(This article belongs to the Special Issue Chaotic Systems and Nonlinear Dynamics)

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13 pages, 5244 KiB

Open AccessArticle

Fractional-Order Analysis of Modified Chua’s Circuit System with the Smooth Degree of 3 and Its Microcontroller-Based Implementation with Analog Circuit Design

by Junxia Wang, Li Xiao, Karthikeyan Rajagopal, Akif Akgul, Serdar Cicek and Burak Aricioglu

Symmetry 2021, 13(2), 340; https://doi.org/10.3390/sym13020340 - 19 Feb 2021

Cited by 16 | Viewed by 2652

Abstract

In the paper, we futher consider a fractional-order system from a modified Chua’s circuit system with the smooth degree of 3 proposed by Fu et al. Bifurcation analysis, multistability and coexisting attractors in the the fractional-order modified Chua’s circuit are studied. In addition, [...] Read more.

In the paper, we futher consider a fractional-order system from a modified Chua’s circuit system with the smooth degree of 3 proposed by Fu et al. Bifurcation analysis, multistability and coexisting attractors in the the fractional-order modified Chua’s circuit are studied. In addition, microcontroller-based circuit was implemented in real digital engineering applications by using the fractional-order Chua’s circuit with the piecewise-smooth continuous system. Full article

(This article belongs to the Special Issue Symmetry in Chaotic Systems and Circuits Ⅱ)

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11 pages, 260 KiB

Open AccessArticle

Refinements on Some Classes of Complex Function Spaces

by Ahmed El-Sayed Ahmed

Symmetry 2021, 13(2), 339; https://doi.org/10.3390/sym13020339 - 19 Feb 2021

Cited by 3 | Viewed by 1177

Abstract

Some weighted classes of hyperbolic function spaces are defined and studied in this paper. Finally, by using the chordal metric concept, some investigations for a class of general hyperbolic functions are also given. Full article

12 pages, 1880 KiB

Open AccessArticle

Evolutive 3D Modeling: A Proposal for a New Generative Design Methodology

by Jaime Nebot, Juan A. Peña and Carmelo López Gómez

Symmetry 2021, 13(2), 338; https://doi.org/10.3390/sym13020338 - 19 Feb 2021

Cited by 1 | Viewed by 2962

Abstract

At present, traditional 3D modeling programs consist of a set of tools that reflect conventional means of mechanical manufacturing and have limitations in relation with the current manufacturing capacities. On the other hand, organic and morphing 3D modeling programs are designed to transform [...] Read more.

At present, traditional 3D modeling programs consist of a set of tools that reflect conventional means of mechanical manufacturing and have limitations in relation with the current manufacturing capacities. On the other hand, organic and morphing 3D modeling programs are designed to transform a model from one known shape to another also known shape. Generative design helps the designers to detach themselves during the design process and can provide them with completely unexpected geometrical solutions. In this paper, starting from 3D morphing techniques and genetic algorithms, a new methodology of product shape definition is developed, capable of imitating processes that occur in nature and aimed at creating new and different product designs. This methodology enables to overcome the limitations imposed by design fixation and allows better exploitation of the great possibilities granted by the new manufacturing techniques, most notably additive manufacturing. The initial process of research and information gathering gives this work a solid basis to develop the new methodology. The results of this initial process are briefly resumed in this paper in order to explain the main motivation for developing this work. The workflow of this methodology is presented as a theoretical process, since its implementation has not been, at least for the moment, put into practice. Before presenting the conclusion for this proposal, several examples have been formulated in order to help the reader to catch the point of the entire process. Full article

(This article belongs to the Special Issue Advances on Engineering Graphics: Improvements and New Proposals)

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12 pages, 1288 KiB

Open AccessArticle

Quantum Universe, Horizon, and Antimatter

by Alexey V. Melkikh

Symmetry 2021, 13(2), 337; https://doi.org/10.3390/sym13020337 - 19 Feb 2021

Viewed by 1638

Abstract

If the isolated system of bosons and fermions was initially in a pure maximally entangled quantum state, then, as a result of decoherence caused by the creation and annihilation of particles, this system not only enters a mixed state but also achieves equilibrium. [...] Read more.

If the isolated system of bosons and fermions was initially in a pure maximally entangled quantum state, then, as a result of decoherence caused by the creation and annihilation of particles, this system not only enters a mixed state but also achieves equilibrium. The time of such a transition does not depend on the size of the system but is determined only by the properties of the particles. This phenomenon allows the problem of the horizon (the homogeneity of the universe) to be solved, since the transition time of different parts of the universe (if they were originally entangled with each other) to equilibrium will not depend on their sizes, and the speed of the interaction may be greater than the speed of light. Based on the decay of entangled states, the problem of the predominance of matter over antimatter in the universe can also be solved. Full article

(This article belongs to the Section Physics)

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13 pages, 864 KiB

Open AccessArticle

Research of Trajectory Optimization Approaches in Synthesized Optimal Control

by Askhat Diveev and Elizaveta Shmalko

Symmetry 2021, 13(2), 336; https://doi.org/10.3390/sym13020336 - 18 Feb 2021

Viewed by 1467

Abstract

This article presents a study devoted to the emerging method of synthesized optimal control. This is a new type of control based on changing the position of a stable equilibrium point. The object stabilization system forces the object to move towards the equilibrium [...] Read more.

This article presents a study devoted to the emerging method of synthesized optimal control. This is a new type of control based on changing the position of a stable equilibrium point. The object stabilization system forces the object to move towards the equilibrium point, and by changing its position over time, it is possible to bring the object to the desired terminal state with the optimal value of the quality criterion. The implementation of such control requires the construction of two control contours. The first contour ensures the stability of the control object relative to some point in the state space. Methods of symbolic regression are applied for numerical synthesis of a stabilization system. The second contour provides optimal control of the stable equilibrium point position. The present paper provides a study of various approaches to find the optimal location of equilibrium points. A new problem statement with the search of function for optimal location of the equilibrium points in the second stage of the synthesized optimal control approach is formulated. Symbolic regression methods of solving the stated problem are discussed. In the presented numerical example, a piece-wise linear function is applied to approximate the location of equilibrium points. Full article

(This article belongs to the Special Issue 2020 Big Data and Artificial Intelligence Conference)

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18 pages, 8352 KiB

Open AccessArticle

Engineering Graphics for Thermal Assessment: 3D Thermal Data Visualisation Based on Infrared Thermography, GIS and 3D Point Cloud Processing Software

by Daniel Antón and José-Lázaro Amaro-Mellado

Symmetry 2021, 13(2), 335; https://doi.org/10.3390/sym13020335 - 18 Feb 2021

Cited by 12 | Viewed by 3096

Abstract

Engineering graphics are present in the design stage, but also constitute a way to communicate, analyse, and synthesise. In the Architecture-Engineering-Construction sector, graphical data become essential in analysing buildings and constructions throughout their lifecycles, such as in the thermal behaviour assessment of building [...] Read more.

Engineering graphics are present in the design stage, but also constitute a way to communicate, analyse, and synthesise. In the Architecture-Engineering-Construction sector, graphical data become essential in analysing buildings and constructions throughout their lifecycles, such as in the thermal behaviour assessment of building envelopes. Scientific research has addressed the thermal image mapping onto three-dimensional (3D) models for visualisation and analysis. However, the 3D point cloud data creation of buildings’ thermal behaviour directly from rectified infrared thermography (IRT) thermograms is yet to be investigated. Therefore, this paper develops an open-source software graphical method to produce 3D thermal data from IRT images for temperature visualisation and subsequent analysis. This low-cost approach uses both a geographic information system for the thermographic image rectification and the point clouds production, and 3D point cloud processing software. The methodology has been proven useful to obtain, without perspective distortions, 3D thermograms even from non-radiometric raster images. The results also revealed that non-rectangular thermograms enable over 95% of the 3D thermal data generated from IRT against rectangular shapes (over 85%). Finally, the 3D thermal data produced allow further thermal behaviour assessment, including calculating the object’s heat loss and thermal transmittance for diverse applications such as energy audits, restoration, monitoring, or product quality control. Full article

(This article belongs to the Special Issue Advances on Engineering Graphics: Improvements and New Proposals)

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20 pages, 1560 KiB

Open AccessArticle

Assessing Renewable Energy Production Capabilities Using DEA Window and Fuzzy TOPSIS Model

by Chia-Nan Wang, Thanh-Tuan Dang, Hector Tibo and Duy-Hung Duong

Symmetry 2021, 13(2), 334; https://doi.org/10.3390/sym13020334 - 18 Feb 2021

Cited by 51 | Viewed by 5053

Abstract

Climate change and air pollution are among the key drivers of energy transition worldwide. The adoption of renewable resources can act as a peacemaker and give stability regarding the damaging effects of fossil fuels challenging public health as well as the tension made [...] Read more.

Climate change and air pollution are among the key drivers of energy transition worldwide. The adoption of renewable resources can act as a peacemaker and give stability regarding the damaging effects of fossil fuels challenging public health as well as the tension made between countries in global prices of oil and gas. Understanding the potential and capabilities to produce renewable energy resources is a crucial pre-requisite for countries to utilize them and to scale up clean and stable sources of electricity generation. This paper presents a hybrid methodology that combines the data envelopment analysis (DEA) Window model, and fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS) in order to evaluate the capabilities of 42 countries in terms of renewable energy production potential. Based on three inputs (population, total energy consumption, and total renewable energy capacity) and two outputs (gross domestic product and total energy production), DEA window analysis chose the list of potential countries, including Norway, United Kingdom, Kuwait, Australia, Netherlands, United Arab Emirates, United States, Japan, Colombia, and Italy. Following that, the FTOPSIS model pointed out the top three countries (United States, Japan, and Australia) that have the greatest capabilities in producing renewable energies based on five main criteria, which are available resources, energy security, technological infrastructure, economic stability, and social acceptance. This paper aims to offer an evaluation method for countries to understand their potential of renewable energy production in designing stimulus packages for a cleaner energy future, thereby accelerating sustainable development. Full article

(This article belongs to the Section Computer)

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