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Volume 16, September
 
 

Symmetry, Volume 16, Issue 10 (October 2024) – 20 articles

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26 pages, 401 KiB  
Review
A Qualitative Survey on Community Detection Attack Algorithms
by Leyla Tekin and Belgin Ergenç Bostanoğlu
Symmetry 2024, 16(10), 1272; https://doi.org/10.3390/sym16101272 - 26 Sep 2024
Abstract
Community detection enables the discovery of more connected segments of complex networks. This capability is essential for effective network analysis. But, it raises a growing concern about the disclosure of user privacy since sensitive information may be over-mined by community detection algorithms. To [...] Read more.
Community detection enables the discovery of more connected segments of complex networks. This capability is essential for effective network analysis. But, it raises a growing concern about the disclosure of user privacy since sensitive information may be over-mined by community detection algorithms. To address this issue, the problem of community detection attacks has emerged to subtly perturb the network structure so that the performance of community detection algorithms deteriorates. Three scales of this problem have been identified in the literature to achieve different levels of concealment, such as target node, target community, or global attack. A broad range of community detection attack algorithms has been proposed, utilizing various approaches to tackle the distinct requirements associated with each attack scale. However, existing surveys of the field usually concentrate on studies focusing on target community attacks. To be self-contained, this survey starts with an overview of community detection algorithms used on the other side, along with the performance measures employed to evaluate the effectiveness of the community detection attacks. The core of the survey is a systematic analysis of the algorithms proposed across all three scales of community detection attacks to provide a comprehensive overview. The survey wraps up with a detailed discussion related to the research opportunities of the field. Overall, the main objective of the survey is to provide a starting and diving point for scientists. Full article
(This article belongs to the Section Computer)
39 pages, 402 KiB  
Review
Mathematics Serving Economics: A Historical Review of Mathematical Methods in Economics
by Artur Czerwinski
Symmetry 2024, 16(10), 1271; https://doi.org/10.3390/sym16101271 - 26 Sep 2024
Abstract
This paper offers a historical review of the evolution of mathematical methods in economics, tracing their development from the earliest attempts in the 18th century to the sophisticated models of the late 20th century. The study begins by examining the initial integration of [...] Read more.
This paper offers a historical review of the evolution of mathematical methods in economics, tracing their development from the earliest attempts in the 18th century to the sophisticated models of the late 20th century. The study begins by examining the initial integration of mathematical techniques into economic thought, highlighting key milestones that shaped the field. Symmetry concepts are naturally embedded in many of these mathematical frameworks, particularly in the balance and equilibrium found in economic models. Symmetry in economics often reflects proportional relationships and equilibrium conditions that are central to both micro- and macroeconomic analyses. Then, the paper elaborates on the progression of economic growth models, including the foundational Solow–Swan model, which introduced the concept of technological progress (knowledge) as a key factor influencing growth. The review also encompasses the Lucas growth model and the Mankiw–Romer–Weil model, both of which incorporate human capital into the growth equation, highlighting its importance in driving economic development. Finally, the paper addresses the Nonneman–Vanhoudt model, which extends the analysis of growth by integrating multiple types of capital, providing a more comprehensive framework for understanding economic dynamics. By documenting these developments, the paper demonstrates the significant role that mathematical modeling has played in advancing economic theory, providing tools to quantitatively analyze complex economic phenomena and driving the discipline towards greater analytical precision and rigor. This analysis emphasizes how symmetry principles, such as balance between inputs and outputs, equilibrium in supply and demand, and proportionality in growth models, underpin many economic theories. Full article
(This article belongs to the Section Mathematics)
14 pages, 704 KiB  
Article
Correlation between Temperature and the Posture of Transmission Line Towers
by Minzhen Wang, Haihang Gao, Zhigang Wang, Keyu Yue, Caiming Zhong, Guangxin Zhang and Jian Wang
Symmetry 2024, 16(10), 1270; https://doi.org/10.3390/sym16101270 - 26 Sep 2024
Abstract
Ensuring the safety of transmission line towers is vital for human safety, power supply, economic development, and environmental protection. This study specifically examines how temperature affects tower inclination. Multifractal detrended cross-correlation analysis (MF-DCCA) is a combination of multifractal detrended fluctuation analysis (MF-DFA) and [...] Read more.
Ensuring the safety of transmission line towers is vital for human safety, power supply, economic development, and environmental protection. This study specifically examines how temperature affects tower inclination. Multifractal detrended cross-correlation analysis (MF-DCCA) is a combination of multifractal detrended fluctuation analysis (MF-DFA) and DCCA that reveals the multifractal features of two cross-correlated non-stationary signals. This paper adopts the MF-DCCA tool to investigate the cross-correlations between the internal temperature of an inclination sensor device and the posture of a transmission line tower. The tilt angle data in the x- and y-axes are used to measure the posture of the transmission line tower. We start by using Pearson correlation to assess the relationship between temperature and two inclination angles, followed by verifying their correlation with a p-value below 0.05 using first-order linear fitting. We initially assess the multifractal features of three time series using MF-DFA before MF-DCCA analysis. All exhibit multifractal traits with H(2)<0.5, indicating negative persistence, especially notable in the temperature series. Finally, we adopt the MF-DCCA approach to examine the multifractal cross-correlation between tilt-angle time series and temperature time series, and the results indicate the negative persistence of the cross-correlation between the time series. Furthermore, the multifractal cross-correlation of temperature and inclination data on the y-axis was also found to be stronger than on the x-axis based on features of the scaling exponent and symmetry exponent. Full article
(This article belongs to the Special Issue Symmetry and Fractals: Theory and Applications)
20 pages, 415 KiB  
Article
Efficient Graph Algorithms in Securing Communication Networks
by Syed Ahtsham Ul Haq Bokhary, Athar Kharal, Fathia M. Al Samman, Mhassen. E. E. Dalam and Ameni Gargouri
Symmetry 2024, 16(10), 1269; https://doi.org/10.3390/sym16101269 (registering DOI) - 26 Sep 2024
Abstract
This paper presents three novel encryption and decryption schemes based on graph theory that aim to improve security and error resistance in communication networks. The novelty of this work lies in the application of complete bipartite graphs in two of the schemes and [...] Read more.
This paper presents three novel encryption and decryption schemes based on graph theory that aim to improve security and error resistance in communication networks. The novelty of this work lies in the application of complete bipartite graphs in two of the schemes and the Cartesian product of graphs in the third, representing a unique approach to cryptographic algorithm development. Unlike traditional cryptographic methods, these graph-based schemes use structural properties of graphs to achieve robust encryption, providing greater resistance to attacks and corruption. Each scheme is illustrated with detailed examples that show how the algorithms can be successfully implemented. The algorithms are written in standard mathematical notation, making them adaptable for machine implementation and scalable for real-world use. The schemes are also rigorously analyzed and compared in terms of their temporal and spatial complexities, using Big O notation. This comprehensive evaluation focuses on their effectiveness, providing valuable insights into their potential for secure communication in modern networks. Full article
(This article belongs to the Special Issue Symmetry and Graph Theory, 2nd Edition)
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34 pages, 1373 KiB  
Article
Modified Heisenberg Commutation Relations and the Infinite-Square Well Potential: Some Simple Consequences
by Mauricio Contreras González, Roberto Ortiz Herrera and José Mauricio Gonzalez
Symmetry 2024, 16(10), 1268; https://doi.org/10.3390/sym16101268 - 26 Sep 2024
Abstract
We explore some consequences of modifying the usual Heisenberg commutation relations of two simple systems: first, the one-dimensional quantum system given by the infinite square-well potential, and second, the case of a gas of N non-interacting particles in a box of volume V [...] Read more.
We explore some consequences of modifying the usual Heisenberg commutation relations of two simple systems: first, the one-dimensional quantum system given by the infinite square-well potential, and second, the case of a gas of N non-interacting particles in a box of volume V, which permit obtaining analytical solutions. We analyse two possible cases of modified Heisenberg commutation relations: one with a linear and non-linear dependence on the position and another with a linear and quadratic dependence on the momentum. We determine the eigenfunctions, probability densities, and energy eigenvalues for the one-dimensional square well for both deformation cases. For linear and non-linear x deformation dependence, the wave functions and energy levels change substantially when the weight factor associated with the modification term increases. Here, the energy levels are rescaled homogeneously. Instead, for linear and quadratic momentum p deformation dependence, the changes in the energy spectrum depend on the energy level. However, the probability densities are the same as those without any modification. For the non-interacting gas, the position deformation implies that the ideal gas state equation is modified, acquiring the form of a virial expansion in the volume, whereas the internal energy is unchanged. Instead, the ideal gas state equation remains unchanged at the lowest order in β for the momentum modification case. However, the temperature modifies the internal energy at the lowest order in β. Thus, this study indicates that gravity could generate forces on particles by modifying the Heisenberg commutation relations. Therefore, gravitation could be the cause of the other three forces of nature. Full article
(This article belongs to the Section Physics)
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13 pages, 321 KiB  
Article
On the Spectral Redundancy of Pineapple Graphs
by Pawan Kumar, Siddique Merajuddin, Shariefuddin Pirzada and Yilun Shang
Symmetry 2024, 16(10), 1267; https://doi.org/10.3390/sym16101267 - 26 Sep 2024
Abstract
In this article, we explore the concept of spectral redundancy within the class of pineapple graphs, denoted as P(α,β). These graphs are constructed by attaching β pendent edges to a single vertex of a complete graph [...] Read more.
In this article, we explore the concept of spectral redundancy within the class of pineapple graphs, denoted as P(α,β). These graphs are constructed by attaching β pendent edges to a single vertex of a complete graph Kα. A connected graph G earns the title of being spectrally non-redundant if the spectral radii of its connected induced subgraphs are all distinct. Spectral redundancy, on the other hand, arises when there is a repetition of spectral radii among the connected induced subgraphs within G. Our study analyzes the adjacency spectrum of P(α,β), identifying distinct eigenvalues such as 0, 1, along with other positive and negative eigenvalues. Our investigation focuses on determining the spectral redundancy within this class of graphs, shedding light on their unique structural properties and implications for graph theory. Understanding spectral redundancy in these graphs is crucial for applications in network design, where distinct spectral radii can indicate different connectivity patterns and resilience features. Full article
(This article belongs to the Section Mathematics)
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20 pages, 10041 KiB  
Article
Deformation and Stress of Rock Masses Surrounding a Tunnel Shaft Considering Seepage and Hard Brittleness Damage
by Zhenping Zhao, Jianxun Chen, Tengfei Fang, Weiwei Liu, Yanbin Luo, Chuanwu Wang, Jialiang Dong, Jian Li, Heqi Wang and Dengxia Huang
Symmetry 2024, 16(10), 1266; https://doi.org/10.3390/sym16101266 - 26 Sep 2024
Abstract
The mechanical and deformation behaviors of the surrounding rock play a crucial role in the structural safety and stability of tunnel shafts. During drilling and blasting construction, seepage failure and hard brittleness damage of the surrounding rock occur frequently. However, previous discussions on [...] Read more.
The mechanical and deformation behaviors of the surrounding rock play a crucial role in the structural safety and stability of tunnel shafts. During drilling and blasting construction, seepage failure and hard brittleness damage of the surrounding rock occur frequently. However, previous discussions on stress deformation in the surrounding rock did not consider these two factors. This paper adopts the theory of elastoplastic to analyze the effects of seepage and hard brittleness damage on the stress and deformation of the surrounding rock of a tunnel shaft. The seepage effect is equivalent to the volumetric force, and a mechanical model of the surrounding rock considering seepage and hard brittleness damage was established. An elastoplastic analytical formula for surrounding rock was derived, and its rationality was verified through numerical examples. Based on these findings, this study revealed the plastic zone as well as stress and deformation laws governing the behavior of surrounding rock. The results showed that the radius of a plastic zone had a significant increase under high geostress conditions, considering the hard brittleness damage characteristics of the surrounding rock. The radius of the plastic zone increased with an increase in the initial water pressure and pore pressure coefficient, and the radius of the plastic zone increased by 5.5% and 3.8% for each 0.2 MPa increase in initial water pressure and 0.2 increase in pore pressure coefficient, respectively. Comparing the significant effects of various factors on the radius of the plastic zone, the effect of support resistance inhibition was the most significant, the effect of the seepage parameter promotion was the second, and the effect of the hard brittleness index promotion was relatively poor. The hard brittleness index and water pressure parameters were positively correlated with the tangential and radial stresses in the surrounding rock, and the radial stresses were overall smaller than the tangential stresses. The deformation of the surrounding rock was twice as large as the initial one when hard brittleness damage and seepage acted together. These findings can provide a reference for the stability evaluation of the surrounding rock in tunnel shafts. Full article
(This article belongs to the Special Issue Symmetry in Civil Transportation Engineering)
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14 pages, 743 KiB  
Article
Modeling and Dynamic Analysis of Algae–Fish Model with Two State-Dependent Impulse Controls
by Ying Liu, Yuan Zhuang, Qiong Liu and Lizhuang Huang
Symmetry 2024, 16(10), 1265; https://doi.org/10.3390/sym16101265 - 26 Sep 2024
Abstract
In ecological modeling, symmetry can manifest in multiple ways, significantly contributing to our understanding of ecosystem stability, species interactions, and ecological balance. Considering the bloom phenomenon caused by excessive algae in ponds and its impact on aquaculture, we establish a class of algae–fish [...] Read more.
In ecological modeling, symmetry can manifest in multiple ways, significantly contributing to our understanding of ecosystem stability, species interactions, and ecological balance. Considering the bloom phenomenon caused by excessive algae in ponds and its impact on aquaculture, we establish a class of algae–fish ecological models with two state-dependent impulse controls. In this paper, we first discuss the existence of positive equilibria in the system without impulses. Second, the existence and asymptotic stability of the order-1 and order-2 periodic solutions are analyzed by applying successor functions and a Similar Poincare Criterion. Finally, numerical simulations demonstrate that the model exhibits order-1 and order-2 periodic solutions, clarifying that the system with two impulses can address the problem more effectively. Full article
(This article belongs to the Section Mathematics)
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21 pages, 5421 KiB  
Article
A Novel Detection Algorithm for the Icing Status of Transmission Lines
by Dongxu Dai, Yan Hu, Hao Qian, Guoqiang Qi and Yan Wang
Symmetry 2024, 16(10), 1264; https://doi.org/10.3390/sym16101264 - 25 Sep 2024
Viewed by 215
Abstract
As more and more transmission lines need to pass through areas with heavy icing, the problem of transmission line faults caused by ice and snow disasters frequently occurs. Existing ice coverage monitoring methods have defects such as the use of a single monitoring [...] Read more.
As more and more transmission lines need to pass through areas with heavy icing, the problem of transmission line faults caused by ice and snow disasters frequently occurs. Existing ice coverage monitoring methods have defects such as the use of a single monitoring type, low accuracy of monitoring results, and an inability to obtain ice coverage data over time. Therefore, this study proposes a new algorithm for detecting the icing status of transmission lines. The algorithm uses two-dimensional multifractal detrended fluctuation analysis (2D MF-DFA) to determine the optimal sliding-window size and wave function and accurately segment and extract local feature areas. Based on the local Hurst exponent (Lh(z)) and the power-law relationship between the fluctuation function and the scale at multiple continuous scales, the ice-covered area of a transmission conductor was accurately detected. By analyzing and calculating the key target pixels, the icing thickness was accurately measured, achieving accurate detection of the icing status of the transmission lines. The experimental results show that this method can accurately detect ice-covered areas and the icing thickness of transmission lines under various working conditions, providing a strong guarantee for the safe and reliable operation of transmission lines under severe weather conditions. Full article
(This article belongs to the Special Issue Symmetry and Fractals: Theory and Applications)
33 pages, 14062 KiB  
Article
Parametric Characterization of Nonlinear Optical Susceptibilities in Four-Wave Mixing: Solvent and Molecular Structure Effects
by José L. Paz, Alberto Garrido-Schaeffer, Marcos A. Loroño, Lenin González-Paz, Edgar Márquez, José R. Mora and Ysaias J. Alvarado
Symmetry 2024, 16(10), 1263; https://doi.org/10.3390/sym16101263 - 25 Sep 2024
Viewed by 258
Abstract
We study the nonlinear absorptive and dispersive optical properties of molecular systems immersed in a thermal reservoir interacting with a four-wave mixing (FWM) signal. Residual spin-orbit Hamiltonians are considered in order to take into account the internal structure of the molecule. As system [...] Read more.
We study the nonlinear absorptive and dispersive optical properties of molecular systems immersed in a thermal reservoir interacting with a four-wave mixing (FWM) signal. Residual spin-orbit Hamiltonians are considered in order to take into account the internal structure of the molecule. As system parameters in the dissipation processes, transverse and longitudinal relaxation times are considered for stochastic solute–solvent interaction processes. The intramolecular coupling effects on the optical responses are studied using a molecule model consisting of two coupled harmonic curves of electronic energies with displaced minima in nuclear energies and positions. In this study, the complete frequency space is considered through the pump–probe detuning, without restricting the derivations to only maximums of population oscillations. This approach opens the possibility of studying the behavior of optical responses, which is very useful in experimental design. Our results indicate the sensitivity of the optical responses to parameters of the molecular structure as well as to those derived from the photonic process of FWM signal generation. Full article
(This article belongs to the Section Physics)
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15 pages, 5543 KiB  
Article
Reflective Adversarial Attacks against Pedestrian Detection Systems for Vehicles at Night
by Yuanwan Chen, Yalun Wu, Xiaoshu Cui, Qiong Li, Jiqiang Liu and Wenjia Niu
Symmetry 2024, 16(10), 1262; https://doi.org/10.3390/sym16101262 - 25 Sep 2024
Viewed by 195
Abstract
The advancements in deep learning have significantly enhanced the accuracy and robustness of pedestrian detection. However, recent studies reveal that adversarial attacks can exploit the vulnerabilities of deep learning models to mislead detection systems. These attacks are effective not only in digital environments [...] Read more.
The advancements in deep learning have significantly enhanced the accuracy and robustness of pedestrian detection. However, recent studies reveal that adversarial attacks can exploit the vulnerabilities of deep learning models to mislead detection systems. These attacks are effective not only in digital environments but also pose significant threats to the reliability of pedestrian detection systems in the physical world. Existing adversarial attacks targeting pedestrian detection primarily focus on daytime scenarios and are easily noticeable by road observers. In this paper, we propose a novel adversarial attack method against vehicle–pedestrian detection systems at night. Our approach utilizes reflective optical materials that can effectively reflect light back to its source. We optimize the placement of these reflective patches using the particle swarm optimization (PSO) algorithm and deploy patches that blend with the color of pedestrian clothing in real-world scenarios. These patches remain inconspicuous during the day or under low-light conditions, but at night, the reflected light from vehicle headlights effectively disrupts the vehicle’s pedestrian detection systems. Considering that real-world detection models are often black-box systems, we propose a “symmetry” strategy, which involves using the behavior of an alternative model to simulate the response of the target model to adversarial patches. We generate adversarial examples using YOLOv5 and apply our attack to various types of pedestrian detection models. Experiments demonstrate that our approach is both effective and broadly applicable. Full article
(This article belongs to the Special Issue Advanced Studies of Symmetry/Asymmetry in Cybersecurity)
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18 pages, 5645 KiB  
Article
Assessing Vulnerabilities in Line Length Parameterization and the Per-Unit-Length Paradigm for Phase Modulation and Figure-of-Merit Evaluation in 60 GHz Liquid Crystal Phase Shifters
by Jinfeng Li and Haorong Li
Symmetry 2024, 16(10), 1261; https://doi.org/10.3390/sym16101261 - 25 Sep 2024
Viewed by 327
Abstract
The figure-of-merit (FoM) is a crucial metric in evaluating liquid crystal (LC) phase shifters, significantly influencing the selection of superior device candidates. This paper identifies, for the first time, a fundamental limitation in the widely-used High-Frequency Structure Simulator (HFSS), a closed-source commercial tool, [...] Read more.
The figure-of-merit (FoM) is a crucial metric in evaluating liquid crystal (LC) phase shifters, significantly influencing the selection of superior device candidates. This paper identifies, for the first time, a fundamental limitation in the widely-used High-Frequency Structure Simulator (HFSS), a closed-source commercial tool, when modeling reconfigurable delay line phase shifters (RDLPS) based on LC at millimeter-wave (mmW) frequencies for Beyond 5G (B5G) and Sixth-Generation (6G) applications. Specifically, the study reveals unreliable predictions of differential phase shifts (DPS) when using the line length parameterization (LLP) approach, with an accuracy of only 47.22%. These LLP-induced inaccuracies lead to misleading FoM calculations, potentially skewing comparative analyses against phase shifters implemented with different geometries or advanced technologies. Additionally, the per-unit-length (PUL) paradigm, commonly employed by microwave circuit engineers for evaluating and optimizing microwave transmission line designs, is also found to have limitations in the context of mmW RDLPS based on LC. The PUL methodology underestimates the FoM by 1.38206°/dB for an LC coaxial RDLPS at 60 GHz. These findings underscore a critical symmetry implication, where the assumed symmetry in phase shift response is violated, resulting in inconsistent performance assessments. To address these challenges, a remediation strategy based on a scenario-based “Length-for-π” (LFP) framework is proposed, offering more accurate performance characterization and enabling better-informed decision-making in mmW phase shifter design. Full article
(This article belongs to the Special Issue Feature Papers in Section "Engineering and Materials" 2024)
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15 pages, 273 KiB  
Article
Some Properties of Reduced Biquaternion Tensors
by Ting-Ting Liu and Shao-Wen Yu
Symmetry 2024, 16(10), 1260; https://doi.org/10.3390/sym16101260 - 25 Sep 2024
Viewed by 223
Abstract
Compared to quaternions, reduced biquaternions satisfy the multiplication commutative rule and are widely employed in applications such as image processing, fuzzy recognition, image compression, and digital signal processing. However, there is little information available regarding reduced biquaternion tensors; thus, in this study, we [...] Read more.
Compared to quaternions, reduced biquaternions satisfy the multiplication commutative rule and are widely employed in applications such as image processing, fuzzy recognition, image compression, and digital signal processing. However, there is little information available regarding reduced biquaternion tensors; thus, in this study, we investigate some properties of reduced biquaternion tensors. Firstly, we introduce the concept of reduced biquaternion tensors, propose the real and complex representations of reduced biquaternion tensors, and prove several fundamental theorems. Subsequently, we provide the definitions for the eigenvalues and eigentensors of reduced biquaternion tensors and present the Gersˇgorin theorem as it applies to their eigenvalues. Additionally, we establish the relationship between the reduced biquaternion tensor and its complex representation. Notably, the complex representation is a symmetry tensor, which significantly simplifies the process and complexity of solving for eigenvalues. Corresponding numerical examples are also provided in the paper. Furthermore, some special properties of eigenvalues of reduced biquaternion tensors are presented. Full article
(This article belongs to the Section Mathematics)
15 pages, 347 KiB  
Article
Stability Analysis and Stabilization of General Conformable Polynomial Fuzzy Models with Time Delay
by Imen Iben Ammar, Hamdi Gassara, Mohamed Rhaima, Lassaad Mchiri and Abdellatif Ben Makhlouf
Symmetry 2024, 16(10), 1259; https://doi.org/10.3390/sym16101259 - 25 Sep 2024
Viewed by 242
Abstract
This paper introduces a sum-of-squares (S-O-S) approach to Stability Analysis and Stabilization (SAS) of nonlinear dynamical systems described by General Conformable Polynomial Fuzzy (GCPF) models with a time delay. First, we present GCPF models, which are more general compared to the widely recognized [...] Read more.
This paper introduces a sum-of-squares (S-O-S) approach to Stability Analysis and Stabilization (SAS) of nonlinear dynamical systems described by General Conformable Polynomial Fuzzy (GCPF) models with a time delay. First, we present GCPF models, which are more general compared to the widely recognized Takagi–Sugeno Fuzzy (T-SF) models. Then, we establish SAS conditions for these models using a Lyapunov–Krasovskii functional and the S-O-S approach, making the SAS conditions in this work less conservative than the Linear Matrix Inequalities (LMI)-based approach to the T-SF models. In addition, the SAS conditions are found by satisfying S-O-S conditions dependent on membership functions that are reliant on the polynomial fitting approximation algorithm. These S-O-S conditions can be solved numerically using the recently developed SOSTOOLS. To demonstrate the effectiveness and practicality of our approach, two numerical examples are provided to demonstrate the effectiveness and practicality of our approach. Full article
(This article belongs to the Special Issue Symmetry and Its Applications in Automation and Control Systems)
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24 pages, 347 KiB  
Article
The Riemann–Hilbert Approach to the Higher-Order Gerdjikov–Ivanov Equation on the Half Line
by Jiawei Hu and Ning Zhang
Symmetry 2024, 16(10), 1258; https://doi.org/10.3390/sym16101258 - 25 Sep 2024
Viewed by 251
Abstract
The Fokas method exhibits remarkable versatility in solving boundary value problems associated with both linear and nonlinear partial differential equations, particularly when conventional approaches encounter challenges in handling intricate boundary conditions. The existing literature often lacks the incorporation of unconventional boundary conditions, and [...] Read more.
The Fokas method exhibits remarkable versatility in solving boundary value problems associated with both linear and nonlinear partial differential equations, particularly when conventional approaches encounter challenges in handling intricate boundary conditions. The existing literature often lacks the incorporation of unconventional boundary conditions, and this study addresses this issue by extending the application of the Fokas method to the higher-order Gerdjikov-Ivanov equation on the half line (,0]. We have demonstrated the exclusive representation of the potential function u(z,t) in the higher-order Gerdjikov–Ivanov equation through the solution of a Riemann–Hilbert problem. The characteristic function is partitioned on the complex plane, and we obtain the jump matrix between each partition based on the positive and negative values of the partition as well as the spectral matrix determined by the initial data and boundary value data. The findings suggest that the spectral functions are not mutually independent; instead, they conform to a global relationship. The novel aspect of this study is the application of the Fokas method to a previously unexplored case, contributing to the theoretical and practical understanding of complex partial differential equations and filling a gap in the treatment of boundary conditions. Full article
(This article belongs to the Special Issue Symmetry in Integrable Systems and Soliton Theories)
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19 pages, 719 KiB  
Article
Transitions between Localised Patterns with Different Spatial Symmetries in Non-Local Hyperbolic Models for Self-Organised Biological Aggregations
by Thanh Trung Le and Raluca Eftimie
Symmetry 2024, 16(10), 1257; https://doi.org/10.3390/sym16101257 - 25 Sep 2024
Viewed by 208
Abstract
Pattern formation in biological aggregations is a topic of great interest, due to the complex spatial structure of various aggregations of cells/bacteria/animals that can be observed in nature. While many such aggregations look similar at the macroscopic level, they might differ in their [...] Read more.
Pattern formation in biological aggregations is a topic of great interest, due to the complex spatial structure of various aggregations of cells/bacteria/animals that can be observed in nature. While many such aggregations look similar at the macroscopic level, they might differ in their microscopic spatial structure. However, the complexity of the non-linear and sometimes non-local interactions among individuals inside these aggregations makes it difficult to investigate these spatial structures. In this study, we investigate numerically the transitions between different spatial patterns of animal aggregations with various symmetries (even, odd or no symmetry) that characterise the microscopic distribution of individuals inside these aggregations. To this end, we construct a bifurcation diagram starting with perturbations of spatially homogeneous solutions with low, medium, and high amplitudes. For perturbations with low amplitudes, the bifurcating structures show transitions among even-symmetric, odd-symmetric, and non-symmetric solutions. For perturbations with large amplitudes, there are wide parameter regions with non-convergent solutions, characterised by oscillatory transitions between different relatively similar solutions. These numerical results emphasize: (i) the effect of nonlinear and non-local interactions on the microscopically different symmetric/non-symmetric structures of macroscopically similar ecological aggregations; (ii) the difficulty of developing continuation algorithms for this class of non-local models. Full article
(This article belongs to the Special Issue Mathematical Modeling in Biology and Life Sciences)
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18 pages, 4432 KiB  
Article
Research on Heave Compensation System Based on Switched Reluctance Motor
by Juan Chen, Lai Jiang and Xiaoping Zhang
Symmetry 2024, 16(10), 1256; https://doi.org/10.3390/sym16101256 - 25 Sep 2024
Viewed by 220
Abstract
Aiming at the requirements of the marine work platform for real-time control, time-varying speed and the time-varying torque control of the motor-driven active heave compensation device, this paper introduces a composite control strategy based on the switched reluctance motor (SRM)-driven active heave compensation [...] Read more.
Aiming at the requirements of the marine work platform for real-time control, time-varying speed and the time-varying torque control of the motor-driven active heave compensation device, this paper introduces a composite control strategy based on the switched reluctance motor (SRM)-driven active heave compensation device. As for the compensation error caused by the time lag in the real-time system, the model prediction trajectory algorithm is used to predict the compensation displacement obtained using the dynamic model. The next time, the control parameters are then provided for the SRM control system in advance to reduce the compensation error. The SRM control strategy selects a double closed-loop compound control strategy of Back Propagation (BP) fuzzy neural network Proportion Integration Differentiation (PID) control. Its outer speed loop uses a fuzzy controller to quickly track a wide range of speed changes. The torque inner loop uses BP neural network adaptive PID control. This helps to reduce torque ripple and to ensure that the electromagnetic torque output of the SRM remains stable. Finally, the system feasibility is verified by setting different wave parameters. The simulation results show that the simulation conditions can reach 97.5% and 96.4% under the 3 and 4 wave levels, respectively. The simulation effect is satisfying, which verifies the feasibility of the proposed scheme. Full article
(This article belongs to the Special Issue Research on Fuzzy Logic and Mathematics with Applications II)
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31 pages, 5528 KiB  
Article
An Enhanced Symmetric Sand Cat Swarm Optimization with Multiple Strategies for Adaptive Infinite Impulse Response System Identification
by Chengtao Du, Jinzhong Zhang and Jie Fang
Symmetry 2024, 16(10), 1255; https://doi.org/10.3390/sym16101255 - 24 Sep 2024
Viewed by 347
Abstract
An infinite impulse response (IIR) system might comprise a multimodal error surface and accurately discovering the appropriate filter parameters for system modeling remains complicated. The swarm intelligence algorithms facilitate the IIR filter’s parameters by exploring parameter domains and exploiting acceptable filter sets. This [...] Read more.
An infinite impulse response (IIR) system might comprise a multimodal error surface and accurately discovering the appropriate filter parameters for system modeling remains complicated. The swarm intelligence algorithms facilitate the IIR filter’s parameters by exploring parameter domains and exploiting acceptable filter sets. This paper presents an enhanced symmetric sand cat swarm optimization with multiple strategies (MSSCSO) to achieve adaptive IIR system identification. The principal objective is to recognize the most appropriate regulating coefficients and to minimize the mean square error (MSE) between an unidentified system’s input and the IIR filter’s output. The MSSCSO with symmetric cooperative swarms integrates the ranking-based mutation operator, elite opposition-based learning strategy, and simplex method to capture supplementary advantages, disrupt regional extreme solutions, and identify the finest potential solutions. The MSSCSO not only receives extensive exploration and exploitation to refrain from precocious convergence and foster computational efficiency; it also endures robustness and reliability to facilitate demographic variability and elevate estimation precision. The experimental results manifest that the practicality and feasibility of the MSSCSO are superior to those of other methods in terms of convergence speed, calculation precision, detection efficiency, regulating coefficients, and MSE fitness value. Full article
(This article belongs to the Section Engineering and Materials)
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14 pages, 6886 KiB  
Article
COMSOL-Based Simulation of Microwave Heating of Al2O3/SiC Composites with Parameter Variations
by Guo Li and Jian Zhou
Symmetry 2024, 16(10), 1254; https://doi.org/10.3390/sym16101254 - 24 Sep 2024
Viewed by 249
Abstract
The process of microwave heating involves the coupling of multiple physical phenomena, specifically including the distribution of the electromagnetic field in the resonant cavity. The electromagnetic effect generates heat and encourages the transfer of heat inside the material. In this numerical study, a [...] Read more.
The process of microwave heating involves the coupling of multiple physical phenomena, specifically including the distribution of the electromagnetic field in the resonant cavity. The electromagnetic effect generates heat and encourages the transfer of heat inside the material. In this numerical study, a 3D computer model of microwave heating of Al2O3/SiC composites using a multimode microwave heating chamber was established based on the simulation software COMSOL Multiphysics 5.6, and the symmetry treatment of the model was carried out, which effectively reduced the amount of model calculations and accurately analyzed the microwave heating characteristics of the samples. The analysis of the microwave heating characteristics of the sample was mainly preformed from the perspective of the electric field distribution in the resonant cavity, the sample heating rate and the sample heating uniformity, and then it was determined how the microwave source power and sample mold selection affect the temperature and electric field parameters of the sample. After experimental verification, the error between the simulation results and the temperature parameters obtained from the actual experiments is less than 2%. This study contributes to further understanding the heating behavior of Al2O3/SiC composites in complex multimode microwave heating environments and can be used to control the dynamic parameters during microwave heating in order to improve the heating rate and heating uniformity of samples. Full article
(This article belongs to the Section Engineering and Materials)
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19 pages, 5022 KiB  
Article
Authentication Framework for Augmented Reality with Data-Hiding Technique
by Chia-Chen Lin, Aristophane Nshimiyimana, Morteza SaberiKamarposhti and Ersin Elbasi
Symmetry 2024, 16(10), 1253; https://doi.org/10.3390/sym16101253 - 24 Sep 2024
Viewed by 300
Abstract
Currently, most existing research on the security of augmented reality (AR) primarily focuses on user-to-user or user-to-infrastructure authentication, aiming to establish secure communication and prevent potential attacks, such as man-in-the-middle attacks, among others. AR techniques enable users to interact with virtual information and [...] Read more.
Currently, most existing research on the security of augmented reality (AR) primarily focuses on user-to-user or user-to-infrastructure authentication, aiming to establish secure communication and prevent potential attacks, such as man-in-the-middle attacks, among others. AR techniques enable users to interact with virtual information and objects within the real environment. However, creating virtual objects can be time-consuming, and unfortunately, malicious individuals may unlawfully copy these objects and integrate them into their own AR scenarios. It is essential to authenticate whether AR objects and the associated content they interact with are legitimately integrated. This paper proposes a novel method for authenticating AR-delivered content using data-hiding techniques with the symmetric property. The proposed method utilizes data hiding to embed data within the content that AR objects interact with, enabling the identification of illegal and tampered AR objects. A scenario involving an AR e-book is defined, and two data-hiding methods are applied to this scenario. The experimental results demonstrate that both data-hiding methods effectively identify the tampered image page of an AR e-book under different tone versions, new trigger image(s) added, or new image(s) replacement. Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Information Security and Network Security)
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