Next Issue
Volume 12, January-2
Previous Issue
Volume 11, December-2
 
 

Mathematics, Volume 12, Issue 1 (January-1 2024) – 168 articles

Cover Story (view full-size image): The authors introduce a novel option pricing model by adding stochastic interest rates and pure jump Lévy processes to an underlying price process driven by stochastic string shocks. They consider four different jump processes leading to different versions of the model: lognormal and double-exponential jump diffusions, CGMY, and generalized hyperbolic Lévy motion. In each case, they obtain closed or semi-closed form expressions for European call option prices. Moreover, they empirically evaluate the model's performance against S&P 500 call options. The findings indicate that (a) model performance is enhanced with the inclusion of jumps; (b) the model outperforms the alternative models with the same jumps; and (c) the model with CGMY jump offers the best fit across volatility regimes. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
20 pages, 4598 KiB  
Article
Ship Infrared Automatic Target Recognition Based on Bipartite Graph Recommendation: A Model-Matching Method
by Haoxiang Zhang, Chao Liu, Jianguang Ma and Hui Sun
Mathematics 2024, 12(1), 168; https://doi.org/10.3390/math12010168 - 4 Jan 2024
Viewed by 834
Abstract
Deep learning technology has greatly propelled the development of intelligent and information-driven research on ship infrared automatic target recognition (SIATR). In future scenarios, there will be various recognition models with different mechanisms to choose from. However, in complex and dynamic environments, ship infrared [...] Read more.
Deep learning technology has greatly propelled the development of intelligent and information-driven research on ship infrared automatic target recognition (SIATR). In future scenarios, there will be various recognition models with different mechanisms to choose from. However, in complex and dynamic environments, ship infrared (IR) data exhibit rich feature space distribution, resulting in performance variations among SIATR models, thus preventing the existence of a universally superior model for all recognition scenarios. In light of this, this study proposes a model-matching method for SIATR tasks based on bipartite graph theory. This method establishes evaluation criteria based on recognition accuracy and feature learning credibility, uncovering the underlying connections between IR attributes of ships and candidate models. The objective is to selectively recommend the optimal candidate model for a given sample, enhancing the overall recognition performance and applicability of the model. We separately conducted tests for the optimization of accuracy and credibility on high-fidelity simulation data, achieving Accuracy and EDMS (our credibility metric) of 95.86% and 0.7781. Our method improves by 1.06% and 0.0274 for each metric compared to the best candidate models (six in total). Subsequently, we created a recommendation system that balances two tasks, resulting in improvements of 0.43% (accuracy) and 0.0071 (EDMS). Additionally, considering the relationship between model resources and performance, we achieved a 28.35% reduction in memory usage while realizing enhancements of 0.33% (accuracy) and 0.0045 (EDMS). Full article
(This article belongs to the Section Computational and Applied Mathematics)
Show Figures

Figure 1

17 pages, 362 KiB  
Article
Finite Difference Models of Dynamical Systems with Quadratic Right-Hand Side
by Mikhail Malykh, Mark Gambaryan, Oleg Kroytor and Alexander Zorin
Mathematics 2024, 12(1), 167; https://doi.org/10.3390/math12010167 - 4 Jan 2024
Viewed by 734
Abstract
Difference schemes that approximate dynamic systems are considered discrete models of the same phenomena that are described by continuous dynamic systems. Difference schemes with t-symmetry and midpoint and trapezoid schemes are considered. It is shown that these schemes are dual to each [...] Read more.
Difference schemes that approximate dynamic systems are considered discrete models of the same phenomena that are described by continuous dynamic systems. Difference schemes with t-symmetry and midpoint and trapezoid schemes are considered. It is shown that these schemes are dual to each other, and, from this fact, we derive theorems on the inheritance of quadratic integrals by these schemes (Cooper’s theorem and its dual theorem on the trapezoidal scheme). Using examples of nonlinear oscillators, it is shown that these schemes poses challenges for theoretical research and practical application due to the problem of extra roots: these schemes do not allow one to unambiguously determine the final values from the initial values and vice versa. Therefore, we consider difference schemes in which the transitions from layer to layer in time are carried out using birational transformations (Cremona transformations). Such schemes are called reversible. It is shown that reversible schemes with t-symmetry can be easily constructed for any dynamical system with a quadratic right-hand side. As an example of such a dynamic system, a top fixed at its center of gravity is considered in detail. In this case, the discrete theory repeats the continuous theory completely: (1) the points of the approximate solution lie on some elliptic curve, which at Δt0 turns into an integral curve; (2) the difference scheme can be represented using quadrature; and (3) the approximate solution can be represented using an elliptic function of a discrete argument. The last section considers the general case. The integral curves are replaced with closures of the orbits of the corresponding Cremona transformation as sets in the projective space over R. The problem of the dimension of this set is discussed. Full article
(This article belongs to the Section Dynamical Systems)
Show Figures

Figure 1

20 pages, 343 KiB  
Article
Cohomology and Deformations of Relative Rota–Baxter Operators on Lie-Yamaguti Algebras
by Jia Zhao and Yu Qiao
Mathematics 2024, 12(1), 166; https://doi.org/10.3390/math12010166 - 4 Jan 2024
Viewed by 718
Abstract
In this paper, we establish the cohomology of relative Rota–Baxter operators on Lie-Yamaguti algebras via the Yamaguti cohomology. Then, we use this type of cohomology to characterize deformations of relative Rota–Baxter operators on Lie-Yamaguti algebras. We show that if two linear or formal [...] Read more.
In this paper, we establish the cohomology of relative Rota–Baxter operators on Lie-Yamaguti algebras via the Yamaguti cohomology. Then, we use this type of cohomology to characterize deformations of relative Rota–Baxter operators on Lie-Yamaguti algebras. We show that if two linear or formal deformations of a relative Rota–Baxter operator are equivalent, then their infinitesimals are in the same cohomology class in the first cohomology group. Moreover, an order n deformation of a relative Rota–Baxter operator can be extended to an order n+1 deformation if and only if the obstruction class in the second cohomology group is trivial. Full article
16 pages, 2197 KiB  
Article
Shear Waves in an Elastic Plate with a Hole Resting on a Rough Base
by Anatoly Nikolaevich Filippov
Mathematics 2024, 12(1), 165; https://doi.org/10.3390/math12010165 - 4 Jan 2024
Viewed by 965
Abstract
The article is devoted to the analytical and numerical study of the pattern of propagation and attenuation, due to Coulomb friction, of shear waves in an infinite elastic thin plate with a circular orifice of radius r0 lying on a rough base. [...] Read more.
The article is devoted to the analytical and numerical study of the pattern of propagation and attenuation, due to Coulomb friction, of shear waves in an infinite elastic thin plate with a circular orifice of radius r0 lying on a rough base. Considering the friction forces and their influence on the sample of wave propagation in extended rods or thin plates is important for calculating the stress–strain state in them and the size of the area of motion. An exact analytical solution of a nonlinear boundary value problem for tangential stresses and velocities is obtained in quadratures by the Laplace transform, with respect to time. It turned out that the complete exhaustion of the wave front of a strong rupture occurs at a finite distance r* from the center of the orifice, and an elementary formula is given for this distance (the case of tangential shock stresses suddenly applied to the orifice boundary is considered). For various ratios of the magnitude of the limiting friction force to the amplitude of the applied load, the stopping (trailing) wave fronts are calculated. After passing them, a state of static equilibrium between the elastic and friction forces with a nonlinear distribution of residual stresses is established in the region r0rr*. For the first time, a precise analytical solution was obtained for the boundary value problem of the propagation of elastic shear waves in an infinite isotropic space with a cylindrical cavity, when a tangential shock load is set on its surface. Full article
Show Figures

Figure 1

21 pages, 682 KiB  
Article
GSRec: A Graph-Sequence Recommendation System Based on Reverse-Order Graph and User Embedding
by Xulin Ma, Jiajia Tan, Linan Zhu, Xiaoran Yan and Xiangjie Kong
Mathematics 2024, 12(1), 164; https://doi.org/10.3390/math12010164 - 4 Jan 2024
Viewed by 865
Abstract
At present, sequence-based models have various applications in recommendation systems; these models recommend the interested items of the user according to the user’s behavioral sequence. However, sequence-based models have a limitation of length. When the length of the user’s behavioral sequence exceeds the [...] Read more.
At present, sequence-based models have various applications in recommendation systems; these models recommend the interested items of the user according to the user’s behavioral sequence. However, sequence-based models have a limitation of length. When the length of the user’s behavioral sequence exceeds the limitation of the model, the model cannot take advantage of the complete behavioral sequence of the user and cannot know the user’s holistic interests. The accuracy of the model then goes down. Meanwhile, sequence-based models only pay attention to the sequential signals of the data but do not pay attention to the spatial signals of the data, which will also affect the model’s accuracy. This paper proposes a graph sequence-based model called GSRec that combines Graph Convolutional Network (GCN) and Transformer to solve these problems. In the GCN part we designed a reverse-order graph, and in the Transformer part we introduced the user embedding. The reverse-order graph and the user embedding can make the combination of GCN and Transformer more efficient. Experiments on six datasets show that GSRec outperforms the current state-of-the-art (SOTA) models. Full article
(This article belongs to the Special Issue Applied Network Analysis and Data Science)
Show Figures

Figure 1

14 pages, 372 KiB  
Article
Distributed Interval Observers with Switching Topology Design for Cyber-Physical Systems
by Junchao Zhang, Jun Huang and Changjie Li
Mathematics 2024, 12(1), 163; https://doi.org/10.3390/math12010163 - 4 Jan 2024
Viewed by 618
Abstract
In this paper, the distributed interval estimation problem for networked Cyber-Physical systems suffering from both disturbances and noise is investigated. In the distributed interval observers, there are some connected interval observers built for the corresponding subsystems. Then, due to the communication burden in [...] Read more.
In this paper, the distributed interval estimation problem for networked Cyber-Physical systems suffering from both disturbances and noise is investigated. In the distributed interval observers, there are some connected interval observers built for the corresponding subsystems. Then, due to the communication burden in Cyber-Physical systems, we consider the case where the communication among distributed interval observers is switching topology. A novel approach that combines L methodology with reachable set analysis is proposed to design distributed interval observers. Finally, the performance of the proposed distributed interval observers with switching topology is verified through a simulation example. Full article
(This article belongs to the Special Issue Dynamical System and Stochastic Analysis)
Show Figures

Figure 1

12 pages, 251 KiB  
Article
Empirical-Likelihood-Based Inference for Partially Linear Models
by Haiyan Su and Linlin Chen
Mathematics 2024, 12(1), 162; https://doi.org/10.3390/math12010162 - 4 Jan 2024
Viewed by 570
Abstract
Partially linear models find extensive application in biometrics, econometrics, social sciences, and various other fields due to their versatility in accommodating both parametric and nonparametric elements. This study aims to establish statistical inference for the parametric component effects within these models, employing a [...] Read more.
Partially linear models find extensive application in biometrics, econometrics, social sciences, and various other fields due to their versatility in accommodating both parametric and nonparametric elements. This study aims to establish statistical inference for the parametric component effects within these models, employing a nonparametric empirical likelihood approach. The proposed method involves a projection step to eliminate the nuisance nonparametric component and utilizes an empirical-likelihood-based technique, along with the Bartlett correction, to enhance the coverage probability of the confidence interval for the parameter of interest. This method demonstrates robustness in handling normally and non-normally distributed errors. The proposed empirical likelihood ratio statistic converges to a limiting chi-square distribution under certain regulations. Simulation studies demonstrate that this method provides better inference in terms of coverage probabilities compared to the conventional normal-approximation-based method. The proposed method is illustrated by analyzing the Boston housing data from a real study. Full article
(This article belongs to the Special Issue Parametric and Nonparametric Statistics: From Theory to Applications)
21 pages, 10922 KiB  
Article
An Improved Rock Damage Characterization Method Based on the Shortest Travel Time Optimization with Active Acoustic Testing
by Jing Zhou, Lang Liu, Yuan Zhao, Mengbo Zhu, Ruofan Wang and Dengdeng Zhuang
Mathematics 2024, 12(1), 161; https://doi.org/10.3390/math12010161 - 4 Jan 2024
Viewed by 624
Abstract
Real-time evaluation of the damage location and level of rock mass is essential for preventing underground engineering disasters. However, the heterogeneity of rock mass, which results from the presence of layered rock media, faults, and pores, makes it difficult to characterize the damage [...] Read more.
Real-time evaluation of the damage location and level of rock mass is essential for preventing underground engineering disasters. However, the heterogeneity of rock mass, which results from the presence of layered rock media, faults, and pores, makes it difficult to characterize the damage evolution accurately in real time. To address this issue, an improved method for rock damage characterization is proposed. This method optimizes the solution of the global shortest acoustic wave propagation path in the medium and verifies it with layered and defective media models. Based on this, the relationship between the inversion results of the wave velocity field and the distribution of rock damage is established, thereby achieving quantitative characterization of rock damage distribution and degree. Thus, the improved method is more suitable for heterogeneous rock media. Finally, the proposed method was used to characterize the damage distribution evolution process of rock media during uniaxial compression experiments. The obtained results were compared and analyzed with digital speckle patterns, and the influencing factors during the use of the proposed method are discussed. Full article
Show Figures

Figure 1

16 pages, 12663 KiB  
Article
Modeling Study of Factors Determining Efficacy of Biological Control of Adventive Weeds
by Yuri V. Tyutyunov, Vasily N. Govorukhin and Vyacheslav G. Tsybulin
Mathematics 2024, 12(1), 160; https://doi.org/10.3390/math12010160 - 4 Jan 2024
Viewed by 701
Abstract
We model the spatiotemporal dynamics of a community consisting of competing weed and cultivated plant species and a population of specialized phytophagous insects used as the weed biocontrol agent. The model is formulated as a PDE system of taxis–diffusion–reaction type and computer-implemented for [...] Read more.
We model the spatiotemporal dynamics of a community consisting of competing weed and cultivated plant species and a population of specialized phytophagous insects used as the weed biocontrol agent. The model is formulated as a PDE system of taxis–diffusion–reaction type and computer-implemented for one-dimensional and two-dimensional cases of spatial habitat for the Neumann zero-flux boundary condition. In order to discretize the original continuous system, we applied the method of lines. The obtained system of ODEs is integrated using the Runge–Kutta method with a variable time step and control of the integration accuracy. The numerical simulations provide insights into the mechanism of formation of solitary population waves (SPWs) of the phytophage, revealing the factors that determine the efficacy of combined application of the phytophagous insect (classical biological method) and cultivated plant (phytocenotic method) to suppress weed foci. In particular, the presented results illustrate the stabilizing action of cultivated plants, which fix the SPW effect by occupying the free area behind the wave front so that the weed remains suppressed in the absence of a phytophage. Full article
Show Figures

Figure 1

20 pages, 936 KiB  
Article
Tensor Conjugate Gradient Methods with Automatically Determination of Regularization Parameters for Ill-Posed Problems with t-Product
by Shi-Wei Wang, Guang-Xin Huang and Feng Yin
Mathematics 2024, 12(1), 159; https://doi.org/10.3390/math12010159 - 3 Jan 2024
Viewed by 663
Abstract
Ill-posed problems arise in many areas of science and engineering. Tikhonov is a usual regularization which replaces the original problem by a minimization problem with a fidelity term and a regularization term. In this paper, a tensor t-production structure preserved Conjugate-Gradient (tCG) method [...] Read more.
Ill-posed problems arise in many areas of science and engineering. Tikhonov is a usual regularization which replaces the original problem by a minimization problem with a fidelity term and a regularization term. In this paper, a tensor t-production structure preserved Conjugate-Gradient (tCG) method is presented to solve the regularization minimization problem. We provide a truncated version of regularization parameters for the tCG method and a preprocessed version of the tCG method. The discrepancy principle is used to automatically determine the regularization parameter. Several examples on image and video recover are given to show the effectiveness of the proposed methods by comparing them with some previous algorithms. Full article
Show Figures

Figure 1

14 pages, 345 KiB  
Article
Feedback Stabilization Applied to Heart Rhythm Dynamics Using an Integro-Differential Method
by Asher Yahalom and Natalia Puzanov
Mathematics 2024, 12(1), 158; https://doi.org/10.3390/math12010158 - 3 Jan 2024
Viewed by 937
Abstract
In this paper, we applied a chaos control method based on integro-differential equations for stabilization of an unstable cardiac rhythm, which is described by a variation of the modified Van der Pol equation. Chaos control with this method may be useful for stabilization [...] Read more.
In this paper, we applied a chaos control method based on integro-differential equations for stabilization of an unstable cardiac rhythm, which is described by a variation of the modified Van der Pol equation. Chaos control with this method may be useful for stabilization of irregular heartbeat using a small perturbation. This method differs from other stabilization strategies by the absence of adjustable parameters and the lack of rough approximations in determining control functions whose control parameters are fixed by the properties of the unstable system itself. Full article
(This article belongs to the Special Issue Nonlinear Stochastic Dynamics and Control and Its Applications)
Show Figures

Figure 1

11 pages, 258 KiB  
Article
On Enriched Suzuki Mappings in Hadamard Spaces
by Teodor Turcanu and Mihai Postolache
Mathematics 2024, 12(1), 157; https://doi.org/10.3390/math12010157 - 3 Jan 2024
Viewed by 703
Abstract
We define and study enriched Suzuki mappings in Hadamard spaces. The results obtained here are extending fundamental findings previously established in related research. The extension is realized with respect to at least two different aspects: the setting and the class of involved operators. [...] Read more.
We define and study enriched Suzuki mappings in Hadamard spaces. The results obtained here are extending fundamental findings previously established in related research. The extension is realized with respect to at least two different aspects: the setting and the class of involved operators. More accurately, Hilbert spaces are particular Hadamard spaces, while enriched Suzuki nonexpansive mappings are natural generalizations of enriched nonexpansive mappings. Next, enriched Suzuki nonexpansive mappings naturally contain Suzuki nonexpansive mappings in Hadamard spaces. Besides technical lemmas, the results of this paper deal with (1) the existence of fixed points for enriched Suzuki nonexpansive mappings and (2) Δ and strong (metric) convergence of Picard iterates of the α-averaged mapping, which are exactly Krasnoselskij iterates for the original mapping. Full article
(This article belongs to the Special Issue Fixed Point, Optimization, and Applications II)
17 pages, 459 KiB  
Article
Scale Mixture of Exponential Distribution with an Application
by Jorge A. Barahona, Yolanda M. Gómez, Emilio Gómez-Déniz, Osvaldo Venegas and Héctor W. Gómez
Mathematics 2024, 12(1), 156; https://doi.org/10.3390/math12010156 - 3 Jan 2024
Viewed by 712
Abstract
This article presents an extended distribution that builds upon the exponential distribution. This extension is based on a scale mixture between the exponential and beta distributions. By utilizing this approach, we obtain a distribution that offers increased flexibility in terms of the kurtosis [...] Read more.
This article presents an extended distribution that builds upon the exponential distribution. This extension is based on a scale mixture between the exponential and beta distributions. By utilizing this approach, we obtain a distribution that offers increased flexibility in terms of the kurtosis coefficient. We explore the general density, properties, moments, asymmetry, and kurtosis coefficients of this distribution. Statistical inference is performed using both the moments and maximum likelihood methods. To show the performance of this new model, it is applied to a real dataset with atypical observations. The results indicate that the new model outperforms two other extensions of the exponential distribution. Full article
(This article belongs to the Special Issue Computational Statistical Methods and Extreme Value Theory)
Show Figures

Figure 1

19 pages, 475 KiB  
Article
Generalized Halanay Inequalities and Asymptotic Behavior of Nonautonomous Neural Networks with Infinite Delays
by Dehao Ruan and Yao Lu
Mathematics 2024, 12(1), 155; https://doi.org/10.3390/math12010155 - 3 Jan 2024
Viewed by 587
Abstract
This paper focuses on the asymptotic behavior of nonautonomous neural networks with delays. We establish criteria for analyzing the asymptotic behavior of nonautonomous recurrent neural networks with delays by means of constructing some new generalized Halanay inequalities. We do not require to constructi [...] Read more.
This paper focuses on the asymptotic behavior of nonautonomous neural networks with delays. We establish criteria for analyzing the asymptotic behavior of nonautonomous recurrent neural networks with delays by means of constructing some new generalized Halanay inequalities. We do not require to constructi any complicated Lyapunov function and our results improve some existing works. Lastly, we provide some illustrative examples to demonstrate the effectiveness of the obtained results. Full article
Show Figures

Figure 1

11 pages, 935 KiB  
Article
On the Bessel Solution of Kepler’s Equation
by Riccardo Borghi
Mathematics 2024, 12(1), 154; https://doi.org/10.3390/math12010154 - 3 Jan 2024
Viewed by 753
Abstract
Since its introduction in 1650, Kepler’s equation has never ceased to fascinate mathematicians, scientists, and engineers. Over the course of five centuries, a large number of different solution strategies have been devised and implemented. Among them, the one originally proposed by J. L. [...] Read more.
Since its introduction in 1650, Kepler’s equation has never ceased to fascinate mathematicians, scientists, and engineers. Over the course of five centuries, a large number of different solution strategies have been devised and implemented. Among them, the one originally proposed by J. L. Lagrange and later by F. W. Bessel still continue to be a source of mathematical treasures. Here, the Bessel solution of the elliptic Kepler equation is explored from a new perspective offered by the theory of the Stieltjes series. In particular, it has been proven that a complex Kapteyn series obtained directly by the Bessel expansion is a Stieltjes series. This mathematical result, to the best of our knowledge, is a new integral representation of the KE solution. Some considerations on possible extensions of our results to more general classes of the Kapteyn series are also presented. Full article
Show Figures

Figure 1

22 pages, 18365 KiB  
Article
Instance Segmentation Frustum–PointPillars: A Lightweight Fusion Algorithm for Camera–LiDAR Perception in Autonomous Driving
by Yongsheng Wang, Xiaobo Han, Xiaoxu Wei and Jie Luo
Mathematics 2024, 12(1), 153; https://doi.org/10.3390/math12010153 - 3 Jan 2024
Cited by 1 | Viewed by 1052
Abstract
The fusion of camera and LiDAR perception has become a research focal point in the autonomous driving field. Existing image–point cloud fusion algorithms are overly complex, and processing large amounts of 3D LiDAR point cloud data requires high computational power, which poses challenges [...] Read more.
The fusion of camera and LiDAR perception has become a research focal point in the autonomous driving field. Existing image–point cloud fusion algorithms are overly complex, and processing large amounts of 3D LiDAR point cloud data requires high computational power, which poses challenges for practical applications. To overcome the above problems, herein, we propose an Instance Segmentation Frustum (ISF)–PointPillars method. Within the framework of our method, input data are derived from both a camera and LiDAR. RGB images are processed using an enhanced 2D object detection network based on YOLOv8, thereby yielding rectangular bounding boxes and edge contours of the objects present within the scenes. Subsequently, the rectangular boxes are extended into 3D space as frustums, and the 3D points located outside them are removed. Afterward, the 2D edge contours are also extended to frustums to filter the remaining points from the preceding stage. Finally, the retained points are sent to our improved 3D object detection network based on PointPillars, and this network infers crucial information, such as object category, scale, and spatial position. In pursuit of a lightweight model, we incorporate attention modules into the 2D detector, thereby refining the focus on essential features, minimizing redundant computations, and enhancing model accuracy and efficiency. Moreover, the point filtering algorithm substantially diminishes the volume of point cloud data while concurrently reducing their dimensionality, thereby ultimately achieving lightweight 3D data. Through comparative experiments on the KITTI dataset, our method outperforms traditional approaches, achieving an average precision (AP) of 88.94% and bird’s-eye view (BEV) accuracy of 90.89% in car detection. Full article
Show Figures

Figure 1

33 pages, 9935 KiB  
Article
Computer Model for an Intelligent Adjustment of Weather Conditions Based on Spatial Features for Soil Moisture Estimation
by Luis Pastor Sánchez-Fernández, Diego Alberto Flores-Carrillo and Luis Alejandro Sánchez-Pérez
Mathematics 2024, 12(1), 152; https://doi.org/10.3390/math12010152 - 2 Jan 2024
Cited by 1 | Viewed by 842
Abstract
In this paper, an intelligent weather conditions fuzzy adjustment based on spatial features (IWeCASF) is developed. It is indispensable for our regional soil moisture estimation approach, complementing a point estimation model of soil moisture from the literature. The point estimation model requires the [...] Read more.
In this paper, an intelligent weather conditions fuzzy adjustment based on spatial features (IWeCASF) is developed. It is indispensable for our regional soil moisture estimation approach, complementing a point estimation model of soil moisture from the literature. The point estimation model requires the weather conditions at the point where an estimate is made. Therefore, IWeCASF’s aim is to determine these weather conditions. The procedure begins measuring them at only one checkpoint, called the primary checkpoint. The model determines the weather conditions anywhere within a region through image processing algorithms and fuzzy inference systems. The results are compared with the measurement records and with a spatial interpolation method. The performance is similar to or better than interpolation, especially in the rain, where the model developed is more accurate due to the certainty of replication. Additionally, IWeCASF does not require more than one measurement point. Therefore, it is a more appropriate approach to complement the point estimation model for enabling a regional soil moisture estimation. Full article
(This article belongs to the Special Issue Data Analytics in Intelligent Systems)
Show Figures

Figure 1

20 pages, 798 KiB  
Article
The Synchronisation Problem of Chaotic Neural Networks Based on Saturation Impulsive Control and Intermittent Control
by Zhengran Cao, Chuandong Li and Man-Fai Leung
Mathematics 2024, 12(1), 151; https://doi.org/10.3390/math12010151 - 2 Jan 2024
Cited by 1 | Viewed by 771
Abstract
This paper primarily focuses on the chaos synchronisation analysis of neural networks (NNs) under a hybrid controller. Firstly, we design a suitable hybrid controller with saturated impulse control, combined with time-dependent intermittent control. Both controls are low-energy consumption and discrete, aligning well with [...] Read more.
This paper primarily focuses on the chaos synchronisation analysis of neural networks (NNs) under a hybrid controller. Firstly, we design a suitable hybrid controller with saturated impulse control, combined with time-dependent intermittent control. Both controls are low-energy consumption and discrete, aligning well with industrial development needs. Secondly, the saturation function in the chaotic neural network is addressed using the polyhedral representation method and the sector nonlinearity method, respectively. By integrating the Lyapunov stability theory, Jensen’s inequality, the mathematical induction method, and the inequality reduction technique, we establish suitable time-dependent Lyapunov generalised equations. This leads to the estimation of the domain of attraction and the derivation of local exponential stability conditions for the error system. The validity of the achieved theoretical criteria is eventually demonstrated through numerical experiment simulations. Full article
(This article belongs to the Special Issue Advances and Applications of Artificial Intelligence Technologies)
Show Figures

Figure 1

5 pages, 159 KiB  
Editorial
“Differential Equations of Mathematical Physics and Related Problems of Mechanics”—Editorial 2021–2023
by Hovik A. Matevossian
Mathematics 2024, 12(1), 150; https://doi.org/10.3390/math12010150 - 2 Jan 2024
Viewed by 696
Abstract
Based on the published papers in this Special Issue of the elite scientific journal Mathematics, we herein present the Editorial for “Differential Equations of Mathematical Physics and Related Problems of Mechanics”, the main topics of which are fundamental and applied research on [...] Read more.
Based on the published papers in this Special Issue of the elite scientific journal Mathematics, we herein present the Editorial for “Differential Equations of Mathematical Physics and Related Problems of Mechanics”, the main topics of which are fundamental and applied research on differential equations in mathematical physics and mechanics [...] Full article
22 pages, 306 KiB  
Article
Exact Results for the Distribution of Randomly Weighted Sums
by Thomas Hitchen and Saralees Nadarajah
Mathematics 2024, 12(1), 149; https://doi.org/10.3390/math12010149 - 2 Jan 2024
Viewed by 610
Abstract
Dependent random variables play a crucial role in various fields, from finance and statistics to engineering and environmental sciences. Often, interest lies in understanding the aggregate sum of a collection of dependent variables with random weights. In this paper, we provide a comprehensive [...] Read more.
Dependent random variables play a crucial role in various fields, from finance and statistics to engineering and environmental sciences. Often, interest lies in understanding the aggregate sum of a collection of dependent variables with random weights. In this paper, we provide a comprehensive study of the distribution of the aggregate sum with random weights. Expressions derived include those for the cumulative distribution function, probability density function, conditional expectation, moment generating function, characteristic function, cumulant generating function, moments, variance, skewness, kurtosis, cumulants, value at risk and the expected shortfall. Real data applications are discussed. Full article
Show Figures

Figure 1

29 pages, 5953 KiB  
Article
Analysis of Transmission System Stability with Distribution Generation Supplying Induction Motor Loads
by Minal S. Salunke, Ramesh S. Karnik, Angadi B. Raju and Vinayak N. Gaitonde
Mathematics 2024, 12(1), 148; https://doi.org/10.3390/math12010148 - 2 Jan 2024
Viewed by 784
Abstract
A distributed-power-generating source (DPGS) is intended to locally supply the increased power demand at a load bus. When applied in small amounts, a DPGS offers many technical and economic benefits. However, with large DPGS penetrations, the stability of the transmission system becomes a [...] Read more.
A distributed-power-generating source (DPGS) is intended to locally supply the increased power demand at a load bus. When applied in small amounts, a DPGS offers many technical and economic benefits. However, with large DPGS penetrations, the stability of the transmission system becomes a significant issue. This paper investigates the stability of a transmission system equipped with a DPGS at load centres supplying power to both a constant power (CP) and induction motor (IM) load. The DPGSs considered in the present study are microturbine and diesel turbine power generators (MTGS and DTGS), both interfaced with synchronous generators. The influence of an IM load supplied by the DPGS on small-signal stability is studied by a critical damping ratio analysis. On the other hand, time-domain indicators of the transient response following a short circuit are employed in the analysis. Further, a variance analysis test (VAT) is performed to determine the contribution of IM and CP loads on the system stability. The study revealed that large penetration levels of IM loads significantly affect the stability and depend on the kind of DPGS technology used. Full article
(This article belongs to the Special Issue Modeling, Simulation, and Analysis of Electrical Power Systems)
Show Figures

Figure 1

27 pages, 11944 KiB  
Article
The Co-Processing Combustion Characteristics of Municipal Sludge within an Industrial Cement Decomposition Furnace via Computational Fluid Dynamics
by Ling Zhu, Ya Mao, Kang Liu, Chengguang Tong, Quan Liu and Qiang Xie
Mathematics 2024, 12(1), 147; https://doi.org/10.3390/math12010147 - 2 Jan 2024
Viewed by 632
Abstract
Dealing with municipal sludge in an effective way is crucial for urban development and environmental protection. Co-processing the sludge by burning it in a decomposition furnace in the cement production line has been found to be a viable solution. This work aims to [...] Read more.
Dealing with municipal sludge in an effective way is crucial for urban development and environmental protection. Co-processing the sludge by burning it in a decomposition furnace in the cement production line has been found to be a viable solution. This work aims to analyze the effects of the co-disposal of municipal sludge on the decomposition reactions and NOx emissions in the decomposing furnaces. Specifically, a practical 6000 t/d decomposition furnace was taken as the research object. To achieve this, ANSYS FLUENT with a UDF (user-defined function) was applied to establish a numerical model coupling the limestone decomposition reaction, fuel combustion, and NOx generation and reduction reactions. The flow, temperature, and component field distributions within the furnace with no sludge were firstly simulated with this model. Compared with site test results, the model was validated. Then, with sludge involved, the structure and operation parameters of the decomposition furnace for the co-disposal of municipal sludge were investigated by simulating the flow field, temperature field, and component field distributions. Parametric studies were carried out in three perspectives, i.e., sludge mixing ratio, preheating furnace arrangement height, and sludge particle size. The results show that all three aspects have great importance in the discomposing process. A set of preferable values, including a sludge mixing ratio of 10%, preheating furnace height of 21.5 m, and sludge particle diameter of 1.0 mm, was obtained, which resulted in a raw material decomposition rate of 89.9% and a NO volume fraction of 251 ppm at the furnace outlet. Full article
(This article belongs to the Special Issue CFD Simulation of Heat Transfer and Applications)
Show Figures

Figure 1

25 pages, 439 KiB  
Article
Merging Intuitionistic and De Morgan Logics
by Minghui Ma and Juntong Guo
Mathematics 2024, 12(1), 146; https://doi.org/10.3390/math12010146 - 2 Jan 2024
Viewed by 1079
Abstract
We introduce De Morgan Heyting logic for Heyting algebras with De Morgan negation (DH-algebras). The variety DH of all DH-algebras is congruence distributive. The lattice of all subvarieties of DH is distributive. We show the discrete dualities between De Morgan frames and DH-algebras. [...] Read more.
We introduce De Morgan Heyting logic for Heyting algebras with De Morgan negation (DH-algebras). The variety DH of all DH-algebras is congruence distributive. The lattice of all subvarieties of DH is distributive. We show the discrete dualities between De Morgan frames and DH-algebras. The Kripke completeness and finite approximability of some DH-logics are proven. Some conservativity of DH expansion of a Kripke complete superintuitionistic logic is shown by the construction of frame expansion. Finally, a cut-free terminating Gentzen sequent calculus for the DH-logic of De Morgan Boolean algebras is developed. Full article
(This article belongs to the Special Issue Algebraic Modal Logic and Proof Theory)
Show Figures

Figure 1

32 pages, 4663 KiB  
Article
Influence of Homo- and Hetero-Junctions on the Propagation Characteristics of Radially Propagated Cylindrical Surface Acoustic Waves in a Piezoelectric Semiconductor Semi-Infinite Medium
by Xiao Guo, Yilin Wang, Chunyu Xu, Zibo Wei and Chenxi Ding
Mathematics 2024, 12(1), 145; https://doi.org/10.3390/math12010145 - 2 Jan 2024
Cited by 1 | Viewed by 690
Abstract
This paper theoretically investigates the influence of homo- and hetero-junctions on the propagation characteristics of radially propagated cylindrical surface acoustic waves in a piezoelectric semiconductor semi-infinite medium. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are mathematically derived. Then, based on [...] Read more.
This paper theoretically investigates the influence of homo- and hetero-junctions on the propagation characteristics of radially propagated cylindrical surface acoustic waves in a piezoelectric semiconductor semi-infinite medium. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are mathematically derived. Then, based on these basic equations and the transfer matrix method, two equivalent mathematical models are established concerning the propagation of radially propagated cylindrical surface acoustic waves in this piezoelectric semiconductor semi-infinite medium. Based on the surface and interface effect theory, the homo- or hetero-junction is theoretically treated as a two-dimensional electrically imperfect interface in the first mathematical model. To legitimately confirm the interface characteristic lengths that appear in the electrically imperfect interface conditions, the homo- or hetero-junction is equivalently treated as a functional gradient thin layer in the second mathematical model. Finally, based on these two mathematical models, the dispersion and attenuation curves of radially propagated cylindrical surface acoustic waves are numerically calculated to discuss the influence of the homo- and hetero-junctions on the dispersion and attenuation characteristics of radially propagated cylindrical surface acoustic waves. The interface characteristic lengths are legitimately confirmed through the comparison of dispersion and attenuation curves calculated using the two equivalent mathematical models. As piezoelectric semiconductor energy harvesters usually work under elastic deformation, the establishment of mathematical models and the revelation of physical mechanisms are both fundamental to the analysis and optimization of micro-scale surface acoustic wave resonators, energy harvesters, and acoustic wave amplification based on the propagation of surface acoustic waves. Full article
(This article belongs to the Special Issue Advances in Applied Mathematics, Mechanics and Engineering)
Show Figures

Figure 1

0 pages, 288 KiB  
Article
Ricci Vector Fields Revisited
by Hanan Alohali, Sharief Deshmukh and Gabriel-Eduard Vîlcu
Mathematics 2024, 12(1), 144; https://doi.org/10.3390/math12010144 - 1 Jan 2024
Cited by 1 | Viewed by 738 | Correction
Abstract
We continue studying the σ-Ricci vector field u on a Riemannian manifold (Nm,g), which is not necessarily closed. A Riemannian manifold with Ricci operator T, a Coddazi-type tensor, is called a T-manifold. [...] Read more.
We continue studying the σ-Ricci vector field u on a Riemannian manifold (Nm,g), which is not necessarily closed. A Riemannian manifold with Ricci operator T, a Coddazi-type tensor, is called a T-manifold. In the first result of this paper, we show that a complete and simply connected T-manifold(Nm,g), m>1, of positive scalar curvature τ, admits a closed σ-Ricci vector field u such that the vector uσ is an eigenvector of T with eigenvalue τm1, if and only if it is isometric to the m-sphere Sαm. In the second result, we show that if a compact and connected T-manifold(Nm,g), m>2, admits a σ-Ricci vector field u with σ0 and is an eigenvector of a rough Laplace operator with the integral of the Ricci curvature Ricu,u that has a suitable lower bound, then (Nm,g) is isometric to the m-sphere Sαm, and the converse also holds. Finally, we show that a compact and connected Riemannian manifold (Nm,g) admits a σ-Ricci vector field u with σ as a nontrivial solution of the static perfect fluid equation, and the integral of the Ricci curvature Ricu,u has a lower bound depending on a positive constant α, if and only if (Nm,g) is isometric to the m-sphere Sαm. Full article
(This article belongs to the Special Issue Special (Pseudo-) Riemannian Manifolds)
9 pages, 253 KiB  
Article
An Approach to Multidimensional Discrete Generating Series
by Svetlana S. Akhtamova, Tom Cuchta and Alexander P. Lyapin
Mathematics 2024, 12(1), 143; https://doi.org/10.3390/math12010143 - 1 Jan 2024
Viewed by 1728
Abstract
We extend existing functional relationships for the discrete generating series associated with a single-variable linear polynomial coefficient difference equation to the multivariable case. Full article
Show Figures

Figure 1

30 pages, 15588 KiB  
Article
Machine Recognition of DDoS Attacks Using Statistical Parameters
by Juraj Smiesko, Pavel Segec and Martin Kontsek
Mathematics 2024, 12(1), 142; https://doi.org/10.3390/math12010142 - 31 Dec 2023
Viewed by 1053
Abstract
As part of the research in the recently ended project SANET II, we were trying to create a new machine-learning system without a teacher. This system was designed to recognize DDoS attacks in real time, based on adaptation to real-time arbitrary traffic and [...] Read more.
As part of the research in the recently ended project SANET II, we were trying to create a new machine-learning system without a teacher. This system was designed to recognize DDoS attacks in real time, based on adaptation to real-time arbitrary traffic and with the ability to be embedded into the hardware implementation of network probes. The reason for considering this goal was our hands-on experience with the high-speed SANET network, which interconnects Slovak universities and high schools and also provides a connection to the Internet. Similar to any other public-facing infrastructure, it is often the target of DDoS attacks. In this article, we are extending our previous research, mainly by dealing with the use of various statistical parameters for DDoS attack detection. We tested the coefficients of Variation, Kurtosis, Skewness, Autoregression, Correlation, Hurst exponent, and Kullback–Leibler Divergence estimates on traffic captures of different types of DDoS attacks. For early machine recognition of the attack, we have proposed several detection functions that use the response of the investigated statistical parameters to the start of a DDoS attack. The proposed detection methods are easily implementable for monitoring actual IP traffic. Full article
Show Figures

Figure 1

15 pages, 5164 KiB  
Article
LIDAR Point Cloud Augmentation for Dusty Weather Based on a Physical Simulation
by Haojie Lian, Pengfei Sun, Zhuxuan Meng, Shengze Li, Peng Wang and Yilin Qu
Mathematics 2024, 12(1), 141; https://doi.org/10.3390/math12010141 - 31 Dec 2023
Viewed by 1199
Abstract
LIDAR is central to the perception systems of autonomous vehicles, but its performance is sensitive to adverse weather. An object detector trained by deep learning with the LIDAR point clouds in clear weather is not able to achieve satisfactory accuracy in adverse weather. [...] Read more.
LIDAR is central to the perception systems of autonomous vehicles, but its performance is sensitive to adverse weather. An object detector trained by deep learning with the LIDAR point clouds in clear weather is not able to achieve satisfactory accuracy in adverse weather. Considering the fact that collecting LIDAR data in adverse weather like dusty storms is a formidable task, we propose a novel data augmentation framework based on physical simulation. Our model takes into account finite laser pulse width and beam divergence. The discrete dusty particles are distributed randomly in the surrounding of LIDAR sensors. The attenuation effects of scatters are represented implicitly with extinction coefficients. The coincidentally returned echoes from multiple particles are evaluated by explicitly superimposing their power reflected from each particle. Based on the above model, the position and intensity of real point clouds collected from dusty weather can be modified. Numerical experiments are provided to demonstrate the effectiveness of the method. Full article
(This article belongs to the Section Mathematics and Computer Science)
Show Figures

Figure 1

25 pages, 10746 KiB  
Article
University Campus as a Complex Pedestrian Dynamic Network: A Case Study of Walkability Patterns at Texas Tech University
by Gisou Salkhi Khasraghi, Dimitri Volchenkov, Ali Nejat and Rodolfo Hernandez
Mathematics 2024, 12(1), 140; https://doi.org/10.3390/math12010140 - 31 Dec 2023
Viewed by 1836
Abstract
Statistical mechanics of walks defined on the spatial graphs of the city of Lubbock (10,421 nodes) and the Texas Tech University (TTU) campus pedestrian network (1466 nodes) are used for evaluating structural isolation and the integration of graph nodes, assessing their accessibility and [...] Read more.
Statistical mechanics of walks defined on the spatial graphs of the city of Lubbock (10,421 nodes) and the Texas Tech University (TTU) campus pedestrian network (1466 nodes) are used for evaluating structural isolation and the integration of graph nodes, assessing their accessibility and navigability in the graph, and predicting possible graph structural modifications driving the campus evolution. We present the betweenness and closeness maps of the campus, the first passage times to the different campus areas by isotropic and anisotropic random walks, as well as the first passage times under the conditions of traffic noise. We further show the isolation and integration indices of all areas on the campus, as well as their navigability and strive scores, and energy and fugacity scores. The TTU university campus, a large pedestrian zone located close to the historical city center of Lubbock, mediates between the historical city going downhill and its runaway sprawling body. Full article
(This article belongs to the Special Issue Dynamic Complex Networks: Models, Algorithms, and Applications)
Show Figures

Figure 1

19 pages, 346 KiB  
Article
On Extended Lr-Norm-Based Derivatives to Intuitionistic Fuzzy Sets
by A. S. Wungreiphi, Fokrul Alom Mazarbhuiya and Mohamed Shenify
Mathematics 2024, 12(1), 139; https://doi.org/10.3390/math12010139 - 31 Dec 2023
Viewed by 614
Abstract
The study of differential equation theory has come a long way, with applications in various fields. In 1961, Zygmund and Calderón introduced the notion of derivatives to metric Lr, which proved to be better in applications than approximate derivatives. However, most [...] Read more.
The study of differential equation theory has come a long way, with applications in various fields. In 1961, Zygmund and Calderón introduced the notion of derivatives to metric Lr, which proved to be better in applications than approximate derivatives. However, most of the studies available are on Fuzzy Set Theory. In view of this, intuitionistic fuzzy Lr-norm-based derivatives deserve study. In this study, the Lr-norm-based derivative for intuitionistic fuzzy number valued functions is introduced. Some of its basic properties are also discussed, along with numerical examples. The results obtained show that the proposed derivative is not dependent on the existence of the Hukuhara difference. Lastly, the Cauchy problem for the intuitionistic fuzzy differential equation is discussed. Full article
Previous Issue
Back to TopTop