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Analysis of the Burgers–Huxley Equation Using the Nondimensionalisation Technique: Universal Solution for Dirichlet and Symmetry Boundary Conditions 利用非尺寸化技术分析伯格斯-赫胥黎方程:迪里夏特和对称边界条件的通用解法
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-11 DOI: 10.3390/axioms12121113
J. Sánchez-Pérez, Joaquín Solano-Ramírez, Enrique Castro, M. Conesa, Fulgencio Marín-García, G. García-Ros
The Burgers–Huxley equation is important because it involves the phenomena of accumulation, drag, diffusion, and the generation or decay of species, which are common in various problems in science and engineering, such as heat transmission, the diffusion of atmospheric contaminants, etc. On the other hand, the mathematical technique of nondimensionalisation has proven to be very useful in the appropriate grouping of the variables involved in a physical–chemical phenomenon and in obtaining universal solutions to different complex engineering problems. Therefore, a deep analysis using this technique of the Burgers–Huxley equation and its possible boundary conditions can facilitate a common understanding of these problems through the appropriate grouping of variables and propose common universal solutions. Thus, in this case, the technique is applied to obtain a universal solution for Dirichlet and symmetric boundary conditions. The validation of the methodology is carried out by comparing different cases, where the coefficients or the value of the boundary condition are varied, with the results obtained through a numerical simulation. Furthermore, one of the cases presented presents a boundary condition that changes at a certain time. Finally, after applying the technique, it is studied which phenomenon is predominant, concluding that from a certain value diffusion predominates, with the rest being practically negligible.
伯格斯-赫胥黎方程之所以重要,是因为它涉及物种的积聚、阻力、扩散和生成或衰变现象,这些现象在科学和工程领域的各种问题中很常见,如热传导、大气污染物的扩散等。另一方面,事实证明,无量纲化数学技术非常有助于对物理化学现象中涉及的变量进行适当分组,并获得不同复杂工程问题的通用解决方案。因此,利用这种技术对伯格斯-赫胥黎方程及其可能的边界条件进行深入分析,可以通过对变量进行适当分组,促进对这些问题的共同理解,并提出通用的通用解决方案。因此,在本案例中,应用该技术获得了 Dirichlet 和对称边界条件的通用解。通过比较不同情况下的系数或边界条件值与数值模拟获得的结果,对该方法进行了验证。此外,其中一个案例中的边界条件在一定时间内会发生变化。最后,在应用该技术后,对哪种现象占主导地位进行了研究,得出的结论是,从某个值开始,扩散现象占主导地位,其他现象实际上可以忽略不计。
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引用次数: 0
Using SNAP to Analyze Policy Measures in e-Learning Roadmaps 使用 SNAP 分析电子学习路线图中的政策措施
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-11 DOI: 10.3390/axioms12121110
Nikola Kadoić, Nina Begičević Ređep, Dragana Kupres
Creating policy measures is the final step in the process of e-learning roadmap development. Policy measures can be seen as long-term activities that need to be implemented and constantly upgraded to achieve strategic goals. For resource allocation, it is useful to prioritize policy measures. Prioritization can be implemented using multi-criteria decision-making methods. This paper analyzes policy measures in the Maldives National University’s e-learning roadmap using the social network analysis process (SNAP), which includes the analytic hierarchy process (AHP), the decision-making trial and evaluation laboratory (DEMATEL), and the PageRank centrality. In policy measure evaluation, there were more than 20 participants: persons with managerial functions at the Maldives National University (MNU) (deans, heads of departments) and persons in lecturer and researcher positions. By using the AHP, participants prioritized policy measures with respect to their importance to them. By using the DEMATEL, participants identified and prioritized policy measures with respect to their effect on other measures. Finally, by using the SNAP, it was possible to determine the prioritization list for resource allocation since it aggregates the aspects of the policy measures, their importance, and their effect on other measures.
制定政策措施是电子学习路线图制定过程的最后一步。政策措施可视为长期活动,需要实施并不断升级,以实现战略目标。在资源分配方面,对政策措施进行优先排序非常有用。可以使用多标准决策方法来确定优先次序。本文利用社会网络分析过程(SNAP)对马尔代夫国立大学电子学习路线图中的政策措施进行了分析,其中包括分析层次过程(AHP)、决策试验和评估实验室(DEMATEL)以及 PageRank 中心性。在政策措施评估中,有 20 多名参与者:在马尔代夫国立大学(MNU)担任管理职务的人员(院长、系主任)以及担任讲师和研究员职务的人员。通过使用 AHP,与会者根据政策措施对他们的重要性确定了优先次序。通过使用 DEMATEL,与会者根据政策措施对其他措施的影响确定了政策措施并排定了优先顺序。最后,通过使用 SNAP,可以确定资源分配的优先顺序清单,因为 SNAP 综合了政策措施的各个方面、其重要性及其对其他措施的影响。
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引用次数: 0
More Effective Criteria for Testing the Asymptotic and Oscillatory Behavior of Solutions of a Class of Third-Order Functional Differential Equations 测试一类三阶函数微分方程解的渐近和振荡行为的更有效标准
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-11 DOI: 10.3390/axioms12121112
Fahd Masood, O. Moaaz, Ghada AlNemer, H. El-Metwally
This paper delves into the investigation of quasi-linear neutral differential equations in the third-order canonical case. In this study, we refine the relationship between the solution and its corresponding function, leading to improved preliminary results. These enhanced results play a crucial role in excluding the existence of positive solutions to the investigated equation. By building upon the improved preliminary results, we introduce novel criteria that shed light on the nature of these solutions. These criteria help to distinguish whether the solutions exhibit oscillatory behavior or tend toward zero. Moreover, we present oscillation criteria for all solutions. To demonstrate the relevance of our results, we present an illustrative example. This example validates the theoretical framework we have developed and offers practical insights into the behavior of solutions for quasi-linear third-order neutral differential equations.
本文深入研究了三阶典型情况下的准线性中性微分方程。在这项研究中,我们完善了解与相应函数之间的关系,从而改进了初步结果。这些改进的结果在排除所研究方程正解的存在方面发挥了关键作用。在改进的初步结果基础上,我们引入了新的标准来揭示这些解的性质。这些标准有助于区分这些解是表现出振荡行为还是趋向于零。此外,我们还提出了所有解的振荡标准。为了证明我们结果的相关性,我们提出了一个示例。这个例子验证了我们开发的理论框架,并为我们提供了关于准线性三阶中性微分方程解的行为的实用见解。
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引用次数: 0
Certain Bounds of Formulas in Free Temporal Algebras 自由时态结构中公式的若干界限
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-11 DOI: 10.3390/axioms12121111
Francisco Miguel García-Olmedo, Antonio Jesús Rodríguez-Salas, P. González-Rodelas
In this paper, we give a basic structure theorem based on the study of extreme cases for the value of ≺ (the classical precedence relation between ultrafilters), i.e., ≺=∅ and no isolated element in ≺. This gives rise, respectively, to the temporal varieties O and W, with the result that O generates a variety of temporal algebras. We also characterize the simple temporal algebras by means of arithmetical properties related to basical temporal operators; we conclude that the simplicity of the temporal algebra lies in being able to make 0 any element less than 1 by repeated application to it of the L operator. We then present an algebraic construction similar to a product but in which the temporal operations are not defined componentwise. This new “product” is shown to be useful in the study of algebra order and finding of bounds by means of something similar to a lifting process. Finally, we give an alternative proof of an already known result on atoms counting in free temporal algebras.
本文基于对≺(超滤波器之间的经典优先关系)值极端情况的研究,给出了一个基本结构定理,即≺=∅且≺中无孤立元素。这就分别产生了时空变项 O 和 W,结果是 O 产生了一个时空代数变项。我们还通过与基本时态算子相关的算术性质来描述简单时态代数的特征;我们得出结论:时态代数的简单性在于,通过对它重复应用 L 算子,可以使任何小于 1 的元素为 0。然后,我们提出了一种类似于积的代数结构,但其中的时态运算不是按分量定义的。这种新的 "乘积 "在研究代数阶和通过类似于提升过程的方法寻找边界时非常有用。最后,我们给出了关于自由时态代数中原子计数的已知结果的另一种证明。
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引用次数: 0
On the Method of Transformations: Obtaining Solutions of Nonlinear Differential Equations by Means of the Solutions of Simpler Linear or Nonlinear Differential Equations 论变换方法:通过较简单线性或非线性微分方程的解获得非线性微分方程的解
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-08 DOI: 10.3390/axioms12121106
N. Vitanov
Transformations are much used to connect complicated nonlinear differential equations to simple equations with known exact solutions. Two examples of this are the Hopf–Cole transformation and the simple equations method. In this article, we follow an idea that is opposite to the idea of Hopf and Cole: we use transformations in order to transform simpler linear or nonlinear differential equations (with known solutions) to more complicated nonlinear differential equations. In such a way, we can obtain numerous exact solutions of nonlinear differential equations. We apply this methodology to the classical parabolic differential equation (the wave equation), to the classical hyperbolic differential equation (the heat equation), and to the classical elliptic differential equation (Laplace equation). In addition, we use the methodology to obtain exact solutions of nonlinear ordinary differential equations by means of the solutions of linear differential equations and by means of the solutions of the nonlinear differential equations of Bernoulli and Riccati. Finally, we demonstrate the capacity of the methodology to lead to exact solutions of nonlinear partial differential equations on the basis of known solutions of other nonlinear partial differential equations. As an example of this, we use the Korteweg–de Vries equation and its solutions. Traveling wave solutions of nonlinear differential equations are of special interest in this article. We demonstrate the existence of the following phenomena described by some of the obtained solutions: (i) occurrence of the solitary wave–solitary antiwave from the solution, which is zero at the initial moment (analogy of an occurrence of particle and antiparticle from the vacuum); (ii) splitting of a nonlinear solitary wave into two solitary waves (analogy of splitting of a particle into two particles); (iii) soliton behavior of some of the obtained waves; (iv) existence of solitons which move with the same velocity despite the different shape and amplitude of the solitons.
变换常用于将复杂的非线性微分方程与具有已知精确解的简单方程联系起来。两个例子是Hopf-Cole变换和简单方程法。在本文中,我们遵循一个与Hopf和Cole的思想相反的思想:我们使用变换来将更简单的线性或非线性微分方程(具有已知解)转换为更复杂的非线性微分方程。用这种方法,我们可以得到许多非线性微分方程的精确解。我们将这种方法应用于经典抛物型微分方程(波动方程)、经典双曲型微分方程(热方程)和经典椭圆型微分方程(拉普拉斯方程)。此外,我们还利用线性微分方程的解和Bernoulli和Riccati的非线性微分方程的解来求非线性常微分方程的精确解。最后,我们证明了该方法在其他非线性偏微分方程已知解的基础上得到非线性偏微分方程精确解的能力。作为一个例子,我们使用Korteweg-de Vries方程及其解。本文特别关注非线性微分方程的行波解。我们证明了一些得到的解所描述的以下现象的存在性:(i)孤波-孤反波从解中出现,它在初始时刻为零(类似于从真空中出现粒子和反粒子);(ii)将一个非线性孤立波分裂成两个孤立波(类似于将一个粒子分裂成两个粒子);(iii)某些所得波的孤子行为;(iv)存在以相同速度运动的孤子,尽管孤子的形状和振幅不同。
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引用次数: 0
A Novel Fractional Multi-Order High-Gain Observer Design to Estimate Temperature in a Heat Exchange Process 估算热交换过程中温度的新型分数多阶高增益观测器设计
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-08 DOI: 10.3390/axioms12121107
Vicente Borja-Jaimes, Manuel Adam-Medina, Jarniel García-Morales, Alan Cruz-Rojas, Alfredo Gil-Velasco, Antonio Coronel-Escamilla
In the present manuscript, we design a fractional multi-order high-gain observer to estimate temperature in a double pipe heat exchange process. For comparison purposes and since we want to prove that when using our novel technique, the estimation is more robust than the classical approach, we design a non-fractional high-gain observer, and then we compare the performance of both observers. We consider three scenarios: The first one considers the estimation of the system states by measuring only one output with no noise added on it and under ideal conditions. Second, we add noise to the measured output and then reconstruct the system states, and, third, in addition to the noise, we increase the gain parameter in both observers (non-fractional and fractional) due to the fact that we want to prove that the robustness changes in this parameter. The results showed that, using our approach, the estimated states can be recovered under noise circumstances in the measured output and under parameter change in the observer, contrary to using classical (non-fractional) observers where the states cannot be recovered. In all our tests, we used the normalized root-mean-square, integral square error, and integral absolute error indices, resulting in a better performance for our approach than that obtained using the classical approach. We concluded that our fractional multi-order high-gain observer is more robust to input noise than the classical high-gain observer.
在本文中,我们设计了一个分数阶多阶高增益观测器来估计双管换热过程中的温度。为了比较的目的,因为我们想证明当使用我们的新技术时,估计比经典方法更鲁棒,我们设计了一个非分数高增益观测器,然后我们比较两个观测器的性能。我们考虑了三种情况:第一种情况是在理想条件下,通过仅测量一个没有噪声的输出来考虑系统状态的估计。其次,我们将噪声添加到测量输出中,然后重建系统状态,第三,除了噪声之外,我们还增加了两个观测器(非分数和分数)中的增益参数,因为我们想证明该参数的鲁棒性发生了变化。结果表明,使用我们的方法,可以在测量输出中的噪声环境和观测器参数变化的情况下恢复估计状态,与使用经典(非分数)观测器的状态无法恢复相反。在我们所有的测试中,我们使用了标准化的均方根、积分平方误差和积分绝对误差指标,结果表明我们的方法比使用经典方法获得的性能更好。结果表明,分数阶多阶高增益观测器对输入噪声的鲁棒性优于传统的高增益观测器。
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引用次数: 0
Describing Conditional Independence Statements Using Undirected Graphs 使用无向图描述条件独立性语句
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-08 DOI: 10.3390/axioms12121109
D. Malouche
This paper investigates the capability of undirected graphs (UGs) to represent a set of Conditional Independence (CI) statements derived from a given probability distribution of a random vector. While it is established that certain axioms can govern this set, providing sufficient conditions for UGs to capture specific CI statements, our focus is on covariance and concentration graphs. These remain the only known families of UGs capable of describing CI statements. We explore the issue of complete representation of CI statements through their corresponding covariance and concentration graphs. Two parameters are defined, one each from the covariance and concentration graphs, to determine the limitations concerning the cardinality of the conditioning subset that the graph can represent. We establish a relationship between these parameters and the cardinality of the separators in each graph, providing a straightforward computational method to evaluate them. In conclusion, we enhance the aforementioned procedure and introduce criteria to ascertain, without additional computations, whether the graphs can fully represent a given set of CI statements. We demonstrate that either the concentration or the covariance graph forms a cycle, and when considered in conjunction, they can represent the entire relation. These criteria also enable us, in specific cases, to deduce the covariance graph from the concentration graph and vice versa.
本文研究了无向图(UGs)表示由给定随机向量概率分布衍生出的一组条件独立性(CI)声明的能力。虽然已经确定某些公理可以支配这组图,为无向图捕捉特定的 CI 语句提供了充分条件,但我们的重点是协方差图和浓度图。这些仍然是唯一已知的能够描述 CI 语句的 UG 系列。我们探讨了通过相应的协方差图和浓度图完整表示 CI 语句的问题。我们定义了两个参数,分别来自协方差图和浓度图,以确定图所能表示的条件子集的心率限制。我们在这些参数和每个图中分离器的卡片数之间建立了一种关系,并提供了一种直接的计算方法来评估这些参数。总之,我们改进了上述程序,并引入了标准,无需额外计算即可确定图形是否能完全代表给定的 CI 语句集。我们证明,无论是浓度图还是协方差图,都能形成一个循环,如果结合起来考虑,它们就能代表整个关系。在特定情况下,这些标准还能让我们从浓度图推导出协方差图,反之亦然。
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引用次数: 0
A Note on Finite Dimensional Odd Contact Lie Superalgebra in Prime Characteristic 素特性有限维奇数接触列超代数注释
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-08 DOI: 10.3390/axioms12121108
Xiaoning Xu, Qiyuan Wang
Over a field of characteristic p>3, let KO(n,n+1;t̲) denote the odd contact Lie superalgebra. In this paper, the super-biderivations of odd Contact Lie superalgebra KO(n,n+1;t̲) are studied. Let TKO be a torus of KO(n,n+1;t̲), which is an abelian subalgebra of KO(n,n+1;t̲). By applying the weight space decomposition approach of KO(n,n+1;t̲) with respect to TKO, we show that all skew-symmetric super-biderivations of KO(n,n+1;t̲) are inner super-biderivations.
在特征p>3的域上,设KO(n,n+1;t _)表示奇接触李超代数。本文研究了奇接触李超代数KO(n,n+1;t _)的超推导。设TKO为KO(n,n+1;t *)的环面,KO(n,n+1;t *)是KO(n,n+1;t *)的一个阿贝尔子代数。利用KO(n,n+1;t′)对TKO的权空间分解方法,证明了KO(n,n+1;t′)的所有偏对称超微分都是内超微分。
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引用次数: 0
A Simplified Approach to the Pricing of Vulnerable Options with Two Underlying Assets in an Intensity-Based Model 在基于强度的模型中为具有两种相关资产的脆弱期权定价的简化方法
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.3390/axioms12121105
Geonwoo Kim
In this paper, we study a simplified approach to determine the pricing formula for vulnerable options involving two correlated underlying assets. We utilize an intensity-based model to describe the credit risk associated with these vulnerable options. Without the change of measure technique, we derive pricing formulas for vulnerable options involving two underlying assets based on the probabilistic approach. We provide closed-form pricing formulas for two specific types of options: the vulnerable exchange option and the vulnerable foreign equity option. Finally, we present numerical results to demonstrate the accuracy of our formulas using the Monte-Carlo method and the effect of various parameters on the price of options.
本文研究了一种确定包含两个相关标的资产的易损期权定价公式的简化方法。我们利用基于强度的模型来描述与这些脆弱期权相关的信用风险。在不使用度量变更技术的情况下,基于概率方法推导了包含两种标的资产的易损期权的定价公式。本文给出了两种期权的封闭式定价公式:易损外汇期权和易损外国股票期权。最后,我们给出了数值结果来证明我们的公式使用蒙特卡罗方法的准确性以及各种参数对期权价格的影响。
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引用次数: 0
Proportional Odds Hazard Model for Discrete Time-to-Event Data 离散时间到事件数据的比例概率危险模型
IF 2 3区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2023-12-06 DOI: 10.3390/axioms12121102
Maria Gabriella Figueiredo Vieira, Marcílio Ramos Pereira Cardial, Raul Y. Matsushita, E. Nakano
In this article, we present the development of the proportional odds hazard model for discrete time-to-event data. In this work, inferences about the model’s parameters were formulated considering the presence of right censoring and the discrete Weibull and log-logistic distributions. Simulation studies were carried out to check the asymptotic properties of the estimators. In addition, procedures for checking the proportional odds assumption were proposed, and the proposed model is illustrated using a dataset on the survival time of patients with low back pain.
在本文中,我们提出了离散时间到事件数据的比例赔率风险模型的发展。在这项工作中,考虑到右审查和离散威布尔分布和逻辑逻辑分布的存在,制定了关于模型参数的推论。通过仿真研究验证了估计量的渐近性。此外,还提出了检查比例赔率假设的程序,并使用腰痛患者生存时间的数据集说明了所提出的模型。
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引用次数: 0
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