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Numerical study of vector solitons with the oscillatory phase backgrounds in the integrable coupled nonlinear Schrödinger equations 可积分耦合非线性薛定谔方程中具有振荡相位背景的矢量孤子的数值研究
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-20 DOI: 10.1016/j.matcom.2024.09.009
Lei Liu , Xuan-Xuan Zhou , Xi-Yang Xie , Wen-Rong Sun
In this paper, we numerically investigate vector solitons with oscillatory phase backgrounds in the integrable coupled nonlinear Schrödinger equations, which are widely applied to varieties of physical contexts such as the simultaneous propagation of nonlinear optical pulses and the dynamics of two-components Bose–Einstein condensates. We develop the time-splitting Chebyshev–Galerkin method based on a transformation to accurately compute the vector soliton solutions. Compared to the finite difference method, numerical experiments show that the method with spectral accuracy and high efficiency is necessary for simulating the dynamics evolution of vector solitons. Combined with modulation instability conditions, linear stability analysis and direct numerical simulation, we reveal that the bright-dark and dark-dark solitons with various combinations of parameters under perturbations have qualitative differences. Particularly, vector solitons in unstable background with different wave numbers present distinct dynamics evolutions. The results help us to understand soliton dynamics with oscillatory phase backgrounds and the superposition between nonlinear waves.
本文对可积分耦合非线性薛定谔方程中具有振荡相位背景的矢量孤子进行了数值研究,该方程被广泛应用于非线性光脉冲的同步传播和双分量玻色-爱因斯坦凝聚体的动力学等多种物理环境。我们开发了基于变换的时间分割 Chebyshev-Galerkin 方法,以精确计算矢量孤子解。与有限差分法相比,数值实验表明,具有频谱精度和高效率的方法是模拟矢量孤子动力学演化所必需的。结合调制不稳定性条件、线性稳定性分析和直接数值模拟,我们发现在扰动作用下,不同参数组合的明暗孤子和暗暗孤子存在质的差异。特别是在不同波数的不稳定背景下,矢量孤子呈现出截然不同的动力学演变。这些结果有助于我们理解具有振荡相位背景的孤子动力学以及非线性波之间的叠加。
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引用次数: 0
Control of a 15MW off-shore wind turbine for black-start operation 控制 15 兆瓦离岸风力涡轮机进行黑启动运行
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-19 DOI: 10.1016/j.matcom.2024.09.013
Gala Navarro-Martínez, Jaime Martínez-Turégano, Ramon Blasco-Gimenez
Grid forming wind turbines are crucial for achieving a 100% renewable based grid. The mechanical control of the wind turbines is usually designed for maximum power tracking operation. This paper includes the development of a wind turbine pitch controller considering the wider operational range of a grid forming wind turbine. The proposed controller tracks the optimal generation characteristic of the wind turbine when grid connected and is designed to cater for the different power levels when the wind turbine is operated in islanded mode (or grid-connected at partial power). The proposed controller does not require wind speed estimation for its operation and shows better performance than standard pitch controllers during grid-forming operation, particularly, limiting wind turbine speed excursion during block de-loading. Moreover, the proposed controller does not increase the mechanical loads of the key wind turbine elements. The performance of the proposed control is validated in a black start procedure with a full wind farm realistic real-time simulator, including detailed electrical and aeroelastic models of the wind turbine generator, wind farm and connecting HVDC link. Time and frequency domain validation using the real-time model has shown the performance of the proposed controller during black start operation.
并网风力涡轮机是实现 100% 可再生能源并网的关键。风力涡轮机的机械控制通常是为最大功率跟踪运行而设计的。本文考虑到并网风力涡轮机更广泛的运行范围,开发了一种风力涡轮机变桨控制器。提议的控制器可跟踪风力发电机并网时的最佳发电特性,并可满足风力发电机在孤岛模式(或部分功率并网)下运行时的不同功率水平。拟议控制器的运行不需要风速估算,在并网运行期间比标准变桨控制器显示出更好的性能,特别是在分块卸载期间限制风机速度偏移。此外,建议的控制器不会增加风力发电机关键部件的机械负荷。利用全风电场实时模拟器,包括风力发电机、风电场和连接高压直流链路的详细电气和气动弹性模型,在黑启动程序中验证了所提控制的性能。使用实时模型进行的时域和频域验证显示了所建议的控制器在黑启动运行期间的性能。
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引用次数: 0
Kinetic description and macroscopic limit of swarming dynamics with continuous leader–follower transitions 具有连续领导者-追随者转换的蜂群动力学动力学描述和宏观极限
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-19 DOI: 10.1016/j.matcom.2024.09.006
Emiliano Cristiani , Nadia Loy , Marta Menci , Andrea Tosin
In this paper, we derive a kinetic description of swarming particle dynamics in an interacting multi-agent system featuring emerging leaders and followers. Agents are classically characterized by their position and velocity plus a continuous parameter quantifying their degree of leadership. The microscopic processes ruling the change of velocity and degree of leadership are independent, non-conservative and non-local in the physical space, so as to account for long-range interactions. Out of the kinetic description, we obtain then a macroscopic model under a hydrodynamic limit reminiscent of that used to tackle the hydrodynamics of weakly dissipative granular gases, thus relying in particular on a regime of small non-conservative and short-range interactions. Numerical simulations in one- and two-dimensional domains show that the limiting macroscopic model is consistent with the original particle dynamics and furthermore can reproduce classical emerging patterns typically observed in swarms.
在本文中,我们推导出了在一个以新出现的领导者和追随者为特征的交互式多代理系统中蜂拥粒子动力学的动力学描述。代理的经典特征是其位置和速度,加上一个量化其领导程度的连续参数。在物理空间中,支配速度和领导程度变化的微观过程是独立的、非保守的和非局部的,以便考虑长程相互作用。从动力学描述中,我们得到了一个流体力学极限下的宏观模型,该模型类似于用于处理弱耗散颗粒气体流体力学的模型,因此特别依赖于小的非保守和短程相互作用机制。一维和二维域中的数值模拟表明,极限宏观模型与原始粒子动力学是一致的,而且能再现通常在蜂群中观察到的经典出现模式。
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引用次数: 0
A study of stochastically perturbed epidemic model of HPV infection and cervical cancer in Indian female population 印度女性 HPV 感染与宫颈癌随机扰动流行模型研究
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-19 DOI: 10.1016/j.matcom.2024.09.008
T.A. Midhun, K. Murugesan
This study introduces a novel stochastic SICR (susceptible, infected, cervical cancer and recovered) model to illustrate HPV (Human papillomavirus) infection dynamics and its impact on cervical cancer in the female population of India. We prove the existence of a unique positive global solution that ensures stochastic boundedness and permanence. Moreover, sufficient conditions for HPV extinction are established through the stochastic extinction parameter R0e, indicating that the infection will die out if R0e<1. Conversely, the persistence of HPV is established by the existence and uniqueness of an ergodic stationary distribution of the solution when the stochastic threshold R0s>1, using the suitable selection of Lyapunov functions. Furthermore, data on cervical cancer cases in India from 2016 to 2020 is fitted to the model, providing parameter values suitable for the region. The theoretical findings are validated using the Positive-Preserving Truncated Euler–Maruyama method. Additionally, effective control strategies for India are suggested based on model predictions and sensitivity of key parameters.
本研究引入了一个新的随机 SICR(易感者、感染者、宫颈癌患者和康复者)模型,以说明人乳头瘤病毒(HPV)的感染动态及其对印度女性宫颈癌的影响。我们证明了唯一的正全局解的存在,该解确保了随机有界性和持久性。此外,通过随机消亡参数 R0e 确定了 HPV 消亡的充分条件,表明如果 R0e<1 ,感染就会消亡。相反,当随机阈值 R0s>1 时,利用适当选择的 Lyapunov 函数,通过解的遍历静态分布的存在性和唯一性确定了 HPV 的持久性。此外,印度 2016 年至 2020 年的宫颈癌病例数据也被拟合到模型中,从而提供了适合该地区的参数值。使用正保留截断欧拉-马鲁山方法验证了理论研究结果。此外,根据模型预测和关键参数的敏感性,为印度提出了有效的控制策略。
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引用次数: 0
A space-time generalized finite difference scheme for long wave propagation based on high-order Korteweg-de Vries type equations 基于高阶 Korteweg-de Vries 型方程的长波传播时空广义有限差分方案
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-19 DOI: 10.1016/j.matcom.2024.09.012
Fan Zhang , Po-Wei Li , Yan Gu , Chia-Ming Fan
In this paper, the space-time generalized finite difference scheme is applied to solve the nonlinear high-order Korteweg-de Vries equations in multiple dimensions. The proposed numerical scheme combines the space-time generalized finite difference method, the Levenberg-Marquardt algorithm, and a time-marching approach. The space-time generalized finite difference method treats the temporal axis as a spatial axis, enabling the proposed scheme to discretize all derivatives in the governing equation. This is accomplished through Taylor series expansion and the moving least squares method. Due to the expandability of the Taylor series to any order, the proposed numerical scheme excels in efficiently handling mixed and higher-order derivatives. These capabilities are distinct advantages of the proposed scheme. The resulting system of algebraic equations is sparse but overdetermined. Therefore, the Levenberg-Marquardt algorithm is directly applied to solve this nonlinear algebraic system. During the calculation process, the time-marching approach reduces computational effort and improves efficiency by dividing the space-time domain.
本文采用时空广义有限差分法求解多维非线性高阶 Korteweg-de Vries 方程。所提出的数值方案结合了时空广义有限差分法、Levenberg-Marquardt 算法和时间行进法。时空广义有限差分法将时间轴视为空间轴,从而使拟议方案能够离散化支配方程中的所有导数。这是通过泰勒级数展开和移动最小二乘法实现的。由于泰勒级数可扩展到任何阶次,拟议的数值方案在有效处理混合导数和高阶导数方面表现出色。这些功能是拟议方案的显著优势。所得到的代数方程系统是稀疏的,但又是过确定的。因此,可以直接采用 Levenberg-Marquardt 算法来求解这个非线性代数系统。在计算过程中,时间行进方法通过划分时空域减少了计算量并提高了效率。
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引用次数: 0
Finding the minimum k-weighted dominating sets using heuristic algorithms 利用启发式算法寻找最小 k 加权支配集
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-18 DOI: 10.1016/j.matcom.2024.09.010
E. Barrena , S. Bermudo , A.G. Hernández-Díaz , A.D. López-Sánchez , J.A. Zamudio
In this work, we propose, analyze, and solve a generalization of the k-dominating set problem in a graph, when we consider a weighted graph. Given a graph with weights in its edges, a set of vertices is a k-weighted dominating set if for every vertex outside the set, the sum of the weights from it to its adjacent vertices in the set is bigger than or equal to k. The k-weighted domination number is the minimum cardinality among all k-weighted dominating sets. Since the problem of finding the k-weighted domination number is NP-hard, we have proposed several problem-adapted construction and reconstruction techniques and embedded them in an Iterated Greedy algorithm. The resulting sixteen variants of the Iterated Greedy algorithm have been compared with an exact algorithm. Computational results show that the proposal is able to find optimal or near-optimal solutions within a short computational time. To the best of our knowledge, the k-weighted dominating set problem has never been studied before in the literature and, therefore, there is no other state-of-the-art algorithm to solve it. We have also included a comparison with a particular case of our problem, the minimum dominating set problem and, on average, we achieve same quality results within around 50% of computation time.
在这项研究中,我们提出、分析并解决了图中 k 主集问题的一般化,即考虑加权图。给定一个边上有权重的图,如果该图外的每个顶点到图中相邻顶点的权重之和大于或等于 k,则该顶点集是一个 k 加权支配集。由于求 k 加权支配数的问题是 NP 难问题,我们提出了几种与问题相适应的构造和重构技术,并将它们嵌入到迭代贪婪算法中。我们将迭代贪心算法的 16 个变体与精确算法进行了比较。计算结果表明,该建议能够在较短的计算时间内找到最优或接近最优的解决方案。据我们所知,文献中从未研究过 k 加权支配集问题,因此也没有其他最先进的算法来解决这个问题。我们还将其与我们问题的一种特殊情况--最小支配集问题--进行了比较,平均而言,我们只用了大约 50% 的计算时间就获得了相同质量的结果。
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引用次数: 0
IMACS Calendar of Events IMACS 活动日历
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-17 DOI: 10.1016/S0378-4754(24)00358-6
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引用次数: 0
News of IMACS IMACS 新闻
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-17 DOI: 10.1016/S0378-4754(24)00357-4
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引用次数: 0
Bistability in a predator–prey model characterized by the Crowley–Martin functional response: Effects of fear, hunting cooperation, additional foods and nonlinear harvesting 以克劳利-马丁功能反应为特征的捕食者-猎物模型的双稳态性:恐惧、狩猎合作、额外食物和非线性收获的影响
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-12 DOI: 10.1016/j.matcom.2024.09.001
Subarna Roy, Pankaj Kumar Tiwari

This study focuses on unraveling key factors influencing predator–prey interactions with Crowley–Martin functional response. Specifically, it explores the roles of additional food sources, harvesting practices, hunting cooperation, fear and its carry-over effects. We analyze equilibrium points and their stability properties through rigorous mathematical methods. Numerical illustrations showcase a diverse range of bifurcations including Hopf, saddle–node, and transcritical, providing a comprehensive understanding of the system’s dynamics. We find that the collaboration among predators during hunting induces instability in the system, leading to the emergence of population cycles from a stable state. Further, we place emphasis on investigating the impact of seasonal forcing by introducing time-varying parameters into our model. We reveal the emergence of periodic solutions, higher periodic solutions and chaotic dynamics due to the seasonal variations of the prey’s birth rate and the degree of hunting cooperation. We also emphasize the significance of incorporating different periodicity of seasonally forced parameters, leading to a more precise understanding of predator–prey dynamics.

这项研究的重点是利用克劳利-马丁功能反应揭示影响捕食者与猎物之间相互作用的关键因素。具体来说,它探讨了额外食物来源、捕食方式、狩猎合作、恐惧及其延续效应的作用。我们通过严格的数学方法分析了平衡点及其稳定性。数值图解展示了霍普夫分岔、鞍节点分岔和跨临界分岔等多种分岔,为我们提供了对系统动力学的全面理解。我们发现,捕食者在狩猎过程中的协作诱发了系统的不稳定性,导致从稳定状态出现种群循环。此外,我们通过在模型中引入时变参数,重点研究了季节性强迫的影响。我们发现,由于猎物出生率和狩猎合作程度的季节性变化,出现了周期解、高周期解和混沌动力学。我们还强调了将不同周期性的季节强迫参数纳入模型的意义,从而更准确地理解捕食者-猎物动力学。
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引用次数: 0
Solving the Laplace equation on the disc using the UAT spline 使用 UAT 花键求解圆盘上的拉普拉斯方程
IF 4.4 2区 数学 Q1 COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS Pub Date : 2024-09-12 DOI: 10.1016/j.matcom.2024.09.004
M. Naimi, M. Lamnii
In this work, we are interested in the resolution of the Laplace equation Δu=f with Dirichlet boundary condition in a closed surface S in R2, which is – topologically – equivalent to the unit disc D={x,y|x2+y21}. It is known that for a function u represented in polar coordinates on D, certain boundary conditions must be satisfied by u so that the surface S is of class C0. More precisely, we construct an approximant of class C0 on D as a tensor product of two quasi-interpolants, one based on UAT-splines and the other based on classical B-splines. Some numerical results are given to validate the work.
在这项工作中,我们感兴趣的是在 R2 中的封闭曲面 S 上解决带有 Dirichlet 边界条件的拉普拉斯方程 -Δu=f 的问题,该曲面在拓扑上等价于单位圆盘 D={x,y|x2+y2⩽1}。众所周知,对于在 D 上以极坐标表示的函数 u,u 必须满足某些边界条件,这样曲面 S 才属于 C0 类。更确切地说,我们在 D 上构建了一个 C0 类近似值,它是两个准内插值的张量乘积,一个基于 UAT 样条曲线,另一个基于经典 B 样条曲线。我们给出了一些数值结果来验证这项工作。
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引用次数: 0
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Mathematics and Computers in Simulation
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