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Mathematical Modelling of Natural Phenomena最新文献

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Lévy flights, optimal foraging strategies, and foragers with a finite lifespan 莱维飞行、最佳觅食策略和寿命有限的觅食者
IF 2.6 4区 数学 Q2 MATHEMATICAL & COMPUTATIONAL BIOLOGY Pub Date : 2024-07-03 DOI: 10.1051/mmnp/2024015
S. Dipierro, Giovanni Giacomin, Enrico Valdinoci
In some recent work, we have introduced some efficiency functionals to account for optimal dispersal strategies of predators in search of food.The optimization parameter in this framework is given by the L'evy exponent of the dispersal of the predators.In this paper,we apply our model to the case of foragers with finite lifetime (i.e., foragers which need to eat a certain amount of food in a given time, otherwise they die).Specifically, we consider the case in which the initial distribution of the forager coincides with a stationary distribution of the targets and we determine the optimal L'evy exponent for the associated efficiency functional.Namely, we show that if the Fourier transform of the prey distribution is supported in a sufficiently small ball, then the optimizer is given by a Gaussian dispersal, and if instead the Fourier transform of the prey distribution is supported in the complement of a suitable ball, thenthe ballistic diffusion provides an optimizer(precise conditions for the uniqueness of these optimizers are also given).
在最近的一些工作中,我们引入了一些效率函数来解释捕食者在寻找食物时的最优分散策略。在这个框架中,优化参数由捕食者分散的 L'evy 指数给出、具体来说,我们考虑了觅食者的初始分布与目标的静态分布重合的情况,并确定了相关效率函数的最优 L'evy 指数。也就是说,我们证明了如果猎物分布的傅立叶变换被支持在一个足够小的球中,那么优化器就是由高斯扩散给出的;如果猎物分布的傅立叶变换被支持在一个合适球的补码中,那么弹道扩散就提供了一个优化器(还给出了这些优化器唯一性的精确条件)。
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引用次数: 0
Patient-specific input data for predictive modeling of the Fontan operation 用于方坦手术预测建模的特定患者输入数据
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-06-12 DOI: 10.1051/mmnp/2024013
T. Dobroserdova, Lyudmila Yurpolskaya, Yuri Vassilevski, Andrey Svobodov
Personalized blood flow models are used for optimization of the Fontan procedure. In this paper we discuss clinical data for model initialization. Before the Fontan procedure patients undergo CT or MRI examination. Computational domain of interest is reconstructed from this data. CT images are shown to have a better spatial resolution and quality and are more suitable for segmentation. MRI data gives information about blood flow rates  and it is utilized for setting boundary conditions in local 3D hemodynamic models. We discovered that the MRI data is contradictory and too inaccurate for setting boundary conditions: the error of measured velocities  is comparable with blood velocities in veins. We discuss a multiscale 1D3D circulation model as  potentially suitable for prediction of the Fontan procedure results. Such model may  be initialized with more reliable data (MR measurements of blood flow in aorta and ultrasound examination of easily accessible vessels) and take into account  collateral and fenestration blood flows which are typical for Fontan patients. We have calculated these flow rates for several patients and demonstrated  that such flows occur systematically.
个性化血流模型用于优化丰坦手术。本文讨论了用于模型初始化的临床数据。在进行丰坦手术前,患者需要接受 CT 或 MRI 检查。根据这些数据重建感兴趣的计算域。CT 图像具有更好的空间分辨率和质量,更适合进行分割。核磁共振成像数据提供了有关血流速率的信息,可用于设置局部三维血液动力学模型的边界条件。我们发现,核磁共振成像数据在设定边界条件时存在矛盾且过于不准确:测得的血流速度误差与静脉中的血流速度相当。我们讨论了一种多尺度一维三维循环模型,该模型可能适用于预测丰坦手术的结果。这种模型可以用更可靠的数据(主动脉血流的磁共振测量数据和易接近血管的超声检查数据)进行初始化,并将Fontan患者典型的侧支血流和栅栏血流考虑在内。我们已经计算了几例患者的这些血流量,并证明这些血流量是系统性的。
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引用次数: 0
Multi-wave modelling and short-term prediction of ICU bed occupancy by patients with COVID-19 in regions of Italy 意大利各地区 COVID-19 患者重症监护病房床位占用率的多波建模和短期预测
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-05-23 DOI: 10.1051/mmnp/2024012
Frederico José Ribeiro Pelogia, Henrique Mohallem Paiva, Roberson Saraiva Polli
Contribution: This study provides insights into COVID-19 dynamics by employing a phenomenological model representing multiple epidemiological waves. It aims to support decision-making for health authorities and hospital administrators, particularly in optimizing Intensive Care Unit (ICU) bed management and implementing effective containment measures. Background: Given the intricate complexity of ICU environments, utilizing a mathematical model to anticipate occupancy is highly beneficial and might mitigate mortality rates associated with COVID-19. The study focuses on the evolution of intensive care patient numbers across multiple epidemiological waves in Italian regions. Methodology: Our methodology involves the application of a low-complexity phenomenological model with an efficient optimization procedure. ICU occupancy data from five populous Italian regions are utilized to demonstrate the model’s efficacy on describing historical data and providing forecasts for two-week intervals. Findings: Drawing from the analyzed ICU occupancy data, the study establishes the effectiveness of the proposed model. It successfully fits historical data and offers accurate forecasts, achieving an average relative RMSE of 0.51% for the whole fit and 0.93% for the predictions, across all regions. Beyond the immediate context, the model low complexity and efficient optimization make it suitable to diverse regions and diseases, supporting the tracking and containment of future epidemics.
贡献:本研究通过采用代表多重流行病学浪潮的现象学模型,深入探讨了 COVID-19 的动态变化。其目的是为卫生部门和医院管理者提供决策支持,尤其是在优化重症监护室(ICU)床位管理和实施有效遏制措施方面。背景:鉴于重症监护室环境错综复杂,利用数学模型预测占用率非常有益,并可能降低与 COVID-19 相关的死亡率。本研究的重点是意大利各地区在多次流行病学浪潮中重症监护患者人数的变化情况。研究方法:我们的方法包括应用低复杂度的现象学模型和高效的优化程序。我们利用意大利五个人口大区的重症监护室入住率数据来证明该模型在描述历史数据和提供两周间隔预测方面的有效性。研究结果:通过分析 ICU 入住率数据,研究证实了所提模型的有效性。该模型成功地拟合了历史数据并提供了准确的预测,在所有地区的整体拟合和预测中,平均相对均方根误差分别为 0.51%和 0.93%。除了眼前的情况,该模型的低复杂性和高效优化使其适用于不同地区和疾病,支持未来流行病的跟踪和遏制。
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引用次数: 0
Mathematical Modelling of Natural Phenomena 自然现象的数学建模
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-05-22 DOI: 10.1051/mmnp/2024010
A. Decoene, Sebastien Martin, Chabane Meziane
We propose a hierarchy of mathematical models for the numerical simulation of active thin structures in a viscous fluid and its application to mucociliary transport. Our aim is to simulate large forests of cilia and analyze the collective dynamics arising in the flow, as well as their impact on the efficiency of the mucus transport. In a 3d model we describe the cilia individually and study their joint actions on the fluid. The model is built upon a 3d Stokes problem with singular source terms that represent the action of the 1d cilia on the fluid, including the background flow (making the problem nonlocal). Surface tension between the periciliary layer and the mucus is taken into account. From the 3d model we also derive a 1d space averaged model, describing the dynamics of the mean velocity of the mucus that is propelled by the cilia, hence allowing lower computational costs and still providing useful characterization of the efficiency of the transport. Mathematical properties of the models (existence and uniqueness of solutions in suitable functional spaces) are analyzed. Numerical simulations highlight the influence of critical parameters on the efficiency of the mucociliary transport in the case of dense forests of cilia.
我们提出了一种用于粘性流体中活性薄结构数值模拟的分层数学模型,并将其应用于粘液运输。我们的目的是模拟大型纤毛林,分析流动中产生的集体动力学及其对粘液运输效率的影响。在三维模型中,我们对纤毛进行了单独描述,并研究了它们对流体的共同作用。该模型建立在三维斯托克斯问题的基础上,其中的奇异源项代表了 1d 纤毛对流体(包括背景流)的作用(使问题非局部化)。纤毛层和粘液之间的表面张力也被考虑在内。根据三维模型,我们还推导出了一个一维空间平均模型,描述了纤毛推动粘液平均速度的动态变化,从而降低了计算成本,并仍然提供了运输效率的有用特征。分析了模型的数学特性(在合适的函数空间中解的存在性和唯一性)。数值模拟强调了在纤毛密集的情况下,关键参数对粘液纤毛运输效率的影响。
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引用次数: 0
Generalities on a delayed spatiotemporal host-pathogen infection model with distinct dispersal rates 具有不同扩散率的延迟时空宿主-病原体感染模型的一般情况
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-05-16 DOI: 10.1051/mmnp/2024008
Djilali salih
We propose a general model to investigate the effect of the distinct dispersal coefficient {for the} infected and susceptible hosts on the pathogen dynamics. The mathematical challenge lies in the fact that the investigated model is partially degenerate and the solution map is not compact. The spatial heterogeneity of the model parameters and the distinct diffusion coefficients induce infection in the low-risk regions. In fact, as infection dispersal increases, the reproduction of the pathogen particles decreases. The dynamics of the investigated model is governed by the value of the basic reproduction number $R_0$. {If $R_0leq1$, then the} pathogen particles extinct, and for $R_0>1$ the pathogen particles persist, and we guarantees of the existence of at least one positive steady state. The asymptotic profile of the positive steady state is shown in the case when one or both diffusion coefficients for the host tends to zero or infinity.
我们提出了一个通用模型来研究{感染宿主和易感宿主的}不同扩散系数对病原体动态的影响。数学上的挑战在于所研究的模型是部分退化的,解图并不紧凑。模型参数的空间异质性和不同的扩散系数会诱发低风险区域的感染。事实上,随着感染扩散的增加,病原体粒子的繁殖会减少。所研究模型的动态受基本繁殖数 $R_0$ 值的支配。{如果 $R_0leq1$,则}病原体粒子灭绝;如果 $R_0>1$,则病原体粒子持续存在,我们保证至少存在一个正稳态。当宿主的一个或两个扩散系数趋于零或无穷大时,正稳态的渐近曲线就会显示出来。
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引用次数: 0
The role of Allee effect in cannibalistic species: An action plan to sustain the declining cod population 阿利效应在食人物种中的作用:维持鳕鱼数量下降的行动计划
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-05-15 DOI: 10.1051/mmnp/2024007
Parimita Roy, Sanjoli Jain, Mohamed Maama
Atlantic cod collapsed in the late 20th century after being harvested heavily for 50 years. This paper aims to design conservation guidelines for the cod population, which is diminishing due to predation by grey seals and cannibalism. For this purpose, we first designed a continuous time ecological model (with and without the Allee effect) using a system of differential equations consisting of juvenile Atlantic cod, adult Atlantic cod, and grey seals. The developed model has set forth global existence, non-negativity, and long-term behavior. Subsequently, to handle the extinction problem cost-effectively, Pontryagin's principle is employed to construct the optimal control, which is then numerically solved using an iterative forward–backward method. We numerically explored the impact of the Allee effect on cod survival within the original model and its two extended versions (i) stochastic and (ii)  reaction-diffusion, to thoroughly understand the possible consequences wherein a population has cannibalistic tendencies. The numerical comparison between the non-Allee and Allee models (Ordinary, Stochastic, Reaction-Diffusion) reveals that the Allee effect may significantly promote recovery and benefit the cannibalistic population.  We adopted a partial rank correlation coefficient (PRCC) to conduct a global sensitivity analysis to estimate the most sensitive parameters responsible for cod prevalence.
大西洋鳕鱼在被大量捕捞 50 年后,于 20 世纪末灭绝。由于灰海豹的捕食和食人行为,鳕鱼种群数量不断减少,本文旨在为鳕鱼种群设计保护指南。为此,我们首先利用由大西洋鳕幼鱼、大西洋鳕成鱼和灰海豹组成的微分方程系统,设计了一个连续时间生态模型(包含和不包含阿利效应)。所建立的模型规定了全局存在性、非负性和长期行为。随后,为了经济有效地处理灭绝问题,我们利用庞特里亚金原理构建了最优控制,并使用迭代前向后向法对其进行数值求解。我们在原始模型及其两个扩展版本(i)随机模型和(ii)反应扩散模型中对阿利效应对鳕鱼存活率的影响进行了数值探索,以深入了解在种群有食人倾向的情况下可能产生的后果。非阿利模式和阿利模式(普通模式、随机模式、反应扩散模式)之间的数值比较显示,阿利效应可能会显著促进食人种群的恢复并使其受益。 我们采用部分秩相关系数(PRCC)进行了全局敏感性分析,以估计造成鳕鱼流行的最敏感参数。
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引用次数: 0
Additive multiple contacts and saturation phenomena in epidemiological models are not detected by $R_0$ R_0$ 检测不到流行病学模型中的加性多重接触和饱和现象
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-04-01 DOI: 10.1051/mmnp/2024006
José Geiser Villavicencio-Pulido, I. Barradas, C. Nila-Luévano
Many infections are transmitted by direct contacts. Usually one single direct contact is needed to transmit the required minimum infectious load. Most models describe contagions by single contacts using a term of the type mass action law. However, modelling infections that are transmitted after the susceptible individual had contact with several sources of infection requires more than mass action law terms. We call additive multiple contacts those that do not produce infection by themselves, but can produce infection if they happen simultaneously. We are interested in understanding the role played by R0 missing the mark in infections in which the minimum infectious load is reached not only by single contacts but also by additive multiple contacts. We propose different mathematical models describing not only infections by one single contact but also by additive multiple contacts. We show all models have the same value of R0, but correspond to different epidemiological mechanisms. Two models show contagions by additive multiple contacts and a third one shows reduction of infections by some saturation process which is not captured by R0. This shows that trying to control the epidemics by controlling R0 could be unsufficient or in some cases waste resources.
许多传染病都是通过直接接触传播的。通常只需一次直接接触就能达到所需的最低传染量。大多数模型使用质量作用定律类型的术语来描述通过单次接触传播的传染病。然而,要模拟易感个体与多个传染源接触后传播的传染病,需要的不仅仅是质量作用定律术语。我们把那些本身不会产生感染,但如果同时发生就会产生感染的多重接触称为叠加接触。我们有兴趣了解 R0 在感染中的作用,在这种感染中,不仅单次接触会达到最小感染量,而且多次接触也会达到最小感染量。我们提出了不同的数学模型,不仅描述了单次接触的感染情况,也描述了多次接触的叠加感染情况。我们表明,所有模型的 R0 值相同,但对应不同的流行病学机制。两个模型显示了通过多重接触的叠加感染,第三个模型则显示了通过 R0 无法捕捉的某种饱和过程来减少感染。这表明,试图通过控制 R0 来控制流行病可能是不够的,在某些情况下甚至会浪费资源。
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引用次数: 0
(3+1)-dimensional Gardner equation deformed from (1+1)-dimensional Gardner equation and its conservation law 由 (1+1) 维加德纳方程变形而来的 (3+1) 维加德纳方程及其守恒定律
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-03-11 DOI: 10.1051/mmnp/2024004
Guiming Jin, Xueping Cheng, Jianan Wang
Through the application of the deformation algorithm, a novel (3+1)-dimensional Gardner equation and its associated Lax pair are derived from the (1+1)-dimensional Gardner equation and its conservation laws. As soon as the (3+1)-dimensional Gardner equation is set to be $y$ or $z$ independent, the Gardner equations in (2+1)-dimension are also obtained. To seek the exact solutions for these higher dimensional equations, the traveling wave method and the symmetry theory are introduced. Hence, the implicit expressions of traveling wave solutions to the (3+1)-dimensional and (2+1)-dimensional Gardner equations, the Lie point symmetry and the group invariant solutions to the (3+1)-dimensional Gardner equation are well investigated. In particular, after selecting some specific parameters, both the traveling wave solutions and the symmetry reduction solutions of hyperbolic function form are given.
通过变形算法的应用,从(1+1)维加德纳方程及其守恒定律推导出了一个新颖的(3+1)维加德纳方程及其相关的拉克斯对。只要将 (3+1)- 维加德纳方程设置为与 $y$ 或 $z$ 无关,就能得到 (2+1)- 维加德纳方程。为了寻求这些高维方程的精确解,引入了行波方法和对称理论。因此,研究了 (3+1)- 维和 (2+1)- 维加德纳方程的行波解的隐式表达、(3+1)- 维加德纳方程的列点对称性和群不变解。特别是,在选择一些特定参数后,给出了双曲函数形式的行波解和对称性还原解。
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引用次数: 0
Global Hopf bifurcation of a delayed diffusive Gause-type predator-prey system with the fear effect and Holling type III functional response 具有恐惧效应和霍林 III 型功能响应的延迟扩散高斯型捕食者-猎物系统的全局霍普夫分岔
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-02-16 DOI: 10.1051/mmnp/2024003
Qian Zhang, Ming Liu, Xiaofeng Xu
In this paper, a delayed diffusive predator-prey system with the fear effect and Holling type III functional response is considered, and Neumann boundary condition is imposed on this system. First, we explore the stability of the unique positive constant steady state and the existence of local Hopf bifurcation. Then the global attraction domain G∗ of system (4) is obtained by the comparison principle and the iterative method. Through constructing the Lyapunov function, we investigate uniform boundedness of periodic solutions’periods. Finally, we prove the global continuation of periodic solutions by  the global Hopf bifurcation theorem of Wu. Moreover, some numerical simulations that support the analysis results are given.
本文考虑了一个具有恐惧效应和霍林 III 型功能响应的延迟扩散捕食者-猎物系统,并对该系统施加了诺伊曼边界条件。首先,我们探讨了唯一正常数稳态的稳定性和局部霍普夫分岔的存在性。然后通过比较原理和迭代法得到系统 (4) 的全局吸引域 G∗。通过构建 Lyapunov 函数,我们研究了周期解的周期均匀有界性。最后,我们通过吴的全局霍普夫分岔定理证明了周期解的全局连续性。此外,我们还给出了一些支持分析结果的数值模拟。
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引用次数: 0
Global Hopf bifurcation of a delayed diffusive Gause-type predator-prey system with the fear effect and Holling type III functional response 具有恐惧效应和霍林 III 型功能响应的延迟扩散高斯型捕食者-猎物系统的全局霍普夫分岔
IF 2.2 4区 数学 Q1 Mathematics Pub Date : 2024-02-16 DOI: 10.1051/mmnp/2024003
Qian Zhang, Ming Liu, Xiaofeng Xu
In this paper, a delayed diffusive predator-prey system with the fear effect and Holling type III functional response is considered, and Neumann boundary condition is imposed on this system. First, we explore the stability of the unique positive constant steady state and the existence of local Hopf bifurcation. Then the global attraction domain G∗ of system (4) is obtained by the comparison principle and the iterative method. Through constructing the Lyapunov function, we investigate uniform boundedness of periodic solutions’periods. Finally, we prove the global continuation of periodic solutions by  the global Hopf bifurcation theorem of Wu. Moreover, some numerical simulations that support the analysis results are given.
本文考虑了一个具有恐惧效应和霍林 III 型功能响应的延迟扩散捕食者-猎物系统,并对该系统施加了诺伊曼边界条件。首先,我们探讨了唯一正常数稳态的稳定性和局部霍普夫分岔的存在性。然后通过比较原理和迭代法得到系统 (4) 的全局吸引域 G∗。通过构建 Lyapunov 函数,我们研究了周期解的周期均匀有界性。最后,我们通过吴的全局霍普夫分岔定理证明了周期解的全局连续性。此外,我们还给出了一些支持分析结果的数值模拟。
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引用次数: 0
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Mathematical Modelling of Natural Phenomena
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