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This paper is concerned with the long term behavior of solutions for Newton–Boussinesq equations with variable delay and distributed delay defined on an unbounded channel. Firstly, the method of uniform tail-estimates is used to surmount the obstacle of the non-compactness of Sobolev embeddings on unbounded domains, and then the existence and uniqueness of tempered pullback attractors is proved. Secondly, we use the idea of Łukaszewicz (Discrete Cont Dyn Syst 34:4211–4222, 2014) to show that the existence of invariant measures. Finally, the upper semicontinuity of pullback attractors as the delay time tends to zero is established. [ABSTRACT FROM AUTHOR]

The mechanism of cytoplasmic incompatibility (CI) is important in the study of Wolbachia invasion in wild mosquitoes. Su et al. (Bull Math Biol 84(9):95, 2022) proposed a delay differential equation model by relating the CI effect to maturation delay. In this paper, we investigate the dynamics of this model by allowing the same density-dependent death rate and distinct density-independent death rates. Through analyzing the existence and stability of equilibria, we obtain the parameter conditions for Wolbachia successful invasion if the maternal transmission is perfect. While if the maternal transmission is imperfect, we give the ranges of parameters to ensure failure invasion, successful invasion and partially suppressing, respectively. Meanwhile, numerical simulations indicate that the system may exhibit monostable and bistable dynamics when parameters vary. Particularly, in the bistable situation an unstable separatrix, like a line, exists when choosing constant functions as initial values; and the maturation delay affects this separatrix in an interesting way. [ABSTRACT FROM AUTHOR]

We consider the numerical stability problem for fractional delay Schrödinger equations involving a Caputo fractional derivative in time, which is developed by Galerkin finite element method (FEM) in space and fractional linear multistep methods (FLMMs) in time. Through rigorous analyses of the characteristic equation yielded by the Laplace transform, we first present an α -dependent coefficient criterion to ensure the stability of spatially semidiscrete Galerkin FEM and extend the stability property to all convergent spatially semidiscrete methods. Secondly, by introducing a decoupling technique after Z transform, we prove the stability of FLMMs generated by both A-stable and A( β )-stable linear multistep methods, without any restriction on the time step size. The stability results are formulated by the fractional exponent, the principal eigenvalue of Dirichlet Laplacian, and the mesh size, but are not related to the delay and time step size. However, for a general spatial region, the principal eigenvalue of Dirichlet Laplacian is always unavailable. In order to provide an effective method for stability detection, when the stability condition is violated, we prove that the fractional trapezoidal rule is an effective method to detect stability because it can not only maintain the stable behavior of the semidiscrete solution, but also the unstable behavior. Extensive numerical experiments for fractional delay Schrödinger equations confirm the long-time decay behaviors of the fully discrete numerical solutions. [ABSTRACT FROM AUTHOR]

In this work, we examine a third-order nonlinear neutral integro-differential equation with constant delay. By building a Lyapunov functional, we obtain some sufficient criteria that ensure the asymptotic stability and boundedness of solutions for an analyzed equation. We present two examples to demonstrate the applicability of our conclusions, which extend and improve several well-known results in the literature. [ABSTRACT FROM AUTHOR]

A version of the Floquet theory for first order delay differential equations is proposed. Formula of solutions representation is obtained. On this basis, the stability of first order delay differential equations is studied. An analogue of the classical integral Lyapunov–Zhukovskii test of stability is proved. New, in comparison with all known, tests of the exponential stability are obtained on the basis of the Floquet theory. A possibility to achieve the exponential stability is connected with oscillation of solutions. [ABSTRACT FROM AUTHOR]

Kinetic chemical reactions find applications across various fields. In industrial processes, they drive the production of essential materials like fertilizers and pharmaceuticals. In environmental science, they are crucial to understanding pollution dynamics. Additionally, in biochemistry, they underpin vital cellular processes, offering insights into disease mechanisms and drug development. In this work, we present a new advancement of a dynamical system for kinetically controlled chemical reactions and the dependency of its solution on the initial conditions using mathematical techniques for fractional orders. By utilizing this fixed-point approach, we can derive the existence and uniqueness theorem of the proposed model. We further show that the chemical kinetics of the fractional model are stable through the Hyers-Ulam stability condition. We finally run a numerical simulation to verify our conclusions. The manuscript concludes with demonstrative examples. [ABSTRACT FROM AUTHOR]

Dengue is one of the most serious vector-borne diseases in the world. Although there is still no effective method to control this rapidly spreading disease, dengue vaccine is the best control measure for the foreseeable future. Dengue vaccine development has made great progress, but a better understanding of how vaccine-induced immune responses are related to vaccine efficacy can accelerate development and testing, and improve potential risks. In this paper, we formulate a dengue disease model with waning vaccine-induced immunity and a time delay depicting the extrinsic incubation period of mosquitoes in dengue transmission. The basic reproduction number is obtained, which is the threshold for distinguishing between the disappearance and prevalence of dengue. By constructing appropriate Lyapunov functionals, the global asymptotic dynamics of the system are established. By using the Pontryagin's minimum principle with delay, we included five time-dependent controls to evaluate the impact of four different schemes on our model, which provides a theoretical basis for people to effectively prevent and control dengue disease. Finally, elasticity and sensitivity analysis are given and data fitting is conducted based on the number of weekly cases reported in Singapore in 2022. This helps one to understand the importance of vaccine-related parameters and provides some perspective on the development trend of the disease. [ABSTRACT FROM AUTHOR]

Despite the availability of successful vaccines, measles outbreaks have occurred frequently in recent years, presumably due to the lack of proper vaccination implementation. Moreover, measles cases in adult groups, albeit small in number, indicate that the previously neglected adult group may need to be brought into vaccine coverage to achieve WHO's goal of measles eradication from the globe. In this study, we develop a novel transmission dynamics model to describe measles cases in adults and children to evaluate the role of adult infection in persistent measles cases and vaccination programs for eradication. Analysis of our model, validated by measles cases from outbreaks in Nepal, provides the vaccination reproduction number (conditions for measles eradication or persistence) and the role of contact network size. Our results highlight that while children are primary targets for measles outbreaks, a small number of infections in adults may act as a reservoir for measles, causing obstacles to eradication. Furthermore, our model analysis shows that while impactful controls can be achieved by children-focused vaccines, a combined adult-child vaccination program may help assert eradication of the disease.

Releasing Wolbachia-infected male mosquitoes to suppress wild females through cytoplasmic incompatibility (CI) has proven to be a safe and effective method for mosquito control. We study a release strategy that males are released with a constant amount c at time t k = k T , k = 0 , 1 , 2 , … . The determination of T is related to the sexually active lifespan of released males T ¯ . By introducing the early lethal effect of CI, we formulate a delay differential equation model for mosquito suppression based on Beverton-Holt-type of birth. After explicitly expressing two thresholds c ∗ and T ∗ , we prove that when c ∈ (0 , c ∗) and T ∈ (T ¯ , T ∗) , the model displays the bistable dynamics, where mosquito population either declines to zero, or approaches a positive periodic state. The rigorous mathematical proof of the exact number of periodic solutions and their stability analyses is obtained by proving that every solution is sandwiched between two “good” solutions, whose initial functions are chosen to be the solutions of the model without delay. [ABSTRACT FROM AUTHOR]

The Ebola virus disease (EVD) has been endemic since 1976, and the case fatality rate is extremely high. EVD is spread by infected animals, symptomatic individuals, dead bodies, and contaminated environment. In this paper, we formulate an EVD model with four transmission modes and a time delay describing the incubation period. Through dynamical analysis, we verify the importance of blocking the infection source of infected animals. We get the basic reproduction number without considering the infection source of infected animals. And, it is proven that the model has a globally attractive disease-free equilibrium when the basic reproduction number is less than unity; the disease eventually becomes endemic when the basic reproduction number is greater than unity. Taking the EVD epidemic in Sierra Leone in 2014–2016 as an example, we complete the data fitting by combining the effect of the media to obtain the unknown parameters, the basic reproduction number and its time-varying reproduction number. It is shown by parameter sensitivity analysis that the contact rate and the removal rate of infected group have the greatest influence on the prevalence of the disease. And, the disease-controlling thresholds of these two parameters are obtained. In addition, according to the existing vaccination strategy, only the inoculation ratio in high-risk areas is greater than 0.4, the effective reproduction number can be less than unity. And, the earlier the vaccination time, the greater the inoculation ratio, and the faster the disease can be controlled. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the notion of practically susceptible population, which is a fraction of the biologically susceptible population. Assuming that the fraction depends on the severity of the epidemic and the public's level of precaution (as a response of the public to the epidemic), we propose a general framework model with the response level evolving with the epidemic. We firstly verify the well-posedness and confirm the disease's eventual vanishing for the framework model under the assumption that the basic reproduction number R 0 < 1 . For R 0 > 1 , we study how the behavioural response evolves with epidemics and how such an evolution impacts the disease dynamics. More specifically, when the precaution level is taken to be the instantaneous best response function in literature, we show that the endemic dynamic is convergence to the endemic equilibrium; while when the precaution level is the delayed best response, the endemic dynamic can be either convergence to the endemic equilibrium, or convergence to a positive periodic solution. Our derivation offers a justification/explanation for the best response used in some literature. By replacing "adopting the best response" with "adapting toward the best response", we also explore the adaptive long-term dynamics. [ABSTRACT FROM AUTHOR]

In this paper, the problems of positivity and exponential stability a BAM-Cohen-Grossberg neural networks model with time-varying delays and nonlinear self-excitation rates are studied. By novel comparison techniques via differential-integral inequalities, the exponential convergence of state trajectories to a unique positive equilibrium is established by tractable linear programming conditions, which can be effectively solved by various convex optimization algorithms. Numerical simulations are given to illustrate the effectiveness of the obtained theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, the existence of positive periodic solutions of neural networks with time-varying delays is discussed by using the fixed point theory on cones. Some necessary and sufficient conditions guaranteeing the existence of one positive periodic solution of the considered system are established. Finally, we exhibit an example to verify the applicability of our abstract results. [ABSTRACT FROM AUTHOR]

In this manuscript, we study an averaging principle for fractional stochastic pantograph differential equations (FSDPEs) in the ψ -sense accompanied by Brownian movement. Under certain assumptions, we are able to approximate solutions for FSPEs by solutions to averaged stochastic systems in the sense of mean square. Analysis of system solutions before and after the average allows extending the classical Khasminskii approach to random fractional differential equations in the sense of ψ -Caputo. For clarity, we present at the end an applied example to facilitate the clarification of the theoretical results obtained [ABSTRACT FROM AUTHOR]

This paper deals with Kalecki's 1935 business cycle model, where a finite time lag in the investment dynamics is assumed. The time lag is the gestation period elapsing between orders for capital goods and deliveries of finished industrial equipment. Including the actual mainstream theory, the economic literature agrees on the consequences that time lag has on the economic activity. It is a cause of persistent economic fluctuations. Following some recent research lines on this model, here we restate the Kalecki approach, assuming sigmoidal functions in addition to Kalecki's linear treatment and further considering a non-constant capital depreciation. Never made until now, this last assumption is such that to yield, in place of a delayed differential equation, a Volterra delayed integro-differential equation. Taken the time delay and the rate of capital depreciation as critical parameters, a qualitative study of that equation is carried out. We proved that with a small-time lag stable equilibria arise. But, when the delay increases, equilibria are destabilized through Hopf bifurcations and stability switches occur. Consequently, a variety of cyclical behaviors appear. [ABSTRACT FROM AUTHOR]

In this article, we apply the Fourier transform to prove the Hyers-Ulam and Hyers-Ulam-Rassias stability for the first- and second-order nonlinear differential equations with initial conditions. Additionally, we extend the results to investigate the Mittag-Leffler-Hyers-Ulam and Mittag-Leffler-Hyers-Ulam-Rassias stability of these differential equations using the proposed method.

In this study, we are concerned with the existence and exponential stability issue of a delayed differential neoclassical growth model with discontinuous control strategy. By employing the Filippov’s theory and dichotomy theory, together with the Lyapunov functional method, novel criteria on existence and exponential stability are established for the addressed model. The established theoretical results extend and supplement the related results in the existing literature. Moreover, a simulation example is presented to verify the practicability of the proposed results.

In this paper, we provide sharp criteria of global attraction for a class of non-autonomous reaction–diffusion equations with delay and Neumann conditions. Our methodology is based on a subtle combination of some dynamical system tools and the maximum principle for parabolic equations. It is worth mentioning that our results are achieved under very weak and verifiable conditions. We apply our results to a wide variety of classical models, including the non-autonomous variants of Nicholson's equation or the Mackey–Glass model. In some cases, our technique gives the optimal conditions for the global attraction. [ABSTRACT FROM AUTHOR]

In this work, we prove a nonlocal Halanay inequality with an exact decay rate. This enables us to analyze behavior of solutions to some classes of nonlocal ODEs and PDEs involving unbounded delays. The obtained results extend and improve the previous ones proved for fractional differential equations and other nonlocal subdiffusion equations. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a class of stochastic differential equations with fixed delays and obtain two conditions to guarantee that the zero solution is globally exponentially stable in mean square by using Gronwall inequality and matric theory, respectively. The results are new and interesting. Some examples are given to illustrate the correctness and effectiveness of our results. [ABSTRACT FROM AUTHOR]

The primary focus of this paper is to investigate the H ∞ state feedback control problem within uncertain fractional-order systems characterized by time-varying delays. Our approach centers on the development of an event-triggered H ∞ control strategy, facilitated by the refined fractional-order Razumikhin theorem. This strategy is aimed at ensuring the uniformly asymptotic stability of the controlled system while adhering to a predefined H ∞ performance index. The central challenge lies in the memory characteristics of the fractional-order calculus operator, particularly in the context of delayed fractional-order systems, where preventing the occurrence of the Zeno phenomenon is paramount. To address this challenge, we introduce a novel theoretical framework and establish a new condition to prevent Zeno behaviors. This condition is derived using inequality techniques and leverages several essential properties of fractional-order calculus. To verify the effectiveness and feasibility of our proposed method, we present two illustrative examples. [ABSTRACT FROM AUTHOR]

This article explores the Hilfer fractional derivative within the context of fractional differential equations and investigates a mathematical model formulated as a three-point boundary value problem (BVP). The primary focus is on the application of these models to analyze the jet flow of the Antarctic Circumpolar Current. The study establishes the existence of stream functions using Schaefer's fixed point theorem under the assumption of the continuity of the vorticity function Φ . Furthermore, the article delves into the existence and uniqueness results of the stream functions by employing the Banach fixed point theorem. This analysis is conducted under the condition that the vorticity function Φ is Lipschitz continuous with respect to the stream function. Additionally, the stability of the stream functions of the BVP is explored through Ulam–Hyers and generalized Ulam–Hyers stability analyses. In contrast to the foundational results presented for the three-point BVP, the article includes illustrative examples aimed at validating the findings. [ABSTRACT FROM AUTHOR]

This paper examines the short-term or transient dynamics of SIR infectious disease models in patch environments. We employ reactivity of an equilibrium and amplification rates, concepts from ecology, to analyze how dispersals/travels between patches, spatial heterogeneity, and other disease-related parameters impact short-term dynamics. Our findings reveal that in certain scenarios, due to the impact of spatial heterogeneity and the dispersals, the short-term disease dynamics over a patch environment may disagree with the long-term disease dynamics that is typically reflected by the basic reproduction number. Such an inconsistence can mislead the public, public healthy agencies and governments when making public health policy and decisions, and hence, these findings are of practical importance. [ABSTRACT FROM AUTHOR]

The problem of designing an event-triggered guaranteed cost controller for uncertain polytopic fractional-order systems subject to unknown time-varying delays is investigated in this paper. An event-triggered guaranteed cost controller is designed, and sufficient conditions for the existence of an event-triggered guaranteed cost state-feedback control for the considered systems are established. We provide a numerical example to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper explains and applies a numerical technique utilizing the cubic B-spline functions and the mean value theorem (MVT) to solve a general time fractional partial differential equation (FPDE). The MVT for integrals enables us to approximate the time fractional derivatives in an appropriate simple form. We use the cubic B-spline functions to construct the numerical solution and its spatial derivatives. The great advantage of our technique is that it enables us to approximate solutions of many time FPDEs for several choices of F(x, t, u, ux, uxx). Two numerical examples have been included to emphasize the accuracy and efficiency of the method. It is demonstrated that the numerical method is unconditionally stable by employing the Von Neumann method (VNM).

In this paper, we consider the inverse coefficients problem of recovering a shear modulus μ and density ρ of a medium from the Neumann-to-Dirichlet map. This inverse problem is motivated by the reconstruction of mechanical properties of tissues in non-destructive testing. We prove Lipschitz stability results for any dimension $ d \geq 2 $ d ≥ 2 , provided that the parameters μ and ρ have upper and lower bounds and belong to a known finite dimensional subspace. The proofs rely on monotonicity relations between the parameters and the Neumann-to-Dirichlet operator, combined with the techniques of localized potentials. [ABSTRACT FROM AUTHOR]

The primary aim of this paper is to focus on the stability analysis of an advanced neural stochastic functional differential equation with finite delay driven by a fractional Brownian motion in a Hilbert space. We examine the existence and uniqueness of mild solution of d x a (s) + g (s , x a (s - ω (s))) = I x a (s) + f (s , x a (s - ϱ (s))) d s + ς (s) d ϖ H (s) , 0 ≤ s ≤ T , x a (s) = ζ (s) , - ρ ≤ s ≤ 0. The main goal of this paper is to investigate the Ulam–Hyers stability of the considered equation. We have also provided numerical examples to illustrate the obtained results. This article also discusses the Euler–Maruyama numerical method through two examples. [ABSTRACT FROM AUTHOR]

In the present paper, for the first time, we consider the problem of non-fragile finite-time guaranteed cost control for a class of fractional-order singular systems with norm-bounded uncertainties. Firstly, we establish a linear quadratic cost function based on the integral of integer order, which serves practical purposes and acts as a performance measure index for the closed-loop system. Then, leveraging finite-time boundedness theory, inequality techniques, and fractional-order calculus properties, we propose a non-fragile state feedback controller that ensures regularity, impulse-free, and finite-time boundedness in the closed-loop system. Furthermore, we establish an upper limit for the performance index. The resulting findings are reliant on the order of the considered fractional-order systems and are obtained through the use of strict linear matrix inequalities (LMIs), devoid of any equality restrictions. Finally, two simulation examples are provided to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper investigates the quasi-uniform stability for fractional-order fuzzy neural networks with uncertain proportional delay. By some analytical techniques, we explore a Henry-type Gronwall integral inequality (HtGII) with proportional delay which is a generalization of known result. With this inequality and the Leray–Schauder fixed point theorem, we prove the existence and uniqueness of solution to the discussed system. Meanwhile, we derive a new quasi-uniform stability condition which can be easily calculated. In particular, this condition can provide the expression for the supremum of settling time. Ultimately, we supply two examples to exhibit the effectiveness of the obtained stability condition. [ABSTRACT FROM AUTHOR]

This paper is concerned with the long-term behaviour of 3D double time-delayed magnetohydrodynamics (MHD)-Voight equations with non-autonomous forcing term. First, we establish the existence, forward compactness and forward stability of pullback attractors by the forward equi-continuity and forward pullback asymptotic compactness of solutions. We then study the upper semi-convergence of pullback attractors as the time parameter tends to positive infinity. Since the solution of this equation has no high regularity, we use the spectrum decomposition technique to prove the forward pointwise pullback asymptotic compactness of solutions. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a Cucker-Smale flocking model with varying time delay. We establish exponential asymptotic flocking without requiring smallness assumptions on the time delay size and the monotonicity of the influence function. [ABSTRACT FROM AUTHOR]

In this paper, we study a nonlinear fractional p-Laplacian boundary value problem containing both left Riemann–Liouville and right Caputo fractional derivatives with initial and integral conditions. Some new results on the existence and uniqueness of a solution for the model are obtained as well as the Ulam stability of the solutions. Two examples are provided to show the applicability of our results. [ABSTRACT FROM AUTHOR]

In this paper, we study the robust stability of implicit dynamic equations with causal operators on time scales. First, we investigate the solvability of these dynamic equations and then consider the preservation of stability under small perturbations. An L p version of Bohl–Perron principle for implicit dynamic equations is also studied. [ABSTRACT FROM AUTHOR]

In this work, we set up a new discrete predator–prey competitive model with time-varying delays and feedback controls. By virtue of the difference inequality knowledge, a sufficient condition which guarantees the permanence of the established discrete predator–prey competitive model with time-varying delays and feedback controls is derived. Under some appropriate parameter conditions, we have proved that the periodic solution of the system without delay exists and globally attractive. To verify the correctness of the derived theoretical fruits, we give two examples and execute computer simulations. Our obtained results are novel and complement previous known results. [ABSTRACT FROM AUTHOR]

This study considers two time delays applied in a commensalism system with a Beddington–DeAngelis functional response. In contrast with existing literature on commensalism systems, the system considered in the present study has two time delays in one species. The local stability of the positive equilibrium and Hopf bifurcation are investigated. The linearized stability is thoroughly examined. Furthermore, the characteristic equations are investigated, and the time delays are applied as the bifurcation parameter. Eventually, the presence of Hopf bifurcation is demonstrated. The Lyapunov functional is constructed, and the system is shown to have uniform persistence. The consistent persistent domain of the system is obtained by constructing a persistent function. Numerical simulations are conducted, demonstrating the reliability of the derived results. [ABSTRACT FROM AUTHOR]

This research paper investigates the problem of guaranteed cost control for a specific class of fractional-order switched systems characterized by both discrete and distributed time delays. By employing the linear matrix inequality (LMI) approach combined with the refined fractional-order Razumikhin theorem, a constructive geometric design of switching laws is developed to design a guaranteed cost controller ensuring the closed loop system not only asymptotically stable but also guarantees an adequate level of performance. The obtained conditions are dependent on the delays arising from the upper bound of the distributed time delays. These conditions are formulated in the form of linear matrix inequalities, which offers the advantage of efficient solvability using established convex algorithms. Two numerical examples with simulation results are provided to validate the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, we present sufficient conditions to ensure the stochastic asymptotic stability of the zero solution for a specific type of fourth-order stochastic differential equation (SDE) with constant delay. By reducing the fourth-order SDE to a system of first-order SDEs, we utilize a fourth-order quadratic function to derive an appropriate Lyapunov functional. This functional is then employed to establish standard criteria for the nonlinear functions present in the SDE. The stability result obtained in this study is novel and extends the existing findings on stability in fourth-order differential equations. Additionally, we provide an illustrative example to demonstrate the significance and accuracy of our main result. [ABSTRACT FROM AUTHOR]

This article proves a stability theorem for the disease-free equilibrium of a stochastic differential equations model of malaria disease dynamics. The theorem is formulated in terms of an invariant which is similar to the basic reproduction number of a related deterministic model. Compared to the deterministic model, stability of the disease-free equilibrium holds more generally for the stochastic model. The optimal control theory is applied to the stochastic model, revealing some important new insights. Theoretical results are illustrated by way of simulations. [ABSTRACT FROM AUTHOR]