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Neural activities of neuron–Astrocyte network under environmental disturbances: Numerical analysis and hardware experiments 环境干扰下神经元-星形胶质细胞网络的神经活动:数值分析和硬件实验
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108564
Kaijie Chen, Zhijun Li, Yang Yin
The normal functioning of the actual brain relies on the collaborative efforts of neurons across multiple functional regions as well as the support and regulation of astrocytes, and its operating environment is both intricate and diverse. Hence, to replicate the electrophysiological properties of the central nervous system more accurately, it is essential to take the neuronal heterogeneity, the role of astrocytes, and environmental effects into account together. To this end, a neuron–astrocyte network comprising an Hindmarsh-Rose (HR) neuron, a FitzHugh-Nagumo (FHN) neuron, and an astrocyte, is proposed in this paper. The network is subjected to a complex environment to mimic the neural firing activities in biological reality. Several numerical analyses are performed to reveal the effects of the environments on the firing activities and the role of the astrocyte on the heterogeneous neuron network. It is found that the astrocyte can reduce coupling strength through neurotransmitter transmission, allowing for real-time regulation of coupling strength between neurons. More interestingly, environmental changes can alter the firing patterns of the neuron–astrocyte network, and greater electromagnetic radiation intensity and higher temperature may contribute to the firing synchronization between the coupled neurons. Finally, a hardware implementation based on the DSP platform is constructed to verify the correctness and feasibility of the neuron–astrocyte network under the interference of complex environment.
实际大脑的正常功能既依赖于多个功能区神经元的协同作用,也依赖于星形胶质细胞的支持和调控,其运行环境复杂多样。因此,为了更准确地复制中枢神经系统的电生理特性,必须综合考虑神经元的异质性、星形胶质细胞的作用和环境效应。为此,本文提出了一个由Hindmarsh-Rose (HR)神经元、FitzHugh-Nagumo (FHN)神经元和星形胶质细胞组成的神经元-星形胶质细胞网络。神经网络被置于一个复杂的环境中,以模拟生物现实中的神经放电活动。通过数值分析揭示了环境对星形胶质细胞放电活动的影响以及星形胶质细胞在异质神经元网络中的作用。发现星形胶质细胞可以通过神经递质传递降低偶联强度,实现神经元间偶联强度的实时调节。更有趣的是,环境变化可以改变神经元-星形胶质细胞网络的放电模式,更高的电磁辐射强度和更高的温度可能有助于耦合神经元之间的放电同步。最后,构建了基于DSP平台的硬件实现,验证了复杂环境干扰下神经元-星形胶质细胞网络的正确性和可行性。
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引用次数: 0
Event-triggered joint adaptive high-gain observer design for delayed output-sampled nonlinear systems with unknown parameters and output injection 具有未知参数和输出注入的延迟输出采样非线性系统的事件触发联合自适应高增益观测器设计
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108541
Xincheng Zhuang, Yang Tian, Haoping Wang, Sofiane Ahmed-Ali
This study presents a novel event-triggered joint adaptive high-gain observer design for delayed output-sampled nonlinear systems with output injection. These systems are characterized by the presence of unknown parameters that influence both the state and output equations. The major difficulty in designing the observer lies in the interplay between event-triggered mechanism, output injection, and time-varying delays. Additionally, the non-affine nature of the parameter’s entry into the system states equation further complicates the design. To address these challenges, a new adaptive law for unknown parameter estimation is developed under delay measurement. A novel non-Zeno dynamic event-triggered mechanism coupled with a closed-loop output predictor is proposed. The resulting observer exhibits two main features: the first one provides an input-to-state stable property, and the second one is the establishment of a theoretical condition for the inter-event time of the proposed dynamic event-triggered mechanism. The effectiveness of the designed observer is demonstrated through numerical simulations and performance comparisons with previous works.
针对具有输出注入的延迟输出采样非线性系统,提出了一种新的事件触发联合自适应高增益观测器设计。这些系统的特点是存在影响状态方程和输出方程的未知参数。观测器设计的主要难点在于事件触发机制、输出注入和时变延迟之间的相互作用。此外,参数进入系统状态方程的非仿射性质进一步使设计复杂化。为了解决这些问题,提出了一种新的基于时延测量的未知参数估计自适应律。提出了一种新的非芝诺动态事件触发机制与闭环输出预测器相结合。所得到的观测器表现出两个主要特征:第一个特征提供了输入到状态的稳定特性,第二个特征是为所提出的动态事件触发机制的事件间时间建立了理论条件。通过数值模拟和与以往工作的性能比较,验证了所设计观测器的有效性。
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引用次数: 0
Axial-torsional coupling vibration model and nonlinear behavior of drill string system in oil and gas wells 油气井钻柱系统轴扭耦合振动模型及非线性特性
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108560
Xiaoqiang Guo, Zhichen Qiu, Mingming Li, Xinye Li, Ning Hu, Libin Zhao, Chengyang Ye
In response to the failure problem of axial-torsional coupling vibration of drill string in oil & gas wells, an axial-torsional coupling nonlinear vibration model of drill string is established using the finite element method, which can effectively simulate the coupling vibration of actual wellbore drill string multi-body systems and the real-time rock breaking effect. Moreover, the correctness and effectiveness of the theoretical model verified by a similar experiment of tubing vibration. Finally, the influences of feed rate and rotary drilling speed on the nonlinear behavior of the vibration of the drill string are investigated. The results obtained demonstrate that, the axial vibration response of the drill string system shows an overall trend of quasi-periodic-chaotic change with the increase of feed rate, and the torsional vibration of the drill string shows the trend of quasi periodic-chaotic. When the feed rate is high, the vibration of the drill string system is mainly for the irregular and complex hybrid motion. Therefore, the appropriate reduction of feed speed can increase the stability of the drill string on-site, and reduce the jump drilling and stick-slip vibration of the drill string. When the rotary drilling speed is 90–210 rpm, the torsional vibration response of the drill string shows a chaotic-quasi-periodic trend and the complexity of the torsional vibration of the drill string decreases with the increase of rotary drilling speed. The axial vibration response of the drill string shows a chaotic-quasi-periodic-chaotic trend with the increase of the rotary drilling speed. When the rotary drilling speed increases to 400–410 rpm, the axial vibration of the drill string becomes a quasi-periodic motion. Therefore, increasing the rotary drilling speed within a certain range can reduce the complexity of the vibration of the drill string and reduce the skip and stick-slip vibration of the drill string.
针对油层钻柱轴扭耦合振动失效问题;采用有限元法建立了气井钻柱轴扭耦合非线性振动模型,能有效模拟实际井筒钻柱多体系统的耦合振动和实时破岩效果。并通过油管振动实验验证了理论模型的正确性和有效性。最后,研究了进给速度和旋转钻进速度对钻柱振动非线性行为的影响。结果表明,钻柱系统的轴向振动响应随进给速率的增加总体上呈现准周期混沌变化趋势,钻柱的扭转振动也呈现准周期混沌变化趋势。当进给速率较大时,钻柱系统的振动主要为不规则复杂的混合运动。因此,适当降低进给速度可以提高现场钻柱的稳定性,减少钻柱的跳钻和粘滑振动。当转速为90 ~ 210 rpm时,钻柱扭转振动响应呈现混沌-准周期趋势,且钻柱扭转振动复杂性随转速的增加而降低。随着转速的增加,钻柱轴向振动响应呈现混沌-准周期-混沌的趋势。当旋转钻井速度增加到400-410 rpm时,钻柱的轴向振动变为准周期运动。因此,在一定范围内提高旋转钻井速度,可以降低钻柱振动的复杂性,减少钻柱的跳钻和粘滑振动。
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引用次数: 0
Nonlinear transient thermal stress investigation of 2D-FG porosity long cylinder sector 二维fg孔隙度长圆柱扇形非线性瞬态热应力研究
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108558
Amir Najibi, Parisa Alizadeh
We present a nonlinear numerical study of the two-dimensional functionally graded porosity (2D-FGP) transient thermo-elastic problem for the infinite cylinder sector with temperature-dependent material properties. The paper employs a higher-order graded finite element method (graded-FEM) to develop the problem and determines the effective values of the 2D material properties using the Kerner micromechanical model. The sequentially coupled nonlinear thermo-elastic problem is solved by an implicit time-marching technique, and the validity of graded FEM using the cell-vertex finite volume method (CV-FVM) is assessed. Then the effects of material and porosity distributions on the temperature, displacement, stresses, and strength of the 2D-FGP plane strain cylinder sector are thoroughly investigated. The findings show that porosity has a smaller impact on normalized effective stresses (NES) than material distribution, as evidenced by higher NES values in the cylinder sector without porosity and the ZrO2 rich cylinder has the lowest NES value. Despite a temperature difference of only 8K, the cylinder with no porosity distribution has 56%, 48%, 68%, and 60% higher radial, hoop, axial, and von Mises stresses than the cylinder with a quadratic porosity distribution. At the specific point, higher porosity at nr=nθ=1 compared to nr=nθ=2 resulted in a 5K temperature decrease and correspondingly lower stresses, indicating that the structure's porosity reduced the effective stress. Because thermal stress is highly sensitive to constituents and porosity distributions, optimizing the parameters is critical to having the most effective stress reductions.
我们提出了一个非线性数值研究的二维功能梯度孔隙率(2D-FGP)瞬态热弹性问题的无限圆柱体扇形与温度相关的材料性质。本文采用高阶梯度有限元法(graded- fem)来求解该问题,并利用Kerner细观力学模型确定了二维材料性能的有效值。采用隐式时间推进法求解了序列耦合非线性热弹性问题,并对单元-顶点有限体积法(CV-FVM)的有效性进行了评价。然后,深入研究了材料和孔隙率分布对2D-FGP平面应变筒扇形的温度、位移、应力和强度的影响。结果表明:孔隙度对归一化有效应力(NES)的影响小于材料分布,无孔隙度圆柱体区域的归一化有效应力值较高,而富ZrO2圆柱体区域的归一化有效应力值最低;尽管温差仅为8°K,但无孔隙度分布的圆柱体的径向、环向、轴向和von Mises应力比二次孔隙度分布的圆柱体高56%、48%、68%和60%。在特定的点上,nr=nθ=1时孔隙率比nr=nθ=2时高,导致5°K温度下降,应力相应降低,说明结构的孔隙率降低了有效应力。由于热应力对组分和孔隙度分布高度敏感,因此优化参数对于实现最有效的应力降低至关重要。
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引用次数: 0
Preservation of dissipativity in dimensionality reduction 在降维中保持耗散性
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108553
Sergey V. Stasenko, Alexander N. Kirdin
Systems with predetermined Lyapunov functions play an important role in many areas of applied mathematics, physics and engineering: dynamic optimization methods (objective functions and their modifications), machine learning (loss functions), thermodynamics and kinetics (free energy and other thermodynamic potentials), adaptive control (various objective functions, stabilization quality criteria and other Lyapunov functions). Dimensionality reduction is one of the main challenges in the modern era of big data and big models. Dimensionality reduction for systems with Lyapunov functions requires preserving dissipativity: the reduced system must also have a Lyapunov function, which is expected to be a restriction of the original Lyapunov function on the manifold of the reduced motion. An additional complexity of the problem is that the equations of motion themselves are often unknown in detail in advance and must be determined in the course of the study, while the Lyapunov function could be determined based on incomplete data. Therefore, the projection problem arises: for a given Lyapunov function, find a field of projectors such that the reduction of any dissipative system is again a dissipative system. In this paper, we present an explicit construction of such projectors and prove their uniqueness. We have also taken the first step beyond the approximation by manifolds. This is required in many applications. For this purpose, we introduce the concept of monotone trees and find a projection of dissipative systems onto monotone trees that preserves dissipativity.
具有预定李雅普诺夫函数的系统在应用数学、物理和工程的许多领域发挥着重要作用:动态优化方法(目标函数及其修改)、机器学习(损失函数)、热力学和动力学(自由能和其他热力学势)、自适应控制(各种目标函数、稳定质量标准和其他李雅普诺夫函数)。降维是当今大数据、大模型时代的主要挑战之一。具有Lyapunov函数的系统的降维要求保持耗散性:降维后的系统还必须有一个Lyapunov函数,这是原始Lyapunov函数在降维运动流形上的限制。这个问题的另一个复杂性是,运动方程本身往往是事先未知的,必须在研究过程中确定,而李雅普诺夫函数可以根据不完整的数据确定。因此,投影问题出现了:对于给定的李雅普诺夫函数,找到一个投影域,使得任何耗散系统的约简都是一个耗散系统。本文给出了这类投影的显式构造,并证明了它们的唯一性。我们也迈出了超越流形近似的第一步。这在许多应用程序中都是必需的。为此,我们引入了单调树的概念,并找到了耗散系统在单调树上保持耗散率的投影。
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引用次数: 0
Vector polynomial based analytical inverse kinematics and configuration design of 6R robotic arms 基于向量多项式的6R机械臂解析运动学逆解与构型设计
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-20 DOI: 10.1016/j.cnsns.2024.108546
Feifei Chen, Xiaoting Rui, Hehua Ju, Guoping Wang, Kaimeng Wang
Robotic arms with high precision play a crucial role in industries like aerospace and intelligent manufacturing. Currently, industrial robotic arms typically adopt spherical wrists to obtain analytical solutions; however, manufacturing-related structural errors significantly reduce the end effector's absolute positioning accuracy, impeding the development towards high-precision autonomous control. This study presents a series of kinematic modelling, configuration design, and analytical inverse solutions for robotic arms with the goal of delivering precise and effective inverse kinematic solutions, while taking the engineering limitation into consideration. Taking the vector polynomial system as the key premise, an iterative kinematic model with the fewest number of equations, independent variables, and orders of magnitude is then established. Through decoupling analysis of the position and attitude in the kinematic model, configuration designs of robotic arms with orthogonal or parallel axes are proposed without adhering to the restrictions of three-axis intersection. Additionally, the inverse kinematic issue is addressed by conversion into polynomial space using the Dixon elimination approach. Eight sets of inverse kinematic solutions are obtained for any reachable position and attitude in simulation. The computation time does not exceed 2 milliseconds, and both position and attitude relative errors are below 10–15, enhancing computational accuracy for robot kinematics. The work of this paper provides a practical kinematic theory for the development of robotic arms with high absolute positioning accuracy and efficiency.
高精度机械臂在航空航天、智能制造等行业中发挥着至关重要的作用。目前,工业机械臂通常采用球形手腕来获得解析解;然而,与制造相关的结构误差极大地降低了末端执行器的绝对定位精度,阻碍了高精度自主控制的发展。本研究针对机械臂进行了一系列的运动学建模、构型设计和解析反解,目的是在考虑工程限制的情况下提供精确有效的运动学反解。以向量多项式系统为关键前提,建立方程数最少、自变量数最少、数量级最少的迭代运动学模型。通过运动学模型中位置和姿态的解耦分析,提出了不受三轴相交约束的正交或平行机械臂构型设计。此外,利用Dixon消去法将逆运动学问题转换为多项式空间来解决。仿真得到了任意可达位置和姿态的八组运动学逆解。计算时间不超过2毫秒,位置和姿态相对误差均在10-15以内,提高了机器人运动学的计算精度。本文的工作为研制具有较高绝对定位精度和效率的机械臂提供了实用的运动学理论依据。
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引用次数: 0
Multi-artificial neural network for inverse eigenvalue problem with the weighted Helmholtz equation 加权Helmholtz方程特征值反问题的多人工神经网络
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-19 DOI: 10.1016/j.cnsns.2024.108544
Zhengfang Zhang, Shizhong Zou, Xihao Zhou, Xinping Shao, Mingyan He, Weifeng Chen
The inverse eigenvalue problem of weighted Helmholtz equations is investigated. The density function is recovered from the observation of the limited spectral data. It is reformulated as an optimization problem and a multi-objective loss function is defined accordingly. A multi-artificial neural network (multi-ANN) algorithm is proposed. The existence and stability of the solution of the optimization problem, and the convergence of the multi-ANN solution towards that of the original optimization problem are proved. The numerical results of one-dimensional and two-dimensional inverse eigenvalue problems of the weighted Helmholtz equation are given. Compared with the traditional finite element method, the robustness and effectiveness of the proposed multi-ANN method are illustrated.
研究了加权亥姆霍兹方程的特征值反问题。密度函数由有限光谱数据的观测恢复。将其重新表述为优化问题,并定义了多目标损失函数。提出了一种多人工神经网络(multi-ANN)算法。证明了该优化问题解的存在性和稳定性,以及多神经网络解对原优化问题解的收敛性。给出了加权亥姆霍兹方程一维和二维特征值反问题的数值结果。通过与传统有限元方法的比较,验证了该方法的鲁棒性和有效性。
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引用次数: 0
Quantized hybrid impulsive control for finite-time synchronization of fractional-order uncertain multiplex networks with multiple time-varying delays 多时变时滞分数阶不确定多路网络有限时间同步的量化混合脉冲控制
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-19 DOI: 10.1016/j.cnsns.2024.108540
Qiu Peng, Siman Lin, Manchun Tan
In this paper, the finite-time synchronization (FTS) problem of fractional-order multiplex networks with internal delay, intra- and inter-layer coupling delays, and uncertain intra- and inter-layer coupling matrices is studied. A new hybrid controller, composed of an impulsive controller and a quantized controller, is designed to achieve FTS for the considered network in order to save control resources and reduce the burden of the network. Based on the fractional-order Lyapunov function method, utilizing the fractional-order impulsive finite-time inequality and other inequality methods, several fresh sufficient conditions for the synchronization of the fractional-order uncertain multiplex network (FOUMN) with multiple time-varying delays in an explicitly estimated finite time are obtained. These sufficient criteria also reflect that the FTS of the network is related to its topology, quantization parameters, the order of the fractional derivative, and the impulse function. Lastly, two numerical examples confirm that the theoretical findings are valid.
研究了具有内部延迟、层内和层间耦合延迟以及层内和层间耦合矩阵不确定的分数阶多路网络的有限时间同步问题。为了节省控制资源,减轻网络负担,设计了一种由脉冲控制器和量化控制器组成的新型混合控制器来实现所考虑的网络的FTS。基于分数阶Lyapunov函数方法,利用分数阶脉冲有限时间不等式等不等式方法,得到了具有多个时变时滞的分数阶不确定多路网络(FOUMN)在显式估计的有限时间内同步的几个新的充分条件。这些充分的准则也反映了网络的FTS与其拓扑结构、量化参数、分数阶导数的阶数和脉冲函数有关。最后,通过两个算例验证了理论结果的正确性。
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引用次数: 0
Computation of domains of analyticity of lower dimensional tori in a weakly dissipative Froeschlé map 弱耗散froeschl<s:1>映射中低维环面解析域的计算
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-19 DOI: 10.1016/j.cnsns.2024.108538
Adrián P. Bustamante
We consider a Froeschlé map and we add a weak dissipation proportional to ɛ3, where ɛ is the parameter of perturbation. We compute formal expansions of lower dimensional tori, both in the conservative and weakly dissipatives cases, and use them to estimate the shape of their domains of analyticity with respect to ɛ. Our results support conjectures in the literature.
我们考虑一个froeschl映射,我们添加了一个成比例的弱耗散,其中,为扰动参数。我们计算了低维环面在保守和弱耗散情况下的形式展开式,并用它们来估计它们的解析域的形状。我们的结果支持文献中的猜想。
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引用次数: 0
Characterization of global centers by the monodromy at infinity 用无穷远处的单态描述全局中心
IF 3.9 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-12-19 DOI: 10.1016/j.cnsns.2024.108543
Isaac A. García, Jaume Giné, Jaume Llibre
In this work we focus in the family of real planar polynomial vector fields of arbitrary degree. We are interested in to characterize when a (local) center singularity of these vector fields becomes a global center, that is, its period annulus foliates the punctured real plane. The characterization of any global center is done by blowing-down the polycycle at infinity into a monodromic singular point.
本文主要研究任意次的实数平面多项式向量场族。我们感兴趣的是描述这些向量场的一个(局部)中心奇点何时成为一个全局中心,即它的周期环叶在被戳破的实平面上。任何全局中心的表征都是通过在无穷远处将多环吹倒成单奇异点来完成的。
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引用次数: 0
期刊
Communications in Nonlinear Science and Numerical Simulation
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