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Introduction of Local Resonators to a Nonlinear Metamaterial with Topological Features 为具有拓扑特征的非线性超材料引入局部谐振器
Pub Date : 2024-02-12 DOI: 10.1115/1.4064726
Joshua LeGrande, A. Malla, M. Bukhari, Oumar Barry
Recent work in nonlinear topological metamaterials has revealed many useful properties such as amplitude dependent localized vibration modes and nonreciprocal wave propagation. However, thus far, there have not been any studies to include the use of local resonators in these systems. This work seeks to fill that gap through investigating a nonlinear quasiperiodic metamaterial with periodic local resonator attachments. We model a 1-dimensional metamaterial lattice as a spring-mass chain with coupled local resonators. Quasiperiodic modulation in the nonlinear connecting springs is utilized to achieve topological features. For comparison, a similar system without local resonators is also modeled. Both analytical and numerical methods are used to study this system. The dispersion relation of the infinite chain of the proposed system is determined analytically through the perturbation method of multiple scales. This analytical solution is compared to the finite chain response, estimated using the method of harmonic balance and solved numerically. The resulting band structures and mode shapes are used to study the effects of quasiperiodic parameters and excitation amplitude on the system behavior both with and without the presence of local resonators. Specifically, the impact of local resonators on topological features such as edge modes is established, demonstrating the appearance of a trivial bandgap and multiple localized edge states for both main cells and local resonators. These results highlight the interplay between local resonance and nonlinearity in a topological metamaterial demonstrating for the first time the presence of an amplitude invariant bandgap alongside amplitude dependent topological bandgaps.
最近在非线性拓扑超材料方面的研究揭示了许多有用的特性,例如与振幅相关的局部振动模式和非互惠波传播。然而,迄今为止,还没有任何研究将局部谐振器应用到这些系统中。本研究试图通过研究带有周期性局部谐振器附件的非线性准周期超材料来填补这一空白。我们将一维超材料晶格建模为带有耦合局部谐振器的弹簧-质量链。利用非线性连接弹簧中的准周期调制来实现拓扑特征。为了进行比较,还模拟了不带局部谐振器的类似系统。分析和数值方法都被用来研究这个系统。通过多尺度扰动法,分析确定了拟议系统无限链的色散关系。将此分析解与有限链响应进行比较,使用谐波平衡法进行估算,并进行数值求解。由此得出的带状结构和模态振型被用来研究准周期参数和激励振幅对存在和不存在局部谐振器的系统行为的影响。具体来说,研究确定了局部谐振器对拓扑特征(如边缘模式)的影响,证明了主单元和局部谐振器都出现了微带隙和多个局部边缘态。这些结果凸显了拓扑超材料中局部谐振和非线性之间的相互作用,首次证明了在存在振幅不变带隙的同时,还存在振幅相关的拓扑带隙。
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引用次数: 0
Long-Term Prediction of Large-Scale and Sporadic COVID-19 Epidemics Induced by the Original Strain in China Based On the Improved Non-Autonomous Delayed SIRD and SIR Models 基于改进的非自主延迟 SIRD 和 SIR 模型对中国原始菌株诱发的大规模和零星 COVID-19 流行病进行长期预测
Pub Date : 2024-02-12 DOI: 10.1115/1.4064720
Xin Xie, Lijun Pei
The COVID-19 virus emerged suddenly in early 2020 and spread rapidly, causing a significant impact on national health. To achieve our goal, we introduce a time-delay factor based on the traditional SIR/SIRD model and perform a sliding average on the data collected from the official website during the data preprocessing stage. The results of this study are in very good agreement with the actual evolution of COVID-19, and the prediction accuracy can all be controlled within 3%. From our model parameter perspective, under strict isolation policies, the transmission rate of COVID-19 in China is relatively low and still significantly reduced, indicating that government intervention has had a positive effect on epidemic prevention in the country. Besides, our model is also successfully applied to predict the outbreaks caused by the SARS virus in 2003 and the COVID-19 outbreak induced by the Omicron virus in 2022, demonstrating its wide application and effectiveness. This work facilitates timely measures and adjustment of medical resources in various regions, ultimately helping to reduce economic and social losses.
2020 年初,COVID-19 病毒突然出现并迅速传播,对国民健康造成了重大影响。为了实现我们的目标,我们在传统 SIR/SIRD 模型的基础上引入了时间延迟因子,并在数据预处理阶段对从官方网站收集的数据进行滑动平均。研究结果与 COVID-19 的实际演变情况非常吻合,预测精度均可控制在 3% 以内。从我们的模型参数来看,在严格的隔离政策下,COVID-19 在中国的传播率相对较低,且仍有明显下降,说明政府干预对中国的防疫工作起到了积极作用。此外,我们的模型还成功预测了 2003 年由 SARS 病毒引起的疫情和 2022 年由 Omicron 病毒诱发的 COVID-19 疫情,证明了其广泛的应用性和有效性。这项工作有助于各地区及时采取措施和调整医疗资源,最终帮助减少经济和社会损失。
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引用次数: 0
The Approximate Analysis of Higher-Order Frequencies of Nonlinear Vibrations of a Cantilever Beam with the Extended Galerkin Method 用扩展伽勒金方法近似分析悬臂梁非线性振动的高阶频率
Pub Date : 2024-02-12 DOI: 10.1115/1.4064724
Baochen Meng, Chencheng Lian, Ji Wang, Huimin Jing, Rongxing Wu, Ji Lin, Isaac Elishakoff
The nonlinear vibrations of elastic beams with large amplitudes are frequently treated as a typical problem of an elastica. As the continuation of the analysis of the deformation of an elastica, the nonlinear vibration equation of the elastic beam in the rotation angle of the cross-section has been established. Using the deformation function, the nonlinear equation with the inertia effect has been solved by the newly proposed extended Galerkin method (EGM). The solution to the vibration problem of the elastica is compared with earlier approximate solutions including the frequencies and mode shapes obtained by other methods, and the rotation angle and energy of each mode at the high-order frequency are also calculated. This solution procedure provides an alternative technique to the elastica problem by the EGM with possible applications to other nonlinear problems in many fields of science and technology.
弹性梁的大振幅非线性振动经常作为弹性体的典型问题来处理。作为弹性体变形分析的延续,建立了弹性梁在横截面旋转角上的非线性振动方程。利用变形函数,新提出的扩展伽勒金方法(EGM)求解了具有惯性效应的非线性方程。弹性体振动问题的解法与早期的近似解法进行了比较,包括其他方法获得的频率和模态振型,并计算了高阶频率下各模态的旋转角和能量。该求解程序提供了一种用 EGM 解决弹性体问题的替代技术,可应用于许多科学和技术领域的其他非线性问题。
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引用次数: 0
Influence of Unbalance and Differential Pressure On the Stability of Vertical Rotor-seal System 不平衡和压差对垂直转子密封系统稳定性的影响
Pub Date : 2024-02-12 DOI: 10.1115/1.4064725
S. Roy Kimura, Tsuyoshi Inoue, Hiroo Taura, Akira Heya
The rotordynamic (RD) fluid force generated in fluid elements such as seals in turbomachinery affects the stability of turbomachinery and causes shaft vibrations. Various studies have been conducted to clarify the effects of seals on the stability of rotor systems. Many studies have investigated the rotor dynamics of horizontal shaft systems, considering the RD fluid force generated in the seals, and in these studies, the stability of horizontal shaft systems has been assessed via eigenvalue analysis using RD coefficients. However, few studies have analyzed vertical shaft systems. The dynamic behavior of vertical shafts differs significantly from that of horizontal shafts because the weight of the rotor does not act on the seal in a vertical shaft system. Vertical shaft systems are generally prone to instability because of the fluid film whirl, and the amplitude of the shaft whirl tends to be large. When the amplitude is large, the RD fluid force cannot be linearized around the equilibrium point using RD coefficients. Therefore, destabilization and stabilization phenomena that appear in vertical shaft systems cannot be predicted using eigenvalue analysis. Fluid-structure interaction (FSI) analysis that considers the interaction between the shaft vibration and the RD fluid force generated in seals is required to predict such phenomena. This study used FSI analysis to investigate the effects of unbalance and differential pressure on the stability of a vertical shaft system subjected to RD fluid force generated in the seal.
涡轮机械密封等流体元件中产生的旋转动力(RD)流体力会影响涡轮机械的稳定性并导致轴振动。为了弄清密封件对转子系统稳定性的影响,已经开展了多项研究。考虑到密封件中产生的 RD 流体力,许多研究对水平轴系统的转子动力学进行了调查,在这些研究中,使用 RD 系数通过特征值分析评估了水平轴系统的稳定性。然而,很少有研究对竖井系统进行分析。垂直轴的动态行为与水平轴有很大不同,因为在垂直轴系统中,转子的重量不会作用在密封件上。垂直轴系统通常容易因流体膜旋流而不稳定,而且轴旋流的振幅往往很大。当振幅较大时,RD 流体力无法使用 RD 系数在平衡点周围线性化。因此,垂直轴系统中出现的失稳和稳定现象无法通过特征值分析进行预测。流固耦合(FSI)分析需要考虑轴振动与密封件中产生的 RD 流体力之间的相互作用,以预测此类现象。本研究使用 FSI 分析法研究了不平衡和压差对受到密封中产生的 RD 流体力影响的垂直轴系统稳定性的影响。
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引用次数: 0
Chaotic Dynamics of a Duffing Oscillator Subjected to External and Nonlinear Parametric Excitations with Delayed Feedbacks 带有延迟反馈的外部和非线性参数激励下的达芬振荡器的混沌动力学
Pub Date : 2024-02-12 DOI: 10.1115/1.4064723
Aijia Ding, Sengen Hu, Liangqiang Zhou
Duffing oscillator with delayed feedbacks is widely used in engineering. Chaos in such system plays an important role in the dynamic response of the system, which may lead to the collapse of the system. Therefore, it is necessary and significant to study the chaotic dynamical behaviors of such systems. Chaotic dynamics of the Duffing oscillator subjected to periodic external and nonlinear parameter excitations with delayed feedbacks are investigated both analytically and numerically in this paper. With the Melnikov method, the critical value of chaos arising from heteroclinic intersection is derived analytically. The feature of the critical curves separating chaotic and non-chaotic regions on the excitation frequency and the time delay is investigated analytically in detail. Under the corresponding system parameters, the monotonicity of the critical value to the excitation frequency, displacement time delay and velocity time delay is obtained rigorously. The chaos threshold obtained by the analytical method is verified by numerical simulations.
具有延迟反馈的达芬振荡器被广泛应用于工程领域。此类系统中的混沌在系统动态响应中起着重要作用,可能导致系统崩溃。因此,研究这类系统的混沌动力学行为是非常必要和重要的。本文从分析和数值两方面研究了受周期性外部和非线性参数激励、具有延迟反馈的达芬振荡器的混沌动力学。利用梅尔尼科夫方法,分析得出了异次元交汇产生的混沌临界值。本文详细分析了混沌区和非混沌区临界曲线在激励频率和时间延迟上的特征。在相应的系统参数下,严格得到了临界值对激励频率、位移时延和速度时延的单调性。通过数值模拟验证了分析方法得到的混沌临界值。
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引用次数: 0
A New Method for Solving Physical Problems with Nonlinear Phoneme within Fractional Derivatives with Singular Kernel 用奇异核分式导数解决非线性音素物理问题的新方法
Pub Date : 2024-02-12 DOI: 10.1115/1.4064719
Sondos M. Syam, Z. Siri, Sami Altoum, M. Aigo, R. Md Kasmani
In this paper, we present a novel numerical approach for solving nonlinear problems with a singular kernel. We prove the existence and uniqueness of the solution for these models as well as the uniform convergence of the function sequence produced by our novel approach to the unique solution. Additionally, we offer a closed form and prove these results for a specific class of these problems where the free term is a fractional polynomial, an exponential, or a trigonometric function. These findings are new to the best of our knowledge. To demonstrate the effectiveness of our numerical method and how to apply our theoretical findings, we solved a number of physical problems. Comparisons with various researchers are reported. Findings demonstrate that our approach is more effective and accurate. In addition, compared to methods that address this type of problems, our approach is simple to implement and has lower computing costs.
在本文中,我们提出了一种解决具有奇异内核的非线性问题的新型数值方法。我们证明了这些模型解的存在性和唯一性,以及由我们的新方法产生的函数序列对唯一解的均匀收敛性。此外,我们还为自由项为分数多项式、指数或三角函数的一类特定问题提供了封闭形式,并证明了这些结果。据我们所知,这些发现都是全新的。为了证明我们的数值方法的有效性以及如何应用我们的理论发现,我们解决了一些物理问题。我们还报告了与不同研究者的比较。研究结果表明,我们的方法更有效、更准确。此外,与解决这类问题的方法相比,我们的方法简单易用,计算成本更低。
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引用次数: 0
Long-Term Prediction of Large-Scale and Sporadic COVID-19 Epidemics Induced by the Original Strain in China Based On the Improved Non-Autonomous Delayed SIRD and SIR Models 基于改进的非自主延迟 SIRD 和 SIR 模型对中国原始菌株诱发的大规模和零星 COVID-19 流行病进行长期预测
Pub Date : 2024-02-12 DOI: 10.1115/1.4064720
Xin Xie, Lijun Pei
The COVID-19 virus emerged suddenly in early 2020 and spread rapidly, causing a significant impact on national health. To achieve our goal, we introduce a time-delay factor based on the traditional SIR/SIRD model and perform a sliding average on the data collected from the official website during the data preprocessing stage. The results of this study are in very good agreement with the actual evolution of COVID-19, and the prediction accuracy can all be controlled within 3%. From our model parameter perspective, under strict isolation policies, the transmission rate of COVID-19 in China is relatively low and still significantly reduced, indicating that government intervention has had a positive effect on epidemic prevention in the country. Besides, our model is also successfully applied to predict the outbreaks caused by the SARS virus in 2003 and the COVID-19 outbreak induced by the Omicron virus in 2022, demonstrating its wide application and effectiveness. This work facilitates timely measures and adjustment of medical resources in various regions, ultimately helping to reduce economic and social losses.
2020 年初,COVID-19 病毒突然出现并迅速传播,对国民健康造成了重大影响。为了实现我们的目标,我们在传统 SIR/SIRD 模型的基础上引入了时间延迟因子,并在数据预处理阶段对从官方网站收集的数据进行滑动平均。研究结果与 COVID-19 的实际演变情况非常吻合,预测精度均可控制在 3% 以内。从我们的模型参数来看,在严格的隔离政策下,COVID-19 在中国的传播率相对较低,且仍有明显下降,说明政府干预对中国的防疫工作起到了积极作用。此外,我们的模型还成功预测了 2003 年由 SARS 病毒引起的疫情和 2022 年由 Omicron 病毒诱发的 COVID-19 疫情,证明了其广泛的应用性和有效性。这项工作有助于各地区及时采取措施和调整医疗资源,最终帮助减少经济和社会损失。
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引用次数: 0
The Presence of Chaos in a Viscoelastic Harmonically Forced Von Mises Truss 粘弹性谐波强制冯米塞斯桁架中的混沌现象
Pub Date : 2024-01-25 DOI: 10.1115/1.4064554
Pritam Ghoshal, James Gibert, Anil K. Bajaj
This work investigates how viscoelasticity affects the dynamic behavior of a lumped-parameter model of a bistable von Mises truss. The system is controlled by a linear first-order equation and a second-order nonlinear Duffing equation with a quadratic nonlinearity that governs mechanical behavior. The second-order equation controls mechanical oscillations, while the linear first-order equation controls viscoelastic force evolution. Combined, the two equations form a third-order jerk equation that controls system dynamics. Viscoelasticity adds time scales and degrees of freedom to material behavior, distinguishing it from viscosity-only systems. Due to harmonic excitation, the system exhibits varied dynamic responses from periodic to quasiperiodic to chaotic. We explore the dynamics of a harmonically forced von Mises truss with viscous damping to address this purpose. We demonstrate this system's rich dynamic behavior due to driving amplitude changes. This helps explain viscoelastic system behavior. A viscoelastic unit replaces the viscous damper, and we show that, although viscous damping merely changes how fast the trajectory decays to an attractor, viscoelasticity modifies both the energy landscape and the rate of decay. In a conventional linear solid model, three viscoelastic parameters control the system's behavior instead of one, as in pure viscous damping. This adds degrees of freedom that affect system dynamics. We present the parameter space for chaotic behavior and the shift from regular to irregular motion. Finally, Melnikov's criteria identify the regular-chaotic threshold. The system's viscous and elastic components affect the chaotic threshold amplitude.
这项研究探讨了粘弹性如何影响双稳态 von Mises 桁架的整块参数模型的动态行为。该系统由一个线性一阶方程和一个二阶非线性达芬方程控制,其中的二次非线性控制着机械行为。二阶方程控制机械振荡,而线性一阶方程控制粘弹力的演变。这两个方程结合在一起,就形成了一个控制系统动力学的三阶抽搐方程。粘弹性为材料行为增加了时间尺度和自由度,使其有别于仅有粘度的系统。由于谐波激励,系统表现出从周期到准周期再到混沌的各种动态响应。为此,我们探索了带有粘性阻尼的谐波强迫 von Mises 桁架的动力学。我们展示了该系统因驱动振幅变化而产生的丰富动态行为。这有助于解释粘弹性系统的行为。粘弹性单元取代了粘性阻尼器,我们证明,虽然粘性阻尼仅仅改变了轨迹衰减到吸引子的速度,但粘弹性同时改变了能量景观和衰减速度。在传统的线性固体模型中,三个粘弹性参数控制着系统的行为,而不是纯粘滞阻尼中的一个参数。这增加了影响系统动力学的自由度。我们介绍了混沌行为的参数空间以及从规则运动到不规则运动的转变。最后,梅尔尼科夫标准确定了规则-混沌阈值。系统的粘性和弹性成分会影响混沌阈值振幅。
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引用次数: 0
Solutions of Time-Space Fractional PDEs Using Picard's Iterative Method 使用皮卡尔迭代法求解时空分式 PDEs
Pub Date : 2024-01-25 DOI: 10.1115/1.4064553
Manoj Kumar, Aman Jhinga, J. T. Majithia
In this paper, we present Picard's iterative method for solving time-space fractional partial differential equations, where the derivatives are considered in the Caputo sense. We prove the existence and uniqueness of solutions. Additionally, we demonstrate the versatility of our proposed approach by obtaining exact solutions for a diverse set of equations. This method is user-friendly and directly applicable to any computer algebra system. The present method avoids intricate computations associated with the Adomian decomposition method, such as calculating Adomian polynomials, or the requirements of other methods like choosing a homotopy in the homotopy perturbation method, identification and manipulation of the invariant subspace in invariant subspace method or constructing a variational function in the variational iteration method. Thus, the proposed method is a versatile and efficient tool for exploring systems that involve both temporal and spatial fractional derivatives.
在本文中,我们介绍了 Picard 解决时空分数偏微分方程的迭代法,其中导数是在 Caputo 意义上考虑的。我们证明了解的存在性和唯一性。此外,我们还通过获得不同方程组的精确解,证明了我们提出的方法的通用性。这种方法对用户友好,可直接应用于任何计算机代数系统。本方法避免了与阿多米分解法相关的复杂计算,如计算阿多米多项式,或其他方法的要求,如在同调扰动法中选择同调,在不变子空间法中识别和操作不变子空间,或在变分迭代法中构建变分函数。因此,所提出的方法是探索涉及时间和空间分数导数的系统的多功能高效工具。
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引用次数: 0
Open-Loop Centering of a Point Mass on a Horizontally Vibrating Frictional Table 水平振动摩擦台上点质量的开环定心
Pub Date : 2024-01-25 DOI: 10.1115/1.4064552
Dheeraj Varma Manthena, C. P. Vyasarayani, Anindya Chatterjee
In this paper we study a particle sliding on a horizontally vibrating frictional table. This dynamical system has applications in parts manipulation within robotics and manufacturing. We first show numerically that, upon vibrating the table in a specific open-loop way, the particle moves to a target location under Coulomb friction alone. We then turn to analytical treatment of the system. The governing equations have strong nonlinearities due to the friction. We apply the method of multiple scales (MMS) near a 1:2 resonance in two frequencies relevant to the forcing. Application of the MMS requires some difficult integrals, for which we develop asymptotic approximations. The MMS slow flow has logarithmic nonlinearities, is valid near the target location on the table, and is easy to integrate numerically since it retains parametric excitation only in slow time. The slow flow matches very well with full numerical solutions. This problem has a practical motivation, novel elements in the application of the MMS, a satisfactory slow flow, and potential for further analytical simplification.
本文研究了在水平振动摩擦台上滑动的粒子。该动力学系统可应用于机器人和制造业中的零件操纵。我们首先从数值上说明,以特定的开环方式振动工作台后,粒子仅在库仑摩擦力作用下就会移动到目标位置。然后,我们转而对系统进行分析处理。由于摩擦的存在,控制方程具有很强的非线性。我们在与强迫相关的两个频率的 1:2 共振附近应用了多尺度法(MMS)。应用多尺度法需要一些困难的积分,为此我们开发了渐近近似值。MMS 慢流具有对数非线性特性,在台面上目标位置附近有效,并且易于数值积分,因为它仅在慢速时间内保留参数激励。慢流与全数值解非常吻合。这个问题具有实用的动机、应用 MMS 的新要素、令人满意的慢速流以及进一步分析简化的潜力。
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引用次数: 0
期刊
Journal of Computational and Nonlinear Dynamics
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