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991.
Recent developments in fluid dynamics have been focusing on nanofluids, which preserve significant thermal conductivity properties and magnify heat transport in fluids. Classical nanofluid studies are generally confined to models described by partial differential equations of an integer order, where the memory effect and hereditary properties of materials are neglected. To overcome these downsides, the present work focuses on studying nanofluids with fractional derivatives formed by differential equations with Caputo time derivatives that provide memory effect on nanofluid characteristics. Further, heat transfer enhancement and boundary layer flow of fractional Maxwell nanofluid with single-wall and multiple walls carbon nanotubes are investigated. The Maxwell nanofluid saturates the porous medium. Also, buoyancy, magnetic, electric, and heating effects are considered. Governing continuity, momentum, and energy equations involving Caputo time-fractional derivatives reduced nondimensional forms using suitable dimensionless quantities. Numerical solutions for arising nonlinear problems are developed using finite difference approximation combined with L1 algorithm. The influence of involved physical parameters on flow and heat transfer characteristics is analyzed and depicted graphically. Our simulations found out that surface drag of Maxwell nanofluid with single-walled carbon nanotubes dominates nanofluids with multiple walls carbon nanotubes, but the reverse trend is noticed for larger Grashof number values. 相似文献
992.
在发动机台架试验时,对机油压力监测通常采用单一静态的机油压力阈值进行机油压力监测。发动机在高转速下发生机油泄漏或低转速时机油通道出现堵塞,台架监测到的机油压力不会立刻达到监测阈值,发动机运动副在短时间出现缺乏机油润滑或是冷却都会给发动机带来严重的机械损伤。采用机油压力动态监测,可涵盖不同工况下故障监测与预警。以发动机转速、负荷及机油温度构建机油压力二阶多项式数学模型,对3台样本发动机的预测值与测量值进行了线性回归分析。通过发动机台架试验,验证了稳态试验、瞬态试验及发生故障时机油压力动态监测的准确性,结果表明机油压力动态监测在发动机台架实验中比单一阈值监测能更加有效地保护发动机。 相似文献
993.
本文提出一种利用多传感器信号深度特征融合的方法实现电机变转速工况下的故障诊断。首先从多传感器节点同步采集电机的多通道振动、声音和漏磁信号。对漏磁信号进行处理获取电机转子的累积转角曲线,随后利用累积转角曲线对振动和声音信号进行阶比分析处理。最后利用双层双向长短期记忆网络从经过预处理的多传感器信号中提取和融合特征以诊断电机故障。实验结果表明,通过提取和融合8通道的电机振动和声音信号,本文提出的方法能够有效识别电机的高阻接触、偏心、霍尔断线、相间短路、轴承等10类运行状态,分类准确率达到99.86%。该方法有望部署在物联网边缘计算节点中,实现电机的远程在线状态监测和故障诊断。 相似文献
994.
为进一步揭示超磁致伸缩致动器(Giant magnetostrictive actuator, GMA)系统非线性运动过程中的内在机理和动力学特征,基于分数阶微积分理论,将GMA动力学系统模型拓展至分数阶,建立含有分数阶阻尼的非线性GMA系统动力学方程,基于平均法分析系统主共振,得到系统的幅频响应方程;使用幂级数方法求解系统的数值解,通过Matlab数值模拟分析不同激励幅值和阻尼阶次对GMA系统的影响机理,从定性和定量的角度研究系统的分岔和混沌运动现象。结果表明:激励幅值和阻尼阶次对系统的幅频特性有显著影响;阻尼阶次对系统的分岔和混沌行为影响较大;不同阻尼阶次下由激励幅值变化引起系统的动力学行为相似但混沌区域不同。该研究有助于更好地了解GMA系统动力学特性,对工程实践中控制GMA系统稳定运行提供新的视角。 相似文献
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《国际计算机数学杂志》2012,89(5):1072-1082
Families of fourth-order methods are presented which are obtained by existing third-order methods applied in succession with the secant method. 相似文献
999.
This paper presents a finite element model based on the first order shear deformation theory to investigate the dynamic behavior of laminated composite plates traversed by a moving oscillator. The oscillator model is assumed to be consisting of two nodal masses that are connected by means of a spring-damper unit. The governing equations of motion of two sub-systems are separately integrated by applying the Newmark’s time integration procedure. Then, the obtained equations are coupled and the responses of system components are calculated in each time step. The accuracy of algorithm is verified by comparing the numerical results of static, free vibration and simplified moving force problems analysis with the available exact solutions and other numerical results in the literature. Also, the effects of mass ratio, damping ratio of system components, stiffness of suspension system, velocity and eccentricity of moving oscillator on dynamic responses is parametrically studied. This algorithm can be applied to various boundary conditions, lamination schemes and fiber angels. 相似文献
1000.
Mojtaba Kooshki Hamid Abdollahi Somayyeh Bozorgzadeh Behzad Haghighi 《Electrochimica acta》2011,(24):8618
Three-way data obtained from different pulse heights of differential pulse voltammetry (DPV) was analyzed using multivariate curve resolution by alternating least squares (MCR-ALS) algorithm. Differential pulse voltammograms of tryptophan were recorded at a gold nanoparticles decorated multiwalled carbon nanotube modified glassy carbon electrode (GCE/MWCNTs-nanoAu). The determination of tryptophan was performed even in the presence of unexpected electroactive interference(s). Both the simulated and experimental data were non-bilinear. Therefore a potential shift algorithm was used to correct the observed shift in the data. After correction, the data was augmented and MCR-ALS was applied to the augmented data. A relative error of prediction of less than 8% for the determination of the simulated analyte of interest and tryptophan in synthetic samples indicated that the methodology employing voltammetry and second-order calibration could be applied to complex analytical systems. 相似文献