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1-3型压电复合材料及其研究进展 总被引:22,自引:0,他引:22
1-3型压电智能复合材料是由一维连通的压电相平行排列于三维连通的聚合物中而形成的两相压电复合材料.简述了1-3型压电智能复合材料形成及其材料结构构成变化的发展历程,并从理论分析、参数辨识、数值计算和试验方法四方面阐述了宏观等效特征参数的研究状况.在此基础上对现有的制备工艺技术的优缺点进行了比较,对声学、医学、控制、航空航天等已应用和可能应用的领域的现状和发展趋势进行了回顾和展望,最后建议了1-3型压电智能复合材料今后几个较为重要的研究方向. 相似文献
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基于DSP和ML4428无刷直流螺电机锁相稳速控制的研究 总被引:3,自引:0,他引:3
提出了一种新的基于数字信号处理器(DSP)TMS320LF2407A和专用驱动芯片ML4428的陀螺用无位置传感器无刷永磁直流电机(BLDCM)稳速控制系统。它采用芯片ML4428实现无刷直流电机速度控制系统中的反电势检测、换相和功率驱动,并使用数字信号处理器TMS320LF2407A作为控制处理器,实现了电机的起停控制、转速给定,转速检测。它还采用了锁相环技术和积分分离的PID控制算法,大大提高了系统的控制性能和可靠性。 相似文献
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重点研究了局部伪弧长方法在处理偏微分方程,尤其是双曲型偏微分方程出现激波间断的奇异性问题,对比分析了全局伪弧长方法空间转化的形式及其网格自适应的性质。为提高求解效率,提出了局部伪弧长方法,利用激波间断的性质,给出了判断奇异点位置以及模板选择的方法,涉及如何处理激波振荡,如何引入弧长参数,以及怎样求解间断等问题。通过数值算例验证了局部伪弧长在激波捕捉和追踪方面的可行性,通过比较局部伪弧长方法与Godunov方法处理不同初值条件的双曲问题,显示出局部伪弧长方法处理双曲偏微分方程的优越性,为伪弧长方法应用到物理问题奠定基础。 相似文献
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本文对目前广泛应用于结构非线性分析之中的弧长法进行改进。改进后的弧长法除保持原有优点外,能够在自动跟踪结构非线性平衡路径的同时,进一步求得位于结构平衡睡径任一区段的任意预先指定的荷载水平及相应的变形。本文的方法可以推广应用于求解预先指定的应力或位移。数值算例表明了本文方法的计算精度、效率及可靠性。 相似文献
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以几何精确梁理论为基础,分别采用高阶拉格朗日插值和埃米特插值构造高精度空间梁单元。提出基于单元层次平衡迭代的自由度凝聚方法,以保证单元的通用性。实现了基于载荷控制或柱面弧长控制的结构几何非线性分析算法。算例研究结果表明,提出的改进方法不但提高了计算效率,而且还具有较高的数值稳定性;特别是基于三次埃米特插值构造的单元表现出较好的性态,适用于结构屈曲后分析。 相似文献
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自适应有限元方法及其工程应用 总被引:16,自引:2,他引:16
自适应有限元方法是一种能通过自适应分析自动调整算法以改进求解过程的数值方法.它以常规有限元法为基础,以误差估计和自适应网格改进技术为核心,是一种效率高、可靠性高的计算方法.文中简要介绍并综述了自适应有限元方法的重要发展及应用情况.并对其发展前景作了概要的预测 相似文献
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本文提出了具有结构,机构耦合形式的自动武器系统的最优化设计问题,建立了这种武器系统在射击载荷作用下的NLP模型。针对武器系统的非线性耦合特性,提出了状态和设计敏度分析的混合预测校正方法。建立的NLP问题用改进的SLP方法求解。通过对-简单的后退式武器后座力的最小化设计说明本文方法是有效的。 相似文献
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Arc-length-type and energy-type methods are two main strategies used in structural nonlinear tracing analysis, but the former
is widely used due to the explicitness and clarity in conception, as well as the convenience and reliability in calculation.
It is very important to trace the complete load-deflection path in order to know comprehensively the characteristics of structures
subjected to loads. Unfortunately, the nonlinear analysis techniques are only workable for tracing the limit-point-type equilibrium
path. For the bifurcation-point-type path, most of them cannot secure a satisfactory result. In this paper, main arc-length-type
methods are reviewed and compared, and the possible reasons of failures in tracing analysis are briefly discussed. Some improvements
are proposed, a displacement perturbation method and a force perturbation method are presented for tracing the bifurcation-point-type
paths. Finally, two examples are analyzed to verify the ideas, and some conclusions are drawn with respect to the arc-length-type
methods.
The project supported by the Special Research Fund for Doctor Program of Universities (9424702) 相似文献
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Based on the classical ( matrix type ) input-output analysis, a type of nonlinear ( continuous type) conditional Leontief model, input-output equation were introduced, as well as three corresponding questions, namely, solvability, continuity and surjectivity , and some fixed point and surjectivity methods in nonlinear analysis were used to deal with these questions. As a result, the main theorems are obtained, which provide some sufficient criterions to solve above questions described by the boundary properties of the enterprise‘s consuming operator. 相似文献
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《International Journal of Solids and Structures》2003,40(11):2875-2887
This paper presents an analysis of buckling/snapping, bending and post-buckling/snapping behaviors of magneto-elastic–plastic interaction and coupling for soft ferromagnetic beam-plates with geometrically nonlinear deformation and unmovable simple supports at the ends of the plates. Based on the expression of magnetic force from the variational principle of ferromagnetic plates, the theory of thin plates with the nonlinear deformation of van Karman’s type, and the Mises yield criterion and the increment theory for plastic deformation, here, we establish a numerical code to quantitatively simulate the behaviors of the nonlinearly multi-coupling problems by the finite element method. Along with that the phenomena of buckling, bending, and post-buckling/snapping, or the characteristic curve of deflection versus magnitude of applied magnetic fields are numerically displayed, the critical values of buckling/snapping and yield magnetic fields, and the expansibility of plastic region after the plates undergo plastic deformation with increasing of the applied magnetic fields, as well as the evolvement of deflection configuration of the plate are numerically obtained in a case study. 相似文献
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Based on the classical (matrix type) input-output analysis, a type of nonlinear (continuous type) conditional Leontief model,
input-output equation were introduced, as well as three corresponding questions, namely, solvability, continuity and surjectivity,
and some fixed point and surjectivity methods in nonlinear analysis were used to deal with these questions. As a result, the
main theorems are obtained, which provide some sufficient criterions to solve above questions described by the boundary properties
of the enterprise’s consuming operator.
Biography: LIU Ying-fan (1948≈), Professor 相似文献
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本文概述了近15年来计算传热学学科的发展概况.特别概括了目前国内外主要研究的方向及数值研究的方法;归纳了在湍流研究中普遍采用的六种模型;并指出无论在数学模型、计算方法和格式方面,还是应用等方面仍有待改进、完善、发展和研究. 相似文献
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A large schlieren system with exceptional sensitivity and a high-speed digital camera are used to visualize loud sounds and
a variety of common phenomena that produce weak shock waves in the atmosphere. Frame rates varied from 10,000 to 30,000 frames/s
with microsecond frame exposures. Sound waves become visible to this instrumentation at frequencies above 10 kHz and sound
pressure levels in the 110 dB (6.3 Pa) range and above. The density gradient produced by a weak shock wave is examined and
found to depend upon the profile and thickness of the shock as well as the density difference across it. Schlieren visualizations
of weak shock waves from common phenomena include loud trumpet notes, various impact phenomena that compress a bubble of air,
bursting a toy balloon, popping a champagne cork, snapping a wooden stick, and snapping a wet towel. The balloon burst, snapping
a ruler on a table, and snapping the towel and a leather belt all produced readily visible shock-wave phenomena. In contrast,
clapping the hands, snapping the stick, and the champagne cork all produced wave trains that were near the weak limit of visibility.
Overall, with sensitive optics and a modern high-speed camera, many nonlinear acoustic phenomena in the air can be observed
and studied. 相似文献
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Gao Yuanwen 《Acta Mechanica Solida Sinica》2007,20(2):180-188
An analysis of buckling/snapping and bending behaviors of magneto-elastic-plastic interaction and coupling for cantilever rectangular soft ferromagnetic plates is presented.Based on the expression of magnetic force from the variational principle of ferromagnetic plates,the buckling and bending theory of thin plates,the Mises yield criterion and the increment theory for plastic deformation,we establish a numerical code to quantitatively simulate the behaviors of the nonlinearly multi-fields coupling problems by the finite element method.Along with the phenom- ena of buckling/snapping and bending,or the characteristic curve of deflection versus magnitude of applied magnetic fields being numerically displayed,the critical loads of buckling/snapping, and the influences of plastic deformation and the width of plate on these critical loads,the plastic regions expanding with the magnitude of applied magnetic field,as well as the evolvement of deflection configuration of the plate are numerically obtained in a case study. 相似文献