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脆性材料I型(张开)-断裂韧性测定的PFC2D和试验研究:一种新方法
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作者 付金伟 Hadi Haeri +6 位作者 Joseph FLabuz Vahab Sarfarazi Pouyan Ebneabbasi MRM Aliha hamid reza karimi Shirin Jahanmiri Mohammad Fatehi Marji 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2024年第2期116-130,共15页
在本文研究中,通过利用优势边缘缺口盘型(END)试样,确定了石灰石的断裂韧性,提出了一种新的石灰石归一化相应力、高相变的计算方法.采用柔性有限元法(FEM)对试样的I型(张开)-断裂韧性进行了精确计算,并得到了相应实用公式.在试验中,还... 在本文研究中,通过利用优势边缘缺口盘型(END)试样,确定了石灰石的断裂韧性,提出了一种新的石灰石归一化相应力、高相变的计算方法.采用柔性有限元法(FEM)对试样的I型(张开)-断裂韧性进行了精确计算,并得到了相应实用公式.在试验中,还使用含缺口巴西圆盘(NBD)试件,测试了END程序的准确性.为了在数值上重现这些测试并验证断裂韧性测量的正确性,还对END测试进行了离散元分析.数值模拟结果与实验结果吻合良好.然而,END研究所确定的韧性水平低于NBD测试规定的韧性水平,这是因为END石灰石样品中的缺口具有均匀的拉伸应力分布. 展开更多
关键词 断裂韧性 脆性材料 实用公式 拉伸应力 巴西圆盘 离散元分析 相变 归一化
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LQG Control Design for Balancing an Inverted Pendulum Mobile Robot 被引量:1
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作者 Ragnar Eide Per Magne Egelid +1 位作者 Alexander Stamso hamid reza karimi 《Intelligent Control and Automation》 2011年第2期160-166,共7页
The objective of this paper is to design linear quadratic controllers for a system with an inverted pendulum on a mobile robot. To this goal, it has to be determined which control strategy delivers better performance ... The objective of this paper is to design linear quadratic controllers for a system with an inverted pendulum on a mobile robot. To this goal, it has to be determined which control strategy delivers better performance with respect to pendulum’s angle and the robot’s position. The inverted pendulum represents a challenging control problem, since it continually moves toward an uncontrolled state. Simulation study has been done in MATLAB Simulink environment shows that both LQR and LQG are capable to control this system successfully. The result shows, however, that LQR produced better response compared to a LQG strategy. 展开更多
关键词 LQG Control Inverted Pendulum Mobile Robot
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Adaptive H_∞ Synchronization of Master-slave Systems with Mixed Time-varying Delays and Nonlinear Perturbations: An LMI Approach
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作者 hamid reza karimi 《International Journal of Automation and computing》 EI 2011年第4期381-390,共10页
This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed tim... This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed time delays. Using an appropriate Lyapunov-Krasovskii functional, some delay-dependent sufficient conditions and an adaptation law including the master-slave parame- ters are established for designing a delayed synchronization law in terms of linear matrix inequalities(LMIs). The time-varying controller guarantees the H ∞ synchronization of the two coupled master and slave systems regardless of their initial states. Particularly, it is shown that the synchronization speed can be controlled by adjusting the updated gain of the synchronization signal. Two numerical examples are given to demonstrate the effectiveness of the method. 展开更多
关键词 Adaptive synchronization master-slave systems DELAY H performance nonlinear perturbations.
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