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Topology optimization of piezoelectric bi-material actuators with velocity feedback control

Frontiers of Mechanical Engineering 2019年第2期14卷 190-200页

作者： Mariana MORETTI Emilio C.N.SILVA School of Engineering University of Sao PauloSao PauloSP 05508-030Brazil

In recent years,the new technologies and discoveries on manufacturing materials have encouraged researchers to investigate the appearance of material properties that are not naturally *** featuring a specific stiffness,or structures that combine non-structural and stmctural functions are applied in the aerospace,electronics and medical industry ***,structures designed for dynamic actuation with reduced vibration response are the focus of this *** bi-material and multifunctional concepts are considered for the design of a controlled piezoelectric actuator with vibration suppression by means of the topology optimization method(TOM).The bi-material piezoelectric actuator(BPEA)has its metallic host layer designed by the TOM,which defines the structural function,and the electric function is given by two piezo-ceramic layers that act as a sensor and an actuator coupled with a constant gain active velocity feedback control(AVFC).The AVFC,provided by the piezoelectric layers,affects the structural damping of the system through the velocity state variables readings in time *** dynamic equation analyzed throughout the optimization procedure is fully elaborated and *** dynamic response for the rectangular fbur-noded finite element analysis is obtained by the Newmark's time-integration method,which is applied to the physical and the adjoint systems,given that the adjoint formulation is needed for the sensitivity analysis.A gradient-based optimization method is applied to minimize the displacement energy output measured at a predefined degree-of-freedom of the BPEA when a transient mechanical load is *** are obtained for different control gain values to evaluate their influence on the final topology.

关键词： topology optimization method bi-material piezoactuator active velocity feedback control timedomain transient analysis host structure design vibration suppression

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Time Domain Synchronous OFDM System for Optical Fiber Communications

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China Communications 2019年第9期16卷 155-164页

作者： Chenxin Jing Xianfeng Tang Xiaoguang Zhang Lixia Xi Wenbo Zhang State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

A spectrum efficient OFDM scheme named Time Domain Synchronous-OFDM(TDS-OFDM)is introduced into coherent optical transmission system,in which the pseudo noise(PN)sequence is exploited as guard interval to realize frame synchronization,compensate the carrier frequency offset(CFO),and estimate and equalize channel *** there is no pilot signals or training symbols in TDS-OFDM,the proposed scheme can achieve higher spectral efficiency(SE)above 10%improvement comparing with *** proposed method is implemented and verified in a 28GBaud QPSK OFDM system and a 28GBaud 16QAM OFDM *** is demonstrated that the proposed scheme shows high CFO estimation accuracy and synchronous *** CFO and linewidth of laser source set as 100MHz and 100kHz respectively,BER of QPSK OFDM system is below 3.8e-3 at the optical signal-to-noise ratio(OSNR)of 13dB,and BER of 16QAM OFDM system is below 3.8e-3 at the OSNR of 20dB.

关键词： channel estimation carrier frequencyoffset (CFO) compensation pseudonoise (PN) sequence synchronization timedomain synchronous OFDM (TDS-OFDM)

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USE OF FINITE-DIFFERENCE TIME-DOMAIN METHOD FOR CALCULATING EM ABSORPTION IN LOSSY DIELECTRIC SCATTERER

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Journal of Electronics(China) 1991年第4期8卷 357-362页

作者：王长清陈金元 Peking University Beijing University of Science and Technology of China Hefei

The problem for calculating EM energy absorption by lossy dielectric scatterer ir-radiated by plane wave are *** factors affecting the accuracy of computation *** calculated results of EM energy absorption and its distribution in homogeneousand layered homogenous lossy dielectric spheres are presented,and a comparison of these resultswith analytical solution is *** calculation is carried out for dielectric cylinder on conduct-ing ground as well,and the results are compared with the image *** the computationsshew that the finite-difference time-domain method can give satisfactory results.

关键词： Lossy dielectric scatterer Electromagnetic absorption Finite-difference timedomain method

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Investigation of Pitch Motion Portion in Vertical Response at Sides of a Tension-Leg Platform

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Journal of Marine Science and Application 2016年第2期15卷 175-181页

作者： Mohammad Reza Tabeshpour Ebrahim Malayjerdi Center of Excellence in Hydrodynamics and Dynamics of Marine Vehicles Mechanical Engineering Department Sharif University of Technology Tehran 11365-11155 Iran

Tendons vertically moor Tension-Leg Platforms （TLPs）, thus, a deep understanding of physical tendon stresses requires the determination of the total axial deformation of the tendons, which is a combination of the heave, pitch, and surging responses. The vertical motion of the lateral sides of the TLP is coupled with surge and constitutes a portion of the pitch motion. Tendons are connected to the sides of the TLP; hence, the total displacement of the lateral sides is related to the total deformation of the tendons and the total axial stress. Therefore, investigating the total vertical response at the sides of the TLP is essential. The coupling between various degrees of freedom is not considered in the Response Amplitude Operator （RAO）. Therefore, in frequency domain analysis, the estimated vertical RAO is incomplete. Also, in the time domain, only the heave motion at the center of TLP is typically studied; this problem needs to be addressed. In this paper, we investigate the portion of the pitch motion in the vertical response at the sides of the TLP in both the frequency and time domains. Numerical results demonstrate a significant effect of the pitch motion in the vertical motion of the edges of the TLP in some period ranges.

关键词： tension-leg platform heave motion pitch motion response amplitude operator sides of TLP frequency domain timedomain

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