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Microstructural Topology Optimization for Minimizing Dynamic Response in the Time Domain
Junpeng Zhao(자오준펭),Heonjun Yoon(윤헌준),Byeng D. Youn(윤병동) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
This paper presents an efficient approach for topology optimization of microstructures for minimizing dynamic response of two-scale hierarchical structures in the time domain. The density-based approach is employed to perform microstructural topology optimization. The numerical homogenization method is used to compute the effective material properties of the porous materials. The differentiate-and-then-discrete approach and the decoupled sensitivity analysis method are combined to perform sensitivity analysis. The model reduction method is employed to efficiently solve the primal and adjoint equations. A modified Heaviside projection method is used to obtain black-and-white design for the microstructure, and the method of moving asymptotes (MMA) is employed to update design variables. Two numerical examples are presented to demonstrate the effectiveness of the proposed approach.
An efficient concurrent topology optimization approach for frequency response problems
Zhao, Junpeng,Yoon, Heonjun,Youn, Byeng D. Elsevier 2019 Computer methods in applied mechanics and engineer Vol.347 No.-
<P><B>Abstract</B></P> <P>The purpose of this work is to develop an efficient concurrent topology optimization approach for minimizing frequency response of two-scale hierarchical structures over a given frequency interval. Compared with static problems, frequency response problems usually involve many load steps, which may lead to intensive computational burdens in both frequency response analysis and sensitivity analysis. This study thus proposes an enhanced decoupled sensitivity analysis method for frequency response problems, which is efficient even when plenty of frequency steps are involved and/or damping is considered. Furthermore, a combined method of modal superposition and model order reduction is incorporated for efficient frequency response analysis of two-scale hierarchical structures. A modified threshold Heaviside projection method is used to obtain black-and-white designs and the method of moving asymptotes (MMA) is employed to update the design variables. Several numerical examples are presented to demonstrate the effectiveness of the proposed approach.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Concurrent topology optimization for frequency response problems. </LI> <LI> Efficient enhanced decoupled sensitivity analysis method for dynamics problems. </LI> <LI> Efficient frequency response analysis method for two-scale structures. </LI> <LI> Black-and-white designs for both macrostructure and micro unit cell. </LI> <LI> Several numerical examples to valid the proposed method. </LI> </UL> </P>
Song, Mingjun,Zhao, Wang,Ran, Weiguang,Xue, Junpeng,Liu, Yanliang,Jeong, Jung Hyun Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.803 No.-
<P><B>Abstract</B></P> <P>In this research, a series of Tb<SUP>3+</SUP> and/or Eu<SUP>3+</SUP> doped KBaGd(WO<SUB>4</SUB>)<SUB>3</SUB> (KBGW for short) phoshpors were prepared by sol-gel method and characterized by X-ray diffraction (XRD), FT-IR and Raman spectra, scanning electron microscope (SEM), excitation and emission spectra, and luminescent decay curves. The results of XRD, SEM, FT-IR and Raman spectra confirmed that a single phase of KBGW with smooth surface and uniform particle size can be synthesized by sol-gel method. Under 250 or 378 nm excitation, multicolor tunable emissions from green to red were achieved in the KBGW:Tb<SUP>3+</SUP>, Eu<SUP>3+</SUP> phosphors by suitably controlling the ratios of Eu<SUP>3+</SUP>/Tb<SUP>3+</SUP>. The energy transfer efficiencies and mechanisms between Eu<SUP>3+</SUP> and Tb<SUP>3+</SUP> were investigated on the basis of photoluminescence (PL) spectra and luminescent decay curves, and a graphic analysis on the energy transfer process between Tb<SUP>3+</SUP> and Eu<SUP>3+</SUP> was presented. The temperature-dependent PL spectra of Eu<SUP>3+</SUP> and/or Tb<SUP>3+</SUP> doped KBGW were recorded and the thermal quenching behavior of the phosphors was analyzed in the framework of crossover model. At the end, green, red and white LEDs were fabricated with the as-prepared KBGW:Tb<SUP>3+</SUP>/Eu<SUP>3+</SUP> phosphors, and the excellent electroluminescence parameters suggest that the KBGW:Tb<SUP>3+</SUP>/Eu<SUP>3+</SUP> phosphors may be a component candidate for NUV excited WLEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A color tunable KBaGd(WO<SUB>4</SUB>)<SUB>3</SUB>:Tb<SUP>3+</SUP>/Eu<SUP>3+</SUP> phosphor was firstly prepared by sol-gel method. </LI> <LI> Its morphology, luminescent property and thermal stability were studied in detail. </LI> <LI> The emission color was tuned from green to red by changing the doping ratio of Eu/Tb. </LI> <LI> The energy transfer is demonstrated to be accomplished by dipole-dipole interactions. </LI> <LI> Green, red and white LEDs were fabricated and their performance were investigated. </LI> </UL> </P>
Three-dimensional trajectory tracking for underactuated AUVs with bio-inspired velocity regulation
Zhou, Jiajia,Ye, Dingqi,Zhao, Junpeng,He, Dongxu The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.3
This paper attempts to address the motion parameter skip problem associated with three-dimensional trajectory tracking of an underactuated Autonomous Underwater Vehicle (AUV) using backstepping-based control, due to the unsmoothness of tracking trajectory. Through kinematics concepts, a three-dimensional dynamic velocity regulation controller is derived. This controller makes use of the surge and angular velocity errors with bio-inspired models and backstepping techniques. It overcomes the frequently occurring problem of parameter skip at inflection point existing in backstepping tracking control method and increases system robustness. Moreover, the proposed method can effectively avoid the singularity problem in backstepping control of virtual velocity error. The control system is proved to be uniformly ultimately bounded using Lyapunov stability theory. Simulation results illustrate the effectiveness and efficiency of the developed controller, which can realize accurate three-dimensional trajectory tracking for an underactuated AUV with constant external disturbances.
Three-dimensional trajectory tracking for underactuated AUVs with bio-inspired velocity regulation
Jiajia Zhou,Dingqi Ye,Junpeng Zhao,Dongxu He 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.3
This paper attempts to address the motion parameter skip problem associated with three-dimensional trajectory tracking of an underactuated Autonomous Underwater Vehicle (AUV) using backstepping-based control, due to the unsmoothness of tracking trajectory. Through kinematics concepts, a three-dimensional dynamic velocity regulation controller is derived. This controller makes use of the surge and angular velocity errors with bio-inspired models and backstepping techniques. It overcomes the frequently occurring problem of parameter skip at inflection point existing in backstepping tracking control method and increases system robustness. Moreover, the proposed method can effectively avoid the singularity problem in backstepping control of virtual velocity error. The control system is proved to be uniformly ultimately bounded using Lyapunov stability theory. Simulation results illustrate the effectiveness and efficiency of the developed controller, which can realize accurate three-dimensional trajectory tracking for an underactuated AUV with constant external disturbances.