Qian, Dong
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/5912
Dong Qian is a Professor in the Department of Mechanical Engineering. Dr. Qian's research interests include:
- Linear and nonlinear finite element and meshfree methods and applications to stress and failure analysis
- Fatigue and life prediction
- Surface engineering, residual stress analysis. Modeling and simulation of manufacturing process (peening, forming, etc.)
- Modeling and simulation of nanostructured materials with focus on mechanical properties and multiphysics coupling mechanisms
- Multiscale methods that seek to bridge the gaps in spatial or temporal scales
- Biomedical implants
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Item An Efficient Solution Algorithm For Space–Time Finite Element Method(Springer Verlag) Zhang, Rui; Wen, L.; Xiao, J.; Qian, Dong; Qian, DongAn efficient solution algorithm has been developed for space–time finite element method that is derived from time discontinuous Galerkin (TDG) formulation. The proposed algorithm features an iterative solver accelerated by a novel and efficient preconditioner. This preconditioner is constructed based on the block structure of coupled space–time system matrix, which is expressed as addition of Kronecker products of temporal and spatial submatrices. With this unique decomposition, the most computationally intensive operations in the iterative solver, i.e. matrix operations, are subsequently optimized and accelerated employing the inverse property of Kronecker product. Theoretical analysis and numerical examples both demonstrate that the proposed algorithm provides significantly better performance than the already developed implementations for TDG-based space–time FEM. It reduces the computational cost of solving space–time equations to the same order of solving stiffness equations associated with regular FEM, thereby enabling practical implementation of the space–time FEM for engineering applications.Item Mechanical Properties of Atomically Thin Boron Nitride and the Role of Interlayer Interactions(Nature Publishing Group) Falin, Aleksey; Cai, Qiran; Santos, Elton J. G.; Scullion, Declan; Qian, Dong; Zhang, Rui; Yang, Zhi; Huang, Shaoming; Watanabe, Kenji; Taniguchi, Takashi; Barnett, Matthew R.; Chen, Ying; Ruoff, Rodney S.; Li, Lu Hua; 295272933 (Qian, D); Qian, Dong; Zhang, RuiAtomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono-and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example, as mechanical reinforcements.Item Photothermal Bimorph Actuators with In-Built Cooler for Light Mills, Frequency Switches, and Soft Robots(Wiley-VCH Verlag) Li, J.; Zhang, Rui; Mou, L.; Jung de Andrade, Monica; Hu, X.; Yu, K.; Sun, J.; Jia, T.; Dou, Y.; Chen, H.; Fang, Shaoli; Qian, Dong; Liu, Z.; 295272933 (Qian, D); Zhang, Rui; Jung de Andrade, Monica; Fang, Shaoli; Qian, DongPhotothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband-light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature-change-normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing-flapping mechanism and a light-modulated frequency switch. A fast-walking robot (with a speed of 26 mm s -1 ) and a fast-and-strong mechanical gripper with a large weight-lifting ratio (˜2142), respectively, are also demonstrated. ©2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem Ultrafast Pulsed Laser Induced Nanocrystal Transformation in Colloidal Plasmonic Vesicles(Wiley-VCH Verlag) Karim, Mohammad R.; Li, Xiuying; Kang, Peiyuan; Kang, Peiyuan; Randrianalisoa, J.; Ranathunga, Dineli; Nielsen, Steven O.; Qin, Zhenpeng; Qian, Dong; 0000-0003-3406-3045 (Qin, Z); 295272933 (Qian, D); Karim, Mohammad R.; Li, Xiuying; Ranathunga, Dineli; Nielsen, Steven O.; Qin, Zhenpeng; Qian, DongPlasmonic vesicle consists of multiple gold nanocrystals within a polymer coating or around a phospholipid core. As a multifunctional nanostructure, it has unique advantages of assembling small nanoparticles (< 5 nm) for rapid renal clearance, strong plasmonic coupling for ultrasensitive biosensing and imaging, and near-infrared light absorption for drug release. Thus, understanding the interaction of plasmonic vesicles with light is critically important for a wide range of applications. In this paper, a combined experimental and computational study is presented on the nanocrystal transformation in colloidal plasmonic vesicles induced by the ultrafast picosecond pulsed laser. Experimentally observed merging and transformation of small nanocrystals into larger nanoparticles when treated by laser pulses is first reported. The underlying mechanisms responsible for the experimental observations are investigated with a multiphysics computational approach featuring coupled electromagnetic/molecular dynamics simulation. This study reveals for the first time that combined nanoparticle heating and laser-enhanced Brownian motion is responsible for the observed nanocrystal merging. Correspondingly, laser fluence, interparticle distance, and presence of water are identified as the most important factors governing the nanocrystal transformation. The guidelines established from this study can be employed to design a host of biomedical and nanomanufacturing applications involving laser interaction with plasmonic nanoparticles.