Nonlocal bending, vibration and buckling of one-dimensional hexagonal quasicrystal layered nanoplates with imperfect interfaces

Haotian Wang,Junhong Guo 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.6

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a threedimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

Effects of β Air Cooling and Subsequent Cold Rolling on Microstructure and Hardness of Zr702 Sheet

Haotian Guan,Lingguo Zeng,Zhijun Li,Linjiang Chai,Yufan Zhu,Yueyuan Wang,Qin Huang,Ke Chen,Liang‑yu Chen,Ning Guo 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.2

In this work, a Zr702 sheet was subjected to β air cooling and then rolled to 15% reduction at room temperature, with theirdetailed microstructural characteristics characterized by electron channeling contrast imaging and electron backscatterdiffraction techniques. Results show that after the β air cooling, the prior equiaxed grains in the as-received material arecompletely transformed into Widmanstätten structures featured by coarse plates with typical phase transformation misorientationsbetween them. The subsequent 15% rolling allows both slip and twinning (especially the {10–12} type) to beactivated readily, leading to significant grain refinement and the appearance of misorientation angle peaks around 3°–5° and85°. Analyses on kernel average misorientations reveal that there exist very low residual strains in the β-air-cooled specimenwhile they are markedly increased after the 15% rolling and preferably distributed near low-angle and twin boundaries. Hardnessmeasurements show that the specimen hardness is evidently decreased from ~ 199 to ~ 170 HV after the β air cooling,which can be attributed to grain coarsening and the scattered orientations associated with the slow β → α transformation. For the 15%-rolled specimen, however, effective grain refinement by twinning and denser low-angle boundaries jointly leadto ~ 35% hardness increment to ~ 228 HV.

Partial Observer Canonical Form Design Method for Single-output Affine Nonlinear System with Simple Validation Conditions

Haotian Xu,Jingcheng Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.7

The problem concerning observer error linearization is to find a new state coordinate transformation (diffeomorphism) to transform the underlying nonlinear system into a Partial Observer Canonical Form (POCF). Since the complexity of the existing verification conditions associated with the existence of POCF, this paper develops a two-steps method for calculating POCF to simplify the verification conditions. This method also shows that POCF is equivalent to a compound diffeomorphism that consists of two coordinate transformations. One of them is a diffeomorphism which transforms the system into an observable canonical form based on maximum invariant distribution, and the other one is a diffeomorphism of transforming the observable subsystem into an observer linearization form. With the help of this method, a part of the original conditions are replaced by a group of new conditions that are easier to be verified, and another part of the original conditions are proved to be redundant and could not be verified anymore. At last, three examples are used to demonstrate the validity of this paper.

Numerical Investigation on Aerodynamic Performance and Interaction of a Lift-Offset Coaxial Rotor in Forward Flight

Haotian Qi,Ping Wang,Linsong Jiang 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.2

A numerical method based on Reynolds Averaged Navier–Stokes (RANS) equations and moving overset mesh technique is developed to simulate the unsteady flow field of a rigid coaxial rotor. A high-efficient hybrid trim model is adopted to ensure the simulation accuracy of lift-offset (LOS). Cases in different advance ratios are trimmed for constant thrust coefficient and torque-balance. The effects of LOS, rotor spacing and RPM on the aerodynamic performance and interaction are analyzed. Results show that, in forward flight the lift–drag ratio can be improved by appropriate LOS. The rotor drag increases with LOS, as there is also a corresponding offset of drag. The optimum LOS varies with flight speed. At large advance ratio the interactions of the coaxial rotor are much weak, except the blade–meeting interaction. The interaction is typically illustrated by the impulsive loads of the upper blade at retreating side (270°), as the flow field is dominated by the advancing blade (90°) of the lower rotor. The interaction intensity is sensitive to LOS, rotor spacing and RPM, as it depends on the flow field gradient induced by the lower blade acting on the upper blade.

Distributed Secondary Control of AC Microgrid and its Frequency Domain Analysis Considering Time Delay

Cheng Zhiping,Wang Kaifang,Li Zhongwen,Wu Haotian,Zhi Changyi,Zhang Jinbin 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1

In this paper, distributed secondary control of AC microgrid (MG) is studied and the infuence of communication delay on its control performance is analyzed and verifed. Firstly, a secondary control strategy for the MG is designed to achieve frequency recovery and proportional active power dispatch. Secondly, the stability of the MG system is analyzed in the frequency domain and a rigorous formula is derived to calculate the delay margin for the stability of the distributed secondary control with communication delays. The theoretical calculation results of the stability margin are approximately consistent with the simulation results, with an error of only 1.27%. The efects of the algorithm gains, communication topology, and connection weights on the delay margin are discussed based on the derived formula. The results demonstrate that the algorithm gain is inversely proportional to the delay margin. Changes in the communication topology and connection weights lead to changes in the maximum eigenvalue of the adjacency matrix L, which in turn afects the delay margin. Moreover, the infuence of time-varying delays is considered. The system can tolerate greater time-varying delays than fxed delays. Simulation and experimental results validate the efectiveness and feasibility of the proposed method.

Improved Switching Ripple Suppression Strategy for Multi-Paralleled Grid-Connected Inverters System

Wu Cao,Haotian Kang,Kangli Liu,Shunyu Wang,Jianfeng Zhao,Xiaochun Ji,Jun Zhao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

The switching operations of inverters in the distributed system inevitably introduce high-frequency harmonics into grid, which may make influences on electrical devices. To address it, this paper proposes a ripple suppression strategy based on active cancellation combined with passive filtering. The active cancellation is realized by carrier-phase-shift (CPS) technique and the passive filtering is achieved by filters. Furthermore, two component-shared LCL-type filters improved by traditional LCL filters are studied from the points of resonance and accuracy of gridinjected current. To valid the effectiveness of the proposed strategy, simulations and experimental test are carried out. The results show that the proposed strategy can effectively suppress high-frequency harmonics and two componentshared LCL-type filters can become promising filters for the multi-paralleled grid-connected inverters.

Finite Horizon Robust Optimal Tracking Control Based on Approximate Dynamic Programming for Switched Systems with Uncertainties

Shangwei Zhao,Jingcheng Wang,Haotian Xu,Hongyuan Wang 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.4

In this paper, an approximate dynamic programming (ADP)-based approach is developed to handle the robust optimal tracking control problem for switched systems with uncertainties in the finite horizon. The switched systems with unknown matched uncertainties are formulated by virtue of system dynamics and reference trajectory, where the complicated tracking problem is converted to a stabilizing robust optimal control problem. To avoid the requirement of system dynamics knowledge, a neural network (NN)-based identifier is utilized to estimate the unknown switched systems dynamics. The actor-critic NNs are constructed to approximate the optimal control input and the corresponding performance index, where the weights are trained backward-in-time in an off-line manner. Benefiting from the Lipschitz continuous condition, the convergence of the proposed approach is proved, which illustrates the iteration approach will converge to the unique solution under a small enough sampling time interval. Finally, two numerical simulation cases are employed to verify the effectiveness of the proposed approach.

Selective Synthesis of N,N-Bis(3-dimethylaminopropyl)amine over Pd/γ-Al2O3

Chenhui Lin,Bowei Wang,Haotian Guo,Ligong Chen,Xilong Yan 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.3

The synthesis of N,N-bis(3-dimethylaminopropyl)amine (BPA) from 3-(dimethylamino)-propionitrile (PN) and 3-(N,N-dimethylamino)propylamine (PA) over Pd/γ-Al2O3 in autoclaves was investigated. A series of Pd catalysts were prepared by different methods and characterized by XRD, TEM, and N2 adsorption–desorption. It was found that their activities were obviously affected by calcination temperature and reducing agent. Among them, the catalyst calcined at 500 °C and reduced with NaBH4 exhibited the best performance in this reaction. It was possibly attributed to the better dispersion of palladium particles on γ-Al2O3. Furthermore, reaction parameters were also optimized. Under optimal conditions (PN/PA molar radio 1:1, toluene as solvent), BPA was obtained in 87.9% yield with 95.6% conversion over the above catalyst. Meanwhile, split of PN was observed. A probable mechanism of retro-Michael reaction was also proposed.

Niederreiter Cascade Combination Cryptosystem Based on the Double Public Keys

Zhou Xue Guang,Li Zhong Yuan,Wang HaoTian,Qv ChengQin 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.7

This paper firstly briefed the basic concepts of N public key cryptosystem, RS code and QC-LDPC code, and then put forward the cascade cryptosystem with the RS code being the outer code and QC-LDPC code being the internal code. At last, the writer analyzed in detail the security and performance of the N cryptosystem based on double public key, and thus proved its better security and performance than the traditional public key cryptosystem based on error correcting code. In addition, it is also endowed with higher practicability in complex environment.

Influence of synthesis parameters on phase evolution and micromorphology of lanthanum hexaaluminate

Xiaoao Li,Jianjiang Xin,,Chao Chen,Zhiqiang Du,Haotian Wang 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

Lanthanum hexaaluminate is a potential candidate for thermal barrier coatings due to its unique lamellar structure andexcellent thermophysical properties. In this work, lanthanum hexaaluminate was prepared by a solid-state reaction synthesisat 1600 oC, and the effects of aluminum source type and molding method on the phase composition and microstructure of thepowder were studied. It can be seen that the synthesis efficiency of alumina as aluminium source is higher than that ofaluminium hydroxide. However, the flake structure is more obvious when aluminium hydroxide is used to synthesizealuminium hydroxide. In addition, the process of compacting green compact can effectively improve the synthesis efficiencyof LaAl11O18, but it will also affect the formation and growth of grains. Consequently, a high yield of LaAl11O18 powder witha particle size of 3 μm and aspect ratio of 9.88 can be obtained by compacting aluminum hydroxide as the aluminum source.