Finite-time Robust Simultaneous Stabilization for Two Nonlinear Descriptor Systems Subject to Disturbances

Meiqing Li,Liying Sun 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10

This paper studies the finite-time robust simultaneous stabilization problem for two nonlinear descriptor systems subject to disturbances by using state undecomposed method. By virtue of a suitable output feedback, a sufficient condition is first given to guarantee the closed-loop system impulse-free. Then, an augmented descriptor system is combined with the two systems subject to disturbances by using the system-augmentation technique. Furthermore, the L₂ gain of the descriptor system is no more than via constructing a suitable output feedback H∞ controller, and when w = 0, the augmented descriptor system is proved the finite-time stabilization, which can guarantee the finite-time simultaneous stabilization of the two nonlinear descriptor systems subject to disturbances. Finally, a numerical example is given to illustrate the effectiveness of the proposed results in this paper.

Stability and Adaptability Analysis for PLL-Synchronized VSC-HVDC with Frequency Regulation Scheme under Islanded Grid

Meiqing Zhang,Xiaoming Yuan,Jiabing Hu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Voltage-source converter (VSC) high voltage direct current (HVDC) connected to islanded grid is becoming a normal system operation mode. However, there is little research on the stability analysis of VSC-HVDC connected to islanded grid. On the basis of previous work, this paper analyzes the stability and adaptability of PLL-synchronized VSC-HVDC adopted with the additional frequency regulation scheme (FRS) under islanded grid. By defining the instantaneous frequency and regarding it as a state variable, the small-signal model of PLL-synchronized VSC under both grid-islanded mode and grid-connected mode is synthetically established. On this basis, the impact of FRS on the stability of PLL-synchronized VSC under islanded grid is analyzed, and then the adaptability of FRS to different grid strengths is investigated via considering different short current ratios (SCRs), including islanded grid (SCR=0), weak grid (SCR<2) and strong grid (SCR>5). The analysis results show that the FRS has important role on enhancing the small signal stability of the islanded grid, and also has excellent adaptability to the wide change of grid conditions, so as to further improve the possibility of the FRS applied in practical projects. These results finally are verified by time-domain simulations.

Effects of regeneration conditions on sulfated CuSSZ-13 catalyst for NH3-SCR

Meiqing Shen,Zhixin Wang,Xinhua Li,Jiaming Wang,Jianqiang Wang,Chen Wang,Jun Wang 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.8

To understand the role of regeneration conditions on sulfur-poisoned Cu/SSZ-13 catalysts for NH3-SCR, the physicochemical characterizations and NOx conversions were investigated. The sulfur-poisoned Cu/SSZ-13 catalysts were treated at different conditions as a function of temperature and duration. TGA results revealed that regeneration at 500 oC only removed parts of sulfur spices and at 700 oC can completely remove all sulfur spices. The physical structural characterizations results illustrate that regeneration below 700 oC has no significant impact on CHA structure for Cu/SSZ-13 catalysts, while dealumination occurs on poisoned Cu/SSZ-13 when regeneration temperature is higher than 700 oC. EPR and H2-TPR results show that the sulfate decomposition and Cu migration reactions involved during regeneration and, as a result, the content of Cu2+ gradually increased as the extent of regeneration increased. The kinetics tests support that NOx conversion recovery is related to the content of Cu2+ increase during regeneration. Our study reveals that the optimum regeneration temperature is 700 oC, because severe dealumination at 750 oC inhibited Cu2+ amount increase.

Graphene and graphene‑like carbon nanomaterials‑based electrochemical biosensors for phytohormone detection

Meiqing Yang,Lu Wang,Haozi Lu,Qizhi Dong,Huimin Li,Song Liu 한국탄소학회 2023 Carbon Letters Vol.33 No.5

Phytohormones (plant hormones) are a class of small-molecule organic compounds synthesized de novo in plants. Although phytohormones are present in trace amounts, they play a key role in regulating plant growth and development, and in response to external stresses. Therefore, the analysis and monitoring of phytohormones have become an important research topic in precision agriculture. Among the various detection methods, electrochemical analysis is favored because of its simplicity, rapidity, high sensitivity, and in-situ monitoring. Graphene and graphene-like carbon materials have abundant sources, exhibiting large specific surface area, and excellent physicochemical properties. Thus, they have been widely used in the preparation of electrochemical biosensors for phytohormone detection. In this paper, the research advances of electrochemical sensors based on graphene and graphene-like carbon materials for phytohormone detection have been reviewed. The properties of graphene and graphene-like carbon materials are first introduced. Then, the research advances of electrochemical biosensors (including conventional electrochemical sensors, photoelectrochemical sensors, and electrochemiluminescence sensors) based on graphene and graphene-like carbon materials for phytohormone detection is summarized, with emphasis on their sensing strategies and the roles of graphene and graphene-like carbon materials in them. Finally, the development of electrochemical sensors based on graphene and graphene-like carbon materials for phytohormone detection is prospected.

Buckling analysis of filament wound composite cylindrical shell for considering the filament undulation and crossover

Zhangxin Guo,Xiaoping Han,Meiqing Guo,Zhijun Han 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.2

The buckling equations of filament wound composite cylindrical shell are established. The coefficients Kij and Lij of the buckling equations are determined by solving the equations. The geometric analysis and the effective stiffness calculation for the fiber crossover and undulation region are respectively accomplished. Using the effective stiffness of the undulation region, the specific formulas of the coefficients Kij and Lij of the buckling equations are determined. Numerical examples of the buckling critical loads have been performed for the different winding angles and stacking sequences cylindrical shell designs. It can be concluded that the fiber undulation results in the less effect on the buckling critical loads Pcr. Pcr increases with the thickness-radius ratio. The effect on Pcr due to the fiber undulation is more obvious with the thickness-radius ratio. Pcr decreases with the length-radius ratio. The effect on Pcr due to the fiber undulation can be neglected when the ratio is large.

Inertia Parameter Selection Method for HVDC Converter Station Based on VSG Control

Yong Shi,Ce Fang,Lei Chen,Meiqing Mao,Zhong Chen 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

With the purpose of improving the frequency support capability of high voltage direct current (HVDC) transmission equipment and ensuring the stable and reliable operation for the receiving end power grid, a virtual synchronous generator (VSG) control algorithm for high voltage direct current converter was proposed in this paper. The virtual synchronous generator control method is analyzed in detail, and the small-signal model of grid-tied high voltage direct current converter is established, and further established the small signal-model of the three-area power system. On the basis of the proposed models, considering the factors such as diff erent short circuit ratios, decoupling performance, stability, dynamics, the selection principle of inertia factor J and damping factor D of virtual synchronous generator is proposed. Finally, the eff ectiveness of the proposed inertia and damping coeffi cient selection method is verifi ed by simulation.

Advances in atomic layer deposited high-κ inorganic materials for gate dielectrics engineering of two-dimensional MoS2 field effect transistors

Zhang Ling,Xing Houying,Yang Meiqing,Dong Qizhi,Li Huimin,Liu Song 한국탄소학회 2022 Carbon Letters Vol.32 No.5

Molybdenum disulfide (MoS2) has been one of the most promising members of transition-metal dichalcogenides materials. Attributed to the excellent electrical performance and special physical properties, MoS2 has been broadly applied in semiconductor devices, such as field effect transistors (FETs). At present, the exploration of further improving the performance of MoS2-based FETs (such as increasing the carrier mobility and scaling) has encountered a bottleneck, and the application of high-κ gate dielectrics has become an effective approach to change this situation. Atomic layer deposition (ALD) enables high-quality integration of MoS2 and high-κ gate dielectrics at the atomic level. In this review, we summarize recent advances in the fabrication of two-dimensional MoS2 FETs using ALD high-κ materials as gate dielectrics. We first briefly discuss the research background of MoS2 FETs. Second, we expound the electrical and other essential properties of high-κ gate dielectrics, which are essential to the performance of MoS2 FETs. Finally, we focus on the advances in fabricating MoS2 FETs with ALD high-κ gate dielectrics on MoS2, as well as the optimized ALD processes. In addition, we also look forward to the development prospect of this field.