Characteristics of Interface States in One-dimensional Composite Photonic Structures

Qingyue Zhang,Weitao Mao,Qiuling Zhao,Maorong Wang,Xia Wang,Wing Yim Tam 한국광학회 2022 Current Optics and Photonics Vol.6 No.3

Based on the transfer-matrix method (TMM), we report the characteristics of the interface states in one-dimensional (1D) composite structures consisting of two photonic crystals (PCs) composed of binary dielectrics A and B, with unit-cell configurations ABA (PC I) and BAB (PC II). The dependence of the interface states on the number of unit cells N and the boundary factor x are displayed. It is verified that the interface states are independent of N when the PC has inversion symmetry (x = 0.5). Besides, the composite structures support the formation of interface states independent of the PC symmetry, except that the positions of the interface states will be varied within the photonic band gaps. Moreover, the robustness of the interface states against nonuniformities is investigated by adding Gaussian noise to the layer thickness. In the case of inversion symmetry (x = 0.5) the most robust interface states are achieved, while for the other cases (x ≠ 0.5) interface states decay linearly with position inside the band gap. This work could shed light on the development of robust photonic devices.

Catalytic performance of amino acid/phosphotungstic acid as bi-functional heterogeneous catalyst for biodiesel production

Qingyu Zhang,Xiaoling Duan,Siyi Tang,Cunwen Wang,Weiguo Wang,Weiliang Feng,Tielin Wang 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.1

In this study, a series of acid-base bi-functional catalysts were prepared by mixing different amounts of basic amino acids (AAs) and phosphotungstic acid (PTA), which exhibited the excellent performance in catalyzing conversion of oleic acid (OA) for the biodiesel production. The physicochemical properties of the catalysts were characterized and analyzed using modern testing techniques and characterization methods such as XRD, FT-IR, XPS, SEM, TEM, and Hammett titration. The various influence parameters were optimized using the central composite design based the response surface methodology, where the maximum biodiesel yield of 97.0% was achieved at the MeOH/OA molar ratio of 5.9, the catalyst loading of 8%, reaction time of 6 h, and reaction temperature of 65℃. Furthermore, the stability and reusability of the prepared catalyst were also demonstrated. At last, the possible catalytic mechanism of the prepared catalyst was comprehensively described.

Finite-time Fault Detection Filtering for Switched Singular Systems with All Modes Unstable: an ADT Approach

Qingyu Su,Zhongxin Fan,Dezhen Zhang,Jian Li 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.8

This paper finishes the fault detection (FD) problem for switched singular systems with all subsystems unstable. Considering the particularity of singular systems, the regularity and impulse-free property analysis on it are carried out. Utilizing a time-driven switching strategy, a switching signal is proposed and the finite-time stability is guaranteed firstly. Then, with the help of discretized Lyapunov function, a piecewise Lyapunov function is employed to accomplish the finite-time boundedness with L2-gain analysis. Through transferring the fault detection filters design into the L2-gain analysis, we can obtain the existence conditions of the FD detector via linear matrices inequalities (LMIs). Finally, the effectiveness and validity are illustrated by two examples.

Loess record of the evolution history of severe sandstorms in the Tengger Desert during the Last Interglacial Period (MIS5)

Qingyu Guan,Baotian Pan,Na Li,Qiong Li,Jundi Zhang,Shujian Xu,Hongshan Gao,Jia Liu 한국지질과학협의회 2010 Geosciences Journal Vol.14 No.2

The Shagou loess section recorded the evolution information of severe sandstorms in the Tengger Desert during the Last Interglacial (MIS 5). By analyzing the grain size data of the loess samples using the grain size class-standard deviation, we selected the grain size component between 209 and 550 µm to reconstruct the evolution history of the severe sandstorms in the Tengger Desert during the Last Interglacial. The results indicate that there were at least 12 periods of frequently occurring severe sandstorms in that location over this time period. There were two periods in each of S1SS1 and S1SS2, four periods in S1LL1, three periods in S1LL2 and one in S1LL4. The occurrence frequency and intensity of the severe sandstorms presented a characteristic increase from the early to the late period of the Last Interglacial. Combined with the calcium carbonate results, this evidence suggests that climatic change is closely related to sandstorms. A warm and wet climate could restrict the occurrence of severe sandstorms; conversely, a cold and dry climate easily induces severe sandstorms. Meanwhile, with a warm and dry climate background, the relationship between climatic change and the occurrence of sandstorms is quite complex: severe sandstorms are also able to occur in such a climate. A cold and dry climate, however, does not mean a certainty of severe sandstorms.

Research on Intelligent Power Supply Control Based on Sensor-less Temperature Identification of Electric Submersible Motor

Haicong Zhang,Jianxiong Yu,Qingyue Jiang,Liguo Wang,Dianguo Xu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

This paper proposes a sensor-less temperature identification and an intelligent power supply method for Electric Submersible Motor (ESM) in oil wells. With measurements obtained from the proposed identification, a thermodynamics module is established for the temperature and the fault detection. Besides, the relationship between the rotor temperature and the load can be calculated. Then based on different loads, suitable ratios of voltage to frequency in different conditions can be captured. Finally, the control of the ratio enables power supply to match the oil pump output automatically. The experimental results from an ESM (12kW) in lab are shown to validate the proposed method. The whole scheme is effective and reliable and is therefore suitable to reduce the maintenance frequency of oil pumps and the power consumption of oil wells.

L2-gain Analysis and Synthesis of Saturated Switched Linear Systems

Xinquan Zhang,Wenhua Tao,Qingyu Su 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.11

The problem of L2-gain analysis and anti-windup compensators design is investigated for saturated switched linear systems via the single Lyapunov function method. Firstly, a sufficient condition about tolerable disturbances is obtained, under which the state trajectory starting from the origin will remain inside a bounded set. Then over this set of tolerable disturbances, we obtain the upper bound of the restricted L2-gain. Furthermore, the anti-windup compensation gains and the switched law, which aim to determine the maximum disturbance tolerance capability and the minimum upper bound of the restricted L2-gain, are presented by solving constraint optimization problem. Finally we give a numerical example to demonstrate the effectiveness of the proposed method.

Few-shot transfer learning with attention for intelligent fault diagnosis of bearing

Yao Hu,Qingyu Xiong,Qiwu Zhu,Zhengyi Yang,Zhiyuan Zhang,Dan Wu,Zihui Wu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

The bearing is one of the key components in modern industrial equipment. In the past few years, many studies have been carried out on bearing diagnosis through datadriven methods. However, there are two practical problems. First, under actual working conditions, the lack of fault samples is a major factor that hinders the application of these methods in industrial environments. Second, there is a lack of full utilization of a priori knowledge in the current stage of methods using relational networks for fault diagnosis. It is manifested by the incompleteness of the relational network structure. To address these problems, we present a new diagnosis method based on few-shot learning, which is suitable for the environment where the data is scarce. In this method, we train the model with the data generated by the artificial damaged bearings instead of the data from the real bearing. We experimentally validate the performance improvement of the complete relational network structure. It is able to perform the few-shot learning task better. In addition, we also reduce the global feature discrepancy by introducing an attention mechanism to improve the performance of the model. And the impact of the number of layers of the attention mechanism on the model is also discussed in detail. In this paper, our model performs better under the same experimental conditions compared with other transfer learning models.

An Approach for Identifying the Temperature of Inductance Motors by Estimating the Rotor Slot Harmonic Based on Model Predictive Control

Liguo Wang,Qingyue Jiang,Chaoyu Zhang,Dongxin Jin,Hui Deng 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.

Earthquake response analysis of series reactor

Changqing Bai,Qingyu Xu,Hongyan Zhang 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.21 No.6

Synthesis of Zirconium Oxides on silicon by Radio - Frequency Magnetron Sputtering Deposition

Chunyu Ma,Qingyu Zhang 한국진공학회(ASCT) 2003 Applied Science and Convergence Technology Vol.12 No.S1

Zirconium oxide films have been synthesized by radio-frequency magnetron sputtering deposition on n-Si(001) substrate with metal zirconium target at variant O₂ partial pressures. The influences of O₂ partial pressures of the morphology, deposition rate, microstructure, and the dielectric constant of ZrO₂ have been discussed. The results show that deposition rate of ZrO₂ films decreases, the roughness, and the thickness of the native SiO₂ interlayer increases with the increase of O₂ partial pressure. ZrO₂ films synthesized at low O₂ partial pressure are amorphous and monoclinic polycrystalline in nanometer scale at low O₂ partial pressure. The relative dielectrics of ZrO₂ films are in the range of 12 to 25.