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1,151 results on '"Liu, Guoquan"'

6. Interface properties of composites from PBO fibers modified by polyurethane sizing agent

Author

JIANG Lei, XU Renxin, WU Shuguang, LIU Guoquan, DING Anxin, and CHEN Yang

Subjects
pbo fiber, waterborne polyurethane, sizing agent, interface property, shear strength, Materials of engineering and construction. Mechanics of materials, TA401-492
Abstract

To improve the interfacial properties of poly-p-phenylenebenzobisoxazole(PBO) fiber/epoxy resin (EP)composites, the surfaces of acidified PBO fibers were coated with the sizing agents of waterborne polyurethane modified using γ-aminopropyltriethoxysilane(KH550). The surface chemical composition of PBO fibers was characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). Scanning electron microscopy (SEM)was employed to characterize the surface morphology of PBO fibers and the tear surface morphology of PBO/EP composites. Furthermore, the mechanical properties of single PBO fibers and PBO/EP composites were analyzed. The results show that the active groups on the surfaces of PBO fibers increase significantly with the values of O/C(atomic ratio)from 0.16 to 0.25 after being coated with the sizing agents, and the defects on the surfaces of PBO fibers can be repaired effectively. By adjusting the contents and structure of the sizing agents on the fibers, the interlaminar shear strength and tensile strength of PBO/EP unidirectional composites reach 41.3 MPa and 1.70 GPa, respectively. In contrast to the untreated ones, the interlaminar shear strength and tensile strength of modified composites increase by 44.9% and 15.6%, respectively.

Published
2024
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8. Tailoring Luminescent Properties of SrS:Ce by Modulating Defects: Sr-Deficiency and Na+ Doping

Author

Chang, Shuqin, Fu, Jipeng, Sun, Xuan, Bai, Guangcan, Liu, Guoquan, Wang, Kaina, Xu, Ligang, Wei, Qi, Meier, Thomas, and Tang, Mingxue

Subjects
Condensed Matter - Materials Science, C.1.1
Abstract

Ce3+ doped SrS phosphors with a charge-compensating Na+ for light-emitting diode (LED) applications have been successfully synthesized via a solid-state reaction method, which can be indexed to rock-salt-like crystal structures of Fm-3m space group. SrS:(Ce3+)x(x=0.005-0.05) and SrS:(Ce3+)0.01,(Na+)y(y=0.005-0.030) phosphors were excited by 430nm UV-VIS light, associated to the 5d1-4f1 transition of Ce3+. The composition-optimized SrS:(Ce3+)0.01,(Na+)0.015 phosphors showed an intense broad emission band at 430-700nm. The doping of Na+ was probed by solid-state nuclear magnetic resonance. The 430 nm pumped with white LED (w-LED) combining SrS:(Ce3+)0.01,(Na+)0.015 phosphors and Sr2Si5N8:Eu2+ phosphors shows a color-rendering index (Ra) of 89.7. The proposed strategy provides new avenues for design and realization of novel high color quality solid-state lighting emitting diodes (SS-LEDS)., Comment: 22 pages, 8figures

Published
2021

43. Non-Invasive Imaging Method of Microwave Near Field Based on Solid State Quantum Sensing

Author

Yang, Bo, Du, Guanxiang, Dong, Yue, Liu, Guoquan, Hu, Zhenzhong, and Wang, Yongjin

Subjects
Physics - Instrumentation and Detectors, Physics - Optics
Abstract

In this paper, we propose a non-invasive imaging method of microwave near field using a diamond containing nitrogen-vacancy centers. We applied synchronous pulsed sequence combined with charge coupled device camera to measure the amplitude of the microwave magnetic field. A full reconstruction formulation of the local field vector, including the amplitude and phase, is developed by measuring both left and right circular polarizations along the four nitrogen-vacancy axes. Compared to the raster scanning approach, the two dimensional imaging method is promising for application to circuit failure analysis. A diamond film with micrometer thinness enables high-resolution near field imaging. The proposed method is expected to have applications in monolithic-microwave-integrated circuit chip local diagnosis, antenna characterization, and field mode imaging of microwave cavities and waveguides.

Published
2018
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46. Speed Control of Permanent Magnet Synchronous Motor Based on Variable Fractional-Order Fuzzy Sliding Mode Controller.

Author

Chen, Liping, Liu, Haoyu, Cao, Ze, Lopes, António M., Yin, Lisheng, Liu, Guoquan, and Chen, Yangquan

Subjects
PERMANENT magnet motors, LYAPUNOV stability, STABILITY theory, FUZZY logic, SPEED
Abstract

A variable fractional-order (VFO) fuzzy sliding mode controller is designed to control the speed of a permanent magnet synchronous motor (PMSM). First, a VFO sliding mode surface is established. Then, a VFO fuzzy sliding mode controller is designed, capable of suppressing the effects of parameter uncertainties and disturbances to achieve precise PMSM speed control. The global stability and finite time convergence of the controlled system state are demonstrated using Lyapunov stability theory. The numerical and experimental results validate the effectiveness of the controller, showing better immunity to disturbances and a smaller overshoot compared to PID and fixed-order fuzzy sliding mode controllers. [ABSTRACT FROM AUTHOR]

Published
2025
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49. A general electrochemical strategy for the Sandmeyer reaction.

Author

Liu, Qianyi, Sun, Beiqi, Liu, Zheng, Kao, Yi, Dong, Bo-Wei, Jiang, Shang-Da, Li, Feng, Liu, Guoquan, Yang, Yang, and Mo, Fanyang

Subjects
Chemical Sciences
Abstract

Herein we report a general electrochemical strategy for the Sandmeyer reaction. Using electricity as the driving force, this protocol employs a simple and inexpensive halogen source, such as NBS, CBrCl3, CH2I2, CCl4, LiCl and NaBr for the halogenation of aryl diazonium salts. In addition, we found that these electrochemical reactions could be performed using anilines as the starting material in a one-pot fashion. Furthermore, the practicality of this process was demonstrated in the multigram scale synthesis of aryl halides using highly inexpensive graphite as the electrode. A series of detailed mechanism studies have been performed, including radical clock and radical scavenger study, cyclic voltammetry analysis and in situ electron paramagnetic resonance (EPR) analysis.

Published
2018

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