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Nonlinear optical properties of silver colloidal solution by in situ synthesis technique
Yan Deng,Youyi Sun,Pei Wang,Douguo Zhang,Xiaojin Jiao,Hai Ming,Qijing Zhang,Yang Jiao,Xiaoquan Sun 한국물리학회 2008 Current Applied Physics Vol.8 No.1
The silver colloidal solutions were prepared by in situ synthesis technique in the presence of the Polymethyl Methacrylate, which was polymerized by reversible addition-fragmentation transfer. The UV–VIS spectra and transmission electron microscopy had shown the formation of sphere silver nanoparticles with average size of 10 nm. Nonlinear optical properties as a function of silver concentration were studied using Z-scan technique with 13 ns pulse duration at 532 nm. The optical nonlinearity enhancement was observed by increasing the concentration. The third-order nonlinear susceptibility v(3) was measured to 1.045 · 1011 esu when the concentration was 2.13 mg/ml. Besides, the sample was founded to exhibit a shift from saturable absorption to reverse saturable absorption at higher incident laser energy. The reverse saturable absorption was observed to be responsible for the optical limiting characteristics in our experiments. 2007 Published by Elsevier B.V. The silver colloidal solutions were prepared by in situ synthesis technique in the presence of the Polymethyl Methacrylate, which was polymerized by reversible addition-fragmentation transfer. The UV–VIS spectra and transmission electron microscopy had shown the formation of sphere silver nanoparticles with average size of 10 nm. Nonlinear optical properties as a function of silver concentration were studied using Z-scan technique with 13 ns pulse duration at 532 nm. The optical nonlinearity enhancement was observed by increasing the concentration. The third-order nonlinear susceptibility v(3) was measured to 1.045 · 1011 esu when the concentration was 2.13 mg/ml. Besides, the sample was founded to exhibit a shift from saturable absorption to reverse saturable absorption at higher incident laser energy. The reverse saturable absorption was observed to be responsible for the optical limiting characteristics in our experiments. 2007 Published by Elsevier B.V.
Design and Application of a Nonlinear Coordinated Excitation and TCPS Controller in Power Systems
Hashmani Ashfaque Ahmed,Wang Youyi,Lie Tek Tjing Institute of Control 2005 International Journal of Control, Automation, and Vol.3 No.S
This paper presents a new approach to Thyristor Controlled Phase Shifter (TCPS) control. In this paper we have proposed a nonlinear coordinated generator excitation and TCPS controller to enhance the transient stability of a power system. The proposed controller is able to control three main parameters affecting a.c. power transmission: namely excitation voltage, phase angle and reactance in a coordinated manner. The TCPS is located at the midpoint of the transmission line. A nonlinear feedback control law is proposed to linearize and decouple the power system. The design of the proposed controller is based on the local measurements only. Simulation results have been shown to demonstrate the effectiveness of the proposed controller for the enhancement of transient stability of the power system under a large sudden fault.
Design and Application of a Nonlinear Coordinated Excitation and TCPS Controller in Power Systems
Ashfaque Ahmed Hashmani,Youyi Wang,Tek Tjing Lie 대한전기학회 2005 International Journal of Control, Automation, and Vol.3 No.2
This paper presents a new approach to Thyristor Controlled Phase Shifter (TCPS) control. In this paper we have proposed a nonlinear coordinated generator excitation and TCPS controller to enhance the transient stability of a power system. The proposed controller is able to control three main parameters affecting a.c. power transmission: namely excitation voltage, phase angle and reactance in a coordinated manner. The TCPS is located at the midpoint of the transmission line. A nonlinear feedback control law is proposed to linearize and decouple the power system. The design of the proposed controller is based on the local measurements only. Simulation results have been shown to demonstrate the effectiveness of the proposed controller for the enhancement of transient stability of the power system under a large sudden fault.
Wen Zhu,Wenfeng Wang,Wencan Xu,Shuang Wu,Wenjun Chen,Youyi Huang,Shengpeng Wang 한국식품과학회 2022 Food Science and Biotechnology Vol.31 No.7
Pile-fermentation is a critical procedure for producing Chinese dark tea, during which thermophilic microorganisms would play an irreplaceable role. However, there have been little researches on the influences of thermophilic microorganism pile-fermentation (TMPF) in high-temperature of Chinese dark tea. Thus, we conducted high-performance liquid chromatography and nontargeted metabolomic to analyze the non-volatile metabolites of TMPF. Our results discovered that the amounts of ( −)-epigallocatechin gallate, ( −)-epigallocatechin, ( −)-epicatechin gallate, and ( −)-epicatechin were decreased significantly (p < 0.05) after TMPF. By using nontargeted metabolomic analysis, a total of 1733 ion features were detected. KEGG pathway enrichment analysis showed that TMPF had a significant impact on caffeine metabolism. Also, theophylline, 3-methylxanthine, and 1,3,7-trimethyluric acid were increased significantly after TMPF, which suggested that demethylation and oxidation reaction might be the main pathways of caffeine metabolism. This study provides a better understanding of the mechanism of TMPF during high-temperature for Chinese dark tea and lays a foundation for further research.
Numerical and experimental investigation of nonlinear vortex induced vibration energy converters
Bao Huy Huynh,Tegoeh Tjahjowidodo,Zhaowei Zhong,Youyi Wang,Narasimalu Srikanth 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8
In this paper, effects of bi-stable stiffness and hardening stiffness on the performance of a Vortex induced vibration (VIV) energy converter are theoretically and experimentally studied through a wake oscillator model and a computer-based force-feedback testing platform. Based on the simulation and experimental results, it is found that the bi-stable stiffness is potential to allow the system to operate at low velocity water flows, while the hardening stiffness will extend the operating range at high velocity flows. Subsequently, in order to take the advantages of both types of stiffness, a combined nonlinear stiffness is proposed and verified experimentally to demonstrate its capability in improving the overall operating range of the VIV energy converter.