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Zhongyang Li,Silei Wang,Mengtao Wang,Weishu Wang 한국광학회 2017 Current Optics and Photonics Vol.1 No.2
Terahertz (THz) generation by periodically-poled KTiOPO4 (PPKTP) with a quasi-phase-matching schemebased on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascadedStokes interaction processes and the cascaded anti-Stokes interaction processes are investigated fromcoupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared withnon-cascaded DFG processes, THz intensities from 10-order cascaded DFG processes are increased to 5.53. The quantum conversion efficiency of 479.4% in cascaded processes, which exceeds the Manley-Rowelimit, can be realized.
Investigation of Stimulated Polariton Scattering from the B₁-symmetry Modes of the KNbO₃ Crystal
Zhongyang Li,Mengtao Wang,Silei Wang,Bin Yuan,Pibin Bing,Degang Xu,Jianquan Yao 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Stimulated polariton scattering from the B₁-symmetry modes of a KNbO₃ crystal to generate a terahertz wave (THz-wave) with a noncollinear phase-matching scheme is investigated. The frequency-tuning characteristics of the THz-wave by varying the phase-matching angle and pump wavelength are analyzed. The expression for the effective parametric gain length under the noncollinear phase-matching condition is deduced. Parametric gain and absorption characteristics of the THz-wave in KNbO₃ are theoretically simulated. The characteristics of KNbO₃ for a terahertz parametric oscillator (TPO) are compared to those of MgO:LiNbO₃. The analysis indicates that KNbO₃ is an excellent optical crystal for a TPO, to enhance the THz-wave output.
Bacterial Cellulose Immobilized S. cerevisiae as Microbial Sensor for Rapid BOD Detection
Chenyu Zhao,Guangshu Wang,Mengtao Sun,Zewei Cai,Zichu Yin,Yurong Cai 한국섬유공학회 2021 Fibers and polymers Vol.22 No.5
As one of the most important parameters to characterize the organic pollution of water, biochemical oxygendemand (BOD) determined through a rapid, in situ and on line method is very attractive. In this paper, a new BOD biosensorhas been developed, which are composed of the ecofriendly precursor of Saccharomyces cerevisiae (S. cerevisiae) embeddedin bacterial cellulose (BC) matrix and the Ketjen Black (KB) modified glassy-carbon electrode. Furthermore, a doublemediatorsystem is constructed using potassium ferricyanide and menadione in reaction cell to transfer electron from themicrobe to electrode. The responses of glucose glutamic acid (GGA) standard solutions are amperomertrically measured withan applied potential of 0.25 V versus Hg/Hg2Cl2 in a three-electrode system. Under the optimum conditions, the (BC/S. cerevisiae-menadione)/KB modified electrode shows a high operational stability with relative standard deviation (RSD) of4.16 % (fourteen assays), a good repeatability (RSD=3.10 %), a fast response time (in 20 minutes) and a wide linear range(from 10-220 mg O2 l-1). The BOD values measured by this method have been highly correlated with the standard BOD 5-daymethod for wastewater samples (R2=0.9859, n=3), indicating that it can meet the requirement of BOD rapid measurement.
Zhongyang Li,Bin Yuan,Silei Wang,Mengtao Wang,Pibin Bing 한국광학회 2018 Current Optics and Photonics Vol.2 No.2
Terahertz (THz) wave generation by periodically poled BaTiO₃ (PPBT) with a quasi-phase-matching (QPM) scheme based on cascaded difference-frequency generation (DFG) is theoretically analyzed. The cascaded DFG processes comprise cascaded Stokes and anti-Stokes processes. The calculated results indicate that the cascaded Stokes processes are stronger than the cascaded anti-Stokes processes. Compared to a noncascaded Stokes process, THz intensities from 20<SUP>th</SUP>-order cascaded Stokes processes increase by a factor of 30. THz waves with a maximum intensity of 0.37 MW/mm² can be generated by 20<SUP>th</SUP>-order cascaded DFG processes when the optical intensity is 10 MW/mm², corresponding to a quantum conversion efficiency of 1033%. The high quantum conversion efficiency of 1033% exceeds the Manley-Rowe limit, which indicates that PPBT is an excellent crystal for THz wave generation via cascaded DFG.
Zhongyang Li,Bin Yuan,Silei Wang,Mengtao Wang,Pibin Bing 한국광학회 2018 Current Optics and Photonics Vol.2 No.3
Stimulated polariton scattering (SPS) from the A₁ transverse optical (TO) modes of BaTiO₃ bulk crystal generating a terahertz (THz) wave with the noncollinear phase-matching (NPM) condition is theoretically investigated. To our best knowledge, this is the first report on THz wave generation from BaTiO₃ bulk crystal via SPS. Phase-matching (PM) characteristics in the NPM configuration are analyzed. Effective parametric gain lengths for the Stokes and THz waves in the NPM configuration are calculated. The effective parametric gain coefficient and absorption coefficient of the THz wave in BaTiO₃ are theoretically simulated. The THz phonon flux densities generated via SPS in BaTiO₃ are theoretically calculated by solving the coupled wave equations under the NPM condition. The PM characteristics and THz-wave parametric gain characteristics in BaTiO₃ are compared to those in MgO:LiNbO₃. The results of the analysis indicate that BaTiO₃ is an attractive optical crystal for efficient THz wave generation via SPS.
Meng, Tao,Ben, Hongqi,Wang, Daqing,Song, Jianfeng The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.3
In this paper a novel passive snubber is proposed, which can suppress the voltage spike across the bridge leg of the isolated full-bridge boost topology. The snubber is composed of capacitors, inductors and diodes. Two capacitors connected in series are used to absorb the voltage spike and the energy of each capacitor can be transferred to the load during one switching cycle by the resonance of the inductors and capacitors. The operational principle of the passive snubber is analyzed in detail based on a three-phase power factor correction (PFC) converter, and the design considerations of both the converter and the snubber are given. Finally, a 3kW laboratory-made prototype is built. The experimental results verify the theoretical analysis and evaluations. They also prove the validity and feasibility of the proposed methods.