A novel widely tunable dual-wavelength mid-IR difference frequency generation (DFG) scheme with uniform grating periodically poled lithium niobate (PPLN) is presented in this paper. By using the temperature-depend...A novel widely tunable dual-wavelength mid-IR difference frequency generation (DFG) scheme with uniform grating periodically poled lithium niobate (PPLN) is presented in this paper. By using the temperature-dependent dispersion property of PPLN, the quasi-phase matching (QPM) peak for the pump may evolve into two separate ones and the wavelength spacing between them increases with the decrease of the crystal temperature. Such two pump QPM peaks may allow simultaneous dual-wavelength mid-IR laser radiations while properly setting the two fundamental pump wavelengths. With this scheme, mid-IR dual-wavelength laser radiations at around 3.228 and 3.548, 3.114 and 3.661, and 3.019 and 3.76 μm, are experimentally achieved for the crystal temperatures of 90, 65, and 30 ℃, respectively, based on the fiber laser fundamental lights.展开更多
Nanocomposites α-Fe/Fe 3B/Y 2O 3 were prepared by a melt-spun technique, and the electromagnetic wave absorption properties were measured in the 0 05~20 05 GHz range. Compared with α-Fe/Y 2O 3 composites, th...Nanocomposites α-Fe/Fe 3B/Y 2O 3 were prepared by a melt-spun technique, and the electromagnetic wave absorption properties were measured in the 0 05~20 05 GHz range. Compared with α-Fe/Y 2O 3 composites, the resonance frequency (f r) of α-Fe/Fe 3B/Y 2O 3 shifted to a higher frequency range due to the large anisotropy field (H A) of tetragonal Fe 3B (~0 4 mA·m -1). The relative permittivity (ε r=ε r′-jε r″) was constantly low over the 0 5~10 GHz region, which indicates that the composite powders have a high resistivity (ρ=~100 Ωm). The effective electromagnetic wave absorption (RL<-20 dB) was obtained in a frequency range of 2.7~6.5 GHz on resin composites of 80% (mass fraction) α-Fe/Fe 3B/Y 2O 3 powders, with thickness of 6~3 mm respectively. A minimum reflection loss of -33 dB was observed at 4.5 GHz with an absorber thickness of 4 mm.展开更多
By incorporating the higher order concept,the piecewise linear recursive convolution(PLRC)method and CrankNicolson Douglas-Gunn(CNDG)algorithm,the unconditionally stable complex frequency shifted nearly perfectly matc...By incorporating the higher order concept,the piecewise linear recursive convolution(PLRC)method and CrankNicolson Douglas-Gunn(CNDG)algorithm,the unconditionally stable complex frequency shifted nearly perfectly matched layer(CFS-NPML)is proposed to terminate the left-handed material(LHM)domain.The proposed scheme takes advantages of CFSNPML formulation,the higher order concept PLRC method and the unconditionally stable CNDG algorithm in terms of absorbing performance,computational efficiency,calculation accuracy and convenient implementation.A numerical example is carried out to demonstrate the effectiveness and efficiency of the proposed scheme.The results indicate that the proposed scheme can not only have considerable absorbing performance but also maintain the unconditional stability of the algorithm with the enlargement of time steps.展开更多
We propose a new proportional-integral-derivative(PID) controller design method for an automatic voltage regulation(AVR) system based on approximate model matching in the frequency domain. The parameters of the PID co...We propose a new proportional-integral-derivative(PID) controller design method for an automatic voltage regulation(AVR) system based on approximate model matching in the frequency domain. The parameters of the PID controller are obtained by approximate frequency response matching between the closed-loop control system and a reference model with the desired specifications. Two low frequency points are required for matching the frequency response, and the design method yields linear algebraic equations, solution of which gives the controller parameters. The effectiveness of the proposed method is demonstrated through examples taken from the literature and comparison with some popular methods.展开更多
Pipeline processing is applied to mutiple flow tables(MFT)in the switch of software-defined network(SDN)to increase the throughput of the flows.However,the processing time of each flow increases as the size or number ...Pipeline processing is applied to mutiple flow tables(MFT)in the switch of software-defined network(SDN)to increase the throughput of the flows.However,the processing time of each flow increases as the size or number of flow tables gets larger.In this paper we propose a novel approach called PopFlow where a table keeping popular flow entries is located up front in the pipeline,and an express path is provided for the flow matching the table.A Markov model is employed for the selection of popular entries considering the match latency and match frequency,and Queuing theory is used to model the flow processing time of the existing MFT-based schemes and the proposed scheme.Computer simulation reveals that the proposed scheme substantially reduces the flow processing time compared to the existing schemes,and the diference gets more significant as the flow arrival rate increases.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11374161)the Open Research Project of Jiangsu Provincial Key Labo-ratory of Meteorological Observation and Information Processing,China(Grant No.KDXS1206)the Project Funded by the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions,China
文摘A novel widely tunable dual-wavelength mid-IR difference frequency generation (DFG) scheme with uniform grating periodically poled lithium niobate (PPLN) is presented in this paper. By using the temperature-dependent dispersion property of PPLN, the quasi-phase matching (QPM) peak for the pump may evolve into two separate ones and the wavelength spacing between them increases with the decrease of the crystal temperature. Such two pump QPM peaks may allow simultaneous dual-wavelength mid-IR laser radiations while properly setting the two fundamental pump wavelengths. With this scheme, mid-IR dual-wavelength laser radiations at around 3.228 and 3.548, 3.114 and 3.661, and 3.019 and 3.76 μm, are experimentally achieved for the crystal temperatures of 90, 65, and 30 ℃, respectively, based on the fiber laser fundamental lights.
文摘Nanocomposites α-Fe/Fe 3B/Y 2O 3 were prepared by a melt-spun technique, and the electromagnetic wave absorption properties were measured in the 0 05~20 05 GHz range. Compared with α-Fe/Y 2O 3 composites, the resonance frequency (f r) of α-Fe/Fe 3B/Y 2O 3 shifted to a higher frequency range due to the large anisotropy field (H A) of tetragonal Fe 3B (~0 4 mA·m -1). The relative permittivity (ε r=ε r′-jε r″) was constantly low over the 0 5~10 GHz region, which indicates that the composite powders have a high resistivity (ρ=~100 Ωm). The effective electromagnetic wave absorption (RL<-20 dB) was obtained in a frequency range of 2.7~6.5 GHz on resin composites of 80% (mass fraction) α-Fe/Fe 3B/Y 2O 3 powders, with thickness of 6~3 mm respectively. A minimum reflection loss of -33 dB was observed at 4.5 GHz with an absorber thickness of 4 mm.
文摘By incorporating the higher order concept,the piecewise linear recursive convolution(PLRC)method and CrankNicolson Douglas-Gunn(CNDG)algorithm,the unconditionally stable complex frequency shifted nearly perfectly matched layer(CFS-NPML)is proposed to terminate the left-handed material(LHM)domain.The proposed scheme takes advantages of CFSNPML formulation,the higher order concept PLRC method and the unconditionally stable CNDG algorithm in terms of absorbing performance,computational efficiency,calculation accuracy and convenient implementation.A numerical example is carried out to demonstrate the effectiveness and efficiency of the proposed scheme.The results indicate that the proposed scheme can not only have considerable absorbing performance but also maintain the unconditional stability of the algorithm with the enlargement of time steps.
文摘We propose a new proportional-integral-derivative(PID) controller design method for an automatic voltage regulation(AVR) system based on approximate model matching in the frequency domain. The parameters of the PID controller are obtained by approximate frequency response matching between the closed-loop control system and a reference model with the desired specifications. Two low frequency points are required for matching the frequency response, and the design method yields linear algebraic equations, solution of which gives the controller parameters. The effectiveness of the proposed method is demonstrated through examples taken from the literature and comparison with some popular methods.
基金supported by Institute for In-fornation&communications Technology Promotion(ITP)grant funded by the Korea government(MSIT)(2016-0-00133,Research on Edge computing via collctive intelligence of hyperconnection IoT nodes)Korea,under the National Program for Excellence in Sw supervised by the ITP(Institute for Information&communications Technology Promotion)(2015-0-00914)Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science and Technology(2016R1A6A3A11931385,Research of key technologies based on software defined wireless sensor network for realtime public safety service,2017R1A2B2009095,Research on SDN-based WSN Supporting Real-time Stream Data Processing and Multi-connectivity,2019R1I1A1A01058780,Eficient Management of SDN-based Wireless Sensor Network Using Machine Learning Technique),the second Brain Korea 21 PLUS project.
文摘Pipeline processing is applied to mutiple flow tables(MFT)in the switch of software-defined network(SDN)to increase the throughput of the flows.However,the processing time of each flow increases as the size or number of flow tables gets larger.In this paper we propose a novel approach called PopFlow where a table keeping popular flow entries is located up front in the pipeline,and an express path is provided for the flow matching the table.A Markov model is employed for the selection of popular entries considering the match latency and match frequency,and Queuing theory is used to model the flow processing time of the existing MFT-based schemes and the proposed scheme.Computer simulation reveals that the proposed scheme substantially reduces the flow processing time compared to the existing schemes,and the diference gets more significant as the flow arrival rate increases.