Flow control valve generally consists of constant pressure difference reducing valve and throttle valve.When it works under the condition of high differential pressure and flow, the pressure loss of reducing valve in-...Flow control valve generally consists of constant pressure difference reducing valve and throttle valve.When it works under the condition of high differential pressure and flow, the pressure loss of reducing valve in-stalled in main loop will get increased and the hydraulic oil temperature will be increased as well. A digital pilotflow control valve is studied in this paper. The main stage is a cartridge valve based on the flow amplifying princi-ple. The pilot stage is digital flow control valve which consists of digital valve and constant pressure difference re-ducing valve. The digital valve controlled by PWM signal has some characteristics such as less throttling loss andgood repeatability. The high pressure loss and hydraulic oil temperature will be effectively reduced by using con-stant pressure difference reducing valve in the small flow pilot circuit. Through theoretical derivation and simula-tion research, the feasibility of this valve is verified, and some conclusions are drawn for the relationships betweenthe performance and structure parameters, which provides theoretical basis for their design.展开更多
In this paper,we study the nonlinear matrix equation X-A^(H)X^(-1)A=Q,where A,Q∈C^(n×n),Q is a Hermitian positive definite matrix and X∈C^(n×n)is an unknown matrix.We prove that the equation always has a u...In this paper,we study the nonlinear matrix equation X-A^(H)X^(-1)A=Q,where A,Q∈C^(n×n),Q is a Hermitian positive definite matrix and X∈C^(n×n)is an unknown matrix.We prove that the equation always has a unique Hermitian positive definite solution.We present two structure-preserving-doubling like algorithms to find the Hermitian positive definite solution of the equation,and the convergence theories are established.Finally,we show the effectiveness of the algorithms by numerical experiments.展开更多
A Patch NAH method based on HELS( helmholtz equation least-squares) algorithm is proposed for the measurement requirement of underwater large structures. This method chooses HELS algorithm to approximate the sound fie...A Patch NAH method based on HELS( helmholtz equation least-squares) algorithm is proposed for the measurement requirement of underwater large structures. This method chooses HELS algorithm to approximate the sound field completely,and calculates the sound field data outside the measurement region to enlarge the measurement aperture. It can reconstruct the sound field by the measurement data and the extrapolation data,through the reconstruction result it can be researched for the minimum measurement surface and the range of the extrapolation data in application. The paper analyzes the effect from the different measurement surfaces and different extrapolation ranges to the extrapolation data by simulations,and compares these reconstructed results with the conventional algorithm results. The simulation results indicate that the method can simplify the holographic measuring system,save the cost of the project and improve the accuracy of the sound field reconstruction,which can be effectively used for measuring and analyzing the underwater large structures.展开更多
In order to study the dynamic characteristics of the single-frequency signal through the nonlinear control system,the system control mode,the outer excitation patterns of the model and the amplitude are investigated b...In order to study the dynamic characteristics of the single-frequency signal through the nonlinear control system,the system control mode,the outer excitation patterns of the model and the amplitude are investigated by using the methods of the nonlinear dynamical analysis. The time-domain diagram,power spectrum,phase diagram and the largest Lyapunov exponent obtained from the process of the signal propagate through different control module are given. The researches on different control systems demonstrate that: after single-frequency signal goes through the nonlinear controller,it is still non-chaotic although the output contains more frequency components; but with the feedback and the external perturbation,the output is a continuous broadband spectrum and the result shows that there is chaos. The energy of the input signal reduces with some appropriate parameters. Therefore,the control system of the nonlinear feedback is a good way to broaden the spectrum of output with inputting a single-frequency signal.展开更多
Tianjin Medical University General Hospital treated 233 wounded in 8.12 Tinjin Port explosion. Here we would like to analyze the treatment process for the wounded, and share the experiences of orga- nization and manag...Tianjin Medical University General Hospital treated 233 wounded in 8.12 Tinjin Port explosion. Here we would like to analyze the treatment process for the wounded, and share the experiences of orga- nization and management for emergency rescue operation.展开更多
基金supported by National Natural Science Foundation of China ( No. 51205271)Specialized Research Fund for the Doctoral Program of Higher Education ( No. 20121402120002)
文摘Flow control valve generally consists of constant pressure difference reducing valve and throttle valve.When it works under the condition of high differential pressure and flow, the pressure loss of reducing valve in-stalled in main loop will get increased and the hydraulic oil temperature will be increased as well. A digital pilotflow control valve is studied in this paper. The main stage is a cartridge valve based on the flow amplifying princi-ple. The pilot stage is digital flow control valve which consists of digital valve and constant pressure difference re-ducing valve. The digital valve controlled by PWM signal has some characteristics such as less throttling loss andgood repeatability. The high pressure loss and hydraulic oil temperature will be effectively reduced by using con-stant pressure difference reducing valve in the small flow pilot circuit. Through theoretical derivation and simula-tion research, the feasibility of this valve is verified, and some conclusions are drawn for the relationships betweenthe performance and structure parameters, which provides theoretical basis for their design.
基金This research is supported by the National Natural Science Foundation of China(No.11871444).
文摘In this paper,we study the nonlinear matrix equation X-A^(H)X^(-1)A=Q,where A,Q∈C^(n×n),Q is a Hermitian positive definite matrix and X∈C^(n×n)is an unknown matrix.We prove that the equation always has a unique Hermitian positive definite solution.We present two structure-preserving-doubling like algorithms to find the Hermitian positive definite solution of the equation,and the convergence theories are established.Finally,we show the effectiveness of the algorithms by numerical experiments.
基金Sponsored by the Scientific Research Fund of Heilongjiang Provincial Education Department(Grant No.12541132)
文摘A Patch NAH method based on HELS( helmholtz equation least-squares) algorithm is proposed for the measurement requirement of underwater large structures. This method chooses HELS algorithm to approximate the sound field completely,and calculates the sound field data outside the measurement region to enlarge the measurement aperture. It can reconstruct the sound field by the measurement data and the extrapolation data,through the reconstruction result it can be researched for the minimum measurement surface and the range of the extrapolation data in application. The paper analyzes the effect from the different measurement surfaces and different extrapolation ranges to the extrapolation data by simulations,and compares these reconstructed results with the conventional algorithm results. The simulation results indicate that the method can simplify the holographic measuring system,save the cost of the project and improve the accuracy of the sound field reconstruction,which can be effectively used for measuring and analyzing the underwater large structures.
基金Sponsored by Basic Research Development Program(Grant No.7131107)the National Natural Science Foundation of China(Grant No.51206101)
文摘In order to study the dynamic characteristics of the single-frequency signal through the nonlinear control system,the system control mode,the outer excitation patterns of the model and the amplitude are investigated by using the methods of the nonlinear dynamical analysis. The time-domain diagram,power spectrum,phase diagram and the largest Lyapunov exponent obtained from the process of the signal propagate through different control module are given. The researches on different control systems demonstrate that: after single-frequency signal goes through the nonlinear controller,it is still non-chaotic although the output contains more frequency components; but with the feedback and the external perturbation,the output is a continuous broadband spectrum and the result shows that there is chaos. The energy of the input signal reduces with some appropriate parameters. Therefore,the control system of the nonlinear feedback is a good way to broaden the spectrum of output with inputting a single-frequency signal.
文摘Tianjin Medical University General Hospital treated 233 wounded in 8.12 Tinjin Port explosion. Here we would like to analyze the treatment process for the wounded, and share the experiences of orga- nization and management for emergency rescue operation.