The problem of estimating direction of arrivals (DOA) and Doppler frequency for many sources is considered in the presence of general array errors (such as amplitude and phase error of sensors, setting position error ...The problem of estimating direction of arrivals (DOA) and Doppler frequency for many sources is considered in the presence of general array errors (such as amplitude and phase error of sensors, setting position error of sensors). Adopting direct array manifold in a uniform circular array (UCA), the estimation of Doppler frequency can be obtained by DOA matrix. Based on analyzing the statistic characters of general array errors, the estimation of DOA can be obtained by Weight Total Least Squares. Numerical results illustrate that the estimator is robust to general array errors and show the capabilities of the estimator.展开更多
This paper presents an efficient numerical method for solving the unsteady Euler equations on stationary Cartesian grids. Wall boundary conditions are implemented on non moving mean wall positions by assuming the airf...This paper presents an efficient numerical method for solving the unsteady Euler equations on stationary Cartesian grids. Wall boundary conditions are implemented on non moving mean wall positions by assuming the airfoil being thin and undergoing small deformation, but the mean angle of attack of the body can still be large and we use the full nonlinear Euler equation in the field for accurate resolution of shock waves and vorticity. The method does not require the generation of moving body fitted grids and thus can be easily deployed in any fluid structure interaction problem involving relatively small deformation of a thin body. We use the first order wall boundary conditions in solving the full Euler equation. Unsteady transonic flow is calculated about an oscillating NACA 0012 airfoil at free stream Mach number M ∞ =0.755, mean angle of attack α m =0.016, amplitude of pitching oscillation α 0 =2.51, reduced frequency κ = 0.081 4. The computed results, including surface pressure distribution, instantaneous lift and moment coefficients are compared with known experimental data. It is shown that the first order boundary conditions are satisfactory for airfoils of typical thicknesses with small deformation for unsteady calculations.展开更多
A new concept is proposed that susceptibility, vulnerability, reliability, maintainability and supportability should be essential factors of aircraft combat survivability. A weight coefficient method and a synthetic m...A new concept is proposed that susceptibility, vulnerability, reliability, maintainability and supportability should be essential factors of aircraft combat survivability. A weight coefficient method and a synthetic method are proposed to estimate aircraft combat survivability based on the essential factors. Considering that it takes cost to enhance aircraft combat survivability, a synthetic tradeoff model between aircraft combat survivability and life cycle cost is built. The aircraft combat survivability estimation methods and synthetic tradeoff with a life cycle cost model will be helpful for aircraft combat survivability design and enhancement.展开更多
In this paper, based on the Quality Function Deployment ( QFD) method, theFuzzy Quality Function Deployment (FQFD) theory and the step-by-step hierarchy structure in aircrafttop decision design are studied. The fuzzy ...In this paper, based on the Quality Function Deployment ( QFD) method, theFuzzy Quality Function Deployment (FQFD) theory and the step-by-step hierarchy structure in aircrafttop decision design are studied. The fuzzy model for computing competitive factor in evaluation ispresented. The decision of key technologies for improving the performance and affordability of afixed-wing aircraft is studied using the model, and the result proves the feasibility of this model.展开更多
文摘The problem of estimating direction of arrivals (DOA) and Doppler frequency for many sources is considered in the presence of general array errors (such as amplitude and phase error of sensors, setting position error of sensors). Adopting direct array manifold in a uniform circular array (UCA), the estimation of Doppler frequency can be obtained by DOA matrix. Based on analyzing the statistic characters of general array errors, the estimation of DOA can be obtained by Weight Total Least Squares. Numerical results illustrate that the estimator is robust to general array errors and show the capabilities of the estimator.
文摘This paper presents an efficient numerical method for solving the unsteady Euler equations on stationary Cartesian grids. Wall boundary conditions are implemented on non moving mean wall positions by assuming the airfoil being thin and undergoing small deformation, but the mean angle of attack of the body can still be large and we use the full nonlinear Euler equation in the field for accurate resolution of shock waves and vorticity. The method does not require the generation of moving body fitted grids and thus can be easily deployed in any fluid structure interaction problem involving relatively small deformation of a thin body. We use the first order wall boundary conditions in solving the full Euler equation. Unsteady transonic flow is calculated about an oscillating NACA 0012 airfoil at free stream Mach number M ∞ =0.755, mean angle of attack α m =0.016, amplitude of pitching oscillation α 0 =2.51, reduced frequency κ = 0.081 4. The computed results, including surface pressure distribution, instantaneous lift and moment coefficients are compared with known experimental data. It is shown that the first order boundary conditions are satisfactory for airfoils of typical thicknesses with small deformation for unsteady calculations.
文摘A new concept is proposed that susceptibility, vulnerability, reliability, maintainability and supportability should be essential factors of aircraft combat survivability. A weight coefficient method and a synthetic method are proposed to estimate aircraft combat survivability based on the essential factors. Considering that it takes cost to enhance aircraft combat survivability, a synthetic tradeoff model between aircraft combat survivability and life cycle cost is built. The aircraft combat survivability estimation methods and synthetic tradeoff with a life cycle cost model will be helpful for aircraft combat survivability design and enhancement.
文摘In this paper, based on the Quality Function Deployment ( QFD) method, theFuzzy Quality Function Deployment (FQFD) theory and the step-by-step hierarchy structure in aircrafttop decision design are studied. The fuzzy model for computing competitive factor in evaluation ispresented. The decision of key technologies for improving the performance and affordability of afixed-wing aircraft is studied using the model, and the result proves the feasibility of this model.
