Liao S.,Guilin Air Force Academy |
Gong M.,Tsinghua University
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2011
In order to overcome the limitations of the nonlinear effects and optical damage, the high power active fibers usually have large mode areas. The current main technical means used in large mode area fibers were reviewed, which include the fiber structural design, mode control and selection, and mode transform. Then the basic idea of the various technical means and the primary characteristics of the relevant large mode area fibers were described. On the basis, it was pointed that the difficult problems like mode distortion as well as the high order mode suppression, the integration analysis for laser systems and the fiber fabrications when they were applied in the actual applications. Finally, by comparing the fiber performance characteristic, processing ease, and the study level of the theoretical and experimental aspects, the mode transform with the higher order mode fiber and the gain guiding, index anti-guiding approach are considered to be the two most effective ways to achieve the large mode area fiber lasers. It is possible to improve the mode areas.
Lin Y.,Guilin Air Force Academy
Binggong Xuebao/Acta Armamentarii | Year: 2010
A method of determining optimum aperture distributions of Cassegrain reflector antennas was presented. The necessity of seeking optimum aperture distribution of Cassegrain reflector antennas was illustrated by comparison of the sidelobe levels between Cassegrain reflector antennas and parabolic reflector antennas of the same aperture distributions as that of the former; optimum aperture distributions of Cassegrain reflector antennas is determined by means of simultaneous equations of constraint conditions of sidelobe level and aperture efficiency; other possible applications of the method of determining optimum aperture distributions of Cassegrain reflector antennas were enumerated. The investigated result demonstrates that compared with common aperture distribution, the optimum aperture distribution has better sidelobe level and aperture efficiency, i.e. the optimum aperture distribution has higher aperture efficiency at the same sidelobe level or lower sidelobe level at the same aperture efficiency.
Xie C.-M.,Beihang University |
Xie C.-M.,Guilin Air Force Academy |
Zhao Y.,Beihang University |
Yang C.-C.,Air Defense Force Command Academy
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2011
Aiming at the remarkable influence of wing flexure noise on transfer alignment (TA) filtering, an online compensation algorithm is proposed on the assumption that the wing flexure noise is a time varying multi-order colored measurement noise from its character analysis. On the basis of typical Kalman filtering equations, new filtering equations capable of compensating multi-order colored noise without dimension extension are derived. According to the series measuring data and aided by a model estimating error F testing method, the algorithm is used to iteratively estimate auto-regressive orders, auto-regressive coefficients and white noise of wing flexure noise online which are thus taken advantage of to construct the measurement data, measurement matrix and measurement noise to perform compensating filtering. Finally, the algorithm is applied to a velocity plus attitude TA matching plan and compared with the method substituting wing flexure noise by pouring white measurement noise and extending system states. Simulation results show that the algorithm is of strong adaptability to new measurement data under time varying wing flexure noise as well as steady convergence and high accuracy estimating performance, which is feasible to achieve rapid and high accuracy airborne missile TA under hard air environment.
Ni Y.,Tsinghua University |
Ni Y.,Guilin Air Force Academy |
Fan Y.-S.,Tsinghua University
Jisuanji Jicheng Zhizao Xitong/Computer Integrated Manufacturing Systems, CIMS | Year: 2011
To resolve the semantic inconsistency of multi-domain business process collaboration in Service Oriented Architecture, a multi-domain business process collaboration architecture based on model transformation was proposed. Collaborative ontology transforming into the Web Services composition model was realized by meta modeling framework of meta-object facility. This method remained the original semantic information in processes and Web Services, provided a flexible method for model transformation so as to ensure the semantic consistency of collaborative business processes. The framework and transformation method were implemented in project ImportNET which was funded by European Commission, and the effectiveness was illustrated.
Ji C.,PLA University of Science and Technology |
Long Y.,PLA University of Science and Technology |
Fang X.,PLA University of Science and Technology |
Tang X.-S.,Guilin Air Force Academy
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012
By means of the explicit nonlinear dynamic finite element computer code LS-DYNA, the nonlinear dynamic response process of a steel-pipe subjected to contact explosion loading was numerically simulated using Lagrangian-Eulerian coupling method. The deformation shape, damage process and evolution of Von-mises stress in pipe were described, and the effects of the explosive mass and pipe thickness to steel-pipe's damage extent were analyzed. An experimental research was also carried out under the same condition, and the numerical simulation results are in good agreement with the experimental data. The study indicates the pit, bump and spallation would happen when the explosive mass is small. However, the fly fragment like EFP (Explosively Formed Projectile) would be shaped due to shear failure if the explosive mass is large, and can perforate the opposite side of the pipe due to the abundant kinetic energy carried by the fly fragments. The method can be applied to the engineering prediction of the damage or safety of pipes under explosive and can provide theoretical reference to safety design.