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Tang B.,Northwestern Polytechnical University | Tang B.,Science and Technology on Aerospace Flight Dynamics Laboratory | Zhu Z.,Northwestern Polytechnical University | Zhu Z.,Science and Technology on Aerospace Flight Dynamics Laboratory | And 3 more authors.
Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University | Year: 2013

This paper applies the improved ant colony algorithm to the planning of the 3D route of the UAV during its mission completion. To avoid the algorithm from easily falling into local optimum and early iterative stagnation, it puts forward a new method for pheromone volatility coefficient random self-adaptive adjustment. Its core consists of: (1) the minimum threat surface is projected horizontally and used to convert the 3D route planning into the 2D route planning; (2) the concept of dynamic window is used to improve the survival probability of the UAV in the complex battlefield environment when the UAV needs to replan its route because of the sudden appearance of unknown threats. The simulation results, given in Figs. 2 through 9 and Tables 1 through 4, and their analysis show preliminarily that: (1) the new method based on the improved ant colony algorithm is superior to the method based on the basic ant colony algorithm because of its better solution and high speed; (2) the new method has strong adaptability to the 3D route replanning of the UAV. Source


Wang W.,Huazhong University of Science and Technology | Qin Y.,Huazhong University of Science and Technology | Xiao Y.,Huazhong University of Science and Technology | Zhong L.,Huazhong University of Science and Technology | And 4 more authors.
Applied Optics | Year: 2016

Large-Fresnel-number unstable-waveguide hybrid resonators employing spherical resonator mirrors suffer from spherical aberration, which adversely affects beam quality and alignment sensitivity. In this paper, we present experimental and numerical wave-optics simulations of the beam characteristics of a negative-branch hybrid resonator having parabolic mirrors with a large equivalent Fresnel number in the unstable direction. These results are compared with a resonator using spherical mirrors. Using parabolic mirrors, the output beam has a smaller beam spot size and higher power density at the focal plane. We found that the power extraction efficiency is 3.5% higher when compared with a resonator using spherical mirrors as the cavity length was varied between -1 and 1 mm from the ideal confocal resonator. In addition, the power extraction efficiency is 5.6% higher for mirror tilt angles varied between -6 and 6 mrad. Furthermore, the output propagating field is similar to a converging wave for a spherical mirror resonator and the output beam direction deviates 3.5 mrad from the optical axis. The simulation results are in good agreement with the experimental results. © 2016 Optical Society of America. Source


Zuo Q.,Hubei Sanjiang Space Hongfeng Control Equipment Co. | Yu H.,Hubei Sanjiang Space Hongfeng Control Equipment Co. | Yang Y.,Hubei Sanjiang Space Hongfeng Control Equipment Co.
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2013

An asymmetric three corrugation-pitch-modulated DFB (3CPM-DFB) laser was proposed for the first time to realize high output efficiency as well as stable single longitudinal mode (SLM) operation. The optimization process based on transfer matrix method was demonstrated to maximize the marginal threshold gain (ΔαL) and the output power ratio between the front and rear facets simultaneously. The simulation results of the optimized asymmetric 3CPM-DFB laser in the above-threshold regime are compared with that of the asymmetric λ/4-shifted DFB laser. The evolutions of ΔαL with current show that both structures are suffered from spatial hole burning effects. However, ΔαL of 0.4 under 5Ith of the optimized asymmetric 3CPM-DFB laser is big enough to ensure stable SLM operation. And the output power-current curves prove that the optimized asymmetric 3CPM-DFB laser can provide higher output efficiency. Source

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