Pose estimation for UAV aerial refueling with serious turbulences based on extended Kalman filter

In recent years, many pose estimation algorithms were developed, and have been successfully applied to solve unmanned aerial vehicle (UAV) aerial refueling pose estimation problems. This paper mainly focuses on solving this problem under serious turbulences circumstance. The extended Kalman filter is a set of mathematical equations to estimate the state of a process, which is able to support estimations of past, present, and even future states. In reference to previous papers and some simulations, we build up the noise models of refueling boom and atmospheric turbulence. Then, an extend Kalman filter is adopted to solve the pose estimation problem in UAV aerial refueling with serious turbulences. The experimental results demonstrate the feasibility and effectiveness of our proposed approach.     

All-angle broadband negative refraction of metal waveguide arrays in the visible range: theoretical analysis and numerical demonstration

In this Letter, we introduce a simple metal waveguide array for realizing all-angle wide frequency bandwidth negative refraction from the visible to infrared frequencies. Theoretical analysis from the rigorous coupled-wave theory reveals that the negative coupling constant resulting from the anomalous coupling of guided surface plasmon polariton modes contributes to the negative refraction. The analytical results are confirmed by finite-difference time-domain numerical simulations. Our result provides an alternative way to construct robust all-angle negative refractive materials operating in a wide range of frequency from the near-infrared to the visible range.     

Experimental characterization and correction of non-equivalence of Solar Irradiance Absolute Radiometer

We experimentally evaluate and correct the non-equivalence between electrical and radiative heating of solar irradiance absolute radiometer to compensate the systematic error of radiant power measurement at ambient pressure. A relative difference of the order of 0.08%-0.27% between electrical and radiative heating sensitivities is shown, and the resulting non-equivalence correction factor is calculated. The radiant power measurement equation is modified using the non-equivalence correction factor, a systematic deviation of 0.19% of radiant power measurement is hence eliminated.     

W波段回旋行波管输入输出段的改进设计

在回旋行波放大器的设计中,输入输出段的性能直接影响到整管输出功率、效率及增益。设计了一种采用渐变过渡段的输入耦合器来减少电子注在前端的截获,而且略微地提高了耦合特性,有效带宽达到4.06 GHz。采用二级切比雪夫渐变波导作为输出结构的耦合输出段,从仿真结果得到,在整个工作频段内,该结构中TE01工作模式的反射低于-20 dB,TE01模向杂模TE02和TE03的耦合分别在-20 dB和-30 dB以下。     

Electrochemical performance of a nonaqueous rechargeable lithium-air battery

Nonaqueous rechargeable lithium-air battery has so high specific capacity and specific energy that it is being widely researched by academia, corporation, and different research institutes. When used in dried air and absorbing oxygen form the air, this battery is called lithium-air battery, and its specific capacity based on cathode active material (oxygen) is infinite. However, its cycle performance is very limited as reported by the state-of-the-art researches. This cycle problem is mainly caused by instability of electrolyte. Based on electroanalysis of materials’ electrochemical property, a stable electrolyte solvent (sulfolane) and a lithium salt LiBF₄ are selected as electrolytes in this work. Coupled with other eligible battery materials and careful assembly, the lithium-air battery exhibits favorable cycle performance. Above all, this lithium-air system is evaluated objectively in this paper.     

Effect of pressure on the performance of plasma synthetic jet actuator

The effects of the ambient air pressure level on the performance of plasma synthetic jet actuator have been investigated through electrical and optical diagnostics.Pressures from 1 atm down to 0.1 atm were tested with a 10 Hz excitation.The discharge measurement demonstrates that there is a voltage range to make the actuator work reliably.Higher pressure level needs a higher breakdown voltage,and a higher discharge current and energy deposition are produced.But when the actuator works with the maximum breakdown voltage,the fraction of the initial capacitor energy delivered to the arc is almost invariable.This preliminary study also confirms the effectiveness of the plasma synthetic jet at low pressure.Indeed,the maximum velocities of the precursor shock and the plasma jet induced by the actuator with maximum breakdown voltage are independent of the ambient pressure level;reach about 530 and 460 m/s respectively.The mass flux of the plasma jet increases with ambient pressure increasing,but the strength of the precursor shock presents a local maximum at 0.6 atm.     

一种新型陀螺动态漂移检测系统的设计

在分析传统陀螺动态漂移测量方法的基础上,介绍了一种新的高、低温陀螺动态漂移测量系统的原理和结构设计。该系统由计算机软件控制其检测全过程,系统的中心部件由CCD摄像机、图像采集卡和处理软件等构成。处理软件用VC开发而成,利用一种快速的目标跟踪算法,它能实时的跟踪目标并能画出其运动轨迹,计算出陀螺的动态漂移。实验证明了该系统的简单性和实用性,其分辨最小动态漂移角度的能力不低于1.8′。     

Q波段回旋行波管宽带高平均功率输出窗设计与热分析

利用场匹配理论建立传输级联矩阵的方法对多层窗片结构输出窗进行研究,通过大量的数值计算给出Q波段回旋行波管一种新型中间风冷结构输出窗的参数,然后通过数值计算和HFSS仿真验证,该新型输出窗在46~50 GHz范围内,S11反射系数小于-20 dB。在此基础上进一步对该输出窗进行热分析,热分析表明：新型输出窗窗片中心与边缘温差与传统输出窗相比大幅下降,热应力大大减小,提高了输出窗的功率容量。回旋行波管工作在TE01模式时,新型输出窗获得的最大饱和功率容量达到90 kW,与传统输出窗相比,功率容量提高了21.8 kW。     

谱峰相对强度比法在碳炔含量测定中应用

碳炔材料是一种不溶不熔高聚物 ,红外谱图是最简易的一种分析测试工具。将 C—H键的振动峰面积与 C C键的振动峰面积相关联 ,用谱峰相对强度比法测定不同制备条件下产生的碳炔材料的相对含量。结果表明 ,两者比值对反应物浓度的变化具有相关性 ,可用作碳炔材料制备中实验条件的优选手段。     

Correlation of the activation volume with the crystallite size in λ-Fe2O3 and Co-modified λ-Fe2O3 fine particles

The activation volume and the crystallite size λ-Fe₂O₃ and Co-modified λ-Fe₂O₃ particles have been determined. For fixed particle volume the variation tendencies of the activation volume and crystallite size are the same. It seems to be that the crystallite size influences the activation volume in these materials.