Distortion minimization for multimedia transmission in NOMA HAP-UAV integrated aerial access networks

Aerial access networks have been envisioned as a promising 6G solution to enhance the ground communication systems in both coverage and capacity. To better utilize the spectrum and fully explore different channel characteristics, this paper constructs an integrated network comprising the High Altitude Platform (HAP) and Unmanned Air Vehicles (UAVs) with the Non-Orthogonal Multiple Access (NOMA) technology. In order to improve the transmission quality of images and videos, a power management scheme is proposed to minimize the distortion of the transmissions from the HAP and UAVs to the terminals. The power control is formulated as a non-convex problem constrained by the maximal transmit power and the minimal terminal rate requirements. The variable substitution and the first-order Tailor’s expansion is used to transform it into a sequence of convex problems, which are subsequently solved through the gradient projection method. Simulation demonstrates the signal distortion and error rate improvement achieved by the proposed algorithm.     

一种高速可变形飞行器智能变形决策方法

针对一类高速可变形飞行器(HMFV)的变形决策问题，提出一种基于深度确定性策略算法(DDPG)下考虑综合性能指标最优的智能变形决策方法。首先，以一类后掠角可连续变化的高速飞行器为研究对象，给出变形飞行器动力学模型，分析模型特性及变形量与关键气动参数之间的定性关系。其次，基于关键气动数据特征分析，考虑包含气动性能、控制误差在内的综合性能指标，设计一种基于DDPG算法的智能变形决策方案。再者，针对带有标称控制器的HMFV进行变形决策训练，实时获得滑翔过程中不同飞行状态下的最优构型。最后，仿真结果表明所设计的智能变形决策算法收敛效果好，且具备较好的泛化性能。相比于固定外形，可通过变形使得在不同状态下的升阻比保持最优，且与考虑单一决策指标相比，考虑综合指标最优的变形决策可进一步缩小姿态动态跟踪误差。     

干式铣削Al-50wt%Si高硅铝合金刀具磨损与表面粗糙度评价

本文以Al-50wt%Si高硅铝合金为研究对象，采用单因素试验方法进行无涂层硬质合金刀具干式铣削试验，分析切削参数对刀具磨损和表面粗糙度的影响。结果表明：表面粗糙度受每齿进给量的影响最显著，随每齿进给量的增加而增加，当每齿进给量从0.07 mm/z增加到0.16 mm/z时，表面粗糙度增加2倍；刀具磨损受切削速度的影响最显著，随切削速度的增加而增加，当切削速度从140 m/min增加到260 m/min时，切削总长度降低3倍，而刀具后刀面磨损量仅是260 m/min速度下的0.8倍；表面粗糙度随刀具磨损的增加呈现先增加后降低的变化趋势，切削长度从350 mm增加到1 750 mm，刀具磨损量平均增加4.5倍，而表面粗糙度却下降2倍；硬质合金刀具主要的磨损形式为磨粒磨损、崩刃。     

High dynamic output feedback robust control of cascaded extended state observer

High dynamic tracking performance is a key technical index of hydraulic flight motion simulator(HFMS). However, the strong nonlinearities, various model uncertainties and measurement noise in hydraulic actuation systems limit the high dynamic performance improvement. In this paper, the outer axis frame of a HFMS is taken as a case study and its nonlinear dynamic model with consideration of strong nonlinearities, matched and mismatched uncertainties is established.A novel cascaded extended state ...     

Macro-phenomenological high-strain-rate elastic fracture model for ice-impact simulations

The ice impact can cause a severe damage to an aircraft’s exposed structure, thus, requiring its prevention. The numerical simulation represents an effective method to overcome this challenge. The establishment of the ice material model is critical. However, ice is not a common structural material and exhibits an extremely complex material behavior. The material models of ice reported so far are not able to accurately simulate the ice behavior at high strain rates. This study proposes a novel high-precision macro-phenomenological elastic fracture model based on the brittle behavior of ice at high strain rates. The developed model has been compared with five reported models by using the smoothed particle hydrodynamics method so as to simulate the ice-impact process with respect to the impact speeds and ice shapes. The important metrics and phenomena (impact force history, deformation and fragmentation of the ice projectile and deflection of the target) were compared with the experimental data reported in the literature. The findings obtained from the developed model are observed to be most consistent with the experimental data, which demonstrates that the model represents the basic physics and phenomena governing the ice impact at high strain rates. The developed model includes a relatively fewer number of material parameters. Further, the used parameters have a clear physical meaning and can be directly obtained through experiments. Moreover, no adjustment of any material parameter is needed, and the consumption duration is also acceptable. These advantages indicate that the developed model is suitable for simulating the ice-impact process and can be applied for the anti-ice impact design in aviation.     

中远红外高功率量子级联激光技术研究进展

量子级联激光器具有体积小，重量轻，波长可调谐，以及光源能够覆盖中远红外和太赫兹波段等特点，使其在痕量气体检测、定向红外对抗、自由空间光通讯以及红外成像和光谱等领域有着广泛的应用。自从1994年第一个量子级联激光器问世以来，大功率、高电光效率以及室温下连续工作的量子级联激光器一直是人们追求的目标。首先介绍了量子级联激光器的有源层设计、波导设计和器件散热设计方面的研究进展；其次重点讨论了4 μm~5 μm 中波红外和 8 μm~12 μm长波红外高功率室温下连续量子级联激光器的发展和演变、以及大功率脉冲量子级联激光器研究情况；最后简要介绍了大功率量子级联激光器芯片的外延制备技术。     

双通道光纤陀螺捷联惯导的设计与实现

针对光纤陀螺惯导精度和动态性能相互矛盾的问题,从实际应用需求出发,提出了一种高精度和大量程的双通道光纤陀螺捷联惯导系统.介绍了设计的基本原理和系统组成,并详细阐述了大小光纤陀螺设计、双通道加速度计设计和软件算法设计等关键技术,最后研制了一套原理样机.通过系统级标定试验、量程和陀螺精度试验、高动态振动环境试验和动态跑车试验等对样机进行验证,结果表明该技术方案具有可行性,为其他光纤陀螺惯导系统提供了新的设计思路.     

一种提升空间三轴激光陀螺性能的谐振腔方案研究

针对现有空间三轴机抖激光陀螺因通道间放电耦合引入了零偏误差导致陀螺性能损失的问题,提出了一种高精度空间三轴谐振腔改进设计实现方案.该方案从空间三轴激光陀螺与单轴激光陀螺放电系统的差异出发,分析了空间三轴激光陀螺不同放电状态引入零偏误差的机理,明确了高精度空间三轴激光陀螺各通道的放电电流控制需求.同时,分析结果表明,减小通道间的放电耦合可降低该型陀螺的零偏耦合误差项,因此需对空间三轴谐振腔进行放电结构的去耦合优化设计.最后,针对提出的空间三轴谐振腔改进设计方案,开展了陀螺性能试验验证,试验结果表明,空间三轴机抖激光陀螺的精度提升了5.7％以上.     

基于B1c/B2a/B3I北斗三频实时 高采样率动态PPP分析

为了分析北斗三号新信号的三频实时动态PPP定位性能，首先推导了三频两两组合无电离层模型和三频非差非组合模型的观测方程。基于山东建筑大学CORS站观测得到的北斗三号B1c/B2a/B3I三频信号1s采样率数据，使用iGMAS提供的超快速精密星历预报部分，制定了基于B1cB3I-B2aB3I三频无电离层两两组合、B1cB2aB3I三频非差非组合以及用于对比分析的B1cB2a、B1IB3I两种双频无电离层共四种定位方案。然后利用Net_Diff软件进行实时动态PPP实验，对超快速精密轨道和钟差预报部分的精度和稳定度以及实验解算结果进行分析，对比不同定位方案的定位性能。实验分析表明，两种三频定位方案定位性能均优于B1cB2a双频定位方案，定位精度能达到0.462m和0.479m，收敛至分米所需时间能达到45.8min和62.8min；B1IB3I方案定位性能优于两种三频定位方案，定位精度和收敛速度能达到0.228m和6.6min。     

RTM成型用聚酰亚胺树脂及其复合材料研究进展

聚酰亚胺复合材料因其优异的耐高温性能和机械性能,在航空航天领域获得了广泛应用,但复杂、高成本的热压罐成型工艺难以满足聚酰亚胺树脂基复合材料快速加工成型,限制了其进一步的应用。本文综述了适用于树脂传递模塑成型（RTM）技术的聚酰亚胺树脂及其复合材料的研究现状与发展趋势,重点论述了苯乙炔基封端的聚酰亚胺树脂及其复合材料的国内外研究情况,提高RTM技术成型聚酰亚胺树脂及其复合材料耐温等级的同时保持低充模黏度和高韧性将会是重要的发展方向。