Study of backward propagating Langmuir waves with PIC simulation

The conversion of Langmuir waves into electromagnetic radiations is an important mechanism of solar type III bursts. Langmuir waves can be easily excited by electron beam instability, and they can be converted into backward propagating Langmuir waves by wave–wave interaction. Generally, the backward propagating Langmuir waves are very important for the second harmonic emission of solar type III bursts. In this work, we pay particular attention to the mechanism of the backward propagating Langmuir waves by particle in cell (PIC) simulations. It is confirmed that the ions play a key role in exiting the backward propagating Langmuir waves. Moreover, the electron beam can hardly generated the backward propagating Langmuir waves directly, but may directly amplify the second harmonic Langmuir waves.     

Determination of optimal samples for robot calibration based on error similarity

Industrial robots are used for automatic drilling and riveting.The absolute position accuracy of an industrial robot is one of the key performance indexes in aircraft assembly,and can be improved through error compensation to meet aircraft assembly requirements.The achievable accuracy and the difficulty of accuracy compensation implementation are closely related to the choice of sampling points.Therefore,based on the error similarity error compensation method,a method for choosing sampling points on a uniform grid is proposed.A simulation is conducted to analyze the influence of the sample point locations on error compensation.In addition,the grid steps of the sampling points are optimized using a statistical analysis method.The method is used to generate grids and optimize the grid steps of a Kuka KR-210 robot.The experimental results show that the method for planning sampling data can be used to effectively optimize the sampling grid.After error compensation,the position accuracy of the robot meets the position accuracy requirements.     

基于MATLAB/Simulink的飞机燃油箱内燃油温度仿真计算

燃油温度是飞机燃油箱可燃性评估的关键参数之一。为了研究飞机燃油箱内温度的分布规律及传热模型的正确性,采用MATLAB/Simulink软件平台搭建出了客机的燃油箱热仿真模型。在输入飞行实验所对应的的边界条件后,通过数值模拟获得燃油箱内部各计算节点处的燃油温度。结果表明,在三种不同的航行条件下,燃油箱热模型仿真结果均能较好地与飞行实验结果吻合,能够将计算误差控制在一定范围内。采用该燃油箱热模型进行热仿真数值模拟可以获得较为准确的飞机燃油箱热特性,能够在飞机设计阶段,用于对燃油箱结构以及内热源部件布置的优化。     

Optimization of beamforming and path planning for UAV-assisted wireless relay networks

Recently, unmanned aerial vehicles （UAVs） acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point （AP） is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming （BF） and UAV path planning. First of all, we study a dual-hop amplify-and-forward （AF） wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station （BS）. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal~to-noise ratio （SNR） of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability （OP） expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.     

Multi-objective optimization of aircraft design for emission and cost reductions

Pollutant gases emitted from the civil jet are doing more and more harm to the environ- ment with the rapid development of the global commercial aviation transport. Low environmental impact has become a new requirement for aircraft design. In this paper, estimation method for emis- sion in aircraft conceptual design stage is improved based on the International Civil Aviation Orga- nization （ICAO） aircraft engine emissions databank and the polynomial curve fitting methods. The greenhouse gas emission （CO2 equivalent） per seat per kilometer is proposed to measure the emis- sions. An approximate sensitive analysis and a multi-objective optimization of aircraft design for tradeoff between greenhouse effect and direct operating cost （DOC） are performed with five geom- etry variables of wing configuration and two flight operational parameters. The results indicate that reducing the cruise altitude and Mach number may result in a decrease of the greenhouse effect but an increase of DOC. And the two flight operational parameters have more effects on the emissions than the wing configuration. The Pareto-optimal front shows that a decrease of 29.8% in DOC is attained at the expense of an increase of 10.8% in greenhouse gases.     

民用飞机生产线自动控制系统的信息安全问题探析

随着信息化技术越来越多地应用到工业控制系统,不可避免地也带来了各类风险和威胁,系统的信息安全问题也就越发需要引起重视。对民用飞机生产线自动化控制系统存在的安全隐患进行了探究和分析,结合其他领域的工控系统安全措施,针对本系统的一些威胁和漏洞提出了安全风险防范方案。     

民用航空器研制中制造符合性声明的使用

制造符合性声明是申请人签署后,提交局方进行制造符合性检查的重要文件。在型号研制阶段,申请人签署制造符合性声明,向局方表明符合设计资料,局方进行检查并确定是否安全可用;在依据型号合格证进行生产阶段,申请人签署制造符合性声明,向局方表明符合设计资料并处于安全可用状态,局方进行检查得到确认后签发适航批准证书;在获得生产批准后,申请人无需提交制造符合性声明,即可获得局方签发的适航批准证书。通过对中国民用航空局、美国联邦航空局和欧洲航空安全局适航规章的要求进行比较,对制造符合性声明在不同阶段的作用进行研究和探讨。     

民用飞机通用地面支援设备选型程序浅析

为了满足航空公司/维修单位高效率、低成本的要求,在飞机的设计过程中,尽量减少专用地面支援设备的种类,以通用地面支援设备取代,成为了飞机主制造商及其供应商共同努力的目标,也成为了一种发展趋势。因此,在飞机运营及维护、维修过程中,通用地面支援设备的选型及程序显得越来越重要。     

民用飞机应急照明触发电路设计

应急照明系统用于为机上人员的应急撤离提供照明,当飞机电源失效后自动开启。因此,应急照明的触发时机及方式将直接影响机上人员应急撤离的效率。目前,民用飞机一般都用应急照明电源充电线路的掉电来触发应急照明,该触发方式限制了应急照明的开启时间,对适航取证存在风险。提出了一种全新的应急照明触发电路设计方法,并详细介绍了其设计原理和控制逻辑。该应急照明触发电路设计可显著降低适航取证的风险和飞机的研发成本,为民用飞机应急照明系统的设计提供重要的指导意义。     

民用飞机复合材料结构制造工艺变化的等效性验证

高性能复合材料已经大量应用于民用运输飞机结构,并以飞机主制造商协同供应商的方式进行复合材料飞机结构的制造。介绍了航空器适航审定对复合材料结构制造的适航要求,引出了复合材料结构制造工艺变化的等效性验证方法。目前,复合材料结构制造工艺变化的等效性验证是通过所制造复合材料物理的、化学和基本力学的性能试验,并对试验结果进行统计分析来实现的。最后提供了等效性验证的接受准则。所述内容,对国内民用飞机复合材料结构在不同供应商处制造以及制造过程中工艺变化如何满足航空器适航审定要求提供借鉴;对其它行业复合材料结构制造的质量控制也有借鉴意义。