脉冲爆震发动机爆震声音信号分析

通过爆震试验测得了爆震声音数据。对单次爆震的声音数据进行傅里叶变换发现,爆震声音数据中包含了与压力数据中同样的主频和多倍频,说明一直作为噪声处理的爆震声音数据可以用来辅助分析爆震发动机性能,对爆震分析和故障诊断起到积极作用。     

ATS-6 Satellite Instructional Television Experiment

The Satellite Instructional Television Experiment (SITE) is scheduled for the second year of satellite operation. Applications Technology Satellite (ATS-6) will receive C-band video signals frorn Abmedabad and Delhi, India, and will retransmitt the video and two audio sub-carriers at 860 MHz to 6 clusters of 400 direct-receive stations for a total of 2400 direct-receive stations. Morning programs of 1.5 hours per day are designed for classroom use, and evening programs of 2.5 hours duration are designed for village adult education. Indian production antennas and television sets have been tested and found to meet specifications, and a successful experiment is anticipated.     

民用飞机甚高频通信系统设计

民用飞机进行可靠的空地、空空通信,对飞行安全尤为重要。甚高频(very high frequency,简称VHF)通信系统是目前应用最为广泛的航空通信方式,VHF通信系统通过与机上音频系统交联实现飞机与外部的语音通信,通过与机上数据链系统交联实现飞机与地面的数据链通信。如何确保民用飞机VHF通信系统可靠、稳定地工作,一直是型号设计和适航部门关注的重点,也是型号设计的难点。首先从VHF通信系统的功能定义出发,提出了VHF通信系统的设计方案,进而提出了VHF通信系统的性能要求,最后重点阐述了VHF通信系统的机上设计要求以及系统功能验证过程,对型号设计和工程排故具有指导意义。     

民用飞机甚高频通信系统适航审定技术分析

民用飞机进行可靠的空地、空空通信,对飞行安全尤为重要。甚高频(very high frequency,简称VHF)通信系统是目前应用最为广泛的航空通信方式,VHF通信系统通过与机上音频系统交联实现飞机与外部的语音通信,通过与机上数据链系统交联实现飞机与地面的数据链通信。甚高频通信系统与民用飞机的安全运行密切相关,也是适航规章和运行规章要求的内容。结合甚高频通信系统功能要求和设计架构,针对适用于甚高频通信系统的中国民用航空规章第25部：运输类飞机适航标准(CCAR-25-R4-2011)条款,分析并给出甚高频通信系统可接受的符合性方法,同时根据型号工作经验给出甚高频通信系统在适航审查中的审定要素。针对甚高频通信系统所涉及的各项条款,为局方提供了适航审查工作需要关注的审定要素和评审要求。研究有助于民机甚高频通信系统的安全设计与适航验证。     

Report on the Geneva Space Telecommunications Conference? Broadcasting Aspects

The growth of the Intelsat Global Commercial Communications Satellite System, which provides the facilities used to exchange television programs among many countries of the world, is described. Service was initiated between North America and Western Europe in 1965. Currently, some 48 separate geographic areas throughout the world are interconnected by the Intelsat System. The unique air-transportable Earth terminal, developed by the General Electric Company, at the request of the television networks, to meet the special requirements for providing live television coverage in color of the Apollo recoveries at sea, will also be described.     

面向地面无人平台的仿生偏振光定向算法

仿生偏振光定向为地面无人平台提供了一种新型的低成本、小型化定向方式。设计了一种基于微阵列式偏振光栅的仿生光罗盘,实现了一种加权平均的偏振光定向算法,分析了大气偏振模式误差、太阳位置误差、偏振光传感器误差和水平姿态角误差等因素对航向角估计精度的影响。实验结果表明,动态车载条件下定向误差小于0.5°。     

A view finder control system for an earth observation satellite

A real time TV view finder is used on-board a low earth orbiting (LEO) satellite to manually select targets for imaging from a ground station within the communication footprint of the satellite. The attitude control system on the satellite is used to steer the satellite using commands from the groundstation and a television camera onboard the satellite will then downlink a television signal in real time to a monitor screen in the ground station. The operator in the feedback loop will be able to manually steer the boresight of the satellite's main imager towards interested target areas e.g. to avoid clouds or correct for any attitude pointing errors. Due to a substantial delay (in the order of a second) in the view finding feedback loop and the narrow field of view of the main imager, the operator has to be assisted by the onboard attitude control system to stabilise and track the target area visible on the monitor screen.This paper will present an extended Kalman filter used to estimate the satellite's attitude angles using quaternions and the bias vector component of the 3-axis inertial rate sensors (gyros). Absolute attitude sensors (i.e. sun, horizon and magnetic) are used to supply the measurement vectors to correct the filter states during the view finder manoeuvres. The target tracking and rate steering reaction wheel controllers to accurately point and with high agility stabilise the satellite, will be presented. The controller reference generator for the satellite-to-target attitude and rate vectors, as used by the reaction wheel controllers, will be derived.     

卫星测控系统多通道地面测试平台设计

一般地面测试平台无法同时支持卫星对地测控测试和中继测控测试,需要开发多通道地面测试平台满足卫星测试需求.基于此,对卫星测控系统多通道地面测试平台设计进行讨论,采用彼此相对独立的2套地面测试设备,通过特定连接关系同时接入卫星对地测控链路和中继测控链路中,实现卫星多通道测控并行测试和地面测试设备的双机备份,在无须更改外部连接关系的基础上,通过模式选择、参数配置,可适用于不同模式下卫星测控通道地面测试需求.经过分析,该平台具有功能完善、适用性广、稳定性好等优点,已应用于某卫星的地面测试.测试结果表明,平台运行稳定,具有良好的使用效果.     

基于混沌加密的盲音频水印算法

将混沌理论引入到音频水印系统的研究中，设计了一种包含版权信息和密钥的二值图像作为水印，利用混沌序列将其加密后嵌入到原始音频信号的DWT域中。该水印方案包含的版权信息量大，且具有双重的安全性，很难提取出水印信号；即使提取出水印信号，如果不知道密钥，也很难恢复出原始水印图像。本算法采用了量化方法嵌入水印，提取水印时不需要原始的音频信号，实现了水印的盲提取。对一般的信号处理进行了试验，水印具有很强的鲁棒性。     

一种提高UDP可靠性的数据传输方法研究

针对传统的UDP协议数据传输效率高但可靠性差的特点,提出了一种基于分区确认的分包与重组方法,使用自适应拥塞控制机制,并提出乘性增加减性减少（multiplicative increase reduced decrease,MIRD）算法对超时间隔进行处理,实现了音频数据的实时可靠传输,满足了特定场合下大量数据的传输实时性强和可靠性高的要求,提高了带宽利用的公平性和稳定性,拓展了UDP协议的使用范围。实验验证了该方法的可行性．音频数据传输的可靠性得到了提高。     

Aeronautical use of semiconductor lasers for short optical pulses

In this paper, we investigate the feasible schemes to generate periodic optical pulses of width between several picoseconds (ps) and tens ps. Gain-switched semiconductor laser diodes are shown to be more suitable for avionics applications than mode-locked laser diodes. In the experiment, we use a low-cost Fabry-Perot laser diode to generate short optical pulse streams. A simple optical injection-locking scheme is then used to reduce the timing jitter and frequency chirp in such laser diodes, which in turn can improve the transmission performance of the generated optical pulses. It is expected that the use of gain-switched semiconductor lasers can meet the requirement of high-speed airborne communication networks or ground supporting systems at airports. Moreover, we discuss the possibility of using the pulsed semiconductor lasers to generate millimetre-wave (mm-wave) signals for future applications to airborne high-resolution, mm-wave radars.     

音频信号联合编码算法码书长度研究

为进一步减小音频信号的码率,针对基于线性预测编码、SOM神经网络矢量编码以及Huffman编码相结合的声音信号联合编码(以下简称联合编码),提出了通过合理选择码书长度值进一步减小声音信号码率的算法。利用Matlab软件编程进行了不同码书长度值的声音信号编解码实验。实验结果表明,在保证声音质量的前提下,通过合理选择码书长度值,可以使声音信号的码率远低于MEPG-1 Layer3的最低64kb/s标准码率,达到11.025kb/s的码率值。文章提出的编码算法可为音频压缩编码的进一步研究提供参考。     

Spacecraft design considerations for small satellite remote sensing

The idea of adapting existing small satellite technology for remote sensing purposes is discussed. The major design problems and constraints influencing the design of a small low-cost remote sensing satellite bus are identified using the subsystem approach. Key design areas include the improvement of battery technology and the development of a deployable solar array, attitude control assemblies, on-board data processing/storage, and ground station data acquisition. Although the eventual satellite would also have to be somewhat larger, more powerful and, above all, more sophisticated than the previous small satellites, this is considered to be a natural progression of research in this area     

高空低雷诺数吸附式压气机叶型耦合优化设计

为了探究高空低雷诺数条件下吸附式叶型的气动设计特性,利用人工蜂群算法对低雷诺数吸附式叶型进行优化设计,该设计方法可以将叶型和抽吸方案进行耦合优化.并且对高空低雷诺数吸附式叶型耦合优化设计的必要性进行了论证.研究结果表明:在地面条件下设计的具有较好性能的吸附式叶型,在高空低雷诺数条件下,性能有可能会显著下降,针对高空低雷诺数条件的吸附式叶型设计有很大必要性;针对研究对象,在高空低雷诺数条件下优化设计后总压损失降低了32%,静压升提高了0.01,并且优化设计后在地面条件下的性能也略有提升;在高空低雷诺数条件下,适当地增加吸附式叶型前段的负荷,通过抽吸来控制层流分离泡的设计效果最为理想;优化后得到的最佳抽吸位置位于层流分离泡中心区域.      

近地低速飞行时旋翼尾涡系的畸变及其诱导速度

本文用一简化自由涡模型模拟旋翼尾涡系,用一简单涡模拟地面涡,对近地低速飞行时旋翼尾涡系的畸变及其引起的诱导速度变化作了研究。在地面涡和地面的影响下,桨盘附近的尾涡几何位置发生很大变化,导致桨盘处的诱导速度发生很大变化。尾涡畸变在桨盘处引起的诱导速度变化远远大于地面涡和地面在桨盘处直接产生的诱导速度。考虑尾涡畸变后计算出的诱导速度在桨盘处的分布和实验符合很好。     

Navigation by Back Triangulation

The development of electronic surveillance systems that can accurately measure the direction of arrival of signals from ground radar stations has opened the possibility of using statistical techniques to determine navigation information for the measuring vehicle. The method of combining "bearing" observations from several radar sites for navigational purposes, referred to as "back triangulation", will be discussed and demonstrated by simulation.     

Combustion Synthesis of h-BN-SiC Ceramic Composites

The feasibility was demonstrated to fabricate h-BN-SiC ceramics through combustion synthesis of the mixture of boron carbide and silicon powders under 100 MPa nitrogen pressure. The mass fraction of BN and SiC in the combustion products were found to be 72 % and 28 % respectively. The thermodynamics of the synthesis reaction and the adiabatic combustion temperature were calculated on the theoretical ground. The bending strengths of the ceramics were measured to be 65.2 MPa at room temperature and 55 MPa at 1350 ℃. The phase composition and microstructure of the combustion products were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

音频信号联合编码的通用码书研究

为了减小音频信号编码算法的运算量,提出了在线性预测编码、SOM神经网络矢量编码以及Huffman编码相结合的声音信号联合编码算法(以下简称联合编码)的基础上,将算法中原有的专用码书改为通用码书的算法。利用Matlab软件编程进行了专用码书和通用码书条件下的声音信号编解码实验。实验结果表明,在码率相等的条件下,使用通用码书和专用码书的联合编码方法可以得到相近的译码声音质量。使用通用码书的联合编码的最低码率在音频编码格式Opus码率的范围内,且接近Opus码率的下限,而且算法较Opus编码简单,因而实时性较好。文章提出的编码算法可为音频压缩编码的进一步研究提供参考。     

DQI-NP application to the OutriderTM Tactical UnmannedAerial Vehicle (TUAV)

A wide variety of applications can benefit from integrated Inertial Navigation System/Global Positioning System (INS/GPS) technology. However, in many situations, the end user has a preference for a specific GPS receiver. Additionally, in most cases, the user does not desire to expend the time and money necessary to perform a custom INS/GPS integration, but instead wants a low-cost off-the-shelf solution. To address these applications, Boeing has developed the Digital Quartz Inertial Measurement Unit (DQI IMU)-Navigation Processor (DQI-NP) product as an extension of its Miniature Integrated GPS/INS Tactical System (MIGITS^TM) family of integrated INS/GPS products. This paper describes the DQI-NP and its application to the Outrider^TM Tactical Unmanned Aerial Vehicle (TUAV). The DQI-NP, as currently integrated into the Outrider^TM TUAV, is coupled with a custom Trimble GPS receiver combined with major embedded firmware modifications by IntegriNautics. In conjunction with differential GPS and ground based pseudolites, the overall system is intended to provide autonomous landing capability to the Outrider TUAV. DQI-NP provides an available, low-cost, commercial-off-the-shelf/non-development item (COTS/NDI) solution to a variety of commercial and military applications, of which the Outrider ^TM TUAV is an excellent example     

复合材料双真空袋成型工艺研究

真空袋成型工艺是一项低成本复合材料制备技术,在此基础上对双真空袋(DB)成型工艺进行了研究,研究表明,采用DB技术制备的复合材料具有较低的孔隙含量和较高的力学性能,因此能够提高真空袋成型复合材料制件的品质.