航材消耗的时间序列分析

本文采用时间序列分析法对某种航材故障率进行预测,用移动平均法消除时间序列的长期趋势和周期变动,然后按月平均法求出季节指数,并对季节指数进行调整,然后根据拟合的趋势方程对此种航材的故障率进行预测.其结果能为航材的可靠性保障提供理论依据.     

Assessment of the suitability of public mobile data networks for aircraft telemetry and control purposes

This paper provides a review of the state of the art of relevant work on the use of public mobile data networks for aircraft telemetry and control proposes. Moreover, it describes the characterisation for airborne uses of the public mobile data communication systems known broadly as 3G. The motivation for this study was to explore how this mature public communication systems could be used for aviation purposes. An experimental system was fitted to a light aircraft to record communication latency, line speed, RF level, packet loss and cell tower identifier. Communications was established using internet protocols and connection was made to a local server. The aircraft was flown in both remote and populous areas at altitudes up to 8500 ft in a region located in South East Queensland, Australia. Results show that the average airborne RF levels are better than those on the ground by 21% and in the order of −77 dbm. Latencies were in the order of 500 ms (1/2 the latency of Iridium), an average download speed of 0.48 Mb/s, average uplink speed of 0.85 Mb/s, a packet of information loss of 6.5%. The maximum communication range was also observed to be 70 km from a single cell station. The paper also describes possible limitations and utility of using such communications architecture for both manned and unmanned aircraft systems.     

Forecasting space weather: Can new econometric methods improve accuracy?

Space weather forecasts are currently used in areas ranging from navigation and communication to electric power system operations. The relevant forecast horizons can range from as little as 24 h to several days. This paper analyzes the predictability of two major space weather measures using new time series methods, many of them derived from econometrics. The data sets are the A_p geomagnetic index and the solar radio flux at 10.7 cm. The methods tested include nonlinear regressions, neural networks, frequency domain algorithms, GARCH models (which utilize the residual variance), state transition models, and models that combine elements of several techniques. While combined models are complex, they can be programmed using modern statistical software. The data frequency is daily, and forecasting experiments are run over horizons ranging from 1 to 7 days. Two major conclusions stand out. First, the frequency domain method forecasts the A_p index more accurately than any time domain model, including both regressions and neural networks. This finding is very robust, and holds for all forecast horizons. Combining the frequency domain method with other techniques yields a further small improvement in accuracy. Second, the neural network forecasts the solar flux more accurately than any other method, although at short horizons (2 days or less) the regression and net yield similar results. The neural net does best when it includes measures of the long-term component in the data.     

卫星舱内无线传输技术的应用探索

针对传统有线连接的整星电缆网其灵活性差、通用性差及操作性差等问题,提出了利用无线网络通信技术解决卫星舱内有线连接在整星布局、装配、集成和测试等方面的不利影响,进行了基于卫星舱内使用的无线传输网络设计和探索,包括无线网络拓扑结构、网络频率配置及通信抗干扰等内容。通过基于某型号卫星的数据传输应用场景进行了方案设计和试验测试,验证了卫星舱内无线传输技术的可行性,为解决卫星平台和有效载荷之间的数据交换和平台自身管理提供了一个高可靠、高效率的实现途径。     

Procedure and methodologies for managing the risk of space object reentry

This paper proposes a procedure for managing the risk of reentering space objects and risk assessment methodologies used for the process. The proposed procedure comprises three phases encompassing the whole reentry stages of space objects. Mathematical models for assessing the impact risk of the reentering space objects by utilizing the information available during different risk management phases and the recommended risk analysis results for public communication are presented. The concept of the conditional casualty expectation is proposed as the metric representing the reentry risk and the method to compute its profile is introduced. A case study on the risk management procedure with the dataset on an actual reentry event is conducted to demonstrate the efficacy of the proposed procedure.     

Distributed cooperative guidance for multiple missiles with fixed and switching communication topologies

This study investigates cooperative guidance problems for multiple missiles with fixed and switching directed communication topologies.A two-step guidance strategy is proposed to realize the simultaneous attack.In the first step,a distributed cooperative guidance law is designed using local neighboring information for multiple missiles to achieve consensus on range-to-go and leading angle.The second step begins when the consensus of multiple missiles is realized.During the second step,multiple missiles disconnect from each other and hit the target using the proportional navigation guidance law.First,based on the local neighboring communications,a sufficient condition for multiple missiles to realize simultaneous attack with a fixed communication topology is presented,where the topology is only required to have a directed spanning tree.Then,the results are extended to the case of switching communication topologies.Finally,numerical simulations are provided to validate the theoretical results.     

某型无人机数据通信系统设计与实现CSCD

为了实现无人机系统的飞行操纵和机载任务设备控制,设计了数据通信系统。介绍了系统基本工作原理和主要功能组成,并对数据通信系统的功能要求和技术指标进行了分析,按照基本功能单元,对系统软硬件进行了模块化、组合化设计。飞行试验表明该设计达到了系统技术指标要求,满足系统对数据通信系统的功能性要求。     

一种天线主面分瓣连接件的设计

设计了一种天线主面分瓣连接件,介绍了该装置的工作原理及工作过程,通过分析、比较,表明该装置动作明确、定位简单准确且夹紧可靠,是一种较好的设计.     

Link budget and background noise for satellite quantum key distribution

Optical quantum communication exploiting satellites is the most promising field to enable global quantum communication.     

Determination of window frequency in the millimeter wave band in the range of 58° north through 45° south over the globe

The radiosonde data available from British Atmospheric Data Centre (BADC) for the latitudinal occupancy of 58° north through 45° south were analyzed to observe the variation of temperature and water vapor density. These two climatological parameters are largely assumed to be the influencing factors in determining the millimeter wave window frequencies over the chosen range of latitudes in between the two successive maxima occurring at 60 and 120 GHz. It is observed that between temperature and water vapor density, the later one is influencing mostly in determining the window frequency. It is also observed that the minima is occurring at 75 GHz through 94 GHz over the globe during the month January–February and 73 GHz through 85 GHz during the month July–August, depending on the latitudinal occupancy. It is observed that the large abundance of water vapor is mainly held responsible for shifting of minima towards the low value of frequencies. Hence, it is becoming most important to look at the climatological parameters in determining the window frequency at the place of choice.