Core-based Shared Tree Multicast Routing Algorithms for LEO Satellite IP Networks

A new core-based shared tree algorithm, viz core-cluster combination-based shared tree （CCST） algorithm and the weighted version （i.e. w-CCST algorithm） are proposed in order to resolve the channel resources waste problem in typical source-based multicast routing algorithms in low earth orbit （LEO） satellite IP networks. The CCST algorithm includes the dynamic approximate center （DAC） core selection method and the core-cluster combination multicast route construction scheme. Without complicated onboard computation, the DAC method is uniquely developed for highly dynamic networks of periodical and regular movement. The core-cluster combination method takes core node as the initial core-cluster, and expands it stepwise to construct an entire multicast tree at the lowest tree cost by a shortest path scheme between the newly-generated core-cluster and surplus group members, which results in great bandwidth utilization. Moreover, the w-CCST algorithm is able to strike a balance between performance of tree cost and that of end-to-end propagation delay by adjusting the weighted factor to meet strict end-to-end delay requirements of some real-time multicast services at the expense of a slight increase in tree cost. Finally, performance comparison is conducted between the proposed algorithms and typical algorithms in LEO satellite IP networks. Simulation results show that the CCST algorithm significantly decreases the average tree cost against to the others, and also the average end-to-end propagation delay ofw-CCST algorithm is lower than that of the CCST algorithm.     

Multiple model particle flter track-before-detect for range ambiguous radar

The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.     

一种移动卫星网络最小费用切换算法(英文)

For mobile satellite networks, an appropriate handover scheme should be devised to shorten handover delay with optimized application of network resources. By introducing the handover cost model of service, this article proposes a rerouting triggering scheme for path optimization after handover and a new minimum cost handover algorithm for mobile satellite networks. This algorithm ensures the quality of service （QoS） parameters, such as delay, during the handover and minimizes the handover costs. Simulation indicates that this algorithm is superior to other current algorithms in guaranteeing the QoS and decreasing handover costs.     

A novel LAAS pseudo-range error over-bound method based on improved pseudo-range error distribution model

The high level of safety demand of civil aviation requests local area augmentation system (LAAS) extremely high navigation integrity performance. A new LAAS pseudo-range error overbound method is proposed in this paper to improve the integrity of LAAS. Firstly, a more practical pseudo-range error distribution model is established. Then, by calculating the relationship between the statistical uncertainty of the model parameter and the integrity risk, a new method is proposed to calculate the pseudo-range error over-bound model. This method can effectively reduce the inflation factor and the resulting conservativeness of the over-bound model. Comparative experiments show that the method proposed in this paper performs better and satisfies the requirements of real applications.     

Testability evaluation using prior information of multiple sources

Testability plays an important role in improving the readiness and decreasing the lifecycle cost of equipment. Testability demonstration and evaluation is of significance in measuring such testability indexes as fault detection rate（FDR） and fault isolation rate（FIR）, which is useful to the producer in mastering the testability level and improving the testability design, and helpful to the consumer in making purchase decisions. Aiming at the problems with a small sample of testability demonstration test data（TDTD） such as low evaluation confidence and inaccurate result, a testability evaluation method is proposed based on the prior information of multiple sources and Bayes theory. Firstly, the types of prior information are analyzed. The maximum entropy method is applied to the prior information with the mean and interval estimate forms on the testability index to obtain the parameters of prior probability density function（PDF）, and the empirical Bayesian method is used to get the parameters for the prior information with a success-fail form. Then, a parametrical data consistency check method is used to check the compatibility between all the sources of prior information and TDTD. For the prior information to pass the check, the prior credibility is calculated. A mixed prior distribution is formed based on the prior PDFs and the corresponding credibility. The Bayesian posterior distribution model is acquired with the mixed prior distribution and TDTD, based on which the point and interval estimates are calculated.Finally, examples of a flying control system are used to verify the proposed method. The results show that the proposed method is feasible and effective.     

A compressing and saving method for structured grid data based on block construction

The increasing grid data in CFD simulation has brought some new difficulties and challenges, such as high storage cost, low transmission efficiency. In order to overcome these problems,a novel method for compressing and saving the structured grid are proposed. In the present method,the geometric coordinates of the six logical domains of one grid block is saved instead of all grid vertex coordinates to reduce the size of the structured grid file when the grid is compressed. And all grid vertex co...     

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.     

Configurationmodelofpartial repairablesparesunder batch ordering policy based on inventory state

Rational planning of spares configuration project is an effective approach to improve equipment availability as well as reduce life cycle cost （LCC）. With an analysis of various impacts on support system, the spares demand rate forecast model is constructed. According to systemic analysis method, spares support effectiveness evaluation indicators system is built, and then, initial spares configuration and optimization method is researched. To the issue of discarding and con-sumption for incomplete repairable items, its expected backorders function is approximated by Laplace demand distribution. Combining the （s-1, s） and （R, Q） inventory policy, the spares resup-ply model is established under the batch ordering policy based on inventory state, and the optimi-zation analysis flow for spares configuration is proposed. Through application on shipborne equipment spares configuration, the given scenarios are analyzed under two constraint targets：one is the support effectiveness, and the other is the spares cost. Analysis reveals that the result is consistent with practical regulation;therefore, the model＇s correctness, method＇s validity as well as optimization project＇s rationality are proved to a certain extent.     

Vulnerability analysis for airport networks based on fuzzy soft sets: From the structural and functional perspective

Recently,much attention has been paid to the reliability and vulnerability of critical infrastructure.In air traffic systems,the vulnerability analysis for airport networks can be used to guide air traffic administrations in their prioritization of the maintenance and repair of airports,as well as to avoid unnecessary disturbances in the planning of flight schedules.In this paper,the evaluation methods of airport importance and network efficiency are established.Firstly,the evaluation indices of airport importance are proposed from both the topological and functional perspectives.The topological characteristics come from the structure of airport network and the functional features stem from the traffic flow distribution taking place inside the network.Secondly,an integrated evaluation method based on fuzzy soft set theory is proposed to identify the key airports,which can fuse together importance indices over different time intervals.Thirdly,an airport network efficiency method is established for the purpose of assessing the accuracy of the evaluation method.Finally,empirical studies using real traffic data of US and China’s airport networks show that the evaluation method proposed in this paper is the most accurate.The vulnerability of US and China’s airport networks is compared.The similarities and differences between airport geography distribution and airport importance distribution are discussed here and the dynamics of airport importance is studied as well.     

Orbital reference frame estimation with power spectral density constraints for drag-free satellites

The drag-free satellites are widely used in the field of fundamental science as they enable the high-precision measurement in pure gravity fields. This paper investigates the estimation of local orbital reference frame (LORF) for drag-free satellites. An approach, taking account of the combi-nation of the minimum estimation error and power spectral density (PSD) constraint in frequency domain, is proposed. Firstly, the relationship between eigenvalues of estimator and transfer func-tion is built to analyze the suppression and amplification effect on input signals and obtain the eigenvalue range. Secondly, an optimization model for state estimator design with minimum estima-tion error in time domain and PSD constraint in frequency domain is established. It is solved by the sequential quadratic programming (SQP) algorithm. Finally, the orbital reference frame estimation of low-earth-orbit satellite is taken as an example, and the estimator of minimum variance with PSD constraint is designed and analyzed using the method proposed in this paper.     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

基于复杂网络的航空制造供应链关键节点识别研究

随着不稳定因素的增加以及航空制造供应链的参与主体增多，航空制造供应链的管理所面临的风险也随之增大。因此针对航空制造供应链网络的风险管理，以复杂网络为工具研究供应链网络中的关键节点识别问题，从而帮助航空供应链提升抗风险能力。通过分析我国航空制造供应链网络现状和特点，提出供应链形成机制并划分供应链层级，对航空制造供应链进行构建及指标界定，对度中心性、介数中心性、接近中心性三种经典中心性算法以及传统K-Shell 分解算法进行加权改进；结合熵值-TOPSIS 法提出一种针对加权网络的供应链关键节点识别算法——WKC 算法，通过构造网络来进行算例分析，验证该种算法的有效性。结果表明：本文提出的WKC 算法原理科学、计算复杂度较低，为航空制造等高端装备制造业供应链的风险管理提供了一定的参考。     

航空制造企业设备资产管理系统研究

航空制造企业生产设备价值高,专业性强,设备维护复杂,实施企业资产管理具有重要意义.针对航空制造企业设备资产管理现状,以提高设备利用率降低生产成本为首要目标,引入企业资产管理理念,提出了企业设备资产数字化管理框架,实施企业层面的设备生命周期全过程管理.以某大型航空制造企业为研究背景,开发了基于WEB的设备资产管理原型系统,初步实现了从设备采购、设备安装、设备维修以及设备报废处置全过程的数字化管理.     

试验IP网故障分析策略及方法应用

针对试验IP（互联网协议）网建设和使用中遇到的网络问题,从TCP（传输控制协议）/IP网络原理和试验IP网的结构模型出发,对网络故障排查方法进行了总结,给出网络分层模型分析法、网络连接结构分析法和网络检测分析法相结合的故障排查策略。对某次测控信息联调中接收不到网络数据的真实故障案例进行了分析,运用网络检测工具对故障进行排查,依据网络结构对故障进行定位,依据网络协议对故障进行分析,验证了该方法可以使问题分析层次清晰、定位准确。     

航空企业成本管理关键技术

航空装备研制、采办成本急剧增长的形势要求我国航空企业变革现行组织管理机制,建立起先进有效的成本管理体系。本文总结提出了成本管理的5项关键技术:成本数据管理、成本估算分析、设计阶段成本控制、协同设计与制造、成本管理团队的建立等。     

航空装备全寿命周期费用多路径管控策略研究

航空装备作为高新技术复杂产品,其经济性设计越来越受到重视。在满足用户需求的前提下,如何控制并尽可能降低全寿命周期费用是航空装备研究的重点。通过对全寿命周期费用管控理论和方法的研究,总结以往航空装备研制中经济性工作的经验和教训,结合我国军工产品经费管理的特点,从思想观念、管理和技术等方面入手,提出一套在设计阶段适合我国航空装备全寿命周期费用多路径管控的策略,并在某型飞机研制中试点应用。结果表明:某型飞机研制费用管控效果较好,验证了该策略的合理性和有效性。     

针对ATN over IP方案的明确拥塞通告模型及映射算法

基于对ATN与IP网络拥塞控制机制的比较,本文针对AT Nover IP方案提出了IP子网隧道中的明确拥塞通告(ECNT)模型,将明确拥塞通告(ECN)引入了AT Nover IP方案;还提出了ECNT模型中实现IP网络明确拥塞通告(ECN)与ATN网络传输层协议COTP中拥塞指示位(CE)的映射算法(ECN/CE),用以解决由于IP网络中TCP协议与ATN网络中COTP协议所采用的两种拥塞避免在机制上的差别而造成的拥塞信息跨网络传输的困难。仿真结果表明,与没有引入ECN的IP子网隧道模型相比,ECNT模型和ECN/CE算法可以解决IP网络为ATN的网络进行数据传输时的拥塞问题。     

一种适用于IP视频会议的混合策略组播密钥管理方案

在分析了现有组播密钥管理方案的基础上,针对IP视频会议的特点,将集中式和分布式密钥管理方案相结合,提出了一种多层次的混合密钥管理方案,其高层为管理层,成员之间通过OFT方案协商产生密钥,并管理密钥;底层采用集中管理方式。该方案避免了单点失效问题,具有高效性和可扩展性的优点,适用于解决大型动态组播的密钥管理问题。     

民用飞机卫星通信系统的设计和适航验证考虑

随着我国航空事业的快速发展,关于机载卫星通信的业务需求越来越强烈。卫星通信覆盖面积大、通信容量大、通信距离远、机动灵活、传输线路稳定可靠,是克服现有甚高频、高频通信系统局限性的最佳选择。首先对卫星通信系统进行了概述,在此基础上全面论述了卫星通信系统设计过程的考虑事项、并提出适航符合性验证的方法建议,为民用飞机卫星通信系统的适航批准提供支持。