基于迁移学习-元学习的ADS-B攻击分类研究

准确分类通航领域ADS-B攻击类型,采取预防攻击措施,对保障通航运行安全性具有重要意义。针对通航领域ADS-B攻击数据样本少,提出一种基于迁移学习-元学习的ADS-B攻击分类模型。该模型将迁移学习与深度卷积自编码器相结合,建立ADS-B攻击特征提取模型,提取数据样本的攻击有效特征表示,并运用元学习策略在特征空间中实现ADS-B攻击准确分类。实例研究表明,基于迁移学习-元学习的攻击分类模型可有效分类小样本ADS-B攻击,且正确率在95%以上。

基于动态离散模型的机场ADS-B攻击威胁影响研究

随着航空业信息技术的发展,空中交通管制系统面临着多种网络攻击的威胁。广播式自动相关监视(ADS-B)系统因其明文广播的数据传输方式,存在着被网络攻击的安全问题。依据“等待降落-降落-停泊-排队起飞-起飞”的航班运行全流程,建立了WLPQD动态离散模型,研究机场流量和航班延误。模型引入了系统冗余能力、处理速率等参数,模拟了攻击场景;通过受影响飞机数量和延误时间等指标研究了机场航班延误的传播影响。模型展示了ADS-B消息注入攻击对降落、起飞航班造成的延误,提出了两种攻击缓解方法。结果表明,延误规模的大小与攻击强度呈现正相关,且攻击对起飞航班的延误影响更大;提升对“幽灵飞机”和合法飞机的处理速率都可提升机场系统的抗毁性,但前者对提升机场系统冗余能力的效果更加显著。所做研究为机场系统抵御网络攻击、增强抗毁性提供了决策分析的参考依据。

Scheduling optimization for UAV communication coverage using virtual force-based PSO model

When the ground communication base stations in the target area are severely destroyed,the deployment of Unmanned Aerial Vehicle(UAV)ad hoc networks can provide people with temporary communication services.Therefore,it is necessary to design a multi-UAVs cooperative control strategy to achieve better communication coverage and lower energy consumption.In this paper,we propose a multi-UAVs coverage model based on Adaptive Virtual Force-directed Particle Swarm Optimization(AVF-PSO)strategy.In particular,we first introduce the gravity model into the traditional Particle Swarm Optimization(PSO)algorithm so as to increase the probability of full coverage.Then,the energy consumption is included in the calculation of the fitness function so that maximum coverage and energy consumption can be balanced.Finally,in order to reduce the communication interference between UAVs,we design an adaptive lift control strategy based on the repulsion model to reduce the repeated coverage of multi-UAVs.Experimental results show that the proposed coverage strategy based on gravity model outperforms the existing state-of-the-art approaches.For example,in the target area of any size,the coverage rate and the repeated coverage rate of the proposed multi-UAVs scheduling are improved by 6.9–29.1%,and 2.0–56.1%,respectively.Moreover,the proposed scheduling algorithm is high adaptable to diverse execution environments.©2022 Published by Elsevier Ltd.

基于正确解码率的ADS-B天线配置模型分析

提出一种广播式自动相关监视(ADS-B)天线配置分析模型,该模型可实现基于本地具体情况获得满足空管管制要求的ADS-B天线部署方案,为后续ADS-B站点部署实施时选择定向/全向天线提供决策工具。本文以报文正确解码率作为评估定向/全向天线效果的直接指标,从飞机数量、雷达/TCAS部署情况、飞机应答/广播速率等3个角度出发,获得空域单目标每秒发送报文的数量,分析其与定向/全向ADS-B接收设备报文解码率的关联性,从而得到定向天线与全向天线配置下报文解码率分析模型,然后设置模型相关参数,通过模型解算获得相应的正确解码率。通过实际录取数据对该模型正确性进行相关验证,结果与理论模型基本保持一致,证明ADS-B天线配置分析模型是正确有效的。

基于IMMKF算法的ADS-B监视应用目标跟踪

目标跟踪是机载广播式自动相关监视(ADS-B)应用的基础功能,对提升航空器周边的弱机动民航飞机目标跟踪性能具有重要意义。提出一种基于交互式多模型卡尔曼滤波(IMMKF)算法的ADS-B监视应用目标跟踪方法。首先,针对弱机动背景下的民航飞机的飞行特点,建立包含匀速模型和标准协同转弯模型的运动模型集,并对模型进行线性化近似;然后,将模型预测和ADS-B状态矢量量测数据作为IMMKF算法中多个并行卡尔曼滤波器的输入,进行并行滤波;最后,计算得到目标状态矢量的估计和模型近似概率,并作为下一次迭代的输入。结果表明:相比于基于匀速模型的卡尔曼滤波目标跟踪方法,IMMKF算法的位置跟踪误差降低了59%,速度跟踪误差降低了77%,显著提升了状态估计性能,具备较高的跟踪精度、稳健性与计算效率,在ADS-B监视应用中具有实际应用价值与借鉴意义。

财政分权与经济周期波动研究:基于AS-AD的视角

文章基于AS-AD的分析框架,利用Blanchard-Quah的SVAR分解方式,研究分析了财政分权对经济周期波动的影响。由于公共投资的挤出效应以及资本效率部门间的差异,财政分权在带来需求冲击增加的同时,也带来了负向的供给冲击效应,二者共同的作用使得:(1)经济运行中表现出"价格与产出正向关联";(2)经济波动表现出"收—放"循环的特征,即分权导致产出增加、物价上涨,限制经济过热则导致产出与物价的下降;(3)分权促进经济增长并非源于分权增加社会供给能力,而是源于分权增加了社会需求水平。根据1952—2007年的数据,文章检验了上述推论,并指出频繁调整的中央与地方财政关系是经济波动"大起大落"的重要因素。

制度促进收入增加的理论分析:AS-AD视角

基于AS-AD模型,从需求拉动和供给推动两个角度考察了制度对收入的影响。研究表明,制度质量越高,消费需求和投资需求越多,从而总需求越多;制度质量越高,全要素生产率越高,通过劳动力市场决定的均衡就业越多,从而总供给越多。上述两个机制决定了制度质量越高,通过总供给和总需求决定的均衡收入水平越高。提高制度质量对于扩大有效需求,促进供给增加,进而实现收入增加有重要意义。

AD-AS-BP模型及其政策效应

"滞胀"现象的出现使凯恩斯理论濒临崩溃,是AD-AS模型使其得以复活。现实中,任何经济系统都是开放的。然而,当我们把AD-AS模型推广到开放经济条件下,通过构建AD-AS-BP模型并据此进行政策效应分析时却发现,凯恩斯主义降低人们等待成本的总需求政策,即便是在短期内对于经济增长、失业和通货膨胀问题的分别解决也总是失效的。

基于ADE的IFC到CityGML层次转换模型

新型城市化建设和管理过程中,借助建筑信息模型(building information modeling,BIM)与地理信息系统(geographic information system,GIS)的数据集成,不但能实现建筑物的精细化表达,而且室外信息得以兼顾,实现空间分析及室内外一体化表达。但BIM与GIS两种不同的数据格式无法直接实现数据的互通。为此,首先分析了模型IFC和CityGML在文档形式等方面的差异,并实现了多个简单建筑物IFC模型到CityGML3.0 LOD2、LOD3的转换。其次,针对上述数据集成实验中语义丢失问题,扩展GIS的CityGML3.0数据格式,提出CityGML B-Con扩展模型,完善IFC到CityGML3.0的一对一映射关系。最后,实现多个不同复杂程度建筑物IFC模型到CityGML B-Con扩展模型的转换。实验结果表明,利用CityGML B-Con模型能实现BIM与GIS的数据集成。宏观层面来说,能够增强转换后建筑物外观的细节程度,微观层面而言,BuildingConstructiveElement和BuildingInstallation的子类得以区分,IfcStair、IfcRamp和IfcBeam等建筑构件都能通过一对一映射的方式转换至CityGML中,克服了CityGML原有标准在建筑物构件表达方面的缺陷,有效减少了BIM源数据语义信息的丢失。

Added Mass Effect and an Extended Unsteady Blade Element Model of Insect Hovering

During the insect flight, the force peak at the start of each stroke contributes a lot to the total aerodynamic force. Yet how this force is generated is still controversial. Two current explanations to this are wake capture and Added Mass Effect （AME） mechanisms. To study the AME, we present an extended unsteady blade element model which takes both the added mass of fluid and rotational effect of the wing into account. Simulation results show a high force peak at the start of each stroke and are quite similar to the measured forces on the physical wing model. We found that although the Added Mass Force （AMF） of the medium contributes a lot to this force peak, the wake capture effect further augments this force and may play a more important role in delayed mode. Furthermore, we also found that there might be an unknown mechanism which may augment the AME during acceleration period at the start of each stroke, and diminish the AME during deceleration at the end of each stroke.

Virtual reality mobility model for wireless ad hoc networks

For wireless ad hoc networks simulation, node＇s mobility pattern and traffic pattern are two key elements. A new simulation model is presented based on the virtual reality collision detection algorithm in obstacle environment, and the model uses the path planning method to avoid obstacles and to compute the node＇s moving path. Obstacles also affect node＇s signal propagation. Considering these factors, this study implements the mobility model for wireless ad hoc networks. Simulation results show that the model has a significant impact on the performance of protocols.

Multilevel security model for ad hoc networks

Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations. As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels.

Adding-Point Strategy for Reduced-Order Hypersonic Aerothermodynamics Modeling Based on Fuzzy Clustering

Reduced order models（ROMs） based on the snapshots on the CFD high-fidelity simulations have been paid great attention recently due to their capability of capturing the features of the complex geometries and flow configurations. To improve the efficiency and precision of the ROMs, it is indispensable to add extra sampling points to the initial snapshots, since the number of sampling points to achieve an adequately accurate ROM is generally unknown in prior, but a large number of initial sampling points reduces the parsimony of the ROMs. A fuzzy-clustering-based adding-point strategy is proposed and the fuzzy clustering acts an indicator of the region in which the precision of ROMs is relatively low. The proposed method is applied to construct the ROMs for the benchmark mathematical examples and a numerical example of hypersonic aerothermodynamics prediction for a typical control surface. The proposed method can achieve a 34.5% improvement on the efficiency than the estimated mean squared error prediction algorithm and shows same-level prediction accuracy.

基于AD-RF模型的互联网金融信用风险评估

基于互联网金融平台非平衡交易记录数据样本,利用“软信息”特征构建评估指标体系,结合ADASYN算法和随机森林模型,提出改进后的AD-RF信用风险评估模型。该信用风险评估模型优于传统随机森林模型。互联网金融面临的信用风险主要源于对借款人的道德水平高低、还款能力大小、违约成本大小的未知和借款利率的变化。

Analysis of reactive routing protocols for mobile ad hoc networks in Markov models

Mobile ad hoc networks （MANETs） have become a hot issue in the area of wireless networks for their non-infrastructure and mobile features. In this paper, a MANET is modeled so that the length of each link in the network is considered as a birthdeath process and the space is reused for n times in the flooding process, which is named as an n-spatiai reuse birth-death model （n-SRBDM）. We analyze the performance of the network under the dynamic source routing protocol （DSR） which is a famous reactive routing protocol. Some performance parameters of the route discovery are studied such as the probability distribution and the expectation of the flooding distance, the probability that a route is discovered by a query packet with a hop limit, the probability that a request packet finds a τ-time-valid route or a symmetric-valid route, and the average time needed to discover a valid route. For the route maintenance, some parameters are introduced and studied such as the average frequency of route recovery and the average time of a route to be valid. We compare the two models with spatial reuse and without spatial reuse by evaluating these parameters. It is shown that the spatial reuse model is much more effective in routing.

The Research on QoS Model Design in Mobile Ad Hoc Networks

Wireless Ad Hoc Networks is a special kind of wireless communication network. With the great development of multimedia applications, how to provide QoS guarantee in the MAC layer is the hot topic in wireless ad hoc network (MANET). This paper designed a QoS model in MANET. The feasibility and reliability of this model is analyzed and verified. Compared with the traditional model, the proposed approach is improved in MAC layer in order to achieve high control rate of low-priority transactions.

DTMC-based Modeling and Analysis of Obstacle Ad hoc Networks

One of the main characteristics of Ad hoc networks is node mobility, which results in constantly changing in network topologies. Consequently, the ability to forecast the future status of mobility nodes plays a key role in QOS routing. We propose a random mobility model based on discretetime Markov chain, called ODM. ODM provides a mathematical framework for calculating some parameters to show the future status of mobility nodes, for instance, the state transition probability matrix of nodes, the probability that an edge is valid, the average number of valid-edges and the probability of a request packet found a valid route. Furthermore, ODM can account for obstacle environment. The state transition probability matrix of nodes can quantify the impact of obstacles. Several theorems are given and proved by using the ODM. Simulation results show that the calculated value can forecast the future status of mobility nodes.

The impact of hidden node on model of ad hoc network

To deal with hidden nodes in ad hoc network, we take throughput as the metric to evaluate the performance of network. Firstly, we modeled the MAC layer of ad hoc network based on 802.11 DCF without the existence of hidden nodes. By means of the proposed model, we evaluated the throughput performance of DCF in multi-hop wireless networks. Secondly, we performed simulations to validate this model. The outcome of comparison is that there exists much difference in throughput between the model and the simulation. For reducing this difference, we modified the model by involving hidden nodes under the condition that the AODV route protocol was chosen, and analytically analyzed the influence of hidden nodes on theoretical throughput. At last, we validated the accuracy of this model by comparing the analytical results with simulation results.

Total Pairwise Quantum Correlation and Entanglement in a Mixed-Three-Spin Ising-XY Model with Added Dzyaloshinskii-Moriya Interaction under Decoherence

We investigate the behavior of geometric global quantum discord （GGQD） and concurrence （C） between half- spins of a mixed-three-spin （1/2, 1, 1/2） system with the Ising-XY model for which spins （1, 1/2） have the Ising interaction and half-spins （1/2, 1/2） have both XY and the Dzyaloshinskii Moriya interactions together, under the decoherence action. A single-ion anisotropy property with coefficient ζ is assumed for the spin-integer. This system which includes an analytical Hamiltonian is considered at the front of an external homogeneous magnetic field B in thermal equilibrium. Finally, we compare GGQD and C and express some interesting phase flip reactions of the total quantum correlation and pairwise entanglement between spins （1/2, 1/2）. Generally, we conclude that the concurrence and GGQD have different behaviors under the phase flip channel.

Experimental and Numerical Investigations on Vibration Characteristics of a Loaded Ship Model

In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method （FEM） by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain.