Machine fault diagnosis with small sample based on variational information constrained generative adversarial network

In actual engineering scenarios, limited fault data leads to insufficient model training and over-fitting, which negatively affects the diagnostic performance of intelligent diagnostic models. To solve the problem, this paper proposes a variational information constrained generative adversarial network (VICGAN) for effective machine fault diagnosis. Firstly, by incorporating the encoder into the discriminator to map the deep features, an improved generative adversarial network with stronger data synthesis capability is established. Secondly, to promote the stable training of the model and guarantee better convergence, a variational information constraint technique is utilized, which constrains the input signals and deep features of the discriminator using the information bottleneck method. In addition, a representation matching module is added to impose restrictions on the generator, avoiding the mode collapse problem and boosting the sample diversity. Two rolling bearing datasets are utilized to verify the effectiveness and stability of the presented network, which demonstrates that the presented network has an admirable ability in processing fault diagnosis with few samples, and performs better than state-of-the-art approaches.     

基于扇形领域扩展的同步双向A*算法

为提高航空器飞行的安全性和平滑性,解决传统A^*算法拐弯角度过大、搜索路径节点过多等问题,提出一种基于扇形领域扩展的同步双向A^*搜索算法。首先,根据栅格图法扩展危险区域边界;其次,设计了基于同步双向搜索的A^*算法,动态定义正反向搜索的目标节点。针对搜索角度有限问题,提出了在5×5领域内的扇形领域扩展策略,并设计了含有双重权重参数的评价函数以减少冗余点的产生。为验证改进算法的有效性,选取方形和不规则形状危险区进行仿真。结果表明改进的同步双向搜索算法搜索的路径更平滑;与传统双向A^*算法的结果相比,在不同形状的危险区域下,搜索路径长度分别减少了1.65%、13.16%,搜索路径节点个数减少了42.6%、46.81%,具有较强的搜索效率。     

Multi-indicator Active Queue Management Method

A considerable number of applications are running over IP networks. This increased the contention on the network resource, which ultimately results in congestion. Active queue management (AQM) aims to reduce the serious consequences of network congestion in the router buffer and its negative effects on network performance. AQM methods implement different techniques in accordance with congestion indicators, such as queue length and average queue length. The performance of the network is evaluated using delay, loss, and throughput. The gap between congestion indicators and network performance measurements leads to the decline in network performance. In this study, delay and loss predictions are used as congestion indicators in a novel stochastic approach for AQM. The proposed method estimates the congestion in the router buffer and then uses the indicators to calculate the dropping probability, which is responsible for managing the router buffer. The experimental results, based on two sets of experiments, have shown that the proposed method outperformed the existing benchmark algorithms including RED, ERED and BLUE algorithms. For instance, in the first experiment, the proposed method resides in the third-place in terms of delay when compared to the benchmark algorithms. In addition, the proposed method outperformed the benchmark algorithms in terms of packet loss, packet dropping, and packet retransmission. Overall, the proposed method outperformed the benchmark algorithms because it preserves packet loss while maintaining reasonable queuing delay.     

基于改进遗传算法的多脉冲交会轨道优化研究

最优空间多脉冲轨道交会是一个复杂的非线性系统。由于结构复杂,存在非线性特性,影响系统的快速性和实时性。建立最优空间多脉冲轨道交会模型,传统遗传算法不能满足要求,因此提出了在自适应遗传算法的基础上引入多位变异的多变异位自适应遗传算法,对空间多脉冲交会轨道优化进行了求解。多变异位自适应遗传算法增加了种群的多样性,可避免算法的早熟收敛现象。仿真结果表明,利用多位变异自适应遗传算法求解空间多脉冲交会轨道优化效果好,避免了早期收敛,提高了全局寻优能力,为多脉冲交会轨道优化提供了较好的方法。     

侧风影响下航空器尾涡LES数值模拟

为保障航空器运行安全、提高飞行效率,用ICEM CFD 和Fluent软件采用大涡模拟（LES）方法对不同侧风下航空器进场尾涡进行数值模拟,研究进近阶段侧风对尾涡的影响。本文阐述了大涡模拟的原理,构建了空客A330-200机翼的构型和高网格质量的计算域,并模拟仿真飞机在无侧风条件下和侧风分别为3、5 、7 m/s的尾涡,量化分析侧风对尾涡演化规律和扩散趋势的影响。结果表明,侧风越大,尾涡的耗散速度越快 ,并且侧风对下风涡的影响大于上风涡。     

运输类飞机运行符合性验证规划方法研究

针对民航当局对运输类飞机运行符合性的评审要求,结合型号研制里程碑节点和飞机设计、制造、试验的不同状态,确定了不同阶段的运行符合性验证工作内容,提出了将运行符合性验证与型号合格审定进行协同规划的方法,提出了与研制、审定过程协调一致的运行符合性验证计划编制方法,构建了基于验证项目、验证资源、验证成本、验证时间等多参数的运行符合性验证规划模型,设计了基于遗传算法的运输类飞机运行符合性验证规划模型求解流程。算例表明,该方法在处理多目标约束的验证成本和验证时间最优解问题上具有可行性。     

Negative Multinomial Reputation for Self-Organized Networks

As an effective supplement to traditional security solutions, reputation mechanism, which can encourage cooperation among individual entities and minimize the damage mainly resulted from insider attacks, has received much concern by the research community. In this article, a negative multinomial reputation model for self-organized networks is proposed. Compared with binary parameter based binomial reputation model, our model is featured with multiple parameters which can depict objective facts more precisely and accurately. Moreover, free from fixed increment on parameters in binomial model, the increment in our model can be 2 or more, which makes our model flexible and suitable for more practical applications such as networks with sleep mechanisms. Through three metrics of measurement, i.e. convergence time to detecting malicious entities, success rate of malicious entities, and success rate of benign entities, our model shows a better performance in the simulations and excels in these three aspects.     

机场综合监视与引导系统运动模块设计及实现

随着民航运输业的迅猛发展,机场起落流量逐年增大,机场内各种车辆的运行给机场场面管理带来巨大的压力。对于目前民航这种发展形势,近年来提出了地面滑行引导与控制系统概念,该概念旨在满足繁忙机场的滑行引导与控制需求。结合传统地面滑行引导与控制系统概念设计了滑行引导运动模块,并通过C＋＋实现。     

基于FCM的驾驶行为险态辨识模型

为实现险性驾驶行为的有效辨识,以事故发生概率为依据,在对驾驶行为状态予以险态分级的前提下,采用单因子方差分析进行险态辨识主因子析取,并基于模糊C均值聚类法构建了险态行为辨识模型。最后,结合实例对模型予以试算,并采用样本回代对模型进行了验证。结果表明,模型误差率为2.5%。     

Numerical analysis of ice accretion effects at super-cooled large droplet conditions on airfoil aerodynamics

Changes in flow field around NACA23012 airfoil from a clean condition to a super-cooled large droplet (SLD) condition were simulated, and variations in aerodynamic parameters were calculated using FLUENT. In the case of numerical simulation for a clean airfoil, flow field characteristics simulated agreed well with theory analysis, indicating that turbulence models and parameters setting are feasible. Aerodynamic parameters for iced airfoil were calculated using the same method and agreed with those measured test data under the same environment in icing wind tunnels by S. Lee. Conclusion is made that the numerical simulation is valid, and it can be an alternative to study ice accretion effects at the SLD condition on airfoil aerodynamics, leading to reduction in research cycle time and cost.