Dual smoothing ionospheric gradient monitoring algorithm for dual-frequency BDS GBAS

In this study, a Dual Smoothing Ionospheric Gradient Monitor Algorithm(DSIGMA)was developed for Code-Carrier Divergence(CCD) faults of dual-frequency Ground-Based Augmentation Systems(GBAS) based on the Bei Dou Navigation Satellite System(BDS).Divergence-Free(DF) combinations of the signals were used to form test statistics for a dualfrequency DSIGMA. First, the single-frequency DSIGMA was reviewed, which supports the GBAS approach service type D(GAST-D) for protection against the effect of larg...     

A double integral method for quantitative evaluation of influence on thin-walled casing response caused by bearing uncertainties

Bearings in a gas turbine engine are the key connecting components transmitting force and motion between rotors and thin-walled flexible casing. The bearing stiffness and damping of squeeze film damper(SFD) nearby bearings are easily affected by many factors, such as assembly process, load condition and temperature variation, resulting in uncertainties. The uncertainties may influence the response of the measuring point on the casing. Hence, it is difficult to carry out the fault diagnosis, whol...     

Impact of receiver inter-frequency bias residual uncertainty on dual-frequency GBAS integrity

Dual-Frequency Ground-Based Augmentation Systems(GBAS) can be affected by receiver Inter-Frequency Bias(IFB) when Ionosphere-Free(Ifree) smoothing is applied. In the framework of the proposed GBAS Approach Service Type F(GAST-F), the IFB in the Ifree smoothed pseudorange can be corrected. However, IFB residual uncertainty still exists, which may threaten the integrity of the system. This paper presents an improved algorithm for the airborne protection level considering the residual uncertainty o...     

Porous Alumina Ceramics Fabricated by Spark Plasma Sintering

Porous alumina of regular spherical particles was fabricated with the spark plasma sintering (SPS) and then compared to those ob-tained through conventional hot pressing (HP). The effects of the parameters of the heating process on porosity were also investigated. Microstructural studies suggest that porous ingots including regular pores be made out of regular spherical alumina particles due to the close sphere packages. A comparative study on the relative necks of the specimens produced by SPS and HP indicates an enhancement of neck growth with SPS. Contrasting the theoretical values to the experimental results over the relative necks indicates that a proper relationship between the relative necks and the porosity can be established by a sintering model.     

Influence of blade negative twist on aerodynamic performance of cycloidal propeller

In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller, a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were established. The characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were provided. The influence of the negative twist on the aerodynamic performance of cycloidal propeller was emphasized. The results showed that, the change of negative twist caused the change of azimuth for cycloidal propeller lift. The larger the absolute value of negative twist, the lower the figure of merit of the cycloidal propeller; the smaller the negative twist, the more gentle the instantaneous aerodynamic fluctuation; the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller''s effective angle of     

Distributed coordinated control scheme of UAV swarm based on heterogeneous roles

This paper proposes a new distributed coordinated control scheme based on heterogeneous roles for Unmanned Aerial Vehicle(UAV) swarm to achieve formation control. First, the framework of the distributed coordinated control scheme is designed on the basis of Distributed Model Predictive Control(DMPC). Then, the effect of heterogeneous roles including leader, coordinator and follower is discussed, and the role-based cost functions are developed to improve the performance of coordinated control for...     

浅谈民航电子商务及其信息安全

InformationSecurityinE－commerce人类经济活动的全球化在过去的几十年进程缓慢。随着信息技术的发展，架构于互联网网络的商务活动即电子商务（E－commerce）得以普及，使经济全球化是加速发展之势，而经济全球化又刺激着电子商务加速发展。电子商务是个人、公司或他们之间利用诸如互联网（Internet）、企业内部网（Intranet）、在线服务（On－lineservices）等提供的媒介从事商务活动的一种方式。信息产业部副部长吕新奎在“第二届信息化法制建设研讨会”上指出，21世纪电子商务将给各国和世界经济带来巨大变革共产生深远影响，从而成…     

Role of hydrogen in the dissociation of CH4 on different graphene by DFT study

The effect of hydrogen on the growth mechanism of pyrocarbon has attracted much attention. The influence of hydrogen on the dissociation from CH4to C2H2on pristine graphene,N-doped graphene and vacancy graphene have been investigated by using density functional theory.There are two kinds of heterogeneous reaction pathways when the hydrogen is involved, i.e., dehydrogenation reactions and H-abstraction reactions. The transition state calculations were performed to acquire the reaction pathways on...     

Auxiliary generative mutual adversarial networks for class-imbalanced fault diagnosis under small samples

The effect of intelligent fault diagnosis of mechanical equipment based on data-driven is often premised on big data and class-balance. However, due to the limitation of working environment, operating conditions and equipment status, the fault data collected by mechanical equipment are often small and imbalanced with normal samples. Therefore, in order to solve the abovementioned dilemma faced by the fault diagnosis of practical mechanical equipment, an auxiliary generative mutual adversarial ne...