As a new generation of air transportation surveillance technology, the automatic dependent surveillance-broadcast (ADS-B) system mainly completes the extraction and processing of the position information and other additional information of the aviation aircraft to form a clear and intuitive background map and trajectory. However, ADS-B broadcasts information via open and unencrypted protocols, it is vulnerable to deliberate intrusions and attacks, which poses a great security risk. This paper studies the security issues of the ADS-B system in information leakage and tampering. Starting from the vulnerability of the ADS-B system, it is divided into vulnerability based on attack intention and vulnerability based on security requirements. Various solutions for solving vulnerabilities from two aspects, secure location authentication, and secure broadcast authentication are proposed, and the solutions are compared in terms of security and feasibility. The research results show that a single solution does not fully protect the security of the ADS-B system. For example, the PKI (Public Key Infrastructure) technology and the SS (Spread Spectrum) technology can resist most attacks, but there are still deficiencies. Therefore, this paper proposes to propose a multi-layered security framework in future research work, which includes detecting and preventing different attacks in the ADS-B system.

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The effect of MnO x /Ti catalyst doped with Ce prepared by sol-gel method at a low temperature on N 2 O formation during the selective catalytic reduction of NO with NH 3 was studied in detail. Results showed that the production of N 2 O was primarily controlled by two paths: (1) direct reaction of NO and NH 3 and (2) oxidation of NH 3 with O 2 . The overoxidation of NH 3 was the dominant step in N 2 O reduction. Addition of Ce to MnO x /Ti catalyst increased the proportion of lattice oxygen on the catalyst surface. Meanwhile, the stability of lattice oxygen, which contributed to the decrease in N 2 O formation by inhibiting the overoxidation of NH 3 , on the catalyst surface was the best when the Ce/Ti mole ratio reached 0.1.

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Although various NO x removal technologies have been commercialized, NO x emissions are still so high that they cannot meet the newest standard and endanger the eco-environment and human health. Meanwhile, some NO x reduction technologies suffer from high costs. Recently, a cheap and pending technology called gas-fired coal preheating has surfaced again. This method introduces hot flue gas to heat a coal stream to high temperatures before the coal stream is injected into a utility boiler for combustion, thus resulting in a reduction in NO x . Considering the complex mechanisms during preheating, the effect of the preheating parameters, including temperature, residence time, excess air ratio, and coal type, are studied in a laboratory-scale drop-tube furnace in detail. Meanwhile, by means of Chemkin coupled with the mature NO x reduction mechanisms of GRI-mesh3.0 and Dagaut, as well as a CPD model, a detailed kinetics analysis on NO removal, including the migration and transformation of hydrocarbons and nitrogenous compounds during PC preheating, is performed. The research provides intuitive guidance, in practice, and a new scientific interpretation, in theory, for NO x reduction during PC combustion with preheating.