Nanjing University of Aeronautics and Astronautics

About: Nanjing University of Aeronautics and Astronautics is a education organization based out in Nanjing, China. It is known for research contribution in the topics: Computer science & Microstructure. The organization has 33704 authors who have published 37321 publications receiving 438855 citations. The organization is also known as: Nanjing College of Aviation Industry & Nanjing Aeronautical Institute.

Double glow plasma surface alloying and plasma nitriding

Abstract: Based on plasma nitriding technique, Double Glow Plasma Surface Alloying Technology (DG Technique) was developed in 1980 This technique breaks the restriction of traditional plasma nitriding and successfully applies solid alloying elements, such as Ni, Cr, W, Mo, Ti, Al, Nb et al, to realize plasma surface alloying Numerous experiment results concerning the DG technique have demonstrated that various alloys and alloy steels, such as high speed steel, nickel base alloy and wear resistant alloys et al, have been produced upon the surfaces of carbon steels, titanium alloys, Ti–Al intermetallic compounds and copper This paper is written in hope that the differences between plasma nitriding and DG technique will become more apparent Some new development and experiment results of the double glow plasma surface alloying are also shown in this paper For example, Ti–Al–Nb–C alloy has been produced on the surface of TiAl and Ti–Cu and Ti–Cr burn-resistant alloys have been formed on the surfaces of titanium and Ti6Al4V alloy by using this process; When solid graphite is used as carbon supplier, hydrogen-free carburizing has been carried out in order to avoid hydrogen embrittlement of titanium materials; Co–W–Mo–Fe age hardened high speed steel has been produced on the surfaces of carbon steels

Tunable and wideband microwave photonic phase shifter based on a single-sideband polarization modulator and a polarizer

Abstract: A novel microwave photonic phase shifter based on a single-sideband (SSB) polarization modulator (PolM) and a polarizer is proposed and demonstrated. In the SSB-PolM, two SSB intensity-modulated signals with a phase difference of π along two orthogonal polarization directions are generated. With the polarizer to combine the two signals, the phase of the optical microwave signal can be tuned from -180 to 180 deg by simply adjusting the polarization direction of the polarizer, whereas the amplitude keeps unchanged. An experiment is carried out. A full-range tunable phase shift in the frequency range of 11-43 GHz is achieved. The flat power response, power independent operation, and high stability of the proposed microwave photonic phase shifter is also confirmed.

Blockchain-Based Secure Spectrum Trading for Unmanned-Aerial-Vehicle-Assisted Cellular Networks: An Operator’s Perspective

Abstract: Unmanned aerial vehicles (UAVs) are envisioned to be widely deployed as an integral component in the next generation cellular networks, where spectrum sharing between the aerial and terrestrial communication systems will play an important role. However, there exist significant security and privacy challenges due to the untrusted broadcast features and wireless transmission of the UAV networks. This article endeavors to resolve the security issues through proposing a novel privacy-preserving secure spectrum trading and sharing scheme based on blockchain technology. Specifically, from the operator’s perspective, a pricing-based incentive mechanism is first introduced, in which a primary mobile network operator (MNO) leases its owned spectrum to a secondary UAV network in exchange for some revenue from the UAV operators. To address the potential security issues, a spectrum blockchain framework is then proposed to illustrate detailed operations of how the blockchain helps to improve the spectrum trading environment. Under this framework, a Stackelberg game is formulated to jointly maximize the profits of the MNO and the UAV operators considering uniform and nonuniform pricing schemes. Security assessment and numerical results confirm the security and efficiency of our schemes for spectrum sharing in UAV-assisted cellular networks.