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Wen K.,China University of Petroleum - Beijing | Geng Z.,Peking University | Zhang Z.,China Petrolum Pipeline Bureau | Zhang L.,China Petrolum Pipeline Bureau
Asian Journal of Control

In this paper, a new model is proposed to describe networked control systems (NCS) with delays and quantization errors. Firstly, the non-idealizations are unified in the classic robust control framework and the entire system is modeled as a discrete system closed via a block uncertainty. Then, the stability criteria are derived using small gain theorem, μ tool and integral quadratic constraint (IQC) method, respectively. Finally, a simulation and a numerical example are provided to demonstrate the effectiveness of the proposed methods. This work is supported by the Science Foundation of China University of Petroleum, Beijing (No.YJRC-2013-11) and National Natural Science Foundation (NNSF) of China under Grant 61374033. ©2014 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd. Source

Di X.-J.,Tianjin University | Di X.-J.,Tianjin Key Laboratory of Advanced Joining Technology | Cai L.,Tianjin University | Cai L.,Tianjin Key Laboratory of Advanced Joining Technology | And 4 more authors.
Acta Metallurgica Sinica (English Letters)

The intercritical heat-affected zone (ICHAZ) of X80 pipeline steel was simulated by using the Gleeble-3500 thermal/mechanical simulator according to the thermal cycle of in-service welding. The microstructures of ICHAZ with different cooling rates were examined, and the hardness, the toughness and corresponding fractography were investigated. Results show that untransformed bainite and ferrite as well as retransformed fine bainite and martensite-austenite (M-A) constituents constitute the microstructure of ICHAZ. The two different morphologies of M-A constituents are stringer and block. Second phase particles which mainly composed of Ti, Nb, C, Fe and Cu coarsened in ICHAZ. Compared with normal welding condition, the toughness of ICHAZ is poor when the cooling time is short under in-service welding condition because of the large area fraction and size of M-A constituents that connect into chains and distribute at the grain boundaries. The Vickers hardness of ICHAZ that decreases with the increase in the cooling time is independent with the area fraction of M-A constituents. Source

Wang W.-G.,China Petrolum Pipeline Bureau | Wang W.-G.,National Engineering Laboratory for Pipeline Safety | Li Y.-M.,China Petrolum Pipeline Bureau | Li Y.-M.,National Engineering Laboratory for Pipeline Safety | And 6 more authors.
Cailiao Gongcheng/Journal of Materials Engineering

The effect of different heat treatment processes on microstructure and mechanical property of X80 bend pipe was studied. By the comparison of two different heat treatment processes, the effect of heat treatment for the microstructure and mechanical property of X80 parent material and weld was discussed. The result showed that the microstructure and mechanical property of X80 bend pipe was seriously affected by the heat process. By the heat process of 950°C quench+500°C tempering, the microstructure of heat-affected zone(HAZ) and girth weld had been refined. Furthermore, the toughness and the micro-hardness of the pipe steel and the girth weld had been improved, which indicated that the heat process of 950°C quench+500°C tempering is suitable for the production of X80 bend pipe. Source

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