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Xu X.,Civil Aviation University of China | Zhao H.,Beihang University | Wang Z.,China Airport Construction Corporation of CAAC
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica

Flight delay is nowadays one of the most critical curbing factors in aviation industry. While the efficiency of air transportation is improved by air traffic flow management, massive research work on wake vortex separation reduction is also performed by researchers all around the world. One of the technologies developed to date is to modify flight procedure aiming at the reduction of the wake vortex separation of closely spaced parallel runways; and another is to build wake turbulence prediction models in order to anticipate the dissipation and transportation of wake vortex. Thus a wake turbulence separation consultative matrix is calculated to acquire more landing and take-off slots. The wake vortex separation reduction systems can alleviate flight delay and increase terminal capacity. They are assorted into two categories according to different principles adopted in design, i. e. , wake vortex separation system based on offset approach procedure and wake vortex separation system based on dynamic prediction. The theory, algorithm and components of each system are thoroughly analyzed. The performance of the systems is compared and the advantages and drawbacks of each system are discussed. Source

Qiao G.,Harbin Institute of Technology | Liu T.,Harbin Institute of Technology | Dai J.,Harbin University of Commerce | Hong Y.,Harbin Institute of Technology | Wan J.,China Airport Construction Corporation of CAAC
IEEE Sensors Journal

Corrosion assessment of the steel bar in reinforced concrete (RC) structures is a very urgent for the structural health monitoring and life-cycle design in civil engineering. Half-cell potential map and guard ring techniques are applied as typical qualitative and quantitative methods to assess the corrosion status, respectively. A RC panel has been formed to be an actual testbed to verify the effectiveness of these techniques. Its potential map and corrosion rate have been investigated by the electrochemical sensors before and after NaCl solution injected, respectively. The results indicate the corrosion status of RC panels can be identified effectively. © 2001-2012 IEEE. Source

Xu X.,Civil Aviation University of China | Zhao H.,Beihang University | Yang C.,Nanjing University of Aeronautics and Astronautics | Wang Z.,China Airport Construction Corporation of CAAC
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics

The wake vortex separation is one of the main limitations of the runway capacity increment. To augment the runway capacity while maintaining safety, the wake vortex separation must be regulated based on the consideration of both the safety and the operation efficiency. It is necessary to research the physical process and the dissipation of the wake turbulence to regulate the correct and appropriate wake vortex separation of the air traffic. In this paper, the wake turbulence of a simplified three-dimensional wing model is calculated by a computational fluid dynamics method. The turbulence model is built based on the large eddy simulation theory. The important parameters, such as inlet air velocity, attack angle, and boundary value conditions are in agreement with the data collected from the approach segment of a flight. The given approach segment is the most dangerous segment as far as the wake turbulence is concerned. Numerical simulation results validate the split dissipation of wake vortex core, and the phenomenon of linkage dissipation and sinkage of vortex pair. The dissipation asymmetry of the vortex pair, before roll-up and after the Crow linkage, is discovered. And the reason of the asymmetrical phenomenon is also analyzed. Source

Zhang Z.-Q.,Changan University | Zhang K.,Changan University | Li Z.-H.,Changan University | Yao X.-G.,Changan University | Wang K.,China Airport Construction Corporation of CAAC
Chang'an Daxue Xuebao (Ziran Kexue Ban)/Journal of Chang'an University (Natural Science Edition)

To solve the problem of hardness and brittleness after the hardening of epoxy asphalt concrete in steel deck pavement, its poor coordination with the bridge deck, and its proneness to crack, a means was introduced to improve the flexibility and toughness of epoxy asphalt concrete by adding rubber particles and polyester fiber. The low-temperature bending test and bending fatigue test were carried out to analyze the influence of rubber particles and polyester fiber on bending failure strain and fatigue life of epoxy asphalt concrete. The results show that the flexibility and toughness of epoxy asphalt concrete can be improved after adding rubber particles and polyester fiber. The flexible performance of the mixture is improved through the crazing effect caused by adding rubber particles, and the optimum dosage of rubber particle is 2.1%. While polyester fiber greatly improves the toughness properties of the mixture through the combined action of structure-asphalt and fiber net developing in the blends, and the optimum dosage of polyester fiber is 0.3%. ©, 2015, Editorial Department of Journal of Chang'an University (Natural Science Edition). All right reserved. Source

Li P.-L.,Changan University | Zhang Z.-Q.,Changan University | Li H.-H.,China Airport Construction Corporation of CAAC | Wang B.-G.,Changan University
Jiaotong Yunshu Gongcheng Xuebao/Journal of Traffic and Transportation Engineering

Four kinds of asphalt mixtures were made and Hamburg wheel tracking tests were conducted with the specimens in the water and in the air at 50°C and 60°C individually, the influence of water and temperature on rutting depth was analyzed. The tests were carried on to analyze the influence of specimen thickness and molding ways on rutting depth. The result indicates that water and raising test temperature can accelerate rutting appearance. The correlation coefficients are over 0.93 when the specimens are in the water at 50°C and in the air at 60°C. According to the application of asphalt types, the right test temperatures of B-grade asphalt, A-grade asphalt and modified asphalt are 45°C, 50°C and 60°C respectively. The rutting depth of 40 mm-thickness specimen is much larger than that of others, which is not applicable for experiments. The test result of SGC cylindrical specimen has good relationship with that of plate specimen, their correlation coefficient is more than 0.95, so it can be used to evaluate the rut-resistance of asphalt mixture instead of plate specimen. Source

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