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He X.,Key Laboratory of Magnetic Levitation Technologies and Maglev Trains | He X.,Southwest Jiaotong University | Feng X.,Key Laboratory of Magnetic Levitation Technologies and Maglev Trains | Feng X.,Southwest Jiaotong University | And 6 more authors.
Journal of Modern Transportation | Year: 2014

In this study, finite element analysis (FEA) has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations. © The Author (s) 2014. This article is published with open access at Springerlink.com. Source


Wei Z.,Key Laboratory of Magnetic Levitation Technologies and Maglev Trains | Wei Z.,Southwest Jiaotong University | Yang X.,Key Laboratory of Magnetic Levitation Technologies and Maglev Trains | Yang X.,Southwest Jiaotong University | And 6 more authors.
Journal of Modern Transportation | Year: 2014

Magnetoresistive sensor can be widely used in modern transportation field, such as the vehicle positioning and navigation system, vehicle detection system, and intelligent transportation system. In order to improve the efficiency of magnetoresistive sensor, we synthesized La0.8Sr0.2MnO3 polycrystalline bulks at different sintering temperatures and investigated their DC and AC transport properties in this work. As a result, all samples showed insulator-metal (I-M) phase transition, and the transition temperature (TI-M) shifted to higher temperature with the increase of sintering temperature. The TI-M measured at different AC frequencies was smaller than that measured at DC condition, which implied that the I-M phase transition was suppressed at AC frequencies. The resistivity measured at high AC frequencies was larger than that measured at low AC frequencies, which could be attributed to the change of the magnetic penetration depth (d). However, the room-temperature AC-magnetoresistance (MR) at low frequencies was much larger than that at high frequencies and room-temperature DC-MR. These findings demonstrate that reducing the AC frequency is an effective way for enhancing the room-temperature MR, which can be used to promote the efficiency of magnetoresistive sensor. © The Author (s) 2014. This article is published with open access at Springerlink.com. Source

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