ABSTRACT
The track foundation is preloaded by multiple wheel loads due to the train weight and, as the pad and ballast are nonlinear, their stiffness depends upon the preload in them. Due to the influence of these resilient components of the track, the track vibration is affected by the wheel loads. It is also affected by the wheel/rail interactions. In this article the preloads in the pad and ballast are calculated by considering the nonlinear properties of the track foundation, and thus the preloaded pad and ballast stiffnesses are determined. The vibration properties are explored for the track under multiple wheel loads and multiple wheel/rail interactions by comparing the results from different track models with and without these effects. It is found that the point receptance of the track is reduced and the vibration decay rate is enhanced at low frequencies due to the wheel loads. The effects of the wheel/rail interactions are most significant for frequencies 400-2000 Hz. Because of the wheel/rail interactions, the point receptance fluctuates and the vibration decay is enhanced in the regions around the wheels.
ABSTRACT
In this paper a multiple-beam model of the rail, which allows all the essential deformations caused by the lateral vibration, has been applied for studying the lateral vibration behavior related to the discrete supports. Detailed investigation of the lateral vibration of a discretely supported rail has been carried out using a Green's function matrix and the superposition principle. Good agreement between the predictions and measurement data has been reached in terms of accelerance.
ABSTRACT
One of the great mysteries of the high-energy gamma-ray sky is the group of approximately 170 unidentified point sources found along the Galactic plane. They are more numerous than all other high-energy gamma-ray sources combined and, despite 20 years of effort, no clear counterparts have been found at other wavelengths. Here we report a new population of such objects. A cluster of approximately 20 faint sources appears north of the Galactic Centre, which is part of a broader class of faint objects at mid-latitudes. In addition, we show in a model-independent way that the mid-latitude sources are distinct from the population of bright unidentified sources along the Galactic plane. The distribution on the sky indicates that the faint mid-latitude sources are associated with the Gould belt of massive stars and gas clouds at approximately 600 light years distance, as has been previously suggested.
