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The noise radiating from a steel bridge can be much greater than the pass-by noise levels of trains at-grade. This is attributed to a special phenomenon known as the steel bridge-borne noise, which occurs when shocks and vibrations due to moving train loads are transferred onto the bridge. To investigate the effectiveness of elastomer mats for reducing vibration and noise in rail transit steel bridges, a frequency domain prediction model is established and calibrated through a field experiment. In this model, the train and track interactions were investigated analytically, and the receptance technique was introduced to determine the force transmitted from a multi-layer track structure to the bridge deck. The local vibrations of the bridge components were solved numerically using a hybrid shell/beam finite element model based on a harmonic response analysis. The bridge vibrations were regarded as the source of noise radiation by considering each bridge component as a rectangular flat plate noise source. There was good agreement between the calculated and measured results in terms of both the magnitude and frequency dependence. The mechanisms of vibration transmission and noise radiation were investigated using numerical simulations. In addition, the vibration and noise reduction effects are discussed by numerically comparing a track system with and without an elastomer mat.

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Voltage stability monitoring simulation system for photovoltaic (PV) grid-connected system is designed, taking the classic three-node power system model with a PV power station for example. The voltage instability theory and application researches for the monitoring simulation system are carried, and the frame, communication protocol and software functions of the voltage stability monitoring system are discussed. The monitoring simulation system can realize two-computer communication and joint debugging, which can not only monitor the basic operational aspects, but also be used to view the voltage equilibrium point curves and voltage response curves as the operating point is affected by various disturbances. And the system load margin index calculation, load shedding and other voltage stability remote control methods are provided to maintain or improve voltage stability. The monitoring simulation system provides a reference scheme for the application of voltage stability theory in practical engineering.