Self-powered realization for synchronous switching circuits is a hot spot for piezoelectric vibration energy harvesting. As a well-known approach, the electronic breaker is widely used for its simplicity and reliability. It plays an important role on the performance of the piezoelectric generator by affecting the available open-circuit voltage and the switching phase lag. In this paper, a comprehensive model is developed for improved performance analysis with missed factors included in comparison with previous investigations. The combined influence of the envelope resistor and the capacitor on both the phase lag and the open-circuit voltage is newly considered while the additional phase lag effect induced by charging the switch parasitic capacitance with the envelope capacitance is supplemented. Experiments and simulations validate the proposed model with better accuracy and the results show that these supplemented factors are important to the generator performance, especially for the micro-power energy harvesting with small piezoelectric capacitance or displacement magnitude. Moreover, more detailed design guidelines are deduced from the proposed model.

The effect of porous sound-absorbing concrete slabs on railway noise reduction is examined in this paper. First, the acoustical absorption coefficients of porous concrete materials with various aggregate types, gradations, fibre contents, and compaction indexes are measured in the laboratory. The laboratory results show that porous concrete that uses a composite of expanded perlite and slag as aggregate can not only obtain good acoustical absorption properties but also satisfy mechanical requirements. Also, the gradation of the combined aggregate has a significant effect on the acoustic absorption performance of the porous concrete, with an optimal aggregate gradation of 1~3 mm. Furthermore, the fibre content and compaction index affect both the strength and the acoustic absorption property of the porous concrete, with the optimum value of 0.3% and 1.6, respectively. Then, the findings from the laboratory studies are used to make porous sound-absorbing concrete slabs, which are applied in a test section. The measurements indicate that porous sound-absorbing concrete slabs can significantly reduce railway noise at different train speeds and that the amount of the noise reduction changes roughly linearly with speed when the train is traveling at less than 200 km/h. The maximum noise reduction is 4.05 dB at a speed of 200 km/h.

Wave propagation in the ordered and randomly disordered periodic track structure in high-speed railways are investigated theoretically and experimentally. Taking the CRTS-I double-block ballastless track structure in China as the research object, a theoretical model of periodic track structure is established. The rail is modelled as a Timoshenko beam considering the bending–torsional coupling. The dispersion curves of the periodic track structure are obtained according to the transfer matrix method and Bloch theory. Based on the Lyapunov exponent algorithm, the elastic wave propagation characteristics of the randomly disordered periodic track structure are further calculated and analyzed considering the random disorder of structure parameters. The obtained results show that the periodic track structure is characterized by band gaps, elastic wave propagation attenuates significantly within the band gap, and random disorder in the track structure can expand the attenuation regions. Finally, the band gap characteristics of the vertical/lateral flexural wave and torsional wave are verified respectively through an in situ experiment.

To estimate the rail axial force of high-speed railway ballastless track, the reasonable index without complex measuring or error correction process is proposed. Taking the ballastless track structure in high-speed railway as the research object, the wave motion of periodic ballastless track is studied using the wave finite element method. It is found that some standing wave modes are linearly correlated with the rail axial force and thus can be considered as the basic indices for rail axial force estimation. A further in situ experiment according to the modal test method is performed and the feasibility of different wave modes for estimating rail axial force is discussed. Experiment results show that the lateral wave mode coincides well with the theoretical result while there is a large difference for the vertical wave mode. To explicate the difference, the temperature-dependent properties of the fastening are tested additionally. Parametric analysis shows that the frequency shift of vertical wave mode is greatly affected by the fastening temperature-dependent characteristics including the rail pad, elastic pad, and fastener clamping force, while the frequency shift of lateral wave mode is mainly determined by the rail axial force.

A promising means of reducing railway noise is to increase the damping of the rail, which decreases the vibration of the rail to reduce noise. To achieve this goal, a slotted stand-off layer damping treatment has been developed, and a compound track model with this treatment is developed for investigating the effectiveness of this treatment in terms of the vibration reduction. Through the dynamic analysis of the track undergoing the slotted stand-off layer damping treatment, some guidelines are proposed on the selection of materials and structure parameters for this treatment. In addition, the prototype of the optimal slotted stand-off layer damping treatment has been built and tested in the laboratory. It is found that the slotted stand-off damping treatment shows significant effects in decreasing the amplitude of the accelerance of the rail and a significant reduction of sound emission reflected as the radiation sound pressure level decreases by 8.2 and 9.4 dB at vertical excitation and lateral excitation, respectively, in the frequency range of 0–4000 Hz.