Modified multi-scale symbolic dynamic entropy and fuzzy broad learning-based fast fault diagnosis of railway point machines

Railway point machine(RPM)condition monitoring has attracted engineers’attention for safe train operation and accident prevention.To realize the fast and accurate fault diagnosis of RPMs,this paper proposes a method based on entropy measurement and broad learning system(BLS).Firstly,the modified multi-scale symbolic dynamic entropy(MMSDE)module extracts dynamic characteristics from the collected acoustic signals as entropy features.Then,the fuzzy BLS takes the above entropy features as input to complete model training.Fuzzy BLS introduces the Takagi-Sug eno fuzzy system into BLS,which improves the model’s classification performance while considering computational speed.Experimental results indicate that the proposed method significantly reduces the running time while maintaining high accuracy.

A One-Dimensional Second-Order Cell-Centered Lagrangian Scheme Satisfying the Entropy Condition

The numerical solutions of gas dynamics equations have to be consistent with the second law of thermodynamics,which is termed entropy condition.However,most cell-centered Lagrangian(CL)schemes do not satisfy the entropy condition.Until 2020,for one-dimensional gas dynamics equations,the first-order CL scheme with the hybridized flux developed by combining the acoustic approximate(AA)flux and the entropy conservative(EC)flux developed by Maire et al.was used.This hybridized CL scheme satisfies the entropy condition;however,it is under-entropic in the part zones of rarefaction waves.Moreover,the EC flux may result in nonphysical numerical oscillations in simulating strong rarefaction waves.Another disadvantage of this scheme is that it is of only first-order accuracy.In this paper,we firstly construct a modified entropy conservative(MEC)flux which can damp effectively numerical oscillations in simulating strong rarefaction waves.Then we design a new hybridized CL scheme satisfying the entropy condition for one-dimensional complex flows.This new hybridized CL scheme is a combination of the AA flux and the MEC flux.In order to prevent the specific entropy of the hybridized CL scheme from being under-entropic,we propose using the third-order TVD-type Runge-Kutta time discretization method.Based on the new hybridized flux,we develop the second-order CL scheme that satisfies the entropy condition.Finally,the characteristics of our new CL scheme using the improved hybridized flux are demonstrated through several numerical examples.

Complexity analysis of the Portevin-Le Chatelier in an Al alloy atdifferent tem peratures

The complexity of the Portevin-Le Chatelier(PLC)effect in an Al alloy at different temperatures was ana-lyzed by modified multiscale entropy.The results show that three evolutions of entropy with scale factor,i.e.,near zero,monotonically increasing and peak-shape,were observed corresponding to the smoothcurves,type-A serrations and type-B/-C serrations,respectively.The scale factor at the peak was one-third of the average serration period.The sample entropy increased initially and then decreased withtemperature,which was opposite to the critical strain.It is also suggested that the type-A serrations cor-responded to self-organized criticality and the type-B/-C serrations corresponded to chaos through theevolutions of entropy with scale factor.

Quantum tunnelling of higher-dimensional Kerr-anti-de Sitter black holes beyond semi-classical approximation

Based on the theory of Klein-Gordon scalar field particles, the Hawking radiation of a higher- dimensional Kerr-anti-de Sitter black hole with one rotational parameter is investigated using the beyond semi-classical approximation method. The corrections of quantum tunnelling probability, Hawking temperature and Bekenstein-Hawking entropy are also included.