A Two-Stage Compression Method for the Fault Detection of Roller Bearings

Data measurement of roller bearings condition monitoring is carried out based on the Shannon sampling theorem, resulting in massive amounts of redundant information, which will lead to a big-data problem increasing the difficulty of roller bearing fault diagnosis. To overcome the aforementioned shortcoming, a two-stage compressed fault detection strategy is proposed in this study. First, a sliding window is utilized to divide the original signals into several segments and a selected symptom parameter is employed to represent each segment, through which a symptom parameter wave can be obtained and the raw vibration signals are compressed to a certain level with the faulty information remaining. Second, a fault detection scheme based on the compressed sensing is applied to extract the fault features, which can compress the symptom parameter wave thoroughly with a random matrix called the measurement matrix. The experimental results validate the effectiveness of the proposed method and the comparison of the three selected symptom parameters is also presented in this paper.

WAVE PROPAGATION IN RECTANGULAR NANOPLATES BASED ON STRAIN GRADIENT THEORY WITH ONE GRADIENT PARAMETER WITH CONSIDERING INITIAL STRESS

In this paper, on the basis of gradient elasticity theory with one gradient parameter, wave propagation in rectangular nanoplates is studied. In the governing equation, the influences of initial stresses and elastic foundation are also considered. An analytical approach is used to solve the governing equation. The effects of different parameters such as gradient parameter on the circular and cut-off frequencies are presented. One can see that the initial stress and gradient parameter play an important role in investigating the wave propagation in nanoplates.

QUARTETTING IN ATTRACTIVE FERMI-SYSTEMS AND ALPHA PARTICLE CONDENSATION IN NUCLEAR SYSTEMS

The famous Hoyle state (02+ at 7.654 MeV in 12 C ) is identified as being an almost ideal condensate of three α-particles, hold together only by the Coulomb barrier. It, therefore, has a 8 Be -α structure of low density. Transition probability and inelastic form factor together with position and other physical quantities are correctly reproduced without any adjustable parameter from our two parameter wave function of α-particle condensate type. The possibility of the existence of α-particle condensed states in heavier nα nuclei is also discussed.

Compact 11S Helium Wave Functions; an 8-Parameter Wave Function and its Sensitivity Analysis

A previously obtained approximate non-relativistic Helium wave function is improved significantly coming within 0.02% of the “exact” value with 8 terms. The sensitivity of this final result to the parameters in the wave function is examined.

VARIATIONAL CALCULATIONS OF CHARGED EXCITONS IN GaAs QUANTUM-WELL WIRES

The binding energy of positively and negatively charged excitons in GaAs quantum-well wires is calculated variationally as a function of the wire width by using a two-parameter wave function and a one-dimensional equivalent model. There is no artificial parameter added in our calculation. It is found that the binding energies are closely correlated to the sizes of the wire, and also that their magnitudes are greater than those in the two-dimensional quantum wells compared. In addition, we also calculate the average interparticle distance and the distribution of the wave function of exciton centre-of-mass as functions of the wires width. The results are discussed in detail.