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The condition monitoring and fault diagnosis of rolling element bearings play an important role in the safe and reliable operation of rotating machinery. Feature extraction based on vibration signals is an effective means to identify the operating condition of rolling element bearings. Methods based on multi-scale mathematical morphology (MM) have recently been developed to extract features from one-dimensional signals. In this paper, a new double-dot structuring element (SE) is constructed for multi-scale MM. A pattern spectrum, obtained from the multi-scale MM, is used as a feature extraction index. A correlation analysis gives the final identification result by utilizing information over a whole pattern spectrum. Compared with the most commonly used flat SE, the double-dot SE can extract more features of original signals at different scales. Vibration signals, measured from defective bearings with outer race faults, inner race faults and ball faults, are used to evaluate the fault detection ability of the proposed SE and bearing fault diagnosis method. Results show that faults at different levels can be identified, including ball fault; and the location of outer race fault can also be differentiated.

As an emerging phenomenon in oxide heterostructures, the ferroelectric control of electronic transport is attracting considerable research attention. However, the effect of ferroelectric polarization on resistive switching (RS) remains controversial. In this study, to determine the effects of ferroelectric polarization on memory characteristics, ferroelectric and non-ferroelectric BaTiO3 (BTO) films were fabricated using different oxygen partial pressures (Po2) during film growth. A correlated electron oxide, SmNiO3 (SNO), was selected as the bottom electrode. Based on piezoelectric force microscopy, ferroelectricity was verified in the BTO films prepared at Po2 ≥ 3 Pa, whereas the films fabricated at lower Po2 did not exhibit ferroelectricity. Remarkable RS with an ON/OFF ratio of 104% was clearly observed in heterostructures containing ferroelectric BTO, while RS was negligible in structures with non-ferroelectric BTO. The strong ferroelectricity dependence of RS behavior on the BTO/SNO heterostructures was attributed to the ferroelectric control of device transport between bulk-limited current in the low-resistance state and interface-limited conductance in the high-resistance state, which results from the modulation of the potential barrier at the BTO/SNO interface. The findings provide strong evidence for the dominant effect of ferroelectric polarization of BTO on the transport properties of BTO/SNO heterostructures.

In this work we build on our previous paper (Harshe, Y. M.; Lattuada, M. Langmuir 2012, 28, 283-292) and compute the breakage rate of colloidal aggregates under the effect of shear forces by means of Stokesian dynamics simulations. A library of clusters made of identical spherical particles covering a broad range of masses and fractal dimension values (from 1.8 to 3.0) was generated by means of a combination of several Monte Carlo methods. DLVO theory has been used to describe the interparticle interactions, and contact forces have been introduced by means of the discrete element method. The aggregate breakage process was investigated by exposing them to well-defined shear forces, generated under both simple shear and uniaxial extensional flow conditions, and by recording the time required to reach the first breakage event. It has been found that the breakage rate of clusters was controlled by the potential well between particles as described by DLVO theory. A semiempirical Arrhenius-type exponential equation that relates the potential well to the breakage rate has been used to fit the simulation results. The dependence of the breakage process on the radius of gyration, on the external shear strength, and on the fractal dimension has been obtained, providing a very general relationship for the breakage rate of clusters. It was also found that the fragment mass distribution is insensitive to the presence of electrostatic repulsive interactions. We also clarify the physical reason for the large difference in the breakage rate of clusters between simple shear and the uniaxial extensional flow using a criterion based on the energy dissipation rate. Finally, in order to answer the question of the minimum cluster size that can break under simple shear conditions, a critical rotation number has been introduced, expressing the maximum number of rotations that a cluster exposed to simple shear could sustain before breakage.