Monitoring Oil Levels Of Journal Bearings Based On The Analysis Of Vibration Signals

This paper presents a study of monitoring the oil starvation of a journal bearing based on vibration analysis. A diagnostic model is established by includ-ing asperity ploughs and collisions. These excitations are more significant as the oil level is reduced due to less oil film effect. However, it has been found by modulation signal bispectrum analysis that the instable oil whirls can affect the measured responses in the middle frequency range (3.5kHz to 5.5kHz), leading to a good detection of the instability but an inconsistent diagnosis. However, the structural resonances in the high frequency range (5.5kHz to 11kHz) can better reflect the excitations and result in a more agreeable separation of different levels under wide operating conditions

Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy

Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 x 10(-20) A m(2), respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution

Microstructure and mechanical property of diamond-like carbon films with ductile copper incorporation

In this paper, a ductile and non-carbide former Cu was incorporated into diamond-like carbon (DLC) films to modify the microstructure and property of the films using a hybrid ion beam system comprising an ion beam source and a magnetron sputtering unit. The composition, microstructure, residual stress and mechanical property of the DLC films with Cu doping were characterized carefully using X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy, stress-tester, and nanoindentation as a function of Cu concentration. The results reveal that the doped Cu atoms had low solubility in the as-deposited DLC films. The maximum solubility was found to lie around 1.93 at.%. When the Cu concentration was lower than this solubility, the doped Cu atoms dissolved in the carbon matrix, and the film exhibited the typical amorphous structure of DLC and showed a low residual stress and high elastic recovery due to the dissolved Cu atoms which could play a role of the interstitial atoms for stress relaxation through the distortion of the atomic bond length and angle. As the doped concentration exceeded the solubility, Cu nanocrystalline was formed in the carbon matrix, which could significantly improve the elastic resilience of the film through strain release via sliding of the nanocrystalline in the amorphous carbon matrix. It is worth noting that when the doped Cu concentration approached the solubility limit, amorphous nano-clusters were formed in the carbon matrix due to the segregation of Cu, resulting in the decrease of the number of the interstitial atoms, and thus caused the increase in the residual stress and the decline in the elastic recovery. (C) 2015 Elsevier B.V. All rights reserved