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Potential faults can be timely detected through online monitoring to the dissolved gases in the transformer oil so as to improve the safety of the electric power system. Firstly, the online monitoring technology of dissolved gases in the transformer oil is discussed in detail. Then, a low cost monitoring method to the characteristics gas dissolved in the(More)
During the Hilbert-Huang transformation (HHT), time-series data are firstly decomposed into several components with different time scale (i.e. intrinsic mode function, IMF), using the empirical mode decomposition (EMD). Then, the Hilbert transformation is applied to every IMF. As a result, the HHT spectrum of the data is constructed. In this paper, the(More)
As the optical penetration depth and thermal diffusion effect are small, shear waves and longitudinal waves generated by a laser pulse in thermoelastic regime are generally weak in metallic materials. The method of laser ultrasonic is rarely applied to inspect the inner cracks. In this paper, phased array laser ultrasonic is developed to focus and steer(More)
The generation and propagation of surface acoustic waves (SAW) in an aluminum rod with variable cross-section subjected to laser beam illumination has been studied quantitatively by using the finite element method (FEM). The physical model of laser-induced SAW in the rod was built and the effects of the variable cross-section of the rod, the line source's(More)
—This paper presents a systematic approach to exponentially stabilize the periodic orbits of multi-domain hybrid systems arising from 3D bipedal walking. Firstly, the method of Poincaré sections is extended to the hybrid systems with multiple domains. Then, based on the properties of the Poincaré maps, a continuous piecewise feedback control strategy is(More)
Thickness measurement is highly useful in industrials both for controlling the thickness of the product and for material characterization considering both mechanical and chemical properties. Longitudinal ultrasonic velocity can be used to measure material thickness provided that sufficient accuracy can be achieved. A new laser ultrasonic thickness(More)
This paper presents a novel type of tree-climbing robot. The main parts of the robot are 2 vehicles, which are attached on the trunk of a tree and were stick tightly on the tree because of a holding device. A kind of spine array is distributed on the wheels, and the friction is enhanced. Static stress analysis shows that the robot can overcome gravity and(More)
Unbalance, fatigue crack and rotor-stator rub are the three common and important faults in a rotor-bearing system. They are originally interconnected each other, and their vibration behaviors do often show strong nonlinear and transient characteristic, especially when more than one of them coexist in the system. This article is aimed to study the vibration(More)
Compound faults diagnosis is an important but difficult task in diagnostics. When several faults arise at the same time, vibration measurements by sensors show themselves as a complex integrated symptom, not as a simple and linear combination of several single faults, which makes it difficult to detect compound faults correctly. We proposed a new ICA-SOM(More)