Northeastern University (China)

About: Northeastern University (China) is a education organization based out in Shenyang, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 36087 authors who have published 36125 publications receiving 426807 citations. The organization is also known as: Dōngběi Dàxué & Northeastern University (东北大学).

Open-Set Domain Adaptation in Machinery Fault Diagnostics Using Instance-Level Weighted Adversarial Learning

Abstract: Data-driven machinery fault diagnosis methods have been successfully developed in the past decades. However, the cross-domain diagnostic problems have not been well addressed, where the training and testing data are collected under different operating conditions. Recently, domain adaptation approaches have been popularly used to bridge this gap, which extract domain-invariant features for diagnostics. Despite the effectiveness, most existing methods assume the label spaces of training and testing data are identical that indicates the fault mode sets are the same in different scenarios. In practice, new fault modes usually occur in testing, which makes the conventional methods focusing on marginal distribution alignment less effective. In order to address this problem, a deep learning-based open-set domain adaptation method is proposed in this study. Adversarial learning is introduced to extract generalized features, and an instance-level weighted mechanism is proposed to reflect the similarities of testing samples with known health states. The unknown fault mode can be effectively identified, and the known states can be also recognized. Entropy minimization scheme is further adopted to improve generalization. Experiments on two practical rotating machinery datasets validate the proposed method. The results suggest the proposed method is promising for open-set domain adaptation problems, which largely enhances the applicability of data-driven approaches in the real industries.

Wide Electrochemical Window of Supercapacitors from Coffee Bean‐Derived Phosphorus‐Rich Carbons

Abstract: Phosphorus-rich carbons (PCs) were prepared by phosphoric acid activation of waste coffee grounds in different impregnation ratios. PCs were characterized by nitrogen and carbon dioxide adsorption and X-ray photoelectron spectroscopy. The results indicate that the activation step not only creates a porous structure, but also introduces various phosphorus and oxygen functional groups to the surface of carbons. As evidenced by cyclic voltammetry, galvanostatic charge/discharge, and wide potential window tests, a supercapacitor constructed from PC-2 (impregnation ratio of 2), with the highest phosphorus content, can operate very stably in 1 M H2SO4 at 1.5V with only 18 % degradation after 10 000cycles at a current density of 5A g-1. Due to the wide electrochemical window, a supercapacitor assembled with PC-2 has a high energy density of 15Wh kg-1 at a power density of 75W kg -1. The possibility of widening the potential window above the theoretical potential for the decomposition of water is attributed to reversible electrochemical hydrogen storage in narrow micropores and the positive effect of phosphorus-rich functional groups, particularly the polyphosphates on the carbon surface. Rich pick-me-up! Waste coffee grounds are used to synthesize phosphorus-rich carbons (PCs), which show intriguing properties as electrode materials of an acidic supercapacitor. Large potentials can be applied, owing to the stabilizing effect of phosphorus on the carbon surface and reversible electrochemical hydrogen storage in pores of the PC. Copyright

Dissipativity Theory for Switched Systems

Abstract: A frame work of dissipativity theory for switched systems using multiple storage functions and multiple supply rates is set up. The exchange of "energy" between the activated subsystem and an inactivated subsystem is characterized by cross supply rates. Stability is reached when all supply rates are non-positive, as long as the total exchanged energy between the activated subsystem and any inactivated subsystems is finite. Passivity and L 2 -gain are addressed. For both cases, asymptotic stability is guaranteed under certain "negative" output feedback. Feedback invariance of passivity and a small-gain theorem are also given.