Siu Wing Or

Prof. Siu Wing Or

Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
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Academic Career Length

29Years (1998-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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31 July 2006 in Applied Physics Letters
Verified
Journal Article
Closed access
GYG. L. Yuan
G. L. Yuan
SOSiu Wing Or
Siu Wing Or
JLJ. M. Liu
J. M. Liu
ZLZ. G. Liu
Z. G. Liu
Single-phase Bi1−xNdxFeO3 (BNFOx) (x=0–0.2) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structure and ferroelectromagnetic behavior. Rietveld refinement of x-ray diffraction data showed a continual transformation of crystal structure from the rhombohedral structure of BNFOx=0 (BiFeO3) to a triclinic structure in BNFOx=0.05–0.15 and a pseudotetragonal structure in BNFOx=0.175–0.2. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of ∼9μC∕cm2 in BNFOx=0–0.175, paraelectricity in BNFOx=0.2, and weak ferromagnetism with remnant magnetizations of 0.07–0.227emu∕g in BNFOx=0.15–0.2. Magnetoelectric coupling was obvious in BNFOx=0.15–0.175 near the Néel temperature of ∼380°C.
15 July 2006 in Journal of Applied Physics
Verified
Journal Article
Closed access
GYG. L. Yuan
G. L. Yuan
SOSiu Wing Or
Siu Wing Or
Single-phase Bi0.875Sm0.125FeO3 ceramics were prepared, and their crystal structure and multiferroic properties were studied. The triclinic structure with P1 space group was confirmed in the ceramics by refining the x-ray diffraction data. Large piezoelectric d33 coefficient of 29pC∕N, together with high remnant polarization of 15.09μC∕cm2, was measured at room temperature, suggesting the existence of long-range ferroelectric order on a macroscopic scale. The observed small remnant magnetization of 0.071emu∕g at room temperature as a result of the collapse of the space-modulated spin structure indicated the presence of long-range canted antiferromagnetic order on a macroscopic scale. The coexistence of the long-range ferroelectric and canted antiferromagnetic orders allowed the magnetoelectric effect below the antiferromagnetic Néel temperature of 265°C near which magnetoelectric coupling was obvious.
1 March 2018 in IEEE Transactions on Industrial Electronics
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Journal Article
Closed access
JUN WUJUN WU
JUN WU
CWChaoyong Wu
Chaoyong Wu
SCShuai Cao
Shuai Cao
SOSiu Wing Or
Siu Wing Or
CDChao Deng
Chao Deng
XSXinyu Shao
Xinyu Shao
Time-to-failure (TTF) prognostics plays a crucial role in predicting remaining lifetime of electrical machines for improving machinery health management. This paper presents a novel three-step degradation data-driven TTF prognostics approach for rolling element bearings (REBs) in electrical machines. In degradation feature extraction step, multiple degradation features, including statistical features, intrinsic energy features, and fault frequency features, are extracted to detect the degradation phenomenon of REBs using complete ensemble empirical mode decomposition with adaptive noise and Hilbert-Huang transform methods. In degradation feature reduction step, the degradation features, which are monotonic, robust, and correlative to the fault evolution of the REBs, are selected and fused into a principal component Mahalanobis distance health index using dynamic principal component analysis and Mahalanobis distance methods. In TTF prediction step, the degradation process and local TTF of the REBs are observed by an exponential regression-based local degradation model, and the global TTF is predicted by an empirical Bayesian algorithm with a continuous update. A practical case study involving run-to-failure experiments of REBs on PRONOSTIA platform is provided to validate the effectiveness of the proposed approach and to show a more accurate prediction of TTF than the existing major approaches.
6 February 2006 in Applied Physics Letters
Verified
Journal Article
Closed access
GYG. L. Yuan
G. L. Yuan
SOSiu Wing Or
Siu Wing Or
Single-phase multiferroic Bi1−xNdxFeO3 (x=0–0.15) ceramics are polarized and their piezoelectric and pyroelectric effects are reported. The success in polarizing the ceramics originates from low electrical conductivities controlled predominantly by the Poole-Frenkel conduction mechanism. Limited internal traps due to reduced oxygen vacancies in the ceramics result in sufficiently low leakage current densities of <30mA∕m2 even at a high electric field of 145kV∕cm. The piezoelectric d33 coefficients of the ceramics before and after annealing at 550°C for 4h are measured to be ∼28 and ∼24pC∕N, respectively. These values are higher than those of most major lead-free high-temperature piezoelectric ceramics.
1 April 2006 in Solid State Communications
Verified
Journal Article
Closed access
GYG.L. Yuan
G.L. Yuan
SOSiu Wing Or
Siu Wing Or
YWY.P. Wang
Y.P. Wang
ZLZ.G. Liu
Z.G. Liu
JLJ.M. Liu
J.M. Liu
30 June 2021 in IEEE Transactions on Industry Applications
Verified
Journal Article
Closed access
KZKuan Zhang
Kuan Zhang
Bin ZhouBin Zhou
Bin Zhou
SOSiu Wing Or
Siu Wing Or
CLCanbing Li
Canbing Li
CCChi Yung Chung
Chi Yung Chung
NVNikolai Voropai
Nikolai Voropai
Under the pressure of climate change, the demands for alternative green hydrogen (H 2 ) production methods have been on the rise to conform to the global trend of transition to a H 2 society. This article proposes a multirenewable-to-hydrogen production method to enhance the green H 2 production efficiency for renewable-dominated hydrogen fueling stations (HFSs). In this method, the aqueous electrolysis of native biomass can be powered by wind and solar generations based on electrochemical effects, and both electrolysis current and temperature are taken into account for facilitating on-site H 2 production and reducing the electricity consumption. Moreover, a capsule network based H 2 demand forecasting model is formulated to estimate the gas load for HFS by extracting the underlying spatial features and temporal dependencies of traffic flows in the transportation network. Furthermore, a hierarchical coordinated control strategy is developed to suppress high fluctuations in electrolysis current caused by volatility of wind and solar outputs based on model predictive control framework. Comparative studies validate the superior performance of the proposed methodology over the power-to-gas scheme on electrolysis efficiency and economic benefits.