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Prof. Siu Wing Or
Department of Electrical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

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Research Keywords & Expertise

0 Electromagnetic absorption and shielding
0 Multifunctional smart materials, devices and applications
0 IoT sensing and condition monitoring
0 Energy harvesting, conversion, storage and management
0 Catalyses and catalysts

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Journal article
Published: 30 June 2021 in IEEE Transactions on Industry Applications
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Under the pressure of climate change, the demands for alternative green hydrogen H2 production methods have been on the rise to conform to the global trend of transition to a H2 society. This paper proposes a multi-renewable-to-hydrogen production method to enhance the green H2 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 of electrolysis current and temperature are taken into account for facilitating on-site H2 production and reducing the electricity consumption. Moreover, a capsule network (CN)-based H2 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 (MPC) framework. Comparative studies validate the superior performance of the proposed methodology over the power-to-gas (P2G) scheme on electrolysis efficiency and economic benefits.

ACS Style

Kuan Zhang; Bin Zhou; Siu Wing Or; Canbing Li; Chi Yung Chung; Nikolai Ivanovich Voropai. Optimal Coordinated Control of Multi-Renewable-to-Hydrogen Production System for Hydrogen Fueling Stations. IEEE Transactions on Industry Applications 2021, PP, 1 -1.

AMA Style

Kuan Zhang, Bin Zhou, Siu Wing Or, Canbing Li, Chi Yung Chung, Nikolai Ivanovich Voropai. Optimal Coordinated Control of Multi-Renewable-to-Hydrogen Production System for Hydrogen Fueling Stations. IEEE Transactions on Industry Applications. 2021; PP (99):1-1.

Chicago/Turabian Style

Kuan Zhang; Bin Zhou; Siu Wing Or; Canbing Li; Chi Yung Chung; Nikolai Ivanovich Voropai. 2021. "Optimal Coordinated Control of Multi-Renewable-to-Hydrogen Production System for Hydrogen Fueling Stations." IEEE Transactions on Industry Applications PP, no. 99: 1-1.

Journal article
Published: 29 May 2021 in Ceramics International
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Al2O3–Ti(C,N) ceramics were fabricated via carbothermal reduction nitridation method with high-titania special-grade bauxite as the raw material. The formation mechanism of in-situ Ti(C,N) phase and its effect on the properties of materials are discussed. After nitrided at 1700 °C, Ti(C,N) phase could be formed in-situ with appropriate C/TiO2 molar ratio. Due to the residual stress field formed by Ti(C,N) particles, the path of crack propagation is changed, leading to the crack deflection and pinning. Therefore, the mechanical properties of the materials are improved by forming in-situ Ti(C,N) phase. With a C/TiO2 molar ratio of 2.2 and nitridation temperature of 1700 °C, Al2O3–Ti(C,N) ceramic with a hardness of 13.9 GPa, a fracture toughness of 8.28 MPa m1/2 and a flexural strength of 387 MPa could be fabricated.

ACS Style

Ziyan Li; Lvping Fu; Huazhi Gu; Siu Wing Or; Ao Huang; Renxiang Lv. Fabrication of in-situ Ti(C,N) phase toughened Al2O3 based ceramics from natural bauxite. Ceramics International 2021, 47, 25497 -25504.

AMA Style

Ziyan Li, Lvping Fu, Huazhi Gu, Siu Wing Or, Ao Huang, Renxiang Lv. Fabrication of in-situ Ti(C,N) phase toughened Al2O3 based ceramics from natural bauxite. Ceramics International. 2021; 47 (18):25497-25504.

Chicago/Turabian Style

Ziyan Li; Lvping Fu; Huazhi Gu; Siu Wing Or; Ao Huang; Renxiang Lv. 2021. "Fabrication of in-situ Ti(C,N) phase toughened Al2O3 based ceramics from natural bauxite." Ceramics International 47, no. 18: 25497-25504.

Journal article
Published: 25 May 2021 in Ceramics International
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In this study, Al2O3-based ceramics were fabricated with natural bauxite powder as the raw material. The phase compositions evolution behavior during the heat treatment and its influence on the properties of fabricated ceramics were investigated. With increasing heat treatment temperature, the sintering degree of high-titania special-grade bauxite became better. The samples showed decreased porosity, increased bulk density, Vickers hardness, fracture toughness and flexural strength. However, when the heat temperature increased to 1650 °C, decomposition of tieillite occurs in sample, leading to increased Al2O3 and TiO2 content in the liquid phase. Corundum and mullite grains with anisotropic growth appeared in the samples, leading to a decrease in the density, the Vickers hardness and flexural strength of samples decreased consequently. However, those anisotropic grains could prolong the crack propagation path and improve the fracture toughness of the material.

ACS Style

Riqing Du; Lvping Fu; Huazhi Gu; Siu Wing Or; Ao Huang; Renxiang Lv; Qiong Luo. Evolution on phase composition and properties of alumina-based ceramics fabricated from high-titania special-grade natural bauxite micropowder. Ceramics International 2021, 1 .

AMA Style

Riqing Du, Lvping Fu, Huazhi Gu, Siu Wing Or, Ao Huang, Renxiang Lv, Qiong Luo. Evolution on phase composition and properties of alumina-based ceramics fabricated from high-titania special-grade natural bauxite micropowder. Ceramics International. 2021; ():1.

Chicago/Turabian Style

Riqing Du; Lvping Fu; Huazhi Gu; Siu Wing Or; Ao Huang; Renxiang Lv; Qiong Luo. 2021. "Evolution on phase composition and properties of alumina-based ceramics fabricated from high-titania special-grade natural bauxite micropowder." Ceramics International , no. : 1.

Journal article
Published: 12 May 2021 in Renewable Energy
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Spatio-temporal wind speed prediction is of great significance to the grid-connected operation of multiple wind farms in smart grid. This paper proposes a spatio-temporal wind speed prediction method based on capsule network (CapsNet) for geographically dispersed wind farms over a region. In the proposed method, the historical wind speed data from the wind farms are originally converted into chronological images in a 3D space, and the spatial features implicit in the images are extracted by the convolutional operation. Then, the temporal information of wind speed spatial properties is encapsulated in multi-dimensional time-capsules and learned by the dynamic routing mechanism, thus capturing the nonlinear temporal dependencies based on the extracted spatial features. A regression layer activated by the leaky rectified linear unit (Leaky ReLU) function integrates the spatio-temporal features and generates the final prediction results. Furthermore, a two-layer iterative training approach is employed to well-tune the model parameters and accelerate the convergence speed. Finally, the real data of multiple wind farms from Ohio are collected in the case studies to demonstrate the superior performance of the proposed method compared with other forecasting methods.

ACS Style

Ling Zheng; Bin Zhou; Siu Wing Or; Yijia Cao; Huaizhi Wang; Yong Li; Ka Wing Chan. Spatio-temporal wind speed prediction of multiple wind farms using capsule network. Renewable Energy 2021, 175, 718 -730.

AMA Style

Ling Zheng, Bin Zhou, Siu Wing Or, Yijia Cao, Huaizhi Wang, Yong Li, Ka Wing Chan. Spatio-temporal wind speed prediction of multiple wind farms using capsule network. Renewable Energy. 2021; 175 ():718-730.

Chicago/Turabian Style

Ling Zheng; Bin Zhou; Siu Wing Or; Yijia Cao; Huaizhi Wang; Yong Li; Ka Wing Chan. 2021. "Spatio-temporal wind speed prediction of multiple wind farms using capsule network." Renewable Energy 175, no. : 718-730.

Journal article
Published: 10 September 2020 in International Journal of Electrical Power & Energy Systems
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Short-term predictions of wind power and its ramp events play a critical role in economic operation and risk management of smart grid. This paper proposes a hybrid forecasting model based on semi-supervised generative adversarial network (GAN) to solve the short-term wind power outputs and ramp event forecasting problems. In the proposed model, the original time series of wind energy data can be decomposed into several sub-series characterized by intrinsic mode functions (IMFs) with different frequencies, and the semi-supervised regression with label learning is employed for data augmentation to extract non-linear and dynamic behaviors from each IMF. Then, the GAN generative model is used to obtain unlabeled virtual samples for capturing data distribution characteristics of wind power outputs, while the discriminative model is redesigned with a semi-supervised regression layer to perform the point prediction of wind power. These two GAN models form a min-max game so as to improve the sample generation quality and reduce forecasting errors. Moreover, a self-tuning forecasting strategy with multi-label classifier is proposed to facilitate the forecasting of wind power ramp events. Finally, the real data of a wind farm from Belgium is collected in the case study to demonstrate the superior performance of the proposed approach compared with other forecasting algorithms.

ACS Style

Bin Zhou; Haoran Duan; Qiuwei Wu; Huaizhi Wang; Siu Wing Or; Ka Wing Chan; Yunfan Meng. Short-term prediction of wind power and its ramp events based on semi-supervised generative adversarial network. International Journal of Electrical Power & Energy Systems 2020, 125, 106411 .

AMA Style

Bin Zhou, Haoran Duan, Qiuwei Wu, Huaizhi Wang, Siu Wing Or, Ka Wing Chan, Yunfan Meng. Short-term prediction of wind power and its ramp events based on semi-supervised generative adversarial network. International Journal of Electrical Power & Energy Systems. 2020; 125 ():106411.

Chicago/Turabian Style

Bin Zhou; Haoran Duan; Qiuwei Wu; Huaizhi Wang; Siu Wing Or; Ka Wing Chan; Yunfan Meng. 2020. "Short-term prediction of wind power and its ramp events based on semi-supervised generative adversarial network." International Journal of Electrical Power & Energy Systems 125, no. : 106411.

Journal article
Published: 01 September 2020 in APL Materials
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Hydrogels with unique three-dimensional (3D) macroscopic porous architectures are attractive electrode materials for supercapacitors because of their superior electrolyte permeabilities and rapid electron/ion transports. In this letter, a cylindrical-type 3D macroscopic graphene/MXene-based hydrogel (GMH) is prepared by self-assembling laminar-structured graphene oxide (GO) and MXene (Ti3C2) nanosheets via a facile one-step hydrothermal method under the existence of ammonia water and hydrazine hydrate. GO is found to self-converge into a 3D macroscopic porous graphene framework during the hydrothermal process, while Ti3C2 nanosheets are able to prevent the graphene nanosheets from self-restacking. The as-prepared GMH shows a larger specific surface area of 161.1 m2 g−1 and a higher pore volume of 0.5 cm3 g−1 in comparison with the pure graphene hydrogel. A symmetric supercapacitor utilizing GMH as electrodes exhibits high energy densities of 9.3 Wh kg−1 and 5.7 Wh kg−1 at different power densities of 500 W kg−1 and 5000 W kg−1, respectively, as well as an outstanding long-term cycle stability with no loss in capacitance in excess of 10 000 continuous charge–discharge cycles. The strategy of preparation of a 3D macroscopic GMH is expected to realize promising high-performance hydrogel electrodes based on graphene and MXene for electrochemical energy storages.

ACS Style

Luojiang Zhang; Siu Wing Or. Self-assembled three-dimensional macroscopic graphene/MXene-based hydrogel as electrode for supercapacitor. APL Materials 2020, 8, 091101 .

AMA Style

Luojiang Zhang, Siu Wing Or. Self-assembled three-dimensional macroscopic graphene/MXene-based hydrogel as electrode for supercapacitor. APL Materials. 2020; 8 (9):091101.

Chicago/Turabian Style

Luojiang Zhang; Siu Wing Or. 2020. "Self-assembled three-dimensional macroscopic graphene/MXene-based hydrogel as electrode for supercapacitor." APL Materials 8, no. 9: 091101.

Journal article
Published: 07 July 2020 in IEEE Access
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Traditional speed control of permanent magnet synchronous motors (PMSMs) includes a cascaded speed loop with proportional-integral (PI) regulators. The output of this outer speed loop, i.e. electromagnetic torque reference, is in turn fed to either the inner current controller or the direct torque controller. This cascaded control structure leads to relatively slow dynamic response, and more importantly, larger speed ripples. This paper presents a new dual cost function model predictive direct speed control (DCF-MPDSC) with duty ratio optimization for PMSM drives. By employing accurate system status prediction, optimized duty ratios between one zero voltage vector and one active voltage vector are firstly deduced based on the deadbeat criterion. Then, two separate cost functions are formulated sequentially to refine the combinations of voltage vectors, which provide two-degree-of-freedom control capability. Specifically, the first cost function results in better dynamic response, while the second one contributes to speed ripple reduction and steady-state offset elimination. The proposed control strategy has been validated by both Simulink simulation and hardware-in-the-loop (HIL) experiment. Compared to existing control methods, the proposed DCF-MPDSC can reach the speed reference rapidly with very small speed ripple and offset.

ACS Style

Ming Liu; Jiefeng Hu; Ka Wing Chan; Siu Wing Or; Siu Lau Ho; Wenzheng Xu; Xian Zhang. Dual Cost Function Model Predictive Direct Speed Control With Duty Ratio Optimization for PMSM Drives. IEEE Access 2020, 8, 126637 -126647.

AMA Style

Ming Liu, Jiefeng Hu, Ka Wing Chan, Siu Wing Or, Siu Lau Ho, Wenzheng Xu, Xian Zhang. Dual Cost Function Model Predictive Direct Speed Control With Duty Ratio Optimization for PMSM Drives. IEEE Access. 2020; 8 ():126637-126647.

Chicago/Turabian Style

Ming Liu; Jiefeng Hu; Ka Wing Chan; Siu Wing Or; Siu Lau Ho; Wenzheng Xu; Xian Zhang. 2020. "Dual Cost Function Model Predictive Direct Speed Control With Duty Ratio Optimization for PMSM Drives." IEEE Access 8, no. : 126637-126647.

Journal article
Published: 20 May 2020 in International Journal of Electrical Power & Energy Systems
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The lifetime cycle and secured service of buried transformers are constrained by their thermal insulation and loading conditions. This paper proposes an extended thermal circuit model for direct-buried transformer substations to dynamically evaluate the transformer loading capability. In the proposed model, the underground thermal interactions and energy balances among heat generation, transfer and storage in the transformer substation are represented with nonlinear thermal resistances and capacitances based on thermal-electrical analogies, and then hot-spot temperature (HST) dynamics can be captured from the nodal analysis on this R-C thermal equivalent circuit. Furthermore, the underground thermal accumulative effect is investigated for dynamic loading capability assessment considering the combined impact of heat accumulation in the surrounding soil caused by fluctuating transformer loads during prior operating periods. Finally, the finite element analysis with measured data is implemented for parameter tuning and model verification of the proposed thermodynamic model, and numerical simulations confirm the improvements of the proposed model for the transformer life extension and load management.

ACS Style

Bin Zhou; Xiaolin Xu; Siu Wing Or; Canbing Li; Qiuwei Wu; Cong Zhang; Wenfang Li. Thermodynamic modelling of buried transformer substations for dynamic loading capability assessment considering underground heat accumulative effect. International Journal of Electrical Power & Energy Systems 2020, 121, 106153 .

AMA Style

Bin Zhou, Xiaolin Xu, Siu Wing Or, Canbing Li, Qiuwei Wu, Cong Zhang, Wenfang Li. Thermodynamic modelling of buried transformer substations for dynamic loading capability assessment considering underground heat accumulative effect. International Journal of Electrical Power & Energy Systems. 2020; 121 ():106153.

Chicago/Turabian Style

Bin Zhou; Xiaolin Xu; Siu Wing Or; Canbing Li; Qiuwei Wu; Cong Zhang; Wenfang Li. 2020. "Thermodynamic modelling of buried transformer substations for dynamic loading capability assessment considering underground heat accumulative effect." International Journal of Electrical Power & Energy Systems 121, no. : 106153.

Journal article
Published: 30 March 2020 in IEEE Transactions on Transportation Electrification
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Three-phase Z-source inverters provide a solution of voltage boosting by a single-stage topology. They are also capable of bi-directional operation as rectifiers, thus have great potential for applications in the field of transportation electrification such as Vehicle-to-Grid (V2G) chargers. In this paper, three new modulation schemes for three-phase Z-source converters are proposed and investigated. The best performed one is further developed to a closed-loop PI control method. While the voltage conversion ratio is flexible, the output voltage Total Harmonics Distortion (THD) is below 3% within the voltage ratio range of 0.5 to 2.5. The effectiveness of the proposed method has been fully validated in MATLAB/Simulink simulations and RTLAB Hardware-In-Loop (HIL) experiments based on the realtime simulator OPAL-RT OP4510. Compared to existing control methods, the proposed one performs better with reduced harmonics, flexible voltage gain, and simpler control algorithm.

ACS Style

Wenzheng Xu; Ka Wing Chan; Siu Wing Or; Siu Lau Ho; Ming Liu. A Low-Harmonic Control Method of Bidirectional Three-Phase Z-Source Converters for Vehicle-to-Grid Applications. IEEE Transactions on Transportation Electrification 2020, 6, 464 -477.

AMA Style

Wenzheng Xu, Ka Wing Chan, Siu Wing Or, Siu Lau Ho, Ming Liu. A Low-Harmonic Control Method of Bidirectional Three-Phase Z-Source Converters for Vehicle-to-Grid Applications. IEEE Transactions on Transportation Electrification. 2020; 6 (2):464-477.

Chicago/Turabian Style

Wenzheng Xu; Ka Wing Chan; Siu Wing Or; Siu Lau Ho; Ming Liu. 2020. "A Low-Harmonic Control Method of Bidirectional Three-Phase Z-Source Converters for Vehicle-to-Grid Applications." IEEE Transactions on Transportation Electrification 6, no. 2: 464-477.

Journal article
Published: 08 February 2020 in Electrochimica Acta
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[email protected], hierarchically porous manganese oxide/cobalt [email protected] carbon (MnO/[email protected]–C) nanorods with interstitially decorated CoMn2O4 nanoparticles are synthesized via one-step carbonization of metal–organic framework (MOF)-coated α˗manganese oxide (α[email protected]) nanorods and are evaluated as bifunctional electrocatalytic cathodes for Li–O2 batteries (LOBs) to improve the bifunctionality, specific discharge capacity, and cyclability of α˗MnO2 nanorod cathode-based LOBs. The MnO/[email protected]–C nanorods feature a MnO nanorod core with CoMn2O4 nanoparticle interstitial decoration, both coated by an N–C conductive shell. The MnO core renders Mn active sites and oxygen vacancies, while the CoMn2O4 interstitial decoration gives additional Mn, Co active sites, thereby enhancing bifunctional electrocatalytic ORR–OER. The N–C shell increases electronic conductivity, hierarchical porosity, specific surface area, and protects the core and interstitial decoration against lithium peroxide (Li2O2) passivation. The improved structural features allow the MnO/[email protected]–C nanorod cathode-based LOB cells to exhibit superior full specific discharge capacity of 8,625 mAh·g−1 and cyclability of 48 discharge–charge cycles at 200 mA·g−1 specific current and 2000 mAhg−1 limited specific discharge capacity compared to their α˗MnO2 nanorod counterparts. An ORR–OER mechanism is proposed to describe the interesting formation of particle- and film-type Li2O2 deposits at different cycles for the MnO/[email protected]–C nanorod cathodes. Such MOF-derived, interstitial nanoparticle-decorated nanoarchitectures can lead to high-performance tunable bifunctional electrocatalysts.

ACS Style

Amrita Chatterjee; Siu Wing Or. Metal–organic framework-derived MnO/[email protected]–C nanorods with nanoparticle interstitial decoration in [email protected] structure as improved bifunctional electrocatalytic cathodes for Li–O2 batteries. Electrochimica Acta 2020, 338, 135809 .

AMA Style

Amrita Chatterjee, Siu Wing Or. Metal–organic framework-derived MnO/[email protected]–C nanorods with nanoparticle interstitial decoration in [email protected] structure as improved bifunctional electrocatalytic cathodes for Li–O2 batteries. Electrochimica Acta. 2020; 338 ():135809.

Chicago/Turabian Style

Amrita Chatterjee; Siu Wing Or. 2020. "Metal–organic framework-derived MnO/[email protected]–C nanorods with nanoparticle interstitial decoration in [email protected] structure as improved bifunctional electrocatalytic cathodes for Li–O2 batteries." Electrochimica Acta 338, no. : 135809.

Journal article
Published: 13 November 2019 in Catalysts
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Core/shell-structured FeSn2/onion-like carbon (FeSn2/OLC) nanocapsules of confined size range of sub-50 nm are synthesized via an in-situ arc-discharge process, and are evaluated in comparison with FeSn2 nanoparticles as an improved stannide-based electrocatalytic anode material for Li-ion batteries (LIBs). The in-situ arc-discharge process allows a facile one-pot procedure for forming crystalline FeSn2 stannide alloy nanoparticle cores coated by defective OLC thin shells in addition to a confined crystal growth of the FeSn2 nanoparticle cores. The LIB cells assembled using the FeSn2/OLC nanocapsules as the electrocatalytic anodes exhibit superior full specific discharge capacity of 519 mAh·g−1 and specific discharge capacity retention of ~62.1% after 100 charge-discharge cycles at 50 mA·g−1 specific current. The electrochemical stability of FeSn2/OLC nanocapsules is demonstrated from the good cycle stability of the LIBs with a high specific discharge capacity retention of 67.5% on a drastic change in specific current from 4000 to 50 mA·g−1. A formation mechanism is proposed to describe the confined crystal growth of the FeSn2 nanoparticle cores and the formation of the FeSn2/OLC core/shell structure. The observed electrochemical performance enhancement is ascribed to the synergetic effects of the enabling of a reversible lithiation process during charge-discharge of the LIB cells by the FeSn2 nanoparticle cores as well as the protection of the FeSn2 nanoparticle cores from volume change-induced pulverization and solid electrolyte interphase-induced passivation by the OLC shells.

ACS Style

Dandan Han; Amrita Chatterjee; Long Hin Man; Siu Wing Or. In-Situ Arc Discharge-Derived FeSn2/Onion-Like Carbon Nanocapsules as Improved Stannide-Based Electrocatalytic Anode Materials for Lithium-Ion Batteries. Catalysts 2019, 9, 950 .

AMA Style

Dandan Han, Amrita Chatterjee, Long Hin Man, Siu Wing Or. In-Situ Arc Discharge-Derived FeSn2/Onion-Like Carbon Nanocapsules as Improved Stannide-Based Electrocatalytic Anode Materials for Lithium-Ion Batteries. Catalysts. 2019; 9 (11):950.

Chicago/Turabian Style

Dandan Han; Amrita Chatterjee; Long Hin Man; Siu Wing Or. 2019. "In-Situ Arc Discharge-Derived FeSn2/Onion-Like Carbon Nanocapsules as Improved Stannide-Based Electrocatalytic Anode Materials for Lithium-Ion Batteries." Catalysts 9, no. 11: 950.

Journal article
Published: 14 December 2018 in Optik
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In this paper, on the basis of considering the influence of charged particles’ (electrons and ions) flow velocity, the absorption characteristic of dusty plasma in THz region is studied. Firstly, based on the model of conductivity which has considered the effect of flow velocity, the absorption coefficient is deduced. And then, the dependence of absorption coefficient on the flow velocity is discussed, which manifests that the absorption coefficient has a turning point (minimum) in the relation. In particular, it is found that the minimal absorption coefficient does not appear at when the flow velocity is comparable to the thermal velocity, which is different from that of the complex conductivity. Finally, the condition where the minimal absorption coefficient appears is theoretically deduced.

ACS Style

Xiao-Gu Huang; Yun-Yun Chen; Ming-Ye Li; Siu-Wing Or. Effect of charged particles’ flow velocity on THz absorption characteristic of dusty plasma. Optik 2018, 181, 666 -672.

AMA Style

Xiao-Gu Huang, Yun-Yun Chen, Ming-Ye Li, Siu-Wing Or. Effect of charged particles’ flow velocity on THz absorption characteristic of dusty plasma. Optik. 2018; 181 ():666-672.

Chicago/Turabian Style

Xiao-Gu Huang; Yun-Yun Chen; Ming-Ye Li; Siu-Wing Or. 2018. "Effect of charged particles’ flow velocity on THz absorption characteristic of dusty plasma." Optik 181, no. : 666-672.

Short communication
Published: 10 December 2018 in Materials Letters
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In this paper, Co-doped ZnO nanoparticle and nanofiber were prepared by electrospinning method. The results showed that Co-doped ZnO nanofiber performed bead-like fibrous shape and exhibited ferromagnetic properties. The dielectric loss and magnetic loss properties of Co-doped ZnO nanofiber were much better than that of Co-doped ZnO nanoparticle due to the improvement of dipole polarization, interfacial polarization and shape anisotropic. The absorptivity of Co-doped ZnO nanofiber can reach to 70% in the frequency range of 5.3-18 GHz when the coating thickness is 1.5-4.0 mm. It is demonstrated that the bead-like fibrousshape is beneficial to optimize electromagnetic loss and microwave absorption properties of Co-doped ZnO.

ACS Style

Xiaogu Huang; Siu Wing Or. Unique electromagnetic loss properties of Co-doped ZnO Nanofiber. Materials Letters 2018, 238, 271 -274.

AMA Style

Xiaogu Huang, Siu Wing Or. Unique electromagnetic loss properties of Co-doped ZnO Nanofiber. Materials Letters. 2018; 238 ():271-274.

Chicago/Turabian Style

Xiaogu Huang; Siu Wing Or. 2018. "Unique electromagnetic loss properties of Co-doped ZnO Nanofiber." Materials Letters 238, no. : 271-274.

Journals
Published: 21 November 2018 in Dalton Transactions
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3D heterostructured [email protected] networks were grown directly on nickel foam for the positive electrode of a high-performance hybrid supercapacitor.

ACS Style

Luojiang Zhang; Kwan San Hui; Siu Wing Or. 3D heterostructured cobalt [email protected] double hydroxide core–shell networks on nickel foam for high-performance hybrid supercapacitor. Dalton Transactions 2018, 48, 150 -157.

AMA Style

Luojiang Zhang, Kwan San Hui, Siu Wing Or. 3D heterostructured cobalt [email protected] double hydroxide core–shell networks on nickel foam for high-performance hybrid supercapacitor. Dalton Transactions. 2018; 48 (1):150-157.

Chicago/Turabian Style

Luojiang Zhang; Kwan San Hui; Siu Wing Or. 2018. "3D heterostructured cobalt [email protected] double hydroxide core–shell networks on nickel foam for high-performance hybrid supercapacitor." Dalton Transactions 48, no. 1: 150-157.

Correction
Published: 20 September 2018 in Nanomaterials
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The authors wish to add the following information to this paper

ACS Style

Amrita Chatterjee; Siu Wing Or; Yulin Cao. Correction: Chatterjee, A.; et al. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries. Nanomaterials 2018, 8, 308. Nanomaterials 2018, 8, 748 .

AMA Style

Amrita Chatterjee, Siu Wing Or, Yulin Cao. Correction: Chatterjee, A.; et al. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries. Nanomaterials 2018, 8, 308. Nanomaterials. 2018; 8 (10):748.

Chicago/Turabian Style

Amrita Chatterjee; Siu Wing Or; Yulin Cao. 2018. "Correction: Chatterjee, A.; et al. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries. Nanomaterials 2018, 8, 308." Nanomaterials 8, no. 10: 748.

Journal article
Published: 05 September 2018 in IEEE Transactions on Magnetics
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We report an obvious improvement in gigahertz electromagnetic (EM) absorption properties in novel core/shell-structured magnetic/dielectric nanocapsule-decorated nanocapsule hybrids, featuring Fe/C nanocapsules of ~ 4 nm mean diameter decorated on the surfaces of Fe₂B/C nanocapsules of ~ 50 nm mean diameter (denoted as Fe/[email protected]₂B/C hybrids), as a result of the simultaneously enhanced dielectric and magnetic losses by an increased interfacial polarization at the Fe/C and Fe₂B/C heterogeneous interfaces and an additional tip effect by the decoration of small Fe/C nanocapsules. The phase, morphology, microstructure, and magnetization of the Fe/[email protected]₂B/C hybrids are investigated using various methods, and their EM absorption properties are evaluated in paraffin-bonded composites with 50 wt.% hybrids over the 2-18 GHz range. The results indicate a giant reflection loss (RL) of -49.5 dB at 10.5 GHz and a broad effective absorption bandwidth (for RL < -10 dB) of 8 GHz at a thin composite thickness of 2.1 mm. An extremely broad coverage of effective absorption bandwidth from 2.5 to 18 GHz is obtained at a very wide composite thickness range of 1-6 mm. The present study provides a new prospective for realizing high-performance EM absorbers at gigahertz frequencies.

ACS Style

Xianguo Liu; Mingji Zhang; Siu Wing Or; Siu Lau Ho. Fe/C Nanocapsule-Decorated Fe2B/C Nanocapsule Hybrids With Improved Gigahertz Electromagnetic Absorption Properties. IEEE Transactions on Magnetics 2018, 55, 1 -5.

AMA Style

Xianguo Liu, Mingji Zhang, Siu Wing Or, Siu Lau Ho. Fe/C Nanocapsule-Decorated Fe2B/C Nanocapsule Hybrids With Improved Gigahertz Electromagnetic Absorption Properties. IEEE Transactions on Magnetics. 2018; 55 (2):1-5.

Chicago/Turabian Style

Xianguo Liu; Mingji Zhang; Siu Wing Or; Siu Lau Ho. 2018. "Fe/C Nanocapsule-Decorated Fe2B/C Nanocapsule Hybrids With Improved Gigahertz Electromagnetic Absorption Properties." IEEE Transactions on Magnetics 55, no. 2: 1-5.

Journal article
Published: 01 September 2018 in Materials & Design
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Core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflakes possessing in-plane [111] easy magnetization (M) and out-of-plane interfacial polarization (P) are synthesized by a three-step liquid chemical method, and their physicochemical properties and growth mechanism are investigated. Three characteristic types of paraffin-bonded ring-shaped nanoflake composites having random (R), vertical–horizontal (V–H), and horizontal–vertical (H–V) orientations of the orthogonal M and P to their two major surfaces are prepared by randomly, vertically, and horizontally aligning the nanoflakes in the paraffin matrix under a magnetic alignment and thermal curing process. The composites are evaluated experimentally and theoretically in the L–Ku (1–18 GHz) bands of microwaves in order to investigate the orientation effect of the orthogonal M and P on their microwave electromagnetic properties. The in-plane M in the H–V-oriented composite and the out-of-plane P in the V–H-oriented composite, which are parallel to the effective magnetic and electric field vectors of incident microwaves, result in a significant enhancement in permeability with multiple magnetic natural resonances and an obvious improvement in permittivity in comparison with other composites, respectively. The observations agree with the theoretical predictions based on the Landau–Lifshitz–Gilbert equation and Bruggeman's effective medium theory for permeability and the Debye's polarization theory for permittivity. As a result, the H–V-oriented composite achieves the best microwave electromagnetic impedance matching and absorption with a broad absorbing bandwidth of 4 GHz, a wide thickness range of 7–10 mm, and a minimal reflection loss of −41.5 dB in the Ku (12–18 GHz) band.

ACS Style

Jiaheng Wang; Siu Wing Or; Jun Tan. Enhanced microwave electromagnetic properties of core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflake composites with preferred magnetization and polarization orientations. Materials & Design 2018, 153, 190 -202.

AMA Style

Jiaheng Wang, Siu Wing Or, Jun Tan. Enhanced microwave electromagnetic properties of core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflake composites with preferred magnetization and polarization orientations. Materials & Design. 2018; 153 ():190-202.

Chicago/Turabian Style

Jiaheng Wang; Siu Wing Or; Jun Tan. 2018. "Enhanced microwave electromagnetic properties of core/shell/shell-structured Ni/SiO2/polyaniline hexagonal nanoflake composites with preferred magnetization and polarization orientations." Materials & Design 153, no. : 190-202.

Journal article
Published: 01 July 2018 in Ceramics International
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Yinghua Tang; Huafang Yang; Xiaogu Huang; Lixi Wang; Qitu Zhang; Siu Wing Or. Low-pressure assisted solution synthesis of CH3NH3PbI3-Cl perovskite solar cells. Ceramics International 2018, 44, 11603 -11609.

AMA Style

Yinghua Tang, Huafang Yang, Xiaogu Huang, Lixi Wang, Qitu Zhang, Siu Wing Or. Low-pressure assisted solution synthesis of CH3NH3PbI3-Cl perovskite solar cells. Ceramics International. 2018; 44 (10):11603-11609.

Chicago/Turabian Style

Yinghua Tang; Huafang Yang; Xiaogu Huang; Lixi Wang; Qitu Zhang; Siu Wing Or. 2018. "Low-pressure assisted solution synthesis of CH3NH3PbI3-Cl perovskite solar cells." Ceramics International 44, no. 10: 11603-11609.

Journal article
Published: 07 May 2018 in Nanomaterials
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As a step towards efficient and cost-effective electrocatalytic cathodes for Li–O2 batteries, highly porous hausmannite-type Mn3O4 hollow nanocages (MOHNs) of a large diameter of ~250 nm and a high surface area of 90.65 m2·g−1 were synthesized and their physicochemical and electrochemical properties were studied in addition to their formation mechanism. A facile approach using carbon spheres as the template and MnCl2 as the precursor was adopted to suit the purpose. The MOHNs/Ketjenblack cathode-based Li–O2 battery demonstrated an improved cyclability of 50 discharge–charge cycles at a specific current of 400 mA·g−1 and a specific capacity of 600 mAh·g−1. In contrast, the Ketjenblack cathode-based one can sustain only 15 cycles under the same electrolytic system comprised of 1 M LiTFSI/TEGDME. It is surmised that the unique hollow nanocage morphology of MOHNs is responsible for the high electrochemical performance. The hollow nanocages were a result of the aggregation of crystalline nanoparticles of 25–35 nm size, and the mesoscopic pores between the nanoparticles gave rise to a loosely mesoporous structure for accommodating the volume change in the MOHNs/Ketjenblack cathode during electrocatalytic reactions. The improved cyclic stability is mainly due to the faster mass transport of the O2 through the mesoscopic pores. This work is comparable to the state-of-the-art experimentations on cathodes for Li–O2 batteries that focus on the use of non-precious transition materials.

ACS Style

Amrita Chatterjee; Siu Wing Or; Yulin Cao. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries. Nanomaterials 2018, 8, 308 .

AMA Style

Amrita Chatterjee, Siu Wing Or, Yulin Cao. Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries. Nanomaterials. 2018; 8 (5):308.

Chicago/Turabian Style

Amrita Chatterjee; Siu Wing Or; Yulin Cao. 2018. "Transition Metal Hollow Nanocages as Promising Cathodes for the Long-Term Cyclability of Li–O2 Batteries." Nanomaterials 8, no. 5: 308.

Journal article
Published: 09 April 2018 in Materials & Design
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(Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) multilayer thin films with different thicknesses of 100–700 nm, corresponding to 2–14 layers with each layer of ~50 nm thickness, are synthesized on Pt(111)/Ti/SiO2/Si substrates to form Pt/NKBT/Pt/Ti/SiO2/Si heterostructures using different spin-coating and annealing conditions in a modified aqueous sol-gel process. The multilayer thin films spin-coated by two steps (step 1/2) at 600/4000 rpm for 6/30 s and annealed at 700 °C for 5 min with a heating rate of 30 °C/s show a dense, uniform, and continuous morphology as well as a pure perovskite structure with a rhombohedral–tetragonal phase transition at ~140 °C and no preferential orientation in the heterostructures. Their structural and electromechanical properties exhibit consistent improvement trends with increasing thickness from 100 to 550 nm (i.e., 2–11 layers). The 550 nm-thick, 11-layer films demonstrate the best ferroelectric, dielectric, piezoelectric, and electric performance in terms of the highest remnant polarization, saturation polarization, dielectric constant, and effective piezoelectric constant of 18.3 μC/cm2, 53.6 μC/cm2, 463, and 64 pm/V, as well as the lowest coercive field, dielectric loss tangent, and leakage current density of 116 kV/cm, 0.057, and 27 μA/cm2, respectively. The observed thickness-dependent improvement is explained by an interfacial passive layer effect where the motion of both 180° and non-180° domain walls is enhanced in the thicker multilayer thin films by weakening the influence of domain pinning in the interfacial passive layers between the multilayer thin films and the substrates.

ACS Style

Yunyi Wu; Siu Wing Or. Thickness-dependent structural and electromechanical properties of (Na0.85K0.15)0.5Bi0.5TiO3 multilayer thin film-based heterostructures. Materials & Design 2018, 149, 153 -164.

AMA Style

Yunyi Wu, Siu Wing Or. Thickness-dependent structural and electromechanical properties of (Na0.85K0.15)0.5Bi0.5TiO3 multilayer thin film-based heterostructures. Materials & Design. 2018; 149 ():153-164.

Chicago/Turabian Style

Yunyi Wu; Siu Wing Or. 2018. "Thickness-dependent structural and electromechanical properties of (Na0.85K0.15)0.5Bi0.5TiO3 multilayer thin film-based heterostructures." Materials & Design 149, no. : 153-164.