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35 results on '"Du, Keqin"'

11. Corrosion and conductivity properties of Ni–P/Ti4O7 coating on carbon steel as bipolar plates for proton exchange membrane fuel cells.

Author

Yu, Haiqiang, Guo, Quanzhong, Du, Keqin, Li, Dongyun, Wang, Chuan, and Wang, Yong

Subjects
ALLOY plating, PROTON exchange membrane fuel cells, COMPOSITE coating, CARBON steel, IRON & steel plates, SURFACE coatings, ELECTROLESS plating, INTERFACIAL resistance
Abstract

Purpose: The purpose of this paper is to investigate the interfacial conductivity and corrosion resistance of the Ni–P/Ti4O7 composite coating that is deposited on a carbon steel substrate as bipolar plates for proton exchange membrane fuel cells. Design/methodology/approach: The Ni–P/Ti4O7 coating was prepared by electroless plating. Scanning electron microscopy, white light interference, energy dispersive spectrometry and X-ray diffraction were used, respectively, to study the surface morphology, chemical composition and phase composition of coated samples. Electrochemical impedance spectroscopy, potentiodynamic and potentiostatic polarization were used to test the electrochemical performance and corrosion behavior. The interfacial contact resistance (ICR) was measured via the standard method. Findings: The surface of the Ni–P/Ti4O7 coating is complete and dense and without obvious defects. The electrochemical test results show that the Ni–P/Ti4O7 coating provides better corrosion resistance than the Ni–P coating and substrate. Compared with the Ni–P coating, the ICR of the Ni–P/Ti4O7 coating is lower by about 82.7%. This is because the coating has more conductive contact points. The more exciting thing is that the ICR of the Ni–P/Ti4O7 coating only increases to 12.38 mΩ·cm2 after 5 h of polarization. Originality/value: This paper provides a method for achieving surface modification of metal bipolar plates. Introducing Ti4O7 particles in the Ni–P layer reduces the contact resistance before and after polarization while ensuring good corrosion resistance. [ABSTRACT FROM AUTHOR]

Published
2022
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15. A Digital Compressed Sensing-Based Energy-Efficient Single-Spot Bluetooth ECG Node

Author

Du Keqin, Jianqing Li, Xiangyu Zhang, Zhipeng Cai, Fumin Zou, and Kan Luo

Subjects
lcsh:Medical technology, Article Subject, Computer science, 0206 medical engineering, Real-time computing, Biomedical Engineering, Health Informatics, 02 engineering and technology, law.invention, Bluetooth, law, 0202 electrical engineering, electronic engineering, information engineering, Discrete cosine transform, Wireless, Humans, lcsh:R5-920, business.industry, Node (networking), 020206 networking & telecommunications, Signal Processing, Computer-Assisted, Energy consumption, Equipment Design, 020601 biomedical engineering, Compressed sensing, lcsh:R855-855.5, Electrocardiography, Ambulatory, Surgery, business, lcsh:Medicine (General), Wireless Technology, Algorithms, Biotechnology, Efficient energy use, Data compression, Research Article
Abstract

Energy efficiency is still the obstacle for long-term real-time wireless ECG monitoring. In this paper, a digital compressed sensing- (CS-) based single-spot Bluetooth ECG node is proposed to deal with the challenge in wireless ECG application. A periodic sleep/wake-up scheme and a CS-based compression algorithm are implemented in a node, which consists of ultra-low-power analog front-end, microcontroller, Bluetooth 4.0 communication module, and so forth. The efficiency improvement and the node’s specifics are evidenced by the experiments using the ECG signals sampled by the proposed node under daily activities of lay, sit, stand, walk, and run. Under using sparse binary matrix (SBM), block sparse Bayesian learning (BSBL) method, and discrete cosine transform (DCT) basis, all ECG signals were essentially undistorted recovered with root-mean-square differences (PRDs) which are less than 6%. The proposed sleep/wake-up scheme and data compression can reduce the airtime over energy-hungry wireless links, the energy consumption of proposed node is 6.53 mJ, and the energy consumption of radio decreases 77.37%. Moreover, the energy consumption increase caused by CS code execution is negligible, which is 1.3% of the total energy consumption.

Published
2018

16. A modified frequency slice wavelet transform for physiological signal time-frequency analysis

Author

Zhipeng Cai, Du Keqin, Jianqing Li, Alfred Cuschieri, Zhigang Wang, and Kan Luo

Subjects
Signal processing, Computer science, 0206 medical engineering, Wavelet transform, 02 engineering and technology, Function (mathematics), 020601 biomedical engineering, Signal, Time–frequency analysis, 020303 mechanical engineering & transports, 0203 mechanical engineering, Frequency domain, Spectrogram, Algorithm
Abstract

As a new signal processing tool, a Modified frequency slice wavelet transform (MFSWT) is proposed for physiological signal time-frequency analysis in this study. The transform generates time-frequency representation from the frequency domain, and the reconstruction is independent of frequency slice function (FSF). To realize accurate time-frequency location of signal components, a bound signal-adaptive FSF was introduced to serve as a dynamic frequency filter for the transform. This method avoids troublesome parameter selection, is signal-adaptive and easy to use. The results of two case studies demonstrate the validity of the proposed method, which has good interpretability with high time-frequency resolution, and hence has significant potential for bio-signal time-frequency analysis.

Published
2017

29. Application of a composite electrolyte in a solid-acid fuel cell system: A micro-arc oxidation alumina support filled with CsH2PO4.

Author

Guo, Xinghua, Du, Keqin, Huang, Yuxi, Ge, Hao, Guo, Quanzhong, Wang, Yong, and Wang, Fuhui

Subjects
*ELECTROLYTES, *SOLID oxide fuel cells, *METALLIC composites, *ALUMINUM oxide, *SOLID state proton conductors, *POLYCRYSTALS, *MICROFABRICATION
Abstract

Abstract: A micro-arc oxidation alumina (MOA) support filled with a CsH2PO4 proton conductor was investigated as an inorganic composite electrolyte for a H2/O2 solid-acid fuel cell (SAFC). The MOA support was polycrystalline and contained α- and γ-Al2O3 phases; while, the proton conductor CsH2PO4 formed an interlaced network within the MOA support. The single-module SAFC using the fabricated MOA/CsH2PO4 membrane delivered a peak power of ∼38.5 m W cm−2 and a proton conductivity of ∼2.1 m S cm−1 at a low temperature (25 °C). Compared to a SAFC using an anodic alumina membrane composite electrolyte (AAM/CsH2PO4 SAFC), which displayed rapid degradation, the SAFC using the MOA/CsH2PO4 composite electrolyte showed improved stability with cycling. This was attributed to the crystalline α-Al2O3 phase that was part of the MOA support that had increased the chemical resistance. [Copyright &y& Elsevier]

Published
2013
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30. Effect of Energy Density on Microstructure and Properties of Al2O3 Plasma Electrolysis Oxidation Film

Author

Guo, Xinghua, Du, Keqin, Guo, Quanzhong, Wang, Yong, and Wang, Fuhui

Abstract

The effect of exported energy density on the plasma electrolysis oxidation (PEO) process was studied under transient self-feedback control (TSFC) mode. Properties of the Al2O3 PEO films were characterized by scanning electron microscopy (SEM), Vickers hardness test and electrochemical impedance spectroscopy (EIS). Experimental results indicated that a hard and compact PEO film was obtained at a correct energy density due to the uniform action of the high-frequency square voltage waveform (HFSVW). On the contrary, the high energy density greatly weakened the uniform action of the HFSVW which resulted in large pores and microcracks in the PEO films.

Published
2013

31. Effect of Carrier Waveform Frequency on the Microstructure of Al2O3 Plasma Electrolyic Oxidation Films

Author

Guo, Xinghua, Du, Keqin, Guo, Quanzhong, Wang, Yong, and Wang, Fuhui

Abstract

Different microstructures of the Al2O3 plasma electrolytic oxidation (PEO) films were obtained by controlling the frequency of applied high-frequency square voltage waveform (HFSVW) under different transient self-feedback control (TSFC). The morphology and compactness of the PEO films were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Experimental results indicated that uniform, compact, small-grained TSFC PEO films can be produced by applying high-frequency HFSVWs.

Published
2013

32. Study of Barrier Property of Composite Film Coated on Mg-Gd-Y Alloy by Water Diffusion

Author

Guo, Xinghua, Du, Keqin, Guo, Quanzhong, Wang, Yong, Wang, Rong, and Wang, Fuhui

Abstract

A composite film was prepared by depositing layers of plasma electrolysis oxidation (PEO) film and self-assembled nanoparticle (SANP) film on a Mg-Gd-Y alloy. The electrochemical impedance spectroscopy (EIS) results showed that the structure of the PEO + thin SANP layers greatly increased the corrosion protection of the composite film. In addition, two water diffusion coefficients (D) of the composite film were obtained using EIS and Kalnin's model. The D values indicated the composite film had a good barrier property against water.

Published
2013

33. Micro-Arc Oxidized Corrosion Resistant Interlayer on Magnesium Alloy with Electromagnetic Wave Absorption Coatings

Author

Guo, Quanzhong, Guo, Xinghua, Wang, Fuhui, Wang, Yanqiu, and Du, Keqin

Abstract

An interlayer film between a magnesium alloy substrate (MAS) and electromagnetic wave absorption coatings (EWACs) has been produced by micro-arc oxidation (MAO) method. A new voltage mode has been developed for use in the MAO technique. The corrosion resistance of MAS has been investigated in 3.5 wt% NaCl solution. The results show that the MAO interlayer not only delays interaction of chloride electrolyte with MAS but also changes corrosion behavior of the metal substrate. The film restricts propagation of filiform corrosion at the coating/substrate interface and simultaneously eliminates galvanic couples by separating absorbents in the EWAC from the MAS.

Published
2012

34. Effect of Energy Density on Microstructure and Properties of Al2O3Plasma Electrolysis Oxidation Film

Author

Guo, Xinghua, Du, Keqin, Guo, Quanzhong, Wang, Yong, and Wang, Fuhui

Abstract

The effect of exported energy density on the plasma electrolysis oxidation (PEO) process was studied under transient self-feedback control (TSFC) mode. Properties of the Al2O3PEO films were characterized by scanning electron microscopy (SEM), Vickers hardness test and electrochemical impedance spectroscopy (EIS). Experimental results indicated that a hard and compact PEO film was obtained at a correct energy density due to the uniform action of the high-frequency square voltage waveform (HFSVW). On the contrary, the high energy density greatly weakened the uniform action of the HFSVW which resulted in large pores and microcracks in the PEO films.

Published
2013
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35. Effect of Carrier Waveform Frequency on the Microstructure of Al2O3Plasma Electrolyic Oxidation Films

Author

Guo, Xinghua, Du, Keqin, Guo, Quanzhong, Wang, Yong, and Wang, Fuhui

Abstract

Different microstructures of the Al2O3plasma electrolytic oxidation (PEO) films were obtained by controlling the frequency of applied high-frequency square voltage waveform (HFSVW) under different transient self-feedback control (TSFC). The morphology and compactness of the PEO films were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Experimental results indicated that uniform, compact, small-grained TSFC PEO films can be produced by applying high-frequency HFSVWs.

Published
2013
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