Electroreduction of H2O2 by Co3O4 and NiCo2O4 nanowires and beta-Ni(OH)2 nanoplates grown on Ni foam.

Hui, K N,Yin, Cui-Lei,Hui, K S,Lee, J Y,Cao, Dianxue,Wang, Guiling American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4

<P>Nanowires (Co3O4 and NiCo2O4) and nanoplates (beta-Ni(OH)2) grown on Ni foam are successfully prepared by a template-free method and used as cathode electrodes for the electroreduction of H2O2, in an alkaline medium. Catalytic performance is investigated via cyclic voltammetry and chronoamperometry. The Co3O4 and NiCo2O4 nanowire electrodes exhibit much better catalytic activity, stability, and mass transfer properties for H2O2 electroreduction than pressed Co3O4 and NiCo2O4 nanoparticle/carbon/PTFE electrodes. A current density of 101.8 mA cm(-2) and 122.7 mA cm(-2) are respectively achieved on Co3O4 and NiCo2O4 nanowire electrodes at -0.4 V in 0.4 mol/L H2O2, and 3.0 mol/L NaOH solution at room temperature.</P>

Synthesis of Co3O4 nanowire arrays supported on Ni foam for removal of volatile organic compounds.

Hui, K N,Yin, Cui-Lei,Hui, K S,Lee, J Y,Li, M,Lee, S K,Tsui, K L,Chao, C Y H,Kwong, C W American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4

<P>Crystalline Co3O4 nanowire arrays freely supported on Ni foam are successfully synthesized using a template-free method. The effects of reaction time, concentration of reactants, and temperature on the morphology of the nanowires are studied. The results indicate that uniform Co3O4 nanowires could be synthesized at 90 degrees C, and a transformation of the samples' morphology from nanoparticles to nanowires to microrods is observed by controlling the concentration of the reactants. The well-ordered nanowires synthesized under the selected reaction conditions are composed of spinel Co3O4 with diameters of 500-580 nm and lengths of 6-8 microm. These nanowires show good catalytic activity for the ozone catalytic oxidation of toluene.</P>

Research on Preparation of Ni/SiO2 Optical Attenuation Slice by Magnetron Sputtering

Lei Li,Hui Tang,Shanshan Hao,Wenxue Wang 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.12

In order to find new methods for preparing and improving the performance of optical attenuation slice. Vacuum magnetron sputtering method was used to prepare Ni/SiO2 composite film optical attenuation slices, with vacuum magnetron sputtering apparatus, at 5,10,15,20,25min sputtering time, 0.2,0.4,0.6,0.8,1.0Pa sputtering pressure and sputtering power 300~1200W. The XRD, SEM, EDS, AFM and 722 spectrophotometer also were used to study the effects of different sputtering time, sputtering pressure and sputtering power on the film structure, surface morphology, composition, three-dimensional structure, surface roughness and light attenuation rate of optical attenuation slice samples. The results indicated that: Ni/SiO2 composite films were formed, instead of simple physical adsorption between Ni film and SiO2 substrates with magnetron sputtering by XRD analysis and calculation, with uniform grain size of 25.96, 32.38, 32.29,26.95, 25.92nm, respectively. The main component element was Ni, but there were few impurities deposited on the substrates. Impurities were reduced gradually with the increase of sputtering time, mainly resulted from two sputtering of Ni atoms by EDS; The film surface was smooth and dense, flatness and organizational structure of Ni film were better, surface roughness was 1.267nm at 25min sputtering time, 0.4Pa pressure and 400W power with SEM and AFM. Light attenuation rate of optical attenuation slices was different in different process parameters, and the maximum reached 0.52, film flatness, impurities and defects were the main reason by the light attenuation performance analysis.

Extremal problems on saturation for the family of k -edge-connected graphs

Lei, Hui,O, Suil,Shi, Yongtang,West, Douglas B.,Zhu, Xuding Elsevier 2019 Discrete Applied Mathematics Vol.260 No.-

<P><B>Abstract</B></P> <P>Let F be a family of graphs. A graph G is F <I>-saturated</I> if G contains no member of F as a subgraph but G + e contains some member of F whenever e ∈ E ( G ¯ ) . The <I>saturation number</I> and <I>extremal number</I> of F , denoted sat ( n , F ) and ex ( n , F ) respectively, are the minimum and maximum numbers of edges among n -vertex F -saturated graphs. For k ∈ N , let <SUB> F k </SUB> and F k ′ be the families of k -connected and k -edge-connected graphs, respectively. Wenger proved sat ( n , <SUB> F k </SUB> ) = ( k − 1 ) n − k 2 ; we prove sat ( n , F k ′ ) = ( k − 1 ) ( n − 1 ) − n k + 1 k − 1 2 . We also prove ex ( n , F k ′ ) = ( k − 1 ) n − k 2 and characterize when equality holds. Finally, we give a lower bound on the spectral radius for <SUB> F k </SUB> -saturated and F k ′ -saturated graphs.</P>

Study on the Temperature Drift Adaptive Compensation Algorithm of a Magneto-Electric Encoder Based on a Simple Neuron

Lei Wang,Shuang-hui Hao,Bao-yu Song,Ming-hui Hao 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

Magneto-electric encoders have been widely used in industry and military applications because of their good shock resistance, small volume, and convenient data processing. However, the characteristics of a magneto-electric encoder’s signal generator and hall sensor changes minimally with temperature variation. These changes cause an angle drift. The main purpose of this study is to construct the compensation system of a neural network and constantly update weight coefficients of temperature correction by finite iteration calculation so that the angle value modified can approach the angle value at the target temperature. This approach is used in adaptive correction of the angle value.

Theoretical Study of the Elastic and the Thermodynamic Properties of Re$_2$C under High Pressure

Hui-Ru Lei,Li-Hong Zhang,Xu Li,Xiao-Zhen Gao,Jing Li 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.11

The structural properties of Re$_2$C in anti-MoS$_2$ and anti-ReB$_2$ structures have been investigated by using the pseudopotential plane wave methods based on the density functional theory. The anti-ReB$_2$ structure is found to be more stable than the anti-MoS$_2$ structure. In particular, for the first time, we have studied the elastic properties of Re$_2$C in the anti-ReB$_2$ structure under high pressure. The ductile-brittle behavior and Vickers hardness for the anti-ReB$_2$ structure are also been analyzed. In addition, the Debye temperature, heat capacity and thermal expansion coefficient are discussed by using the quasiharmonic Debye model method.

Controllable preparation of 2D nickel aluminum layered double hydroxide nanoplates for high-performance supercapacitors

Li, Lei,Fu, Jianjian,Hui, Kwan San,Hui, Kwun Nam,Cho, Young-Rae Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.20

High-performance solid-state flexible supercapacitor based on reduced graphene oxide/hierarchical core-shell Ag nanowire@NiAl layered double hydroxide film electrode

Li, Lei,Hui, Kwan San,Hui, Kwun Nam,Zhang, Tengfei,Fu, Jianjian,Cho, Young-Rae Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.348 No.-

<P><B>Abstract</B></P> <P>All-solid-state flexible supercapacitor (AFSC) is a promising energy storage device due to its high flexibility, security, and environmental friendliness. However, high electrical resistance and low specific capacitance of electrodes limit its application for potential portable electronic devices. In this study, we design a novel hybrid film electrode composed of reduced graphene oxide (rGO)/silver nanowire (Ag NW)@nickel aluminum layered double hydroxide (NiAl LDH; herein, GAL) possessing high electrochemical performance by using hydrothermal and vacuum filtration techniques. The Ag NW@NiAl LDH (AL) composites with hierarchical core-shell structure are utilized to increase electroactive surface area and improve electrical conductivity, while the rGO nanosheets serve as a prominent carbon material with outstanding electrical conductivity and mechanical flexibility. The freestanding GAL electrode shows high specific capacitance of 1148 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> compared with rGO/NiAl LDH (GL) of 765.2 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>. Furthermore, the bind-free symmetric AFSC device is successfully prepared using GAL hybrid film as electrodes and PVA-KOH as solid-state gel electrolyte. The GAL//GAL AFSC device delivers a superior specific capacitance of 127.2 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>, a high energy density of 35.75 mWh cm<SUP>−3</SUP> at a power density of 1.01 W cm<SUP>−3</SUP>, and great cycling ability of 83.2% over 10,000 cycles at 5 A g<SUP>−1</SUP>. This study introduces a novel design of flexible electrode structure for advanced energy storage applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A well-designed rGO/Ag NW@NiAl-LDH (GAL) hybrid film was prepared. </LI> <LI> The Ag NWs improved the conductivity of the hybrid film. </LI> <LI> The GAL electrode shows high specific capacitance of 1148 F g<SUP>−1</SUP>. </LI> <LI> The flexible device displays high energy density of 35.75 mWh cm<SUP>−3</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ultrathin petal-like NiAl layered double oxide/sulfide composites as an advanced electrode for high-performance asymmetric supercapacitors

Li, Lei,Hui, Kwan San,Hui, Kwun Nam,Cho, Young-Rae The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.37

<▼1><P>We develop a facile approach to synthesize ultrathin petal-like NiAl layered double oxide/sulfide (LDO/LDS) composites with high electrochemical activity using hydrothermal reaction followed by sulfidation process.</P></▼1><▼2><P>Layered double hydroxide (LDH) is an important layer-structured material for supercapacitors because of its versatile compositions, high theoretical capacitance, environmental friendliness, and low cost. However, the high resistivity of this material results in capacity fading, limiting its application in energy storage. Herein, we develop a facile approach to synthesize ultrathin petal-like NiAl layered double oxide/sulfide (LDO/LDS) composites with high electrochemical activity using a hydrothermal reaction followed by a sulfidation process. Scanning electron micrographs show that the petal-like NiAl LDO/LDS composites are as thin as ∼10 nm with a mean lateral dimension of ∼1 μm. The NiAl LDO/LDS electrode delivers a remarkably high specific capacitance of 2250.5 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> compared with that of NiAl LDH (1740.5 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>) and possesses a good cycling stability of 88.9% capacitance retention over 5000 cycles at 5 A g<SUP>−1</SUP>. An asymmetric supercapacitor (ASC) is fabricated using NiAl LDO/LDS and graphene as positive and negative electrodes, respectively. The NiAl LDO/LDS//G ASC exhibits a specific capacitance of 153.3 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>, a high energy density of 47.9 W h kg<SUP>−1</SUP> at a power density of 750 W kg<SUP>−1</SUP>, and a reliable cycling stability of 95.68% capacitance retention after 5000 cycles. The results highlight that NiAl LDO/LDS composites are promising materials for energy storage devices with long cycling stability.</P></▼2>

The Stent-Assisted Coil-Jailing Technique Facilitates Efficient Embolization of Tiny Cerebral Aneurysms

Cong-Hui Li,Xian-Hui Su,Bo Zhang,Yong-Feng Han,Er-Wei Zhang,Lei Yang,Dong-Liang Zhang,Song-Tao Yang,Zhen-Quan Yan,Bu-Lang Gao 대한영상의학회 2014 Korean Journal of Radiology Vol.15 No.6

Objective: Tiny cerebral aneurysms are difficult to embolize because the aneurysm’s sac is too small for a single small coil, and coils within the aneurysm may escape from the confinement of a stent. This study was performed to introduce the stent-assisted coil-jailing technique and to investigate its effect on the coil embolization of tiny intracranial aneurysms. Materials and Methods: Sixteen patients with tiny intracranial aneurysms treated with the stent-assisted coil-jailing technique between January 2011 and December 2013 were retrospectively reviewed and followed-up. Results: All aneurysms were successfully treated with the coil-jailing technique, and at the end of embolization, complete occlusion of the aneurysm was achieved in 9 cases (56.3%), incomplete occlusion in 6 (37.5%), and partial occlusion in 1 (6.3%). Intraprocedural complications included acute thrombosis in one case (6.3%) and re-rupture in another (6.3%). Both complications were managed appropriately with no sequela. Follow-up was performed in all patients for 3–24 months (mean, 7.7 months) after embolization. Complete occlusion was sustained in the 9 aneurysms with initial complete occlusion, progressive thrombosis to complete occlusion occurred in the 6 aneurysms with initial near-complete occlusion, and one aneurysm resulted in progressive thrombosis to complete occlusion after initial partial occlusion. No migration of stents or coils occurred at follow-up as compared with their positions immediately after embolization. At follow-up, all patients had recovered with no sequela. Conclusion: The stent-assisted coil-jailing technique can be an efficient approach for tiny intracranial aneurysms, even though no definite conclusion regarding its safety can be drawn from the current data.