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Zhou, Yuanyuan,Lee, Ilbok,Kim, Daeun,Han, Seunghee,Kim, Jae-Kwang,Lee, Donghyun,Ko, Song Won,Pyo, Sung Gyu,Son, Hyungbin,Yoon, Songhun American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.1
<P>Using a stabilizing agent-assisted co-assembly method, a novel nanocomposite of mesoporous carbon embedded with uniform tungsten oxide nanorods is obtained, which is converted into carbon-sheathed tungsten oxide nanoparticles by delicate calcination and further reduction. Through optimization of tungsten content, it is found that highly crystalline tungsten oxide nanoparticles are uniformly coated with an ultra-thin carbon layer. When applied into electrochemical charge-storage electrodes for supercapacitor and lithium-ion battery, an excellent average capacitance (129 F g(-1), above 400 F cm(-3)), higher rate performance and significantly advanced cycle stability are observed. These improved charge storage properties are attributed to improved electrical conductivity and enhanced structural stability, which is induced by uniform carbon coating on partially reduced tungsten oxide nanoparticles.</P>
Zhou, Yuanyuan,Lee, Jinwoo,Lee, Chul Wee,Wu, Mihye,Yoon, Songhun Wiley-VCH 2012 ChemSusChem Vol.5 No.12
<P>Nanocomposites of crystalline-controlled TiO(2) -carbon are prepared by a novel one-step approach and applied in anodes of lithium ion batteries. In our nanocomposite anodes, the Li(+) capacity contribution from the TiO(2) phase was enormous, above 400 mAh g(-1) (Li(1+x) TiO(2) , x>0.2), and the volumetric capacity was as high as 877 mAh cm(-3) with full voltage utilization to 0 V versus Li/Li(+) , which resulted in higher energy density than that of state-of-the-art titania anodes. For the first time, it was clearly revealed that the capacity at 1.2 and 2.0 V corresponded to Li(+) storage at amorphous and crystalline TiO(2) , respectively. Furthermore, improvements in the rate capability and cycle performance were observed; this was attributed to resistance reduction induced by higher electrical/Li(+) conduction and faster Li(+) diffusion.</P>
Zhou, Yuanyuan,Kim, Younghun,Jo, Changshin,Lee, Jinwoo,Lee, Chul Wee,Yoon, Songhun Royal Society of Chemistry 2011 Chemical communications Vol.47 No.17
<P>An ordered mesoporous carbon–silica–titania material was prepared using the tetra-constituents co-assembly method. As regards its anode performance in lithium ion batteries, the composite material anode exhibited a high capacity (875 mAh g<SUP>−1</SUP>), a higher initial efficiency (56%) and an improved rate.</P> <P>Graphic Abstract</P><P>An ordered mesoporous carbon nanocomposite with silica and titania was prepared by the tetra-constituent co-assembly method. When used as the anode in lithium ion batteries, higher performances were observed, which were attributed to the well-ordered mesopores and the amorphous TiO<SUB>2</SUB>. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cc10539f'> </P>
Yuanyuan Zhou,Jianying Deng,Shimei Li,Zefeng Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.5
Core–shell Cu@Ni chains were successfully synthesized through a mild hydrothermal reaction. The morphology, structure and microwave electromagnetic properties of the composite were then characterized by X-ray diffraction, energy-dispersive spectroscopy, scanning electron microscopy and vector network analysis. The formation mechanisms of the core–shell structure and one-dimensional chains were ascribed to the varying redox potentials of Cu and Ni ions and the magnetic dipole–dipole attraction. Furthermore, a minimal reflection loss (RL) of -20.7 dB was observed at 9.6 GHz with a thickness of 2.0mm and the effective absorption ( ≤10 dB, 90% microwave attenuation) bandwidth can be adjusted between 5.2 GHz and 16.6 GHz for the thin absorber thickness of 2.0–4.0 mm. The novel core–shell chain-like Cu@Ni alloy can be used as a promising absorbing material because it shows numerous features such as thin thickness, strong absorption, low cost and lightweight.
Tianyi Zhou,Xuehua Li,Chunyu Pan,Mingyu Zhou,Yuanyuan Yao 한국통신학회 2021 Journal of communications and networks Vol.23 No.6
Federated edge learning (FEL) deploys a machinelearning algorithm by using devices distributed on the edge ofa network, trains massive local data, uploads the local modelto update the parameters after training, and performs alternateupdating with global model parameters to reduce the pressurefor uplink data transmission, prevent systematic time delay andensure data security. This paper proposes that an optimal balancebetween time delay and energy consumption be achieved by optimizingthe transmission power and bandwidth allocation basedon user quality of experience (QoE) in a multi-server intelligentedge network. Given the limited computing capability of devicesinvolved in FEL local training, the transmission power is modeledas a quasi-convex uplink power allocation (UPA) problem, anda lower energy consumption bandwidth allocation algorithm isproposed for solution-seeking. The proposed algorithm allocatesappropriate power to the device by adapting the computingpower and channel state of the device, thereby reducing energyconsumption. As the theoretical deduction result suggests thatadditional bandwidth should be allocated to those devices withweak computing capabilities and poor channel conditions torealize minimal energy consumption within the restraint time. The simulation result indicates that, the maximum gain of theproposed algorithm can be optimized by 31% compared with thebaseline.
Yuanyuan Liu,Junyong Zhou,Jianxu Su,Junping Zhang 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.4
The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the nonstationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The nonstationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.
Synthesis and Gas Adsorption Properties of Carbide-Derived Carbons from Titanium Tin Carbide
Yuanyuan Zhu,Aiguo Zhou,Jin Jia,Junjun Wang,Jiang Liu,Baolin Xing,Chuanxiang Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.4
Here we reported the synthesis of nanoporous carbide-derived carbons (CDCs) from a new precursor, titanium tin carbides (Ti2SnC), via chlorination at 400–1100℃. At low chlorination temperature (400–500℃), as-synthesized CDCs mainly consisted of amorphous carbon and chlorides. As the chlorination temperature increased up to 600℃, chlorides disappeared, and the main composition of CDCs was amorphous carbon. At high chlorination temperature, there was a trend of graphitization. The microstructure of CDCs was observed and characterized by scanning electron microscopy and transmission electron microscopy. Some graphite-like sheet structures in CDCs were found. Specific surface area (SSA) and pore volume of CDCs increased with chlorination temperature, except an abnormal decrease of the CDC chlorinated at 900℃. CDC chlorinated at 1100℃ had the largest SSA, 1580 m2 /g. In order to apply these materials as novel hydrogen/methane storage media in the area of energy efficient transport, gas adsorption properties of CDCs were measured. For CDC chlorinated at 1100℃, pore volume uptakes are 206 cm3 /g at 60 bar (25℃) for methane, and ~442 cm3 /g at 35 bar (-196℃) for hydrogen, respectively. It was suggested that CDCs from Ti2SnC are promising materials for hydrogen/ methane adsorptive storage.
Acetalization of glycerol over sulfated UiO-66 under mild condition
Yuanyuan Jiang,Ruru Zhou,Boyong Ye,Zhaoyin Hou 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.110 No.-
Sulfated metal–organic framework has attracted much attention as a versatile heterogeneous acid for itsstrong acid strength, large surface area and regular pore channels. In this work, sulfated UiO-66 (UiOSO3H-x) was prepared via the direct oxidation of 2-mercaptobenzoic acid substituted UiO-66. The structureand property of the synthesized UiO-SO3H-x were characterized via XRD, FTIR, static water contactangles, XPS, TG-DTA, N2 adsorption–desorption, SEM and TEM in detail. It was found that sulfonic acidgroups dispersed homogenously in the framework of UiO-SO3H-x. And UiO-SO3H-0.2 exhibited excellentperformance and stability for the synthesis of solketal from surplus glycerol among the tested solid acids(H3PW12O40, Amberlyst-45, HY, HBEA, HZSM-5 and ZrHP). The detected conversion of glycerol reached70.3% with a 99.8% selectivity toward solketal at 60 C, and it could maintain its initial activity in fiverecycles. The highest TOF of each acid site in UiO-SO3H-0.2 reached 676.0 h1. Moreover, it was versatilefor the acetalization of glycerol with other ketones/aldehydes.