期刊：
Journal of Alloys and Compounds,2017年704:348-358 ISSN：0925-8388
通讯作者：
Hu, Renzong
作者机构：
[Sun, Wei; Hu, Renzong; Zhu, Min; Zhang, Hanyin; Liu, Hui] South China Univ Technol, Sch Mat Sci & Engn, Guangdong Prov Key Lab Adv Energy Storage Mat, Guangzhou 510640, Guangdong, Peoples R China.;[Liu, Hui] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Huang, Cunke] Guangxi Univ, Guangxi Coll, Nanning 530004, Peoples R China.;[Huang, Cunke] Guangxi Univ, Univ Key Lab Novel Energy Mat & Related Technol, Coll Phys Sci & Technol, Nanning 530004, Peoples R China.
通讯机构：
[Hu, Renzong] S;South China Univ Technol, Sch Mat Sci & Engn, Guangdong Prov Key Lab Adv Energy Storage Mat, Guangzhou 510640, Guangdong, Peoples R China.
关键词：
Deformation;Lithium ion batteries;Structural design;Tin anode;Whisker growth
摘要：
To explore the capacity fading mechanism during long-term cycling of the milled Sn-C lithium storage anodes, the structural stability of the cycled Sn-C electrodes has been investigated using internal strain distribution as indicator by simulation with different two-dimensional core/shell nanostructure models solved by Lagrangian description, combining with experimental results. It is revealed that the Sn-C composite of a double-coating structure with the smaller Sn coated by a stiff layer Li2O and embedding in graphite sustains less deformation, and has higher structural stability than the single-coating one. Due to the lithiation-induced stress and strain effect, Sn particles aggregate and the Sn whiskers grow in the cycled Sn-C electrodes that observed by SEM and TEM, which is closely related to the Sn transportation. This strain induced structural damage causes the capacity fading of Sn anodes. Based on the simulation of strain distribution induced by lithiation, the nanostructure has been designed for Sn-C electrodes of smaller Sn particles embedded in matrix with large elastic modulus and proper thickness to obtain optimized combination of capacity and cycleability. It would provide a guideline for designing material and microstructure of anodes for lithium ion batteries. (C) 2017 Elsevier B.V. All rights reserved.
通讯机构：
[Tang, Weijun] S;Shaanxi Normal Univ, Key Lab Appl Surface & Colloid Chem, Minist Educ, Xian 710062, Peoples R China.;Shaanxi Normal Univ, Sch Chem & Chem Engn, Xian 710062, Peoples R China.
摘要：
A ruthenium pincer catalyst has been shown to be highly efficient for the hydrogenation of a wide range of alpha-ketimino esters derived from alpha-keto esters and chiral 2-methylpropyl-2-sulfinamide, affording chiral aryl glycine derivatives with high yields and diasteroselectivities (20 examples, dr values up to 99 : 1).
作者机构：
[王海宁; 方海泉; 薛惠锋] Graduate School, China Aerospace Academy of Systems Science and Engineering, Beijing, 100048, China;[万毅] Water Resources Management Center, Ministry of Water Resources, Beijing, 100053, China;[周铁军] College of Science, Hunan Agricultural University, Changsha, 410128, China;[蒋云钟] Institute of Water Resources, China Institute of Water Resources and Hydropower Research, Beijing, 100038, China
期刊：
Journal of Solid State Electrochemistry,2016年20(4):943-948 ISSN：1432-8488
通讯作者：
Wu, Xiongwei;Ye, Hongqi;Wu, Yuping;Holze, Rudolf
作者机构：
[Wu, XW; Ye, HQ; Wu, Xiongwei; Ye, Hongqi; Wang, Zhian] Cent S Univ, Sch Chem & Chem Engn, Changsha 410083, Peoples R China.;[Wu, Xiongwei; Hu, Junping; Zhou, Weibin; Wu, XW; Wu, Yuping] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Wu, Yuping] Nanjing Tech Univ, Coll Energy, Nanjing 211816, Jiangsu, Peoples R China.;[Holze, Rudolf] Tech Univ Chemnitz, Inst Chem, AG Elektrochem, D-09107 Chemnitz, Germany.
通讯机构：
[Wu, XW; Ye, HQ] C;[Wu, XW; Wu, YP] H;[Wu, Yuping] N;[Holze, Rudolf] T;Cent S Univ, Sch Chem & Chem Engn, Changsha 410083, Peoples R China.
关键词：
Energy efficiency;Ion exchange membranes;Polystyrene;Vanadium solid-salt battery
摘要：
An ion exchange membrane (IEM) usually serves as a separator between the two half-cells and provides an ionic conduction path in redox flow batteries. The new vanadium solid-salt battery (VSSB) presents higher energy density than the traditional vanadium redox flow batteries (VRFBs). However, present IEMs are based on very expensive Nafion® membranes. In pursuit of lower cost, a membrane from sulfonated polystyrene (PE-01) is used for VSSB. In comparison with the traditional Nafion® 1135, PE-01 shows high energy efficiency with good cycling performance at current densities less than 10 mA cm−2. This suggests that sulfonated polystyrene membrane is a promising candidate as separator for VSSB.
作者机构：
[李建辉; 张永棠] Department of Computer Science and Technology, Guangdong Neusoft Institute, Fushan;Guangdong;528225, China;[王访] School of Management, Hunan Agricultural University, Changsha;410000, China
通讯机构：
[Zhang, Y.-T.] D;Department of Computer Science and Technology, Guangdong Neusoft Institute, Fushan, Guangdong, China
摘要：
The single-mode fiber was heated tapering by flame brush method, forming an optical waveguide structure which has a core radius of micro-nanometer level, and the low-loss optical fiber tapered was optimized by the different coefficients of thermal insulation to meet insulation standards. The tapered optical fiber with the best shape was designed, whose constant cone angle is 2 mrad, wavelength is 400 μm and fiber radius is 4 μm. Matlab simulation results show that, the transmission perspective of tapered optical fiber with length of 23 mm is 99.7%, the radiation resistance of tapered optical fiber with length of 63mm is 99.6%. Since the power is coupled to the high-order mode, the loss is sufficiently suppressed, so that the optical coupling transmission of the tapered fiber with a constant taper angle can be achieved without sacrificing the quality of the transmission.
摘要：
Two-dimensional (2D) multifractal detrended fluctuation analysis (MF-DFA) has been used to study monofractality and multifractality on 2D surfaces, but when it is used to calculate the generalized Hurst exponent in a fixed time scale, the presence of crossovers can bias the outcome. To solve this problem, multiscale multifractal analysis (MMA) was recent employed in a one-dimensional case. MMA produces a Hurst surface h(q,s) that provides a spectrum of local scaling exponents at different scale ranges such that the positions of the crossovers can be located. We apply this MMA method to a 2D surface and identify factors that influence the results. We generate several synthesized surfaces and find that crossovers are consistently present, which means that their fractal properties differ at different scales. We apply MMA to the surfaces, and the results allow us to observe these differences and accurately estimate the generalized Hurst exponents. We then study eight natural texture images and two real-world images and find (i) that the moving window length (WL) and the slide length (SL) are the key parameters in the MMA method, that the WL more strongly influences the Hurst surface than the SL, and that the combination of WL=4 and SL=4 is optimal for a 2D image; (ii) that the robustness of h(2,s) to four common noises is high at large scales but variable at small scales; and (iii) that the long-term correlations in the images weaken as the intensity of Gaussian noise and salt and pepper noise is increased. Our findings greatly improve the performance of the MMA method on 2D surfaces.
摘要：
In this paper, a new multifunctional electrochemical platform for hydrogen peroxide (H2O2) and nitrite (NO2) based on silver/carbon nano-composite (Ag/C NC) was firstly proposed. Ag/C NC was synthesized by using carbon dots (C-dots) as the reductant by a facile one-step synthesis method and confirmed by UV-Vis, Fourier transforms infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and dynamic light scattering. The Ag/C NC based electrodes showed excellent electrocatalytic activity toward the reduction of H2O2 and the oxidation of NO2. When Ag/C NC was dropped on the bare GCE, the electrocatalytic reduction of H2O2 occurred and showed wide linear range from 5.00 mu M to 11.05 mu M with the detection limit of 0.51 mu M. When Ag/C NC was dropped on graphene (GR) modified electrode, the Ag/C NC/GR/GCE showed extremely fast direct electron transfer and good electrocatalytic activity toward oxidation of nitrite. It showed wide linear range from 4.00 mu M to 2.00 mu M with the detection limit of 0.48 mu M. The Ag/C NC/GR/GCE was successfully applied in analysis of nitrite in real samples and gained good testing recovery. Therefore, the proposed electrochemical sensors for H2O2 and NO2 exhibited many advantages, such as operational simplicity, rapid responses, good reproducibility and stability, and can be simply tuned to utilize for electrochemical detection of H2O2 and NO2. This study will open a facial and simple synthesis method for preparing carbon based noble metal nanocomposite and utilizes them in detection for different purposes, which may provide new opportunity and prospect in the field of electrochemical biosensing. (C) 2016 Elsevier Ltd. All rights reserved.
摘要：
series of semi-fluorinated sulfonated polyimides (6F-SPIs) are designed and synthesized via a one-step high-temperature polycondensation reaction. The sulfonation degrees of 6F-SPIs are controlled through changing the ratio of sulfonated diamine to non-sulfonated diamine in the casting solution. The physicochemical properties and single cell performance of 6F-SPI membranes are thoroughly evaluated and compared to a non-fluorinated SPI membrane (6H-SPI-50) and a Nafion 115 membrane. The results show that the designed 6F-SPI membrane with a 50% sulfonation degree (6F-SPI-50) possesses the highest proton selectivity (1.613 x 10(5) S min cm(-3)) among all tested membranes. Besides, the 6F-SPI-50 membrane exhibits a promising performance for vanadium redox flow batteries (VRFBs), showing higher coulombic efficiencies (96.90-99.20%) and energy efficiencies (88.25-64.80%) than the Nafion 115 membrane (with coulombic efficiencies of 90.60-96.70% and energy efficiencies of 81.04-60.10%) at the current densities ranging from 20 to 100 mA cm(-2). Moreover, the 6F-SPI-50 membrane shows excellent chemical stability in the VRFB system. This work paves the way for the development of a new class of 6F-SPI membranes for the VRFB application. (C) 2016 Elsevier Ltd. All rights reserved.
摘要：
To improve the thermal stability, Al2O3 has been successfully coated on a Y3Al5O12:Ce3+ (YAG:Ce) phosphor powder host by using the Atomic Layer Deposition (ALD) approach in a fluidized bed reactor. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis indicate that coating an Al2O3 thin layer by ALD is highly feasible. The luminescence properties (such as excitation and emission as well as quantum efficiency and UV-absorption of the coated YAG:Ce phosphor) were systematically analysed, with the further examination of the thermal resistance characteristics. The Al2O3 thin layer coating with precisely controlled thickness by ALD can obviously improve the luminescence intensity and greatly enhances the thermal stability of the YAG:Ce phosphor. It is suggested that the alumina coating with tailoring thickness seems not only to act like a barrier to decrease the thermal quenching, but also as a great help to promote the light absorption and transfer.
摘要：
This study aims to characterize the interactions between substitutional solutes (3d, 4d and 5d transition metals) and interstitial impurities (C and O) in vanadium alloys, with or without the presence of an adjacent vacancy. For this purpose, the binding energies for solute-impurity and vacancy-impurity pairs, as well as solute-vacancy-impurity complexes are investigated by means of first-principles calculations, with or without the elastic correction. The vacancy-impurity binding energies suggest that it is energetically favorable to form stable 1nn vacancy-impurity pairs. For large-sized solutes, the solute-impurity interactions present strong repulsive interactions when a vacancy is absent, while showing strong attractive ones in the presence of a vacancy. Furthermore, a comprehensive study on the binding energy of defects revealed a positive correlation between the elastic correction energies and solute volumes, indicating that the elastic correction for the binding energies needs to be considered when a vacancy is absent in the vicinity of defects. Based on the binding preference, we can infer that a vacancy prefers to bond with large solutes adjacent to it and thus the resulting solute-vacancy pair can serve as a strong impurity trapper to form a defect complex, enhancing the nucleation and growth of precipitates in V alloys.
摘要：
In this paper, multi-fractal characteristics of speech signals are analyzed based on MF-DFA, and it is found that the multi-fractal features are influenced greatly by frame length and noise, besides, there is a little difference between them among speech frames. Secondly, motivated by framing and using frame shift to ensure the continuity and smooth transition of speech in speech signals processing, an advanced MF-DFA (MF-DFA with forward moving overlapping windows) is proposed. The length of moving overlapping windows is determined by parameter θ. Given the value of time scale s, we have MF-DFA with the maximum moving overlapping windows and MF-DFA with half overlapping windows when θ=1/s and θ=1/2 respectively. Moreover, when θ=1 we exactly have MF-DFA. Numerical experiments and analysis illustrate that the multi-fractal characteristics based on AMF-DFA outperform MF-DFA and MF-DMA in stability, noise immunity and discrimination.
