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71.
72.
Weihua Pu Xiangming He Li Wang Zheng Tian Changyin Jiang Chunrong Wan 《Journal of membrane science》2006,280(1-2):6-9
A novel process was proposed for preparation of microporous poly(acrylonitrile–methyl methacrylate) (P(AN–MMA)) membranes by phase inversion techniques using ultrasonic humidifier. Being prepared by dissolving the polymer (PAN–MMA) in the N,N-dimethylformamide (DMF) solution with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Successively, the glass plate was exposed to the water vapor produced by ultrasonic humidifier, inducing the phase inversion. It is found the pore size is much more uniform across the cross-section of the membrane than that of the porous membrane prepared by conventional water bath coagulation technique. The microporous membranes were directly obtained after the washing and drying. It had about 1–5 μm of pores and presented an ionic conductivity of 2.52 × 10−3 S/cm at room temperature when gelled with 1 M LiPF6/EC-DMC (1:1 vol.%) electrolyte solution. The test cells with the gel electrolytes prepared from as-prepared microporous membranes showed stable cycling capacities, indicating that the microporous membrane, which was prepared from cheap starting materials acrylonitrile and methyl methacrylate, can be used for the gel electrolyte of lithium batteries. 相似文献
73.
提高电压是提高锂离子电池比能量的重要途径之一。例如,LiNi0.5Mn1.5O4(4.7 V)、LiNiPO4(5.1 V)和富锂锰基等电极材料在较高的充电截止电压下表现出较高的能量密度和较低的成本,具有很好的应用前景。另外,提高LiCoO2和三元电池体系的充电截止电压是提升电池能量密度的简单有效措施。但是,当电池充电截止电压提高时,不仅会造成电解液在正极/电解液界面的氧化分解,还会加速正极中金属阳离子在电解液中的溶解,造成电池循环性能和安全性下降。采用不同的正极界面修饰用电解液添加剂,既可以有效钝化正极/电解液界面,抑制电解液的分解,还可以有效抑制正极结构的破坏。本文从添加剂的分子结构出发,介绍了磺酸酯、硼酸酯、磷酸酯、氟代碳酸酯、腈类、酸酐和锂盐等添加剂在正极界面的相关研究成果,并对不同添加剂的作用机理进行了详细的解释和归纳;另外,介绍了添加剂的联用技术在不同电池体系中的最新研究成果;最后,对新型正极界面修饰用电解液添加剂的开发进行了展望。 相似文献
74.
The nonlinear Schrödinger equation is of tremendous interest in both theory and applications. Various regimes of pulse propagation in optical fibers are modeled by some form of the nonlinear Schrödinger equation. In this paper we introduce sequential and parallel split-step Fourier methods for numerical simulations of the nonlinear Schrödinger-type equations. The parallel methods are implemented on the Origin 2000 multiprocessor computer. Our numerical experiments have shown that these methods give accurate results and considerable speedup. 相似文献
75.
The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated. The
sulfur composites showed novel electrochemical characteristics as well as high specific capacity and good cycleability. The
sulfur composite presented the average discharge voltage of 1.9 V, which was just the half of conventional LiCoO2 cathode materials, indicating that the double cells in series presented the same working voltage as conventional LiCoO2 cells and meaning that the sulfur composite cells will have good interchangeability with conventional LiCoO2 cells. The overcharge test showed that the sulfur composite cell cannot be charged over 5.0 V, indicating that the sulfur
composite cell presented the intrinsic safety for overcharge. Overcharge can cause serious problems for the conventional Li
ion cells. The overcharge test also showed that the sulfur composite cell was destroyed when the cell was charged over 4.0 V,
resulting in that the cell cannot normally be discharged again. It is found, however, that the sulfur composite cell can be
discharged again at very low current density of a 0.002-C rate after the cell was overcharged. Being much safer than lithium
metal anode, the graphite anode was used to fabricate sulfur composite/graphite lithium ion cells with a prelithiated sulfur
composite cathode, which was produced by electrochemical lithiation. The charge/discharge and cycling characteristics of the
sulfur composite/graphite cell was investigated. The result showed that the sulfur composite/graphite cells can be normally
cycled and showed the different voltages from that of the cell with the lithium metal anode. This paves the effective way
to fabricate safer sulfur composite/graphite lithium ion cells. 相似文献
76.
Multi‐analysis strategy for metabolism of Andrographis paniculata in rat using liquid chromatography/quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
Wenlan Li Xiangming Sun Ying Xu Xuezhi Wang Jing Bai Yubin Ji 《Biomedical chromatography : BMC》2015,29(7):1016-1026
Compared with chemical drugs, it is a huge challenge to identify active ingredients of multicomponent traditional Chinese medicine (TCM). For most TCMs, metabolism investigation of absorbed constituents is a feasible way to clarify the active material basis. Although Andrographis paniculata (AP) has been extensively researched by domestic and foreign scholars, its metabolism has seldom been fully addressed to date. In this paper, high‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry was applied to analysis and characterization of AP metabolism in rat urine and feces samples after oral administration of ethanol extract. The differences in metabolites and metabolic pathways between the two biological samples were further compared. The chemical structures of 20 components were tentatively identified from drug‐treated biological samples, including six prototype components and 14 metabolites, which underwent such main metabolic pathways as hydrolyzation, hydrogenation, dehydroxylation, deoxygenation, methylation, glucuronidation, sulfonation and sulfation. Two co‐existing components were found in urine and feces samples, suggesting that some ingredients' metabolic processes were not unique. This study provides a comprehensive report on the metabolism of AP in rats, which will be helpful for understanding its mechanism. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
77.
设ρ(M)是微分流形M上的左四元数矢丛,文中给出ρ(M)的辛Pontryagin示性类和辛Pontryagin示性式的定义,并给出说明它们之间的联系的积分公式。 相似文献
78.
DEGREE OF COPOSITIVE POLYNOMIAL APPROXIMATION 总被引:2,自引:0,他引:2
Yu Xiangming 《数学年刊B辑(英文版)》1989,10(3):409-415
Denoteby _n(f) the degree of copositive approximation to f(x) by polynomials of degree≤n. For function f(x) ∈ C~k[-1, 1] which alternates in sign finitely many timesin [-1, 1], the author obtains the following Jackson type estimates_n(f)≤Cn~(-k)w(f~(k), 1/n)foa any positive integer k. 相似文献
79.
A new simple method for the synthesis of alpha-glycosyl thiols is described. Ring-opening of 1,6-anhydrosugars with commercially available bis(trimethylsilyl)sulfide under the action of catalytic amounts of TMSOTf smoothly afforded alpha-glycosyl thiols in very high yields and in a stereospecific way. 相似文献
80.
Jiasen Yan Dr. Xianying Han Zhaohan Dang Prof. Dr. Jiangang Li Prof. Dr. Xiangming He 《Chemphyschem》2023,24(23):e202300320
Paraffin (PA)/expanded graphite (EG) is an important composite phase change material with low cost, high heat storage, good thermal conductivity and cycling stability. Its thermal conductivity needs to be further improved for application in the thermal management system of power lithium-ion batteries. In this paper, copper plated expanded graphite (CPEG) with 3D porous structure was prepared by electroless copper plating method, which was used as thermal conductivity enhancing material to replace part of EG in PA/EG composite materials. For the optimized phase change material composed of 80 %PA-14 %EG-6 %CPEG, the copper content is very low (0.768 wt %), but its thermal conductivity can be significantly improved without loss of latent heat and thermal cycling stability. Its thermal conductivity is increased from 11 times to 16.5 times that of paraffin while compared with the copper-free composite material (80 %PA-20 %EG). The PA/EG/CPEG composite material exhibits good temperature control effect on power lithium-ion batteries. 相似文献