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901.
902.
稀土对等离子喷涂镍—碳化钛陶瓷涂层摩擦学性能的影响 总被引:15,自引:1,他引:14
用销盘摩擦磨损试验机模拟齿面的相对滑动,经测定摩擦系数和上下试样的磨损体积损失、涂层的金相分析,磨痕形貌及成分的扫描微镜观察及分析,研究硅铁稀土混合物对高能等离子喷涂金属陶瓷涂层摩擦学特性的影响,试验结果表明:添加稀土使涂层致密性提高,摩擦系数有所降低,上下试样的磨损体积损失分别减小33%和74%,摩擦副表面温升降低,表明添加稀土有且于在涂层表面形成连续的氧化膜,从而防止胶合并提高耐磨性。 相似文献
903.
磁性流体密封的优化设计 总被引:10,自引:3,他引:7
通过数值计算及实验对磁性流体密封的结构与参数进行了优化设计,给出了磁钢材料及尺寸的设计原则,研究了单级密封的密封压差与磁极斜角、极尖宽度和密封间隙的关系。分析了多级密封的级数、齿宽、槽宽及齿高对磁性流体多级密封的影响,给出了最优取值范围。 相似文献
904.
基于RSA算法的网络安全体系构造 总被引:2,自引:0,他引:2
提出了一种完全基于RSA算法的网络安全参考模型NetRSA.采用分布式KDC分配方案,并且对通信报文以加密方式进行数字签名,有效地防止了报文被非法窃听、篡改或伪造.本模型实现了密钥管理、加密管理、数字签名以及身份认证等功能, 相似文献
905.
Zhaolong Wang Yiming Hu Wenjun Liu Dr. Li Xu Dr. Meili Guan Dr. Yan Zhao Dr. Jian Bao Prof. Huaming Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9382-9388
Hydrogen production by energy-efficient water electrolysis is a green avenue for the development of contemporary society. However, the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR) occurring at the anode are impeded by the sluggish reaction kinetics during the water-splitting process. Consequently, it is promising to develop bifunctional anodic electrocatalysts consisting of nonprecious metals. Herein, a bifunctional CoMn layered double hydroxide (LDH) was grown on nickel foam (NF) with a 1D–2D–3D hierarchical structure for efficient OER and UOR performance in alkaline solution. Owing to the significant synergistic effect of Mn doping and heterostructure engineering, the obtained Co1Mn1 LDH/NF exhibits satisfactory OER activity with a low potential of 1.515 V to attain 10 mA cm−2. Besides, the potential of the Co1Mn1 LDH/NF catalyst for UOR at the same current density is only 1.326 V, which is much lower than those of its counterparts and most reported electrocatalysts. An urea electrolytic cell with a Co1Mn1 LDH/NF anode and a Pt–C/NF cathode was established, and a low cell voltage of 1.354 V at 10 mA cm−2 was acquired. The optimized strategy may result in promising candidates for developing a new generation of bifunctional electrocatalysts for clean energy production. 相似文献
906.
We study the following mean field equation$$\Delta_{g}u+\rho\left(\frac{e^{u}}{\int_{\mathbb{S}^{2}}e^{u}d\mu}-\frac{1}{4\pi}\right)=0\ \ \mbox{in}\ \ \mathbb{S}^{2},$$where $\rho$ is a real parameter. We obtain the existence of multiple axially asymmetric solutions bifurcating from $u=0$ at the values $\rho=4n(n+1)\pi$ for any odd integer $n\geq3$. 相似文献
907.
908.
Li Liu Zhi Qiang Zhou Jie Ping Shi Chang Gui Lu Yi Ping Cui Guo Yuan Lu 《中国化学快报》2011,22(10):1147-1150
Two tribranched chromophores,1,3,5-triazine as electron deficient core,9,9-dimethylfluorene asπ-conjugated bridge, diphenylamino(4a) and naphthylamino(4b) as electron-donating end-groups,were successfully prepared via Buchwald-Hartwig coupling reaction.Their linear photophysical and two-photon absorption(TPA) properties were investigated by absorption, fluorescence and nonlinear transmission method,respectively.The absorption cut-offs of the chromophores are below 550 nm and both chromophores have strong fluorescence emission.The compound 4a(206.3 GM) exhibits larger TPA cross-section than 4b (57.8 GM) in the femtosecond regime at 800 nm. 相似文献
909.
Wenbo Wu Prof. Gui Yu Prof. Yunqi Liu Prof. Cheng Ye Prof. Jingui Qin Prof. Zhen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):630-641
Herein, through a combination of divergent and convergent approaches, coupled with the utilization of the powerful Sharpless “click chemistry” reaction, two series of high‐generation nonlinear optical (NLO) dendrimers have been conveniently prepared in high purity and satisfactory yields. Perfluoroaromatic rings and isolation chromophores were introduced to further improve their comprehensive performance. Thanks to the effects of Ar? ArF self‐assembly and the isolation chromophores, coupled with perfect 3D spatial isolation from the highly branched structure of the dendrimer, G5‐PFPh‐NS displayed very large NLO efficiency (up to 257 pm V?1), which is, to the best of our knowledge, the new record highest value reported so far for simple azo chromophore moieties. High‐quality wide optical transparency and good stability were also achieved. 相似文献
910.
Lingyao Li Emily A. Franckowiak Yi Xu Evan McClain Wenjun Du 《Journal of polymer science. Part A, Polymer chemistry》2013,51(17):3693-3699
A microwave‐assisted glycosylation method was developed for efficient synthesis of oligosaccharides. Di‐functional AB monomers, 2,3,4‐tri‐O‐acetyl‐α‐d ‐galactopyranosyl bromide ( 3a ) and 2,3,4‐tri‐O‐acetyl‐α‐d ‐glucopyranosyl bromide ( 3b ) were designed and synthesized as weakly reactive monomers to avoid unwanted glycosylation or degradation during preparation and storage. The glycosylations of these monomers gave low conversions and low molecular weight oligosaccharides at rt, reflux, and under low microwave energy irradiation. However, the glycosylation became very effective when high microwave energy was applied, giving 100% conversion and producing oligosaccharides with Mn = 4.76 kDa for 3a and Mn = 4.05 kDa for 3b. The acetylated oligosaccharides were further subjected to deprotection for structural analysis, which indicated the oligosaccharides contain predominantly linear β‐(1,6)‐glycosyl linkages. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3693–3699 相似文献