Influence of the tetravalent cation on the high-voltage electrochemical activity of LiNi0.5M1.5O4 spinel cathode materials

The electrochemical properties of substituted LiNi_0.5Mn_1.5−xM_xO₄ spinels at high potential (>4 V vs Li⁺/Li) have been investigated for M = Ti and Ru, in order to determine the role of the tetravalent cation in such systems where nickel is a priori the only electroactive species. These systems are found to form extended solid solutions (up to x = 1.3 and x = 1.0 for Ti and Ru, respectively) that were characterized by X-ray diffraction and Raman spectroscopy. Titanium substitution induces a drastic decrease in high potential electrochemical capacity, whereas the capacity is maintained and the kinetics are even improved in the presence of ruthenium. These results are completed by new results on the Li_4−2xNi_3xTi_5−xO₁₂ spinel system, which shows not any high potential activity in spite of the presence of up to 0.5 Ni²⁺ per spinel formula unit on the octahedral site. Taking into account previous data on LiNi_0.5Ge_1.5O₄, we clearly show that even if the tetravalent cation does not participate in the overall redox reaction, electrochemical activity is only possible when nickel is surrounded by tetravalent cations able to accept a local variation of valence (Mn, Ru), whereas full-shell cations such as Ti⁴⁺ and Ge⁴⁺ block the necessary electron transfer pathways in the spinel oxide electrode.     

基于Femtocell的CDMA室内覆盖技术研究

文章首先介绍了Femtocell飞小区的特性和网络架构,分析了Femtocell相比传统的CDMA室内覆盖技术的优点,最后深入剖析了目前Femtocell室内覆盖技术存在的问题并提出解决方案。     

Probing enzyme promiscuity of SGNH hydrolases

Several hydrolases of the SGNH superfamily, including the lipase SrLip from Streptomyces rimosus (Q93MW7), the acyl-CoA thioesterase I TesA from Pseudomonas aeruginosa (Q9HZY8) and the two lipolytic enzymes EstA (from P. aeruginosa, O33407) and EstP (from Pseudomonas putida, Q88QS0), were examined for promiscuity. These enzymes were tested against four chemically different classes of a total of 34 substrates known to be hydrolysed by esterases, thioesterases, lipases, phospholipases, Tweenases and proteases. Furthermore, they were also analysed with respect to their amino acid sequences and structural homology, and their phylogenetic relationship was determined. The Pseudomonas esterases EstA and EstP each have an N-terminal domain with catalytic activity together with a C-terminal autotransporter domain, and so the hybrid enzymes EstA(N)-EstP(C) and EstP(N)-EstA(C) were constructed by swapping the corresponding N- and C-terminal domains, and their hydrolytic activities were compared. Interestingly, substrate specificity and kinetic measurements indicated a significant influence of the autotransporter domains on the catalytic activities of these enzymes in solution. TesA, EstA and EstP were shown to function as esterases with different affinities and catalytic efficacies towards p-nitrophenyl butyrate. Of all the enzymes tested, only SrLip revealed lipase, phospholipase, esterase, thioesterase and Tweenase activities.     

Synthesis,structure and catalytic activities for hydrogen transfer reaction of the carbonyl ruthenium(II) complex containing polypyridine and phosphine ligands

The synthesis and characterization of new ruthenium(II) carbonyl complexes containing polypyridine and triphenylphosphine ligands is reported. Crystallographic information obtained for the trans-PPh₃-[Ru(biq)(PPh₃)₂(CO)]Cl₂ complex (biq = 2,2’-biquinoline) reveals five-coordination on the metal. The complexes were studied as catalysts in hydrogen transfer reactions in basic solution. Turnover frequencies in the 2250-817 h^-1 range were determined in 1 hour of reaction with a substrate/catalysts ratio of 830.     

Modified ESPRIT (M-ESPRIT) algorithm for time delay estimation in both any noise and any radar pulse context by a GPR radar

This paper presents M-ESPRIT, a modified version of the ESPRIT algorithm, for the purpose of time delay estimation of backscattered radar signals. The proposed algorithm takes both the transmitted pulse shape and any noise into account. It can process raw data from experimental device without the preprocessing which would be required with the conventional ESPRIT algorithm.     

A 1 GHz Digital Channel Multiplexer for Satellite Outdoor Unit

A digital channel multiplexer for satellite outdoor unit running at 1 GHz clock frequency is implemented in 65 nm CMOS mixed oxide dual voltage technology. This multiplexer, based on a 1 GS/s digital signal processor (DSP) approach with 500 MHz input and output bandwidth, embeds two 8 bit 1 GS/s analog-digital converters (ADCs) and two 8 bit 1 GS/s digital-analog converter (DACs). It consumes less that 1022 mW at ambient temperature while achieving noise rejection up to 42.5 dB on a single tone, and > 37 dB on modulated satellite channels.     

两性离子型聚丙烯酰胺的研究进展

从制备和应用两个方面系统阐述了国内外两性聚丙烯酰胺的研究现状及进展,并针对两性聚丙烯酰胺的应用优势及制备难点,对今后的研究工作提出了一些建议。     

预应力钢骨混凝土梁非线性分析

为进一步研究预应力钢骨混凝土梁的工作性能,运用有限条带法,考虑材料非线性,编制计算程序,对其在单调荷载作用下的整个受力过程进行分析。计算得到预应力与普通钢骨混凝土梁在开裂阶段、屈服阶段、极限阶段的荷载、位移值,及混凝土强度、含钢率、有效预应力、非预应力筋配筋率对预应力钢骨混凝土梁荷载—变形关系的影响曲线。结果表明,对钢骨混凝土梁施加预应力,能显著提高构件的开裂承载力和极限承载力,但其延性有所降低;混凝土强度等级越高,梁的开裂承载力和极限承载力越大;含钢率越大,截面刚度越大,构件承载力提高越明显;开裂前阶段,非预应力筋配筋率对构件承载力的影响较小,开裂后,非预应力筋配筋率越大,梁的极限承载力越大。     

宁夏水利信息化现状及建设构想

宁夏水利信息化建设目前仍处于封闭、落后状态,大量资料和信息仍然以传统的手工作业为主。宁夏需要实现水利现代化,而水利信息化是宁夏水利现代化的必然选择,那就必须改变目前的水利信息化建设现状。在此就宁夏水利信息化的建设目标及建设内容展开论述,为未来宁夏水利信息化建设提供参考。     

泸定水电站岸塔式进水塔结构动力响应分析

根据泸定水电站岸塔式进水塔的结构特点,建立了进水塔结构—水体—地基的三维动力有限元附加质量模型。分析了进水塔结构在施工完建期空库工况和正常蓄水位工况下分别与水平向、三向地震作用叠加的动力特性,确定了可能引起结构破坏的最不利位置。计算结果表明,水平向地震作用对结构应力应变影响较大,竖向地震作用的影响较小。