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941.
Alkali aggregate reaction (AAR) affects numerous civil engineering structures and causes irreversible expansion and cracking. In order to control the safety level and the maintenance cost of its hydraulic dams, Electricité de France (EDF) must reach better comprehension and better prediction of the expansion phenomena. For this purpose, EDF has developed a numerical model based on the finite element method in order to assess the mechanical behaviour of damaged structures. The model takes the following phenomena into account: concrete creep, the stress induced by the formation of AAR gel and the mechanical damage. A rheological model was developed to assess the coupling between the different phenomena (creep, AAR and anisotropic damage). Experimental results were used to test the model. The results show the capability of the model to predict the experimental behaviour of beams subjected to AAR. In order to obtain such prediction, it is necessary to take all the phenomena occurring in the concrete into consideration. 相似文献
942.
Le Yu 《Electrochimica acta》2010,55(3):1258-348
Li2Se-Sb2Se3 nanocomposites with a highly heterogeneous mixture have been fabricated by reactive pulsed laser deposition method. The electrochemical properties of the as-deposited Li2Se-Sb2Se3 thin film during the first charging and discharging have been investigated by the galvanostatic cycling and cyclic voltammetry measurements for the first time. By using ex situ X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) measurements, the decomposition of Li2Se driven by Sb2Se3 under the electrochemical potential is revealed. In the first cycle, the oxidation peaks at 2.5 V and 3.2 V and the reduction peaks at 2.0 V can be attributed to the decomposition and formation of Li2Se with the conversion reaction of Sb2Se3 into Sb2Se5. Our findings demonstrate that nanocomposite Li2Se-Sb2Se3 can possess very high electrochemical activity. These results present a special case of solid-state heterogeneous electrochemistry with both nanostructured binary materials. 相似文献
943.
The electrochemical properties of substituted LiNi0.5Mn1.5−xMxO4 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 Li4−2xNi3xTi5−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 LiNi0.5Ge1.5O4, 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. 相似文献
944.
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。 相似文献
945.
Leščić Ašler I Ivić N Kovačić F Schell S Knorr J Krauss U Wilhelm S Kojić-Prodić B Jaeger KE 《Chembiochem : a European journal of chemical biology》2010,11(15):2158-2167
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. 相似文献
946.
S.A. Moya M. Vidal G. Abarca C. Martinez V. Guerchais H. Le Bozec M.T. Garland S. Rodriguez P. Aguirre 《Inorganic chemistry communications》2010,13(12):1519-1521
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. 相似文献
947.
Modified ESPRIT (M-ESPRIT) algorithm for time delay estimation in both any noise and any radar pulse context by a GPR radar 总被引:1,自引:0,他引:1
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. 相似文献
948.
Busson P. Chawla N. Bach J. Le Tual S. Singh H. Gupta V. Urard P. 《Solid-State Circuits, IEEE Journal of》2010,45(1):84-94
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. 相似文献
949.
950.
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。 相似文献