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101.
耗资百亿之巨的国家重点工程──万家寨引黄入晋工程以其规模宏大、技术复杂而驰名。本文在对工程概况进行扼要介绍的基础上,重点概述了输水隧洞工程中存在的几个主要工程地质问题及所应采取的工程对策,并从工程地质角度论证了兴建该工程的可行性。 相似文献
102.
Christopher J. Teskey Andrew Y. W. Lui Michael F. Greaney 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(40):11843-11846
The first example of a transition‐metal‐catalyzed, meta‐selective C H bromination procedure is reported. In the presence of catalytic [{Ru(p‐cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C H bond of 2‐phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one‐pot bromination/arylation and bromination/alkenylation procedures to deliver meta‐arylated and meta‐alkenylated products, respectively, in a single step. 相似文献
103.
Claire Yuet Yan Wong Alex Wing-Tat Choi Matthew Y. Lui Bálint Fridrich Attila K. Horváth László T. Mika István T. Horváth 《Structural chemistry》2017,28(2):423-429
Dry gamma-valerolactone (GVL) is stable for several weeks at 150 °C and its thermal decomposition only proceeds in the presence of appropriate catalysts. Since GVL does not react with water up to 60 °C for several weeks, it could be used as a green solvent at mild conditions. At higher temperatures, GVL reacts with water to form 4-hydroxyvaleric acid (4-HVA) and reaches the equilibrium in a few days at 100 °C. Aqueous solutions of acids (HCl and H2SO4) catalyze the ring opening of GVL even at room temperature, which leads to the establishment of an equilibrium between GVL, water, and 4-HVA. Although the 4-HVA concentration would be below 4 mol% in the presence of acids, it could be higher than the concentration of a reagent or a catalyst precursor, not to mention a catalytically active species. The latter could be especially worrisome as 4-HVA could be an excellent bi- or even a tri-dentate ligand for transition metals. Aqueous solution of bases (NaOH and NH4OH) also catalyzes the reversible ring opening of GVL. While in the case of NaOH, the product is the sodium salt of 4-hydroxyvalerate, the reversible reaction of GVL, with NH4OH results in the formation of 4-hydroxyvaleric amide. The reversible ring opening of (S)-GVL in the presence of HCl or NaOH has no effect on the stability of the chiral center. 相似文献
104.
刘满凤 《南昌大学学报(理科版)》1991,15(3):1
本文讨论了在锥控意义下的多目标规划ε—有效解的最优性条件,提出了ε—共轭映射的概念,ε—共轭映射的一些基本性质,并利用这些性质建立了关于ε—有效解的共轭对偶理论。 相似文献
105.
106.
RE Tribble A Azhari HL Clark CA Gagliardi Y-W Lui AM Mukhamedzhanov A Sattaroy X Tang L Trache V Burjan J Cejpek V Kroha S Piskor J Vincour F Carstoiu 《Pramana》1999,53(3):585-594
S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which
provide the normalization of the tail of the overlap function. For example the overlap for 8B → 7Be+p defines the S-factor for 7Be (p, γ)8B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of
the technique, the 16O(3He, d)17F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited
states of 17F. The S-factors for 16O(p, γ)17F calculated from these 17F → 16O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same
technique, the 10B(7Be, 8B)9Be and 14N(7Be, 8B)13C reactions have been used to measure the asymptotic normalization coefficient for 7Be(p, γ)8B. This result provides an indirect determination of S
17(0). 相似文献
107.
研究了掺铒TeO2-ZnO-PbCl2碲酸盐基氧卤玻璃在977nm激光二极管抽运下的发光和上转换发光特性,结果发现除红外153μm4I13/2→4I15/2发光外(荧光半高宽高达69nm),该玻璃还存在很强的2H11/2→4I15/2(527nm),4S3/2→4I15/2(549nm)和4F9/2→4I15/2(666nm)可见上转换发光.应用Judd-Ofelt理论计算得到玻璃强度参数Ωt(t=2,4,6)分别为Ω2=587×10-20cm2,Ω4=208×10-20cm2,Ω6=116×10-20cm2,计算了铒离子跃迁振子强度、自发辐射概率、荧光分支比、荧光寿命等光谱参量.应用McCumber理论计算得153μm处的玻璃受激发射截面可达875×10-21cm2实验结果表明,与硅酸盐玻璃、磷酸盐玻璃、氟化物玻璃等比较,掺铒碲酸盐基氧卤玻璃在宽带掺铒光纤放大器和上转换激光器中有着极大的研究和应用潜力.
关键词:
掺Er3+
碲酸盐玻璃
氧卤玻璃
Judd-Ofelt理论
光谱性质 相似文献
108.
Bruna Carolina Lui Dias Mariana Millan Fachi Michel Leandro de Campos Flvia Lada Degaut Degaut Rosngela Gonalves Peccinini Roberto Pontarolo 《Biomedical chromatography : BMC》2019,33(11)
Monitoring the plasma concentrations of metformin and sodium‐glucose cotransporter‐2 inhibitors (canagliflozin, dapagliflozin and empagliflozin) is essential for pharmacokinetic and bioequivalence studies and therapeutic monitoring. The present work therefore aimed to develop and validate a high‐performance liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS) method for the simultaneous quantification of these drugs in human plasma. The analyses were performed using an Agilent 1200 HPLC system coupled to an Applied Biosystems API 3200 triple quadrupole MS/MS with electrospray ionization in positive ion mode. After one‐step protein precipitation of plasma with acetonitrile containing 0.1% formic acid, chromatographic separation was achieved on an Xbridge C18 column, with a mobile phase consisting of a gradient of water and acetonitrile, both containing 1 mm ammonium formate and 0.1% formic acid. Quantification was performed in multiple reaction monitoring mode using m/z 130.1 → 71.1 for metformin, m/z 462.0 → 191.2 for canagliflozin, m/z 426.1 → 167.1 for dapagliflozin and m/z 468.0 → 354.9 for empagliflozin. The proposed method was validated and demonstrated to be adequate for the quantification of metformin, canagliflozin, dapagliflozin and empagliflozin for clinical monitoring, pharmacokinetics and bioequivalence studies. 相似文献
109.
Melanie W. Lui Nathan R. Paisley Dr. Robert McDonald Dr. Michael J. Ferguson Prof. Dr. Eric Rivard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):2134-2145
We report the synthesis of structurally tunable boron complexes supported by N‐heterocyclic imine ligands IPr=N?BR2 (IPr=[(HCNDipp)2C], Dipp=2,6‐iPr2C6H3, R=Cl and/or Ph) that have the ability to abstract dihydrogen from amine‐boranes, and instigate their dehydrocoupling. In one instance, mild heating of the hydrogen addition product IPr=NH?B(Ph)HCl releases H2 to regenerate the starting N‐heterocyclic iminoborane; accordingly IPr=N?B(Ph)Cl can be used as a metal‐free catalyst to promote the dehydrocoupling of MeNH2 ? BH3 to yield N‐methylaminoborane oligomers [MeNH‐BH2]x. 相似文献
110.
Li Z Lui CH Cappelluti E Benfatto L Mak KF Carr GL Shan J Heinz TF 《Physical review letters》2012,108(15):156801
The in-plane optical phonons around 200?meV in few-layer graphene are investigated utilizing infrared absorption spectroscopy. The phonon spectra exhibit unusual asymmetric features characteristic of Fano resonances, which depend critically on the layer thickness and stacking order of the sample. The phonon intensities in samples with rhombohedral (ABC) stacking are significantly higher than those with Bernal (AB) stacking. These observations reflect the strong coupling between phonons and interband electronic transitions in these systems and the distinctive variation in the joint density of electronic states in samples of differing thickness and stacking order. 相似文献