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91.
92.
Dr. Nan Wang Dr. Shuping Wang Prof. Luping Tang Dr. Lilei Ye Björn Cullbrand Abdelhafid Zehri Dr. Behabitu Ergette Tebikachew Prof. Johan Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6561-6568
Poor bonding strength between nanomaterials and cement composites inevitably lead to the failure of reinforcement. Herein, a novel functionalization method for the fabrication of functionalized graphene oxide (FGO), which is capable of forming highly reliable covalent bonds with cement hydration products, and therefore, suitable for use as an efficient reinforcing agent for cement composites, is discussed. The bonding strength between cement and aggregates was improved more than 21 times with the reinforcement of FGO. The fabricated FGO also demonstrated many important features, including high reliability in cement pastes, good dispersibility, and efficient structural refinement of cement hydration products. With the incorporation of FGO, cement mortar samples demonstrated up to 40 % increased early and ultimate strength. Such results make the fast demolding and manufacture of light constructions become highly possible, and show strong advantages on improving productivity, saving cost, and reducing CO2 emissions in practical applications. 相似文献
93.
94.
Eric Johnsen Johan Larsson Ankit V. Bhagatwala William H. Cabot Parviz Moin Britton J. Olson Pradeep S. Rawat Santhosh K. Shankar Bj?rn Sj?green H.C. Yee Xiaolin Zhong Sanjiva K. Lele 《Journal of computational physics》2010,229(4):1213-1237
Flows in which shock waves and turbulence are present and interact dynamically occur in a wide range of applications, including inertial confinement fusion, supernovae explosion, and scramjet propulsion. Accurate simulations of such problems are challenging because of the contradictory requirements of numerical methods used to simulate turbulence, which must minimize any numerical dissipation that would otherwise overwhelm the small scales, and shock-capturing schemes, which introduce numerical dissipation to stabilize the solution. The objective of the present work is to evaluate the performance of several numerical methods capable of simultaneously handling turbulence and shock waves. A comprehensive range of high-resolution methods (WENO, hybrid WENO/central difference, artificial diffusivity, adaptive characteristic-based filter, and shock fitting) and suite of test cases (Taylor–Green vortex, Shu–Osher problem, shock-vorticity/entropy wave interaction, Noh problem, compressible isotropic turbulence) relevant to problems with shocks and turbulence are considered. The results indicate that the WENO methods provide sharp shock profiles, but overwhelm the physical dissipation. The hybrid method is minimally dissipative and leads to sharp shocks and well-resolved broadband turbulence, but relies on an appropriate shock sensor. Artificial diffusivity methods in which the artificial bulk viscosity is based on the magnitude of the strain-rate tensor resolve vortical structures well but damp dilatational modes in compressible turbulence; dilatation-based artificial bulk viscosity methods significantly improve this behavior. For well-defined shocks, the shock fitting approach yields good results. 相似文献
95.
Gunnar Aksnes Fayez Y. Khalil Piotr J. Majewski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):157-161
Abstract This study reports rate data of the alkoxide promoted decomposition of triphenyl 3-hydroxypropyl phosphonium chloride, diphenyl di(3-hydroxypropyl)phosphonium chloride, and tetraphenyl phosphonium bromide. Comparison of kinetics, rate constants, and activation parameters of the alkoxide promoted decompositions points to different mechanism as compared to the hydroxyl promoted reaction. The alkoxide reaction is believed to proceed via a hexacovalent intermediate. Reasons for the hexacovalent route are discussed. 相似文献
96.
Gunnar Aksnes Roald Gierstae Erik A. Wulvik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):141-152
Abstract A study of alkaline decomposition of several aromatic phosphine oxides containing p- and o-nitrobenzyl, and trichloromethyl as leaving groups, is reported. The property of the trichloromethyl group as leaving group, and the CCl? 3-group's further decomposition in the hydrolysis of diethyl and disodium trichloromethanephosphonates, have also been investigated. 相似文献
97.
Marie Kjærgaard Bjørk Kirsten Wiese Simonsen David Wederkinck Andersen Petur Weihe Dalsgaard Stella Rögn Sigurðardóttir Kristian Linnet Brian Schou Rasmussen 《Analytical and bioanalytical chemistry》2013,405(8):2607-2617
An efficient method for analyzing illegal and medicinal drugs in whole blood using fully automated sample preparation and short ultra-high-performance liquid chromatography–tandem mass spectrometry (MS/MS) run time is presented. A selection of 31 drugs, including amphetamines, cocaine, opioids, and benzodiazepines, was used. In order to increase the efficiency of routine analysis, a robotic system based on automated liquid handling and capable of handling all unit operation for sample preparation was built on a Freedom Evo 200 platform with several add-ons from Tecan and third-party vendors. Solid-phase extraction was performed using Strata X-C plates. Extraction time for 96 samples was less than 3 h. Chromatography was performed using an ACQUITY UPLC system (Waters Corporation, Milford, USA). Analytes were separated on a 100 mm?×?2.1 mm, 1.7 μm Acquity UPLC CSH C18 column using a 6.5 min 0.1 % ammonia (25 %) in water/0.1 % ammonia (25 %) in methanol gradient and quantified by MS/MS (Waters Quattro Premier XE) in multiple-reaction monitoring mode. Full validation, including linearity, precision and trueness, matrix effect, ion suppression/enhancement of co-eluting analytes, recovery, and specificity, was performed. The method was employed successfully in the laboratory and used for routine analysis of forensic material. In combination with tetrahydrocannabinol analysis, the method covered 96 % of cases involving driving under the influence of drugs. The manual labor involved in preparing blood samples, solvents, etc., was reduced to a half an hour per batch. The automated sample preparation setup also minimized human exposure to hazardous materials, provided highly improved ergonomics, and eliminated manual pipetting. Figure
Robotic setup for fully automated solid-phase extraction of whole blood 相似文献
98.
Vidar Bj⊘rnstad 《合成通讯》2013,43(10):1793-1800
Conversion of a cyclic carbonyl carbon into a quaternary carbon has been effected by a Wittig–Horner reaction with diethyl (N-benzyliden)aminomethylphosphonate and a subsequent alkylation with a protected vinyl ketone. The product was a substrate for spiroannulation after initial hydrolysis. The reaction sequence was carried out as a one-pot reaction. 相似文献
99.
100.
Filipe E. Antunes Luís Alves Claudia Duarte Björn Lindman Björn Klotz Axel Böttcher 《Journal of Dispersion Science and Technology》2013,34(9):1368-1372
Physical properties of aqueous solutions of hydrophobically modified crosslinked polyacrylic acids change quite extensively as the polymer is charged up. A study is carried out concerning the similarities between two polymer ionization processes, that is, by pH increment and anionic surfactant addition. The two processes charge the polymer by distinctly different mechanisms. At sufficiently high pH the carboxylic groups of the polymer are virtually all ionized and the polymer is, therefore, fully charged. The effective repulsion among the charged groups due to the entropy of the counterions promotes an increased stiffness as well as an expansion of the polymer particles. We investigate here how the ionization and swelling will be if, instead of high pH, the polymer is at low pH conditions but associated to ionic surfactants. Surfactants associate to the polymer both in a noncooperative way by the binding of individual surfactant molecules and in a cooperative way as micelles since the polymer promotes surfactant self-assembly. This binding leads to a highly charged polymer-surfactant complex and leads to an osmotic swelling as well. The swelling and the gelation were monitored by rheology and dynamic light scattering, of polymer solutions by varying the pHs and adding ionic surfactants at low pH. The results show that ionization by surfactants and by pH lead to approximately the same gelation degree, as can be seen by similar viscosity values. Both processes result in dramatic viscosity increases, up to 8 orders of magnitude. More hydrophobic surfactants, with longer alkyl chain, are shown to be more efficient as enhancers of swelling and gelation. The network that is formed at high pH or at sufficiently high concentration of surfactant can be weakened or even disrupted if monovalent or divalent salts are added, demonstrating the role of counterion entropy. 相似文献