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1.
Impact of the Oxygen Defects and the Hydrogen Concentration on the Surface of Tetragonal and Monoclinic ZrO2 on the Reduction Rates of Stearic Acid on Ni/ZrO2 下载免费PDF全文
Sebastian Foraita Dr. John L. Fulton Zizwe A. Chase Aleksei Vjunov Pinghong Xu Dr. Eszter Baráth Dr. Donald M. Camaioni Dr. Chen Zhao Prof. Dr. Johannes A. Lercher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2423-2434
The role of the specific physicochemical properties of ZrO2 phases on Ni/ZrO2 has been explored with respect to the reduction of stearic acid. Conversion on pure m‐ZrO2 is 1.3 times more active than on t‐ZrO2, whereas Ni/m‐ZrO2 is three times more active than Ni/t‐ZrO2. Although the hydrodeoxygenation of stearic acid can be catalyzed solely by Ni, the synergistic interaction between Ni and the ZrO2 support causes the variations in the reaction rates. Adsorption of the carboxylic acid group on an oxygen vacancy of ZrO2 and the abstraction of the α‐hydrogen atom with the elimination of the oxygen atom to produce a ketene is the key to enhance the overall rate. The hydrogenated intermediate 1‐octadecanol is in turn decarbonylated to heptadecane with identical rates on all catalysts. Decarbonylation of 1‐octadecanol is concluded to be limited by the competitive adsorption of reactants and intermediate. The substantially higher adsorption of propionic acid demonstrated by IR spectroscopy and the higher reactivity to O2 exchange reactions with the more active catalyst indicate that the higher concentration of active oxygen defects on m‐ZrO2 compared to t‐ZrO2 causes the higher activity of Ni/m‐ZrO2. 相似文献
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Reflections from geometric discontinuities can be used with ultrasonic energy to predict the temperature of an interface where classical temperature measurement techniques are impractical because of physical access limitations or harsh environmental conditions. Additionally, these same ultrasonic measurements can be used with inversion methods commonly applied to ill-posed heat transfer problems to increase the accuracy of the measurement of surface temperature or heat flux at the surface of interest. Both methods for determining surface temperature are presented, along with a comparison of results both from a verification example and using data gathered in a field test of the methods. The results obtained with these two methods are shown to be in good agreement with an empirical relationship used in the design of large caliber guns. 相似文献
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Naijing Su Juliana A. Theorell Prof. Dr. Donald J. Wink Prof. Dr. Tom G. Driver 《Angewandte Chemie (International ed. in English)》2015,54(44):12942-12946
The combination of 20 mol % of copper iodide and lithium tert‐butoxide triggers the formation of a broad range of substituted, functionalized α‐alkoxy 2H‐naphthalenones from readily available N‐tosylhydrazones. The data suggests that this transformation occurs through cycloaddition of a copper carbenoid with an ester, followed by a Lewis acid‐catalyzed [1,2] alkyl shift of the in situ generated alkoxyepoxide intermediate. 相似文献
6.
Donald E. Carlson 《Journal of Elasticity》1973,3(3):169-178
Necessary and sufficient conditions for the displacement and/or the stress to be independent of Poisson's ratio or the shear modulus or the mass density in the standard boundary-initial-value problems of three-dimensional classical elastodynamics are determined.
Department of Theoretical and Applied Mechanics, University of Illinois at Urbana 相似文献
Résumé On détermine des conditions nécessaires et suffisantes pour que les déplacements et (ou) les contraintes soient indépendants du coefficient de Poisson ou du module de rigidité ou du densité de masse dans les problémes classiques de l'élasticité tri-dimensionnelle dynamique.
Department of Theoretical and Applied Mechanics, University of Illinois at Urbana 相似文献
7.
The initial theory of Frenkel and Eshelby for the coalescence of drops in air (or sintering) of Newtonian fluids, which equated the work of surface tension to the work done by viscous stresses while assuming biaxial extensional flow kinematics, was extended to the case of time-dependent material functions using the Upper Convected Maxwell (UCM) model. A numerical scheme was developed to solve the ordinary differential equations (ODE) for the stresses, which are embedded in the ODE based on the mechanical energy balance. Initial conditions required to solve the set of non-linear ODEs were obtained from visualization experiments of the coalescing drops as the theory for elastic contact gave unrealistically high values of the initial neck radius. The transient model predicted that coalescence was accelerated by increasing the relaxation time, the opposite relationship of what was predicted by the steady-state UCM formulation, and was capable of quantitatively predicting the experimental coalescence rates at times when viscoelasticity was important. 相似文献
8.
Donald D. Gray 《Applied Scientific Research》1977,33(5-6):437-457
The dynamics of a buoyant plume rising above a horizontal line heat source in a transverse, horizontal magnetic field is investigated.
Similarity is shown to occur when the magnetic field strength varies as the −2/5 power of vertical distance from the source.
The plume depends on two parameters — the Prandtl number (Pr) and the Lykoudis number (Z
L). Families of exact closed form solutions are derived for Pr=5/9 and Pr≥2. A family of numerical integrations for Pr=0.01 (typical of liquid metals) is also reported. The magnetic field is shown to affect the profiles of velocity and temperature
by altering the similarity functions, the coefficients, and the value of the independent similarity variable corresponding
to a fixed physical position. An approximate closed form solution valid for low Pr and high Z
L is presented. Possible experimental tests of the theory are proposed.
Research sponsored by the U.S. Energy Research and Development Administration under interagency agreement with Union Carbide
Corporation. 相似文献
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10.
The transition of the thermal boundary layer from start-up to a quasi-steady state in a side-heated cavity is observed using a shadowgraph technique. Three stages of the transition, including an initial growth stage, an entrainment development stage and a quasi-steady stage, are demonstrated. A significant feature of the transition revealed from the present flow visualisation is the formation of a double-layer structure along the sidewall at the entrainment development stage. It is believed that the reverse flow in the double-layer structure is the likely cause responsible for the unstable travelling waves at the quasi-steady state. 相似文献