30 research outputs found
Nanomaterials From Imogolite: Structure, Properties, and Functional Materials
International audienceHollow cylinders with a diameter in the nanometer range are carving out prime positions in nanoscience. Thanks to their physico-chemical properties, they could be key elements for next-generation nanofluidics devices, for selective molecular sieving, energy conversion or as catalytic nanoreactors. Several difficult problems such as fine diameter and interface control are solved for imogolite nanotubes. This chapter will present an overview of this unique class of clay nanotubes, from their geological occurrence to their synthesis and their applications. In particular, emphasis will be put on providing an up-to-date description of their structure and properties, their synthesis and the strategies developed to modify their interfaces in a controlled manner. Developments on their applications, in particular for polymer/imogolite nanotubes composites, molecular confinement or catalysis, are presented
Hypervalent iodine(III)-mediated oxidative acetoxylation of 2-methoxyphenols for regiocontrolled nitrogen benzannulation
Nitrogen-tethered 2-methoxyphenols are conveniently dearomatized into synthetically useful orthoquinol acetates by treatment with phenyliodine(III) diacetate in methylene chloride at low temperature. Subsequent fluoride- or base-induce intramolecular nucleophilic addition reactions furnish indole and quinoline derivatives. The potential of this methodology for the synthesis or a functionalized lycorine-type alkaloid skeleton is introduced here. (C) 2001 Elsevier Science Ltd. All rights reserved
Hypervalent iodine(III)-mediated oxidative acetoxylation of 2-methoxyphenols for regiocontrolled nitrogen benzannulation
Nitrogen-tethered 2-methoxyphenols are conveniently dearomatized into synthetically useful orthoquinol acetates by treatment with phenyliodine(III) diacetate in methylene chloride at low temperature. Subsequent fluoride- or base-induce intramolecular nucleophilic addition reactions furnish indole and quinoline derivatives. The potential of this methodology for the synthesis or a functionalized lycorine-type alkaloid skeleton is introduced here. (C) 2001 Elsevier Science Ltd. All rights reserved
Exponential asymptotics
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Modal behavior of a reduced scale pump-turbine impeller. Part II. Numerical Simulation
A numerical simulation has been carried out to analyze the modal behavior of a
reduced scale pump-turbine impeller. The simulation has been done using FEM method, in air
and in water. The same boundary conditions than in the experiment were considered: free body
in air and free body submerged in a reservoir of water. A sensitivity analysis to determine the
influence of the number of elements was done. The influence of the input parameters was also
taken into account. Finally, a mesh with 165000 elements for the impeller in air and of 508676
for the impeller in water was used. The results obtained with the simulation have been
compared with the experimental ones (paper 1). Both the natural frequency values and the
mode-shapes were compared. The numerical results showed small deviation from experiment
in the first modes in modes with low modal density. In some coupled modes been found. With
the updated model the mode-shapes have been analyzed. Some modes with high modal density
have been found. As indicated in the experiment, the effect of the added mass reduces the
natural frequencies and also changes the characteristics of the coupled mode
Analysis if the dynamic response of pump-turbine runners- Part I: Experiment
When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed.Postprint (published version
Design optimization and evaluation of integrating sound level meters
Incl. 6 reprints at backAvailable from British Library Document Supply Centre- DSC:D76116 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
Analysis if the dynamic response of pump-turbine runners- Part I: Experiment
When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed
Analysis of the dynamic response of pump-turbine runners. Part I: Experiment
When in operation, pump-turbine runners have to withstand large pressure pulsations generated by the rotor-stator interaction. The analysis of the dynamic behavior of these structures is necessary to avoid damage. For this analysis a realistic model of the runner is necessary. When the runner is submerged in water and inside the casing, its dynamic response is greatly affected. The added mass effects of the surrounding fluid and the proximity of the head-cover and bottom-cover may reduce the natural frequencies. The frequency reduction produced by the added mass effects and the influence of the boundary conditions has to be known for a safe design of the runner. In this paper an experimental investigation on the dynamic response of a model runner is presented. A reduced scale model of a pump-turbine was tested outside and inside the casing with different boundary conditions. For the excitation of the runner at different frequencies piezoelectric patches were used. The response was measured with miniature accelerometers located in several positions inside the runner. From the measurements the natural frequencies and mode-shapes of the runner were calculated using EMA. The influence of the added mass and of the boundary conditions is presented and discussed