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21.
A. Celaya Sanfiz T. W. Hansen F. Girgsdies O. Timpe E. Rödel T. Ressler A. Trunschke R. Schlögl 《Topics in Catalysis》2008,50(1-4):19-32
This work presents a detailed investigation of the preparation of MoVTeNbO x catalysts by hydrothermal synthesis. Phase-pure synthesis of M1 has been achieved applying the metals in a molar ratio Mo/V/Te/Nb = 1/0.25/0.23/0.12. Raman, UV/Vis spectroscopy, and SEM/EDX analysis show that the elements are inhomogeneously distributed in the initial suspension that is formed after mixing the metal salts in an aqueous medium. Iso- and heteropoly anions of molybdenum, free telluric acid as well as supra-molecular polyoxometalate clusters are observed in the solution, whereas all metals have been found in the precipitate. Complete rearrangement of molecular building blocks under hydrothermal conditions is essential for formation of phase-pure materials. Optimized synthesis conditions with respect to temperature and time result in the formation of a precursor consisting of nano-structured M1 characterized by an extended periodic organization in the [001] direction and a fairly homogeneous distribution of the elements. Residual ammonium containing supra-molecular species in the precursor result in the formation of phase mixtures during the subsequent crystallization by heat treatment in inert gas. Phase-pure M1 exhibits a distinct degree of flexibility with respect to the chemical composition that becomes obvious by incorporating Nb not exclusively into pentagonal bi-pyramidal units, but also into octahedral coordinated positions as shown by EXAFS. Anisotropic growth of the needle-like M1 crystals has been observed during the final heat treatment performed at 873–923 K in inert atmosphere disclosing a potential method to control the catalytic properties of MoVTeNbO x catalysts. 相似文献
22.
A semiautomated electron backscatter diffraction technique for extracting reliable twin statistics 总被引:2,自引:0,他引:2
B. L. Henrie T. A. Mason B. L. Hansen 《Metallurgical and Materials Transactions A》2004,35(12):3745-3751
A framework has been developed for extracting reliable twin statistics from a deformed microstructure using crystallographic
twin identification techniques with spatially correlated electron backscatter diffraction (EBSD) data. The key features of
this analysis are the use of the mathematical definition of twin relationships, the inclination of the common K
1 plane at a twin boundary, and the correct identification of the parent orientation in a parent/twin pair. Methods for identifying
the parent in a parent/twin pair will be briefly discussed and compared. Twin area fractions are then categorized by operative
twin systems, number of active twin variants in each system, and corrected twin widths. These statistics are reported here
for α-zirconium samples deformed in quasi-static four-point bend beams and in a 100 m/s Taylor cylinder impact test. Analysis of
the statistics also begins to reveal the roles that deformation rate and relative orientation of the boundary conditions to
the material’s symmetry axes play in determining the twinning activity that accommodates the imposed boundary conditions.
These improved twin statistics can help quantify the deformation processes in materials that deform by twinning as well as
serve to provide better validation of proposed models of the deformation processes. 相似文献
23.
24.
Two cases of adverse reactions to intravesical treatment with bacillus Calmette-Guérin are reported. The first patient presented with a severe suppurating epididymo-orchitis three months after his last treatment. The second patient developed Reiter's disease with arthritis of one knee and conjunctivitis 1 week after the fourth instillation. 相似文献
25.
Current sanitation concepts of decentralised wastewater treatment and reuse raise the issue of monitoring and maintenance of such systems. To guarantee high quality of the recycled water, systems with high requirements concerning process technology are essential. With increasing numbers of decentralised treatment systems spread over far distances it will become more and more impossible and uneconomic to have expert personnel on site. Therefore, new visualisation and intelligent information systems are necessary. The paper describes the structure and 3D-demonstrations as a base for information visualisation. Up-to-date visualisation techniques, facilitating the cognition of context-adapted information, make it possible to maximise the amount of information presented to the user without overwhelming her or him. Concerning diagnosis and decision support systems in the domain of wastewater treatment, several interesting approaches are presented, estimating their applicability for decentralised wastewater treatment systems. The intelligent decision support system presented here consists of a combined ontology- and case-based reasoning system in addition to a process monitoring system. It is responsible for plausibility checks, error diagnosis, solution proposals, and optimisation suggestions. 相似文献
26.
27.
Combined-Stage Sintering Model 总被引:8,自引:0,他引:8
James D. Hansen Richard P. Rusin Mao-Hua Teng D. Lynn Johnson 《Journal of the American Ceramic Society》1992,75(5):1129-1135
By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted T, comprises five scaling factors that relate specific microstructural featuers (e.g., surface curvature) to the scale (grain diameter). Calculations of T from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on T, and (c) changes in T with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed. 相似文献
28.
Jeffrey E. Marchese Matteo Cirillo Niels Grøch-Jensen 《Open Systems & Information Dynamics》2007,14(2):189-196
We present evidence for a close analogy between the nonlinear behaviour of a pulsed microwave-driven Josephson junction at
low temperature and the experimentally observed behaviour of Josephson systems operated below the quantum transition temperature
under similar conditions. We specifically address observations of Ramsey-type fringe oscillations, which can be understood
in classical nonlinear dynamics as results of slow transient oscillations in a pulsed microwave environment. Simulations are
conducted to mimic experimental measurements by recording the statistics of microwave-induced escape events from the anharmonic
potential well of a zero-voltage state. Observations consistent with experimentally obtained Ramsey-type oscillations are
found in the classical model.
An erratum to this article can be found at 相似文献
29.
A. K. Hansen A. C. Boxer J. L. Ellsworth D. T. Garnier I. Karim J. Kesner M. E. Mauel E. E. Ortiz 《Journal of Fusion Energy》2007,26(1-2):57-60
Plasmas in the Levitated Dipole Experiment (LDX) are formed and sustained currently via two electron cyclotron resonance heating
(ECRH) sources: 2.5 kW at 2.45 GHz and 2.5 kW at 6.4 GHz. An important topic being investigated is how varying the ECRH affects
the confinement and stability of the plasma. We report the results of using different operational combinations of our RF sources,
such as varying the power composition, changing the power levels, and sequencing of the onset time. 相似文献
30.