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991.
Else Breval Maria Klimkiewicz Chiping Wang Joseph P. Dougherty Ann Crespi 《Journal of the American Ceramic Society》2007,90(8):2664-2666
Annealing of a sintered pellet of Pb0.9175 La0.055 Zr0.975 Ti0.025 O3 in air without any precautions against PbO evaporation results in a core–shell microstructure with a solid PLZT core and a porous ZrO2 -rich shell. 相似文献
992.
Maria D. Salazar-Villalpando David A. BerryTodd H. Gardner 《International Journal of Hydrogen Energy》2008
Partial oxidation of methane (POM) was studied over Rh/(Ce0.56Zr0.44)O2−x, Rh/(Ce0.91Gd0.09)O2−x, Rh/(Ce0.71Gd0.29)O2−x and Rh/(Ce0.88La0.12)O2−x. The effect of catalyst reducibility and redox cycles was investigated. It was found that the type of doped-ceria support and its reducibility played an important role in catalyst activity. It was also observed that redox cycles had a positive influence on H2 production, which was enhanced as the number of redox cycle increased. Results of carbon formation are discussed as a function of ionic conductivity. Temperature programmed reduction (TPR) profiles, BET surface area, ionic conductivity and XRD patterns were determined to characterize catalysts. Catalytic tests revealed that of the materials tested, Rh/(Ce0.56Zr0.44)O2−x was the most active material for the production of syngas, which correlates with its TPR profile. It was observed that doping CeO2 with Zr, rather than with La or Gd caused an enhanced reducibility of Rh/supported-ceria catalysts. 相似文献
993.
Rinaldo Cervellati Emanuela Greco Stefano Costa Maria Clelia Guerra Ester Speroni 《International Journal of Food Science & Technology》2008,43(10):1866-1870
The antioxidant capacities and the total phenolic content in cocoa liquor directly manufactured chocolate from an artisan manufacturer were measured using different in vitro methods (BR, TEAC, and Folin–Ciocalteu Reagent). These parameters were then compared with those of a chocolate made by a leading manufacturing company producing chocolate and cocoa‐containing products. A statistical analysis of the collected data showed that the antioxidant properties of the artisan‐made chocolate are significantly better than those of the factory‐produced one. These results were ascribed to the fact that all the bioactive components in the cocoa beans are better preserved in the artisan‐made chocolate. 相似文献
994.
Maria Elena De Giuli Dean Fantazzini Mario Alessandro Maggi 《Computational Economics》2008,31(2):161-180
In this paper we present a new model to assess the firm value and the default probability by using a bivariate contingent
claim analysis and copula theory. First we discuss an unfeasible case, given the current derivative market on corporate bonds,
which involves univariate digital options to compute the risk neutral probabilities. We then discuss a feasible model, which
considers risky interest rates, instead. Moreover, we develop in this framework a new methodology to extract default probabilities
from stock prices, only, going beyond the standard KMV-Merton model. Besides, the non-observability of the Merton model’s
state variable requires numerical methods, but the results can be unstable with noisy risky data. We show how the null price
can be used as a useful barrier to separate an operative firm from a defaulted one, and to estimate its default probability.
We then present an empirical application with both operative and defaulted firms to show the advantages of our approach.
相似文献
995.
Development and the Implementation of High-Temperature Reliable Heaters in Plasma Spray Technology 总被引:1,自引:1,他引:0
Maria Prudenziati 《Journal of Thermal Spray Technology》2008,17(2):234-243
Many problems have been encountered during development of reliable high-temperature heaters by means of atmospheric plasma
spray and procedures commonly adopted in thermal spray technology, especially due to poor steel substrate corrosion resistance,
notably affected by grit-blasting operations, but also deriving from contamination of insulating layers, dielectric arcs,
and failures due to hot spots in the heating elements. While seeking the origin of these problems, a close scrutiny of every
single step of the preparation process and analyses of the coatings were carried out using laser confocal scanning microscopy,
optical and electronic microscopy, fluorescence analysis, X-ray diffraction, and ancillary techniques. The electrical properties
of both alumina layers and metal strips prepared with Ni, NiCr, NiAl commercial powders for the heating elements were studied
and cross-related to the failures in the heaters. The article reports the main results of these investigations, delineates
the innovations introduced to overcome or circumvent the problems, and underlines the distinct characteristics of new heaters,
whose reliability has been proven up to now with temperatures of up to 600 °C in air. 相似文献
996.
Oils and asphaltenes derived from direct extraction and several mild depolymerization processes have been studied. The asphaltenes have been fractionated by column adsorption chromatography (with deactivated silica gel) and benzene, THF and MeOH were used in sequence as eluothropic series. Clear chemical separation between one aromatic and two polar fractions has been obtained, giving high percentages recovery. The fractions have been characterized by VPO, FT-IR, 1H-NMR and elemental analysis. Several structural parameters of oils have been calculated. These oils can be assimilated to equivalent average hydrocarbons having between 10 and 20 carbon atoms and an aromatic carbon percentage oscillating between 47 and 66%. In general, the degree of substitution in aromatic rings is low and the presence of phenolic groups is limited. The majority of the carbons are aromatic and these rings show low degrees of condensation. 相似文献
997.
Maria Da Penha Pereira Albuquerque Linda V. Ehlin Caldas 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1989,280(2-3):310-313
Two new ionization chambers were designed, constructed and tested in beta and X-radiation fields. They have a circular form, a sensitive volume of 0.6 cm3 and collecting electrodes of graphite and aluminium. The short- and long-term stability checks and the lack of current leakage indicate that the present performance of the chambers is comparable to that expected from secondary standards. The differential energy dependence of both chambers permits effective-energy determination of unknown X-radiation fields. The chambers display applicability for 90Sr + 90Y radiation detection. 相似文献
998.
María C. Caracoche Jorge A. Martinez Patricia C. Rivas Fernanda Andreola Federica Bondioli Anna Maria Ferrari Tiziano Manfredini 《Journal of the American Ceramic Society》2008,91(7):2357-2359
This paper deals with the phase stability of an aqueous suspension of tetragonal Zr0.9 Pr0.1 O2 (20 wt%/vol%) at room temperature as a function of the aging time. The suspension is investigated in situ using the highly localized Perturbed Angular Correlations technique. The results indicate that an almost fully reversible degradation process toward monoclinic zirconia takes place through a first-order reaction of rate constant k =0.7 day−1 . Two successive diffusion mechanisms are observed that are interpreted as OH− ions' migration in the grain surface and then, as proton defects' diffusion into the bulk. 相似文献
999.
1000.
Isabel C.F.R. Ferreira Lillian Barros Maria Elisa Soares Maria Lourdes Bastos José Alberto Pereira 《Food chemistry》2007,103(1):188-195
Olive trees (Olea europaea L. Cv. Cobrançosa) from the northeast of Portugal were sprayed with three different copper formulations [bordeaux mixture (copper sulphate + calcium hydroxide − 20% Cu), copper hydroxide (40% Cu) and copper oxychloride (50% Cu)] to control olive fungal diseases. The residues of copper in olive leaves, harvested at different times, were evaluated by atomic absorption spectrometry. At all the collection times, treated olive leaves had significantly higher copper contents, compared to the control. The different copper amounts in pesticide formulations lowered the leaves contents in total phenols and hence their antioxidant properties. Olive leaves sprayed with copper oxychloride possessed the highest copper levels and the lowest content in phenols, which influenced its antioxidant activity (higher EC50 values for reducing power, scavenging effect on DPPH radicals and inhibition of erythrocyte hemolysis). Leaves without copper residues proved to be a good natural source of antioxidants, giving values comparable to the reference compounds. 相似文献