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101.
Carlo Marini Anna M. Diaz-Rovira B. J. Kennedy Boby Joseph 《Journal of Materials Engineering and Performance》2018,27(12):6322-6327
The effort to find thermoelectric materials suitable for different applications is an intense research topic of a large material science community. In this context, A-site-deficient La1/3NbO3, which shows an irreversible pressure-induced amorphization at above 15 GPa, has attracted recent attention. Here, we present a temperature-dependent Nb K-edge extended x-ray absorption fine structure (EXAFS) study of La1/3NbO3 in the range 77-500 K probing the Nb-O bond correlations. These results are compared with the Nb-O bond correlations in two related oxides NbO2 and Nb2O5. In comparison with NbO2 and Nb2O5, the Nb-O bond mean square relative displacements in La1/3NbO3 show much weaker temperature dependence revealing its enhanced spring constant. The “A” site deficiency in La1/3NbO3 may allow the oxygen atoms to preserve their local geometry and thus are less responsive to the external stimuli like temperature, which may be important in determining the thermal and electrical conductivity properties of this system. 相似文献
102.
Nanomachining and beam-assisted Pt deposition by a focused ion beam (FIB) was used to modify AFM probes for improved electric force measurements. Si(3)N(4) cantilevers have been endowed with a nano-electrode at the tip apex to confine the electro-sensitive area at the very tip. This action results in both a marked decrease of the parasitic capacitive effect and in an improved electric force microscopy (EFM) contrast and resolution, with respect to usual, full metal-coated cantilevers. This fabrication approach is suited to the development of innovative electro-sensitive probes, useful in different scanning probe techniques. 相似文献
103.
J.J. Williams Z. Flom A.A. Amell N. Chawla X. Xiao F. De Carlo 《Acta Materialia》2010,58(18):6194-6205
Metal matrix composites (MMCs) have a combination of high strength, high stiffness, and low density. The damage behavior of MMCs has been studied extensively by a combination of traditional mechanical testing, microstructural characterization, and post-experiment fractographic analysis. X-ray tomography is an excellent technique that eliminates destructive cross-sectioning, and allows for superior resolution and image quality with minimal sample preparation. In this work, we have carried out a detailed investigation of the damage behavior of SiC particle reinforced 2080 Al alloy matrix composites by X-ray synchrotron tomography. This work is unique, relative to the existing work in the literature, because it: (a) focuses on a technologically relevant MMC system (2080/SiCp), (b) uses a combination of image analysis techniques to enable visualization and damage characterization, and (c) entails a significant amount of quantitative and statistical analyses of particle fracture and void growth in the composite. A statistically significant number of particles and volume of the composite were characterized, enabling a meaningful and realistic interpretation of the results. Based on this, a detailed understanding of the micromechanisms of fracture and the quantitative influence of particle size and aspect ratio were obtained. 相似文献
104.
Cristina Siligardi Maria Cristina D'Arrigo Cristina Leonelli Gian Carlo Pellacani Tom E. Cross 《Journal of the American Ceramic Society》2000,83(4):1001-1003
This paper reports results that show the effect of microwave absorption on the bulk crystallization of two glasses in the CaO—ZrO2 —SiO2 system. The glass samples were devitrified using either microwave or conventional heating, to compare the results obtained from the two different techniques. Remarkably different crystallization paths were observed, depending mostly on the composition of the glass. This observation was especially true when microwave heating was used, where the dielectric losses observed in silicate glasses are related to the ZrO2 content. X-ray diffraction analysis was performed on the powdered samples, to determine the crystalline phases present. The microstructure and microanalysis results of these glass-ceramic compositions are presented and are related to the different ZrO2 contents. 相似文献
105.
Marko Saban George Liebermann Alex Jay An‐Chang Shi Nam Ro William Dale Pat Forgione 《加拿大化工杂志》2000,78(2):320-329
Anionic polymerization of styrene in THF with n‐butyllithium/alpha‐methylstyrene initiator is described as a first step in preparation of a styrenic block copoly‐mer. In order to suppress rapid decay of living alpha‐methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at ?20(+5)°C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modelling of styrene propagation reaction all key process parameters were defined for l‐L, 38‐L, and 189‐L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well‐defined polymers up to Mn 22 000 via the “living” polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30). 相似文献
106.
Subset ARMA Model Identification Using Genetic Algorithms 总被引:1,自引:0,他引:1
Carlo Gaetan 《时间序列分析杂志》2000,21(5):559-570
Subset models are often useful in the analysis of stationary time series. Although subset autoregressive models have received a lot of attention, the same attention has not been given to subset autoregressive moving-average (ARMA) models, as their identification can be computationally cumbersome. In this paper we propose to overcome this disadvantage by employing a genetic algorithm. After encoding each ARMA model as a binary string, the iterative algorithm attempts to mimic the natural evolution of the population of such strings by allowing strings to reproduce, creating new models that compete for survival in the next population. The success of the proposed procedure is illustrated by showing its efficiency in identifying the true model for simulated data. An application to real data is also considered. 相似文献
107.
Carlo Giorgio Visconti Enrico Tronconi Luca Lietti Gianpiero Groppi Pio Forzatti Cinzia Cristiani Roberto Zennaro Stefano Rossini 《Applied Catalysis A: General》2009,370(1-2):93-101
In principle, the application of monolithic catalysts to the Fischer–Tropsch synthesis can solve many of the problems related to the classical Fischer–Tropsch reactors, in particular concerning the necessity to operate with short diffusion distances and low pressure drops, preferably according to the ideal plug-flow behavior, while still maintaining a reasonable inventory of catalytic material in the reactor volume.The preparation of prototype cobalt-based catalysts, washcoated onto metallic structured supports with different geometries, is described herein, together with the evaluation of the catalytic properties of such systems in the Fischer–Tropsch synthesis at industrially relevant process conditions (220–235 °C, 20 bar, 2.1 molH2/molCO, 5000 cm3(STP)CO+H2/h/gcat). Comparative tests with the same catalyst in the powdered form were also carried out at the same process conditions.It was found that the structured catalysts maintained the activity and the selectivity of the original powdered catalyst, provided that the washcoat thickness is sufficiently thin. 相似文献
108.
Ferruccio Ceriotti Emma Guagnellini Francesco Zoppi Norberto Montalbetti Carlo Okely Pierangelo Bonini 《Journal of Automated Methods and Management in Chemistry》1989,11(5):206-211
A multicentre evaluation of the Monarch centrifugal analyser is
reported. Precision, linearity and accuracy were assessed by
comparison with routine methods. Calibration stability, photometric
and dispensing accuracy, and carry-over related to samples
and reagents were also evaluated. The overall performance of the
instrument was good, showing an excellent photometric and
dispensing accuracy, absence of sample-dependent carry-over, and almost
negligible reagent carry-over. Good precision, linearity and
correlation with routine methods were found for the parameters
tested. The instrument is reliable and is now used as the routine
clinical chemistry analyser in two of the three laboratories taking
part in the evaluation. 相似文献
109.
Christian Müller Dr. Maria Antonia Gomez‐Zurita Frau Dr. Dario Ballinari Dr. Sonia Colombo Dr. Alessandro Bitto Dr. Enzo Martegani Prof. Cristina Airoldi Dr. Anske Stephanie van Neuren Dr. Matthias Stein Dr. Jörg Weiser Dr. Carlo Battistini Dr. Francesco Peri Prof. 《ChemMedChem》2009,4(4):524-528
A panel of new potential Ras ligands was generated by decorating a tricyclic levoglucosenone‐derived scaffold with aromatic moieties. Some members of the panel show in vitro inhibitory activity toward the nucleotide exchange process on Ras and are toxic to some human cancer cell lines.
110.
Igor Maria De Rosa Carlo Santulli Fabrizio Sarasini Marco Valente 《Polymer Composites》2009,30(12):1879-1887
The production of glass/plant fiber hybrid laminates is a possibility for obtaining semistructural materials with sufficient impact properties, and a better life cycle analysis (LCA) profile than fiberglass. The simplest and possibly the most effective configuration for the production of these hybrids would involve the use of a plant fiber reinforced laminate as the core between two glass fiber reinforced laminates. A main limitation to the use of composites including plant fibers is that their properties may be significantly affected by the presence of damage, so that even the application of a low stress level can result in laminate failure. In particular, it is suggested that when loading is repeatedly applied and removed, residual properties may vary in an unpredictable way. In this work, E‐glass/jute hybrid reinforced laminates, impacted in a range of energies (10, 12.5, and 15 J), have been subjected to post‐impact cyclic flexural tests with a step loading procedure. This would allow evaluating the effect of damage dissipation offered by the plant fiber reinforced core. The tests have also been monitored by acoustic emission (AE), which has confirmed the existence of severe limitations to the use of this hybrid material when impacted at energies close to penetration. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers 相似文献