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排序方式: 共有262条查询结果,搜索用时 390 毫秒
71.
Julien Gurt SantanachClaude Estournès Alicia WeibelGeoffroy Chevallier Vincent BleyChristophe Laurent Alain Peigney 《Journal of the European Ceramic Society》2011,31(13):2247-2254
Spark Plasma Sintering (SPS) is increasingly used. The temperature and current are not independent parameters, making it difficult to separate the current intrinsic role from Joule heating. There is a debate on whether there are any specific SPS mechanisms. The influence of a key parameter, the (on:off) pulse pattern, is studied on the SPS of reactive α-Al2−2xFe2xO3 (x = 0.02; 0.05; 0.07; 0.10) powders. Changing it modifies the current crest intensity and has a great influence on the materials microstructure. Comparisons with runs where the current is blocked and hot-pressing reveal three competing phenomena: formation of FeAl2O4, dominant in the core and not peculiar to SPS, formation of Fe, producing Fe-Al2O3 composite surface layers, and most notably electrical-field induced diffusion of Fe3+ ions towards the cathode, which could have far-ranging implications for the consolidation of ionic materials and the in situ reactive shaping of composites and multimaterials. 相似文献
72.
73.
Nanoscale Microstructural and Chemical Analysis of SiO2–Zn1−xAlxO Nanocomposites: Towards a Better Understanding of Si and Al Substitution in ZnO
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Matthieu Gilbert Celine Byl David Berardan Alexandre Gloter Nita Dragoe François Vurpillot 《Journal of the American Ceramic Society》2015,98(12):3948-3955
In this study, we report on the microstructure of SiO2‐coated Al‐doped ZnO nanoparticles densified by spark plasma sintering(SPS), using a multiscale approach. Our observations show that it is possible to successfully prepare dense pellets while keeping the nanostructure with well‐defined Si‐rich grain boundaries. Although a very limited partial solubility of Si in the ZnO matrix has been observed, Si is mostly concentrated at the grain boundaries. More surprisingly, we evidenced some areas with nanoscale inhomogeneity of the Al concentration, which can locally strongly exceed the average composition of the matrix. It could explain the apparent discrepancy observed in the literature between the simultaneous presence of ZnAl2O4 in Al‐doped ZnO, which should be the signature of the doping level exceeding the solubility limit, and the concentration of carriers that still depends on the nominal Al concentration in ZnO even in the presence of ZnAl2O4. 相似文献
74.
Alex Bauer Chaojie Song Rob Hui Laure Chevallier Jacques Rozière 《Electrochimica acta》2010,55(28):8365-8370
The electrochemical stability of Pt deposited on mesoporous carbon, which was either applied in its unmodified state or coated with 20 wt% TiO2, was investigated by cyclic voltammetry in N2 purged 0.5 M sulfuric acid. XRD analysis revealed that TiO2 was present in the anatase phase. The mean Pt particle diameter was ∼6 and ∼4 nm for mesoporous carbon with and without TiO2, respectively. Pt supported on TiO2 modified substrates was more stable than Pt supported on conventional mesoporous carbon when subjected to 1000 cycles in the potential range from 0.05 to 1.25 V vs. RHE. This was evident from the observation that the support with TiO2 retained ∼53% of the electrochemically active surface area relative to the state observed after 100 cycles, whereas ∼33% of the active area remained in the case without TiO2. The oxygen reduction mass activity was identical for both fresh samples (i.e., ). After 1000 cycles the mass activity decreased to for the case without TiO2, whereas with TiO2 the deactivation was minor; i.e., the mass activity after 1000 cycles was . 相似文献
75.
76.
Celine Abecassis‐Moedas Sihem Ben Mahmoud‐Jouini Claudio Dell'Era Delphine Manceau Roberto Verganti 《Creativity & Innovation Management》2012,21(3):315-331
In the ‘knowledge economy’, knowledge‐intensive business services (KIBS) are a key driver for innovation and competitiveness. The internationalization of these businesses raises challenges given their specificities such as knowledge intensity, the importance of customer interaction and intimacy in service delivery. This paper focuses on design consultancies as a specific type of creative KIBS for which these characteristics are emphasized. The objective of this research is to analyse the resources leveraged by the firms to compete internationally. It is based on 11 case studies of design consultancies located in five different countries (France, Italy, Portugal, Spain and the UK) that were selected for their capacity to perform at the international level for several years. The paper advances three internationalization modes depending on contingent variables and focusing on specific resources that enable international competitiveness: star‐based, process‐based and glocality‐based. In star‐based creative KIBS, the individual designer has developed a reputation that attracts customers internationally, operating as a brand. In process‐based creative KIBS, the reputation of a collective creative process attracts clients from other countries. In glocality‐based creative KIBS, the geographical proximity obtained by opening international offices helps to develop a close understanding of the client through frequent interactions, and also to know the client's market well and to better understand local codes and signs. These modes complement those presented in the existing internationalization literature which takes the peculiarities of creative KIBS into consideration. 相似文献
77.
Mahmoud Elashiry Ana Carolina Morandini Celine Joyce Cornelius Timothius Mira Ghaly Christopher W. Cutler 《International journal of molecular sciences》2021,22(12)
Traditional antimicrobial therapies for periodontitis (PD) have long focused on non-selective and direct approaches. Professional cleaning of the subgingival biofilm by instrumentation of dental root surfaces, known as scaling and root planning (SRP), is the mainstay of periodontal therapy and is indisputably effective. Non-physical approaches used as adjuncts to SRP, such as chemical and biological agents, will be the focus of this review. In this regard, traditional agents such as oral antiseptics and antibiotics, delivered either locally or systemically, were briefly reviewed as a backdrop. While generally effective in winning the “battle” against PD in the short term, by reducing its signs and symptoms, patients receiving such therapies are more susceptible to recurrence of PD. Moreover, the long-term consequences of such therapies are still in question. In particular, concern about chronic use of systemic antibiotics and their influence on the oral and gut microbiota is warranted, considering antibiotic resistance plasmids, and potential transfer between oral and non-oral microbes. In the interest of winning the “battle and the war”, new more selective and targeted antimicrobials and biologics for PD are being studied. These are principally indirect, blocking pathways involved in bacterial colonization, nutrient acquisition, inflammation or cellular invasion without directly killing the pathogens. This review will focus on current and prospective antimicrobial therapies for PD, emphasizing therapies that act indirectly on the microbiota, with clearly defined cellular and molecular targets. 相似文献
78.
Characterization and selection of Lactobacillus sakei strains isolated from traditional dry sausage for their potential use as starter cultures 总被引:1,自引:0,他引:1
Salim Ammor Eric Dufour Monique Zagorec Stphane Chaillou Isabelle Chevallier 《Food microbiology》2005,22(6):529-538
A total of 36 Lactobacillus sakei strains isolated from traditional dry sausage, produced without the use of starter cultures, were characterized in respect to their technological properties, i.e. growth and acidification kinetics, ability to grow at different temperatures, pH values or salt concentrations, gas production from glucose, heme-dependent catalase activity, inhibitory activity against pathogens and proteolytic and lipolytic activities.Growth rates were comprised between 0.12 and 0.55 gen/h; while acidification rates varied from 0.01 and 0.07 pH unit/h. All isolates were able to grow at pH 4.2–9.6 and at 15 °C on acetate agar supplemented with 4% NaCl, but were not able to grow at 0 and 45 °C and with 10% NaCl in the same pH conditions. However, 97% of the isolates were able to grow at 4 °C, but only 11%, and 55% were able to grow at pH 3.9 and with 6.5% NaCl, respectively. All isolates were homofermentative from glucose. Heme-dependant catalase activity was found for 97% of the isolates and 3% displayed antibacterial activity against Listeria innocua. Most isolates showed leucine and valine arylamidase and only one exhibited a lipase (C14) activity.Two strains were selected using a multi-variate analysis. Both of them showed a panel of properties highly desirable in sausage fermentation. We propose the use of these strains, in combination with coagulase-negative staphylococci as starter cultures in the studied small-scale facility in order to improve and standardize sausage safety and quality while preserving their typicality. 相似文献
79.
Cohen Robin Allaby Coralee Cumbaa Christian Fitzgerald Mark Ho Kinson Hui Bowen Latulipe Celine Lu Fletcher Moussa Nancy Pooley David Qian Alex Siddiqi Saheem 《User Modeling and User-Adapted Interaction》1998,8(3-4):171-214
This paper presents some alternate theories for explaining the term 'initiative', as it is used in the design of mixed-initiative AI systems. Although there is now active research in the area of mixed initiative interactive systems, there appears to be no true consensus in the field as to what the term 'initiative' actually means. In describing different possible approaches to the modeling of initiative, we aim to show the potential importance of each particular theory for the design of mixed initiative systems. The paper concludes by summarizing some of the key points in common to the theories, and by commenting on the inherent difficulties of the exercise, thereby elucidating the limitations which are necessarily encountered in designing such theories as the basis for designing mixed-initiative systems. 相似文献
80.
Decision trees for hierarchical multi-label classification 总被引:3,自引:0,他引:3
Celine Vens Jan Struyf Leander Schietgat Sašo Džeroski Hendrik Blockeel 《Machine Learning》2008,73(2):185-214
Hierarchical multi-label classification (HMC) is a variant of classification where instances may belong to multiple classes
at the same time and these classes are organized in a hierarchy. This article presents several approaches to the induction
of decision trees for HMC, as well as an empirical study of their use in functional genomics. We compare learning a single
HMC tree (which makes predictions for all classes together) to two approaches that learn a set of regular classification trees
(one for each class). The first approach defines an independent single-label classification task for each class (SC). Obviously,
the hierarchy introduces dependencies between the classes. While they are ignored by the first approach, they are exploited
by the second approach, named hierarchical single-label classification (HSC). Depending on the application at hand, the hierarchy
of classes can be such that each class has at most one parent (tree structure) or such that classes may have multiple parents
(DAG structure). The latter case has not been considered before and we show how the HMC and HSC approaches can be modified
to support this setting. We compare the three approaches on 24 yeast data sets using as classification schemes MIPS’s FunCat
(tree structure) and the Gene Ontology (DAG structure). We show that HMC trees outperform HSC and SC trees along three dimensions:
predictive accuracy, model size, and induction time. We conclude that HMC trees should definitely be considered in HMC tasks
where interpretable models are desired. 相似文献