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排序方式: 共有920条查询结果,搜索用时 15 毫秒
1.
Assessed the reliability and validity of the French-Canadian version of H. Levenson's (1973) internality, powerful others, and chance locus of control scales. Data from 2 studies of 294 middle-class adults show that the French-Canadian version of the scales was comparable to that of the original version. The importance of utilizing the appropriate statistical models of analysis to benefit from the multidimensional model of locus of control is emphasized. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Polycrystalline Ag treated with O2 at pressures up to 1 bar and at temperatures up to 920 K was examined by TDS. It was found that the peak commonly observed at 595±25 K and assigned to adsorbed atomic oxygen (Oa) is shifted to higher desorption temperatures with rising dosing temperatures. Since saturation of the uptake was not possible either, this peak was identified as dissolved atomic oxygen (Od). The existence of a maximum for the O2 uptake after exposure at 820 K was found. Hence, under conditions of formaldehyde synthesis ( 920 K) the ability of the catalyst to dissolve oxygen is near its maximum. 相似文献
3.
Angkoon Phinyomark Franck Quaine Sylvie Charbonnier Christine Serviere Franck Tarpin-Bernard Yann Laurillau 《Computer methods and programs in biomedicine》2014
This paper demonstrates the utility of a differencing technique to transform surface EMG signals measured during both static and dynamic contractions such that they become more stationary. The technique was evaluated by three stationarity tests consisting of the variation of two statistical properties, i.e., mean and standard deviation, and the reverse arrangements test. As a result of the proposed technique, the first difference of EMG time series became more stationary compared to the original measured signal. Based on this finding, the performance of time-domain features extracted from raw and transformed EMG was investigated via an EMG classification problem (i.e., eight dynamic motions and four EMG channels) on data from 18 subjects. The results show that the classification accuracies of all features extracted from the transformed signals were higher than features extracted from the original signals for six different classifiers including quadratic discriminant analysis. On average, the proposed differencing technique improved classification accuracies by 2–8%. 相似文献
4.
The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester-MMA) copolymers (MMA-MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA-MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA-MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory-Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ12 increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ12 values as compared to VDF-TFE or particularly to VDF-TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values. 相似文献
5.
A model system for the study of structural and chemical properties of monolayers and multilayers of vanadium oxide immobilized on titania is presented. Investigation of the planar oxide-oxide interface by XP, UV and IS spectroscopy indicated that vanadium immobilized by a single impregnation step exists as an incomplete heterogeneous layer containing well dispersed V4+ species. Increase of the vanadia loading by multiple impregnations led to vanadia agglomerates with higher apparent oxidation state of the vanadium. TD spectroscopy with O2 and CO2 as probe molecules revealed that the chemical reactivity of the vanadia surface species depends on their structure. The surface containing well-dispersed vanadia species exchanged oxygen more easily and showed pronounced interactions with CO2. 相似文献
6.
The industrial catalyst for high temperature dehydrogenation of ethylbenzene based on iron and potassium oxides undergoes, under reaction conditions, essentially a transformation into magnetite, Fe3O4, and a mixture of ternary oxides containing trivalent iron, viz. K2Fe22O34 and KFeO2. The latter compound constitutes the outside of the catalyst particles and is indeed the catalytically active phase. 相似文献
7.
Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques. 相似文献
8.
Bulk silver catalysts were found to be active for the oxidative coupling of methane to ethane and ethylene if operated under oxygen-limited conditions at atmospheric pressure and at temperatures above 1020 K. The addition of small amounts of sodium phosphate as promoter increases markedly the C2 selectivity (to values above 90%) and yield (>10%) by efficient suppression of reaction steps leading to total oxidation. Further improvement of the yields might be achieved by more appropriate reactor design. 相似文献
9.
A kinetic study of the anionic polymerization of ethylene oxide has been made in tetrahydrofuran at 20°C, with the cryptate Cs+ + [TC] as counterion, [TC] being a spheroidal macrotricyclic ligand. Conductance measurements have been made on THF solutions of ?4BCs + [TC]. Ionic associations higher than cryptated ion pairs are negligible for living end concentrations lower than 3 × 10?4 moll?1. k± and the alkoxide ion pair dissociation constant KD were determined from both sets of kinetic data obtained with and without added salt knowing the value of k? from kinetic data performed with K+ + [222] as counterion. Free alkoxide ions are about twenty times more reactive than cryptated caesium ion pairs. 相似文献
10.
Radim Belohlavek Dhouha Grissa Sylvie Guillaume Engelbert Mephu Nguifo Jan Outrata 《Annals of Mathematics and Artificial Intelligence》2014,70(1-2):151-184
Measures of interestingness play a crucial role in association rule mining. An important methodological problem, on which several papers appeared in the literature, is to provide a reasonable classification of the measures. In this paper, we explore Boolean factor analysis, which uses formal concepts corresponding to classes of measures as factors, for the purpose of clustering of the measures. Unlike the existing studies, our method reveals overlapping clusters of interestingness measures. We argue that the overlap between clusters is a desired feature of natural groupings of measures and that because formal concepts are used as factors in Boolean factor analysis, the resulting clusters have a clear meaning and are easy to interpret. We conduct three case studies on clustering of measures, provide interpretations of the resulting clusters and compare the results to those of the previous approaches reported in the literature. 相似文献