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Nektarios K. Nasikas Andreas Retsinas George N. Papatheodorou 《Journal of the American Ceramic Society》2014,97(7):2054-2060
Aerodynamic levitation and CO2 laser melting have been used to synthesize the yttrium aluminosilicate glasses zY2O3–yAl2O3–xSiO2 with z/y = 3/5 corresponding to the YAG (Y3Al5O12) composition and x between ~5 and ~45 mol%. The low‐ and high‐density (LDA inclusion and HDA matrix) polyamorphic phases in glasses with less than ~14 mol% SiO2 were identified with backscattering electron imaging. Polarized and depolarized Raman spectra show the formation of various Qn SiO4 species whose relative populations change smoothly as the SiO2 content is altered. The AlOs (s = 4–6) and YOz (z = 6–9) polyhedra formed in the YAG glass are preserved upon silica additions while the terminal oxygens of the Q2AlO4 tetrahedra are gradually bridged to the Qn‐SiO4 species. The low‐frequency Boson Peak overlaps with the vibrational spectrum and its maximum is redshifted with increasing silica content. Micro‐Raman spectra measured for the LDA and HDA amorphous phases are found to be similar to the spectra of the bulk glass indicating common structural characteristics. The stability of the LDA phase against crystallization appears to be lower than that of the HDA phase. The crystallinity on certain inclusions consisted of YAG microcrystals and a new unidentified microcrystalline phase within Y4Al2(1?x)Si2xO(9+x) solid solution. 相似文献
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Nektarios K. Nasikas Alexandra Navrotsky 《Journal of the American Ceramic Society》2014,97(2):451-456
A series of alkaline‐earth silicate glasses, with compositions ranging from the metasilicate to the ortho‐ and suborthosilicate, have been synthesized by aerodynamic levitation and CO2 laser melting. They have been studied by high‐temperature oxide melt solution calorimetry with 2PbO·B2O3 as solvent. The enthalpies of formation from the oxides at room temperature () have been calculated from the solution enthalpies. Glasses in the Ca0.5Mg0.5O–SiO2 system show greater energetic stability than those in the MgO–SiO2 system, with a more pronounced negative enthalpy of mixing near the orthosilicate composition. This stabilization may explain why it is possible to prepare glasses poorer in silica (suborthosilicate) in the Ca0.5Mg0.5O–SiO2 system but not in the MgO–SiO2 system. The thermodynamic observations support earlier structural studies in these systems. 相似文献
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Pervasive service creation entails a complex process that involves a diversity of development aspects. Context-awareness is an important facet of pervasive service creation, which deals with the acquisition, rendering, representation and utilisation of context information. In this paper we tackle context-awareness at the application level dealing with the representation and utilisation of context by services. We propose a model-driven approach that facilitates the creation of a context modelling framework and simplifies the design and implementation of pervasive services. To conclude, we demonstrate the benefits of our model-driven approach via the creation of a pervasive museum service and its evaluation using selected software metrics. 相似文献
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Patrick Jackman Da-Wen Sun Paul Allen Nektarios A. Valous Fernando Mendoza Paddy Ward 《Meat science》2010
A method to discriminate between various grades of pork and turkey ham was developed using colour and wavelet texture features. Image analysis methods originally developed for predicting the palatability of beef were applied to rapidly identify the ham grade. With high quality digital images of 50–94 slices per ham it was possible to identify the greyscale that best expressed the differences between the various ham grades. The best 10 discriminating image features were then found with a genetic algorithm. Using the best 10 image features, simple linear discriminant analysis models produced 100% correct classifications for both pork and turkey on both calibration and validation sets. 相似文献
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Levels of carbon tetrachloride and tetrachloroethene were determined for the first time in Athens in the summer of 2000. The mean CCl4 and C2Cl4 concentrations were 0.060 and 0.18 ppb, respectively. CCl4 did not exhibit significant variation throughout the measurement period or with wind direction. C2Cl4 under strong eastern winds had less than half the concentrations observed during other meteorological conditions. No diurnal variation was observed for either compound. 相似文献
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