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11.
Amir H. Tavakoli Renzo Campostrini Christel Gervais Florence Babonneau Joachim Bill Gian D. Sorarù Alexandra Navrotsky 《Journal of the American Ceramic Society》2014,97(1):303-309
The structure and properties of polymer‐derived Si–(B–)O–C glasses have been shown to be significantly influenced by the boron content and pyrolysis temperature. This work determined the impact of these two parameters on the thermodynamic stability of these glasses. High‐temperature oxide melt solution calorimetry was performed on a series of amorphous samples, with varying boron contents (0–7.7 at.%), obtained by pyrolysis of precursors made by a sol–gel technique. Thermodynamic analysis of the calorimetric results demonstrated that at a constant pyrolysis temperature, adding boron makes the materials energetically less stable. While the B‐containing glasses pyrolyzed at 1000°C were energetically less stable than the competitive crystalline components, increasing the pyrolysis temperature to 1200°C led to their enthalpic stability. 29Si and 11B MAS nuclear magnetic resonance (NMR) spectroscopy measurements on selected samples confirmed a decrease in the concentrations of mixed Si‐centered SOiC4?i and B‐centered BOjC3?j bonds at the expense of formation of SiO4 and B(OSi)3 species (indicating a tendency toward phase separation) when the boron content and pyrolysis temperature increased. In light of the findings from calorimetry and NMR spectroscopy, we propose a structure–energetic relationship in Si–(B–)O–C glasses. 相似文献
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In this letter, we propose an exact analytical framework for analyzing the performance of impulse radio (IR) ultra wide band (UWB) receiver architectures. In particular, the framework can handle i. various multipath fading distributions, ii. correlated fading, iii. channel sparseness, iv. time overlap among multipath components (MPCs), i.e., intra-pulse interference and v. both all-rake and transmitted-reference (TR) receiver architectures. The proposed methodology is based on estimating the characteristic function (CF) of the signal-to- noise ratio at the receiver, which can be reduced to a quadratic form of a random vector. 相似文献
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A plug flow reactor (PFR) which permits the growth of bacteria in a microwave environment is described. The apparatus is used to analyse the effect of microwave radiation at the frequency of 2.45 GHz and at 37°C on the growth rate of three bacterial species: Bacillus clausii, Pseudomonas aeruginosa, and Staphylococcus aureus. The growth constant is determined for reacting mixtures irradiated with microwaves of different powers ranging from 0 to 400 mW. Analyses show that (a) the apparatus is able to perform the experimental runs maintaining an aseptic environment; (b) under the microwave power levels examined in the present study, no effects are detected for the Bacillus clausii and Pseudomonas aeruginosa species, while for the Staphylococcus aureus species, a few small effects are found (a minimum value of the growth constant at 200 mW and an increase of the constant between 200 and 400 mW). © 2009 American Institute of Chemical Engineers AIChE J, 2010 相似文献
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Daniele Mirabile Gattia Marco Vittori Antisari Renzo Marazzi Amelia Montone Silvia Licoccia 《Journal of power sources》2009,194(1):243-251
Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction. 相似文献
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项目地点:美国加州项目类型:建筑(教育)开工日期:2005年9月该项目综合考虑了可持续性和建筑方面的因素,并将其纳入大型公共建筑之中。该项目获2005年豪瑞可持续建筑大奖赛北美地区银奖 相似文献
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Roberto Grena Raffaele Scafè Fabrizio Pisacane Renzo Pilato Tommaso Crescenzi Domenico Mazzei 《Solar Energy》2010,84(1):51-58
Solar plants that use molten salts as heat transfer fluid need careful control to avoid the freezing of the salt in the pipes; if such a problem occurs, a diagnostic instrument to localize where is the frozen salt plug and to determine its length is useful. If the salt contains potassium (as is the case of the most common mixture used in solar plants, NaNO3/KNO3 60/40% by weight), the gamma decay of the natural unstable isotope 40K can be exploited to detect the frozen salt in a non-invasive way. Simulations and experimental results regarding the detectability of such plugs with different masses/lengths are presented. 相似文献
20.
Renzo Shamey Juan Lin Weethima Sawatwarakul Renbo Cao 《Color research and application》2014,39(6):589-598
The objective of this study was to develop a specific visual dataset comprising black‐appearing samples with low lightness (L* ranging from approximately 10.4 to 19.5), varying in hue and chroma, evaluating their visual differences against a reference sample, and testing the performance of major color difference formulas currently in use as well as OSA‐UCS‐based models and more recent CAM02 color difference formulas including CAM02‐SCD and CAM02‐UCS models. The dataset comprised 50 dyed black fabric samples of similar structure, and a standard (L*= 15.33, a* = 0.14, b* = ?0.82), with a distribution of small color differences, in ΔE*ab, from 0 to approximately 5. The visual color difference between each sample and the standard was assessed by 19 observers in three separate sittings with an interval of at least 24 hours between trials using an AATCC standard gray scale for color change, and a total of 2850 assessments were obtained. A third‐degree polynomial equation was used to convert gray scale ratings to visual differences. The Standard Residual Sum of Squares index (STRESS) and Pearson's correlation coefficient (r), were used to evaluate the performance of various color difference formulae based on visual results. According to the analysis of STRESS index and correlation coefficient results CAM02 color difference equations exhibited the best agreement against visual data with statistically significant improvement over other models tested. The CIEDE2000 (1:1:1) equation also showed good performance in this region of the color space. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 589–598, 2014 相似文献