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Pearce, J V,Edler, F,Elliott, C J,Greenen, A,Harris, P M,Izquierdo, C Garcia,Kim, Y-G,Martin, M J,Smith, I M,Tucker, D,Veltcheva, R I BUREAU INTERNATIONAL DES POIDS ET MESURES 2018 METROLOGIA -BERLIN- Vol.55 No.4
<P>By using a simple model to relate the electromotive force drift rate of Pt–Rh thermoelements to d<I>S</I>/d<I>c</I>, i.e. the sensitivity of the Seebeck coefficient, <I>S</I>, to rhodium mass fraction, <I>c</I>, the composition of the optimal pair of Pt–Rh wires that minimizes thermoelectric drift can be determined. The model has been applied to four multi-wire thermocouples each comprising 5 or 7 Pt–Rh wires of different composition. Two thermocouples were exposed to a temperature of around 1324 °C, one thermocouple to around 1492 °C, i.e. the melting points of the Co–C and Pd–C high temperature fixed points, respectively, and one thermocouple to a series of temperatures between 1315 °C and 1450 °C. The duration of exposure at each temperature was several thousand hours. By performing repeated calibrations <I>in situ</I> with the appropriate fixed point during the high temperature exposure, the drift performance has been quantified with high accuracy, entirely free from errors associated with thermoelectric homogeneity. By combining these results it is concluded that the Pt-40%Rh versus Pt-6%Rh is the most stable at the temperatures investigated. A preliminary reference function was determined and is presented.</P>
F. B. ROMERO,J. M. MCWILLIAMS,E. A. FAZIO,F. A. IZQUIERDO 한국자동차공학회 2014 International journal of automotive technology Vol.15 No.6
This paper has been developed in the framework of the alternative beam T-junction solution previouslypropoused by the authors (Alcalá et al., 2013), with the scope of optimizing the behavior of buses and coaches upper structuresmodeled with beam type elements. The alternative beam T-junction model proposed by the authors, had a total of six elasticelements at the junction level allowing to modify the localized rigidity of any modeled T-junctions, therefore improving theirbehavior and avoiding the well known rigidity issue these elements have. A fundamental aspect behind the use of thesealternative beam models is related to the necessity of correctly estimating the rigidity values of the elastic elements for eachmodeled T-junction. In this context, we propose applying a surrogate model for the reference calculations which is based onstatistical Bayesian kriging predictors. Statistical predictions have the added value, with respect to deterministic solutions, ofproviding a quantification of uncertainty. The development of the kriging predictors has required the application of a statisticalmethodology including computer experiment design, computation of moments of inertia, graphical and ANOVA typesensitivity analysis and Monte Carlo computation of Bayesian inference. The results of the application have been a verysatisfactory trade-off between accuracy of approximation (prediction) and computational cost. The surrogate kriging modelsalso provide an useful tool for a better understanding of the input-output relationships involved in the reference computations.
M.A. Izquierdo,F.J. Navarro,F.J. Martınez-Boza,C. Gallegos 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2
Dimensionally stable bituminous foams were prepared by using 4,40-diphenylmethane diisocyanate/polypropylene glycol (MDI–PPG) quasi-prepolymers, with different molecular weights. From the results obtained, it may be concluded that, after foam formation, the rheological properties are remarkably affected, especially at high temperatures. Paradoxically, the greater the molecular weight of MDI–PPG,the lower the values of viscosities at 60 8C, and the linear viscoelasticity functions of the resulting foams. This result seems to be related to the improved ability of small MDI–PPG molecules to interact strongly with polar bitumen compounds, leading to the formation of larger molecular-sized compounds.