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Previous Experimental Data (previous + experimental_data)
Selected AbstractsDarcy's law-based model for wicking in paper-like swelling porous mediaAICHE JOURNAL, Issue 9 2010Reza Masoodi Abstract The wicking of liquid into a paper-like swelling porous medium made from cellulose and superabsorbent fibers was modeled using Darcy's law. The work is built on a previous study in which the Washburn equation, modified to account for swelling, was used to predict wicking in a composite of cellulose and superabsorbent fibers. In a new wicking model proposed here, Darcy's law for flow in porous media is coupled with the mass conservation equation containing an added sink or source term to account for matrix swelling and liquid absorption. The wicking-rate predicted by the new model compares well with the previous experimental data, as well as the modified Washburn equation predictions. The effectiveness of various permeability models used with the new wicking model is also investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Experimental deformation of partially melted granite revisited: implications for the continental crustJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2005C. L. ROSENBERG Abstract A review and reinterpretation of previous experimental data on the deformation of partially melted crustal rocks reveals that the relationship of aggregate strength to melt fraction is non-linear, even if plotted on a linear ordinate and abscissa. At melt fractions, , < 0.07, the dependence of aggregate strength on , is significantly greater than at , > 0.07. This melt fraction (, = 0.07) marks the transition from a significant increase in the proportion of melt-bearing grain boundaries up to this point to a minor increase thereafter. Therefore, we suggest that it is the increase of melt-interconnectivity that causes the dramatic strength drop between the solidus and a melt fraction of 0.07. We term this drop the ,melt connectivity transition' (MCT). A second, less-pronounced strength drop occurs at higher melt fractions and corresponds to the breakdown of the solid (crystal) framework. This is the ,solid-to-liquid transition' (SLT), corresponding to the well known ,rheologically critical melt percentage'. Although the strength drop at the SLT is about four orders of magnitude, the absolute value of this drop is small compared with the absolute strength of the unmelted aggregate, rendering the SLT invisible in a linear aggregate strength v. melt-fraction diagram. On the other hand, the more important MCT has been overlooked in previous work because experimental data usually are plotted in logarithmic strength v. melt-fraction diagrams, obscuring large strength drops at high absolute strength values. We propose that crustal-scale localization of deformation effectively coincides with the onset of melting, pre-empting attainment of the SLT in most geological settings. The SLT may be restricted to controlling flow localization within magmatic bodies, especially where melt accumulates. [source] Incubation period in the 2,2,4,4-tetramethyl-1-piperidinyloxy-mediated thermal autopolymerization of styrene: Kinetics and simulationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2006Enrique Saldívar-Guerra Abstract Mechanisms and simulations of the induction period and the initial polymerization stages in the nitroxide-mediated autopolymerization of styrene are discussed. At 120,125 °C and moderate 2,2,4,4-tetramethyl-1-piperidinyloxy (TEMPO) concentrations (0.02,0.08 M), the main source of radicals is the hydrogen abstraction of the Mayo dimer by TEMPO [with the kinetic constant of hydrogen abstraction (kh)]. At higher TEMPO concentrations ([N,] > 0.1 M), this reaction is still dominant, but radical generation by the direct attack against styrene by TEMPO, with kinetic constant of addition kad, also becomes relevant. From previous experimental data and simulations, initial estimates of kh , 1 and kad , 6 × 10,7 L mol,1 s,1 are obtained at 125 °C. From the induction period to the polymerization regime, there is an abrupt change in the dominant mechanism generating radicals because of the sudden decrease in the nitroxide radicals. Under induction-period conditions, the simulations confirm the validity of the quasi-steady-state assumption (QSSA) for the Mayo dimer in this regime; however, after the induction period, the QSSA for the dimer is not valid, and this brings into question the scientific basis of the well-known expression kth[M]3 (where [M] is the monomer concentration and kth is the kinetic constant of autoinitiation) for the autoinitiation rate in styrene polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6962-6979, 2006 [source] Theory of polychromatic microwave photonsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2004T. Koryu Ishii Abstract In this paper, the possibility of superluminal speed of polychromatic microwave photons is analytically shown. The analytical results are correlated with previous experimental data. In this theoretical analysis, a generic-wave equation is used as the basis and the Maxwellian phase-velocity concept of monochromatic microwave photons is applied to microwave spectra of polychromatic photons. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 213,218, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20097 [source] Applying a Thermodynamic Model to the Non-Stoichiometric Precipitation of Barium SulfateCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2003L. Vicum Abstract Thermodynamic models for aqueous Ba2+ -SO42, -Na+ -Cl, -solutions are compared in their accuracy to predict ion activities in saturated and supersaturated solutions. The Pitzer and the Bromley model are employed, taking into account ion pair formation of barium sulfate. Such models are then used to describe particle nucleation and growth, and finally they are imbedded in a mechanistic mixing-precipitation model for a single feed semibatch process. The effect of the key operating parameters on the mean particle size is analyzed through simulations. The results are compared with previous experimental data, thus highlighting the significance of a proper choice of the thermodynamic model. [source] Theory of Ion Transport in Electrochemically Switchable Nanoporous Metallized MembranesCHEMPHYSCHEM, Issue 1 2009Christian Amatore Dr. Abstract A physicomathematical model of ion transport through a synthetic electrochemically switchable membrane with nanometric metal-plated pores is presented. Due to the extremely small size of the cylindrical pores, electrical double layers formed inside overlap, and thus, strong electrostatic fields whose intensities vary across the cross-sections of the nanopores are created. Based on the proposed model a relationship between the relative electrostatic energies experienced by ions in the nanopores and the potential applied to the membrane is established. This allows the prediction of transference numbers and explains quantitatively the ion-transport switching capability of such synthetic membranes. The predictions of this model agree satisfactorily with previous experimental data obtained for this type of devices by Martin and co-workers. [source] | ||||||||||