1,329 research outputs found
Densities and phase equilibria of hydrogen, propane and vegetable oil mixtures. Experimental data and thermodynamic modeling
Heterogeneous catalytic gas-liquid reactions are intensified when carried out in the homogenous fluid phase by means of a supercritical co-solvent. For instance, supercritical propane is used to enhance yield in the hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data of the reactive mixture H2+sunflower oil+propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK-PR equations of state, respectively. The isochoric method not only provides PvT information under the reaction conditions, but also the reactive system compressibility, key variable to attain enhanced transport properties in the supercritical reactors.Fil: Hegel, Pablo Ezequiel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Planta Piloto de IngenierĂa QuĂmica. Universidad Nacional del Sur. Planta Piloto de IngenierĂa QuĂmica; ArgentinaFil: Cotabarren, Natalia Soledad. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Planta Piloto de IngenierĂa QuĂmica. Universidad Nacional del Sur. Planta Piloto de IngenierĂa QuĂmica; ArgentinaFil: Brignole, Esteban Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Planta Piloto de IngenierĂa QuĂmica. Universidad Nacional del Sur. Planta Piloto de IngenierĂa QuĂmica; ArgentinaFil: Pereda, Selva. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Planta Piloto de IngenierĂa QuĂmica. Universidad Nacional del Sur. Planta Piloto de IngenierĂa QuĂmica; Argentina. University of KwaZulu-Natal; SudĂĄfric
Opaque Service Virtualisation: A Practical Tool for Emulating Endpoint Systems
Large enterprise software systems make many complex interactions with other
services in their environment. Developing and testing for production-like
conditions is therefore a very challenging task. Current approaches include
emulation of dependent services using either explicit modelling or
record-and-replay approaches. Models require deep knowledge of the target
services while record-and-replay is limited in accuracy. Both face
developmental and scaling issues. We present a new technique that improves the
accuracy of record-and-replay approaches, without requiring prior knowledge of
the service protocols. The approach uses Multiple Sequence Alignment to derive
message prototypes from recorded system interactions and a scheme to match
incoming request messages against prototypes to generate response messages. We
use a modified Needleman-Wunsch algorithm for distance calculation during
message matching. Our approach has shown greater than 99% accuracy for four
evaluated enterprise system messaging protocols. The approach has been
successfully integrated into the CA Service Virtualization commercial product
to complement its existing techniques.Comment: In Proceedings of the 38th International Conference on Software
Engineering Companion (pp. 202-211). arXiv admin note: text overlap with
arXiv:1510.0142
Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction
International audienceHypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45-70wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201-252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H*=104-107mol L-1atm-1. H* is inversely dependent on temperature, with ?H=-45.0±5.4 kJ mol-1 and ?S=-101±24 J mol-1K-1 for 55-70wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55-70wt% H2SO4, the solubility is described by log H*=(2349±280)/T-(5.27±1.24). At temperatures colder than ~213K, the solubility of HOBr in 45wt% H2SO4 is at least a factor of five larger than in 70wt% H2SO4, with log H*=(3665±270)/T-(10.63±1.23). The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2
Real-Gas Effects and Phase Separation in Underexpanded Jets at Engine-Relevant Conditions
A numerical framework implemented in the open-source tool OpenFOAM is
presented in this work combining a hybrid, pressure-based solver with a
vapor-liquid equilibrium model based on the cubic equation of state. This
framework is used in the present work to investigate underexpanded jets at
engine-relevant conditions where real-gas effects and mixture induced phase
separation are probable to occur. A thorough validation and discussion of the
applied vapor-liquid equilibrium model is conducted by means of general
thermodynamic relations and measurement data available in the literature.
Engine-relevant simulation cases for two different fuels were defined. Analyses
of the flow field show that the used fuel has a first order effect on the
occurrence of phase separation. In the case of phase separation two different
effects could be revealed causing the single-phase instability, namely the
strong expansion and the mixing of the fuel with the chamber gas. A comparison
of single-phase and two-phase jets disclosed that the phase separation leads to
a completely different penetration depth in contrast to single-phase injection
and therefore commonly used analytical approaches fail to predict the
penetration depth.Comment: Preprint submitted to AIAA Scitech 2018, Kissimmee, Florid
Extended morphometric analysis of neuronal cells with Minkowski valuations
Minkowski valuations provide a systematic framework for quantifying different
aspects of morphology. In this paper we apply vector- and tensor-valued
Minkowski valuations to neuronal cells from the cat's retina in order to
describe their morphological structure in a comprehensive way. We introduce the
framework of Minkowski valuations, discuss their implementation for neuronal
cells and show how they can discriminate between cells of different types.Comment: 14 pages, 18 postscript figure
Stratospheric observations of CH_3D and HDO from ATMOS infrared solar spectra: Enrichments of deuterium in methane and implications for HD
Stratospheric mixing ratios of CH_3D from 100 mb to 17 mb (â 15 to 28 km) and HDO from 100 mb to 10 mb (â 15 to 32 km) have been inferred from high resolution solar occultation infrared spectra from the Atmospheric Trace MOlecule Spectroscopy (ATMOS) Fourier-transform interferometer. The spectra, taken on board the Space Shuttle during the Spacelab 3 and ATLAS-1, -2, and -3 missions, extend in latitude from 70°S to 65°N. We find CH_3D entering the stratosphere at an average mixing ratio of (9.9±0.8) Ă 10^(â10) with a D/H ratio in methane (7.1±7.4)% less than that in Standard Mean Ocean Water (SMOW) (1Ï combined precision and systematic error). In the mid to lower stratosphere, the average lifetime of CH_3D is found to be (1.19±0.02) times that of CH_4, resulting in an increasing D/H ratio in methane as air âagesâ and the methane mixing ratio decreases. We find an average of (1.0±0.1) molecules of stratospheric HDO are produced for each CH_3D destroyed (1Ï combined precision and systematic error), indicating that the rate of HDO production is approximately equal to the rate of CH_3D destruction. Assuming negligible amounts of deuterium in species other than HDO, CH_3D and HD, this limits the possible change in the stratospheric HD mixing ratio below about 10 mb to be ±0.1 molecules HD created per molecule CH_3D destroyed
Predicting phase equilibria in polydisperse systems
Many materials containing colloids or polymers are polydisperse: They
comprise particles with properties (such as particle diameter, charge, or
polymer chain length) that depend continuously on one or several parameters.
This review focusses on the theoretical prediction of phase equilibria in
polydisperse systems; the presence of an effectively infinite number of
distinguishable particle species makes this a highly nontrivial task. I first
describe qualitatively some of the novel features of polydisperse phase
behaviour, and outline a theoretical framework within which they can be
explored. Current techniques for predicting polydisperse phase equilibria are
then reviewed. I also discuss applications to some simple model systems
including homopolymers and random copolymers, spherical colloids and
colloid-polymer mixtures, and liquid crystals formed from rod- and plate-like
colloidal particles; the results surveyed give an idea of the rich
phenomenology of polydisperse phase behaviour. Extensions to the study of
polydispersity effects on interfacial behaviour and phase separation kinetics
are outlined briefly.Comment: 48 pages, invited topical review for Journal of Physics: Condensed
Matter; uses Institute of Physics style file iopart.cls (included
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