Search results for "absorption."
showing 10 items of 2682 documents
Optimizing and Modeling the drying process of the Natural Gas through the Taguchi method
2018
The aim of this study is to highlight the optimization method of the drying process of natural gas, using the Taguchi method. The natural gas undergoes several stages from its extraction until reaching its end consumer. As the natural gas contains several impurities and a certain quantity of water and vapors, the drying process is very important to obtain a product of high quality. Gas dehydration can be obtained through several methods, the method presented here being the absorption method - by use of a drying station with triglycol. This method is considered to be the most convenient one taking into account the obtained results. Nevertheless, cost reducing is the main objective for compan…
Guidelines for the assessment of the rate law of slurry photocatalytic reactions
2017
Abstract The assessment of the rate law of slurry photocatalytic reactions appears to be a hard task, mainly because in this type of reactions the average rate of reaction, which is experimentally observed in a real reactor, could be very different from the “true” (intrinsic) rate of reaction, which cannot be measured directly. In the present work, it is shown how a proper mathematical model allows the utilization of the differential and/or the integral methods of kinetic analysis. The mathematical model must take into account not only the momentum and the mass balances, but also the radiative transfer equation. However, the discrimination among different proposed kinetic laws remains diffi…
Excitonic States in Semiconducting Two-dimensional Perovskites
2018
Hybrid organic/inorganic perovskites have emerged as efficient semiconductor materials for applications in photovoltaic solar cells with conversion efficiency above 20 \%. Recent experiments have synthesized ultra-thin two-dimensional (2D) organic perovskites with optical properties similar to those of 2D materials like monolayer MoS$_2$: large exciton binding energy and excitonic effects at room temperature. In addition, 2D perovskites are synthesized with a simple fabrication process with potential low-cost and large-scale manufacture. Up to now, state-of-the-art simulations of the excitonic states have been limited to the study of bulk organic perovskites. A large number of atoms in the …
Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures
2018
In this work, we have investigated the crystalline-size dependence of optical absorption and photoluminescence emission of CH3NH3PbI3 films, which is necessary to identify the potential practical applications of the gadgets based on perovskite films. This study was carried out at low temperatures to minimize the extra complexity induced by thermal effects. The purpose was to clarify the origin of the dual emission peak previously reported in the literature. We found that the grain size is responsible for the appearance or disappearance of this dual emission on CH3NH3PbI3 at low temperatures, whereas we have inferred that the thickness of the perovskite layer is a much more important factor …
Optical properties of TiO2 suspensions: Influence of pH and powder concentration on mean particle size
2007
WOS: 000250584100025
A reaction engineering approach to kinetic analysis of photocatalytic reactions in slurry systems
2016
Abstract The knowledge of the rate equation is fundamental for the assessment of the activity of the photocatalytic material and for the study, design and optimization of photocatalytic reactors. In the case of photocatalytic reactions, the local volumetric rate of photon absorption (LVRPA) affects the reaction rate and its inherently uneven distribution within a “slurry” reactor makes complex a correct kinetic analysis. In the present work it is shown which are the critical aspects of the kinetic analysis in slurry reactors and how to carry out photocatalytic experiments to minimize the misinterpretations of the experimental results. In particular, the influence of the type of illumination…
Quasi-isoactinic reactor for photocatalytic kinetics studies
2007
Photochemical reactors characterized by almost uniform values of the local volumetric rate of photon absorption (LVRPA), i.e., quasi-isoactinic photoreactors, are particularly suitable for assessing the influence of radiant field intensity in kinetic studies. In this work, Monte Carlo simulations have been performed to obtain LVRPA values in a flat photoreactor irradiated on both sides. This configuration appears to be particularly suitable for obtaining quasi-isoactinic conditions. The influence of catalyst albedo and scattering phase function is assessed, and the conditions for obtaining iso-actinicity are discussed. Finally, these conditions are related to an easy-to-measure parameter, n…
Escala de Utrecht de implicación en el trabajo en los profesores dominicanos: dimensionalidad, fiabilidad y validez
2018
ABSTRACT Work engagement is described by dedication, vigor, and absorption. The most widely used measure of engagement is the Utrecht Work Engagement Scale (UWES), intended to measure engagement for any occupational group. This research aims to study psychometric properties of the UWES for its use in the Dominican Republic and other Caribbean Spanish-speaking countries. The Composite Reliability Index (CRI) as well as alphas were calculated, indicating good internal consistency. Confirmatory factor analyses were carried out to test its dimensionality. Both tested models showed extremely good fit to the data, which called for model comparison. The three-factor solution was retained as the on…
EXAFS studies on the local structure of Er3+ ions in silica xerogels co-doped with aluminium
2001
The local environment around Er3+ ions in wet and densified (at 900°C) silica xerogels (pure and co-doped with aluminium) has been studied at the Er L3-edge by X-ray absorption spectroscopy using the fluorescence detection technique. The radial distribution functions (RDF), reconstructed from X-ray absorption fine structure (EXAFS), show several changes in the local co-ordination of erbium ions upon densification: shortening of the Er-O and Er-Si/Al distances, decrease of the co-ordination numbers and broadening of the Er-O RDF. The effect of Al co-doping is clearly discerned by EXAFS in both the first and second co-ordination shells for densified gels and mainly in the second shell for wet…
STUDY OF CAPILLARY ABSORPTION KINETICS BY X-RAY CT IMAGING TECHNIQUES: A SURVEY ON SEDIMENTARY ROCKS OF SICILY
2008
Sedimentary rocks are natural porous materials with a great percent of microscopic interconnected pores: they contain fluids, permitting their movement on macroscopic scale. Generally, these rocks present porosity higher then metamorphic rocks. Under certain points of view, this feature represents an advantage; on the other hand, this can constitute an obstacle for cultural heritage applications, because the porosity grade can lead to a deterioration of the lapideous monument for water capillary absorption. In this paper, CT (Computerized Tomography) image techniques are applied to capillary absorption kinetics in sedimentary rocks utilized for the Greek temples as well as baroc monuments, …