scholarly journals Effect of a Support on the Properties of Zinc Oxide Based Sorbents

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Maciej Chomiak ◽  
Bartłomiej M. Szyja ◽  
Marta Jędrysiak ◽  
Janusz Trawczyński
Keyword(s):  
Phase Composition ◽  
Hydrogen Sulphide ◽  
Computational Analysis ◽  
Subsequent Work ◽  
Multiphase Materials ◽  
Slurry Impregnation ◽  
Unit Cells ◽  
Hot Coal Gas ◽  
H2s Adsorption ◽  
Experimental Findings

We present the comparative analysis of three Zn-based sorbents for the process of sulphur removal from hot coal gas. The sorbents were prepared by a slurry impregnation of TiO2, SiO2 and Al2O3, resulting in complex, multiphase materials, with the dominant phases of Zn2TiO4, Zn2SiO4 and ZnAl2O4, respectively. We have analyzed the effect of supports on the phase composition, texture, reducibility and H2S sorption. We have found that the phase composition significantly influences the susceptibility of the investigated materials to reduction by hydrogen. Zn2TiO4 have been found to be the easiest to reduce which correlates with its ability to adsorb the largest amount of hydrogen sulphide—up to 4.2 gS/100 g—compared to the other sorbents, which absorb up to 2.2 gS/100 g. In the case of Zn2SiO4 and ZnAl2O4, this effect also correlates with reducibility—these sorbents have been found to be highly resistant to reduction by hydrogen and to absorb much less hydrogen sulphide. In addition, the capacity of ZnAl2O4 for H2S adsorption decreases in the subsequent work cycles—from 2.2 gS/100 g in the first cycle to 0.8 gS/100 g in the third one. Computational analysis on the DFT level has shown that these materials show different thermodynamic stability of sulphur sites within the unit cells of the sorbents. For Zn2TiO4 and Zn2SiO4, the adsorption is favorable in both the first and second layers of the former and only the top layer of the latter, while for zinc aluminate it is not favorable, which is consistent with the experimental findings.

On The Mechanism of Nucleation in Pulsed-laser Quenched Si Films on SiO2

2010 ◽  
Vol 1245 ◽  
Author(s):  
Yikang Deng ◽  
Qiongying Hu ◽  
Ui-Jin Chung ◽  
Adrian Chitu ◽  
Alexander Limanov ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Pulsed Laser ◽  
Nucleation Mechanism ◽  
Si Films ◽  
Experimental Findings ◽  
Solid Nucleation

AbstractWe have investigated the solid nucleation mechanism in laser-quenched Si films on SiO2. Previously neglected experimental steps, consisting of BHF-etching and irradiation in vacuum, were implemented to reduce potential extrinsic influences. The resulting experimental findings and computational analysis lead us to conclude that solid nucleation consistently takes place heterogeneously at, and only at, the bottom liquid Si-SiO2 interface.

A Second Look at the Higher-Order Theory for Periodic Multiphase Materials

2005 ◽  
Vol 72 (2) ◽  
pp. 177-195 ◽  
Author(s):  
Yogesh Bansal ◽  
Marek-Jerzy Pindera
Keyword(s):  
Order Theory ◽  
Higher Order ◽  
Unit Cell ◽  
Material Symmetry ◽  
Original Formulation ◽  
Predictive Capability ◽  
Multiphase Materials ◽  
Periodic Composites ◽  
Unit Cells ◽  
Higher Order Theory

In this communication, we present a reformulation, based on the local/global stiffness matrix approach, of the recently developed higher-order theory for periodic multiphase materials, Aboudi et al. [“Linear Thermoelastic Higher-Order Theory for Periodic Multiphase Materials,” J. Appl. Mech., 68(5), pp. 697–707]. This reformulation reveals that the higher-order theory employs an approximate, and standard, elasticity approach to the solution of the unit cell problem of periodic multiphase materials based on direct volume-averaging of the local field equations and satisfaction of the local continuity conditions in a surface-averge sense. This contrasts with the original formulation in which different moments of the local equilibrium equations were employed, suggesting that the theory is a variant of a micropolar, continuum-based model. The reformulation simplifies the derivation of the global system of equations governing the unit cell response, whose size is substantially reduced through elimination of redundant continuity equations employed in the original formulation, allowing one to test the theory’s predictive capability in most demanding situations. Herein, we do so by estimating the elastic moduli of periodic composites characterized by repeating unit cells obtained by rotation of an infinite square fiber array through an angle about the fiber axis. Such unit cells possess no planes of material symmetry in the rotated coordinate system, and may contain a few or many fibers, depending on the rotation angle, which the reformulated theory can easily accommodate. The excellent agreement with the corresponding results obtained from the standard transformation equations confirms the new model’s previously untested predictive capability for a class of periodic composites characterized by nonstandard, multi-inclusion repeating unit cells lacking planes of material symmetry. Comparison of the effective moduli and local stress fields with the corresponding results obtained from the original Generalized Method of Cells, which the higher-order theory supersedes, confirms the need for this new model, and dramatically highlights the original model’s shortcomings for a certain class of unidirectional composites.

scholarly journals Generalized locally-exact homogenization theory for evaluation of electric conductivity and resistance of multiphase materials

2020 ◽  
Vol 9 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Guannan Wang ◽  
Qiang Chen ◽  
Mengyuan Gao ◽  
Bo Yang ◽  
David Hui
Keyword(s):  
Electric Fields ◽  
Unidirectional Composite ◽  
Homogenization Theory ◽  
Governing Equations ◽  
Multiphase Materials ◽  
Micromechanics Models ◽  
Present Technique ◽  
Unit Cells ◽  
Electric Behavior ◽  
Fiber Matrix

AbstractThe locally-exact homogenization theory is further extended to investigate the homogenized and localized electric behavior of unidirectional composite and porous materials. Distinct from the classical and numerical micromechanics models, the present technique is advantageous by developing exact analytical solutions of repeating unit cells (RUC) with hexagonal and rhomboid geometries that satisfy the internal governing equations and fiber/matrix interfacial continuities in a point-wise manner. A balanced variational principle is proposed to impose the periodic boundary conditions on mirror faces of an RUC, ensuring rapid convergence of homogenized and localized responses. The present simulations are validated against the generalized Eshelby solution with electric capability and the finite-volume direct averaging micromechanics, where excellent agreements are obtained. Several micromechanical parameters are then tested of their effects on the responses of composites, such as the fiber/matrix ratio and RUC geometry. The efficiency of the theory is also proved and only a few seconds are required to generate a full set of properties and concomitant local electric fields in an uncompiled MATLAB environment. Finally, the related programs may be encapsulated with an input/output (I/O) interface such that even non-professionals can execute the programs without learning the mathematical details.

Dielectric resonances and B 1 field inhomogeneity in UHFMRI: computational analysis and experimental findings

2001 ◽  
Vol 19 (2) ◽  
pp. 219-226 ◽  
Author(s):  
Tamer S. Ibrahim ◽  
Robert Lee ◽  
Amir M. Abduljalil ◽  
Brian A. Baertlein ◽  
Pierre-Marie L. Robitaille
Keyword(s):  
Computational Analysis ◽  
Field Inhomogeneity ◽  
Experimental Findings

Trace Hydrogen Sulphide Gas Sensor Based on Cu/rGO Membrane-Coated Photonic Crystal Fibre Michelson Interferometer

2020 ◽  
Vol 75 (4) ◽  
pp. 293-299
Author(s):  
Taiming Luo ◽  
Jianwei Wei ◽  
Xiaozhan Yang ◽  
Daoyuan Wang ◽  
Wenlin Feng
Keyword(s):  
Photonic Crystal ◽  
Hydrogen Sulphide ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Michelson Interferometer ◽  
Single Mode ◽  
Dip Coating ◽  
Photonic Crystal Fibre ◽  
Experimental Findings ◽  
Sensing Membrane

AbstractA novel Michelson interferometric hydrogen sulphide sensor coated with copper/reduced graphene oxide (Cu/rGO) composite membrane is proposed and fabricated. A section of endlessly photonic crystal fibre (EPCF) was sandwiched in two single-mode fibres (SMFs). One SMF was spliced and tapered with EPCF; the other SMF was connected with the Faraday rotator mirror to construct the Michelson structure. The cladding of the EPCF was coated by the Cu/rGO-sensing membrane, which was prepared by the dip-coating method. The obtained Cu/rGO-sensing film has a length of 25.0 mm. The fabricated sensing membrane is characterised by the scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and so on. Experimental results demonstrated that the Cu/rGO-sensing film has a 24.56-nm thickness with a compact and uniform appearance. The XPS and Raman spectra indicate that there are three elements (C, O, and Cu), which are consistent with the expected compositions of the Cu/rGO membrane. With the increase of concentration of hydrogen sulphide, the interference spectra appear red-shifted. The linearity of 0.97662 and the sensitivity of 13.23 pm/ppm are achieved. In addition, the dynamic response and recovery time of the sensor are approximately 70 and 88 s, respectively. The surface adsorption energies of the film are calculated by the density functional theory. The theoretical results are in good agreement with the experimental findings. This sensor has some key advantages of small size, simple structure, easy fabrication, and great applicability for detecting the trace hydrogen sulphide.

scholarly journals Revisiting Nonlinear Functional Brain Co-activations: Directed, Dynamic, and Delayed

2021 ◽  
Vol 15 ◽  
Author(s):  
Ignacio Cifre ◽  
Maria T. Miller Flores ◽  
Lucia Penalba ◽  
Jeremi K. Ochab ◽  
Dante R. Chialvo
Keyword(s):  
Functional Connectivity ◽  
Brain Regions ◽  
Significant Loss ◽  
Subsequent Work ◽  
Activation Patterns ◽  
Nonlinear Functional ◽  
Co Activation ◽  
Neuro Imaging ◽  
Experimental Findings ◽  
Correlation Properties

The center stage of neuro-imaging is currently occupied by studies of functional correlations between brain regions. These correlations define the brain functional networks, which are the most frequently used framework to represent and interpret a variety of experimental findings. In the previous study, we first demonstrated that the relatively stronger blood oxygenated level dependent (BOLD) activations contain most of the information relevant to understand functional connectivity, and subsequent work confirmed that a large compression of the original signals can be obtained without significant loss of information. In this study, we revisit the correlation properties of these epochs to define a measure of nonlinear dynamic directed functional connectivity (nldFC) across regions of interest. We show that the proposed metric provides at once, without extensive numerical complications, directed information of the functional correlations, as well as a measure of temporal lags across regions, overall offering a different and complementary perspective in the analysis of brain co-activation patterns. In this study, we provide further details for the computations of these measures and for a proof of concept based on replicating existing results from an Autistic Syndrome database, and discuss the main features and advantages of the proposed strategy for the study of brain functional correlations.

Multi-Objective Optimization of Layered Elastic Metamaterials With Multiphase Microstructures

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Weikai Xu ◽  
Wei Wang ◽  
Tianzhi Yang
Keyword(s):  
Negative Refraction ◽  
Negative Refractive Index ◽  
Mass Density ◽  
Unit Cell ◽  
Multi Objective Optimization ◽  
Multiphase Materials ◽  
Negative Effective Mass ◽  
Unit Cells ◽  
Elastic Metamaterials ◽  
Periodic Unit Cell

Layered elastic metamaterials, which simultaneously exhibit negative effective mass density and bulk modulus, can be obtained with a unit cell of multiphase materials. In this paper, a systematic method for the design of multiphase layered elastic metamaterials is presented, and single objective along with multiobjective optimization models are proposed. Using the multiobjective genetic algorithm, the topologies of the layered periodic unit cell are designed for target frequency band structures characterizing negative wavenumbers. These obtained metamaterials with periodic unit cells can exhibit a negative refractive index in several frequency spectrums. This will be a reference for the design of 2/3-D elastic/acoustic negative refraction metamaterials.

scholarly journals Theory of concentric β-barrel structures: models of amyloid beta 42 oligomers, annular protofibrils, and transmembrane channels

2018 ◽  
Author(s):  
Stewart R. Durell ◽  
Rakez Kayed ◽  
H. Robert Guy
Keyword(s):  
Amyloid Beta ◽  
Molecular Models ◽  
Membrane Unit ◽  
Aβ Peptides ◽  
C Terminus ◽  
Extensive Range ◽  
Unit Cells ◽  
Transmembrane Channels ◽  
Experimental Findings ◽  
Microscopy Images

AbstractAmyloid beta (Aβ) peptides are a major contributor to Alzheimer’s disease. Previously, our group proposed molecular models of Aβ42 hexamers with two concentric antiparallel β-barrels that act as seeds from which dodecamers, octadecamers, both smooth and beaded annular protofibrils, and transmembrane channels form. Since then, numerous aspects of our models have been supported by experimental findings. Here we develop a more extensive range of models to be consistent with dimensions of assemblies observed in electron microscopy images of annular protofibrils and transmembrane assemblies. These models have the following features: Dodecamers with 2-concentric β-barrels are the major components of beaded annular protofibrils (bAPFs). These beads merge to form smooth annular protofibrils (sAPFs) that have three or four concentric β-barrels. Channels form from two to nine hexamers. Antiparallel C-terminus S3 segments form an outer transmembrane β-barrel. Half of the monomers of vertically asymmetric 12mer to 36mer channels form parallel transmembrane S2 β-barrels, and S1-S2 (N-terminus and middle) segments of the other half of the monomers form aqueous domains on the cis side of the membrane. Unit cells of 42-54mers have two more transmembrane S2 segments, with four concentric β-barrels in the transmembrane region and two concentric β-barrels on the cis side of the membrane.

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