Homogenization Procedure Research Articles

Homogenization of a Thermoelastic Bristly Structure Immersed in a Thermofluid

The article considers the mathematical model describing the joint motion of a viscous compressible heat-conducting fluid and a thermoelastic plate with a fine two-level thermoelastic bristly microstructure attached to it. The bristly microstructure consists of a great amount of taller and shorter bristles, which are periodically located on the surface of the plate, and the model under consideration incorporates a small parameter, which is the ratio of the characteristic lengths of the microstructure and the entire plate. Using classical methods in the theory of partial differential equations, we prove that the initial-boundary value problem for the considered model is well-posed. After this, we fulfill the homogenization procedure, i.e., we pass to the limit as the small parameter tends to zero, and, as a result, we derive the effective macroscopic model in which the dynamics of the interaction of the ‘liquid–bristly structure’ is described by equations of two homogeneous thermoviscoelastic layers with memory effects. The homogenization procedure is rigorously justified by means of the Allaire–Briane three-scale convergence method. The developed effective macroscopic model can potentially find application in further mathematical modeling in biotechnology and bionics taking account of heat transfer.

Framework for electrochemical-mechanical behavior of all-solid-state batteries: From the reconstruction method to multi-physics and multi-scale modeling

All-solid-state batteries (ASSBs) are high-energy, high-power batteries. To enhance the understanding of the electrochemical-mechanical behavior in ASSBs across different scales, we developed a multi-physics and multi-scale modeling framework. This framework incorporates elastoplastic finite deformation and electrode microstructures of ASSBs, and the role of gradient plasticity in the governing equation for multiple physical fields was discussed. Utilizing X-ray computed tomography, we reconstructed the microstructure through a machine learning (ML)-informed image segmentation process. Our study clarifies the impact of electrode microstructures on concentration, stress, voltage, delamination and buckling from AM to electrode scale. Comparative analysis of the Feret diameter distribution of active materials (AMs) shows that ML-informed image segmentation outperforms two traditional segmentation methods. We observed that the asynchronous diffusion saturation of AMs, varying in shape and size, significantly influences the electrochemical-mechanical behavior of ASSBs, resulting in complicated debonding indices and J-integral distribution at the interface. The proposed upscaling homogenization procedure is demonstrated to be efficient for buckling analysis, with the shape mode closely matching existing experimental observations. These results shed light on the critical multi-physics and multi-scale coupling mechanisms in ASSBs.

Enhanced Solubility and Increased Bioavailability with Engineered Nanocrystals

Abstract: The exploration of nanocrystal technology is currently receiving significant attention in various fields, including therapeutic formulation, clinical formulation, in-vivo and in-vitro correlation research, and related investigations. The domain of nanocrystals in pharmaceutical delivery has received significant interest as a potential solution for the difficulties associated with medications that have low solubility. The nanocrystals demonstrate promise in improving solubility and bioavailability, presenting a potential resolution to significant challenges. Significantly, nanocrystals have exhibited efficacy in the context of oral administration, showcasing prompt absorption due to their quick breakdown, hence fitting with the requirements of medications that necessitate fast commencement of action. In addition, the adaptability of drug nanocrystals encompasses several methods of administration, including oral, parenteral, ophthalmic, cutaneous, pulmonary, and targeted delivery modalities. The observed consistency can be ascribed to the increased solubility of nanocrystals of the medicine, which effectively counteracts the influence of food on the absorption of the drug. Surface modification tactics have a significant influence on insoluble medicines by enhancing hydrophilicity and reducing plasma protein adsorption on the crystal surface. The surface properties of nanocrystals are modified through the utilization of specific surfactants and polymers, which are subsequently incorporated into polymer solutions via high-pressure homogenization procedures. This article encompasses an examination of the drug distribution mechanism, the nanocrystal formulation technology, the therapeutic applications, the potential future developments, and the challenges associated with the solubility and bioavailability of tailored nanocrystals, as discussed in this article. Consequently, it possesses the capacity to provide guidance for future investigations pertaining to nanocrystal technology.

Relative Homogenization of Climatic Time Series

Homogenization of the time series of observed climatic data aims to remove non-climatic biases caused by technical changes during the history of the climate observations. The spatial redundancy of climate information helps to recognize station-specific inhomogeneities with statistical methods, but the correct detection and removal of inhomogeneity biases is generally not easy for the combined effects of individual inhomogeneities. In a homogenization procedure, several time series of a given climatic variable observed in one climatic region are usually homogenized together via a large number of spatial comparisons between them. Such procedures are called relative homogenization. A relative homogenization procedure may include one or more homogenization cycles where a cycle includes the steps of time series comparison, inhomogeneity detection and corrections for inhomogeneities, and they may include other steps like the filtering of outlier values or spatial interpolations for infilling data gaps. Relative homogenization methods differ according to the number and content of the individual homogenization cycles, the procedure for the time series comparisons, the statistical inhomogeneity detection method, the way of the inhomogeneity bias removal, among other specifics. Efficient homogenization needs the use of tested statistical methods to be included in partly or fully automated homogenization procedures. Due to the large number and high variety of homogenization experiments fulfilled in the Spanish MULTITEST project (2015–2017), its method comparison test results are still the most informative about the efficiencies of homogenization methods in use. This study presents a brief review of the advances in relative homogenization, recalls some key results of the MULTITEST project, and analyzes some theoretical aspects of successful homogenization.

CNN-based prediction of microstructure-derived random property fields of composite materials

The simulation of random spatial variation in the mechanical properties of composite materials using random fields derived from their microstructure can be computationally demanding, since it often requires numerical homogenization of a large number of stochastic volume elements (SVEs). These SVEs are usually extracted from an initial image of the composite microstructure by using a moving window technique and their homogenized properties constitute the discrete data points of the random field at the centroid of each SVE. By replacing the expensive and highly repetitive homogenization procedure with a convolutional neural network (CNN), it is possible to perform nearly instant computations of random property fields. In this work, a CNN is proposed, that takes as input an SVE image and returns its apparent mechanical properties, and can therefore be applied along with the moving window technique. Training is performed on randomly generated SVEs with varying volume fractions and inclusion positions, which are representative of the SVEs obtained during processing of the initial large composite image. It is shown that the proposed CNN can accurately predict the mechanical properties of SVEs and it is subsequently applied for the prediction of random property fields derived from computer simulated and real microstructure images. Results show that, with the proposed methodology, it is possible to make accurate predictions of random fields within a few seconds, a procedure which could potentially require hours of computation time with the finite element based approach.

Multiscale characterization of effective mechanical properties of graphene-chitosan composite aerogels

This work reports on numerical characterizations of effective mechanical properties associated with graphene-polymer composite aerogels produced using an environmentally friendly freeze-drying process. To this purpose, a multiscale approach was implemented, in which geometrical configurations were constructed based on the results of experimental characterizations. A homogenization procedure based on molecular mechanics, the Milton method, and the asymptotic homogenization method was applied. In the asymptotic homogenization method, cell problems were formulated and solved within a representative volume element using the finite element method. After validating the numerical model through experimental results from compression tests, a parametric study on the influence of microstructural parameters of the materials, such as dispersion state, aspect ratio, volume fraction of nanoinclusions, and material porosity, on the macroscopic mechanical behavior of the composite aerogels was conducted. The simulation results provided a deeper understanding of the mechanisms that enhanced the mechanical properties of such aerogels by adding various graphene derivatives, allowing for adjustments in the elaboration process to obtain materials with improved mechanical properties.

Analysis on thermal stability of Rutherford cable fabricated by quasi-isotropic strands

A preliminary design of a Rutherford cable (Rfc) consisting of a copper core and 10 Quasi-isotropic Strands (Q-ISs) with symmetrical geometry is proposed. The current sharing temperature (Tcs), minimum quench energy (MQE), and normal zone propagation velocity (NZPV) are significant for determining the thermal stability performance of the superconducting cable. Firstly, an electric model of the conductor equivalent circuit is established, and the algebraic equations are derived. The model is validated with the empirical formula by calculating the Tcs of a single Q-IS. Using the validated model, the Tcs of Rfc fabricated by Q-ISs operating in liquid helium temperature at different magnetic fields are obtained. Then, to quantitatively characterize the effect of Q-ISs located at different positions on Rfc after a heating disturbance, the MQE and NZPV of Rfc are numerically simulated by the finite element method, which uses a 3-D thermal model with a homogenization procedure and coupled with the previous electrical model. The analyzed results provide a preliminary assessment of the thermal stability of the high-current superconducting cable and provide important guidance for subsequent experiments and prospective engineering applications.

Ultrathin Freestanding Nanocellulose Film Prepared from TEMPO-Mediated Oxidation and Homogenized Hydrogel.

This paper presents a versatile method to fabricate ultrathin nanofibrillated cellulose (NFC) films as thin as 800 nm by blade coating, which is compatible with a roll-to-roll process on a large scale. Our approach allows obtaining a dried nanocellulose film within a span of 1 h subsequent to 2,2,6,6-tetramethylpiperidine-1-oxyl radical-assisted oxidation and homogenization procedures. One of the thinnest freestanding NFC films with a thickness of 800 nm is achieved using a blade coating of nanocellulose after 72 h of oxidation followed by homogenization with a channel size of 65 μm. Incorporating water-soluble CdTe core-type quantum dots into the nanocellulose film led to a uniform emission under 385 nm UV irradiation, indicating excellent material compatibility. We anticipate nanocellulose developed in our study to be beneficial in biomimicry flying objects, environmentally friendly encapsulation, color filters, and energy storage device membranes, to name a few.

Hydromechanical coupling in unsaturated clayey rocks with double porosity based on a multiscale homogenization procedure

Shales and clay rocks are porous media with multiscale microstructures used in many engineering applications. Intact clay rocks often exhibit a bimodal pore size distribution in which the nanopores are related to the interlayer spacing in the clay platelet and the micropores are related to the interparticle pores between clay particles. The double-porosity microstructure has significant implications for the hydromechanical behavior of these rocks especially in unsaturated conditions. In this study, we develop a double-porosity hydromechanical framework incorporating a homogenization scheme to simulate fluid flow and elastic deformation in anisotropic clay rocks. The homogenization scheme provides an enriched description of the elastic behavior of clay rocks during changes in the degree of saturation by bridging the nano, micro, and macroscale characterizations. We also model the nanopores and micropores as two independent pore networks with distinct fluid flow mechanisms and permeabilities. The proposed framework is cast into a three-field mixed finite element formulation for solving fully coupled flow and deformation problems. Numerical examples of free and confined swelling in Opalinus clay samples are presented to demonstrate the impacts of a multiscale microstructure on wetting processes in clay rocks.

A multiscale micromechanical progressive elastic-damage model for cementitious composites featuring superabsorbent polymer (SAP)

A multiscale micromechanics-based progressive damage model is developed to investigate the overall mechanical behavior and the interfacial microcrack evolutions of the cementitious composites featuring superabsorbent polymer (SAP) under uniaxial tension. Elastic properties, progressive damage process, and homogenization procedure of cementitious composites are systematically integrated in this model. The effective elastic moduli of the composites are determined based on a multiscale micromechanical framework. According to the small strain assumption, the total strain tensor and the elastic-damage compliance tensor are additively decomposed into elastic and damage-induced components. The damage-induced strains and compliances are then deduced from micromechanics. To characterize the progressive elastic-damage induced by microcracks, stages of microcrack propagation are identified from the interface contact stress and the matrix cleavage stress. The complex potentials and stress intensity factors for kinked interface cracks are derived from the distributed dislocations method. By implementing the homogenization process, the macroscopic mechanical behavior is obtained from the micro/mesoscale. The results indicate that the material parameters have clear mechanical significance. Different parameters, such as the SAP addition ratio, aggregate content, initial interfacial crack size, and initial interfacial crack location, are revealed to be influential in the overall mechanical behavior of the composites. The proposed model can be generalized to other particle-reinforced composites with different constituent properties, which can potentially contribute to the design and optimization of durable composites.

Development and Evaluation of Acitretin Loaded Solid Lipid Nanoparticles for Topical Drug Delivery System

In order to understand the in vitro drug release of the produced gel, the goal of the current investigation was to construct and characterize. Acitretin loaded Solid Lipid Nanoparticles (ActSLNs). Act SLNs were created utilizing the Box Benhken design and the hot homogenization procedure. Act SLN's average diameter and surface morphology were assessed. Act SLNs were lyophilized, then they underwent stability testing, powder X-Ray diffraction, Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared (FT-IR) tests to characterize them. The SLNs were added to a 0.25% w/w Carbopol 940 gel base the Stability study, ex vivo drug release in vitro drug releases in rat skin were carried out. The optimized Act SLNs had a spherical form, an entrapment efficiency of 78.82% to 85.73%, and an average particle size of 123.24nm to 409nm. The generation of SLNs was confirmed by DSC, FTIR, and XRD data. ActSLN gel (0.056mg/cm2) significantly increased the amount of accutane deposited in rat skin compared to Act plain gel (0.012mg/cm2).No discernible change was found in the stability studies, according to stability studies.

Development of a new continuous homogenous liquid phase microextraction procedure based on in-situ preparation of deep eutectic solvent; application in the analysis of aliphatic amines in urine samples by GC–MS

In the present work, a new microextraction procedure combined with gas chromatography-mass spectrometry has been developed for the analysis of several aliphatic amines from urine sample. The sample preparation method was a continuous homogenous liquid phase microextraction that was based on in-situ preparation of 4-chlorophenol: choline chloride deep eutectic solvent. The deep eutectic solvent was prepared by passing the mixture of related compounds through a syringe barrel filled with exothermic salts (calcium chloride and potassium bromide). The released heat by dissolving the salts and increasing the solution ionic strength assists the formation of the deep eutectic solvent. The influence of various factors on the efficiency of the proposed procedure including salts amount, flow rate, pH, salting-out effect, and extraction solvent volume was studied. The calibration curves were linear broadly over the concentration range of 1.2–250 ng mL−1 with coefficient of determinations ≥0.996. The enrichment factors were in the range of 188–246 and the limits of detection and quantification were 0.16–0.37 and 0.56–1.2 ng mL−1, respectively. Based on the results, the offered method was sensitive, rapid, eco-friendly, and efficient for extracting and determining aliphatic amines in urine samples.

Pathways to formulate lightweight and ultra-lightweight 3D printable cementitious composites

This paper studies the pathways to formulate lightweight and ultra-lightweight 3D printable cementitious composites. A hybrid approach was proposed by combining the advantages of traditional chemical-induced foaming (foaming approach) and lightweight particulate inclusions (synthetic foam approach). A comprehensive experimental program was conducted to evaluate the effects of foaming agents and fly ash cenosphere (FAC) on the printability, microstructure, mechanical and thermal properties of 3D printed samples. The results showed that the hybrid approach could produce a mixture with a density as low as 470 kg/m3 while ensuring good flowability and buildability owing to the lubricating effect of foaming and supporting skeleton formed by FAC. In addition, a three-step homogenization procedure was also developed to predict the effective elastic modulus and thermal conductivity of 3D printable cementitious composites and cementitious foam. The findings of the study highlighted the effectiveness of the hybrid approach in formulating 3D printable ultra-lightweight cementitious composites in thermal insulation and acoustic applications.

Simplified homogenization technique for nonlinear finite element analysis of in-plane loaded masonry walls

The present investigation focuses on the nonlinear modelling of masonry walls under in-plane loading. To conduct this macro-scale study, a homogenization technique is applied to derive the equivalent secant moduli according to damage and friction sliding at the micro scale level for both bed mortar joint and brick material constituents. In the homogenization process the representative unit cell of masonry panel with a regular arrangement is first defined. Then a simplified kinematical model is proposed to describe the behaviour of the homogenized unit-cell under combined axial and shear stresses. This is based on the cohesive model for pure mode I and II and by allowing for the Coulomb's friction law for bed joint and the scalar damage model is adopted for the brick material. In the first stage, the proposed homogenization technique is verified for various unit cell constituents at micro-scale level. In the second step, this homogenization procedure was incorporated into proposed in-house finite elements software. To achieve this end, a new beam finite element is formulated in the context of the fibre higher order shear deformation theory HSDT. Using the proposed finite elements model, a numerical investigation is conducted to check the validity of the proposed model against the available experimental and numerical investigations. This allowed for the study of the effect of the applied compressive load on the lateral ultimate load.

Efficient heterogeneous synthesis of nucleophilic carboxymethyl hydrazides of polysaccharides.

Nucleophilic moieties in polysaccharides (PS) with distinct higher reactivity compared with the hydroxy group are interesting for sustainable applications in chemistry, medicine, and pharmacy. An efficient heterogeneous method for the formation of such nucleophilic PS is described. Employing alcohols as slurry medium, protonated carboxymethyl (CM) PS and hydrazine hydrate are allowed to react at elevated temperatures. The CM derivatives of starch and pullulan can be transformed almost quantitatively to the corresponding hydrazides. The reaction is less efficient for CM dextrans and CM xylans. As slurry media, 2-propanol and ethanol were probed, and the results are compared with a homogeneous procedure performed in water. Overall, the heterogeneous procedure is superior compared with the homogeneous route. 2-Propanol is the best slurry medium investigated yielding PS hydrazides with the highest nitrogen content.

Turbulent transition in a channel with superhydrophobic walls: anisotropic slip and shear misalignment effects

Superhydrophobic surfaces dramatically reduce skin friction of overlying liquid flows. These surfaces are complex and numerical simulations usually rely on models to reduce this complexity. One of the simplest consists of finding an equivalent boundary condition through a homogenisation procedure, which in the case of channel flow over oriented riblets, leads to the presence of a small spanwise component in the homogenised base flow velocity. This work aims at investigating the influence of such a three-dimensionality of the base flow on stability and transition in a channel with walls covered by oriented riblets. Linear stability for this base flow is investigated: a new instability region, linked to cross-flow effects, is observed. Tollmien–Schlichting waves are also retrieved but the most unstable are three-dimensional. Transient growth is also affected as oblique streaks with non-zero streamwise wavenumber become the most amplified perturbations. When transition is induced by Tollmien–Schlichting waves, after an initial exponential growth regime, streaky structures with large spanwise wavenumber rapidly arise. Modal mechanisms appear to play a leading role in the development of these structures and a secondary stability analysis is performed to retrieve successfully some of their characteristics. The second scenario, initiated with cross-flow vortices, displays a strong influence of nonlinearities. The flow develops into large quasi-spanwise-invariant structures before breaking down to turbulence. Secondary stability on the saturated cross-flow vortices sheds light on this stage of transition. In both cases, cross-flow effects dominate the flow dynamics, suggesting the need to consider the anisotropicity of the wall condition when modelling superhydrophobic surfaces.

Energy attenuation of seismic metamaterials composed of a periodic array of coated elliptical cylinders

Abstract We present a numerical study on energy attenuation of seismic metamaterials consisting of a periodic array of coated elliptical cylinders. The aim is to perceive the effect of aspect ratio for different wave modes so that the metamaterials can interact with the incoming wave causing them to interfere with each other destructively, especially for low-frequency seismic waves with relatively wide bandgap. Previous studies mainly focused on the configuration of coated circular cylinders or spheres, in which the metamaterial is composed of a hard inclusion surrounded by a soft coating layer and dispersed within a hard matrix. Here we utilize numerical simulations based on finite element calculation to analyze the local fields within the unit cell. Effective mass density, mass moment of inertia and shear modulus are analyzed through a homogenization procedure to characterize the macroscopic behavior of the effective medium. The effective behavior will be dependent for different aspect ratios and for different types of wave motions. To verify the effectiveness of energy attenuation, a full-scale model is adopted. Specifically, to identify optimal energy attenuation configurations, we illustrate the attenuation effects of elliptical metamaterials under longitudinal and shear horizontal types of waves. The present study demonstrates that elliptical metamaterials will have more reflexibilities to tune with the aspect ratio of the elliptical geometry as well as the directionality of incidence waves. Based on our simulations, we show the ability of the designed configuration in tuning local resonance frequencies and bandwidths for real implementations and applications of seismic metamaterials.

Turing patterns in domains with periodic inhomogeneities; a homogenization approach

In this work, we study reaction–diffusion equations with space-dependent, differentiable, and ɛ-periodic diffusion coefficients, using the asymptotic homogenization technique. The importance of this problem is that experimental evidence suggests that in some biological systems, spatial inhomogeneities are important to regulate spatial patterns, and several pattern-forming systems are regulated by a stratified domain that determines the transport properties. Here, we consider the case when the stratification is periodic with a period ɛ; consequently, the diffusion coefficient is a space-dependent ɛ-periodic function. A methodology based on the asymptotic homogenization technique was developed to solve this problem, and the conditions for Turing instability were found in terms of the effective coefficients of the equivalent homogenized domain. Additionally, extensive numerical calculations were performed to validate the results predicted by the homogenization procedure; one- and two-dimensional examples are presented. We conclude that the homogenization method is useful in the field of pattern formation to handle problems involving spatial inhomogeneities or stratified domains. In addition, the proposed generalization of Turing analysis for a homogenized problem enriches the field of pattern formation.

Exploring Forms of Political Violence Against Women and their Effect on Women’s Political Participation in Matero Constituency of Lusaka District, Zambia.

This article explored the forms of political violence against women and their effects on women’s political participation in Matero Constituency of Lusaka District, Zambia. This research took a qualitative approach and rode on a case study design to generate evidence. A sample of 24 political party leaders were recruited through homogenous purposive sampling procedure. The data was generated using interviews and was analysed thematically. This research found that five (5) forms of political violence against women were in existence in Matero Constituency. These included: physical, psychological, sexual, economic and semiotic violence. This research also revealed that political violence against women affected the political participation of women negatively as cases of resignations, disenfranchisement and fear to participate, confinement to lower positions and reduced freedom of expression were prominent in the constituency. This research concluded that there was a growing increase in the forms of political violence against women in Matero constituency and this discouraged women from participating in political processes as expected. Among others, it is recommended that the Zambia Center for Inter-party Dialogue (ZCID), the Electoral Commission of Zambia (ECZ) and Civil Society Organisations (CSOs) should convene wider consultative seminars and workshops to familiarize themselves and the general public with the forms of political violence against women.

Thermal conductivity of functional fibrous inhomogeneous materials

The study focuses on developing new methods for assessing the effective properties and modeling the thermal conductivity of fibrous composites with functional fibers for lightning protection systems on aircraft. The aim is to create more efficient and lightweight composites to enhance flight safety and reduce maintenance costs. The research methodology involves analyzing two types of whiskerized interphase layers in composites and modeling their thermal conductivity using a two-step homogenization procedure. The results indicate that composites with functional fibers can significantly outperform classical composites in terms of thermal conductivity. For composites where the whiskerized layer is formed by randomly grown and interwoven carbon nanotubes, the effective thermal conductivity in the plane perpendicular to the fiber axis and in the direction along the fiber can exceed those of classical composites by more than 2 and 1.2 times, respectively. For composites where the whiskerized layer consists of carbon nanotubes grown perpendicular to the fiber surface, these values can exceed those of classical composites by more than 3 and 1.1 times, respectively. Such findings suggest the potential use of functional composites as an effective replacement for metallic meshes in lightning protection systems on aircraft.