Layered Structure Model Research Articles

Calculation of adsorption apparatuses with a layer of expanded substances

This work is a part of the project for investigations of hydrodynamics and mass transfer in an adsorption apparatus with ion-exchange resins during the extraction of stevioside from stevia extract. The issues of improving the structural-sorption characteristics while increasing selectivity to certain substances, expanding the range, simplifying the manufacturing technology and reducing the cost of production of industrial adsorbents are extremely relevant. The work is devoted to mathematical modeling and a theoretical description of adsorption in the layer of expanded ion-exchange resins. The main aspects of adsorption in a layer of porous material have been considered, and a model of the adsorption layer structure has been developed. The contribution of the work and its scientific novelty lie in the fact that a mathematical model of the evolution of a two-component dispersed phase has been developed and qualitatively analyzed taking into account competitive adsorption and the non-equilibrium nature of mass transfer between the adsorption surface of the porous material and the dispersed phase. The results and conclusions are recommended to be used in planning and conducting research work for intensification of heat and mass transfer processes and for engineering design of adsorption chemical apparatuses and adsorption columns.

A 3D modeling method of layered acoustic material structures with finite dimensions

Modeling of layered acoustic structures to predict the sound absorption characteristics of complex materials is a widely used method in room acoustic practice. Commonly used modeling techniques-such as the transfer matrix method-typically assume locally reacting surfaces of infinite lateral dimensions and provide one-dimensional calculations only, offering limited accuracy, especially for resonant absorbers with finite dimensions. We present the direct, analytical modeling of sound propagation in extendedly reacting layered materials of finite dimensions allowing the estimation of the surface impedance or admittance distribution of layered structures, from which sound absorption properties can be calculated. The theoretical results are validated by measurements, performed on a small-sized resonant panel absorber. We present the implementation of the method in the soundy.ai application.

A multiphase hybrid-stress finite element method for macroscopic and microscopic modeling of composites: An element with multiple interfaces

A multiphase hybrid-stress finite element method (MHSFEM) for microscopic modeling of randomly dispersed closer microstructures and macroscopic modeling of layered structures include adhesive layer of laminated composites is proposed in the work. The stress functions for each phase within the element are constructed taking into account the shape of phase interfaces. The traction reciprocity conditions on the phase-phase interfaces within the element are introduced into the element functional, which is derived based on the minimum complimentary energy principle, by the Lagrange multiplier method. By several numerical examples, the effectiveness and accuracy of the proposed MHSFEM is verified by comparing its results with those of conventional finite element method and those of Voronoi cell finite element method. The proposed method is certainly an effective way for the microscopic and macroscopic mechanical analysis of composite materials with lower computational costs.

The application of measuring atmospheric properties in overlap factor region using scanning Lidar

This paper explores the effects of different factors on the results and accuracy of aerosol optical property measurements made in overlap factor regions using scanning lidar, simulation calculations and aerosol detection experiments. First, the measurement principle was analysed using the atmospheric layered structure model. The slope inversion of the simulated backscattering coefficient of the aerosols was performed using the Fernald method. Second, the measurement errors caused by the inhomogeneity of the horizontal atmospheric layers and scanning angle errors were analysed for different weather conditions. Finally, the aerosol detection accuracies of the scanning lidar under different weather conditions were explored by employing comparative experiments. The experimental results showed that the aerosol extinction characteristics in the overlap factor region can be effectively obtained using the proposed method and that the measurement results were affected by the systematic errors in the scanning angle. The proposed method would effectively solve the problems caused by the unavailability of optical properties of aerosols in the overlap factor region of lidar. Moreover, the signal inversion of slant detection also provides an accurate theoretical basis for field experiments and has a good aerosol detection capability and potential application prospects.

Frosting mechanism and behaviors on surfaces with simple geometries: A state-of-the-art literature review

• Correlations of frosting characteristic parameters are summarized and analysed. • Effects of frosting conditions on average frost layer characteristics are reviewed. • Frosting distribution characteristic for different cold surfaces are reviewed. • Eight research gaps relating to frosting mechanism and behaviors are identified. Frosting causes negative impacts in many technical and engineering fields, such as refrigeration, air source heat pump, aircraft, wind power generation, and power grids. To alleviate the negative impacts of frosting, studies on frosting characteristics, avoiding and delaying frosting, and defrosting mechanisms and methods have been carried out for decades. Among these studies, frosting characteristics, which are the fundamental basis for defrosting, avoiding, and delaying frosting are consistently the hot research spots. Considering that complex structures can be usually regarded as the combination of simple geometries, in this paper, a comprehensive review of the literature related to the frosting mechanism and behaviors on surfaces with simple geometries is presented. The former covers frost formation process and morphology, frost layer structure model, and frosting characteristic parameters, such as frost thickness and effective frost thermal conductivity. The latter is further divided into six parts based on the configurations of cold surfaces, including flat plates with a fixed surface temperature, flat plates with a fixed base temperature, cylinders, parallel plates, set of fins and semipermeable membranes. Based on the review, the research gaps in the related study fields are identified, and recommendations for further research are offered. The literature review presented in this paper can provide a comprehensive and systematic reference for the people who are working in the study fields where frosting is commonly encountered.

An innovative clustering technique to generate hybrid modeling of cooling coils for energy analysis: A case study for control performance in HVAC systems

Despite past studies, no comprehensive models or empirical correlations cover all aspects of performances of cooling coils under different flow regimes (laminar, transition, and turbulent). Moreover, the cooling coil is characterized by a highly nonlinear dynamic subject to multiple inputs, coupling between the latent and sensible heat transfer modes, uncertain disturbances, and strong dependence of the overall heat transfer coefficient on the flow type, all causing significant challenges when it comes to modeling. Therefore, a hybrid layer structure model was adopted in this study to overcome these challenges. The new approach used two different optimization methods, Neural Networks' Weights and Takagi-Sugeno (TS) fuzzy, and the hybrid layers tuned by the Gauss-Newton algorithm (GNA). The proposed model covered three types of fluid flow to represent the dynamic behavior of the water-side and air-side heat transfer coefficients, each of which was divided into seven clusters and had its unique TS consequence. This study also administered meaningful fitness tests in the responses of the eleven independent variables that serve as its inputs. Furthermore, its application shows the control performance saving more than 44% of HVAC system energy. Based on the results, it was concluded that the proposed model is suitable for estimating energy and cost savings for electric power and water flow rate efficiency. In addition, the response of all types of output flow can be evaluated when changing eleven independent variables that are manipulated by three different controllers.

Molecular Dynamics Study of the Diffusion between Virgin and Aged Asphalt Binder

The diffusion between the virgin and aged asphalt binder in the recycled asphalt mixture is a crucial factor affecting its macro-mechanical performance. In this study, a combined model of the virgin-aged layered asphalt structure was assembled based on the molecular dynamics (MD) method. A four-component and twelve-category molecule were used to model the asphalt. The diffusion behaviors of the virgin and aged asphalt were characterized by mean square displacement (MSD), diffusion coefficient, relative concentration and cohesive energy density (CED). Results indicated that at the same temperature, the diffusion coefficient of the virgin asphalt was the largest, followed by the virgin-aged asphalt and the aged asphalt. As the temperature increased, the relative concentration on both sides of the virgin-aged asphalt overlapped to a certain extent. The covered lengths of the virgin asphalt were larger than those of the aged asphalt, indicating the diffusion between the virgin asphalt and aged asphalt was mainly manifested as the diffusion from the virgin asphalt to the aged asphalt. The development of CED and the fraction of free volume (FFV) indicated the mutual attractive interactions among the molecules in virgin and aged asphalt layers became strong and the cohesion properties inside the model became better.

Liquid cell transmission electron microscopy reveals C-S-H growth mechanism during Portland cement hydration

We report the first application of in-situ liquid cell transmission electron microscopy (LC-TEM) to research hydration reactions of nano OPC, providing nanoscale insight into early reaction mechanisms. We demonstrate that the formation and growth of C-S-H precipitates starts through lateral growth of planar silicate sheets, but soon continues in all directions resulting in a 3D microstructure. Furthermore, nanocrystalline C-S-H structures with sizes between 5 nm to 10 nm were observed inside the amorphous or highly disordered C-S-H matrix, denoting that C-S-H growth is conformed to layered structure model. Crack formation and propagation inside C-S-H precipitates confirms the presence of increasing lattice strain due to growing defects that limits the growth of a fully crystalline structure by buckling and separating the sheets. The rolling up and crumbling of C-S-H sheets promotes the formation of new embryos, leading to the growth of precipitates in all direction and finally their coalescence.

The cause of foaming in polishing porcelain stoneware tile residues during sintering: Interface corrosion of Silicate-SiC

The SiO2 layer preferentially generated on the surface of silicon carbide abrasives in Polishing Porcelain stoneware tile Residues (PPR) is corroded by silicate liquid during firing, resulting in continuous oxidation and foaming of silicon carbide, which makes the PPR difficult to be reused. The PPR is fired to form a silicate liquid that wraps micron silicon carbide in it. In this work, it is possible to study the corrosion of silicate to silicon carbide at high temperature by using two (Ceramic-SiC) and three (Ceramic-SiO2-SiC) layer structure model to simulate the corrosion of silicate to silicon carbide. The corrosion mechanism of SiC in PPR by silicate liquid during firing is revealed that the corrosion rate at its two sides (interfaces) determines the ultimate change in the thickness of the corrosion layer between the ceramic and the SiO2 layer. Importantly, the corrosion layer thickness with time on the silicate-SiO2 cross-section periodically presents wave-like changes, which can be attributed to the ionic migration between layers and the rate at which cations cross the corrosion layer when studying the three-layer model.

An Improved Approach for Hydrocarbon Detection Using Bayesian Inversion of Frequency- and Angle-Dependent Seismic Signatures of Highly Attenuative Reservoirs

Studies of frequency dependence of seismic data anomalies on partially gas-saturated reservoir have been performed for many years. Essentially, the frequency-dependent seismic signature represents a potential and largely untapped source of information for the detections of subsurface target properties. Through analyzing the anomalous feathers of amplitude variations with the angle of incidence and frequency (AVAF), both theoretically and algorithmically, it is possible to discriminate hydrocarbon from variations in other reservoir properties. For a layered structure model, however, it can be challenging to employ the conventional Zoeppritz equation-based method that may not accurately describe complex reflections considering the effects of both the layered structure of a reservoir and the attenuative and dispersive property of rocks. We introduce a novel hydrocarbon detection approach based on Bayesian inversion of frequency- and angle-dependent reflection signatures from a tight gas sandstone reservoir having strong attenuation and velocity dispersion. The proposed inversion scheme employs the propagator matrix method as a description of seismic responses for the stratified model and spectral decomposition technique to obtain multifrequency amplitude information. The synthetic test and real application show the proposed inversion approach has the potential to be useful in detections of hydrocarbon accumulation.

Multiple Reflective Cracks in Semirigid Base Asphalt Pavement under Traffic Load Using XFEM

This paper built a three‐dimensional layered structure model of semirigid base asphalt pavement with single and double transverse reflective cracks based on the Extended Finite Element Method and fatigue fracture theory. The effects of the number of cracks, crack spacing, and crack length on the stress intensity factors (KI, KII, and Keff) under moving vehicle loads were studied. The fracture life of the asphalt pavement structure was calculated based on the Pairs formula. The results demonstrate that reflective cracks in semirigid asphalt pavement are composite cracks of type I and type II under moving vehicle loads, and shear fracture is the main reason for the failure of the base. The damage to the pavement base will be accelerated with the increase in the number of cracks and the length of the cracks. As the distance between the two reflection fractures is closer, the interaction between the cracks has a superimposed enhancement effect on the crack propagation. Compared with the single nonpenetrating crack model, the fatigue life of the nonpenetrating reflective crack in the double crack pavement structure with a crack spacing of 30 cm is reduced by 46.87%. The research on the propagation mechanism of reflective cracks in this paper provides the essential theoretical and numerical basis for the design, construction, working condition evaluation, and maintenance of pavement structures.

Dynamics and criteria of CFRP destruction by lightning currents

The article discusses a promising conductive composite material such as carbon-plastic. This material has significant strength, not inferior to metal, has a low specific weight and has interesting electrophysical characteristics. For a wider use of the material in various structural products, it is necessary to consider its unique characteristics. The work is devoted to the study of the conductive properties of carbon fiber under the influence of lightning currents and the development of criteria for its destruction. Based on two models of destruction of CFRP by lightning currents, a theoretical analysis of its destruction has been carried out. The first model considered the composite material as a continuous medium with anisotropic-conducting properties. The solution of the Laplace equation with the Neumann boundary conditions made it possible to find the distribution of current densities over the material and theoretically determine the radius and depth of damage. The second model, the layered structure model, took into account the structure of real CFRP. The dynamics of layer-by-layer destruction is considered on the basis of the equivalent circuit of carbon fiber reinforced plastic, which takes into account the longitudinal and transverse resistivity of the composite. The distributions of the radial current density along the radius and depth of the material are constructed and the analysis of the spreading of currents at various degrees of material anisotropy is carried out. Strong anisotropy, leading to the release of total energy in the first layer. Destruction of the upper layer changes the distribution of currents in the rest of the layers. The results of numerical modeling of layer-by-layer destruction of CFRP for five layers are presented. The process of destruction under the action of large current pulses is considered. The fracture criteria for various degrees of material anisotropy are obtained and refined. The resulting formulas contain values that are reproduced in the experiment. The calculation results are in good agreement with experiment. In conclusion, it is concluded that the criteria are applied to predict the effects of lightning and optimize lightning protection at the design stage of an aircraft.

Transient thermal analysis of layered media based on thermal quadrupoles

ABSTRACT The transient heat transfer within a layered structure can be modeled efficiently using the thermal quadrupole methods. Such numerical simulations would contribute to effective experimental design for thermography inspection applications of composite materials. Current research is part of such effort that focuses on the parametric study on both a two-layer model and a four-layer model. The variation of amplitude curves agrees with the lateral position of the interfacial discontinuity in general. The sudden increase in the phase value distinctively indicates the end point of the same discontinuity. Hence the lateral location of an embedded interfacial discontinuity can be readily identified from the Laplace surface temperature. The layer thickness does not have significant effect on the general trend observed in the parametric analysis presented in this work. The advantage of the numerical modeling of layered structures using thermal quadrupoles lies in that thermal quadrupoles can be easily extended to multiple layers containing internal anomaly between different layers.

Transient thermal analysis of layered media based on thermal quadrupoles

The transient heat transfer within a layered structure can be modeled efficiently using the thermal quadrupole methods. Such numerical simulations would contribute to effective experimental design for thermography inspection applications of composite materials. Current research is part of such effort that focuses on the parametric study on both a two-layer model and a four-layer model. The variation of amplitude curves agrees with the lateral position of the interfacial discontinuity in general. The sudden increase in the phase value distinctively indicates the end point of the same discontinuity. Hence the lateral location of an embedded interfacial discontinuity can be readily identified from the Laplace surface temperature. The layer thickness does not have significant effect on the general trend observed in the parametric analysis presented in this work. The advantage of the numerical modeling of layered structures using thermal quadrupoles lies in that thermal quadrupoles can be easily extended to multiple layers containing internal anomaly between different layers.

Liquid Cell Transmission Electron Microscopy Reveals C-S-H Growth Mechanism During Portland Cement Hydration

We report the first application of in-situ liquid cell transmission electron microscopy (LC-TEM) to research hydration reactions of nano OPC, providing nanoscale insight into early reaction mechanisms. We demonstrate that the formation and growth of C-S-H precipitates starts through lateral growth of planar silicate sheets, but soon continues in all directions resulting in a 3D microstructure. Furthermore, nanocrystalline C-S-H structures with sizes between 5 nm to 10 nm were observed inside the amorphous or highly disordered C-S-H matrix, denoting that C-S-H growth is conformed to layered structure model. Crack formation and propagation inside C-S-H precipitates confirms the presence of increasing lattice strain due to growing defects that limits the growth of a fully crystalline structure by buckling and separating the sheets. The rolling up and crumbling of C-S-H sheets promotes the formation of new embryos, leading to the growth of precipitates in all direction and finally their coalescence.

Measurement method for dispersion states of filler particles in particulate composite materials by macroscopic permittivity

A new model for estimating macroscopic permittivity was proposed to predict filler particles' dispersion states in a particulate composite material. In the model, the estimation targets are randomly packed composite materials. The composite materials were represented as a cluster of unit cells. A proposed layer structure model connected the unit cells. The macroscopic permittivity was estimated by calculating the synthetic capacity of the cluster. The proposed model was validated by comparisons between estimated and measured macroscopic permittivity of several particulate composite materials. It was also identified that the proposed model could estimate the permittivity more accurately than an existing theoretical equation's one due to considering the effects for the dispersion states of filler particles. Furthermore, it was indicated that the proposed model could also estimate the dispersion states of filler particles by the measured permittivity. The applicability of the method was confirmed by comparisons between estimated and experimental dispersion states of filler particles.

Numerical study of the strength characteristics of the V-shaped tail of an unmanned aerial vehicle based on composite materials

In this research, we investigate the strength characteristics of the V-shaped tail of an unmanned aerial vehicle made of polymer composite materials based on an epoxy matrix filled with fiberglass and carbon fibre. The study was carried out by numerical modelling of the stress-strain state of the system in the Ansys Mechanical software and the Composite Prep-Post module allowing a model of layered structures of polymer composite materials to be set up. The values of stresses and strains under static loading conditions were determined. The numerical calculation was verified by comparing its results with the values obtained during a full-scale exper-iment. It is shown that the values obtained by numerical calculation differ from those obtained in the full-scale experiment by 10–15 %. An assumption is made that this discrepancy can be associated with macro-structural inhomogeneities of polymer composite materials appearing as a result of using the autoclave-free moulding method, which are not considered by numerical modelling based on idealized micro-models. In order to increase the accuracy of numerical modelling in the first approximation, it is proposed to introduce a correction factor when calculating the amount of deformation in problems on the rigidity of design structures.

Design and Application of E-Learning Environment Layered Structure Model in Colleges and Universities

There are problems such as unclear labor division and insufficient contact between departments in the e-learning education environment in higher education. Each of colleges or universities needs to design its own model and apply it to the education and teaching environment based on the unique structure, organization, management system and other conditions to improve the management efficiency of learning, education and teaching, which improves the level of management and gives full play to its role. This article briefly discusses the design and application of e-learning environment layered structure model in colleges and universities.

DYNAMICS OF LAYER-BY-LAYER DESTRUCTION OF CARBON PLASTIC BY LIGHTNING CURRENTS: THEORY AND EXPERIMENT

On the basis of two models of lightning currents spreading on carbon plastic, the criteria of material destruction are determined. One of the models – the anisotropic conductive medium model from the Laplace equation with specified Neumann boundary conditions – makes it possible to obtain an exact solution in the form of Bessel functions for longitudinal and transverse current densities and to consider the material destruction zones by the radius and the depth. The model adequately describes the experiment with different arrangement of electrodes simulating the passage of lightning currents on constructions made of conductive composite and metal. The second – the model of composite layered structure – is constructed using the diagram of carbon plastic substitution and makes it possible to find the distribution of currents by a numerical method. The results of the calculations for both models are well consistent. The dynamics analysis of carbon plastic destruction revealed the criteria of destruction with parameters of real carbon plastic and experiment data that do not contradict the parameters of carbon plastic destruction obtained in foreign experimental studies. These criteria allow to determine the dependence between the value of the current integral and the number of layers of the composite material. Options with a small number of layers and with a large one when the reach-through breakdown criterion is possible were taken into account. Comparison of calculated and experimental destruction data showed good curve matching. The obtained criteria make it possible to predict the effects of lightning exposure under different material parameters and to take measures to improve the lightning resistance of carbon plastic products at the stage of aircraft design.

Analysis of the electrodynamic model of a biologically active point of animal skin

Flat-layered dielectric structure was considered as an electrodynamic model of bioactive point (BAP). This structure is formed by three flat dielectric layers and eventual cylinder filled by a dielectric (by the albumen of collagen). The upper layer designs burly cages, middle layer is blood and lymphatic vessels and an understratum is formed by nervous fibres that conduct and pass management signals from BAP to the central nervous system.Such electrodynamic structure is the dielectric resonator (eventual cylinder) located in a dielectric environment.We will examine affecting of informative electromagnetic radiation on bioactive point, the wave-length of which considerably excels geometrical sizes bioactive point. This fact allows averaging of material parameters on a coordinate . Therefore, it was assumed further, that material parameters (dielectric constant) of flat layered structure (model of bioactive point) does not depend on a coordinate , i.e. the electromagnetic field is axisymmetric.Such electromagnetic field can be excited by the circular electric current located at some distance from the external surface of bioactive point. It was supposed that this current excited harmonic oscillation with circular frequency and modulated on amplitude with frequency of modulation .The problem of the interaction of radio-pulse waves with a biologically active point is an unsteady diffraction problem. Using the complex amplitude method, this problem was reduced to the diffraction problem for electromagnetic fields that depend exponentially on time.By virtue of the principle of superposition, the solution to the original problem can be obtained as a superposition of the solutions of three problems using the complex amplitude method.Such electrodynamic structure allows defining the necessary parameters of the informative electromagnetic field for treatment of dyspepsia of newborn calves.