Size-dependent Analysis Research Articles

Long‐run Effects of Austerity: An Analysis of Size Dependence and Persistence in Fiscal Multipliers

Long‐run Effects of Austerity: An Analysis of Size Dependence and Persistence in Fiscal Multipliers

Size-Dependent Analysis of Strain Energy Release Rate of Buckling Delamination Based on the Modified Couple Stress Theory

Size-Dependent Analysis of Strain Energy Release Rate of Buckling Delamination Based on the Modified Couple Stress Theory

Quantifying mine waste rock physical weathering rate and processes for improved geomorphic post-mining landforms

Erodibility of landform surfaces depends on several factors and numerical methods are needed to predict erosion and landform evolution particularly for post-mining landscapes. Surface armouring caused by immobile coarse particles tends to reduce the erosion potential of landform surfaces significantly. However, the breakdown of such material through weathering could destabilise this armour and lead to high erosion rates. Hence, the surface erodibility of newly constructed landforms (here we focus on post-mining landforms) can rapidly change over a few years to decades. At present, it is difficult to predict with certainty the rate, or in some cases the dominant processes and pathways, of soil erodibility and soil production over post-mining landscape design lifetimes (typically 100–1000 years). To improve our understandings of soil evolution and its relationship to soil erosion, data is needed to determine the rate at which fine transportable material is produced from the weathering of larger, non-transportable particles, the resultant fragment size distribution together, and how that distribution evolves over time.Here, laboratory weathering experiments were conducted for four different materials from a single coal mine in the Bowen Basin, Queensland, Australia. Wetting and drying cycles were found to rapidly weather all materials. After 32 wet and dry cycles, all materials had a less coarse particle size distribution than at the start. Heating and cooling had no measurable influence on weathering. Due to the rapid reduction of particle sizes caused by high weathering rates, the materials examined would not provide surface armour capability. A new mathematical methodology was developed to determine the weathering parameters for an existing numerical model based on the weathering mechanism and particle size-dependent weathering rate. Although the materials were collected from the same geographical location, they undergo weathering through different mechanisms and rates. Size dependent weathering rate analysis showed that most samples have high weathering rates for large particles and lower weathering rates for smaller particles. The methods used here are simple and inexpensive and can be easily employed to assess mine rehabilitation materials' weathering and armour potential.

Size-dependent finite element analysis of FGMs in thermal environment based on the modified couple stress theory

PurposeThe paper aims to the size-dependent analysis of functionally graded materials in thermal environment based on the modified couple stress theory using finite element method.Design/methodology/approachThe element formulation is developed within the framework of the penalty unsymmetric finite element method (FEM) in that the C1 continuity requirement is satisfied in weak sense and thus, C0 continuous interpolation enhanced by independent nodal rotation is employed as the test function. Meanwhile, the trial function is designed based on the stress functions and the weighted residual method. Besides, the special Gauss quadrature scheme is employed for integrals of matrices in accordance with the graded variation of the material properties.FindingsThe numerical results reveal that in thermal environment, functionally graded materials exhibit better bending performance compared to homogeneous materials, Moreover, the findings also indicate that with an increase in MLSP, the natural frequencies of out-of-plane modes gradually increase, while the natural frequencies of in-plane modes show much less variation, leading to a mode switch phenomenon.Originality/valueThe work provides an efficient numerical tool for analyzing and designing the functionally graded structures in thermal environment in practical engineering applications.

Computing Accurate True Self-Diffusion Coefficients and Shear Viscosities Using the OrthoBoXY Approach.

In a recent paper [Busch, J.; Paschek, D. J. Phys. Chem. B 2023, 127, 7983-7987], we have shown that for molecular dynamics (MD) simulations using orthorhombic periodic boundary conditions with "magic" box length ratios of Lz/Lx = Lz/Ly = 2.7933596497, the self-diffusion coefficients Dx and Dy in x- and y-directions are independent of the system size. They both represent the true self-diffusion coefficient D0 = (Dx + Dy)/2, while the shear viscosity can be calculated from diffusion coefficients in x-, y-, and z-directions, using η = kBT·8.1711245653/[3πLz(Dx + Dy - 2Dz)]. In this contribution, we test this "OrthoBoXY" approach by its application to a variety of different systems: liquid water, dimethyl ether, methanol, triglyme, water/methanol mixtures, water/triglyme mixtures, and imidazolium-based ionic liquids. The chosen systems range from small-sized molecular liquids to complex mixtures and ionic liquids, while spanning a viscosity range of almost 3 orders of magnitude. We assess the efficiency of the method for computing true self-diffusion and viscosity data and provide simple formulas for estimating the required MD simulation lengths and sizes for delivering reliable data with targeted uncertainty levels. Our analysis of the system size dependence of statistical uncertainties for both the viscosity and the self-diffusion coefficient leads us to the conclusion that it is preferable to extend the simulation length instead of increasing the system size. MD simulations consisting of 768 molecules or ion pairs seem to be perfectly adequate.

Aero-Hygro-Thermoelastic size-dependent analysis of NCMF-reinforced GNPs sector microplates located between piezoelectric patches in supersonic flow considering surface stress effects

Lately, metal foams have been widely used in various engineering structures due to their exceptional mechanical properties, including their lightweight. However, scientists have proposed adding nano-fillers like graphene nanoplatelets (GNPs) to overcome the issue of low stiffness caused by increased porosity. Hence, aerodynamic stability and vibrational behaviors of nanocomposite metal foams (NCMF)-reinforced GNPs sector microplate with piezoelectric/metallic face sheets are provided in this work. The microstructure is sited on Kerr elastic substrate and also is in a hygro-thermo-electrical media, subjected to supersonic flow based on first-order piston’s theory (FPT). Gaussian random field (GRF), Halpin-Tsai, and extended rule of mixture (ERM) in conjunction with Gurtin-Morduch, modified strain gradient theories, and Hamilton’s principle are used to derive the governing equations and linked boundary conditions. Generalized differential quadrature (GDQ) scheme is chosen to attain the results. By validating the results’ precision, the effects of different parameters on the natural frequencies (NFs) and critical aerodynamic pressures (CAPs) are observed. It is perceived that adding GNPs enhances both NFs and CAPs significantly, and increasing porosity up to seventy percent, leads the results to drop. Various industries use simpler models to evaluate the microstructure, therefore the present model can pave the way for future uses and push the boundaries of knowledge in these industries based on the results it produces.

A consistent comparison of lattice thermal conductivities and phonon properties of single layer and bilayer graphene systems

Using nonequilibrium molecular dynamics (NEMD) based direct method and spectral energy density (SED) method, we calculate the size-dependent thermal conductivities (TCs) of single layer graphene (SLG), AB-stacked bilayer graphene (AB-BLG), and 21.78° twisted BLG (tBLG) in a robust and consistent manner. Our NEMD analysis reveals discrepancies in high TC reported for graphene systems in some of the earlier studies. Similarly, some of the previous SED based studies were done with unreliable SED Φ′ approach. We conduct size-dependent analysis of the graphene systems by the SED method for the first time and report that bulk TCs for SLG and tBLG systems are nearly the same when calculated by either the direct or the SED method. Contrary to studies that claim that phonon group velocities of AB-BLG and tBLG samples do not change, we find that although average group velocities in SLG and AB-BLG are almost the same, they are around 30% higher when compared to tBLG samples with different twist angles. On the other hand, average phonon lifetimes are almost similar for AB-BLG and 21.78° tBLG samples but around 43% lower than the average phonon lifetime of SLG. Together these trends suggest the reason behind the decreasing order of TCs across three systems. We also systematically study the basic phonon mode contributions to TCs and their properties and find that the high-symmetry modes contribute the most in all three systems.

Implementation of Legendre wavelet method for the size dependent bending analysis of nano beam resonator under nonlocal strain gradient theory

The bending analysis due to thermoelastic loading in nanoscale materials is primarily determined by the physical aspect of the material and the modeling of structures. This paper examines the prediction of bending characteristics of the Euler-Bernoulli beam using Moore-Gibson-Thompson (MGT) thermoelasticity theory in conjunction with nonlocal strain gradient theory (NSGT). The coupled equations for dimensionless deflection and temperature change with ramp-type heating boundary conditions are formulated and solved using the Laplace transform method and the wavelet approximation method. The stiffness softening and hardening effects due to nonlocal and length-scale parameters are assessed, and their discrepancies are discussed. Findings further reveal that the impact of the thermal relaxation parameter on deflection and temperature is negligible. Moreover, the different aspect ratios of the beam's structure depict the prominently behavior of structural simulations in bending.

A Higher-Order Shear Deformation Theory and Modified Couple Stress Theory for Size-Dependent Analysis of Porous Microbeams Resting on a Foundation

This paper presents a novel shear deformation theory for analyzing porous microbeams’ bending, buckling, and free vibration resting on a foundation. The proposed shear function incorporating three kinetic variables satisfies zero-traction boundary conditions on the top and bottom surfaces of the beams and does not require a shear correction factor. The modified couple stress theory accounts for the size-dependent effects, and the governing equations are derived from Lagrange’s equation using the proposed shear function. Legendre–Ritz functions are developed to analyze the porous microbeams’ buckling, free vibration, and bending behaviors. The effects of material length scale parameter, porosity, span-to-height ratio, boundary condition, and foundation parameter on the mechanical responses of beams are investigated. Numerical results demonstrate the accuracy and efficiency of the proposed theory and can serve as benchmarks for future analysis of porous microbeams on elastic foundations.

On comprehensive nonlinear size-dependent analysis of nano-scale flexoelectric energy harvesters considering strain gradient, surface elasticity and thickness size effect

On comprehensive nonlinear size-dependent analysis of nano-scale flexoelectric energy harvesters considering strain gradient, surface elasticity and thickness size effect

A strategy for 2D MXenes as thermal management materials by laser shock nanoshaping

The two-dimensional (2D) titanium carbides () belong to the MXene family, with carbon and titanium alternating in a flake structure, and are emerging options for nanoelectronics applications. In this study, the feasibility of nanoshaping of 2D titanium carbides for tunable thermal management materials was investigated. 2D titanium carbides demonstrate high degrees of formability on nanoscale and efficiency as thermal management systems in nanoelectronics components. The thermal conductivity of various MXene 2D flakes was studied using molecular dynamics simulations. A robust thermal management behavior has been predicted for 2D MXenes after nanoshaping on various nanomold patterns, which will facilitate the development of MXene-based metamaterials for thermal management in electric nanocomponents. The size dependence analysis shows that the MXenes thermal conductivity is highly influenced by the flake size leading to a variation in experimental values due to scale factors. Our model showed that Ti2C is more sensible to strain at both supported and suspended conditions, while the thicker MXenes are not too influenced by strain. When supported, the thermal conductivities of all simulated MXenes considerably decrease due to Z phonon modes suppression. Bending strain also showed an effect in the MXenes thermal conductivity by scattering phonon modes. This makes MXenes an attractive option for the management of thermal fields.

Isogeometric bending and free vibration analyses of carbon nanotube-reinforced magneto-electric-elastic microplates using a four variable refined plate theory

The classical continuum mechanics theory is inadequate for modeling the mechanical responses of the microstructures due to its failure to account for size effects. Instead, modified strain gradient theory (MSGT) is considered as one of the most accurate theories due to its ability to adjust three length scale parameters (LSPs). Isogeometric approach (IGA) is a computational technique that is capable of accurately solving complex problems. For those reasons, the size-dependent analysis of carbon nanotube-reinforced magneto-electric-elastic microplates based on the MSGT are firstly proposed. The present approach uses the refined plate theory (RPT) with four variables, the MSGT and IGA. The magnetic and electric potentials are assumed to be a combination of a half-cosine and linear variation to satisfy Maxwell’s equations. Different types of functionally graded carbon nanotubes (CNTs) including UD, FG-X, FG-O and FG-V are reinforced in the magneto-electric-elastic matrix of the microplates. Governing equations are derived using the extended virtual work principle and then solved by IGA to determine the deflection and natural frequency of the microplates. The influence of the LSPs, CNT distributions, CNT’s volume fraction, matrix’s volume fraction, magnetic potential, electric voltage and geometry on the deflection and natural frequency of the microplates are studied and discussed.

A Chebyshev–Ritz solution for size-dependent analysis of the porous microbeams with various boundary conditions

A Chebyshev–Ritz solution for size-dependent analysis of the porous microbeams with various boundary conditions

Grain size dependent mechanical behavior and TRIP effect in a metastable austenitic stainless steel

The change in the trends of mechanical behavior and martensite formation of austenitic steels versus grain size has not yet been explained for the coarse-grained regime. Moreover, the effect of grain size needs systematic investigation by considering a wide range of grain sizes from the ultrafine-grained (UFG) regime to the coarse-grained one. In response, the effect of a wide range of austenite average grain sizes from 0.5 to 192 µm on the mechanical behavior and transformation-induced plasticity (TRIP) effect in an AISI 304L stainless steel was systematically investigated in the present work. Analysis of the tensile properties revealed that there is a transition grain size range of 34 to 90 µm, where a meaningful change in the trends of the ultimate tensile strength (UTS), total elongation, tensile toughness, work-hardening capacity, and yield ratio was observed. For instance, the total elongation increased with increasing average grain size up to the transition range but decreased at coarser grain sizes. However, the yield stress followed the Hall-Petch relationship of YS(MPa)=134.2+632.6/D(μm) for the whole grain size range, indicating that the presence of the transition grain size range is related to the work-hardening behavior, especially the TRIP effect. The apparent stacking fault energy decreased with increasing the grain size and reached a plateau after the transition grain size range. The same trends were found for the critical strain for the onset of the TRIP effect. Moreover, increasing the grain size up to this transition range promoted the formation of deformation-induced martensite, which was followed by its suppression at coarser grain sizes. The same trends were found for the maximum work-hardening rate related to the TRIP effect. The evolution of mechanical properties and TRIP effect with the grain size up to the transition range was explained based on the dependency of apparent stacking fault energy on the grain size. However, with the constancy of apparent stacking fault energy at coarser grain sizes, the decline in the formation of shear band intersections was found to play a significant role. The latter effect was further supported by Olson-Cohen analysis and investigation of the grain size dependency of the rate of shear-band formation (α) and the probability of generation of the martensite embryo at shear-band intersections (β).

Size-dependent analysis of porous multi-directional FG shell structures based on the modified couple stress theory using the unsymmetric finite element method

Size-dependent analysis of porous multi-directional FG shell structures based on the modified couple stress theory using the unsymmetric finite element method

Analysis of size dependence and the behavior under ultrahigh current density injection condition of GaN-based Micro-LEDs with pixel size down to 3 μm

In this paper, the GaN-based green micro light-emitting diodes (Micro-LEDs) with various sizes (from 3 to 100 μm) were fabricated and electro-optically characterized. Atom layer deposition (ALD) passivation and potassium hydroxide (KOH) treatment were applied to eliminate the sidewall damage. The size dependence of Micro-LED was systematically analyzed with current-versus-voltage and current density-versus-voltage relationship. According to the favorable ideality factor results (<1.5), the optimized sidewall treatment was achieved when the device size shrank down to <10 μm. In addition, the external quantum efficiency (EQE) droop phenomenon, luminance and output power density characteristics were depicted up to the highest current density injection condition to date (120 kA cm−2), and 6 μm device exhibited an improved EQE performance with the peak EQE value of 16.59% at 20 A cm−2 and over 600k and 6M cd cm−2 at 1 and 10 A cm−2, indicating a greater brightness quality for over 3000 PPI multiple display application. Lastly, the blue shift of 6 μm device with elevating current density was observed in electroluminescence spectra and converted to CIE 1931 color space. The whole shifting track and color variation from 1 A cm−2 to 120 kA cm−2 were demonstrated by color coordinates.

Size dependent torsional electro-mechanical analysis of flexoelectric micro/nanotubes

The free vibration and static torsion of a coupling electromechanical flexoelectric micro/nanotube have been investigated, in the present study. Using the non-classical theory of continuum mechanics which is based on a strain gradient, the coupling governing equations of torsional flexoelectric micro/nanotubes have been developed. To derive the coupling governing equations the variational method has been used and the formulation with the classical and non-classical boundary conditions is generally derived for torsional flexoelectric micro/nanotubes. For the first time, the formulation of micro/nanotube torsional flexoelectric coupling with independent polarization effect is presented in this paper which can be used for specific applications. At last, the static analysis and free vibrations results are presented for specific mechanical and electrical boundary conditions. The parameter of mechanical and electrical size effect changes has a great effect on the results. However, the effect of the mechanical and electrical size effect parameter on direct flexoelectric torsion is also opposite, but the effect of mechanical and electrical size effect parameter on reverse flexoelectric torsion is similar. Polarization is also introduced as a new variable in the equations and its effect is investigated as an independent variable of the electric field in the results, in this paper. As a significant parameter, the results show that polarization plays an important role to simulate the torsional electromechanical structures.

Multilayer thin-film based nanophotonic windows: static versus electrotunable design

To meet the global energy demand, rapid growth in fossil fuel consumption has significantly contributed to global warming. Judicious utilization of renewable energy resources could help to combat this global challenge. Here, we present a comparative study on the designs of static and electro-tunable ‘smart’ windows that could help to reduce the energy need of typical air-conditioning systems deployed in buildings and motor vehicles. Our design comprises insulator–metal–insulator multi-layered thin-films deposited over a silica glass substrate to filter visible and infrared solar radiation selectively. For static windows, we optimize our design to operate in diverse climatic conditions by choosing different combinations and thicknesses of metal and insulator layers. Whereas for electro-tunable windows, we use an electro–optic polymer as the insulator layers to dynamically control portions of transmitted solar radiation over a voltage range of −12 to +12 V. Through size-dependence analysis, we could safely assume that the performance of smart windows is less likely to degrade during experimental realization. Our designs are lithography-free, large-area compatible, polarization-independent, angle-insensitive, and robust to fabrication imperfections. The analytical results show a near-perfect match with the simulation findings. The theoretically calculated figure of merit indicates that our proposed smart windows can outperform industry-standard commercial windows.

Size-dependent analysis of the spherical nanoshells subjected to a moving harmonic load in hygro-thermo environment

In the current research, the dynamic behavior of the spherical nanoshell subjected to a moving harmonic load in hygro-thermo environment is examined for the first time. A size-dependent nonlocal shell theory is dedicated to ponder the nonlocality. The first-order shear deformation theory is dedicated to inquire the shear impacts along with the thickness of the shell. To ponder the effects of the thermal and moisture conditions on the dynamic responses of the nanoshell, we apply the nonlinear relations for temperature and moisture fields. In the current study, it is assumed that the nanoshell is subjected to a moving harmonic load which moves the upper surface of the nanoshell with a certain velocity along the path . Hamilton’s axiom is dedicated to achieve the governing equations of motion. Then, the Navier solution technique is dedicated to derive the dynamic responses of the nanoshell with simply-supported boundary conditions. The impacts of several parameters are examined on the dynamic behavior of the nanoshell.

Size-dependent analysis of functionally graded carbon nanotube-reinforced composite nanoshells with double curvature based on nonlocal strain gradient theory

Size-dependent analysis of functionally graded carbon nanotube-reinforced composite nanoshells with double curvature based on nonlocal strain gradient theory