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The Proton Exchange Membrane Fuel Cell (PEMFC) performances are strongly impacted by the compression of the Gas Diffusion Layer (GDL). Despite its fibrous microstructure, this material is usually considered as a continuous medium and characterized with uniform loading. However, the GDL is subjected to a heterogeneous compression onto rib/channel patterns in the fuel cell assembly. In the present study, a complex behavior of the GDL response is experimentally revealed when the material is loaded with a rib/channel pattern, compared to uniform compression. The tests are simulated by finite element modeling using a classical strain-dependent elastic law, using parameters fitted from uniform compression experiments. It is shown that the numerical results do not reproduce the effect of pattern observed experimentally. Hypotheses to interpret these results involve mechanisms at the fiber microscale including fiber fracture, cross-link breakage and fiber rearrangement, which are exacerbated by larger material deformation caused by the heterogeneous loading. • Unexpected impact of rib/channel patterns on GDL compression. • Experimental investigation of the effect of rib/channel width on GDL deformation. • Numerical study with classical model unable to reproduce experimental results. • Interpretations based on mechanisms at the fiber microscale. [ABSTRACT FROM AUTHOR]

Femoral deformities are highly prevalent in children with cerebral palsy (CP) and can have a severe impact on patients' gait abilities. While the mechanical stress regime within the distal femoral growth plate remains underexplored, understanding it is crucial given bone's adaptive response to mechanical stimuli. We quantified stresses at the distal femoral growth plate to deepen our understanding of the relationship between healthy and pathological gait patterns, internal loading, and femoral growth patterns. This study included three-dimensional motion capture data and magnetic resonance images of 13 typically developing children and twelve participants with cerebral palsy. Employing a multi-scale mechanobiological approach, integrating musculoskeletal simulations and subject-specific finite element analysis, we investigated the orientation of the distal femoral growth plate and the stresses within it. Limbs of participants with CP were grouped depending on their knee flexion kinematics during stance phase as this potentially changes the stresses induced by knee and patellofemoral joint contact forces. Despite similar growth plate orientation across groups, significant differences were observed in the shape and distribution of growth values. Higher growth rates were noted in the anterior compartment in CP limbs with high knee flexion while CP limbs with normal knee flexion showed high similarity to the group of healthy participants. Results indicate that the knee flexion angle during the stance phase is of high relevance for typical bone growth at the distal femur. The evaluated growth rates reveal plausible results, as long-term promoted growth in the anterior compartment leads to anterior bending of the femur which was confirmed for the group with high knee flexion through analyses of the femoral geometry. The framework for these multi-scale simulations has been made accessible on GitHub, empowering peers to conduct similar mechanobiological studies. Advancing our understanding of femoral bone development could ultimately support clinical decision-making. • Distal femoral growth plate stresses quantified with subject-specific simulations. • Large dataset of 50 femurs – 26 healthy, 24 femurs of participants with cerebral palsy. • Knee flexion angle is of high relevance for typical bone growth at the distal femur. • Workflow reveals plausible growth results supported by geometrical analysis. • Multi-scale workflow based on free software published on GitHub. [ABSTRACT FROM AUTHOR]

Alumina-based multilayer laminates with layers of varied porosities and ceramic fiber reinforcements, which can be achieved by including paper-derived ceramic layers, are interesting candidates for chemically stable and thermal shock resistant materials. In order to investigate the complex sintering behavior of these laminates, the sintering of each alumina layer contained within a laminate, each one with its individual sintering anisotropy and sintering shrinkage, has to be considered separately. For this purpose, sintering curves are determined by dilatometry measurements, serving a consecutive examination by an analytical model. Modeling parameters specific to each layer, are applied in finite-element-type sintering simulations for symmetrical multilayer laminates. Differences in the sintering shrinkages may cause internal stresses at layer interfaces and, in turn, may influence the thermal and mechanical properties of multilayer laminates after sintering. Accordingly, the prediction of developing internal stresses within alumina-based multilayer laminates by the presented sintering simulations is a key aspect of this study. [Display omitted] • Individual laminates sintering dilatometry. • Anisotropic sintering assessment by analytic modeling. • Finite element simulation of multilayer laminates sintering. [ABSTRACT FROM AUTHOR]

Paper, a porous-fibrous network, is made up of hydrophilic fibres, which are notably susceptible to deformations due to variations in moisture content. The response of paper sheets to full or partial wetting, based on the water-induced fibre swelling, has mostly been predicted in the past using highly idealised two-dimensional network geometries. The purpose of the present paper is to establish how precisely the two-stage process of determining effective hygro-expansivity under uniform wetting by a two-dimensional model followed by bending analysis using a continuum model predicts the curl of a fully three-dimensional network. In the present multi-scale modelling work, the moisture-induced homogenised sheet scale curl, derived from hygro-elastic deformations using non-uniform moisture profiles, is analysed based on an idealised non-woven three-dimensional fibrous network finite element model. First, the effective paper sheet swelling properties, derived computationally for the uniform wetting condition, are compared with analytically homogenised hygro-elastic properties. Whereas the analytically predicted elastic modulus has an inaccuracy of only ∼ 5%, the hygro-expansivity coefficient is over-predicted by roughly a third for a network with straight fibres. The difference is smaller if waviness of the fibres and wrap-around in the fibre bonds are taken into account. Fibre alignment turns out to have little influence. Subsequently, paper sheet curl predictions made by the analytical model are compared with that computed from the three-dimensional network model. The inaccuracy of the fully analytical model, based on the two-dimensional network description, relative to the fully detailed three-dimensional computational model with straight fibres is on the order of 40%–50%. The fidelity of the simple model is primarily constrained by the inaccuracy of the effective hygro-expansion coefficient. If the expansivity extracted from the three-dimensional simulations under uniform wetting is inserted, the inaccuracy drops to less than 10%. The continuum bending description hence performs adequately, provided it is based on a reliable estimation of the uniform expansion behaviour of the material. • Hygroscopic curl of paper sheets may be predicted using homogenised models. • We assess the accuracy of such predictions. • As a reference simulations of an idealised three-dimensional fibre network are used. • The predictions are accurate provided an accurate hygro-expansivity is used. • Two-dimensional network models may not be sufficient for this. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the beneficial reuse of paper mill sludge as landfill cover and bottom liner material in municipal solid waste landfills. For this purpose, two-dimensional finite element analyses of a typical landfill geometry were carried out using PLAXIS finite element program. The results of the analyses were evaluated in terms of displacement and factor of safety (FS) values, and compared with those of the compacted clay. The results of this study showed that, vertical and lateral displacements of the landfill slightly increased while the FS of the landfill slopes decreased with increasing surface loading. However, for all the cases studied, lower vertical and lateral displacements and higher FS values were obtained for the landfills with paper mill sludge as the cover and bottom liner material in comparison to those of the compacted clay. Besides, for all the cases studied, FS values greater than 1.5 were obtained, indicating that the landfill slopes were stable under the proposed loadings and landfill cover and bottom liner materials. Based on these results, it can be stated that the paper mill sludge examined in this paper has geotechnical properties that are desirable for a landfill cover and bottom liner material for use as a substitute of compacted clay in municipal solid waste landfills. [ABSTRACT FROM AUTHOR]

A computationally efficient method to study the in-plane and out-of-plane dimensional instability of thin paper sheets under the influence of moisture changes is presented. The method explicitly resolves the bonded and the free segments of fibers in the sheet, capturing the effect of anisotropic hygroexpansion at the fiber level. The method is verified against a volumetric model. The importance of longitudinal fiber hygroexpansion is demonstrated in spite of the absolute value of longitudinal hygroexpansion being an order of magnitude lower than the transverse hygroexpansion component. Finally, the method is used to demonstrate the formation of macroscopic sheet curl due to a moisture gradient in structurally uniform sheets in the absence of viscoelastic or plastic constitutive behavior and through-thickness residual stress profiles. [ABSTRACT FROM AUTHOR]

A fully printed piezoelectric based touch sensor device has been successfully fabricated on flexible polyethylene terephthalate (PET) and paper substrates using screen printing technique. The device, consisting of a 4 × 4 array of printed sensors and interconnect lines, was fabricated using silver (Ag) ink. Screen printed polyvinylidene fluoride (PVDF), as a piezoelectric layer, was sandwiched between the printed Ag top and bottom electrode metallization layers. A linear relationship between the sensor response and varying applied forces to the device was obtained through finite element analysis (FEA) method simulation. X-ray diffraction (XRD) analysis was performed to verify the formation of the β-phase crystals in the PVDF layer during the curing process. The effective polarization of the printed piezoelectric layer was analyzed using capacitance-voltage analysis. A sensitivity of 1.2 V/N and 0.3 V/N, with correlation coefficient of 0.9954 and 0.9859, was obtained for the PET and paper based printed touch sensors, respectively. The piezoelectric-voltage analysis demonstrated that the printed sensors can be used for both touch and force based applications. [ABSTRACT FROM AUTHOR]

The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko–Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young’s modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko–Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose. [ABSTRACT FROM AUTHOR]

• Numerical model for solution of heat diffusion equation. • Thermographic investigation in optically semi-transparent materials. • Non-destructive detection of graphic features buried in cultural heritage artefacts. • Selective configurations for optical and thermal properties investigation in paper. In this paper, infrared thermography is applied to the quantitative characterization of optically semi-transparent media by using a newly introduced mathematical model. The method is specifically aimed to the detection and evaluations in graphic features buried beneath the surface of some particular kind of cultural heritage artefacts, such as books and documents. A numerical approach based on the finite element method, is proposed for solving the model equations. The computed thermographic signal depends on different inspected material physical properties, which have been selectively evaluated by comparing the theoretical results with the experimental ones in specifically designed test samples. Thereafter, the model is applied to the analysis of the results obtained in the case of graphic elements buried within samples constituted by the same previously characterized materials. [ABSTRACT FROM AUTHOR]

• Elasticity and failure behaviors of the resin-coated aramid paper are analysed. • A novel segmented equivalent mechanical model of the material is proposed. • Equivalent mechanical parameters of multi-layer structure are derived theoretically. • Proposed model performs well in ultrasonic cutting simulation of Nomex honeycomb. • Difficulty of modelling and CPU time of simulation are reduced significantly. Nomex honeycomb, as the core part of sandwich structure, has been widely used in the aviation and aerospace industries. Ultrasonic cutting, as a technology that can reduce machining defects, has been highlighted in recent years, but some problems in the cutting process still need to be investigated significantly. Finite element method (FEM) offers an alternative way of in-depth understanding of the problems. However, the multi-layer structure of the Nomex honeycomb cell wall, which is the resin-coated aramid paper, makes it difficult to establish a detailed multi-layered finite element (FE) model at a macro-scale level. Therefore, a novel segmented material mechanical model, which is applicable to the equivalent single-layer model, is proposed based on the analysis of the mechanical behaviour of the multi-layer structure of the resin-coated aramid paper. Moreover, the calculating method of equivalent mechanical parameters of the multi-layer structure are proposed theoretically. The proposed method is first verified by FE models at a micro-scale level in both single-layer and multi-layer approaches. Additionally, simulations and experiments are performed to verify that the proposed method performs well in the simulation of ultrasonic cutting for Nomex honeycomb, and the difficulty of modelling and CPU time of simulation are reduced significantly. [Display omitted] [ABSTRACT FROM AUTHOR]

The tensile response of dense fiber-based materials like paper or paperboard is mainly dependent of the properties of the fibers, which store most of the elastic energy. In this paper, we investigate the influence of geometrical and material parameters on the mechanical response of the pulp fibers used in paper manufacturing. We developed a three-dimensional finite element model of the fiber, which accounts for microfibril orientation of cellulose fibril, and the presence of lignin in the secondary cell wall. The results showed that the change in the microfibril orientation upon axial straining is mainly a geometrical effect, and is independent of the material properties of the fiber, as long as the deformations are elastic. Plastic strain accelerates the change in microfibril orientation and thus makes it material-dependent. The results also showed that the elastic modulus of the fiber has a non-linear dependency on microfibril angle, with elastic modulus being more sensitive to the change of microfibril angle around small initial values of microfibril angles. Based on numerical results acquired from a 3D fiber model supported by available experimental evidence, we propose an anisotropic-kinematic hardening plasticity model for a fiber within a beam framework. The proposed fiber model is capable of reproducing the main features of the cyclic tensile response of a pulp fiber, such as stiffening due to changing microfibril angle. The constitutive model of the fiber was implemented in a finite-element model of the fiber network. By using the fiber network model, we estimated the level of strain that fiber segments accumulate before the typical failure strain of the entire network is reached. [ABSTRACT FROM AUTHOR]

The mechanical response of three different structural core sandwich panels in out-of-plane compression and shear has been analyzed. Specific core shapes examined are arc-tangent, wavy trapezoidal and hemispherical. Unit cells consisting of representative elements of the core attached to face sheets were selected for analysis. Both face sheets and core were assumed made from paper. Finite element analysis employing large deformation and rotations and orthotropic elastic–plastic behavior was used. The results show that the arc-tangent and trapezoidal cores are prone to collapse by extensive bending and buckling, whereas the hemispherical core behaved more stably in compression and shear. Core sheets with a hemispherical shape were prepared from copy paper sheets in a specially designed forming machine. Sandwich test specimens were prepared from this core and tested in out-of-plane compression, and the load-displacement response was compared to predictions from finite element simulations. The experimental and finite element results were consistent. [ABSTRACT FROM AUTHOR]

In order to satisfy the demands for both safety and global warming reduction, a high-strength seismic reinforced steel bar is required in the structural steel market. Recent developments in computational thermodynamics and related application software have made it possible to design a suitable material as well as support engineers of steel manufacturing companies in the production of the designed material with minimum benchmarks in practical operations. This paper reports our recent success in developing grade 600 MPa reinforced steel bars for seismic safety in South Korea. First, conventional alloy design based on CALPHAD-type computational thermodynamics was carried out. For this purpose, a typical alloy system of Fe-0.30C-0.23Si-1.37Mn-0.14V-0.22Cu (in wt%) was selected, and thermodynamic and kinetic calculations were carried out using MatCalc and JMatPro software. Second, in order to reduce V content in the steel for economic reasons, a cooling process designed using finite element (FE) simulation based on the thermodynamic database was performed. For this application, Fe-0.34C-0.22Si-1.34Mn-0.04 V (in wt%) alloy was chosen, and the FE software ABAQUS was applied for modeling the TempCore process. The mechanical properties of the steel products with a diameter of 32 mm produced based on the simulated results satisfy the required properties for grade 600 MPa seismic reinforced steel bars. [ABSTRACT FROM AUTHOR]

In fibrous paper materials, an exposure to a variation in moisture content causes changes in the geometrical and mechanical properties. Such changes are strongly affected by the inter-fibre bonds, which are responsible for the transfer of the hygro-mechanical response from one fibre to its neighbours in the network, resulting in sheet-scale deformation. Most models developed in literature assume perfect bonding between fibres. In the 3D reality, there is some flexibility in the bond region, even for the perfectly bonded fibres, because of the possibility of deformation gradients through the fibre thickness. In earlier 2D idealizations, perfectly bonded fibres were assumed, implying full kinematic constraint through the entire thickness of the sheet. The purpose of the present study is to assess the effect of this assumption. Using a homogenization approach, a random network of fibres is generated with different coverages and modelled using finite elements. In order to understand the role of bonding between fibres on the hygro-expansive behaviour of a network, a bond model is developed. In this model, the fibres are modelled using 2D regular bulk finite elements and the bonds are represented by interfacial elements of finite stiffness, which are introduced between each pair of fibres bonded in the network. These embedded interfacial elements form a connection between two respective fibres, allowing relative displacements between their mid-planes. The hygro-elastic response of networks obtained with this bond model is investigated by varying the bond stiffness and the network coverage under the application of mechanical loading and changes in moisture content. Furthermore, the bond model is used to analyse the influence of inter-fibre bonds on the anisotropic response of the paper fibre network. [ABSTRACT FROM AUTHOR]

Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

Orthodontic archwire rotation around its long axis, known as third-order torque, is utilised to correct tooth rotational misalignments moving the tooth root closer to or away from the cheek through engagement with an orthodontic bracket. Studying the behaviour of archwire and brackets during an applied rotation can aid in better understanding and appreciating the mechanics of third-order torque, potentially allowing for more effective orthodontic treatment protocols. Mechanically characterising archwire behaviour during third-order torque application is a complex task due to their physical scale and geometries. An advanced measurement technique was needed to address these constraints. A three-dimensional (3D) non-contact optical method using a digital image correlation (DIC) system was developed. An orthodontic torque simulator (OTS) was used to apply and measure third-order torque with 0.483 × 0.635 mm (0.019″ x 0.025″) rectangular archwires in tandem with a 3D DIC system, whereby surface deformations and strains could be computed using correlation algorithms. The 3D DIC system was implemented to enable third-order torque experimentation with the OTS while imaging the archwire and bracket surfaces. The 3D DIC system's ability to measure 3D archwire deformations and strains was verified using a finite element model, where comparisons between 3D DIC measurements and calculated results from the model were made to ensure the measurement capabilities of 3D DIC in the context of third-order torque. The 3D DIC system was then used to compare archwire behaviour between stainless steel (SS) and titanium molybdenum alloy (TMA) archwires to study potential clinical differences in archwire behaviour, in which the archwires were rotated with a custom SS rigid dowel (RD) as well as commercial Damon Q orthodontic brackets. The quantification of third-order torque and archwire deformations and strains led to the conclusion that SS archwires led to larger torque magnitudes compared to TMA archwires. The RD resulted in larger archwire strains compared to Damon Q brackets. The 3D DIC system provides a non-contact measurement technique that can further be used with third-order torque experimentation with the OTS. Image 1 • Isolated orthodontic archwire response to torsion is studied. • Finite element analysis is used to verify optical measurements. • Three-dimensional digital image correlation strain measurement method is validated. • Stainless steel and titanium molybdenum alloy archwire responses are compared. • Three-dimensional orthodontic archwire and bracket strain measurements are obtained. [ABSTRACT FROM AUTHOR]

Poly-(meta-phenylene isophthal-amide) (PMIA) is regarded as an ideal insulating medium for electronic devices owing to its excellent chemical stability and breakdown strength. However, the poor thermal conductivity limited the application under complex electrical-thermal environment. In this work, the size-graded AlN/PMIA composite papers were fabricated, with a multi-scale structure of matrix and fillers, and maintain qualified stability, mechanical strength and electrical insulation properties. With doping 40 wt% of 10 μm AlN and 10 wt% of 200 nm AlN, the optimum paper with in-plane (λ ∥) and out-of-plane (λ ⊥) of optimal paper reached thermal conductivity of 17.3 W/(mK) and 1.96 W/(mK) is obtained, and the breakdown strength increased to 69 kV/mm. The improvement mechanism brought by size-graded fillers was further revealed by the co-simulation of finite element method and loop nesting algorithm. [Display omitted] [ABSTRACT FROM AUTHOR]

Paper-like electronics with thin multi-layer structures, which can be repeatedly bent and twisted like paper, are promising for diverse innovation application. Employing surface-mounted flexible strain sensors is a general way to monitor the bending characteristics of each layer inside paper-like electronics, however, the deviation of measured strain will reach up to 15% on account of the layer-to-layer interface sliding, neutral axes offset resulted from the extra effect of the flexible strain sensor. Here, we proposed a precise measurement method to evaluate the surface bending strain of paper-like electronics by using flexible sensors. In combination with the effects of the thickness, length, etc, a strain compensation model has been established to compensate the measurement deviation. Meanwhile, a slip failure model has been developed to guide the design of the sensitivity unit within the non-sliding area of the flexible sensor. Validated by finite element analysis and experiment, the bending strain of paper-like electronics (eg., ∼50 μm) can be evaluated much more accurate compared to the frequent access one. The newly-proposed method provides a powerful basis for further research of paper-like electronics. [ABSTRACT FROM AUTHOR]

Carbon nanotube buckypaper has been considered as one of the promising candidates for chemiresistive sensor applications, especially with environmental monitoring purpose due to large surface area, device flexibility, and the broad spectrum of responsive chemical vapor molecules. However, one of typical drawbacks in carbon-based sensors is incomplete recovery to their initial state after chemical reactions with analytes, degrading sensing reproducibility. In this work, we present a thermally stable and robust boron nitride nanotube/carbon nanotube (BNCNT) hybrid paper for self-enhanced chemiresistive sensing with full reversibility. Boron nitride nanotube (BNNT) plays an essential role in long-term reliability (33 days) at the operating temperature of 200 °C. In addition, a finite-element method was applied to understand the thermal behavior of the BNCNT network structure. The BNCNT paper-based chemiresisitve sensor exhibited highly sensitive, selective, and fully reversible responses to NO 2 without external heating. Also, the sensor demonstrated the detection limit of parts per billion (ppb)-levels under strain with high reliability. With these remarkable strengths, significantly facile and cost-effective fabrication processes provide an environmental sensing platform for use in smart clothing with wearable electronics. • Boron nitride nanotube/carbon nanotube (BNCNT)-based chemiresistive sensor with full reversibility was developed. • The BNCNT paper exhibits a highly sensitive detection to NO 2 at room temperature. • The detection limit (DL) is 3.41 parts per billion (ppb) even under strained conditions with high reliability. • The BNCNT papers maintained its self-enhanced temperature of 200 °C during a long-term stability test for 33 days. • The BNNT plays a major role in the long-term reliability of maintaining a temperature of CNT networks. [ABSTRACT FROM AUTHOR]

Paper is a complex material consisting of a network of cellulose fibres at the micro-level. During manufacturing, the network is dried under restraint conditions due to tension in the paper web in machine direction. This gives rise to internal strains that are stored in the produced sheet. Upon exposure to a moisture cycle, these strains may be released. This results in permanent shrinkage that may cause instabilities such as curl or waviness of the sheet. The prime objective of this paper is to model this irreversible shrinkage and to link its magnitude to the properties of the fibres and of the network. For this purpose, randomly generated fibrous networks of different coverages (i.e. ratio of the area occupied by fibres and that of the sheet) are modeled by means of a periodic representative volume element (RVE). Within such RVEs, a finite element method combined with a kinematic hardening plasticity model at the scale of the fibres is used to capture the irreversible response. The computational results obtained demonstrate that the magnitude of the irreversible strains increases with coverage until a certain coverage and beyond that coverage decreases in magnitude. This phenomenon is explained by considering the area fraction of free-standing fibre segments relative to bonded fibre segments in the network. A structure–property dependency of irreversible strains at the sheet-level on the micro-structural parameters of the network is thereby established. [ABSTRACT FROM AUTHOR]

Owing to overheating of electronic components during work, more and more attention has been paid to the research of high thermal conductivity polymer composites in recent years. However, traditional way to improve the thermal conductivity of polymer is not ideal. Here, a high-performance polyline-folded graphite paper (PFGP)/epoxy resin (EP) composite was prepared by using polyline-folded graphite paper and liquid epoxy resin as fillers and matrix, respectively. Its out-of-plane thermal conductivity and the improvement efficiency per 1 wt% are as high as 24.19 Wm −1 K −1 and 349%, respectively. Most importantly, this approach is very simple and can be industrialized compared to traditional polymer compounding methods. The thermodynamic finite element analysis in this work simulated the thermal conductivity of PFGP/EP composite at different mass fractions, which can verify the accuracy of the experimental values. These results indicate that the PFGP/EP composites have great prospects in the field of thermal interface materials. • Polyline-Folded graphene paper can create ultra-efficient heat transfer paths. • The prepared composite has an extremely high thermal conductivity. (24.19 Wm−1K−1). • The prepared composite is an excellent candidate for CPU heat dissipation. • The prepared composite can be initially industrialized. [ABSTRACT FROM AUTHOR]

In this paper, we focus on some aspects of the finite element simulations of robotic paper folding and the reconstruction of models from the origami crease patterns by the robot arms. The paper highlights the simulation problems, which should be solved in developing our recent study in mechanical and geometrical design of the origami-performing robot. The basic premise underlying the study is that folding operations with the origami crease patterns are considered as the functions of the mechanical systems such as a robot. Manipulations with the foldable objects, such as a sheet of paper (the origami crease pattern), by the robot arms in the simulation environment lead to understanding the design of the origami-performing robot without testing physical prototypes at each design stage. In this case, dynamic and kinematic behavior of the robot arms in forming the 3D origami objects is modelled by using the finite element method (FEM) in LS-DYNA solver. For simulating, two forms of origami are considered: flexible, if bending is used for paper folding, and rigid, if origami patterns are considered as the kinematic systems. Results of the simulation are presented and provided by the illustrations. [ABSTRACT FROM AUTHOR]

Dispersant is critical in the ceramic vat photopolymerization (VP) due to its decisive impact on ceramic particle dispersion and suspension stability. However, the mechanisms by which dispersants influence photopolymerization of suspension remain underexplored. In this paper, the effects of the dispersants' refractive index and absorption coefficient on the light intensity distribution within suspension was investigated using a finite element method (FEM) simulation. The results indicate that the absorption coefficient is the primary influencing factor; as the absorption coefficient increases, the light transmittance of the suspension significantly decreases. Additionally, the photopolymerization performances of Al 2 O 3 ceramic suspensions formulated with different dispersants were investigated. We found the mechanisms by which dispersants influence photopolymerization behavior: by affecting light absorption through absorption coefficient and by directly impacting the polymerization reaction through functional groups. The study successfully achieved VP 3D printing of high-precision ceramic architectures with micron-sized features via dispersant optimization. This paper provided a new insight into optimizing fabricating resolution in ceramics VP 3D printing. [ABSTRACT FROM AUTHOR]

This paper presents a numerical comparison of finite-element methods resulting in local mass conservation at the element level for Poisson's problem, namely the primal hybrid and mixed methods. These formulations result in an indefinite system. Alternative formulations yielding a positive-definite system are obtained after hybridizing each method. The choice of approximation spaces yields methods with enhanced accuracy for the pressure variable, and results in systems with identical size and structure after static condensation. A regular pressure precision mixed formulation is also considered based on the classical RT k space. The simulations are accelerated using Open multi-processing (OMP) and Thread-Building Blocks (TBB) multithreading paradigms alongside either a coloring strategy or atomic operations ensuring a thread-safe execution. An additional parallel strategy is developed using C++ threads, which is based on the producer-consumer paradigm, and uses locks and semaphores as synchronization primitives. Numerical tests show the optimal parallel strategy for these finite-element formulations, and the computational performance of the methods are compared in terms of simulation time and approximation errors. Additional results are developed during the process. Numerical solvers often fail to find an accurate solution to the highly indefinite systems arising from finite-element formulations, and this paper documents a matrix ordering strategy to stabilize the resolution. A procedure to enable static condensation based on the introduction of piecewise constant functions that also fulfills Neumann's compatibility condition, and yet computes an average pressure per element is presented. • Numerical comparison of the mixed, primal hybrid, and other locally conservatives finite element methods. • Introduction of a twice hybridized primal hybrid method, yielding a positive definite matrix after static condensation. • Comparison of multi-threaded strategies and thread-safety mechanisms. • A numerical procedure to stabilize the linear system resolution for indefinite matrices is described. • A general procedure that enables static condensation and fulfills Neumann's compatibility condition. [ABSTRACT FROM AUTHOR]

Research laboratories worldwide use the spark plasma sintering (SPS) technique for sintering metallic and ceramic matrix composites. Typically, the SPS sintered parts are low circular cylinders (discs). The upscaling and industrialization of SPS technology face two challenges: the limitation of shaping non-cylindrical parts and the inhomogeneous sintering of large-sized products. This paper addresses these challenges in sintering axisymmetric shells within an SPS setup with improved thermal insulation. The paper considers the sintering of a 75 mm shell as a case study. The shell material is a zirconia-carbon nanotube composite. Finite element analysis revealed that homogeneous sintering of such a shell requires careful thermal insulation of the entire setup. Investigation of phases, microstructure, density, microhardness, and fracture toughness in the sintered shell showed a homogeneous structure and uniform properties. [ABSTRACT FROM AUTHOR]

• Nonlinear model for a bended piezoelectric semiconductor beam is established. • Differential quadrature method based iteration procedure is developed. • Nonlinearity of constitutive relation and non-uniformity of structure are focused. • Potential barriers and wells are realized through designing structures. In this paper, the effects of nonlinear constitutive relation on the electro-elastic coupling behaviors in non-uniform piezoelectric semiconductor beams are investigated. On the basis of three-dimensional theory for piezoelectric semiconductor and double power series, one-dimensional bending model is developed. In order to deal with the nonlinear problem, a differential quadrature method based iteration procedure is proposed. Comparing with the results from finite element method, the proposed method has good convergence and high accuracy. In numerical analysis, the effects of nonlinearity and non-uniformity in piezoelectric semiconductor are discussed thoroughly. It is found the introduction of nonlinearity induces the loss of symmetric for all electrical field quantities but little changes the mechanical quantities. While the reduction of width along the length direction produces larger mechanical and electrical responses. Importantly, the effects of nonlinearity on the electrical field quantities are more evident in a piezoelectric semiconductor beam with rapidly varied cross section. Besides, we designed the piezoelectric semiconductor beams subject to double shear forces and a beam with locally varied cross section. In the designed structures, the potential barriers and wells are realized, which provide new approaches adjusting the electro-elastic behaviors in piezoelectric semiconductors. The study in this paper could be the guidance designing high performance electronic devices. [ABSTRACT FROM AUTHOR]

In the paper "Abhimanyu Kumar and Souvik Ganguli 'A new Hall-effect enabled voltage amplifier device based on magnetic and thermal properties of materials.' Journal of Magnetism and Magnetic Materials 514 (2020): 167054." it is claimed that the output voltage V out of a Hall plate can be larger than its input voltage V in. This clearly contradicts the well-known "no-voltage amplification property" of Hall plates. Within this comment we proof the no-voltage amplification theorem by simple methods. Hence, the main statement of Kumar et al. is proven to be incorrect. In addition, we give a simple proof that the solution of the governed equation has a unique solution with regards to the current flow. To illustrate the current flow and the obtained output voltage numerical examples using the finite element method are given. [ABSTRACT FROM AUTHOR]

In this paper, we present explicit expressions for conforming finite element function spaces, basis functions, and degrees of freedom on the pentatope (the 4-simplex) and tetrahedral prism elements. More generally, our objective is to construct high-order finite element function spaces that maintain conformity with infinite-dimensional spaces of a carefully chosen de Rham complex in four dimensions. This paper is a natural extension of the companion paper entitled "Conforming finite element function spaces in four dimensions, part I: Foundational principles and the tesseract" by Nigam and Williams (2024). In contrast to Part I, in this paper we focus on two of the most popular elements which do not possess a full tensor-product structure in all four coordinate directions. We note that these elements appear frequently in existing space-time finite element methods. In order to build our finite element spaces, we utilize powerful techniques from the recently developed 'Finite Element Exterior Calculus'. Subsequently, we translate our results into the well-known language of linear algebra (vectors and matrices) in order to facilitate implementation by scientists and engineers. [ABSTRACT FROM AUTHOR]

The stability, robustness, accuracy, and efficiency of space-time finite element methods crucially depend on the choice of approximation spaces for test and trial functions. This is especially true for high-order, mixed finite element methods which often must satisfy an inf-sup condition in order to ensure stability. With this in mind, the primary objective of this paper and a companion paper is to provide a wide range of explicitly stated, conforming, finite element spaces in four dimensions. In this paper, we construct explicit high-order conforming finite elements on 4-cubes (tesseracts); our construction uses tools from the recently developed 'Finite Element Exterior Calculus'. With a focus on practical implementation, we provide details including Piola-type transformations, and explicit expressions for the volumetric, facet, face, edge, and vertex degrees of freedom. In addition, we establish important theoretical properties, such as the exactness of the finite element sequences, and the unisolvence of the degrees of freedom. [ABSTRACT FROM AUTHOR]

This paper delves into the numerical analysis of the extended Fisher-Kolmogorov (EFK) equation within open bounded convex domains R ⊂ R d , where d ≤ 3. Two distinct finite element schemes are introduced, namely the semi-discrete and fully-discrete finite element approximations. The existence and uniqueness of solutions are established for both the semi-discrete and fully-discrete finite element approximations. Error bounds are investigated across different scenarios, including comparisons between the semi-discrete and exact solutions, as well as between the semi-discrete and fully-discrete solutions, along with the fully-discrete and exact solutions. An effective algorithm has been proposed to solve the nonlinear system resulting from the fully-discrete finite element approximation at each time step. The paper also provides computed numerical error results and showcases a variety of numerical experiments to further illustrate and support the findings. [ABSTRACT FROM AUTHOR]

This research proposes an Optimized Current chopping Control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements, comprising minimized torque ripple to reduce vibrations and acoustic noises, maximized output torque to enhance vehicle acceleration, and improved efficiency, which contributes to extending the EV's battery life. Therefore, an optimization problem is formulated and solved offline, incorporating a CCC-based SRM drive model. The control variables for this optimization problem are the switching angles of the SRM. A multi-objective function is chosen to combine three performance indices: torque ripple, average torque, and efficiency. The Harris Hawks Optimization (HHO) method is utilized in this paper to solve the optimization problem and find the optimal switching angles based on the selected objective function. HHO demonstrates a strong search capability that can effectively handle the nonlinear magnetization characteristics of SRMs. Constraints on the switching angles are also included in the optimization problem to control the phase current's RMS value and power consumption. The optimized switching angles are applied to a current chopping control (CCC) strategy and an asymmetric half-bridge converter to implement the proposed HHO-based CCC drive. Moreover, to demonstrate the effectiveness of the proposed HHO-based CCC drive, a comparative analysis based on simulations and experimental measurements is presented against other CCC approaches for SRM drives, including modified particle swarm algorithm (MPSO)-based CCC drives and analytical-based CCC drives. • A finite element analysis (FEA) software is utilized to determine the magnetic characteristics of SRMs accurately. • The obtained magnetic characteristics are then verified using a series of indirect experimental measurements to build an accurate four-phase 8/6 SRM model. • The Harris Hawks optimization (HHO) method is employed in this paper to find the optimal switching angles based on the selected objective function. • This research proposes an optimized current chopping control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements. • The proposed HHO-based CCC drive is validated and compared based on simulations and experimental measurements against other CCC approaches for SRM drives, including modified particle swarm algorithm(MPSO)-based CCC drives and analytical-based CCC drives. [ABSTRACT FROM AUTHOR]

A novel higher-order multi-scale computational approach for efficient nonlocal gradient elasticity simulation of composite materials is proposed in this paper. Based on the use of decoupling technique, raw fourth-order nonlocal gradient equations with periodically oscillatory coefficients are decoupled as the new second-order multi-scale equations for reducing the continuity requirements when implementing multi-scale simulation. Next, a novel macro-micro coupled multi-scale computational model with higher-order corrected terms is rigorously devised for high-resolution multi-scale and nonlocal analysis of composite materials via multi-scale asymptotic analysis. Then, the local error analysis of higher-order multi-scale solutions in the point-wise sense illustrates that establishing higher-order asymptotic corrected terms plays a vital role in investigating the micromechanical mechanisms. Moreover, a rigorous global error estimation with an explicit rate of higher-order multi-scale solutions is first derived in the energy norm sense. In addition, an efficient multi-scale numerical algorithm is presented to effectively simulate nonlocal gradient elasticity problems of composite materials based on finite element method (FEM). And we also derive the convergence estimation of the proposed numerical algorithm. Finally, numerical experiments are conducted to gauge the efficiency and accuracy of the proposed higher-order multi-scale method. This paper offers a unified higher-order two-scale computational framework for enabling nonlocal gradient elasticity behavior simulation of composite materials. [ABSTRACT FROM AUTHOR]

This paper designs, analyzes, and implements a finite element analysis for the simulation of the nonlinear advection-diffusion model. The key feature of the proposed work is to provide novel a priori error estimates in Bôchner norms L 2 (0 , T ; H 0 1 (Ω)) and L ∞ (0 , T ; H 0 1 (Ω)) simultaneously. To achieve the desired error estimates for both semidiscrete and fully discrete schemes, our idea is to introduce the Ritz projection operator that allows us to enforce the known estimates for P 1 and P 2 finite elements in the formulation of the desired results. Further, this paper establishes the stability, existence, and uniqueness in the precise normed spaces. Finally, we prove the fully discrete error estimates using the Backward Euler and Crank-Nicolson's schemes which are corroborated by numerical experiments to validate the developed theory on various domains for both schemes. To the best of author's knowledge, this is the first finite element simulation that provides the estimates in the L 2 Bôchner norm for any such types of time-dependent problems. [ABSTRACT FROM AUTHOR]

Grinding damage of hard and brittle materials has a direct impact on part strength and subsequent polishing efficiency. Damage suppression is one of the key research issues in hard and brittle material processing. Due to the uncertain damage evolution law, there is still a lack of optimization methods for the multi-step grinding process under given damage constraints. In this paper, the extended finite element method is used to establish a model between the prefabricated crack depth and final crack depth, which reveals the influence of various existing subsurface damages on crack propagation. It is found that only when the prefabricated crack depth is close to the indentation crack depth on the perfect surface, the final crack depth will be affected to some extent. To optimize the grinding process to achieve low damage, a semi-empirical model for predicting grinding damage is proposed which is suitable for process optimization and does not rely on some difficult-to-obtain parameters. Finally, based on the damage evolution law and prediction model, the core content of this paper is proposed, that is, a multi-step grinding process optimization method with variable grinding depth. This method can minimize the damage while ensuring the same processing efficiency, the damage depth is reduced by 25 %. The effectiveness of the optimization method and the correctness of the damage evolution law are proved by experiments. This method is suitable for engineering applications and has practical significance for understanding the damage evolution mechanism, which is helpful for the suppression of grinding damage and the optimization of the grinding process. • Reveal the evolution mechanism of various existing subsurface damage on crack propagation by XFEM. • Propose a semi-empirical model for grinding damage prediction suitable for process optimization. • Propose a multi-step grinding process optimization method for hard brittle materials with variable grinding depth. • Prove the effectiveness of the optimization method and the evolutionary model through experiments. [ABSTRACT FROM AUTHOR]

In this paper, further in-depth research on chip formation mechanism is conducted on the cutting of metallic glasses. The study of chips contributes to a better understanding of the machining nature of materials, which is of significant importance for improving product quality, reducing energy consumption, and resource utilization. This paper employs a combination of simulation and experimental methods, wihch not only analyzes the mechanism of chip formation in depth, but also investigates the time-varying characteristics of cutting forces. The results indicate that, when comparing simulation with experiments, the average error in cutting forces is 7.62%, and the chip morphology is also quite similar. Observations in the simulation show that as the cutting thickness increases from 7.96 μm to 23.87 μm, the free surface of the chip exhibits serrated features, and the main shear zone of the chip becomes clearer. Cutting forces exhibit periodic variations, with alternating peaks and valleys representing the formation of shear zones in the chip. In the experiment, observed chips displays a wrinkled free surface and a smooth non-free surface, with some chip edges exhibiting a burr phenomenon. By selecting appropriate machining parameters, the generation of secondary shear bands on the free surface was effectively reduced. By observing the chip morphology, it is found that the chip formation is accompanied by the material removal of plasticity and brittleness, which is the result of the combined action of heat, stress, and free volume. It should be considered to lower temperature to reduce the phenomenon of chip adhesion, providing guidance for further optimizing the cutting process of metallic glass. This paper can provide to readers further understanding of the chip formation mechanism in milling metal glass. • 2D finite element modeling was used to simulate the chip formation. • The shear zones appeared on the serrated chips. • The experimental results verified the accuracy of the simulation model. • The chips of BMG have smooth non-free surface and wrinkled free surface. • The serrated chips are the result of heat, stress, and free volume. [ABSTRACT FROM AUTHOR]

In order to solve the deficiencies of traditional board-level assembly CubeSat, such as low modularity, complex assembly process and poor scalability, a sandwich module assembly structure and method with no drive components is proposed, which can achieve quick connection and flexible assembly between modules. First, the proposed CubeSat standard module can be compatible with the standard interface of traditional CubeSat. The 4-in-1 interface of Mechanical-Electrical-Thermal-Data does not occupy the internal space of the standard module, and the electrical and thermal interfaces meet the requirements of CubeSat in-orbit work. Secondly, in order to improve the reliability of the connection between the modules, a plug-in connection scheme of the mechanical interface was designed. Finally, a genetic algorithm was used to optimize the interface size, so that it has better plug-in performance. The simulation results show that the performance of the male interface of titanium alloy material is the best, and the error between the finite element analysis and genetic algorithm results is less than 4.8 %, which is consistent with the actual tensile test results of the optimized prototype, and meets the mechanical requirements of the launch process and space orbit operation for CubeSat. The test results can guide production and provide a reference for subsequent engineering applications of CubeSat modular assembly. • In this paper, a standardized modular assembly method of CubeSat sandwich structure is designed. The assembly structure does not include driving parts, is simple in form, can be quickly connected, is flexible in assembly mode, and does not occupy the internal space of the standard module. • A standard 4-in-1 connection device was designed in this paper, including four interfaces: mechanical, electrical, thermal and data, which can achieve "plug and play". • This paper uses genetic algorithm to optimize the structure of the mechanical connection male joint, and obtains the optimal configuration of the male joint. This ensures the reliability, firmness and stability of mechanical connections, and meets the mechanical requirements of CubeSats during launch and in orbit. [ABSTRACT FROM AUTHOR]

This paper summarizes the effective components of computer-aided design and computer-aided manufacturing (CAD-CAM) resin composites that contribute to achieving greater mechanical properties and further development. In silico multi-scale analysis, in silico nonlinear dynamic finite element analysis (FEA), and artificial intelligence (AI) were used to explore the effective components of CAD-CAM resin composites. The effects of the filler diameter and silane coupling ratio on the mechanical properties of CAD-CAM resin composites have been clarified through multi-scale analysis. The effects of the filler contents, and filler and monomer compositions have been investigated by AI algorithms. The fracture behavior of CAD-CAM composite crown was analyzed using in silico non-linear dynamic FEA. The longevity of CAD-CAM composite crown was assessed through step-stress accelerating life testing (SSALT). As the filler diameter decreases, there is an increase in elastic moduli and compressive strengths at the macroscale. At the nanoscale, a decrease in the filler diameter results in a decrease in the maximum value of the maximum principal strain. When the silane coupling ratio decreases, there is a decrease in the elastic modulus and compressive strength. According to the exhaustive search and feature importance analysis based on the AI algorithm, the combination of certain components was narrowed down to achieve a flexural strength of 269.5 MPa. The in silico non-linear FEA successfully detected the sign of the initial crack of the CAD-CAM composite molar crown. The SSALT revealed that CAD-CAM resin composite molar crowns containing nanofillers with a high fraction of resin matrix demonstrated great longevity. This paper summarized the effective components of CAD-CAM resin composites for their further development. The integration of in vitro and in silico approaches will expedite the advancement of CAD-CAM resin composites, offering benefits such as time efficiency and reduction of material waste for researchers and manufacturers. • The effective components of CAD-CAM resin composites (RC) have been summarized. • A smaller filler and a high silane coupling ratio enhance the mechanical properties of CAD-CAM RC. • Non-linear FEA has detected the sign of the initial crack in the CAD-CAM composite crown. • AI has been utilized to narrow down the effective components that achieve high flexural strength. • CAD-CAM composite crowns with a high fraction of resin matrix demonstrate remarkable longevity. [ABSTRACT FROM AUTHOR]

CORC superconducting cable is a compact and flexible composite superconductor. It is widely used in large power systems because of its good flexibility and high engineering current density. In these applications, reducing the AC loss generated by the superconductor is a key factor in studying the electromagnetic field of the superconducting conductor, which affects the operational stability of the entire superconducting power device. Currently, the use of striated tape-wound cables not only allows for flexible wiring at design time but also effectively reduces AC losses. This technology has been widely used in large superconducting magnet equipment. In this paper, the finite element model of single superconducting tape and CORC superconducting cable is established based on the finite element idea. The electromagnetic properties and mechanical changes are numerically calculated by H-method. The results show that both the current density and the magnetic field of a single superconducting tape show a gradual penetration from the two sides to the center. The area of maximum current density and magnetic field distribution is at the tape boundary. The distribution of current density, magnetic field and Lorentz force of three-dimensional CORC superconducting cable is similar. All of them are gradually attenuated from the maximum value at the boundary to the center position. It is worth noting that the current density, magnetic field and Lorentz force of the striated superconducting cables are smaller than the values without striations. The calculation results of the finite element model in this paper show that the striations weaken the current density, magnetic field and Lorentz force of the CORC superconducting cable by about 8.77%, 16.21% and 9.23%. Moreover, the presence of striations can effectively reduce the AC loss of superconductors. [ABSTRACT FROM AUTHOR]

In our previous work, the coaxial electrostatic spinning method was applied to construct nanofiber/SiBCN ceramic aerogel with an elytra-mimetic structure. The material presented excellent mechanical, insulation, oxidation resistance, and other properties. Based on preliminary experiments and literature reports, the integrated heat transfer behavior of nanofiber/SiBCN composite ceramic aerogels in high-temperature environments was affected by several factors, such as coaxial fiber size properties, fiber particle content, interactions, and spatial distribution. Moreover, the above factors overlapped and interacted with each other, and it was hard to generalize a clear law of action through traditional experiments and characterization. Therefore, the paper constructed a representative volume unit (RVE) model based on the complex spatial distribution characteristics of composite aerogels, using fractal theory, Rosseland equation theory, and multiphase model theory. This paper investigated the fiber and particle content, the size characteristics of the coaxial fibers, and the overall heat transfer process in high-temperature environments using the finite element method. The finite element simulated the effective thermal conductivity of multiphase aerogel composites under multiple parameters, such as fiber occupancy, fiber core-shell diameter ratio, temperature, and heat transfer mode. We obtained the property parameters of the complex composition of the material through fractal theory. The model was combined with finite elements to study the fiber particle content, the size characteristics of coaxial fibers, and the integrated heat transfer process in high-temperature environments. The fibers improved the absorption and reflection of thermal radiation with increasing fiber mass fraction, leading to improved ability of ceramic fiber aerogel to extinguish light. The fibers had a larger area to absorb and reflect thermal radiation. Based on the excellent extinction ability of SiC fibers, the composite ceramic aerogel had improved thermal performance at a specifically fiber-to-shell diameter ratio through a comprehensive multifactor simulation analysis. [ABSTRACT FROM AUTHOR]

• Realization of an experimental heat pump based on elastocaloric effect. • The device is made of elastocaloric wires crossed by air as heat transfer fluid. • The energy and environmental impacts of the device with many elastocaloric materials were tested. • Evaluation of the environmental impact through a TEWI analysis compared with a HFC32 heat pump. • Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) with respect to HFC32 heat pump. Solid-state refrigeration can constitute a breakthrough point since based on solid-state refrigerants that do not have any direct greenhouse effect (GWP = 0). The refrigeration systems based on caloric effect can be categorized as: magnetocaloric, electrocaloric, elastocaloric or barocaloric. The theme of interest for the investigation introduced in this paper is elastoCaloric Effect (eCE). In this paper the environmental impact in terms of Total Equivalent Warming Impact (TEWI) of an elastocaloric rotary device ensuring continuous fluxes of cold/hot air for the air conditioning applications is evaluated. The final aim is the construction of an experimental device based on eCE working as a heat pump that operates at peak performance and that would be eco-friendly. Indeed, a rotary two-dimensional model based on finite element method was developed to couple with the device during its realization. The device has been virtually tested while mounting various elastocaloric effect materials to examine and select the ones resulting most suitable both from energetical and environmental points of view. The evaluation of the environmental impact has been perpetuated through a TEWI analysis comparing the indexes of the elastocaloric prototype operating with different elastocaloric materials (Ni 50.8 Ti 49.2 , Ni 55.9 Ti 44.1 , Ni 45 Ti 47.2 Cu 5 V 2.75 , (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 and PbTiO 3) and a vapor compression heat pump (A ++/ A +) working with HFC32. The analysis was perpetuated for both the functioning modes: cooling and heating modes. The most remarkable data on the analysis is that only Ni 55.92 Ti 44.08 and (Ni 50 Mn 31.5 Ti 18.5) 99.8 B 0.2 provide a significant reduction of the environmental impact (−50/−60 %) appropriately selecting the operative conditions (air velocity ranging from 9 to 12 ms−1 and cycle frequency 0.4 ÷ 0.5 Hz). [ABSTRACT FROM AUTHOR]

This paper studies adaptive least-squares finite element methods for convection-dominated diffusion-reaction problems. The least-squares methods are based on the first-order system of the primal and dual variables with various ways of imposing outflow boundary conditions. The coercivity of the homogeneous least-squares functionals are established, and the a priori error estimates of the least-squares methods are obtained in a norm that incorporates the streamline derivative. All methods have the same convergence rate provided that meshes in the layer regions are fine enough. To increase computational accuracy and reduce computational cost, adaptive least-squares methods are implemented and numerical results are presented for some test problems. [ABSTRACT FROM AUTHOR]

In this paper, we propose a low rank approximation method for efficiently solving stochastic partial differential equations. Specifically, our method utilizes a novel low rank approximation of the stiffness matrices, which can significantly reduce the computational load and storage requirements associated with matrix inversion without losing accuracy. To demonstrate the versatility and applicability of our method, we apply it to address two crucial uncertainty quantification problems: stochastic elliptic equations and optimal control problems governed by stochastic elliptic PDE constraints. Based on varying dimension reduction ratios, our algorithm exhibits the capability to yield a high-precision numerical solution for stochastic partial differential equations, or provides a rough representation of the exact solutions as a pre-processing phase. Meanwhile, our algorithm for solving stochastic optimal control problems allows a diverse range of gradient-based unconstrained optimization methods, rendering it particularly appealing for computationally intensive large-scale problems. Numerical experiments are conducted and the results provide strong validation of the feasibility and effectiveness of our algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a residual-type a posteriori error estimator is proposed and analyzed for a weak Galerkin finite element method for solving linear elasticity problems. The error estimator is proven to be both reliable and efficient, and be used for adaptive refinement. Numerical experiments are presented to illustrate the effectiveness of this error estimator. [ABSTRACT FROM AUTHOR]

Stability and optimal convergence analysis of a non-uniform implicit-explicit L1 finite element method (IMEX-L1-FEM) is studied for a class of time-fractional linear partial differential/integro-differential equations with non-self-adjoint elliptic part having (space-time) variable coefficients. The proposed scheme is based on a combination of an IMEX-L1 method on graded mesh in the temporal direction and a finite element method in the spatial direction. With the help of a discrete fractional Grönwall inequality, global almost optimal error estimates in L 2 - and H 1 -norms are derived for the problem with initial data u 0 ∈ H 0 1 (Ω) ∩ H 2 (Ω). The novelty of our approach is based on managing the interaction of the L1 approximation of the fractional derivative and the time discrete elliptic operator to derive the optimal estimate in H 1 -norm directly. Furthermore, a super convergence result is established when the elliptic operator is self-adjoint with time and space varying coefficients, and as a consequence, an L ∞ error estimate is obtained for 2D problems that too with the initial condition is in H 0 1 (Ω) ∩ H 2 (Ω). All results proved in this paper are valid uniformly as α → 1 − , where α is the order of the Caputo fractional derivative. Numerical experiments are presented to validate our theoretical findings. [ABSTRACT FROM AUTHOR]

• A type of metamaterial isolation beam consisting a cantilever beam with flexoelectric film attached is provided. • A closed-form analytical expression for the bandgap range is derived. • The operating bandgap of the metamaterial isolation beam is widened by flexoelectric effect. • Parameter analysis and simulation validation of the model are performed, and optimal values are provided. • The flexoelectric beam significantly outperforms piezoelectric beams in microscale high-frequency passive isolation. In this paper, a type of metamaterial isolation beam consisting a cantilever beam with flexoelectric film attached is provided. Electrodes interconnect on the surface to create parallel resonant shunt circuits, enabling band-stop filtering. The electromechanical control equations are derived using the Hamiltonian principle. A closed-form analytical expression for the bandgap range is obtained via the root locus method. Theoretical results are validated through finite element methods. Findings reveal that the operational bandgap of millimeter-scale flexoelectric metamaterial isolation beams is 5.2 times greater than that of conventional piezoelectric metamaterial beams. Furthermore, the vibration excitation amplitude is reduced by 99.9%. These results highlight the significant advantages of flexoelectric materials for microscale high-frequency passive isolation, providing superior stability in complex vibration environments. The research investigates the effects of end mass, electrode plate count, and external resistance on the vibration isolation performance of flexoelectric metamaterial beams. The study also examines the variations in relative bandgap width between flexoelectric and piezoelectric metamaterial beams concerning material, size, and structural parameters, identifying optimal values. Notable differences in bandgap characteristics are observed between flexoelectric and piezoelectric beams; for instance, while piezoelectric beams have an optimal substrate elastic modulus, flexoelectric beams do not, and the optimal film thickness for flexoelectric beams is 2.2 times that for piezoelectric beams. [ABSTRACT FROM AUTHOR]