Explicit Numerical Model Research Articles

A shared model-based linguistic space for transmitting our thoughts from brain to brain in natural conversations

Effective communication hinges on a mutual understanding of word meaning in different contexts. We recorded brain activity using electrocorticography during spontaneous, face-to-face conversations in five pairs of epilepsy patients. We developed a model-based coupling framework that aligns brain activity in both speaker and listener to a shared embedding space from a large language model (LLM). The context-sensitive LLM embeddings allow us to track the exchange of linguistic information, word by word, from one brain to another in natural conversations. Linguistic content emerges in the speaker's brain before word articulation and rapidly re-emerges in the listener's brain after word articulation. The contextual embeddings better capture word-by-word neural alignment between speaker and listener than syntactic and articulatory models. Our findings indicate that the contextual embeddings learned by LLMs can serve as an explicit numerical model of the shared, context-rich meaning space humans use to communicate their thoughts to one another.

Appraising the Risk Assessment of Non-Structural Components via Simplified and Machine-Learning-Based Approaches

ABSTRACT Uncertainties in building element modelling and ground motions are indispensable for rigorous seismic risk quantification. demand–intensity models simply relate building performance to intensity and subsequently risk. This article describes developments toward non-structural element (NSEs) risk quantification. The demand–intensity models are applied to infilled reinforced concrete (RC) case-study buildings. Implicit and explicit NSE numerical modelling is used to validate the models versus the direct integration of risk exceedance. For faster estimation techniques, machine learning models are trained to estimate the demand–intensity model fitting parameters on a modest dataset of RC infilled buildings. Among these, the extreme gradient boosting (XGBoost) demonstrated superior performance, indicating further possible directions for improvement where larger datasets are available. These models facilitate the simple retrieving of demand–intensity models without extensive structural analysis and can be utilized for both structural and non-structural elements when assessing risk in single or multiple buildings as part of portfolio analysis.

Effect of wingtip bending morphing on gust-induced aerodynamics based on fluid-structure interaction method

This paper investigates the effect of wingtip bending morphing on gust-induced aerodynamics based on the fluid–structure interaction (FSI) method at Re = 40 000. First, an explicit spatiotemporal numerical model for a wingtip bending morphing on a wing with a semi-aspect ratio of 4 is deduced, considering geometrical nonlinearity under large morphing amplitude. A modal-based FSI framework is developed to consider the elastic deformation, active wingtip morphing, and gust. The shear-stress transport-γ model is introduced. The above FSI method is validated by gust response experimental results. The mitigation effects of active bending morphing on gust-induced aerodynamics at different phase offset, gust ratios (GR), and flare angles are investigated. Under GR = 0.2 and flare angle = 0, wingtip bending morphing achieves the best mitigation effect when the phase offset is π/2. As GR increases to 0.4, the optimum phase offset shifts to π/3 and the alleviation rate decreases. The mitigation rate increases with the flare angle. Under GR = 0.4 and flare angle = 30°, the optimum phase offset is π/6, in which case the lift response is reduced by 37%, and wing root bending moment response is reduced by 73% relative to the baseline case. The flow field and vortex evolution result infers that the wingtip bending morphing decreases the spanwise width of the leading-edge vortex and reduces the area of low-pressure zones on the suction side, thereby mitigating gust-induced aerodynamics. The results indicate that active wingtip bending morphing has great potential for gust load alleviation for future aircraft.

Numerical analysis of the impact behaviour of a composite eco-structure

An explicit numerical model is developed for the impact behaviour of a new composite eco-structure made of a plywood core and flax/epoxy composite skin. A constitutive orthotropic material behaviour is imposed to model the elastic response of plies of plywood core and flax skin. A stress-based modified Hashin-3D damage model with four independent failure criteria in tensile and compressive mode is incorporated for predicting the damage initiation. A strain threshold based exponential method is adopted to predict the damage scaling and its evolution. The above proposed model is implemented through user material subroutine (VUMAT) in ABAQUS Explicit. The developed model is validated with experimental low-velocity impact test results and can accurately predict the stiffness degradation, plateau, and post-peak softening of wooden plies. A good agreement with the better accuracy is achieved between the predictions and the test results.

Assessing the Feasibility of an Explicit Numerical Model for Simulating Water Surface Profiles over Weirs

Assessing the Feasibility of an Explicit Numerical Model for Simulating Water Surface Profiles over Weirs

Two‐dimensional meso‐structural simulation of concrete fracture by the implementation of zero‐thickness cohesive interface elements

AbstractConcrete is considered as a non‐homogeneous material and from a mesoscopic point of view is constituted of three main phases, namely aggregates, mortar matrix and interfacial transition zone (ITZ). To investigate the damage process of concrete materials at the mesoscale due to mechanical loading, an explicit numerical model with full representation of the three mesoscopic phases is required. To this end, in this work, a Python code is developed to generate zero‐thickness cohesive interface elements in two‐dimensions (2D). The generated code is capable of generating two‐dimensional quadratic cohesive interface elements (i) within the mortar elements, (ii) within the aggregates elements and (iii) at interfaces between mortar and aggregates. To simulate the crack propagation, the generated zero thickness‐cohesive elements are preinserted at the interface of solid elements and different traction‐separation laws are assigned to them to simulate all potential crack paths. The implemented algorithms to generate the cohesive elements are discussed in detail and numerical examples of crack propagation in concrete is presented using Abaqus/CAE. The numerical results are compared with those in the literature qualitatively to validate the performance of the model. The developed method provides the possibility to investigate the damage processes in meso‐and micro‐scales underlying the macroscopic behavior of the semi‐brittle materials.

Three-dimensional modeling of joint kinematic of ductile iron pipelines subjected to normal faulting

Buried ductile iron (DI) pipelines are of paramount importance for urban water networks. The joint sealing performance can be seriously affected by fault offset, showing failures of axial pull-out of joint, joint crushing, joint rotation, and circular cracking caused by pipe bending. Analytical or beam-on-spring based numerical models and physical experiments have been done in the past, but the kinematic mechanism of DI pipes subjected to normal fault deserves to be understood using the three-dimensional (3D) finite element method. In this study, an explicit 3D numerical model is calibrated against a full-scale experiment, and is further adopted to analyze the impact of different parameters. It is demonstrated that joint rotation leakage dominates the failure mode, showing leakage at a single joint or two joints closest to the fault trace. The most unsafe fault-pipe crossing position is derived when the fault acts on one quarter of the rotated pipe barrel from the spigot, which can result in highly consistent pipe rotation pattern in the even configuration as proposed in existing theories. When the fault passes through the middle of the pipe barrel perpendicularly, the joints of DN 400 pipeline are more susceptible to leakage.

Stiffness and strength parameters for the hardening soil model of a reconstituted diatomaceous soil

Centrifuge modelling has been widely used to study the geotechnical behaviour of structures built on soft soils and to calibrate and validate numerical models. In the finite element method (FEM), the mechanical behaviour of the soils is established through a constitutive model, and the correct selection and calibration of its parameters are essential to obtain accurate results. In this article, the mechanical parameters of an artificial reconstituted soft soil proposed for centrifuge modelling are obtained, calibrated and validated for the hardening soil (HS) model based on laboratory test results. The reconstituted soil consists of 50% kaolin clay and 50% diatomaceous soil from Bogotá, Colombia. First, geotechnical characterization of the reconstituted soil is presented. The model preparation technique to generate the effective stress profile for the centrifuge model is described. The strength and compressibility parameters are obtained from CU triaxial tests and a one-dimensional consolidation test, respectively. Finally, the obtained parameters are calibrated via explicit numerical modelling using the FEM and the SoilTest module of Plaxis software. It is concluded that the reconstituted artificial soft soil proposed herein mimics most of the natural lacustrine deposits of soft soils worldwide and can be modelled using the HS model for FEM analyses.

Proposal for a New Bioactive Kinetic Screw in an Implant, Using a Numerical Model

A new biomechanism, Bioactive Kinetic Screw (BKS) for screws and bone implants created by the first author, is presented using a bone dental implant screw, in which the bone particles, blood, cells, and protein molecules removed during bone drilling are used as a homogeneous autogenous transplant in the same implant site, aiming to obtain primary and secondary bone stability, simplifying the surgical procedure, and improving the healing process. The new BKS is based on complex geometry. In this work, we describe the growth factor (GF) delivery properties and the in situ optimization of the use of the GF in the fixation of bone screws through a dental implant. To describe the drilling process, an explicit dynamic numerical model was created, where the results show a significant impact of the drilling process on the bone material. The simulation demonstrates that the space occupied by the screw causes stress and deformation in the bone during the perforation and removal of the particulate bone, resulting in the accumulation of material removed within the implant screw, filling the limit hole of the drill grooves present on the new BKS.

Investigation of support type effect on plastic hinges in RC beam under impact load

AbstractThis study investigates the effect of support types on plastic hinges in reinforced concrete (RC) beam under the influence of impact loading. In previous studies, the assumption of the linear distribution of inertia force under impact loading was examined and verified according to experimental, analytical, and numerical results. Furthermore, it was emphasized that the most important parameters affecting the behavior of RC beams under impact loading were plastic hinges. A three‐stage study was planned to investigate this subject. The first stage was an experimental study. In this part, four RC beams with simple and fixed supports were tested under the low‐velocity impact load with two different impact energy levels by using a free‐weight test setup with advanced measurement techniques. The time histories of the accelerations, the displacements, and the impact loads acting on RC beams were recorded, and the cracks from impact loading were observed. The dynamic responses obtained from experiments have been interpreted in detail. The most important issue about plastic hinges was that the hinges do not reach the supports and remain on the beam. This is valid for both hinge support and fixed support. In the second stage of the study, an explicit numerical analysis model, which was verified with experimental results, was developed. The clear agreement between the experimental and numerical results was demonstrated. It has been concluded that proposed finite element procedures can be used for evaluation of the dynamic responses and failure modes of RC beams under low‐velocity impact loading. The last part was an analytical study. In this part, the proposed analytical procedure in the previous studies considering the plastic joint formed in a simple support beam under impact loading was confirmed, and a new coefficient for fixed support was proposed. A good agreement has been achieved between analytical and experimental work.

Explicit Numerical Model of Solar Cells to Determine Current and Voltage

This paper deals with the extraction of the physical parameters of solar cells (a single diode model) from the equivalent circuit of the cell. The extraction is carried out by three different numerical methods with a comparison between them. The first and second methods are a difference of the Newton Raphson algorithm (NRM) and Aitken’s extrapolation algorithm (AEM), respectively. The roots of the nonlinear equation of this cell have been described and solved using the three methods. The proposed method is tested to solve the output voltage; current and power of this cell from the roots of this equation with the various values of load resistance RL.

Influence of asymmetric factor on spur gears to dynamic bending stress

Asymmetric spur gear is used in one-way rotation transmission. This spur gear has a higher bending strength than symmetric spur gear. In this research, the effect of asymmetrical spur gear level on bending stresses is studied dynamically. The asymmetric spur gear level is expressed as asymmetric factor (K). Asymmetric factors K = 1, K = 1.05, K = 1.06, K = 1.07 and K = 1.08 are used. Dynamic analysis is performed by explicit dynamics numerical modeling. Material used for five asymmetric factor is AISI 1045. Two variables applied on this spur gears are torque loads and rotational speeds to investigate that effect on bending stress. Torque loads varied from 100 Nm to 250 Nm with 50 Nm increment and rotational speeds varied from 1000 rpm to 2500 rpm with 500 rpm increment. The results of this study show that the asymmetric factor can reduce more significantly bending stress cause of torque loads than cause of rotational speeds.

Change in Concentration-Dependent Diffusion Activation Energy and Frequency Factor with Time: Identified by Numerical Analyses of Experimental Data

A newly developed fully explicit numerical diffusion model coupled with a forward simulation technique, to avoid flaws in conventional methods such as the Boltzmann–Matano, Sauer–Freise and Hall procedures, is used to compute the concentration-dependent activation energy and frequency factor for diffusion in two different alloy systems. In contrast to what has been commonly reported in the literature, the results show that the concentration dependence of activation energy and frequency factor can significantly change with time. In this situation, the use of concentration-dependent activation energy and frequency factor that does not vary with time to predict diffusion effect can lead to considerable error. Furthermore, when there is a time variation in the dependence of activation energy and frequency factor on concentration, a common expectation that diffusion-controlled kinetics would increase with an increase in temperature may not always apply for all time durations.

Biomedical soft robots: current status and perspective.

This paper reviews the current status of soft robots in biomedical field. Soft robots are made of materials that have comparable modulus of elasticity to that of biological systems. Several advantages of soft robots over rigid robots are safe human interaction, ease of adaptation with wearable electronics and simpler gripping. We review design factors of soft robots including modeling, controls, actuation, fabrication and application, as well as their limitations and future work. For modeling, we survey kinematic, multibody and numerical finite element methods. Finite element methods are better suited for the analysis of soft robots, since they can accurately model nonlinearities in geometry and materials. However, their real-time integration with controls is challenging. We categorize the controls of soft robots as model-based and model-free. Model-free controllers do not rely on an explicit analytical or numerical model of the soft robot to perform actuation. Actuation is the ability to exert a force using actuators such as shape memory alloys, fluid gels, elastomers and piezoelectrics. Nonlinear geometry and materials of soft robots restrict using conventional rigid body controls. The fabrication techniques used for soft robots differ significantly from that of rigid robots. We survey a wide range of techniques used for fabrication of soft robots from simple molding to more advanced additive manufacturing methods such as 3D printing. We discuss the applications and limitations of biomedical soft robots covering aspects such as functionality, ease of use and cost. The paper concludes with the future discoveries in the emerging field of soft robots.

An efficient numerical model for the simulation of coupled heat, air, and moisture transfer in porous media

AbstractThis article proposes an efficient explicit numerical model with a relaxed stability condition for the simulation of heat, air, and moisture transfer in porous material. Three innovative approaches are combined to solve the system of two differential advection‐diffusion equations coupled with a purely diffusive equation. First, the DU FORT‐FRANKEL scheme is used to solve the diffusion equation, providing an explicit scheme with an extended stability region. Then, the two advection‐diffusion equations are solved using both the SCHARFETTER‐GUMMEL numerical scheme for the space discretisation and the two‐step RUNGE‐KUTTA method for the time variable. This combination enables to relax the stability condition by one order. The proposed numerical model is evaluated on three case studies. The first one considers quasi‐linear coefficients. The theoretical results of the numerical schemes are confirmed by our computations. Indeed, the stability condition is relaxed by a factor of 40 compared to the standard EULER explicit approach. The second case provides an analytical solution for a weakly nonlinear problem. A very satisfactory accuracy is observed between the reference solution and the one provided by the numerical model. The last case study assumes a more realistic application with nonlinear coefficients and ROBIN‐type boundary conditions. The computational time is reduced 10 times by using the proposed model in comparison with the explicit EULER method.

On the numerical and structural properties of a logarithmic scheme for diffusion–reaction equations

In this work, we investigate numerically some relevant solutions of a diffusion problem with a general reaction term. The system under investigation is governed by a partial differential equation that generalizes the classical Fisher's equation and the Hodgkin–Huxley model. In a first stage, we provide an equivalent presentation of the problem, and recall an explicit logarithmic numerical model to solve it. As one of the most important outcomes of this work, we prove that logarithmic scheme is a structure-preserving model under suitable conditions. Concretely, we show that the numerical model is capable of preserving the positivity, the boundedness and the monotonicity of the approximations. This feature of the numerical integrator is in agreement with the fact that the continuous model has solutions with the same characteristics. Also, for the first time in the literature, we show that the logarithmic models are consistent schemes which are stable and convergent. Some numerical simulations confirm that the numerical model is a convergent technique, with first order of convergence in time and second order in space.

Numerical modeling of impact on wood-based sandwich structures

The impact behavior of innovative wood based sandwich structures with plywood core and skins made either of aluminum or of fiber reinforced polymer (carbon, glass, or flax composite skins) was investigated numerically. The wood based sandwich structures were subjected to low-velocity/low-energy impacts. An explicit nonlinear numerical model based on volume elements with a cohesive layer was developed. A plastic wood law already implemented in LS-DYNA was used in association with composite type damage criteria. Comparisons with experiments in terms of layer deformations and overall contact laws during impact showed satisfactory results.

Explicit numerical modeling assessment of basalt reinforced composites for low-velocity impact

Several studies have been carried out lately in order to evaluate the low-velocity impact response of polymeric composite materials allying experimental tests to numerical simulations. The many distinct ways of performing such analyze in the literature have raised the dubiousness on which are the most suitable simulation guidelines to perform a computational analysis that is both faithful to experimental tests as it can get, and at the same time is numerically-efficient dispensing excessively complex virtual models. Thus, the present study aims at defining the most appropriate guidelines to model a basalt fibre reinforced laminate when subjected to falling weight impact tests, comparing experimental results with explicit simulations that consider models with different numbers of plies and focusing on the calibration of essential parameters inherent of the constitutive equations attributed to the material. A precise yet intelligible model was constituted not only generating a correlation of over 97% to experimental data, but also accurately reproducing the indentation, showing that with an adequate modeling routine it is possible to numerically reproduce low-velocity impact tests on polymeric composites with a simplified virtual geometry.

The Potential for Upscaling Kelp (Saccharina latissima) Cultivation in Salmon-Driven Integrated Multi-Trophic Aquaculture (IMTA)

Integrated multi-trophic aquaculture (IMTA) has the potential of reducing open-cage fish farming impacts on the environment while also introducing new value chains. The aim of this study was to investigate the growth and composition of the kelp Saccharina latissima in salmon-driven IMTA, and to assess the spatial extent of the influence of salmon derived nitrogen in order to evaluate the upscaling potential for IMTA. S. latissima was cultivated 100, 200 and 1,000 m east and 1,000 m west of a 5,000 tonnes salmon farm in Western Norway from February to September 2013. The proportion of salmon derived nitrogen available for the kelp showed a clear decline with distance from the farm. Accordingly, the kelp cultivated near the salmon cages grew faster during the spring season, and growth rate decreased with increasing distance from the farm. A spatially explicit numerical model system (SINMOD), including compartments for dissolved nutrients and kelp growth, was tuned to the field data and used to investigate the potential for upscaling IMTA production. The model was used to introduce a new metric – the impacted area IA - for the areal effects of IMTA in terms of the increase in production by IMTA. The model showed that a 25 hectare kelp farm in the vicinity of the studied salmon farm could take up 1.6 of the 13.5 tonnes of dissolved inorganic nitrogen released during kelp cultivation, amounting to almost 12 % of the ammonia released during the cultivation period from February to June. The 25 hectare kelp farm would have a production yield of 1,125 tonnes fresh weight (FW), being 60 % more than that of a non-IMTA kelp farm, while a 20 % increase of kelp FW could be obtained over a 110 hectar area in salmon-driven IMTA. To achieve an even mass balance, an area of approximately 220 ha-1 would be needed to cultivate enough kelp to fix an equivalent of the nitrogen released by the fish.

Predicting pillar burst by an explicit modelling of kinetic energy

Violent pillar failures known as pillar bursts are suspected to be a possible cause of large collapses in underground mines. A classical stability criterion for mine pillars, based on the relative stiffness of the host rock and the pillars during their post-peak unloading, was proposed by Starfield & Fairhurst (1968)6 and further demonstrated by Salamon (1970)7. An energy balance indicates that an excess kinetic energy is generated when this pillar stability criterion is violated. The present study focuses on demonstrating how an explicit numerical modelling method may be used to calculate and locate the damping of this kinetic energy during pillar failure, considering simple 2D geometries. Arguments in favour of the validation of the numerical results are provided by comparison to analytical calculations and to an empirical classification of rockbursts proposed by Ortlepp (1997)1. The good correlation between numerical, analytical and empirical approaches suggest that explicit numerical modelling of kinetic energy damping, following a procedure proposed in this paper, could be a useful tool for predicting zones submitted to a pillar burst hazard in underground mines and for consequently optimizing the mining method.