One-dimensional Description Research Articles

Plasticity analysis and a homogenized constitutive model of compressible multi-layer structure of battery

A homogenized constitutive model for the compressible multi-layer structure of battery (CMLSB) under external loading is essential for optimizing the structural design of electric assemblies. Currently, there is no specific constitutive model that is both mechanically explanatory and operationally applicable to CMLSB under varied loading conditions. In this study, due to limited understanding of the in-plane behavior of CMLSB, an analytical model was developed to investigate plasticity in this specific direction using the strain probing method. The observed plastic characteristics inspired the formulation of a novel two-dimensional constitutive framework for CMLSB in the in-plane direction.By integrating this new constitutive framework with one-dimensional plastic descriptions, a hybrid constitutive model was introduced and implemented in finite element software. Calibration and validation of the model were performed using a commercial pouch cell battery and its segments under various loading conditions. Finite element simulations with the hybrid model demonstrated remarkable accuracy in predicting the mechanical behavior of the cell under various in-plane and out-of-plane compression scenarios. Additionally, simulations were carried out to analyze the impact of cell packaging and air pressure. The new hybrid battery model is considered a user-friendly, physically interpretable, and high-fidelity tool, poised to significantly facilitate the comprehensive design of electric devices.

An Improved Positive Displacement Pump Model Accounting for Suction Cavitation

Abstract Positive displacement (PD) pumps are widely employed in industrial settings due to their inherent simplicity and reliability, serving a variety of applications from slurry transport to jet washing. Although their operational principles are straightforward, the fluid dynamics of the pumped medium exhibit nontrivial characteristics, including intricate transient phenomena. Consequently, a comprehensive fluid dynamic description, such as a three-dimensional fluid analysis, presents challenges due to its demanding computational requirements. While simpler analytical PD pump models are available, they often fail to adequately represent the primary system behaviors, particularly when dealing with cavitation. Motivated by these challenges, this study aims to develop a novel one-dimensional model for PD pumps, offering a representation of essential fluid phenomena without imposing significant computational burdens. After assessing the relative importance of the fluid dynamic behaviors that the model must capture, we construct a pump model based on a one-dimensional fluid description and solve it using a second-order in time and space monotone upwind scheme for conservative law and total variation diminishing (MUSCL-TVD) scheme. The model's validity is confirmed by its application to both single-chamber and three-chamber diaphragm PD pumps, which are instrumented for experimental validation. The results of the one-dimensional model exhibit strong agreement with physical experiments, both in controlled laboratory environments and field conditions. This success suggests a promising approach for industrial applications.

High repetition rate coherent terahertz synchrotron radiation via self-amplified energy modulation

Coherent terahertz (THz) radiation sources based on a storage ring hold a significant future for generating high average power terahertz radiation, as the electron beam possesses a high revolution frequency. We propose a novel scheme to generate a high repetition rate coherent THz radiation leveraging the energy modulation self-amplification technology. In this scheme, utilizing the interaction of external intensity-modulated laser pulses with the electron beam can lead to a customized manipulation of the electron beam, such as a periodic longitudinal density modulation with a submillimeter scale for coherent THz radiation. Positively, it can propel the repetition rate when the peak power requirement of an external laser system is decreased. Thus, we employ a self-modulation method to enhance the initial weak energy modulation induced by the laser directly. In the meanwhile, the use of self-modulation can bypass the limitation that the bandwidth of a long modulator should be smaller than that of the external wideband laser source, which is necessary to shape the intensity envelope flexibly. The one-dimensional analytical description of electron longitudinal dynamic during the self-modulation process is given, which confirms the effective enhancement of the modulation at THz band. Three-dimensional time-dependent simulation results based on the parameters of Hefei light source-II show that the coherent THz radiation pulses with a repetition rate of 10 kHz can be generated. Published by the American Physical Society 2024

Are there distinct levels of language comprehension in autistic individuals – cluster analysis

AbstractAutism is a neurodevelopmental condition characterized by deficits in social communication. We assessed 14-language comprehension abilities in 31,845 autistic individuals 4 to 21 years of age using parent-generated reports. Data-driven cluster analysis identified three distinct levels of language comprehension: (1) individuals in the command-language-phenotype were limited to comprehension of simple commands; (2) individuals in the modifier-language-phenotype showed additional comprehension of color, size, and number modifiers; 3) individuals in the most-advanced syntactic-language-phenotype added comprehension of spatial prepositions, verb tenses, flexible syntax, possessive pronouns, and complex narratives. The observation of three distinct language levels was consistent across different age groups. Autistic individuals’ communication level is currently commonly characterized as nonverbal, minimally-verbal, or verbal. This one-dimensional description is not ideal for characterizing an individual’s communication ability. In fact, a nonverbal individual with syntactic-language-phenotype may have normal ability to communicate albeit nonverbally, while a verbal person with command-language-phenotype does not have a normal ability to communicate by any means. Identification of the three distinct language-comprehension-phenotypes provides an opportunity to enhance characterization of individuals’ communication level. A composite description in terms of both, verbal abilities and a language-comprehension-level, will not only be more precise, but can improve language therapy by focusing it on both aspects of language development.

No yield stress required: Stress-activated flow in simple yield-stress fluids

An elastoviscoplastic constitutive equation is proposed to describe both the elastic and rate-dependent plastic deformation behavior of Carbopol® dispersions, commonly used to study yield-stress fluids. The model, a variant of the nonlinear Maxwell model with stress-dependent relaxation time, eliminates the need for a separate Herschel–Bulkley yield stress. The stress dependence of the viscosity was determined experimentally by evaluating the steady-state flow stress at a constant applied shear rate and by measuring the steady-state creep rate at constant applied shear stress. Experimentally, the viscosity’s stress-dependence was confirmed to follow the Ree–Eyring model. Furthermore, it is shown that the Carbopol® dispersions used here obey time-stress superposition, indicating that all relaxation times experience the same stress dependence. This was demonstrated by building a compliance mastercurve using horizontal shifting on a logarithmic time axis of creep curves measured at different stress levels and by constructing mastercurves of the storage- and loss-modulus curves determined independently by orthogonal superposition measurements at different applied constant shear stresses. Overall, the key feature of the proposed constitutive equation is its incorporation of a nonlinear stress-activated change in relaxation time, which enables a smooth transition from elastic to viscous behavior during start-up flow experiments. This approach bypasses the need for a distinct Herschel–Bulkley yield stress as a separate material characteristic. Additionally, the model successfully replicates the observed steady-state flow stress in transient-flow scenarios and the steady-state flow rate in creep experiments, underlining its effectiveness in capturing the material’s dynamic response. Finally, the one-dimensional description is readily extended to a full three-dimensional finite-strain elastoviscoplastic constitutive equation.

Solute translocation probability, lifetime, and "rectification" in membrane channels with localized constriction.

We study the translocation probability and lifetime of a solute molecule in a cylindrical membrane channel that contains a localized constriction at an arbitrary location. Using a one-dimensional continuous diffusion description of solute dynamics in the channel, we explore two models. The first one describes a molecule's interaction with the constriction in terms of a narrow rectangular barrier in the potential of mean force. The second novel model proposed here represents this interaction by introducing an infinitely thin permeable partition. It is shown that when the parameters of the two models are chosen to warrant the same translocation probability, both models predict the same mean lifetime of the molecule in the channel. While the translocation probability is independent of the constriction location, the mean lifetime is a function of the location. The benefit of the thin partition model is that it allows one to lump together the height and length of the potential barrier into a single parameter, which is the partition's permeability. It is shown that in the case of an asymmetric location of the localized constriction and strong repulsion between the solutes, the solute flux through the channel is a function of the direction in which it goes, analogous to the phenomenon known in ion channel electrophysiology as rectification.

Surface hopping molecular dynamics simulation of ultrafast methyl iodide photodissociation mapped by Coulomb explosion imaging.

We present a highly efficient approach to directly and reliably simulate photodissociation followed by Coulomb explosion of methyl iodide. In order to achieve statistical reliability, more than 40 000 trajectories are calculated on accurate potential energy surfaces of both the neutral molecule and the doubly charged cation. Non-adiabatic effects during photodissociation are treated using a Landau-Zener surface hopping algorithm. The simulation is performed analogous to a recent pump-probe experiment using coincident ion momentum imaging [Ziaee et al., Phys. Chem. Chem. Phys., 2023, 25, 9999-10010]. At large pump-probe delays, the simulated delay-dependent kinetic energy release signals show overall good agreement with the experiment, with two major dissociation channels leading to I(2P3/2) and I*(2P1/2) products. At short pump-probe delays, the simulated kinetic energy release differs significantly from the values obtained by a purely Coulombic approximation or a one-dimensional description of the dicationic potential energy surfaces, and shows a clear bifurcation near 12 fs, owing to non-adiabatic transitions through a conical intersection. The proposed approach is particularly suitable and efficient in simulating processes that highly rely on statistics or for identifying rare reaction channels.

Radiative flamelet generated manifolds for solid fuel flame spread in microgravity

Recently, U-shape flammability maps have been constructed showing minimal oxygen concentration vs. flame strain for opposed flame spread in microgravity. Due to the absence of buoyancy in microgravity, flammability experiments require a microgravity environment and are costly to perform. Alternatively, detailed numerical simulations can be conducted to explore the flammability maps if sufficiently detailed chemistry mechanisms and radiation models are available. The purpose of this study is to develop such an approach and to explore the viability of using flamelet modeling descriptions. For this effort, a detailed two-dimensional (2D) flame spread model is developed that includes multi-step complex chemistry and fully coupled radiation heat transfer. The model is validated against measurements using the NASA BASS data and is shown to predict reasonable flame spread rates over a range of far-field oxygen levels. Next, newly developed coupled radiative flamelet generated manifolds (CR-FGM’s) are created using a simplified one-dimensional (1D) descriptions that include a quasi-coupled, fuel boundary that is shown to be critically important for capturing the spatially dependent variation of mixture fraction on fuel surfaces. Differences between the 2D model data and the CR-FGM’s are then identified to be from flame-wall interactions and curved flame structure effects. These differences are addressed using an a-priori error analysis conducted for various intermediate species comparing detailed 2D simulations with the CR-FGM. Results show the CR-FGM’s are capable in predicting the wide range of chemical states for most of the flow regions.

Population dynamics of head-direction neurons during drift and reorientation

The head direction (HD) system functions as the brain’s internal compass1,2, classically formalized as a one-dimensional ring attractor network3,4. In contrast to a globally consistent magnetic compass, the HD system does not have a universal reference frame. Instead, it anchors to local cues, maintaining a stable offset when cues rotate5–8 and drifting in the absence of referents5,8–10. However, questions about the mechanisms that underlie anchoring and drift remain unresolved and are best addressed at the population level. For example, the extent to which the one-dimensional description of population activity holds under conditions of reorientation and drift is unclear. Here we performed population recordings of thalamic HD cells using calcium imaging during controlled rotations of a visual landmark. Across experiments, population activity varied along a second dimension, which we refer to as network gain, especially under circumstances of cue conflict and ambiguity. Activity along this dimension predicted realignment and drift dynamics, including the speed of network realignment. In the dark, network gain maintained a ‘memory trace’ of the previously displayed landmark. Further experiments demonstrated that the HD network returned to its baseline orientation after brief, but not longer, exposures to a rotated cue. This experience dependence suggests that memory of previous associations between HD neurons and allocentric cues is maintained and influences the internal HD representation. Building on these results, we show that continuous rotation of a visual landmark induced rotation of the HD representation that persisted in darkness, demonstrating experience-dependent recalibration of the HD system. Finally, we propose a computational model to formalize how the neural compass flexibly adapts to changing environmental cues to maintain a reliable representation of HD. These results challenge classical one-dimensional interpretations of the HD system and provide insights into the interactions between this system and the cues to which it anchors.

Numerical Modelling of Moisture Transport Between Two Enclosures Connected by a Tube

The electronics is protected using plastic or metallic enclosures. Although, the electronics is protected by the enclosures from the surrounding environment, the moisture can still enter the enclosure via gasket, plastic enclosure walls, cable feedthroughs. The moisture existing inside enclosure may condense on PCBA or components due to a temperature changes or different temperature levels and can lead to a moisture-related failures. The temperature in the enclosure is also very dependent on the location and the heating of electronic components. Furthermore, the electronics can be mounted nearby to other heating or cooling components in the complex mechanical systems, such as water pump or water meter. The paper concerns the complex transient heat and mass transfer processes between two connected enclosures with one being warm and another cold. The objective of the paper is to develop an in-house code based on the RC approach for predicting and studying the temperature and moisture behaviour inside two connected enclosures. The developed RC model combines one-dimensional description and lumped analysis for heat and mass transport. The modelling of temperature and moisture response is carried out under non-isothermal B3 STANAG ambient conditions. Moreover, the effect of different material of warm enclosure and the heating are considered.

A combined potential flow–BEM model to study the tower shadow effect in wind turbines

This paper aims to improve the understanding of the wind turbine tower shadow effect by developing a model that combines potential flow and blade-element momentum theory. The change in the flow field due to the presence of the tower is discussed in detail, together with the resulting variations in the aerodynamic forces acting on the rotating blades, as well as the effect on the output power and the blade root bending moment. The tower shadow effect is not only due to the change in wind speed but also to the change in angle of attack. A one-dimensional description of the flow field is therefore bound to be inadequate. The impact of the tower diameter and blade-tower clearance on the rotor power and blade root bending moment can be expressed as a quadratic function of a non-dimensional parameter. Apart from a mild Reynolds-number effect, the results presented are independent of turbine size.

Multi-fidelity uncertainty quantification of particle deposition in turbulent pipe flow

Particle deposition in fully-developed turbulent pipe flow is quantified taking into account uncertainty in electric charge, van der Waals strength, and temperature effects. A framework is presented for obtaining variance-based sensitivity in multiphase flow systems via a multi-fidelity Monte Carlo approach that optimally manages model evaluations for a given computational budget. The approach combines a high-fidelity model based on direct numerical simulation and a lower-order model based on a one-dimensional Eulerian description of the two-phase flow. Significant speedup is obtained compared to classical Monte Carlo estimation. Deposition is found to be most sensitive to electrostatic interactions and exhibits largest uncertainty for mid-sized (i.e., moderate Stokes number) particles.

Quantum Tunnelling Driven H2 Formation on Graphene.

It is commonly believed that it is unfavorable for adsorbed H atoms on carbonaceous surfaces to form H2 without the help of incident H atoms. Using ring-polymer instanton theory to describe multidimensional tunnelling effects, combined with ab initio electronic structure calculations, we find that these quantum-mechanical simulations reveal a qualitatively different picture. Recombination of adsorbed H atoms, which was believed to be irrelevant at low temperature due to high barriers, is enabled by deep tunnelling, with reaction rates enhanced by tens of orders of magnitude. Furthermore, we identify a new path for H recombination that proceeds via multidimensional tunnelling but would have been predicted to be unfeasible by a simple one-dimensional description of the reaction. The results suggest that hydrogen molecule formation at low temperatures are rather fast processes that should not be ignored in experimental settings and natural environments with graphene, graphite, and other planar carbon segments.

A Constant Equivalence Ratio Multi-Zone Approach for a Detailed and Fast Prediction of Performances and Emission in CI Engines

<div class="section abstract"><div class="htmlview paragraph">The paper illustrates and validates a novel predictive combustion model for the estimation of performances and pollutant production in CI engines. The numerical methodology was developed by the authors for near real-time applications, while aiming at an accurate description of the air mixing process by means of a multi-zone approach of the air-fuel mass. Charge stratification is estimated via a 2D representation of the fuel spray distribution that is numerically derived by an axial one-dimensional control-volume description of the direct injection. The radial coordinate of each control volume is reconstructed a posteriori by means of a local distribution function. Fuel mass clustered in each zone is further split in ‘liquid’, ‘unburnt’ and ‘burnt’ sub-zones, given the local properties of the fuel spray control volumes with respect to space-time location of modelled ignition delay, liquid length, and flame lift-off. Multiple injections are described on the same numerical grid to account for jet-to-jet axial interactions, whose effects reflect on improved ignition characteristics. The multi-zones are open systems which are discretized on the equivalence ratio; mass is allowed to travel from one to another, causing a 2D charge stratification. For each zone, local thermodynamic properties and NOx production are determined to estimate cylinder-average performances and emissions. The apparent heat release rate, in-cylinder pressure, BSFC and NOx emissions are validated against experimental data of full map of a light-duty engine. The computational effort of the model is relatively low, which makes the approach suitable for static optimization, to be used in 1-D simulation codes for transient’s optimization and can be run in parallel with a real time 1-D gas model for the simulation of long driving cycles.</div></div>

Influence of Xe-gas concentration on the amplification of macroscopic instabilities in Ne/Xe/HCl pulsed discharge

The effect of varying xenon content in Ne/Xe/HCl mixtures on the discharge characteristics, with a non-uniform preionization conditions, is clarified in the frame of this work. With these mixtures, the excimer lasers and lamps are generated. The present study is performed using a transverse one-dimensional description of the plasma discharge. In this description, a set of resistances in a parallel connection represents the plasma, and in which the value of each one depending on the electron density. The computational results show clearly, that the xenon content can also contribute to the worsening of the macroscopic non-uniformity occurring in such mixtures. At the plasma center, the densities of current and deposited power pass from values 0.4 kA/cm2, 9.7 MW/cm3 for [Xe]=0.5% to values 0.75 kA/cm2, 24.6 MW/cm3 for [Xe]=5%, respectively.

A Kirchhoff-like theory for hard magnetic rods under geometrically nonlinear deformation in three dimensions

Magneto-rheological elastomers (MREs) are functional materials that can be actuated by applying an external magnetic field. MREs comprise a composite of hard magnetic particles dispersed into a nonmagnetic elastomeric (soft) matrix. Hard MREs have been receiving particular attention because the programmed magnetization remains unchanged upon actuation. Motivated by a new realm of applications, there have been significant theoretical developments in the continuum (three-dimensional) description of hard MREs. In this paper, we derive an effective theory for MRE rods (slender, mono-dimensional structures) under geometrically nonlinear deformation in three dimensions. Our theory is based on reducing the three-dimensional magneto-elastic energy functional for the hard MREs into an one-dimensional Kirchhoff-like description (centerline-based). Restricting the theory to two dimensions, we reproduce previous works on planar deformations. For further validation in the general case of three-dimensional deformation, we perform precision experiments with both naturally straight and curved rods under either constant or constant-gradient magnetic fields. Our theoretical predictions are in excellent agreement with both discrete simulations and precision-model experiments. Finally, we discuss some limitations of our framework, as highlighted by the experiments, where long-range dipole–dipole interactions, which are neglected in the theory, can play a role.

Plasma-wall self-organization in magnetic fusion

This paper introduces the concept of plasma-wall self-organization (PWSO) in magnetic fusion. The basic idea is the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates. Both a zero and a one-dimensional description of PWSO are provided. They lead to an iterative equation whose equilibrium fixed point is unstable above some threshold. This threshold corresponds to a radiative density limit, which can be reached for a ratio of total radiated power to total input power as low as 1/2. When detachment develops and physical sputtering dominates, this limit is progressively pushed to very high values if the radiation of non-plate impurities stays low. Therefore, PWSO comes with two basins for this organization: the usual one with a density limit, and a new one with density freedom, in particular for machines using high-Z materials. Two basins of attraction of PWSO are shown to exist for the tokamak during start-up, with a high density one leading to this freedom. This basin might be reached by a proper tailoring of ECRH assisted ohmic start-up in present middle-size tokamaks, mimicking present stellarator start-up. In view of the impressive tokamak DEMO wall load challenge, it is worth considering and checking this possibility, which comes with that of more margins for ITER and of smaller reactors.

Dichotomic ratchet in a two-dimensional corrugated channel.

We consider a particle diffusing in a two-dimensional (2D) channel of varying width h(x). It is driven by a force of constant magnitude f but random orientation there or back along the channel. We derive the effective generalized Fick-Jacobs equation for this system, which describes the dynamics of such a particle in the longitudinal coordinate x. Aside from the effective diffusion coefficient D(x), our mapping also generates an additional effective potential -γ(x) added to the entropic potential -log[h(x)]. It acquires an increasing or decreasing component in asymmetric periodic channels, and thus it explains appearance of the ratchet current. We study this effect on a trial example and compare the results of our true 2D theory with a commonly used effective one-dimensional description; the data are verified by the numerical solution of the full 2D problem.

Two-dimensional diffusion biased by a transverse gravitational force in an asymmetric channel: Reduction to an effective one-dimensional description.

We focus on the derivation of a general position-dependent effective diffusion coefficient to describe two-dimensional (2D) diffusion in a narrow and smoothly asymmetric channel of varying width under a transverse gravitational external field, a generalization of the symmetric channel case using the projection method introduced earlier by Kalinay and Percus [P. Kalinay and J. K. Percus, J. Chem. Phys. 122, 204701 (2005)10.1063/1.1899150]. To this end, we project the 2D Smoluchowski equation into an effective one-dimensional generalized Fick-Jacobs equation in the presence of constant force in the transverse direction. The expression for the diffusion coefficient given in Eq.(34) is our main result. This expression is a more general effective diffusion coefficient for narrow 2D channels in the presence of constant transverse force, which contains the well-known previous results for a symmetric channel obtained by Kalinay, as well as the limiting cases when the transverse gravitational external field goes to zero and infinity. Finally, we show that diffusivity can be described by the interpolation formula proposed by Kalinay, D_{0}/[1+(1/4)w^{'2}(x)]^{-η}, where spatial confinement, asymmetry, and the presence of a constant transverse force can be encoded in η, which is a function of channel width (w), channel centerline, and transverse force. The interpolation formula also reduces to well-known previous results, namely, those obtained by Reguera and Rubi [D. Reguera and J. M. Rubi, Phys. Rev. E 64, 061106 (2001)10.1103/PhysRevE.64.061106] and by Kalinay [P. Kalinay, Phys. Rev. E 84, 011118 (2011)10.1103/PhysRevE.84.011118].

Current reversal and particle separation in Brownian transport

In transport of micro- or nanosized particles through a confined structure driven by thermal fluctuations and external forcing---a situation that arises commonly in a variety of fields in physical and biological sciences, efficient and controllable separation of particles of different sizes is an important but challenging problem. We study, numerically and analytically, the diffusion dynamics of Brownian particles through the biologically relevant setting of a spatially periodic structure, subject to static and temporally periodic forcing. Molecular dynamical simulations reveal that the mean velocity in general depends sensitively on the particle size. The phenomenon of current reversal is uncovered, where particles larger than or smaller than a critical size diffuse in exactly opposite directions. This striking behavior occurs in a wide range of the forcing amplitude and provides a mechanism to separate the Brownian particles of different sizes. Besides the forcing amplitude, other parametric quantities characterizing the forcing profile, such as the temporal asymmetry, can also be exploited to modulate or control the transport dynamics of particles of different sizes. To gain a theoretical understanding, we exploit the Fick-Jacobs approximation to obtain a one-dimensional description of the diffusion problem, which enables key quantities characterizing the diffusion process, such as the mean velocity, to be predicted. In the regime of weak forcing, a reasonable agreement between theory and numerical results is achieved. Beyond the weakly forcing regime, the diffusion approximation breaks down, causing the theoretical predictions to deviate from the numerical results, into which we provide physical insights. Our findings have potential applications in optimizing transport in microfluidic devices or through biological channels.