Field Computation Research Articles

Navigating a male dominated domain: experiences of female STEM students in higher education in Ireland

ABSTRACT It is well established that female participation in STEM diminishes at all stages of the education pipeline. National policy in Ireland is focussed on initiatives to address the STEM gender gap from early years to the end of secondary school (age 18/19) education. However, strategy in higher education is limited, with gender equality policy primarily aimed at staff and the broader institution. This qualitative research study, involving in-depth interviews with 21 female STEM students provides new insights into the experiences of female students who choose mathematics-intensive STEM fields (physics, computer science, engineering, and mathematics), where the gender gap is most pronounced. The aim of the study was to identify how a predominately male-dominated STEM course and environment influenced female students’ experiences. Prior to entering university, participants held high self-concept and interest in STEM. Using a situated expectancy-value theoretical lens to interpret the data, the research found that unconscious gender bias in university led female students to feel undervalued by their male peers. This negatively impacted their self-beliefs and interest, resulting in female students feeling more pressure to perform and less willing to participate in the learning environment. The implications for policy, practice, and future research are considered.

Improved cosmic microwave background (de-)lensing using general spherical harmonic transforms

Deep cosmic microwave background polarization experiments allow a very precise internal reconstruction of the gravitational lensing signal in principle. For this aim, likelihood-based or Bayesian methods are typically necessary, where very large numbers of lensing and delensing remappings on the sphere are sometimes required before satisfactory convergence. We discuss here an optimized piece of numerical code in some detail that is able to efficiently perform both the lensing operation and its adjoint (closely related to delensing) to arbitrary accuracy, using nonuniform fast Fourier transform technology. Where applicable, we find that the code outperforms current widespread software by a very wide margin. It is able to produce high-resolution maps that are accurate enough for next-generation cosmic microwave background experiments on the timescale of seconds on a modern laptop. The adjoint operation performs similarly well and removes the need for the computation of inverse deflection fields. This publicly available code enables de facto efficient spherical harmonic transforms on completely arbitrary grids, and it might be applied in other areas as well.

Cosmology inference at the field level from biased tracers in redshift-space

Cosmology inference of galaxy clustering at the field level with the EFT likelihood in principle allows for extracting all non-Gaussian information from quasi-linear scales, while robustly marginalizing over any astrophysical uncertainties. A pipeline in this spirit is implemented in the LEFTfield code, which we extend in this work to describe the clustering of galaxies in redshift space. Our main additions are: the computation of the velocity field in the LPT gravity model, the fully nonlinear displacement of the evolved, biased density field to redshift space, and a systematic expansion of velocity bias. We test the resulting analysis pipeline by applying it to synthetic data sets with a known ground truth at increasing complexity: mock data generated from the perturbative forward model itself, sub-sampled matter particles, and dark matter halos in N-body simulations. By fixing the initial-time density contrast to the ground truth, while varying the growth rate f, bias coefficients and noise amplitudes, we perform a stringent set of checks. These show that indeed a systematic higher-order expansion of the velocity bias is required to infer a growth rate consistent with the ground truth within errors. Applied to dark matter halos, our analysis yields unbiased constraints on f at the level of a few percent for a variety of halo masses at redshifts z = 0, 0.5, 1 and for a broad range of cutoff scales 0.08 h/Mpc≤ Λ ≤ 0.20 h/Mpc. Importantly, deviations between true and inferred growth rate exhibit the scaling with halo mass, redshift and cutoff that one expects based on the EFT of Large Scale Structure. Further, we obtain a robust detection of velocity bias through its effect on the redshift-space density field and are able to disentangle it from higher-derivative bias contributions.

Thermogravitational Convection in a Multiple Baffled Enclosure Filled with Magneto-Hybrid Nanofluid Subjected to Magnetic Field Dependent Viscosity

This study explores the significant impacts of thin baffles and magnetic field dependent viscosity on magnetohydrodynamic (MHD) thermogravitational convection of Cu-Al2O3 (50%–50%) water hybrid nanoliquid in a cavity. Considering different arrangements of baffle sticks on both the vertical walls, four geometrical configurations (Case-I, Case-II, Case-III and Case-IV) have been analyzed. Numerical simulation has been performed for the governing Navier-Stokes (N-S) equations in streamfunction - vorticity form having energy equation. These coupled equations are solved by proposing a higher-order compact finite difference method. The combination of five important aspects (hybrid nanofluid, multiple baffles, magnetic field dependent viscosity (MFDV), magnetic field and compact computation) signifies the novelty of this work. Fluid flow and transportation of thermal energy within the stipulated domain are presented for various flow pertinent parameters. The outcomes show that the increase in number of baffles diminishes the average Nusselt number values. It is concluded here that an increase in Hartmann number from 0 to 90 leads to a decrease in average Nusselt number up to 23.7% for Case-I, 23.8% for Case-II, 21.2% for Case-III and 28% for Case-IV in presence of MFDV effects.

Quantum Computing: Fundamentals, Progress, and Implications

Abstract: Quantum computing, an interdisciplinary field blending quantum mechanics and computer science, holds promise to revolutionize computational capabilities. Unlike classical computers, which utilize bits to process information in a binary fashion, quantum computers deploy qubits, capable of existing in multiple states simultaneously due to superposition. This unique property, paired with entanglement, offers unparalleled processing power, positioning quantum computing to tackle problems deemed unsolvable by classical means. While heralded for potential applications in cryptography, drug discovery, and complex modeling, quantum computing faces challenges including decoherence, scalability, and error correction. This paper delves into the foundational principles of quantum computing, its current advancements, the vast applications it could revolutionize, and the significant challenges and societal implications it brings. Through comprehensive exploration, we aim to shed light on both the transformative potential of quantum computing and the hurdles that lay in its path.

LibFastMesh: An optimized finite-volume framework for computational aeroacoustics

This paper presents an optimized framework for simulating aeroacoustic flow on unstructured meshes. The libFastMesh (LFM) framework is based on a low-dissipation finite–volume discretization, together with high-order explicit time integration, for direct computation of aeroacoustic fields. These methods were previously implemented in caafoam, an OpenFOAM-based solver developed by D'Alessandro et al. [1] to resolve aeroacoustic flows. The new framework is specifically developed from scratch to alleviate two of the main bottlenecks currently limiting the performance of OpenFOAM-based solvers at large scale: memory bandwidth and inter-node communication. Compact data structures and compute kernel fusion are employed to enhance cache utilization and re-use, respectively. Separate treatment of inter-process boundary cells, together with non-blocking MPI communication enable effective overlap between communication and flux computations. The accuracy and robustness of libFastMesh are established via simulations of well-established aeroacoustic flow benchmarks. Comparison to previous simulation results obtained with caafoam, and to DNS data serve to validate the code. Finally, the effectiveness of the aforementioned optimizations is demonstrated through rigorous analysis of the proposed solver performance in single-node and multi-node operation modes. The obtained results show that libFastMesh offers a speed-up of up to 20x with respect to the previously developed OpenFOAM-based solver, caafoam, in large-scale computations. Moreover, LFM is shown to scale extremely for cell-per-core ratios of less than 500. These results are particularly appealing given the highly resource-demanding nature of direct computational aeroacoustics (CAA). Consequently, LFM could be an extremely attractive tool for scientists who wish to conduct large-scale CAA simulations on modern, exascale architectures. Program summaryProgram Title: libFastMeshCPC Library link to program files:https://doi.org/10.17632/7w9fy2xtcf.1Developer's repository link:https://github.com/TRC-HPC/LFM_PublicLicensing provisions: GPLv3Programming language: C++Nature of problem: This software solves compressible Navier–Stokes equations. The adopted numerics and flow models allow to capture with high accuracy aerodinamically generated sound. The solver is also designed to take advantage of the massively parallel computing systems which are strictly required for facing real–life aeroacoustic problems.Solution method: The libFastMesh (LFM) framework is based on a low-dissipation finite–volume discretization, together with high-order explicit time integration, for direct computation of aeroacoustic fields on unstructured meshes. Convective terms can be approximated using either the Kurganov–Noelle–Petrova (KNP) scheme or Pirozzoli's energy conserving approach. Time integration is fully–explicit and relies on a low-storage, 4th order Runge–Kutta scheme. The solver is specifically developed to run efficiently on modern many-core CPUs, and at large-scale where it exhibits excellent strong scaling features. This is made possible thanks to several optimizations that alleviate memory bandwidth and inter-node communication bottlenecks.Additional comments: OpenFOAM-v2112+ is an installation prerequisite. Standard OpenFOAM pre-processing and post-processing tools, as well as mesh decomposition and reordering methods may be used with the solver.

A well-balanced and exactly divergence-free staggered semi-implicit hybrid finite volume / finite element scheme for the incompressible MHD equations

We present a new exactly divergence-free and well-balanced hybrid finite volume/finite element scheme for the numerical solution of the incompressible viscous and resistive magnetohydrodynamics (MHD) equations on staggered unstructured mixed-element meshes in two and three space dimensions. The equations are split into several subsystems, each of which is then discretized with a particular scheme that allows to preserve some fundamental structural features of the underlying governing PDE system also at the discrete level. The pressure is defined on the vertices of the primary mesh, while the velocity field and the normal components of the magnetic field are defined on an edge-based/face-based dual mesh in two and three space dimensions, respectively. This allows to account for the divergence-free conditions of the velocity field and of the magnetic field in a rather natural manner. The non-linear convective and the viscous terms in the momentum equation are solved at the aid of an explicit finite volume scheme, while the magnetic field is evolved in an exactly divergence-free manner via an explicit finite volume method based on a discrete form of the Stokes law in the edges/faces of each primary element. The latter method is stabilized by the proper choice of the numerical resistivity in the computation of the electric field in the vertices/edges of the 2D/3D elements. To achieve higher order of accuracy, a piecewise linear polynomial is reconstructed for the magnetic field, which is guaranteed to be exactly divergence-free via a constrained L2 projection. Finally, the pressure subsystem is solved implicitly at the aid of a classical continuous finite element method in the vertices of the primary mesh and making use of the staggered arrangement of the velocity, which is typical for incompressible Navier-Stokes solvers. In order to maintain non-trivial stationary equilibrium solutions of the governing PDE system exactly, which are assumed to be known a priori, each step of the new algorithm takes the known equilibrium solution explicitly into account so that the method becomes exactly well-balanced. We show numerous test cases in two and three space dimensions in order to validate our new method carefully against known exact and numerical reference solutions. In particular, this paper includes a very thorough study of the lid-driven MHD cavity problem in the presence of different magnetic fields and the obtained numerical solutions are provided as free supplementary electronic material to allow other research groups to reproduce our results and to compare with our data. We finally present long-time simulations of Soloviev equilibrium solutions in several simplified 3D tokamak configurations, showing that the new well-balanced scheme introduced in this paper is able to maintain stationary equilibria exactly over very long integration times even on very coarse unstructured meshes that, in general, do not need to be aligned with the magnetic field.

Modern Methods of Sound Propagation Modeling Based on the Expansion of Acoustic Fields over Normal Modes

A review of modern methods of modeling acoustic fields based on their representation as a superposition of normal modes is presented. Most of the described methods are based on an approach to calculating mode amplitudes by solving parabolic equations of various types, both narrow-angle and wide-angle. We also consider two-dimensional methods for calculating acoustic fields, to which the above-mentioned three-dimensional approaches are reduced in the absence of dependence of the field and medium parameters on one of the horizontal coordinates. The computation of both time-harmonic acoustic fields and pulsed sound signals is discussed. A number of numerical examples are considered in which such calculations are performed taking into account three-dimensional sound propagation effects. For the first time within the framework of this approach, the calculation of particle accelerations at the pulse signal reception points, as well as the calculation of the energy density flux of the vector field were performed.

Effective Government Management of Flood Discharge in Drainage Channels using HEC-RAS 6.3.1 Application

Flooding remains one of the most significant natural disasters affecting communities around the world. Proper management of flood discharge in drainage channels is essential to mitigate its impacts on public safety, infrastructure, and the environment. In recent years, advancements in hydrodynamic modeling tools, such as the Hydraulic Engineering Center's River Analysis System (HEC-RAS) 6.3.1, have provided governments with powerful tools to analyze and manage flood discharges effectively. This research aims to investigate the role of government-led management strategies in handling flood discharge within drainage channels using the HEC-RAS 6.3.1 application. The study assesses how the application's features and capabilities can be harnessed by governmental agencies to make informed decisions and implement effective flood management plans. The research methodology involves a combination of field surveys, data collection, and computer simulations using the HEC-RAS 6.3.1 software. Geographic information systems (GIS) data, topographical surveys, and historical flood records are utilized to calibrate and validate the model's accuracy. Various flood scenarios are simulated to assess the performance of different government-led management strategies. The findings of this study reveal that the integration of HEC-RAS 6.3.1 with government-led management approaches enhances the understanding of flood dynamics within drainage channels. The application facilitates the identification of critical flood-prone areas, prediction of potential flood events, and evaluation of flood mitigation measures. The government can utilize this valuable information to formulate more effective flood management policies and allocate resources efficiently.

Hygromechanical Behavior of Polyamide 6.6: Experiments and Modeling.

This paper investigates water absorption in polyamide 6.6 and the resulting hygroscopic swelling and changes in mechanical properties. First, sorption and swelling experiments on specimens from injection molded plates are presented. The observed swelling behavior is dependent on the melt flow direction of the injection molding process. Additionally, thermal analysis and mechanical tensile tests were performed for different conditioning states. The water sorption is accompanied by a decrease in the glass transition temperature and a significant reduction in stiffness and strength. Next, a sequentially coupled modeling approach is presented. A nonlinear diffusion model is followed by mechanical simulations accounting for swelling and concentration-dependent properties. For the mechanical properties, the notion of a "gap" temperature caused by the shift of the glass transition range due to water-induced plasticization is employed. This model enables the computation of local moisture concentration fields and the resultant swelling and changes in stress-strain behavior.

Computation of Electric Field and Potential Distribution of 110KV Polymer Insulator

The electric field (E-Field) and potential distribution are more important in deciding the lifetime of the insulator. Different climate conditions and several pollution conditions lead to the deterioration and degradation of the insulator's properties, increasing the electric stress and exceeding the threshold value during long working conditions, leading to the failure of the insulator. This project mainly focuses on improving the reduction of electric stress by using different side positions of the corona ring an optimizing corona ring placement on a 110 kV AC transmission line composite insulator. The Corona ring plays a significant role in the reduction of electric stress. Analyze the performance of three different positions of the corona ring: HV and LV side, LV side, and HV side, and implement the three different optimizations in the Bobyqa, Nelder-Mead, and Cobyla optimizations to achieve uniform distribution. The results show that HV-side corona ring placement significantly reduces electric stress, and Bobyqa optimization greatly reduces electrical stress compared to other optimization techniques.

Brauer-Manin obstructions on hyperelliptic curves

We describe a practical algorithm for computing Brauer-Manin obstructions to the existence of rational points on hyperelliptic curves defined over number fields. This offers advantages over descent based methods in that its correctness does not rely on rigorous class and unit group computations of large degree number fields. We report on experiments showing it to be a very effective tool for deciding existence of rational points: Among a random samples of curves over Q of genus at least 5 we were able to decide existence of rational points for over 99% of curves. We also demonstrate its effectiveness for high genus curves, giving an example of a genus 50 hyperelliptic curve with a Brauer-Manin obstruction to the Hasse Principle. The main theoretical development allowing for this algorithm is an extension of the descent theory for abelian torsors to a framework of torsors with restricted ramification.

A MATLAB toolbox for computation of velocity and strain rate field from GNSS coordinate time series

We propose a MATLAB toolbox for the computation of the strain rate field from the coordinate time series of some continuous GNSS stations. It consists of several functions, also compatible with GNU Octave, implementing the following steps: (i) time series download from a data repository (e.g., the Nevada Geodetic Laboratory database); (ii) calculation of velocities of the selected stations by means of the Maximum Likelihood Estimation (MLE) method implemented in the external package Hector, including modeling of offsets, outliers, noise and periodic components; (iii) (optional) filtering of Common Mode Errors; (iv) calculation of the strain rate field with the modified least squares method, in which a scale factor can be introduced to define the locality of the deformation analysis and, besides uncertainty estimation, a geometric evaluation of the significance of the results is provided; (v) visualization of the results for immediate use and easy interpretation for scientific purposes. The toolbox is divided into two components: the first one, named StaVel, performs the steps (i)-(iii) and the second component, GridStrain, performs the steps (iv) and (v). The potential of the toolbox is demonstrated on a real dataset. Time series from several continuous GNSS stations in South-Eastern Sicily (Southern Italy) are processed by means of StaVel and GridStrain in order to provide the strain rate field.

Phased array probes for air-coupled ultrasonic testing based on cellular polymer

Air-coupled ultrasonic testing is an established alternative to conventional ultrasonic methods for testing of light-weight components in aerospace and automotive industry. Compared to direct coupled contact technique or immersion technique it is less invasive, so that it offers numerous financial incentives. While phased arrays are already an industrial standard in fluid-coupled mechanized ultrasonic testing, air-coupled testing is usually performed using two single-element probes and a transmission technique. Therefore, advantages of phased arrays such as active focussing and manipulation of the incidence angle are rarely used with air-coupled testing. This paper presents a newly developed air-coupled phased array device with the emphasis on the characterization of the probes. The device consists of a linear array probe, a transmitter unit and a receiver unit. The main novelty is that the array probe is based on high-voltage excitation of charged cellular polypropylene. Charged cellular polymers are referred to as ferroelectrets or as piezoelectrets. They exhibit an extremely low stiffness and acoustic impedance, so that a matching layer is not necessary. Extremely low mechanical cross-coupling enables independent excitation of the elements of the array. The development of the phased array probes is supported by computations of the sound field using point source synthesis. The main intended applications are transmission with focussing, transmission with an electronic sweep and testing with air-coupled guided waves by using beam steering, applied to carbon-fibre-reinforced plates and similar materials. Air-coupled guided waves enable testing of objects with one-sided access. This work was funded from the “Technologietransfer-Programm Leichtbau” by the German Federal Ministry for Economic Affairs and Climate Action, project 03LB1001A.

A Review of Formulations, Boundary Value Problems and Solutions for Numerical Computation of Transcranial Magnetic Stimulation Fields.

Since the inception of the transcranial magnetic stimulation (TMS) technique, it has become imperative to numerically compute the distribution of the electric field induced in the brain. Various models of the coil-brain system have been proposed for this purpose. These models yield a set of formulations and boundary conditions that can be employed to calculate the induced electric field. However, the literature on TMS simulation presents several of these formulations, leading to potential confusion regarding the interpretation and contribution of each source of electric field. The present study undertakes an extensive compilation of widely utilized formulations, boundary value problems and numerical solutions employed in TMS fields simulations, analyzing the advantages and disadvantages associated with each used formulation and numerical method. Additionally, it explores the implementation strategies employed for their numerical computation. Furthermore, this work provides numerical expressions that can be utilized for the numerical computation of TMS fields using the finite difference and finite element methods. Notably, some of these expressions are deduced within the present study. Finally, an overview of some of the most significant results obtained from numerical computation of TMS fields is presented. The aim of this work is to serve as a guide for future research endeavors concerning the numerical simulation of TMS.

Second-order accurate normal reconstruction from volume fractions on unstructured meshes with arbitrary polyhedral cells

This paper introduces a novel method for the computation of accurate normal fields from volume fractions on unstructured polyhedral meshes. For surfaces of considerable curvature variation, the method is second-order accurate with respect to symmetric volume differences and first-order accurate with respect to normal field angular deviation. For this purpose, an averaged normal is locally computed, i.e. in each mesh cell, by fitting a plane in a least squares sense with appropriate weights to the volume fraction data of neighbouring cells while explicitly accounting for volume conservation in the cell at hand. The resulting minimization problem is solved approximately by means of a Newton-type method. Moreover, employing the Reynolds transport theorem allows for both assessing the regularity of the derivatives of the least squares error functional with respect to the free parameters and to exactly compute these derivatives at small additional costs. Since the divergence theorem implies that the volume fraction can be written as a sum of face-based quantities, our method considerably simplifies the numerical procedure for applications in three spatial dimensions while demonstrating an inherent ability to robustly deal with unstructured meshes.We discuss the theoretical foundations, regularity and appropriate error measures, along with the details of the numerical algorithm. Finally, numerical results for convex and non-convex hypersurfaces embedded in cuboidal and tetrahedral meshes are presented together with a convergence study considering two different error measures. Moreover, our findings are complemented by profound insights into the minimization procedure.

Activity Design for Secondary School Students’ Modeling Skills: A Design-Based Research

Models and modeling process have been used for many years in science education courses, which contain many concepts that are difficult to understand and abstract. With the help of models, students improve their knowledge level related to the subject and realize learning by hands-on activities in the production process. In the model production process, they perform some behaviours called modeling skills. The purpose of this study is to design computer-based activities to develop students' skills. In this context, design-based research method was used in the activity development process. Activities were developed within the framework of a total of two cycles. Within the scope of the first cycle, drafts of the activities were made, and the activities were transferred to Adobe Flash environment with field educators and computer experts. In the first cycle, the activities applied to 11 middle school students were made necessary arrangements before the second cycle, and after the second cycle, the activities were finalized. At the end of the development process, a total of six computer-based activities were achieved. With the help of these activities, various applications can be made for the students' related modeling skills. In this way, students can produce better models and develop their level of conceptual knowledge about science lesson subjects.

A GPU-parallelized interpolation-based fast multipole method for the relativistic space-charge field calculation

The fast multipole method (FMM) has received growing attention in the beam physics simulation. In this study, we formulate an interpolation-based FMM for the computation of the relativistic space-charge field. Different to the quasi-electrostatic model, our FMM is formulated in the lab-frame and can be applied without the assistance of the Lorentz transformation. In particular, we derive a modified admissibility condition which can effectively control the interpolation error of the proposed FMM. The algorithms and their GPU parallelization are discussed in detail. A package containing serial and GPU-parallelized solvers is implemented in the Julia programming language. The GPU-parallelized solver can reach a speedup of more than a hundred compared to the execution on a single CPU core.

Computational Description of Alkylated Iron-Sulfur Organometallic Clusters.

The radical S-adenosyl methionine (SAM) enzyme superfamily has widespread roles in hydrogen atom abstraction reactions of crucial biological importance. In these enzymes, reductive cleavage of SAM bound to a [4Fe-4S]1+ cluster generates the 5'-deoxyadenosyl radical (5'-dAdo•) which ultimately abstracts an H atom from the substrate. However, overwhelming experimental evidence has surprisingly revealed an obligatory organometallic intermediate Ω exhibiting an Fe-C5'-adenosyl bond, whose properties are the target of this theoretical investigation. We report a readily applied, two-configuration version of broken symmetry DFT, denoted 2C-DFT, designed to allow the accurate description of the hyperfine coupling constants and g-tensors of an alkyl group bound to a multimetallic iron-sulfur cluster. This approach has been validated by the excellent agreement of its results both with those of multiconfigurational complete active space self-consistent field computations for a series of model complexes and with the results from electron nuclear double-resonance/electron paramagnetic resonance spectroscopic studies for the crystallographically characterized complex, M-CH3, a [4Fe-4S] cluster with a Fe-CH3 bond. The likewise excellent agreement between spectroscopic results and 2C-DFT computations for Ω confirm its identity as an organometallic complex with a bond between an Fe of the [4Fe-4S] cluster and C5' of the deoxyadenosyl moiety, as first proposed.

Investigating Supply and Demand in European Cohesion Policy: Micro-Foundations of Macro-Behaviours

European Cohesion Policy is a complex scheme that allocates financial resources to European regions. The implementation of the policy is based on an articulated multi-level governance that involves local and national authorities and the European Commission. Local authorities often face difficulties in using structural funds due to limits in their administrative capacity (supply) and/or inefficiencies in adequately stimulating applications’ submission (demand). By modelling and simulating the implementation of the policy, we explore how operations and decisions at the local authorities’ and potential applicants’ level (micro-foundations) explain emerging patterns of funds’ absorption at a regional level (macro-behaviours). Building upon a mixed-methods approach combining field research and computer simulation, we develop a model capturing the key cause–effect relationships among agents and resources within the Cohesion Policy supply-and-demand system. The outcomes elucidate how poor local administrative capabilities, including staff skills, may entail delays and low absorption performances, while showcasing the factors affecting potential applicants’ decision to submit.