Fidelity Approach Research Articles

A variable fidelity approach for predicting aerodynamic wall quantities of hypersonic vehicles using the ConvNeXt encoder-decoder framework

Computational fluid dynamics (CFD) simulations for obtaining three-dimensional hypersonic vehicle aerodynamic characteristics are resource-intensive. Deep learning offers a promising alternative for predicting aerodynamic wall quantities but typically requires a large dataset, which conflicts with the intention to reduce CFD costs. To address this, we propose a novel prediction model leveraging variable fidelity data to alleviate computational demands. The model utilizes an encoder-decoder architecture with ConvNeXt blocks as operators, processing variable fidelity data as inputs and outputs. We also developed a U-Net with residual blocks (ResUNet) for performance comparison. Transformation and topology patching techniques were applied to tackle the challenges posed by large grid volumes and complex topologies in three-dimensional vehicles. Results demonstrate that the ConvNeXt Encoder-Decoder predicts peak regions more accurately than ResUNet and aligns closely with CFD in low-value areas. The ConvNeXt Encoder-Decoder maintains maximum heat flux errors below 1 % and viscous drag errors below 3.81 % across varying angles of attack. It exhibits superior fitting performance with minimal deviation from CFD compared to ResUNet. Prediction accuracy decreases under multiple inflow changes compared to the angle of attack variations alone. Heat flux predictions show high consistency with CFD, with relative errors below 6.38 %, whereas friction predictions exhibit higher errors with 10.28 % maximum error and 0.28 % minimum error. The model accurately predicts friction variation trends in peak regions at the blunt edge's central plane but performs poorly in low-value areas. In summary, the ConvNeXt Encoder-Decoder accurately predicts the wall quantities under varying multiple inflow conditions.

Real-time millimeter wave holography with an arrayed detector.

Millimeter and terahertz wave imaging has emerged as a powerful tool for applications such as security screening, biomedical imaging, and material analysis. However, intensity images alone are often insufficient for detecting variations in the dielectric constant of a sample, and extraction of material properties without additional phase information requires extensive prior knowledge of the sample. Digital holography provides a means for intensity-only detectors to reconstruct both amplitude and phase images. Here we utilize a commercially available source and detector array, both operating at room temperature, to perform digital holography in real-time for the first time in the mm-wave band (at 290 GHz). We compare the off-axis and phase-shifting approaches to digital holography and discuss their trade-offs and practical challenges in this regime. Owing to the low pixel count, we find phase-shifting holography to be the most practical and high fidelity approach for such commercial mm-wave cameras even under real-time operational requirements.

A machine learning method of accelerating multiscale analysis for spatially varying microstructures

Multiscale computing for heterogeneous materials provides a powerful and fidelity approach to handling situations where a suitable macroscopic constitutive model is unavailable. However, there have been very few instances in the industrial sector where concurrent multiscale modeling techniques have been adopted, primarily because they require significant computational resources. In particular, when dealing with large numbers of representative volume elements (RVEs) with different microstructure morphologies throughout the macrostructure. In this paper, the novelty lies in providing an artificial neural network (ANN) model-based multiscale approach for accelerating multiscale analysis of the elliptical inclusion-reinforced composites with spatially varying microstructures, which give up the assumption of global periodicity. To tackle this challenge, firstly, a series of RVEs with different microstructure morphologies characterized by inclusion orientations and aspect ratios, under different load conditions, are simulated to generate training data. Second, the back propagation neural network (BPNN) is trained offline using data acquired from the RVE simulation for learning the underlying and possibly RVE morphologies. The trained BPNN replaces the complex microscopic mechanical solution problems over each macroscopic integration point at each iteration, to update the macroscopic stress-strain responses and it significantly reduces the computational cost of multiscale simulations. Then, the trained neural network is implemented on ABAQUS via user-defined materials (UMAT) and its effectiveness is verified by comparison with the classical multiscale finite element method (FE2) method. Finally, the outstanding computational capability of the proposed approach is further demonstrated through two numerical examples.

A high fidelity approach to assembling the complex Borrelia genome

BackgroundBacteria of the Borrelia burgdorferi sensu lato (s.l.) complex can cause Lyme borreliosis. Different B. burgdorferi s.l. genospecies vary in their host and vector associations and human pathogenicity but the genetic basis for these adaptations is unresolved and requires completed and reliable genomes for comparative analyses. The de novo assembly of a complete Borrelia genome is challenging due to the high levels of complexity, represented by a high number of circular and linear plasmids that are dynamic, showing mosaic structure and sequence homology. Previous work demonstrated that even advanced approaches, such as a combination of short-read and long-read data, might lead to incomplete plasmid reconstruction. Here, using recently developed high-fidelity (HiFi) PacBio sequencing, we explored strategies to obtain gap-free, complete and high quality Borrelia genome assemblies. Optimizing genome assembly, quality control and refinement steps, we critically appraised existing techniques to create a workflow that lead to improved genome reconstruction.ResultsDespite the latest available technologies, stand-alone sequencing and assembly methods are insufficient for the generation of complete and high quality Borrelia genome assemblies. We developed a workflow pipeline for the de novo genome assembly for Borrelia using several types of sequence data and incorporating multiple assemblers to recover the complete genome including both circular and linear plasmid sequences.ConclusionOur study demonstrates that, with HiFi data and an ensemble reconstruction pipeline with refinement steps, chromosomal and plasmid sequences can be fully resolved, even for complex genomes such as Borrelia. The presented pipeline may be of interest for the assembly of further complex microbial genomes.

Simulating the helix wake within an actuator disk framework: verification against discrete-blade type simulations

Dynamic flow control strategies are raising interest for wake mitigation purposes. Among the different strategies, the so-called helix one relies on individual pitch control (IPC). The numerical simulation of the helix is thus readily performed by means of discrete-blade capturing methods. Yet, if this control strategy is considered at the scale of wind farms, the resolution required by such methods becomes prohibitive and actuator disk (AD) models should be envisioned. It is however not trivial to translate IPC strategies to an AD framework which by definition considers rotor-averaged effects. This work assesses the ability of an AD method to simulate the helix strategy by comparing it to a higher fidelity approach relying on a discrete-blade capturing model. Results show that the disk-type approach supplemented with a disk-adapted IPC scheme is able to capture both the forced motion of the wake at low turbulence and the faster wake recovery at moderate turbulence. From a quantitative perspective, the disk-type approach predicts bigger power gains, compared to those foreseen by the discrete-blade type approach, for a downstream turbine in the wake of a helix-operated one.

Curriculum Implementation Approaches of Secondary School English Teachers: A Case Study

Purpose: The purpose of this study is to identify the curriculum implementation approaches of secondary school English teachers.
 Design/Methodology/Approach: The study group of this qualitative case study consists of 14 English teachers and students studying in the classes of these teachers. In determination of the study group, maximum variation and criterion sampling was used. The data of the study was obtained by observations, interviews, document review and it was analyzed by qualitative content analysis technique with an interpretive qualitative approach.
 Findings: Study results indicated that English teachers have basically three different approaches while implementing the curriculum: curriculum fidelity, curriculum adaptation and curriculum design. In each three approaches teachers make student-based and exam-based implementations. However, under the curriculum adaptation approach, the student-based and exam-based adaptations made by teachers during their implementations are philosophically so different from each other that they worth mentioning under a different sub-title as student-based adaptation and exam-based adaptation. Teachers who adopt curriculum fidelity approach tend to apply the curriculum materials without making any change while teachers with curriculum adaptation approach make some adaptations in these materials. In the student-based adaptation approach, teachers make these adaptations by taking student characteristics into account, while in the exam-based approach, the focus of the teachers is to prepare students for national exams or the exam of the course. Teachers with curriculum design approach teach in private schools and do not make use of curriculum materials during their instruction. These teachers have more flexibility in their classroom practices compared to the teachers with curriculum fidelity and adaptation approaches.
 Highlights: Based on the results of this study, it can be suggested to investigate the effect of teachers’ curriculum implementation approaches on their professional development and on their students’ motivation and academic success.

Hybrid data fidelity term approach for quantitative susceptibility mapping

PurposeSusceptibility maps are usually derived from local magnetic field estimations by minimizing a functional composed of a data consistency term and a regularization term. The data‐consistency term measures the difference between the desired solution and the measured data using typically the L2‐norm. It has been proposed to replace this L2‐norm with the L1‐norm, due to its robustness to outliers and reduction of streaking artifacts arising from highly noisy or strongly perturbed regions. However, in regions with high SNR, the L1‐norm yields a suboptimal denoising performance. In this work, we present a hybrid data fidelity approach that uses the L1‐norm and subsequently the L2‐norm to exploit the strengths of both norms.MethodsWe developed a hybrid data fidelity term approach for QSM (HD‐QSM) based on linear susceptibility inversion methods, with total variation regularization. Each functional is solved with ADMM. The HD‐QSM approach is a two‐stage method that first finds a fast solution of the L1‐norm functional and then uses this solution to initialize the L2‐norm functional. In both norms we included spatially variable weights that improve the quality of the reconstructions.ResultsThe HD‐QSM approach produced good quantitative reconstructions in terms of structural definition, noise reduction, and avoiding streaking artifacts comparable with nonlinear methods, but with higher computational efficiency. Reconstructions performed with this method achieved first place at the lowest RMS error category in stage 1 of the 2019 QSM Reconstruction Challenge.ConclusionsThe proposed method allows robust and accurate QSM reconstructions, obtaining superior performance to state‐of‐the‐art methods.

LIVE Digital Twin: Developing a Sensor Network to Monitor the Health of Belt Conveyor System

Industry 4.0 requires developing smart systems to maximize the uptime of machines and components. Digital Twins can be defined as a real time exchange of the information between a physical asset and a virtual portrayal in a bidirectional manner. This relationship is best established with a sensor network. LIVE Digital Twin presents a methodology to design model-based Digital Twins for asset management through sensors. This methodology is increasingly useful when the fault history of an asset is not readily available. The LIVE Digital Twin methodology consists of four principle phases, Learn, Identify, Verify, Extend. The goal of this research is to review the application of the LIVE Digital Twin methodology on a case study of a Belt Conveyor System found in the mining industry. Belt Conveyor Systems and their rollers are critical in material transportation and are susceptible to various faulty cases. Using a multi fidelity approach, a case study demonstrates the first two phases of LIVE Digital Twin and identifying the sensor locations. The study concludes with the successful location of 2 sensors on a subassembly of a Belt Conveyor System frame.

Particle-scale computational fluid dynamics simulation on selective parallel dual-laser melting of nickel-based superalloy

A three-dimensional high-fidelity particle-scale computational fluid dynamics (CFD) modeling of a selective parallel dual-laser melting (SPDLM) process is developed, on which dynamics behavior of molten pools of Nickel-based superalloy during SPDLM is simulated. The phenomena of wetting, necking, and pores near the overlapping region in the parallel dual-laser molten pools are especially investigated. The simulated results show that the SPDLM process improves the re-melting rate of the molten pool and the wettability of the overlapping region of the SPDLM molten pool, reducing the probability of defects, especially the probability of lack of fusion. Due to the uniform temperature distribution in the overlapping region of the two tracks and the complete melting, the product quality at the overlapping region of the two molten pools can be better guaranteed when the interval between the parallel dual lasers is 2.5 times of the laser beam radius. The results suggest that the SPDLM technique together with appropriate process parameters can not only increase the printing efficiency, but also improve the surface quality of the overlapping area of the two molten pools. The simulated results also reveal the formation mechanisms of pore defects during the selective multi-laser melting process on a mesoscopic scale. This study shows that the proposed particle-scale CFD model provides a high fidelity approach to characterize the molten pool in the SPDLM process and, therefore, is helpful for the optimal process design for the selective multi-laser melting.

An untested approach to facilitating visually enhanced mental simulation online with multiple learners: A mini guide

Background: The COVID-19 pandemic has affected the world in every aspect. Many universities and education centres adapted their teaching to online education. Virtual simulation has been endorsed by stakeholders not only for teaching healthcare students and workers, but also to be counted as practice hours for students. We propose an approach to facilitate simulation-based education (SBE) online in an interactive manner for multiple participants. Methods: Visually enhanced mental simulation (VEMS) is a low fidelity yet very immersive and engaging educational activity used for participants to practise non-technical skills such as decision-making and communication while others observe. Unlike ordinary mental simulation, participants can engage in VEMS as in a full-scale scenario-based simulation session, while being observed by peers. It is supported with visual elements such as a patient poster and laminated equipment cards for participants to illustrate the actions performed. Actions and patient parameters are also recorded with the timing by a facilitator on a white board. The scenario is followed by a debriefing involving all participants and observers. Recommendations: VEMS can be adapted to the online environment and be facilitated through platforms such as Microsoft Teams, Skype, Zoom, GoToMeeting, or Cisco WebEx easily using a shared screen with Microsoft PowerPoint and their associated chat function or the facilitator's web camera facing a noticeboard. A patient pictogram and transparent background equipment images can be used in PowerPoint to illustrate the actions verbalised by the participants. The facilitator can speak as the patient and illustrate and write down everything in PowerPoint as the participants engage in the scenario, so all the other session attendees can observe. Everyone can then attend the scenario debriefing online. Conclusion: Online VEMS offers an opportunity for participants to practise non-technical and communication skills. It is a low fidelity and low-cost approach to facilitating SBE that still needs to be tested with actual learners for ease of use, acceptability, and educational effectiveness.

Streaking artifact suppression of quantitative susceptibility mapping reconstructions via L1-norm data fidelity optimization (L1-QSM).

The presence of dipole-inconsistent data due to substantial noise or artifacts causes streaking artifacts in quantitative susceptibility mapping (QSM) reconstructions. Often used Bayesian approaches rely on regularizers, which in turn yield reduced sharpness. To overcome this problem, we present a novel L1-norm data fidelity approach that is robust with respect to outliers, and therefore prevents streaking artifacts. QSM functionals are solved with linear and nonlinear L1-norm data fidelity terms using functional augmentation, and are compared with equivalent L2-norm methods. Algorithms were tested on synthetic data, with phase inconsistencies added to mimic lesions, QSM Challenge 2.0 data, and in vivo brain images with hemorrhages. The nonlinear L1-norm-based approach achieved the best overall error metric scores and better streaking artifact suppression. Notably, L1-norm methods could reconstruct QSM images without using a brain mask, with similar regularization weights for different data fidelity weighting or masking setups. The proposed L1-approach provides a robust method to prevent streaking artifacts generated by dipole-inconsistent data, renders brain mask calculation unessential, and opens novel challenging clinical applications such asassessing brain hemorrhages and cortical layers.

Influence of kinetic energy on the metrology of Rabi frequency

The interacting model describing the Rabi transition is essential in studying atom-photon interactions, where the kinetic energy term is often neglected for the convenience of analysis. We first study the approximation through the fidelity approach and verify its valid region in the parameter space of detuning and momentum. We find that as the radiation field’s momentum and the absolute value of detuning decrease, the approximation becomes valid. We further discover that the omission of the kinetic energy term will overestimate the measuring accuracy of the Rabi frequency in some parameter regions and underestimate the precision in other regimes with Fisher information tools’ help. Notably, a specific choice of the initial Gaussian state’s variance in position space will improve the measuring accuracy when we take the kinetic energy term into account. We also study the realistic measurement of the Rabi frequency for cases with and without the kinetic energy.

‘Their Voices Ring in My Ears’: Laura, the Fugue, and Adaptation

Abstract This essay analyzes Vera Caspary’s novel Laura (1943) and the 1944 film adaptation (Preminger) in order to demonstrate an approach to adaptation studies we call fugal. If a fugue is a composition based on a ‘subject’ or short melodic phrase and its various ‘answers’—in other words, variations that maintain elements of the melody but also play with and revise it—how might we position the film as a variation on, rather than a reproduction of, Caspary’s novel? To explore this question, we analyze the sonic register of both the novel and film. Caspary doesn’t want us to merely read her novel; she wants us to listen to the voices that narrate it and the tunes that populate it. Similarly, listening to the film—not simply the dialogue but also the voiceover narration and David Raksin’s groundbreaking score—allows us to identify content not overt in, and sometimes at odds with, the visuals. When we listen critically and carefully, we can distinguish nuances that get lost in a strict fidelity approach; in particular, we can identify both works’ feminist content, especially their attempts to decentre patriarchal hard-boiled conventions and to confound notions of a singular truth.

Measuring the complex spectrum of orbital angular momentum and radial index with a single-pixel detector.

Typical methods to decode a complex orbital-angular-momentum (OAM) spectrum suffer from issues such as a narrow OAM range, unstable interferometer, and long measuring time. In this Letter, we use a single-beam interferometer to measure the complex OAM spectrum with a single-pixel detector. The complex OAM spectrum ranging from -10 to 10 can be measured in 11 ms with the fidelity approach of 97.0%, experimentally. Our approach allows one to characterize an unknown coherent field with any complex basis, e.g., the Laguerre-Gaussian (LG) basis is used for radial index spectrum measurement. Furthermore, single-pixel complex amplitude imaging based on the LG spectrum acquisition is presented, and the advantages in resolution and flexibility are demonstrated.

Reply to "Comment on 'Quantum fidelity approach to the ground-state properties of the one-dimensional axial next-nearest-neighbor Ising model in a transverse field' ".

We disagree with the objections raised by Nemati etal. regarding the phase transitions reported in our paper, where we used the fidelity method. Contrary to their claims, our fidelity calculations do not depend on energy level crossing between excited states. We obtain the same results just by analyzing the second derivative of the ground-state energy with respect to the interaction energy coupling J_{2}.

Teachers’ fidelity to curriculum: an insight from teachers’ implementation of the Indonesian EFL curriculum policy

While the notion of partnership has become the new genre of curriculum implementation, Indonesian government has decided to shift back to centralized curriculum policy by issuing the 2013 curriculum (K-13). The reason is that teachers are incapable of shaping their own school curriculum based on the National Standards of Education. Centralized curriculum policy leaves the classroom as the end of the chain of decisions in which the position of teachers is merely as implementers, rather than involved decision-makers. This type of curriculum clearly demands high degree of teachers’ fidelity. The purpose of this study is to investigate the extent to which EFL teachers faithfully commit themselves to fidelity approach to curriculum implementation of the K-13 at Senior High Schools in Makassar, Indonesia. Four EFL teachers were interviewed using ethnographic interviewing technique. The findings showed that these EFL teachers implement the K-13 with high degree of fidelity. The findings, however, indicate that these teachers’ commitment to fidelity approach split into two distinctive reasons: interactive and coercive. The former means that teachers adhered to K-13 because they perceived it as being comprehensible through their interaction with the K-13 documents, while the latter seemed to be influenced by the K-13 curriculum policy that was typically coercive and top down practice.

Comment on "Quantum fidelity approach to the ground-state properties of the one-dimensional axial next-nearest-neighbor Ising model in a transverse field".

Here we show that, although quantum fidelity can truly identify two quantum phase transitions of a one-dimensional spin-1/2 quantum Ising model with competing nearest and next-nearest neighbor interactions in a transverse magnetic field, it may not be a suitable approach for analyzing its ground-state phase diagram.

Entanglement Detection beyond Measuring Fidelities.

One of the most widespread methods to determine if a quantum state is entangled, or to quantify its entanglement dimensionality, is by measuring its fidelity with respect to a pure state. In this Letter, we find a large class of states whose entanglement cannot be detected in this manner; we call them unfaithful. Wefind that unfaithful states are ubiquitous in information theory. For small dimensions, we check numerically that most bipartite states are both entangled and unfaithful. Similarly, numerical searches in low dimensions show that most pure entangled states remain entangled but become unfaithful when a certain amount of white noise is added. We also find that faithfulness can be self-activated, i.e., there exist instances of unfaithful states whose tensor powers are faithful. To explore how the fidelity approach limits the quantification of entanglement dimensionality, we generalize the notion of an unfaithful state to that of a D unfaithful state, one that cannot be certified as D-dimensionally entangled by measuring its fidelity with respect to a pure state. For describing such states, we additionally introduce a hierarchy of semidefinite programming relaxations that fully characterizes the set of states of Schmidt rank at most D.

Duality and ground-state phase diagram for the quantum XYZ model with arbitrary spin in one spatial dimension

Five duality transformations are unveiled for the quantum XYZ model with arbitrary spin in one spatial dimension. The presence of these duality transformations, together with an extra Hamiltonian symmetry, drastically reduce the entire ground-state phase diagram to two finite regimes—the principal regimes, with all the other ten regimes dual to them. Combining with the determination of critical points from the conventional order parameter approach and/or the fidelity approach to quantum phase transitions, we are able to map out the ground-state phase diagram for the quantum XYZ model with arbitrary spin . This is explicitly demonstrated for and 2. As it turns out, all the critical points, with central charge , are self-dual for half-integer as well as integer spin . However, in the latter case, the presence of the Haldane phase results in extra lines of critical points with central charge , which are not self-dual.

Efficient multi-objective shape optimization using proper orthogonal decomposition with variable fidelity concept

A variable fidelity concept is introduced in a re-parameterization approach based on the proper orthogonal decomposition (POD) to efficiently solve multi-objective aerodynamic shape optimization problems. The re-parameterization approach enables to extract dominant shape deformation modes from a database of good designs and to reduce the number of design variables. The present variable fidelity approach is proposed by utilizing low-fidelity functional evaluations to select the good designs. The proposed approach is investigated in two multi-objective aerodynamic shape optimization problems of 2D airfoil in which the combinations of viscous/inviscid simulations or fine/coarse grid simulations are treated as the high/low-fidelity evaluation methods. It can be confirmed that dominant POD modes obtained from low-fidelity evaluations are qualitatively equivalent with that obtained from high-fidelity evaluations. Non-dominated solutions obtained from a conventional optimization approach can be reproduced with smaller numbers of design variables using the dominant POD modes. The computational costs to solve the multi-objective aerodynamic shape optimization problems can be dramatically reduced by introducing the variable fidelity concept.