Material Boundary Research Articles

Anisotropic quantum transport in a programmable photonic topological insulator

Quantum transport in materials describes the behavior of particles at the quantum level. Topological materials exhibit nontrivial transport properties with topological invariants, leading to the emergence of protected states that are immune against disorders at the material boundaries. In many real-world materials, especially those with anisotropic crystal structures, the transport properties can vary significantly along different directions within the material bulk. Here, we experimentally observe counterintuitive quantum transport phenomena in anisotropic topological insulators with controllable anisotropy and disorder, implemented on a programmable topological photonic chip. We examine phase transition from the topological phase to the Anderson phase, between which a new quasi-diffusive phase emerges. Anisotropic topological transport demonstrates unconventional superior robustness in the bulk mode compared to the edge mode, in the presence of disorder and loss in realistic systems. Peculiar topological transport with sophisticated gradient anisotropy, emulating stretched topological materials, occurs at the gradient domain wall that can be reconfigured. Our findings provide fresh insights into the intricate interplay between anisotropy within the bulk and robustness at the boundary of topological materials, which could lead to advancements in the field of topological material science and the development of topological devices with tailored functionalities.

Chiral Twist Interface Modulation Enhances Thermoelectric Properties of Tellurium Crystal.

Manipulating the grain boundary and chiral structure of enantiomorphic inorganic thermoelectric materials facilitates a new degree of freedom for enhancing thermoelectric energy conversion. Chiral twist mechanisms evolve by the screw dislocation phenomenon in the nanostructures; however, contributions of such chiral transport have been neglected for bulk crystals. Tellurium (Te) has a chiral trigonal crystal structure, high band degeneracy, and lattice anharmonicity for high thermoelectric performance. Here, Sb-doped Te crystals are grown to minimize the severe grain boundary effects on carrier transport and investigate the interface of chiral Te matrix and embedded achiral Sb2Te3 precipitates, which induce unusual lattice twists. The low grain boundary scattering and conformational grain restructuring provide electrical-favorable semicoherent interfaces. This maintains high electrical conductivity leading to a twofold increase in power factor compared to polycrystal samples. The embedded Sb2Te3 precipitates concurrently enable moderate phonon scattering leading to a remarkable decrease in lattice thermal conductivity and a high dimensionless figure of merit(zT)of 1.1 at 623 K. The crystal growth and chiral atomic reorientation unravel the emerging benefits of interface engineering as a crucial contributor to effectively enhancing carrier transport and minimizing phonon propagation in thermoelectric materials.

Magnetic field interference suppression method based on phase-compensation vector resonance control in near-zero magnetic field environment

The traditional PI controller has limited ability to suppress magnetic field noise with high power spectral density and specific frequencies, leading to degradation in magnetocardiographic imaging quality. A phase-compensated vector resonance controller (PVRC) is proposed to suppress these disturbances. Firstly, by analyzing the coupling effect between the magnetic field and the ferromagnetic boundary of high permeability materials, the magnetic field response is divided into a first-order inertia link and a delay link. Then, the PVRC controller compensates for the phase lag of the disturbance in two stages. Additionally, the discretization method of PVRC is improved by replacing the cosine function with a Taylor series expansion to enhance response speed. The interference suppression effect of PI-PVRC is 27.5% higher than that of PI control.

Thermal postbuckling and thermally induced postbuckled flutter of tri-directional functionally graded plates in yawed supersonic flow

The current work examines the thermal postbuckling, aero-elastic flutter and thermally induced postbuckled flutter about a static equilibrium state of tri-directional functionally graded (TFGM) rectangular and tapered plates in yawed supersonic flow. Based on the von Kármán nonlinear strains, the general higher-order shear deformation theory (GHSDT) and the first-order piston theory, the governing equations of motion for TFGM plates in yawed supersonic flow are established via the Hamilton's principle. The isogemetric analysis (IGA), the load continue strategy associated with the Newton Raphson iterative technique are exploited synthetically to capture the postbuckling paths, and then the postbuckled flutter behaviors are acquired with the static equilibrium state being obtained. Comparative and convergence studies are provided to improve reliabilities of the present material model, formulae and code implementations. Subsequently, detailed parametric investigations are carried out to evaluate the influences of material volume fractions, boundary conditions and airflow angles on the thermal postbuckling, aero-elastic flutter and postbuckled flutter behaviors of TFGM plates. The results show that it is the in-plane volume fractions, rather than the thickness volume fraction, that exert a greater influence on the thermal postbuckling and flutter behaviors of TFGM plates. Furthermore, TFGM plates exhibit more diverse postbuckling paths and more complex deformations due to the inhomogeneity of the in-plane material properties compared with z-directional FGM plates.

Consumer Dirtwork: What Extraordinary Consumption Reveals about the Usefulness of Dirt

Abstract Societies create material, social, and moral boundaries that define who and what is dirty. “Dirt” encompasses literal and figurative things—objects, beings, ideas—that transgress these boundaries and thus are “out of place.” Previous research describing how consumers avoid and manage dirt assumes that dirt is aversive. The concept of consumer dirtwork emerged from our examination of self-described “dirtbag” wilderness consumers. Dirtwork reveals the potential usefulness of dirt. Instead of cleaning, dirtworkers redraw dirt boundaries, revealing resources they then work to capture. Boundary redrawing describes a continuum of adjustments to dirt boundaries, ranging from small shifts to complete inversions. Resourcing work describes the efforts required to capture the resources that are uncovered by boundary redrawing. Dirtwork results in challenges and rewards, and offers the possibility of continued dirtwork-resourced consumption. Dirtwork contributes by revealing the process wherein consumers make use of dirt, thus demonstrating the usefulness of dirt and fluidity of dirt boundaries. Dirtwork provides a useful lens for understanding consumer behaviors that do not aspire or cannot conform to socially-imposed cleanliness rules, including stigmatized, mundane, and extraordinary consumption. Dirtwork challenges assumptions that clean is good, socially-valuable, safe, and sustainable, and implicit associations of dirt with danger, stigma, and unsustainability.

Thermal vibration analysis of bi-directionally stepped porous functionally graded plates with segment-specific material property variation supported by Kerr foundation

This paper presents a comprehensive analysis of the nonlinear dynamic response of stepped rectangular plates made of functionally graded porous material (FGPM), supported by the Kerr foundation, in a thermal environment. A novel analytical framework is developed to explore geometric and material variations. The study investigates structural variations in plate thickness with abrupt changes in uni- or bi-directional orientations, examining both single and double stepped thickness profiles. Material properties vary with thickness, featuring distinct horizontal discontinuities across plate segments. Porosity distributions, both even and uneven, are addressed using modified mixture rules. Nonlinear kinematic relationships are established using Reddy’s third-order shear deformation plate theory and von Kármán’s nonlinear geometric assumptions, with equations of motion solved via Galerkin’s technique. This improved model effectively addresses non-continuous thickness variation through integral calculus, enhancing computational efficiency. Validation is achieved by comparing outcomes with published literature and Finite Element Analysis (FEA). The study investigates the influence of material properties, elastic foundation, boundary conditions, and geometric parameters on the free vibration and nonlinear behaviors of the plates. Some of the key findings include: increasing the thickness of the stepped segment significantly heightens the fundamental frequency while reducing vibrational amplitudes; optimizing the location of the stepped segment directly impacts the plate’s fundamental frequency and vibrational amplitudes; and as the load factor increases, the difference between linear and nonlinear deflection becomes evident. Therefore, accurate FGPM stepped plate design requires incorporating nonlinear terms in the strain–displacement relationships. Suggestions for future model modifications are also discussed, contributing to advancements in structural design and analysis.

Influence of Spatially Varying Boundary Conditions Based on Material Heterogeneity

When conducting numerical analyses, boundary conditions are generally applied homogeneously, neglecting the inherent heterogeneity of the material being represented. Whilst the heterogeneity is often considered within the medium, its influence on the response at the boundary should also be accounted for. In this study, A novel approach to applying heterogeneous boundary conditions in the simulation of physical systems is presented, particularly focusing on moisture transport in unsaturated soils. The proposed method divides the surface into blocks or “macro-elements” and scales the boundary conditions based on the variation of material properties within these blocks. The principle of using overlapping kernel functions allows local effects to be considered, impacting neighbouring regions. To demonstrate the efficacy of the approach, a set of analyses were conducted that considered infiltration into a body of unsaturated soil, with various configurations of material properties and boundary conditions. The numerical simulations indicate that the application of scaled boundary conditions leads to a more natural and realistic response in the system. The applied method is independent on the numerical techniques employed in the simulation process, making it adaptable to existing computational codes, offering flexibility in capturing complex behaviours, and providing insights into how heterogeneity influences the system’s overall response.

Determining structural properties of a prestressed concrete bridge through the combination of static and dynamic load testing

Examining structural safety requires hypotheses on several properties of the bridge structure, such as material properties, boundary conditions, and self-weight. The traditional approach relies on conservative assumptions for each structural property, following the conventional new-design approach. Nonetheless, this approach leads to conservative evaluations of the bridge capacity and may lead to the erroneous conclusion that the structure is deficient. Over-conservatism in structural safety assessments may have large environmental and economic impacts on global infrastructure management. A more advanced approach is to conduct multiple tests and monitoring activities on the structural system to provide more accurate values of these bridge properties. This paper presents a methodology to determine several parameters, including the structural stiffness, the boundary conditions, and the self-weight of concrete bridges based on static and dynamic load testing and robust data-interpretation techniques. The methodology is used on a prestressed concrete bridge in Switzerland. This bridge from 1958 has a single span of 35 meters. Prior to monitoring, conservative evaluations (using the conventional approach) led to the conclusion that the bridge has structural deficiencies. After monitoring, the bridge demonstrates significant reserve capacity, mostly due to the reduction of the self-weight safety factor. This study shows the potential of monitoring techniques for more sustainable and economic infrastructure management.

Study of Experimental and Assembly Uncertainties on Modal Parameter Estimates of Axial Piston Pumps

Finite Element Model Updating (FEMU) plays a pivotal role in enhancing the accuracy and reliability of structural dynamics models. Nonetheless, uncertainties related to experimental vibration testing and natural manufacturing variability introduce unavoidable variability in the results of Modal Parameter Extraction (MPE), which is the basis for updating. In this regard, this study delves into the inherent variability of estimates from MPE following from experimental vibration testing Axial Piston Pumps (APPs). Accordingly, we investigate the effect of material properties, boundary conditions and measurement noise, through several experimental vibration tests involving assembly-disassembly and exchange of components. These variations account for inherent manufacturing variability and tolerances both at the component and material level. The obtained vibration data is processed using non-parametric FRF estimates and the Stochastic Subspace Identification (SSI) algorithm, resulting in a collection of FRFs and modal parameter estimates (natural frequencies, damping ratios and mode shapes). We use multivariate analysis techniques to quantify the uncertainty of these estimates and to assess the individual effect of assembly and population uncertainties. These results serve as a basis for further investigation towards the updating of a FE model of the APP, and the quantification of modal parameter uncertainties within the material and substructure connectivity properties.

Response properties of lattice metamaterials under periodically distributed boundary loads

We discuss response properties of lattice metamaterials to sinusoidal distributed static loads applied on a material edge. Analytical displacement solutions are obtained using a Fourier domain transfer matrix for both essential and natural boundary conditions, which are valid for a state of plane strain in orthorhombic lattices, as well as for planar metasurfaces. These solutions give sinusoidal displacement profiles in the material interior of the same wavenumber (spatial frequency) as the boundary load. Their amplitudes decay in the material interior in one of two possible ways, exponential or oscillatory exponential, depending on the lattice design and on the spatial frequency of the load. There is a tendency for the oscillatory exponential behavior to occur at lower wavenumbers representing smoother boundary loads. As explained on a specific example, comparing the metamaterial’s response amplitudes with those of a homogenous material also allows studying an effective, wavenumber-dependent shear modulus of the lattice, which can take both positive and negative values.

A Survey of Multimaterial Treatments for Thermal Radiative Transfer

Arbitrary Lagrangian-Eulerian methods are a popular choice for hydrodynamic modeling in radiation (rad-hydro) simulations. Because these methods involve a relaxation step that moves the mesh relative to material boundaries, multimaterial spatial zones are generally present. Accurate treatments of these zones are needed to resolve various physical phenomena of interest for inertial confinement fusion applications. However, these codes are often paired with single-material, deterministic thermal radiative transfer (TRT) codes that are oblivious to the material compositions of each zone. These single-material TRT codes can only accept homogenized material properties (opacities, specific heats, etc.) from the hydrodynamic code and output homogenized solutions. After each TRT time step, the multimaterial hydrodynamic code must dehomogenize the quantities computed by the TRT package in order to update subzonal material temperatures. The process by which hydrodynamic codes perform this dehomogenization has not been well documented in previous literature, and the methods can vary significantly from code to code. The purpose of this paper is to document, study, and compare existing techniques used for rad-hydro simulations as well as present a new method with potentially promising results. We summarize several methods and give comparisons on infinite-medium problems as well a finite-medium problem for two of the methods.

Thermomechanical-induced cracking model for ceramic matrix composite laminates subjected to thermal gradients and transients

Regarding the potential damage and failure issues that may occur in high-temperature transient environments during the service process of ceramic matrix composite laminates, the present work proposes a multi-layer thermomechanical induced crack initiation model for ceramic matrix composite laminates subjected to thermal gradients and transients. This model can determine the history of temperature, deformation, and stress distribution within each layer of the material, as well as the steady-state energy release rate of all possible crack locations. Then the influence of bending constraints on material stress distribution and energy release rate is investigated, finding that maximum stress and energy release rate values are significantly lower without bending constraints compared to those under bending constraints. Furthermore, the study explores the impact of material structural parameters and boundary conditions on the energy release rate of ceramic matrix composite laminates, providing direct insights for designing laboratory tests and evaluating the lifespan of these materials under in-service conditions.

Size-dependent nonlinear bending of microbeams based on a third-order shear deformation theory

In this paper, the size-dependent nonlinear bending of microbeams subjected to mechanical loading is studied using a finite element formulation. Based on the von Kármán nonlinear relationship and the third-order shear deformation theory, a size-dependent nonlinear beam element is derived by using the modified couple stress theory (MCST) to capture the microstructural size effect. The element with explicit expressions for the element vector of internal forces and tangent stiffness matrix is derived by employing the transverse shear rotation as a variable. Nonlinear bending of microbeams under different mechanical loading is predicted with the aid of Newton–Raphson iterative method. Numerical investigation shows that the derived element is efficient, and it is capable of giving accurate results by several elements. The obtained results reveal the importance of the micro-size effect on the nonlinear behavior of the microbeams, and the deflections are overestimated when the microstructural effect is ignored. The effects of the material length scale parameter, boundary conditions and loading type on the bending response of the microbeams are studied and highlighted.

Boundaries of the built environment: defining the significance of the material presence of spatial morphology in social life

Settled societies inhabit environments shaped by building activity. Geographic data in social scientific and geographical research are generally composed of architectural and social categories derived from commonplace lived experience and societal knowledge, thus carrying socio-culturally specific meaning. The mundane pragmatism of such categories conflate spaces and buildings with their use and may obstruct effective comparison. Here I introduce a set of formally redescriptive ontological concepts for built environments that operates on the basis of how differentiation and subdivision constitute distinct occupiable spaces through boundaries. An ontology of the inhabited built environment arises from the application of these socio-spatial and material concepts called ‘Boundary Line Types’ (BLT). I present and photographically illustrate the definitions of the BLTs, which are conceived on a critical realist basis and rooted in a multidisciplinary body of theory concerning the development and inhabitation of built space. Considering inhabited built environments through BLTs foregrounds the emergent logic by which spaces are divided and connected, creating configurations of boundaries as material frames that afford everyday social life. Since BLTs offer transferrable empirical principles from which these material frames emerge, they also enable diachronic and cross-cultural comparative social research. My proposition to approach social scientific built environment research through constitutive material boundaries offers a comparative complement to commonplace and socio-culturally specific spatial categories that compose most geographic data, enabling formal thick redescriptions and the potential for quantitative spatial analysis.

Optimization of composite aeronautical components by Re-designing with double-double laminates

This paper introduces a novel approach to optimize aircraft structural design for enhanced performance and environmental sustainability. Traditional constraints on composite laminate stacking sequences, such as the symmetrical and balanced nature of classical quasi-isotropic laminates, often lead to over-dimensioning of aeronautical components. To overcome these limitations, the adoption of a new class of laminates known as Double-Double laminates, originally introduced by Prof. S.W. Tsai, is proposed. Unlike traditional laminates, Double-Double laminates offer flexibility in layer orientations, small building blocks, easy homogenization, and tapering capability.This study presents various case studies of increasing complexity to assess the effectiveness of the proposed methodology. First, a multicopter frame is redesigned to reveal the methodology's ability to reduce component weight while ensuring strength requirements under typical service loads. Then, the “DD Automated Design Tool”, a newly developed Finite Element Method tool interfacing with the Lamsearch engine, is introduced. This tool facilitates the rapid identification of optimal composite double-double laminate layups based on material properties, applied loads, and boundary conditions. By iteratively interacting between the Finite Element Method software and the Lamsearch engine, the tool efficiently identifies the best laminate angles to meet specific strength requirements.To validate the weight-saving capability of the proposed methodology, the optimizations on a composite fuselage section and a real composite wing-box under realistic loading conditions have been carried out. Both cases resulted in significant weight reductions compared to initial configurations, demonstrating the effectiveness of Double-Double laminates in achieving structural efficiency and meeting performance demands.

Physics-aware recurrent convolutional neural networks for modeling multiphase compressible flows

Multiphase compressible flow systems can exhibit unsteady and fast-transient dynamics, marked by sharp gradients and discontinuities, and material boundaries that interact with the evolving flow. The transient nature of the dynamics presents challenges to employing artificial intelligence (AI) and data-driven models for predicting flow behaviors. In this study, we explore the potential of physics-aware recurrent convolutional neural networks (PARC) to model the spatiotemporal dynamics of multiphase flows in the presence of shocks and reaction fronts. PARC is a neural network model that incorporates the generic form of the diffusion–advection–reaction equation in its network architecture, which mimics the process of solving the governing equations of fluid flows. In contrast to physics-informed machine learning approaches such as physics-informed neural networks (PINNs) where models are trained to directly minimize the residual of governing equations, PARC takes a dynamical systems viewpoint and does not seek to minimize potentially nonconvex and nonlinear loss terms. To assess the ability of PARC to accurately learn and simulate the physics of multiphase flows, we train and test PARC on various flow simulation problems, including the Burgers’ equation, fluid flow behind a cylindrical cross-section, and unsteady shock interactions with a particle at varying Mach numbers. We analyze PARC’s performance and examine sources of error in its prediction, in terms of differentiation and integration schemes and different weighting strategies for the model update. Based on our observations, we discuss PARC’s capabilities and limitations in multiphase flow applications and propose future research directions.

Designing and Constructing a Skyrmion Diode Device via Antiferromagnetic Exchange Bias Engineering

AbstractMagnetic skyrmions are topologically protected spin textures with nanoscale dimensions. They hold great promises as the building blocks for new generations of racetrack memories and computing devices due to their prominent properties. However, skyrmionic devices fabricated within the framework of conventional lithography usually suffer from magnetic disorders at material boundaries where spin disorders can easily pin and destroy magnetic skyrmions. In the present work, a new paradigm is demonstrated that enables the precise patterning and control of micro‐scale skyrmion bubble devices using the domain walls rather than the physical boundaries of the material. Such a paradigm patterns the background magnetic domain to stage the skyrmion motion, which is precise, reconfigurable, nondestructive, and can resolve the conventional issues introduced by disorders. This paradigm is demonstrated by implementing a skyrmion diode using a precisely patterned asymmetric racetrack defined by magnetic domains. The interaction between a moving skyrmion and the staging domain walls is well understood by both skyrmion motion experiments and micromagnetic simulations. Such a new paradigm serves as a crucial foundation for device applications of magnetic skyrmions in general.

In spirit and in truth: (re)searching Christianity and racial liberation in education

As educational justice scholarship addressing racial oppression continues to name the role of the spirit, there is a need for Black and Brown Christian educators and researchers to locate ourselves as grounded in the epistemologies and pedagogies of Christ as our spiritual home. This paper brings together eight Black and Brown Christian educators and researchers to grapple with what it means to be Christians committed to racial justice in education against the backdrop of centuries of religious corruption. Through collaborative autoethnography, we turn to our spiritual and religious lives situated within our racialized identities to challenge the disciplinary and material boundaries of what critical qualitative research counts as “knowing.” In doing this, we give ourselves, and all educators and researchers, permission to make evident the unseen forces that shape our ways of being in research and teaching.

Inverse analysis of granular flows using differentiable graph neural network simulator

Inverse problems in granular flows, such as landslides and debris flows, involve estimating material parameters or boundary conditions based on a target runout profile. Traditional high-fidelity simulators for these inverse problems are computationally expensive, restricting the number of possible simulations. These simulators are also non-differentiable, making efficient gradient-based optimization methods for high-dimensional spaces inapplicable. Machine learning-based surrogate models offer computational efficiency and differentiability. However, they often struggle to generalize beyond their training data due to relying on low-dimensional input–output mappings that fail to capture the complete physics of granular flows. We propose a novel differentiable graph neural network simulator (GNS) that combines reverse mode automatic differentiation of graph neural networks with gradient-based optimization for solving inverse problems. GNS learns the dynamics of granular flow by representing the system as a graph and predicts the evolution of the graph at the next timestep, given the current state. The differentiable GNS demonstrates optimization capabilities beyond the training data. We demonstrate the effectiveness of our method for inverse estimation across single and multi-parameter optimization problems, including evaluating material properties and boundary conditions for a target runout distance and designing baffle locations to limit a landslide runout. Our proposed differentiable GNS framework solves inverse problems with orders of magnitude faster convergence than the conventional gradient-based optimization approach using finite difference.

Determination of transient heat transfer by cooling channel in high-pressure die casting using inverse method

Complex shapes of aluminum castings are typically manufactured during the short cycle process known as the high-pressure die casting (HPDC). High productivity is ensured by introducing die cooling through a system of channels, die inserts or jet coolers. Die cooling can also effectively help in reducing internal porosity in cast components. Accurate simulations based on sophisticated numerical models require accurate input data such as material properties, initial and boundary conditions. Although the heat is dominantly dissipated through die cooling, indicating the importance of knowing precise thermal boundary conditions, open literature lacks a detailed information about the spatial distribution of heat transfer coefficient. This study presents an inverse method to determine accurate heat transfer coefficients of a die insert based on temperature measurements in multiple points by 0.5 mm K-type thermocouples and a subsequent solution of the two-dimensional inverse heat conduction problem. The solver was built in the open-source CFD code OpenFOAM and the free library for nonlinear optimization NLopt. The results are presented for the commonly used 10 mm die insert with a hemispherical tip and coolant flow rates ranging from 100 l/h to 200 l/h. Heat transfer coefficients reach values well above 50 kW/m2K in the hemispherical tip, which is followed by a secondary peak and then a gradual drop to values around 1 kW/m2K further downstream.