Local Phase Research Articles

Local phase structure evolution and ferroelectric response in novel Bi-layered structure relaxor BaBi2Ta2O9 ceramic

It is of importance to discover new type ferroelectric materials with enhanced functionalities to meet various demand of applications, here we prepared the BaBi2Ta2O9 ceramic with orthogonal structure and oxygen octahedral rotation. This type of material had been screened out to be a candidate ferroelectric previously based on high-throughput first-principles density functional theory (DFT) calculations. The relationship between local phase structure and ferroelectric properties of this system is investigated by dielectric spectrum. Low-temperature relaxor behavior is described by using the Curie-Weiss law and the Vogel-Fulcher relationship. The polarization response and size of Polar nanoregions (PNRs) are described using the phenomenological statistical model. The P(E) loops imply that long-range-order ferroelectric is destroyed formation frozen randomly interacting PNRs. Element segregation and lattice distortion are directly observed using TEM, which is associated with the substitution of multiple atoms for the one cation occupation.

A third generation CalPhaD assessment of the Fe–Mn–Ti system Part II: The ternary system Fe–Mn–Ti

The ternary Fe–Mn–Ti system plays an important role in the development of several different functional and structural materials, which can be applied e.g., as shape-memory alloys or for hydrogen storage. Since the corresponding materials properties are closely connected to the thermodynamic behavior of the individual phases in the alloys, thermodynamic calculations can provide useful information for a sustainable and straightforward alloy development. Therefore, a 3rd generation CalPhaD description of the Fe–Mn–Ti system was developed, which applies advanced sublattice models for several phases such as A12, A13 and C14, to ensure physically meaningful estimations of their thermodynamic properties. Moreover, the modelling was supported by experimental investigations on the phase relations in the ternary Fe–Mn–Ti system, based on diffusion-couple experiments at 800, 900 and 1000 °C. During these experiments, several local phase equilibria between A1, A2, A3, A12, B2, C14 and MnTi1-x were established and subsequently investigated using SEM/BSE-imaging, EPMA and EBSD.

ExHiF: Alzheimer's disease detection using exemplar histogram-based features with CT and MR images

The classification of medical images is an important priority for clinical research and helps to improve the diagnosis of various disorders. This work aims to classify the neuroradiological features of patients with Alzheimer's disease (AD) using an automatic hand-modeled method with high accuracy. This work uses two (private and public) datasets. The private dataset consists of 3807 magnetic resonance imaging (MRI) and computer tomography (CT) images belonging to two (normal and AD) classes. The second public (Kaggle AD) dataset contains 6400 MR images. The presented classification model comprises three fundamental phases: feature extraction using an exemplar hybrid feature extractor, neighborhood component analysis-based feature selection, and classification utilizing eight different classifiers. The novelty of this model is feature extraction. Vision transformers inspire this phase, and hence 16 exemplars are generated. Histogram-oriented gradients (HOG), local binary pattern (LBP) and local phase quantization (LPQ) feature extraction functions have been applied to each exemplar/patch and raw brain image. Finally, the created features are merged, and the best features are selected using neighborhood component analysis (NCA). These features are fed to eight classifiers to obtain highest classification performance using our proposed method. The presented image classification model uses exemplar histogram-based features; hence, it is called ExHiF. We have developed the ExHiF model with a ten-fold cross-validation strategy using two (private and public) datasets with shallow classifiers. We have obtained 100% classification accuracy using cubic support vector machine (CSVM) and fine k nearest neighbor (FkNN) classifiers for both datasets. Our developed model is ready to be validated with more datasets and has the potential to be employed in mental hospitals to assist neurologists in confirming their manual screening of AD using MRI/CT images.

Integrable Floquet systems related to logarithmic conformal field theory

We study an integrable Floquet quantum system related to lattice statistical systems in the universality class of dense polymers. These systems are described by a particular non-unitary representation of the Temperley-Lieb algebra. We find a simple Lie algebra structure for the elements of Temperley-Lieb algebra which are invariant under shift by two lattice sites, and show how the local Floquet conserved charges and the Floquet Hamiltonian are expressed in terms of this algebra. The system has a phase transition between local and non-local phases of the Floquet Hamiltonian. We provide a strong indication that in the scaling limit this non-equilibrium system is described by the logarithmic conformal field theory.

Observation of critical phase transition in a generalized Aubry-André-Harper model with superconducting circuits

Quantum simulation enables study of many-body systems in non-equilibrium by mapping to a controllable quantum system, providing a powerful tool for computational intractable problems. Here, using a programmable quantum processor with a chain of 10 superconducting qubits interacted through tunable couplers, we simulate the one-dimensional generalized Aubry-André-Harper model for three different phases, i.e., extended, localized and critical phases. The properties of phase transitions and many-body dynamics are studied in the presence of quasi-periodic modulations for both off-diagonal hopping coefficients and on-site potentials of the model controlled respectively by adjusting strength of couplings and qubit frequencies. We observe the spin transport for initial single- and multi-excitation states in different phases, and characterize phase transitions by experimentally measuring dynamics of participation entropies. Our experimental results demonstrate that the recently developed tunable coupling architecture of superconducting processor extends greatly the simulation realms for a wide variety of Hamiltonians, and can be used to study various quantum and topological phenomena.

Characterization of graphite–chromium carbide composites manufactured by spark plasma sintering

AbstractThis manuscript contains an investigation about the influence of the chromium content on the properties of novel graphite–chromium composites obtained by spark plasma sintering (SPS), with great potential application in heat dissipation. Green compacts of 40 mm in diameter were first obtained by uniaxial pressing at 60 MPa, and then the composite was sintered at 1800°C in SPS under vacuum conditions and a pressure of 30 MPa. These sintering conditions involved local liquid phase, which promoted the densification of the composite up to values close to 90%. Different chromium contents were studied, 0, 1, 2, 5, 7, and 10 vol.%, where the best properties (densification, young modulus, electrical conductivity, thermal conductivity, and flexural strength) were obtained in the case of the composite with 7 vol.% Cr: 86.22%, 52.7 GPa, 0.79 MS/m, 264 W/m K, and 38.97 MPa, respectively, measured in the in‐plane direction due to the anisotropic behavior of the composite.

INFLUENCE OF DEFORMATION GUIDANCE CONDITIONS ON CHARACTERISTICS OF Ni49,5Ti48Hf2,5 ALLOY WITH HIGH-TEMPERATURE SHAPE MEMORY EFFECT

Complex studies of the properties of Ni49,5Ti48Hf2,5 alloy featuring high-temperature shape memory effect were carried out on samples made of 2,34 mm-thick strip after high-temperature annealing in vacuum (850 ºС, 1 h). Data on element, phase compositions and structure state was obtained. Results of studies of phase transition temperatures, mechanical and thermomechanical characteristics of the alloy are given. According to the results of studying the local phase composition of alloy samples, it was found that the main matrix of samples is formed by solid solution of Ti, Ni, Hf elements. When analyzing diffraction patterns, it was found that the main phase of samples is titanium nickelide in the low-temperature martensitic state TiNi (B19`) with a monoclinically distorted orthorhombic crystal lattice. It was found that the best average values of the shape memory characteristics εSME = 4,4 % and ηSME = 53 % were obtained for alloy samples with a previously induced total deformation of eо = 11 % in the temperature range tD=(–5 ÷ 23) ºС and deformation rate ε ≈ 2,8·10–3 s–1. The average values of temperatures of the start and the end of the main form recovery are Аs SME = 133 ºС, Аf SME = 149 ºС. These thermomechanical characteristics are suitable for alloy selected to create safety devices such as devices of pushing type.

Phase stability and phase transformation related to Nb/Ta additions in a Ni-based superalloy

Alloys based on Inconel 725, and with elevated levels of Nb and Ta, have been designed for application in environments requiring high strength and corrosion resistance at elevated temperatures. The present study further examines the phase stability and subsequent phase transformation in those alloys following aging and long-term exposure of up to 10,000 h at 700 °C. Changes in the microstructure were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Two alloy bases with different Ti/Al ratio were considered. Following aging, the Nb/Ta additions favor the development of γ′/γ″ co-precipitates in the low Ti/Al ratio alloy, whereas the high Ti/Al ratio counterpart only contained γ″ precipitates. Upon 10,000 h exposure, complex geometrical closed-packed (GCP) phases formed from the γ′/γ″ co-precipitates in a layer-by-layer manner, i.e., the plate-like δ phase precipitates became decorated by blocky α-Cr and enveloped by a wavy γ′ film. Increasing the concentration of Nb and/or Ta did not change the basic characteristic of this phase transformation; however, the precipitate number density increased in the grain interior. On the other hand, the Ta addition in the alloy with low Ti/Al ratio promoted the formation of Ta-rich η precipitates at the grain boundaries while Nb promoted δ precipitates. The underlying phase transformation behavior of the layer-by-layer structure is likely initiating from the γ″-δ phase transition that ejects Cr and Ti into the neighboring phases, thus resulting in local phase separation into α-Cr and γ′ thin film. This phase transformation process had a significant impact on the phase morphologies in the high Nb/Ta alloys exposed at 700 °C for 10,000 h, with experimental results contradicting those from computational prediction.

Entropy of the quantum work distribution

A measure of the complexity of the quantum distribution of work outcomes is presented with general upper and lower bounds in terms of well-known thermodynamic and quantum quantities, thus clearly separating the classical and quantum contributions. This measure is shown to possess a strong signature of the localization phase transition in a quasiperiodic crystal.

Defect Detection and Depth Estimation in Composite Materials for Pulsed Thermography Images by Nonuniform Heating Correction and Oriented Gradient Information.

Pulsed thermography is a nondestructive method commonly used to explore anomalies in composite materials. This paper presents a procedure for the automated detection of defects in thermal images of composite materials obtained with pulsed thermography experiments. The proposed methodology is simple and novel as it is reliable in low-contrast and nonuniform heating conditions and does not require data preprocessing. Nonuniform heating correction and the gradient direction information combined with a local and global segmentation phase are used to analyze carbon fiber-reinforced plastic (CFRP) thermal images with Teflon inserts with different length/depth ratios. Additionally, a comparison between the actual depths and estimated depths of detected defects is performed. The performance of the nonuniform heating correction proposed method is superior to that obtained on the same CFRP sample analyzed with a deep learning algorithm and the background thermal compensation by filtering strategy.

Application of a hybrid multiphase CFD approach to the simulation of gas–liquid flow at a trapezoid fixed valve for distillation trays

In the present contribution, we demonstrate the application of a hybrid multiphase CFD approach, which allows for simulating dispersed phases as well as resolved interfaces within an Eulerian framework, for the flow on distillation trays for the first time. The morphology adaptive multifield two–fluid model is exemplified for continuous gas–liquid flow on a generic tray setup with a single trapezoid fixed valve. Instead of fully resolving its geometry in the computational grid, the gas inlets are emulated by implementing mass and momentum sources that are applied to local cell zones. Different zone types in terms of volume and curtain area are tested and compared. The simulation results are verified with experimental data from a lab–scale test rig with air–water flow. Local phase fractions were measured using a conductivity sensor array. The comparison of simulated and experimental results reveals that the relevant time–averaged and transient flow characteristics can be predicted satisfactorily if at least an approximate representation of the valve’s geometry in the computational grid is given. However, local differences are observed among the simulated phase distributions due to the varying cell zone volume and hence maximum intensity of the injected momentum.

Electrical Phase Modulation Based on Mid‐Infrared Intersubband Polaritonic Metasurfaces

Electrically reconfigurable metasurfaces that overcome the static limitations in controlling the fundamental properties of scattered light are opening new avenues for functional flat optics. This work proposes and experimentally demonstrates electrically phase-tunable mid-infrared metasurfaces based on the polaritonic coupling of Stark-tunable intersubband transitions in semiconductor heterostructures and electromagnetic modes in plasmonic nanoresonators. In the applied voltage range of -3 to +3V, the local phase tuning of the light reflects from the metasurface, which enables the electrical control of the polarization state and wavefront of the reflected wave. Electrical beam polarization control, electrical beam diffraction control, and electrical beam steering are experimentally demonstrated as applications for local phase tunability. The proposed electrically tunable metasurfaces can easily tune the operating wavelength and function at relatively low voltages, which will enable various applications in the mid-infrared region.

Quantum neuronal sensing of quantum many-body states on a 61-qubit programmable superconducting processor

Classifying many-body quantum states with distinct properties and phases of matter is one of the most fundamental tasks in quantum many-body physics. However, due to the exponential complexity that emerges from the enormous numbers of interacting particles, classifying large-scale quantum states has been extremely challenging for classical approaches. Here, we propose a new approach called quantum neuronal sensing. Utilizing a 61-qubit superconducting quantum processor, we show that our scheme can efficiently classify two different types of many-body phenomena: namely the ergodic and localized phases of matter. Our quantum neuronal sensing process allows us to extract the necessary information coming from the statistical characteristics of the eigenspectrum to distinguish these phases of matter by measuring only one qubit and offers better phase resolution than conventional methods, such as measuring the imbalance. Our work demonstrates the feasibility and scalability of quantum neuronal sensing for near-term quantum processors and opens new avenues for exploring quantum many-body phenomena in larger-scale systems.

The effect of high strain rate impact in Yttria stabilized zirconia

Yttria stabilized zirconia (6-8YSZ) is widely used as a top coat in Thermal Barrier Coatings (TBCs) to protect metallic substrates. These coatings are exposed to severe high strain rate fields along their life, for example during the impact of debris happening in service or during coating removal in repair processes. In this work a water jet and a high strain rate nanoindenter are used to understand the effect of the strain rate (from 10-3 to 108 s−1) on the behaviour of 8YSZ at a small scale. It is observed how, at extremely high strain rates (106–108 s−1), the material suffers from a brittle-dominated failure which induces localized phase transformation. At lower strain rates (10-3−1 s−1), plasticity dominates, and phase transformation is not observed.

Local–nonlocal stress-driven model for multi-cracked nanobeams

Exact closed-form solutions for multi-cracked Euler–Bernoulli nanobeams are provided by proposing two equivalent approaches. The considered multi-cracked nanobeams are modeled with a well-posed local–nonlocal stress-driven model and contain an arbitrary number n of isolated damaged cross-sections. In order to simulate the damaged sections, it is assumed that the nanobeam bending flexibility contains n Dirac delta functions, with a Dirac delta located at each damaged section: this representation of cracked sections, already used in local problem, is adopted for the first time here in the local–nonlocal stress-driven model. The first approach providing closed-form solutions is based on the integral definition of the local–nonlocal stress-driven model, where the bending curvature is given by the superposition of the local and nonlocal phases, and the nonlocal phase is an integral convolution of the bending moment. This approach provides an integro-differential equation, which is solved by taking firstly the Laplace transform and then the anti-transform. In the second approach, it is shown that the integral definition of the stress-driven multi-cracked nanobeam model is equivalent to a differential equation together with suitable constitutive boundary conditions. This equation is solved by making use of Laplace transform again. The two approaches provide the same solution, with the second one resulting computationally faster. Interesting results show that a jump of the rotation at the damaged cross-sections occurs in local beam, but does not occur in pure nonlocal nanobeams (i.e. local phase is absent): contrary to the local elasticity theory, the bending curvature of pure nonlocal nanobeams has no singularity at damaged sections. The typical stiffness increase, due to the increase in nonlocal fraction of the mixture or to the increase in the length-scale parameter, also appears in multi-cracked nanobeams and this stiffening nonlocal effect is more pronounced in more constrained nanobeams.

Identifying many-body localization transitions in a random-field Heisenberg chain via quantum nonlocality

Characterizing the many-body localization (MBL) transition and revealing its inherent mechanisms from the ergodic phase to the localized phase is an increasing interest issue. In this paper, we use quantum nonlocality, the hierarchy of multipartite correlations, to identify the MBL transition in an XXZ spin chain with random on-site magnetic fields. We use the shift-invert exact diagonalization method to explore the properties of two-qubit nonlocality and multipartite nonlocality in the many-body localized system. We then use their first derivatives to estimate the critical disorder strength, which is found to be range in hc/J∈[3,4]. Correspondingly, two quantities and their first derivatives, the energy level statistics and the half-chain entanglement entropy that are promising for the study of the MBL transition, are also investigated and as comparisons to quantum nonlocality.

Two-beam interferometry with a definitive phase-shift sign

Subject of study. The shift direction of interference fringes depending on the sign of the local phase shift introduced to one of the interfering waves was investigated in terms of two-beam interferometry. Aim of study. This study aimed to validate the fact that two-beam interferometry based on a single interferogram enables definitive determination of the phase-shift sign using the shift direction of the interference fringe. Method. Positions of the interference fringes and their shifts were calculated considering the phase distribution of interfering waves in the observation plane. The Mach–Zehnder interferometer was used to experimentally confirm the obtained theoretical results. Two closely adjacent substrates were used as objects. A subwavelength layer of a standard material was deposited on a part of the surface of one substrate, and a layer of metamaterial was deposited on the part of the second substrate. Main results. Expressions determining the direction and amplitude of the shift of interference fringes depending on the sign and amplitude of the local phase shift in one of the two interfering waves with a plane or spherical front were obtained. Strict rules of interference fringe shift depending on the sign of the phase shift were formulated based on the calculations. Results of the experiment using the Mach–Zehnder interferometer with different combinations of beams with spherical and plane wavefronts confirmed the theoretical calculations. Practical significance. Classic interferometric methods require significant time and the application of complex experimental procedures to determine the sign of the phase shift. The application of the results obtained in this study enables the determination of the sign of the introduced local phase shift based on a single interferogram without additional time expenditures. Thus, the method investigating the metamaterial layers of a subwavelength thickness is significantly simplified.

Characterizing the delocalized–localized Anderson phase transition based on the system’s response to boundary conditions

A new characterization of the Anderson phase transition, based on the response of the system to the boundary conditions is introduced. We change the boundary conditions from periodic to antiperiodic and look for its effects on the eigenstate of the system. To characterize these effects, we use the overlap of the states. In particular, we numerically calculate the overlap between the ground-state of the system with periodic and antiperiodic boundary conditions in one-dimensional models with delocalized-localized phase transitions. We observe that the overlap is close to one in the localized phase, and it gets appreciably smaller in the delocalized phase. In addition, in models with mobility edges, we calculate the overlaps between single-particle eigenstate with periodic and antiperiodic boundary conditions to characterize the entire spectrum. By this single-particle overlap, we can locate the mobility edges between delocalized and localized states.

Federated Imitation Learning for UAV Swarm Coordination in Urban Traffic Monitoring

The popularization of unmanned aerial vehicles (UAVs) has boosted various civil applications such as traffic monitoring, in which the effective coordination of the UAV swarm plays a significant role in expanding the monitoring range and enhancing the execution efficiency. However, due to the isolated local environments as well as the heterogeneous execution capabilities, it is challenging to achieve highly consistent actions. In this article, we incorporate the federated learning framework with the imitation learning technique to coordinate the UAVs' maneuvers by interactively imitating the leader UAV's operations. During the interagent global model download phase, we utilize the generative adversarial imitation learning (GAIL) model to accurately follow the leader UAV's operations by removing the biased estimates of imitation parameters. While in the intraagent local model training phase, we utilize the self-imitation learning (SIL) model to correct delicate imitation errors by virtue of the follower UAVs' own historical valuable experiences. In order to achieve more efficient distributed parameter interactions, we regularize the federated gradient updates and eventually yield coordinated swarm policies. We evaluate the proposed algorithm in the UAV-based traffic monitoring scenario. Evaluation results demonstrate the superiorities on training and execution efficiencies.

Solving Expensive Multimodal Optimization Problem by a Decomposition Differential Evolution Algorithm.

An expensive multimodal optimization problem (EMMOP) is that the computation of the objective function is time consuming and it has multiple global optima. This article proposes a decomposition differential evolution (DE) based on the radial basis function (RBF) for EMMOPs, called D/REM. It mainly consists of two phases: the promising subregions detection (PSD) and the local search phase (LSP). In PSD, a population update strategy is designed and the mean-shift clustering is employed to predict the promising subregions of EMMOP. In LSP, a local RBF surrogate model is constructed for each promising subregion and each local RBF surrogate model tracks a global optimum of EMMOP. In this way, an EMMOP is decomposed into many expensive global optimization subproblems. To handle these subproblems, a popular DE variant, JADE, acts as the search engine to deal with these subproblems. A large number of numerical experiments unambiguously validate that D/REM can solve EMMOPs effectively and efficiently.