Space Inversion Research Articles

Research on defect image inversion method based on multiple lift-off values magnetic memory signals

Metal magnetic memory (MMM) technique can detect macroscopic defects and stress concentration zones of ferromagnets, and it can identify the approximate positions of these flaws, while a little further information about defects characteristics can be provided. To promote study in this area, defects were modeled as located magnetic dipoles whose strength and locations should be determined, and the technique of truncated generalized inverse and reduced space inversion were used to image the dipole strength. Through the simulation experiment, we found that the inversion image quality was influenced by the lift-off value. When the magnetic field data for inversion was measured with a small lift-off value, the inner dipoles contributions were easily buried and the inversion image can only shown the surface dipole well. In contrast, if the magnetic field data was measured with a greater lift-off value, it was possible to inverse the deep dipoles while the image was somewhat out of focus. To overcome this limitation, we composed the magnetic field data measured under different lift-off values together for inversion. We used the same model to test this approach and applied it on real crack defects magnetic field data. It demonstrates that the new inversion approach shows better accuracy than the single lift-off value and it was possible to infer the location and size of defect by the evaluation of preset dipoles.

2D Janus Polarization Functioned by Mechanical Force.

2Dpolarization materials have emerged as promising candidates for meeting the demands of device miniaturization, attributed to their unique electronic configurations and transport characteristics. Although the existing inherent and sliding mechanisms are increasingly investigated in recent years, strategies for inducing 2D polarization with innovative mechanisms remain rare. This study introduces a novel 2D Janus state by modulating the puckered structure. Combining scanning probe microscopy, transmission electron microscopy, and density functional theory calculations, this work realizes force-triggered out-of-plane and in-plane dipoles with distorted smaller warping in GeSe. The Janus state is preserved after removing the external mechanical perturbation, which could be switched by modulating the sliding direction. This work offers a versatile method to break the space inversion symmetry in a 2D system to trigger polarization in the atomic scale, which may open an innovative insight into configuring novel 2D polarization materials.

Valleytronics in bulk MoS2 with a topologic optical field.

The valley degree of freedom1-4 of electrons in materials promises routes towards energy-efficient information storage with enticing prospects for quantum information processing5-7. Current challenges in utilizing valley polarization are symmetry conditions that require monolayer structures8,9 or specific material engineering10-13, non-resonant optical control to avoid energy dissipation and the ability to switch valley polarization at optical speed. We demonstrate all-optical and non-resonant control over valley polarization using bulk MoS2, a centrosymmetric material without Berry curvature at the valleys. Our universal method utilizes spin angular momentum-shaped trefoil optical control pulses14,15 to switch the material's electronic topology and induce valley polarization by transiently breaking time and space inversion symmetry16 through a simple phase rotation. We confirm valley polarization through the transient generation of the second harmonic of a non-collinear optical probe pulse, depending on the trefoil phase rotation. The investigation shows that direct optical control over the valley degree of freedom is not limited to monolayer structures. Indeed, such control is possible for systems with an arbitrary number of layers and for bulk materials. Non-resonant valley control is universal and, at optical speeds, unlocks the possibility of engineering efficient multimaterial valleytronic devices operating on quantum coherent timescales.

Geoacoustic inversion using 3D modal rays on the New England Shelf Break

During the Seabed Characterization Experiment in 2021 (SBCEX21), hydrophones deployed on the seabed of the New England Shelf Break recorded acoustic signals from SUS charge explosions. Acoustic data from one of these TOSSIT hydrophones displays evident modal structures which cannot be fully captured with 2D propagation models. In this presentation, 3D acoustic modal ray tracing is shown to provide a stronger match for recorded modal travel times, and is used to invert for geoacoustic parameters of the seabed. Performance of 2D and 3D modal propagation models are presented, and limitations of the methods are shown in the context of large parameter space inversion efforts. [This research is supported by The Office of Naval Research.]

The physical interpretation of point interactions in one-dimensional relativistic quantum mechanics

We investigate point interactions (PIs) in one-dimensional relativistic quantum mechanics using a distributional approach based on Schwartz’s theory of distributions. From the properties of the most general covariant distribution describing relativistic PIs (RPIs) we obtain the physical parameters associated with the point potentials that behave as a scalar, a pseudo-scalar and a vector under Lorentz transformations. Then, we establish a one-to-one relationship between these physical parameters and the well-known set of four parameters giving the boundary conditions at the singular point(s), which define a self-adjoint Hamiltonian. By considering the non-relativistic limit, we obtain the most general PI in the Schrödinger equation in terms of these four physical point potentials. Finally, we study the symmetries of the RPIs under space inversion, time reversal and charge conjugation, and investigate how requirements of invariance under these symmetry transformations can be used to restrict the set of physical parameters.

Spin resolved topological bulk state in acoustics

Extremely rare topologically protected acoustic energy sink is presented in this article. Acoustic topological phenomena are generally described using quantum anomalous hall effects (QAHE), quantum valley hall effects (QVHE), and quantum spin hall effects (QSHE) where spin orbit coupling is predominant. Topological edge states are demonstrated by bulk-boundary distinction when the bulk is insulated. In this article topological acoustic conductor and its phenomena are theoretically demonstrated where the boundaries are insulated. This is exactly opposite to the behavior of a topological acoustic insulator. Phenomena presented in this article could not be explained by any of the trio Quantum Hall effects. To explain the phenomenon phononic crystals or PnCs were designed to obtain accidental triple degeneracies, resulting a Dirac-like cone at the Γ point (k→=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overrightarrow{k}=0$$\\end{document}). The phenomenon is microarchitecture and microrotation field independent. Here time reversal symmetry or the space inversion symmetry is not broken, and the degenerated ‘Deaf band’ dominates the local dispersion with a syncline top band. This scenario results in continuously changing ‘up spin’ and ‘down spin’ of the wave energy in the media and remain trapped without specific preferential direction of wave transport. The spin was found to generate the spin angular momentum, causing the switching in geometric phase from 0-2π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0-2\\pi$$\\end{document} in cyclic pattern, keeping the energy trapped inside the bulk media.

Translating pumping test data into groundwater model parameters: a workflow to reveal aquifer heterogeneities and implications in regional model parameterization

Groundwater modelers frequently grapple with the challenge of integrating aquifer test interpretations into parameters used by regional models. This task is complicated by issues of upscaling, data assimilation, and the need to assign prior probability distributions to numerical model parameters in order to support model predictive uncertainty analysis. To address this, we introduce a new framework that bridges the significant scale differences between aquifer tests and regional models. This framework also accounts for loss of original datasets and the heterogeneous nature of geological media in which aquifer testing often takes place. Using a fine numerical grid, the aquifer test is reproduced in a way that allows stochastic representation of site hydraulic properties at an arbitrary level of complexity. Data space inversion is then used to endow regional model cells with upscaled, aquifer-test-constrained realizations of numerical model properties. An example application demonstrates that assimilation of historical pumping test interpretations in this manner can be done relatively quickly. Furthermore, the assimilation process has the potential to significantly influence the posterior means of decision-pertinent model predictions. However, for the examples that we discuss, posterior predictive uncertainties do not undergo significant reduction. These results highlight the need for further research.

Superconductivity in a ferroelectric-like topological semimetal SrAuBi

Given the rarity of metallic systems that exhibit ferroelectric-like transitions, it is apparently challenging to find a system that simultaneously possesses superconductivity and ferroelectric-like structural instability. Here, we report the observation of superconductivity at 2.4 K in a layered semimetal SrAuBi characterized by strong spin–orbit coupling (SOC) and ferroelectric-like lattice distortion. Single crystals of SrAuBi have been successfully synthesized and found to show a polar-nonpolar structure transition at 214 K, which is associated with the buckling of Au-Bi honeycomb lattice. On the basis of the band calculations considering SOC, we found significant Rashba-type spin splitting and symmetry-protected multiple Dirac points near the Fermi level. We believe that this discovery opens up new possibilities of pursuing exotic superconducting states associated with the semimetallic band structure without space inversion symmetry and the topological surface state with the strong SOC.

Reservoir closed-loop optimization method based on connection elements and data space inversion with variable controls

Reservoir simulation faces challenges in computational efficiency and uncertainty management for large-scale assets. This study presents an integrated framework combining the connection element method (CEM) and data space inversion with variable controls (DSIVC) for efficient history matching and optimized forecasting of reservoir performance. CEM reduces the computational cost of numerical simulation while retaining accuracy. DSIVC enables direct production forecasting after history matching without repeated model inversion. The CEM–DSIVC approach is applied to two reservoir cases. CEM efficiently constructs reservoir models honoring complex geology. DSIVC mathematically integrates production data to reduce uncertainty and parameter space. Without repeated forward simulation, optimized forecasts are obtained under different control strategies. Compared to conventional methods, CEM–DSIVC achieves reliable uncertainty quantification and optimized forecasting with significantly improved efficiency. This provides an effective solution to overcome limitations in simulating and managing uncertainty for large-scale reservoirs. The proposed approach leverages the complementary strengths of CEM and DSIVC, synergistically improving reservoir modeling, management, and decision-making. This integrated data-driven framework demonstrates strong potential as an advanced tool for efficient field development planning and optimization.

Emergence of topological and spin valley hallmarks in buckled Xene bilayers

A subclass of two-dimensional materials with honeycomb structure, namely buckled Xene monolayers, are efficient for topological applications due to varying degrees of buckling in their lattice structure and have received a significant revival of interest in the last few years. However, to-date, less attention, as compared to, planer Xene bilayers has been assigned to the buckled Xene bilayers. The buckled Xene bilayers can offer a unique platform to study transport properties in bilayer systems. In this study, we explore the unknown topological behaviour of buckled Xene bilayers by exploiting the space inversion and time-reversal (TR) symmetries in these solids. In order to exploit the underline symmetries, we use light irradiation, layered antiferromagnetic exchange magnetization and vertical electric field as an external means. By mixing these three ingredients in a proper way, we achieve various topological phases in bilayers of buckled Xene solids, including TR-broken quantum spin Hall insulator, photo-induced quantum Hall insulator, photo-induced spin-polarized quantum Hall insulator, and quantum spin-valley Hall insulator. Furthermore, we establish a topological phase diagram and identify a topological domain wall in buckled Xene bilayers when subjected to circularly polarized light and gated voltage, which opens up possibilities for the propagation of perfectly valley-polarized channels.

Improving the Accuracy of Range Migration in 3-D Near-Field Microwave Imaging

Calibration measurements play a crucial role in improving the accuracy of both qualitative and quantitative microwave imaging. Ideally, in 3-D near-field imaging, a calibration measurement should be performed at each desired range (or depth) position, which can be very time-consuming. An analytical prediction of the range behavior of the resolvent kernel of scattering can reduce the calibration effort to a single measurement at a reference range position. Range-translation (or range-migration) analytical expressions are already widely used in far-zone radar and acoustic imaging; however, their accuracy deteriorates significantly in near-field scenarios. Here, we propose a range-migration technique for near-field microwave imaging with monostatic and bistatic measurement configurations. From a single measurement of the system point-spread function (PSF), the PSF magnitude and phase are accurately predicted at any desired range position. The proposed migration is performed in real space; however, it can also be applied with Fourier-domain (or <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$</tex-math> </inline-formula> -space) inversion methods. Here, it is applied with quantitative microwave holography in simulation-based and experimental examples, which validate its performance and illustrate its limitations.

Data space inversion for efficient uncertainty quantification using an integrated surface and sub-surface hydrologic model

Abstract. It is incumbent on decision-support hydrological modelling to make predictions of uncertain quantities in a decision-support context. In implementing decision-support modelling, data assimilation and uncertainty quantification are often the most difficult and time-consuming tasks. This is because the imposition of history-matching constraints on model parameters usually requires a large number of model runs. Data space inversion (DSI) provides a highly model-run-efficient method for predictive uncertainty quantification. It does this by evaluating covariances between model outputs used for history matching (e.g. hydraulic heads) and model predictions based on model runs that sample the prior parameter probability distribution. By directly focusing on the relationship between model outputs under historical conditions and predictions of system behaviour under future conditions, DSI avoids the need to estimate or adjust model parameters. This is advantageous when using integrated surface and sub-surface hydrologic models (ISSHMs) because these models are associated with long run times, numerical instability and ideally complex parameterization schemes that are designed to respect geological realism. This paper demonstrates that DSI provides a robust and efficient means of quantifying the uncertainties of complex model predictions. At the same time, DSI provides a basis for complementary linear analysis that allows the worth of available observations to be explored, as well as of observations which are yet to be acquired. This allows for the design of highly efficient, future data acquisition campaigns. DSI is applied in conjunction with an ISSHM representing a synthetic but realistic river–aquifer system. Predictions of interest are fast travel times and surface water infiltration. Linear and non-linear estimates of predictive uncertainty based on DSI are validated against a more traditional uncertainty quantification which requires the adjustment of a large number of parameters. A DSI-generated surrogate model is then used to investigate the effectiveness and efficiency of existing and possible future monitoring networks. The example demonstrates the benefits of using DSI in conjunction with a complex numerical model to quantify predictive uncertainty and support data worth analysis in complex hydrogeological environments.

Net Dzyaloshinskii–Moriya interaction in defect-enriched ferromagnet

The Dzyaloshinskii–Moriya interaction (DMI), which typically occurs in lattices without space inversion symmetry, can also be induced in a highly symmetric lattice by local symmetry breaking due to any lattice defect. We recently presented an experimental study of polarized small angle neutron scattering (SANS) on the nanocrystalline soft magnet Vitroperm (Fe73Si16B7Nb3Cu1), where the interface between the FeSi nanoparticles and the amorphous magnetic matrix serves as such a defect. The SANS cross sections exhibited the polarization-dependent asymmetric term originating from the DMI. One would naturally expect the defects characterized by a positive and a negative DMI constant D to be randomly distributed and this DMI-induced asymmetry to disappear. Thus, the observation of such an asymmetry indicates that there exists an extra symmetry breaking. In the present work we experimentally explore the possible causes by measuring the DMI-induced asymmetry in the SANS cross sections of the Vitroperm sample tilted in different directions with respect to the external magnetic field. Furthermore, we analyzed the scattered neutron beam using a spin filter based on polarized protons and confirm that the asymmetric DMI signal originates from the difference between the two spin-flip scattering cross-sections.

Quantum kinetic theory of nonlinear thermal current

We investigate the second-order nonlinear electronic thermal transport induced by the temperature gradient. We develop the quantum kinetic theory framework to describe thermal transport in the presence of a temperature gradient. Using this, we predict an intrinsic scattering time-independent nonlinear thermal current in addition to the known extrinsic nonlinear Drude and Berry curvature dipole contributions. We show that the intrinsic thermal current is determined by the band geometric quantities and is nonzero only in systems in which both the space inversion and time-reversal symmetries are broken. We employ the developed theory to study the thermal response in tilted massive Dirac systems. We show that besides the different scattering time dependencies, the various current contributions have distinct temperature dependencies in the low-temperature limit. Our systematic and comprehensive theory for nonlinear thermal transport paves the way for future theoretical and experimental studies on intrinsic thermal responses.

Anomalous valley Hall effect induced by mirror symmetry breaking in transition metal dichalcogenides

The control of the valley degree of freedom in Bloch electrons has opened up new avenues for information processing. The synthesis of ferrovalley materials, however, has been limited due to the stringent requirements for breaking both time and space inversion symmetries. To address this challenge, we propose a Janus method for inducing valley polarization in nonmagnetic transition metal dichalcogenides. Our study shows that the magnetic moment in monolayer TiTeI arises from the breaking of mirror symmetry and the presence of unpaired electrons. The Stoner criterion ${I}_{ex}N({E}_{F})&gt;1$ confirms that the band splitting originates from the $d$ orbital of titanium. Moreover, the exchange interaction combined with spin-orbit coupling opens up the valley splitting. The anomalous valley Hall effect (AVHE) can be realized by applying an in-plane electric field, as a result of the valley-contrasting Berry curvature. The modulation of valley-selective circular dichroism and AVHE by optical, electronic, and magnetic fields make TiTeI a promising material for future studies and applications in valleytronics.

Application of deep learning for seismicity analysis in Ghana

We present the characterization of regional seismicity in Ghana by processing the Ghana Digital Seismic Network (GHDSN) data set recorded between September 2012 and April 2014, implementing deep learning (DL). Local earthquakes are detected in this dataset using EQTransformer, a DL model with a hierarchical attentive mechanism (HAM) for simultaneous earthquake detection and P- and S-phase picking. A Conservative Strategy (CS) is devised to detect the missing phases and to associate the detected phases to circumvent the false-negative issue of EQTrans-former processing low signal-to-noise ratio (SNR) seismograms. We performed a joint inversion by grid search in 1D velocity model space and simultaneous inversion for the hypocentral parameters, incorporating 559 detected arrival times (292 P and 267 S phases). The results obtained by velocity inversion contain thicknesses of 1, 13, 8, 13, and 10 km, from the surface to a depth of 45 km, with Vp = 5.9, 6.1, 6.3, 6.5, 6.9, and 7.2 km/s, respectively. The updated velocities for the first and last layers are 6% and 26% and the Vp/Vs (=1.70) is 3.03% higher than the previously reported values. A total number of 73 earthquakes with a local magnitude of 2.5 < Ml < 3.9 are located, comprising four main clusters of events, showing a high correlation with the mapped faults zones. The hypocentral depth distribution is mainly in the range of 7-15 km, confined to the upper crust in the region. No specific seismic activity in the eastern branch of Coastal Boundary Fault (CBF) and the continuation of Romanche Fracture Zone (RFZ) in the study period was observed, casting further doubt on the activity of this branch and the hypothesis of stress transfer from RFZ to southern Ghana. The results reinforce the intraplate nature of the tectonic activities in the region. Finally, an updated seismic catalog up to April 2022 is presented for Ghana by incorporating all reported catalogs and combining the newly detected events.

Observation of Uniaxial Strain Tuned Spin Cycloid in a Freestanding BiFeO3 Film

AbstractBismuth ferrite (BiFeO3) possesses a non‐collinear spin order while the ferroelectric order breaks space inversion symmetry. This allows efficient electric‐field control of magnetism and makes it a promising candidate for applications in low‐power spintronic devices. Epitaxial strain effects have been intensively studied and exhibit significant modulation of the magnetic order in bismuthBiFeO3, but tuning its spin structure with continuously varied uniaxial strain is still lacking at this moment. Herein, in situ uniaxial tensile strain is applied to a freestanding BiFeO3 film by mechanically stretching an organic substrate. A scanning nitrogen‐vacancy (NV) microscopy is applied to image the nanoscale magnetic order in real space. The strain is continuously increased from 0% to 1.5% and four images under different strains are acquired during this period. The images show that the spin cycloid tilts by ≈12.6° when strain approaches 1.5%. A first principle calculation is processed to show that the tilting is energetically favorable under such strain. The in situ strain applying method in combination with scanning NV microscope real‐space imaging ability paves a new way in studying the coupling between magnetic order and strain in BiFeO3 films.

Remote Sensing Monitoring of Soil Salinity in Weigan River–Kuqa River Delta Oasis Based on Two-Dimensional Feature Space

Soil salinization is a serious resource and ecological problem globally. The Weigan River–Kuqa River Delta Oasis is a key region in the arid and semi-arid regions of China with prominent soil salinization. The saline soils in the oasis are widely distributed over a large area, causing great harm to agricultural development and the environment. Remote sensing monitoring can provide a reference method for the management of regional salinization. We extracted the spectral indices and performed a correlation analysis using soil measurement data and Sentinel-2 remote sensing data. Then, two-dimensional feature space inversion models for soil salinity were constructed based on the preferred spectral indices, namely, the canopy response salinity index (CRSI), composite spectral response index (COSRI), normalized difference water index (NDWI), and green atmospherically resistant vegetation index (GARI). The soil salinity in a typical saline zone in the Weigan River–Kuqa River Delta Oasis was monitored and analyzed. We found that the inversion of the CRSI-COSRI model was optimal (R2 of 0.669), followed by the CRSI-NDWI (0.656) and CRSI-GARI (0.604) models. Therefore, a model based on the CRSI-COSRI feature space can effectively extract the soil salinization information for the study area. This is of great significance to understanding the salinization situation in the Weigan River–Kuqa River Delta Oasis, enriching salinization remote sensing monitoring methods, and solving the soil salinization problem in China.

Driver Decision Space Inversion Method Based on DC-GAN

In the driving process, drivers need to constantly perceive the surrounding environment to make decisions and perform operations. This cognitive space formed in the driver's mind is the driver's decision space. For the actual driving environment, factors such as complex road sign settings, unreasonable road planning, long-time fatigue driving, and reduced reaction ability of elderly drivers may interfere with the normal perception of the driver's decision space, resulting in reduced driving safety. In this paper, a driver decision space inversion method based on deep convolutional neural networks and generative adversarial networks is proposed to study driver perception in near-domain traffic scenarios. The steps of the method include: near-domain target element extraction, driving data collection, sample data generation, adversarial generative network model learning, data enhancement and decision space inversion. The experimental results show that the method in this paper can accurately identify the driver's decision space in both real and simulated driving scenarios by implementing real-time monitoring of driver perception. The method is important for studying the driver's decision space, which can promote the development of intelligent driving technology and the synergistic development of human-vehicle-road-loop. In the context of today's sustainable transportation and smart mobility, driver decision space research is not only an important basic research, but also an inevitable requirement to promote innovation and upgrading in the transportation field.

40.2: Programmable topological waveguide via nematic liquid crystals

With the rapid development of display technology, liquid crystals have gained significant attention. The unique optical properties of liquid crystals, such as birefringent optical performance and adaptive stimulus-responsiveness, provide a soft material platform for optical communication, biosensing, spatial light modulation, and topological photons. In this paper, based on the tunable refractive index of nematic liquid crystal and the robust transmission characteristics of topological photonic crystals, a valley photonic crystal based on liquid crystal (LCs-VPC) is proposed. The LCs-VPC has graphene-like lattice structure, and the liquid crystal molecules with different refractive indexes are confined in cylinders and hopingly arranged at six vertices of the lattice to break the space inversion symmetry. The topological non-trivial state is generated by adjusting the LCs’ refractive index via bias voltages. Topological waveguides with valley-protected edge modes are designed by stacking different states of lattice cells in the plane. The programmability of the waveguide is achieved by applying an external voltage to encode the state of the LCs in each cylinder. Based on the programmable topological waveguide, a programmable beam splitter has been designed. Our proposed LCs-VPC devices are beneficial for the development of integrated topological photonic circuits.