Search Results (26)

Nanodefect engineering has emerged as an effective strategy to address the inherent strength–ductility trade-off and limited damage tolerance of wrought and cast magnesium alloys through controlled manipulation of their defect structures. Recent advances demonstrate that introducing and tailoring nanoscale defects can significantly enhance mechanical performance and, under appropriate defect architectures and processing conditions, may enable improved strength–ductility balance. This review provides a concise, mechanism-oriented overview of nanodefect-mediated strengthening in Mg alloys, focusing on the roles of nanograins, nanoprecipitates, nanotwins, and nano-stacking faults. Grain refinement via severe plastic deformation and other processing routes enhances strength through Hall–Petch effects while modifying texture and activating non-basal slip. Concurrently, nanoscale precipitates contribute through dislocation shearing and Orowan bypassing, whereas planar defects such as nanotwins and stacking faults introduce high-density interfaces that both impede dislocation motion and facilitate plastic accommodation. Emphasis is placed on the synergistic interactions among these defect populations, which govern strain hardening, deformation stability, and the overall strength–ductility balance. The review underscores that tailored defect architectures, achieved through integrated processing and alloy design, provide a viable pathway for developing next-generation Mg alloys with improved and tunable mechanical performance. Full article

The β grain size in titanium alloys during industrial forging is critical for balancing toughness, cost-effectiveness, and processability. To address the industrial challenge of high cost and difficulty in refining β grains to the tens of micrometers scale, this study investigates the feasibility of achieving a superior strength–ductility balance in TC18 alloy with near-industrial coarse β grains (296~857 μm) under room temperature tension. A pronounced inverse correlation is observed between β grain size and both strength and ductility. The yield strength–grain size relationship follows the Hall–Petch effect, while the anomalous increase in ductility for fine-grained specimens is attributed to three factors. First, smaller grains provide a higher grain boundary density, promoting stress redistribution and mitigating stress concentrations. Second, more uniform stress distribution induces thinner, denser kink bands that enhance plasticity. Third, strain-induced martensite evolves from discrete nanoscale particles to discontinuous lines and ultimately coalesces into continuous planar bands along the (112)β and (110)β planes. This phase transformation, which initiates below a critical grain size of ~500 μm, further alleviates stress concentrations towards slip bands and contributes to dynamic work hardening. The findings demonstrate that coordinated deformation mechanisms enable excellent mechanical performance even in coarse-grained microstructures, providing a practical pathway for optimizing industrial-grade titanium alloys. Full article

The acoustic design of outpatient halls is often ignored, yet the acoustic environment significantly impacts patients’ physical and mental well-being as well as their visit experience. This paper takes the outpatient hall of a hospital in South China as a case, employs in-situ acoustic measurement, and conducts a quantitative analysis of its indoor acoustic environment through acoustic simulation. The in-situ measurements show that the noise level, speech intelligibility and reverberation time in the hall all fail to meet standard requirements. The poor acoustic quality is mainly due to the lack of acoustic design. Consequently, this study proposes measures to improve the outpatient hall’s acoustic environment from two aspects, namely sound absorption and building form design. These measures include sound absorption treatment, adjustment of the hall’s floor height and optimization of planar length-to-width ratio. The redesigned outpatient hall plan demonstrates an evident enhancement in acoustic quality and validates the effectiveness of the proposed redesign strategy. This study can provide practical guidance for the design and acoustic renovation of healthcare buildings and can also offer new insights for the redesign of hospital outpatient halls from the perspective of improving the acoustic environments. Full article

Electric propulsion (EP) has become a pivotal technology in modern space exploration, enabling prolonged mission durations, increased payload capacity, and precise deep-space navigation through its superior thrust efficiency and low propellant consumption. However, the performance of EP systems is fundamentally limited by the power processing unit (PPU), with the DC-DC power converter serving as the core of the PPU. Existing research on DC-DC converters often focuses on generic topologies, failing to address the divergent power demands of distinct EP types and the harsh space-specific constraints. This review aims to fill this gap by systematically analyzing DC-DC power converters tailored for EP systems. First, the core requirements of converters across major EP categories are classified. Then, converter topologies are compared by evaluating the suitability for EP operational and space constraints. Moreover, high step-up conversion techniques are explored that bridge the gap between low-voltage spacecraft buses and thruster power needs. Furthermore, this review highlights emerging technologies driving EP converter advancement, such as wide-bandgap semiconductors for improved power density and efficiency, planar magnetics for miniaturization, and direct-drive architecture for simplified Hall-effect thruster integration. It also identifies unresolved challenges, including balancing power density with thermal robustness, mitigating radiation-induced degradation, and suppressing electromagnetic interference (EMI). Finally, it outlines future research directions, such as optimizing WBG-compatible converter topologies, developing advanced thermal management solutions, and standardizing EP-specific design guidelines. This work provides a practical reference for PPU engineers, linking converter design to EP unique demands and space constraints while guiding innovations to advance EP technology for next-generation space missions, from low-Earth orbit satellites to interplanetary exploration. Full article

In this study, the stress–strain constitutive models of Cu-Cu joints in hybrid bonding after primary and secondary annealing were determined using nanoindentation experiments and finite element inverse analysis, and the correlation mechanism between the microstructure and macroscopic mechanical properties in hybrid bonding Cu-Cu joints during secondary annealing was revealed. The 350–400 °C secondary annealing facilitates recrystallization–grain growth, increasing grain size from 0.62 μm after primary annealing to 0.71 μm, accompanied by a 12% reduction in kernel average misorientation (KAM) values. This process enhances interface non-planarization and optimizes bonding quality. Concurrently, the secondary annealed Cu-Cu joints exhibit a softening effect, manifested by decreasing trends in elastic modulus (131.02 → 118.98 GPa), hardness (1.78 → 1.51 GPa), and yield strength (70.52 → 56.12 MPa), primarily attributed to the Hall–Petch effect and residual stress release. Notably, the yield strength of secondary annealed Cu-Cu joints demonstrates 31.0% and 68.5% enhancements compared to TSV-Cu (42.83 MPa) and bulk Cu (33.3 MPa), respectively. Full article

Quasi-one-dimensional (quasi-1D) topological matter Bi₄X₄ (X = Br, I) possesses versatile topological phases determined by its molar ratio of halide and the stacking mode. Establishing the intrinsic relationship between these topological orders and the quantum transport properties is extremely crucial for both of fundamental research and device applications. Here we review the recent work on the characteristic quantum transport behavior of the Bi₄X₄ system originating from various electronic states, including three-dimensional (3D) bulk states, two-dimensional (2D) surface states, and one-dimensional (1D) topological hinge states. Specifically, variable range hopping effect, Lifshitz transition, metal–insulator transition, and Shubnikov de Haas oscillations are evoked by the gapped bulk states with significant doping carriers. In 2D limits, the (100) surface states exhibit Dirac-type dispersion to produce weak antilocalization, which is a strong 1D nature due to quasi-1D crystal and electronic structure and evidenced by anomalous planar Hall effect. Last but not the least, coherent transport with Aharonov–Bohm oscillations is observed in thin-layer devices, implying the existence of 1D topological hinge states separated by the (100) surface. These unconventional quantum transport features verify the topological nature of Bi₄X₄ in different dimensions, signifying an ideal platform to design and utilize multiple topological orders in this quasi-one-dimensional material system. Full article

We report high-resolution, cavity-enhanced direct frequency comb Fourier transform spectroscopy of cold acetylene (C₂H₂) molecules in a planar supersonic jet expansion. The experiment is based on a near-infrared frequency comb with a 300 MHz effective repetition rate, matched to a high-finesse enhancement cavity traversing the jet. The rotational and translational cooling of acetylene was achieved via expansion in argon carrier gas through a slit nozzle. By interleaving successive mode-resolved spectra measured at different comb repetition rates, we retrieved full absorption line profiles. Spectroscopic analysis reveals sharp, Doppler-limited transitions corresponding to a jet core rotational temperature below 7 K. Frequency comb and cavity stabilization were achieved through active Pound–Drever–Hall locking and mechanical vibration damping, enabling a spectral precision better than 2 MHz, limited by the vibrations induced by the pumping system. The demonstrated sensitivity reaches a minimum detectable absorption of 7.8 × 10⁻⁷ cm⁻¹ over an 18 m effective path length in the jet core. This work illustrates the potential of cavity-enhanced direct frequency comb spectroscopy for precise spectroscopic characterization of cold supersonic expansions, with implications for studies in molecular dynamics, reaction kinetics, and laboratory astrophysics. Full article

Real-time acquisition of high-precision 3D spatial information is critical for intelligent maintenance of urban infrastructure. While SLAM technology based on LiDAR–IMU sensor fusion has become a core approach for infrastructure monitoring, its accuracy remains limited by vertical pose estimation drift. To address this challenge, this paper proposes a LiDAR–IMU fusion SLAM algorithm incorporating a dynamic coplanarity constraint and a joint observation model within an improved error-state Kalman filter framework. A threshold-driven ground segmentation method is developed to robustly extract planar features in structured environments, enabling dynamic activation of ground constraints to suppress vertical drift. Extensive experiments on a self-collected long-corridor dataset and the public M2DGR dataset demonstrate that the proposed method significantly improves pose estimation accuracy. In structured environments, the method reduces z-axis endpoint errors by 85.8% compared with Fast-LIO2, achieving an average z-axis RMSE of 0.0104 m. On the M2DGR Hall04 sequence, the algorithm attains a z-axis RMSE of 0.007 m, outperforming four mainstream LiDAR-based SLAM methods. These results validate the proposed approach as an effective solution for high-precision 3D mapping in infrastructure monitoring applications. Full article

Spin transport behaviors in heavy metal/ferromagnetic insulator (HM/FI) bilayers have attracted considerable attention due to various novel phenomena and applications in spintronic devices. Herein, we investigate the planar Hall effect (PHE) in Pt/Tm₃Fe₅O₁₂ (Pt/TmIG) heterostructures at low temperatures; moment switching in the ferrimagnetic insulator TmIG is detected by using electrical measurements. Double switching hysteresis PHE curves are found in Pt/TmIG bilayers, closely related to the magnetic moment of Tm³⁺ ions, which makes a key contribution to the total magnetic moment of TmIG film at low temperature. More importantly, a magnetoresistance (MR) curve with double switching is found, which has not been reported in this simple HM/FI bilayer, and the sign of this MR effect is sensitive to the angle between the magnetic field and current directions. Our findings of these effects in this HM/rare earth iron garnet (HM/REIG) bilayer provide insights into tuning the spin transport properties of HM/REIG by changing the rare earth. Full article

Planar Hall magnetoresistance (PHMR) sensors are widely utilized due to their high sensitivity, simple structure, and cost-effectiveness. However, their performance is influenced by both the driving mode and the thickness of the ferromagnetic layer, yet the combined effects of these factors remain insufficiently explored. This study systematically investigates the impact of Ni₈₀Fe₂₀ thickness (5–35 nm) on PHMR sensor performance under constant current (CC) and constant voltage (CV) modes, with a focus on optimizing the peak-to-peak voltage (V_p-p). In CC mode, electron surface scattering at 5–10 nm increases resistance, leading to a sharp rise in V_p-p, followed by a decline as the thickness increases. In contrast, CV mode minimizes resistance-related effects, with sensor signals predominantly governed by magnetization-dependent resistivity. Experimentally, the optimal V_p-p was observed at 25 nm in CV mode. However, for thicknesses beyond this point, the reduction in sensor resistance suggests that voltage distribution across both the sensor and external load resistance significantly influences performance. These findings provide practical insights into optimizing PHMR sensors by elucidating the interplay between driving modes and material properties. The results contribute to the advancement of high-performance PHMR sensors with enhanced signal stability and sensitivity for industrial and scientific applications. Full article

We use an array of nine elliptical Planar Hall Effect (PHE) sensors and machine learning algorithms to map the magnetic signal generated by a magnetic source. Based on the obtained mapping, the location and nature of the magnetic source can be determined. The sensors are positioned at the vertices of a symmetrical and evenly spaced 3 × 3 grid. The main electronic card orchestrates their measurement by supplying the required driving current and amplifying and sampling their output in a synchronized manner. A two-dimensional interpolation of the data collected from the nine sensors fails to yield a satisfactory mapping. To address this, we employed the Levenberg–Marquardt Algorithm (LMA) as a deterministic optimization method to estimate the magnetic source’s position and parameters, as well as machine earning (ML) algorithms, which consist of a Fully Connected Neural Network (FCNN). While LMA provided reasonable results, its reliance on a sparse sensor network and initial guesses for variables limited its accuracy. We show that the mapping is significantly improved if the data are processed with an FCNN that undergoes training and testing. Using simulations, we demonstrate that achieving similar improvement without ML would require increasing the number of sensors to more than 50. Full article

Charged quasiparticles, which are constrained to move on a plane, interact by means of electromagnetic (EM) fields which are not subject to this constraint, living, thus, in three-dimensional space. We have, consequently, a hybrid situation where the particles of a given system and the EM fields (through which they interact) live in different dimensions. Pseudo-Quantum Electrodynamics (PQED) is a U(1) gauge field theory that, despite being strictly formulated in two-dimensional space, precisely describes the real EM interaction of charged particles confined to a plane. PQED is completely different from QED(2 + 1), namely, Quantum Electrodynamics of a planar gauge field. It produces, for instance, the correct $1/r$ Coulomb potential between static charges, whereas QED(2 + 1) produces $lnr$ potential. In spite of possessing a nonlocal Lagrangian, it has been shown that PQED preserves both causality and unitarity, as well as the Huygens principle. PQED has been applied successfully to describe the EM interaction of numerous systems containing charged particles constrained to move on a plane. Among these are p-electrons in graphene, silicene, and transition-metal dichalcogenides; systems exhibiting the Valley Quantum Hall Effect; systems inside cavities; and bosonization in (2 + 1)D. Here, we present a review article on PQED (also known as Reduced Quantum Electrodynamics). Full article

The magnetic field range in which a magnetic sensor operates is an important consideration for many applications. Elliptical planar Hall effect (EPHE) sensors exhibit outstanding equivalent magnetic noise (EMN) on the order of $\mathrm{pT}/\sqrt{\mathrm{Hz}}$, which makes them promising for many applications. Unfortunately, the current field range in which EPHE sensors with $\mathrm{pT}/\sqrt{\mathrm{Hz}}$ EMN can operate is sub-mT, which limits their potential use. Here, we fabricate EPHE sensors with an increased field range and measure their EMN. The larger field range is obtained by increasing the uniaxial shape-induced anisotropy parallel to the long axis of the ellipse. We present measurements of EPHE sensors with magnetic anisotropy which ranges between 12 Oe and 120 Oe and show that their EMN at 10 Hz changes from 800 $\mathrm{pT}/\sqrt{\mathrm{Hz}}$ to 56 $\mathrm{nT}/\sqrt{\mathrm{Hz}}$. Furthermore, we show that the EPHE sensors behave effectively as single magnetic domains with negligible hysteresis. We discuss the potential use of EPHE sensors with extended field range and compare them with sensors that are widely used in such applications. Full article

An exchanged-biased anisotropic magnetoresistance bridge sensor for low currents measurement is designed and implemented. The sensor has a simple construction (single mask) and is based on results from micromagnetic simulations. For increasing the sensitivity of the sensor, the magnetic field generated by the measurement current passing through the printed circuit board trace is determined through an analytical method and, for comparative analysis, finite elements method simulations are used. The sensor performance is experimentally tested with a demonstrator chip. Four case studies are considered in the analytical method: neglecting the thickness of the trace, dividing the thickness of the trace in several layers, and assuming a finite or very long conductive trace. Additionally, the influence of several adjacent traces in the sensor area is evaluated. The study shows that the analytical design method can be used for optimizing the geometric selectivity of a non-contacting magnetoresistive bridge sensor setup in single trace, differential, and multi-trace (planar coil) configurations. Further, the results can be applied for developing highly performant magnetoresistance sensors and optimizations for low field detection, small dimensions, and low costs. Full article

Sp²-hybridized monolayer semiconductors (e.g., planar group III-V and IV-IV binary compounds) with inversion symmetry breaking (ISB) display piezoelectricity governed by their σ- and π-bond electrons. Here, we studied their bond-orbital-resolved electronic piezoelectricity (i.e., the σ- and π-piezoelectricity). We formulated a tight-binding piezoelectric model to reveal the different variations of σ- and π-piezoelectricity with the ISB strength ($\Delta$). As $\Delta$ varied from positive to negative, the former decreased continuously, but the latter increased piecewise and jumped at $\Delta =0$ due to the criticality of the π-electrons’ ground-state geometry near this quantum phase-transition point. This led to a piezoelectricity predominated by the π-electrons for a small $|\Delta |$. By constructing an analytical model, we clarified the microscopic mechanisms underlying the anomalous π-piezoelectricity and its subtle relations with the valley Hall effect. The validation of our models was justified by applying them to the typical sp² monolayers including hexagonal silicon carbide, Boron-X (X = N, P, As, Ab), and a BN-doped graphene superlattice. Full article