Search Results (1,173)

The uniformity of local photoelectric properties in infrared detectors is critical for detection sensitivity. However, micro-nano-scale surface abnormalities introduced during mercury cadmium telluride (HgCdTe) fabrication systematically degrade in-plane photoelectric response consistency. To overcome the optical diffraction limits of standard far-field metrology, we utilized a cryogenic scattering-type scanning near-field optical microscopy (Cryo-SNOM) system to achieve the first super-resolution, in situ imaging of local near-field photocurrent in HgCdTe photoconductive detectors at 10 K. Device-level measurements reveal that sub-wavelength surface protrusions (~tens of nanometers high) act as strong recombination centers, suppressing local photocurrent and causing a consistent 10~20% relative signal attenuation compared to planar regions. Power and bias-dependent testing indicate these defects function as unsaturated linear recombination states. Increasing bias voltage amplifies the coupling between the external field and the defect’s built-in field, broadening the local depletion region and driving a non-linear escalation in the attenuation ratio. This study establishes quantitative engineering tolerances for morphological deviations at the nanoscale, providing critical criteria for the chip integration, structural optimization, and precision manufacturing of high-performance infrared sensing arrays. Full article

Laser-induced graphene (LIG) enables rapid conversion of polymer substrates into conductive carbon materials. In this study, nitrogen-containing carbon nanomaterials were fabricated on polyetherimide (PEI) substrates using empirical screening of two specific process points. The resulting materials were characterized using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy to correlate structural features with electron-transfer behavior. Raman and XPS analyses showed different structure and morphology depending on irradiation regime. The carbon materials with a higher sp³ fraction (≈55–59%), larger in-plane crystallite size (L_a up to 8.0 nm), and pronounced π–π* shake-up satellites indicated enhanced graphitic ordering when a shorter nanosecond laser was used. These structural differences resulted in substantially lower charge-transfer resistance (0.53–0.79 kΩ·cm³) and larger electroactive surface areas for the porous electrodes compared with foam structured carbon nanomaterials. The results show that, under the selected fabrication conditions, variations in laser processing parameters correspond to differences in graphitic ordering and electron-transfer properties in PEI-derived laser-induced carbon materials. Full article

The formation and growth of isolated domains during local switching by a biased tip of a scanning probe microscope in a (100) cut of a bismuth titanate Bi₄Ti₃O₁₂ single crystal were studied experimentally. The as-grown domain structure consists of two domain types: a-type (out-of-plane) and b-type (in-plane). Local switching of the a-type domain area leads to anisotropic growth of a hexagonal a-type domain (a-a switching) with 180° walls. The dependence of the domain size on the pulse duration during domain growth along the b-axis was considered in terms of the anisotropic current-limited domain wall motion. Local switching of the b-type domain area leads to formation of a hexagonal a-type domain (b-a switching) with 90° walls increasing in size linearly with the applied voltage. The dependence of the domain size on the pulse duration was measured over a wide range of humidities. The increase in the domain size at moderate humidity is attributed to the effect of the water meniscus. The decrease in the domain size at high humidity is attributed to backswitching under the action of the residual depolarization field, facilitated by a conductive water layer on the side surfaces of the sample. The obtained results provide useful insights into the domain kinetics of ferroelectrics with C₂ symmetry and can pave the way for the development of domain engineering techniques. The obtained results establish a direct relationship between local switching kinetics, crystallographic anisotropy, and environmental conditions. This provides the scientific community with a new framework for understanding domain wall motion in multiaxial ferroelectrics, which is essential for the development of stable and reliable domain-engineered devices. Full article

This paper presents a computationally feasible/time-effective Scan-to-BrIM workflow for generating a highly detailed digital model of a complex steel pedestrian bridge. The proposed methodology integrates rapid and accurate point cloud acquisition with advanced parametric modelling and structural information management. First, a high-resolution point cloud is produced using a fast survey strategy that ensures the geometric precision required for a faithful representation of the existing structure. Second, the point cloud is processed in Rhinoceros/Grasshopper, where a custom Python (version 3.13) algorithm automatically detects and generates reference planes containing the structural components, enabling the creation of a consistent and fully parametric BrIM model. The latter approach includes metric normalization, voxel-based downsampling, reliable under tested conditions ground and outlier removal, and PCA (Principal Component Analysis)-based reorientation, followed by guided slicing of the point cloud and projection of each slice onto its section plane. The proposed workflow achieved a geometric RMSE of 2.5 mm with a total processing time of 7.3 h. The resulting parametric model achieves geometric consistency with the source point cloud within an operational tolerance range of approximately 5–10 mm, in line with the requirements of structural applications. Finally, the model is organised and managed within the BrIM environment and then transferred to a downstream FEM environment for preliminary structural application. The workflow is tested on a case study of a 40-m steel pedestrian bridge located in central Italy. Results demonstrate that the integrated approach provides a reproducible and semi-automated solution that reduces manual intervention in Scan-to-BrIM processes for producing accurate parametric models of steel pedestrian bridges, supporting structural assessment, asset management, and future maintenance strategies. Full article

Background: This study aimed to evaluate the image quality of non-contrast-enhanced whole-heart coronary MR angiography (CMRA) using three different sequences: coronal-plane balanced turbo field echo (BTFE) at 3T, axial-plane modified Dixon (mDixon) at 3T, and axial-plane mDixon at 5T. Methods: Healthy young volunteers were prospectively enrolled from January 2025 to April 2025. Each participant underwent three CMRA scans—3T BTFE, 3T mDixon, and 5T mDixon—using customized MR protocols, all performed within 48 h. Subjective image quality was assessed based on the society of cardiovascular computed tomography 18-segment model using a four-point scale (1 = non-assessable to 4 = excellent). The assessability rate was defined as the percentage of segments receiving a score ≥ 2. Objective evaluation of the main coronary arteries included measurements of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel edge sharpness (VES), and visible vessel length. The Friedman test and one-way repeated measures analysis of variance (ANOVA) were performed to compare parameters obtained from 3T BTFE, 3T mDixon, and 5T mDixon. Results: A total of 20 participants (10 men; mean age, 24 ± 2 years) were included. Both 5T mDixon and 3T BTFE showed more favorable subjective image quality than 3T mDixon, particularly in distal and branch-level coronary segments. All three sequences achieved high vessel assessability. Quantitatively, 5T mDixon provided the highest SNR and CNR, while 3T BTFE showed the highest VES. Visible vessel lengths in LAD and RCA were longer with 5T mDixon and 3T BTFE versus 3T mDixon. However, 5T mDixon required the longest acquisition time (12.55 ± 2.80 min), consistent with its higher spatial resolution. Conclusions: In conclusion, in healthy volunteers, both 5T mDixon and 3T BTFE outperformed 3T mDixon in non-contrast CMRA, particularly in distal and branch-level coronary segments. While 5T mDixon provided the highest SNR and CNR, 3T BTFE achieved the greatest VES. These findings support the technical feasibility of both approaches, but further studies in patients are needed to confirm their clinical applicability Full article

To achieve autonomous ultrasound scanning skill transfer across different physical equipment instances and address the limitations of traditional imitation learning methods—which struggle with cross-instance generalization due to their reliance on specific manipulator parameters—this study proposes a physical-parameter-decoupled imitation learning method based on waypoint representation. This approach utilizes a greedy algorithm to automatically extract key nodes within the task space from expert demonstration trajectories, constructing a trajectory representation decoupled from low-level kinematic parameters and base calibration errors. Simultaneously, a velocity-aware adaptive error precision adjustment mechanism is introduced to dynamically modulate waypoint extraction thresholds, simulating the speed-accuracy strategies employed by sonographers across different scanning phases. Cross-validation across two mainstream generative architectures—Action Chunking Transformer (ACT) and Diffusion Policy—on an offline dataset confirms the plug-and-play capability of waypoint representation in suppressing long-horizon error accumulation, with both architectures achieving significant reductions in prediction errors. For physical deployment, a complete ACT-waypoint system featuring low-level triple safety redundancy was validated. In kidney long-axis standard plane scanning tasks, the system achieved a 92% success rate on the source domain manipulator and maintained an 84% success rate on the target deployment manipulator, despite incompatible low-level kinematic parameters and base coordinates. Force control accuracy remained stable around the target value of 12 N. The results demonstrate that the proposed method effectively overcomes base coordinate and D-H parameter discrepancies to achieve cross-instance zero-shot skill transfer, significantly enhancing the adaptability across physical instances and the scanning success rate of imitation learning models. Full article

High-throughput and compact volume phase holographic (VPH) grating transmission spectrometers are widely employed in scientific research, agriculture, and industrial applications. Conventional transmission spectrometers generally adopt a fixed configuration and therefore have limitations in simultaneously achieving high spectral resolution and broad wavelength coverage. To address the limited tunability of transmission spectrometers, this work presents the theoretical analysis and experimental validation of a transmission spectrometer incorporating a novel catadioptric grating assembly, which consists of a transmitting VPH and a planar reflector. A catadioptric system is a combination of reflective (catoptric) and refractive (dioptric) elements. In the proposed configuration, a VPH grating and a plane mirror arranged at a fixed 90° angle form the catadioptric dispersion module. Synchronous rotation of this assembly enables wavelength scanning. The structure ensures that the diffracted ray along the optical axis of the imaging lens maintains the Bragg condition across the scanning range, thereby preserving maximum diffraction efficiency. The optical configuration and structural parameters of the spectrometer were theoretically derived, and a prototype spectrometer with an f-number of 1.8 employing a 2400 g/mm grating was constructed. Measurements demonstrate that, when the rotation angle is tuned from 30.5° to 50.5°, the accessible spectral range covers from 410 nm to 650 nm. Spectral response measurements using a tungsten–halogen light source confirm that the spectrometer maintains an acceptable diffraction efficiency across the entire tuning range. The measured spectral resolution is 0.1 nm at 626 nm with a 2400 g/mm grating and 0.18 nm with a 1500 g/mm grating. The spectrometer was further applied to fiber-enhanced gas Raman spectroscopy, where it successfully resolved the closely spaced Raman peaks of CH₄ and C₂H₆ that are difficult to distinguish using conventional compact spectrometers. These results demonstrate that the proposed tunable catadioptric spectrometer simultaneously provides excellent wavelength tunability and high spectral resolution. Full article

An empirical model of the kinetics of Hydrogen-Induced Cracking (HIC) in API 5L steels was derived using the best-fit equation for experimental data obtained from cathodic charging tests. The model represents the growth of both individual and interconnecting cracks, using a double exponential equation known as the Gumbel distribution. Current density was the main independent input variable, as it is related to the hydrogen influx during the cathodic charging experiment. The results indicated that in the initial hours of cathodic charging most of the available HIC nucleation sites are activated, the growth of these individual cracks being the main contribution to the overall kinetics. Further crack growth is due to the interconnection of individual cracks, decreasing the growth rate until it becomes nearly zero. The proposed model is used in a simulation algorithm that accurately describes the complete HIC kinetics, for both short- and long-term hydrogen charging exposure, reproducing the effects of applied current density on the total cracked area and growth rates. Finally, the simulation algorithm adequately predicts the spatial distribution of HIC in a bidimensional plane that emulates the detection of HIC by C-scan ultrasonic inspection. Full article

Background: Magnetic Particle Imaging (MPI) is an emerging biomedical imaging modality that detects superparamagnetic iron oxide nanoparticles (SPIONs), providing high contrast, sensitivity, and quantification capabilities without ionizing radiation, making it particularly suitable for cancer diagnostics. Considerable engineering efforts are underway to translate MPI technology to clinical settings. Most of these MPI scanners feature a cylindrical bore geometry similar to that of other clinical imaging modalities, which limits their potential application primarily to head scanning. Methods: We have developed a single-sided MPI scanner designed to expand the modality’s applicability to other regions of the human body through a unique hardware design developed in our previous work. Imaging experiments were performed on an anatomical breast phantom containing implanted SPION point sources placed at anatomically plausible locations for breast tumors. These point sources served as artificial tumors for evaluating the system’s suitability for breast imaging applications. Results: The scanner successfully detected and clearly resolved the implanted SPION tumors in two orthogonal imaging planes. Tumor positioning was independently validated by ultrasound imaging, confirming MPI’s accurate localization. In addition, sensitivity measurements demonstrated a detection limit of 4.0 $\mathsf{\mu }\mathrm{g}$ of iron, below the estimated 4.8 $\mathsf{\mu }\mathrm{g}$ sensitivity threshold required for breast tumor detection with electronic depth scanning up to 3.5 cm deep. Conclusions: Together, these results demonstrate the capability of a single-sided MPI geometry for breast imaging applications. Imaging an anatomical breast-shaped volume presents significant challenges for MPI due to the size and accessibility constraints of conventional hardware. The results presented highlight the advantages of this approach and support its potential to extend MPI from small-animal imaging to clinically relevant applications. Full article

Descemet stripping automated endothelial keratoplasty (DSAEK) is a well-established surgical technique for the treatment of endothelial dysfunction, in which intracameral gas tamponade plays a critical role in graft adherence. We report the case of a 67-year-old pseudophakic woman with advanced Fuchs endothelial corneal dystrophy and symptomatic pseudophakic bullous keratopathy in the right eye, who presented with progressive visual deterioration and underwent DSAEK using an 8.25 mm donor graft inserted with a Busin glide and tamponaded with a 25% sulfur hexafluoride (SF6) gas–air mixture. On the first postoperative day, slit-lamp examination suggested an appropriate anterior chamber configuration and satisfactory graft attachment. However, detailed multiplanar anterior segment optical coherence tomography (AS-OCT), defined here as assessment using vertical, horizontal, and rotational scan orientations, revealed subtle posterior migration of the gas bubble beneath the iris plane. This clinically occult finding indicated altered anterior segment anatomy associated with a risk of secondary angle-closure mechanisms and raised concern for malignant glaucoma. Prompt surgical re-intervention was undertaken on postoperative day one, involving decompression of the misdirected gas bubble and reinjection of a centrally positioned tamponade. This resulted in restoration of normal anterior chamber configuration and stable graft adherence. Best-corrected visual acuity (BCVA) improved from 0.1 Snellen (1.0 logMAR) preoperatively to 0.7 Snellen (0.15 logMAR) at 2 weeks following surgery. This case highlights the added value of multiplanar AS-OCT in detecting clinically occult posterior gas migration after DSAEK, particularly when the abnormality is scan-orientation-dependent and not apparent on slit-lamp examination, thereby enabling timely intervention in the presence of a potentially sight-threatening postoperative configuration. Full article

Compared with the conventional push-broom imaging mode, conical scanning extends the imaging swath through rotational scanning and is suitable for high-resolution, wide-swath remote sensing. To achieve continuous full-coverage imaging, the camera must be mounted at a certain tilt angle and employ an off-axis optical system with a sufficiently large field of view (FOV). However, the tilted installation causes nonuniform irradiance and increased off-axis distortion, while wide-field off-axis imaging also introduces radiometric consistency problems in focal-plane multi-detector stitching. To address these issues, this study investigates the optical design of a tilted off-axis camera for conical-scan imaging. Under the constraints of full coverage and swath requirements, key optical parameters were jointly determined, and a lightweight wide-coverage off-axis three-mirror system was designed, optimized, and evaluated. The final system has a focal length of 1545 mm, an F-number of 8.4, and a full FOV of 23.4° × 11.7°. The modulation transfer function is greater than 0.41 at the Nyquist frequency, and the maximum distortion is less than 2.5446%. In addition, for the focal-plane optical stitching structure, the coupled effects of local structural vignetting and global geometric vignetting induced by the tilted installation were analyzed. The results show that the gray-level difference in the adjacent detector overlap regions is only 0.31–0.53 digital numbers (DN), and the full focal plane shows a smooth gray-level attenuation rate of 5.39–6.77%. These results indicate that vignetting has no significant effect on focal-plane stitching. The proposed camera is well suited for conical-scan imaging. Full article

Infrared focal plane arrays (IRFPAs) often suffer from spatiotemporal nonuniformity that persists after conventional two-point nonuniformity correction (NUC), especially under temperature drift and time-varying readout conditions. These residuals are typically structured, including column-group striping caused by shared column-end circuits and row-wise baseline/common-mode drift induced by row-scanning paths. We propose a structured, digital-twin-inspired detector-side refinement of two-point NUC that augments the bias term with interpretable low-dimensional components: a static column bias vector capturing group-correlated residuals and a row-related structured term consisting of a static row baseline and a frame-synchronous common-mode component with row-dependent sensitivity, while keeping the two-point gain/offset backbone unchanged. Rather than representing a full system-level digital twin of the infrared payload, the proposed framework serves as a detector-side virtual representation of dominant readout-induced structured residual states that can be estimated and updated from calibration data. Experiments on blackbody calibration data across multiple temperature points demonstrate that the column-related structured component significantly reduces group-wise column residuals, the row-related structured component suppresses time-varying row striping, and the combined method improves both column- and row-direction metrics consistently across temperatures. Full article

Accurate and real-time localization is a fundamental prerequisite for the autonomous navigation of mobile robots. LiDAR–Inertial Odometry (LIO) achieves high-precision state estimation and scene reconstruction in unknown environments by effectively fusing data from LiDAR and Inertial Measurement Units (IMU). However, conventional LIO methods typically rely solely on geometric features during point cloud registration. In complex scenarios, such as outdoor unstructured or dynamic environments, these methods are often susceptible to reduced localization accuracy due to geometric degeneration or mismatches. To address these challenges, we propose SV-LIO, A Probabilistic Adaptive Semantic Voxel Map for LiDAR–Inertial Odometry, which leverages point-wise semantic information from semantic segmentation to enhance registration accuracy and system robustness. Specifically, we construct a probabilistic adaptive semantic voxel map that extracts multi-scale spatial planes attached with semantic information. Building on this representation, we employ a semantic-guided strategy for nearest-neighbor plane association between LiDAR scans and the local map, and construct semantic-weighted point-to-plane residuals to constrain pose estimation. By jointly optimizing the IMU-propagated pose prior and semantic-guided LiDAR observation constraints, SV-LIO realizes high-precision real-time state estimation and semantic scene reconstruction. Extensive experiments on the KITTI dataset demonstrate that SV-LIO achieves significant improvements in both localization accuracy compared to state-of-the-art (SOTA) LIO methods, while also constructing semantic maps capable of providing rich environmental information. Full article

Lanthanum silicate oxyapatite (LSO) is a promising oxide ion conductor for low-temperature-operating electrochemical devices owing to its high ionic conductivity along the c-axis. However, the fabrication of thin films with controlled crystallographic orientation remains challenging. In this study, polymer-assisted deposition (PAD), a solution-based technique offering precise microstructural and compositional control, was employed to fabricate c-axis-oriented LSO thin films. The fabrication of undoped LSO and the effects of Al and Mg incorporation on its microstructure, orientation, and ionic conductivity were systematically investigated. Undoped LSO thin films crystallised with a preferential c-axis orientation in the annealing temperature range of 800 and 1100 °C, and scanning transmission electron microscopy observations revealed a highly crystalline, void-free microstructure. Upon annealing at 1200 °C, the undoped LSO exhibited columnar grains with anisotropic in-plane grain growth, whereas Al- or Mg-doped LSO suppressed anisotropic in-plane grain growth and retained an out-of-plane c-axis orientation. The undoped LSO showed higher in-plane ionic conductivity than the doped thin films, consistent with their distinct crystallographic orientations. These results demonstrate that PAD provides a viable pathway for tailoring the microstructure and the composition of LSO thin films, thereby facilitating their applications in solid oxide electrochemical devices. Full article

To address the demand for wide-swath, high-resolution short-wave infrared (SWIR) imaging on resource-constrained spaceborne platforms, this study presents the design and on-orbit validation of a compact dual-channel push-broom (line-scanning) imaging system. The system adopts a transmissive optical architecture and a centralized, compact electronic control unit (ECU) configuration. By interleaving and mosaicking sixteen InGaAs linear array detectors, the system achieves an imaging swath of approximately 187 km and a nominal ground sampling distance of about 24 m, while maintaining a total instrument mass of 10.62 kg and a power consumption of approximately 12 W, thereby demonstrating a high level of integration and efficient resource utilization. To address focal plane consistency issues arising from multi-detector mosaicking, a closed-loop leveling method was developed using the modulation transfer function (MTF) as the primary performance metric. Through defocus estimation and quantitative correction of protrusions on a SiC substrate, convergence toward a unified confocal focal plane among multiple detectors was achieved. On-orbit image quality assessment indicates that the full width at half maximum (FWHM) of the line spread function (LSF) for both channels is approximately 1.38 pixels, with favorable signal-to-noise ratio (SNR) performance. These results validate the effectiveness of the proposed focal plane leveling strategy as well as the opto-mechanical-thermal design of the system. The proposed approach provides a practical pathway for the engineering implementation and consistency control of multi-detector mosaicked SWIR payloads under stringent resource constraints. Full article