bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distortion correction algorithm based on absolute phase image in structured light 3D reconstruction
Authors: Feng Yun , Li Peiwu , Tao Guoren , Wu Rongyu , Lin Jiahao , Liu Xiaojun , Chen Liangzhou 
Published: November 2024

Abstract
This paper proposes a distortion correction algorithm based on absolute phase maps for a dual-projector, single-camera structured light 3D shape measurement system. Distortion correction is performed separately for the projector-camera pairs on the left and right. By projecting a ninth-order complementary Gray code combined with the eight-step phase-shifting method onto a white board, absolute phase maps are obtained, solving the impact of radial and tangential lens distortion. A sub-pixel level distortion error lookup table is introduced to address the influence of residual error after distortion correction on measurement accuracy, improving the overall precision by at least 95.7%. Experiments demonstrate that the dual-projector, single-camera structured light 3D shape measurement system expands the system’s measurement range while reducing shadowing issues caused by single-projector illumination. The proposed distortion correction and error compensation algorithms effectively enhance the overall measurement accuracy of the system and significantly improve issues like warping caused by distortion.
Strengthening effect of nanoprecipitates on twinned copper: a discrete dislocation dynamics simulation study
Authors: Yu Junshi , Wei Dean , Zhao Ke , Yuan Fuping , Kang Guozheng , Zhang Xu 
Published: November 2024

Abstract
Introducing twin boundaries (TBs) and nanoprecipitates has emerged as a highly effective approach for enhancing the mechanical properties of metallic materials. In this paper, the dislocation–precipitate and dislocation-TB interaction models were incorporated into the three-dimensional discrete dislocation dynamics (DDD) framework. The effect of nanoprecipitates on the mechanical properties of single crystal and twinned copper under various loading direction angles was investigated. For single crystal copper containing precipitates, the synergistic strengthening effects of forest dislocations and precipitates were explored by theoretical models. For twinned copper, the TB strengthening effect is derived from DDD simulation results and theoretical models. Analyses revealed that when the loading direction angle is 0° and 90°, the introduction of precipitates has almost no impact on the TB strengthening effect. When the loading direction angle is 90°, the trans-twin dislocations spanning across two lamellae were identified, and the nanoprecipitates hindered the slip of the trans-twin dislocations. When the loading direction angle is 75°, the nanoprecipitates suppressed the strength softening caused by twinning deformation. Furthermore, the accumulation of twinning dislocations on TBs, facilitated by nanoprecipitates, increased the difficulty for dislocations to interact with TB. This study shows the potential of employing DDD for investigating plasticity mechanisms in materials with diverse microstructures, paving the way for future designs of metallic materials through DDD simulations.
Mapping nanoparticle formation and substrate heating effects: a fluence-resolved approach to pulsed laser-induced dewetting
Authors: Mazón-Martínez Artemisa , García-Fernández Tupak , Martínez-Fuentes Marco Antonio , Sánchez-Aké Citlali 
Published: November 2024

Abstract
This study investigates the fluence-dependent evolution of gold nanoparticles formed through single nanosecond pulsed laser dewetting of a gold thin film on a fused silica substrate. By employing a well-defined Airy-like laser spatial profile and reconstructing scanning electron microscope images across the irradiation spot into a panoramic view, we achieve a detailed continuous analysis of the nanoparticle formation process. Our morphological analysis, combined with finite element thermal simulations directly correlated with the applied fluence, identifies two distinct thresholds. The first threshold corresponds to the dewetting of the gold film at its melting point, resulting in large, sparse nanoparticles. The second threshold, where the substrate temperature reaches values near its melting point, leads to the formation of numerous small nanoparticles and a significant increase in coverage area. Notably, the formation of these small nanoparticles is attributed to substrate heating, which alters the interaction between the molten gold film and the substrate, increasing adhesion. Contact angle measurements of the nanoparticles confirm this change, revealing a shift in wettability, and highlighting the crucial role of substrate heating in modulating the interactions leading to nanoparticle formation. Our findings underscore the intricate interplay between laser fluence, material properties, and substrate interactions in pulsed laser dewetting, with the well-defined laser profile offering valuable insights into these dynamics.
Quantum dots synthesis within ternary III–V nanowire towards light emitters in quantum photonic circuits: a review
Authors: Boras Giorgos , Zeng Haotian , Park Jae-Seong , Deng Huiwen , Tang Mingchu , Liu Huiyun 
Published: November 2024

Abstract
The positioning of quantum dots (QDs) in nanowires (NWs) on-axis has emerged as a controllable method of QD fabrication that has given rise to structures with exciting potential in novel applications in the field of Si photonics. In particular, III–V NWQDs attract a great deal of interest owing to their vibrant optical properties, high carrier mobility, facilitation in integration with Si and bandgap tunability, which render them highly versatile. Moreover, unlike Stranski–Krastanov or self-assembled QDs, this configuration allows for deterministic position and size of the dots, enhancing the sample uniformity and enabling beneficial functions. Among these functions, single photon emission has presented significant interest due to its key role in quantum information processing. This has led to efforts for the integration of ternary III–V NWQD non-classical light emitters on-chip, which is promising for the commercial expansion of quantum photonic circuits. In the current review, we will describe the recent progress in the synthesis of ternary III–V NWQDs, including the growth methods and the material platforms in the available literature. Furthermore, we will present the results related to single photon emission and the integration of III–V NWQDs as single photon sources in quantum photonic circuits, highlighting their promising potential in quantum information processing. Our work demonstrates the up-to-date landscape in this field of research and pronounces the importance of ternary III–V NWQDs in quantum information and optoelectronic applications.
Deep learning methods for 3D magnetic resonance image denoising, bias field and motion artifact correction: a comprehensive review
Authors: Singh Ram , Singh Navdeep , Kaur Lakhwinder 
Published: November 2024

Abstract
Magnetic resonance imaging (MRI) provides detailed structural information of the internal body organs and soft tissue regions of a patient in clinical diagnosis for disease detection, localization, and progress monitoring. MRI scanner hardware manufacturers incorporate various post-acquisition image-processing techniques into the scanner’s computer software tools for different post-processing tasks. These tools provide a final image of adequate quality and essential features for accurate clinical reporting and predictive interpretation for better treatment planning. Different post-acquisition image-processing tasks for MRI quality enhancement include noise removal, motion artifact reduction, magnetic bias field correction, and eddy electric current effect removal. Recently, deep learning (DL) methods have shown great success in many research fields, including image and video applications. DL-based data-driven feature-learning approaches have great potential for MR image denoising and image-quality-degrading artifact correction. Recent studies have demonstrated significant improvements in image-analysis tasks using DL-based convolutional neural network techniques. The promising capabilities and performance of DL techniques in various problem-solving domains have motivated researchers to adapt DL methods to medical image analysis and quality enhancement tasks. This paper presents a comprehensive review of DL-based state-of-the-art MRI quality enhancement and artifact removal methods for regenerating high-quality images while preserving essential anatomical and physiological feature maps without destroying important image information. Existing research gaps and future directions have also been provided by highlighting potential research areas for future developments, along with their importance and advantages in medical imaging.
Automated classification of cerebral arteries and veins in the neonate using ultrafast doppler spectrogram
Authors: Fakhari Nikan , Aguet Julien , Nguyen Minh B , Zhang Naiyuan , Mertens Luc , Jain Amish , Sled John G , Villemain Olivier , Baranger Jérôme 
Published: November 2024

Abstract

Objective. Cerebral arterial and venous flow (A/V) classification is a key parameter for understanding dynamic changes in neonatal brain perfusion. Currently, transfontanellar ultrasound Doppler imaging is the reference clinical technique able to discriminate between A/V using vascular indices such as resistivity index (RI) or pulsatility index (PI). However, under conditions of slow arterial and venular flow, small signal fluctuations can lead to potential misclassifications of vessels. Recently, ultrafast ultrasound imaging has paved the way for better sensitivity and spatial resolution. Here, we show that A/V classification can be performed robustly using ultrafast Doppler spectrogram. Approach. The overall classification steps are as follows: for any pixel within a vessel, a normalized Doppler spectrogram (NDS) is computed that allows for normalized correlation analysis with ground-truth signals that were established semi-automatically based on anatomical/physiological references. Furthermore, A/V classification is performed by computing Pearson correlation coefficient between NDS in ground-truth domains and the individual pixel’s NDS inside vessels and finding an optimal threshold. Main Results. When applied to human newborns (n = 40), the overall accuracy, sensitivity, and specificity were found to be 88.5% ± 6.7%, 88.5% ± 6.5%, and 87.0% ± 8.8% respectively. We also examined strategies to fully automate this process, leading to a moderate decrease of 1%–3% in the same metrics. Additionally, when compared to the main clinical metrics such as RI, and PI, the receiver operating characteristic curves exhibited higher areas under the curve; on average by +36% (p < 0.0001) in the full imaging sector, +35% (p = 0.0116) in the cortical regions, +53% (p < 0.0001) in the basal ganglia, +28% (p = 0.0051) in the cingulate gyrus, and +35% (p < 0.0001) in the remaining brain structures. Significance: Our findings suggest that the proposed NDS-based approach can distinguish between A/V when studying cerebral perfusion in neonates.
Nonlinear parameter estimation with physics-constrained spectral–spatial priors for highly accelerated chemical exchange saturation transfer MRI
Authors: Nguyen Chinh Dinh , Kim HyungGoo R , Yoo Roh Eul , Choi Seung-Hong , Park Jaeseok 
Published: November 2024

Abstract

Objective. To develop a nonlinear, model-based parameter estimation method directly from incomplete measurements in k − w space for robust spectral analysis in highly accelerated chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI). Approach. A CEST-specific, separable nonlinear model, which describes spectral decomposition using multi-pool Lorentzian functions (conventional magnetization transfer (MT), direct saturation of water signals (DS), amide, amine, and nuclear Overhauser effect) derived from the steady-state Bloch McConnel equation, is incorporated into a measurement model in CEST MRI. Furthermore, signal drop in saturation transfer experiments is formulated by an additional, separable nonlinear spectral prior indicating that the symmetric z-spectra synthesized using conventional MT and DS always remain higher or equal to the whole z-spectra with all pools. Given the above considerations, linear and nonlinear parameters in the proposed method are estimated in an alternating fashion directly from highly incomplete measurements in k − w space by solving a constrained optimization problem with the physics-constrained spectral priors while imposing additional sparsity priors on spatial parameter maps. Main results. Compared with conventional methods, the proposed method yields clearer delineation of tumor-specific CEST maps without apparent artifact and noise. Significance. We successfully demonstrated the feasibility of the proposed method for CEST MRI with highly incomplete measurements thus enabling high-resolution whole brain CEST MRI in clinically reasonable imaging time.
An improved calibration procedure for accurate plastic scintillation dosimetry on an MR-linac
Authors: van den Dobbelsteen Madelon , Lessard Boby , Côté Benjamin , Hackett Sara L , Mugnes Jean-Michel , Therriault-Proulx François , Lambert-Girard Simon , Uijtewaal Prescilla , de Vries Laurie J M , Archambault Louis , Bosma Tom , van Asselen Bram , Raaymakers Bas W , Fast Martin F 
Published: November 2024

Abstract

Objective. Plastic scintillation dosimeters (PSDs) are highly suitable for real-time dosimetry on the MR-linac. For optimal performance, the primary signal (scintillation) needs to be separated from secondary optical effects (Cerenkov, fluorescence and optical fiber attenuation). This requires a spectral separation approach and careful calibration. Currently, the ‘classic’ calibration is a multi-step procedure using both kV and MV x-ray sources, requiring an uninterrupted optical connection between the dosimeter and read-out system, complicating efficient use of PSDs. Therefore, we present a more time-efficient and more practical novel calibration technique for PSDs suitable for MR-linac dosimetry. Approach. The novel calibration relies on prior spectral information combined with two 10 × 10 cm2 field irradiations on the 1.5 T MR-linac. Performance of the novel calibration technique was evaluated focusing on its reproducibility, performance characteristics (repeatability, linearity, dose rate dependency, output factors, angular response and detector angle dependency) and IMRT deliveries. To investigate the calibration stability over time, prior spectral information up to 315 days old was used. To quantify the time efficiency, each step of the novel and classic calibration was timed. Main results. The novel calibration showed a high reproducibility with a maximum relative standard deviation of 0.2%. The novel method showed maximum differences of 1.2% compared to the gold-standard calibration, while reusing old classic calibrations after reconnecting fibers showed differences up to 3.0%. The novel calibration improved time efficiency from 105 to 30 min compared to the classic method. Significance. The novel calibration method showed a gain in time efficiency and practicality while preserving the dosimetric accuracy. Therefore, this method can replace the traditional method for PSDs suitable for MR-linac dosimetry, using prior spectral information of up to a year. This novel calibration facilitates reconnecting the detector to the read-out system which would lead to unacceptable dosimetric results with the classic calibration method.
Low current iodine-fed hollow cathode discharge: insights from fluid model
Authors: Liu Ran , Liu Wei , Li Yifei , Wang Weizong , Zhang Guangchuan , Tang Haibin 
Published: November 2024

Abstract
As one of the fundamental components, hollow cathodes using noble gas propellant are widely used in electric thrusters. Iodine has become one of the ideal alternative propellants due to its economy and good chemical properties, while due to the complex reactions, characteristics and proper functioning of iodine-fed hollow cathodes are still unknown. Therefore, a model is needed to understand the physical-chemical process of the iodine-fed hollow cathode discharge. In this work, a self-consistent two-dimensional fluid model of the low-current iodine-fed hollow cathode discharge with detailed non-equilibrium plasma chemistry is developed and verified by the voltages of the keeper and anode obtained in the experiments. Simulations show that the electron impact ionization with iodine atoms dominates the discharge process as the density of iodine atoms is much higher than that of iodine molecules due to the electron impact dissociation and thermal dissociation. Moreover, the power balance analysis shows the heating of electrons contributed by the electric field mainly takes place near the keeper and the orifice. Ion current heating contributes significantly to the gas heating compared with the heating by the electron elastic collisions with I and I2 and the heat release or consumption during the neutral reactions. Furthermore, the influence of electronegativity on plasma characteristics is analysed. Simulations involving I− ions bring higher values of ionization degree, discharge power as well as maximum electron and gas temperatures compared with those without I−. This is similar to the differences in the plasma properties between the iodine-fed and xenon-fed hollow cathode to which the low ionization energy, large collision ionization cross-section and the electronegativity of iodine contribute together. In all, these findings can better predict the plasma behaviours in the iodine-fed hollow cathode discharge and may promote the development of the electric propulsion system using iodine propellant.
Ar/CF4 capacitively coupled plasma generated using 40 MHz sinusoidal and 800 kHz rectangular waveform voltages
Authors: Rauf Shahid , Ganta Sathya , Shi Xingyi , Bera Kallol , Kenney Jason 
Published: November 2024

Abstract
This article discusses the characteristics of an Ar/CF4 capacitively coupled plasma (CCP) excited using 40 MHz sinusoidal and 800 kHz rectangular voltage waveforms. The simulations focus on the effect of the low frequency (LF) rectangular wave duty cycle (defined as the period at negative voltage) on the plasma properties and uniformity for constant 100 W power at 40 MHz and 20 mTorr gas pressure. Given the importance of kinetic effects in low pressure CCPs, a hybrid plasma model is used. This model treats electrons as particles using the particle-in-cell formalism while ions and neutral species are represented as fluids. By incorporating electron kinetic effects, this approach allows for the accurate modeling of low-pressure CCPs with complex plasma chemistries. Results show that, at 80% duty cycle, the peak in the density of all species is near the edge of the electrodes. As the LF rectangular wave duty cycle is decreased while keeping the 40 MHz power fixed, the species’ densities increase, the 40 MHz radio-frequency voltage decreases, and the peak in species’ densities shifts towards the chamber center. These trends can be explained based on how the LF voltage modulates the coupling of 40 MHz power to the electrons. Under the conditions considered, the plasma is mostly produced through electron stochastic heating at the sheath edge by the 40 MHz voltage. The 40 MHz couples to the electrons more efficiently when the LF voltage at the powered electrode sheath is small and the sheath is thin. The plasma is produced relatively uniformly in the inter-electrode region during this phase. Therefore, at small duty cycles when the powered electrode sheath is thin for a long time, the plasma is uniform and requires a smaller 40 MHz voltage to deposit 100 W at 40 MHz in the plasma. When the LF voltage in the powered electrode sheath is large and negative, plasma production is weak and occurs at the edge of the powered electrode where the sheath is thinner. At large duty cycles, the plasma is efficiently produced for only a short period, necessitating a larger 40 MHz voltage. The plasma density also peaks near the electrode edge at large duty cycles.
GaN planar SBD grown and fabricated on SiC substrate with a cutoff frequency of 2.17 THz
Authors: Gu Guodong , Hao Xiaolin , Wang Yawei , Song Xubo , Zhang Lisen , Liang Shixiong , Lv Yuanjie , Feng Zhihong 
Published: November 2024

Abstract
To attain a higher cutoff frequency in GaN planar Schottky Barrier Diodes (SBDs), we investigated the relationship between various structural parameters of the device and its electrical characteristics. Our investigation primarily focused on how the series resistance (R
s) and junction capacitance are affected by the thickness and doping concentration of the N− GaN layer, as well as the anode size, with the goal of improving the diode’s operating frequency. The results indicate that by employing an appropriate doping concentration and epitaxial layer thickness, the cutoff frequency of GaN diodes can exceed 2 THz. At last, by increasing the N− GaN doping concentration to 8e17 cm−3 and decreasing the N− GaN layer thickness to 100 nm, the fabricated GaN SBD with a diameter of 1.2 μm and cathode-to-anode distance of 0.8 μm exhibits a series resistance (R
s) of 27.2 Ω and a zero-biased junction capacitance (Cj

0) of 2.69 fF, yielding a record cutoff frequency of 2.17 THz. The results suggest that the working frequency of GaN-based multipliers could be further improved for high-power terahertz source applications.
A tri-functional integrated hybrid energy harvester for the efficient collection of low-frequency environmental vibrational energy
Authors: Deng Long , Zhang Hu , Chen Yurun , Zhu Xifeng , Xu Caihua , Wu Xubin , Chen Ping , Li Wenqi , Xie Liqiang 
Published: November 2024

Abstract
To address the power supply challenges of Internet of Things (IoT) devices, this study proposes a novel tri-functional integrated hybrid energy harvester (TF-HEH) for efficiently capturing low-frequency environmental vibrations. The TF-HEH integrates triboelectric, electromagnetic, and piezoelectric mechanisms within a compact, 60 g cylindrical structure. Optimized for a 40 mm magnet length, the proposed TF-HEH exhibited high efficiency in converting vibrations into electricity, with peak outputs of 13 μW (pipe wall triboelectric generator), 17 μW (pipe cap triboelectric generator), 51.2 μW (piezoelectric nanogenerators), and 12.3 mW (electromagnetic generator) under a swing input with a 0.5 Hz frequency and 30° amplitude. The lightweight and portable design renders the device suitable for self-powered sensor operation in IoT applications.
Development of a dual-DOF vibration energy harvester using a foldable spring pendulum mechanism
Authors: Li Jiarong , Wang Tao , Zeng Fanqin , Liu Shuo 
Published: November 2024

Abstract
The novelty of this design is that it changes the traditional idea of an unchangeable pendulum length to achieve folding and stretching through the shear fork structure. The concept of spring as the modulation mechanism of the vibration energy harvester is introduced to complete the dynamic change of the pendulum length and realize the dual degrees of freedom output of the roll and heave motions. The spring mechanism integrated into the design, including tension and torsion springs, not only realizes the flexible expansion of the structure but also significantly enhances the ability of the vibration energy harvester to capture external vibration energy through the unique energy storage and release mechanism. The vibration energy harvester has been designed, mathematically simulated, constructed, and experimentally tested with good results, characterized by dual mode state, low-frequency characteristics, and high-power output. Experimental results show that the prototype can achieve an average power output of 5.47 W at an excitation frequency of 0.8 Hz, corresponding to a normalized power output of 377.42 W g−2 and a normalized power density of 26.25 W g−2 kg−1.