bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a microwave-induced atmospheric-pressure plasma source based on cylindrical resonant cavity TM010 mode
Authors: Liu Tao , Zhang Xianyu , Wu Li , Tao Junwu , Zhang Wencong
Published: November 2024

A microwave-induced low-temperature atmospheric-pressure source based on cylindrical resonant cavity TM010 mode was designed. The microwave power was fed into the cavity from a rectangular waveguide on top of it through a coupling hole. A metal pin with adjustable insertion depth was added to the cavity to tune its resonant frequency. The fed waveguide was connected by a sliding short. By tuning the sliding short, the energy transfer efficiency from the waveguide to the cavity was changed. Experiments showed that it could induce an argon discharge in the resonant cavity at atmospheric pressure with as low as 30 W incident wave power without any extra trigger. The plasma length reached 50 mm when the incident wave power was 200 W. By exciting the argon with an extra ignitor in the feeding waveguide, the length of the plasma plume could be extended to 260 mm when the incident wave power was 800 W. The plasma generated by this device was filamentous for both cases. The emission spectrum proved the uniformity of the plasma along its length. This work will be helpful in providing a new alternative microwave plasma device for waste gas treatment or chemical reactions that require plasma catalysis.
Simultaneous determination of refined values of mobility, channel and contact resistance in organic field-effect transistors utilizing the four- and three-probe methods
Authors: Saikh Samayun , Mukherjee Ayash Kanto
Published: November 2024

Accurate determination of charge carrier mobility is a critical aspect in an organic field-effect transistor (OFET) as it is tightly correlated to the development of new materials, better device designs and improved fabrication methods. The presence of high contact resistance at the metal–organic semiconductor interface introduces an intrinsic error in the extraction of charge carrier mobility. In this report, electrical circuit analysis for the determination of the refined channel mobility, total contact resistance and channel resistance values is showcased for a poly(3-hexylthiophene) OFET with bottom-gate bottom-contact architecture. The process of determination is based on the combination of the conventional four-probe and three-probe measurement techniques. These two techniques are used in conjunction to assess refined mobility values in the channel region. This is followed by the determination of total contact resistance and channel resistances. The results show that, at a fixed drain current, mobility increases with the gate voltage while both the contact and channel resistances decrease.
The finite volume effects of the Nambu–Jona–Lasinio model with the running coupling constant
Authors: Su Shou-Zheng , Zhao Ye-Yin , Wen Xin-Jian
Published: November 2024

With Schwinger’s proper-time formalism of the Nambu–Jona–Lasinio model, we investigate the finite volume effects with the anti-periodic boundary condition in the presence of magnetic fields. The model is solved with a running coupling constant G(B), which is properly fitted by the lattice average (Σ
u
 + Σ
d
)/2 and the difference Σ
u
 − Σ
d
. For the model in a finite or infinite volume, the magnetic fields can increase the constituent quark mass M while the temperatures can decrease it. M is close to the infinite volume limit when the box length L is appropriately large. For a sufficiently small value of L, M is close to the chiral limit. The finite volume effects behave intensely in the narrow ranges of L where the partial derivative ∂M/∂L is greater than zero. These narrow ranges can be reduced by stronger magnetic fields and by higher temperatures. In addition, the chiral limit can be restored by a sufficiently small finite volume and be broken by sufficiently strong magnetic fields. Finally, we discuss the thermal susceptibility and the crossover phase transition depending on the temperature at finite volume in the presence of magnetic fields.
A novel end-to-end anomaly detection framework for spacecraft using MINE and LSTM-VAE with attention mechanism
Authors: Yu Bing , Yu Yang , Yang Zhiming , Xiang Gang
Published: November 2024

Anomaly detection in spacecraft plays a pivotal role in ensuring the safety and reliability of aerospace missions. As contemporary spacecraft systems become intricate with the integration of numerous subsystems and components, it is crucial to have effective methods to detect anomalies to maintain the normal operation of the spacecraft and prevent potential failures. However, due to the complexity of the space environment and the high level of integration of systems, conventional anomaly detection methods are often inadequate in dealing with multi-source, high-dimensional, and nonlinear data within spacecraft. To address these problems, this paper proposes a spacecraft end-to-end anomaly detection framework based on Mutual Information Neural Estimation (MINE) and long short-term memory networks-variational autoencoder (LSTM-VAE). This framework employs MINE to capture complex dependencies between features and utilizes LSTM-VAE for temporal modeling and anomaly detection, while an attention mechanism is also incorporated to enhance model interpretability. Specifically, MINE is used to learn nonlinear, high-order dependencies among variables in the aerospace system. LSTM-VAE manages to blend the temporal modeling capability of recurrent neural networks and the advantaged latent representation learning of variational autoencoders, providing deeply integrated modeling of the telemetric data dynamics and latent structure. The introduction of the attention mechanism elevates the model’s interpretability, making it possible to trace anomaly detection results back to specific time points and related features. The research conducted comparative experiments on two novel aerospace telemetry datasets. The results indicate that the proposed framework significantly outperforms existing methods in terms of anomaly detection accuracy, precision, recall rate, and F1 score. Additionally, through case study analysis, we demonstrate this framework’s application in actual spacecraft anomaly detection tasks, thereby illustrating its potential in aiding anomaly source tracing in spacecraft.
A wideband MUSIC algorithm using an improved empirical wavelet transform
Authors: Hu Yi-Ding , Deng Wei-Yao , Wu Gu-Xin , Yang Dong
Published: November 2024

The traditional multiple signal classification (MUSIC) algorithm is only suitable for narrowband array signals, however for wideband signals, sub-band division is required, most of which are based on preset filters or time–frequency analysis. These methods usually require manual selection of the parameters of the filters, basis functions, etc., according to different circumstances, which leads to reduced applicability. This paper proposes a wideband MUSIC algorithm using an improved empirical wavelet transform (EWT), which resolves the sub-band division issue by adaptively constructing a series of empirical wavelet functions to decompose the array received signals. In order to adapt EWT to array signal processing, the spectral division method of EWT is improved by utilizing the spectral mean value and order statistical filter of the array element signals, enabling EWT to uniformly decompose the received signal of each array element. Theoretical research and simulation analysis demonstrate that the wideband MUSIC algorithm using the improved EWT enables effective estimation of arrival angles of wideband signals. Due to the utilization of a more refined adaptive uniform sub-band division technique for array signal, the proposed algorithm has the lowest angle estimation error compared to the MUSIC algorithms based on short-time Fourier transform, auditory filter, and continuous wavelet transform.
A lightweight road traffic sign detection algorithm based on adaptive sparse channel pruning
Authors: Zheng Xiaolong , Guan Zhiwei , Chen Qiang , Wen Guoqiang , Lu Xiaofeng
Published: November 2024

The development of traffic sign recognition (TSR) has become increasingly important for enhancing the safety and convenience of assisted driving. To achieve high accuracy, faster inference speed, and a lightweight model, an improved lightweight TSR network, termed YOLOv8-ALWP, has been proposed. This network incorporates adaptive downsampling to replace the original convolution module in YOLOv8. By employing multiple pooling and convolution operations, it reduces the spatial resolution to extract additional feature information. To accommodate the varying scale characteristics of different traffic signs, large separable kernel attention is introduced to enhance spatial pyramid pooling-fast. Furthermore, the complete intersection over union loss has been improved, and a new Wise-Focaler-EIoU Loss has been proposed to accelerate model convergence and enhance generalization capabilities. Finally, layer-adaptive sparsity for magnitude-based pruning is employed to reduce the model’s parameters, decrease computational complexity, and improve inference speed. Experiments were conducted using the TT100K, Roadsign, CCTSDB, and GTSDB datasets. In the TT100K dataset, compared to the baseline model, the improved algorithm significantly reduced parameters by 64.67%, FLOPs by 44.44%, and increased mAP by 1.7%, precision by 5.5%, and FPS from 70.3 to 81.7, respectively. Under four specific conditions, the improved algorithm effectively addressed the shortcomings of the baseline model, such as missed detections and reduced accuracy. These experimental results indicate that the YOLOv8-ALWP algorithm achieves model lightweighting while enhancing detection accuracy.
Conception and calibration of low-cost diagnostic tool for the evaluation of the thermal, acoustic, and visual comforts in buildings
Authors: Cormier Pierre-Antoine , Laporte-Chabasse Quentin , Berton Julien , Penot Jean-Daniel
Published: November 2024

The comfort of indoor occupants is the primary factor influencing the energy consumption in a building. Even if it is a highly subjective notion, a better understanding of its links with the environmental parameters represents a promising way to optimize building energy consumption. The environmental physical parameters can be easily measured but usually require multiple and/or expensive systems. In this work, we present the conception and the calibration of an inexpensive and straightforward homemade diagnostic tool named VisAcTh, dedicated to measuring the environmental parameters related to indoor thermal, visual, and acoustic comforts. We paid particular attention to the simplicity of the different methods and concepts used in the conception, operation, and calibration. The VisAcTh tool comprises six inexpensive sensors controlled by an ESP32 microcontroller integrated into a 3D-printed PLA box. It allows measuring air temperature, air velocity, mean radiant temperature, relative humidity, atmospheric pressure, noise level, and illuminance. Three sensors require a calibration step to operate in specific indoor conditions, i.e. the homemade globe thermometer, the noise level, and the air velocity sensors. We designed protocols based on a homemade experimental setup that can be easily built using machines available in most fablabs and by scientists with limited knowledge. The last part of the paper is dedicated to evaluating the reliability and performance of the device. Two sets of experiments are performed, during which we monitor the noise level, the illuminance, and the well-known predicted mean vote, which depends on thermal physical parameters. The first one aims to evaluate the reliability of the VisAcTh device by comparing it with reference sensors over a period of a few hours in three spaces of an education building (a classroom, a lobby, and an office). A good agreement was found between these measurements and similar ones obtained from commercial and calibrated sensors. Second, we aim to evaluate the monitoring capability of the device during an extended period. Thus, four new VisAcTh are built, calibrated, and placed in four rooms of a modular education building for four months. The results are in line with the environmental conditions.
Gradient adaptive data augmentation and locally compensated feature fusion network for strip steel surface defect classification based on long tailed distribution
Authors: Zeng Liang , Feng Zheng , Chang Xinyu , Chen Jia , Wang Shanshan
Published: November 2024

Defect classification is a crucial aspect of strip production. The existing methods for strip steel surface defect classification still require improvement due to the multi-category nature and complexity of defects, as well as the long-tailed distribution characteristics of the defect dataset. In this paper, a gradient-adaptive data augmentation and locally compensated feature fusion network for strip steel surface defect classification is proposed. Firstly, we put forward a gradient-adaptive data augmentation method based on the number of category samples to solve the long-tail distribution problem, which uses gradient-adaptive sample expansion to avoid increasing inter-class variation and preserves the probabilistic information contained in the category distribution through an average-based undersampling operation of the category samples. Secondly, a locally compensated feature fusion network is proposed, which is the first method to increase the multi-scale perception capability of the network using local compensation, mimicking the human behaviour of observing complex image patterns, which is compensating the feature information of the global image with the help of the feature information from the local image. The method not only improves the model’s ability to perceive defects, but also mitigates the negative effects of image compression. The experimental results on one public dataset and three private datasets demonstrate that the proposed method achieves significant classification performance improvement. Thus, it is founded that our method provides a promising solution for the strip surface defect classification problem.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Beam heating explains critical current suppression measured during ion irradiation of REBCO tapes
Authors: Devitre A R , Fischer D X , Riva N , Rae M , Kortman L D , Woller K B , Fisher Z L , Short M P , Whyte D G , Hartwig Z S
Published: November 2024

Reports of critical current (

I

c

) suppression during cryogenic ion irradiation of rare earth barium copper oxide (REBCO) tapes have raised concerns for the operational margins of fusion power plant (FPP) magnets. However, the data remain inconclusive regarding beam heating due to the difficulty of measuring local temperatures with contact probes. This leaves a critical knowledge gap concerning the mechanism behind

I

c

suppression, and whether the so-called beam on effect is to be expected under neutron irradiation during FPP operation. In this paper, we show that

I

c

suppression is independent of atomic displacement rate in the REBCO layer, the latter of which increases twelve-fold as we reduce the ion energy from 2400 to 800 keV. At fixed power, we observe statistically identical suppression with 150 keV protons, which do not have enough energy to reach the REBCO layer, refuting hypotheses about beam on effects being caused by nuclear displacements or direct ion-Cooper pair interactions. These results show that REBCO temperature rise alone can explain

I

c

suppression, leaving little to no margin for alternative mechanisms. With this insight, we developed a method to measure beam spot temperature that does not depend on the specific installation of our temperature sensor. With this new method, we measured the temperature gradient across the tape during irradiation and found that thermal resistance at the tape/target interface is the controlling variable in

I

c

suppression. As such, accelerator-based facilities aiming to reproduce the operation of REBCO magnets in a nuclear fusion environment should find strategies to minimize interface thermal resistance. Most importantly, we find that the dose rates expected in a FPP will not change

I

c

due to ballistic radiation damage or ion-Cooper pair interactions, allowing us to safely ignore these effects when designing FPP magnets.
Extended state observer based adaptive fuzzy sliding mode control for multi-motor systems
Authors: Wu Jia-Meng , Huang Xin , Liu Cheng-Lin
Published: November 2024

This paper focuses on the tracking and synchronization control of multi-motor systems and proposes an adaptive fuzzy sliding mode control approach based on an extended state observer. First, a nonsingular sliding mode controller is designed by using the coupling error of multi-motor systems, ensuring that the error converges to a smaller region within a fixed time. Second, fuzzy logic system takes the role of the control signal's discontinuous switching term, which allows the system to adaptively modify its parameters and successfully lessen chattering. Finally, to handle the system's inherent uncertainties and external disturbances, an extended state observer is constructed and integrated into the controller, with its stability proven via the Lyapunov function. Comparative experiments demonstrate that the proposed controller outperforms traditional controllers in terms of control accuracy and response speed.
Inertia of decomposable entanglement witnesses
Authors: Chen Lin , Jiang Bohan
Published: November 2024

We investigate the inertia (i.e., the array of numbers of negative, zero and positive eigenvalues of an Hermitian matrix) of decomposable entanglement witnesses (EWs). We show that the 2 × n and two-qutrit decomposable EWs have the same inertias as those of non-positive-transpose (NPT) EWs. We also show that if an m × n EW W has inertia (p, a

p
, mn − p − a

p
) with p≥1, then for every integer b ∈ [0, a

p
], then we can find an EW W

b
such that InW

b
 = (p, b, mn − p − b). If W is a decomposable (resp. NPT) EW, then we can choose W

b
as also a decomposable (resp. NPT) EW. We further show that the m × n decomposable EW with the maximum number of negative eigenvalues can be chosen as an NPT EW. Then we explicitly characterize the 2 × 3 EWs, and decomposable EWs P
Γ + Q with positive semidefinite matrices P of rank one and Q. We also show that a 2 × 4 non-decomposable EW has no inertia (3, 2, 3). Then we show some properties of a 2 × 4 non-decomposable EW of inertia (2, 3, 3), if it exists.
Trajectory-dependent highly charged ion-induced electron yield from single-layer graphene
Authors: Niggas A , Aumayr F , Wilhelm R A
Published: November 2024

We study the neutralisation dynamics of highly charged ions by transmission through a free-standing single layer of graphene in dependence of the particle trajectory. Both the secondary electron yield and the neutralisation of the ion increase for increasing scattering angles (smaller impact parameters). This supports the current understanding of highly charged ion deexcitation, according to which the presence of an interatomic deexcitation mechanism with improved efficiency in the proximity of neighbours is necessary in addition to intraatomic radiative- and non-radiative decay pathways.
Dual-core photonic crystal fiber based surface plasmon resonance for refractive index and temperature sensing and polarization filtering
Authors: Ullah Sajid , Chen Hailiang , Li Kaifeng , Pei Menglei , Hu Linchuan , Zhang Sa , Wang Chun , Guo Pengxiao , Li Shuguang
Published: November 2024

A dual-core photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor for measuring refractive index (RI) and temperature sensing and polarization filtering performance, is presented in this paper. The proposed sensor’s cladding upper polished surface was coated with a gold film for refractive index sensing (RI) while lower polished surface with a composite film of silver and polydimethylsiloxane (PDMS) for temperature sensing. Proposed sensor was designed and simulated using finite element method (FEM) through commercially available Comsol Multiphysics software. Wavelength sensitivity of 18400 nm/RIU along with resolution of 5.43 × 10−6 RIU and amplitude sensitivity of 150.74 RIU−1 were obtained for core 1 as RI sensing, while wavelength sensitivity of 12.0 nm °C−1 along with resolution of 8.33 × 10−3 °C for core 2 as temperature sensing. It has a maximum loss of 30822 dB m−1 towards Y-polarization which makes it ideal for polarization filtering, as Y has a higher loss than X-polarization. An extinction ratio (ER) of −92.31 dB at a transferring length of 3 mm was obtained showing its polarization filtering capabilities. Overall results indicate that our sensor is highly sensitive for both RI and temperature sensing and expected to perform better in polarization filtering performances. Its wide detection range in RI combined with temperature sensing increases its potential applications in the medical, chemical, environmental, and biosensor detection industry.
On the one-classical-bit quantum teleportation
Authors: Taufiqi Muhammad , Purwanto Agus , Subagyo Bintoro Anang
Published: November 2024

This study re-evaluates Parakh’s one-classical-bit quantum teleportation protocol, in which the proposed protocol replaces the traditional two-classical-bit requirement with a reset procedure, resulting in only one classical bit. However, if the input (to-be-teleported) state is unknown, the reset procedure cannot always work effectively, thereby limiting the protocol’s performance. This study modifies the protocol by adding simple CNOT operations, which ensures that the reset procedure always works properly even when the input state is unknown. We also compute the upper bound of the teleportation success probability and the classical bit resource cost inequality using the one-classical-bit protocol. Finally, we simulate the protocol in Qiskit and discuss the results.
Exploring Hasimoto surfaces within equiform geometry in Minkowski space
Authors: Elsharkawy Ayman
Published: November 2024

In this study, we investigate the equiform geometry of Hasimoto surfaces within the context of three-dimensional Minkowski space. We analyze the geometric characteristics inherent to these surfaces, focusing on their Gaussian and mean equiform curvatures. This analysis encompasses three distinct scenarios involving non-lightlike curves. Additionally, we propose a method for characterizing the parameter curves associated with the equiform Hasimoto surfaces in Minkowski space. To illustrate our findings, we present several examples of these surfaces within this geometric framework.
Obtaining the multiple Debever null directions
Authors: Sáez Juan Antonio , Mengual Salvador , Ferrando Joan Josep
Published: November 2024

The explicit expression of the multiple Debever null directions of an algebraically special spacetime are obtained in terms of the electric and magnetic parts of the Weyl tensor. An algorithm for the determination of the Petrov-Bel type and the algorithm to obtain the multiple Debever null directions are implemented as functions of a new package of xAct, a Mathematica suite of packages for tensor manipulations. These functions are applied to two examples.