bluuebunny/crossref_metadata_2025 huggingface dataset:
MnTiO3 as a carbon-free cathode for rechargeable Li–O2 batteries
Authors: Ahmed Doaa Aasef , Çelik Mustafa , Mayr-Schmölzer Wernfried , Kızılaslan Abdulkadir , Vonbun-Feldbauer Gregor B.
Published: January 2025

Advancing carbon-free cathodes is vital for enhancing Li–O2 battery performance. Here, we report for the first time the use of MnTiO3 as a carbon-free cathode, exhibiting low overpotential and exceptional electrochemical properties.
Two-dimensional conjugated polymers with weakened interlayer interaction for highly sensitive visible responsiveness to compression stresses
Authors: Takeuchi Yui , Imai Hiroaki , Oaki Yuya
Published: January 2025

Here, we have found that a new layered polydiacetylene (PDA) with weakened interlayer interactions exhibits visible color changes in response to weak compression stresses in the range of P = 2.5–125 MPa.
VSDRL: A robust and accurate unmanned aerial vehicle autonomous landing scheme
Authors: Chen Dechao , Shi Chentong , Pan Xiaofeng , Jin Jie , Li Shuai
Published: January 2025

Visually assisted unmanned aerial vehicle (UAV) autonomous landing has drawn a lot of interest as a vital technology with the quick development of UAV systems. From the perspective of robustness, a visual servoing disturbance rejection landing (VSDRL) scheme based on fractional‐order linear active disturbance rejection control is novelly proposed to achieve the disturbance‐resistant landing. The proposed VSDRL scheme is constructed by two modules: (i) A visual positioning algorithm combining YOLOv5 with Kalman filtering to solve the occlusion problem in the visual positioning module obtaining the relative position relationship; (ii) On the basis of linear active disturbance rejection control, fractional order is introduced to improve the antidisturbance ability and response speed. Theoretical analysis, computer simulations and real UAV experiments all verify the effectiveness and superiority of the proposed VSDRL scheme.
OLODN: An efficient lightweight people detection method for occlusion and crowding scenarios
Authors: Sheng Wei , Liu Mingjian , Li Xiang , Zhang Mingbao
Published: January 2025

Addressing the real‐time object detection problem for devices with limited computing resources in densely populated and occluded scenarios, a novel occlusion‐aware lightweight object detection network (OLODN) is proposed. This network integrates innovative components to significantly enhance detection efficiency while maintaining high accuracy. Firstly, OLODN employs FasterNet blocks and reparameterised generalised‐FPN to reduce computational complexity and preserve feature extraction and fusion capabilities. Secondly, a reinforced coordination attention mechanism is designed to strengthen the network's ability to capture occlusion boundary information. Additionally, a spatial pyramid pooling feature concatenation module is introduced to integrate multi‐scale features and enhance the algorithm's robustness to occlusions. Lastly, OLODN adopts a task‐aligned one‐stage object detection strategy, optimising the anchor alignment of classification and localisation tasks, effectively improving detection accuracy under occluded conditions. Experiments demonstrate the superiority of the proposed method. On the WiderPerson dataset, OLODN achieved a recall rate of 68.0%, which is 2.8% higher than YOLOv11's 65.2%, while running at 35.3 frames per second (f/s) on CPU and 76.6 f/s on GPU, faster than YOLOv11's 34.1 f/s and 74.5 f/s by 1.2 f/s and 2.1 f/s, respectively.
Detecting clusters and groups of galaxies populating the local Universe in large optical spectroscopic surveys
Authors: Marini I. , Popesso P. , Dolag K. , Bravo M. , Robotham A. , Tempel E. , Li Q. , Yang X. , Csizi B. , Behroozi P. , Biffi V. , Biviano A. , Lamer G. , Malavasi N. , Mazengo D. , Toptun V.
Published: January 2025

Context. With the advent of wide-field cosmological surveys, samples of hundreds of thousands of spectroscopically confirmed galaxy groups and clusters are becoming available. While these large datasets offer a valuable tool to trace the baryonic matter distribution, controlling systematics in the identification of host dark-matter halos and estimating their properties remains crucial.

Aims. We intend to evaluate the predictions of retrieving the population of cluster and group of galaxies using three group-detection methods on a simulated dataset replicating the GAMA survey selection. Our goal is to understand the systematics and selection effects of each group finder, which will be instrumental for interpreting the unprecedented volume of spectroscopic data from SDSS, GAMA, DESI, and WAVES, and for leveraging optical catalogues in the (X-ray) eROSITA era to quantify the baryonic mass in galaxy groups.

Methods. We simulated a spectroscopic galaxy survey in the local Universe (down to z < 0.2 and stellar mass completeness M⋆ ≥ 109.8 M⊙) using a lightcone based on the cosmological hydrodynamical simulation Magneticum. We assessed the completeness and contamination levels of the reconstructed halo catalogues and analysed the reconstructed membership. Finally, we evaluated the halo-mass recovery rate of the group finders and explored potential improvements.

Results. All three group finders demonstrate high completeness levels (> 80%) on the galaxy group and cluster scales, confirming that optical selection is suitable for probing dense regions in the Universe. Contamination at the low-mass end (M200 < 1013 M⊙) is caused by interlopers and fragmentation. Galaxy membership is at least 70% accurate above the group-mass scale; however, inaccuracies can lead to systematic biases in halo-mass determination using the velocity dispersion of galaxy members. We recommend using other halo-mass proxies less affected by contamination – such as total stellar luminosity or mass – to recover accurate halo masses. Further analysis of the cumulative luminosity function of the galaxy members has shown remarkable accuracy in the group finders’ predictions of the galaxy population.

Conclusions. These results confirm the reliability and completeness of the spectroscopic catalogues compiled by these state-of-the-art group finders. This paves the way for studies that require large sets of spectroscopically confirmed galaxy groups and clusters or studies of galaxy evolution in different environments.
The Solar System’s passage through the Radcliffe wave during the middle Miocene
Authors: Maconi E. , Alves J. , Swiggum C. , Ratzenböck S. , Großschedl J. , Köhler P. , Miret-Roig N. , Meingast S. , Konietzka R. , Zucker C. , Goodman A. , Lombardi M. , Knorr G. , Lohmann G. , Forbes J. C. , Burkert A. , Opher M.
Published: January 2025

Context. As the Solar System orbits the Milky Way, it encounters various Galactic environments, including dense regions of the interstellar medium (ISM). These encounters can compress the heliosphere, exposing parts of the Solar System to the ISM, while also increasing the influx of interstellar dust into the Solar System and Earth’s atmosphere. The discovery of new Galactic structures, such as the Radcliffe wave, raises the question of whether the Sun has encountered any of them.

Aims. The present study investigates the potential passage of the Solar System through the Radcliffe wave gas structure over the past 30 million years (Myr).

Methods. We used a sample of 56 high-quality, young (≤30 Myr) open clusters associated with a region of interest of the Radcliffe wave to trace its motion back and investigate a potential crossing with the Solar System’s past orbit.

Results. We find that the Solar System’s trajectory intersected the Radcliffe wave in the Orion region. We have constrained the timing of this event to between 18.2 and 11.5 Myr ago, with the closest approach occurring between 14.8 and 12.4 Myr ago. Notably, this period coincides with the Middle Miocene climate transition on Earth, providing an interdisciplinary link with paleoclimatology. The potential impact of the crossing of the Radcliffe wave on the climate on Earth is estimated. This crossing could also lead to anomalies in radionuclide abundances, which is an important research topic in the field of geology and nuclear astrophysics.
Frozen and β-equilibrated f and p modes of cold neutron stars: Nuclear metamodel predictions
Authors: Montefusco Gabriele , Antonelli Marco , Gulminelli Francesca
Published: January 2025

Context. When the chemical re-equilibration timescale is sufficiently long, the normal and quasi-normal mode frequencies of neutron stars should be calculated in the idealised limit that the internal composition of each fluid element is fixed over the oscillation period. However, many studies rely on a barotropic equation of state, implicitly overlooking potential out-of-β-equilibrium effects.

Aims. We investigate potential biases that may arise from the assumption of purely barotropic models in studies of oscillation modes. To address this, we calculated the non-radial fundamental (f) and first pressure (p1) modes for a wide range of neutron star structures, each characterised by different nucleonic equations of state. This approach also yields posterior distributions for the oscillation frequencies, which could be detected by next-generation gravitational wave interferometers.

Methods. A wide range of nuclear equations of state are generated with the metamodel technique, a phenomenological framework that incorporates constraints from astrophysical observations, experimental nuclear physics, and chiral effective field theory. The metamodel also provides the internal composition of β-equilibrated npeμ matter, allowing us to calculate oscillation modes beyond those supported by a purely barotropic fluid.

Results. By exploiting the observed validity of quasi-universal relations, we developed a simple technique to estimate the general relativity corrections in relation to the commonly used Cowling approximation and provide a posterior predictive distribution of expected f- and p1-mode frequencies.
Probing the low-energy particle content of blazar jets through MeV observations
Authors: Tavecchio F. , Nava L. , Sciaccaluga A. , Coppi P.
Published: January 2025

Many of the blazars observed by Fermi actually have the peak of their time-averaged gamma-ray emission outside the ∼GeV Fermi energy range, at ∼MeV energies. The detailed shape of the emission spectrum around the ∼MeV peak places important constraints on acceleration and radiation mechanisms in the blazar jet and may not be the simple broken power law obtained by extrapolating from the observed X-ray and GeV gamma-ray spectra. In particular, state-of-the-art simulations of particle acceleration by shocks show that a significant fraction (possibly up to ≈90%) of the available energy may go into bulk quasi-thermal heating of the plasma crossing the shock rather than producing a nonthermal power-law tail. Other gentler but possibly more pervasive acceleration mechanisms, such as shear acceleration at the jet boundary, may result in a further build-up of the low-energy (γ ≲ 102) particle population in the jet. As already discussed for the case of gamma-ray bursts, the presence of a low-energy Maxwellian-like bump in the jet particle energy distribution can strongly affect the spectrum of the emitted radiation, for example producing an excess over the emission expected from a power-law extrapolation of a blazar’s GeV-TeV spectrum. We explore the potential detectability of the spectral component ascribable to a hot quasi-thermal population of electrons in the high-energy emission of flat-spectrum radio quasars (FSRQs). We show that for the typical physical parameters of FSRQs, the expected spectral signature is located at ∼MeV energies. For the brightest Fermi FSRQ sources, the presence of such a component will be constrained by the upcoming MeV Compton Spectrometer and Imager (COSI) satellite.
Experimental setup for labyrinth seals: Pressure, temperature, mass flow rate, rotation velocity, and pressure drop simultaneous measurement
Authors: Ribeiro L. N. B. S. , Freire A. D. , Barros G. P. S. , Maffei F. S. , Azevêdo A. S. C. , Siqueira L. O. , Alonso D. H. , Picelli R. , Machado I. F. , de Sá L. F. N. , Martinez C. B. , Meneghini J. R. , Silva E. C. N.
Published: January 2025

Labyrinth seals (LSs) in turbomachinery are used to minimize leaks. This study presents an experimental setup designed to test and validate LS designs. The test bench (TB) described in this paper can evaluate different LS designs obtained through various methods to find better solutions to mitigate greenhouse gas (GHG) emissions. Prototypes with conventional geometry, such as straight-through and interlaced LSs, are initially implemented and tested. A measurement procedure and experimental methodology for collecting leakage data are defined. The experimental methodology includes a measurement TB that supports a pressure difference of up to 5 bar. The leakage rate is measured in g/s using instrumentation that corrects the mass flow rate based on pressure and temperature measurements. The experimental results are compared to the Computational Fluid Dynamics results. Thus, the setup given in this article is a new and versatile TB setup focused on leakage measurement, which allows being used for analyzing various types of LS (with or without rotor structures) and is effective for evaluating the performance of LSs, helping the development of new LS geometries that can reduce GHG emissions.
Investigation into the stability of chemical doping and the structure of carbon nanotube
Authors: Suzuki Daichi , Terasaki Nao , Nonoguchi Yoshiyuki
Published: January 2025

Thermoelectric power generation using carbon nanotubes (CNTs) has attracted considerable attention as a clean energy technology. A variety of chemical dopants that are stable in air have been reported to improve the thermoelectric performance of CNT; however, the stability of the chemical dopants is sometimes not reproducible. Therefore, we focused on the effects of CNT and chemical n-dopant structures on the stability and thermoelectric properties. We n-doped CNTs with different properties and measured their transient responses for 180 days. The stability was found to strongly depend on not only the dopant structure but also the structure of the CNT, especially the diameter. This is because CNTs with small diameters have a wide bandgap and a high energy level of the conduction band, and chemical dopants with a stronger electron-donating ability are required to obtain stable n-type CNTs. Therefore, the stability of chemical dopants strongly depends not only on the dopant structure but also on the structure of the CNT itself. This study focuses on the diameter among all the different structural parameters of CNTs. However, our findings indicate that the structure of CNTs is an essential factor to be considered while discussing the stability of chemical dopants.
Cavitating vortex rope in a diffuser at different operation conditions
Authors: Puga Diana , Geng Chen , Wang Ziyang , Luo Xianwu
Published: January 2025

A self-induced instability known as vortex rope enhanced by cavitation usually occurs at part load operation conditions in the draft tube and negatively affects the normal operation of Francis turbines. In the present study, the Francis turbine draft tube was simplified and modeled as a diffuser with swirling flow to analyze and understand the flow patterns of the cavitating turbulent flow with strong vortex oscillation. The numerical simulation used the modified shear stress transport partially averaged Navier–Stokes, i.e., MSST PANS turbulence model, and the Zwart–Gerber–Belamri cavitation model to investigate the flow characteristics of the cavitating vortex rope in the diffuser at different cavitation and swirl numbers. The vortex precession and the cavitation surge predicted by simulations agree with the available experimental data, indicating the applied numerical method is suitable for the present study. The results reveal that a smaller cavitation number and larger swirl number promote vortical flow oscillations, which induce pressure fluctuations in the diffuser. Furthermore, the pressure fluctuations can be enhanced by the increase in swirl number, and the frequency and amplitude of the dominant pressure pulsation component significantly increase with the swirl number. It is also depicted that the interaction between vortex rope precession and cavitation surge directly determines the pressure fluctuations in the diffuser at different operation conditions. The analysis based on the vorticity transport equation indicates that the vortex stretching term has an extremely important effect on vortex production for the cavitating vortex rope evolution under the present operation conditions.
Dynamics of single bubble between a moving spherical boundary and a plate structure
Authors: Gu Jintong , Dong Zhanwang , Yao Yuan , Huan Haixiang , Zeng Yong , Li Liang , Zhang Leen
Published: January 2025

Boundary conditions significantly influence the near-field dynamics of bubbles. This study employs numerical simulations to investigate the coupling characteristics of high-pressure bubbles near solid boundaries and moving spherical boundaries. It focuses on the effects of the sinking velocity of the sphere and the initial bubble–boundary distance on bubble evolution and loading characteristics. The results indicate that an increase in the sphere's sinking velocity or a decrease in the initial bubble–boundary distance leads to bubble tearing during the collapse process. This generates high-speed water jets directed either toward the bubble center or the boundary, significantly reducing the kinetic energy of the sphere. The shock waves and water jets caused by bubble tearing temporarily impede the sphere's motion, while the lagging flow induced by bubble expansion and contraction has a relatively minor impact. As the initial bubble–boundary distance increases, the bubble tearing phenomenon gradually weakens and may even disappear. This attenuation is attributed to the suppression of the Bjerknes effect by the boundary, which reduces the tendency of the bubble to migrate toward the boundary. Furthermore, the intensity of the tearing phenomenon significantly affects the pressure distribution near the bubble region around the sphere. Strong tearing induces a double-peaked pressure profile, while weak tearing results in a single-peaked profile primarily dominated by bubble collapse. This study reveals the critical influence of bubble–boundary interactions on sphere motion and pressure distribution, providing valuable insights for engineering design and applications in related fields.
Numerical modeling of asphaltene deposition in CO2-flooded porous media
Authors: Chen Shun , Dong Pingchuan , Adoum Abakar Y. , Zhang Youheng , Li Lili
Published: January 2025

CO2 flooding disrupts asphaltene balance, causing deposition and reservoir damage. Most models lack core verification, resulting in inaccurate predictions of asphaltene deposition and reservoir performance. The Discrete Phase Model (DPM) of Volume model for characterizing asphaltene deposition during CO2 flooding was established by coupling Volume of Fluid with DPM, which simulates the complex interaction between CO2-flooded crude oil and asphaltene flow deposition dynamics. Key factors such as CO2 mole fraction, displacement velocity, crude oil viscosity, asphaltene density, and particle size on asphaltene deposition, as well as the impact on reservoir porosity and permeability degradation, were comprehensively examined. The findings show that increasing CO2 mole fraction from 0.2 to 1 enhances asphaltene deposition rate by 53.6% and damages porosity and permeability by factors of 2.4 and 5.78, respectively. Raising CO2 injection velocity rises from 0.006 to 0.016 m/s reduces the deposition rate by 17.97%, the porosity damage factor drops from 1.981 to 1.075 and the permeability damage factor decreases from 3.926 to 1.556. Higher crude oil viscosity significantly reduces both deposition rate and related damage, while increasing particle density and diameter correlate with greater deposition and damage rates. Asphaltene particles accumulate within the throats of porous media as dispersed particulates, while they densely pack within the pores. Gray correlation analysis reveals that CO2 mole fraction exhibits the highest relationship with both the rate of asphaltene particle deposition and the extent of pore permeability impairment. This study enhances understanding of asphaltene deposition dynamics and reservoir damage mechanisms in CO2-flooded.
Polaronic transport and magnetic field dependence of conduction parameters in rGO-CFO nanocomposites
Authors: Manzoor Sadia , Anwar Rohina , Hussain Shahzad , Arshad Zuharia , Darr Jawwad Arshad
Published: January 2025

In this paper we report the AC conductivity σ and magnetoconductivity Δσ of a series of reduced graphene oxide-cobalt ferrite (rGO-CFO) composites in which the mass ratio of rGO:CFO has been systematically varied over six compositions. The conductivity measured in the frequency range of 20 Hz to 3 MHz showed an anomalous increase with CFO content in the composite, even though the conductivity of CFO is at least three orders of magnitude smaller than that of rGO. Magnetoconductivity measured in fields upto 2000 Oe displayed both negative and positive values depending on the rGO:CFO ratio. Maximum magnetoconductivity of ∼ +14% was obtained at room temperature in a magnetic field of only 750 Oe. Samples having the largest σ and Δσ values also showed significant softening/hardening of the Raman active modes of CFO, indicating polaronic transport in these composites. Fits of σ(f) data to a power law σ(f) = σ
o + Afn
showed that parameters A and n depend strongly on the applied magnetic field. This dependence is qualitatively and quantitatively different for samples that display positive or negative magnetoconductivity. Although the temperature dependence of these conduction parameters has been extensively studied, we have not come across any reports of their magnetic field dependence. Based on these observations we present a surface polaron model in which hybridization of π-orbitals of graphene with surface states of CFO nanoparticles provides for a polaron conduction mechanism through a grid of CFO nanoparticles intercalated with rGO sheets.
High-temporal dynamic self-powered β-Ga2O3/GaN heterojunction ultraviolet photodetector
Authors: Wang Lisheng , Zhang Yifan , Dong Junxing , Wang Runchen , Wang Jingzhuo , Wang Zenan , Wang Xianghu , Shen Si , Zhu Hai
Published: January 2025

In this report, we successfully fabricate a high-temporal-response β-Ga2O3/GaN heterojunction ultraviolet (UV) photodetector. A high-quality 2-inch single-crystalline β-Ga2O3 film is grown on GaN template with a GaO
x
buffer layer using plasma-assisted molecule beam epitaxy. Based on the as-grown film, a self-powered heterojunction detector with a unilateral recessed interdigital electrode is constructed. The device exhibits a broad-spectrum UV selective response characteristics with a cut-off edge at 330 nm and achieves a responsivity of 0.7 A W−1 under zero bias. Under a bias of 5 V, the rapid photoresponse rise time and decay time are 30 μs and 10.8 ms, respectively, and the photo-to-dark current ratio reaches 103. Considering the heterojunction energy band structure of β-Ga2O3/GaN, the work function difference of 0.43 eV facilitates electron migration and enables the self-powered operation. These results demonstrate a promising and efficient approach for developing high-performance, self-powered UV photodetectors and offer a robust alternative to conventional high-energy-consuming UV detection systems.
Scaling theory for non-Hermitian topological transitions
Authors: Kartik Y R , R Kumar Ranjith
Published: January 2025

Understanding the critical properties is essential for determining the physical behavior of topological systems. In this context, scaling theories based on the curvature function in momentum space, the renormalization group (RG) method, and the universality of critical exponents have proven effective. In this work, we develop a scaling theory for non-Hermitian topological states of matter. We utilize the curvature function renormalization group (CRG) method, incorporating biorthonormal vectors for a one dimensional

2
×
2

non-Hermitian Dirac model. This approach allows us to analyze the Wannier state correlation function (WCF) and determine the corresponding localization critical exponent. The CRG method successfully identifies topological phase transitions and locates stable and unstable fixed points. To account for non-Hermitian effects, we construct the curvature function in the generalized Brillouin zone using non-Bloch wave functions, enabling a comprehensive WCF and CRG analysis.
Quantum transport under oscillatory drive with disordered amplitude
Authors: Tiwari Vatsana , Dattagupta Sushanta , Singh Bhakuni Devendra , Sharma Auditya
Published: January 2025

We investigate the dynamics of non-interacting particles in a one-dimensional tight-binding chain in the presence of an electric field with random amplitude drawn from a Gaussian distribution, and explicitly focus on the nature of quantum transport. We derive an exact expression for the probability propagator and the mean-squared displacement in the clean limit and generalize it for the disordered case using the Liouville operator method. Our analysis reveals that in the presence a random static field, the system follows diffusive transport; however, an increase in the field strength causes a suppression in the transport and thus asymptotically leads towards localization. We further extend the analysis for a time-dependent disordered electric field and show that the dynamics of mean-squared-displacement deviates from the parabolic path as the field strength increases, unlike the clean limit where ballistic transport occurs.
A novel fault diagnosis method based on convolutional neural network with adaptive noise injection
Authors: Xiao Lei , Wang Jun , Liu Ximing , Sun Huanan , Zhao Hailong
Published: January 2025

In most existing intelligent fault diagnosis methods, noise is considered harmful and may decrease diagnosis accuracy. In contrast to these methods, this study proposes a novel fault diagnosis method with extra noise injection, termed an adaptive-noise-injected convolutional neural network (CNN). Noise is intentionally injected into a CNN model’s softmax layer to improve fault diagnosis accuracy. The injected noise is used in the iteration of the CNN model and adaptively adjusted according to the change in model loss. Bearing datasets from Case Western Reserve University and Paderborn University were used to validate the effectiveness of the proposed method. The robustness of the proposed method was illustrated by injecting Gaussian and uniform noise. By comparing the ablation study results with those of the state-of-the-art methods, and t-test results before and after noise injection, the effectiveness of noise injection in enhancing diagnosis accuracy was demonstrated. The proposed method performed well on small samples and in complex working conditions, and possesses good generalizability and the ability to deal with real-world datasets.
Demonstration of checking an audit trail for a measuring instrument using runtime verification
Authors: Okamoto Junichi
Published: January 2025

An audit trail check is expected to be incorporated as a new task for the verification of a measuring instrument in legal metrology. To prepare for this incorporation, an idea of an audit trail check using runtime verification (RV) and abstract formal specifications were proposed. The idea was to allow an RV tool to judge whether an audit trail satisfied the check formula, and the specification was a template for the check formula. In the present study, we demonstrate this idea. The target of our demonstration is a weighing instrument, which is only defined in a design document and not implemented. We adopt a first-order temporal logic to describe the check formulas and use MONPOLY as an RV tool. For the demonstration, we generate an audit trail of the instrument based on the behavior specified in the design document, derive check formulas from the abstract formal specifications, and then run MONPOLY. This study presents not only the demonstration, but also both our audit trail design for generating an audit trail and the derivation of check formulas. They will be helpful in the implementation of audit trail checks using RV for various measuring instruments.
Fabrication of hierarchical sapphire nanostructures using ultrafast laser induced morphology change
Authors: Cheung Joshua , Chien Kun-Chieh , Sokalski Peter , Shi Li , Chang Chih-Hao
Published: January 2025

Sapphire is an attractive material that stands to benefit from surface functionalization effects stemming from micro/nanostructures. Here we investigate the use of ultrafast lasers for fabricating sapphire nanostructures by exploring the relationship between irradiation parameters, morphology change, and selective etching. In this approach a femtosecond laser pulse is focused on the substrate to change the crystalline morphology to amorphous or polycrystalline, which is characterized by examining different vibrational modes using Raman spectroscopy. The irradiated regions are removed using a subsequent hydrofluoric acid etch. Laser confocal measurements quantify the degree of selective etching. The results indicate a threshold laser pulse intensity required for selective etching. This process was used to fabricate hierarchical sapphire nanostructures over large areas with enhanced hydrophobicity, with an apparent contact angle of 140 degrees, and a high roll-off angle, characteristic of the rose petal effect. Additionally, the structures have high broadband diffuse transmittance of up to 81.8% with low loss, with applications in optical diffusers. Our findings provide new insights into the interplay between the light-matter interactions, where Raman shifts associated with different vibrational modes can predict selective etching. These results advance sapphire nanostructure fabrication, with applications in infrared optics, protective windows, and consumer electronics.
Comparison of spoke dynamics in an obstructed direct-current magnetron operating on a range of noble gases
Authors: Przybocki R C , Cappelli M A
Published: January 2025

Fluctuations in discharge current are observed using a segmented anode on a direct-current planar magnetron discharge. The oscillations have frequencies in the 350–3400 kHz range and are indicative of coherent plasma structures propagating in the closed-drift azimuthal direction, commonly referred to as ‘rotating spokes.’ The structures are studied across a range of discharge and ambient pressure conditions for the inert gases neon, argon, krypton, and xenon. It is found that the argon, krypton, and xenon plasmas exhibit a transition from spoke propagation opposite the

E

×

B

drift direction at low current densities to propagation in

E

×

B

at higher current densities. This reversal occurs at a threshold current density of 5–17 mA 

cm

−
2

, depending on the pressure and ion species. The wave dispersion properties of the oscillations are also studied, and the transition to

+

E

×

B

-directed modes is shown to be accompanied by lower frequencies and higher phase velocities. The number of spoke structures exhibits a non-linear dependence on pressure and current. The frequency and wavenumber of the disturbances are modeled with a similarity solution that suggests a dependence on the critical ionization velocity in the wave dispersion, which points to ionization wave phenomena governing the spoke dynamics.
Collisional radiative model based investigation on the color appearance of xenon plasma in Hall thruster plumes
Authors: Feng Kun , Zhang Zhongkai , Qi Jiayun , Yi Tianlang , Zhang Guangchuan , Wang Yibai , Zhang Zun , Ren Junxue , Wang Weizong , Tang Haibin
Published: January 2025

Hall thruster is a type of electric propulsion system used for spacecraft. The study of the Hall thruster plume, which is a plasma, reveals the thruster’s performance. Images of Hall thruster operating can be found from various online sources, the thruster plumes are typically transparent with a slight blue or green hue. However, some plumes are colorful instead of being monochromatic, with distinguishable regions. In this study, we investigated the xenon plasma color using a collisional radiative model and explained the color appearance of Hall thruster plumes. We show that xenon atoms and ions appear in different colors. For a standard observer, singly charged xenon ions appear in green, irrespective of the plasma environment. Xenon atoms, on the other hand, can appear blue, violet, or magenta. Through the investigation, we found that the resulting plasma color is related to the mass utilization efficiency and ion velocity of the thruster plume. We introduce an approach to produce color from collisional radiative models, where we use color as a property of the plasma, and demonstrate its usefulness for plasma studies.
Electron dynamics and particle transport in capacitively coupled Ar/O2 discharges driven by sawtooth up voltage waveforms
Authors: Dong Wan , Gao Zhuo-Yao , Wang Li , Zhang Ming-Jian , Tian Chong-Biao , Liu Yong-Xin , Song Yuan-Hong , Schulze Julian
Published: January 2025

One dimensional fluid/electron Monte Carlo simulations of capacitively coupled Ar/O2 discharges driven by sawtooth up voltage waveforms are performed as a function of the number of consecutive harmonics driving frequencies of 13.56 MHz, N (1–3), pressure (200–500 mTorr) and gas mixture (10%–90% admixture of O2 to Ar). The effects of these external parameters on the electron dynamics, and the transport of ions and neutrals are revealed at constant peak-to-peak driving voltage. The electronegativity is found to decline as the number of consecutive harmonics increases and the DC self-bias voltage decreases. Increasing the pressure also leads to a decrease in electronegativity. The combination of a decrease in the mean free path of electrons and the presence of the electrical asymmetry effect result in different spatio-temporal distributions of the ionization rate, which lead to a reduction in the amplitude of the DC self-bias at higher pressure. As the admixture of electronegative O2 increases, the electronegativity is enhanced, and the discharge mode changes from an α—drift ambipolar (DA) hybrid to DA mode. This work focuses on linking these fundamental changes of the plasma physics induced by changing external parameters to process relevant charged particle and neutral fluxes to the electrodes. Particular attention is paid to O(1D) flux, because it is a precursor of deposition. In discharges driven by sawtooth up voltage waveforms, placing the substrate on the grounded electrode and increasing the number of consecutive harmonics, N, can facilitate the deposition process, since the O(1D) flux to the substrate is higher in these scenarios. Moreover, at an O2 admixture of 20%, the O(1D) flux is nearly as high as that at an O2 admixture of 90%, indicating that a higher O(1D) flux can be achieved without excessively increasing the O2 admixture.
Research on hybrid processing of silicon carbide based on laser cutting
Authors: Wang Jinhu , Jiang Kai , Yue Xiuhui , Zhang Qianyong , Wang Cuishan , Jing Xueting , Wang Jing , Tang Wenjing , Xia Wei
Published: January 2025

With the rapid development of semiconductor technology, silicon carbide has been widely used in various power electronic device. However, the material has an extremely high hardness ranking second only to diamond, which makes processing difficult. In this work, the two methods of laser cutting and dicing saw are utilized to test the cutting process of silicon carbide respectively, then the appropriate through-cutting process parameters are obtained. The two methods are combined to compare the cutting quality of the three approaches. As a result, the laser cutting is affected by heat with through-cutting 0.5 mm-thick silicon carbide, which results in the rough front-surface edge and much residue, and the cutting groove of the back surface is irregular. The dicing saw having more mechanical stress, resulting in serious tool wear, prone to chipping and micro-cracks and other phenomena, the back surface chipping is as high as 171.6 µm. The hybrid processing method not only reduces the degree of thermal damage, but also reduces tool wear, and the front surface is flat and clean after cutting, without a chipping phenomenon, and the back surface chipping is only 7.9 µm, which is 20 times lower than the dicing saw method.
REBCO coated conductors: enabling the next generation of tokamak reactors
Authors: Li Xiaodong , Ainslie Mark , Song Dongbin , Yang Wenjiang , Macián-Juan Rafael
Published: January 2025

The discovery of rare-earth barium copper oxide (REBCO) materials with high critical temperatures, and the continued advancements in the fabrication of REBCO coated conductors with extremely high critical current densities, has enabled the development of ultra-high-field (>20 T) compact and large-scale thermonuclear fusion devices. At present, around a dozen global commercial manufacturers are able to supply high-quality REBCO coated conductors with excellent performance. Significant advancements have been made for high-temperature, low-field applications such as motors, generators, long-length transmission cables, and so on using REBCO coated conductors. Nonetheless, multiple ongoing critical challenges under low-temperature, high-field conditions, such as irreversible degradation of the critical current, along with insufficient mechanical protection and inadequate reduction of AC losses, remain unsolved, collectively hindering their utilization in high-field thermonuclear fusion reactors. This paper provides a comprehensive theoretical and technical review of the current state-of-the-art, associated challenges, and prospects in the research and development (R&D) of REBCO coated conductors, cables, and magnet systems for high-field fusion. It highlights the significant enhancements in current-carrying capacity, mechanical protection, and AC loss reduction achieved over the past decade. The paper delves into detailed analyses of potential cabling solutions that offer exceptional current-carrying capacity while ensuring an optimal inductance balance for toroidal, poloidal, and central solenoid coils in tokamak devices. This work endeavours to lay the groundwork for the R&D of the next-generation REBCO magnets to facilitate the construction of ultra-high-field compact and large-scale tokamak reactors.
Distinguishing Majorana bound states from Andreev bound states through differential conductance and current noise spectrum
Authors: Zhao Huajin , Wang Junrong , Mao Hong , Jin Jinshuang
Published: January 2025

We investigate the quantum transport through a quantum dot coupled with a superconducting (SC) nanowire. By elaborating the differential conductance and current noise spectrum, we focus on the distinct characteristics of the topological Majorana bound states (MBSs) and trivial Andereev bound states (ABSs) hosted in SC wire. For MBSs with a topological quality factor q = 1, we observe the degenerate features manifested as the zero-bias peak (ZBP) in differential conductance and the Rabi dips degeneracy (RDD) in noise spectrum. In contrast, for ABSs with q < 1, the splitting of these degenerate features depends on the linewidth, arising from realistic measurement conditions. Furthermore, we identify the critical quality factors

q

c

and

q

S

associated with the emergences of ZBP and RDD, respectively. The value of

q

c

is temperature-dependent, and we establish a suitable temperature window to ensure the visibility of single ZBP in the experiments. Whereas,

q

c

depends on the coupling strength rather than the temperature. Typical values for these quality factors are approximately

q

c

≈
0.93

and

q

S

≈
0.99

. Our results suggest that the degenerate Rabi spectrum signal could serve as a hallmark for the presence of MBSs, which goes beyond the scope of differential conductance.
Effect of combined Kappa-Cairns distributed electrons on modulational instability and envelope soliton of ion-acoustic waves in electron-ion dusty plasma
Authors: Pain Rittika , Dalui Sandip , Sardar Sankirtan , Bandyopadhyay Anup
Published: January 2025

Theoretical and numerical investigations are performed to study the amplitude modulation of ion-acoustic waves in an unmagnetized collisionless dusty plasma system whose components are warm ions (adiabatic), charged (negative) dust particles and Combined Kappa-Cairns distributed electrons. Modulational instability of ion-acoustic waves is analyzed through derivation of the nonlinear Schrödinger equation using the reductive perturbation technique by implementing hydrodynamic equations for this system. The conditions for modulational instability for this electron-ion dusty plasma system have been developed, and the impacts of the relevant physical parameters on the instability region along with the maximum growth rate of instability are demonstrated. Bright and dark envelope solitons are presented, and it is observed that the profiles of envelope solitons are significantly influenced by the existence of high-energy Combined Kappa-Cairns distributed electrons.
A new thermoelectric ECG model: influence of bundle branch block and variations in body temperature
Authors: Pascaline Dongmo Vougmo Inès , Thierry Djoumessi René , Beceau Pelap François , Médard Fogue
Published: January 2025

This work proposes a thermoelectric model to investigate the behavior of specific pathological situation, such as bundle branch block. Impact of temperature is evaluated and its role in controlling the pathology determined. Our proposed 2D thermoelectric model incorporates the heart, lungs, torso, and blood cavities. The Fitzhugh-Nagumo equations that simulate the electrical activity of cardiac myocytes are coupled with temperature equations while considering the parameters of the bundle branch block to analyze their impact on the electrocardiogram. We establish that the presence of bundle branch block significantly affects electrocardiogram morphology, resulting in changes in wave amplitude and interval durations. Moreover, our findings reveal that variations in body temperature alter this pathological condition leading to further distortions in the electrocardiogram. Our thermoelectric model provides valuable insights into the behavior of bundle branch block under temperature variations. This knowledge may potentially contribute to the development of novel treatment and management strategies utilizing thermal control to enhance outcomes for patients presenting similar symptoms.
Influence of axis magnetic field on operation of hall thruster with internally mounted cathode
Authors: Che Xingdong , Zeng Demai , Lian Huibin , Ding Yongjie , Wei Liqiu , Yu Daren , Li Hong
Published: January 2025

Hall thrusters with internal cathodes achieve higher efficiency, smaller plume divergence angles, and improved plume symmetry compared with those with external cathodes. Electrons from the internal cathodes first encounter an axis magnetic field and are coupled with the plasma plume. However, few studies have focused on the influence of axis magnetic field on the operation of Hall thrusters with internally mounted cathodes. Two approaches–applying an additional inner coil and modifying the diameter of the central aperture–are proposed to change the axis magnetic field, and the discharge characteristics are tested. As the number of ampere turns of the additional coil current in-creased, the maximum magnetic-field strength increased by 11%, and the gradient at the exit of the internal cathode decreased by 83%, thus resulting in relative reductions of 0.81% and 1.75% in the thrust and efficiency, respectively, under the rated operating condition. As the diameter of the central aperture decreased, the maximum magnetic strength increased by 9.1% and the gradient at the exit of the cathode increased by 36.3%, thus resulting in relative reductions of 1.88% and 5.71% in the thrust and efficiency, respectively, under the rated condition. Although the performance tendencies are the same, quantitative differences are observed. An analysis of the mechanism indicates that an axis magnetic field with weak strength and a gradual gradient are conducive to electrons traversing down-stream and crossing the magnetic field to couple with the plasma plume. Thus, the differences between the discharge characteristic variations under the two approaches can be explained qualitatively, and guidance is provided for op-timizing the axis magnetic field of Hall thrusters with internal cathodes.
New approach to modeling of thermal electrons heating rate in ionosphere F-layer
Authors: Lu Zhijian , Yao Jingfeng , Aktaev Nurken E , Kudryavtsev A A , Yerzhanov K K , Zhou Zhongxiang , Wang Ying , Li Hui , Wu Jian , Yuan Chengxun
Published: January 2025

Heating rate of thermal electrons by superthermal electrons in ionospheric F-layer at altitudes of 150–350 km was studied over a wide range of zenith angles 45–90 degrees. As a result, a simple and universal formula for calculating the heating rate was obtained. The generalized Hoegy theory was used to obtain the formula. Within the framework of the Hoegy theory, the heating rate is determined by superthermal electrons flux and energy loss function. The energy dependence of the superthermal electron flux was obtained using the bi-exponential function. The kinetic approach was used to receive an analytical expression for the energy loss function. It has been shown that the obtained expression in good agreement with the widely used Swartz approximation. The applicability limits of the obtained expression for energy losses are discussed. It was demonstrated that the heating rate calculations using the formula obtained in the work has a good agreement with the experiments.
Determining oscillator strengths of cesium from magic wavelengths of the D1 line
Authors: Liu Yang , Fan Shaofeng , Liu Wenyuan , Li Yijun , Bai Jiandong
Published: January 2025

A magic-wavelength optical dipole trap (ODT) can eliminate the differential light shift of the transition between atomic states, so that transition frequency between the two states is the same as that in free space, which is of great significance for exploring atomic structure. Here we calculate the dynamic polarizabilities of the 6S1/2 ground state and 6P1/2 excited state of the cesium atom which are connected by the D1 line, by using the relativistic coupled cluster method, and obtain magic wavelengths of ODT laser for trapping the two states simultaneously. By using these magic wavelengths, we calculate oscillator strength of the 6P1/2 → 7D3/2 transition for linearly and circularly polarized lights. Furthermore, we analyze the influence of magic wavelengths on oscillator strengths.
Dual high-Q bound states in the continuum based Fano resonances in bulk WS2 meta-lattice
Authors: Danaeifar Mohammad
Published: January 2025

Bound states in the continuum (BICs) play a promising role in enhancing light–matter interaction with a high quality (Q) factor in transition metal dichalcogenides (TMDCs). In this work, a structured meta-lattice of bulk tungsten disulfide (WS2), a well-known material of TMDCs, with double high-Q resonances governed by quasi-BIC is presented. Two types of quasi-BIC are exploited simultaneously by rotational and longitudinal asymmetries of WS2 rods, acting as the meta-atoms. These Fano line shaped quasi-BIC resonances have a very high quality factor of 1.6 × 104 with a reasonable asymmetric parameter of 1%. Although, tuning the asymmetric parameter changes the linewidth of the resonances and the resulting Q-factor, for all values of these parameters the amplitude of reflection remains constant at one. In addition to exploring and analysing two quasi-BICs, strong coupling between exciton and quasi-BICs is illustrated with Rabi splitting of 116.6 meV and 54.2 meV for rotational and longitudinal asymmetries, respectively. These findings show promise for the development of high-Q photonic devices and applications in polaritonics.