bluuebunny/crossref_metadata_2025 huggingface dataset:
Exact solution for heat transfer across the Sakiadis boundary layer
Authors: Reinberger W. Cade , Barlow Nathaniel S. , Samaha Mohamed A. , Weinstein Steven J.
Published: July 2024

We consider the problem of convective heat transfer across the laminar boundary layer induced by an isothermal moving surface in a Newtonian fluid. In a previous work [Barlow et al., “Exact and explicit analytical solution for the Sakiadis boundary layer,” Phys. Fluids 36, 031703 (2024)], an exact power series solution was provided for the hydrodynamic flow, often referred to as the Sakiadis boundary layer. Here, we utilize this expression to develop an exact solution for the associated thermal boundary layer as characterized by the Prandtl number (Pr) and local Reynolds number along the surface. To extract the location-dependent heat transfer coefficient (expressed in dimensionless form as the Nusselt number), the dimensionless temperature gradient at the wall is required; this gradient is solely a function of Pr and is expressed as an integral of the exact boundary layer flow solution. We find that the exact solution for the temperature gradient is computationally unstable at large Pr, and a large Pr expansion for the temperature gradient is obtained using Laplace's method. A composite solution is obtained, which is accurate to O(10−10). Although divergent, the classical power series solution for the Sakiadis boundary layer—expanded about the wall—may be used to obtain all higher-order corrections in the asymptotic expansion. We show that this result is connected to the physics of large Prandtl number flows where the thickness of the hydrodynamic boundary layer is much larger than that of the thermal boundary layer. The present model is valid for all Prandtl numbers and attractive for ease of use.
Coastal processes and dune stability: Insights from wave transmission and runup modeling
Authors: Qu Zhipeng , Meng Ye , Liang Bingchen
Published: July 2024

Dunes not only serve as natural landscapes but also act as crucial natural barriers protecting coastlines from storm surges. However, the stability of coastlines and dunes is further affected by climate change-induced sea level rise and increased storm activity. An effective evaluation of dune stability necessitates the collection of parameters such as wave height, changes in dune crest elevation, and dune erosion rates. This research employs wave flumes and high-speed camera technology in laboratory settings to observe and simulate coastal dynamics under overwash and collision regimes. The study investigates wave propagation under both regimes using the XBeach model. In the overwash regime, the model slightly overestimates the values of infragravity waves, whereas its accuracy improved under the collision regime. Moreover, in the overwash regime, higher wave skewness results in more sediment transport to the shore, exhibiting a linear relationship between sediment erosion volume and shoreline retreat distance. Through comparison with time series wave runup data obtained by cameras and traditional predictive formulas, the study validates the applicability of the formula proposed by Stockdon as a predictive tool for wave runup in this experiment. To evaluate dune stability, the study introduces the dimensionless overwash threshold parameter Cs, which is based on wave runup and dune crest elevation, to distinguish between dunes in a collision regime or an overwash regime. These findings help identify dune stability patterns, aiding in early detection of coastal erosion and assisting authorities in ecosystem management.
Cycling and spiral-wave modes in an active cyclic Potts model
Authors: Noguchi Hiroshi , van Wijland Frédéric , Fournier Jean-Baptiste
Published: July 2024

We studied the nonequilibrium dynamics of a cycling three-state Potts model using simulations and theory. This model can be tuned from thermal-equilibrium to far-from-equilibrium conditions. At low cycling energy, the homogeneous dominant state cycles via nucleation and growth, while spiral waves are formed at high energy. For large systems, a discontinuous transition occurs from these cyclic homogeneous phases to spiral waves, while the opposite transition is absent. Conversely, these two modes can coexist for small systems. The waves can be reproduced by a continuum theory, and the transition can be understood from the competition between nucleation and growth.
A right-handed molecule is coaxed to behave like a left-handed one
Authors: Lopatka Alex
Published: July 2024

Electrons in a chiral molecule, if excited by ultrafast light pulses, can give the molecule entirely different properties.
Tracking 4 years in the life of a female whale shark shows consistent migrations in the Gulf of Mexico and Caribbean
Authors: Daye Daniel , de la Parra Rafael , Vaudo Jeremy , Harvey Jessica , Harvey Guy , Shivji Mahmood , Wetherbee Bradley
Published: July 2024

Context Satellite telemetry has revolutionised the study of animal movement, particularly for mobile marine animals, whose movements and habitat make consistent, long-term observation difficult. Aims Summarise the movements of Rio Lady, a mature female whale shark (Rhincodon typus), to characterise these movements, and to predict expected behaviour throughout the Gulf of Mexico (GOM). Methods Rio Lady was tracked using satellite telemetry for over 1600 days, generating over 1400 locations and travelling over 40,000 km. State–space and move persistence modelling enabled characterisation of behaviour, and machine learning (ML) enabled the development of habitat-suitability models to predict habitat utilisation, on the basis of location transmissions and their environmental covariates. Key results Rio Lady exhibited annually consistent patterns of movements among three regions within the GOM. Final ML models produced seasonally dynamic predictions of habitat use throughout the GOM. Conclusions The application of these methods to long-term location data exemplifies how long-term movement patterns and core areas can be discovered and predicted for marine animals. Implications Despite our limited dataset, our integrative approach advances methods to summarise and predict behaviour of mobile species and improve understanding of their ecology.
New record of the giant freshwater whipray from the Lesser Sunda region, Indonesia
Authors: Oktaviyani Selvia , Fahmi
Published: July 2024

Context The taxonomic nomenclature of species can change with the discovery of a distinct species. Such nomenclatural changes occurred for the giant freshwater whipray with the discovery of a similar species in the Indo-Australian region in 2008. Aims This paper reports a finding of the giant freshwater whipray in the Lesser Sunda region as the first confirmed record from the area. Methods The specimen was identified as the giant freshwater whipray based on its morphological features. Morphometric measurements were taken directly in the field and also based on the scale provided in the photographs. Key results The female specimen was recorded from the Alas Strait, West Nusa Tenggara Province, Indonesia on 20 July 2020. It was identified as Urogymnus cf. dalyensis due to its similar morphological characteristics with U. dalyensis from northern Australia but it had a shorter preoral snout and greater distance between the left and right fifth gill slits. Conclusions The occurrence of this species in the Lesser Sunda region may confuse U. dalyensis with the close relative from south-east Asia, U. polylepis. Implications This record may provide a link between the two species, either as a population structure of the same species or showing a clear separation between the two as distinct species.
Recombinant OC43 SARS-CoV-2 spike replacement virus: An improved BSL-2 proxy virus for SARS-CoV-2 neutralization assays
Authors: Hu Zhe , López-Muñoz Alberto Domingo , Kosik Ivan , Li Tiansheng , Callahan Victoria , Brooks Kelsie , Yee Debra S. , Holly Jaroslav , Santos Jefferson J. S. , Castro Brant Ayslan , Johnson Reed F. , Takeda Kazuyo , Zheng Zhi-Ming , Brenchley Jason M. , Yewdell Jonathan W. , Fox Julie M.
Published: July 2024

We generated a replication-competent OC43 human seasonal coronavirus (CoV) expressing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike in place of the native spike (rOC43-CoV2 S). This virus is highly attenuated relative to OC43 and SARS-CoV-2 in cultured cells and animals and is classified as a biosafety level 2 (BSL-2) agent by the NIH biosafety committee. Neutralization of rOC43-CoV2 S and SARS-CoV-2 by S-specific monoclonal antibodies and human sera is highly correlated, unlike recombinant vesicular stomatitis virus-CoV2 S. Single-dose immunization with rOC43-CoV2 S generates high levels of neutralizing antibodies against SARS-CoV-2 and fully protects human ACE2 transgenic mice from SARS-CoV-2 lethal challenge, despite nondetectable replication in respiratory and nonrespiratory organs. rOC43-CoV2 S induces S-specific serum and airway mucosal immunoglobulin A and IgG responses in rhesus macaques. rOC43-CoV2 S has enormous value as a BSL-2 agent to measure S-specific antibodies in the context of a bona fide CoV and is a candidate live attenuated SARS-CoV-2 mucosal vaccine that preferentially replicates in the upper airway.
A wound-induced differentiation trajectory for neurons
Authors: Hulett Ryan E. , Rivera-López Carlos , Gehrke Andrew R. , Gompers Annika , Srivastava Mansi
Published: July 2024

Animals capable of whole-body regeneration can replace any missing cell type and regenerate fully functional new organs, including new brains, de novo. The regeneration of a new brain requires the formation of diverse neural cell types and their assembly into an organized structure with correctly wired circuits. Recent work in various regenerative animals has revealed transcriptional programs required for the differentiation of distinct neural subpopulations, however, how these transcriptional programs are initiated in response to injury remains unknown. Here, we focused on the highly regenerative acoel worm,
Hofstenia miamia
, to study wound-induced transcriptional regulatory events that lead to the production of neurons and subsequently a functional brain. Footprinting analysis using chromatin accessibility data on a chromosome-scale genome assembly revealed that binding sites for the Nuclear Factor Y (NFY) transcription factor complex were significantly bound during regeneration, showing a dynamic increase in binding within one hour upon amputation specifically in tail fragments, which will regenerate a new brain. Strikingly, NFY targets were highly enriched for genes with neuronal function. Single-cell transcriptome analysis combined with functional studies identified

soxC
+

stem cells as a putative progenitor population for multiple neural subtypes. Further, we found that wound-induced
soxC
expression is likely under direct transcriptional control by NFY, uncovering a mechanism for the initiation of a neural differentiation pathway by early wound-induced binding of a transcriptional regulator.
The dynamic behavior of chromatophores marks the transition from bands to spots in leopard geckos
Authors: Ullate-Agote Asier , Tzika Athanasia C.
Published: July 2024

Reptilian skin coloration is spectacular and diverse, yet little is known about the ontogenetic processes that govern its establishment and the molecular signaling pathways that determine it. Here, we focus on the development of the banded pattern of leopard gecko hatchlings and the transition to black spots in the adult. With our histological analyses, we show that iridophores are present in the white and yellow bands of the hatchling and they gradually perish in the adult skin. Furthermore, we demonstrate that melanophores can autonomously form spots in the absence of the other chromatophores both on the regenerated skin of the tail and on the dorsal skin of the Mack Super Snow (MSS) leopard geckos. This color morph is characterized by uniform black coloration in hatchlings and black spots in adulthood; we establish that their skin is devoid of xanthophores and iridophores at both stages. Our genetic analyses identified a 13-nucleotide deletion in the
PAX7
transcription factor of MSS geckos, affecting its protein coding sequence. With our single-cell transcriptomics analysis of embryonic skin, we confirm that
PAX7
is expressed in iridophores and xanthophores, suggesting that it plays a key role in the differentiation of both chromatophores. Our in situ hybridizations on whole-mount embryos document the dynamics of the skin pattern formation and how it is impacted in the
PAX7
mutants. We hypothesize that the melanophores–iridophores interactions give rise to the banded pattern of the hatchlings and black spot formation is an intrinsic capacity of melanophores in the postembryonic skin.
Unearthing the disabling perplexities of a Filipino PLHIV online community on X’s #PLHIVDiaries as socially shared
inquiry fostering pakikipagkapwa
Authors: Gamayo George Vincent F. , Santos Yhna Therese P. , Tanchuan Vonn Vincent V. , Villacastin Juven Niño A.
Published: July 2024

Filipino People living with HIV (PLHIV) have used X, formerly Twitter, as an avenue to make sense of what it means
to live with HIV in the Philippines. However, big data analyses do not provide a comprehensive investigation of X as a community.
Grounded in the concepts of Alfonso’s (1992) socially shared inquiry (SSI), this paper
discusses how this discursive process of sense-making and sense-giving occurs in an X hashtag called #PLHIVDiaries through
analyzing and interpreting tweets (n = 1089) that narrate the daily experiences of Filipino PLHIV. This describes
how their different struggles are framed and reframed through SSI process which unravels disabling perplexities such as problem,
barrier, conflict, absence, dilemma, and error. Among the non-disabling frames that serve as a foil to disabling perplexities, we
identified a variety of tweets that contained testimonies, personal triumphant stories, and answers to problems that were endorsed
and authenticated by community members.
Constant-roll inflation with tachyon field in the holographic braneworld
Authors: Stojanovic Marko , Bilić Neven , Dimitrijevic Dragoljub D , Djordjevic Goran S , Milosevic Milan
Published: July 2024

We study inflation driven by the tachyon field in the holographic braneworld by assuming the second slow-roll parameter η is constant. The parameter η can be either defined by the tachyon scalar field and the Hubble parameter or by the Hubble parameter only. By assuming a constant η, we derive and numerically solve a differential equation for the Hubble expansion rate. We calculate numerically the scalar spectral index and the tensor-to-scalar ratio. We confront the results with the observational data and find some constraints on the free model parameters. The swampland conjectures are discussed in the context of the constant-roll inflation, with some accent on the holographic model.
Characteristic time scales for the geometry transition of a black hole to a white hole from spinfoams
Authors: Christodoulou Marios , D’Ambrosio Fabio
Published: July 2024

Quantum fluctuations of the metric may provide a decay mechanism for black holes through a transition to a white hole geometry. Previous studies formulated Loop Quantum Gravity amplitudes with a view to describe this process. We identify two timescales to be extracted which we call the crossing time and the lifetime and complete a calculation that gives explicit estimates using the asymptotics of the EPRL model. The crossing time is found to scale linearly in the mass, in agreement with previous results by Ambrus and Hájíček and more recent results by Barceló, Carballo–Rubio and Garay. The lifetime is found to depend instead on the spread of the quantum state, and thus its dependence on the mass can take a large range of values. This indicates that the truncation/approximation used here is not appropriate to estimate this observable with any certainty. The simplest choice of a balanced semiclassical state is shown to yield an exponential scaling of the lifetime in the mass squared. Our analysis only considers 2-complexes without bulk faces, a significant limitation. In particular it is not clear how our estimates will be affected under refinements. This work should be understood as a step towards a fuller calculation in the context of covariant Loop Quantum Gravity.
Using students’ critical aspects to deepen understanding of nuclear physics concepts
Authors: Atlabachew Tafesse Kabtihymer , Kriek Jeanne
Published: July 2024

Identifying students’ understanding provides a pathway to develop focused teaching to facilitate conceptual understanding. This study aims to gain more insight into undergraduate students’ conceptual understanding of two nuclear physics concepts: nuclear binding energy (NBE) and nuclear force; as the literature has shown that students face difficulties in learning and understanding such concepts. Phenomenography was used to provide a special qualitative research approach to exploring students’ in-depth understanding which was not addressed in previous studies. Data was collected from purposively selected students (N = 30) through semi-structured interviews. Phenomenography was used to reveal the different ways in which students understand these concepts and serves as indicators of potential conceptual difficulties. Based on these, the relevant and irrelevant critical aspects discerned by students are identified using the variation theory of learning. These critical aspects illustrate how the students understand each concept. For instance, NBE is the energy that must be added to a nucleus to separate it into its constituents and relates to a relevant critical aspect. However, NBE is also the energy that binds nucleons and this relates to an irrelevant critical aspect. These critical aspects can provide crucial information that can assist physics instructors in developing focused teaching and learning strategies. Thus, the responses to the interview can be used as a basis for teaching and learning nuclear physics concepts.
Inertia from radiation: A semiclassical approach
Authors: Figueroa C , Saracho S
Published: July 2024

Starting from a thought experiment based on an accelerated reflecting cavity containing a radiation bath, the cavity-radiation dynamical interaction is evaluated. The radiation is considered as a monochromatic flux of photons that bounces forwards and backwards in the direction of acceleration. In this case, in each reflection, the delay originating from the time of flight of photons causes a difference in velocity between the receiving and emitting reflecting faces at the opposite ends of the cavity, and consequently, a Doppler shift. Despite the ends of the cavity being at rest relative to each other, this phenomenon generates a difference of radiation pressure between both ends, which acts as the inertia of the radiation bath and verifies Newton’s 2nd Law for non-relativistic conditions. This result has interesting implications for the current theoretical pictures of dynamical properties of photons.
Simple methods for converting equations between the SI, Heaviside–Lorentz and Gaussian systems
Authors: Quincey Paul
Published: July 2024

School and undergraduate students are almost always taught the equations of electromagnetism using a set of conventions that are described as the SI. More advanced students are often introduced to different conventions that produce different equations for the same relationships, using either the Gaussian or Heaviside–Lorentz systems. In general, the connection between these equations is not simple. However, if the basis of each system is understood, conversion from SI equations to either Gaussian or Heaviside–Lorentz ones is very straightforward. The reverse processes are less straightforward, but more comprehensible when the fundamental differences are understood. Simple methods for these processes are presented, using a novel application of dimensional analysis, without factors of ε
0
1/2 or (4πε
0)1/2 appearing. It is also shown that when different physical quantities are given different symbols, and these are used consistently, the SI can be seen to provide general equations, with the Gaussian and Heaviside–Lorentz ones being simplifications of them. This removes any need for ‘system-independent’ versions of electromagnetic equations, with additional parameters that take different values in the different systems, which have been proposed in various forms over many decades.
Helium line emission spectroscopy to measure plasma parameters using modeling and machine learning in low-temperature plasmas
Authors: Kajita Shin , Nishijima Daisuke
Published: July 2024

Line intensity ratios (LIRs) of helium (He) atoms are known to depend on electron density,

n
e

, and temperature,

T
e

, and thus are widely utilized to evaluate these parameters, known as the

H
e
 
I

LIR method. In this conventional method, the measured LIRs are compared with theoretical values calculated using a collisional-radiative (CR) model to find the best possible

n
e

and

T
e

. Basic CR models have been improved to take into account several effects. For instance, radiation trapping can occur to a significant degree in weakly ionized plasmas, leading to major alterations of LIRs. This effect has been included with optical escape factors in CR models. A new approach to the evaluation of

n
e

and

T
e

from He I LIRs has recently been explored using machine learning (ML). In the ML-aided LIR method, a predictive model is developed with training data, which consists of an input (measured LIRs) and a desired/known output (measured

n
e

or

T
e

from other diagnostics). It has been demonstrated that this new method predicts

n
e

and

T
e

better than using the conventional method coupled with a CR model, not only for He but also for other species. This review focuses mainly on low-temperature plasmas with

T
e

⩽
10

eV in linear plasma devices.
Solid-mechanics analysis and modeling of the alloyed ohmic contact proximity in GaN HEMTs using µRaman spectroscopy
Authors: Güneş Burak , Bütün Bayram , Özbay Ekmel
Published: July 2024

This study explores the impact of alloyed ohmic contact separation on ungated GaN high electron mobility transistors (HEMTs) lattice stress by employing Raman spectroscopy and solid mechanics simulations for comprehensive analysis. Focusing on the substantial stresses exerted by ohmic contacts, our research introduces a novel mechanical calibration procedure. The proposed procedure demonstrates that the stress in the GaN buffer can be precisely modelled using Raman measurements taken from patterns of varying length, which in return reveals the impact of ohmic contacts on stress. We show that this technique shows a good alignment to the Raman measurement results. Moreover, we identify ohmic contact edges as potential sites for defect generation due to the accumulation of substantial elastic energy, a finding supported by experimental observations of crack formations in related studies. Our calibrated mechanical model not only enhances the understanding of stress distributions within GaN HEMTs but also lays the groundwork for future improvements in electro-thermo-mechanical simulations.
Electric field driven focusing and transport of plasma ion beams by micro-glass capillaries beyond the self-focusing limit
Authors: Barman Sushanta , Bhattacharjee Sudeep
Published: July 2024

Micro-glass capillaries emerge as an important tool for the lossless guiding and focusing of ion beams (Kojima 2018 J. Phys. B: At. Mol. Opt. Phys.
51 042001). The self-focusing mechanism of the capillaries is primarily governed by charged patches induced on their inner walls by the incident beam (Stolterfoht et al 2002 Phys. Rev. Lett.
88 133201). However, the dominance of space charge forces over self-focusing forces in intense (J ≈ 1 A m−2) ion beams establishes a self-focusing limit (Maurya et al 2019 J. Phys. D: Appl. Phys.
52 055205), posing challenges to beam focusing beyond this limit. In this work, a novel method is introduced, demonstrating electrical control over the charge patch dynamics through an externally applied bias voltage, thereby enabling the focusing of Ar ion beams beyond the self-focusing limit. Experimental results reveal that adjusting the biasing voltage allows overcoming the self-focusing limit, resulting in the generation of a high-intensity (

J

out

≈
3.05
×

10
5

A m−2) nano-beam (∼160 nm). Furthermore, electrical control is shown to enhance the performance of both straight and tapered capillaries (SC/TC), with the TC being more effective for nano-beam generation. A Particle-In-Cell (PIC) simulation code has been developed to explain the experimental results. The implications of high-intensity nano ion beams in advancing nanopatterning, nanoscale material analysis, and matter wave interferometry, underscore significant contributions to research and innovation within electronics, materials science, nanotechnology, and emerging quantum technologies.
Study of the thermal characteristics of propellant tanks in microgravity and its application to propellant gauging
Authors: Zeng Zhoumo , Gao Hexin , Zhang Jin , Rui Xiaobo , Qi Lei , Chen Yong , Wu Zongyu , Cui Yuhao , Yu Yao , Wu Yu , Zhang Yu
Published: July 2024

The use of the thermal propellant gauging (TPG) method for propellant mass detection in aerospace tanks inevitably involves the continuous heating of the tank, and the understanding of the heat transfer mechanism of the tanks in a microgravity environment plays a guiding role in the implementation of the TPG. In this paper, the thermal characteristics of propellant tanks under microgravity are investigated by simulation and it is found that with the weakening of gravity, the heat transfer slows down and ‘heat concentration’ occurs in the vicinity of the heater. The effect of this property on the implementation of the TPG was then investigated by simulation, and it was found that in the microgravity environment, the accuracy of the TPG detection can be improved by adjusting the locations of the heaters and temperature sensors on the external side of the tank wall.
Interplay of size, deformability, and device layout on cell transport in microfluidics
Authors: Hood Michael C , Gardner Karl , Li Wei , Tan Jifu
Published: July 2024

Microfluidics have been widely used for cell sorting and capture. In this work, numerical simulations of cell transport in microfluidic devices were studied considering cell sizes, deformability, and five different device designs. Among these five designs, deterministic lateral displacement device (DLD) and hyperuniform device (HU) performed better in promoting cell-micropost collision due to the continuously shifted micropost positions as compared with regular grid, staggered, and hexagonal layout designs. However, the grid and the hexagonal layouts showed best in differentiating cells by their size dependent velocity due to the size exclusion effect for cell transport in clear and straight paths in the flow direction. A systematic study of the velocity differentiation under different dimensionless groups was performed showing that the velocity difference is dominated by the micropost separation distance perpendicular to the direction of flow. Microfluidic experiments also confirmed the velocity differentiation results. The study can provide guiding principles for microfluidic design.
Phonon excitations in Eu2Ir2O7 probed by inelastic x-ray scattering
Authors: Wang Han , Kaneko Ryoma , Ueda Kentaro , Zhang Yang , Baron Alfred Q R , Ishikawa Daisuke , Wehinger Björn , Dagotto Elbio , Tokura Yoshinori , Arima Taka-hisa , Gao Shang
Published: July 2024

The study of phonon dynamics and its interplay with magnetic ordering is crucial for understanding the unique quantum phases in the pyrochlore iridates. Here, through inelastic x-ray scattering on a single crystal sample of the pyrochlore iridate Eu2Ir2O7, we map out the phonon excitation spectra in Eu2Ir2O7 and compare them with the theoretical phonon spectra calculated using the density functional theory. Possible phonon renormalization across the magnetic long-range order transition is observed in our experiments, which is consistent with the results of the previous Raman scattering experiments.
Tribological behavior of graphene/h-BN vdW heterostructures: the role of defects at the BN layer
Authors: Han Zongfang , Ru Guoliang , Li Yuqiong , Ma Ming
Published: July 2024

Molecular dynamics simulations and first principles calculations were performed to study the tribological behavior of graphene/h-BN (G/h-BN) heterostructures with vacancy and Stone–Wales (SW) defect under uniform normal load, revealing the mechanism of the effect of defect types on friction, and discussing the coupling effect of temperature and interfacial defects on the tribological behavior of G/h-BN heterostructures. Under the normal force of 0.2 nN/atom, the friction force of the four systems is 0.0057, 0.0096, 0.0077, and 0.26 nN, respectively. The friction force of SW defect heterostructure is 45 times that of perfect interface heterostructure. The influence of defect type on friction force is SW > SV > DV. By observing the dynamic change of the Z-direction coordinate position of the sliding layer atoms, the slip potential energy curves and the evolution law of the moiré pattern, the relationship between the structural morphology and the energy change of different defective heterostructures and the frictional behavior was investigated comprehensively and intuitively for the first time. From the perspective of atomic strain, the deformation of heterostructures at the atomic level was quantified. The results showed that at 300 K and 0 K, the maximum strain of atoms in the sliding layer was 11.25% and 9.85%, respectively. The thermal perturbation mainly occurs in the out-of-plane direction, which in turn affects the friction. Through density functional theory, it is found that under uniform load, it is difficult to form bonds between the graphene sliding layer and the substrate layer when the defects are in the h-BN substrate layer, which has less influence on the friction of the system, thus making the defective heterostructures also remainsuperlubricity state. These results provide a new understanding of the interfacial friction of G/h-BN defective heterostructure.
Machine learning assisted understanding of the layer-thickness dependent thermal conductivity in fluorinated graphene
Authors: Liang Jun-Nan , Tong Hua , Zeng Yu-Jia , Zhou Wu-Xing
Published: July 2024

Manipulating thermal conductivity (κ) plays vital role in high-performance thermoelectric conversion, thermal insulation and thermal management devices. In this work, we using the machine learning-based interatomic potential and the phonon Boltzmann transport equation to systematically investigate layer thickness dependent κ of fluorinated graphene (FG). We show that the lattice κ of FG can be significantly decreased with Bernal bilayer stacking. Surprisingly, the further increasing of stacking layer can no longer affect the κ, however, the κ is increased in the bulk configuration. The variation of κ can be attributed to the crystal symmetry change from P-3m1 (164) at single layer to P3m1 (156) at multilayer. The decreasing crystal symmetry from single layer to bilayer resulting stronger phonon scattering and thus leading a lower κ. Moreover, we also show that the contribution of acoustic mode to κ decreases with the increase of layers, while the contribution of optical mode to κ is increased with increasing layers. These results provide a further understanding for the phonon scattering mechanism of layer thickness dependent κ.
A multi-sensor fusion framework for localization using LiDAR, IMU and RGB-D camera
Authors: Guan Meng , Hao ZhiLong , Zhang Shitong , Chen Songming
Published: July 2024

In recent years, the increasing demand for precise and intelligent systems has been driven by advancements in indoor unmanned navigation and positioning technologies. Nonetheless, the indoor environment poses challenges as objects often intersect or obstruct each other due to spatial constraints, significantly impeding sensor recognition capabilities and compromising localization accuracy. This paper presented a multi-sensor fusion framework within a system primarily comprised of LiDAR, complemented by RGB-D and IMU sensors, to mitigate these challenges. To mitigate point cloud misalignment arising from occlusions, an improved PL-ICP algorithm have been proposed,resulting in improved accuracy and speed in occlusion scenarios. Meanwhile, this paper enhanced the Otsu algorithm by leveraging RGB-D matching to extract additional feature information, consequently enhancing the system’s convergence when occlusion happens. Ultimately, the Extended Kalman Filter (EKF) algorithm is employed to fuse point cloud and image data. Extensive experimental results demonstrate that the proposed approach not only enhances localization accuracy and stability but also exhibits superior convergence characteristics, offering an economical and efficient solution for robotic navigation.
Attention mechanism based on deep learning for defect detection of wind turbine blade via multi-scale features
Authors: Zhang Yu , Fang Yu , Gao Weiwei , Liu Xintian , Yang Hao , Tong Yimin , Wang Manyi
Published: July 2024

An enhanced wind turbine blade surface defect detection algorithm, CGIW-YOLOv8, has been introduced to tackle the problems of uneven distribution of defect samples, confusion between defects and background, and variations in target scales that arise during drone maintenance of wind turbine blades. This algorithm is given based on the YOLOv8 model. Initially, a data augmentation method based on geometric changes and Poisson mixing was used to enrich the dataset and address the problem of uneven sample distribution. Subsequently, the incorporation of the Coordinate Attention (CA) mechanism into the Backbone network improved the feature extraction capability in complex backgrounds. In the Neck, the Reparameterized Generalized Feature Pyramid Network (Rep-GFPN) was introduced as a path fusion strategy and multiple cross-scale connections are fused, which effectively enhances the multi-scale expression ability of the network. Finally, the original CIOU loss function was replaced with Inner-WIoU, which was created by applying the Inner-IoU loss function to the Wise-IoU loss function. It improved detection accuracy while simultaneously speeding up the model’s rate of convergence. Experimental results show that the mAP of the method for defect detection reaches 92%, which is 5.5% higher than the baseline network. The detection speed is 120.5 FPS, which meets the needs of real-time detection.
Soldered chip reversed polarity detection based on semi-combinatorial attention and size-sensitive IoU
Authors: Zheng Liming , Wu Yuxiang , Chen Enze
Published: July 2024

Chips that have been automatically soldered may have defects such as short circuits, reversed polarity, offsets, and missing components. This paper proposes a reversed polarity detection algorithm (RPDNet) for soldered chips based on semi-combinatorial attention and size-sensitive IoU to solve the polarity reversal problem. To distinguish characters or patterns similar to polarity markings in the background, a semi-combination attention module (SCAM) is introduced, which effectively distinguishes the subtle feature differences between polarity markings and background elements by integrating the long-range dependence of the self-attention mechanism and the local focusing ability of the general attention mechanism, thereby reducing misdetection of polarity markings. Aiming at the problem of blurred chip polarity markings, a differential pooling module (DPM) is proposed, which optimizes the downsampling process of fuzzy polarity markings by combining the differential features obtained from subtracting the results of max pooling from average pooling with features derived solely from average pooling, thereby reducing the information loss of fuzzy markings during the feature extraction process. In order to solve the lack of sensitivity of CIoU to the side length of the bounding box, a size-sensitive IoU (SIoU) is introduced. Through the size-sensitivity factor and area difference loss term, the model strengthens the focus on boundary regression and achieves faster and more accurate target positioning. Using the Chip-Set provided by the company for experiments and tests, the detection accuracy reached 97.79% and the processing speed reached 107 FPS.
Semantic segmentation algorithm for video from UAV based on adaptive keyframe scheduling via similarity measurement
Authors: Gao Weiwei , Fan Bo , Fang Yu
Published: July 2024

Unmanned aerial vehicle (UAV) videos exhibit complex object motion features and significant differences between frame features. To solve the problems of feature information loss and drastic accuracy decline in applying the video semantic segmentation method based on the fixed-period update strategy of keyframes, a keyframe recognition method based on similarity measurement is proposed, forming a video semantic segmentation algorithm based on adaptive keyframe scheduling. One keyframe recognition method based on pixel similarity measurement is established by modeling the similarity relationship between low-level pixels in adjacent frames. Meanwhile, the other keyframe recognition method based on feature similarity measurement is established by constructing a shallow Siamese network to measure the similarity relationship between features of frames. Then a discriminative network is constructed based on the obtained similarity of inter frames, and the segmentation process is accelerated by reusing features of keyframes through the optical flow network. Thereby a video semantic segmentation method for UAV based on adaptive keyframe strategy is established. The effectiveness of the proposed video semantic segmentation algorithm is verified on UAVid dataset. The results demonstrated that the speed of the proposed algorithm reaches 53.2 frames per second (FPS) and 54.5 FPS on the premise that the mean intersection over union is higher than 40% (this value is compared with the segmentation accuracy in the balanced mode when the similarity threshold is 0.76 and 0.88, respectively), which is 18.5 FPS and 19.8 FPS higher than the PSPNet image semantic segmentation algorithm. In addition, analysis of experiment results shows that the pixel-similarity-based keyframe recognition is suitable for high-precision video semantic segmentation scenes that need to improve segmentation efficiency, and the feature-similarity-based keyframe recognition is more suitable for high real-time video semantic segmentation tasks that require a small decrease in overall algorithm accuracy. In a word, the proposed video semantic segmentation algorithm based on adaptive keyframe scheduling via similarity measurement can improve segmentation speed while ensuring segmentation accuracy and stability.
Thermodynamic analysis of a heat engine: experiments with the Stirling cycle
Authors: Butler Colin
Published: July 2024

This paper presents a practical thermodynamic analysis of a desktop Stirling engine to demonstrate some of the fundamental principles involving the conversion of heat to work as part of an introductory undergraduate course. Experimental measurements of temperature, pressure and volume using an Arduino microcontroller allows for the construction of P-ν and T-s process diagrams from thermodynamic relationships. By comparing the quantitative data from actual and ideal cycles, the Stirling engine represents an effective teaching tool for reinforcing core content with students.
DIY of dye cleaning from water using plasma and smartphone colorimetry
Authors: Dubey Shivam , Thakur Abhay Singh , Vaish Rahul
Published: July 2024

Plasma has been generated using high voltage DC transformer. This plasma was further utilized in dye aqueous solution. Smartphone-based colourimetry was utilized to quantify dye degradation. These handy experiments will be helpful to understand plasma, its generation and potential applications.
A low cost and simple webcam spectrometer for exploring the visible wavelengths of light
Authors: Cahill Gary
Published: July 2024

This paper presents a method for constructing a simple, cost-effective, and versatile spectrometer using readily available materials such as a basic webcam, a DVD, tin foil, a cardboard tube, and a microphone boom arm. Building upon previous designs (Widiatmoko et al 2011 Phys. Educ.
46 332, Lorenz 2014 Am. J. Phys.
82 169–73, Rodrigues et al 2016 Phys. Educ.
51 014002, Likith et al 2021 J. Opt.
50 489–94), this spectrometer is mounted on a microphone boom arm, enhancing flexibility in capturing spectra from various angles and distant light sources. The spectrometer, coupled with Theremino Spectrometer V3.1 software, achieves sufficient resolution to measure solar Fraunhofer lines and closely spaced Mercury double lines at 436 nm and 577 nm. The procedure for assembling the spectrometer is detailed, including calibration using a Mercury CFL lamp or phone screens. Results demonstrate the spectrometer’s capability to capture high-resolution spectra of the blue sky and light sources, identifying significant spectral lines. This DIY spectrometer offers an accessible tool for amateur scientists and educators to explore visible light spectra, facilitating both qualitative and quantitative analyses. Also, through measuring the light from phone screens work, perception of colour can be explored.
Fundamental properties of ideal and resistive infernal modes in tokamaks
Authors: Coste-Sarguet M , Graves J P
Published: July 2024

Infernal modes are unstable in regions of weak magnetic shear and significant pressure gradients. These modes comprise a broad class of instabilities, encompassing interchange modes and kink modes, with both short and long length scales. Toroidal effects and fully electromagnetic fields are of crucial importance for their description. The role of resistive diffusion and compressibility are also critical. In order to investigate this awkward problem while still enabling fundamental physics interpretation, a new resistive MHD eigensolver has been developed. An outcome of this study is the identification of an unstable spectrum of resistive infernal modes in regions of the plasma with weak average curvature, and in regions where the average curvature is destabilising. These fast growing modes may be collectively important for our understanding of global reconnection events, stochastic magnetic fields states, and neighbouring supercritical bifurcations.
Hidden corrosion monitoring via phase shift evaluation of Lamb wave modes
Authors: Huang Liping , Zeng Liang , Zhang Xuhui , Wan Xiang , Chen Feiyu
Published: July 2024

Lamb wave inspection is a promising candidate for real-time monitoring of hidden corrosion in thin-walled metallic structures. The time-of-flight (ToF) which represents the variation of group velocity due to thickness reduction is commonly used, but its sensitivity is limited at the early stage of corrosion. To address this issue, the phase shift as a function of the phase velocity is defined and evaluated for corrosion detection in this paper. Specifically, the analytic cross-correlation method is applied, which estimates the group delay and the phase shift between two Lamb wave responses before and after the existence of corrosion simultaneously. The simulated examples show that the phase shift performs an obvious improvement on corrosion sensitivity compared to the ToF, and its value increases nearly linearly as the corrosion gets deeper. Ultimately, an experimental example is also introduced, where an active sensor network is deployed and a probabilistic imaging algorithm is introduced. The imaging results demonstrate that the proposed method could successfully identify and accurately localize the hidden corrosion.
A flexible piezoelectric energy harvester featuring an eccentric pendulum via frequency up-conversion for human motion
Authors: Zhu Yue , Chen Gantong , Zhang Jiaqin , Li Zhiyuan , Zhou Shengxi
Published: July 2024

This paper presents an innovative design of a flexible piezoelectric energy harvester featuring an eccentric pendulum (FPEH-P), which has two major characteristics: frequency up-conversion and large deformation that can improve output capacity. To clarify operational principles, we establish a dynamic model of the pendulum, and the vibration of the flexible piezoelectric plate is analyzed. Then, the two major characteristics of the FPEH-P are verified by experiments and simulations. Furthermore, it is verified that the FPEH-P can work at a low frequency (about 2 Hz) experimentally. Due to the large deformation of the piezoelectric plate, the maximum peak open-circuit voltage can reach 6.82 V. At an excitation frequency of 1.9 Hz and amplitude of 100 mm, the maximum average power can reach 6.06 μW. The FPEH-P can efficiently harvest energy from individuals engaged in walking, jogging, and running, as evidenced by the output load voltage and average power. Moreover, it can also output voltage under multiple motion actions. Finally, it has been verified that the high-instantaneous voltage characteristic of the harvester can provide sustainable power to a timer.
Anodization-free fabrication process for high-quality cross-type Josephson tunnel junctions based on a Nb/Al-AlO
x
/Nb trilayer
Authors: Adam F , Enss C , Kempf S
Published: July 2024

Josephson tunnel junctions form the basis for various superconductor electronic devices. For this reason, enormous efforts are routinely taken to establish and later on maintain a scalable and reproducible wafer-scale manufacturing process for high-quality Josephson junctions. Here, we present an anodization-free fabrication process for Nb/Al-AlO
x
/Nb cross-type Josephson junctions that requires only a small number of process steps and that is in general intrinsically compatible with wafer-scale fabrication. We show that the fabricated junctions are of very high quality and, compared to other junction types, exhibit not only a significantly reduced capacitance but also an almost rectangular critical current density profile. Our process hence enables the usage of low capacitance Josephson junctions for superconductor electronic devices such as ultra-low noise dc-superconducting quantum interference devices (SQUIDs), microwave SQUID multiplexers based on non-hysteretic rf-SQUIDs and RFSQ circuits.
Investigation of normal zone propagation velocity in AgSn/Ag/Ba122 superconducting tapes using a conduction cooling test system
Authors: Li Chunyan , Zhou Jin , Zhao Ling , Zhu Yanchang , Kang Rui , Li Wei , Wang Chengtao , Wang Yingzhe , Wang Juan , Hou Zhilong , Ma Rui , Zhang Hongjun , Liao Kai , Zhang Xianping , Wang Dongliang , Liu Fang , Ma Yanwei , Xu Qingjin
Published: July 2024

The investigation of the behavior of quench propagation in iron-based superconducting (IBS) tapes is important for their application in magnets and the design of quench protection systems. However, little research has been done in this area. In this work, a conduction cooling test system for IBS tapes and coils has been built, which has functions such as charging test, temperature and voltage data acquisition, pulse current heating, quench detection and protection. A series of experiments were performed on several 27 cm long IBS tapes to measure their normal zone propagation velocity (NZPV). The variation trends of NZPV with different operating temperatures, and with different ratios of operating current to critical current were systematically explored. In addition, monitoring all the voltages between different positions of an IBS tape, including two joints, has provided more detailed results and findings.