bluuebunny/crossref_metadata_2025 huggingface dataset:
Scale-resolving simulations of turbulent flows with coherent structures: Toward cut-off dependent data-driven closure modeling
Authors: Taghizadeh Salar , Witherden Freddie D. , Girimaji Sharath S.
Published: June 2024

Complex turbulent flows with large-scale instabilities and coherent structures pose challenges to both traditional and data-driven Reynolds-averaged Navier–Stokes methods. The difficulty arises due to the strong flow-dependence (the non-universality) of the unsteady coherent structures, which translates to poor generalizability of data-driven models. It is well-accepted that the dynamically active coherent structures reside in the larger scales, while the smaller scales of turbulence exhibit more “universal” (generalizable) characteristics. In such flows, it is prudent to separate the treatment of the flow-dependent aspects from the universal features of the turbulence field. Scale resolving simulations (SRS), such as the partially averaged Navier–Stokes (PANS) method, seek to resolve the flow-dependent coherent scales of motion and model only the universal stochastic features. Such an approach requires the development of scale-sensitive turbulence closures that not only allow for generalizability but also exhibit appropriate dependence on the cut-off length scale. The objectives of this work are to (i) establish the physical characteristics of cut-off dependent closures in stochastic turbulence; (ii) develop a procedure for subfilter stress neural network development at different cut-offs using high-fidelity data; and (iii) examine the optimal approach for the incorporation of the unsteady features in the network for consistent a posteriori use. The scale-dependent closure physics analysis is performed in the context of the PANS approach, but the technique can be extended to other SRS methods. The benchmark “flow past periodic hills” case is considered for proof of concept. The appropriate self-similarity parameters for incorporating unsteady features are identified. The study demonstrates that when the subfilter data are suitably normalized, the machine learning based SRS model is indeed insensitive to the cut-off scale.
Onset of spin entanglement in doped carbon nanotubes studied by EPR
Authors: Sperlich Andreas , Eckstein Klaus H. , Oberndorfer Florian , Sturdza Bernd K. , Auth Michael , Dyakonov Vladimir , Mitric Roland , Hertel Tobias
Published: June 2024

Nanoscale semiconductors with isolated spin impurities have been touted as promising materials for their potential use at the intersection of quantum, spin, and information technologies. Electron paramagnetic resonance (EPR) studies of spins in semiconducting carbon nanotubes have overwhelmingly focused on spins more strongly localized by sp3-type lattice defects. However, the creation of such impurities is irreversible and requires specific reactions to generate them. Shallow charge impurities, on the other hand, are more readily and widely produced by simple redox chemistry, but have not yet been investigated for their spin properties. Here, we use EPR to study p-doped (6,5) semiconducting single-wall carbon nanotubes (s-SWNTs) and elucidate the role of impurity–impurity interactions in conjunction with exchange and correlation effects for the spin behavior of this material. A quantitative comparison of the EPR signals with phenomenological modeling combined with configuration interaction electronic structure calculations of impurity pairs shows that orbital overlap, combined with exchange and correlation effects, causes the EPR signal to disappear due to spin entanglement for doping levels corresponding to impurity spacings of 14 nm (at 30 K). This transition is predicted to shift to higher doping levels with increasing temperature and to lower levels with increasing screening, providing an opportunity for improved spin control in doped s-SWNTs.
Using optical vortex laser induced forward transfer to fabricate a twisted ferrite microcrystal array
Authors: Kaneko Akihiko , Iwata Muneaki , Wei Rong , Yuyama Ken-ichi , Omatsu Takashige
Published: June 2024

We demonstrate direct printing from donor ink containing ferrite nanoparticles by employing laser induced forward transfer with an optical vortex possessing orbital angular momentum (OAM). We show, for the first time, that the as-printed dots are twisted and exhibit spinel Fe3O4 monocrystalline properties without the need for a sintering process. The helicity of the as-printed dots is shown to be selectively controlled merely by reversing the handedness of optical vortices. The diameter of the printed dots was typically measured to be less than 1/10th of the irradiated laser spot (diffraction limit). These results imply that the optical vortex twists and confines the sintered nanoparticles within its dark core to form chiral spinel monocrystalline dots. The observation of mono-crystallization with optical vortex induced forward transfer will offer new fundamental physics such as OAM light–matter interactions and could pave the way toward advanced printable magnetic devices, such as high-density magnetic data storage.
Magnetoelectric coupling at the domain level in polycrystalline hexagonal ErMnO3
Authors: Schultheiß J. , Puntigam L. , Winkler M. , Krohns S. , Meier D. , Das H. , Evans D. M. , Kézsmárki I.
Published: June 2024

We explore the impact of a magnetic field on the ferroelectric domain pattern in polycrystalline hexagonal ErMnO3 at cryogenic temperatures. Utilizing piezoelectric force microscopy measurements at 1.65 K, we observe modifications of the topologically protected ferroelectric domain structure induced by the magnetic field. These alterations likely result from strain induced by the magnetic field, facilitated by intergranular coupling in polycrystalline multiferroic ErMnO3. Our findings give insights into the interplay between electric and magnetic properties at the domain scale and represent a so far unexplored pathway for manipulating topologically protected ferroelectric vortex patterns in hexagonal manganites.
Native defects and their complexes in spinel LiGa5O8
Authors: Dabsamut Klichchupong , Takahashi Kaito , Lambrecht Walter R. L.
Published: June 2024

Recently, LiGa5O8 was identified as a cubic spinel type ultra-wide-bandgap semiconductor with a gap of about 5.36 eV and reported to be unintentionally p-type. Here, we present first-principles calculations of native defects and their various complexes to try to explain the occurrence of p-type doping. Although we find Li vacancies (0.74 eV above VBM) to be shallower acceptors than in LiGaO2 (1.63 eV above VBM), and becoming slightly shallower in complexes with donors such as VO (0.58 eV above VBM) and GaLi antisites (0.65 eV above VBM), these VLi based defects are not sufficiently shallow to explain p-type doping. The dominant defects are donors and, in equilibrium, the Fermi level would be determined by compensation between donors and acceptors and pinned deep in the gap.
Exploring potential energy surfaces to reach saddle points above convex regions
Authors: Gunde M. , Jay A. , Poberžnik M. , Salles N. , Richard N. , Landa G. , Mousseau N. , Martin-Samos L. , Hemeryck A.
Published: June 2024

Saddle points on high-dimensional potential energy surfaces (PES) play a determining role in the activated dynamics of molecules and materials. Building on approaches dating back more than 50 years, many open-ended transition-state search methods have been developed to follow the direction of negative curvature from a local minimum to an adjacent first-order saddle point. Despite the mathematical justification, these methods can display a high failure rate: using small deformation steps, up to 80% of the explorations can end up in a convex region of the PES, where all directions of negative curvature vanish, while if the deformation is aggressive, a similar fraction of attempts lead to saddle points that are not directly connected to the initial minimum. In high-dimension PES, these reproducible failures were thought to only increase the overall computational cost, without having any effect on the methods’ capacity to find all saddle points surrounding a minimum. Using activation-relaxation technique nouveau (ARTn), we characterize the nature of the PES around minima, considerably expanding on previous knowledge. We show that convex regions can lie on activation pathways and that not exploring beyond them can introduce significant bias in the saddle-point search. We introduce an efficient approach for traversing the convex regions, almost eliminating exploration failures, while multiplying by almost 10 the number of identified unique and connected saddle points as compared to the standard ARTn, thus underlining the importance of correctly handling convex regions for completeness of saddle point explorations.
Effect of the Womersley number on transition to turbulence in pipe flow: An experimental study
Authors: El-Khader Baha Al-Deen T. , Brindise Melissa C.
Published: June 2024

The mechanisms driving the transition to turbulence in pulsatile flows are not well understood. Prior studies in this domain have noted the dynamics of this flow regime to depend on the mean Reynolds number, pulsation frequency (i.e., Womersley number), and inflow pulsatile waveform shape. Conflicting findings, particularly regarding the role of the Womersley number on the critical Reynolds number and the development of turbulence, have been reported. The discord has primarily been observed for flows, with Womersley numbers ranging from 4 to 12. Hence, in this work, we use particle image velocimetry to explore the effects of the Womersley number within this 4–12 range on the dynamics of the pulsatile transition. Eighteen test cases were captured using six mean Reynolds numbers (range 800–4200) and five Womersley numbers. Turbulent kinetic energy, turbulence intensity (TI), and phase lag were computed. Our results indicated that the critical Reynolds number was roughly independent of the Womersley number. At high Womersley numbers, the TI trend maintained lower pulsatility, and the flow was observed to mimic a steady transitional flow regime. A plateau of the TI-velocity and TI-acceleration phase lag was observed at a Womersley number of 8, highlighting that this may be the critical value where further increases to the Womersley number do not alter the transition dynamics. Furthermore, this suggests that the phase lag may provide a universal indicator of the specific influence of the Womersley number on transition for a given flow. Overall, these findings elucidate critical details regarding the role of the Womersley number in the transition to turbulence.
Two-dimensional direct numerical simulation study of multicomponent mixing with phase transition in a transcritical shear layer
Authors: Doehring Alexander , Trummler Theresa , Pfitzner Michael , Klein Markus
Published: June 2024

In this paper, we investigate two-dimensional direct numerical simulations of a transcritical shear layer. Three configurations are chosen, which are distinguished by the level of presence of two-phase phenomena. The thermodynamic model is based on a cubic equation of state. It was extended for multicomponent mixtures, and it is able to account for vapor–liquid equilibrium. The thermodynamic modeling with phase-transition is validated using experimental data from the literature. Special focus is put on the effect of the density gradient and the density changes caused by phase-transition on the development of the turbulent shear layer and the associated mixing. In addition to this, the vorticity distribution and the components of its transport equation are analyzed and compared for the different configurations.
Numerical investigation of hydroxyl radicals produced by a single bubble in jet pump cavitation reactor
Authors: Mo Xiaoyu , Xu Shuangjie , Chai Tongshan , Cheng Huaiyu , Li Honggang , Zhang Zuti , Long Xinping
Published: June 2024

Jet pump cavitation reactors (JPCRs) have significant potential to be used in water treatment applications. During their operation, the hydroxyl radicals generated by cavitation collapse produce a strong oxidation capacity, which is one of the key mechanisms in disrupting algal cells. In this paper, we investigate the hydroxyl radicals produced by single cavitation bubble in a JPCR. The numerical method includes a bubble dynamic model, molecular diffusion model, energy balance equation, and chemical reaction model for predicting the hydroxyl radical production. Additionally, the pressure distribution within a JPCR is tested and used to analyze the single-bubble performance. The effects of the JPCR operating conditions and structure parameters on hydroxyl radical production are further discussed. Our results indicate that, when the flow rate ratio is positive, the number of hydroxyl radicals is closely related to the development and collapse of the cavitation bubble and reaches a peak value under the critical condition. When the flow rate ratio is negative, the maximum production of hydroxyl radicals appears under backflow stagnation condition. In general, increasing the throat length–diameter ratio and diffuser angle encourages the production of hydroxyl radicals, whereas increasing the area ratio inhibits their generation.
On the rearrangement and dissociation mechanism of SiH4+ in its triply-degenerate ground state
Authors: Mondal T. , Varandas A. J. C.
Published: June 2024

An ab initio molecular orbital study has been performed to explore the structural rearrangement and dissociation of SiH4+ radical cation at the X̃2T2 ground electronic state. All stationary points located on the lowest adiabatic sheet of Jahn–Teller (JT) split X̃2T2 state are fully optimized and characterized by performing harmonic vibrational frequency calculations. The structural rearrangement is predicted to start with JT distortions involving the doubly-degenerate (e) and triply-degenerate (t2) modes. The e mode reduces the initial Td symmetry of the SiH4+ ground state to a D2d saddle point, which eventually dissociates into the SiH3+(2A1) + H products via C3v local minimum. In turn, an e-type bending of αH-Si-H yields the SiH2+(2A1) + H2 products through the first C3v local minimum and then the Cs(2A′) global minimum. In the alternative pathway, the t2 mode distorts the initial Td symmetry into a loosely bound C3v local minimum, which further dissociates into the SiH3+(2A1) + H asymptote via totally symmetric Si–H stretching mode, and SiH2+(2A1) + H2 products via H–Si–H bending (e) mode through the Cs(2A′) global minimum. It is further predicted that the Cs global minimum interconverts equivalent structures via a C2v transition structure. In addition, the two dissociation products are found to be connected by a second C2v transition structure.
Vibrational coherences in half-broadband 2D electronic spectroscopy: Spectral filtering to identify excited state displacements
Authors: Green Dale , Bressan Giovanni , Heisler Ismael A. , Meech Stephen R. , Jones Garth A.
Published: June 2024

Vibrational coherences in ultrafast pump–probe (PP) and 2D electronic spectroscopy (2DES) provide insights into the excited state dynamics of molecules. Femtosecond coherence spectra and 2D beat maps yield information about displacements of excited state surfaces for key vibrational modes. Half-broadband 2DES uses a PP configuration with a white light continuum probe to extend the detection range and resolve vibrational coherences in the excited state absorption (ESA). However, the interpretation of these spectra is difficult as they are strongly dependent on the spectrum of the pump laser and the relative displacement of the excited states along the vibrational coordinates. We demonstrate the impact of these convoluting factors for a model based upon cresyl violet. A careful consideration of the position of the pump spectrum can be a powerful tool in resolving the ESA coherences to gain insights into excited state displacements. This paper also highlights the need for caution in considering the spectral window of the pulse when interpreting these spectra.
Superfluid excitations in rotating two-dimensional ring traps
Authors: Tomishiyo Guilherme , Madeira Lucas , Caracanhas Mônica A.
Published: June 2024

We studied a rotating Bose–Einstein condensate confined in ring trap configurations that can be produced starting with a bubble trap confinement, approximated by a Mexican hat and shift harmonic oscillator potentials. Using a variational technique and perturbation theory, we determined the vortex configurations in this system by varying the interparticle interaction and the angular velocity of the atomic cloud. We found that the phase diagram of the system has macrovortex structures for small positive values of the interaction parameter, and the charge of the central vortex increases with rotation. Strengthening the atomic interaction makes the macrovortex unstable, and it decays into multiple singly charged vortices that arrange themselves in a lattice configuration. We also look for experimentally realizable methods to determine the vortex configuration without relying upon absorption imaging since the structures are not always visible in the latter. More specifically, we study how the vortex distribution affects the collective modes of the condensate by solving the Gross–Pitaevskii equation numerically and by analytical predictions using the sum-rule approach for the frequencies of the modes. These results reveal important signatures to characterize the macrovortices and vortex lattice transitions in the experiments.
2D materials for marine corrosion protection: A review
Authors: Shang Caiyi , Sang Dandan , Li Changxing , Zou Liangrui , Wu Jinfei , Wang Qinglin
Published: June 2024

The pervasive issue of metal corrosion in various industrial environments, especially in marine settings, incurs significant economic costs and hazardous failures. Traditional protection methods, although diverse, fall short in durability and environmental adaptability, necessitating advanced solutions, such as two-dimensional (2D) materials, including graphene, layered double hydroxides, boron nitride, MXenes, and MoS2. These materials offer exceptional barrier properties against corrosive agents due to their high surface area and minimal thickness, enhancing the lifespan and reliability of metal assets under harsh conditions. Innovations such as self-repairing coatings and advanced application techniques, such as automated spraying and rapid photocuring, further augment their effectiveness. In this Review, recent advancements in the development and application of 2D material-enhanced coatings are reviewed, underscoring their potential in revolutionizing marine corrosion protection through improved performance metrics and sustainability. The challenges and prospects of these novel materials are also discussed, highlighting the need for further research to overcome application hurdles and realize their full potential in industrial uses.
High-intensity polarized electron gun featuring distributed Bragg reflector GaAs photocathode
Authors: Wang Erdong , Rahman Omer , Biswas Jyoti , Skaritka John , Inacker Patrick , Liu Wei , Napoli Ronald , Paniccia Matthew
Published: June 2024

The polarized electron source is a critical component in accelerator facilities such as the electron–ion collider, which requires a polarized electron gun with higher voltage and higher bunch charge than existing sources. One challenge we faced was the surface charge limit of the distributed Bragg reflector GaAs/GaAsP superlattice (DBR-SL-GaAs) photocathode. We suppressed this effect by optimizing the surface doping and heat cleaning procedures. We achieved up to 11.6 nC bunch charge of polarized electron beam. In this report, we discuss the performance of tests of a DBR-SL-GaAs photocathode in the high voltage direct current gun. Possible reasons for the observed peak quantum efficiency wavelength shift are analyzed, and we addressed it by using a wavelength tunable laser. In addition, the impact of the DBR layer and laser on the lifetime is investigated in this paper. The optimal DBR-SL-GaAs operating zone has been proposed, which gave us a long lifetime and high polarization at 30 μA operation. The success of this polarized gun will be key to the future of the nuclear sciences.
Can simple, on-ground vegetation and soil measures reliably indicate the health of rangelands? An application in Australia’s semi-arid woodlands
Authors: Ludwig John A. , Tongway David J. , Hindley Norman
Published: June 2024

Sustainably managing grazing lands is aided by monitoring and responding to simple and reliable indicators of how well the vegetation and soils of these landscapes are functioning to capture scarce resources such as water and nutrients. Indicators are needed because direct measurement of resource capture is time consuming and costly. Our aim was to assess how simple measures of vegetation patch cover and size, and soil surface condition, would apply to patchy (run-on/run-off) semi-arid landscapes being grazed at different intensities. We used the grazing gradient design where distance from water serves as a surrogate for grazing intensity, which is a combination of herbage consumption and trampling. From 0.5 to 8.9 km distance from water, we measured vegetation and soil indicators of landscape function on 12 sites, six along a grazing gradient in a mulga (Acacia aneura) woodland and six in a gidgee (Acacia cambagei) woodland. We found the size of tree groves, at both mulga and gidgee sites, declined near water, indicating a loss in the capacity of these groves to capture mobile resources in run-off. Enhancing this capacity at sites in ‘good’ rangeland condition was the presence of a thick band of grass upslope of tree groves. The number of soil erosion features (rills) was also a reliable indicator of landscape function at both gidgee and mulga sites. Soil surface condition indices of stability, infiltration and nutrient cycling had no detectable trends with distance from water at gidgee and mulga sites, but these three indicator values were always significantly higher within groves than inter-groves, confirming the important role of maintaining healthy groves of trees and upslope bands of grass within these semi-arid rangelands.
It pays to follow the leader: Metabolic cost of flight is lower for trailing birds in small groups
Authors: Friman Sonja I. , Elowe Cory R. , Hao Siyang , Mendez Laura , Ayala Raul , Brown Ian , Hagood Caylan , Hedlund Yseult , Jackson Dayna , Killi Justin , Orfanides Gabriella , Ozcan Evrim , Ramirez Jared , Gerson Alexander R. , Breuer Kenneth S. , Hedrick Tyson L.
Published: June 2024

Many bird species commonly aggregate in flocks for reasons ranging from predator defense to navigation. Available evidence suggests that certain types of flocks—the V and echelon formations of large birds—may provide a benefit that reduces the aerodynamic cost of flight, whereas cluster flocks typical of smaller birds may increase flight costs. However, metabolic flight costs have not been directly measured in any of these group flight contexts [Zhang and Lauder,
J. Exp. Biol.
226
, jeb245617 (2023)]. Here, we measured the energetic benefits of flight in small groups of two or three birds and the requirements for realizing those benefits, using metabolic energy expenditure and flight position measurements from European Starlings flying in a wind tunnel. The starlings continuously varied their relative position during flights but adopted a V formation motif on average, with a modal spanwise and streamwise spacing of [0.81, 0.91] wingspans. As measured via CO
2
production, flight costs for follower birds were significantly reduced compared to their individual solo flight benchmarks. However, followers with more positional variability with respect to leaders did less well, even increasing their costs above solo flight. Thus, we directly demonstrate energetic costs and benefits for group flight followers in an experimental context amenable to further investigation of the underlying aerodynamics, wake interactions, and bird characteristics that produce these metabolic effects.
Transitional probability between characters as a component of
sentence processing in Chinese
Authors: Wang Tianlin , Cooper Borkenhagen Matthew J.
Published: June 2024

This study explores the role of transitional probability (TP) in
sentence processing in Chinese, a writing system that presents unique challenges
due to its character-based structure and lack of word boundaries. The research
investigates how the statistical regularities of character meaning, as captured
by TP, aid in word segmentation and impact reading comprehension. Utilizing a
moving window task, the study examines the processing speed of characters in
high versus low TP conditions. Findings reveal that characters in high TP bigram
conditions (indicating a consistent semantic association within a bigram) are
processed more quickly, underscoring the importance of this statistical property
of characters in Chinese sentence reading. These findings challenge conventional
notions in Chinese linguistics concerning the relationship between characters,
morphemes, and semantics, and suggests an alternative perspective on (and the
need for reevaluation of) character-level semantics. The study also highlights
the influence of prosodic context on reading speed, indicating that anticipatory
linguistic patterns shape reader processing.
Visualisation of counter-rotating dust disks using ray tracing methods
Authors: de Leon Eddy B , Frauendiener Jörg , Klein Christian
Published: June 2024

Physical aspects of stationary axisymmetric vacuum spacetimes given by exact solutions of the Einstein equations are discussed via ray tracing. A detailed study of the spacetime generated by a disk of counter-rotating dust is presented. The spacetime is given in explicit form in terms of hyperelliptic theta functions. The numerical approach to ray tracing is set up for general stationary axisymmetric spacetimes and tested at the well-studied example of the Kerr solution. Similar features as in the case of a rotating black hole, are explored in the case of a dust disk. The effect of the central redshift varying between a Newtonian disk and the ultrarelativistic disk, where the exterior of the disk can be interpreted as the extreme Kerr solution, and the transition from a single component disk to a static disk is explored. Frame dragging, as well as photon spheres, are discussed.
Design of tensile-strained GeSn/SiGeSn structure for low threshold mid-infrared laser application
Authors: Zhang Qingfang , Lu Wenxiang , Zhang Jitao , Chen Qianyu , Zhang Pei , Qin Zirui , Cao Lingzhi , Han Genquan
Published: June 2024

The plasticity of GeSn alloy energy band has promoted the development of silicon-based photoelectric integration and optical interconnection. A tensile-strained GeSn/SiGeSn double heterostructure laser wrapped with Si3N4 stress liner is designed and characterized theoretically. The triaxial tensile strain is introduced into the GeSn/SiGeSn heterostructure laser by the Si3N4 linear stressor. The lower threshold current density and higher optical gain of the GeSn/SiGeSn laser can be achieved by tuning the band structure and carrier distribution in the active region with tensile strain and Sn compositions. Compared with the relaxed device, the value of ne

,Γ/ne

,total for the Ge0.90Sn0.10/Si0.315Ge0.499Sn0.186 heterostructure laser wrapped with 300 nm Si3N4 linear stressor is increased to 30.6% at n
e,total of 1018 cm−3, the laser λ can be extended to 3.44 μm, and the J
th is reduced from 206 to 59 A/cm2.
Theoretical study of the compatibility between environmentally friendly insulation gas CF3SO2F and silver, zinc, and zinc oxide materials in gas-insulated equipment
Authors: Han Rong , Wan Xuhao , Yu Wei , Su Jinhao , Wang Anyang , Ke Xue , Wang Ruilin , Zhou Wenjun , Zheng Yu , Guo Yuzheng
Published: June 2024

Exploring the gas-solid compatibility between insulating gas and solids materials used in electrical equipment is of great significance for determining the long-term behavior of insulating gas trifluoromethanesulonyl fluoride (CF3SO2F). The gas-solid compatibility of CF3SO2F and its decomposition products with Ag, Zn, and ZnO common surfaces has been assessed based on first-principles calculations, with SF6 as the control group. CF3SO2F has excellent gas-solid compatibility with the solid surfaces by analyzing the adsorption configurations, adsorption energies, charge transfer, adsorption height, density of states, and ab initio molecular dynamics (AIMD) results. The external electric fields do not affect the excellent compatibility between CF3SO2F and the solid surfaces. Besides, the Ag(111) surface exhibits fine gas-solid compatibility with all decomposition products benefitting from its low surface energy. Originating in the existence of the three-center-four-electron (3c4e) π bond and F atoms with strong electronegativity in SO2F2, SO2F2 has poor compatibility with the Ag(110), (100), and Zn(001) surface. SO2, COF2, and HF gases may accelerate equipment failure due to the strong adsorption strength and poor compatibility with ZnO(100) and (110) surfaces. The results provide the theoretical guidance for the engineering application and long-term performance evaluation of CF3SO2F.
Collective spin waves in RKKY interlayer-coupled Ni80Fe20/Ru/Ni80Fe20 nanowire arrays
Authors: Adeyeye Adekunle O , Hussain Bushra , Cottam Michael G , Gubbiotti Gianluca
Published: June 2024

We report on a comprehensive investigation of collective spin waves in Ruderman–Kittel–Kasuya–Yosida (RKKY) interlayer-coupled Ni80Fe20 (10 nm)/Ru(1.0 nm)/ Ni80Fe20 (10 nm) nanowire (NW) arrays. We employed Brillouin light scattering to probe the field- and wavevector-dependences of the spin-wave frequency spectra. The acquired data were subsequently analyzed and interpreted within the framework of a microscopic Hamiltonian-based method, enabling a detailed understanding of the observed spin-wave behavior. We observed the propagation of Bloch-type collective spin waves within the arrays, characterized by distinct magnonic bandwidths that stem from the combined influence of RKKY interlayer and inter-NW dynamical dipolar interactions.
Physical model of neutron scattering by clathrate hydrate and C

60

hosting paramagnetic oxygen molecules
Authors: Xu (许树琪) S , DiJulio D D , Marquez Damian J I , Kittelmann T , Bernasconi M , Campi D , Abou El Kheir O , Laporte S I , Rataj B , Czamler V , Zimmer O , Gorini G , Santoro V , Muhrer G
Published: June 2024

This paper describes the physical modelling of neutron scattering in two polycrystalline inclusion compounds, fully deuterated clathrate hydrate and

C

60

, each with paramagnetic oxygen as guest molecules. For studying the suitability of these materials for neutron moderation to very low energies, the model includes, in addition to the magnetic neutron scattering by the oxygen, the nuclear scattering by all constituents. The theoretical total cross sections are calculated based on the phonon density of states obtained by density functional theory and molecular dynamics simulations. At low temperatures, the developed scattering kernels are in good agreement with experimental neutron scattering data reported in the literature. At 20 K and above, a Lorentzian distribution for the zero-field splitting of the magnetic substates of the spin triplet of the oxygen molecules helps to reproduce magnetic peaks observed in inelastic neutron scattering experiments better than the original theory based on a single-valued splitting constant. Neutron spectra obtained by Monte Carlo simulations in infinite media are presented, highlighting the potential use of

O

2

-containing fully deuterated clathrate hydrate as a neutron moderator for the production of very cold neutrons.
Analysis of radon mitigation methods: 10-year review
Authors: Kouroukla E , Gooding T D , Fonseca H S
Published: June 2024

Exposure to the radon gas within a building can result in an increased risk of lung cancer. To minimise the health risk, indoor radon concentrations can be reduced using well-established mitigation methods. The performance of various radon reduction methods, their combination as well as other factors that can impact the efficiency of radon mitigation, were analysed using data collected from approximately 2800 dwellings that had installed radon mitigation techniques during the period 2007–2017. As demonstrated previously (Hodgson 2011), active methods are the most effective at reducing high concentrations of radon to below the Action and Target Levels (200 Bq m−3 and 100 Bq m−3 respectively). Reduction factors of up to 5.5 using single active methods and 8.3 using a combination of active methods were estimated in this study. For indoor radon levels greater than 1 000 Bq m−3, the Active Sump remained the most efficient technique, with the Active Underfloor Ventilation being the second most effective method. Passive methods alone or in combination with other passive methods offered moderate reductions at high radon concentration. Of the passive methods, Underfloor Ventilation was found to have the highest performance with a reduction factor of 1.8. The conclusions of this study should be used to update guidance for stakeholders including householders, contractors, radon awareness campaigns and the UKradon.org website.
Construction of a measurement system and analytical solution for docking pose of large aircraft components based on draw-wire displacement sensors
Authors: Sun Zhengyang , Wang Hongxi , Wang Guanwei , Tian Huihui , Liang Wenhong
Published: June 2024

Relative pose detection is a key technology in large component automatic docking systems. In this paper, a measurement system has been developed to detect the relative pose of large aircraft components with draw-wire displacement sensors, while an analytical calculation method has been proposed to determine the docking pose of large aircraft components. This method establishes a measurement model for the docking pose of large components and separates the position and orientation solutions based on the distances between seven sets of measurement points measured by the draw-wire displacement sensors. First, the principle of three-dimensional rendezvous positioning is refined to ascertain the relative position of the components. Then, by analyzing the properties of the rotation matrix and the coupling relationship between the position and orientation variables of the movable component, 15 compatible equations containing only two variables with a maximum degree of four are obtained. Based on this set of equations, a unique solution for the rotation matrix was obtained through the variable substitution method, gradually eliminating higher-order terms. Finally, the correctness of the method is verified through numerical examples. Unlike typical parallel mechanism models, this model can directly obtain 15 compatible equations without the need for methods such as Gröbner bases. Moreover, compared to the measurement method using six draw-wire displacement sensors, a unique solution can be directly determined, solving the problem of multiple solution selection. This measurement method only requires measuring the distance between measurement points to solve the relative pose, with low equipment costs and less susceptibility to external environmental factors.
Identification of exfoliated monolayer hexagonal boron nitride films with a digital color camera under white light illumination
Authors: Hattori Yoshiaki , Taniguchi Takashi , Watanabe Kenji , Kitamura Masatoshi
Published: June 2024

Optical microscopy with white light illumination has been employed when obtaining exfoliated monolayer hexagonal boron nitride (1L hBN) films from a large number of randomly placed films on a substrate. However, real-time observation of 1L hBN using a color camera under white light illumination remains challenging since hBN is transparent in the visible wavelength range. The poor optical constant of 1L hBN films in microphotographs is significantly improved using a Si substrate coated with a SiN
x
thin-film (SiN
x
/Si). When observing hBN thin films on SiN
x
/Si using a color digital camera in an optical microscope under white light illumination, the clarity of the captured color images depends on the thickness of the SiN
x
film (d). For real-time direct observation, the d was optimized based on quantitative chromatic studies tailored to Bayer filters of a color image sensor. Through image simulation, it was determined that the color difference between 1L hBN and the bare substrate is maximized at d = 59 or 70 nm, which was experimentally verified. The SiN
x
/Si with optimized d values visualized 1L hBN films without requiring significant contrast enhancement via image processing under white light illumination in real-time. Furthermore, the captured color photographs facilitate the reliable determination of the number of layers in few-layer hBN films using the contrast of the green channel of the images.
Cross-tokamak deployment study of plasma disruption predictors based on convolutional autoencoder
Authors: Ai X K , Zheng W , Zhang M , Ding Y H , Chen D L , Chen Z Y , Shen C S , Guo B H , Wang N C , Yang Z J , Chen Z P , Pan Y , Shen B , Xiao B J ,   J-TEXT Team
Published: June 2024

In the initial stages of operation for future tokamak, facing limited data availability, deploying data-driven disruption predictors requires optimal performance with minimal use of new device data. This paper studies the issue of data utilization in data-driven disruption predictor during cross tokamak deployment. Current predictors primarily employ supervised learning methods and require a large number of disruption and non-disruption shots for training. However, the scarcity and high cost of obtaining disruption shots for future tokamaks result in imbalanced training datasets, reducing the performance of supervised learning predictors. To solve this problem, we propose the Enhanced Convolutional Autoencoder Anomaly Detection (E-CAAD) predictor. E-CAAD can be trained only by non-disruption samples and can also be trained by disruption precursor samples when disruption shots occur. This model not only overcomes the sample imbalance in supervised learning predictors, but also overcomes the inefficient dataset utilization faced by traditional anomaly detection predictors that cannot use disruption precursor samples for training, making it more suitable for the unpredictable datasets of future tokamaks. Compared to traditional anomaly detection predictors, the E-CAAD predictor performs better in disruption prediction and is deployed faster on new devices. Additionally, we explore strategies to accelerate the deployment of the E-CAAD predictor on the new device by using data from existing devices. Two deployment strategies are presented: mixing data from existing devices and fine-tuning the predictor trained on existing devices. Our comparisons indicate that the data from existing device can accelerate the deployment of predictor on new device. Notably, the fine-tuning strategy yields the fastest deployment on new device among the designed strategies.
Simulation on the effect of oxygen concentration on the positive secondary streamer generated in oxygen-rich nitrogen–oxygen mixtures under atmospheric pressure
Authors: Wei Zhenyu , Ono Ryo , Komuro Atsushi
Published: June 2024

In this study, we investigated the effect of various

O

2

concentrations, from 20% to 90%, in nitrogen–oxygen (

N

2

/

O

2

) mixtures on the characteristics of secondary streamers. As oxygen molecules have different molecular characteristics from nitrogen molecules in terms of ionisation threshold and electron attachment property, streamer discharges generated under various nitrogen–oxygen ratios may exhibit differing characteristics such as electron density, electric field, and radical formation. We focused on the changes in these parameters in secondary streamers using simulations. Simulations were first performed under the same conditions as those in previous experiments to compare the results of the ozone production, discharge current, and discharge emission characteristics. To compare the ozone production characteristics, simulated O radicals–the precursor of ozone–were used in the simulation for simplicity. This comparison showed that, although the absolute values of each parameter were different, the simulation exhibited a similar trend in the case of the experimentally obtained oxygen concentration dependence. After the validity of the simulation was verified to some extent via a comparison with the experiment, the results obtained from the simulation were analysed in detail. The results showed that, although the electric field strength in the secondary streamer did not change much as the oxygen concentration increased, the decrease rate of the electron density was greatly accelerated by the electron attachment reaction of oxygen. As a result, many of the electrons had already dissipate during the development of the primary streamer, and few electrons remained when the secondary streamer was formed. This effect suggests that the ratio of the amount of O radicals produced in the primary streamer to that produced in the secondary streamer changes as the oxygen concentration changes.
Spray pyrolysis synthesis of Sr2Si5N8:Eu2+ nanoparticles for light conversion film enhancing photosynthesis in greenhouses
Authors: Wang Yan , Zhou Lina , Cheng Lichun
Published: June 2024

This study presents a comparative analysis of Sr2Si5N8:Eu2+ nanoparticles synthesized using Spray Pyrolysis (SP) and Solid-State Synthesis (SSS). Through meticulous characterization, we found that the SP method significantly enhanced the morphological and optical properties of the nanoparticles. SP-produced nanoparticles demonstrated a 30% higher crystallinity and a 25% increase in luminescence intensity compared to their SSS counterparts. Additionally, the mesoporous structure characteristic of SP-synthesized particles exhibited a 15% greater surface area, measured at 124.7 m2 g−1, which contributed to improved light absorption capabilities. These attributes are crucial for the intended application of enhancing photosynthesis in greenhouse environments. The UV–Visible spectra confirmed that SP nanoparticles possess superior light conversion capabilities, with notable implications for optimizing light distribution to facilitate plant growth. This research highlighted the advantages of SP, including ease of scalability and enhanced optical performance, which are pivotal for agricultural applications. The study emphasized that the choice of synthesis method played a critical role in tailoring the properties of Sr2Si5N8:Eu2+ nanoparticles for specific functional requirements in optical and agricultural technologies.
Preparation of MoS2/CdS/TNAs ternary composite structures and study of their photocatalytic properties
Authors: Xiong Xudong , Liu Yang , Duan Zhenkun , Xiong Xiaobo , Wang Yongqian
Published: June 2024

TiO2 has long been favored by researchers as a representative of semiconductor photocatalysts. Titanium dioxide nanotubes (TNAs) have a larger specific surface area, which makes them more valuable for the design of photocatalyst carriers. CdS is also a typical photocatalytic semiconductor material with a narrow bandwidth, which has a better performance in the visible light region. However, it also has certain problems such as photocorrosion. The composite MoS2 has a better inhibition effect. In this study, MoS2 and CdS were composited on TNAs using electrochemical deposition for the first time, and MoS2/CdS/TNAs (MCT) ternary composite nanostructures were successfully prepared. The effects of electrochemical deposition voltage, reaction time, and the ratios of molybdenum and sulfur sources in the electrolyte on the MCT composite structures were investigated. In this work, the photocatalytic degradation of organic water pollutants was simulated using methylene blue, and the degradation rate reached 93.1% at 150 min. After cycling the degradation experiments for five times, the photocatalysts still had good stability. The results showed that the MCT has good photocatalytic activity, which provides a feasible way for TNAs in the design of photocatalyst carriers.
Investigating the optoelectronic characteristics of multilayer C and BN corographene using density functional theory
Authors: Majidi Roya , Ayesh Ahmad I
Published: June 2024

This study investigates the structural, optical, and electronic properties of multilayer carbon (C) and boron nitride (BN) corographene structures using first-principles calculations. The results confirm that these sheets, kept together through van der Waals forces, are energetically favorable and thermally stable. Mono-, bi-, and tri-layer C corographene sheets display semiconducting behavior, while the multilayer BN corographene sheets are insulators. Controlling the band gap can be achieved by increasing the number of layers. The optical characteristics of the sheets are anisotropic when applying electric fields polarized perpendicular or parallel to the sheets. They exhibit a high constant of static dielectric, as well as optical absorption with optical conductivity that increases according to the increase in the number of layers. The reflection and transmission constants showed that multilayer C and BN corographene sheets exhibit transparency, especially in the high-energy range. These findings suggest promising capabilities of C and BN corographene sheets for use in optoelectronic devices.
Pressure generation under deformation in a large-volume press
Authors: Wang 王 Saisai 赛赛 , Zhao 赵 Xinyu 鑫宇 , Hu 胡 Kuo 阔 , Feng 丰 Bingtao 丙涛 , Hou 侯 Xuyuan 旭远 , Zhang 张 Yiming 羿鸣 , Liu 刘 Shucheng 书成 , Shang 尚 Yuchen 宇琛 , Liu 刘 Zhaodong 兆东 , Yao 姚 Mingguang 明光 , Liu 刘 Bingbing 冰冰
Published: June 2024

Deformation can change the transition pathway of materials under high pressure, thus significantly affects physical and chemical properties of matters. However, accurate pressure calibration under deformation is challenging and thereby causes relatively large pressure uncertainties in deformation experiments, resulting in the synthesis of complex multiphase materials. Here, pressure generations of three types of deformation assemblies were well calibrated in a Walker-type large-volume press (LVP) by electrical resistance measurements combined with finite element simulations (FESs). Hard Al2O3 or diamond pistons in shear and uniaxial deformation assemblies significantly increase the efficiency of pressure generation compared with the conventional quasi-hydrostatic assembly. The uniaxial deformation assembly using flat diamond pistons possesses the highest efficiency in these deformation assemblies. This finding is further confirmed by stress distribution analysis based on FESs. With this deformation assembly, we found shear can effectively promote the transformation of C60 into diamond under high pressure and realized the synthesis of phase-pure diamond at relatively moderate pressure and temperature conditions. The present developed techniques will help improve pressure efficiencies in LVP and explore the new physical and chemical properties of materials under deformation in both science and technology.