bluuebunny/crossref_metadata_2025 huggingface dataset:
Finger Sprains, Ultrasound Anatomy, and Pathology of Finger Ligaments
Authors: Lapegue Franck , André Aymeric , Lafourcade François , Filliole Antoine , Lambeaux Constance , Van Viet-Tam , Adamski Elorie , Bachour Rafy , Goumarre Céline , Chiavassa Hélène , Faruch Bilfeld Marie , Sans Nicolas
Published: November 2024

The joints of the fingers play an important role in prehension. They must accomplish both great mobility in the sagittal plane to allow the fingers to roll up and great stability to ensure the grip is both precise and firm. The collateral ligaments and palmar plates are the main passive stabilizing structures between the interphalangeal (IP) and metacarpophalangeal (MCP) joints. Sprains with or without dislocation of the proximal IP joints of the fingers are common injuries in sports pathology and may involve not only the ligaments but also their bony insertion on the phalanges or extensor tendons. Certain entities are specific to the MCP joints: ligament ruptures with Stener-like effect under the sagittal bands and MCP flexion locking (locked finger). Radiographs and ultrasound usually enable a precise diagnosis, so appropriate treatment can be provided.
On the concept of the pluriverse in Walter Mignolo and the European New Right
Authors: Davidson Miri
Published: November 2024

Today, the ‘pluriverse’ is considered to be a radical new concept capable of decolonising political thought. However, it is not only decolonial scholarship that has taken up the concept of the pluriverse; far-right intellectuals, too, have been cultivating a decolonial imaginary based on the idea of the pluriverse. This article compares the way the concept of the pluriverse appears in certain strands of Latin American decolonial theory exemplified by Walter Mignolo, on the one hand, and the ethnopluralism of the European New Right represented by Alain de Benoist and Alexander Dugin, on the other. Despite Mignolo’s pluriverse being an ‘open pluriverse’ of entanglement between peoples, while the European New Right’s is a ‘closed pluriverse’ of ethnic separation, I argue that these uses of the pluriverse are nevertheless underpinned by a shared analytical and normative framework. This framework is defined by a simple refrain: that what oppresses the world is ontological and epistemological sameness, and what will liberate it is ontological and epistemological difference. I argue that this schema, which misapprehends imperialism as a form of epistemic domination geared purely towards homogenisation, rather than as a set of material relationships that also produce (e.g. racial, sexual, and class) difference, does not provide a solid foundation for contesting colonial relations.
Spin diffusion at low temperatures
Authors: Sabirov R. Kh.
Published: November 2024

The method of Zubarev nonequilibrium statistical operators is used to examine the temperature dependence of the spin-diffusion coefficient in a concentrated solid paramagnet. The diffusion coefficient is found to be relatively insensitive to temperature variation, although the value is somewhat larger at low temperatures than at high temperatures. The second moment of the cross-relaxation-line shape is calculated. It is shown to be impossible to reduce the cross-relaxation-line shape to that of the magnetic-resonance line at low temperatures.
Pressure dependence of zero-field splitting of two magnetic centers in a binary-nitrate crystal
Authors: Galkin A. A. , Lukin S. N. , Tsintsadze G. A.
Published: November 2024

The ESR spectra of two physically nonequivalent centers of divalent nickel ions in a crystal of lanthanum magnesium nitrate were studied under the condition hv > D. The values obtained for the parameter of the zero-field axial splitting were as follows: D = +0.200 cm−1 (X center); −2.22 cm−1 (Y center). The changes in the ESR spectra of the nickel ions under three-dimensional compression were investigated at 4.2 °K and pressures up to 10 kbar. The parameters characterizing the zero-field splitting of the spin levels of the two centers were found to depend significantly on the applied pressure; this dependence was qualitatively in agreement with the anisotropy of the compressibility of the binary-nitrate crystal lattice.
Dynamic characteristics of subsurface atoms allowing for changes in interatomic interactions
Authors: Syrkin E. S.
Published: November 2024

The mean-square displacement of subsurface atoms is investigated as a function of temperature allowing for changes in the interatomic interaction close to the surface. A method of calculation previously proposed by V. I. Peresada [V. I. Peresada, in: Physics of the Condensed State, No. 2 (FTINT, AN UkrSSR), Khar'kov (1968), p. 172] is employed. The results enable available experimental values of the mean-square displacements of atoms situated in a (100) type surface of fee crystals to be explained satisfactorily.
The mobility of surface electrons in helium
Authors: Monarkha Yu. P.
Published: November 2024

The adiabatic theory for the electron-ripplon interaction has been employed to calculate the temperature dependence of the surface electron mobility in helium. From 0.9 to 0.5°K the electron mobility is approximately inversely proportional to the temperature T, which differs significantly from the low-temperature asymptotic form, proportional to T−2.
Softening of superconductors with an anomalous thermal conductivity
Authors: Soldatov V. P. , Abraimov V. V. , Startsev V. I.
Published: November 2024

The behavior of the N−S transition-induced creep jump δϵns is investigated in single crystals of pure lead (in transverse and longitudinal magnetic fields) and in lead-bismuth alloys having anomalous thermal conductivities in the N and S states. A detailed comparison with the theory of local thermal heating in the N−S transition shows that the fundamental results of the theory are not adequate to account for the experimental data.
Multiphoton absorption in “dirty” superconductors
Authors: Genkin V. M.
Published: November 2024

The multiphoton absorption of an electromagnetic field of frequency ω0 < 2Δ is studied theoretically in “dirty” superconductors with nonmagnetic impurities at zero temperature. It is shown that for a sufficiently strong field the multiphoton absorption probability at ω0 < 2Δ may exceed that of single photon absorption with ω0 > 2Δ. It is noted that multiphoton absorption allows one to study the angular dependence of the cross section for electron scattering by impurities.
Temperature dependence of the magnetoresistivity of aluminum in a narrow magnetic breakdown layer of open trajectories
Authors: Morgun V. N. , Khotkevich V. I. , Chebotaev N. N. , Bondar' V. A.
Published: November 2024

The temperature dependence of the transverse magnetoresistivity (MR) of aluminum (ρ293°K/ρ4.2°K = 27,000) was investigated under the conditions of magnetic breakdown (MB) for H ‖ [001]±0.5°(j ‖ [100]) in the temperature range 4.2–40'K in fields up to 60 kOe. In this case, for fields greater than 8 kOe in aluminum, a narrow one-dimensional MB layer of open trajectories occurs with δp/pF∼ 1/40 and H0≈40kOe. The nonoscillatory monotonic part of the MR ρH,T,montot exhibits a minimum at T∼ 10°K, which is associated with contributions to the resistance from open MB trajectories ρH,T,monMB∼T−n2, and closed trajectories ρH,Tclose∼T−n1(n1=3). Analysis shows that the monotonic part of the MR ρH,T,monMB, caused by the contribution of open MB trajectories, varies with temperature according to a law close to T−3 (i.e. n2≈3 in the interval 13−20°K, H = 54 kOe). It was found that for the narrow MB layer the electrical conductivity is proportional to T−3 (instead of obeying the Bloch law σ ∼ T−5), when vphon⪢vimp+vdisl and δp⪡qphon. The experimental result σmon∼T−3, connected with the increase in the efficiency of scattering by phonons under the conditions of a layer of open trajectories, and caused by the fact that almost every collision with a phonon removes an electron from the layer, is in complete agreement with theoretical conclusions.
Inducing the ferromagnetic phase in the Mn0.97Fe0.03As alloy with a magnetic field
Authors: Gribanov I. F. , Zavadskii É. A.
Published: November 2024

The magnetic properties of the Mn0.97Fe0.03As alloy were studied over a wide temperature range in magnetic fields up to 70 kOe and under pressures of up to 11 kbar. It has been shown that, within a definite range of temperatures and pressures, the ferromagnetic phase can be induced by means of a strong magnetic field without structural transformation. Both reversible and irreversible induction of the ferromagnetic state have been revealed.
Transport phenomena in a deformed metal
Authors: Dubrovskii I. M.
Published: November 2024

The kinetic equation for electrons in a uniformly deformed metal is analyzed and solved in the first approximation with respect to strain. The dispersion law is assumed isotropic in an undeformed metal and the temperatures are assumed so low as to render scatter by phonons negligible in comparison with scatter by impurities. Expressions are derived for the thermomagnetic and the solenoidal strain effects, which have been discovered experimentally, as well as for other effects of similar nature.
Resistivity and anomalous superconducting transition in Ti1−xFexalloys (0<x≤0.2)
Authors: Prekul A. F. , Shcherbakov A. S. , Volkenshtein N. V.
Published: November 2024

It has been established that in the region of β-solid solutions Ti-Fe alloys simultaneously display superconductivity and a nonmetallic type of temperature dependence of their resistivity. The alloys are found to be divided distinctly into two groups, with low- and high-temperature minima on the ρ(T) curve. Both groups of alloys exhibit anomalously wide resistive transitions into the superconducting state.
Effect of impurity type on conduction electron scattering in lithium at 4.2°K
Authors: Aleksandrov B. N. , Dukin V. V. , Dalakova N. V.
Published: November 2024

The effect of eleven impurities (Cd, Al, Ag, Au, Mg, Zn, Hg, In, Tl, Ga, Pb) on the residual resistivity ρ0 of lithium has been studied. The alloys were prepared from commerical lithium of reduced residual resistivity δ0 = ρ0/ρ293 = (1 to 4)·10−3 with impurity concentrations 2·10−3 to 5 at.%. The solubility limits of In, Tl, Zn, Al, Ga, Pb, and Au impurities in solid lithium were determined for the first time. The measured values of Δρ0/c (the change in residual resistivity resulting from the solution of 1 at.% of an impurity) show a quadratic dependence on ΔZ, the difference between the valency of the V or VI period impurity and that of the host material. The Δρ/c values calculated by the phase shift method and pseudopotential theory (using the Appapillai form factors, derived from “first principles”, and the Ashcroft model potential) are in fair (the second calculation) and satisfactory (the first and third calculations) agreement with experiment. It is suggested that the sphericity of the Fermi surface is apparently a necessary though not the main condition for the applicability of all three calculations.
Low-temperature electrical and galvanomagnetic properties of the Fe-Ni and Fe65(Ni1−xCrx)35 system
Authors: Deryabin A. V. , Rode V. E.
Published: November 2024

The paper is concerned with features of the low-temperature electrical and galvanomagnetic properties of the Fe-Ni and Fe65(Ni1−xCrx)35 alloy systems with mixed exchange interaction. Maxima in the temperature dependences of R−1(ΔR/ΔH of Fe-Ni alloys, changes in the temperature dependence of magnetoresistance with increasing chromium content in the Fe65(Ni1−xCrx)35 systems, and an anomalous temperature dependence of the resistivity of a number of alloys of the Fe65(Ni1−xCrx)35 system have been discovered. The experimental results are interpreted by taking into account additional electron scattering mechanisms in antiferromagnetic regions and at ferro–antiferromagnetic interfaces.
Interaction of light with hexagonal antiferromagnets
Authors: Petrov É. G. , Ostrovskii V. S.
Published: November 2024

A theoretical study is made of dipole transitions in hexagonal antiferromagnets containing magnetic dipoles with unfilled 3d-shells displaced and undisplaced from the center of inversion. It is shown that, unlike antiferromagnets containing only centrosymmetric magnetic ions, hexagonal antiferromagnets with spin noncollinearity induced by a magnetic field exhibit pure exciton transitions as a result of the interaction of light with pairs of ions. The polarization characteristics of the spectrum in this case will differ significantly from the polarization characteristics associated with dipole transitions allowed by the single-ion mechanism. A specific analysis carried out for the 6A1(6S) →4E(4G), 4A1(4G) exciton transitions in CsMnF3 shows that the mechanism allowing a dipole transition in a pair of ions gives rise to an absorption line of frequency 6A1(6S) → A1(4G) that is forbidden in the single-ion approximation. Furthermore, the mechanism allowing a light-induced transition to occur in a pair of ions is such that only ions displaced from the center of inversion can be excited
Effect of structure on internal friction in tantalum at the N-S transition
Authors: Miloshenko V. E. , Shukhalov E. I.
Published: November 2024

Results are presented on the low frequency (∼ 1000 Hz) internal friction (Q−1) in tantalum as a function of the specimen structure. It is found that the peak in Q−l, which has a phase character, shifts along the temperature axis depending on the structure. This displacement attains a value of 0.14°K for a 99% strained specimen.
Electrical properties of heavily doped semiconductors whose order parameter depends on the electron concentration
Authors: Kashin V. A. , Nagaev É. L.
Published: November 2024

Conduction electrons in a conducting crystal of high initial symmetry tend to reduce its symmetry and so produce a gain in energy. The reduction in symmetry may only occur above some critical value of the concentration nA. If, for n < nA, the crystal is subjected to an external field H that reduces its symmetry, the conduction electrons significantly intensify its effect on the crystal and, in such crystals, the order parameter is a function of the electron concentration. In connection with this, to the response function ϵ (q) is added a nondiagonal response function λ (q) that describes the dependence of the order parameter on the external electric field. It is shown that both the response functions have singularities in the vicinity of the concentrational phase transition. For n < nA, when the field is switched on, there is an additional mechanism of carrier scattering from order fluctuations, associated with the combined action of the field H and the electrical field of the crystal defects. This leads to anomalies in the dependence of the resistance on the field. The theory is developed in detail for degenerate antiferromagnetic semiconductors. It is established that giant positive magneto resistance may be observed.
Magnetoplastic effect and heating by eddy currents
Authors: Bol'shutkin D. N. , Desnenko V. A. , Il'ichev V. Ya.
Published: November 2024

The effect of an alternating magnetic field on the plastic deformation of nickel and aluminum was examined at 4.2, 77, and 300°K, and the energy loss due to eddy currents was measured at 77°K only. It has been found that the characteristics of metal softening in an alternating magnetic field, the magnetoplastic effect, can be fully attributed to the temperature increase due to Joule heating by eddy currents.
Quantum-mechanical calculation of elastic forces in rare gas crystals
Authors: Ratner A. M. , Shamfarova O. Ya.
Published: November 2024

The energy of a crystal whose atoms are displaced from the lattice sites is calculated. No restrictions are imposed on the displacement vectors, provided they are small in comparison with the lattice constant. In particular, the atomic configuration may correspond to short-wave lattice oscillations. An essentially anharmonic dependence of elastic energy on displacement is obtained. The energy of interatomic pair interaction is extracted from the elastic energy, and the contribution of residual many-body interactions is estimated. The calculated sound velocity is compared with experimental data.
Direct-drive ICF target with compound ablator containing a low-density component
Authors: Demchenko N. N. , Gus'kov S. Yu. , Kuchugov P. A. , Yakhin R. A. , Zmitrenko N. V.
Published: November 2024

The results of theoretical investigation of implosion and combustion of a direct-drive inertial confinement fusion (ICF) target as a shell with compound outer layer (ablator) intended to absorb laser radiation and produce the ablation pressure compressing the target are presented. It is proposed to supplement the solid ablator of conventional ICF target with an outer layer of a low-density porous substance with density corresponding to the nearly critical one of laser-produced plasma. It is shown that for a laser pulse with energy of 2–3 MJ, designed to ignite the deuterium-tritium reaction in modern experiments, the target with a compound ablator can provide a significant increase in fusion energy yield when the mass fraction of low-density component is in (10–15) % interval.
Investigation of cross-association behavior in water–ethanol solutions: A combined computational-ATR spectroscopy study
Authors: Drougkas Evangelos , Frøstrup Carsten F. , Bohr Henrik G. , Bache Michael , Kontogeorgis Georgios M. , Liang Xiaodong
Published: November 2024

The water/ethanol system possesses complexities at the molecular level, which render its description a difficult task. For the elucidation of the system’s hydrogen bonding features that are the key factors in its complex behavior, we conduct a Density Functional Theory analysis on relevant water/ethanol clusters inside implicit solvent cavities for the determination of the ethanol donor hydrogen bond strength. We record Attenuated Total Reflectance spectra of water/ethanol-OD solutions and utilize our density and refractive index measurements for post-processing. The application of the Badger–Bauer rule reveals a minimum in the strength of the ethanol donor hydrogen bond for a composition of xwater = 0.74. We attempt to analyze further this result by estimating the effect of the implicit solvent on the ethanol donor hydrogen bond strength, finding it to be incremental. A brief analysis of different cluster conformations is carried out to determine the cooperativity conditions that can potentially explain the observed minimum in the ethanol donor hydrogen bond strength. These observations are related to notions of microheterogeneity in water/alcohol mixtures and provide context toward a more elaborate picture of association in heteroclusters.
Photo-rechargeable Mg-ion cell based on PLA/PVDF film
Authors: Molla Sanoar , Khatun Farha , Banerjee Subhobrata , Rajak Ujjwal , Baugh Nirmal , Bagchi Biswajoy , Thakur Pradip
Published: November 2024

Mg2+ ion based self-charging prototype polymeric photo-power cell has been developed in a very simple and inexpensive way. Eosin Y/MgCl2/PVA mixed aqueous solution and poly(lactic acid) /polyvinylidene fluoride (3:1) composite film are the main assembling components of the device responsible for photo-electrons generation and storage. According to the study of the photovoltaic performance of the cell, a maximum of ∼1 V is obtained under the light intensity of ∼110 mW/cm2. The storage capacity of the device is evaluated to be ∼4.0 F/m2 with an energy density of ∼0.6 mWh/m2 and a power density of ∼2. 5 W/m2 by analyzing the charging–discharging data of the power cell. The charging–discharging data are also recorded for 20 cyclic performances (one cycle per day) to check the longevity of our fabricated Mg2+ ion system. A series connection of four devices can be used as a photo-power bank, which is able to lightened up commercially available 18 LEDs with high intensity, which ensures practical utilizations.
Non-Fourier thermal focusing by gradient thermal metamaterials based on the Cattaneo–Vernotte model
Authors: Li Zheng-Yang , Ma Tian-Xue , Yan Dongjia , Wang Hao , Golub Mikhail V. , Hosseini Seyed Mahmoud , Liu Donghuan , Wei Peijun , Zhang Chuanzeng
Published: November 2024

Direct methods to manipulate internal heat conduction in solids remain nearly elusive. In this work, we propose a two-dimensional (2D) gradient thermal metamaterial lens designed to control the internal non-Fourier heat conduction. This gradient thermal metamaterial comprises cylindrical structures made of dermis immersed in a stratum background with an effective refractive index adhering to the hyperbolic secant profile rule. Subsequently, the effective refractive index of the thermal metamaterial is defined and numerically assessed using the extended plane wave expansion method. Thereafter, the non-Fourier heat conduction is analyzed numerically via the finite element method in the time-domain. Our findings indicate that the proposed gradient thermal metamaterial can focus the heat effectively and is akin to a flat thermal lens. The proposed flat thermal lens offers promising avenues for enhancing the material properties by laser-based technologies.
Mechanism of generating collisionless shock in magnetized gas plasma driven by laser-ablated target plasma
Authors: Matsukiyo S. , Oshida K. , Isayama S. , Yamazaki R. , Morita T. , Takezaki T. , Kuramitsu Y. , Tanaka S. J. , Sano T. , Tomita K. , Sakawa Y.
Published: November 2024

The mechanism of generating collisionless shock in magnetized gas plasma driven by laser-ablated target plasma is investigated by using one-dimensional full particle-in-cell simulation. The effect of finite injection time of target plasma, mimicking the finite width of laser pulse, is taken into account. It was found that the formation of a seed-shock requires a precursor. The precursor is driven by gyrating ions, and its origin varies depending on the injection time of the target plasma. When the injection time is short, the target plasma entering the gas plasma creates a precursor; otherwise, gas ions reflected by the strong piston effect of the target plasma create a precursor. The precursor compresses the background gas plasma, and subsequently, a compressed seed-shock forms in the gas plasma. The parameter dependence on the formation process and propagation characteristics of the seed-shock was discussed. It was confirmed that the seed-shock propagates through the gas plasma exhibiting behavior similar to the shock front of supercritical shocks.
MXene-TiO2 heterostructured iontronic neural devices based on ion-dynamic capacitance enabling optoelectronic modulation
Authors: Chang Quanhong , Chen Wei , Xing Fudu , Li Wanhua , Peng Xun , Du Weijie , Wang Huishan , Xiao Guina , Huang Lei
Published: November 2024

The development of neuromorphic systems necessitates the use of memcapacitors that can adapt to optoelectronic modulation. Two-dimensional (2D) materials with atomically thin features and their derived heterostructures are able to allow for controlling local transfer of charge carrier but reports on 2D materials-enabled capacitive-type photoelectric synapses have not been experimentally exploited yet. Herein, MXene-TiO2 heterostructured iontronic neural devices based on ion-dynamic capacitance enabling optoelectronic modulation are designed. According to the electrochemical insight, under UV light illustration, photoexcited electrons in TiO2 flow to MXene, leading to the localized accumulation of electrons as the trapping center and thus inducing the embedding of H+ for participating in the pseudo-intercalation. On removing the UV light, a part of trapped H+ are not instantly returned to the initial state. As a result, this memcapacitor features hysteresis ion-dynamic capacitance under optoelectronic modulation. Through assessing its applicability to neuromorphic computing, this memcapacitor achieves the high recognition accuracy (93.5%) of handwritten digits by recognizing and sharpening the input signal trajectory.
Large perpendicular magnetic anisotropy at Fe/rock-salt-type Cr-oxide interface synthesized via oxygen-driven chemical layer exchange process
Authors: Iida Yuki , Xiang Qingyi , Scheike Thomas , Wen Zhenchao , Okabayashi Jun , Uzuhashi Jun , Ohkubo Tadakatsu , Hono Kazuhiro , Sukegawa Hiroaki , Mitani Seiji
Published: November 2024

Perpendicular magnetic anisotropy (PMA) induced at the interface of the metallic magnetic layer/oxide layer plays a major role in scaling of state-of-the-art spin-transfer-torque magnetoresistive random access memory. The realization of PMA requires the development of mature interface manipulation techniques as well as materials constituting the interface. Herein, we report large PMA using stacks developed with an ultrathin (∼0.7 nm) Fe/rock-salt CrO(001) interface via an oxygen-driven diffusion process. The stacks were prepared by sputter-deposition and post-annealing of the Cr buffer/ultrathin Fe/MgO structure. Significant oxidation of the Fe layer and Cr diffusion into the MgO layer occurred during the deposition. After post-annealing, the oxidized Fe layer was reduced to form an Fe/rock-salt-type Cr-monoxide structure due to chemical layer exchange. The lattice-matched Fe/CrO interface with a large interfacial PMA energy of 1.55 mJ/m2 was confirmed after annealing at 500 °C. X-ray absorption spectroscopy measurements revealed that the post-annealing promoted the redox reaction from the Fe oxide to the metallic Fe and the formation of the CrO. The observed PMA indicates that the oxygen-driven diffusion process by annealing resulted in the well-controlled Fe/CrO interface. The demonstrated diffusion process provides a new chemical route to fabricate artificial, well-controlled PMA interfaces, even containing metastable materials, beyond the conventional sequential layer stacking for the development of spintronic devices.
Influence of the RF-power on the etching yields and surface morphology in reactive ion beam etching of Si and photoresist
Authors: Rohkamm Erik , Spemann Daniel , Scholze Frank , Frost Frank
Published: November 2024

The change in ion energy distribution and composition of a reactive ion beam produced by an RF-excited ion beam source and operation with a mixture of CHF3 and O2 was investigated and correlated with the etching behavior. To this end, measurements were performed with an energy-selective mass spectrometer to determine ion energy distributions, current density measurements for the measurement of current density distributions of the ion beam, and tactile measurements to determine the etching rates of Si and photoresist. The morphology of the photoresist was measured with a scanning force microscope. In particular, alterations in the etching yield and surface morphology of the photoresist can be observed in response to changes in the applied RF-power. An increase in plasma density leads to an increase in fragmentation processes of the injected reactive gases, resulting in the formation of smaller fragments. These smaller fragments have a chemical impact on the substrate surface, which affects the etching performance. These effects can have significant consequences in the context of long-time reactive ion beam processing for patterning applications.
Reconstruction of physical field characteristics of underwater vehicle wake based on data-driven approach
Authors: Luo Feiyang , Shuai Changgeng , Du Yongcheng , Gao Chengzhe , Ren Feng , Zhao Yuanpu
Published: November 2024

The characteristics of underwater vehicle wakes are intricately linked to multiple parameters, such as speed, depth, and environmental factors. Obtaining wake characteristic information for various operating conditions solely through numerical simulation methods can result in computational space explosion, rendering the time and computational resource costs prohibitive. This paper harnesses the robust image processing capabilities of convolutional neural networks and incorporates strategies such as attention mechanisms, dilated convolution techniques, and multi-scale feature fusion to design and construct a neural network architecture. Through a data-driven approach, it reconstructs multiple physical wake field characteristics resulting from underwater vehicle, including underwater velocity fields, surface divergence fields, surface kelvin wake, and surface thermal wakes. The study establishes a “black box” mapping between relevant parameters and the physical fields of wakes. The results demonstrate that the constructed network model achieves high accuracy in capturing both the macroscopic structures and pixel-level details of various physical fields. In comparison with the truth-values, the average normalized root mean square errors for the underwater velocity field, surface divergence field, surface kelvin wake, and surface thermal wakes are 6.10%, 3.40%, 8.21%, and 10.96%, respectively. The average structural similarity index values are 0.955, 0.966, 0.923, and 0.904, respectively. The predicted results closely match the truth-values for each physical field characteristic, effectively addressing the challenges of nonlinearity and multi-scale feature extraction in predicting complex flow fields, offering support for the rapid forecasting of multi-dimensional and multi-physical field characteristics of underwater vehicle wakes.
On the statistical theory of self-gravitating collisionless dark matter flow: Scale and redshift variation of velocity and density distributions
Authors: Xu Zhijie (Jay)
Published: November 2024

The statistics of velocity and density fields are crucial for cosmic structure formation and evolution. This paper extends our previous work on the two-point second-order statistics for the velocity field [Xu, Phys. Fluids 35, 077105 (2023)] to one-point probability distributions for both density and velocity fields. The scale and redshift variation of density and velocity distributions are studied by a halo-based non-projection approach. First, all particles are divided into halo and out-of-halo particles so that the redshift variation can be studied via generalized kurtosis of distributions for halo and out-of-halo particles, respectively. Second, without projecting particle fields onto a structured grid, the scale variation is analyzed by identifying all particle pairs on different scales r. We demonstrate that: (i) the Delaunay tessellation can be used to reconstruct the density field. The density correlation, spectrum, and dispersion functions were obtained, modeled, and compared with the N-body simulation; (ii) the velocity distributions are symmetric on both small and large scales and are non-symmetric with a negative skewness on intermediate scales due to the inverse energy cascade on small scales with a constant rate εu; (iii) on small scales, the even-order moments of pairwise velocity ΔuL follow a two-thirds law ∝(−εur)2/3, while the odd-order moments follow a linear scaling ⟨(ΔuL)2n+1⟩=(2n+1)⟨(ΔuL)2n⟩⟨ΔuL⟩∝r; (iv) the scale variation of the velocity distributions was studied for longitudinal velocities uL or uL′, pairwise velocity (velocity difference) ΔuL = uL′ − uL, and velocity sum ΣuL = uL′ + uL. Fully developed velocity fields are never Gaussian on any scale, despite that they can initially be Gaussian; (v) on small scales, uL and ΣuL can be modeled by a X distribution to maximize the entropy of the system. The distribution of ΔuL can be different; (vi) on large scales, ΔuL and ΣuL can be modeled by a logistic or a X distribution, while uL has a different distribution; and (vii) the redshift variation of the velocity distributions follows the evolution of the X distribution involving a shape parameter α(z) decreasing with time.
Stability of two-phase flow with interfacial flux in porous media: CO2 mineralization
Authors: Roded Roi , Dalton Laura E.
Published: November 2024

The primary objective of carbon capture, utilization, and storage (CCUS) applications in various natural and engineered porous materials is to achieve a stable and planar CO2 displacement front, thereby suppressing viscous fingering. A stable front can ensure uniform and exhaustive CO2 mineralization throughout a reactive medium (i.e., mineral carbonation). Drawing inspiration from experimental observations of CO2 flooding into cores of portland cement-based materials, we examine the stability of such systems. Under these conditions, the injected CO2 continuously dissolves into the resident water phase, which becomes chemically disequilibrated with the solid minerals and leads to mineral carbonation on the wetted surfaces. Focusing on the early injection time allows us to reduce the complex multiphysical problem to a simple two-phase flow scenario of immiscible displacement with a CO2 interfacial flux sink. The formulated equations are investigated using numerical simulations and linear stability analysis, which results in a closed-form criterion, and provide fundamental insights into system stability. Overall, the results show that several effects combine to stabilize the system, including the sink effect, which acts to eliminate instability; the reduction in flow velocity along the flow path, which limits flow focusing; and the relative increase in stabilizing capillary forces. Therefore, if the system is stable at early stages, it will likely remain stable later on. Finally, this research demonstrates the use of theory to simplify complex problems and shows that even when flow is inherently coupled, the state of systems can often be determined from fluid stability alone.
Production of high intensity high charge state uranium ion beams in afterglow mode with advanced electron cyclotron resonance (ECR) ion sources
Authors: Li L. X. , Li J. B. , Ma J. D. , Feng Y. C. , Zhang Z. H. , Zhang W. H. , Hitz D. , Ma H. Y. , Wang X. Y. , Lu W. , Sun L. T. , Zhao H. W.
Published: November 2024

To satisfy the requirement of heavy ion synchrotron for intense highly charged ion beams, a comprehensive study of the afterglow mode was performed with two advanced electron cyclotron resonance (ECR) ion sources, i.e., a second-generation ECR ion source (LECR4) and a third-generation ECR ion source (SECRAL-II). Intense pulsed uranium ion beams of highly charged states were produced with both ion sources (e.g., 58 eμA of 238U39+ in LECR4 and 124 eμA of 238U46+ in SECRAL-II). Compared to the beam intensity records obtained in continuous wave mode, the gain factor is up to ∼6. It was found that the optimum microwave pulse width and the decay time in SECRAL-II operating at 24 GHz are obviously longer than those in LECR4 operating at 14.5 GHz, aligning with a previous observation made with SECRAL-II ion source.
Assessment of the free shear boundary condition in a capillary meniscus via molecular dynamics
Authors: Shuvo Abdul Aziz , Gonzalez-Valle C. Ulises , Yang Xiang , Ramos-Alvarado Bladimir
Published: November 2024

Computational fluid dynamics models often employ the free shear boundary condition at free surfaces, a result from the continuity of the stress and the large viscosity contrast at liquid–gas interfaces. This study leverages nonequilibrium molecular dynamics simulations to investigate the validity of the free shear boundary condition on the exposed surface of a liquid meniscus at the nanoscale. The primary objective is elucidating the fundamental mechanisms and behavior of fluid interactions within a capillary meniscus formed between two carbon nanotubes (CNTs) in shear-driven flow. Shear-driven flow simulations were conducted by varying the velocity of a solid slab to induce different shear rates in the adjacent water molecules. The results demonstrate, for the first time, negligible shear at the free surface, supporting the free shear assumption from the nanoscale point of view. A force balance analysis reveals that capillary and surface tension forces dominate within the meniscus, dictating its shape and stability. Meniscus deformation was observed and primarily attributed to interatomic interactions between water molecules and CNTs, driven by a combination of short-range repulsive forces and van der Waals attractions. The minimal contribution from shear forces suggests that interatomic forces, rather than applied shear stress, are the primary drivers of the meniscus deformation. These findings offer valuable insights into fluid behavior and a sound fundamental analysis of the free shear boundary condition at the nanoscale.
Accelerating aerodynamic simulations with a hybrid fine-tuned deep learning model
Authors: Li Jiahui , Zhang Xiaoya , Peng Wei , Liu Xu , Wang Wenhui , Yao Wen
Published: November 2024

High-fidelity computational fluid dynamics simulations play an essential role in predicting complex aerodynamic flow fields, but their employment are hindered due to the high computational burdens involving fine spatial discretizations. While recent data-driven methods offer a promising avenue for performance improvements, they often face challenges related to excessive reliance on labeled data and insufficient accuracy. Consequently, we propose a novel hybrid model, which integrates a deep learning model into the fluid simulation workflow, harnessing the predictive capabilities to accelerate the fluid simulations. The acceleration is performed by a coarse-to-fine flow field mapping. To mitigate over-reliance on labeled data, the model is first pre-trained using pseudo-labeled data and then fine-tuned with a new designed attention mechanism. Acceleration efficiency of the hybrid model is demonstrated through two cases: aerodynamic simulations of an airfoil and a spherical blunt cone under varied operating conditions. Numerical experiments reveal that the proposed model achieves a substantial reduction in labeled data as well as prediction accuracy improvement, in comparison with traditional data-driven methods.
Numerical investigation on the internal flow and wear characteristics of solid–liquid two-phase flow in a centrifugal pump under different stall levels
Authors: Wang Yong , Li Ming , Chen Jie , Xu Qiang , Wang Xiaolin , Mao Yanhong , Liu Houlin
Published: November 2024

This paper investigates the flow structures and wear characteristics of solid–liquid two-phase flow in a centrifugal pump under stall conditions using the numerical method. The Computational Fluid Dynamics-Discrete Element Method coupling approach is employed to model the particle–particle and particle–liquid interactions; furthermore, the entropy theory is utilized to evaluate the energy loss and Erosion-Corrosion Research Center model is used to predict wear characteristics. The results indicate that compared to the critical stall condition, deep stall condition leads to a significant increase in the number and size of stall vortices within the impeller channel, which results in a 22% increase in channel blockage and a more uneven particle distribution. The dominant frequency of pressure pulsation in the impeller is the shaft frequency (fn), and the secondary frequency of 0.11 fn is the characteristic frequency of stall vortex. As the stall degree increases, the amplitude of pressure pulsation increases. Turbulent dissipation entropy production and wall entropy production are identified as the primary contribution to energy loss. The majority of energy loss in the centrifugal pump occurs within the impeller and volute, and the entropy production increases proportionally to the stall degree. Wear rate is strongly correlated with the impact frequency, as the stall degree increases, both the impact frequency and wear rate exhibit a gradual decrease.
Machine-learning surrogate models for particle insertions and element substitutions
Authors: Jinnouchi Ryosuke
Published: November 2024

Two machine-learning-aided thermodynamic integration schemes to compute the chemical potentials of atoms and molecules have been developed and compared. One is the particle insertion method, and the other combines particle insertion with element substitution. In the former method, the species is gradually inserted into the liquid and its chemical potential is computed. In the latter method, after the particle insertion, the inserted species is substituted with another species, and the chemical potential of this new species is computed. In both methods, the thermodynamic integrations are conducted using machine-learned potentials trained on first-principles datasets. The errors of the machine-learned surrogate models are further corrected by performing thermodynamic integrations from the machine-learned potentials to the first-principles potentials, accurately providing the first-principles chemical potentials. These two methods are applied to compute the real potentials of proton, alkali metal cations, and halide anions in water. The applications indicate that these two entirely different thermodynamic pathways yield identical real potentials within statistical error bars, demonstrating that both methods provide reproducible real potentials. The computed real potentials and solvation structures are also in good agreement with past experiments and simulations. These results indicate that machine-learning surrogate models enabling particle insertion and element substitution provide a precise method for determining the chemical potentials of atoms and molecules.
Dynamic response of an aeroelastic airfoil within ground effects of flat and wavy surfaces
Authors: Liu Hao , Sun Jianhong , Zhao Weidong , Wang Bin , Wang Zhe , Zheng Daren
Published: November 2024

Due to the significant threat posed by waves to the safety of ground-effect vehicle, a numerical study has been conducted to reveal the impact patterns on the dynamic response of an aeroelastic airfoil flying above flat and wavy ground surfaces compared with the case of in far field. The two degrees of freedom dynamic equations are coupled with the governing equations of incompressible flow with the Reynolds number based on a chord length of Re=6.85×107. The airfoil is capable of pitching and plunging motions driven by both elastic and aerodynamic forces. The effects of spring stiffness and damping ratio on aeroelastic flutter of the airfoil are explored within flat ground effect and wavy ground effect conditions, respectively. Compared to the airfoil in the far field, the aeroelastic airfoil exhibits better stability within the flat ground effect. Within the ground effect of flat surface, as the spring stiffness decreases, the dynamic response of the airfoil can be categorized into four different types: static state (U*=5, 6, and 7), limit cycle oscillation (U*=8), nonlinear random oscillation (U*=9), and stall-induced collision with the ground (U*=10). When flying above waves, the airfoil experiences sustained wave excitation, resulting in intensified velocity fluctuations and increased susceptibility to collision with ground. The effectiveness of damping in mitigating flutter and preventing crashes is demonstrated for airfoils within the ground effect. These findings provide valuable insights into the risks associated with aeroelastic flutter of the airfoil within the ground effect, offering implications for the safety design of wing-in-ground vehicles.
Large eddy simulation study: The impact of fuel injection modes on the dynamic performance of low-emission tower-type coaxial-staged combustor
Authors: Shi Yunjiao , Liu Enhui , Liu Xiao , Hu Chuanlong , Li Shengnan , Lv Guangpu , Zheng Hongtao
Published: November 2024

The low-emission technology of gas turbine combustors is currently an active area of research. In light-duty lean-premixed combustors, achieving rapid and uniform fuel mixing presents significant challenges. Additionally, combustion instability issues are also likely to occur. To address these challenges, large eddy simulation and the flamelet generation manifold combustion model are used to predict the velocity field, fuel distribution, vortex structure, flame structure, and flame liftoff phenomenon in a low-emission tower-type coaxial-staged combustor. The results indicate that variations in the position of the fuel holes in the second main stage result in two types of fuel injection modes: coupling and decoupling. These variations do not significantly influence the velocity and vortex structure in a non-reacting flow. The dominant frequency of the non-reacting flow field in the combustor is 810 Hz. The position of the precessing vortex core affects the distribution of fuel. Furthermore, the uniformity of fuel distribution at the outlet of the second main stage is notably affected by different fuel injection modes. The spatial distribution of fuel is more uniform. In the reacting flow, compared to the decoupling mode, the fuel expansion angle decreases by 4.5° under the coupling mode, and the heat release at the flame front is more intense. Additionally, it is found that fuel injection modes significantly influence the dynamic characteristics at the flame root. Better flame stability is observed under the decoupling mode, while flame liftoff phenomena occur under the coupling mode. The lifted flame root shifts downstream by 12.3 mm.
Adaptive mesh refinement for a particle level simulation of supercritical water fluidized bed reactors
Authors: Su Haozhe , Jin Hui , Wang Bingcheng , Guo Liejin
Published: November 2024

High-precision computational fluid dynamics-discrete element method (CFD-DEM) simulation serves as a foundation for the detailed design of supercritical water fluidized bed reactors (SCWFBRs). However, as the scale of these reactors increases, the computational domain and reacting particles expand exponentially. Traditional adaptive mesh refinement is constrained in dealing with dense phase zones in SCWFBRs, as the nonlinear characteristics of the dense reacting particle flow render local-field error estimation ineffective. To address this limitation, an efficient and accurate CFD-DEM framework is established, integrating adaptive mesh refinement and heterogeneous computing. The mesh adaptation strategy is based on whole-field error estimation and is defined by a set of cell-marking criteria. The effect of the criteria on the accuracy and efficiency of the computational process is evaluated. This method reduces the demand for computational resources, thereby enabling the simulation of large-scale reactors at the particle level. The optimized adaptation strategy maintains an error of 1.67% while saving 51.59% of mesh cells required and 28.4% computation time. The primary factors influencing computational accuracy are identified as fluid velocity gradient and the particle reaction rate. The scalability of the adaptation strategy is also validated. For a fivefold radial scaled-up reactor, the cell count is reduced by 46.86% and the computation time by 22.2%, while the maximum error is limited to 2.79%. This work provides a solution that can consider both the computational scale and accuracy, thereby enabling the detailed design of large-scale SCWFBRs.