bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation on multiphase flow and steel grades mixing in a slab continuous casting tundish
Authors: Zhang Shaohai , Chen Wei , Zhang Lifeng
Published: January 2025

Four comprehensive numerical models, including the Volume of Fluid (VOF), Mixture, Eulerian, and Species, were established to explore the multiphase flow and replacement of old steel grades with new ones during the continuous casting of different grades in a slab tundish. A water model was employed to validate the accuracy of the numerical model. The result shown that the VOF multiphase model and standard k-ε turbulence model were specifically utilized to analyse the complex four-phase flow dynamics involving the new molten steel, old molten steel, slag, and air. Moreover, the effect of varying casting speeds on the replacement process, mixed casting slab length, and molten steel exposure time were performed. With constant emptying times, an increase in casting speed led to a reduction in replacement liquid level and lower residual old steel content, shortening the mixed slab length. However, higher speeds required longer refilling periods, consequently intensifying the exposure of molten steel and potentially affecting steel quality. At a casting speed of 1.7 m/min, the exposure time of the molten steel was 82.6 s, and the mixed casting slab length was 5.78 m. At a casting speed of 1.1 m/min, the exposure time was dropped to 42.5 s, while the mixed casting slab length was increased to 13.02 m. Considering both steel mixing and its exposure behaviour, a casting speed of 1.4 m/s was considered more suitable, ensuring an appropriate mixed casting slab length and maintaining the quality of molten steel.
Enhancing the quality of AZ31/10% SiC composite: optimization of ultrasonic squeeze casting parameters for enhanced hardness and structural integrity
Authors: Edlabadkar Ajinkya P. , Packkirisamy Vignesh , Laxmaiah Gundagani , Kumar Annam Sunny , Subashini Kasivisvanathan
Published: January 2025

AZ31 alloys are gaining considerable research interest owing to their commendable applications in automobile and aerospace applications because of their high strength-to-weight ratio to reduce the overall weight of the vehicle. However, these alloys are more susceptible to porosity and material shrinkage during casting, which in turn results in poor mechanical behavior. Ultrasonic-assisted squeeze casting is a non-traditional casting technique that involves the application of ultrasonic waves to distribute the reinforced particles homogenously in the melt, improving the integrity of the alloy composites by reducing agglomeration. While various materials have demonstrated the efficacy of these processing techniques, their potential for casting AZ31/10% SiC alloy composites remains unexplored. The present work aims to investigate the impact of three major process parameters, namely ultrasonic power (UP), squeeze time (ST), and stirring speed (SS), on the responses of porosity and microhardness, using the response surface methodology (RSM) central composite design (CCD) approach. The analysis of variance (ANOVA) technique is used to determine the most significant process parameter and to check the model’s adequacy. The analysis indicates that ultrasonic power has the highest F-value and is the most influential factor on porosity and microhardness. Microstructural studies reveal the composites’ structural morphology. Apart from identifying the optimal individual process parameters, the desirability approach was also deployed to carry out the multi-objective optimization. Further, empirical models were developed, and confirmatory tests were performed to validate the models. The observed confirmatory results indicate that the developed models have a good prediction tendency.
Malignant Biliary Strictures: Preoperative and Palliative Interventions
Authors: Priyadarshi Rajeev N. , Nag Piyal , Kumar Ramesh , Anand Utpal
Published: January 2025

Malignant biliary strictures represent a significant clinical challenge worldwide, with the majority of cases being unresectable at the time of diagnosis, necessitating palliative biliary drainage. In some cases, preoperative drainage is required to optimize surgical outcomes. Biliary drainage can be performed through either endoscopic or percutaneous methods, each tailored to specific clinical scenarios. Endoscopic techniques include endoscopic retrograde cholangiopancreatography, endoscopic nasobiliary drainage, and endoscopic ultrasound-guided biliary drainage, while percutaneous options involve percutaneous transhepatic biliary drainage and biliary stenting. The choice of technique is guided by imaging findings, the clinical condition of the patient, and the expertise of the interventionist to ensure effective drainage and minimize complications. Although endoscopic methods are well-established and extensively studied, the percutaneous approach offers distinct advantages in certain complex cases. This review provides a comprehensive overview of biliary drainage techniques, with a particular focus on the percutaneous approach.
Spin relaxation of conduction electrons in dilute magnetic alloys at low temperatures
Authors: Mironov G. I. , Fazleev N. G.
Published: January 2025

The spin dynamics of conduction electrons in dilute magnetic alloys at low temperatures is studied. The field, temperature, and frequency dependences of the transverse spin relaxation rate of conduction electrons, due to the s-d exchange interaction, are studied.
Nuclear magnetic resonance in the system NbSe2—hydrogen
Authors: Skripov A. V. , Stepanov A. P. , Obolenskii M. A.
Published: January 2025

The temperature dependence of the spectral and relaxation characteristics of NMR on the nuclei 93Nb, 77Se, and 1H in the compounds NbSe2Hx with x <0.01 and ≃0.2 was studied. The experimental data lead to the conclusion that the hydrogen atoms in NbSe2H0.2 lie not in the interlayer space, but rather in the sandwich Se–Nb–Se. The measurements of the Knight shift and the spin-lattice relaxation time of 77Se indicate that the electronic density of states at the Fermi level in NbSe2 decreases significantly on hydrogenation up to x = 0.2.
Crystal-field potential for a substitutional impurity in monoatomic molecular cryocrystals
Authors: Chishko K. A.
Published: January 2025

An expression is derived for the crystal field of nearest neighbors in the vicinity of a site in static monoatomic fcc and hcp lattices in the approximation of atom–atom central potentials of the power-law type. The results obtained are employed to calculate the crystal-field potential for rotational motion of diatomic homo- and heteronuclear substitutional impurities. The numerical calculations were performed using the constants for the Lennard-Jones atom–atom interaction for nitrogen and carbon monoxide impurities in argon and krypton matrices.
Effect of temperature on single-electron and Bloch oscillations in tunnel junctions
Authors: Averin D. V.
Published: January 2025

The I–V characteristics and frequency spectra of the voltage across nonshunted tunnel junctions having a low capacitance and conductance are calculated for temperatures other than zero. A quantitative pattern of thermal destruction of coherent oscillations is obtained for such junctions between normal as well as superconducting metals.
Two-magnon bound states in quasi-low-dimensional easy-axis ferromagnets
Authors: Goncharuk A. N. , Krivoruchko V. N.
Published: January 2025

We have found the critical value of “easy-axis” anisotropy, starting from which a bound state of two magnons with wave vector k = 0 first appears in quasi-one-dimensional ferromagnets with nearest-neighbor interaction. This value is shown to be much higher than the magnitude of the weak three-dimensional interchain (interlayer) exchange interaction.
Pressure studies on the Fermi surface of rhenium
Authors: Bud’ko S. L. , Vinokurova L. I. , Gapotchenko A. G. , Itskevich E. S. , Kulatov É. T. , Pomirchi L. M.
Published: January 2025

The de Haas–van Alphen effect in rhenium was studied experimentally under pressures of up to ∼25 kbar and a self-consistent LMTO calculation of the rhenium band structure under pressure was carried out to obtain data on the electron-topological transition in rhenium. Possible reasons for the anomalies in the electron properties of rhenium under pressure are discussed.
Molecular rotator in an atomic inert-gas matrix. Quasistatic renormalizations
Authors: Kal’noĭ S. E. , Strzhemechnyĭ M. A. , Sumarokov V. V. , Freĭman Yu. A.
Published: January 2025

A microscopic calculation of the relaxational renormalization of the crystal field, acting on a molecular rotator in the matrix of an atomic inert-gas crystal, is carried out in the quasistatic approximation. It is shown that the relaxation of the lattice around the rotator does not alter the symmetry of the crystal field. The renormalized crystal field constant is calculated; the renormalization is significant, and for specific systems (N2 and CO impurities in Ar, Kr, and Xe matrices) equals 1.6–1.7. The concept of a cubic order parameter, which can be employed as a quantitative characteristic of the degree of rotational localization (hindrance) in a field with cubic symmetry is introduced. The tunneling approach to the rotational dynamics of a molecular rotator is formulated for the low-energy part of the spectrum. The tendency for the rotational constant to be renormalized is determined in a rough approximation. The effect of renormalization on the heat capacity and thermal expansion of atomic inert-gas matrices with diatomic impurities is discussed.
Critical density of states in the superconducting ceramic La1.8Sr0.2CuO4 in S–c–N point contacts
Authors: Yanson I. K. , Rybal’chenko L. F. , Bobrov N. L. , Fisun V. V.
Published: January 2025

Measurement of the current–voltage characteristics of point contacts makes it possible to study the properties of individual crystallites in a superconducting ceramic. The critical current density in the superconducting regions of the ceramic La1.8Sr0.2CuO4, with a size of the order of several tens of angströms, is found to attain values of 108 A/cm2, which are of the same order of magnitude as the pair-breaking current density, as evaluated from the formulas of the standard theory of superconductivity.
Critical superconducting transition temperature in the generalized Hubbard model
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The version of the microscopic theory of superconductivity proposed here is based on the generalized Hubbard model, which takes into account the repulsion of electrons at one site and attraction electrons at the neighboring sites. The critical superconducting transition temperature in this model is a nonmonotonic function of the carrier concentration.
Thermal conductivity of the chalcogenide glasses As–S
Authors: Babushkina N. A. , Inyushkin A. V. , Ozhogin V. I. , Florent’ev V. V.
Published: January 2025

Measurements of the thermal conductivity K(T) in the temperature range from 1 to 30 °K have been carried out on chalcogenide glasses based on As–S (As40S60, As36S58I6, Ge2As34S58I6, and As20S80), in which the structure changes with a change in composition. It was found that the K(T) dependences have features characteristic for the speciments studied: in glasses of composition As20S80 a plateau in K(T) was observed at temperatures from 3 to 10 °K and a minimum in K(T) was observed at T ∼ 11 °K for the specimens As40S60, As36S58I6 and Ge2As34S58I6. The experimental results obtained can be explained qualitatively within the framework of the concept of the fractal structure of amorphous compounds.
Properties of a model of two-band superconductors with electron singlet pair exchange between narrow and wide bands
Authors: Galaiko V. P.
Published: January 2025

The possibility of a superconducting transition with a critical temperature higher than in the BCS mechanism is demonstrated within the model of two-band superconductors with narrow band near the Fermi level and predominating interband interaction of arbitrary nature. Because of the specific features of the narrow band occupancy, the normal “hybridization” of bands, which could have suppressed the superconducting transition, does not occur. The critical temperature is nonzero and maximum in the range of electron concentrations in which the narrow band is occupied.
Relaxation of nonequilibrium quasiparticles in a superconductor normal metal point contact
Authors: Yanson I. K. , Bobrov N. L. , Rybal’chenko L. F. , Fisun V. V.
Published: January 2025

The point-contact spectra of tantalum in the superconducting state, with Ta, Cu, and Au counterelectrodes, have been studied. We discovered some new distinctive features, whose position on the eV axis is determined by the critical power required for the injection of nonequilibrium quasiparticles. At this level of power the band gap Δ decreases abruptly in the vicinity of the contact. A correction to the point-contact spectrum, with the sign opposite to that of the usual correction, arises in the region of phonon energies. The maxima in the Ta spectrum become sharper and their position on the energy axis becomes stabilized near the values eVph = 7.0, 11.3, 15.5, and 18 MeV, which correspond to low phonon group velocities ∂ω/∂q≃0 in Ta. This is confirmed by the existence of corresponding flattenings on the dispersion relations ω(q) of lattice vibrations. Slow phonons are created near the N-S interface in quasiparticle recombination and relaxation processes and cause a decrease in Δ and an increase in the differential resistance in the vicinity of eVph. An excess quasiparticle charge is accumulated in the region of the contact, producing a correction to the resistance, which decreases as eV, T, and H increase. These mechanisms are particularly effective in dirty contacts, thus permitting phonon spectroscopy in the superconducting state even when the current flow occurs in a nearly thermal mode.
Appearance of a saddle point in the energy spectrum of Bi1−xSbx alloys under band inversion as x varies
Authors: Brandt N. B. , Golysheva G. I. , Thieu Nguyen Mihn , Sudakova M. V. , Kashirin K. N. , Ponomarev Ya. G.
Published: January 2025

In a Lifshitz electron-topological transition, which we have observed in semimetallic Bi1−x Sbx alloys, two separate portions of the electron Fermi surface that are displaced in opposite directions relative to the L-point in the mirror plane merge into a single dumbbell-shaped Fermi surface in the range of compositions 0.255 <x <0.26. This topological transition can be considered to be the result of the appearance of a saddle point in the energy spectrum of Bi1−xSbx alloys under band inversion at the L-point with increasing x.
Supermetal conductivity and the Shubnikov–de Haas effect in the first-stage graphite heterointercalation compound C10CuCl2 · 0.6ICl
Authors: Brandt N. B. , Kul’bachinskii V. A. , Nikitina O. M. , Avdeev V. V. , Akim V. Ya. , Ionov S. G. , Semenenko K. N.
Published: January 2025

The first synthesis of a new type of first-stage graphite intercalation compound, C10CuCl2 · 0.6ICl, is reported, where layers of cupric chloride CuCl2, graphite, and iodine monochloride IC1 alternate in succession. An unexpected phenomenon is observed; The density of holes in the graphite layers and the conductivity are significantly higher (two- or threefold) than in monointercalation compounds of CuCl2, and IC1. The Shubnikov–de Haas effect exhibits two frequencies instead of the usual single frequency for first-state graphite monointercalation compounds.
Rb
2
Ti
2
O
5
: A layered ionic conductor at the sub-micrometer scale
Authors: Digiorgio Valerio , Sobnath Karen , Della Rocca Maria Luisa , Barraud Clément , Federicci Rémi , Descamps-Mandine Armel , Leridon Brigitte
Published: January 2025

Over the past few years, ionic conductors have gained a lot of attention because of the possibility of implementing them in various applications such as supercapacitors, batteries or fuel cells, and resistive memories. Especially, layered two-dimensional (2D) crystals, such as h-BN, graphene oxide, and MoSe2, have been shown to provide unique properties originating from the specific 2D confinement of moving ions. Two important parameters are the ion conductivity and the chemical stability over a wide range of operating conditions. In this vein, Rb2Ti2O5 (RTO) has recently been found displaying remarkable properties such as superionic conduction and equivalent colossal dielectric constant. Here, an approach to the study of the electrical properties of the layered RTO 100-nm scale is presented. Characterizations by means of micro-Raman spectroscopy and atomic force microscopy measurements of mechanically exfoliated RTO micro-flakes via the so-called adhesive-tape technique are reported. Finally, the results of electrical measurements performed on an exfoliated RTO micro-flake are presented and are found to be consistent with the results obtained on macroscopic bulk crystals.
Effect of doping in small-size hybrid nanostructures for plasmonic catalysis
Authors: Smetanin Igor V. , Uskov Alexander V. , Nikonorov Nikolay V.
Published: January 2025

The effect of doping on the lowest quantum state of hot electron trapped in the semiconductor shell of small size hybrid nanoparticles is investigated. Assuming a spherical Ag-AgBr hybrid nanoparticle with a metal core and a semiconductor shell, we study the changes in the spatial profile of the contact electric potential in the Schottky barrier as a function of the doping density under the Sze approximation of a completely depleted layer. The energy of the lowest quantum state of an electron in the semiconductor shell is estimated along with the tunneling time into the metal core. It is found that when the characteristic size of the depletion layer of the Schottky barrier exceeds the size of the semiconductor shell, this energy varies throughout the Schottky barrier height by changing the shell thickness and the doping density, with the tunneling lifetime varying from subpicoseconds to submicroseconds. This possibility can be exploited to improve the efficiency of plasmonic photocatalysis with small-sized hybrid nanoparticles: By adjusting the energy of the discrete electron state to the given lowest unoccupied molecular orbit level of the chemical adsorbed on the surface of the hybrid nanoparticle, one should expect the resonance transfer of an electron, thus a dramatic increase in the rate of photocatalysis. The proposed method introduces Quantum-Size Resonance-Enhanced Photocatalysis in the hybrid structure.
Efficacy of impinging air jets under various cross-flow conditions
Authors: Jose Vivek Mathew
Published: January 2025

The performance of a turbulent air jet impinging on a flat surface and subjected to cross flow is investigated. The study considers many different parameters, including Reynolds number Re, the normalized orifice-to-target spacing Z/D, and the ratio α of cross-flow to jet Reynolds numbers. As reported by other investigators, the optimum value of Z/D is 6. At this optimum Z/D, when the Reynolds number is raised from 5100 to 23 000, the stagnation Nusselt number Nu increases by 150%. A correlation is proposed to estimate stagnation point heat transfer. Velocity profiles are used to examine the cooling characteristics of jets with and without cross flow. Cooling in both the upstream and downstream regions is estimated and compared with the performance of a jet without cross flow. For Z/D = 6, the stagnation Nu decreases by 84% when α is increased from 0 to 2. The corresponding decrease in the stagnation Nu for Z/D = 2 is 75%. Cross flow significantly affects the flow pattern of fluid near the target surface, and anomalous flow behavior is observed in the stagnation region. Without cross flow, the radial velocity is close to zero at r/D = 0, and the fluid velocity increases in the outward direction and attains a maximum value at r/D = 1. With cross flow, the position of the peak velocity shifts. Average, stagnation point, and peak heat transfer coefficients are discussed in terms of the Stanton number. At low values of α, there is an increase in the peak Nu. With cross flow, the location of the peak velocity changes. The augmentation in cooling in the downstream region and the reduction in cooling in the upstream region depend strongly on Z/D and α. For Z/D = 2, at α = 1, the average heat transfer downstream increases by 15% and the corresponding decrease upstream is 35%.
Improved gate leakage current and breakdown voltage of InAlN/GaN MIS-HEMTs by HfAlOx-based charge-trapping layer dielectric and in situ O3 treatment
Authors: Du Fangzhou , Jiang Yang , Wang Peiran , Wen Kangyao , Tang Chuying , He Jiaqi , Deng Chenkai , Zhang Yi , Li Mujun , Wang Xiaohui , Hu Qiaoyu , Yu Wenyue , Wang Qing , Yu HongYu
Published: January 2025

In this study, high-performance InAlN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) are fabricated using HfAlOx-based charge-trapping layer dielectric stack combined with in situ O3 treatment. A positive threshold voltage shift (ΔVTH) of 8.9 V is achieved due to the charge-trapping effect. The device also shows a high Ion/Ioff ratio of ∼1010, a low gate leakage current of ∼10−7 mA/mm, and a relatively high BVDS of 400 V. The suppression of gate leakage current results in an ultra-high gate breakdown voltage of 22.5 V, owing to the superior current blocking capability of the O3-based Al2O3/HfO2 blocking layers and the interface improvement between dielectric and InAlN barrier achieved through in situ O3 treatment. The time-dependent dielectric breakdown measurements reveal the quality and reliability of the dielectric layer, predicting a maximum VGS of 9.66 and 9.31 V for a 10-year lifetime at failure rates of 63.2% and 0.10%, respectively. Additionally, x-ray photoelectron spectroscopy, atomic force microscopy, and multi-frequency C–V measurements further verify the effectiveness of the in situ O3 treatment in the optimization of the dielectric/GaN interface. These results demonstrate a practical approach to significantly improve the performance of InAlN/GaN MIS-HEMTs.
A composite hydrogel of porous gold nanorods and gelatin: Nanoscale structure and rheomechanical properties
Authors: Khan Irfan , Panda Snigdharani , Kumar Sugam , Srivastava Sunita
Published: January 2025

Incorporating nanomaterials into hydrogels allows for the creation of versatile materials with properties that can be precisely tailored by manipulating their nanoscale structures, leading to a wide range of bulk properties. Investigating the structural and property characteristics of composite hydrogels is crucial in tailoring their performance for specific applications. This study focuses on investigating the correlation between the structural arrangement and properties of a composite hydrogel of thermoresponsive polymer, gelatin, and light-responsive antimicrobial porous gold nanorods (PAuNRs). The rheomechanical properties of the composite hydrogels are correlated with their nanoscale structural characteristics, investigated using small-angle neutron scattering (SANS). Analysis of SANS data reveals a decrease in the fractal dimension of PAuNRs incorporated hydrogel matrix, as compared to pure gelatin. Incorporating PAuNRs results in the formation of a softer composite hydrogel, as evident from the decrease in viscoelastic moduli, critical yield strain, denaturation temperature, and swelling ratio. Our results demonstrate that the structural modulation at the nanoscale can be precisely controlled through adjusting PAuNRs concentration and temperature, providing a fabrication mechanism for hydrogels with desired elastic properties. The reduced elasticity of the composite hydrogel and light-sensitive/antimicrobial property of the PAuNRs make this system suitable for specific biomedical applications, such as tissue engineering, device fabrication, and stimuli-based controlled drug delivery devices.
Electron temperature measurement from neutral atomic tungsten emission line ratio
Authors: Adams Steven F. , Murray Chase S. , Pohl Neil A.
Published: January 2025

A method to determine electron temperature within a plasma by the spectral analysis of atomic tungsten emission has been explored. The technique was applied to a post-discharge region immediately following a high voltage nanosecond pulsed discharge in air with tungsten electrodes. Atomic tungsten lines are readily observed in the weak emission spectrum within the post-discharge region for many microseconds. Intensity ratios were measured at various times after the pulsed discharge for a select pair of neutral tungsten emission lines at 400.88 and 401.52 nm, where the upper electronic levels of each transition are at 3.46 and 5.52 eV respectively. This significant difference in upper state energy causes their line intensity ratio to vary as the electron temperature changes. In addition to the emission spectra, the absolute electron temperature could be accurately measured in our lab using laser Thomson scattering to calibrate the new tungsten emission line intensity ratio method. An analysis is presented that calculates electron temperature from these tungsten emission data assuming a Maxwellian electron energy distribution contributing to direct electron impact excitation to the upper states of each transition. The results included the derivation of a calibration factor between the two experimental methods representing a previously unreported ratio of Einstein A coefficients for the 400.88–401.52 nm transitions. This derivation provides a method for future measurement of absolute electron temperature by the 400.88–401.52 nm tungsten line intensity ratio without the need for laser Thomson scattering calibration.
Heteroatomic doping induces charge rearrangement to optimize carrier dynamics in 2D halide perovskites
Authors: Zhou Jixiang , Yang Jing , Yu Xueke , Liu Yongfeng , Zhou Si , Zhao Jijun , Pei Wei
Published: January 2025

It is well established that a number of techniques, including applied electric fields, interfacial engineering, structural torsion, and doping, can modulate the geometric and electronic structures of materials, thereby enhancing their photoelectronic properties in two-dimensional (2D) halide perovskites. Among these strategies, doping has proven to be an extremely effective approach; however, the precise mechanisms underlying this effect remain elusive. Herein, we systematically investigated how heteroatom doping, specifically using Sn and Bi dopants, influences the excited-state dynamics of 2D (MA)2PbI4 perovskites using ab initio calculations combined with real-time nonadiabatic molecular dynamics simulations. Our results indicate that the doped systems maintain the octahedral configuration characteristics of the parent material. Notably, doping leads to a significant electron–hole separation in real space, corresponding to an extended carrier lifetime of approximately 140–150 ns, compared to just 2.70 ns for pristine (MA)2PbI4 perovskites. This behavior is primarily governed by a low-frequency vibration mode around ∼200 cm−1. These calculations provide important insights into the potential for atomically modulating carrier behaviors to achieve excellent photovoltaic properties.
Adjoint-based data assimilation in a subdomain using omnidirectional-integration-enabled pressure Dirichlet boundary conditions
Authors: Abassi Mohamed Amine , Wang Qi , Liu Xiaofeng
Published: January 2025

Solving the pressure Poisson equation within the Navier–Stokes solver for incompressible flows with a subdomain presents challenges, particularly due to the selection of boundary conditions. Typically, assumptions such as a large fluid domain with zero normal pressure gradient on the boundaries are often employed. However, this approach of using a larger domain exceeds the inherently needed, and often relies on inaccurate assumptions, especially when the focus is on a smaller subdomain. Moreover, when Neumann boundary conditions obtained from experimental data that inevitably includes noise are used, the accuracy of pressure reconstruction deteriorates. This issue is especially prevalent in the context of data assimilation where observational data is integrated into a numerical model using gradient-based optimization to enhance the model accuracy. To overcome the aforementioned difficulties, this study introduces a novel technique that utilizes the Omnidirectional Integration/Green's Function Integral (ODI/GFI) method to compute appropriate Dirichlet boundary conditions for pressure fields within an in-house two-dimensional Navier–Stokes solver. An adjoint-based framework for data assimilation is adopted for the reconstruction of velocity and pressure fields in a subdomain based on sparse observations. The method is validated with 1000 statistically independent realizations (50 base flows each coupled with 20 different noise distributions) of error-embedded two-dimensional decaying isotropic turbulence flows at a Reynolds number of Re = 200, thus enabling detailed statistical comparisons. The validation test results clearly demonstrate that the ODI/GFI method significantly outperforms the conventional Neumann boundary condition approach in providing not only accurate pressure predictions, but also improved accuracy of the velocity and the vorticity calculations. This improvement is evidenced by the comparison of a variety of metrics including the cost function, the instantaneous error distribution, the probability density function, the error spectrum, the standard deviation of the error and the time variation of flow quantities during the computation process of the data assimilation. The successful demonstration of the capability of the new ODI/GFI method in handling error-embedded instantaneous data in a subdomain immersed in a turbulent flow field provides a promising path for innovation in computation in data assimilation in particular and computational fluid dynamics in general.
Solvatochromic charge model of isonitrile probes for investigating hydrogen-bond dynamics with 2DIR spectroscopy
Authors: Maj Michał
Published: January 2025

Isonitrile-derivatized amino acids are emerging as highly effective infrared (IR) probes for investigating the structures and dynamics of hydrogen (H)-bonds. These probes enable the quantification of chemical exchange processes in solute–solvent complexes via two-dimensional IR spectroscopy and hold significant promise for site-specific dynamic studies within proteins. Despite their potential, theoretical models that elucidate the solvatochromism of isonitriles remain underdeveloped. Here, we present the development and validation of a solvatochromic charge model for isonitrile (N≡C) probes. Using density functional theory calculations, we parameterized solvatochromic charges for isonitrile and integrated them into classical molecular dynamics (MD) simulations of β-isocyanoalanine in various solvents, including water and fluorinated alcohols. The model incorporates solvent-induced frequency shifts and accurately reproduces complex experimental line shapes, including asymmetric features from non-Gaussian dynamics. The model successfully reproduced the bimodal distribution of frequency shifts corresponding to free and H-bonded species in alcohols, as well as cross-peaks due to chemical exchange. Achieving reproducibility required long MD trajectories, which were computationally demanding. To manage this, we implemented graphics processing unit acceleration, drastically reducing the computational time and enabling the efficient processing of extensive MD data. While some discrepancies in population ratios suggest the need for refined solvent force field parameters and modeling transition dipole moment variations, the developed solvatochromic model is a reliable tool for studying the solvation dynamics. The model enables more detailed investigations of ultrafast dynamics in solute–solvent complexes and represents important steps toward modeling site-specific dynamics of biomolecules with isonitrile probes.
The power of internal wave attractor
Authors: Shmakova Natalia , Makridin Zakhar , Rudaya Yana , Chebotnikov Alexey , Boyko Olga , Ermanyuk Evgeny
Published: January 2025

This paper presents a joint experimental and numerical study of quasi-two-dimensional internal wave attractors generated by the angular oscillations of a vertical plate in a trapezoidal domain filled with a uniformly stratified liquid, with a focus on evaluation of the injected power. Experimental velocity fields are measured using standard particle image velocimetry technique, while the direct numerical simulation with Nek5000 is used to solve the two- and three-dimensional Navier–Stokes equations in the Boussinesq approximation. The pressure is obtained by applying a quasi-analytical method to the measured velocity components. The energy flux is calculated using either the, thus, obtained pressure from the experimental data or the pressure calculated directly in the numerical simulations. The oscillating plate is equipped with sensors to simultaneously measure the torque and angular oscillations, allowing for direct experimental measurement of the injected power. Quantitatively, very good agreement is observed between the results of direct measurement of the injected power and the results of three-dimensional numerical simulations. Application of other methods leads to consistent departures, which have an acceptable level and can be attributed either to non-accounted physical effects, e.g., friction at lateral walls absent in two-dimensional simulations, or to the absence of data in some subdomains of the flow, which reduce the quality of the pressure field reconstruction.
Effects of oscillating curved wall on behavior of a collapsing cavitation bubble
Authors: Nguyen Quang-Thai , Nguyen Van-Tu , Sagar Hemant , Moctar Ould el , Park Warn-Gyu
Published: January 2025

The behaviors of a collapsing cavitation bubble were investigated using numerical simulations, focusing on the effects of a controlled oscillating wall with a spherically curved geometry. Different wall-controlled oscillation conditions were modeled. The collapse of the laser-induced cavitation bubble near the curved wall was observed experimentally to validate the numerical model at the same fixed standoff condition S = 1.2. A good agreement was observed between experimental and numerical results. A compressible model for the two-phase flow, based on a geometric volume of the fluid technique, was employed for numerical simulation. High-speed camera experiments captured the behaviors of the laser-induced cavitation bubbles. Both in-phase and out-of-phase oscillating motion of a rigid with spherical surface was modeled by using a sinusoidal function within a curvilinear moving grid framework. The study explored the effects of oscillating walls through numerical comparisons between the fixed and oscillating conditions, considering different initial phase conditions as φ0=−90°, 0°, φ0=+90°, and +180°. The upward jet flow forms at φ0=−90°, 0°, and +90°, while the downward jet flow forms at φ0=+180°. Numerical analyses reveal significant effects of motion conditions at in-phase (φ0=−90°, 0°) and out-of-phase (φ0=+90°, +180°) conditions, which vary with the scaled amplitude parameter, As=A/R0, defined by the ratio of the oscillating amplitude, A, and the maximum bubble radius, R0. Various features were analyzed, including oscillation and deformation of bubble shape, the formation of jet flow, and pressure peaks on the wall. Critical values of As = 0.1, 0.2, and 0.3 were identified, influencing bubble collapse time, jet flow speed, and peaks of pressure under both in-phase and out-oscillation motion.
Research progress in hydrofoil cavitation prediction and suppression methods
Authors: Qiu Qianfeng , Gu Yunqing , Ren Yun , Mou Chengqi , Hu Chaoxiang , Ding Hongxin , Wu Denghao , Wu Zhenxing , Mou Jiegang
Published: January 2025

To reduce the adverse damage caused by cavitation phenomena to the hydraulic machinery, such as surface erosion of the equipment, increased mechanical vibration, and decreased service life, this review summarizes from the aspects of cavitation instability mechanisms, cavitation prediction methods, and cavitation suppression methods. In terms of cavitation flow instability mechanisms, two main mechanisms that affect the shedding of cloud cavitation, reentrant jet, and bubbly shock wave, were thoroughly summarized. It is pointed out that the shedding behavior of the cavity is greatly influenced by the thickness of the reentrant jet relative to the cavity, and the bubbly shock wave is also one of the important factors in cavitation vortex dynamics. In terms of cavitation prediction methods, a detailed comparison and analysis were made between the traditional cavitation prediction methods based on numerical simulation and the currently popular cavitation prediction methods based on neural networks. The former mainly includes cavitation models and turbulence models, while the latter mainly summarizes the application of chain physics-informed neural network, pressure–velocity network, long short-term memory, and other neural networks in cavitation prediction. It is pointed out that artificial intelligence predictive models have advantages in model order reduction and accurate prediction of cavitation flow field feature parameters. In terms of cavitation suppression methods, active and passive cavitation suppression methods were thoroughly summarized. Finally, based on the current research status of hydrofoil cavitation prediction methods and cavitation suppression methods, this article discusses and looks forward to the direction of development.
Air–water interaction in a partially filled circular pipe
Authors: Zuo Jinlong , Qian Yu , Zhu David Z. , Zhang Zhiqiang
Published: January 2025

This study investigates the combined effects of water drag forces and air pressure gradients on air movement within the headspace of a circular pipe. Under free ventilation conditions, where air enters the system solely through natural suction induced by water flow, positive pressure gradients were observed. The air pressure gradients increased with both the filling ratio and water flow rate. It was also found that air near the water surface flowed downstream due to water drag force, while air near the pipe crown moved upstream. Forced ventilation was introduced through air extractors positioned at the upstream and downstream vents, with adjustable power to create varying airflow rates. Results showed that beyond certain thresholds, increased air extractor power did not further enhance ventilation. Under forced ventilation, air velocity profiles in the non-boundary zone exhibited a more uniform distribution due to higher ventilation power. The effects of water drag, air pressure gradients, and pipe wall friction were analyzed. The critical pressure gradients with negligible water drag under forced ventilation were obtained. The drag coefficients of water on the airflow were calculated, ranging from 0.018 to 0.081 for free ventilation and from 0.002 to 0.038 for forced ventilation. A semi-empirical equation for calculating the drag coefficients under free ventilation was proposed. This study provides valuable insight into the dynamics of air movement in sewer systems, emphasizing the critical role of proper ventilation design in mitigating odor and corrosion issues.
Direct numerical simulation and modal analyses on transition flow with streamwise adjacent roughness elements
Authors: Ling Weihao , Gao Song , Wang Zhiheng , Zeng Min , Huang Wenlin , Xi Guang
Published: January 2025

Direct numerical simulation has been employed to investigate the transition in a flat plate boundary layer induced by streamwise adjacent roughness elements, with cylinder or ramp serving as the front roughness element. This study elucidates the impacts on time-averaged and fluctuating velocity fields, vortex structures, and energetic structures, revealing the interplay between the leading modes and the sweep and ejection events. Findings indicate that the ramp's ability to excite fluctuating kinetic energy exceeds that of adjacent cylinders. Moreover, the strong correlation between fluctuating kinetic energy and vorticity gradient is tied to the dissipation term of fluctuating kinetic energy and the production term of enstrophy. The robust vortex pair generated by the ramp, along with its lift-up effect, and the substantial mainstream dilution due to increased streamwise spacing augment the time-averaged velocity gradient and the fluctuating kinetic energy downstream of the back roughness element. Such an enhancement further differentiates the sweep and ejection events corresponding to the cylinder. However, these distinct events corresponding to the ramp remain inseparable. The inherent characteristics of the varicose mode remain invariant with respect to streamwise spacing and the morphology of the front roughness element. The energetic wavepacket induced by the ramp disturbance is closely associated with the time-averaged velocity gradient. The correlation coefficients between the extracted leading mode's sweep and ejection events and the actual physical field's two events range from 0.3 to 0.4, suggesting that the Reynolds shear stress −u′v′¯ induced by streamwise adjacent roughness elements embodies low-rank linear unstable dynamics.
Impulse response of linear disturbances in a skewed Stokes layer
Authors: Thomas Christian , Pretty Alexander
Published: January 2025

The spatiotemporal development of impulsively excited two-dimensional linear disturbances in acceleration-skewed and velocity-skewed Stokes layers is investigated using numerical simulations of the linearized Navier–Stokes equations. This study focuses on the long-term behavior of linearly unstable disturbances within these skewed flows. The onset of linear instability in the symmetric Stokes layer is known to coincide with absolute instability, with disturbances forming family tree structures, characterized by multiple wavepackets spread across the spatiotemporal plane, coupled with pointwise subharmonic temporal growth [Ramage et al., “Numerical simulation of the spatiotemporal development of linear disturbances in Stokes layers: Absolute instability and the effects of high-frequency harmonics,” Phys. Rev. Fluids 5, 103901 (2020)]. However, the introduction of acceleration and velocity skewness disrupts the formation of the family tree structure. Instead, the onset of linearly unstable behavior is matched to convective instability, with disturbances predominantly propagating in the direction of the maximum acceleration or maximum velocity. As the Reynolds number increases, absolute instability emerges, albeit with pointwise temporal growth less than the growth obtained by the disturbance maximum.
Inland aquatic systems and their fauna at Two Peoples Bay Nature Reserve, Western Australia, with emphasis on microinvertebrates
Authors: Halse Stuart A. , Storey Andrew W.
Published: January 2025

Context Decisions about fauna conservation priorities in a region, and management actions required to facilitate conservation objectives, require as much information as possible about the ecology of fauna species present. Aims This paper summarises information on the inland aquatic fauna of Two Peoples Bay Nature Reserve as part of the process of documenting the Reserve’s conservation values. Key Results Surveys in the early 1990s, and subsequently, show that rivers, creeks, and lakes of the Reserve support a rich aquatic invertebrate fauna. The microinvertebrate community is unusually rich in rotifers and cladocerans. Probably nine Indigenous fish species occur in the Reserve, including the vulnerable Nannatherina balstoni, restricted Galaxias maculatus and critically endangered Galaxias truttaceus. The installation of a vertical slot fish ladder on the Goodga River weir has likely helped these species by expanding available habitat. Although the low nutrient status and relatively deep water of the lakes limit their waterbird value, considered together the Reserve’s lakes fall just outside the top 10% of nature reserves in Western Australian for number of waterbird species supported. Conclusions The richness of aquatic invertebrate species in the Reserve’s lakes contrasted with previous results from rivers in south-western Australia and has led to a changed understanding of both the diversity and conservation significance of the inland aquatic invertebrate fauna in Western Australian lakes. Implications Invertebrate community composition and conservation values are not recognised unless surveyed by people with appropriate taxonomic expertise. Without such surveys the focus of conservation effort and management may be, at least partially, misdirected.
Exploring oral health challenges and integration strategies in opioid treatment programs: perspectives from clinicians and clients
Authors: Wong Grace , Cheng Anna , Cheng Kyle , Masoe Angela , D’Hary Sanjana , Montebello Mark Enea
Published: January 2025

Background Despite the paramount importance of oral health, individuals undergoing treatment for opioid use disorder face unique challenges beyond traditional addiction care. This qualitative study explores the challenges Opioid Treatment Program (OTP) clients in Australia encounter when accessing oral health care, aiming to understand the underlying factors and identify effective strategies for integrating oral health into an OTP. Methods Semi-structured interviews were conducted with OTP clients, OTP clinicians and oral health clinicians using tested interview guides. Thematic analysis identified patterns and themes across participants’ responses. Results Client behaviour and traits such as inadequate health prioritisation, crisis-driven care and lack of motivation, shaped by a complex social environment, contribute significantly to inconsistent care and neglected oral health. Addiction exacerbates oral health issues as clients prioritise drug use over oral care and financial constraints, resulting in poor oral hygiene and a higher prevalence of dental problems. Psychological barriers such as dental anxiety deter clients from seeking care, while access issues including administrative burdens and system barriers, lost phones and unstable living conditions hinder consistent management of oral health. Stakeholders recommend actionable steps to address OTP clients’ challenges, including integrating holistic care, establishing collaborative support systems, improving awareness and education and enhancing accessibility and flexible scheduling. Conclusion This study established a framework for improving OTP clients’ oral health through integrated, holistic strategies. By addressing gaps in existing research, it supports the development of public health policies integrating oral health care into OTPs, aiming to foster collaboration, improve access and advance client education for better health outcomes.
Crosslinguistic perspectives on the source of first/second person pronouns
Authors: Ishiyama Osamu
Published: January 2025

This study investigates demonstratives as the diachronic source of first/second person pronouns and shows that
though several languages use them to designate the speaker/addressee, most usage does not conventionalize as first/second person
pronouns despite the claim in previous studies. It then presents functional reasons that demonstratives rarely give rise to
first/second person pronouns. This study additionally examines nouns and reflexives as the source of first/second person pronouns
and shows that while it is relatively common for nouns to develop into first/second person pronouns, the same conclusion as
demonstratives can be drawn for reflexives. I argue that the historical development of first/second person pronouns differs from
that of third person pronouns due to speech-functional and discourse-pragmatic reasons. The development of the former concerns the
speaker-addressee axis, thus more strongly affected than the latter by the tug of war between efficiency in linguistic
communication and social success in interpersonal communication.