bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine structure of the “Atkins sphere” in solid helium
Authors: Potapov S. G. , Sukhanov L. P.
Published: January 2025

The Hartree–Fock–Roothaan method for calculating the potential energy surfaces of interaction of positive charges of proton type with n atoms of helium is used to model the formation of the second coordination sphere. It is shown that the second coordination sphere is formed in a plane perpendicular to the linear molecular ion He2H+. Five helium atoms are located in this plane at the vertices of a regular pentagon. In the case of solid helium, the positive charge (being an interstitial defect) reorganizes the lattice in such a way that a fifth-order axis is formed around it.
Collective excitations in a superfluid Fermi liquid
Authors: Krasil’nikov V. V. , Rozhkov A. A. , Yatsenko A. A.
Published: January 2025

The superfluid and normal states of a Fermi liquid are described by using a semiphenomenological theory. The collective excitation spectrum in the superfluid Fermi liquid is investigated on the basis of linearized kinetic equations for the normal and anomalous distribution functions.
Shape of the coexistence curve near the critical point of neon and deuterohydrogen
Authors: Shimanskaya E. T. , Oleinikova A. V. , Shimanskii Yu. I.
Published: January 2025

The experimental data on the temperature dependence of the density of neon and deuterohydrogen along the coexistence curve are analyzed in the vicinity of the critical point in order to obtain the value of the critical exponent β0. It is shown that while using the scaling equation for describing the experimental data, preference should be given to the value β0 ≈ 0.35 over the value β0 ≈ 0.325 obtained in some theoretical works for a number of reasons.
Thermal expansion of solid deuterohydrogen at helium temperatures
Authors: Aleksandrovskii A. N. , Palei V. V. , Soldatov A. V. , Parbuzin V. S.
Published: January 2025

For the first time, the thermal expansion of solid deuterohydrogen (HD) is studied in the temperature range 1.2 to 5 K. The isotopic impurity concentrations are 1.5% H2 and 0.4% D2, the other impurities totalling less than 5·10 −4%. It is shown that the thermal expansion coefficient of solid HD can be described by the expression αHD (K−1) = 1.38·10−7T3 in the investigated temperature range. The isothermal compressibility χT = (34 ± 6)·10−10 Pa−1 is predicted on the basis of the experimental results and literature data.
X-ray photoelectron spectra of La2CuO4 doped with strontium and scandium
Authors: Dobrotvorskaya M. V. , Obolenskii M. A. , Poltoratskii Yu. B. , Sobolev V. L.
Published: January 2025

The changes in the structure of x-ray photoelectron spectra from the surface of La2CuO4 samples are investigated for different degrees of doping with strontium and scandium after mechanical purification and heating in vacuum, as well as under ion and x irradiation. The structure of the spectra of the core shells of the elements constituting the samples is identified. It is shown that the existence of copper in the mixed valence state is essential for the emergence of high-temperature superconductivity in the investigated cuprates, and the ratio of contributions of Cu+ and Cu2+ states to the electron structure of the compounds must be quite definite.
Self-oscillations in a system with an S-shaped IVC of the n–s junction
Authors: Tszyan Yu. N. , Shevchenko O. G.
Published: January 2025

Self-oscillations are detected and investigated in a chain with an S-shaped conduction nonlinearity due to non-Andreev reflection of “sliding” electrons at the normal metal–superconductor interface (indium–bismuth system).
Solitons in ferrimagnets close to the compensation point
Authors: Zhmudskii A. A. , Ivanov B. A. , Oksyuk G. K. , Sukstanskii A. L.
Published: January 2025

The nonlinear dynamics of a two-sublattice magnet with compensated spins of sublattices is investigated. It is shown that nonlinear magnetization waves in such a system differ considerably from magnetization waves in pure antiferromagnets. In the case under investigation, one-dimensional solitons (domain walls) are asymmetric. Three-dimensional solitons have the form of “magnon bubbles” with zero magnon number density within the solitons.
Detection of gap in the low-frequency AFMR mode and magnetic phase transitions in Gd2CuO4
Authors: Zvyagin A. I. , Stepanov A. A. , Pashchenko V. A. , Kobets M. I. , Panfilov A. S. , Barilo S. N. , Zhigunov D. I.
Published: January 2025

Resonance and magnetic measurements of Gd2CuO4 single crystals have been made at low temperatures including the region of magnetic ordering of the gadolinium subsystem. It is found that there is a gap ω10/2π ≃ 10 GHz (T = 4.2 K) in the low frequency AFMR mode, and the magnetic structure of Gd2CuO4 in weak magnetic fields undergoes an orientation phase transition (Hc ≃ 3.5 kOe) according to the AFMR data, Hc1 ≃ 2 kOe and Hc2 ≃ 5.5 kOe according to the magnetic measurement data for different magnetic field orientations in the (a, b plane).
Self-modulated nonlinear shear surface acoustic waves in crystals
Authors: Gorentsveig V. I. , Kivshar’ Yu. S. , Kosevich A. M. , Syrkin E. S.
Published: January 2025

Nonlinear, purely shear surface acoustic waves (SAW) are investigated in crystals. A set of such SAW described by N-soliton solutions of the nonlinear Schrödinger equation is obtained. The simplest of these waves was detected earlier by V. G. Mozhaev [Phys. Lett. A139, 333 (1989)]. Higher-order waves exhibit self-modulation along the direction of propagation with a spatial frequency proportional to U02 (U0 is the peak amplitude on the surface of a crystal), and a decrease in their amplitude with increasing depth can be nonmonotonic. The characteristic localization length for such SAW is proportional to U0−1. The excitation of waves of each order by synphase oscillations localized at the crystal surface is of a threshold nature. The stability of obtained waves to small changes in the boundary conditions and to a random perturbation of the oscillation phase in the initial section (which varies with the depth) is determined.
Direct measurements of the critical current density in YBa2Cu3O7–x single crystals
Authors: Dmitriev V. M. , Prikhod’ko O. R. , Khristenko E. V. , Bondarenko A. V. , Obolenskii M. A.
Published: January 2025

The critical current densities Jc are measured directly in single crystals of HTS compounds YBa2Cu3O7–x near the superconducting transition temperature Tc. Extrapolation of the temperature dependence Jc(T) to low-temperature region (∼ 77 K) makes it possible to obtain very high values of the current density Jc (∼ 106 A/cm2) in these systems, which confirms the preliminary estimates of Jc obtained from the magnetic data. It is also shown that in HTS single crystals, the external magnetic field suppresses the critical current to a lesser extent than in polycrystals. Measurements of the critical current at various temperatures and magnetic fields have been used to estimate the second critical field in these compounds (Hc2 ∼ 35 T), whose order of magnitude is the same as the typical value for a wide range of HTS compounds.
Optical spectroscopy of antiferromagnetics with different dimensionalities of structures (a review)
Authors: Eremenko V. V. , Shapiro V. V.
Published: January 2025

The results of investigations of spectral properties of antiferromagnetic compounds of transition metal ions with a high structural dimensionality are analyzed briefly. The problems connected with the evidence for the collective nature of optical excitations in magnetically ordered crystals are discussed. The conditions for observing the magnetic resonance splitting in two-sublattice antiferromagnets, which are a direct proof of the exciton nature of optical excitations, are considered. Optical transitions in antiferromagnetic crystals involving the participation of the spin-wave subsystem (exciton-magnon transitions) are described, a well as the principles of the unified mathematical approach for describing exciton-magnon processes in absorption and luminescence. The peculiarities of the formation of the fine structure of optical spectra of antiferromagnetic crystals with decreasing structural dimensionality are analyzed. One of the most important characteristics which predetermines the basic spectral properties of antiferromagnets in the visible region is the spectral distribution of the density of magnon states, which depends on the dimensionality of the magnetic structure of the crystals. The shape of the exciton-magnon absorption bands and the peculiarities of exciton scattering by spin waves in low-dimensional magnets are discussed. A number of new phenomena associated with the optical reorientation of ion spins in antiferromagnetic crystals, i.e., with the deviation of the spin-quantization axes of photoelectrically excited ions from the direction of magnetization of the corresponding sublattices, are described. It is shown that the small number of nearest neighbors surrounding a photoelectrically excited ion in a low-dimensional antiferromagnetic crystal creates conditions for the emergence of a basically new state, viz., the inhomogeneous magnetization state, which is a sort of spin coat consisting of nearest unexcited magnetic ions whose spins are not coaxial with the direction of magnetization of the corresponding sublattices.
Anomalous response of YBCO films to ultraweak magnetic fields
Authors: Grishin A. M. , Drobot’ko V. F. , Emel’yanenkov D. G. , Inkin Yu. N. , Nikonets I. V. , Khokhlov V. A.
Published: January 2025

The diamagnetic response of thin YBa2Cu3O7–x films in the vicinity of the superconducting transition temperature is studied experimentally as a function of the exciting magnetic field Hac. The films were a granular medium with a broad transition ΔT ≈ 50 K as determined from the temperature dependence R(T). It is found that in the region of ultraweak magnetic fields 0.1–5 mOe, the hysteresis losses are drastically reduced χ″ = 0.02 χ′max at Hac = 0.1 mOe) and the dissipative loss curve χ″(T) has a fine structure. With increasing Hac, the χ″ peak is displaced towards lower temperatures according to the law T = Tc [1–(Hac/H*)2/3].
Concentration ferromagnetic spin glass–spin glass (FSG–SG) transition in disordered systems based on dilute ferrimagnetic oxides
Authors: Efimova N. N. , Popkov Yu. A. , Tkachenko N. V.
Published: January 2025

Magnetic properties of two systems of ferrimagnetic oxides, viz. Li0.5Fe2.5–x, GaxO4 (GaxS), x = 0.90–1.90, and BaFe12–xGaxO19 (GaxM), x = 4.00–8.50, which are similar in the type of exchange interaction, but different in the value and type of macroscopic anisotropy, are investigated in a wide temperature range (4.2–600 K) in magnetic fields from zero to 4 · 106 kA/m. It is found that in these systems at low temperatures, two types of disordered nonergodic states are realized: the ferrimagnetic spin glass (FSG) state for a nonmagnetic ion concentration C0 < 67%, and the spin glass (SG) state for C0 > 67%. In addition to the disappearance of the long-range ferrimagnetic order at the multicritical point on the x–T phase diagram for the concentration FSG–SG transition, an abrupt change is observed in the coefficient S of the long-term logarithmic viscosity. The existence of the FSG–SG transition is also manifested in a qualitative change in the form of the temperature dependence σFC(T) of equilibrium magnetization upon a transition through C0.
Magnetic phase transition and hole concentration in YBa2Cu3O6+x
Authors: Bogdan M. M. , Kovalev A. S.
Published: January 2025

Experimental dependences of the Néel temperatures, the superconducting transition temperature, the concentration of nonmagnetic copper ions, and the density of holes in the CuO2 planes in YBa2Cu3O6+x. are analyzed theoretically by using the model proposed by Tranquada et al. It is shown that the simple mechanism of hole generation upon a change in the oxygen concentration yields theoretical estimates of these quantities as well as for pair interaction potentials of nonstoichiometric oxygen, which are in quantitative agreement with experimental results.
Spectral modeling of turbulence distortion effect on cross-wind loading of high-rise buildings in wind tunnel tests
Authors: Li Shaopeng , Li Xin , Li Jingyang , Yang Qingshan , Li Tian , Zeng Jiadong , Liao Zhiwei
Published: January 2025

This paper mainly studies the impact of turbulence scale on unsteady cross-wind loading (CWL) on high-rise buildings (HRBs) in wind tunnel tests. Wind tunnel tests were conducted utilizing a 2:1 rectangular rigid segment pressure measurement model to analyze the influence of the scale ratio Lw/B (where Lw represents the turbulence scale in cross-wind direction and B denotes the cross-wind model size) on the unsteadiness of CWL. This investigation concentrated on the unsteady effects of CWL, encompassing both three-dimensional effects and turbulence distortion effects. The results indicate that the scale ratio Lw/B has a significant impact on the unsteady characteristics of CWL. An increase in the Lw/B ratio results in a higher peak value of the CWL spectrum and a shift toward lower frequencies. Conversely, a reduction in the Lw/B results in an increased high-frequency decay slope of CWL, due to the distortion effect. Moreover, a reduction in Lw/B results in a decrease in the spatial correlation of CWL, although it remains significantly higher than that of the cross-wind gusts. Therefore, a two-dimensional aerodynamic admittance function model to modify the distortion effects on HRBs was developed based on small-scale turbulence wind tunnel tests. Finally, a 2:1 rectangular cross section HRB model pressure measurements in the atmospheric boundary layer are conducted. The results indicate that the proposed model is highly accurate in modifying the distortion effect. Meanwhile, the applicability of the strip theory is also clarified.
A flexible PI/MXene triboelectric nanogenerator for energy harvesting and motion monitoring in table tennis
Authors: Xu Dazhong , Ma Xiaoxin , Ma Yong
Published: January 2025

Electrospun materials are ideal substrates for wearable devices, offering high surface area, porosity, and mechanical flexibility. A polyimide/MXene (MXene) spinning film and cellulose acetate/polyamide 6 were used to fabricate a triboelectric nanogenerator (PC-TENG) for efficient mechanical energy harvesting. The results identify 5% MXene as the optimal weight fraction, achieving maximum performance by balancing material properties for enhanced energy conversion. The PC-TENG achieves a peak power output of 1.16 mW at an optimal load resistance of 10 MΩ. While the open-circuit voltage (VOC, ∼105 V) and transferred charge (QSC, ∼63.14 nC) remain stable across 2–6 Hz, the short-circuit current (ISC) increases significantly from 14.91 μA at 2 Hz to 41.41 μA at 6 Hz. A strong linear correlation between applied force and output performance is observed, with VOC rising from 63.41 V at 10 N to 148.14 V at 50 N, ISC from 7.31 to 17.98 μA, and QSC from 29.69 to 69.73 nC, demonstrating the device’s potential for precise force sensing. Integration into a table tennis paddle highlights its applicability in real-time sports monitoring, while its frequency-responsive current output underscores adaptability to dynamic sensing scenarios. This research demonstrates the PC-TENG’s potential for efficient energy harvesting and dynamic sensing, offering innovative solutions for self-powered devices and monitoring systems.
Unconventional magnetic oscillations in a kagome Mott insulator
Authors: Zheng Guoxin , Zhu Yuan , Chen Kuan-Wen , Kang Byungmin , Zhang Dechen , Jenkins Kaila , Chan Aaron , Zeng Zhenyuan , Xu Aini , Valenzuela Oscar A. , Blawat Joanna , Singleton John , Li Shiliang , Lee Patrick A. , Li Lu
Published: January 2025

In metals, electrons in a magnetic field undergo cyclotron motion, leading to oscillations in physical properties called quantum oscillations. This phenomenon has never been seen in a robust insulator because there are no mobile electrons. We report an exception to this rule. We study a Mott insulator on a kagome lattice which does not order magnetically down to milli-Kelvin temperatures despite antiferromagnetic interactions. We observe a plateau at magnetization equal to

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Bohr magneton per magnetic ion, accompanied by oscillations in the magnetic torque, reminiscent of quantum oscillations in metals. The temperature dependence obeys Fermi distribution. These phenomena are consistent with a quantum spin liquid state whose excitations are fermionic spinons with a Dirac-like spectrum coupled to an emergent gauge field.
Development of millimeter-scaled ultrasonic haptic module based on PMUT phased array with a noticeable touch sensation in centimeter-range
Authors: Xie Danni , Yang Haolin , Lyu Haochen , Gu Yuandong Alex , Zhang Songsong
Published: January 2025

In this paper, we reported a piezoelectric micromachined ultrasonic transducer (PMUT) phased array with a millimeter-scaled acoustic aperture to achieve a perceptible haptic sensation from up to 1.5 cm distance away. As indicated by feedback from 18 volunteers, a threshold acoustic pressure of about 2955 Pa was first reported to be necessary to achieve a noticeable haptic sensation on hand. The designed PMUT phased array with an area of 1 cm2 and an operating frequency of 194.3 kHz produced an acoustic pressure of 3661.7 Pa at 1 cm, which is higher than that reported so far for PMUT modules used for haptic sensing. This value far exceeded the above threshold and was sufficient to produce haptic sensations. The beam focusing capability of the phased array is noteworthy. The acoustic pressure at the focal point after focusing is 284% of that without focusing. Finally, the lateral modulation on the beam focusing trajectory was implemented and the minimum haptic threshold pressure was effectively reduced by 20%. With its capability to generate unparalleled acoustic pressure with only a miniaturized footprint, the presented module validates the potential of PMUT-based ultrasonic haptic sensing technology for applications such as virtual reality and augmented reality.
Study on electroaerodynamic characteristics of helium plasma jet under repetitive nanosecond pulsed discharge excitation
Authors: Wang Manyu , Li Pengfei , Han Ruoyu , Chen Xi
Published: January 2025

This paper explores the aerodynamic characteristics of the He plasma jet under nanosecond pulse needle-ring discharge excitation (dielectric-barrier), and the influence of typical pulse parameters on the flow field is preliminarily ascertained. Schlieren photography is employed to visualize the flow field of the jet, and dynamic processes from plasma generation to post-discharge evolution are recorded in detail by a high-speed camera. The visualized images reveal a transition from a laminar to a turbulent region in the flow field outside the tube following discharge excitation. The turning point (turbulent vortex) propagates at a speed of m s−1. The results show that a higher driving voltage leads to an earlier onset of the turbulent vortex and further shortens the laminar zone length, with a maximum reduction of 36%. The turbulent vortex dynamics gradually diminish as the frequency increases, resulting in a maximum 30% reduction in the laminar zone length after the cumulative effect of several cycles. Also, the impact of the pulse width parameter on the flow field is minimal. By observing the changes in the distribution of gas temperature under different discharge parameters, it is concluded that the thermal effect is the main factor influencing the kinetic process of the flow field.
Advancements in 2D blood vessel angiography using magneto-thermo-acoustic imaging
Authors: Zhao Fanzhe , Li Yanhong , Liu Guoqiang
Published: January 2025

Based on the thermoacoustic (TA) effect of magnetic nanoparticles (MNPs), we propose a novel TA imaging method for 2D vascular distribution mapping under a single-pulse magnetic field. By numerically simulating the forward problem, we model the propagation process of the TA signal, incorporating gradient-concentration MNPs to demonstrate the functional imaging capabilities of MTA. We constructed a 2D vessel model based on real vessels for the inverse problem. By comparing the filtered inverse projection algorithm with the time-reversal method, we verified the feasibility of reconstructing the vessel model image using magnetic-thermo-imaging. One major innovation of this work is the development and use of a 16-channel array ultrasound (US) transducer (16-CAUT) with a center frequency of 2.25 MHz. This device represents a significant advancement, achieving a spatial resolution of 0.35 mm in vascular phantoms for the first time. Additionally, we investigated the effect of different US transducer sampling numbers on image quality. We evaluated the image metrics using root mean square error, peak signal-to-noise ratio, and structural similarity. contrast-to-noise ratio and full width at half maximum were also evaluated for different filtering levels. Our results demonstrated the effectiveness of bilateral filtering, a post-filtering method suited for time-reversal image reconstruction. This method is particularly effective at preserving edges while removing background noise, due to its capability to handle the boundary inversion of the acoustic source. Experimentally, our magneto-thermo-acoustic imaging platform achieved high contrast and a spatial resolution greater than 0.35 mm, demonstrating the potential to assist in image monitoring for vascular thrombolysis therapy.
All-dielectric metasurfaces: generating optical vortices through quasi-bound states in the continuum and thermal tunability
Authors: Li Hao , Zhang Jia Nan , Su Ming Rui , Qi Yunping , Ren Qun , You Jian Wei , Pang Yanwei
Published: January 2025

When the in-plane inversion symmetry is broken, it leads to intercoupling between free space and the eigenmodes, thereby establishing a radiation channel for bound states in the continuum (BICs). Consequently, BIC evolve into quasi-BIC (q-BICs), which are protected by symmetry. The q-BIC then forms a Pancharatnam–Berry phase upon induction of its topological phase by a Gaussian circularly polarized wave. This process results in an optical vortex (OV) with a topological charge l = +2. Creation of this OV does not require an exact geometric center, thereby addressing the challenge of beam alignment and obviating the need for a precise unit design. Considering this, the designed metasurface holds extensive potential for future applications in nonlinear optics, imaging, sensing, and measurement.
Sharp interface limit of a two-time scale phase field model of a binary mixture
Authors: Lebedev V G , Ankudinov V E , Kropotin N V , Provatas N , Galenko P K
Published: January 2025

Due to its analytical flexibility and thermodynamic consistency, the phase field methodology is widely used in the analysis of equilibrium states and transformation between phases. The present review is devoted to a class of hyperbolic phase field models, which applies to slow and fast phase transformations. Focusing on the example of solidification of metastable liquid, an analysis is presented for the important procedure of reducing the diffuse interface to the sharp interface. An asymptotic analysis is discussed for application to solidifying binary mixture with diffuse phase interface under arbitrary concentration of species and isothermal and isobaric conditions. The analysis reveals that the hyperbolic phase field model can be mapped onto the known hyperbolic Stefan problem within the sharp interface limit. This result, together with the common tangent construction, allows us to analyze (i) nonequilibrium effects in the form of solute trapping and (ii) the complete transition from the diffusion-limited to the diffusionless (chemically partitionless) solidification at finite interface velocity. A comparison with other theoretical models is summarized and a discussion, which is attributed to experimental results, is given.
Enhancing the electroactive β-phase of PVDF filaments via feedstock processing
Authors: Ali Fawad , Parvez Imran , Albakri Mohammad
Published: January 2025

Polyvinylidene fluoride (PVDF) is a smart piezoelectric material with remarkable properties, offering vast potential for applications in areas such as energy harvesting, biomedical devices, and sensors. Among its various crystalline phases, the β-phase is the most electroactive, characterized by high dielectric properties. Recently, PVDF has been processed using 3D printing due to the technology’s ability to fabricate complex and intricate structures, along with advantages such as design flexibility, material efficiency, and rapid prototyping. While the β-phase content in PVDF is often enhanced through additives or post-processing, limited attention has been given to the role of feedstock preparation and extrusion parameters in phase enhancement. In this study, we investigated how feedstock preparation and extrusion parameters influence the β-phase content of PVDF, aiming to optimize its piezoelectric properties for 3D printing applications. PVDF filaments were produced using two different methods: direct extrusion from PVDF pellets and a solution-based process involving dissolution in a solvent, followed by extrusion. Phase content, structural changes, and thermal stability were assessed using x-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and differential scanning calorimetry. Results show that feedstock processing conditions significantly impact the crystallinity and β-phase concentration in PVDF filaments. Notably, solution-processed PVDF exhibited a higher β-phase concentration compared to the pellet-based method, suggesting that this approach may enhance piezoelectric performance. This study highlights the importance of feedstock processing techniques as a means of tailoring the electroactive properties of PVDF for advanced 3D-printed applications.
Influence of SiO2/C nanoparticles on specific strength and stiffness in agro-waste reinforced polymer composites: experimental and numerical investigations
Authors: Singh Jasminder , Gupta Akash , Singh Manjeet , Saini J S
Published: January 2025

Effective and advanced management methods are needed to utilize agricultural waste residue. The present study highlights the effectiveness of nanoparticles in strengthening of composites and repurposing agro-waste into sustainable materials. SiO2/C nanoparticles (NPs) were developed using the sol–gel technique. The influence of NPs on the specific strength and specific modulus (ranging from 0.1 wt% to 0.5 wt%) was investigated in the paddy straw as per ASTM standards. At a loading of 0.4 wt% nanoparticles, the composite exhibited a 69.9% increase in specific strength and a 50.4% increase in specific stiffness compared to the neat paddy straw composite. This improvement is attributed to the uniform dispersion of nanoparticles, which promotes even stress distribution and strengthens interfacial bonding between the fibers and matrix. Moreover, the tensile properties of the composites were also determined using the Finite Element Method (FEM), a computational technique that simulates the response of the material to physical forces which were further compared with the experimental findings.
Performance analysis and eco-friendly design of all-inorganic 2D/3D multi-junction perovskite tandem solar cells with 28.15% efficiency
Authors: Bankura Swagata , Biswas Abhijit
Published: January 2025

Multi-junction tandem solar cells hold great potential as advanced photovoltaic devices for achieving superior solar energy conversion efficiency. In this study, we leverage device simulation techniques to thoroughly investigate the performance of a lead-free all-inorganic perovskite tandem solar cell. Our proposed device incorporates a two-dimensional perovskite absorber in the top cell (ITO/WS2/Cs3Bi2I9/Cu2O) and a three-dimensional perovskite absorber in the bottom cell (ITO/WS2/RbGeI3/Cu2O/Au). This design strategy is meticulously tailored to ensure optimal light absorption across the visible solar spectrum. By utilizing a standard AM 1.5G spectrum and a filtered spectrum for the top and bottom cells, respectively, coupled with thickness optimization to achieve current matching conditions, we propose a champion tandem structure. Notably, the champion tandem cell, featuring top and bottom cell thicknesses of 900 nm and 263 nm, respectively, exhibits improved performance metrics: a power conversion efficiency of 28.15%, a fill factor of 88.67%, a short-circuit current density of 14.30 mA cm−2, and an open-circuit voltage of 2.22 V. The obtained results indicate a significant advancement in enhancing the efficiency of eco-friendly perovskite solar cells.
Nonclassical effects in the repeated noisy measurement of photon number
Authors: Luis Alfredo
Published: January 2025

We look for nonclassical effects in the parallel repeated noisy measurement of photon number carried out via beam splitting. We utilize an inversion procedure to extract the noiseless photon-number statistics from each of the two measurements by removing the extra uncertainty. Nonclassicality emerges when the so inverted joint distribution takes negative values. As a necessary condition, we find that the field states must be nonclassical in the Glauber-Sudarshan criterion. We also find a nonclassical phenomenon based on correlations of measurement results satisfied by all states different from vacuum.
Relativistic theory of reflection and refraction of electromagnetic waves at a moving interface
Authors: Chen Jiangwei , Qiu Xu
Published: January 2025

In this work, we shall show that, referring to general relativity and Fermat’s principle, in material media, the usual definition of interval should be modified to correctly describe behaviors of an electromagnetic wave obliquely traveling through an interface. Correspondingly, the modified Lorentz transformations (MLTs, in which speed of light in vacuum is replaced by phase speed of electromagnetic wave in the material medium involved) are proposed. Furthermore, it is demonstrated that, based on MLTs of both 4-dimensional wave vectors (4-DWVs) and electromagnetic field tensors (EMFTs), at a moving interface, boundary condition equations, and then laws of reflection and refraction may be derived. The later can also be self-consistently obtained by applying Snell’s law, Fresnel’s law and MLTs of both 4-DWVs and EMFTs. This work provides a possible candidate for solution of reflection and refraction of electromagnetic waves at a moving interface, which may be helpful to deepen the understanding of foundations of electrodynamics of moving media.
Influence of different Irradiation sources on the photocatalytic degradation of Rh-6G dye using g-C3N4 photocatalyst
Authors: Sekar Ilakiya , Soundhariya S , Paramasivam Thangadurai
Published: January 2025

The g-C3N4 nanosheet photocatalyst was synthesized by a pyrolysis method. The g-C3N4 nanosheets were used in the photocatalytic degradation of Rh-6G dye under three different light sources: sunlight, UV, and visible light. Its degradation efficiency to photodegrade the Rh-6G dye under these light sources was investigated. The sunlight showed the best degradation efficiency of 97.1% within 45 min, whereas the UV and visible light showed 98.5% and 90.1% efficiency in 300 min and 720 min, respectively. The ·OH radical generation during the photocatalysis was analyzed using PL emission spectroscopy, and the hydroxyl radicals were so rapidly generated under sunlight compared to the other two radiations, and therefore, the g-C3N4 showed the best degradation under sunlight. A thorough investigation on the type of active species contributed to the photodegradation, and a recyclability study was also done and g-C3N4 morphology were analyzed before and after three consecutive cycles for three different irradiation sources. The degradation of Rh-6G’s primary m/z value of 443 to lower m/z values is evidence of the possibilities of CO2 and H2O. These results have good potential for further improving photocatalytic application-oriented research for having a sustainable environment.
Periodic wave solutions and solitary wave solutions of Kundu equation
Authors: Zhang Weiguo , Guo Yuli , Zhang Xue
Published: January 2025

The periodic wave solutions of the Kundu equation with cubic-quintic nonlinearity and the evolutionary relations of these solutions with the Hamilton system energy which corresponds to their amplitude are investigated in this paper. The analytical approaches, based on the first-integral and some suitable transformations, are used in this paper to find all seven groups of elliptic function periodic wave solutions for this equation under different conditions. All nine pairs of solitary wave solutions for the studied equation are also given in the paper under various parameters, and many of them we provided are new. This is done by investigating the evolutional limits of these periodic wave solutions in terms of the Hamiltonian energy and straightforwardly applying the analytical approach starting from the first-integral. The connection between the Hamiltonian energy of the system and the periodic wave solution, the solitary wave solution of the system is established. From the analysis, it is clear that the Hamiltonian energy of the dynamic system with varied values taking in diverse ranges is the key factor for the appearance of periodic or solitary wave solutions to the Kundu equation, and the Hamiltonian energy is corresponded by the amplitudes of these solutions.
Efficient solar trapping with vanadium oxide hole transport layer in perovskite solar cells
Authors: Kumar Kapil , Giri Pushpa
Published: January 2025

Proper selection of the hole transport material is essential for improving the stability of perovskite solar cell devices under open environmental conditions. Therefore, it is necessary to introduce a hole material that can resist moisture absorption and shows a less hygroscopic tendency compared to other organic/inorganic hole materials. Vanadium oxide (V2O5) exhibits these desirable properties. In this research, the primary focus is to analyze the performance of formamidinium lead iodide (FAPbI3) and methyl ammonium antimony iodide (MA3Sb2I9) perovskite solar cells with the hole transport layer (HTL) as Vanadium Oxide (V2O5). FAPbI3 and MA3Sb2I9 are lead and lead-free materials respectively. Numerical simulator SCAPS-1D software has been utilized for analyzing the effect of V2O5 on their performance efficiency under the photo illumination of AM1.5G. Incorporation of V2O5 as an HTL in FAPbI3 and MA3Sb2I9 based perovskite solar cells resulted in performance efficiency of 25.04% and 7.07% respectively at optimized simulation parameters (ETL (50 nm)/perovskite layer(350 nm)/HTL (300 nm)). The optimized PSCs configurations ITO/ZnO/FAPbI3/V2O5/Au and ITO/ZnO/ MA3Sb2I9/V2O5/Au shows open circuit voltage (Voc), current density (Jsc) and fill factor (FF) values of 1.29 V, 23.08 mA cm−2, 84.06% and 1.31 V, 6.77 mA cm−2, 79.10% respectively. In the meantime, the effect of perovskite layer thickness, the effect of hole/electron layer (HTL/ETL) thickness, the impact of perovskite layer doping, and the effect of temperature variations have also been analyzed. The thorough analysis of the proposed device provides a reference for the future development of highly efficient and stable perovskite solar cells using V2O5 as an HTL.
Enhancing performance of AlGaN deep-UV LEDs by p-Al0.6Ga0.4 N/p-GaN thin-wells superlattice as hole injection layer
Authors: Yang Pan , Kong Lijing , Gao Na , Li Shuping , Kang Junyong , Zhang Rong
Published: January 2025

The low carrier injection efficiency and the efficiency droop at high current injection have seriously affected the optoelectronic performance of AlGaN-based deep ultraviolet LEDs. In this work, we propose the deep-UV LED incorporating the p-Al0.6Ga0.4N/p-GaN superlattice with thin wells (1 nm) as the hole injection layer to improve carrier injection efficiency and optoelectronic performance of the device. Theoretical simulations show an enhancement of the hole concentration in the quantum wells, which increased by one order of magnitude with the designed p-type superlattice structure due to the induced strong polarization field. In contrast to the traditional p-type Al0.6Ga0.4N structure, the radiative recombination rate of the p-Al0.6Ga0.4N/p-GaN superlattice increases by approximately 8 times. Furthermore, the sharp drop in internal quantum efficiency at the high current density is significantly suppressed. This work provides valuable insights for designing and implementing high-efficiency deep ultraviolet LEDs.
The role of spin-orbit perturbations in the rovibrational structure of the N2(C3Πu, v) electronic state. Importance in N(4S) and N(2D) formation in Lewis-Rayleigh afterglows
Authors: Ventura Laiz R , da Silva Ramon S , Fellows Carlos E , Amorim Jayr
Published: January 2025

Nitrogen molecules, N2, are involved in several physico-chemical processes in the Earth’s atmosphere, including phenomena such as afterglow and aurora. These processes are crucial for understanding the dynamics of the upper atmosphere and interactions between solar radiation and atmospheric gases. The rovibrational spectrum is rich in information and exhibits a wide range of forbidden transitions. In this study, we propose that the rovibrational structure of the N2(C3Π
u
, v) is severally perturbed by spin-orbit interaction with A

′
5

Σ

g

+

, C

″

5

Π

u

, 2

5

Σ

g

+

and 1

5

Σ

g

−

states. This effect disturbs the measurements of N(2D) and N(4S) atomic states in late post-discharges. By analyzing the vibrational distribution function of N2(B3Π
g
, 10 < v < 12) and N2(C3Π
u
, 1 < v < 4), and taking into account these spin-orbit interactions, the density of N(4S) and N(2D) are deduced. It is found that [N(2D)] is around 4% [N(4S)] in Lewis-Rayleigh afterglow, i.e. residence times  > 10−2 s.
Widely tunable mode-locked fiber laser operating in O-band spectral region
Authors: Amouzandeh Narges , Long Pin , Légaré François , Soltanian M R K
Published: January 2025

This paper investigates the generation of passive tunable mode-locked fiber laser utilizing a figure-9 configuration in a 1.3 μm spectral region. Mode-locking is achieved through reflective nonlinear amplifying loop mirror technique with nonreciprocal beam splitter. The system demonstrates stable pulse generation across a 120 nm tunable wavelength range centered at 1310 nm with a fundamental repetition rate of 12.7 MHz. The pulse duration, which can vary with changes in the repetition rate, ranges from 10.4 ns to 58.8 ns, with a 3 dB spectral bandwidth of 0.21–0.41 nm. The stable and self-start mode-locking is guaranteed by polarization controller and fiber-based phase shifter. Moreover, this achievement highlights its potential as a compact photonic source for optical communications and precision metrology.
Enhancing detection of SSVEPs using discriminant compacted network
Authors: Li Dian , Huang Yongzhi , Luo Ruixin , Zhao Lingjie , Xiao Xiaolin , Wang Kun , Yi Weibo , Xu Minpeng , Ming Dong
Published: January 2025

Objective. Steady-state visual evoked potential-based brain–computer interfaces (SSVEP-BCIs) have gained significant attention due to their simplicity, high signal to noise ratio and high information transfer rates (ITRs). Currently, accurate detection is a critical issue for enhancing the performance of SSVEP-BCI systems. Approach. This study proposed a novel decoding method called Discriminant Compacted Network (Dis-ComNet), which exploited the advantages of both spatial filtering and deep learning (DL). Specifically, this study enhanced SSVEP features using global template alignment and discriminant spatial pattern, and then designed a compacted temporal-spatio module (CTSM) to extract finer features. The proposed method was evaluated on a self-collected high-frequency dataset, a public Benchmark dataset and a public wearable dataset. Main Results. The results showed that Dis-ComNet significantly outperformed state-of-the-art spatial filtering methods, DL methods, and other fusion methods. Remarkably, Dis-ComNet improved the classification accuracy by 3.9%, 3.5%, 3.2%, 13.3%, 17.4%, 37.5%, and 2.5% when comparing with eTRCA, eTRCA-R, TDCA, DNN, EEGnet, Ensemble-DNN, and TRCA-Net respectively in the high-frequency dataset. The achieved results were 4.7%, 4.6%, 23.6%, 52.5%, 31.7%, and 7.0% higher than those of eTRCA, eTRCA-R, DNN, EEGnet, Ensemble-DNN, and TRCA-Net, respectively, and were comparable to those of TDCA in Benchmark dataset. The accuracy of Dis-ComNet in the wearable dataset was 9.5%, 7.1%, 36.1%, 26.3%, 15.7% and 4.7% higher than eTRCA, eTRCA-R, DNN, EEGnet, Ensemble-DNN, and TRCA-Net respectively, and comparable to TDCA. Besides, our model achieved the ITRs up to 126.0 bits/min, 236.4 bits/min and 103.6 bits/min in the high-frequency, Benchmark and the wearable datasets respectively. Significance. This study develops an effective model for the detection of SSVEPs, facilitating the development of high accuracy SSVEP-BCI systems.
CNN-BiLSTM combined with Bayesian optimization for short-term wind power prediction
Authors: Song Yahao , Wu Yajun , Duan Songtao , Dou Chendan , Liu Bei , Hou Bingxue
Published: January 2025

Aiming at the difficulty of wind power prediction due to the volatility and uncertainty of wind power generation, this paper proposes a hybrid model based on Convolutional Neural Network (CNN) and Bidirectional Long Short-Term Memory Network (BiLSTM), and optimises the model hyper-parameters using Bayesian Optimization Algorithm (BO) in order to improve the prediction accuracy. Firstly, the input features that are highly correlated with wind power are screened using the Pearson Coefficient method (PCC). Then, CNN is used to extract features from the screened data. Next, the features extracted by CNN are further processed using BiLSTM to capture the long-term dependence and bi-directional information of the time series data. Finally, the hyperparameters of the model are adjusted by BO to obtain the best prediction performance. The experimental results show that the proposed BO-CNN-BiLSTM model reduces the RMSE by 35.3%, the MAE by 46.7%, and the R2 improves by 1.5% compared with the BiLSTM model.
The study of CO2-organic solvent phase equilibrium in the SAS process
Authors: Xu Changfei , Wang Feibo , Hu Dedong , Sun Xuemei , Liu Ruisheng , Zhang Zhuo
Published: January 2025

The supercritical anti-solvent (SAS) process is a novel preparation method to enhance the low dissolution of poorly soluble drugs by reducing their particle size. The equation of state (EOS) is the most widely used method to study the phase behavior in the SAS process due to its simple expression and high prediction accuracy. This paper employed the RK, SRK, and PR EOS to calculate the phase equilibrium of three systems: CO2-toluene, CO2-DMF, and CO2-ethanol. The calculation results are then compared and analyzed with experimental data from the literature. It was found that the PR EOS has higher calculation accuracy than the RK EOS and SRK EOS. Therefore, the PR EOS is selected as the basis for determining the experimental operating conditions of the three mixtures mentioned in this article. This provides a prerequisite for the successful preparation of fine particles using SAS.
The simulation optimization of structural parameters for annular gap scrubber
Authors: Jian Jie , Jin Xin , Zhang Yushu , Jiang Qingbo , Chen Jiexue , Zhang Baocai , Ren Tingzhi
Published: January 2025

As a critical device for blast furnace gas dust removal, the development of the annular gap scrubber aims to reduce equipment pressure loss and water consumption while ensuring dust removal rate. In this study, numerical simulations of the two-phase flow field within the scrubber were conducted to calculate the pressure loss of the existing equipment under the target dust removal rate. Based on the design principles of a Venturi tube and simulation results, the scrubber’s structure was optimized. The optimized design significantly reduced pressure loss under various operating conditions, with an average reduction of over 10% and a maximum reduction of 15.83%. Additionally, dust removal performance improved at low water-gas ratios. The new design increased the gas residual pressure power generation efficiency by approximately 1.9%, resulting in an additional power output of around 200 kW. This study provides a new optimization strategy for the structural parameters of the annular gap scrubber, contributing to enhanced energy efficiency and reduced resource waste in the steel industry.
Deep neural network-based frequency cross-over amplifier design: A simulation study
Authors: Zhu Hao , Yu Haoxuan , Liu Yang
Published: January 2025

Designing frequency cross-over is important for loudspeakers to gain better control, reduce distortion, and improve efficiency. Engineers have introduced the DSP-based digital feedback FIR filter to overcome the drawbacks of analog cross-over, such as intermodulation distortion (ID) and transient intermodulation distortion (TIM). However, the digital feedback loop introduces an additional time delay (TD) and phase shift that lowers the system’s stability and elongates the relaxation time, decreasing the damping factor and the total gain. Using the deep neural network (DNN) can overcome these disadvantages. With machine learning algorithms like backward propagation, DNN can model the nonlinear response of the system and compensate them to obtain better control of the speaker with less gain loss. This work simulates a frequency cross-over using DNN and compares it to the open loop and FIR direct digital feedback amplifier (DDFA) systems. Our simulation shows that the DNN filter can approach the best filter result (FFT filter). With nonlinear load, the DNN filter can function as both frequency cross-over and distortion compensator with a great nonlinearity suppression with a time constant of 0.05 while the DDFA of 0.11 and the open loop of 0.32. The overall gain of the DNN filter (1.13) is close to the open loop (1.1) and better than the DDFA (1.25). With such superiority, DNN-based cross-over will be a good platform for designing the next-generation cross-over.
Numerical analysis of the deviation characteristics of ship wake flow fields under the combined effect of wind, wave, and current in confined waters
Authors: Huang Yilin , Sun Xiaoxiao , Zhu Jinshan
Published: January 2025

When a vessel enters restricted waters, the hydrodynamic interactions between the hull, the seabed, and the shore, combined with the effects of wind, wave, and current, can cause significant changes in the wake field of the hull. These changes consequently impact the ship’s hydrodynamic performance and the operating conditions of the propeller. In this paper, the characterization of the wake field of a large tanker KVLCC2 under wind, wave, and current for near-shore navigation is investigated by an unsteady Reynolds-averaged Navier-Stokes (URANS) method. The turbulence model SST k-ω is applied, releasing the three degrees of freedom of roll, trim, and sinkage. The motion with multiple degrees of freedom is simulated by the dynamic mesh technique, while the air-water interface is captured by the Volume of Fluid (VOF) multiphase flow method. The reliability of the present numerical method is first verified by comparing it with the test. Subsequently, the near-shore navigation of the ship with different ship-shore distances and different incoming currents is simulated, and the offset characteristics of the ship’s wake current field are analyzed. The results show that the ship-shore distance and the incoming flow direction will affect the offset of the wake flow field and the distribution of the companion flow number on the paddle disk, which in turn affects the propeller performance.