bluuebunny/crossref_metadata_2025 huggingface dataset:
The T–S phase state diagram of 4He l–4He II
Authors: Vishnev I. P. , Vishnev A. I. , Novikov I. I.
Published: January 2025

The relevant experimental and theoretical works known thus far are analyzed. The problem of the vapor and liquid state and the phase transition of helium II is formulated, the T–S diagram is proposed, and an analysis of the phase transition is given in terms of quantum physics.
T–q diagram for the analysis of refrigerator circuits working on superfluid helium
Authors: Sidyganov V. U. , Kupchikhin P. M.
Published: January 2025

A special diagram of state is presented: the T–q diagram, which permits us to make a thermodynamic analysis of a technical system in which He II is a working substance. The basis of the description of the process is Landau’s equation complemented by a term connected with the specific dissipation of Gorter and Mellink.
Theory of lateral heat transfer in multilayer insulation
Authors: Zhitomirskii I. S.
Published: January 2025

A method is proposed for taking into account the effect of small thickness of aluminum coating of shields on the heat and electric conductivity of coating. Based on the previously developed (by the author) quasi-diffusion approximation for describing the transfer processes in narrow gaps, analytical dependences are obtained for the effective radiant and molecular heat conductivities of the gap between the shields. The expressions for the reduced spectral emissivity and reduced energy accommodation coefficient on the surface of the shield closing the end of insulation blankets are found. The boundary conditions for the lateral heat conductivity problem are formulated.
Stability of rotating superconducting windings for electric machines
Authors: Gavrilov R. V. , Ishchenko L. A. , Kompantseva V. G. , Pestryakov V. A.
Published: January 2025

In this paper the perturbation and stability of a rotating superconducting winding is analyzed. The heat release due to the ac components of the brush-device current and field is considered. The thermal condition of the compound winding with indirect cooling is analyzed. The mechanism of interaction between adiabatic and isothermal perturbations is examined. It is shown that isothermal perturbations can suppress the threshold of the winding sensitivity to adiabatic perturbations without destruction of the superconducting state.
Analysis of superfluid helium nonventing storage schemes in the cryogenic system of a space infrared telescope
Authors: Pletnev F. M. , Stepanova M. V. , Yastrzhembskii A. I.
Published: January 2025

The problem of superfluid helium storage in a telescope cryogenic system with closed drain line is discussed, and two variants of heat protection of helium tanks are proposed. Both variants ensure storage of helium in the superfluid state during the present time (one week).
Effect of thermodynamic factors on heat transfer in liquid cryogen during storage without vent
Authors: Suprunova Zh. A.
Published: January 2025

This paper considers the features of an isochoric process occurring in a two-phase medium arising during nonvented storage of cryogenic liquids. Examples are given representing various mechanical states of the medium which is responsible for the character of phase transitions at the liquid–vapor interface (evaporation or condensation) and which depends on the initial and boundary conditions of the process. The conditions of the liquid–vapor interface equilibrium are considered. It is shown how the phase transitions influence the main characteristics of heat transfer (pressure in the vessel, temperature stratification of the liquid) during nonvented storage of liquid cryogens.
Transient heat transfer problem for the transition state of superconductors cooled by superfluid helium
Authors: Lutset M. O.
Published: January 2025

Possible reasons of agreement with experimental values of the velocity of normal zone propagation along a superconductor cooled by He I and He II are discussed. The problems of transient heat transfer to He II are formulated on the basis of the approach developed previously.
Critical heat flux at transient heat generation and change in dynamics of the boiling regime
Authors: Pavlenko A. N. , Chekhovich V. Yu.
Published: January 2025

In this study the calculated dependences for minimum critical heat flux at transient heat generation are presented, based on a model of the crisis onset mechanism. It is shown that the character of the influence of relative pressure on value of transient critical heat flux in nitrogen depends essentially on the presence of heterogeneous centers of nucleation on the heat-generating surface. Experimental data for the velocity of movement of the boundary of the film boiling regime in helium are presented.
Effect of tube diameter and duct cross-section shape on heat transfer during flow boiling of cryogenic fluids. Part 1: Forced convective boiling region
Authors: Baumann P. , Steiner D.
Published: January 2025

Heat transfer in the forced convective boiling region for noncircular cross sections can be predicted by using the hydraulic diameter. This concept gives reasonable accuracy as long as the perimeter of the duct is completely wetted, e.g., for vertical ducts. For horizontal ducts, further information on the secondary flow and partial wetting in connection with the flow pattern is needed.
New methods of measuring vortex-line density during passage of a supercritical second-sound pulse
Authors: Stamm G. , von Schwerdtner M. , Fiszdon W.
Published: January 2025

The evolution of second-sound pulses in superfluid helium for axisymmetric flow geometry has been studied for the main flow parameters: input heat flux, pulse duration, and repetition time between two consecutive pulses. It is shown that the onset of the observed strong distortions of the temperature pulse shapes can be related to the above parameters by a simple equation. The main reason for this impediment of heat transport is the mutual friction between superfluid vortex lines, present as a chaotic tangle (superfluid turbulence), and the normal component. A new method is presented for evaluating the temporal evolution of the vortex line density during the passage of a second-sound pulse, and the results are compared with theoretical predictions.
Preparation and properties of HTSC Y–Ba–Cu–O films on various single-crystal substrates
Authors: Rudenko E. N. , Usoskin A. I.
Published: January 2025

The results of a study to obtain HTSC films of Y–Ba–Cu–O on various single-crystal substrates (SrTiO3, Al2O3, YAlO3, LiNbO3) by laser deposition are described. The microphotographs of Y–Ba–Cu–O films on SrTiO3 (100) substrates illustrate the mechanism of film structure formation.
Pairing interaction and superconductivity in oxides and hydrides
Authors: Kulik I. O.
Published: January 2025

A model of superconductivity is considered taking into account the overlap and correlation effects in p- or s-shells of electronegative ions O2− and H− in the rigid lattice formed by other elements in the oxygen- and hydrogen-related compounds. Pairing force within the model arises as a consequence of orbital size dependence upon its filling and is characteristic for the above “electronegative” metals with moderate overlap between hole orbitals.
Role of oxygen deficiency in the change of sound velocity in YBa2Cu3O7–δ below 20 K
Authors: Gaiduk A. I. , Gasan V. M. , Demirskii V. V. , Zherlitsyn S. V. , Kolobov I. G. , Tabachnikova E. D. , Fil’ V. D.
Published: January 2025

The logarithmic rise in sound velocity S vs. temperature T for T < 1 and the linear fall of S(T) between 2 and 20 K in YBCO ceramics are the usual features of the glasslike behavior associated with the two-level systems (TLS). The linear dependence, supposedly caused by the anharmonicity of the interatomic potential connected with TLS, correlates with the level of oxygen deficiency δ: an increase in δ leads to an increase in slope of the S(T) plot. Most likely, TLS in ceramics are connected with tunneling of oxygen atoms and the density of tunneling states rises with δ. Results have been obtained for the same sample (modifying its state by successive heat treatments) and are well reproducible, so we conclude that the S(δ) dependence has a more or less universal character.
High-current-density YBa2Cu3Ox liquid-quenched superconductor layers
Authors: Dorofeev G. L. , Dorofeeva E. A. , Ovcharov V. P. , Frolov S. V.
Published: January 2025

YBa2Cu3Ox and YBa2Cu3Ox + Ag melts were quenched on heated Zr substrates in an oxygen atmosphere. The critical temperature of the samples was about 70 K. We observed a weak magnetic field dependence of the critical current. The current density was about 105 A/cm2 in 0–3 T fields. A liquid quenching method for the fabrication of high-Tc superconductors with large current-carrying capacity at nitrogen temperatures is discussed.
Organometallic chemical vapor deposition of superconducting YBa2Cu3O7–δ
Authors: Schmaderer F. , Wahl G. , Jahnke B.
Published: January 2025

Chemical vapor deposition is a very promising method of depositing high-Tc superconductors because of the following reasons: deposition is possible at very high oxygen potential, deposition rates are high compared to those achieved by other deposition techniques, and the method has excellent throwing power which is necessary if complicated substrates (e.g., continuous fibers) have to be coated. As source materials for the YBa2Cu3O7–δ deposition experiments β-diketone chelates have been used for Y, Ba, and Cu, respectively. In order to define the deposition process, the gas flow phenomena in the reactor were studied by TiO2 fume experiments and by computer simulations. The deposition experiments were carried out on single crystalline SrTiO3- and Y-stabilized polycrystalline ZrO2 substrates (YSZ) showing in each case superconductivity above 95 K.
Magnetic response of n-doped Ln2–xCexCuO4–δ with Ln = Nd, Pr, Sm in the superconducting and normal states
Authors: Ströbel J. P. , Klauda M. , Saemann-lschenko G.
Published: January 2025

We report on the supeconducting and normal-state properties of electron-doped cuprates Ln2−xCexCuO4−δ with Ln = Nd, Pr, Sm. Furthermore, we present results for the upper and lower critical fields and calculate from these the superconducting parameters ξ, k and λ, within the framework of the anisotropic Ginzburg–Landau theory. The Hall coefficient is negative over the entire normal-conducting temperature range.
Ways to increase the critical temperature in Bi and Tl systems
Authors: Kotok L. A. , Itskovich R. Yu. , Saliychuk E. K. , Kvichko L. A. , Deineka T. G. , Teplitskaya T. S. , Rosenberg G. Kh.
Published: January 2025

Using X-ray, electron microprobe analyses, and resistivity and magnetic measurements, we have determined the initial compositions and conditions for solid-state synthesis of Bi- and Tl-containing HTSC samples having a maximum content of the 2223 phase. Values of Tc0∼125 and 108 K in Tl and Bi compounds were obtained, respectively.
Superconducting properties of ZrxYzBa2Cu3Oy ceramics
Authors: Tikhenko E. V. , Nechiporenko I. N. , Ben’ko V. Yu. , Batrak A. G. , Artsebasheva N. G.
Published: January 2025

The dependence of the critical current density jc of superconducting Zrx Yz Ba2Cu3Oy ceramics (z = 1, 2) on different values of x (0 ≤ x ≤ 1) is studied. The positive influence of ZrO2 addition in the Y–Ba–Cu–O system on superconducting ceramic properties is shown.
Investigation of HTSC impedance properties in the millimeter wave range
Authors: Kirichenko A. Ya. , Cherpak N. T.
Published: January 2025

The results of a study of high-Tc superconductor impedance in the 8-mm wave range are given. A quasi-optical dielectric resonator with a higher-order azimuthal wave and metallic cyclinder resonator with an H011-type oscillation are used. The first one is used for the measurement of the surface impedance versus temperature dependence, and the second resonator is used for the measurement of the absolute value of Rs. HTSC samples of two compsoitions are investigated. It is shown that there is no distinct exponential dependence Rs(T) in ceramic YBa2Cu3O7–δ. The energy gap value of T/Tc ≃ 0.5 equals 2Δ/kTc ≃ 4, while at T/Tc = 0.5 – 2 it reaches only 2Δ/kTc = 0.6. In polycrystalline Bi–Sr–Ca–Cu–O the temperature dependence of Rs indicates the presence of at least two superconducting phases. Superconducting phases with Tc = 50 and 20 K have not been observed. Enhancement of the superconducting properties of the sample microwave stimulation of superconductivity with an increase in the microwave signal at > 50 K has been shown.
Dissipation in a Coulomb capacitor
Authors: Nazarov Yu. V.
Published: January 2025

A tunnel junction under the Coulomb blocking is shown to be a peculiar Coulomb capacitor in which the direct tunnel current is exponentially small in the limit of low voltage and temperature. The electric properties of such a capacitor are investigated at a finite frequency. It is shown that dissipation in the tunnel junction is a quantum effect. The losses in a single tunnel junction are calculated, and their temperature dependence and dissipation are determined for the tunneling from a granule. Some nonlinear effects are also considered.
Peculiarities of current–voltage characteristics of bismuth under elastic wave generation
Authors: Bengus S. V. , Bogod Yu. A. , Finkel’ P. E.
Published: January 2025

Steady-state IVC of a monocrystalline bismuth sample of thickness d ≃ 2.7 mm in strong crossed electric and magnetic fields (E ∼ Hs/c, Ωτl = (eH/m*c) τl ≫ 1, s being the velocity of sound and τl the relaxation time for mobile charge carriers) reveal two inflections, the first one towards increasing resistance (downwards) and the second one towards decreasing resistance (upwards). The first inflection (from the smaller current side) is observed only at helium temperatures and can be related to phonon generation along the current direction I(I ‖ y, H ‖ z), and the second one to the bulk generation of phonons in a plane normal to the current (Esaki effect). This interpretation is supported by the recordings of nonsteady effects typical of electroacoustics. The longitudinal phonon generation is attributed both to high values of current density in sample areas where the electron mean free path ls ∼ υF/Ω (e.g., in the vicinity of slip and twinning planes), and to a nonuniform concentration of conduction electrons which, in turn, facilitates an increase in the local current density. The characteristic size of the current concentration region h, defined by the relation ⟨jk1⟩ ≃ nesh/d (⟨jk1⟩ is the average current density corresponding to the downward inflection) is about 2·10−3 cm and is practically independent of the magnetic field in the interval 25–140 kOe.

Nonlinear IVC for Hall contacts (nondiagonal IVC) have been studied for the first time. The Ux(I) dependences measured under steady-state conditions contain sections with negative differential resistance (NDR). For T = 4.2 K, the transition to NDR correlates with the downward inflection on the diagonal IVC, while for T = 20.4, it correlates with the upward inflection. The observed phenomena are attributed to the phonon electron drag before the Esaki effect and to an increase in the magnetoresistance after the realization of this effect, respectively. At T = 4.2 K, the nonlinear component of the nondiagonal IVC shows a reversal of the sign of the Hall emf under static and dynamic conditions, which is interpreted as a manifestation of the drag effect for I>Ik1. At T = 20.4 K, acoustoelectronic vibrations of Ux with a period T ≃ d/s are recorded. Signals of the nonlinear response to two successive current pulses with a controllable relative pulse duration are studied. The first pulse leads to nonequilibrium while the second marks its state in time.
Hall effect in intermetallic compounds GdZnxCu1–x
Authors: Kourov N. I.
Published: January 2025

Investigations of the Hall effect (HE) in GdZnx Cu1–x compounds are carried out in strong magnetic fields (H ≤ 107 A/m). In the region of the ferromagnetic-antiferromagnetic (FM–AFM) phase transition at 4.2 K, as well as in the paramagnetic (PM) state at T ∼300 K, the normal (NHE) and anomalous (AHE) components of the Hall effect are isolated. It is shown that in the FW-AFM transition the AHE has a negative sign due to asymmetric scattering of carriers by the in homogeneities of the exchange part of the Coulomb potential. The peculiarities in the behavior of the NHE can be explained by assuming the existence of a narrow (Δ ∼ 20 meV) peak in the density of d-states near the Fermi energy Ef.
On the change in the thermally activated component of flow stress upon superconducting transition in lead alloys
Authors: Shepel’ I. A.
Published: January 2025

Temperature dependences of the yield stress are measured in the temperature range 4.2–293 K and the components associated with the thermally activated motion of dislocations in the short-range fields of obstacles (τ*) are determined. The changes ΔτSN in the flow stress associated with the S–N transition are measured at 4.2 K. Numerical estimates of the relative values ΔτSN/τ* of the effect indicate that the thermoinertial mechanism makes a decisive contribution to the variation of yield stress in the case of superconducting transition.
Effect of doping on the Néel temperature of metal-oxide compounds
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The effect of doping on the band structure and Néel temperature TN of metal-oxide compounds of the La2CuO4 type is investigated. A theoretical interpretation of the concentration dependence of TN based on the assumption that the electronic properties of such systems are determined mainly by the Cu–O plane is proposed. Theoretical results are compared with experimental data.
Low-temperature peculiarities of quantum galvanomagnetic effects in a two-dimensional electron gas at the surface of liquid helium
Authors: Grigor’ev V. N. , Kirichek O. I. , Kovdrya Yu. Z. , Monarkha Yu. P.
Published: January 2025

Low-temperature peculiarities (maximum and minimum) of the longitudinal resistivity ρxx of surface electrons (SE) at liquid helium surface in a quantizing magnetic field are observed experimentally and interpreted theoretically. It is shown that the minimum on the ρxx(T) curve at T ∼ 1.1 K is associated with a competition between the gas and ripplon scattering of SE, while the peak at T ∼ 0.55 K is due to a coincidence of the quite narrow Landau ground level Γ with the characteristic frequency ω1 of ripplons with a wave vector ∼ l−1 (l is the magnetic length) participating in the scattering.
Statistical analysis of temperature–frequency internal friction spectra of high-T
c ceramics YBa2Cu3Ox
Authors: Natsik V. D. , Pal’-val’ P. P.
Published: January 2025

The original results of the authors obtained in studies of the acoustical properties of some kinds of YBa2Cu3Ox ceramics at frequencies of 105 and 7.5·106 Hz over the temperature range 6–300 K, as well as the results of other investigators (more than 80 works), obtained within the frequency interval 1–108 Hz and over the same temperature range are systematized and discussed from a unified point of view. Two main features the considerable sound velocity hysteresis at thermocycling and the presence of several low-temperature sound absorption peaks are discussed in detail.
One-dimensional superconductivity in two-band superconductors
Authors: Shevchenko S. I.
Published: January 2025

We consider the problem of conductivity (for T > 0) and criteria of superconductivity (for T = 0) of one-dimensional two-band conductors. It is found that the superconducting transition does not depend on the sign of the interband interaction constant λ and depends essentially on the sign of the intraband interaction constant γ. For γ < 0, the system is superconducting for any value of λ; for γ > 0, superconductivity depends on whether λ is larger than a critical value determined by the value of γ. The effect of randomly distributed impurity centers on the conducting properties of the system is studied. It is shown that in the case of weak interaction between charge carriers (the quantitative criterion of weakness of interaction has been found), impurities cause localization of carriers. If the interaction is sufficiently strong, there is no localization, and the system can become superconducting even in the presence of impurities. The character of the effect of interband jumps on the phase diagram for T = 0 is studied and the conditions under which the interband jumps do not prevent a transition to superconductivity are found.
On the theory of two-component superconducting Fermi liquid
Authors: Krasil’nikov V. V. , Poluéktov Yu. M.
Published: January 2025

The theory developed for a two-component superconducting Fermi liquid is applicable for describing superconductivity in metals and alloys with two overlapping conduction bands. The proposed approach permits intraband and interband superconducting correlations, Fermi liquid effects and electron–hole pairing. The possibility of using the two-band model for investigating high-temperature superconductors is discussed. The resultant system of nonlinear equations generalizes the Ginzburg–Landau equations for superconductors described by two order parameters.
Surface electron mobility in helium under strong electron–electron interaction
Authors: Buntar’ V. A. , Sokolov S. S.
Published: January 2025

Experimental results on the electron mobility over liquid helium surface in the temperature region of 0.5–1.3 K, with a charge concentration ns = (2.8–12)·108 cm−2 and a frequency ω = 324 MHz of the driving electric field are reported. These results are compared with theoretical values of electron mobility calculated for different limiting cases relative to electron–electron collision frequency. It is shown that the complete control approximation, when the electron–electron collision frequency is much higher than the electron momentum relaxation frequency, successfully describes the kinetic properties of surface electrons in the region of concentrations exceeding 4·108 cm −2.
Interaction of plasma oscillations with the surface second sound in superfluid helium
Authors: Pushkina N. I.
Published: January 2025

The nonlinear interaction of plasma waves in the two-dimensional layer of positive ions on the surface of 3He–4He superfluid solutions with a surface second sound is considered. An expression for the scattering amplitude of a plasma wave on the surface sound is derived. The possibility of experimental observation of such an interaction is estimated.
Thermoelectric power of Y–Ba–Cu–O ceramics with different oxygen contents under hydrostatic pressure up to 12 kbar
Authors: Kraidenov V. F. , Itskevich E. S. , Kotov N. M.
Published: January 2025

Temperatures dependences of thermoelectric power α and electrical conductivity σ of YBa2Cu3Ox ceramics with x = 6.4, 6.6, and 6.9 are investigated at 50–300 K under hydrostatic pressure up to 12 kbar. The thermoelectric power is positive for all studied values of T, x and P. A. peak is observed on the α(T) curve in the region 100–160 K. It is found that the effect of pressure on the peak is the same as an increase in the oxygen content x: the peak is reduced and shifted towards lower temperatures; d ln αm/dP = –(1–3) · 10−5 bar−1, d ln Tm/P = −1 · 10−5 bar−1.
Effect of pressure on energy spectrum parameters of antimony
Authors: Broide E. L. , Ponomarev Ya. G.
Published: January 2025

The partial chemical potentials for electrons (εFL) and holes (εFH) in antimony are measured in the pressure interval 1 bar ≤ p ≤ 10 kbar at two temperatures T = 100 and 300 K by using pressure dependences of the tensor components of the differential thermo-emf. The calculations are made by using the Lax model with the scattering parameter r = 1/2. Calculations show that the band overlapping for antimony under pressure increases considerably.
Magnetic properties of GdZnxCu1–x compounds in the ferromagnet–antiferromagnet phase transition region
Authors: Kourov N. I. , Tsiovkin Yu. N. , Mydlars T.
Published: January 2025

The field and temperature dependences of magnetization of intermetallic compounds GdZnx Cu1–x are investigated in the temperature range 4.2 K ≤ T < 300 K at H ≲ 107 A/m. The concentration dependences of the susceptibility of a “paraprocess” and of spontaneous magnetization are investigated in the region of phase transition between GdZn ferromagnet and GdCu antiferromagnet. The peculiarities of the magnetic properties of compounds are considered in the transition concentration region.
Vibrational spectrum of a quasi-one-dimensional crystal with weakly bound interstitial atoms
Authors: Ivanov M. A. , Skripnik Yu. V.
Published: January 2025

The rearrangement of flexural and inflexural vibrational spectra of a quasi-one-dimensional crystal with increasing concentration of interstitial impurity centers leading to the emergence of low-frequency states is considered. It is shown that in spite of a variety of parameters characterizing impurity centers (their mass and force interaction with the host crystal), there are only two basic types of rearrangement, viz., normal and anomalous. The main parameters of both types of rearrangement are determined as well as ther egion of existence of phonon-like states. The dependence of the impurity–host interaction parameter on the direction of the wave vector is found to affect the behavior of the emerging peculiarities.
On the behavior of “Ising” magnets in a transverse field
Authors: Ostrovskii V. S.
Published: January 2025

The behavior of real, highly anisotropic easy-axis (“Ising”) magnets in a transverse field generally differs qualitatively from the mode predicted on the basis of the two-level Ising model and is determined by the total number of states and by the symmetry of ions as well as the relation between anisotropy and exchange parameters and the value of the external field.
Magnetic structure and high-frequency properties of the quasi-one-dimensional magnet CsCuCl3
Authors: Alistratov A. L. , Stefanovskii E. P. , Yablonskii D. A.
Published: January 2025

An SS-type incommensurate magnetic phase of exchange-relativistic origin is studied theoretically. The phase is realized in the multisublattice hexagonal quasi-one-dimensional system CsCuCl3 and is formed by long-periodic modulations of the triangular antiferromagnetic structure. The magnetic phase transition to the ferromagnetic state in an external magnetic field and the spin dynamics of the system in the two magnetic phases are investigated.
Field dependences of differential magnetic susceptibility of an easy-axis ferromagnet in a tilted field
Authors: Bogdanov A. N. , Granovskii I. Ya.
Published: January 2025

It is shown that the magnetic susceptibility of an easy-axis ferromagnetic plate in a tilted field has typical peculiarities of the type of maxima and minima in the region of homogeneous state adjoining the region of existence of domain structure. The evolution of these peculiarities with a change in the magnetic field is investigated and the extrema lines of the χxx and χxz components are obtained. Such an analysis makes it possible to determine the characteristic parameters of magnet, such as the saturation magnetization, anisotropy field, and the angle of deviation of the easy axis from the normal to the surface, from the position and magnitude of susceptibility singularities as well as from the asymptotes of the extrema lines of the χxx and χxz components.
Nuclear spin–lattice relaxation through paramagnetic ions at ultralow temperatures
Authors: Sabirov R. Kh.
Published: January 2025

Nuclear relaxation in crystals with a magnetic impurity is analyzed theoretically for the case when the coupled spin–phonon vibrational modes play an important role. The obtained results are compared with the available theoretical data.
On nonlinear scattering of light in superfluid solutions
Authors: Pushkina N. I.
Published: January 2025

The induced scattering of light by isobaric concentration fluctuations and the second sound in superfluid 3He–4He solutions is considered. The possibility of the experimental observation of scattering is discussed.
Superconductivity and plasticity of Al–Li alloys near 1 K
Authors: Isaev N. V. , Fomenko V. S. , Shumilin S. É. , Kolobnev N. I. , Pustovalov V. V. , Fridlyander I. N.
Published: January 2025

Superconductivity has been detected in Al–Li alloys. The critical parameters of the superconductors are determined, and the sensitivity of the flow stress to the electron state of the sample is investigated in the temperature range from Tc to 0.5 K.
Hall emf under acousto-electronic nonlinearity in bismuth
Authors: Bengus S. V. , Bogod Yu. A. , Finkel’ P. E.
Published: January 2025

The Hall emf of a bismuth sample with a nonuniform current density distribution is measured under the conditions of acousto-electronic nonlinearity. The magnetic field range was 20–140 kOe at T = 4.2 K. The experimental results are explained by the contribution of drag effects and of phonon–phonon interaction to the quantity being measured.
Influence of pressure up to 2.0 GPa on magnetic ordering in the system GdBa2Cu3O7–δ (δ ∼ 1)
Authors: D’yakonov V. P. , Levchenko G. G. , Markovich V. I. , Oleinik A. V. , Polyakov P. I. , Fita I. M.
Published: January 2025

The influence of a high hydrostatic pressure (up to 2.0 GPa) on the Néel temperature and the H–T phase diagram of GdBa2Cu3O7–δ) (δ ∼ 1) is studied. The value of TN is found to increase with pressure at the rate dTN/dP = 0.1 K/GPa. It is shown that the spin–flop transition field Hc1(0) is practically independent of pressure, while the spin–flip transition field Hc2(0) increases by 2.5 kOe at P = 2.0 GPa as compared to its value at P = 0. This increase is attributed to an increase in the exchange field and a decrease in the anisotropy field under a uniform compression.
Magnetic symmetry and spin dynamics of exchange-noncollinear antiferromagnets with a CsNiCl3 structure
Authors: Vitebskii I. M. , Sobolev V. L. , Chabanov A. A.
Published: January 2025

A symmetry analysis is carried out for triangular antiferromagnetic structures realized in hexagonal crystals with a CsNiCl3 structure. The ground states and the spin dynamics are considered. The role of magnetoelastic interactions and hexagonal anisotropy in the activation of acoustic magnon branches is determined.
Local modes of hydrogen atoms in V3Si
Authors: Ivanitskii P. G. , Pan V. M. , Slisenko V. I. , Morozovskii A. E. , Vasil’kevich A. A. , Kobzenko G. F. , Krotenko V. T. , Shkola A. A.
Published: January 2025

The inelastic scattering of slow neutrons is used to obtain the density of phonon states of the compounds V3Si and V3Si–H. A peak in the energy region of 1.5 meV is observed. The phonon parts of the specific heat of these compounds are calculated and compared with the experimental data.
Effect of electron state hybridization on the critical temperature of oxide superconductors
Authors: Moskalenko V. A. , Dogotar’ L. A. , Vladimir M. I.
Published: January 2025

The effect of the hybridization of p- and d-states on the critical temperature Tc of oxide superconductors is studied. A generalized canonical Bogolyubov transformation of electron operators is proposed for the Anderson periodic model. The equation for Tc is obtained as a function of the hybridization gap V, the renormalized energy ε of the localized state in the paramagnetic assumption and the energy bandwidth ωD which is quite significant for the superconductivity. The critical value of Vc for which Tc = 0 is determined.
Energy saving of residential buildings using simultaneous application of DSF, PCM, and PV cells
Authors: Pouran Mahdi , Fazelpour Farivar , Gharehpetian G. B. , Saraei Alireza
Published: January 2025

Recent research studies have shown the advantages of using double-skin façade (DSF) and phase change material (PCM) in reducing the amount of building heat, especially for tropical and subtropical climates. Also, by adding photovoltaic (PV) cells in the facade of buildings, the solar heat of the building can be reduced and the electricity generated can lower the energy cost of the building. Since there is a strong interdependence among the energy performance of DSF, PV, and PCM as well as weather conditions, geography, and building orientation, in this paper, their simultaneous energy performance is studied under different climatic conditions of Iran. Also, all the cases are compared from an economic point of view. Based on the results obtained in this research, it can be concluded that the implementation of DSF and integration of PCM with it in the Mediterranean climate, the cold semi-arid climate, and the warm semi-arid climate of Iran is technically possible and offers the benefits of energy saving by changing the quality of spaces by using daylight as well as controlling the solar system, natural ventilation, sound insulation, and thermal insulation in winter and summer.
Demonstration of space-time wave packet carrying orbital angular momentum across scattering media
Authors: Diouf Mbaye , Toussaint Kimani C.
Published: January 2025

In this article, we experimentally generate a vortex space-time (ST) wave packet carrying orbital angular momentum (OAM) and confirm that the OAM of the beam survives after propagating either in the presence of a line obstruction or across a thin scattering medium. A comparison of our findings with both Bessel and standard Gaussian beams carrying OAM reveals that ST-OAM wave packets exhibit a significantly higher mean Pearson’s correlation coefficient compared to these other beams. In addition, we employ a standard 3-mm thick glass microscope slide as a waveguide and find that the OAM belonging to ST wave packets remains protected after propagation. Our findings have potential utility in communication applications, sensing, imaging, and optical trapping.
Brillouin–Mandelstam scattering in telecommunications optical fiber at millikelvin temperatures
Authors: Cryer-Jenkins E. A. , Leung A. C. , Rathee H. , Tan A. K. C. , Major K. D. , Vanner M. R.
Published: January 2025

Brillouin–Mandelstam scattering is a strong and readily accessible optical nonlinearity, enabling a wide array of applications and research directions. For instance, the three-wave mixing process has been employed to great success in narrow-linewidth lasers, sensing applications, microscopy, and signal processing. While most of these avenues focus on room temperature operation, there is now increasing interest in cryogenic operation owing to the scattering mechanism’s significant potential for applications and fundamental physics at low temperatures. Here, we measure the Brillouin scattering spectrum in standard single-mode telecommunication optical fibers at millikelvin temperatures using a closed-cycle dilution refrigerator and optical heterodyne detection. Our experiments are performed with a cryostat temperature from 50 mK to 27 K, extending previously reported measurements that utilized liquid helium-4 cryostats with temperatures greater than 1 K. At millikelvin temperatures, our experiment observes coherent acoustic interactions with microscopic defects in the amorphous material—two-level-systems (TLSs)—which has not been previously observed in optical fibers. The measured behavior of the linewidth with temperature is in agreement with the well-established models of ultrasonic attenuation in amorphous materials comprising a background intrinsic scattering, thermally activated scattering, and incoherent and coherent TLS interactions. This work provides a foundation for a wide range of applications and further research, including sensing applications, new approaches to investigate TLS physics, and Brillouin-scattering-based quantum science and technology.
Art promotes exploration of negative content
Authors: Ozbay Yagmur , Stamkou Eftychia , Oosterwijk Suzanne
Published: January 2025

Experiencing negative content through art has a unique power to transform our perceptions and foster engagement. While this idea has been widely discussed, empirical evidence is scarce, since experimental testing of art experiences poses significant challenges. Here, we aimed to fill this gap by quantifying and comparing individuals’ preference for engaging with art and nonart depicting matched negative content via two behavioral measures: the choice to engage vs. avoid and the duration of engagement. Across five studies (total
N
= 1,063), results revealed a preference for engaging with negative content through art as compared to nonart. Specifically, people more frequently chose to view negative art images, and looked at them for longer, as compared to photographs of similar content. To understand what underlies this preference for art, we examined the psychological impact of engaging with negative content through art and nonart depictions. Results showed that art experiences evoked higher aesthetic appreciation, while nonart gave the viewer a more realistic perspective and was emotionally more costly to engage with. Further, our analysis of engagement motives revealed that individuals were driven by expectations of aesthetic appreciation, thought-provocativeness, and an original perspective, both in art and nonart, while they were discouraged by emotional costs, even more strongly when engaging with nonart. These findings align with the idea of aesthetic distance, where art, as an abstraction of reality, facilitates exploration of negative content with less emotional costs and the prospect of aesthetic rewards.
When one nucleus is not enough: Intestinal polyploidy fuels healthier progeny in C. elegans
Authors: Sivaramakrishnan Priya
Published: January 2025

In this issue, Lessenger and colleagues (https://doi.org/10.1083/jcb.202403154) investigate why certain differentiated tissues require extremely high DNA content. Using the nematode worm Caenorhabditis elegans, they show that restricting genome copies in intestinal cells triggers compensatory gene expression adaptations, which maintain organismal fitness at the expense of offspring vitality.
Observation of Superconducting Pair Density Modulation within Lattice Unit Cell
Authors: Wei 魏 Tianheng 天恒 , Liu 刘 Yanzhao 彦昭 , Ren 任 Wei 伟 , Liang 梁 Zhen 振 , Wang 汪 Ziqiang 自强 , Wang 王 Jian 健
Published: January 2025

In unconventional high-temperature (high-T
c) superconductors, the pair density wave state, an exotic superconducting order showing spatially periodic order parameter modulations with the period of several unit cells and translational symmetry breaking, has attracted broad attention. However, the superconducting pair density modulation (PDM) within a single unit cell has never been carefully investigated before. Here, using scanning tunneling microscopy/spectroscopy, we report the observation of PDM in monolayer high-T
c iron chalcogenide films epitaxially grown on SrTiO3(001). The superconductivity modulations are characterized by the superconducting gap size and the coherence peak sharpness. Further analysis shows that the local maxima and minima in the superconducting gap modulation are centered at the crystallographic locations of the chalcogen atoms, revealing the breaking of the glide-mirror symmetry of the chalcogen atoms in monolayer high-T
c iron chalcogenide films grown on SrTiO3(001). Our findings provide precise microscopic information on superconductivity within the lattice unit cell and may promote the understanding of unconventional high-T
c superconductivity.
Underwater acoustic target signal enhancement algorithm optimized by feature preservation and noise update
Authors: Qu Jianyue , Li Dawei , Liu Xianzhong , Sun Mingming
Published: January 2025

With the development of shock absorption and noise reduction technology, it is difficult to use existing aquatic target feature extraction techniques to extract weak signal features from complex marine environments. Therefore, underwater acoustic signal enhancement has become more important. The overlapping characteristics of underwater acoustic target signals and the variability of the ocean acoustic field make the application of Non-negative Matrix Factorization (NMF) in enhancing underwater acoustic target signals ineffective. To this end, the classic NMF algorithm is adaptively improved by combining the characteristics of underwater acoustic target signals, and an improved NMF underwater acoustic signal enhancement algorithm based on feature preservation is proposed. The algorithm first applies divergence constraints and similarity detection to the NMF feature base matrix to eliminate redundancy, optimizing the NMF features with size invariant characteristics while avoiding coefficient dispersion caused by base vector similarity and resulting in base vector loss. Then, the real-time environmental noise received by sonar is used to improve the adaptability of NMF noise basis vectors, achieving noise reduction and enhancement of underwater acoustic target signals. The experimental results show that compared with classical NMF, manifold-constrained NMF, and other algorithms applied to underwater acoustic target signal enhancement, the method proposed in this paper achieves a better signal enhancement effect.
Directional analysis of aerodynamic noise sources of a high-speed maglev train head based on frequency characteristics
Authors: Liang Yiwen , Huang Jingyu , Zhang Ziyang , Zhang Xinqi
Published: January 2025

The rising speeds of maglev trains have led to increasing concerns regarding aerodynamic noise, which impacts passenger comfort and environmental quality. To investigate the aerodynamic noise characteristics of the front of a high-speed maglev train, the TR08 maglev train is analyzed using Delayed Detached Eddy Simulation (DDES) and the k-epsilon turbulence model to compute the transient flow field around the train. An acoustic finite element-infinite element model is constructed based on Lighthill’s acoustic analogy, focusing on major noise source regions, for numerical calculations of sound propagation and directional analysis of noise. The study reveals that noise directionality is significantly frequency-dependent: low-frequency noise exhibits strong directionality, concentrated at specific angles, while high-frequency noise tends to be isotropic. As the distance from the nose increases, noise directionality broadens, with high-frequency noise becoming significantly omnidirectional in the far field.
The engineering modification of a double-wall plate sound insulation algorithm
Authors: Huang Yikang , Ma Yuchao , Sun Fugui , Qi Wen
Published: January 2025

This paper introduces the impedance analysis method to theoretically refine the conventional sound insulation theory of double-wall plates. It proposes an enhanced model for calculating sound insulation performance, focusing specifically on double-wall aluminum plates as the research object to measure the STL. The results indicate that the improved model significantly enhances the accuracy of sound insulation predictions across various frequency bands, and more accurately represents the actual sound insulation performance, which lays a foundation for the optimized design of future double-wall sound insulation systems.
Numerical study of the flow noise generated by an underwater vehicle with appendages
Authors: Wu Jiafeng , Xu Ziqi , Li Qiaojiao , Wei Wei
Published: January 2025

The appendages of underwater vehicles, such as the stern, are a primary source of flow noise. In the present study, we investigate an underwater vehicle model and analyze the effects of cross-shaped and X-shaped sterns on flow noise using numerical simulation methods. The results indicate that the underwater vehicle with an X-shaped stern exhibits lower resistance and sound pressure levels compared to one with a cross-shaped stern.
Flow characteristics and phase transition analysis of a supercritical carbon dioxide centrifugal compressor
Authors: Hong Shuli , Wang Zetao , Zhang Junyu
Published: January 2025

Micro centrifugal compressors are a key component of the Brayton cycle system with supercritical carbon dioxide (S-CO2) as the working medium in which the system can achieve a higher efficiency cycle. A typical micro centrifugal compressor is investigated. Then, the numerical simulations are performed for two working media; the S-CO2 and air. The results of the 3D flow simulation show that the fluid in the S-CO2 compressor can be divided into three zones: the supercritical zone, the liquid region, and the gas-liquid mixing zone. Research shows that the mechanism of phase transition occurrence is as follows. The larger inertia force of S-CO2 results in a flow separation from the leading edge of the compressor’s suction side, and generates additional centrifugal-effect in such separation zone; this then makes an oblique vortex structure at the suction side of the S-CO2 compressor, because of the higher density of S-CO2. The oblique vortex structure forms a special area with low pressure at the leading edge of the acceleration section, ensuring that the S-CO2 property transfers are sharply leading to the occurrence of a phase transition. Such results show that a special S-CO2 compressor design is necessary to overcome the phase transition problem.
Thermodynamic performance simulation analysis of 2.0T gasoline engine based on GT power
Authors: Zhao Hongxia , Zhu Qingsong , Li Huanhuan , Xing Xiangpeng
Published: January 2025

According to the requirements of the new project development, this analysis applied GT power software to establish a thermodynamic simulation analysis model for a 2.0T direct injection turbocharged inter-cooled gasoline engine with an exhaust cam of 8 mm lift. The input of the calculation model was calibrated based on benchmark prototype test data, and the thermodynamic performance indicators of the external characteristics were simulated and calculated at various operating points. The feasibility of the development goals and related performance and structural design parameters were evaluated, focusing on optimizing the turbocharger matching and valve timing at various operating points of the external characteristics. Main characteristic parameters: rated inlet air flow rate of 650 kg/h, inlet system pressure drop <8 kPa, intercooler pressure drop <15 kPa, and exhaust system pressure drop <60 kPa. Three computational simulation schemes are adopted. The results show that Scheme One is the best, Scheme Two can meet the requirements of the development goals, and Scheme Three has poor performance at low speeds and cannot meet the development goals. By optimizing the phase, a good charging coefficient can be achieved, and the residual exhaust gas in the cylinder is within a reasonable range. The valve timing can meet the performance requirements of the entire machine. The next step is to comprehensively consider factors such as power performance, economy, and residual exhaust gas for more reasonable phase optimization.
Numerical simulation of the vacuum casting process of solid propellants
Authors: Gao Zhe , Wei Ming , Li Wensen , Chen Cunzhuang , Li Changle , Zhao Jie
Published: January 2025

Solid propellant is one of the main components of rocket engines, and the casting of low-viscosity propellant slurry usually uses a vacuum casting process. During the vacuum casting process, the rheological properties of solid propellant slurry are complex, and the theoretical analytical method cannot intuitively and accurately analyze its flow characteristics. Therefore, this paper numerically simulates the casting process through simulation software, uses the Herschel-Bulkley model to characterize the changes in the flow characteristics of solid propellant slurry during the vacuum casting process, and studies the effects of different hopper angles and anti-break vacuum plug shapes on the slurry’s rheological properties. By analyzing parameters such as slurry mass flow rate, velocity, residual amount in the hopper, and surface pressure of the plug, the appropriate hopper angle and the bottom edge angle of the anti-break vacuum plug are selected. Finally, the slurry leveling characteristics under suitable hopper and plug conditions are analyzed. The results indicate that a hopper angle of 140° and an anti-break vacuum plug bottom angle of 120° are optimal. The entire vacuum casting process takes approximately 42 seconds, and the overall slurry leveling is good. As the casting progresses, the slurry gradually compacts and levels out, and the bubbles at the bottom of both sides of the combustion chamber gradually disappear.