Equivalent Field Research Articles

First Observation of the Complete Rotation Period of the Ultraslowly Rotating Magnetic O Star HD 54879

HD 54879 is the most recently discovered magnetic O-type star. Previous studies ruled out a rotation period shorter than 7 yr, implying that HD 54879 is the second most slowly rotating known magnetic O-type star. We report new high-resolution spectropolarimetric measurements of HD 54879, which confirm that a full stellar rotation cycle has been observed. We derive a stellar rotation period from the longitudinal magnetic field measurements of P=2562−58+63 days (about 7.02 yr). The radial velocity of HD 54879 has been stable over the last decade of observations. We explore equivalent widths and longitudinal magnetic fields calculated from lines of different elements, and conclude the atmosphere of HD 54879 is likely chemically homogeneous, with no strong evidence for chemical stratification or lateral abundance nonuniformities. We present the first detailed magnetic map of the star, with an average surface-magnetic-field strength of 2954 G, and a strength for the dipole component of 3939 G. There is a significant amount of magnetic energy in the quadrupole components of the field (23%). Thus, we find HD 54879 has a strong magnetic field with a significantly complex topology.

Complementing the method of areas of Gaussian characteristic figures for the rapid diagnosis of the technical condition of the low-pressure gas-phase injectors

The Fit for 55 package has significantly reduced CO2 emissions from combustion propulsion sources. Therefore, it is considered important to maintain the efficiency of drive units at the required level. One of the main causes of changes in this area is the failure of the power system. This study focuses on the diagnosis of the gas injector, where the Gauss characteristic figure area method was used. The choice of the method was due to its analytical approach, which is different from the commonly used ones, and its easy interpretation of the results. However, the Gauss method was found to lack sensitivity in certain areas. Hence the proposal to supplement it with a trend line, which is a novelty of the study. The trend line, and in fact its indicators, allowed for improved inference relative to the original Gauss approach. This eliminated the fact of equivalent fields of figures that are rotated or distorted. The trend line indicators accurately identified the position of the characteristic figure and its shape. To confirm the expediency of using the proposed approach, tests were carried out for injectors: brand-new, in-operation, end-of-life and remanufactured, as well as those with artificially simulated deficiencies. The test results and analysis presented in the paper can be useful for further work, but also as a guideline for supplementing existing test stands with the described diagnostic functions. The proposed innovative approach was used for the case of gas injectors, but it is possible to apply it to testing injectors of other fuels.

A Triple-Tunable Dual-Band Metamaterial Absorber Based on Dirac Semimetal and InSb

The dynamically triple-tunable dual-band metamaterial absorber that can be electrically, thermally, and magnetically controlled is proposed in this paper. The absorber is composed of bulk Dirac Semimetal (BDS), SiO2, and InSb layers. The physical absorption mechanism can be analyzed theoretically by the equivalent circuit model (ECM) and electric field intensity distributions at absorption peaks. In the absence of applied magnetic field, based on the bright–bright coupling effect, the average absorption rate of dual-band absorber can reach 99.4% when the Fermi energy of the BDS is 0.13 eV and the temperature of the InSb is 475 K. When the applied magnetic field is along the X axis, the absorption frequencies and rates of dual-band absorber can be electrically tuned by adjusting the BDS Fermi energy and thermally and magnetically controlled by adjusting the InSb temperature and magnetic field. Furthermore, the impacts of parameters in dual-band absorbers and the application prospects of the dual-band absorber model as a refractive index sensor are further discussed. This work provides a theoretical basis for the designs of triple-tunable absorbers and sensors.

Thermal error analytical modeling of gear grinding machine full-closed-loop feed system based on equivalent temperature field

Thermal errors affect the machining quality to a great extent. The basis for error compensation and thermal structure optimization is thermal error modeling. However, existing analytical models encounter challenges in dealing with complex structures, determining boundary conditions and solving the temperature and deformation fields. In this paper, a thermal error analytical model of full-closed-loop feed systems based on equivalent temperature fields (ETF) is established. Firstly, the structural simplification and thermal parameter equivalence method is proposed. The machine components are equivalent to equivalent solid cuboid (ESC) with anisotropy so that the actual complex unsolvable problems are transformed into three-dimensional analytically solvable problems. Considering the ambient temperature variation and other nonhomogeneous influences, the transient ETF model is obtained based on Green’s function method. Secondly, the complex structure problems are separated into simple solvable one-dimensional problems. The functional relationship between measurable temperature and key thermal parameters is established. And the optimal key thermal parameters are solved inversely. Thirdly, the equivalent thermal deformation fields (ETDFs) are calculated by the Rayleigh-Ritz method combined with the obtained ETFs and subsequently corrected with the Gamma Distribution. The thermal positioning error model of the full-closed-loop feed system is established by combining the ETDF of each component with the gear grinding machine structure. Finally, the experiments and simulations are carried out to verify the proposed method. The results show that the proposed method can accurately describe the temperature field, deformation field, and thermal error of machine tools. Compared with the classical data-driven method, it is superior in prediction accuracy and robustness.

A speed limit on tachyon fields from cosmological and fine-structure data

The rolling tachyon is a non-canonical scalar field model well motivated in string theory which naturally predicts variations of the fine-structure constant. Such variations can in principle lead to interesting observable consequences, but they can also lead to extremely tight constraints on these kinds of models. In this work we subject the rolling tachyon model evolving in a variety of potentials to current data and show that most cosmologically interesting evolutions are already strongly excluded. We find |1 + w 0| < 10-3 from cosmological data and |1 + w 0| < 10-9 from fine-structure data, leaving the rolling tachyon to either play a role almost entirely equivalent to a cosmological constant or that of a test field. We also find that in most of the allowed parameter space the field evolves very slowly, allowing its evolution to be approximated as an equivalent canonical scalar field.

Molecular dynamics of deformation and fragmentation processes in liquid droplets under pulsed electric field

The deformation and breakup of droplets are widely observed in various aspects of production and daily life. Using molecular dynamics simulations, this study primarily investigated the deformation and breakup of droplets in a nitrogen environment under pulsed electric fields of different frequencies. The results indicate that the droplet deformation undergoes periodic changes under the influence of the pulsed electric field. At equivalent electric field strengths, droplets are more likely to break under a 6.25 GHz pulsed electric field compared to a 25 GHz pulsed electric field, where droplet deformation remains stable without breaking. At every frequency, the bond energy of water molecules consistently decreases. The solvent-accessible surface area changes with the electric field at 6.25 GHz. Furthermore, the minimum value of hydrogen bond quantity reached under high-frequency pulsed fields is higher than that under low-frequency fields. The change in hydrogen bond quantity is inversely proportional to the solvent-accessible surface area. These findings provide insights into the microscopic mechanisms of droplet deformation and breakup, offering a reference for future studies.

Temperature tunable broadband filter based on hybridized vanadium dioxide (VO2) metasurface

Abstract In this paper, a novel temperature tunable terahertz (THz) broadband filter based on hybridized vanadium dioxide (VO2) metasurface (MS) was proposed. The designed MS is composed of subwavelength metallic square-grid structure situated between two layers of metallic square-patch structure integrated with VO2 film pad spaced with two layers of dielectric substrate. Utilizing the insulator-metal phase transition characterizations of VO2 in the THz regime, the operation mode of the proposed MS filter accomplishes the broadband transmission-to-reflection transition. Simulation results show that when VO2 is in the insulating state with a lower external temperature, the proposed MS behaves like a broadband filter with transparent window and a transmittance of above 80% over the frequency range of 0.66–1.12 THz. However, when VO2 undergoes the metallic state with a higher external temperature, the MS becomes a broadband filter with low-transmission shielding and exhibiting a transmittance of below 10% across the frequency spectrum from 0.56 THz to 1.4 THz. The physical mechanism of the proposed MS based tunable broadband filter is illustrated by introducing impedance matching theory, equivalent circuit model and field analysis. In addition, the proposed MS structure offers exceptional angular stability and polarization insensitivity, opening up new opportunities for the utilization of energy selective surface in THz applications.

An Ultrasensitive Programmable 2D Photoelectric Synaptic Transistor

AbstractThe burgeoning advancement of information technology has engendered a discernible surge in the examination of neuromorphic devices, notably drawing broader attention to artificial vision systems endowed with sensory recognition capabilities. Current photoelectric synapse devices employed in artificial vision systems are generally well‐suited for well‐illuminated conditions, yet exhibit diminished sensitivity in weak‐light scenarios, resulting in a pronounced deterioration of recognition accuracy. Here, an ultrasensitive photoelectric synaptic transistor based on negative quantum capacitance effect resulted from the 2D semi‐metallic graphene layer that partially enclosed within the gate dielectric layer, which manifests a noteworthy reduction in device control voltage and exhibits perception and storage capabilities for weak light of 39.4 nW cm−2 with detectivity above 1016 cm Hz1/2 W−1 is demonstrated. The voltage amplification effect and the concomitant formation of an equivalent local electrostatic field induced by the negative quantum capacitance effect engenders a robust programmable synaptic plasticity for extremely weak light by modifying the control gate. These results represent the inaugural integration of the negative quantum capacitance effect into optoelectronic devices and furnish a robust hardware foundation for developing vision systems in weak‐light environments.

Multifractal Characteristics of Gain Structures: A Universal Law of Polycrystalline Strain-Hardening Behaviors

The quantitative relationship between material microstructures, such as grain distributions, and the nonlinear strain-hardening behaviors of polycrystalline metals has not yet been completely understood. This study finds that the grain correlation dimension of polycrystals D is universally equal to the reciprocal of the strain-hardening exponent by experimental research and fractal geometry analysis. From a geometric perspective, the correlation dimension of grains is consistent with that of the equivalent plastic strain field, which represents the correlation dimension of the material manifold. According to the definition of the Hausdorff measure and Ludwik constitutive model, the strain-hardening exponent represents the exponent derived from the Dth root of the measure relationship. This universal law indicates that the strain-hardening behaviors are fractal geometrized and that the strain-hardening exponent represents a geometrical parameter reflecting the multifractal characteristics of grain structures. This conclusion can enhance the comprehension of the relationship between microstructure and mechanical properties of materials and highlights the importance of designing materials with non-uniform grain distributions to achieve desired hardening properties.

INVESTIGATION INTO THE THERMAL DEFORMATION BEHAVIOR AND THE ESTABLISHMENT OF A CONSTITUTIVE RELATIONSHIP FOR Mn-Cr-Ni-Mo STEEL

Isothermal compression tests were conducted on Mn-Cr-Ni-Mo steel at temperatures ranging from 1173 K to 1473 K and strain rates from 0.01 s–1 to 10 s–1 using a Gleeble-3800 thermal simulation tester. Four constitutive models for Mn-Cr-Ni-Mo steel, namely the Arrhenius model, Fields-Backofen model (F-B), original Johnson-Cook model (J-C), and the improved Johnson-Cook model (mJ-C) were established. A correlation coefficient (R) and the average absolute relative error (AARE) were employed to evaluate the predictive capability of these four models. Among them, the Arrhenius model exhibited superior accuracy in predicting the behavior of Mn-Cr-Ni-Mo steel. It and the isothermal thermal compression finite-element model were imported into Deform-3D software for a numerical simulation, aiming to analyze the distribution law of the equivalent stress field. A comparison was made between the time-stress data obtained from numerical simulation under different conditions and that from the isothermal compression tests. The results demonstrate good agreement between the time-stress curves of the numerical simulation and the experimental measurements, indicating that the established Arrhenius model can effectively simulate the thermal deformation of Mn-Cr-Ni-Mo steel. These research findings provide valuable fundamental data for simulating the plastic-deformation process of Mn-Cr-Ni-Mo steel.

Terahertz magneto-optical sampling in quartz glass.

In this Letter, we demonstrate terahertz (THz) magnetic field detection in fused silica with sensitivity that can be easily controlled by sample tilting (for both amplitude and polarization). The proposed technique remains in the linear regime at magnetic fields exceeding 0.3 T (0.9 MV/cm of equivalent electric field) and allows the use of low-cost amorphous materials. Furthermore, the demonstrated effects should be present in a wide variety of materials used as substrates in different THz-pump laser-probe experiments and need to be considered in order to disentangle different contributions to the measured signals.

High-speed machining simulation of Ti6Al4V using a thermo-mechanical coupling model and velocity-dependent friction model

PurposeThis study aims to establish a thermally coupled two-dimensional orthogonal cutting model to further improve the modeling process for systematic evaluation of material damage, stiffness degradation, equivalent plastic strain and other material properties, along with cutting temperature distribution and cutting forces. This enhances modeling efficiency and accuracy.Design/methodology/approachA two-dimensional orthogonal cutting thermo-mechanical coupled finite element model is established in this study. The tanh material constitutive model is used to simulate the mechanical properties of the material. Velocity-dependent friction model between the workpiece and the tool is considered. Material characteristics such as material damage, stiffness degradation, equivalent plastic strain and temperature field during cutting are evaluated through computation. Contact pressure and shear stress on the tool surface are extracted for friction analysis.FindingsSpeed-dependent friction models predict cutting force errors as low as 8.6%. The prediction errors of various friction models increase with increasing cutting forces and depths of cut, and simulation results tend to be higher than experimental data.Social implicationsThe current research results provide insights into understanding and controlling tool-chip friction in metal cutting, offering practical recommendations for friction modeling and machining simulation work.Originality/valueThe originality of this research is guaranteed, as it has not been previously published in any journal or publication.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0162/

Heterogeneous spatial tuning in the auditory pathway of the Mongolian Gerbil (Meriones unguiculatus).

Sound-source localization is based on spatial cues arising due to interactions of sound waves with the torso, head and ears. Here, we evaluated neural responses to free-field sound sources in the central nucleus of the inferior colliculus (CIC), the medial geniculate body (MGB) and the primary auditory cortex (A1) of Mongolian gerbils. Using silicon probes we recorded from anaesthetized gerbils positioned in the centre of a sound-attenuating, anechoic chamber. We measured rate-azimuth functions (RAFs) with broad-band noise of varying levels presented from loudspeakers spanning 210° in azimuth and characterized RAFs by calculating spatial centroids, Equivalent Rectangular Receptive Fields (ERRFs), steepest slope locations and spatial-separation thresholds. To compare neuronal responses with behavioural discrimination thresholds from the literature we performed a neurometric analysis based on signal-detection theory. All structures demonstrated heterogeneous spatial tuning with a clear dominance of contralateral tuning. However, the relative amount of contralateral tuning decreased from the CIC to A1. In all three structures spatial tuning broadened with increasing sound-level. This effect was strongest in CIC and weakest in A1. Neurometric spatial-separation thresholds compared well with behavioural discrimination thresholds for locations directly in front of the animal. Our findings contrast with those reported for another rodent, the rat, which exhibits homogenous and sharply delimited contralateral spatial tuning. Spatial tuning in gerbils resembles more closely the tuning reported in A1 of cats, ferrets and non-human primates. Interestingly, gerbils, in contrast to rats, share good low-frequency hearing with carnivores and non-human primates, which may account for the observed spatial tuning properties.

Magnetic resonance behavior modulation of Ba3Co1.6−xZnxCu0.4Fe24O41 hexaferrites for microwave absorption and surface wave suppression

The intrinsic high magnetocrystalline anisotropy equivalent field can help the hexaferrites break through Snoek's limit and increase the resonance frequency. This is advantageous for microwave absorption applications in the mid to low-frequency range of gigahertz. In this study, we prepared Z-type Ba3Co1.6−xZnxCu0.4Fe24O41 hexaferrites using the sol-gel auto-combustion method. By changing the ratio of Co and Zn ions, the magnetocrystalline anisotropy of ferrite is further manipulated, resulting in significant changes in their magnetic resonance frequency and intensity. Ba3Zn1.6Cu0.4Fe24O41 with high-frequency resonance achieved the lowest reflectivity of −72.18 dB at 15.56 GHz, while Ba3Co1.5Zn0.1Cu0.4Fe24O41 with stronger loss obtained the widest bandwidth of 4.93 GHz (6.14–11.07). Additionally, we investigated surface wave suppression properties previously overlooked. Ba3Co1.5Zn0.1Cu0.4Fe24O41 can achieve a larger attenuation at low frequency under low thickness, which has an excellent effect on reducing backscattering. This work provides a useful reference for the preparation and application of high-performance magnetic-loss materials.

Development and Application of a Constitutive Equation for 25CrMo4 Steel

The material constitutive equation of 25CrMo4 steel was established through an isothermal compression experiment. First, a thermal compression experiment was carried out with a Gleeble-3500 thermal simulator to study the thermoplastic deformation behaviour of 25CrMo4 steel at various temperatures (850, 950, 1050, and 1150 °C) and strain rates (0.01, 0.1, 1.0, and 10 s−1). The measured true stress–strain curve showed that when the temperature is constant, the flow stress increases with the strain rate, whereas when the strain rate is constant, the flow stress decreases with the temperature. Then, the constitutive model of peak stress of 25CrMo4 was established after analyzing the stress and strain statistics. The model parameters were optimized. The accuracy of the flow stress constitutive model was verified by comparing the flow stress prediction model with the experimental results. The hot forging process of the inner core wheel was numerically simulated based on DEFORM-3D v11 software, and the parameters of this process were formulated by analyzing the metal flow rate and equivalent stress and strain fields.

Field theory equivalences as spans of L∞ -algebras

Semi-classically equivalent field theories are related by a quasi-isomorphism between their underlying L∞ -algebras, but such a quasi-isomorphism is not necessarily a homotopy transfer. We demonstrate that all quasi-isomorphisms can be lifted to spans of L∞ -algebras in which the quasi-isomorphic L∞ -algebras are obtained from a correspondence L∞ -algebra by a homotopy transfer. Our construction is very useful: homotopy transfer is computationally tractable, and physically, it amounts to integrating out fields in a Feynman diagram expansion. Spans of L∞ -algebras allow for a clean definition of quasi-isomorphisms of cyclic L∞ -algebras. Furthermore, they appear naturally in many contexts within physics. As examples, we first consider scalar field theory with interaction vertices blown up in different ways. We then show that (non-Abelian) T-duality can be seen as a span of L∞ -algebras, and we provide full details in the case of the principal chiral model. We also present the relevant span of L∞ -algebras for the Penrose–Ward transform in the context of self-dual Yang–Mills theory and Bogomolny monopoles.

Enhancement of Charge-Discharge Properties and Temperature Stability of (Ba0.975Na0.05)Ti0.99Nb0.01O3 Ceramic by Doping High-Entropy Oxide

A bidirectional optimization strategy was adopted to fabricate (1-x)(Ba0.975Na0.05)Ti0.99Nb0.01O3)-xBi(Zn0.2Mg0.2Al0.2Sn0.2Zr0.2)O3(abbreviated as (1-x)BNNT-xBZMASZ, x = 0.02–0.10) ceramics, aimed to improve the energy storage performance. X-ray diffraction results revealed that Bi2+ cations entered the A site and the multiple cations occupied the B site of BNNT, thereby decreased the remnant polarization intensity and refined the hysteresis loop. Scanning electron microscopy images showed uniform morphologies with clear grain boundaries of the ceramics, and the average size decreased with x increasing. The substitution of multiple cations at the B-site induced the splitting of macroscopic ferroelectric domains into smaller polar nanodomains, leading to the formation of high-dynamic polar nanoregions and accelerating the transition from BNNT to relaxor ferroelectrics, thus improving relaxation properties of the material. The excellent energy storage density (Wrec ∼ 2.80 J cm−3) and efficiency (∼90.0%) can be obtained under 200 kV cm−1. Moreover, the discharge-charge testing revealed excellent current density (∼589.5 A cm−2), high power density (∼20.63 MW cm−2), and extremely short discharge time (t0.9 ∼ 50.4 ns), along with exceptional temperature stability and cycling stability under the equivalent electric field of 120 kV cm−1. The 0.92BNNT-0.08BZMASZ ceramic offers a new approach to the design and an improvement of pulsed dielectric capacitor materials.

On the anisotropic coalescence of elliptic cylindrical voids considering the geometric and distributive properties

The geometric and distributive properties of voids significantly influence anisotropic coalescence behaviour. However, this problem has received little attention owing to the complexity of considering all the properties in the current analytical framework of limit analysis. To address this issue, this study proposes an analytical framework based on an elliptic coordinate system, including the determination of the ligament zone, characterization of plastic flow, and derivation of the void coalescence criterion, for porous materials with various geometric and distributive properties, including size, shape, spacing, and orientation. This framework is motivated by our observations that the evolution of the void geometry and surrounding plastic flow can be well characterized by the grid of the elliptic coordinate system. Subsequently, an analytical function is proposed to determine the ligament zone and coalescence direction with various void properties. A hollow nonaxisymmetric cylindrical unit cell is proposed to describe this ligament zone, and the corresponding trial velocity field is derived by extending the previous Gurson-like velocity field into the elliptic cylindrical coordinate system. The rationality of the field is validated by comparing its equivalent strain rate field with numerical simulations. Finally, a coalescence criterion is derived via the limit analysis of the proposed unit cell undergoing internal necking. Two heuristic adjustments are formulated for the overflow phenomenon in the rigid zone and outer ligament zones. Numerical assessments with various void properties confirm the accuracy of the analytical model. The coalescence criterion can predict the independent and coupling effects of geometric and distributive properties on anisotropic void coalescence. This study provides possible solutions to future plasticity problems of ellipsoidal inclusions.

The Xe isotope nuclear resonance frequency shift of NMR angular velocity sensors due to transverse gradient magnetic fields

The nuclear magnetic resonance (NMR) angular velocity sensor detects angular velocity by measuring the shift in the nuclear spin precession frequency, which is of fundamental interest. Recent studies have revealed the parameter dependency of nuclei frequency shifts induced by non-uniformly distributed polarized pump beams, temperature, and magnetic field properties. In this study, we investigated the effect of the linear transverse gradient magnetic field on the frequency ratio shift of the Xe isotope nuclear resonance frequency in the NMR sensors. A theoretical analysis method was proposed based on the Fermi contact interaction in atomic polarization and the spin-diffusion relaxation of 129Xe and 131Xe nuclei. The frequency ratio shift of the Xe isotope under different x-axis gradient magnetic fields was measured experimentally. Furthermore, we eliminated the equivalent residual magnetic field through a feedback system and compensated for the original gradient magnetic field in the system, which contributed to accurately revealing the frequency shift induced by the magnetic field gradient. The results indicate that the frequency ratio shift of the Xe isotope is proportional to the strength of the second-order linear transverse gradient magnetic field. This study provides a reference for the analysis and evaluation of the presence of the gradient magnetic field in the NMR angular velocity sensor.

Studies on the motion and radiation of interior plasmas in gas-filled hohlraums with different laser entrance hole sizes

An experiment on 100 kJ laser facility is performed to study the motive features and radiation properties of plasmas from different areas inside gas-filled cylindrical hohlraums. These hohlraums are designed to possess one open end and one laser entrance hole (LEH) with different diameters, which would or not result in the blocking of the LEH. An x-ray streak camera that is set at 16 degrees with respect to the hohlraum axis is applied to acquire the time-resolved x-ray images from the open end. Based on the images, we can study the evolutions of the wall plasma, corona bubble plasma and LEH plasma simultaneously through an equivalent view field of hohlraum interior. Multi-group flat response x-ray detectors are applied to measure the x-ray fluxes. In order to understand these characteristics, our two-dimensional radiation hydrodynamic code is used to simulate the experimental results. For the accuracy of reproduction, dielectronic recombination and two parameter corrections are applied in our code. Based on the comparison between experiments and simulations, we quantitatively understand the blocking process of LEH and the motion effects of other plasmas. The calibrated code is beneficial to design the gas-filled hohlraum in a nearby parameter space, especially the limit size of LEH.