Newsfeeds

Journal of Physics D: Applied Physics - latest papers

Latest articles for Journal of Physics D: Applied Physics

IOPscience

  • Roadmap on metamaterial theory, modelling and design
    This Roadmap surveys the diversity of different approaches for characterising, modelling and designing metamaterials. It contains articles covering the wide range of physical settings in which metamaterials have been realised, from acoustics and electromagnetics to water waves and mechanical systems. In doing so, we highlight synergies between the many different physical domains and identify commonality between the main challenges. The articles also survey a variety of different strategies and philosophies, from analytic methods such as classical homogenisation to numerical optimisation and data-driven approaches. We highlight how the challenging and many-degree-of-freedom nature of metamaterial design problems call for techniques to be used in partnership, such that physical modelling and intuition can be combined with the computational might of modern optimisation and machine learning to facilitate future breakthroughs in the field.

  • Enhanced magneto-dielectric and ferromagnetic properties in Sm and Mn co-doped bismuth ferrite
    This paper discusses the improvement in functional properties of bismuth ferrite (BiFeO3) powder through appropriate co-doping with Samarium (Sm3+) and Manganese (Mn3+). The compounds with x = 0.04, 0.08, 0.12, and 0.16 were synthesized through the solid-state reaction method. Structural crystallography was confirmed by x-ray diffraction techniques involving Williamson–Hall analysis and Rietveld refinement. Scanning electron microscopy showed marked changes in morphology due to the process of co-doping. The dielectric measurements showed excellent compatibility in a wide range of frequency, and magnetic characterization revealed an increase in magnetization up to a maximum of 63.54%. Analysis of ferroelectric showed a significant improvement in polarization at all doping levels. These results thus confirm the efficacy of co-doping BiFeO3 particles with Sm3+ and Mn3+ to enhance dielectric, magnetic, and ferroelectric properties and open new avenues for the development of advanced multifunctional materials.

  • Modeling high-temperature non-equilibrium gasdynamic control by nanosecond pulsed surface dielectric barrier discharge
    The nanosecond pulsed surface dielectric barrier discharge for gasdynamic control in high-temperature non-equilibrium flows is modeled using the multi-species Navier–Stokes equations coupled with self-consistent drift-diffusion equations, encompassing 16 species and 36 reactions. A ‘plasma-to-fluid’ loose coupling strategy is employed, with corresponding spatial and temporal discretization applied. The simulation focuses on a proposed annular dielectric barrier discharge actuator configuration integrated into the outer surface of a simplified semi-sphere experimental model. A nanosecond voltage pulse with a peak voltage of 14 kV and a width of 35 ns is applied to the actuator to control the high-temperature non-equilibrium flow at a Mach number of 15.3. The energy characteristics, temperature distributions and species variations are analyzed, and the pressure perturbation and gasdynamic force evolution are also illustrated. Results indicate that the dominant dissociation and compound reactions produce atomic species and consume molecular and charged species, driven by the rapid temperature rise induced by the discharge. Due to the generation and propagation of the compression wave perturbations, the gasdynamic drag is observed to peak at a 20.5% increase, and an average rise of 3.7% within 200 ns, demonstrating potential applications in gasdynamic deceleration for re-entry vehicles.

  • Ultra-high-speed laser cladding process and properties of copper-based micro-multi-electrodes
    To enhance the ablation resistance of cathodes in high-power arc heaters, this study pioneered an innovative methodology through synergistic integration of ultra-high-speed laser cladding with micro-multi-electrodes technology. Capitalizing on the matched emissivity characteristics between LaB6 and copper matrix, in situ fabrication of arc dielectric coating was achieved on the copper matrix. LaB6 has strong electron emission and tolerance to cation bombardment. It can attract and disperse the arc, forming separated arc spots that reduce electrode erosion. Analysis revealed the influence of laser cladding process parameters and LaB6 particle size on the performance of the coating and the distribution of LaB6, with the coating’s microhardness being evaluated. Subsequently, a discharge ablation test was conducted to assess the cladding coating’s performance. Laser power was systematically set at 5.4 kW and 4.8 kW, with powder feeding rates of 48.4–24.2 g min−1. LaB6 particle sizes were precisely controlled at 1 μm and 48 μm. The results demonstrated that at the laser power of 5.4 kW, powder feeding rate exhibited significant control over coating thickness. A reduction in feeding rate from 48.4 to 24.2 g min−1 resulted in a linear thickness decrease from 2.37 to 1.75 mm; At a powder feed rate of 24.2 g min−1, laser power dominantly controlled LaB6 melting behavior, with a laser power of 5.4 kW, there is a higher quantity of LaB6 precipitate in the coating; The microhardness of the coating ranged from 80.4 to 82.9 HV under varying processing conditions, corresponding to a 60% increase relative to the bare copper matrix. The coating generates separated arc spots during discharge, which contributes to minimizing electrode erosion. Notably, 48 μm LaB6 shows a broader spotted arc spot region and a more obvious arc spot dispersion effect. The reduction in electrode erosion is mainly attributed to the formation of separated arc spots by adding LaB6, which diminishes the heat concentration in the arc spot region.

  • Investigation of miniaturized ultra-wideband circulator based on composite ferrite
    This paper presents the design and implementation of an ultra-wideband ferrite circulator. The main transmission line of the circulator adopts the form of Y junction and quarter-wavelength impedance converter. To extend the lower-frequency operating bandwidth, the design adopts double-Y and single-stub (DYSS) matching technology. DYSS is equivalent to parallel LC resonance and plays the role of reactance compensation. In addition, the composite ferrite (CF) technology is introduced innovatively which broadens the high-frequency working bandwidth effectively. CF effectively improves the magnetic vector distribution in the center of the circulator. Considering the actual magnetization state of ferrite, non-uniform simulation of ferrite is also carried out in this paper. The results of non-uniform simulation are more consistent with the test results. In the operating frequency range of 2.3 GHz–6.5 GHz, the insertion loss is controlled within 0.7 dB, and the return loss and isolation are better than 15 dB. In particular, the circulator has a compact size of 0.37λ0 × 0.37λ0 (λ0 is the free-space wavelength at 4.4 GHz) and an impressive relative bandwidth of 95%, which is rare among its counterparts. This design approach provides a reference for the miniaturization and broadband design of microstrip circulators.