Dispersion Characteristics Research Articles

Internal waves and Rayleigh–Taylor instability in magnetized compressible strongly coupled dusty plasmas

This paper investigates the influence of compressibility on the internal wave modes and the density gradient-driven Rayleigh–Taylor (R–T) instability in magnetized strongly coupled dusty plasmas. The dusty magnetohydrodynamic model is formulated for compressible fluids, accounting for the effects of weakly coupled electrons/ions and strongly coupled dust particles under the influence of the gravitational field. The effect of the magnetic field on the dust dynamics has been incorporated through the magnetic force on the electrons and ions in quasineutral dusty plasmas. A dispersion relation of the R–T instability has been derived which has been modified because of the compressibility effect, dust acoustic wave speed and viscoelastic coefficients. The shear Alfvén and compressional viscoelastic wave modes become coupled in the dispersion characteristics. The modified R–T instability criterion is derived in terms of the Alfvén speed, viscoelastic effects and dust grain parameters. The graphical illustrations show that the growth rate of R–T instability has been suppressed due to compressibility, viscoelastic coefficients and dust acoustic speed. The results are useful to discuss the development of R–T instability in magnetized astrophysical dusty plasmas.

Tunable bandgaps of guided waves by periodic shunting circuits in multilayered piezoelectric plates

The multi-mode and dispersion characteristics of guided waves in plate bring great challenges to the manipulation of guided waves and controlling vibration and noise. In this study, the Stroh formalism is developed to establish a theoretical model for deriving the dispersion relations of guided waves in a multilayered piezoelectric plate. The dispersion characteristics under different electrical boundary conditions introduced by periodic shunting circuits are discussed to reveal the influences of external circuits on guided wave propagation. The proper shunting circuit is not only the key point to obtain the specific frequency of bandgap, but also the effective method to control the bandwidth. Furthermore, for the separation of symmetric and anti-symmetric modes of guided waves, the multilayered piezoelectric plate with a mirror plane is studied by using an equivalent model. Results indicate that the propagation behaviors of guided waves in multilayered piezoelectric plates can be interpreted by developed Stroh formalism, and their bandgaps can be effectively manipulated by periodically external circuits. The tunable bandgaps in this work could be helpful for designing smart devices of wave isolation based on multilayered piezoelectric plate.

Spatiotemporal Characterization of the Three-Dimensional Morphology of Urban Buildings Based on Moran’s I

The three-dimensional morphological analysis of urban buildings constitutes a pivotal component of urban planning and sustainable development. Nevertheless, the majority of current research is two-dimensional in nature, which constrains the comprehensive understanding of urban spatial–temporal evolution. The existing body of three-dimensional studies frequently fails to consider the temporal dimension of architectural change and lacks a detailed examination of micro areas such as communities and streets. In order to accurately identify the patterns of spatial–temporal evolution in urban architectural morphology, this study focuses on the Yau Tsim Mong District in Hong Kong, utilizing three-dimensional data. By innovatively integrating temporal factors, constructing a spatial–temporal weight matrix, and applying the spatial–temporal Moran’s I, this study conducts an in-depth quantitative analysis of Coverage, Staggeredness, and Duty Cycle at the community scale, neighborhood scale, and urban scale. From 2014 to 2023, the global spatial–temporal Moran’s I of key urban morphology indicators in Yau Tsim Mong District has exhibited a marked increase, underscoring the close interrelationship and significant optimization between urban morphology and overall development. The findings illustrate that urban architecture is undergoing a process of agglomeration and high homogeneity, with strategic shifts emphasizing efficient spatial utilization and refined design. The analysis at the neighborhood scale is of particular importance, as its independent and complete spatial structure effectively captures local dynamics, revealing high-value agglomeration and low-value dispersion characteristics. This suggests that buildings in the Yau Tsim Mong District are being constructed in a more compact manner at the neighborhood level, which reflects the precision and efficiency of urban planning and the rationality of spatial planning. These significant findings provide valuable references for the development planning and governance of sustainable cities. They enhance urban governance capabilities and promote the optimization of urban development strategies, ensuring steady progress on the path of efficiency, harmony, and sustainability.

Large-scale calcium imaging reveals a systematic V4 map for encoding natural scenes

Biological visual systems have evolved to process natural scenes. A full understanding of visual cortical functions requires a comprehensive characterization of how neuronal populations in each visual area encode natural scenes. Here, we utilized widefield calcium imaging to record V4 cortical response to tens of thousands of natural images in male macaques. Using this large dataset, we developed a deep-learning digital twin of V4 that allowed us to map the natural image preferences of the neural population at 100-µm scale. This detailed map revealed a diverse set of functional domains in V4, each encoding distinct natural image features. We validated these model predictions using additional widefield imaging and single-cell resolution two-photon imaging. Feature attribution analysis revealed that these domains lie along a continuum from preferring spatially localized shape features to preferring spatially dispersed surface features. These results provide insights into the organizing principles that govern natural scene encoding in V4.

Delamination detection in composite pipes using higher harmonic generation of flexural waves

This paper investigates delamination detection in composite pipes using higher harmonic generation technique for the first time. The semi-analytical finite element (SAFE) method is developed to analyze the dispersion characteristics of the composite pipe. Then, a flexural mode at low frequency is selected to detect delamination. The three-dimensional (3D) finite element (FE) model is developed to simulate the flexural mode propagating in the composite pipe and its interaction with delamination. By comparing the simulated radial displacement signals with and without delamination, it is observed that the delamination can contribute to the higher harmonic generation. Subsequently, the ultrasonic measurements are conducted to demonstrate the numerical results. Using a relatively simple piezoelectric transducer (PZT) configuration, an almost pure flexural mode can be excited in the experiment. More importantly, experimental results indicate the higher harmonics induced by the delamination can be observed obviously. Finally, extensive parametric studies are performed to reveal the sensitivity of higher harmonics to the delamination with various sizes and at different interface. The proposed higher harmonic generation of flexural waves is promising for the practical application of delamination detection in composite pipes.

Thickness-modulated electronic band structures and exciton behavior of non-van-der-waals 2D Bi2O2Se films

Bi2O2Se, as a non-van-der-waals (non-vdW) interlayer coupling two-dimensional material, its electronic band structures and exciton behavior still merit further in-depth studies, especially in the consideration of thickness tuning degrees of freedom. Here, we reveal the broadband excitonic performance and critical point properties of Bi2O2Se films with different thicknesses (3.54–16.33 nm). Five critical points are determined and assigned to specific optical transitions. Moreover, we observe that electronic bandstructures in the Γ valley are stable with variable thicknesses, while the deeper electron levels received more pronounced thickness modulation. And we first report four excitons in wide spectral range (1.24–6.20 eV) through absorption coefficient fitting. Significantly, due to the strong localization of electrons and holes induced by the intralayer built-in electric field, the exciton binding energy (Eb) value of 3.54 nm-Bi2O2Se (234 meV at Γ position) is apparently larger than typical multi-layer TMDCs, which offering unprecedented opportunities in applications in optoelectronic devices. Furthermore, Eb of two excitons at low energy region (Eb1, Eb2) red-shift with increasing thickness, while Eb of higher-energy excitons (Eb3, Eb4) blue-shift, owing to the dispersion characteristic of the effect dielectric screening effects. Our results are vital to wide-ranging applications of Bi2O2Se from fundamental science to optoelectronic devices.

In-Plane heterogeneous Structure-Boosted interfacial polarization in graphene for wide-band and wide-temperature microwave absorption

Theoretically, the strong permittivity dispersion characteristic of materials is essential for achieving broadband electromagnetic wave (EMW) absorption, which can be realized via amplified interfacial polarization effects between a dielectric phase and a lossy phase, such as by increasing the accumulated charge density in their interface area. Herein, we propose a novel strategy to boost interfacial polarization based on heterogeneous structure design in in-plane graphene (Gr) since the in-plane conductivity of Gr is significantly higher than its out-of-plane conductivity. To this end, Gr is grown on Si3N4 nanowires skeleton using chemical vapor deposition (CVD). Subsequently, Gr is controllably etched by Ni nanoparticles, and then, open graphite nanosteps are formed, which help construct in-plane heterogeneous interfaces between Gr and a dielectric phase. Such interfaces also help improve the impedance matching performance by disrupting the long-range conductive network of CVD-grown Gr. Notably, an effective absorption bandwidth of 8.48 GHz is achieved with a thickness of 2.85 mm, which is significantly wider than the EAB (5 GHz) of the out-of-plane heterogeneous structure. In addition, the in-plane heterogeneous structure also endows the EMW absorption material with excellent high-temperature insensitivity, realizing full-frequency absorption in the X-band in the 298–873 K range. This strategy to boost interfacial polarization via novel in-plane heterogeneous structure construction in Gr provides an alternative approach to explore the potential of Gr-based hybrids with planified structures to achieve wide-band and wide-temperature EMW absorption.

Simulation on Critical Frequency of Polymer in Electrostrictive Properties

AbstractThe critical frequency and the relaxation time are analyzed through deformation and displacement during electrostriction which is induced by the electrical field at different frequencies. First, when the frequency is 50 Hz and the field strength is 2.5 kV mm−1, the electrostrictive displacement of polyethylene is 6.72 × 10−4 mm. After the data fitting, it is found that the displacement increases linearly with the square of field strength and that the proportional coefficient of 50 Hz is 1.08 × 10−4. Second, due to the influence of relaxation polarization and power loss, with the increase of frequency, the displacement and the proportional coefficient first increases then decreases, and when the frequency is 10 kHz, the displacement of 2.20 × 10−6 mm and the proportional coefficient of 3.51 × 10−7 have minimum values, which are 99.67% and 99.68% lower than that of 50 Hz, respectively. There is the critical frequency. Finally, based on the characteristic of anomalous dispersion, the relaxation time of polyethylene is 9.19 × 10−6s, which is in the time range of thermionic relaxation polarization and consistent with the actual situation. This analysis confirms the quantitative relationship between electrostrictive characteristics, field strength, and polarization. In addition, the relationship between frequency and strain is discussed, and the critical frequency in polymer and the relaxation time are confirmed.

Comparative analysis of bioaerosol emissions: Seasonal dynamics and exposure risks in hospital vs. municipal wastewater treatment systems

Hospital wastewater is known to contain various pathogenic microorganisms and harmful substances. During the hospital wastewater treatment process, the bioaerosols released may encapsulate these pathogens, leading to human infection. This study undertook an investigation to compare the dispersion characteristics and seasonal variations of bioaerosols from hospital and municipal sewage. The results indicated that the airborne bacterial concentration from hospital sewage (119 ± 118 CFU/m3) was higher than municipal sewage (46 ± 19 CFU/m3), with the highest concentration observed in summer. The dominant bacterial genera present in bioaerosols from both sewages were alike, with the proportions varied by sewage types and the structure mainly influenced by seasonal factors. Bacteroides, Escherichia-Shigella and Streptococcus were identified as the most prevalent pathogenic genera in spring, summer and winter bioaerosols, respectively, while Pseudomonas and Acinetobacter were abundant in autumn. Although the non-carcinogenic risk associated with bioaerosols was low (<1), the presence of pathogenic species and their potential synergistic interactions elevated the overall exposure risk. The diffusion modeling results demonstrated that bioaerosol emissions from the surface of hospital sewage can reach up to 10570 CFU/m3 in summer and can spread more than 300 m downwind. The potential pathogenicity of bioaerosols was also highest in summer, which may pose a health hazard to populations located downwind. Therefore, the management and control of bioaerosols from sewage should be strengthened, especially in summer.

A multifunctional inverter power quality coordinated optimization strategy based on comprehensive evaluation

The large-scale integration of renewable energy sources and power electronic devices has led to increasingly dispersed and networked characteristics of power quality disturbances in distribution systems. Traditional control devices, limited by their fixed-point control, no longer meet the development needs of modern distribution systems. Considering the distribution and structural characteristics of the current new-type sources and loads, a multifunctional inverter power quality coordinated control strategy based on comprehensive evaluation is proposed. This strategy aims to achieve power quality coordinated control by utilizing optimal compensation capacity while the grid-connected inverter provides active power output. Firstly, the traditional ipiq power quality detection method is analyzed and improved to enable detection of harmonics, reactive power, and three-phase imbalance currents in single-phase systems or three-phase four-wire systems. Secondly, in the power quality assessment, a balanced algorithm is employed to obtain the comprehensive evaluation index of power quality, thereby improving the deficiencies of single-weight evaluation. Next, to ensure the grid-connected inverter achieves optimal power quality coordinated control with minimal compensation capacity, an optimization compensation function is established between compensation capacity and comprehensive power quality index. This function is optimized using non-dominated sorting genetic algorithm to enhance equipment utilization and system economy. Finally, the feasibility and effectiveness of the proposed method are validated through simulations, demonstrating the achievement of optimal capacity configuration for power quality coordinated control while ensuring active power output by the grid-connected inverter.

Research on the algorithm for optimal selection of detection modes for rail crack detection

In the application of ultrasonic guided wave testing for rail crack detection, it is necessary to select a guided wave mode that is more sensitive to cracks as the detection mode. However, ultrasonic guided waves have multi-mode and dispersive characteristics. In order to extract mode information from complex signals, this paper proposes an optimal detection mode selection method based on the sensitivity of guided wave modes to cracks. This method is different from the traditional method of determining mode types by calculating the mode velocity through the arrival time of wave packets in the time domain signal. Based on the dispersion characteristics and mode features of guided wave modes, this paper establishes a crack sensitivity evaluation index. In a wide frequency band and among numerous modes, the guided wave modes suitable for detecting cracks in different regions of the full cross-section of rails are accurately selected. Experimental results show that the guided wave modes selected by the mode selection method proposed in this paper, based on the crack area energy and crack reflection intensity evaluation indexes, can accurately identify rail cracks, laying a foundation for the research on rail crack detection and localization methods.

Groundwater health risk assessment and its temporal and spatial evolution based on trapezoidal fuzzy number-Monte Carlo stochastic simulation: A case study in western Jilin province

The United States Environmental Protection Agency (USEPA) Four-step-Method (FSM) is a straightforward and extensively utilized tool for evaluating regional health risks, However, the complex and heterogeneous groundwater environment system causes great uncertainty in the assessment process. Triangular stochastic simulation (TSS) possesses certain advantages in solving uncertainty problems, but its inadequacy with discrete data reveals limitations in this aspect. To solve the above problems, this study proposes to construct trapezoidal fuzzy number-Monte Carlo stochastic simulation (TFN-MCSS) to compensate for the shortcomings of the first two methods. This method adopted trapezoidal fuzzy number (TFN) analysis to comprehensively consider the characteristics of a large dispersion of water quality monitoring data and the uncertainty of the human health risk assessment (HHRA) process. Concurrently, to overcome the subjectivity and uncertainty of artificially determining the interval of TFN in traditional methods, the slope was used to select the most probable interval value (TMPIV) of TFN combined with the α-truncated set technique (α-TST) and MCSS. Based on these, a TFN-MCSS was constructed and applied to groundwater HHRA in western Jilin Province. First, the groundwater chemical characteristic determination and water quality evaluation in western Jilin were performed to identify the main pollution indicators, and the health risk effects of pollutants in groundwater of different aquifers at different time periods on adults and children were evaluated using the TFN-MCSS. The uncertainty and sensitivity were analyzed, and the primary risk control indicators were identified and compared to FSM and TSS. The results reveal that TFN-MCSS was more sensitive to data and could reduce the uncertainty of assessment process. It indicated that over a 10-year period, the health risks associated with unconfined groundwater (UW) and confined water (CW) decreased by greater than 52 %. However, the highest total non-carcinogenic risk index (THI) was 1.3-fold higher than the safety threshold, and this posed a health risk.

A Functionally Arranged Phononic Crystal Rod Enabling Ultra-Wideband Vibration Attenuation and Orderly Frequency Distillation

In this study, a functionally arranged phononic crystal rod, incorporating sub-periodic structures featuring distinct lattice constants, is designed. This rod seamlessly combines two distinct capabilities: highly efficient broadband vibration suppression and orderly frequency distillation. In the pursuit of this design, the dispersion characteristics of a periodic rod are first analytically calculated to determine the precise cut-on and cut-off frequencies of the resulting band gaps. Following this, the transmission of longitudinal waves traveling through a finite functionally arranged rod is elucidated. Based on these calculations, careful parameter selection yields a compact configuration for a functionally arranged phononic crystal rod, boasting an exceptionally wide band gap spanning frequencies from 100 Hz to 10,000 Hz. Finite element simulations vividly demonstrate its ultra-broadband vibration attenuation capability, nonsymmetrical wave propagation behavior, and orderly frequency distillation phenomenon. Our study underscores the advantages of employing constituent materials with a higher impedance ratio in obtaining a more compact topological structure while preserving the broadband required for vibration attenuation. This research provides essential insights for tackling the need for broadband vibration suppression in engineering and also sets the stage for achieving orderly frequency extraction and energy localization.

Metal edge confined platinum atoms in metal/hydroxide hierarchy structure for multiple hydrogen conversion and evolution

Single-atom catalysts (SACs), as a thriving subfield of catalysis, have progressed tremendously. However, the contradiction between the isolated dispersion feature of metal sites and the high mass-specific activity of the catalyst inhibits the advances of the SACs. Herein, the Pt atoms are confined at the metallic Co phase edge in two-dimensional Co/Co(OH)2 hierarchy structure (PtSA-Co@Co-Co(OH)2) by the defect inducted order electrodeposition strategy. Both integrations of in-situ/ex-situ experimental characterizations and theoretical calculation reveal that such metal edge confined Pt atoms possess an enlarged atom exposure ratio, high stability, and the like-metal electronic state contributed by metal Co 3d, which enables the Pt atoms with more suitable affinity to simultaneously bind the multiple H atoms for durable H*-H2 conversion and H2 evolution. Moreover, the metallic PtSA-Co collaborated Co/Co(OH)2 interfaces demonstrate a strong H2O dissociation capacity by the preference adsorption of H* on metallic PtSA-Co and OH*on Co/Co(OH)2 interfaces. Combining a further enhancement of constructing the catalysts on an Ag nanowire network to form a seamlessly conductive nanostructure, the PtSA-Co@Co-Co(OH)2 achieves a high mass activity with 5.92 A mg−1 at the overpotential of 100 mV in alkaline condition, 37 times to that of the benchmark Pt/C catalyst and significantly outperforming the reported catalysts. While our work has focused on the hydrogen evolution reaction, this class of metal edge collaborated single-atom catalysts may be conducive to unlock the low mass-specific activity of atomically dispersed catalysts for various processes, such as oxygen evolution reactions (OER), CO2 reduction, and biomass conversion, etc.

Effects of external magnetic field on the reflection and transmission of thermoelastic coupled waves with consideration of fractional order thermoelasticity

Effects of external magnetic field on the dispersion and attenuation feature as well as the reflection and transmission behavior of thermoelastic coupled waves are studied in the paper. The heat conduction behavior at instant heating is modeled by non-Fourier law with the fractional order derivatives. The effects of external magnetic field are incorporated into the motion equation by consideration of the Lorentz force. The dispersion and attenuation feature of the two longitudinal waves and one transversal wave and their reflection and transmission behaviors at interface are studied. The effects of external magnetic field on the dispersion and attenuation and on the reflection and transmission behavior are discussed based on the theoretic formulation and the numerical examples. It is found that the external magnetic field have influences on three kinds of coupled wave while the fractional order heat conduction only has evident influences on the thermal wave.

Waveguide modes of exchange spin waves in epitaxial YIG films

It has been shown that exchange spin wave (ESW) waveguide modes can be excited in epitaxial ferrite films. This is facilitated by the presence of a thin transition layer at the interface between the ferrite film and the non-magnetic substrate. A method for calculating the dispersion and energy characteristics of ESW waveguide modes is proposed. It is shown that the propagation of ESW modes is accompanied by the transfer of exchange power in the plane of the film. As the wave numbers increase indefinitely, the dispersion of the ESW modes asymptotically approaches the quadratic dispersion law. At zero wave numbers, the frequencies of the ESW modes coincide with the frequencies of uniform spin wave resonances. The possibility of crossing the dispersion branches of different ESW modes is demonstrated, which indicates the possibility of intermodal magnon-magnon hybridization.

Velocity And Concentration Measurements Of Supersonic Underexpanded Jets

The release of high-speed gas jets due to a tank leakage can pose a substantial safety hazard, as it can give rise to flammable, explosive, or toxic mixtures. Hence, understanding jet dispersion in real-world conditions is crucial for designing effective safety measures. Existing targeted or traceable studies provide velocity field data, but limitations in source-driven-pressures, nozzle geometries, or cross-flow conditions restrict their representativeness under real conditions. Indeed, an exhaustive experimental dataset for supersonic underexpanded gas jet dispersion under the influence of an Atmospheric Boundary Layer (ABL) is currently lacking. As part of a collaboration with the CEA, the von Karman Institute is continuing research efforts towards the development of high quality nonintrusive, optical measurement techniques for the characterization of the velocity and the concentration of a supersonic underexpanded jet submitted to different cross-flow conditions. The research explicitly targets measurements far from the release point within the self-similar region. Such measurements have already been tried on a supersonic jet without cross-flow and with a uniform velocity low-speed cross-flow [2], but never under the influence of an ABL. By filling this gap, the objective of the present work is to further improve the dispersion characterization by combining different techniques, such as Laser Mie Scattering and Light Extinction Spectroscopy (LES). To evaluate the dispersion within the self-similar region up to x/D ≈ 100, a significant FOV 1 is required. Therefore, Large-Scale Particle Image Velocimetry (LS-PIV) has been adapted and successfully applied to measure the velocity field. Prominent results have been obtained and comparable to standard PIV measurements. The pronounced variation in velocity magnitude observed while transitioning from the potential core to the self-similar region requires collecting multiple datasets to cover the broad spectrum of velocities comprehensively. A Mie scattering theory-based technique has been used to retrieve a relative concentration field. It is a non-intrusive technique that operates on the same experimental images produced by the LS-PIV campaign, assuming that light scattered by particles within a specific volume is proportional to the number of particles within this volume. The algorithm for concentration retrieval was adapted from and consequently improved for the present case. Discrepancies in the scaled concentration evolution among different nozzle diameters highlighted the necessity for refining the technique. This emphasizes accurately determining the reference concentration in a region free from intricate phenomena such as multiple scattering. The absolute and independent concentration measurement is done via Light Extinction Spectroscopy (LES). The LES technique measures the transmittance spectrum T of a collimated light beam passing through the particle-laden flow. This method has successfully been applied to several types of flows with similar seeding particles and concentration quantities (e.g. PSD 2 ). The extrapolation of absolute concentration parameters relies on the regularized solution of an ill-conditioned inverse problem. This solution is derived using the transmittance recorded during the test as the primary input parameter. The system to solve exhibits high sensitivity to small perturbations, making it challenging to employ numerical techniques confidently. Due to the substantial impact of minor perturbations in initial conditions on the system solution, a meticulous adaptation of the technique to the demands of compressible flows is necessary and still ongoing. The setup consists of a Deuterium-Tungsten Halogen UV-NIR light source emitting a divergent beam of light towards a 90◦ off-axis parabolic mirror, which collimates and deviates it into a beam to the jet. After passing through the jet, the resulting attenuated light beam goes into a collector mirror, redirecting it into a composite grating spectrometer UV-NIR with a 200 − 1100 nm wavelength range with 0.5 nm optical resolution. The results will examine the dispersion pattern and feature in terms of velocity and concentration of a supersonic underexpanded jet produced by an upstream tank with total pressure ranging from 5 to 9 bar without cross-flows. The latter will provide a foundation for successive studies on supersonic underexpanded jets subjected to an ABL.

Tailoring band gap properties of curved hexagonal lattices with nodal cantilevers

Metamaterials find applications across diverse domains such as electromagnetics, elasticity, and acoustics by creating band gaps. Lattice-based metamaterials also exhibit band gaps, which have a great potential to influence engineering design in vibration and noise reduction problems. The geometry of the repetitive unit cell in the lattice plays a crucial role in diversifying the location and number of stop bands across the frequency range. One of the key hurdles is devising unit cell architectures that can effectively suppress vibrations across diverse frequency ranges. This work proposes an innovative two-dimensional hexagonal lattice with tailored band gap characteristics through curved beam members and auxiliary cantilever beams at the nodes. We have thoroughly explored the impact of various design parameters on dispersion characteristics, wave directionality through iso-frequency contours of dispersion surfaces, and the transmission loss considering finite lattice. The investigation demonstrates an improvement in band gap characteristics, indicating the generation of more band gaps across the entire frequency range and the widening of the same. This study has the potential to serve as a future benchmark in the development of lattice-based elastic/acoustic metamaterials, particularly for addressing vibration reduction challenges at user-defined frequencies.

The collisional study of EIC waves in a magnetized dusty plasma with the inclusion of a DC electric field

This study investigates Electrostatic Ion Cyclotron (EIC) waves and their behaviour in weakly collisional plasmas, utilizing a proposed kinetic analytical model. The findings include alterations in EIC wave dispersion characteristics due to collisions, with parameters such as dust density, collision frequency, gyro-radius, magnetic field, density ratio, and electric field influencing wave growth rate and frequency. Temperature analysis reveals that higher electron-to-ion temperature ratios lead to increased frequency and critical drift velocity, while decreasing the growth rate. In addition, the critical drift velocity is studied for the unstable mode and it is observed that the relative density ratio increases with a reduction in critical drift velocity. Electron collisions destabilize EIC waves, while ion collisions stabilize them. Furthermore, the presence of dust particles decreases the growth rate of EIC waves as dust grain density increases. These results align with observations reported in previous literature.

Electrical property enhancement of non-heat-treatable wrought aluminum alloys using graphene additives

With growing efforts of electrification, aluminum’s role as a light-weight conductor material has become increasingly prominent. There is a critical need to improve the electrical performance of aluminum at room temperature and high operating temperatures. In this study, the effect of graphene nanoparticle additives on the electrical performance of a non-heat treatable alloy were (AA3003) explored. Graphene’s unusual structure and electronic properties were used to improve AA3003 properties. Here, the effects of graphene on the evolution of electrical properties and microstructural features have been explored on lab scale hot extruded AA3003-graphene composites. Hot pressing schedules and extrusion temperatures were varied to investigate changes in intermetallic dispersion characteristics in the presence of dispersed graphene. We measured a reduction of 10.3 % in the temperature coefficient of resistance in the AA3003 sample with 0.05 wt% graphene extruded at 400 °C, along with a maximum increase of 1.1 % in electrical conductivity at 20 °C. Increasing the hot-pressing times up to 8 hours was also found to consistently increase the electrical conductivity, due to increased precipitation of intermetallic phases. Despite being a non-heat treatable alloy, AA3003 displays interesting precipitation dynamics and grain recrystallization trends that can be modulated with varying levels of heat treatment, graphene concentrations, and hot extrusion process parameters.