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The thermocapillary-driven core release of double-emulsion droplets offers advantages such as simplicity in implementation and a broad range of applications, providing unique strengths in the field of core component release. However, the characteristics and mechanisms related to thermocapillary-driven core release were still unknown. This article employed the Volume of Fluid method to investigate the core release characteristics of double-emulsion droplets driven by thermocapillary. The range of Marangoni (Ma) numbers is from 10 to 500. The results indicate that effective control of the migration and release dynamics of double-emulsion droplets can be achieved through viscosity regulation, which induces the obvious difference between the two types of double-emulsion droplets. The regulation of both viscosity and surface tension is efficient in controlling the release type of the core. A phase diagram distinguishing between one-off and two-off release types is presented. Additionally, by characterizing dimensionless numbers, a formula for the characteristic release time of double-emulsion droplets is derived. The current study contributes to achieving precise control of double-emulsion droplets, expanding the scope of applications for double-emulsion droplets and establishing a fundamental groundwork for subsequent investigations into the release methods of double-emulsion droplets driven by thermocapillary. [ABSTRACT FROM AUTHOR]

Plasmas with a component of low-temperature (colder) ions are frequently observed in solar-terrestrial space with plasmaspheric and ionospheric origins. In addition, in fusion plasmas, massive fueling in the burning plasma provides a colder ion source in the fueling region. Therefore, such mixtures of multiple-temperature ions are common and inevitable in plasmas. In this paper, we focus on multiple ion temperature effects on magnetic reconnection by two-dimensional particle-in-cell simulations. Two typical scenarios are discussed. From group 1 runs, it can be found that if the colder ion density is increased but the warmer ion density is kept the same, the reconnection rate is reduced and the onset of the fast reconnection is delayed, mainly due to the mass-loading effect. Meanwhile, an additional spatial scale is introduced by the multi-temperature ions to form a nested structure of diffusion regions of the electrons, as well as colder and warmer ions, which are demagnetized (inflow) and remagnetized (outflow) in different spatial positions and accelerated to different levels. For the three species, the closer accessible position from the X-point is that the higher speed can be reached by acceleration in the diffusion regions. On the other hand, from group 2 runs, it can be found that if one keeps the total background ion density fixed while only changing the ratio of the warmer to the colder ions, the mass-loading effect can then be ignored. As the colder ion proportion increases, the peak inflows and outflows of both warmer and colder ions are getting higher as more ions can get closer to the X-point, leading to the rise of the reconnection rate with reconnection characteristics undergoing a transition from the warmer ion dominant to the colder ion dominant. [ABSTRACT FROM AUTHOR]

In this paper, the lattice Boltzmann method is used to simulate the diffusion and ionization process of a two-dimensional energetic electron beam that is injected into the background gases under the sub-atmospheric pressure, and the characteristics of such plasmas are revealed. It is found that the penetration distance of the electron beam from the exit of the electron beam reduced to 10% of the maximum value at the axis is about 35 cm, whereas the envelope of the plasma distribution is like a spindle with the penetration distance of about 130 cm, under the pressure of 5 kPa. The gas pressure has a significant impact on the penetration distance of the electron beam and the plasma that is produced. The increase in gas pressure will reduce the penetration distance of the electron beam and the plasma because higher pressure will increase the collisional probability between the electrons and the gas molecules, and the energy transfer becomes stronger. [ABSTRACT FROM AUTHOR]

In this paper, the collisionless electrostatic instability of the entropy mode is investigated linearly in multi-component plasmas confined by a dipole magnetic field, which commonly exists in space environments, as well as laboratory plasmas, such as Collisionless Terrella eXperiment, Levitated Dipole eXperiment, and Dipole Research EXperiment. We focus on characteristics of the entropy mode driven by the plasma density or/and the temperature gradient at low plasma beta (=8πP0/B02). The theoretical analysis of this work agrees with the calculated results qualitatively. It is indicated that the peak growth rate of the instability is in the regime of k⊥ρi ∼ 1, and the entropy mode tends to be more stable as the percentage of the heavy ion increases. For multi-component plasmas, each component has the entropy mode feature of its own, instead of simply averaging all the components. While for the electron with an isotropic temperature, the use of weighted harmonic average can be a good approximation for simplification. [ABSTRACT FROM AUTHOR]

Energy absorption of electromagnetic (EM) waves in collisional dusty plasmas is attracting much attention from researchers due to its applications in many fields, such as plasma antennas, blackout research during reentry, plasma stealth technology, and the design of microwave transmission in plasmas. In this paper, the propagation characteristics, in particular, the energy absorption effects of EM waves in partially ionized unmagnetized collisional dusty plasmas, are investigated. The results show that the effective energy absorption of EM waves is mainly due to the interaction between electrons and waves, and the plasmas with proper collisional frequencies can be used as a broadband frequency EM wave absorption medium with moderate absorption efficiency. Quantitative analyses of the characteristics of the EM waves that propagate in the collisional dusty plasmas are also included in this study. [ABSTRACT FROM AUTHOR]

The magnetostriction curves and minor loops of the TbDyFe [110] oriented crystal are tested under different compressive pre-stress from 0 to 120 MPa. It is observed that the magnetostriction hysteresis first increases from about 33 Oe under 0 MPa, achieves the maximum of about 70 Oe under 30 MPa, and then decreases to about 16 Oe under 120 MPa (near disappearance) with an increase in the compressive pre-stress. By the theoretical simulation, it is found that upon increasing the compressive pre-stress the dominant energy changes from magnetocrystalline anisotropy energy to magnetoelastic energy. This leads to the domain rotation mode changing from irreversibility to reversibility and consequently results in the decrease of magnetostriction hysteresis, which explains the experimental results very well. [ABSTRACT FROM AUTHOR]

Entropy modes are typical instabilities particularly seen in dipole field confined plasmas. In this paper, linear gyrokinetic calculations, together with the integral dispersion relation method, are applied to study the electrostatic entropy mode in such plasmas with an anisotropic temperature. The numerical approach is verified for certain typical conditions with previous studies. We then further focus on the anisotropic temperature effect on the entropy mode. Basic characteristics of the entropy mode are obtained with the effect. The results show that the entropy mode has a peak growth rate at kρi ∼ 1, and the mode is shifted from the ion to the electron diamagnetic regimes at small k⊥ρi. This work can be applied for various dipole magnetic field confined plasmas as well as certain other configurations, such as Z-pinch and field reversed configurations. [ABSTRACT FROM AUTHOR]

Chorus waves are widely investigated in space physics due to their significant role played in the radiation belts. Multiple structures of chorus frequency chirping elements, such as rising-tone structure, falling-tone structure, and hook-like structure, are observed in both space plasmas and the ground simulation experiments. In this paper, the numerical simulation on the generation of descending elements of chorus waves with parameters of a launching device, Dipole Research EXperiment, is conducted by a hybrid code named DAWN. The descending element of chorus waves is self-consistently generated without additional requirements except for a hot electron component as the free energy source. A case of ascending element under the magnetosphere parameters is also carried out to verify our simulations. Phase space distributions of electrons for the two chirping structures are analyzed, and the simulation results are consistent with previous theoretical predictions. It is obtained from the simulation results that the ascending element of chorus is observed together with an electron phase space hole (a depleted distribution function), while the descending elemet is observed together with an electron phase space clump. [ABSTRACT FROM AUTHOR]

Mn-based phosphors with the wavelength of 700–750 nm are an important category of far-red phosphors that have promising potential in the application of plant lighting, and the higher ability of the far-red light emitting of the phosphors is beneficial to plant growth. Herein, a series of Mn4+- and Mn4+/Ca2+-doped double perovskite SrGd2Al2O7 red-emitting phosphors with wavelengths centered at about 709 nm were successfully synthesized by means of a traditional high-temperature solid-state method. First-principles calculations were conducted to explore the intrinsic electronic structure of SrGd2Al2O7 for a better understanding of the luminescence behavior in this material. Extensive analysis demonstrates that the introduction of Ca2+ ions into the SrGd2Al2O7:Mn4+ phosphor has significantly boosted the emission intensity, internal quantum efficiency, and thermal stability by 170%, 173.4%, and 113.7%, respectively, which are superior to those of most other Mn4+-based far-red phosphors. The mechanism of the concentration quench effect and the positive effect of co-doping Ca2+ ions in the phosphor were extensively explored. All studies suggest that the SrGd2Al2O7:0.1%Mn4+, 11%Ca2+ phosphor is a novel phosphor that can be used to effectively promote the growth of plants and regulate the flowering cycle. Therefore, promising applications can be anticipated from this new phosphor. [ABSTRACT FROM AUTHOR]

This study investigates the pattern-forming behavior of ferrofluid droplets under the influence of radial magnetic fields. The experimental setup involves depositing initially circular ferrofluid drops surrounded by an immiscible nonmagnetic fluid on a plate with an electromagnet placed below. Through systematic experimentation and theoretical analysis, we explore the effects of two distinct radial magnetic fields on the outer and inner shapes of the droplets. Results reveal the emergence of various intricate interface patterns, including spike-like structures and fingerlike protrusions, as the magnetic Bond number and droplet initial diameter vary. The experimental observations are supported by theoretical predictions derived from mode-coupling differential equations, which provide insight into the underlying dynamics governing pattern formation. This study sheds light on the complex interplay between magnetic and hydrodynamic effects in ferrofluid systems, with implications for diverse applications ranging from microfluidics to biomedical engineering. [ABSTRACT FROM AUTHOR]

This paper first prepared a water-based magnetic fluid using a chemical co-precipitation method and conducted a detailed characterization and calculation of its important magnetization properties. Key parameters for analyzing the influence mechanism on the rheological properties of the water-based magnetic fluid were obtained. Subsequently, the impact of different magnetic field and shear rates on the magnetoviscous effect, shear-thinning behavior, and yield stress of the water-based magnetic fluid was studied through steady rotation measurements. The results showed a positive correlation between viscosity, shear stress, and yield stress with the magnetic field. Additionally, we also provide theoretical prediction formulas for the magnetoviscous effect based on the influence of microstructures formed by solid-phase magnetic particles in the magnetic field. The dimensionless Mason number was used to establish the scaling law relationship between viscosity measurements and theoretical values, with results showing good agreement between measured and theoretical values. The Herschel–Bulkley model and the Casson model were employed to obtain the dynamic yield stress values of the sample, and a quadratic linear increase relationship between yield stress and magnetic field was derived. These research findings provide important references for a deeper understanding of the physical and chemical properties of water-based magnetic fluid and for optimizing its application. [ABSTRACT FROM AUTHOR]

In this work, the control of the droplet generation by a focused infrared (IR) laser with a wavelength of 1550 nm was studied, in which the liquid water and the oil with the surfactant of Span 80 were employed as the disperse and continuous phases, respectively. The characteristics of the droplet generation controlled by the laser was explored under various flow rates, laser powers and spot positions and the comparison between the cases with/without the laser was also performed. The results showed that when the laser was focused on the region away from the outlet of the liquid water inflow channel, the droplet shedding was blocked due to the IR laser heating induced thermocapillary flow, leading to the increase of the droplet volume and the cycle time of the droplet generation as compared to the case without the laser. Decreasing the continuous phase flow rate led to the increase of the droplet volume, cycle time of the droplet generation and the volume increase ratio, while increasing the disperse phase flow rate led to the increase of the droplet volume and the decrease of the cycle time and volume increase ratio. For a given flow rate ratio between the continuous and disperse phases, the increase of the flow rates decreased the volume increase ratio. In addition, it is also found that the droplet volume, the cycle time and the volume increase ratio all increased with the laser power. When the laser was focused at the inlet of the downstream channel, the droplet volume, the cycle time and the volume increase ratio were the largest. Moving the laser spot to the downstream or upstream led to the decrease of them. When the laser was focused on the outlet of the liquid water inflow channel, the generated droplet volume and cycle time of the droplet generation were even lower than the case without the laser because of the lowered viscosity. This works provides a comprehensive understanding of the characteristics of the droplet generation controlled by the laser, which is beneficial to promote the application of this optical method in the droplet based microfluidics. [ABSTRACT FROM AUTHOR]

Electron beam-generated plasmas (EBPs) have been used to modify the surface properties. In certain applications, EBPs are transversely confined and their properties are of value to the treatment. In this paper, the characteristics of an electron beam-generated argon plasma, confined within a narrow gap, are investigated using a two-dimensional particle-in-cell simulation. The employed particle-in-cell/Monte Carlo collision model accounts for the electron and ion kinetics, as well as collisions between electrons and the background gas, including the elastic scattering, excitation, and impact ionization. Our simulations reveal a strong correlation between the plasma density and the beam density within the plasma bulk. The excitation of obliquely growing waves is observed, which is found to have a significant impact on the transport of beam electrons, thereby leading to the non-uniformities of plasma density and electron temperature. Specifically, the obliquely growing waves increase the local plasma density while reducing the electron temperature. These contrasting effects compensate for each other, and therefore, to some extent, smooth out the distributions of ion flux and energy flux. We further examine the variations of plasma parameters with respect to the beam current density, beam energy, and gas pressure. Increasing the beam current density or decreasing the beam energy results in higher plasma density and electron temperature, while increasing pressure leads to a higher plasma density but electron temperature scarcely changes. Based on the simulation results, we propose an approach to achieve independent control of the ion flux and energy flux by adjusting beam current density, beam energy, and pressure. [ABSTRACT FROM AUTHOR]

A scientific research device for geospace physics, the Space Plasma Environment Research Facility (SPERF), is going to be in operation this year at the Harbin Institute of Technology, China. One of its laboratory simulation platforms, the Asymmetric Reconnection EXperiment (AREX), is designed to investigate the asymmetric magnetic reconnection relevant to the process in the dayside magnetopause of the Earth. As a ground-based experimental platform, AREX emphasizes three-dimensional (3D) asymmetric driving features with topological similarity relevant to dayside reconnection. Thus, in this paper, we focus on topological analysis based on numerical simulation of AREX reconnection processes. 3D topological features in various scenarios relevant to magnetopause reconnection in different interplanetary magnetic field (IMF) conditions are investigated by adjusting setup parameters of plasma sources and magnetic coils. The simulation results reveal that the plasma distribution of asymmetric reconnection in SPERF-AREX is analogous to that at the magnetopause. Various types of the 3D magnetic topology relevant to typical IMF conditions, including the X-line and the A–B null chain structures, are, respectively, identified and analyzed in detail. [ABSTRACT FROM AUTHOR]

Resonant absorption is a process that electromagnetic (EM) energy is converted to plasma energy with a mode conversion on the resonant layer where the incident EM wave frequency equals to the local frequency of a plasma normal modes. With a finite collision between charged and background neutral particles in a plasma, the plasma oscillation is dissipated to widen the resonance layer and heat the plasma. In this work a modified scattering matrix methods (SMM) are applied to study the effects of the collision frequency, incident angle, and plasma thickness on resonant absorption. We analyze the energy absorption caused by resonance in comparison with collisional absorption for different parameters. It is found that the resonant absorption dissipates about nearly half of the incident EM energy in an overdense inhomogeneous plasma when the collision is weak, and the rest half portion is reflected. If the collision is strong, however, the collisional absorption is then more significant than the resonant and affects the entire wave propagation process. [ABSTRACT FROM AUTHOR]

The authors predict a superhard semiconductor phase of Be3N2 with cubic structure using first-principles calculations. The structural, mechanical, electronic, and optical properties of the Be3N2 have been investigated. Results indicate that the predicted Be3N2 phase is a wide gap semiconductor with a direct band gap of about 2.51 eV. The calculated hardness of cubic γ-Be3N2 based on Mulliken overlap population analysis in first-principles technique approaches those of B4C and B6O. The higher mechanical property can be attributed to the existence of strong Be–N–Be covalent bond chains in the cubic structure. The obtained static dielectric constant of Be3N2 (4.6 eV) is close to the spinel structure of Si3N4 (4.7 eV). [ABSTRACT FROM AUTHOR]