Increasing Field Strength Research Articles

Investigating high harmonic yield from different alignments of WSe2 semiconductor

This paper theoretically investigates high harmonic generation from a monolayer WSe2 driven by a laser pulse with different alignments, in-plane and out-of-plane polarizations. Our simulations are performed in the framework of the time-dependent density functional theory. Analysis of the dependence of the cutoff energy on the laser field strength shows that the cutoff energy increases linearly/quadratically with the increase of the electric field strength for the out-of-plane/in-plane laser field. Also, the wavelength dependence of high harmonic yield exhibits a sharp decrease with a rate of λ−10 for the in-plane laser field, and a more gradual decline with a rate of λ−4.75 for the out-of-plane laser field. These wavelength dependencies are explained by the tunneling rate and the spatial spread of electron wave-packet due to propagation in time and space. Additionally, it is demonstrated that the maximum harmonic yield is obtained when the in-plane laser is aligned along the armchair direction, or when the out-of-plane laser is polarized at a 20° angle relative to the normal axis of the monolayer plane.

Enhanced energy storage properties and good stability of novel (1–x)Na0.5Bi0.5TiO3–xCa(Mg1/3Nb2/3)O3 relaxor ferroelectric ceramics prepared by chemical modification

The increase in energy consumption and its collateral damage on the environment has encouraged the development of environment-friendly ceramic materials with good energy storage properties. In this work, (1–x)Na0.5Bi0.5TiO3-xCa(Mg1/3Nb2/3)O3 ceramics were synthesized by the solid-state reaction method. The 0.88Na0.5Bi0.5TiO3-0.12Ca(Mg1/3Nb2/3)O3 ceramic exhibited a high recoverable energy storage density of 8.1 J/cm3 and energy storage efficiency of 82.4% at 550 kV/cm. The introduction of Ca(Mg1/3Nb2/3)O3 reduced the grain size and increased the band gap, thereby enhancing the breakdown field strength of the ceramic materials. The method also resulted in good temperature stability (20–140 °C), frequency stability (1–200 Hz), and fatigue stability over 106 cycles. In addition, an ultrahigh power density of 187 MW/cm3 and a fast charge-discharge rate (t0.9 = 57.2 ns) can be obtained simultaneously. Finite element method analysis revealed that the decrease of grain size was beneficial to the increase of breakdown field strength. Therefore, the 0.88Na0.5Bi0.5TiO3-0.12Ca(Mg1/3Nb2/3)O3 ceramics resulted in high energy storage properties with good stability and were promising environment-friendly materials for advanced pulsed power systems applications.

Attenuation characteristics analysis of the THz circularly polarized waves in inhomogeneous fully ionized dusty plasma using FPL model

When the hypersonic vehicle is flying, the plasma in the area near the stagnation point of the front end of the vehicle can be approximately seen as the fully ionized dusty plasma. Due to the existence of dust particles, dusty plasma affects the communication quality of the hypersonic vehicle. In this paper, the general Boltzmann equation applicable to dusty plasmas containing electrons and the Fokker–Planck–Landau collision model are combined to derive a general formula for the electron distribution function of fully ionized dusty plasmas. Considering the contribution of the collision effect and charging effect to the dispersion relationship of fully ionized dusty plasma, the dielectric constant of fully ionized dusty plasma under an external magnetic field is solved. The Wentzel–Kramers–Brillouin method is used to calculate the attenuation coefficient (α) of the THz wave in fully ionized dusty plasma, and the influence of the external magnetic field strength and other dusty plasma parameters on the attenuation characteristics of the THz circularly polarized wave is analyzed. The research results show that the α of the THz left-hand circularly polarized wave decreases with the increase in the external magnetic field strength, while the α of the THz right-hand circularly polarized wave increases. In addition, increasing the dust particle radius, dust particle density, and electron density in a certain frequency range can increase the α of the THz circularly polarized waves. These research results provide theoretical guidance for the exploration of the interaction mechanism between the THz waves and fully ionized dusty plasma.

The stability of the MHD flow over a shrinking cylinder with surface heat flux and volumetric thermal power

In this analysis, the stability of MHD stagnation point flow and heat transfer of an electrically conducting viscous incompressible fluid on a horizontally stretching/shrinking permeable cylinder with volumetric heat source are investigated. The cylindrical surface is subjected to a cross flow and a heat flux. This analysis finds applications in the areas of polymeric processing unit due to stretching/shrinking of surface and biofluid flows with therapeutic effects through the arteries, vein and digestive system that have a tube-like structure. Other aspects of the analysis are: magnetic field intensity whose strength can be remotely controlled and embodied generating/absorbing thermal power. The solution of the boundary value problems (BVP) is carried out with MATLAB’s inbuilt solver bvp4c. The most significant findings are recorded as: an increase in magnetic field strength increases the skin friction at the solid surface which is consistent with progressive thinning of boundary layer. This striking result is of interest in industrial applications because it is easy to regulate the magnetic field strength by electromagnetic devices such as controlling the voltage in the electric circuit. There is a point of neutrality of thermal energy distribution during the high fluctuation of temperature irrespective of the presence of heat generation or absorption. This can be attributed to the dominating effect of stretching/shrinking of the surface. The first solution provides stability of the flow with an increase in velocity in the presence of heat sink that is commensurate with the strength.

Applicability of the 0–1 test for chaos in magnetized Kerr–Newman spacetimes

The dynamics of electrically neutral or charged particles around a magnetized Kerr–Newman black hole immersed in an external electromagnetic field can be described by a dimensionless Hamiltonian system. This Hamiltonian is given an appropriate time transformation, which allows for construction of explicit symplectic integrators. Selecting one of the integrators with good accuracy, long-term stabilized Hamiltonian error behavior and less computational cost, we employ the 0–1 binary test correlation method to distinguish between regular and chaotic dynamics of electrically neutral or charged particles. The correlation method is almost the same as the techniques of Poincaré map and fast Lyapunov indicators in identifying the regular and chaotic two cases. It can well describe the dependence of the transition from regularity to chaos on varying one or two dynamical parameters. From a statistical viewpoint, chaos occurs easily under some circumstances with an increase of the external magnetic field strength and the particle electric charge and energy or a decrease of the black hole spin and the particle angular momentum. A small change of the black hole electric charge does not very sensitively affect the dynamics of neutral particles. With the black hole electric charge increasing, positively charged particles do not easily yield chaotic motions, but negatively charged particles do. On the other hand, the effect of a small change of the black hole magnetic charge on the dynamical transition from order to chaos has no universal rule.

Electrohydrodynamic capillary instability of Rivlin–Ericksen viscoelastic fluid film with mass and heat transfer

AbstractThis paper presents an analysis of viscous fluids and a Rivlin–Ericksen (R‐E) viscoelastic fluid interface under the influence of heat and mass transfer, while both fluids are exposed to an axial electric field. The fluids are restricted within an annular region that is enclosed by two rigid cylinders. The outer section of the annular region holds the R‐E viscoelastic fluid, while the inner section is filled with the viscous fluid. To ascertain the correlation between perturbation growth and wavenumber, the theory of potential flow on viscoelastic–viscous fluids is applied, and the result is represented as a second‐order polynomial. This correlation is numerically solved using the Newton–Raphson method. Variables of viscous flow, such as electric field strength, heat transfer coefficient, viscoelasticity, viscosity, and so forth, are numerically studied. With an increase in electric field strength, the perturbation growth decays and expands for the particular combinations of permittivity and conductivity ratio, showing the dual effect of the axial electric field.

Effect of normal magnetic field on the exact coherent state of channel flow at large Reynolds number

Laminar-turbulent subcritical transition has been always a hot issue in fluid mechanics. Exact coherent states are important for predicting the path of transition and understanding the cycle of turbulent self-sustaining process. One of the most common methods of investigating subcritical transition is dynamical system method and many different forms of invariant solutions have been obtained in many shear flows. In order to study the effect of magnetic field on the exact coherent state of channel flow at large Reynolds number, the direct numerical simulation combined with bisection method is used to calculate the exact coherent state-periodic orbit solution with different magnetic field strength at Re ⩾ 9000, and the structure and morphology in the flow field are compared. The results show that the magnetic field strength does not change the structure and shape of the solution and the scaling law between the transition threshold and Reynolds number does not change significantly, which shows obviously self-similarity. As the magnetic field strength increases, the period of the exact coherent state decreases and the perturbation energy in each direction exhibits periodical oscillation changes. In addition the shape of the amplitude curve also changes due to the magnetic field effect. The above results show that the magnetic field has a certain inhibition effect on the disturbance at large Reynolds number, and the flow field remains relatively stable.

Effect of pulsed electric field on spore germination rate and enzyme activity of Aspergillus niger

Pulsed electric field (PEF) treatment on Aspergillus niger, which is an important source of several enzymes, was conducted to investigate the effects of different PEF parameters on spore germination of A. niger and the production of lipase and glucoamylase. The results showed that the spore germination rate and the relative activities of lipase and glucoamylase could be promoted when the electric field strength was in the range of 5– 15 kV/cm and the treatment time was in the range of 1– 7.5 ms. During the processing, the concentration of spores was maintained within a range of approximately 3.5 × 106 CFU/mL. Maximum increase of spore germination rate, lipase and glucoamylase activities were 217%, 25.6% and 31.3% respectively, which were observed when the spore suspension was subjected to PEF treatment with 10 kV/cm field strength for 5 ms. Lipase activity was inhibited with the increase of field strength and treatment time. Further analysis of the input energy density during PEF showed that the spore germination rate and the relative activities of enzymes were also promoted and then inhibited with increasing input energy density, but the electric field strength was more decisive. Industrial relevancePEF is an emerging non-thermal microbial treatment technology with the characteristics of short treatment time and low energy consumption. Aspergillus niger is an important microbial species in the food industry, as the enzymes it produces play an important role in various fields. This study applied PEF technology to A. niger and significantly promoted the germination of its spores, and the activity of its lipase and glucoamylase, which suggests PEF technology has the potential to be used to shorten the industrial production cycle of A. niger and its enzyme products.

Toward a Mesoscopic Modeling Approach of Magnetohydrodynamic Blood Flow in Pathological Vessels: A Comprehensive Review.

The investigation of magnetohydrodynamic (MHD) blood flow within configurations that are pertinent to the human anatomy holds significant importance in the realm of scientific inquiry because of its practical implications within the medical field. This article presents an exhaustive appraisal of the diverse applications of magnetohydrodynamics and their computational modeling in biological contexts. These applications are classified into two categories: simple flow and pulsatile flow. An alternative approach of traditional CFD methods called Lattice Boltzmann Method (LBM), a mesoscopic method based on kinetic theory, is introduced to solve complex problems, such as hemodynamics. The results show that the flow velocity reduces considerably by increasing the magnetic field intensity, and the flow separation area is minimized by the increase of magnetic field strength. The LBM with BGK collision model has shown good results in terms of precision. Finally, this literature review has revealed a number of potential avenues for further research. Suggestions for future works are proposed accordingly.

Enhanced tunable terahertz Mie resonance and magnetoplasmonic effect through chain formation in ferrofluid

We present experimental and theoretical evidence demonstrating the Mie resonance effect in the terahertz (THz) range, utilizing Fe3O4/Kerosene ferrofluid. Our findings indicate a significant and rapid change in the complex refractive indices at 0.5 THz with an increase in the magnetic field strength. Moreover, we observed a prominent absorption peak at 0.5 THz in transmittance and absorption coefficient measurements, corresponding to a magnetic field intensity of 178.0 mT. This phenomenon occurs due to the adjustment of particle spacing, leading to resonance under different magnetic field conditions. These research results hold immense potential in advancing the development of magneto-optical THz modulators for imaging and communication applications.

Effect of spinodal decomposition structure of alnico alloy on magnetic viscosity and magnetization reversal

The slow decay of permanent magnet magnetization with storage time will greatly affect the accuracy of precision instruments. The alnico is a traditional permanent magnetic material with excellent stability, and the research on its stability cannot be ignored. Magnetic field heat treatment is a key process that affects the microstructure of the alnico alloy. The alnico alloys with different α1 phase orientations and aspect ratios were prepared by adjusting the magnetic field intensity during spinodal decomposition. With the increase of magnetic field strength, the aspect ratio of the α1 phase increases significantly, and the orientation becomes better, which leads to the increase of coercive force and remanent magnetization, but the magnetic viscosity coefficient decreases. The demagnetization process of alnico samples was characterized by Lorentz transmission electron microscopy (LTEM) and electron holography. At the magnetic field interval of 200 Oe, the area of irreversible magnetization reversal of the S3 is significantly larger than that of the S0. The first-order reversal curves (FORC) show that most the randomly oriented α1 phases are reversible magnetization reversal, and the interaction field is smaller than that of neatly arranged α1 phases. This structure results in better stability. The alnico alloy without a magnetic field during spinodal decomposition sacrifices some magnetic properties but obtains better stability, which provides a research direction for stabilizing treatment by adjusting microstructure.

Polyvinylidene Fluoride (PVDF) Crystallization Kinetics in an Electric Field

To study the effect of applied electric field on polymer crystallization, the crystallization of polyvinylidene fluoride (PVDF) was observed under modified polarized optical microscopy. The PVDF melts were crystallized based on programmed temperature, changes between two transparent conductive glass electrodes, on which a DC electric field was applied. The observations revealed that without the electric field, crystallizations below 160 °C resulted in only α-form crystals, while, at elevated temperatures, the formation of γ-form crystals also occurred. By applying the electric field at 1.7 kV/cm, γ-form crystals started emerging at the slightly lower temperature of 158 °C. Further examinations showed that both crystals, α-form and γ-form, grew at a greater rate with increasing field strength. A careful calculation of the Avrami parameters supported the data that the electric field enhanced the crystallization kinetics. Careful calculation based on the Laurientz–Hoffmann approach revealed that applying the electric field decreased the required energy for PVDF crystallization. The folding surface free energy of the PVDF crystallization, 1.76 × 10−2 Jm−2, was reduced to 1.57 × 10−2 Jm−2 and 1.43 × 10−2 Jm−2 after applying electric fields of 0.8 and 1.7 kVcm−1, respectively. We suggest that the electric field promoted the polymer chain alignment during the crystallization; as a result, it accelerated the polymer crystallization and lowered the energy requirement for crystallization.

3T vs. 7T fMRI: capturing early human memory consolidation after motor task utilizing the observed higher functional specificity of 7T.

Functional magnetic resonance imaging (fMRI) visualizes brain structures at increasingly higher resolution and better signal-to-noise ratio (SNR) as field strength increases. Yet, mapping the blood oxygen level dependent (BOLD) response to distinct neuronal processes continues to be challenging. Here, we investigated the characteristics of 7 T-fMRI compared to 3 T-fMRI in the human brain beyond the effect of increased SNR and verified the benefits of 7 T-fMRI in the detection of tiny, highly specific modulations of functional connectivity in the resting state following a motor task. 18 healthy volunteers underwent two resting state and a stimulus driven measurement using a finger tapping motor task at 3 and 7 T, respectively. The SNR for each field strength was adjusted by targeted voxel size variation to minimize the effect of SNR on the field strength specific outcome. Spatial and temporal characteristics of resting state ICA, network graphs, and motor task related activated areas were compared. Finally, a graph theoretical approach was used to detect resting state modulation subsequent to a simple motor task. Spatial extensions of resting state ICA and motor task related activated areas were consistent between field strengths, but temporal characteristics varied, indicating that 7 T achieved a higher functional specificity of the BOLD response than 3 T-fMRI. Following the motor task, only 7 T-fMRI enabled the detection of highly specific connectivity modulations representing an "offline replay" of previous motor activation. Modulated connections of the motor cortex were directly linked to brain regions associated with memory consolidation. These findings reveal how memory processing is initiated even after simple motor tasks, and that it begins earlier than previously shown. Thus, the superior capability of 7 T-fMRI to detect subtle functional dynamics promises to improve diagnostics and therapeutic assessment of neurological diseases.

Electric field as a crystallization switch of heterogeneous ice formation

Using molecular dynamics simulations, we investigated the effect of external electric field on ice formation with the present of a substrate surface. It turns out that the electric field can affect the ice formation on substrate surface by altering the dipole orientation of interfacial water molecules (IWs): a crossover from inhibiting to promoting ice formation with the increase of electric field strength. According to the influence of the electric field on ice formation, the electric field strength range of 0.0 V nm−1–7.0 V nm−1 can be divided into three regions. In the region I and region III, there are both ice formation on the substrate surface. While, the behavior of IWs in the region I and region III are distinguished, including the arrangements of oxygen atoms and the dipole orientation distribution. In region II, ice formation does not occur in the system within 5 × 200 ns simulations. The IWs show a disorder structure, preventing the ice formation process on substrate. The interfacial water molecular orientation distribution and two-dimensional free energy landscape reveals that the electric field can alter the dipole orientation of the interfacial water and lead a free energy barrier, making the ice formation process harder. Our result demonstrates the external electric field can regulate the behavior of IWs, and further affect the ice formation process. The external electric field act as a crystallization switch of ice formation on substrate, shedding light into the studies on the control of ice crystallization.

Study on low-rank coal surface wettability effect and recyclability of different anionic magnetic ionic liquids

Three types of magnetic ionic liquids (MIL) ([C12mim]FeCl4, [C12mim]2CoCl4, and [C12mim]2NiCl4) were chosen to study the enhancement of the quality and utilization of low-rank coal (LRC). The mechanism of coal wettability modification was explained from the macrocosm and microcosm points of view by contact angle, adhesion work, and adsorption studies, and the recovery of MIL was realized by salting out the separation-strong magnetic recovery (SMR). The contact angle and adhesion work results showed that [C12mim]FeCl4 had the greatest effect on coal wettability. The adsorption on the LRC surface was as follows: [C12mim]FeCl4 > [C12mim]2CoCl4 > [C12mim]2NiCl4. The adsorption thermodynamics indicated that MIL conformed to the Langmuir isotherm model, which is a spontaneous reaction of exothermic entropy minus physical adsorption. The adsorption kinetic process belong to the pseudo-second-order kinetic model and was influenced by the combined action of intraparticle and liquid film diffusion. From the contact angles and adsorption thermodynamics, it can be inferred that [C12mim]FeCl4 has the highest activity and can better adsorb onto the LRC surface, covering the oxygen-containing functional groups and reducing the wettability to achieve efficient quality improvement and utilization of LRC. Through the research of salting-out separation-SMR, the most suitable salting-out reagent was found to be NaCl, and the highest recovery was obtained when the concentration reached the solubility level. As the magnetic field strength increases, the recovery rate gradually increases. The recovery of [C12mim]FeCl4 was more than 90% when it reaches 1.5 T, and it could be recovered by magnetic separation.

Numerical Study of Free-Surface Electro-Hydrodynamic Wave Turbulence

Direct numerical simulation of threedimensional chaotic motion of a dielectric liquid with a free surface under the action of external horizontal electric field is carried out. The numerical model takes into account the effects of surface tension, viscosity, and external isotropic random forcing acting at large scales. A transition from dispersive capillary wave turbulence to quasi-isotropic nondispersive EHD surface turbulence with increase of the external electric field strength is numerically observed for the first time. At the regime of developed EHD wave turbulence, the total electrical energy is found to be much greater than the energy of capillary waves, i.e., electrohydrodynamic effects play a dominant role. At the same time, anisotropic effects are detected that lead to the generation of capillary wave packets traveling perpendicular to the external field direction. Despite the revealed anisotropy, the calculated spectrum of EHD wave turbulence is in very good agreement with the analytical spectrum obtained on the basis of dimensional analysis of weak turbulence spectra.

A Large Magnetic Hump in the VLISM Observed by Voyager 1 in 2020–2022

Voyager 1 has been moving through the very local interstellar medium (VLISM) for approximately one solar cycle, from 122.58 au on 2012/DOY 238 (August 25) to 158.5 au on 2023.0. Previously, an abrupt increase (“jump”) in the magnetic field strength B and proton density N by a factor of 1.35 and 1.36, respectively, was observed during an interval of ∼8 days in 2020.40. After the jump, B continued to increase to a maximum value ∼0.56 nT at ∼2021.4 and then declined until B returned to the postjump value of 0.5 nT on 2021.85, 1.45 yr after the jump. The magnetic field strength declined briefly from 0.5 nT on 2021.85 to 0.47 nT on 2021.95 and then increased sporadically to 0.52 nT at 2023.0. Thus, the magnetic field strength remained strong for at least 2.6 yr. The magnetic hump and the density hump were a compression wave propagating through the VLISM. The compression wave was generated by a region with large dynamic pressure in the solar wind that propagated through the inner heliosheath and collided with the heliopause. The magnetic field strength continued to remain strong, with slow variations, until the end of our observations at 2023.0. It is suggested that the magnetic hump evolved from the large dynamic pressure, high speeds, and density observed at 1 au between ∼2015 and ∼2017.

Ab initio study of electric field effects on phonon vibrations in tetragonal ZrO2

The effects of external electric fields on phonon-associated phenomena, such as phase transformation and diffusion in ZrO2 ceramics, have been reported from recent experiments. This study examined the effects of external direct current (DC) electric fields on the phonon vibration properties in a tetragonal ZrO2 unit cell based on the density-functional perturbation theory. Phonon dispersions and densities of states were analyzed with optimized structures under varying external DC electric fields up to 45 mV/Å. The field sensitivities of phonon characteristics exhibited significant orientation dependence and were attributed to ionic polarization associated with symmetry breaking in dielectric properties. Optical phonons showed considerable field sensitivities particularly near the Brillouin zone boundaries, such as in the M (π/a, π/a, 0) to X (0, π/a, 0) and A (π/a, π/a, π/c) to R (0, π/a, π/c) directions, where doubly degenerate phonon frequencies exhibited splitting behaviors associated with the symmetry breaking between two unique oxygen atoms in the original unit cell. In contrast, transversal acoustic phonons demonstrated a softening trend with increasing field strengths around the Z (0, 0, π/c) point, where imaginary and splitting frequencies were obtained under electric fields of >40 mV/Å, indicating the potential phase transformation from the tetragonal to orthorhombic symmetries under strong external electric fields.

Experimental evidence of various mode numbers of azimuthal waves in an Penning source for semiconductor processing

This study presents the first experimental evidence for the existence of various mode numbers of azimuthal waves in an E × B Penning source used for semiconductor processing. To accurately measure these mode numbers, we utilized an eight-tip probe array aligned in an azimuthal direction to acquire spatiotemporal signals and applied the Beall analysis to obtain the dispersion relations. We combined seven dispersion relations obtained from distinct probe pairs to derive a single dispersion relation. This method allowed us to enhance the accuracy and reliability of the measurements. Our results show that the amplitude of the fast Fourier transformation (FFT) undergoes significant changes as the discharge voltage and magnetic field strength are varied. We observed that a distinguishable peak seen at higher discharge voltage is divided into a wide range of dominant peaks up to eight when the discharge voltage is decreased. The dispersion relation reveals that the phase velocity of each mode is proportional to the frequency. As the magnetic field strength increases, the amplitude of the FFT rapidly decreases except for a dominant peak corresponding to mode number 3. Ultimately, the low azimuthal mode dominates the azimuthal oscillation. Moreover, the radial profile of the FFT results shows that the frequencies of modes are nearly constant along the radial direction and have a maximum spectral magnitude at the periphery of the plasma core. Notably, as the amplitude of the modes increased, the maximum amplitude transitioned away from the core region. The findings from experiment with the multi-arrayed probe suggest the presence of a characteristics eigenmode in the E × B Penning source. This eigenmode appears to be a fundamental and pervasive feature of the system, spanning a range of mode numbers from low to high.

DYNAMIC SELF-ASSEMBLY IN E.COLI BACTERIA SUSPENSION

We experimentally investigate self-assembly in bacteria suspension under low frequency alternating electric field. We observe the emergence of electric field-induced bacterial clusters as a function of electric field strength and bacterial concentrations. Above the electric critical field, bacterial cell self-organize into clusters, with further increase in field strength or bacteria concentration, a second critical point is reached, where 3D out of equilibrium structures are formed. Our findings demonstrates that the self-assembly of microswimmers can be controlled via external electric field. The observed cluster size dynamic equilibrium is in contrast with the features of cluster dynamics observed in cancer cells driven by adhesion where the cluster size distribution never reaches dynamic equilibrium. These results can offer a new pathway to self-organize living cells in biomaterials