Permeability Dispersion Research Articles

Effect of external force on the dispersion of particles and permeability of substances via carbon nanotubes in reverse electrodialysis using molecular dynamics simulation

BackgroundUsing novel technologies and solutions is crucial for producing clean water. There are different ways to remove dissolved salts from water. MethodsThis study aimed to analyze the effect of an external force (EF) on the morphology of channels, the dispersion of particles, and the permeability of substances via carbon nanotubes in reverse electrodialysis. It was done using a computer simulation that studied the movement of molecules. This research aimed to study the effect of EF on the dispersion of particles and permeability of substances via carbon nanotubes using a reverse electrodialysis approach. The results show that increasing the EF from 0.0001 to 0.0005 eV/Å increased the electric current and fluid flow intensity from 5.31 e/ns and 211.31 atom/ns to 5.62 e/ns and 263.01 atom/ns. Moreover, the density decreased from 4.83 to 4.66 atom/nm3. Furthermore, the number of broken hydrogen bonds increased from 116 to 166. Significant findingsBy understanding the effect of EF on particle movement and material passage through carbon nanotubes, researchers can optimize the design of reverse electrodialysis systems to enhance their performance. This can lead to more effective and cost-efficient water treatment solutions, crucial for producing clean water.

Effective medium approximation for the electromagnetic properties of rocks with surface conductivity

We present an approach to calculate the complex dielectric permittivity of a microheterogeneous rock composed of non-conductive solid grains with surface conductivity and a conductive liquid.We have calculated the effective electrical properties of a rock using the model that consider the complex structure of the conducting double layer between a solid grain and the electrolyte in the pores. The influence of two parts of double layer: the Stern (inner) layer on the solid surface and the diffuse (outer) layer was considered.Previously, the Differential Effective Medium (DEM) scheme was used to calculate the effective conductivity and dielectric permittivity. In contrast, we have adopted the Effective Medium Approximation (EMA) method for calculation of the effective electromagnetic properties of a rock with high inclusion concentration. This method allows one to describe both elastic and electromagnetic properties of the rock based on the unified model of the pore space.The calculations were performed both for the rock model with a fixed grain size and for the model with a fractal distribution of grain sizes.Our calculations have shown that the value of the dielectric permittivity in the low frequency range depends on the concentration and dimension of solid grains. However, the frequency-dispersion behavior is a function of the inclusion size only and it does not relate to the inclusion concentration in the porosity range typical for sedimentary rocks. This effect confirms the feasibility of the determination of the inclusion concentration and dimension by using the dielectric permeability and electrical conductivity dispersion curves.

Improving the accuracy of measurement of bistatic scattering characteristics of material samples in various conf gurations

The infl uence of diffraction effects at the edges of fl at samples of small (2–4 wavelengths of incident wave) sizes on the results of measurements of the refl ection coeffi cient of the sample material, a bistatic characteristic that depends on the frequency of radiation in a wide (10–85°) range of incidence angles is considered. To reduce the infl uence of diffraction effects, samples of various confi gurations have been developed, made of magnetodielectric with frequency dispersion of dielectric and magnetic permeability. The samples are a metal plate, on one side of which the material under study is applied, and the other surfaces of the plate are covered with radiation-absorbent material. The scattering characteristics of samples of the developed confi gurations are numerically calculated and experimentally measured on a bistatic facility in an anechoic chamber. The experimental results correspond with the calculated data. A noticeable reduction in the infl uence of diffraction effects on the refl ectivity values in a wide angular and frequency range has been shown. Using numerical methods in the FEKO software package, the infl uence of the sample confi guration on the methodical error in refl ectance measurements was studied. It is shown that this error can be reduced by using a substrate of an extended shape in the plane of incidence (samples of a hybrid confi guration). The results obtained can be used to measure the scattering characteristics of materials in free space.

Polymer composites with magnetically active Eu-substituted NiZn ferrite fillers

In this research, the influence of Eu substitution on structural, quasi-static as well as dynamic (electro)magnetic properties of nickel zinc ferrites has been studied. The correlation of increasing europium content in the substituted NiZn ferrite filler with constant concentration (60 vol%) and the frequency dispersion of the complex permeability in magnetically active composite samples has been explored as well. Eu-substituted nickel-zinc ferrites with chemical composition Ni0.3Zn0.7EuxFe2-xO4, where x changes from 0.00 to 0.10 (step 0.02) ions per formula unit (i./f.u.), have been selected for their high initial permeability and in general good other magnetic parameters. On contrary, non-substituted ferrite of this composition exhibits undesirably low Curie temperature inconvenient for the use of these materials even at room temperatures. Therefore, Eu has been selected as a substituent for its known ability to increase the Curie temperature of prepared ferrites. The ferrites have been synthesized by means of the conventional solid state reaction method including double sintering at the temperatures of 950 °C and 1200 °C and used as magnetically active fillers incorporated into the magnetic polymer composites. Polyvinylchloride (PVC) has been used as the polymeric matrix. In spite of substituent amount x being the only parameter changing intentionally, the behavior of both the ferrite filler (deterministic until the creation of the second, non-magnetic, phase above x = 0.04) and the ferrite/PVC composites is quite hard to explain, and validate quantitatively, on the basis of simple theoretical assumptions. Nevertheless, the experiments confirmed positive effect of europium on the increase of Curie temperature. Also, the peak frequency of the imaginary component of the complex permeability has been found to be very sensitive to x, thus offering an effective tool for tuning the high-frequency properties of the composites useable for various applications, especially the shielding of microwave electromagnetic fields.

Considerations on the modified Maxwell electrodynamics in the presence of an electric and magnetic background

The properties of the modified Maxwell electrodynamics (ModMax) are investigated in the presence of external and uniform electric and magnetic fields. We expand the nonlinear theory around an electromagnetic background up to second order in the propagating fields to obtain the permittivity and permeability tensors, dispersion relations, group velocity and refractive indices as functions of external fields. The case with perpendicular background fields is contemplated. The phenomenon of birefringence is discussed and the fundamental role of the ModMax parameter becomes clear. We calculate the difference of the refractive indices in terms of this parameter and the external fields. Finally, we set up a scenario where the axion is present and compute the interaction energy for the coupled axion-ModMax electrodynamics if a magnetic background field is considered. This calculation is carried out in the framework of the gauge-invariant, but path-dependent variables formalism. Our results show that the interaction energy contains a linear component, leading to the confinement of static probe charges where the interference between the ModMax parameter, the axion mass, and the axion-photon coupling constant is pointed out.

Influence of Permeability Dispersion on Radiation of BAW Antenna: Modeling of Multiphysics Dynamic Coupling

Coupling of multiphysics including electrodynamics, elastodynamics, magnetodynamics, and electromagnetic (EM) radiation is involved in the operating process of bulk acoustic wave (BAW) antenna. There is still no good way to design the structure and evaluate the performance of the antenna in theory. Therefore, the multiphysics dynamic coupling model of the antenna is constructed by uniting Newton’s equation for acoustic wave, Maxwell’s equation for EM wave, and Landau–Lifshitz–Gilbert (LLG) equation for spin wave with constitutive relations of multiferroic materials to discuss the dispersion law of permeability and magnetomechanical coupling factor for the magnetostrictive layer. The importance of consistency between ferromagnetic resonance (FMR) frequency and BAW resonant frequency is demonstrated. The analysis shows that both increasing the anisotropic field or the saturation magnetization and decreasing the FMR linewidth are beneficial to improving the internal energy conversion efficiency and the average radiated power for BAW antenna. In addition, a micromagnetic module is introduced into finite element analysis (FEA) software to simulate the precession of unit magnetic moment at different frequencies. Thus, the analytical model is verified from the perspective of power absorption.

Resonance frequency above 20 GHz in superparamagnetic NiZn-ferrite

We investigate the frequency dispersion of complex permeability in the GHz range in superparamagnetic nickel–zinc ferrite thin films with different Ni/Zn ratios using a microstrip probe. The films, comprising crystallites as small as 3 nm and deposited by a microwave-irradiation-assisted solvothermal method, exhibit the coexistence of two resonance characteristics—a ferromagnetic resonance peak (fr) at ∼2 GHz and a superparamagnetic resonance peak (fb) above 20 GHz, breaching Snoek's limit. The high value of fr is attributed to the high surface anisotropy and far-from-equilibrium distribution of cations in the lattice, while fb is attributed to the thermally driven superparamagnetic relaxation of ferrite nanocrystallites in the thin films. This work demonstrates the feasibility of employing superparamagnetic ferrite thin films so deposited as excellent CMOS-integrable magnetic components for high-speed and high-frequency electromagnetic device applications.

Dispersion coding of ENZ media via multiple photonic dopants

Epsilon-near-zero (ENZ) media are opening up exciting opportunities to observe exotic wave phenomena. In this work, we demonstrate that the ENZ medium comprising multiple dielectric photonic dopants would yield a comb-like dispersion of the effective permeability, with each magnetic resonance dominated by one specific dopant. Furthermore, at multiple frequencies of interest, the resonant supercouplings appearing or not can be controlled discretely via whether corresponding dopants are assigned or not. Importantly, the multiple dopants in the ENZ host at their magnetic resonances are demonstrated to be independent. Based on this platform, the concept of dispersion coding is proposed, where photonic dopants serve as “bits” to program the spectral response of the whole composite medium. As a proof of concept, a compact multi-doped ENZ cavity is fabricated and experimentally characterized, whose transmission spectrum is manifested as a multi-bit reconfigurable frequency comb. The dispersion coding is demonstrated to fuel a batch of innovative applications including dynamically tunable comb-like dispersion profiled filters, radio-frequency identification tags, etc.

Study of radar absorbing characteristics of polymer composites with ferrite fillers

The search for effective radio-absorbing materials is an urgent task in solving the problems of electromagnetic compatibility, electromagnetic pollution, as well as stealth and stealth technologies. We present the results of studying the electrophysical and radio-absorbing characteristics of ferrite-polymer composites depending on the structure and magnetic properties of the ferrite filler, as well as the dielectric properties of the polymer matrix. The radio absorbing characteristics of composites F-42/Mn-Zn-ferrite, F-42/Ni-Zn-ferrite, F-42/yttrium iron garnet, F-42/BaFe12O19, F2M/LiMnZn-spinel, PS525/Mn-Zn -ferrite, PVA/Mn-Zn ferrite, and PVA/Ni-Zn ferrite have been studied. Experimental data on the reflection coefficient, determined on a metal plate in a frequency range of 0.1 – 7 GHz showed that spinel ferrites and composites containing them are effective radio absorbing materials. Analysis of the spectra of complex dielectric and magnetic permeability revealed that composites with spinel ferrites and yttrium iron garnet are characterized by a dispersion of the magnetic permeability, which arises as a result of resonance processes of the motion of domain boundaries and natural ferromagnetic resonance. Moreover, the electrical properties of ferrites can affect the high-frequency spectra of the permittivity and permeability. It is shown that the use of electroactive polymers as matrices makes it possible to increase dielectric losses in the high-frequency range and obtain the maximum attenuation of electromagnetic radiation within 25 – 40 dB with a width of 10 dB up to 2.5 GHz in 2 – 7 GHz range. The results obtained can be used in further study of the functional properties of radio-absorbing materials in the high-frequency range.

Changes and significance of retinal blood oxygen saturation and oxidative stress indexes in patients with diabetic retinopathy.

BACKGROUNDDiabetic retinopathy (DR) is a diabetic complication that can severely affect the patients’ vision, eventually leading to blindness. DR is the most important manifestation of diabetic micro-vasculopathy and is mainly related to the course of diabetes and the degree of blood glucose control, while the age of diabetes onset, sex, and type of diabetes have little influence on it. AIMTo explore the changes in blood oxygen saturation and oxidative stress indices of retinal vessels in patients with DR.METHODSIn total, 94 patients (94 eyes) with DR (DR group) diagnosed at Jianyang people’s Hospital between March 2019 and June 2020, and 100 volunteers (100 eyes) (control group) without eye diseases, were included in this study. Arterial and venous blood oxygen saturation, retinal arteriovenous vessel diameter, and serum oxidative stress indicators in the two groups were compared. Based on the stage of the disease, the DR group was divided into the simple DR and proliferative DR groups for stratified analysis. RESULTSThe oxygen saturation of the retinal vessels in the DR group was significantly higher than that in the control group (P < 0.05). The retinal vessel diameters between the DR and control groups were not significantly different. The serum malondialdehyde (MDA) and 8-hydroxydehydroguanosine (8-OHdG) levels in the DR group were significantly higher than those in the control group (P < 0.05). The serum superoxide dismutase (SOD) and reduced glutathione (GSH) levels in the DR group were significantly lower than those in the control group (P < 0.05). The oxygen saturation of the retinal vessels in the patients with proliferative DR was significantly higher than that in the patients with simple DR (P < 0.05). The retinal vessel diameter in patients with proliferative DR was not significantly different from that of patients with simple DR (P > 0.05). Serum MDA and 8-OHdG levels in patients with proliferative DR were significantly higher than those in patients with simple DR (P < 0.05). Serum SOD and GSH levels in patients with proliferative DR were significantly lower than those in patients with simple DR (P < 0.05).CONCLUSIONIncreased blood oxygen saturation of retinal arteries and veins and increased oxidative stress damage in patients with DR may be associated with decreased retinal capillary permeability and arterial oxygen dispersion, possibly reflecting the patient’s condition.

Probing the Frequency Dispersion of Magnetic Permeability of a Sample during Dynamic Interaction with a Magnetized Probe

Probing the Frequency Dispersion of Magnetic Permeability of a Sample during Dynamic Interaction with a Magnetized Probe

Influence of two-step sintering on power loss and permeability dispersion of MnZnNi ferrite

Manganese-zinc-nickel (MnZnNi) ferrite nanoparticles with the chemical composition Mn0.2Zn0.5Ni0.3Fe2O4 were prepared via co-precipitation method. Using the prepared nanoparticles, ring-shaped cores were formed and subjected to two-step sintering. Then, magnetic permeability, magnetic losses, density and microstructure of the samples were examined and compared with those of ferrites produced by the single-step sintering process. It was found that upon reducing the isothermal temperature from 1350 °C to 1250 °C, the density of the samples increased from 4.39 to 4.71 gr/cm3 and the average grain size diminished from 10.1 to 2.2 µm. The samples prepared through the two-step sintering method with a high temperature of 1350 °C and a lower temperature of 1250 °C exhibited a good performance in terms of loss and permeability. The two-step sintering process is an efficient method to produce high density and permeability plus low-loss ferrites.

Probing the Frequency Dispersion of the Magnetic Permeability of a Sample During Dynamic Interaction with a Magnetized Probe

The forces acting on a magnetic particle during nonrelativistic motion parallel to the surface of a homogeneous medium with a frequency dispersion of magnetic permeability are considered. General expressions are obtained for the normal (attractive) and lateral (braking) forces acting on a small dipole particle and an extended probe. It is shown that for an arbitrary orientation of the vector of the dipole magnetic moment of the particle, along with the force of attraction and the stopping force, there also appears a velocity-dependent lateral force perpendicular to the velocity vector. The possibility of using the results to study the frequency-dependent magnetic permeability of nanostructured materials and films in the dynamic scanning mode of magnetic force microscopy with magnetic probes is discussed. Numerical estimates are given for the magnitude of the expected forces, friction coefficients, and changes in the quality factor of the MFM oscillators in the case of frequency dispersion of relaxation-type magnetic permeability. Keywords: nanostructured magnetic materials, frequency dispersion of magnetic permeability, magnetic force microscopy.

Зондирование частотной дисперсии магнитной проницаемости образца при динамическом взаимодействии с намагниченным зондом

The forces acting on a magnetic particle during nonrelativistic motion parallel to the surface of a homogeneous medium with a frequency dispersion of magnetic permeability are considered. General expressions are obtained for the normal (attractive) and lateral (braking) forces acting on a small dipole particle and an extended probe. It is shown that for an arbitrary orientation of the vector of the dipole magnetic moment of the particle, along with the force of attraction and the stopping force, there also appears a velocity-dependent lateral force perpendicular to the velocity vector. The possibility of using the results to study the frequency-dependent magnetic permeability of nanostructured materials and films in the dynamic scanning mode of magnetic force microscopy (MCM) with magnetic probes is discussed. Numerical estimates are given for the magnitude of the expected forces, friction coefficients, and changes in the quality factor of the MFM oscillators in the case of frequency dispersion of relaxation-type magnetic permeability.

Study on groundwater recharge assessment by rainfall in coastal district Thai Thuy, Thai Binh province

Groundwater always plays a vital role in socio-economic development. One of the components of groundwater resource potential is the recharge from rainfall and surface water. The paper presents finite element modeling in the moisture transfer simulation in unsaturated soils through the relationship between soil moisture, soil suction, unsaturated permeability, and moisture dispersion coefficient. Parameters required for moisture transfer in four subsurface soil types have been collected and analyzed: Saturated permeability, porosity and field moisture content. Hourly rainfall data of 2015 have been studied and grouped into different rainfall duration (1-hour, 2-hour,... 36-hour continuous rainfall). The different duration rainfall and temporal infiltration determined by the moisture transfer modeling allow calculating the groundwater recharge from the downpour. We had applied the methodology to coastal district Thai Thuy, Thai Binh province. The results show that during the rainy months from June to October 2015, the groundwater recharge from the rainfall is: Through silty clay 0.233 m, through silt 0.338 m, through sandy silt 0.374 and through silty sands 0.561 m. The rainfall recharge to groundwater through those four soil types in terms of percentage of total 2015 rainfall respectively is 12.85%, 18.65%, 20.63% and 30.95%. The methodology may be applied to other areas with an advantage in the minimal expense of budget and time and relatively high reliable results.

High-Frequency Magnetoimpedance (MI) and Stress-MI in Amorphous Microwires with Different Anisotropies.

Magnetoimpedance (MI) in Co-based microwires with an amorphous and partially crystalline state was investigated at elevated frequencies (up to several GHz), with particular attention paid to the influence of tensile stress on the MI behavior, which is called stress-MI. Two mechanisms of MI sensitivity related to the DC magnetization re-orientation and AC permeability dispersion were discussed. Remarkable sensitivity of impedance changes with respect to applied tensile stress at GHz frequencies was obtained in partially crystalline wires subjected to current annealing. Increasing the annealing current enhanced the axial easy anisotropy of a magnetoelastic origin, which made it possible to increase the frequency of large stress-MI: for 90mA-annealed wire, the impedance at 2 GHz increased by about 300% when a stress of 450 MPa was applied. Potential applications included sensing elements in stretchable substrates for flexible electronics, wireless sensors, and tunable smart materials. For reliable microwave measurements, an improved SOLT (short-open-load-thru) calibration technique was developed that required specially designed strip cells as wire holders. The method made it possible to precisely measure the impedance characteristics of individual wires, which can be further employed to characterize the microwave scattering at wire inclusions used as composites fillers.

Modelling of structure of material for the description of frequency dispersion of dielectric permeability of quartz glass

Statement of a problem the empirical models of calculation of frequency dispersion of dielectric permeability based on dipol representations of structure material are known. Modeling of representation of substance in the form of non-uniform multilayered structure also allows to find electrodynamic parameters of materials therefore the possibility of the description by means of this model of frequency properties of dielectric permeability of quartz glass in a strip of frequencies from radio to optical range is considered. Purpose. Calculation of frequency dependence of dielectric permeability material at the expense of an interference of the falling wave on the plate presented in the form of model of non-uniform multilayered structure. Results. The model of representation of non-uniform material in the form of multilayered plane-parallel structure for calculations within geometrical optics of parameters of the reflected wave when falling a flat wave on a plate is investigated at an angle of Brewster. Practical importance. The model of non-uniform material in the form of multilayered plane-parallel structure is developed and calculations of frequency dispersion of dielectric permeability of quartz glass are carried out.

Sustainable Construction of Earth Dams: Use of Heterogeneous Material from the Dam Site

The volumes of soil required for the construction of an earth dam are usually of importance, so that, consequently, a key aspect to mitigate the negative impacts of dam construction, both from an economic and environmental point of view, is the use of materials in the vicinity of the dam location. However, this is often complicated because the existence of good quality materials with homogeneous properties, necessary for the dam core, is scarce in sites near the dam and their presence in sufficient volume for its construction is not usual. Unfortunately, using and transporting soil with good geotechnical characteristics to construct the core in a faraway location is economically and environmentally unsustainable. Therefore, the possibility of using less suitable material at the dam site as part of the core must be studied. Thus, in the present research the use of a soil of great heterogeneity in its geotechnical properties with a great dispersion of permeability is analyzed. Considering permeability as a random variable, combinations of representative values of heterogeneous soils are analyzed using their mean permeability and coefficients of variation that allow generating different lognormal distribution functions to carry out a Monte Carlo analysis. By maintaining the soil’s global heterogeneity, it was possible to study an unlimited disposition of lifts of different permeability. The statistical formulation allowed the research of the variation of the seepage flows and maximum gradients produced as a function of the variability of their mean permeability, being able to detect the factors with the greatest influence on the generation of high flows and gradients. Thus, it was possible to verify how high gradients were obtained for situations in which the seepage flow rates were moderate and low; the highest maximum gradients were observed in the lowest lifts of the dam core. In addition, based on the results of the Monte Carlo analysis, design charts have been developed for flow rates and maximum gradients, dependent on the mean permeability and the coefficient of variation, which allow judging whether heterogeneous material can be used, under conditions of safety, for the construction of the core of a dam.

Optimized Design of Earth Dams: Analysis of Zoning and Heterogeneous Material in Its Core

To control the seepage in the design of an earth dam, guidelines prescribe a high proportion of fines and high homogeneity of geotechnical characteristics in the material used for the dam core. However, on many occasions there is no material of this nature near the dam placement and, from an economic or environmental point of view, it is not possible to locate and transport material with good geotechnical characteristics close to the dam. This research demonstrated the possibility of using impermeable materials in earth dam cores, as well as soils considered unsuitable according to the classic recommendations and guidelines. For an optimized design, two situations are analyzed here. First, we examined the possibility of using soil with a marked difference in grain size as the core of the dam, each with homogeneous geotechnical properties. In this case, the optimal zoning of up to three types of materials was studied to ensure adequate seepage control. Second, we examined the use of soil with great geotechnical heterogeneity, which presents high permeability dispersion. In such a case, the conditions that would allow its use were studied via the of Montecarlo analysis. By maintaining the soil’s global heterogeneity, it was possible to study an unlimited disposition of layers of different permeability. In the first situation, the results showed that the most effective zoning for decreasing seepage flow corresponded with three vertically set materials. In this design, the most optimized zoning (minimal seepage flow rates) corresponded to the most impermeable soil situated downstream when water heights were under 90% of the height of the dam core. However, for maximum water height, more optimized cases corresponded to the intermediate permeability material located downstream. In the second situation, when heterogeneous materials were used to construct the impervious element of the dams, the Montecarlo analysis indicated that the seepage flow rates were limited to sufficiently low values despite the large dispersion of material permeability. In addition, the highest maximum hydraulic gradients were observed in the lowest lifts of the dam core and for situations in which the seepage flow rates were moderate and low.

Comparison of various 3D pore space reconstruction methods and implications on transport properties of nanoporous rocks

Understanding fluid flow and transport within clay rock is essential for predicting caprock integrity in underground gas storage or as host rock in deep radioactive waste storage. The connectivity and topology of the nanopore space, which drive the transfer mechanisms of these materials, are still poorly known and direct 3D imaging is particularly challenging. In this work, we investigate and compare different stochastic reconstruction approaches based on two-point and multiple-point statistics (MPS) methods and using information from 2D training images for 3D volume rendering at submicron scale. A particular emphasis is given to the maximal critical distance of sampling between two consecutive 2D images which is necessary to obtain a coherent 3D reconstruction of the nanopore structure. We assess how these realizations honour various crucial transport properties of material, namely permeability, effective diffusion and longitudinal dispersion. Morphological features such as pore volume, specific surface, Euler characteristic and tortuosity are used to analyze the results. The methods are employed on a synthetic clay of nanometric porosity for which FIB-SEM images are available. Results indicate that the 3DA-MPS and weighted-3DA-MPS approaches are the most suited for preserving pore space features and transport properties, the choice depending on the level of conditioning data available.