Two-layer Medium Research Articles

Evaluation of Electrophysical Properties of Soils in the Slope Zones of the Foundation During GPR Survey

The article describes a new method for conducting a ground penetrating radar survey of slope zones of soil objects of transport infrastructure. In the lithological section of these objects, there are sub-horizontal and inclined soil boundaries, as well as slope zones. Traditional survey methods (drilling, pitting), as well as the standard GPR method, make it possible to reliably survey at these objects, as a rule, only the zones under the horizontal main ground of the subgrade and sub-horizontal sections of the ground outside its boundaries. Survey under inclined surfaces is often difficult or technically impossible; geophysical methods, just like traditional ones, provide initial information that is exceedingly difficult for further decoding. The sections are filled with re-reflections and noises, and the process of decoding them is associated with great methodological problems.This paper presents a new method for determining speed of propagation of radio waves in the slope zones of the foundation. The initial information is the data obtained during the survey using the common depth point (CDP) method, using a well-known survey technique and a standard set of hardware. The novelty of the article results is determined by the algorithm for processing the measurement results developed by the authors. The software implementation made on its basis makes it possible to obtain the hodograph equation considering the slope of the layers. Defining geometric characteristics of embankments associated with the presence of slopes of variable steepness have been considered. A technique for calculating propagation speed of radio waves for a two-layer medium with a boundary inclined to the scanning surface has been proposed. The validity of the developed method was verified using finite-difference time-domain modelling.The article provides examples of practical application of the developed method in the GPR survey of real track foundation objects (transport infrastructure objects). The method proposed in the article makes it possible to increase the informative area of the surveyed diameters. At the same time, the accuracy of the GPR method is preserved, the area of its application for obtaining reliable information is increased to 60 % of the cross-sectional area of the foundation.

Optimal Algorithm of Full Focus Array Based on Sparse Matrix

Ultrasonic phased array all-focus imaging algorithm has the advantages of high accuracy and full range dynamic focusing, but the existing imaging time-consuming problem limits its practical industrial application. In order to meet the requirements of real-time imaging and clear and distinguishable image defects in all-focus array ultrasound scanning. In this paper, a sparse optimization model of TFM phased array is established. Based on the Fermat principle, the delay time of each element under two layers of media is calculated, and a two-layer media phased array all-focus imaging algorithm is established, using minimal redundancy. The sparse design of the MRLA is carried out, and the all-focus imaging and sparse all-focus imaging experiments of the two-layer medium are carried out, and the influence of the sparse emission array on the defect quantitative accuracy and the calculation efficiency of the all-focus algorithm is discussed. The final optimized sparse array is compared with the sound field beam pattern of the full array, the smallest redundant array, and the genetic algorithm optimized array, and an all-focus scanning environment is established based on the array. Scanning images can not only obtain the maximum amount of information under minimum redundancy, but also have good sidelobe characteristics. At the same time, the array is sparse, which greatly improves the efficiency of all-focus scanning, and provides a certain reference value for the research of all-focus imaging technology.

Trefftz Method of Solving a 1D Coupled Thermoelasticity Problem for One- and Two-Layered Media

This paper discusses a 1D one-dimensional mathematical model for the thermoelasticity problem in a two-layer plate. Basic equations in dimensionless form contain both temperature and displacement. General solutions of homogeneous equations (displacement and temperature equations) are assumed to be a linear combination of Trefftz functions. Particular solutions of these equations are then expressed with appropriately constructed sums of derivatives of general solutions. Next, the inverse operators to those appearing in homogeneous equations are defined and applied to the right-hand sides of inhomogeneous equations. Thus, two systems of functions are obtained, satisfying strictly a fully coupled system of equations. To determine the unknown coefficients of these linear combinations, a functional is constructed that describes the error of meeting the initial and boundary conditions by approximate solutions. The minimization of the functional leads to an approximate solution to the problem under consideration. The solutions for one layer and for a two-layer plate are graphically presented and analyzed, illustrating the possible application of the method. Our results show that increasing the number of Trefftz functions leads to the reduction of differences between successive approximations.

Radiative transfer technique for retrieving the radiative properties of agricultural soils

The knowledge of soil optical properties is very important for agriculture production and decision making in selecting and managing land to cultivate. These properties can be retrieved from the radiative transfer technique if appropriate method is used to solve the direct problem of the radiative transfer equation. The radiative transfer equation describes the propagation of the radiation in the soil. Thus, understanding the interactions of the radiation with agricultural soil is an active research area. In this paper, the reflectance characteristics of typical agricultural soil are retrieved. The soil, considered as a semitransparent plane parallel two-layered media with the refractive index mismatch, is illuminated at the top by a collimated radiation. This refractive index mismatch causes reflection and refraction to occur at the soil boundaries and interfaces. The two layered agricultural soil radiative properties and the scattering phase function are determined from the Mie theory assuming that the soil layers consist of only clay particles. With these radiative properties, the equation of radiative transfer is solved using the discrete spherical harmonics method (DSHM) under Marshak boundary conditions. The computational results are in agreement with existing literature results on two-layered media. The two-layered agricultural soil is then studied with a constant or spatial variation of the refractive index. The effects of soil radiative properties and the scattering phase function on the radiation characteristics are discussed. The anisotropy of the soil reflectance is analyzed and results demonstrate that a predominantly backscattering soil reflects more radiation than the predominantly forward scattering and Rayleigh scattering soil. These findings are applicable in the context of agricultural soil as it provides insight for developing optical equipment for quick soil properties measurement before crop planting.

Imaging of buried obstacles in a two-layered medium with phaseless far-field data

This paper is concerned with the inverse problem of reconstructing the location and shape of buried obstacles in the lower half-space of an unbounded two-layered medium in two dimensions from phaseless far-field data. Similarly to the homogenous background medium case, for this problem it is also true that the modulus of the far-field pattern is invariant under translations of the scattering obstacle if only one plane wave is used as the incident field, and thus it is impossible to determine the location of the obstacle from such phaseless far-field data. Based on the idea of using superpositions of two plane waves with different directions as the incident fields, a direct imaging algorithm is developed in this paper to locate the position of small anomalies with the intensity of the far-field pattern measured in the upper half-space. This is a nontrivial extension of our previous work (2018 Inverse Problems 34 104005) from the homogenous background medium case to the two-layered background medium case. Both the limited aperture measurement data and the presence of the two-layered background medium lead to difficulties in the theoretical analysis of the proposed imaging algorithm. To overcome the difficulties we employ the theory of oscillatory integrals. Further, with the aid of the imaging algorithm, a recursive Newton-type iteration algorithm in frequencies is proposed to reconstruct both the location and shape of extended obstacles. Finally, numerical experiments are presented to illustrate the feasibility of our algorithms.

Dielectric contribution of the IR absorption bands of porous organosilicate glass thin films on a platinum sublayer

Reduction of interconnect capacitance is one of the key ways to increase the speed of an ultra-large-scale integrated circuit (ULSI). A porous organosilicate glass (OSG) thin film on a platinum sublayer was used as a test vehicle for modelling the conductor–insulator electrodynamic properties in an ULSI. Investigation of the structure and residual effect on the dielectric contributions of the IR absorption bands is a direct approach to control the dielectric properties of the film. The absorption band dispersion was simulated by the Drude–Lorentz equations within a framework consisting of a two-layer medium model. The contributions to the dielectric permittivity of IR absorption bands in thin OSG films with different volume porosities were determined. It was shown that the total dielectric permittivity in the IR region was approximately 10% lower than that at low frequencies of the order of 100 kHz. An additional contribution can arise as a result of low-energy excitations and H2O electrodipole relaxation in the microwave—THz range.

Sensitivity of frequency-domain optical measurements to brain hemodynamics: simulations and human study of cerebral blood flow during hypercapnia.

This study characterizes the sensitivity of noninvasive measurements of cerebral blood flow (CBF) by using frequency-domain near-infrared spectroscopy (FD-NIRS) and coherent hemodynamics spectroscopy (CHS). We considered six FD-NIRS methods: single-distance intensity and phase (SDI and SDϕ), single-slope intensity and phase (SSI and SSϕ), and dual-slope intensity and phase (DSI and DSϕ). Cerebrovascular reactivity (CVR) was obtained from the relative change in measured CBF during a step hypercapnic challenge. Greater measured values of CVR are assigned to a greater sensitivity to cerebral hemodynamics. In a first experiment with eight subjects, CVRSDϕ was greater than CVRSDI (p < 0.01), whereas CVRDSI and CVRDSϕ showed no significant difference (p > 0.5). In a second experiment with four subjects, a 5 mm scattering layer was added between the optical probe and the scalp tissue to increase the extracerebral layer thickness (L ec ), which caused CVRDSϕ to become significantly greater than CVRDSI (p < 0.05). CVRSS measurements yielded similar results as CVRDS measurements but with a greater variability, possibly resulting from instrumental artifacts in SS measurements. Theoretical simulations with two-layered media confirmed that, if the top (extracerebral) layer is more scattering than the bottom (brain) layer, the relative values of CVRDSI and CVRDSϕ depend on L ec . Specifically, the sensitivity to the brain is greater for DSI than DSϕ for a thin extracerebral layer (L ec < 13 mm), whereas it is greater for DSϕ than DSI for a thicker extracerebral layer.

Absolute Measurement of Material Nonlinear Parameters Using Noncontact Air-Coupled Reception.

Nonlinear ultrasound is often employed to assess microdamage or nonlinear elastic properties of a material, and the nonlinear parameter is commonly used to quantify damage sate and material properties. Among the various factors that influence the measurement of nonlinear parameters, maintaining a constant contact pressure between the receiver and specimen is important for repeatability of the measurement. The use of an air-coupled transducer may be considered to replace the contact receiver. In this paper, a method of measuring the relative and absolute nonlinear parameters of materials is described using an air-coupled transducer as a receiver. The diffraction and attenuation corrections are newly derived from an acoustic model for a two-layer medium and the nonlinear parameter formula with all corrections is defined. Then, we show that the ratio of the relative nonlinear parameter of the target sample to the reference sample is equal to that of the absolute nonlinear parameter, and this equivalence is confirmed by measurements on three systems of aluminum samples. The proposed method allows the absolute measurement of the nonlinear parameter ratio or the nonlinear parameter without calibration of the air-coupled receiver and removes restrictions on the selection of reference samples.

Quasi-Stationary Approximation in the Problem of Excitation of Low-Frequency Electromagnetic Fields in Lithosphere

Excitation of electromagnetic field at ultralow, extremely low, and lower frequencies by a horizontal grounded antenna in a two-layer medium is considered. Approximate analytical formulas are derived to describe field evolution in the low-frequency range. Accuracy of the quasi-stationary approximation is analyzed. Substitution of the impedance of a plane wave that is normally incident on the interface for a real surface impedance is estimated. Frequency limits of the approximate approach in the estimation of the Earth conductivity are determined for several experiments performed on the Kola Peninsula in the framework of the FENIСS-2014 and FENICS-2019 International Projects.

Near-field imaging for an obstacle above rough surfaces with limited aperture data

&lt;p style='text-indent:20px;'&gt;This paper is concerned with the scattering and inverse scattering problems for a point source incident wave by an obstacle embedded in a two-layered background medium. It is a nontrivial extension of the previous theoretical work on the inverse obstacle scattering in an unbounded structure [Commun. Comput. Phys., 26 (2019), 1274-1306]. By the potential theory of boundary integral equations, we derive a novel integral equation formula for the scattering problem, then the well-posedness of the system is proved. Based on the singularity analysis of integral kernels, we presented a numerical method for the integral equations. Furthermore, we developed a reverse time migration method for the corresponding composite inverse scattering problem with the limited aperture data. Numerical experiments show that the proposed method is effective to recover the support of an unknown obstacle and the shape, location of the surfaces.&lt;/p&gt;

Nonlinear convection regimes of a ternary mixture in a two-layer porous medium

Numerical experiments have been performed to study the onset and nonlinear regimes of convection of a ternary mixture of methane (35%), ethane (35%), and butane (30%) in a horizontally elongated rectangular region of a porous medium under the action of a geothermal gradient. The region has rigid, impermeable boundaries and is divided into two horizontal layers with equal porosity but different permeability and having the heights in ratio 1:3. The values of medium porosity and permeability are chosen close to those of real media, such as sands, sandstones or limestones. The components of the mixture belong to the main groups of chemical compounds present in oil and gas fields. The configuration under study is a model of hydrocarbon field. The calculations are carried out for the cases when the value of permeability of the upper layer is higher than that of the lower one and, conversely, when the lower layer is more permeable than the upper one. The rest of the parameters of the porous medium are considered to be the same in the entire computational domain. The problem is solved within the framework of the Darcy-Boussinesq model taking into account the effect of thermal diffusion. The temporal evolution of the local characteristics of the flow, the structure of the forming flow, and the distribution of the mixture components is evaluated. Analysis of the data shows that in the case of a more permeable narrow layer, the onset of convection has a local character. The flow arises in a more permeable layer and, as soon as convection develops, it begins to penetrate into a less permeable layer. However, the centers of the forming vortices are noticeably shifted towards the more permeable layer. Similar vortex displacements are observed in a thick layer with higher permeability, yet convection, in this case, is of the "large-scale" character.

Control of spiral wave and spatiotemporal chaos in two-layer aging cardiac tissues

Cardiac arrhythmias can be caused by the occurrence of electrical spiral waves and spatiotemporal chaos in the cardiac tissues, as well as by the changes of cardiac tissues resulting from the electrical coupling of cardiomyocytes to fibroblasts (M-F coupling). How to control the arrhythmia induced by spiral wave or spatiotemporal chaos is the problem which has attracted much attention of scientists. In this paper, a two-layer composite medium is constructed by using cardiomyocytes and fibroblasts. Luo-Rudy phase I cardiac model and passive model of fibroblast are used to study the effects of the M-F coupling on the formation of spiral wave and the control of spiral wave and spatiotemporal chaos in a two-layer composite medium. A control scheme that the spiral waves and spatiotemporal chaos are controlled by increasing the coupling strength between cells is proposed. The numerical results show that the M-F coupling has an important influence on the dynamics of spiral wave. With the increase of the density of fibroblasts, the M-F coupling may result in spiral wave meandering and spiral wave breaking into spatiotemporal chaos, and even induce the transition from spatiotemporal chaos (or spiral wave) to no wave. The eliminating spiral wave and spatiotemporal chaos in the composite medium by increasing the coupling strength between cells is only effective in most of cases, depending on the role played by fibroblasts. When fibroblasts act as current sinks for the cardiomyocyte, the spiral wave and spatiotemporal chaos are effectively eliminated only in most of cases by increasing the coupling strength between cells, and the controlled area is small. When fibroblasts act as a current source for the cardiomyocyte, increasing the coupling strength between cells to a value higher than a critical value can effectively terminate spiral wave and spatiotemporal chaos, and the controllable area is greatly increased compared with the former. Increasing the coupling strength between cardiomyocytes is a key factor in controlling the spiral waves and spatiotemporal chaos.

Sensor Arrangement in Monostatic Subsurface Radar Imaging

This article deals with microwave subsurface imaging achieved by inverting the linearized scattering operator. The focus is on the determination of a strategy for spatially sampling the data which allows to reduce the spatial data measurements and at the same time to keep the same achievable performance in the reconstructions. To this end, the measurement points are determined in order to approximate the point-spread function corresponding to the ideal continuous case (i.e., the case in which the data space is not sampled at all). For the sake of simplicity, the study is developed for a 2D scalar configuration. Also, the standard mono-static measurement arrangement is considered. However, in order to mimic a subsurface imaging scenario, a two-layered background medium is addressed. The main idea is to introduce suitable variable transformations which allow to express the point-spread functions as a Fourier-like transformation; this then provides insights for devising the sampling scheme. It is shown the resulting measurement spatial positions must be non-uniformly arranged across the measurement domain and their number can be much lower than the one provided by some commonly used literature sampling criteria.

Validation of a comprehensive analytical model for photothermal therapy planning in a layered medium with gold nanoparticles

Photothermal therapy (PTT) is a minimally invasive alternative to conventional surgery and can provide faster recovery times as well as reduction in complication rates. Successfully targeting of gold nanoparticles to the tumor increases its light absorption leading to more important temperature rise in the tumor than surrounding tissue. Hence, it is possible to heat tumor with a minimal damage to the surrounding tissue only if the appropriate laser parameters are employed. In this study, our purpose is to develop a simulation tool capable of determining temperature rise and duration in the tissue for therapy planning. This simulation tool is based on a new analytical approach which models laser-induced temperature in a two-layered medium mimicking concentric tumor and its surrounding healthy tissue. First, the diffusion equation is used to model the light propagation in tissue and then a comprehensive solution is derived by obtaining a special Greens’ function. Next, the Pennes' bioheat equation is analytically solved for a source term defined as the product of local optical absorption and the solution of the diffusion equation. Our approach is validated by comparing the spatiotemporal temperature distribution obtained by our method, finite element method, and experimental studies, respectively. The obtained results are in very good agreement with an average R-squared of 0.953. This analytical approach can provide a suitable and fast platform for modeling laser-induced temperature distribution for thermal therapy applications.

Isolated buoyant convection in a two-layered porous medium with an inclined permeability jump

Abstract

АCCOUNTING THE SEISMIC COMPONENT OF THE LATERAL PRESSURE OF AN HETEROGENEOUS ANISOTROPIC SOIL ON MASSIVE HYDROTECHNICAL STRUCTURES

Abstract. Strength anisotropy is characteristic of layered soil bases and has been confirmed by numerous tests. The relevance and novelty of this research is to study the effect of the seismic factor on the active pressure of the friable soil medium having strength anisotropy. A numerical experiment was carried out using a specially developed computer program, the algorithm of which used the method for determining the lateral pressure of a heterogeneous anisotropic soil, taking into account the seismic effect. The proposed method is based on the solutions of the classical theory of Coulomb, the seismic component is taken into account on the basis of the static theory of the earthquake stability of structures. We considered a vertically ideally smooth wall in contact with a two-layer incoherent soil medium, the anisotropy of the strength properties of which is represented by hodographs of friction angle. The layers are parallel, no surface load. A numerical research was to determine the parameters of the active pressure of the soil of the lower layer during rotation of the hodograph of friction angle with steps of 300. We used 4 hodographs: 1) φ1=150-200; 2) φ2=200-250; 3) φ3=250-300; 4) φ4=300-350 with a horizontal plane of isotropy. Seismic impact was taken into account by the seismicity coefficient, taken equal to depending on the scale 0.025 (7), 0.05 (8), 0.1 (9). The horizontal orientation of the seismic force and with an angle of 200 to the horizontal plane was set. The obtained results make it possible to evaluate the seismic effect on the lateral pressure of anisotropic soil by comparing it with the corresponding indicators obtained earlier without taking into account the seismic factor. An analysis of computer solutions indicates the increase of the active pressure in seismic conditions by 14%-45% compared with the same indicator, which was determined without taking into account the seismic factor.

Application of Independent Finite Element Modeling for Estimating the Effect of Simplest Landforms on Results of Inversion of Electrical Resistivity Tomography Data (Example of a Trench with the Triangular Cross-Section)

In solving the problems of shallow depth electrical prospecting of the daylight surface, the topography is a factor that has a significant impact on the results of the inversion of electrical resistivity tomography data. Verification of the results of inversion of the field data is a laborious task due to the complex structure of the original geological medium. At the same time, the development of computer numerical simulation methods allows obtaining electrical resistivity tomography data for simple models of the medium. The results of estimating the effect of the simplest landforms on the results of the inversion of electrical resistivity tomography data obtained by numerical simulation by the example of the model of a trench with the triangular cross-section are presented. Numerical simulation is performed based on the finite element method by an inversion-independent technique. It is determined that the inversion of the tomography data for the trench in a homogeneous half-space produces false anomalies, with the maximum located under the axis of the trench. It is shown separately that in the presence of real inhomogeneity at this position, it can, depending on its resistance, be masked (compensated) by the false anomaly, or strengthen it. If the trench is in a two-layer medium, then there is a distortion of the boundary between the layers at some interval under the trench, repeating the trench shape.

Semi-graphical method for plotting a frequency characteristic of impact noise level’s reducing

The article describes the application of rolled floor materials for sound insulation of impact noise by the floors. A detailed classification of such materials is given, including such materials as linoleum, rubber linoleum and carpet. The described method is appropriate for testing the floor to obtain the frequency characteristics of the normalized level of impact noise of the whole structure and for the frequency characteristics of improvement of sound insulation due to the use of roll coverings. Methods for normalized impact noise level indices calculation in case of composite construction and only roll covering are also briefly described. A new semi-graphical method for constructing the frequency response of reducing the level of impact noise by floor covering for inserted floors is presented. A computational model for solving the contact problem of the impact noise isolation by floor in the form of an oscillatory system, consisting of an absolutely solid body and a two-layer elastic medium, is presented. The solution of the contact problem for obtaining an adjustment for reducing the normalized level of impact noise due to the application of a roll material is shown. The equation for frequency of crumpling for the linoleum surface crumpling in the process of standard striking machine’s impact is shown. The effect of local crumpling occurs and the growth of sound insulation starts in two-layer floor from this frequency’s value. The analysis of calculations accordingly the proposed calculation method is carried out. The practical algorithm for semi-graphical method and for the frequency response plotting of impact noise sound insulation improving by the roll floor covering is proposed. Graphs of the magnitude of impact noise improvement by the most common roll materials, that can be used to obtain the frequency response of impact noise isolation by a two-layer floor, are given.

Characterization of Bacillus spp. from the rhizosphere of potato Granola varieties as an antibacterial against Ralstonia solanacearum

Abstract. Prihatiningsih N, Arwiyanto T, Hadisutrisno B, Widada J. 2020. Characterization of Bacillus spp. from the rhizosphere of potato Granola varieties as an antibacterial against Ralstonia solanacearum. Biodiversitas 21: 4199-4204. Ralstonia solanacearum is one of the important wilt pathogens that significantly decreased potato yields in Indonesia. One of the strategies to control wilt disease is the use of Bacillus sp. that isolated from potato rhizosphere. Bacillus sp. is an antagonist against some phytopathogenic fungi and bacteria. The objectives of the study were to identify 5 strains of Bacillus spp. (B46, B209, B211, B298, and B315) that is capable of suppressing the growth of R. solanacearum. Experimental assays were performed to determine the growth inhibition of R. solanacearum by culturing in a two-layer medium. The identification of Bacillus spp. was performed based on physiological and biochemical characters and molecular identification. Results showed that all of Bacillus spp. are capable of suppressing the growth of R. solanacearum. B. subtilis B315 isolate was the most effective biocontrol agent in inhibiting R. solanacearum growth by a bacteriostatic mechanism. All Bacillus spp. have similarities in physiological and biochemical characters. Based on the molecular analysis, Bacillus sp. B46, B209, B211, and B298 were homologous to B. subtilis subspecies spizizeni RRLKE2, whereas Bacillus sp. B315 was homologous to B. subtilis strain WIFD5.

The effect of snow covers properties and air temperature on the ice freezing thickness near Yakutsk

This study is devoted to the possible Yakutsk Lena–river automobile and railway bridge construction and estimation of icing and ice blockage formation possibility variation. So, according to developed algorithm and calculating scheme the calculations of ice freezing thickness variations for observation site of Yakutsk Lena-river hydrological station were performed on basis of meteorological data on air temperature and snow cover thickness for winter periods of 1980/81-2018/19. The comparison of calculated and available in open access observation data on ice freezing thickness for these winter periods was also conducted and the coefficient of correlation of equal 0.7-0.8 for them was stated. The calculating scheme for ice freezing is constructed on basis of two-layer media heat conductivity problem (snow cover, ice) with phase transition on the boundary of ice and unfrozen water. Heat balance equation includes phase transition energy on the interface and outflow of heat through ice and snow cover into the atmosphere. The heat flux is calculated on basis of Fourier law as a product of heat conductivity and temperature gradient. It is supposed, that temperature changes in each media linearly.