Two-layer Slab Research Articles

Dimensionality and strain-dependent properties of Orthorhombic (100) NaTaO3 thin films: A comprehensive DFT investigation

The modulation of perovskite oxide thin films’ properties, through both intrinsic and extrinsic methods, has been extensively studied to enhance their photocatalytic performance. We employed ab initio density functional theory calculations to investigate the layer-dependent structural and electronic properties of orthorhombic NaTaO3 thin films. Our findings reveal that slabs comprising five, four, and three layers retain the non-magnetic and semiconducting characteristics of the bulk material, with their properties progressively converging towards those of an infinite-surface slab as the number of layers increases. Biaxial in-plane strain induces a linear change in the structure of surface TaO4 tetrahedra, thereby altering the film’s band gap. Notably, the two-layer slab exhibits a transitional behavior between the bulk-like nature of thicker films and the unique features of a NaTaO3 monolayer, showing heightened sensitivity to strain. Under compression, this bilayered system acquires bulk-like properties, whereas its strain-free state is magnetic and metallic akin to the monolayer. Similar transitions are observed in the latter, though under higher compression values. We provide an in-depth discussion of the structural and electronic mechanisms underlying these transitions. Additionally, the relative band-edge alignment with water-splitting photocatalytic potentials underscores the complex interplay between strain and dimensionality. This work offers valuable insights towards the design of more efficient photocatalysts, highlighting the potential of engineered NaTaO3 thin-film structures for advancing photocatalytic applications.

Flexural behavior of two-layer reinforced concrete slab with hollow cores

Flexural behavior of a concrete slab system with an optimal weight-to-strength ratio comprising layered and hollow-core slab structures was investigated using two-layered slabs with hollow cores (LS/HCS). Six slabs with dimensions of 180, 450, and 1600 mm were tested experimentally and numerically using ANSYS software. Each layered slab comprises a 90-mm-thick lightweight concrete bottom layer and a 90-mm-thick high-strength concrete top layer. Three parameters were studied: core diameter (58, 86, and 110 mm), reinforcement ratio (0.37%, 0.53%, 0.95%), and treatment type (bonding agent, nails). Treatment types were analyzed via push-out testing; both nails and agents connected the slabs with sufficient bond strength. A control slab with 86-mm core diameter, shear-span-to-effective-depth ratio of 4, reinforcement ratio of 0.53%, and agent material was used. Concrete, steel bars, and loading support plates were modeled using SOLID65, LINK180, and SOLID185 elements, respectively. Analytical results were validated experimentally. A parametric study analyzed other parameters affecting LS/HCS behavior, including compressive strength, opening numbers, core shape, applied loading type, added top steel reinforcement, slab type, and slab height. Core diameter reduction, increased reinforcement ratios, and using nails enhanced the failure load. The LS/HCS gives an optimum weight-to-strength ratio with a 33.672% reduction compared with solid slabs.

Coupled heat transfers resolution by Monte Carlo in urban geometry including direct and diffuse solar irradiations

Modelling transient combined heat transfer in complex urban geometry is a key step to predict human exposure or energy consumption and to quantify the effect of climate change mitigation and adaptation measures. A difficulty lies in the possibility for a model to scale up and integrate large and complex urban morphology. We develop a probabilistic approach to solve heat transfers with the Monte Carlo method that is insensitive to the complexity of both the urban geometry and the boundary conditions. The integral formulation that includes random walks for each heat transfer mode is presented and the computation of absorbed solar irradiations at walls with the double randomization technique is detailed. Numerical validations are given through comparisons with deterministic method results for single and two-layer slabs, but also a three-dimensional thermal bridge geometry. The developed probabilistic heat transfer model is then used in a demonstration heat wave scenario where are computed: the outdoor mean radiant temperature showing the influence of trees; and the indoor average wall temperature showing the influence of solar gains through windows.

Lattice Boltzmann method for radiative transfer in two-layered slab with graded-index and Fresnel reflecting surfaces

Analysis of transport of radiative transfer in an inhomogeneous two-layered slab with graded refractive indices and bounded by Fresnel's reflecting walls is carried out using the lattice Boltzmann method. The radiative intensity in each layer is found as a superposition of two radiative waves, which undergo multiple reflections and refractions at the boundaries and interface. The accuracy and efficiency of the methodology is first tested for steady-state problems with constant or variable refractive indices and for time-resolved reflectance and transmittance in a single layer with graded-index. The effect of the governing parameters is examined and the results show that these parameters significantly influence radiative transfer. Especially, the curvature of the incoming beam due to refractive index variation changes when considering the increasing or decreasing variation of the refractive index. The smaller refractive index gap at the interface induces smaller reflection and radiative intensity discontinuity at the interface, while increasing the scattering albedo has no significant effect on the transmittance signal but corresponds to increasing the reflectance signal which takes more time to show the steady state profile. Moreover, the developed LBM is an efficient, powerful, and accurate solver for radiative transport in inhomogeneous layered media with graded-index.

Assessment of Impact Strength of Two-layer Fibrous Concrete Slab Using Polypropylene & Steel Fiber with Mineral Admixture

Introduction. The impact strength through of Two-layer (600 mm × 600 mm × 60 mm) concrete slab was experimentally investigated by the following method using Weight falling test (ACI committee 544). Result. Nine numbers of slab specimens were cast (S1 to S9), with one specimen (S1) was normal plain cement concrete slab (control specimen). The purpose of the study, The addition of Polypropylene fibre (PPF) in the top 30 mm depth of the slab was from 0.2 % to 0.8 % in step of 0.2 % and the addition of hooked end steel fibre (SF) in the bottom 30 mm depth of the slab was from 0.5 % to 2 % in step of 0.5 % for the other two layered slab specimens (S2 to S9). Also, a fixed 20 % (out of the total requirement of the binder) of mineral admixture namely Ground Granulated Blast Furnace Slag (GGBS) was used as a partial replacement of binder in all the slab specimens. Each specimen was tested under weight falling test. The number of blows required to obtain final crack failures in specimens was 30, 98, 168, 125, 252, 102, 153, 245 and 46 respectively for S1 to S9. Conclusions. The comparative analysis of crack pattern and impact strength of 2-layer fibre reinforced concrete slab specimens (S2 to S9) were presented. The performance of slab specimen S5 was the best among other slab specimen and it had absorbed more impact energy and controlled crack less than the normal plain cement concrete slab specimen (S1).

Interlaminar shifts of two-layer aggressive-resistant combined plates based on metal and fiberglass

In this work, the stress and deformation states of plates made of metal layers wrapped with composite materials in the inner or outer layers were studied. The main goal of this research is to create durable, long-lasting and aggressive environment-resistant structures that can easily bear external dynamic and static loads. The work used the Navier method to study the effects of interlayer displacement. It was found that the lower the modulus, the greater the effect of joint compliance on the deformation of laminated composite plates. A regularity has been established that the greater the thickness of the bearing fiberglass layer, the less the effect of the shear modulus of the seam on the stresses and deformability of two-layer combined slabs. A regularity has been established, the greater the thickness of the bearing metal layer, the less the effect of the shear modulus of the seam on the stresses and deformation of two-layer combined plates.

THE STANDARD HASSUNA POTTERY OF THE YARIM TEPE I SETTLEMENT FROM THE COLLECTION OF THE PUSHKIN STATE MUSEUM OF FINE ARTS

The article overviews the distribution of Neolithic pottery of the Standard Hassuna period in Upper Mesopotamia: from the foothills of the Taurus in the north to approximately the region of the Diyala river in the south; from the foothills of the Zagros in the east to the Balikh river, or possibly as far as the Euphrates river, in the west. In addition, the pottery of the Standard Hassuna (or the influence of this pottery tradition) is recorded in the hinterland of the Zagros. Based on the materials of the Yarim Tepe I settlement from the collection of the Pushkin State Museum of Fine Arts, the paper examines technological features of the Standard Hassuna pottery. They demonstrate a connection with the pottery technology of the previous periods of the Hassuna culture – Proto-Hassuna and Archaic Hassuna: the presence of an organic plant admixture (dung) in the pottery paste of a part of the vessels and the use of a two-layer slab construction. The innovations include the use of a light slip, as well as the improvement in the quality of firing, associated with the significant development of firing devices at that time. It is possible to assume the appearance of pictographic images on the Samarra pottery represented on the site as items of import.

Time-Domain P3 Equation for Light Transmission in Two-Layer Slab Medium

Time-Domain P3 Equation for Light Transmission in Two-Layer Slab Medium

Analysis of Neolithic Pottery Technology along the Iranian Zagros Foothills

The article presents the results of a technological analysis of the ceramic samples from Neolithic settlements of Ali Kosh, Mahtaj and Guran (the 7th mill. BC). The use of sheep and goat dung in the paste prevailed. While two-layer slabs were applied as the main construction method across the region, a few samples from Guran show the appearance of coil construction around the middle of the 7th millennium BC. First an overall coating with the same clay and red colouring appeared, and later a new type of red slip emerged – a mixture of clay with red pigment.

Far-Field Subwavelength Straight-Line Projection/Imaging by Means of a Novel Double-Near-Zero Index-Based Two-Layer Metamaterial.

In this paper, for the first time, tuned near-zero-index materials are used in a structure for the long-distance projection of very closely spaced objects with subwavelength separation. Near-zero-index materials have never been used for subwavelength projection/imaging. The proposed novel structure is composed of a two-layer slab that can project two slits with a subwavelength separation distance to a long distance without diverged/converged interference of the two imaged waves. The two-layer slab consists of a thin double-near-zero (DNZ) slab with an obtained tuned index of 0.05 and thickness of 0.04λ0 coupled with a high-index dielectric slab with specific thicknesses. Through a parametric study, the non-zero index of the DNZ layer is tuned to create a clear image when it is coupled with the high-index dielectric layer. The minimum size for the aperture of the proposed two-layer slab is 2λ0 to provide a clear projection of the two slits. The space between the slits is λ0/8, which is five times beyond the diffraction limit. It is shown that, through the conventional methods (e.g., only with high-index dielectric slabs, uncoupled with a DNZ layer), it is impossible to clearly project slits at a large distance (~λ0) due to the diffraction limit. An analytical analysis, as well as numerical results in a finite-element-based simulator, confirm the function of the proposed structure.

The ordinate weighting method for solving radiative heat transfer through a Fresnel interface

Refraction of electromagnetic waves at Fresnel interfaces, i.e. the boundaries between media with different refractive indices, is important not only in explaining many natural phenomena but also in radiation heat transfer in energy conversion and combustion systems, such as solar energy, spray cooling and combustion, and the evaporation of liquid fuels in pool fires. This paper presents a novel model for the efficient consideration of Fresnel interfaces in the Finite Volume Method-based solvers of thermal radiation. By conserving the transmitted radiative heat flux at the Fresnel interface, the new model accurately estimates the directional distribution of radiative intensities on the second side of the interface. To do so, a matrix of weighting coefficients is obtained, representing the transferred radiation energy from the control angles on the first side of the Fresnel interface into each control angle on the second side. To assess the accuracy of the novel ordinate weighting method (OWM), its predictions are compared with the analytical solutions that we obtained for one- and two-layer slabs with various combinations of absorption and scattering properties. The validations are shown for normalized heat flux and irradiation, reflectivity, transmissivity, and intensity. The predictions of the OWM show an excellent agreement with the results of the analytical solutions. Compared to Murthy’s pixelation method, the OWM method provides better accuracy with lower computational cost. Finally, the sensitivity of the OWM method to uniform and non-uniform directional discretizations, used in the finite volume solution of the radiative heat transfer, is investigated.

Influence of Reinforcement Fiberglass Grids Used in Asphalt Pavement on the Bonding of Layers

The paper deals with the influence of geosynthetic reinforcement systems on the quality of asphalt bonding layers. A reinforcing element in the form of a fiberglass grid is incorporated into the road structure between two asphalt layers to prevent the formation of cracks and to reduce the tendency of their subsequent propagation throughout the asphalt layers. At the same time, however, they form a potential weak interlayer on which adjacent asphalt layers may slip. The total 90 drilled cores taken from a laboratory-produced two-layer slabs were subjected to the Leutner shear test. The selection of individual specimens took into account both the type of reinforcement element and the amount of applied bituminous emulsion.

The Use of a Monte Carlo Markov Chain Method for Snow-Depth Retrievals: A Case Study Based on Airborne Microwave Observations and Emission Modeling Experiments of Tundra Snow

Snow-depth retrieval from passive microwave observations without a priori information is a highly undetermined problem. Achieving accurate snow-depth retrievals requires a priori information on the snowpack properties, such as grain size, density, physical temperature, and stratigraphy. On a practical level, however, retrieval algorithms must consider prior information, while minimizing the dependence on it, as accurate ancillary data are not globally available. In this study, we build on the previously published Bayesian Algorithm for Snow Water Equivalent Estimation (BASE) to retrieve snow depth using an airborne passive microwave data set over the tundra snow in the Eureka region. The method computes the optimal estimates of snow depth, density, grain size, and other variables, given the brightness temperature observations and prior information, using Markov chain Monte Carlo (MCMC). The airborne data set includes passive microwave brightness temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> ) at 18.7 and 36.5 GHz. The in situ measurements of the snow depth provide validation data for 464 sensor footprints. The microwave radiative transfer (RT) model used is the Dense Media RT-Multilayered (DMRT-ML) model. We use a two-layer wind slab and depth hoar assumption based on the local snow cover knowledge from the previous research on the study area. To improve our understanding of the results using the airborne T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> s, the inversion was also applied using the synthetic observations, where T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> s were generated from the RT model. For the case with synthetic observations, the snow-depth RMSE was 0.07 cm. When the airborne T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> s are used, the snow-depth RMSE was 21.8 cm. This discrepancy is due to the large spatial variability in the MagnaProbe snow-depth measurements and the fact that not all physical processes affecting the airborne T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> s are represented in the RT model. Our work verifies the feasibility and applicability of the proposed methodology regionally for the airborne retrievals and reinforces the tractable applicability of a physics-based RT model in the SWE retrievals.

ОПТИМИЗАЦИЯ СТРУКТУРЫ ПОЛА ПРОМЫШЛЕННОГО ЗДАНИЯ

When determining the design of the floor, choosing materials and technology of its device, it is advisable to apply a systematic approach that takes into account its stress-strain state. The physical model of the floor of an industrial building in a simplified form is represented as a two-layer slab on an elastic base. The physical model of the floor of an industrial building in a simplified form is represented as a two-layer slab on an elastic base. The deformation of the ground base is inherent in the stress-strain state of the structure, which is manifested through geometric and mechanical characteristics, boundary conditions., glass fiber concrete is proposed as a coating material. It provides the compressive strength inherent in concrete and a proper crack resistance. The mathematical model is based on the S. Germain equation and the Winkler dependence. When solving the optimization problem in a linear elastic formulation, the criterion of the minimum potential energy of deformation is used, which leads to a minimum of material consumption. Its effectiveness is confirmed by comparing the results on a variational basis with the analysis of the regression equation. The modulus of longitudinal elasticity and the thickness of the layer are accepted as variable parameters. The calculation procedure uses a finite-difference analog of the mathematical model. A two-factor experiment is conducted to complete the study, the results of which are in good agreement with the theoretical calculations performed.

Phytoplankton acclimation to changing light intensity in a turbulent mixed layer: A Lagrangian modelling study

A new individual-based plankton model is used to test the hypothesis that the timescale of photoacclimation of phytoplankton within the surface mixing layer of the ocean is slow relative to mixing, in which case the chlorophyll to carbon (Chl:C) ratio of individual cells shows little adjustment in response to changes in light environment driven by vertical displacement. Rates of photoacclimation are shown to be a strongly non-linear function of light intensity that depends on the balance of intrinsic chlorophyll synthesis at low irradiance versus increasing growth rate at high irradiance. Predicted photoacclimation was negligible for cells experiencing rates of turbulent mixing typical of the open ocean surface boundary layer (10−3 to 10-1 m2 s-1), in which case Chl:C is set by mean light intensity. The model was extended to incorporate a simple ecosystem of nutrient, phytoplankton, zooplankton and detritus and, using two-layer slab physics, used to study photoacclimation in a more realistic setting, the seasonal cycle of plankton dynamics at Ocean Weather Station India in the North Atlantic (59 °N, 20 °W). Results were remarkably similar when compared with an equivalent ecosystem model that used an Eulerian representation of phytoplankton, reinforcing our conclusion that mixing rates within the surface mixed layer of the ocean are typically too fast to permit photoacclimation by phytoplankton to ambient light.

A Circularly Polarized Horn Antenna Based on an FSS Polarization Converter

This letter designed a circularly polarized horn antenna by loading a frequency selective surface (FSS) polarization converter at the aperture of a standard horn. The proposed polarization converter is based on multilayer nonresonant FSS. It is composed of a two-layer dielectric slab and three printed metal layers, which are etched on the top, middle, and bottom layers of the slab. The three metal layers consist of a two-layer patch with a square truncated corner and a one-layer grid line with a slot. By introducing perturbation to both the patch and the grid line, the polarization converter shows a low profile and subwavelength unit size, whose dimension is 0.18 λ 0 × 0.18 λ 0 while the thickness is only 0.1 λ 0. The simulated results show that the axial ratio (AR) is less than 3 dB in the frequency range of 9.6–11.7 GHz, i.e., a fractional bandwidth of 19.7% within the targeted frequency band. The measurement results are in a good agreement with the simulation results, which proves the feasibility of the design.

Mutual coupling reduction in planar Yagi antenna array using bidirectional absorbing metasurface

An effective method for reducing the mutual coupling between the antenna arrays using a bidirectional absorbing metasurface is proposed in this article. This is achieved by embedding the bidirectional absorbing metasurface between the two planar Yagi antennas. The metasurface is mainly composed of 3 × 6 unit cells. Each unit cell includes three-layer metal rings and two-layer dielectric slabs. Since the front and back of the metasurface are completely consistent, a bidirectional absorptivity can reach to 86% or more. Using the proposed metasurface, the mutual coupling at the resonance point can be reduced to about 38 dB. And it has little effect on other performances of the Yagi antennas. Moreover, the proposed metasurface can improve the radiation performance of the antenna array, and make it have a smaller back lobe and a larger front-to-back ratio.

STRENGTH ANALYSIS OF VARIABLE RIGIDITY SLABS ON ELASTIC SUPPORT WITH VARIABLE SUBGRADE RATIO

The paper presents the strength analysis of variable rigidity slabs on elastic support with the variable subgrade ratio. The analysis is based on a solution of the differential equation of the slab flexure using the finite element method. The results are obtained for different slabs on the elastic support. The results are presented for the different thickness of the upper layer of the two-layer slab on the elastic support with the variable subgrade ratio.

Investigation of single- and double-layer slabs supported on four sides.

Presented method and results of experimental research of deflection of single-layer and two-layer slabs influenced by short-term lateral load. Proposed method of calculation based on the limit equilibrium method, calculation of slab deflections values by LIRA-CAD bundled software. The comparison of experimental and theoretical results of the calculation of deflections slabs.

Circumferentially conformal slot array antenna and its Ka‐band multibeam applications

A standing-wave slot array covered with a two-layer dielectric slab based on substrate integrated waveguide (SIW) technology, which is circumferentially conformed to a cylinder, is designed, fabricated and measured at Ka-band. The radiating part consists of seven slotted cylindrical SIWs, each of which has four-element longitudinal slots. Several such slot arrays fed by Rotman lenses are grouped on a cylinder along the circumferential direction to cover a 2D field of view. The microstrip Rotman lens is employed as the beamforming network with seven input ports, which can generate a corresponding number of beams to cover -35° to 35° along 1D ( E -plane). Another dimension ( H -plane) is covered from -52° to 52° with four beams generated by the slot arrays group. A prototype antenna is fabricated, the measured results demonstrate its ability of scanning over a 2D field of view with multiple beams. This type of multibeam conformal antenna is a good candidate for high-speed vehicles or communication base stations requiring electronic beam-scanning capabilities and considering conformal reasons.