Multilayer Slab Research Articles

Approximate P3 equation analysis in multi-layer slab media: steady-state and time-domain based on the diffusion model

This study aimed to establish a steady-state and time-domain solutions for the approximate P3 equation in arbitrary multi-layer slab media for light propagation, based on a diffusion model with an isotropic point source in the first layer and extrapolated boundary conditions. Spatially resolved diffuse reflectance and transmittance were calculated using the steady-state approximation of the P3 equation, whereas temporally resolved diffuse reflectance and transmittance were derived from the time-domain approximation. The validity of the approximate P3 solutions was confirmed by comparing their results with Monte Carlo simulations. In steady-state analysis, the approximate P3 equation demonstrated superior accuracy to the diffusion equation for reflectance, particularly at smaller thicknesses. Accuracy further improved as the absorption coefficient and detection distance increased. For transmittance, the approximate P3 equation closely matched the diffusion equation at low thickness, but divergence occurred with higher absorption. In time-domain analysis, the approximate P3 equation aligned closely with Monte Carlo simulations at peak values, while its numerical values were close approximations of the diffusion equation away from the peak. The potential application of the approximate P3 equation in multi-layer media offers significant advancements for optical non-invasive detection and treatment techniques, enabling the extraction of optical parameters from such media.

Halide Perovskite Thin Film Lasing Mode Control.

Metal halide perovskite semiconductors have emerged as highly efficient amplifying materials; to ensure practical applicability, it is important to have precise control over the spectral and polarization characteristics of lasing emission. In this study, we present effective strategies for manipulating single- and multimode lasing from surface-emitting and optically pumped perovskite distributed feedback lasers. We show that cladding structures can be made to modify the optical properties of guided transverse electric and magnetic modes within the gain medium. This leads to spectral tuning of multipeak lasing emission and the generation of linear polarization modes. Our results are supported with a comprehensive multilayer slab waveguide model and confirmed with two different perovskite materials: methylammonium lead iodide and cesium lead bromide.

Effect of active site size in dispersed MoS2 nanocatalysts on slurry-phase hydrocracking of residue

This work investigates the influence of active site size in dispersed MoS2 on the slurry-phase hydrocracking of Merey residue (MRR). MoS2 nanocatalysts with varying morphologies were synthesized using the ligand sulfurization method, employing molybdenum oleate as the Mo precursor. The results demonstrate that mono-layered or double-layered MoS2 plates with slab sizes of 3 ∼ 10 nm can be synthesized at a sulfurization temperature of 400 °C and a sulfurization time of 0.5 h. Prolonged sulfurization time results in the growth and agglomeration of MoS2 plates, leading to multi-layered slabs with increased length and larger particle size, as well as a wider distribution range. The MoS2-0.5 (prepared with a sulfurization time of 0.5 h) exhibits superior hydrocracking activity, effectively converting resin and asphaltene into light fractions and significantly suppressing coke formation. Specifically, the conversion rates of resin and asphaltene are 51.3 wt% and 92.1 wt%, respectively, with the minimal coke yield of 0.6 wt% under conditions of 430 °C, 1 h, 7 MPa initial H2, and a catalyst dosage of 500 μg/g. The catalytic activity of the MoS2 nanocatalysts exhibits a strong correlation with their size and morphology obtained at different sulfurization times. Density functional theory (DFT) calculations reveal that MoS2 with smaller slab sizes are more beneficial for the adsorption and dissociation of H2, due to higher adsorption energy (Eads) and lower activation barrier (Ea). This facilitates the generation of sufficient active hydrogen to encourage the hydrocracking of residue and suppress coke formation.

Design of high-efficiency InP/InGaAsP diluted waveguide for edge couplers

To transition integrated optical communication devices from laboratory settings to practical applications, efficient coupling between optical fibers and chip waveguides remains pivotal. This paper presents a systematic design of a diluted waveguide, a key component in the edge couplers of photonic integrated circuits. The primary purpose of the diluted waveguide lies in facilitating superior edge coupling with fiber waveguides, thereby seamlessly integrating external light sources into the waveguide structure. To commence, we employ the transfer matrix and effective refractive index techniques to simplify the 3-dimensional diluted waveguide into 2-dimensional multi-layer slab waveguides. By computing the field distribution of the fundamental mode within the diluted waveguide, the fiber-to-waveguide coupling efficiency can be derived using a simplified overlap equation and optimized diluted waveguide structure through particle swarm optimization algorithms. Consequently, we achieve a remarkable fiber-to-waveguide coupling efficiency exceeding 95% for TE-mode and 92% for TM-mode, with a polarization dependent loss (PDL) of merely 0.13 dB. Interestingly, the optimized diluted waveguide exhibits quasi-single mode behavior, as the fundamental mode containing 98% of the total energy propagates within it. Additionally, the diluted waveguide edge coupler demonstrates favorable alignment tolerance, with 1-dB excess losses of ±2.3 μm and (−2.5, +3) μm along the horizontal and vertical directions, respectively. Notably, our approach offers a versatile methodology for designing multi-layer waveguides across various materials. This method has the potential to be universally applied.

Finite Element Analysis of Sandwich Plates with Different Percentages of Delamination

Abstract: The present study pinpoints the effect of delamination in multilayer glass fiber-reinforced composite slabs. The unit cell method of homogenization has been used to find the effect of air inclusion in the glass fiber-reinforced polymer composite. The natural frequency has been obtained up to different modes on every condition. The modal analysis module of ANSYS has been used to obtain the natural frequency for different boundary conditions The present study considered 0% to 10 % of total volume as delamination in four steps (0.5, 1.0, 5.0, and 10%). Two types of boundary were considered in the present study, in the first condition the plate is fixed from all four sides, the second two sides are assumed to be free, and the remaining two sides are fixed.

Bayesian optimization of periodic multilayered slabs for passive absorptivity control

A vanadium dioxide (VO2) film grown on a titanium oxide crystal shows a metal–insulator transition at room temperature with drastically changed optical properties. A multilayered slab with a sub-micron scale VO2 film was proposed to utilize its unique properties for passive intensity control of sunlight absorption and radiative cooling. Its optimal geometries were numerically explored using the Bayesian optimization (BO) method. BO was applied for three types of multilayered slabs, those having one, two, or three isolated slabs of different widths. For each type of multilayered slab, BO could optimize geometric variables with practical calculation times considering the total number of possible combinations of variables, which is subsequently referred to as the total number of candidates. Optimization results revealed that two isolated slabs had the most suitable spectral absorptivity in both hot and cold environments. The infrared absorptivity of the double slab was kept low in cold conditions to suppress radiative cooling. However, the double slab exhibited good radiative cooling performance under hot conditions. Electromagnetic energy density surrounding the slab illustrated that metallic VO2 and gold placed in a parallel manner excited the coupled mode of surface plasmon polaritons to enhance absorptivity. Radiative cooling faded for the triple slab because each slab could couple with radiation propagating only across a portion of the cross-sectional area. Through three BO trials, improvement of the VO2 visible reflectivity was recognized as a future issue for further development of passive sunlight absorption control.

Advantages and Disadvantages of Computational Dosimetry Strategies in the Low mmW Range: Comparison Between Multilayer Slab and Anthropomorphic Models

Wireless technologies spanning at the higher bands of microwave range (i.e., Ka-band) are gaining increasing importance in everyday life. Most recent wireless power transfer (WPT) applications work in the microwave and millimeter wave (mmW) frequencies, overlapping with the new frequency bands of the fifth-generation (5G) mobile technology. The spread of such novel electromagnetic (EM) sources raised the need to investigate their possible effects on population’s health. Numerical dosimetry is fundamental to assess the exposure of the human body. In the range 24–28 GHz, i.e., the low-band spectrum of the mmW, and bridge between microwaves and mmW, there is poor consensus on the best strategy to model the human body. This article proposes a comparison between the two numerical methodologies typically adopted for this frequency range: the use of multilayer planar slabs and realistic anthropomorphic numerical models. The aim is to highlight the advantages and limits of each method, by comparing EM exposure results obtained on the Virtual Population (ViP) model Duke with several multilayer planar slabs. The differences between the two methods are non-negligible, suggesting the need of further studies and the necessity of improving both modeling approaches, depending on the frequency of work and the investigated application.

Study of the moving multilayer slab acted by oblique incidence electromagnetic wave using the transfer matrix method

The boundary conditions of the moving layered medium are analyzed and the expressions of electromagnetic field are deduced. The reflection and transmission coefficients in fixed coordinates are obtained by using the covariance characteristic of Maxwell Equations. It is very complicated to apply boundary conditions many times in analyzing a multi-layer slab. In this paper, the results obtained from the boundary conditions of single-layer slab are analogous with those obtained by the transfer matrix method. Through improvement and generalization, the transfer matrix method can be used to calculate the moving multi-layer slabs. It can be applied to calculate the reflection and transmission coefficients of one-dimensional moving photonic crystal as well as deal with TM and TE polarization for the oblique incident. The zero reflection points of TM and TE polarization for layered slab are calculated. The results calculated in this study are matching well with the reference. It shows that the reflection oscillation enhances with the increase of [Formula: see text] and layer number, while the changing rule of reflections about TM polarization is relatively complex. The reflections of both TE wave and TM wave are all related to the incidence angle.

Analysis of transmission performance on wireless power transfer system with metamaterial

Abstract In order to solve the problems of low power transfer efficiency (PTE) and limited distance in magnetic coupling resonant wireless power transfer (MCR-WPT) technology. In this paper, based on the magnetic field control ability of metamaterials (MMs), the way to improve the performance of MCR-WPT systems is studied. First, the influence of MMs on the coupling of MCR-WPT system is theoretically analyzed by establishing an equivalent circuit model. Through a series of simulations and experiments, the relationships between the PTE and the array and placement of the MM slab are investigated. The results demonstrate that when one MM slab is placed in the middle, near the Tx coil or the Rx coil, the optimal PTE can be obtained by inserting one slab with $6 \times 6$ , $1 \times 1$ , and $6 \times 6$ arrays, respectively. Moreover, the systems with multilayer MM slabs are also studied. The measured PTEs on one, two, and three layers of MM slabs can increase by 20.6%, 29.3%, and 22.6%, respectively. The efficiency improvement capability of one MM slab is better than three slabs but worse than two slabs. This paper discusses the application of MMs in MCR-WPT systems, which has a certain reference significance.

Near-field thermal modulator between nanoparticles based on the multilayered structure

• We develop the calculation model for radiative heat flux between arbitrary multiple nanoparticles placed on opposite sides of the multilayered slab. • The coupling of particle resonance and excited multilayered surface polaritons plays a dominant role in RHT between particles. • The phase change feature of VO 2 can achieve the dramatically active modulation of the RHT between two particles. • The impacts of particle-slab distance and the thickness of the multilayered slab on the thermal control effect are studied. • We can achieve various thermal modulation effects between particle clusters, including thermal switching, thermal modulation, and thermal amplification. We propose a near-field thermal modulator between nanoparticles based on a multilayered slab consisting of the phase change material. Initially, we present a calculation model for radiative heat transfer (RHT) between multiple nanoparticles placed on opposite sides of the multilayered slab. Subsequently, we proceed to analyze the case of two particles, demonstrating that the multilayered slab is capable of providing a robust transmission channel for RHT between the particles. This is achieved through the coupling of particle resonance and excited surface polaritons of the multilayer. Furthermore, the phase change feature can be utilized to switch the transmission channel, thereby achieving active modulation of the RHT. The impact of particle-slab distance and the thickness of the multilayered slab on the thermal control effect is investigated. Moreover, we explore the thermal modulation functions of the RHT in a more complex system where particle clusters are located on opposite sides of the multilayered slab, achieving various thermal modulation effects between particle clusters, including thermal switching, thermal modulation, and thermal amplification.

Twist-tunable moiré optical resonances

Multilayer stacks of twisted optical metasurfaces are considered as a prospective platform for chiral nanophotonic devices. Such structures are primarily used for the realization of circularly polarized light sources, artificial optical rotation, and circular dichroism. At the same time, the behavior of their hybrid photonic modes is strongly affected by the moir\'e-pattern of superimposed periodic constituents. In this work, we show that moir\'e-periodicity in bilayer dielectric photonic crystal slabs leads to an arise of unlimitedly narrow optical resonances, which are very sensitive to the relative twist and gap width between the sublayers. We demonstrate the structure providing twist-tuning of the hybrid mode wavelength in the range of 300--600~nm with quality factor varying from~$10^2$~up~to~$10^5$ correspondingly. The obtained results pave the wave for the utilization of moir\'e-assisted effects in multilayer photonic crystal slabs.

Multi-layered slab 1D conduction heat transfer for buildings discrete event simulations

The 1D conduction heat transfer in multi-layered slabs is fundamental to building energy simulation. Its solution could be split into two big categories: finite difference and root-finding methods. These latter are also known as Laplace or Conduction heat Transfer Function methods (CTF).The paper briefly reviews why none of them, in its current formulation, fits the new trend based on event-driven simulation. It proposes a new CTF whose inputs are the conduction heat fluxes q̇ and the responses are the superficial temperature speeds Ṫ on both slab sides. Thus it could be classified as a root-finding procedure. However, it employs a solution rooted in the uncommon Successive State Transition (SST) method from the 80’s Japanese school. Moreover, it proves that both superficial temperatures T can also be solved using this SST method. The outcome is a solution procedure with many advantages; the main one is that it does suit the novel event-driven paradigm.Finally, the paper illustrates the procedure with an example.

Calculation of the strength of multilayer floor slabs supported on three sides

The article considers the calculation of the ultimate rupture load of multilayer floor slabs supported on three sides (two short and one long). The calculation is carried out taking into account three fracture schemes: the first scheme consists of three main destructive cracks that converge at one point, forming an "envelope"; the second scheme consists of two main inclined cracks passing from the corners towards the non-supported side and not converging on the plate field; the third scheme consists of a horizontal crack forming trapezoid in combination with angular cracks, which is the case when testing prototypes. The reduction of a three-layer section to a single-layer section is carried out according to the elasticity modules of the concretes that make up the section. The value of the rupture load is determined from the condition of equilibrium of external and internal forces. The results of the VAT analysis of multilayer reinforced concrete structures according to the proposed schemes were carried out by the authors on the basis of static tests of prototypes of flat reinforced concrete three-layer slabs. The obtained research results allow us to determine rational parameters for the design of multilayer slab structures with reinforced concrete layers of various strength.

Contact interaction of multilayer slabs with an inhomogeneous base

Contact interaction of multilayer slabs with an inhomogeneous base

Active control of near-field radiative heat transfer between nanoparticles and slab via the multilayered surface modes

We derive the formula for the near-field radiative heat flux between dipole particles and a multilayered slab composed of the uniaxial medium. Based on that, the multilayered structure consisting of SiC and VO2 materials is applied to actively modulate the radiative heat transfer between nanoparticles and slab. Utilizing the modulation feature of the multilayer, surface modes from the multilayer can be strongly coupled to the particle resonance, greatly enhancing the heat flux between the particle and slab. The phase change feature of VO2 allows the active control of multilayered surface modes by changing the slab's temperature, greatly tuning the heat flux. We address the role of multilayer parameters on the modulation effect. We also demonstrate that the multilayered structure can also actively tune the heat flux between the nanoparticle array and slab.

Experimental Research on Dynamic Response of Layered Medium under Impact Load

Stress waves propagating through multiple parallel fractures are attenuated due to the multiple wave reflections and transmissions at the fractures. The dynamic response of a layered medium under an impact load is systematically studied by a model test in this paper. The effects of the impact energy, number of joints, thickness of the medium and joint layer, material properties of the cementation layer, and other factors of the dynamic stress propagation and attenuation of layered media are analyzed. Studies have shown that Sadovsky’s empirical formula fits the attenuation law of vertical peak velocity well, and the obtained attenuation coefficient k and index b can be used for reflecting the dynamic response characteristics of layered media. The attenuation coefficient k is positively correlated with the impact height and negatively correlated with the plate thickness in a single-layer plate impact test. The thickness of the medium layer is the main factor affecting the vibration response of the layered medium in the impact test of the multi-layer slab. The medium thickness, the number of medium layers, and the number of joints have little influence. The different cementation materials and the change of cementation thickness will have a great influence on the dynamic response of layered media, when the cementation layer is filled with joint surfaces for the impact test of multi-layer plates.

Experimental and numerical investigation of G-UHPC based novel multi-layer protective slabs under contact explosions

Geopolymer based ultra-high performance concrete (G-UHPC) has been recognized as a ‘eco-friendly’ form of ultra-high performance concrete owing to its beneficial characteristics, e.g. waste utilization, reduction in carbon dioxide emission, low energy consumption, superior mechanical behavior and adjustable hardening time. Thus, G-UHPC is well suitable for the rapid construction of blast-resistant structures. In this study, four slabs, including a reference normal strength concrete (NSC) slab and three novel multi-layered composite slabs fabricated by G-UHPC, steel wire mesh (SWM) and energy absorber foam materials, were tested on their blast resistance against contact explosions and the corresponding numerical simulations were carried out. Four failure patterns (crater, crater and spalling, breach-perforation and breach-punching) were quantitatively characterized. The G-UHPC slab reinforced with SWM exhibited superior blast resistance as compared to the referenced NSC specimen. The low stiffness and shear strength of the energy absorber foam materials were the main reasons for the breach-punching failure mode. The acoustic impedance and compressibility of the energy absorber foam materials must be reasonably considered to achieve a positive effect on the blast resistance of the concrete slabs. The developed finite element mode could effectively predict the failure characteristics of the specimens.

A novel SAR reduction technique for implantable antenna using conformal absorber metasurface.

In this paper, a conformal absorber metasurface has been designed and used for reducing the specific absorption rate (SAR) of an implantable antenna. SAR reduction of implantable antennas is one of the significant design aspects to be considered for their use in modern-day healthcare applications. The introduction of the absorber metasurface restricts the back radiation of the antenna to control the SAR value. This technique decreases the maximum SAR value by 24% and also reduces the average SAR distribution significantly without affecting the desired antenna gain. A reduction in SAR value indicates the decrease in radiation absorption by human tissue, and thus, decreases the possibility of health hazards due to EM radiation. Later, this antenna-absorber system is designed as a capsule module for increased mobility and less-invasiveness. The redundancy of invasive surgery increases acceptance of the capsule module designs of implantable antennas and devices for various biomedical usages. In vitro testing of the fabricated prototype has been carried out inside a multi-layer porcine slab to verify the effectiveness of this unique SAR reduction technique.

Analytical and Numerical Analyses of Multilayer Photonic Metamaterial Slab Optical Waveguide Structures with Kerr-Type Nonlinear Cladding and Substrate

In this paper, we propose the analytical and numerical analyses of multilayer photonic metamaterial slab optical waveguide structures with Kerr-type nonlinear cladding and substrate. The multiple-quantum-well (MQW) photonic metamaterial optical waveguide structure with Kerr-type nonlinear cladding and substrate was also analyzed. We can use the proposed method to study the multilayer optical metamaterial slab optical waveguide structure with the linear cladding and substrate.

Thermal Switching of Near-Field Radiative Heat Transfer Between Nanoparticles via Multilayered Surface Modes

We theoretically demonstrate near-field radiative thermal switching between two nanoparticles located above a multilayered slab. We propose a multilayered structure composed of $\mathrm{Si}\mathrm{C}$ and the phase transition material ${\mathrm{VO}}_{2}$. The high tunability of the multilayered structure enables the active modulation of surface polaritons when combined with the phase transition feature of ${\mathrm{VO}}_{2}$, overcoming the intrinsic resonance of the thermal radiation of ${\mathrm{VO}}_{2}$. Utilizing this feature, the surface polaritons enormously excited at the particle's resonant frequency above the multilayer can be switched on or off, resulting in the efficient modulation of heat flux between nanoparticles. The effects of interparticle distance and multilayer parameters on thermal switching ratios are investigated. We demonstrate that the multilayer with metallic ${\mathrm{VO}}_{2}$ can significantly inhibit the heat flux between particles as a result of the destructive interference between direct and reflected waves. The excited surface modes above the multilayer with insulating ${\mathrm{VO}}_{2}$ can still improve the heat flux between nanoparticles, resulting in a thermal switching ratio of ${10}^{\ensuremath{-}5}$ at the particle resonant frequency at a large interparticle distance.