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Configuration of the parabolic reflector. The parabola is described by fx=x2/0.60.4. The viewers are located in strategic points so to measure the quality of the solution. The source is located in the parabola’s focus, within the hood feeder.
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FDTD method opened a fertile research area on the numerical analysis of electromagnetic phenomena under a wide range of media and propagation conditions, providing a richful analysis of electromagnetic behaviour like propagation , reflection, refraction, multi-trajectory phenomena, among others. In this paper we present an optimised FDTD-CPML algor...
Citations
... to ensure numerical stability [52,53], where c 0 is the speed of light in a vacuum, and ε r and µ r are the propagating medium's relative permittivity and permeability, respectively. Several numerical experiments in the context of electromagnetic propagation have shown that a relation of ∆x = ∆y = λ /20, where λ is the propagated wavelength, allows the quality of the numerical solution to be maintained [53]. ...
... to ensure numerical stability [52,53], where c 0 is the speed of light in a vacuum, and ε r and µ r are the propagating medium's relative permittivity and permeability, respectively. Several numerical experiments in the context of electromagnetic propagation have shown that a relation of ∆x = ∆y = λ /20, where λ is the propagated wavelength, allows the quality of the numerical solution to be maintained [53]. That is, when setting the computational grid, there should be at least 20 spatial grid cells of the FDTD method for an accurate resolution of one wavelength of the signal. ...
... Following the numerical experiments' development in [53], where α(x), κ(x), and d(x) are studied as polynomial functions in the domain of the CPML boundary, and N is the number of layers, thus T h = N ∆x is the thickness of the CPML. Then, the following equations are defined as ...
Rainfall has always been a concern for wireless communications systems. As 5G technology relies on high-frequency bands, it is fundamental to model and simulate the interaction of such radio waves with rainfall, as the deployment of large-scale infrastructure for 5G is highly expensive. This research presents a reformulation of the Maxwell equations for a bi-dimensional space in a transverse electric propagation mode, for a linear, inhomogeneous, and isotropic propagation medium with its magnetic and electric properties dependent on time. This reformulation was solved using the Finite Differences in Time Domain (FDTD) method with the Convolutional Perfectly Matched Layer (CPML) boundary condition. Two main frequency propagation scenarios were studied: 5 GHz (corresponding to Wi-Fi in the 802.11n standard as well as to the lowest bands of 5G) and 25 GHz (corresponding to 5G), within a 10 m × 3 m rectangular domain in air and with rain. The rainfall was simulated using a parallel Ziggurat algorithm. According to the findings, while 5 GHz waves experience scattering processes, 25 GHz waves experience substantial dispersion and attenuation throughout the domain in low-to moderate-intensity rain.
... Instead, Chujaibacter, Rhodanobacter, Taibaiella, and Comamonas became predominant, with high relative abundances of 18.2 ± 0.5%, 12.0 ± 0.7%, 9.3 ± 0.9%, 5.0 ± 0.2%, respectively. Chujaibacter was found in sludge and soils and has been reported to be able to degrade organic matter (Rodríguez-Sánchez et al., 2018;Rodriguez-Sanchez et al., 2018;Zhang et al., 2022). Rhodanobacter is able to conduct denitrification utilizing nitrite, nitrate, or nitrous oxide as electron acceptors (Ma et al., 2019;Peng et al., 2014;Rodríguez-Sánchez et al., 2018;Rodriguez-Sanchez et al., 2018). ...
... Chujaibacter was found in sludge and soils and has been reported to be able to degrade organic matter (Rodríguez-Sánchez et al., 2018;Rodriguez-Sanchez et al., 2018;Zhang et al., 2022). Rhodanobacter is able to conduct denitrification utilizing nitrite, nitrate, or nitrous oxide as electron acceptors (Ma et al., 2019;Peng et al., 2014;Rodríguez-Sánchez et al., 2018;Rodriguez-Sanchez et al., 2018). Taibaiella was reported to participate in the lignin decomposition (Diallo et al., 2021;Qi et al., 2022), and Comamonas was the potential denitrifying bacteria found in estuarine waters (Zhu et al., 2018). ...
The acidic (i.e., pH ∼5) activated sludge process is attracting attention because it enables stable nitrite accumulation and enhances sludge reduction and stabilization, compared to the conventional process at neutral pH. Here, this study examined the production and potential pathways of nitric oxide (NO) and nitrous oxide (N2O) during acidic sludge digestion. With continuous operation of a laboratory-scale aerobic digester at high dissolved oxygen concentration (DO>4 mg O2 L-1) and low pH (4.7±0.6), a significant amount of total nitrogen (TN) loss (i.e., 18.6±1.5% of TN in feed sludge) was detected. Notably, ∼40% of the removed TN was emitted as NO, with ∼8% as N2O. A series of batch assays were then designed to explain the observed TN loss under aerobic conditions. All assays were conducted with a low concentration of volatile solids (VS), i.e., VS<4.5 g L-1. This VS concentration is commensurate with the values commonly found in the aeration tanks of full-scale wastewater treatment systems, and thus no significant nitrogen loss should be expected when DO is controlled above 4 mg O2 L-1. However, nitrite disappeared at a significant rate (with the chemical decomposition of nitrite excluded), leading to NO production in the batch assays at pH 5. The nitrite reduction could be associated with endogenous microbial activities, e.g., nitrite detoxification. The significant NO production illustrates the importance of aerobic nitrite reduction during acidic aerobic sludge digestion, suggesting this process cannot be neglected in developing acidic activated sludge technology.
... The study cases selected in this work have already been studied in [26], and the scenarios consist in simulating wave propagation in transverse electric mode (TE) in free space, in a parabolic reflector, and in a coplanar nanowaveguide at different frequencies based on Maxwell Curl equations solved by Yee's finite-difference algorithm [27]. ...
Although GPUs can offer higher computing power at low power consumption, their low-level programming can be relatively complex and consume programming time. For this reason, directive-based alternatives such as OpenACC could be used to specify high-level parallelism without original code modification, giving very accurate results. Nevertheless, in the FDTD method, absorbing boundary conditions are commonly used. The key to successful performance is correctly implementing the boundary conditions that play an essential role in memory use. This work accelerates the simulations of electromagnetic wave propagation that solve the Maxwell curl equations by FDTD using CMPL boundary in TE mode using OpenACC directives. A gain of acceleration optimizing the use of memory is shows, checking the loops intensities, and the use of single precision to improve the performance is also analyzed, producing an acceleration of around 5X for double precision and 11X for single precision respectively, comparing with the serial vectorized version, without introducing errors in long-term simulations. The scenarios of simulation established are common of interest and are solved at different frequencies supported by a Mid-range cards GeForce RTX 3060 and Titan RTX.
... A proposal that has been widely accepted is the representation of models through synthetic images, mainly in the improvement of microstructural behavior of various types of materials. Among the applications using synthetic images are the development of renewable energy such as synthesis of materials and prediction of behaviors for fuel cells [9], devices and apps for medicine (magnetic resonance imaging) [11], neural networks mainly with the use of Deep Learning [12], materials for ultra-fast devices in the telecommunications area (ultra-fast devices) [13,14], military applications such as radars and ship detection simulators [15], and topographical images of polymer solar cells [16]. There are other works involved in the improvement of microstructures related to comparison of different morphologies on 3D reconstructions [17], the behavior of their geometry to conversion of triangular to hexagonal models [18], synthesis of palladium nanoparticles in triangular form [19], Finite Volume Method (FVM) for morphology studies of microstructures with mechanoluminescent particles [20], heat and humidity transfer in clothing sets, using the finite volume method for the nonlinear parabolic equations system [21], computational thermal conductivity and membrane pore geometry simulation in porous materials [22,23], tortuosity, permeability and threshold percolation studies from membrane SEM images and transport pore structure [24][25][26], images generation from mathematical descriptors for 3D shapes analysis using formal segmentation [27], structural detail analysis of woven fabric based on synthetic images [28], thermal expansion coefficients calculation for one and two phases from SEM models and three-dimensional synthetic images of polycrystals [29], geometric and topological characterizations to establish a relationship of the structure owned by two phases using the Voronoi diagram in geometry of synthetic images [30,31], neutron imaging in fuel cells research [32], and a systematic classification implemented by its geometric and topological properties focus on imitating morphology through mathematical tools, such as digital image correlation, tessellation, random field generation, and differential equation solvers [33]. ...
The study of the microstructure of random heterogeneous materials, related to an electrochemical device, is relevant because their effective macroscopic properties, e.g., electrical or proton conductivity, are a function of their effective transport coefficients (ETC). The magnitude of ETC depends on the distribution and properties of the material phase. In this work, an algorithm is developed to generate stochastic two-phase (binary) image configurations with multiple geometries and polydispersed particle sizes. The recognizable geometry in the images is represented by the white phase dispersed and characterized by statistical descriptors (two-point and line-path correlation functions). Percolation is obtained for the geometries by identifying an infinite cluster to guarantee the connection between the edges of the microstructures. Finally, the finite volume method is used to determine the ETC. Agglomerate phase results show that the geometry with the highest local current distribution is the triangular geometry. In the matrix phase, the most significant results are obtained by circular geometry, while the lowest is obtained by the 3-sided polygon. The proposed methodology allows to establish criteria based on percolation and surface fraction to assure effective electrical conduction according to their geometric distribution; results provide an insight for the microstructure development with high projection to be used to improve the electrode of a Membrane Electrode Assembly (MEA).
... En el caso del experimento con forzamiento, el término Las características tanto de la propagación como del dominio computacional en el cual se resuelven numéricamente las ecuaciones (10)-(12) se muestran en la Tabla 1. Las condiciones de frontera aplicadas son condiciones tradicionales de Dirichlet [8]. El resultado principal se obtiene de la comparación entre la forma en que se manejan los términos de la fuente, por lo que se realiza la prueba tanto con la fuente colocada de manera forzada, es decir, cada paso de la simulación se obliga al campo eléctrico con la función de la ecuación (13) [6]. La Figura 2 muestra la forma que tiene la propagación del campo en este caso, para un paso de tiempo en la simulación de 570 n Es claro que dependiendo de la práctica de programación respecto a los términos fuente, se modifica el comportamiento del campo eléctrico y en particular la atenuación de la onda propagada, aun cuando ambos casos se realiza la simulación con los mismos parámetros y características. ...
A widely extended in the scholar literature practice with respect to the development of applications of computational electromagnetics is that of introducing source terms as a direct forcing of the electromagnetic field within the computational domain. Moreover, Maxwell equations ought to be posed as homogeneous PDEs. Although the results of taking this approximation are qualitatively correct, it must be remarked that such practice do not reproduces physical attenuation behavior in the performed electromagnetic propagation. In this work we tackle this problem through the demonstration of the quantitative differences in the behaviour of electromagnetic field in both the aforementioned case as well as adequately considering the current density term featured in the inhomogeneous Maxwell equations. We show the comparison between both cases for a bidimensional propagation in vacuum for the traverse electric mode, where the quantitative differences between both programming practices are clearly observed.
Precision in optics has always been a challenge, which has persistently demanding new methods of design. Achieving a high performance imaging system with a compact form factor such as AR/VR displays, cameras and microscopes requires extra degrees of freedom. Recently, emerging science like freeform conformal meta-optics, which is an integrated technology of metamaterials combined with freeform optical surface profiles, offers lighter, simple and more compact assemblies. We propose a new inverse synthesis method based on the Dirac distribution of the E-M fields at an arbitrary interface and come up with with an extension of the Generalized Sheet Transition Conditions (GSTCs) valid for any arbitrary surface which we called Conformal-GSTCs (or C-GSTCs in short). We model the CGSTCs using a three dimensional FDTD method and demonstrate the validity of our modelling technique by numerically implementing the scheme for optical devices such as lenses and deflectors using home made parallel FDTD codes. We have used our numerical simulations to study the effect of the shape of the metasurface interface on the performances of metalenses. These performances were numerically characterized using standard methods of optics such as the Full Wave at Half Maximum (FWHM), Point Spread Function (PSF) or optical aberrations calculation through Zernike polynomial analysis. Our numerical implementation can serve as a tool to design freeform meta-optics, and can help in evaluating and optimizing the optical response of complex freeform optical assemblies.On the other direction, we have come up with certain characterization techniques to measure the phase data experimentally by using an in-house experimental set up. The measured phase data is processed for the evaluation of the susceptibilities. The transmitted field data arising from the metaoptical devices are computed numerically using Fourier beam propagation methods with the help of measured susceptibilities. Finally, the performance of the optical devices such as metalenses and deflectors are studied and reported. This technique could help in characterizing optical devices without the need of much complicated tools & devices in experimental labs, which could save a huge amount of resources.We have developed a full vectorial mesoscopic model to investigate the light-metasurface interaction. In this method, we obtain the distributed form of the susceptibilities from the geometric design of the metasurface by the lattice representation of nano-antennas, an approach which is similar to the concept of solid state physics. We obtain an analytical expression for the propagation of the field through the metasurface by solving Maxwell's equations for a given susceptibility function. We prove that the transmitted co-polarized beam alone acquires a global phase associated with the antenna response. Contrarily to the co-polarization beam, the transmitted cross-polarized beam is influenced by both PB and propagation phases. We extend this phase phenomenon to a general situation by decomposing the arbitrary polarization of a normally incident light in circular basis, showing that each eigenstate acquires an opposite extra phase delay due to the topological phase retardation associated with the PB phase. The diffractive properties of topological phase gradient metasurfaces are analyzed in depth via the analytical derivations, and the results are verified with optical measurements. The other physical mechanisms such as the universal principles of co-polarization and cross-polarization transmission, and the coexistence of the zero and nonzero phase gradient leading to the ordinary and generalized Snell’s law, are illustrated using the present framework. Our model an initiative to develop an intuitive understanding of topological and functional beam splitters for future applications in quantum optics and quantum information protocols.
