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Multi-objective optimization of a hypersonic airbreathing engine (scramjet technology) was carried out with the aim of maximizing thrust and minimizing drag while satisfying a series of design constraints, such as avoiding unstart (blockage of supersonic flow within the combustion chamber) by ensuring that the pressure ratio across the shock waves remains below the adverse pressure gradient given by the Korkegi limit, geometry correction to achieve shock on-lip condition, and temperature and pressure requirements at the inlet exit. Using the relations presented in the literature, pressure and viscous drag are estimated analytically. The analytical approach is verified against computational fluid dynamics data from Ansys Fluent to solve two-dimensional compressible Reynolds-averaged Navier–Stokes flow equations, with transition shear stress transport as the turbulence closure model. Comparing the total drag and the flow properties at the combustion chamber entrance shows the model's feasibility for the optimization approach. Three different approaches were conducted to formulate the multi-objective function to determine the one that can find the highest number of geometries satisfying the Korkegi limit with the highest net thrust. The best approach was the multi-objective function formulated with the uninstalled thrust, total pressure recovery, and pressure drag, concentrating the search in the region with greater uninstalled thrust and lower drag and nearly doubling the value of net thrust compared to the first formulation, which uses the uninstalled thrust, pressure drag, and viscous drag. [ABSTRACT FROM AUTHOR]

In this work, a review of the theoretical aspects and an assessment to validate a Computational Fluid Dynamics (CFD) opensource code for applications in aerospace problems are discussed. !e code uses a "nite volume method, with cell-centered implementation, and it is suitable for simulations of inviscid, laminar, and turbulent #ows. !e code considers two-dimensional cases with unstructured meshes and employs the turbulence model known as Spalart-Allmaras. !e implementation is detailed presenting the spatial discretization, including the upwind scheme, the linear reconstruction algorithm, and the calculation applying the method of gradients. !e temporal discretization considers the application of a multistage explicit algorithm using a 5 stages Runge-Kutta method. !e validation was done considering three cases of study: the inviscid shock tube, the laminar #at plate, and the #ow over a rocket fairing. !ese cases are simulated using the so$ware developed and the results are compared with analytical and experimental results. !e rocket fairing case is related to the analysis of the Brazilian VLS launch during its transonic #ight and it exempli"es the e%ect of the shock wave/boundary-layer interaction in its pressure distribution. !e simulation results present a good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This work presents the application of a scalar finite element formulation for [E.sup.x] (TE-like) modes in anisotropic planar and channel waveguides with diagonal permittivity tensor, diffused in both transversal directions. This extended formulation considers explicitly both the variations of the refractive index and their spatial derivates inside of each finite element. Dispersion curves for [E.sup.x] modes in planar and channel waveguides are shown, and the results compared with solutions obtained by other formulations. Index terms - Finite element methods, nonhomogeneously loaded waveguides, optical strip waveguides, anisotropic media.

A MATHEMATICA notebook to compute the elements of the matrices which arise in the solution of the Helmholtz equation by the finite element method (nodal approximation) for tetrahedral elements of any approximation order is presented. The results of the notebook enable a fast computational implementation of finite element codes for high order simplex 3D elements reducing the overheads due to implementation and test of the complex mathematical expressions obtained from the analytical integrations. These matrices can be used in a large number of applications related to physical phenomena described by the Poisson, Laplace and Schrodinger equations with anisotropic physical properties. Index terms - Helmholtz equations, finite element methods, anisotropic media, software tools.

A procedure to model optical diffused-channel waveguides is presented in this work. The dielectric waveguides present anisotropic refractive indexes which are calculated from the proton concentration. The proton concentration inside the channel is calculated by the anisotropic 2D-linear diffusion equation and converted to the refractive indexes using mathematical relations obtained from experimental data. The arbitrary refractive index profile is modeled by a nodal expansion in the base functions. The TE and TM-like propagation properties (effective index) and the electromagnetic fields for well-annealed proton-exchanged (APE) [LiNbO.sub.3] waveguides are computed by the finite element method. Index terms - Finite element methods, nonhomogeneously loaded waveguides, optical strip waveguides, anisotropic media, diffusion processes.

LMAG-2D is an educational Finite-Element Analysis software package with CAD/CAE technology used to teach the finite element method to undergraduate and graduate students of electrical engineering. A user-friendly interface encapsulates the technical complexity of the method, allowing students and professionals, even in their first contact with this methodology, to appreciate its relevance to practical problems. LMAG-2D can be used to simulate complex two dimensional 'real-world' electrostatic, magnetostatic and electrokinetic models, with planar and axial symmetries. Linear and nonlinear phenomena can also be simulated.

A reading of the book of Wisdom leaves one with the impression of having listened to a splendid oratorio. The musical image of chapter 19, with some technical precision, confirms this impression. In fact, this poetic work of 502 verses, enveloped in mystery about its authorship and debate about its date of composition, is replete with sentiments of wonder before the harmony of the works of God. This paper is part of a broader study that seeks to describe the evolution of the author's discourse with regard to the composition history of the sections making up the book. For each section there is an attempt to grasp the interpretative implications of the literary analysis. The current article concentrates on the third part of the book, the sunkrisis. [ABSTRACT FROM AUTHOR]

Recent advances in deep learning for automatic target recognition have inspired studies for maritime surveillance with synthetic aperture radar (SAR). In this context, oil rigs monitoring is of particular interest. There are offshore platforms of different types and sizes which poses challenges for classification methods. In this letter, we compare the recognition of oil rigs on Sentinel-1 SAR images, discriminating them from false alarms, through a convolutional neural network with a different number of layers named models VGG-16 and VGG-19. We used the Sentinel-1 GRD product, which has a resolution of about 20 m, with VV and VH channel image data sets separated to observe polarization influences on target recognition. The experiments show that the VH polarization image embedding contributes with the best classification values, with the mean global accuracy of fifty random sampling tests equal to 86.4% and 84.1% using the VGG-16 and VGG-19 architectures, respectively, to extract features and feed a logistic regression classifier method. Results suggest that these approaches are a useful alternative for maritime surveillance employing SAR images of medium resolution and large swaths. Furthermore, the database balancing for wind conditions did not provide significant contributions to the accuracy of classification algorithms. [ABSTRACT FROM AUTHOR]

A reading of the book of Wisdom leaves one with the impression of having listened to a splendid oratorio. The musical image of chapter 19, with some technical precision, confirms this impression. In fact, this poetic work of 502 verses, enveloped in mystery about its authorship and debate about its date of composition, is replete with sentiments of wonder before the harmony of the works of God. This paper is part of a broader study that seeks to describe the evolution of the author's discourse with regard to the composition history of the sections making up the book. For each section there is an attempt to grasp the interpretative implications of the literary analysis. The current article concentrates on the third part of the book, the sunkrisis. [ABSTRACT FROM AUTHOR]

In a periodic structure, the magnetic flux density profile of a hybrid undulator depends strongly on the characteristics of its permanent magnets. A simple procedure to select the best permanent magnets for periodic magnetic structures is presented here. We used a very simple apparatus for the magnetic field measurements. We tested by assembling periodic structure prototypes formed by brick-shaped permanent magnets. Index Terms--Free electron lasers, periodic structures, permanent magnets, undulators.

Electrostatic or capacitive accelerometers are among the highest volume microelectromechanical systems (MEMS) products nowadays. The design of such devices is a complex task, since they depend on many performance requirements, which are often conflicting. Therefore, optimization techniques are often used in the design stage of these MEMS devices. Because of problems with reliability, the technology of MEMS is not yet well established. Thus, in this work, size optimization is combined with the reliability-based design optimization (RBDO) method to improve the performance of accelerometers. To account for uncertainties in the dimensions and material properties of these devices, the first order reliability method is applied to calculate the probabilities involved in the RBDO formulation. Practical examples of bulk-type capacitive accelerometer designs are presented and discussed to evaluate the potential of the implemented RBDO solver. [ABSTRACT FROM AUTHOR]

This work presents a self-consistent optimization of multi-quantum well based nanostructured semiconductors. A Genetic Algorithm is used for the search module. The simulation module is based on the self-consistent solution of the coupled Poisson and Schrödinger equations by using the finite-element method. The results of two case tests are presented and discussed. [ABSTRACT FROM AUTHOR]

Self-consistent calculations of multi-quantum well semiconductor structures based on a Finite-Element Method are presented. The self-consistent calculation is specially needed when wells of different width are present in the structure, generating a larger charge separation and affecting significantly the tunneling conditions. The object-oriented computer code used was implemented using a finite-element class library developed and used in previous works. Results for an asymmetric heterostructure with a larger well and contact layers are also presented. [ABSTRACT FROM AUTHOR]

This work describes an optical device for the simultaneous recording of shadowgrams and schlieren images, and some results are presented concerning its applications to the study of plasma assisted flow control in airfoil models. This approach offers many advantages in comparison to other methods, specially because the use of tracer particles (like smoke in wind tunnels) is not required for the experiments, thus avoiding contaminations in the electric discharges or air flows. Besides, while schlieren images reveal the refractive index gradients in the area of study, shadowgrams detect the second order spatial derivatives of the refractive indexes. Therefore, the simultaneous recording of these different images may give interesting information about the phenomena under study. In this paper, these images were used to confirm the existence of vortex structures in the flow induced by corona discharges on airfoil models. These structures are a possible explanation for the effects of drag reduction and lift force increasing, which have been reported in experiments of plasma assisted Aerodynamics. [ABSTRACT FROM AUTHOR]

We present an in-depth theoretical and numerical discussion on the Fano signatures observed in differential transmission spectra obtained from multiquantum well structures. These signatures stem from ponderomotive and intersubband polarization currents modified by the coupling between the optical responses of different layers. A detailed discussion of this process is provided, evaluating quantitatively the amplitude and shape of the Fano signatures and their dependence on structural parameters, such as carrier concentration and layer width. The theoretical model described here aims to predict quantitatively the weight of the contributions of the ponderomotive currents in relation to the intersubband ones. In order to include the effect of the entire structure in the theoretical spectra, the optical response of each layer is addressed within the density matrix formalism and encompassed in an optical transfer matrix. This method also ensures the correct inclusion of the phase sensitive superposition of optical responses of different layers on which the Fano signatures are based. Numerical simulations obtained from the presented theoretical approach are in excellent agreement with the behavior observed in previous experiments.