Goal-oriented self-adaptive hp-strategies for finite element analysis of electromagnetic scattering and radiation problems

In this paper, a fully automatic goal-oriented hp-adaptive finite element strategy for open region electromagnetic problems (radiation and scattering) is presented. The methodology leads to exponential rates of convergence in terms of an upper bound of an user-prescribed quantity of interest. Thus, the adaptivity may be guided to provide an optimal error, not globally for the field in the whole finite element domain, but for specific parameters of engineering interest. For instance, the error on the numerical computation of the S-parameters of an antenna array, the field radiated by an antenna, or the Radar Cross Section on given directions, can be minimized. The efficiency of the approach is illustrated with several numerical simulations with two dimensional problem domains. Results include the comparison with the previously developed energy-norm based hp-adaptivity.

A comparison between PML, infinite elements and an iterative BEM as mesh truncation methods for HP self-adaptive procedures in electromagnetics

Finite element hp-adaptivity is a technology that allows for very accurate numerical solutions. When applied to open region problems such as radar cross section prediction or antenna analysis, a mesh truncation method needs to be used. This paper compares the following mesh truncation methods in the context of hp-adaptive methods: Infinite Elements, Perfectly Matched Layers and an iterative boundary element based methodology. These methods have been selected because they are exact at the continuous level (a desirable feature required by the extreme accuracy delivered by the hp-adaptive strategy) and they are easy to integrate with the logic of hp-adaptivity. The comparison is mainly based on the number of degrees of freedom needed for each method to achieve a given level of accuracy. Computational times are also included. Two-dimensional examples are used, but the conclusions directly extrapolated to the three dimensional case.

Provisos for classic linear oscillator design methods. New linear oscillator design based on the NDF/RRT

In this paper, the classic oscillator design methods are reviewed, and their strengths and weaknesses are shown. Provisos for avoiding the misuse of classic methods are also proposed. If the required provisos are satisfied, the solutions provided by the classic methods (oscillator start-up linear approximation) will be correct. The provisos verification needs to use the NDF (Network Determinant Function). The use of the NDF or the most suitable RRT (Return Relation Transponse), which is directly related to the NDF, as a tool to analyze oscillators leads to a new oscillator design method. The RRT is the "true" loop-gain of oscillators. The use of the new method is demonstrated with examples. Finally, a comparison of NDF/RRT results with the HB (Harmonic Balance) simulation and practical implementation measurements prove the universal use of the new methods.

Transpose return relation method for designing low noise oscillators

In this paper, a new linear method for optimizing compact low noise oscillators for RF/MW applications will be presented. The first part of this paper makes an overview of Leeson's model. It is pointed out, and it is demonstrates that the phase noise is always the same inside the oscillator loop. It is presented a general phase noise optimization method for reference plane oscillators. The new method uses Transpose Return Relations (RRT) as true loop gain functions for obtaining the optimum values of the elements of the oscillator, whatever scheme it has. With this method, oscillator topologies that have been designed and optimized using negative resistance, negative conductance or reflection coefficient methods, until now, can be studied like a loop gain method. Subsequently, the main disadvantage of Leeson's model is overcome, and now it is not only valid for loop gain methods, but it is valid for any oscillator topology. The last section of this paper lists the steps to be performed to use this method for proper phase noise optimization during the linear design process and before the final non-linear optimization. The power of the proposed RRT method is shown with its use for optimizing a common oscillator, which is later simulated using Harmonic Balance (HB) and manufactured. Then, the comparison of the linear, HB and measurements of the phase noise are compared.

Photoacoustic effect measurement in aqueous suspensions of gold nanorods caused by low-frequency and low-power near-infrared pulsing laser irradiation

When aqueous suspensions of gold nanorods are irradiated with a pulsing laser (808 nm), pressure waves appear even at low frequencies (pulse repetition rate of 25 kHz). We found that the pressure wave amplitude depends on the dynamics of the phenomenon. For fixed concentration and average laser current intensity, the amplitude of the pressure waves shows a trend of increasing with the pulse slope and the pulse maximum amplitude.We postulate that the detected ultrasonic pressure waves are a sort of shock waves that would be generated at the beginning of each pulse, because the pressure wave amplitude would be the result of the positive interference of all the individual shock waves.

Descripcion de las demonstraciones feruorosas ... con que festejò gozoso este ... pueblo de Zaragoza a ... Maria Santissima del Pilar al ver descubierto el ... tabernaculo de su ... capilla

Sign.: [A]-D4, E2

O ESTUDANTE DA EAD (EDUCAÇÃO A DISTÂNCIA): UM ESTUDO DE PERFIL E INTERAÇÃO GERACIONAL

A aprendizagem formal e tradicional tem dado lugar a um cenário desafiador no qual educador e educando não comungam do mesmo espaço físico. A Educação a Distância (EAD), ainda é vista como uma solução que agrega cada vez mais alunos de diferentes idades que desejam uma graduação de ensino superior ou a continuidade dela. A pesquisa com o título: “O estudante da EAD (educação a distância): um estudo de perfil e interação geracional” propõe conhecer as características do perfil atual do estudante da EAD, abordando o diálogo entre as gerações no ambiente social escolar. O enfoque da pesquisa é qualitativa, exploratória e descritiva com dados que foram coletados através de entrevista com 08 alunos das gerações X e Y para assim entender se este perfil tem sido renovado com alunos mais jovens, do que a faixa etária de 25 a 45 anos. O resultado demonstra que alunos na faixa de 17 a 24 anos a cada ano aumentam 1% das matrículas. Já a faixa de 25 a 45 anos prevalece com 70% das matrículas. Portanto, este resultado revela que o perfil do aluno EAD ainda é o do jovem adulto, para adulto mais experiente, que busca a graduação com o propósito de progressão no ambiente profissional. As duas gerações citadas geração X e geração Y, mesmo em contextos históricos diferenciados de valores, crenças e comportamentos participam atualmente de uma transformação social que contempla os meios de produção do trabalho, a formação educacional e as relações sociais. O diálogo intergeracional direciona a um aprendizado compartilhado, participativo na troca de experiências mutuas. Para a geração X o jovem atual não é mais nomeado como o que precisa escutar e aprender, mas tem muito a partilhar, principalmente diante da facilidade com os meios tecnológicos. E para a geração Y, na partilha não há barreiras de idade, mas a segurança de interagir e se comunicar diante da troca de experiências

Polarimetric SAR model for soil moisture estimation over vineyards at C-band

In this paper we propose a two-component polarimetric model for soil moisture estimation on vineyards suited for C-band radar data. According to a polarimetric analysis carried out here, this scenario is made up of one dominant direct return from the soil and a multiple scattering component accounting for disturbing and nonmodeled signal fluctuations from soil and short vegetation. We propose a combined X-Bragg/Fresnel approach to characterize the polarized direct response from soil. A validation of this polarimetric model has been performed in terms of its consistency with respect to the available data both from RADARSAT-2 and from indoor measurements. High inversion rates are reported for different phenological stages of vines, and the model gives a consistent interpretation of the data as long as the volume component power remains about or below 50% of the surface contribution power. However, the scarcity of soil moisture measurements in this study prevents the validation of the algorithm in terms of the accuracy of soil moisture retrieval and an extensive campaign is required to fully demonstrate the validity of the model. Different sources of mismatches between the model and the data have been also discussed and analyzed.

Synthesis of Chromen[4,3-b]pyrrolidines by Intramolecular 1,3-Dipolar Cycloadditions of Azomethine Ylides: An Experimental and Computational Assessment of the Origin of Stereocontrol

Azomethine ylides, generated from imine-derived O-cinnamyl or O-crotonyl salicylaldeyde and α-amino acids, undergo intramolecular 1,3-dipolar cycloaddition, leading to chromene[4,3-b]pyrrolidines. Two reaction conditions are used: (a) microwave-assisted heating (200 W, 185 °C) of a neat mixture of reagents, and (b) conventional heating (170 °C) in PEG-400 as solvent. In both cases, a mixture of two epimers at the α-position of the nitrogen atom in the pyrrolidine nucleus was formed through the less energetic endo-approach (B/C ring fusion). In many cases, the formation of the stereoisomer bearing a trans-arrangement into the B/C ring fusion was observed in high proportions. Comprehensive computational and kinetic simulation studies are detailed. An analysis of the stability of transient 1,3-dipoles, followed by an assessment of the intramolecular pathways and kinetics are also reported.

Traite de matiere medicale /

Mode of access: Internet.

Tratado completo de medicina práctica : fundado en la experiencia de cincuenta años /

Mode of access: Internet.

O ESTUDANTE DA EAD (EDUCAÇÃO A DISTÂNCIA): UM ESTUDO DE PERFIL E INTERAÇÃO GERACIONAL

A aprendizagem formal e tradicional tem dado lugar a um cenário desafiador no qual educador e educando não comungam do mesmo espaço físico. A Educação a Distância (EAD), ainda é vista como uma solução que agrega cada vez mais alunos de diferentes idades que desejam uma graduação de ensino superior ou a continuidade dela. A pesquisa com o título: “O estudante da EAD (educação a distância): um estudo de perfil e interação geracional” propõe conhecer as características do perfil atual do estudante da EAD, abordando o diálogo entre as gerações no ambiente social escolar. O enfoque da pesquisa é qualitativa, exploratória e descritiva com dados que foram coletados através de entrevista com 08 alunos das gerações X e Y para assim entender se este perfil tem sido renovado com alunos mais jovens, do que a faixa etária de 25 a 45 anos. O resultado demonstra que alunos na faixa de 17 a 24 anos a cada ano aumentam 1% das matrículas. Já a faixa de 25 a 45 anos prevalece com 70% das matrículas. Portanto, este resultado revela que o perfil do aluno EAD ainda é o do jovem adulto, para adulto mais experiente, que busca a graduação com o propósito de progressão no ambiente profissional. As duas gerações citadas geração X e geração Y, mesmo em contextos históricos diferenciados de valores, crenças e comportamentos participam atualmente de uma transformação social que contempla os meios de produção do trabalho, a formação educacional e as relações sociais. O diálogo intergeracional direciona a um aprendizado compartilhado, participativo na troca de experiências mutuas. Para a geração X o jovem atual não é mais nomeado como o que precisa escutar e aprender, mas tem muito a partilhar, principalmente diante da facilidade com os meios tecnológicos. E para a geração Y, na partilha não há barreiras de idade, mas a segurança de interagir e se comunicar diante da troca de experiências

Adding constrained discontinuities to Gaussian process models of wind fields

Gaussian Processes provide good prior models for spatial data, but can be too smooth. In many physical situations there are discontinuities along bounding surfaces, for example fronts in near-surface wind fields. We describe a modelling method for such a constrained discontinuity and demonstrate how to infer the model parameters in wind fields with MCMC sampling.