Resumo A partir da técnica de velocidade de propagação de onda ultrassônica (VPU) é possível avaliar propriedades mecânicas de concretos, incluindo o concreto reforçado com fibras (CRF). Assim, o objetivo deste trabalho é verificar possíveis correlações entre as propriedades mecânicas do CRF e VPU, com base em dados experimentais de publicações selecionados após uma revisão sistemática da literatura. Também foram avaliadas relações entre a VPU e a resistência à compressão a partir de modelos propostos por pesquisadores. Aplicou-se a técnica de rede neural artificial (RNA) para analisar quais propriedades, quando associadas com a VPU, auxiliam na estimativa da resistência à compressão do CRF. Observou-se que os modelos propostos pela literatura para estimar a resistência à compressão por meio da VPU não foram eficazes. O modelo de RNA resultou em um coeficiente de determinação de 0,973, uma acurácia de 3,18 MPa e utilizou como dados de entrada a VPU, o consumo de cimento e a relação a/c, além de três neurônios na camada escondida e um dado de saída (resistência à compressão). (VPU concretos . (CRF) Assim pesquisadores Aplicouse Aplicou se (RNA Observouse Observou eficazes 0973 0 973 0,973 318 3 18 3,1 ac c a/c compressão. compressão) (CRF 097 97 0,97 31 1 3, 09 9 0,9 0,

Abstract The ultrasonic wave propagation velocity (UPV) technique enables the evaluation of mechanical properties of concrete, including fiber reinforced concrete (FRC). Therefore, the objective of this study is to verify potential correlations between the mechanical properties of FRC and UPV, based on experimental data selected after a systematic literature review. Additionally, relationships between UPV and compressive strength were assessed using models proposed by researchers. An artificial neural network (ANN) technique was applied to analyze which properties, when associated with UPV, assist in estimating the compressive strength of FRC. It was observed that the literature-proposed models for estimating compressive strength using UPV proved to be ineffective. The ANN model resulted in a determination coefficient of 0.973, an accuracy of 3.18 MPa, utilizing UPV, cement consumption, and the water-to-cement ratio as input data, with three neurons in the hidden layer and one output data (compressive strength). (UPV . (FRC) Therefore review Additionally researchers (ANN literatureproposed ineffective 0973 0 973 0.973 318 3 18 3.1 MPa consumption watertocement water strength. strength) (FRC 097 97 0.97 31 1 3. 09 9 0.9 0.

Abstract Introduction. During the development of the SARS-CoV-2 pandemic in Antioquia, we experienced epidemiological peaks related to the α, ɣ, β, μ, ƛ, and δ variants. δ had the highest incidence and prevalence. This lineage is of concern due to its clinical manifestations and epidemiological characteristics. A total of 253 δ sublineages have been reported in the PANGOLIN database. The sublineage identification through genomic analysis has made it possible to trace their evolution and propagation. Objective. To characterize the genetic diversity of the different SARS-CoV-2 δ sublineages in Antioquia and to describe its prevalence. Materials and methods. We collected sociodemographic information from 2,675 samples, and obtained 1,115 genomes from the GISAID database between July 12th, 2021, and January 18th, 2022. From the analyzed genomes, 515 were selected because of their high coverage values (>90%) to perform phylogenetic analysis and to infer allele frequencies of mutations of interest. Results. We characterized 24 sublineages. The most prevalent was AY.25. Mutations of interest as L452R, P681R, and P681H were identified in this sublineage, comprising a frequency close to 0.99. Conclusions. This study identified that the AY.25 sublineage has a transmission advantage compared to the other δ sublineages. This attribute may be related to the presence of the L452R and P681R mutations associated in other studies with higher evasion of the immune system and less efficacy of drugs against SARS-CoV-2.

Resumen Introducción. Durante el desarrollo de la pandemia por SARS-CoV-2 en Antioquia se presentaron picos epidemiológicos relacionados con las variantes α, ɣ, β, μ, ƛ y δ, donde δ tuvo la mayor incidencia y prevalencia. Este linaje se considera una variante de preocupación dadas las manifestaciones clínicas que desencadena y sus características epidemiológicas. Se han informado 253 sublinajes δ en la base de datos PANGOLIN. La identificación de estos sublinajes mediante análisis genómico ha permitido rastrear su evolución y propagación. Objetivo. Caracterizar la diversidad genética de los diferentes sublinajes δ de SARSCoV-2 en Antioquia y determinar su prevalencia. Materiales y métodos. Se recopiló información sociodemográfica de 2.675 muestras y de 1.115 genomas del repositorio GISAID entre el 12 de julio de 2021 y el 18 de enero de 2022. Se seleccionaron 501 por su alto porcentaje de cobertura (>90 %) para realizar análisis filogenéticos e inferencia de frecuencias alélicas de mutaciones de interés. Resultados. Se caracterizaron 24 sublinajes donde el más prevalente fue AY.25. En este sublinaje se identificaron mutaciones de interés como L452R, P681R y P681H, que comprendían una frecuencia cercana a 0,99. Conclusiones. Este estudio permitió identificar que el sublinaje AY.25 tiene una ventaja de transmisión en comparación con los otros sublinajes δ. Esto puede estar relacionado con la presencia de las mutaciones L452R y P681R que en otros estudios se han visto asociadas con una mayor transmisibilidad, evasión del sistema inmunitario y menor eficacia de los medicamentos contra SARS-CoV-2.

Abstract This study used non-destructive testing with ultrasonic and stress wave propagation to evaluate bending strength and stiffness of wood-polymer composites. Twelve composite plate products were produced with different formulations of polymer matrix (high- and low-density polyethylene and polypropylene) and type and proportion of flour (coconut shell and wood). Mechanical and acoustic properties were influenced primarily by the type of matrix used in the composite. The greater the proportion of wood and coconut shell flour the higher the wave propagation velocity, stiffness, and strength. We found a correlation between mechanical properties (strength and stiffness) and wave velocity and stiffness coefficient. We also present linear regression equations of the stiffness and strength of the specimen as a function of wave velocity and stiffness coefficient obtained through non-destructive testing. For polypropylene and high-density polyethylene matrix composites, the stiffness coefficient provided a better estimate of stiffness, while for low-density polyethylene the wave velocity provided better results.

Abstract The formulations of the boundary element method for dynamic problems, whether acoustic or elastodynamic, that use a more straightforward fundamental solution and consequently require the use of Radial basis functions to transform domain integrals into boundary integrals present instability when reduced time increments are used. This problem does not arise in numerical techniques like finite element and finite difference methods. Despite the higher quality of results presented by the Direct Interpolation Method (DIBEM), a new radial basis formulation, instability problems persist for very small time steps, demanding mesh refinement. Several factors were examined, such as the robustness of the inertia DIBEM matrix concerning conditioning and positivity, densification of the number of internal interpolation points inside, the type of radial basis function, the composition of the time marching scheme, and others. This work evaluates if the cause of this stability is linked to the modal participation of non-real frequencies, which arise in the high spectrum due to numerical inaccuracy when dealing with non-symmetric matrices. elastodynamic used methods DIBEM, , (DIBEM) formulation steps refinement examined positivity inside function scheme others nonreal non real frequencies nonsymmetric symmetric matrices (DIBEM

Abstract Background Spreading depression (SD) is an intriguing phenomenon characterized by massive slow brain depolarizations that affect neurons and glial cells. This phenomenon is repetitive and produces a metabolic overload that increases secondary damage. However, the mechanisms associated with the initiation and propagation of SD are unknown. Multiple lines of evidence indicate that persistent and uncontrolled opening of hemichannels could participate in the pathogenesis and progression of several neurological disorders including acute brain injuries. Here, we explored the contribution of astroglial hemichannels composed of connexin-43 (Cx43) or pannexin-1 (Panx1) to SD evoked by high-K+ stimulation in brain slices. Results Focal high-K+ stimulation rapidly evoked a wave of SD linked to increased activity of the Cx43 and Panx1 hemichannels in the brain cortex, as measured by light transmittance and dye uptake analysis, respectively. The activation of these channels occurs mainly in astrocytes but also in neurons. More importantly, the inhibition of both the Cx43 and Panx1 hemichannels completely prevented high K+-induced SD in the brain cortex. Electrophysiological recordings also revealed that Cx43 and Panx1 hemichannels critically contribute to the SD-induced decrease in synaptic transmission in the brain cortex and hippocampus. Conclusions Targeting Cx43 and Panx1 hemichannels could serve as a new therapeutic strategy to prevent the initiation and propagation of SD in several acute brain injuries.

Abstract The in-situ small-strain shear modulus of soil and rock materials is a parameter of paramount importance in geotechnical modeling. It can be derived from non-invasive geophysical surveys, which provide the possibility of testing the subsurface in its natural and undisturbed condition by inferring the velocity of propagation of shear waves. In addition, for soil dynamics and earthquake engineering applications, the small-strain damping ratio plays a relevant role, yet its estimation is still challenging, lacking consolidated approaches for its in-situ evaluation. Recent advancements in instrumentation, such as distributed acoustic sensing (DAS), combined with advanced analysis methodologies for the interpretation of seismic wave propagation (e.g., machine learning and full waveform inversion), open new frontiers in site characterization. This paper presents and compares some advanced applications of measuring 1D and 2D variations in shear wave velocity and attenuation in-situ with reference to a specific case history. insitu situ smallstrain small strain modeling noninvasive non invasive surveys waves addition role challenging evaluation instrumentation DAS, DAS , (DAS) e.g., eg e g (e.g. inversion, inversion inversion) characterization D history (DAS e.g. (e.g e.g

Abstract To study the propagation and evolution of one-dimensional elastoplastic waves within the system under rectangular, trapezoidal, and half-sine incident waves, leveraging elastoplastic incremental wave theory and numerical simulation calculations, the research qualitatively investigates the distribution and evolution of the stress field within the specimen, the impact of Bar 2 parameters, and the deformation characteristics of Bar 2 under these three types of incident waves. The findings indicate: Regardingthe overall stress uniformity of Bar 2 during the entire loading phase, the rectangular incident wave is the most effective, while the half-sine and trapezoidal waves are more advantageous for analyzing the stress conditions in Bar 2 during the early loading phase. The diameter and dimensionless density of the specimen significantly influence the stress non-uniformity, showing an approximate negative and positive correlation, respectively. onedimensional one dimensional halfsine half sine calculations parameters indicate phase effective nonuniformity, nonuniformity non uniformity, non-uniformity correlation respectively

Abstract In this article, a comprehensive analysis of the approach known as Split-Step Wavelet Parabolic Equation (SSW-PE) in modeling radio wave propagation is presented. The SSW-PE introduces innovations, such as the application of narrow-angle and wideangle approaches, referred to as NAPE and WAPE, respectively. Furthermore, the SSW-PE demonstrates the incorporation of refractivity variations, modifications in terrain modeling for better representation, and considerations of surface boundary conditions. In addition to its innovative aspects, this study aims to provide a complete guide for effectively replicating the algorithm, thereby promoting the advancement of propagation studies using wavelets. The effectiveness and applicability of this approach are validated through comparative studies with well-established solutions, including the Discrete Mixed Fourier Transform (DMFT) version of the Split-Step Parabolic Equation (SSPE) method. Comparisons with measurements from real propagation cases are also conducted. Statistical analysis confirms the innovative potential of the SSW-PE algorithm, which also offers computational efficiency for rapid and consistent simulations. Thus, this article contributes to a comprehensive and innovative analysis, providing tangible resources for the research community interested in expanding this methodology. SplitStep Split Step SSWPE SSW PE (SSW-PE presented innovations narrowangle narrow angle approaches WAPE respectively Furthermore variations representation conditions aspects algorithm wavelets wellestablished well established solutions DMFT (DMFT SSPE (SSPE method conducted simulations Thus methodology

Resumo Ensaios não destrutivos (END) que avaliam a constituição ou degradação de estruturas são de grande interesse na Engenharia Civil. Entre as técnicas de END, destaca-se o teste de Velocidade de Pulso Ultrassônico (UPV); no entanto, embora seu uso seja difundido, ainda não existem aplicações que empreguem esse método para determinar a constituição do concreto in situ. Portanto, este artigo aborda a identificação do teor de agregados graúdos em amostras de concreto por meio de uma Rede Neural Artificial (RNA) treinada com um banco de dados de ensaios numéricos que simularam UPV. Neste artigo, o teor de agregados graúdos será descrito como uma porcentagem da área total de um modelo bidimensional de concreto. Três arquiteturas de redes neurais artificiais foram avaliadas. As duas primeiras, treinadas com 13 ou 22 trajetórias, resolveram um problema de classificação para cinco teores de agregados, e a terceira, treinada com 22 trajetórias, resolveu um problema de regressão. Seu desempenho foi comparado com o de outras soluções de regressão, a saber, Regressor XGB, Random Forest e Mínimos Quadrados Ordinários, e mostrou-se superior, com desvios médios de -2,55% a +2,17%. Assim, este artigo demonstrou que o uso da RNA em combinação com o teste UPV tem o potencial de identificar o teor de agregados graúdos em concretos. Os resultados positivos sugerem que essa abordagem é promissora e ressaltam a necessidade de validação experimental adicional em pesquisas futuras. END (END Civil destacase destaca se (UPV) entanto difundido situ Portanto (RNA avaliadas primeiras 1 2 trajetórias terceira regressão saber XGB Ordinários mostrouse mostrou superior 2,55% 255 55 -2,55 217 17 +2,17% Assim concretos futuras (UPV 2,55 25 5 -2,5 21 +2,17 2,5 -2, +2,1 2, -2 +2, - +2 +

Abstract Nondestructive tests that assess the constitution or degradation of structures are of great interest in Civil Engineering. Among the non-destructive testing techniques, the Ultrasonic Pulse Velocity (UPV) test stands out; however, although its use is widespread, there are still no applications that employ this method to determine the constitution of concrete in situ. Therefore, this article addresses the identification of the coarse aggregate content in concrete specimens by an Artificial Neural Network (ANN) trained with a database of numerical tests that simulated UPV. In this paper, the coarse aggregate content will be described as a percentage of the total area of a two-dimensional concrete model. Three artificial neural network architectures were evaluated. The first two, trained with 13 or 22 paths, solved a classification problem for five aggregate contents, and the third, trained with 22 paths, solved a regression problem. Its performance was compared with those of other regression solutions, namely XGB Regressor, Random Forest, and OLS (Ordinary Least Squares), and showed superior, with -2.55% to +2.17% average deviations. Thus, this paper demonstrated that the use of ANN in combination with UPV test has the potential to identify the coarse aggregate content in concretes. The positive results suggest that this approach is promising and highlights the need for further experimental validation in future research. Engineering nondestructive non destructive techniques (UPV out however widespread situ Therefore (ANN twodimensional two dimensional model evaluated 1 2 paths contents third solutions Regressor Forest Ordinary Squares, Squares , Squares) superior 2.55% 255 55 -2.55 217 17 +2.17 deviations Thus concretes research 2.55 25 5 -2.5 21 +2.1 2.5 -2. +2. 2. -2 +2 - +

Resumo Este estudo avaliou a influência da variabilidade da temperatura de aquecimento no nível de degradação de concretos, variando-se temperatura de exposição (200°C, 450°C e 800°C) e resistência de projeto do concreto (C25 e C40). Os concretos foram submetidos a ensaios de ultrassom (antes e depois do aquecimento), e, posteriormente, foram rompidos à compressão axial. Após a ruptura foram retiradas amostras da seção de fratura dos corpos de prova para análises microestruturais, por microscópio eletrônico de varredura (MEV), e análises moleculares, por espectroscopia Raman. Os resultados mostraram que a resistência residual dos concretos pode mudar de maneira significativa (valores divergindo em mais de 100%) com a variabilidade de temperatura no forno. Houve alterações físico-químicas dos constituintes do concreto. As variações nos espectros Raman e as alterações morfológicas (imagens em MEV) permitiram verificar a variação do nível de degradação do concreto após exposição ao fogo, em uma mesma etapa de queima, devido variação de temperatura nos fornos, sendo compatíveis com os resultados de resistência à compressão e com os de ultrassom (velocidade do pulso ultrassônico). Dessa forma, o estudo evidencia a necessidade do mapeamento adequado do calor no forno e do monitoramento da temperatura dos corpos de prova, em estudos sobre concretos sob altas temperaturas. variandose variando se 200°C, 200C C 200 (200°C 450C 450 800°C 800C 800 C25 (C2 C40. C40 . C40) antes aquecimento, , aquecimento) posteriormente axial microestruturais MEV, MEV (MEV) moleculares valores 100% 100 físicoquímicas físico químicas imagens fogo queima fornos velocidade ultrassônico. ultrassônico ultrassônico) forma temperaturas 200°C 20 45 80 C2 (C C4 (MEV 10 2 4 8 1

Abstract This study evaluated the influence of heating temperature variability on the degradation level of concrete by varying the exposure temperatures (200°C, 450°C, and 800°C) and concrete design strength (C25 and C40). The concretes were submitted to ultrasound tests (before and after heating) and then were ruptured by axial compression. After rupture, samples were taken from the fracture section of the specimens for microstructural analysis by scanning electron microscope (SEM), and molecular analysis by Raman spectroscopy. The results showed that the residual strength of the concrete can change significantly (values differing by more than 100%) with temperature variability in the oven. There were physicochemical changes in the concrete constituents. The variations in Raman spectra and morphological changes (SEM images) allowed to analyze the variation in the level of degradation of concrete after exposure to fire, at the same firing step, due to temperature variation in the ovens, being compatible with the results of compressive strength and ultrasonic wave propagation velocity (UPV). Thus, the study highlights the need for adequate mapping of the heat in the oven and monitoring of the temperature of specimens in studies of concrete at high temperatures. 200°C, 200C C 200 (200°C 450C 450 450°C 800°C 800C 800 C25 (C2 C40. C40 . C40) before compression rupture SEM, SEM , (SEM) spectroscopy values 100% 100 constituents images fire step ovens UPV. UPV (UPV) Thus 200°C 20 45 80 C2 (C C4 10 (UPV 2 4 8 1

Resumo Em muitas edificações urbanas há a presença de centrais de gás, as quais contém tanques pressurizados. Nesses locais, um dos principais riscos existentes é a explosão, que pode ser seguida ou não de incêndio. Em geral, a onda de choque formada por este tipo de fenômeno é desastrosa e pode ocasionar diversos danos materiais e até mesmo fatalidades. Pesquisas recentes têm contribuído para o entendimento dos sistemas protetivos contra este fenômeno, entretanto, é necessário avançar no desenvolvimento de dispositivos de proteção quanto as centrais de gás. Nessa perspectiva, a implementação destes para mitigação dos efeitos danosos das explosões é imprescindível para elevar o patamar de segurança nas construções. As barreiras físicas de proteção são soluções apropriadas para proteção de edificações, principalmente em locais onde há a impossibilidade de enterrar os reservatórios de gás. Além do potencial em reduzir os níveis de sobrepressão na parte posterior, os muros de proteção, quando corretamente projetados, também são capazes de impedir a propagação dos detritos oriundos da explosão. Outro tipo de barreira que influencia na propagação da onda de choque próxima ao solo são as valetas, cuja função está relacionada à absorção e redirecionamento da energia da onda. A compreensão sobre o posicionamento, geometria e potencial de atenuação de sobrepressões das barreiras físicas é indispensável no desenvolvimento de projetos mais seguros e confiáveis. Este artigo objetiva o estudo de barreiras protetivas em edificações com tanques de gás pressurizados. O estudo foi desenvolvido numericamente por meio do software Autodyn. Este programa é uma ferramenta baseada na dinâmica dos fluidos computacional (CFD). Avaliou-se qualitativamente e quantitativamente a capacidade protetiva dos tipos de proteção propostos quanto à mitigação das sobrepressões incidentes. pressurizados explosão incêndio geral fatalidades entretanto perspectiva construções posterior projetados valetas posicionamento confiáveis Autodyn CFD. CFD . (CFD) Avaliouse Avaliou se incidentes (CFD

Abstract In many urban buildings, there is the presence of gas central storage, which contain pressurized tanks. One of the main risks in these places is an explosion, which may or may not is followed by fire. In general, the shock wave formed by this phenomenon is disastrous and can cause material damage and even fatalities. Recent research has contributed to understanding protective systems against this phenomenon; however, it is necessary to advance in developing protection devices for gas central storage. From this perspective, the implementation plan of these devices in order to mitigate the harmful effects of explosions are essential to raise the safety level in construction. Physical protection barriers are appropriate solutions for the protection of buildings, especially in places where it is impossible to bury gas reservoirs. In addition to the potential to reduce back pressure levels, protective walls, when properly designed, can also prevent the spread of debris from the explosion. Another kind of barrier that influences the propagation of the shock wave close to the ground is the ditches, whose function is related to the absorption and redirection of wave energy. Understanding the positioning, geometry, and overpressure attenuation potential of physical barriers are essential in developing safer and more reliable projects. This article aims to study protective barriers in buildings with pressurized gas tanks. The study was developed numerically using the Autodyn software. This program is a tool based on computational fluid dynamics (CFD). The protective capacity of the proposed types of protection regarding the mitigation of incident overpressures was evaluated qualitatively and quantitatively. storage tanks explosion fire general fatalities however perspective construction reservoirs levels walls designed ditches energy positioning geometry projects software CFD. CFD . (CFD) quantitatively (CFD

RESUMO A resistência à compressão do concreto (fck) geralmente é estimulada pelo ensaio de compressão axial, sendo os métodos não destrutivos apontados como segunda opção. O objetivo do estudo é avaliar a qualidade do concreto através de ensaios ultrassônicos e esclerométricos, correlacionando-os ao método de compressão axial. Foram realizados 60 corpos de prova de concreto com idades de 7, 14 e 28 dias. Os resultados dos ensaios de ultrassom apresentaram maior dispersão para 7 dias de idade, possivelmente devido ao seu estágio inicial de cura. Com o avanço da cura, a precisão do ensaio de ultrassom melhorou significativamente, especialmente aos 28 dias. Pode-se afirmar, com 95% de confiança, que resultados de velocidade de propagação de onda acima de 4550 m/s representam resistência à compressão característica superiores a 25 MPa e resistência média superior a 30 MPa. No ensaio de esclerometria, os resultados indicaram resistências superiores às obtidas no ensaio de compressão axial. Para resultados de resistência característica à compressão esclerométrica superior a 38 MPa, os resultados do fckk esperados são de 25 MPa, com 95% de confiança. Concluiu-se que os resultados deste estudo apontam para a existência de uma correlação eficaz entre a resistência à compressão obtida nos ensaios distintos. fck (fck axial opção esclerométricos correlacionandoos correlacionando 6 1 2 idade cura significativamente Podese Pode se afirmar 95 confiança 455 ms m s 3 esclerometria Concluiuse Concluiu distintos 9 45 4

ABSTRACT Concrete compressive strength (fck) is generally estimated by the axial compression test, with non-destructive methods considered as a second option. The objective of the study is to evaluate the quality of concrete through ultrasonic and sclerometric tests, correlating them with the axial compression method. 60 concrete specimens aged 7, 14 and 28 days were made. The results of the ultrasound tests showed greater dispersion for 7 days of age, possibly due to its initial stage of healing. As healing progressed, the accuracy of the ultrasound assay improved significantly, especially at 28 days. It can be stated, with 95% confidence, that for wave propagation speed results above 4550 m/s, they represent characteristic compressive strength greater than 25 MPa and average resistance greater than 30 MPa. In the sclerometry test, the results indicated higher characteristic resistances than those obtained in the axial compression test. For sclerometric compression strength results greater than 38 MPa, the expected fck results are 25 MPa, with 95% confidence. It was concluded that the results of this study point to the existence of an effective correlation between the compressive strength obtained in the different tests. (fck test nondestructive non destructive option method 6 1 2 made age progressed significantly stated 95 confidence 455 ms m s m/s 3 9 45 4

A física ondulatória descreve sistemas físicos nos quais uma força restauradora comanda o movimento oscilatório do sistema em torno de um ponto de equilíbrio. Essas oscilações se manifestam em diferentes tipos de ondas e se propagam com velocidades associadas às distintas características do meio de propagação. Uma manifestação que impressiona pela simetria, pela própria elegância, são os padrões de Chladni, que inclusive são utilizados como indicador de qualidade na fabricação de instrumentos musicais. Neste trabalho são apresentados um aparato experimental simples e uma interface gráfica matemática interativa, desenvolvida na plataforma GeoGebra a partir das soluções da equação de onda em placas quadradas para explorar o estudo de ondas estacionárias bidimensionais das placas de Chladni. Várias Figuras de Chladni foram criadas experimentalmente a partir de grãos depositados sobre diferentes placas metálicas sujeitas à vibração. Foram utilizadas placas quadradas de diferentes tamanhos com extremidades livres com o objetivo de observar a relação de proporção entre a frequência de ressonância dos padrões de onda estacionária com o inverso do quadrado do lado. Foi constatado que a associação entre os resultados experimentais obtidos pela modelagem computacional na formação das Figuras de Chladni permite uma melhor compreensão dos princípios que controlam a formação desses padrões. equilíbrio propagação simetria elegância musicais interativa vibração lado

Wave physics describes physical systems in which a restoring force governs the oscillatory motion of the system around an equilibrium point. These oscillations manifest themselves in different types of waves and propagate at speeds associated with the different characteristics of the propagation medium. One of the phenomena that impresses by their symmetry and elegance are the Chladni patterns, which are even used as an indicator of quality in the manufacture of musical instruments. In this paper, a simple experimental apparatus and an interactive mathematical graphical interface, which was createad at the GeoGebra platform by equations solutions from the wave equation in square plates, were developed to study two dimensional Waves of the Chladni plates. Several Chladni figures were experimentally created from grains deposited on different metal plates under vibration. Square plates of different sizes with free edges were used to observe the ratio relationship between the resonance frequency of the stationary wave patterns and the inverse of the square of the side. It was found that the association between the experimental results and those obtained by computer modeling in the formation of Chladni figures allows for a better understanding of the principles that control the formation of these patterns. point medium instruments paper interface vibration side

In 1887, Lord Rayleigh published a theory of a surface wave that later became known as the Rayleigh wave. The main features of this wave are its attenuation with depth and the fact that its velocity is always less than the S-wave velocity. Classical textbooks on elastic waves propagation and seismology usually consider the so-called Poisson solid, in which the Poisson’s ratio is equal to 0.25. In this study, we present some mathematical details and geometrical aspects that are not discussed in the textbooks. We obtain the Rayleigh cubic equation and compute its three roots as a function of the Poisson’s ratio. Then, we compute the particle displacements in a given depth, U(z) and W(z), as well as the instantaneous displacements, u(x, z, t) and w(x, z, t), to demonstrate the elliptical polarization of the particle motion and to indicate the rotation direction of the geometrical locus. We find that for each value of Poisson’s ratio, at a critical depth, the rotation direction changes from retrograde to prograde. Finally, we find the critical depth by three different approaches. 1887 Swave S socalled so called solid Poissons s 025 0 25 0.25 study Then Uz U z U(z Wz, Wz W , W(z) ux, ux u x, x u(x t wx, wx w w(x t, locus prograde Finally approaches 188 02 2 0.2 W(z 18 0. 1

RESUMO Os ensaios não destrutivos que utilizam o princípio de propagação de ondas têm potencial para predizer as propriedades mecânicas da madeira ainda em campo, se conhecida as variáveis deste processo. Este trabalho teve o objetivo de estimar o módulo de elasticidade à flexão estática da madeira de Eucalyptus sp., por meio de duas técnicas não destrutivas: ultrassom e stress wave. Para tal foram usados 60 corpos de provas com dimensões nominais de 2,5 x 2,5 x 57,5 cm (tangencial x radial x longitudinal), estando na umidade de equilíbrio. Os testes não destrutivos foram realizados por meio de um equipamento de ultrassom e um de ondas de tensão, enquanto que os testes destrutivos de flexão estática foram realizados em uma máquina universal de ensaios. Os resultados experimentais mostraram que os módulos de elasticidade obtidos pelas técnicas não destrutivas foram superiores à obtida pela técnica destrutiva. Os modelos matemáticos ajustados apresentaram erro padrão da estimativa (Syx) de 11,39 e 10,78%. Logo, houve correlação média positiva entre o módulo estático e dinâmico. As técnicas de ondas de tensão e ultrassom podem ser empregadas com o intuito de estimar o módulo de elasticidade da madeira de Eucalyptus sp. campo processo sp wave 6 25 2 5 2, 575 57 57, tangencial longitudinal, longitudinal , longitudinal) equilíbrio destrutiva Syx (Syx 1139 11 39 11,3 1078 10 78 10,78% Logo dinâmico 113 1 3 11, 107 7 10,78 10,7 10,

ABSTRACT Non-destructive tests that use the principle of wave propagation have the potential to predict the mechanical properties of wood while still in the field, if the variables of this process are known. This work aimed to estimate the modulus of elasticity to static bending of Eucalyptus sp. wood, using two non-destructive techniques: ultrasound and stress wave. For this, 60 specimens with nominal dimensions of 2.5 x 2.5 x 57.5 cm (tangential x radial x longitudinal) were used, being in equilibrium humidity. The non-destructive tests were carried out using an ultrasound and a stress wave equipment, while the destructive static bending tests were carried out in a universal testing machine. The experimental results showed that the elastic modulus obtained by the non-destructive techniques were superior to that obtained by the destructive technique. The adjusted mathematical models presented standard error of the estimate (Syx) of 11.39 and 10.78%. There was a positive mean correlation between the static and dynamic module. Stress wave and ultrasound techniques can be used to estimate the modulus of elasticity of Eucalyptus sp. Nondestructive Non field known sp nondestructive non 6 25 2 5 2. 575 57 57. tangential longitudinal humidity equipment machine technique Syx (Syx 1139 11 39 11.3 1078 10 78 10.78% module 113 1 3 11. 107 7 10.78 10.7 10.