Solution of the Dynamic Interaction Problem between a Framed Structure and an Acoustic Cavity Using Imposed Deformation Functions at the Interface

This article presents an analytical procedure for solution of the dynamic interaction problem of a vibrating framed structure connected to a bidimensional cavity, containing an acoustic fluid. Initially the pressure solution for the fluid domain is developed, using the separation of variables technique. In a next step, this solution is applied to an entirely open cavity and to a closed cavity in the transversal direction, both containing a vibrating boundary with an arbitrary deformation. The generalized parameters of the structure (mass, rigidity, and force) are obtained by means of the virtual work principle, with the generalized force represented by the dynamic pressures acting on the interface. The dynamic equilibrium equation of the system is established for an imposed deformation, making a parametric study of the involved variables possible. Finally, it is demonstrated that this procedure can be generalized, allowing the construction of practical abacuses for other boundary conditions of both the structure and the cavity, and that these results allow a reasonable interpretation of the coupling regions, including the prediction of added mass and added stiffness effects, as well as corresponding frequencies and mode shapes of the coupled problem

Effects of soil-structure interaction in seismic analysis of buildings with multiple pressurized tuned liquid column dampers

In this paper soil-structure interaction (SSI) effects are investigated while an array of Pressurized Tuned Liquid Column Dampers (PTLCD) is employed for seismic vibration control of buildings. This device represents the most general case of a passive damper, with different reduction options to other control devices obtained by simplifying the involved parameters. Soil conditions considerably affect the control device functioning, because dynamic parameters such as natural frequency, damping factor, and natural modes depend on the soil properties. A simplified mathematical model is developed for the building with multiple degrees of freedom connected to a flexible base. For the time-domain analysis, a computational routine is developed for the linearization of the equilibrium equations of the PTLCD, as well as details for the reduction to the other types of passive dampers. Several numerical examples are selected for the analysis of the damper efficiency in reducing seismic vibration considering SSI. These simulations include Kobe earthquake data, which is applied to the model to evaluate the device performance under different scenarios. It is verified the influence of SSI in the natural frequency and structural response, which is related to the earthquake frequency components. Results confirm that the array of PTLCD’s can reduce the vibration amplitudes, being more effective for soils with higher stiffness values

Aspectos técnico-científicos de barragens no Brasil: uma abordagem teórica

The safety of a dam is the result of a series of factors, including structural, geotechnical, hydraulic, operational and environmental aspects. In Brazil, Law No. 12.334 of September 2010 establishes the National Dam Safety Policy, which requires safety reports and monitoring inspections for existing dams. The inspection comprises a set of devices installed on the dam, which are used to assess the structural behavior based on performance parameters of the structure, such as displacements, flows, stresses, slopes and others. Dam auscultation procedures, historically, have been performed since the 1950s. Since then, there have been significant advances in instrumentation and dam auscultation methods. This work presents a theoretical approach on technical and scientific aspects of dams in Brazil, based on a state-of-the-art literature review, involving auscultation of dams in the context of design codes, concepts, instrumentation, safety, procedures and monitoring methods.A segurança de uma barragem é resultante de uma série de fatores, dentre os quais podem ser citados aspectos estruturais, geotécnicos, hidráulicos, operacionais e ambientais. No Brasil, a Lei nº 12.334 de setembro de 2010 estabelece a Política Nacional de Segurança de Barragens. A instrumentação compõe um conjunto de dispositivos instalados nas barragens, que são utilizados para avaliar o seu comportamento estrutural a partir de parâmetros de desempenho da estrutura, tais como deslocamentos, vazões, tensões, inclinações e outros. Procedimentos de auscultação de barragens, historicamente, tem sido realizado desde a década de 50, conforme a literatura. Desde então, houve avanços significativos na instrumentação e nos métodos de auscultação de barragens. Este trabalho tem como objetivo apresentar uma abordagem teórica sobre aspectos técnico-científicos de barragens no Brasil, fundamentada numa revisão de literatura no estado da arte, envolvendo auscultação de barragens no contexto de normas, conceitos, instrumentação, segurança, procedimentos e métodos de monitoramento.Uminho -Universidade do Minho(undefined

Simplified expressions for dynamic behavior of cylindrical shells uncoupled and coupled with liquids

The dynamic behavior of cylindrical shells is essential in many practical applications. These include in-vacuum and coupled vibrations of structures with contained fluids. Closed-form solutions are extremely complex since they involve many terms and algebraic operations that require numerical solvers. In this work, a simplified closed-form solution for the free vibration analysis of an empty or filled with an inviscid and incompressible fluid cylindrical tank is presented. The proposed analytical method is developed for a simply supported cylindrical shell, based on an energy formulation obtained with variational calculus, and provides explicit expressions for natural frequencies, which can be easily programmed in a spreadsheet. The fluid is represented by an acoustic cavity, modeled by the wave equation, and the fluid-structure interaction is reduced to an added mass of fluid in the uncoupled shell equations of motion. A finite element model was built using ANSYS software to validate the proposed procedure. The natural frequencies and mode shapes were studied, and the results obtained are consistent with analytical, numerical and experimental results

MÉTODO SEM MALHA COM DIFERENÇAS FINITAS GENERALIZADAS PARA SOLUÇÃO DE EQUAÇÕES DIFERENCIAIS PARCIAIS

O desenvolvimento nas técnicas de soluções de EDPs vem apresentando enorme evolução nas últimas décadas, em parte com a popularização dos métodos numéricos, que são aplicados a problemas complexos, onde soluções analíticas não são possíveis. O Método dos Elementos Finitos (MEF) recebe destaque nessa evolução e é atualmente o método numérico mais difundido para solução de EDPs. Por outro lado, o MEF necessita de uma etapa prévia de pré-processamento, que consiste na elaboração da malha do domínio, em um procedimento conhecido com discretização. Dependendo da forma do domínio a ser solucionado, essa etapa pode demandar tempo considerável na preparação do problema numérico (pré-processamento). Pesquisas associadas a métodos sem malha vêm ganhando importância nas últimas décadas, pois evitam esta demora. O Método das Diferenças Finitas Generalizadas (MDFG) representa uma categoria interessante nesse aspecto, com uma extensão do procedimento tradicional (MDF) ao caso onde um grid ortogonal é desnecessário. Este aspecto traz em si a tendência de resoluções das EDPs comdomínios cada vez mais complexos. Desta forma, o presente trabalho busca desenvolver códigos no MATLAB que busquem boa eficiência na resolução do problema em duas dimensões de Laplace para diferentes configurações de fronteira pelo MDFG

Assessing the Potential of Sensors Based on LbL and Sputtering Films

Funding text This research was funded by the project PCIF/GFC/0078/2018: influence of forest VOCs (volatile organic compounds) on extreme fire behavior at Fundação para a Ciência e a Tecnologia (FCT). The authors also thankful for the research center grants no. UIDB/FIS/04559/2020 and no. UIDP/FIS/04559/2020 (LIBPhys) from FCT/MCTES, Portugal.A new theory suggests that flammable gases generated by heated vegetation, in particular the volatile organic compounds (VOC) common to Mediterranean plants, may, under certain topographic and wind conditions, accumulate in locations where, after the arrival of the ignition source, they rapidly burst into flames as explosions. Hence, there is a need for the development of a system that can monitor the development of these compounds. In this work, a sensor's array is proposed as a method for monitoring the amount of eucalyptol and α-pinene, the major VOC compounds of the Eucalyptus and Pine trees. The detection of the target compounds was assessed using the impedance spectroscopy response of thin films. Combinations of layers of polyelectrolytes, such as poly(allylamine hydrochloride) (PAH), polyethyleneimine (PEI), poly(sodium 4-sytrenesulfonate) (PSS) graphene oxide (GO), and non/functionalized multiwall nanotubes (MWCNT-COOH or MWCNT), namely, PAH/GO, PEI/PSS, PEI/GO, PAH/MWCNT, PAH/MWCNT-COOH, films, and TiO2 and ZnO sputtered films, were deposited onto ceramic supports coated with gold interdigitated electrodes. The results showed that concentrations of the target VOCs, within the range of 68 to 999 ppmv, can be easily distinguished by analyzing the impedance spectra, particularly in the case of the ZnO- and PAH/GO-film-based sensors, which showed the best results in the detection of the target compounds. Through principal component analysis (PCA), the best set of features attained for the ZnO and PAH/GO based sensor devices revealed a linear trend of the PCA's first principal component with the concentration within the range 109 and 807 ppmv. Thus, the values of sensitivity to eucalyptol and α-pinene concentrations, which were (2.2 ± 0.3) × 10-4 and (5.0 ± 0.7) × 10-5 per decade, respectively, as well as resolutions of 118 and 136 ppbv, respectively, were identified.publishersversionpublishe

Finite Element Modal Analysis of Transient Water Flow in Aquifers

In this paper a modal superposition method is applied for the numerical modeling of aquifers. The proximity of aquifers to populated regions requires special care in their management to avoid problems that affect the quantity and quality of the water they supply. To contribute to the management of this type of natural resource, we propose a numerical strategy based on modal analysis using the finite element method. This procedure assist water production scenarios, performing the mass balance where water extraction is done through wells, in aquifers that are subject to natural recharge. This mathematical procedure is based on the modal superposition for transient flow in porous media. To evaluate its efficiency, this strategy was compared with the classical finite element method. The advantage of the proposed method resides in the possibility of reusing the properties of the global matrix of the finite element method in transient problems, for different production conditions given by the distributed recharge and by the water extraction rate from the wells, solving the numerical problem with a more efficient use of computational resources. This strategy is useful in studies of uncertainty quantification, history matching and optimization of water production in aquifers, since these types of analysis are resource intensive for the very large number of numerical simulations required for these scenarios

Verificação de desempenho de metodologia para determinação de íon nitrato em amostras de água potável

Contaminated water is one of the main public health risks. One way to assess its quality is by quantifying nitrate through ultraviolet (UV) spectrophotometry. In this work, the performance of the UV spectrophotometric method for nitrate ion determination in water was studied, with linearity, precision, accuracy, limit of detection (LOD), limit of quantification (LOQ) and robustness being verified. In the working range studied (5.0-25.0 mgN·L-1), all validation parameters are in accordance with the acceptance criteria established by INMETRO. In linearity, the value of r (0.999) was higher than the criterion (0.995). In the study of precision and accuracy, the coefficients of variation for repeatability and intra-laboratory reproducibility were 1.79 and 2.34%, and 1.44 and 2.52%, respectively (<5%). The value of the relative error (15.8 and 8.1%) was also lower than the criterion (≤ 20%). The LOD and LOQ obtained were 0.56 and 1.70 mgN·L-1, respectively. In the evaluation of the robustness no factor had a significant effect on the final result. Analyzing real samples, the percentages of recovery were between 88.5 and 103.6%, according to the established criteria (80-110%). In this way, it can be said that the method presents reliability to the intended purpose.Águas contaminadas representam um dos principais riscos à saúde pública. Uma forma de avaliar sua qualidade é pela quantificação de nitrato via espectrofotometria de ultravioleta (UV). Neste trabalho foi realizada a verificação de desempenho do método espectrofotométrico de UV para determinação de íon nitrato em água, estudando-se a linearidade, precisão, exatidão, limite de detecção (LOD), limite de quantificação (LOQ) e robustez. Na faixa de trabalho estudada (5.0-25.0 mgN·L-1), todos os parâmetros de validação estão em concordância com os critérios de aceitação estabelecidos pelo INMETRO. Na linearidade, o valor de r (0,999) apresentou-se maior que o critério (0.995). No estudo da precisão e exatidão, os coeficientes de variação para a repetitividade e reprodutibilidade intralaboratorial foram de 1.79 e 2.34 %, e 1.44 e 2.52 %, respectivamente (<5%). O valor do erro relativo (15.8 e 8.1 %) também foi inferior ao critério (≤ 20 %). O LOD e LOQ obtidos foram de 0.56 e 1.70 mgN·L-1, respectivamente. Na avaliação da robustez nenhum fator apresentou efeito significativo no resultado final. Analisando-se amostras reais, os percentuais de recuperação ficaram entre 88.5 e 103.6 % atendendo ao critério estabelecido (80-110 %). Desse modo, pode-se afirmar que o método apresenta confiabilidade à finalidade pretendida

Doença de Chagas na Amazônia Ocidental Brasileira: panorama epidemiológico no período de 2007 a 2018

Introduction: Chagas disease (CD) is a disease caused by the protozoan flagellates of the Kinetoplastid order Trypanosoma cruzi. Approximately 8,000,000 people are infected worldwide, mainly in Latin America, causing disabilities and more than 10,000 deaths per year. Objective: This study aimed to describe the epidemiological panorama of CD in the Western Brazilian Amazon from 2007 to 2018. Methods: In this ecological study, secondary data regarding the confirmed cases of T. cruzi infection in the states of Acre, Amazonas, Rondônia, and Roraima were collected from the Single Health System Notification Information System of the Department of Informatics of the Single Health System and were analyzed. The data were used to characterize the epidemiological profile of T. cruzi infection and to determine the frequency of infection in Western Amazonia. Results: A total of 184 cases of CD were reported in Western Amazonia, and the highest number of cases was reported in the states of Amazonas and Acre. Conclusion: The epidemiological panorama of the Western Brazilian Amazon from 2007 to 2018 includes a greater number of cases of T. cruzi infection in men aged 20–39 years and those living in rural areas. Oral transmission was prevalent in the region during the study, and the highest number of cases was reported in the months of April and December. Epidemiological data are an important resource for understanding the dynamics of CD and the main aspects related to the health-disease process.Introdução: A doença de Chagas (DC) é uma enfermidade causada pelo protozoário flagelado da ordem Kinetoplastida denominado Trypanosoma cruzi. Estima-se que oito milhões de pessoas estejam infectadas em todo o mundo, principalmente na América Latina, causando incapacidades e mais de dez mil mortes por ano. Objetivo: Descrever o panorama epidemiológico da doença de Chagas na Amazônia Ocidental brasileira no período de 2007 a 2018. Método: Trata-se de um estudo ecológico e com coleta e análise de dados referentes aos casos confirmados de infecção por T. cruzi nos estados do Acre, Amazonas, Rondônia e Roraima, por meio de fontes secundárias oriundos do Sistema de Informação de Agravos de Notificação do Sistema Único de Saúde (SINAN) do Departamento de Informática do Sistema Único de Saúde (DATASUS). Os dados foram utilizados para caracterizar o perfil epidemiológico dos infectados por T. cruzi e determinar a frequência da infecção na Amazônia Ocidental. Resultados: Houve a notificação de 184 casos de doença de Chagas na Amazônia Ocidental com mais registros nos estados do Amazonas e Acre. Conclusão: O panorama epidemiológico da Amazônia Ocidental Brasileira no período de 2007 a 2018, compreende uma maior quantidade de casos em indivíduos do sexo masculino, na faixa etária dos 20-39 anos, e provenientes de zona rural.  A forma de contágio prevalente na região durante o estudo foi a oral e a maior sazonalidade compreendeu os meses de abril e dezembro. Dados epidemiológicos são um importante recurso para a compreensão da dinâmica da DC e os principais aspectos relacionados no processo saúde-doença.