Nonlinear analysis of plane frames using a co-rotating Timoshenko beam element

En este trabajo se describe la formulación corrotacional de un elemento de viga unificado que integra las teorías de vigas de Euler-Bernoulli y de Timoshenko y que no presenta bloqueo por deformación a cortante. La cinemática corrotacional se basa en la separación del movimiento de un sólido en una parte deformacional, y la otra, en movimiento de cuerpo rígido. La parte deformacional del movimiento es representada por tres modos de deformaciones naturales que son generados por el esfuerzo axil, la flexíon pura y la flexíon simple, respectivamente. Los esfuerzos generados por los modos naturales de deformación son auto-equilibrados lo que posibilita la obtención de la matriz de rigidez tangente corrotacional consistente. Se describe de forma detallada la obtención de las matrices de rigideces elástica, geométrica y corrotacional. A través de algunos ejemplos numéricos se muestra la habilidad del elemento de tratar con grandes rotaciones de cuerpo rígido.The present work describes a co-rotating shear flexible beam element without shear locking and integrating Euler-Bernoullis and Timoshenkos beam theories. The co-rotational kinematics is based on the separation of the motion in deformational and rigid body components. The deformation of the beam element is composed by three natural modes of deformation: the extension mode, the symmetric bending mode, and the anti-symmetric bending mode. The respective generalized stresses from these natural modes are self-balanced allowing the achievement of a consistent tangent stiffness matrix. In this paper, it is detailed and deduced all the algebraic steps for the deduction of the elastic stiffness matrix, the geometric stiffness matrix, and the co-rotation stiffness matrix. Some examples are presented and the numerical results demonstrate that the beam element here presented is able to handle large rotations.Peer Reviewe

Catalytic bi-reforming of methane for carbon dioxide ennoblement

6th International Conference on Energy and Environment Research (ICEER)New processes that may reduce the net carbon emissions and contribute to a more circular economy are needed. Bi-reforming of methane (BRM) is a promising method for syngas production, with a hydrogen-to-carbon monoxide ratio of two in the reaction products, relevant for example when the purpose is methanol synthesis. In this work, reaction studies were carried out over a nickel-based catalyst varying the temperature (798–1123 K). Three main temperature zones have been identified; a low temperature zone where the conversion of carbon dioxide is almost null, a middle temperature range where steam reforming of methane (SRM) is dominant while the conversion of carbon dioxide via dry reforming of methane (DRM) is low, and finally a high temperature range where DRM becomes more significant. The results show that syngas can be successfully produced using this process. For the range of operating conditions studied, the carbon dioxide and methane conversions increase with temperature, reaching 40% and 100%, respectively at the largest temperature studied. However, the production of syngas in a molar ratio of 1:2 for CO-to-H requires the use of high temperatures. Most probably the nickel agglomerates on top of the -alumina support are responsible for the poor catalyst performance.FCT, Portugal funded research grants SFRH/BPD/112003/2015, SFRH/BPD/105623/2015 and IF/01093/2014 and Center for Innovation in Engineering and Industrial Technology — CIETI, Portugal, UID/EQU/00305/2013. Project UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology and Energy — LEPABE funded by national funds through FCT/MCTES (PIDDAC), Portugal; Project “LEPABE-2-ECO-INNOVATION” – NORTE-01-0145-FEDER-000005, funded by Norte Portugal Regional Operational Programme (NORTE 2020), Portugal, under PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work was financially supported by: Associate Laboratory LSRE-LCM, Portugal – UID/EQU/50020/2019 – funded by national funds through FCT/MCTES (PIDDAC), Portugal .info:eu-repo/semantics/publishedVersio

Identificaçao modal estocástica de estruturas de engengharia civil

Neste contexto, as técnicas de identificaçao dos parámetros modais da estrutura (frequencias naturais, configuraçoes dos modos de vibraçao e coeficientes de amortecimento modais) com base na realizaçao de ensaios dinámicos surgem com ferramentas de grande interesse, no sentido de dar suporte à análise de correlaçao entre parámetros identificados e calculados, à actualizaçao e validaçao experimental das modelaçoes numéricas desenvolvidas e subsequente avalidaçao experimental das modelaçoes numéricad desenvolvidas e subsequente avaliaçao da capacidade de carga efectiva das estruturas

Associação da prática de atividade física e do estado de saúde sobre a qualidade de vida de mulheres com fibromialgia

This study analyzed the association between physical activity, health status and life quality among women with fibromyalgia. Cross-sectional study based on the clinical information of 177 women (42.1 ± 8.6 years old) diagnosed with fibromyalgia and assisted in rheumatology clinics of the private sector of the Unified Health System (UHS) in the city of Maringá-PR, Brazil. The instruments were the International Physical Activity Questionnaire (IPAQ), the Fibromyalgia Impact Questionnaire (FIQ) and the WHOQOL-Bref. Data analysis was conducted through Mann-Whitney test, Spearman correlation and Structural Equation Analysis (p<0.05). Results showed positive correlations between physical activity and life quality domain. Health status showed negative correlation life quality domains. Structural Equation Analysis revealed days of walking per week showed positive association with life quality domains. Model 3 showed that the impact of fibromyalgia on the health status showed a moderate negative association with life quality domains. Based on the results obtained, the conclusion is that light physical activity, characterized as walking, represents a positive factor in the domains of quality of life in women with fibromyalgia and also, the impact of this disease on the health status of the patients is associated negatively areas of quality of life.301Este estudo analisou a associação entre atividade física, estado de saúde e qualidade de vida de mulheres com fibromialgia. Estudo transversal baseado na informação clínica de 177 mulheres (42,1 ± 8,6 anos) diagnosticadas com fibromialgia e auxiliadas em clínicas de reumatologia do setor privado do Sistema Único de Saúde (SUS) na cidade de Maringá-PR, Brasil. Os instrumentos utilizados foram o Questionário Internacional de Atividade Física (IPAQ), o Questionário de Impacto da Fibromialgia (FIQ) e o WHOQOL-Bref. A análise dos dados foi realizada através do teste de Mann-Whitney, correlação de Spearman e Análise de Equações Estruturais (p <0,05). Os resultados mostraram correlações positivas entre a atividade física e o domínio da qualidade de vida. O estado de saúde apresentou correlações negativas com a qualidade de vida. A Análise de Equação Estrutural revelou que os dias de caminhada por semana se associou positivamente com domínios de qualidade de vida. O modelo 3 mostrou que o impacto da fibromialgia no estado de saúde apresentou associação negativa e moderada com os domínios de qualidade de vida. Com base nos resultados obtidos, conclui-se que a atividade física leve, caracterizada pela caminhada, representa um fator positivo nos domínios da qualidade de vida em mulheres com fibromialgia e também, o impacto desta doença sobre o estado de saúde dos pacientes está associado negativamente domínios da qualidade de vida

Ricci-flat deformation of orbifolds and localized tachyonic modes

We study Ricci-flat deformations of orbifolds in type II theory. We obtain a simple formula for mass corrections to the twisted modes due to the deformations, and apply it to originally tachyonic and massless states in several examples. In the case of supersymmetric orbifolds, we find that tachyonic states appear when the deformation breaks all the supersymmetries. We also study nonsupersymmetric orbifolds C^2/Z_{2N(2N+1)}, which is T-dual to N type 0 NS5-branes. For N>=2, we compute mass corrections for states, which have string scale tachyonic masses. We find that the corrected masses coincide to ones obtained by solving the wave equation for the tachyon field in the smeared type 0 NS5-brane background geometry. For N=1, we show that the unstable mode representing the bubble creation is the unique tachyonic mode.Comment: 20 pages, minor collection

Two-dimensional lattice polymers: adaptive windows simulations

We report a numerical study of self-avoiding polymers on the square lattice, including an attractive potential between nonconsecutive monomers. Using Wang-Landau sampling (WLS) with adaptive windows, we obtain the density of states for chains of up to N=300 monomers and associated thermodynamic quantities. The method enables one to simulate accurately the low-temperature regime, which is virtually inaccessible using traditional methods. Instead of defining fixed energy windows, as in usual WLS, this method uses windows with boundaries that depend on the set of energy values on which the histogram is flat at a given stage of the simulation. Shifting the windows each time the modification factor $f$ is reduced, we eliminate border effects that arise in simulations using fixed windows.Comment: 8 pages, 5 figure

Closed String Tachyon Condensation at c=1

The c=1 matrix model, with or without a type 0 hat, has an exact quantum solution corresponding to closed string tachyon condensation along a null surface. The condensation occurs, and spacetime dissolves, at a finite retarded time on I^+. The outgoing quantum state of tachyon fluctuations in this time-dependent background is computed using both the collective field and exact fermion pictures. Perturbative particle production induced by the moving tachyon wall is shown to be similar to that induced by a soft moving mirror. Hence, despite the fact that I^+ for the tachyon is geodesicaly incomplete, quantum correlations in the incoming state are unitarily transmitted to the outgoing state in perturbation theory. It is also shown that, non-perturbatively, information can leak across the tachyon wall, and tachyon scattering is not unitary. Exact unitarity remains intact only in the free fermion picture.Comment: Minor corrections; References added; 24 pages, 2 figures, harvma

Off-Shell Interactions for Closed-String Tachyons

Off-shell interactions for localized closed-string tachyons in C/Z_N superstring backgrounds are analyzed and a conjecture for the effective height of the tachyon potential is elaborated. At large N, some of the relevant tachyons are nearly massless and their interactions can be deduced from the S-matrix. The cubic interactions between these tachyons and the massless fields are computed in a closed form using orbifold CFT techniques. The cubic interaction between nearly-massless tachyons with different charges is shown to vanish and thus condensation of one tachyon does not source the others. It is shown that to leading order in N, the quartic contact interaction vanishes and the massless exchanges completely account for the four point scattering amplitude. This indicates that it is necessary to go beyond quartic interactions or to include other fields to test the conjecture for the height of the tachyon potential.Comment: 37 pages, 3 figures, LaTeX, JHEP class. Typos corrected, references added, published versio

Transfer learning for galaxy morphology from one survey to another

© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.Deep Learning (DL) algorithms for morphological classification of galaxies have proven very successful, mimicking (or even improving) visual classifications. However, these algorithms rely on large training samples of labelled galaxies (typically thousands of them). A key question for using DL classifications in future Big Data surveys is how much of the knowledge acquired from an existing survey can be exported to a new dataset, i.e. if the features learned by the machines are meaningful for different data. We test the performance of DL models, trained with Sloan Digital Sky Survey (SDSS) data, on Dark Energy survey (DES) using images for a sample of $\sim$5000 galaxies with a similar redshift distribution to SDSS. Applying the models directly to DES data provides a reasonable global accuracy ($\sim$ 90%), but small completeness and purity values. A fast domain adaptation step, consisting in a further training with a small DES sample of galaxies ($\sim$500-300), is enough for obtaining an accuracy > 95% and a significant improvement in the completeness and purity values. This demonstrates that, once trained with a particular dataset, machines can quickly adapt to new instrument characteristics (e.g., PSF, seeing, depth), reducing by almost one order of magnitude the necessary training sample for morphological classification. Redshift evolution effects or significant depth differences are not taken into account in this study.Peer reviewedFinal Accepted Versio