692 research outputs found
50 anos do golpe no Brasil: perguntas e debates face à produção historiográfica
Anais das IV Jornadas Internacionais de Problemas Latino-Americanos: Lutas, Experiências e Debates na América Latina - ISBN 978-950-793-223-6 - Orgs. Paulo Renato da Silva ; Mario Ayala ; Fabricio Pereira da Silva ; Fernando José MartinsAl cumplirse este año el cincuentenario del inicio del Golpe de Estado en Brasil, asistimos a un
incremento de las publicaciones sobre la temática. En las mismas, encontramos un predominio
de las visiones que se centran en estudiar el consenso, las “zonas grises” y la participación civil
en términos ampliados. Como estudiantes e investigadoras argentinas nos surgieron varios in-
terrogantes acerca de las consecuencias polĂticas de dichas investigaciones. En este trabajo nos
proponemos abordar crĂticamente las perspectivas historiográficas que se expresan en dichos
escritos. Entendemos que la producciĂłn acadĂ©mica no puede estar escindida de la disputa polĂ-
tica de conseguir juzgar a los responsables de la dictadura cĂvico militar que tuvo lugar entre
1964 y 1985.PPG – IELA – UNIL
Open-charm mesons in nuclear matter at finite temperature beyond the zero-range approximation
The properties of open charm mesons, D, D, D{sub s}, and D{sub s} in nuclear matter at finite temperature are studied within a self-consistent coupled-channel approach. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm sector is derived from a t-channel vector-exchange model. The in-medium scattering amplitudes are obtained by solving the Lippmann-Schwinger equation at finite temperature including Pauli blocking effects, baryon dressing, as well as D, D, D{sub s}, and D{sub s} self-energies taking their mutual influence into account. We find that the in-medium properties of the D meson are affected by the D{sub s}-meson self-energy through the intermediate D{sub s}Y loops coupled to DN states. Similarly, dressing the D meson in the DY loops has an influence over the properties of the D{sub s} meson
Agroforestry Innovation and CAP, impact on climate change, bio-economy and circular economy
This PhD analyses the current status of the two most important agroforestry
practices in the Mediterranean region: silvoarable and silvopasture as well also evaluate the fertilization with urban
sewage sludge as fertilizer in a silvopasture system in Galicia as sustainable land management techniques. The
reduced extent of silvoarable and silvopasture practices in Europe is an opportunity that should be promoted by the
CAP through supportive actions involving bioeconomy and circular economy concepts. Carbon sequestration in
silvopasture depends on the input of external fertilizers to overcome the cation extractions but also depends on
weather conditions, which make necessary to establish control plots to account carbon sequestration related with
management in the post 2020 CAP
Numerical assessment of T-Stub component subject to impact loading
Since the partial collapse of the Ronan Point apartment in London in 1968, requirements for the avoidance of disproportionate collapse are addressed in the design codes. Despite these requirements, the ability of steel connections to sustain large tensile forces whilst undergoing significant rotations has been questioned by recent studies and real evidences (as for example the collapse of the WTC towers in 2001). A point raised in FEMA’s report is: “Connection performance under impact loads… needs to be analytically understood and quantified for improved design capabilities and performance as critical components in structural frames”. Additionally, a recent report presented by Arup made the following recommendation (rec. nº 26): “… the strain rate enhancement of yield strengths in connections could still be important. It is recommended that research is undertaken to examine this effect using rate-sensitive material models”.
Ductility of joints under accidental loadings, such as impact and fire are being investigated in the scope of the FCT project “IMPACTFIRE”, at the University of Coimbra. This paper presents and describes the results of a finite element model for the characterization of: i) the nonlinear behaviour of a bolted t-stub component under impact loading and ii) its strain-rate sensitivity. In order to identify relevant parameters that influence the dynamic behaviour of the t-stub, the effect of the loading magnitude, the effect of t-stub thickness and advantages of using implicit or explicit integration procedures are also studied
Transport Properties of Superfluid Phonons in Neutron Stars
We review the effective field theory associated with the superfluid phonons that we use for the study of transport properties in the core of superfluid neutrons stars in their low temperature regime. We then discuss the shear and bulk viscosities together with the thermal conductivity coming from the collisions of superfluid phonons in neutron stars. With regard to shear, bulk, and thermal transport coefficients, the phonon collisional processes are obtained in terms of the equation of state and the superfluid gap. We compare the shear coefficient due to the interaction among superfluid phonons with other dominant processes in neutron stars, such as electron collisions. We also analyze the possible consequences for the r-mode instability in neutron stars. As for the bulk viscosities, we determine that phonon collisions contribute decisively to the bulk viscosities inside neutron stars. For the thermal conductivity resulting from phonon collisions, we find that it is temperature independent well below the transition temperature. We also obtain that the thermal conductivity due to superfluid phonons dominates over the one resulting from electron-muon interactions once phonons are in the hydrodynamic regime. As the phonons couple to the Z electroweak gauge boson, we estimate the associated neutrino emissivity. We also briefly comment on how the superfluid phonon interactions are modified in the presence of a gravitational field or in a moving background.publishedVersio
T-stub model under impact load – numerical model validation
Este artigo apresenta a validação de um modelo numĂ©rico para o estudo da resposta dinâmica nĂŁo-linear de T-stub’s, desenvolvido com o software ABAQUS. O T-stub Ă© usado no “mĂ©todo das componentes” para definição da resposta das componentes que mais contribuem para a ductilidade de ligações metálicas aparafusadas, nomeadamente a chapa de extremidade em flexĂŁo. O comportamento numĂ©rico do T-stub Ă© validado recorrendo aos resultados obtidos em ensaios experimentais sob regime quase estático e tambĂ©m sob carregamentos dinâmicos de curta duração. Neste estudo sĂŁo considerados T-stub’s soldados com banzos de espessura 10 e 15 mm em aço S355 e parafusos de dimensĂŁo M20 e de classe 8.8. O modelo numĂ©rico inclui a representação dos efeitos de possĂveis taxas de deformação elevadas, com base na caracterização do material a partir de testes de Split Hopkinson Bar em compressĂŁo com uma taxa de deformação de 600 s-1.ABSTRACT: This article presents the validation of a finite element model developed to study the non-linear dynamic response of the T-stub model. The T-stub model is used in the “component method” to establish the behaviour of components contributing the most for a joint’s ductility, namely the “end-plate” in bending. The numerical model is built with the software ABAQUS and validated against experimental tests under quasi-static and short transient dynamic loads. The study comprises welded T-stubs with flange thicknesses of 10 and 15 mm made of steel S355 and bolted with M20’s class 8.8. The numerical model takes into account possible elevated strain rate effects according to material characterization performed with compressive Spilt Hopkinson Bar tests at 600 s-
Numerical validation of t-stub componente subject to impact load
Accidental loadings due to blast or impact may easily cause failure of the elements that are exposed
or located in the vicinity of the hazard, leading in some cases, to the progressive collapse of the
whole structure; therefore, assessment of the structural over strength is critical for structural
engineers to ensure a certain level of security and validate alternative unloading paths. The T-stub
model is used to describe the behaviour of components i) “column flange in bending” and ii) “endplate
in bending” usually present in a beam-to-column bending resistant connection [1]. These
components are responsible for the behaviour in the tension zone of connections, being able to
provide ductility to a connection; thus, proper characterization of T-stub behaviour under impact
loading is crucial.
In this paper, a 3D finite element model exploring the behaviour of a welded T-stub with flange
thickness of 10 mm (T-10) (Fig. 1) is validated against experimental results from:
i) one quasi-static loading (reference case) (grey dotted line Fig. 2 and Fig. 4);
ii) and two rapidly applied dynamic loadings according to the gas pressure in the chamber:
a. 120 Bar (Impact #1 - T10-D120-160 - Fig. 2); and
b. 160 Bar (Impact #1 - T10-D160 - Fig. 4) [2].
The steel grade of the T-stub is S355 and the bolts M20 grade 8.8 are fully threaded. The dynamic
loading simulations take into account the elevated strain rate effects in the stress enhancement,
based on dynamic increase factors, following the Johnson-Cook material model [3]. The dynamic
loadings are applied as a boundary condition in the “pull out surface” (Fig. 1) considering the Tstub’s
transient displacement responses obtained from experimental tests; maximum displacement
values are reached in approximately 0.08 sec. The accuracy of the numerical force-displacement
predictions for both quasi-static and dynamic loading schemes confirms that the Johnson-Cook
material model used, provide accurate stress enhancement to describe the behaviour of bolted steel
connections subject to impact loadings.
From Fig. 2 and Fig. 4, it can be observed that the elastic stiffness remains unchanged for all
loading schemes: ki = 180 kN/m, as the steel’s elastic modulus introduced in the numerical models
are the same for both quasi-static and dynamic situations; moreover, the strain rates developed are
similar for both dynamic loading (Fig. 3), inducing the same dynamic increase factors for the stress
enhancement; the F-δ flows are therefore, similar for both numerical dynamic responses but with
different failure displacements. Plastic resistances of the T-stub: FRd,quasi-static = 161 kN and
FRd,120 Bar = FRd,160 Bar = 195 kN; corresponding to an enhancement of +21% of the plastic resistance
due to the elevated strain rate effects.
Fig. 3 illustrates the pattern of the strain rate (ER), ranging from 1/s to 3/s in the plastic hinge
developed next to the weld toe, corresponding to a DIFs of 1.27 and 1.31. Furthermore, comparison
of the equivalent plastic strain (PEEQ) pattern for both loading situations, shows that two plastic
hinges are developed per flange leg, consistently with the plastic failure mode type 1 predicted by
the Eurocode 3, part 1.8 [1]. However, in the dynamic case, the plastic hinges are slightly
underdeveloped and higher strains are required in the bolt to meet the same deformation level
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