The nature of the LINER in the galaxy NGC 404

NGC 404, at a distance of 3.4 Mpc, is the nearest S0 galaxy. This galaxy harbors a LINER; however, since the spectrum does not show a broad H{\alpha} emission, it is not certain that this LINER is a low luminosity AGN and its nature is still an open question. HST observations show the existence of stellar populations with an age of 3 x 10^8 years years in the galactic bulge and with an age of 6-15 x 10^9 years in the galactic disk. In this work, we present an analysis of the data cube of NGC 404 obtained with the IFU (Integral Field Unity) of the GMOS (Gemini Multi-Object Spectrograph) on the Gemini North telescope.Comment: 2 pages, 2 figure

Built-in self test of high speed analog-to-digital converters

Signals found in nature need to be converted to the digital domain through analog-to-digital converters (ADCs) to be processed by digital means [1]. For applications in communication and measurement [2], [3], high conversion rates are required. With advances of the complementary metal oxide semiconductor (CMOS) technology, the conversion rates of CMOS ADCs are now well beyond the gigasamples per second (GS/s) range, but only moderate resolutions are required [4]. These ADCs need to be tested after fabrication and, if possible, during field operation. The test costs are a very significant fraction of their production cost [5]. This is mainly due to lengthy use of very expensive automated test equipment (ATE) to apply specific test stimuli to the devices under test (DUT) and to collect and analyze their responses.publishe

Comportamento sísmico da igreja do Mosteiro dos Jerónimos

Para avaliar o comportamento sísmico da Igreja do Mosteiro dos Jerónimos tendo em vista o diagnóstico das suas capacidades e vulnerabilidades estruturais bem como a avaliação da segurança sísmica para cenários de diferente perigosidade, foram realizadas um conjunto de análises numéricas estáticas e dinâmicas, admitindo comportamento não linear material e geométrico, cujos resultados se apresentam. A investigação numérica é antecedida pela caracterização (quantitativa e qualitativa) da construção e pela caracterização da acção sísmica com base em estudos de casualidade e em modelos sismológicos. A realização das análises dinâmicas não lineares, no domínio do tempo, é efectuada para acções sísmicas correspondentes a cenários com 475, 975 e 5000 anos de período de retorno e visa caracterizar o desempenho sísmico da Igreja, nomeadamente das potenciais vulnerabilidades identificadas. Para ao efeito, realiza-se previamente, um conjunto de análises estáticas, lineares e não lineares, e análises dinâmicas modais. As análises dinâmicas modais e as análises estáticas, sob a acção das cargas verticais permanentes, são utilizadas para a calibração/validação do modelo numérico. As análises estáticas lineares equivalentes à acção sísmica são utilizadas para uma estimativa prévia da exigência sísmica (incluindo a localização potencial das incidências não lineares) e das vulnerabilidades virtuais associadas. As análises estáticas não lineares (do tipo “pushover”) são utilizadas para estimar a capacidade da construção sob acções horizontais e para identificar os potenciais mecanismos de colapso. De acordo com os resultados das análises dinâmicas realizadas, para os cenários sísmicos com 475 e 975 anos de período de retorno, a Igreja ficará sob importantes estados de tensão e de fendilhação não sendo expectável a sua ruína parcial ou global. Para os cenários de perigosidade sísmica mais severos, correspondentes a 5000 anos de período de retorno, identificou-se uma potencial incidência de danos nos pilares da nave da Igreja cuja ruína conduz ao colapso da abóbada da nave

Numerical analysis on the behaviour of concrete masonry walls subjected to fire

This paper presents a numerical study on the structural behaviour of concrete masonry at elevated temperatures. Based on an experimental research previously performed on half-scale walls in fire situations, numerical models were developed and validated. The heat transfer models led to thermal fields with good agreement with the temperatures measured by thermocouples installed in the wall, a bigger scatter of temperatures was found in the experimental research. The mechanical analysis led to vertical and out-of-plane displacements in good agreement with the displacements measured by LVDTs. The numerical model was validated and will be used in future researches to perform parametric studies

Risk assessment due to terrorist actions: A case study in Lisbon

The occurrence of unanticipated extreme events in modern societies typically induces significant damage and losses to the built heritage and people, but also concern and fear in the population. The capacity of structures to resist to extreme events has been deserving the attention of researchers during the last decades. The occurrence of explosion-based terrorist attacks in the last two decades has caused a great concern among decision makers and had led to important investments towards the characterization of the structural response of buildings subjected to blast loads. The work presented in this paper was performed in collaboration with one of the largest Public Transportation Operators in Portugal and addresses the problem of risk assessment due to terrorist actions in the case of external explosions, and structural safety evaluation of buildings when subjected to different explosion scenarios.This work was supported by FCT (Portuguese Foundation for Science and Technology) under Project CHSECURE (PTDC/EMC/120118/2010), and within ISISE, project UID/ECI/04029/2013. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008

Seismic safety assessment of the church of Monastery of Jerónimos, Portugal

Preservation of historical constructions with high cultural heritage value is an actual theme in modern societies as these constructions play an important role in the industry of tourism and culture, and consequently in the economy and in the image of countries and self-esteem of people. The seismic hazard of Portugal and, due to its vicinity, of the Mediterranean basin puts under potential risk of damage and collapse a high number of historical constructions, namely most of the old masonry constructions, particularly vulnerable to seismic actions. The seismic behaviour of the Church of Monastery of Jerónimos, Portugal, is discussed here with a numerical simulation, using artificial seismic acceleration time histories in agreement with three seismic hazard scenarios for 475, 975 and 5000 years return periods, allowing to assess its seismic safety

Possibilidades de intervenção estrutural para mitigar o risco sísmico da Igreja do Mosteiro dos Jerónimos

De acordo com um diagnóstico previamente estabelecido, o comportamento dinâmico da Igreja do Mosteiro dos Jerónimos, para acções horizontais, é condicionado pelo comportamento dos pilares da nave que aparecem como os elementos mais vulneráveis [1]. Os resultados de simulações numéricas do comportamento sísmico da Igreja sugerem mesmo a possibilidade de colapso dos pilares para cenários de casualidade sísmica com períodos de retorno iguais ou superiores a 5000 anos. Os resultados para estes cenários sugerem também a eminência de colapso do campanário da torre Sul. Neste contexto, tendo presente o elevado valor patrimonial do monumento – Igreja do Mosteiro dos Jerónimos – apresentam-se neste trabalho um conjunto de possibilidades de intervenção estrutural, compatíveis com o valor arquitectónico da construção, com vista à melhoria do desempenho dinâmico e à mitigação do risco sísmico da Igreja. As soluções de intervenção propostas visam essencialmente a melhoria do desempenho sísmico dos pilares, pela incidência das vulnerabilidades detectadas no diagnóstico e pela sua importância na segurança global da nave da Igreja. Com base em resultados de ensaios de simulação numérica, discutem-se as vantagens e as desvantagens das diferentes estratégias de solução e indica-se aquela que conduz ao melhor desempenho dos pilares de forma a salvaguardar a integridade estrutural da Igreja para aqueles cenários sísmicos

Normal and tangential behaviour of dry joints in refractory masonry

Industrial vessels used in high temperature processes of steel and cement production are protected by refractory linings built with mortarless joints. These dry joints, formed by stacked bricks have a crucial importance on the mechanical behaviour of the lining. The stiffness and consequently the stresses generated by thermal expansion are reduced due to the joints. The present article presents the results of experimental and numerical tests on the thermomechanical behaviour of these joints. The compressive strength of the brick was assessed at ambient and high temperatures and a statistical analysis of the distribution of the bricks’ shape imperfections was carried out. Several studies were carried out on the normal behaviour of the joints: classical joint closure test; bed joint closing action in a masonry wallet measured with a DIC; effects of brick’s height imperfections on its loadbearing capacity; effects of brick’s height imperfections on the wall’s behaviour at ambient and high temperatures and a comparison between the bed and head joints behaviour. To characterize the joint’s tangential behaviour at high temperatures a novel device was developed and presented.The authors would like to thank the support of European Commission under the framework of Marie Sklodowska-Curie Actions Innovative Training Networks, project ATHOR -Advanced THermomechanical multiscale mOdelling of Refractory linings 764987 Grant

Experimental and numerical analysis on the structural fire behaviour of three-cell hollowed concrete masonry walls

Preprint versionMasonry is one of the oldest and most traditional materials in building construction. Nevertheless, the knowledge on the structural fire behaviour of masonry elements is not yet well consolidated. The literature on the load-bearing capacity of masonry walls in case of fire showed an enhanced performance of these elements, however the lack of normative documents, characterization of material properties at high temperatures and experimental results, for calibrating and validating the numerical models, indicates the need of further research. A research study on the structural fire behaviour of three-cell hollowed concrete masonry walls subjected to fire is presented based on results of experimental and numerical studies. First, several loadbearing capacity tests at high temperatures and fire resistance tests on the walls, were carried out in order to assess their behaviour, critical times, failure modes and temperature distribution. The specimens were built with three cell concrete blocks and M10 mortar and were then subjected to an in-plane serviceability load during test. The temperatures, loads and displacements were measured. Second, finite element models were developed and validated with the experimental results. The experimental and numerical results were also compared with the ones given by EN1996-1–2 provisions.European Union (European Commission), Marie Skłodowska-Curie Actions Innovative Training Networks in the frame of the project ATHOR - Advanced THermomechanical multiscale modelling of Refractory linings 764987 Gran