Distant activity of 67P/Churyumov-Gerasimenko in 2014: Ground-based results during the Rosetta pre-landing phase

As the ESA Rosetta mission approached, orbited, and sent a lander to comet 67P/Churyumov-Gerasimenko in 2014, a large campaign of ground-based observations also followed the comet. We constrain the total activity level of the comet by photometry and spectroscopy to place Rosetta results in context and to understand the large-scale structure of the comet's coma pre-perihelion. We performed observations using a number of telescopes, but concentrate on results from the 8m VLT and Gemini South telescopes in Chile. We use R-band imaging to measure the dust coma contribution to the comet's brightness and UV-visible spectroscopy to search for gas emissions, primarily using VLT/FORS. In addition we imaged the comet in near-infrared wavelengths (JHK) in late 2014 with Gemini-S/Flamingos 2. We find that the comet was already active in early 2014 at heliocentric distances beyond 4 au. The evolution of the total activity (measured by dust) followed previous predictions. No gas emissions were detected despite sensitive searches. The comet maintains a similar level of activity from orbit to orbit, and is in that sense predictable, meaning that Rosetta results correspond to typical behaviour for this comet. The gas production (for CN at least) is highly asymmetric with respect to perihelion, as our upper limits are below the measured production rates for similar distances post-perihelion in previous orbits.

Development and Validation of a Procedure for Numerical Vibration Analysis of an Oscillating Wave Surge Converter

During extreme sea states so called impact events can be observed on the wave energy converter Oyster. In small scale experimental tests these impact events cause high frequency signals in the measured load which decrease confidence in the data obtained. These loads depend on the structural dynamics of the model. Amplification of the loads can occur and is transferred through the structure from the point of impact to the load cell located in the foundation. Since the determination of design data and load cases for Wave Energy Converters originate from scale experiments, this lack of confidence has a direct effect on the development.

Numerical vibration analysis is a valuable tool in the research of the structural load response of Oyster to impact events, but must take into account the effect of the surrounding water. This can be done efficiently by adding an added mass distribution, computed with a linearised potential boundary element method. This paper presents the development and validation of a numerical procedure, which couples the OpenSource boundary element code NEMOH with the Finite Element Analysis tool CodeAster. Numerical results of the natural frequencies and mode shapes of the structure under the influence of added mass due to specific structural modes are compared with experimental results.

Electron-impact ionization of C+ in both ground and metastable states

Electron-impact ionization cross sections are calculated for the ground and metastable states of C+. Com- parisons between perturbative distorted-wave and nonperturbative time-dependent close-coupling calculations find reductions in the peak direct ionization cross sections due to electron coupling effects of approximately 5% for ground state C+ and approximately 15% for metastable state C+. Fairly small excitation-autoionization contributions are found for ground state C+, while larger excitation-autoionization contributions are found for metastable state C+. Comparisons between perturbative distorted-wave and nonperturbative R-matrix with pseudostates calculations find reductions in the peak total ionization cross sections due to electron coupling effects of approximately 15–20 % for ground state C+ and approximately 25–35 % for metastable state C+. Finally, comparisons between theory and experiment find that present and previous C+ crossed-beam measure- ments are in excellent agreement with ground state nonperturbative R-matrix with pseudostates calculations for total ionization cross sections. Combined with previous non-perturbative calculations for C, C2+, and C3+, accurate ionization cross sections and rate coefficients are now available for the ground and metastable states of all carbon ion stages.

Rocking behaviour of multi-block columns subjected to pulse-type ground motion accelerations

Ancient columns, made with a variety of materials such as marble, granite, stone or masonry are an important part of the
European cultural heritage. In particular columns of ancient temples in Greece and Sicily which support only the architrave are
characterized by small axial load values. This feature together with the slenderness typical of these structural members clearly
highlights as the evaluation of the rocking behaviour is a key aspect of their safety assessment and maintenance. It has to be noted
that the rocking response of rectangular cross-sectional columns modelled as monolithic rigid elements, has been widely investigated
since the first theoretical study carried out by Housner (1963). However, the assumption of monolithic member, although being
widely used and accepted for practical engineering applications, is not valid for more complex systems such as multi-block columns
made of stacked stone blocks, with or without mortar beds. In these cases, in fact, a correct analysis of the system should consider
rocking and sliding phenomena between the individual blocks of the structure. Due to the high non-linearity of the problem, the
evaluation of the dynamic behaviour of multi-block columns has been mostly studied in the literature using a numerical approach
such as the Discrete Element Method (DEM). This paper presents an introductory study about a proposed analytical-numerical
approach for analysing the rocking behaviour of multi-block columns subjected to a sine-pulse type ground motion. Based on the
approach proposed by Spanos (2001) for a system made of two rigid blocks, the Eulero-Lagrange method to obtain the motion
equations of the system is discussed and numerical applications are performed with case studies reported in the literature and with a
real acceleration record. The rocking response of single block and multi-block columns is compared and considerations are made
about the overturning conditions and on the effect of forcing function’s frequency.
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Áquila Earthquake (2009): influence of seismic source model and structure to modeling the strong ground motions

O sismo, ocorrido em 6 de Abril de 2009 (Mw 6,3) junto à cidade de Áquila (Itália), provocou uma grande destruição. Uma das consequências deste evento foi o impacto na opinião pública em torno da capacidade científica para a estimação da perigosidade sísmica e a necessidade de criação de sistemas de alerta sísmico. A determinação dos mecanismos de fonte sísmica de eventos sísmicos ocorridos e registados permite melhores caracterizações dos movimentos sísmicos para uma determinada área de estudo e consequentemente melhores cenários de risco. Se a região em estudo possuir propriedades físicas específicas e muito distintas de local para local, capazes de provocar alterações locais dos movimentos sísmicos (efeitos de sítio), torna-se imperativo uma caracterização bem definida do meio de propagação das ondas sísmicas de forma a poder sintetizar informação capaz de contribuir para a boa estimação da perigosidade sísmica. No âmbito deste trabalho pretende-se estudar a influência do mecanismo de fonte sísmica e da estrutura na modelação de movimentos sísmicos no caso de Áquila. A metodologia adoptada consiste na determinação da distribuição de deslizamentos sobre o plano de falha e utilização desta informação na modelação de sismogramas sintéticos (com recurso ao algoritmo E3D). Será igualmente estabelecida uma comparação de resultados considerando-se um meio com e sem bacia e considerando-se uma fonte pontual e uma fonte extensa.

Stochastic ground motion simulation with geological site effects in damage asessment

Damage assessment of structures with a mechanical non linear model demands the representation of seismic action in terms of an accelerogram (dynamic analysis) or a response spectrum (pushover analysis). Stochastic ground motion simulation is largely used in regions where seismic strong-motion records are available in insufficient number. In this work we present a variation of the stochastic finite-fault method with dynamic corner frequency that includes the geological site effects. The method was implemented in a computer program named SIMULSIS that generate time series (accelerograms) and response spectra. The program was tested with the MW= 7.3 Landers earthquake (June 28, 1992) and managed to reproduce its effects. In the present work we used it to reproduce the effects of the 1980’s Azores earthquake (January 1, 1980) in several islands, with different possible local site conditions. In those places, the response spectra are presented and compared with the buildings damage observed.

Core and patch position optimizations for vibration control of piezolaminated structures

This paper deals with a finite formulation baserd on the classical laminated plate tehory, for active control of thin late laminated structures with integrated piezoelectric layers, acting as sensors and actuators. The control is initialized through a previuos optimization of the core of the laminated structure, in order to minimize the vibration amplitude. Also the optimization of the patches position in performed to maximize the piezoelectric actuator efficiency. the simulating annealing mthod is used for these purposes. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of fredom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, wich can be surface bonded or imbedded on the laminate. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorirhm is used, coupling the sensor and active piezoelectric layers. To calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the solution of an illustrative case and the results are presented and discussed.

Prediction of the solar radiation using RBF neural networks and ground-to-sky images

In this study, Artificial Neural Networks are applied to multistep long term solar radiation prediction. The networks are trained as one-step-ahead predictors and iterated over time to obtain multi-step longer term predictions. Auto-regressive and Auto-regressive with exogenous inputs solar radiationmodels are compared, considering cloudiness indices as inputs in the latter case. These indices are obtained through pixel classification of ground-to-sky images. The input-output structure of the neural network models is selected using evolutionary computation methods.

Imaginative Mislocation: Hiroshima’s Genbaku Dome, Ground Zero of the Twentieth Century

The controversy that erupted in March over the publication of Charles Pellegrino’s account of the atomic bombings of Japan, The Last Train from Hiroshima, suggests that the historical legacy of the first military use of atomic weaponry is still fiercely contested in the USA. The spat is merely the latest conflict in a long war over the significance of the bombings, which resurfaces with each new book, exhibition or programme that appears. When the ruins of the Genbaku (Atomic Bomb) Dome – formerly the Hiroshima Prefectural Commercial Exhibition Hall – were nominated as a UNESCO World Heritage Site in 1995, the United States objected on the basis of concerns over a ‘lack of historical perspective’, arguing that the ‘events antecedent to the United States’ use of atomic weapons to end World War II are key to understanding the tragedy of Hiroshima’. The appeal to historical facts by both US diplomats and, more recently, military veterans contrasts with the dehistoricized emphasis of other Western cultural responses to Hiroshima. But what both kinds of reception share is an occlusion of the prehistory of capitalist liberalism, colonialism and imperialism which produces Japanese modernity,a prehistory which is itself built into the Genbaku Dome’s concrete structure, and an afterlife of nuclear pacification which produces the global context of terrorism as the continuation of war by other means.

From the high ground to the swamp: A model for immersive journalism research

This article examines a reflexive, praxis-based methodology for conducting journalism research from a practitioner-academic perspective. Journalism research methods that are interactive, iterative and which rest on a dynamic communicative partnership between academics and practitioners, offer the best way for understanding change in our dynamic field. This permits the researcher to coalesce and strengthen their identity as a practitioner-academic and develop research projects that are mutually beneficial for advancing scholarship and practice. Drawing on reflexive methodologies in the human sciences, such as hermeneutics, cybernetics and constructivism, this article envisions an immersive approach embracing phenomenology and Gestalt as a fully reflexive method of data collection.

Role of the wider Azores region as a nursery ground for North Atlantic blue shark (Prionace glauca)

Tese de Doutoramento, Ciências do Mar (Ecologia Marinha)

Ground reaction forces and plantar pressure distribution during occasional loaded gait

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait.