Charging of flexible solar array substrates in kilovolt electron beams

A series of survey tests were conducted to evaluate samples of flexible solar arrays. The samples used woven carbon fibers and/or coatings to increase the surface conductivity of the KAPTON substrate and thereby reduce surface charging. Four different samples were evaluated by exposing them to monoenergetic electron beams of 2 to 20 KeV at a current density of 1 nA sq cm. Simulated eclipse tests were also conducted. The results were as expected; the more continuous the conductive pattern, the lower the surface charging

Testing of typical spacecraft materials in a simulated substorm environment

The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed

“Uma praça em cada bairro” program: Analysis and contribution to the requalification of Lisbon’s

The traditional role of the urban public space has shifted during the 20th century and in particular throughout the post-second world war. The global trend to adjust the public space to the car traffic and parking needs was observed in Lisbon as in many other industrialized cities. By the end of the century, some projects to value public space through the pedestrianization of streets were attempted without significant impact. The 1998 World Exhibition in Lisbon created the opportunity to rethink, recreate the city and renovate its public space in a former brownfield area. Despite its legacy, there was a little spillover effect to other public spaces in Lisbon, even when considering the partial reconversion of the riverfront, and the intervention on the Praça do Comércio, in 2007. This paper reflects on the impact of the program “Uma praça em cada bairro” [“A square in each neighborhood”] started in 2014 by the Lisbon City Council whose main goal is to transform and benefit Lisbon’s public spaces. There were over the 150 micro-centralities identified and the interventions were diverse in terms of scale. They include major projects like the “Eixo Central” [“Central Axis”] of Lisbon connecting the Marquês de Pombal square to Entrecampos square and, simultaneously, small public squares across the city neighborhoods. The methodology used consists of i) the study of satellite images, from 2014 to 2020, ii) the identification of areas allotted to different uses of space (people, traffic, green space), and iii) the quantification of urban elements in the analysis. This paper assesses the results of the “Uma praça em cada bairro” program, through the quantification of the areas dedicated to different functions, against the stated goals to transform and renovate public spaces.info:eu-repo/semantics/publishedVersio

La Golondrina : The Swallow

https://digitalcommons.library.umaine.edu/mmb-ps/1545/thumbnail.jp

The impact of public health crises on Lisbon public space policies: From the 19th century to the present days

Cities have been affected, throughout History, by earthquakes, big fires, epidemics, and pandemics that sparked moments of reflection and change in the city form and public space quantity and quality. For example, this happened after the Great Fire of London (1666) or the Great Earthquake of Lisbon (1755). After episodes of destruction or disruption, debates and projects forge the urban answer to diminish future losses and risks. From this starting point, we discuss the impact of two distinct public health crisis - the epidemics of the 19th century and the current COVID-19 pandemic - on Lisbon's public spaces. For both periods, we analyze primary sources - strategies, plans, projects, and papers - designed by Lisbon City Council and that depict the ideas and tactics to tackle the urban challenges imposed by the public health crises. With this research, we discuss the impact of public health crises on public spaces policies design through two particular examples in Lisbon, from the 19th century and the current days. Furthermore, we question if these crises served, to any extent, the intentions to qualify public places and introduce a new form and image on Lisbon public spaces.info:eu-repo/semantics/publishedVersio

Developing a site-conditions map for seismic hazard Assessment in Portugal

The evaluation of site effects on a broad scale is a critical issue for seismic hazard and risk assessment, land use planning and emergency planning. As characterization of site conditions based on the shear-wave velocity has become increasingly important, several methods have been proposed in the literature to estimate its average over the first thirty meters (Vs30) from more extensively available data. These methods include correlations with geologic-geographic defined units and topographic slope. In this paper we present the first steps towards the development of a site–conditions map for Portugal, based on a regional database of shear-wave velocity data, together with geological, geographic, and lithological information. We computed Vs30 for each database site and classified it according to the corresponding geological-lithological information using maps at the smallest scale available (usually 1:50000). We evaluated the consistency of Vs30 values within generalized-geological classes, and assessed the performance of expedient methodologies proposed in the literature

Migrant Networks and the Spread of Misinformation

Diaspora networks provide information to future migrants and influence both their decision to migrate and their success in the host country. While the existing literature explains the effect of networks on migration decisions through the size of the migrant community, we show that the quality of the network is an equally important determinant. We argue that networks that are more integrated in the society of the host country can give more accurate information about job prospects to future migrants. In a decision model with imperfect signalling we show that migrants with access to a better network are more likely to make the right decision they migrate only if they gain and they migrate earlier. We test these predictions empirically using data on recent Mexican migrants to the US, and exploit the geographic diffusion of Mexicans since the 1980s as well as the settlement of immigrants that came during the Bracero program in the 1950s to instrument for the quality of networks. The results provide strong evidence that connections to a better-integrated network lead to better outcomes after migration. Yet we find no evidence that the quality of the network affects the timing of migration

Tetanus. A Review of 54 Cases

O tétano continua a ser uma doença frequente e de mortalidade elevada que envolve particularmente os doentes mais idosos. Em face desta realidade, estudaram-se 54 casos tratados em cuidados intensivos entre 1983 e 1991. Concluí-se ter sido fundamental para a redução da mortalidade verificada neste período, além do uso de medidas de suporte ventilatório, a utilização de novos fármacos que permitiram uma sedação e um relaxamento muscular mais eficaz e também um melhor controlo da hiperactividade do sistema nervoso autónomo

Social media disinformation in the pre-electoral period in Portugal

Since the North American presidential election of 2016, the role of social media on the propagation of misleading news and its instrumentalization by partisan groups has raised concerns. In this article we analyse the contents of 47 Facebook pages and 39 Facebook groups prior to the Portuguese parliamentary election of 6th of October of 2019 to track disinformation. Groups and pages to monitor were selected through a process that combined the number of fans or members, the proportion of political content, and the number of posts per week. We concluded that disinformative content was prevalent in the pages and groups monitored, that several political actors had a relevant influence on the debate and that most disinformation stemmed from the spinning of both mainstream and non-mainstream news to serve a political purpose

Wetting in infiltration of alumina particle preforms with molten copper

The high-temperature wettability of alumina particulate preforms by copper is investigated by means of infiltration experiments conducted at 1473 K under low oxygen partial pressure. Wetting is quantified in terms of drainage curves, which plot the volume fraction of metal in the porous medium vs. the applied pressure. Mercury porosimetry is also used on similar preforms for comparison. The effect of volume fraction, particle geometry and capillary parameters on the drainage curve are studied and compared with the expression proposed by Brooks and Corey. The influence of the particle volume fraction and capillary parameters characterizing wetting in the two systems is discussed to derive an effective contact angle for wetting of alumina particles by molten coppe