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Sub‐annual moraine formation at an active temperate Icelandic glacier

This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterised by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognise two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low‐relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub‐annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub‐annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt‐driven squeeze events and (ii) larger push moraines formed during winter re‐advances. We suggest the development of this process‐form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed, and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice‐marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process‐form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin

Information management and social networks in organizational innovation networks

Tese de mestrado. Ciência da Informação. Faculdade de Engenharia. Universidade do Porto. 201

Seismic performance of offshore concrete gravity platforms

The seismic performance of concrete offshore gravity platforms is investigated. Aspects of dynamic structural analysis are discussed with particular reference to offshore gravity platforms, including soil-structure and water-structure interaction. Results of a seismic hazard analysis using currently available information are presented, and appropriate acceleration response spectra for design purposes are suggested. Site response effects are examined to investigate whether seismic hazard analysis results could be adjusted in a rational manner to account for the response of flexible nonlinear foundation materials. Artificial earthquake records are discussed and a suite of artificial accelerograms are generated to match the suggested design acceleration response spectra for offshore platforms in New Zealand. An experimental testing programme was undertaken to examine the strength and ductility characteristics of circular hollow reinforced and partially prestressed concrete members. Six columns were tested, representing scale models of members which could be used in the critical regions of possible offshore concrete platform configurations. A companion theoretical study was carried out to examine the strength and ductility of circular hollow sections. Results are presented in a design chart form suitable for use by designers. Finally, preliminary design studies were carried out for two different concrete gravity platform types to assess their likely feasibility. Of particular interest was the required distribution of strength to resist moderate earthquake effects and the ductility demands during severe earthquakes

Impact of Space Weather on Climate and Habitability of Terrestrial Type Exoplanets

The current progress in the detection of terrestrial type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favorable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of astrospheric, atmospheric and surface environments of exoplanets in habitable zones around G-K-M dwarfs including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles, and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favorable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro) physical, chemical, and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the habitable zone to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.Comment: 206 pages, 24 figures, 1 table; Review paper. International Journal of Astrobiology (2019

Determination of the main parameters affecting the performance of bridge falsework systems

Bridge falsework systems are one of the most common temporary structures used in the construction industry, namely to support the formwork during the construction, rehabilitation or retrofit works of concrete bridges and viaducts. This Thesis presents new results and research that improve the available knowledge about the structural behaviour, reliability, robustness and risk of these structures. The main, internal and external, hazards are identified and detailed, including the procedural, enabling and triggering hazards. The use of reduction factors to determine the values of the applied loads to design bridge falsework, and other temporary structures, is critically analysed and it is recommended not to use them, unless supported by specific site data. The importance of implementing effective quality control, inspection and communication measures to manage human errors during planning, designing and operation is highlighted. From the 192 tests carried out during the experimental campaign, consisting of five different tests using three different joint types, new results are obtained concerning bridge falsework components, namely the bending behaviour and resistance of spigot joints and forkhead joints (falsework to formwork interface) from which no published research was found. Existing joint models are evaluated and improved alternative models are developed. The results of numerical studies of a selected structural system are presented using a novel joint finite element and information gathered from the experimental tests. This new finite element has features that the available elements in ABAQUS® program do not have, specifically the capability of simulating an analytical modelling of the cyclic behaviour of joints with allowance for stiffness and resistance degradation and joint failure. The accuracy and precision of the developed numerical models improves the existing numerical results of full-scale tests of bridge falsework systems, in respect to structural behaviour and resistance. It is recommended that formwork should be explicitly modelled and modelling of spigot joints should follow the model presented in this Thesis. From a sensitivity analysis of the bridge falsework systems to modelling hypothesis, it is found that the most important joints are the beam-to-column joint, followed by the forkhead joint and the spigot joint, with variations of up to 70% between the resistance of the system when the joints are modelled as continuous or as pinned. A key contribution of the Thesis is to introduce a novel risk management methodology based on newly developed robustness and fragility indices. This new methodology is applicable, in principle, to all structural analyses not only those concerning bridge falsework systems. Based on advanced deterministic studies, the main parameters affecting the performance of bridge falsework are identified, analysed and discussed. These studies involved a comprehensive set of external and internal hazards: (i) applied external actions of different nature and (ii) structural configurations to design bridge falsework. It is found that differential ground settlements are a critical action and that stiffer systems are more sensitive. Also, it is highlighted by use of plenty examples that bracing is an essential design requirement. Advanced stochastic investigations are also carried out, in which the key random variables that control the stochastic behaviour of bridge falsework systems are identified, namely joint looseness and initial stiffness after looseness. Possible strategies to increase robustness and decrease fragility are discussed and based on an application example the cost-benefit of alternative solutions is investigated. It is concluded that implementing quality control and quality assurance procedures to bridge falsework elements is an extremely effective and efficient way of reducing existing risks. The information gathered in this Thesis can be used to develop more rational and reliable bridge falsework structures thus safer and more design efficient

The Intrinsic Connectome of the Rat Amygdala

The connectomes of nervous systems or parts there of are becoming important subjects of study as the amount of connectivity data increases. Because most tract-tracing studies are performed on the rat, we conducted a comprehensive analysis of the amygdala connectome of this species resulting in a meta-study. The data were imported into the neuroVIISAS system, where regions of the connectome are organized in a controlled ontology and network analysis can be performed. A weighted digraph represents the bilateral intrinsic (connections of regions of the amygdala) and extrinsic (connections of regions of the amygdala to non-amygdaloid regions) connectome of the amygdala. Its structure as well as its local and global network parameters depend on the arrangement of neuronal entities in the ontology. The intrinsic amygdala connectome is a small-world and scale-free network. The anterior cortical nucleus (72 in- and out-going edges), the posterior nucleus (45), and the anterior basomedial nucleus (44) are the nuclear regions that posses most in- and outdegrees. The posterior nucleus turns out to be the most important nucleus of the intrinsic amygdala network since its Shapley rate is minimal. Within the intrinsic amygdala, regions were determined that are essential for network integrity. These regions are important for behavioral (processing of emotions and motivation) and functional (memory) performances of the amygdala as reported in other studies

Conceptual design of a concrete staircase based on topology optimization : A feasibility study on the development and application of topology optimization on a concrete staircase

Master's thesis in Civil and structural engineering (BYG508