1,144 research outputs found
Development of a computational tool for limiter edge plasma modeling with application to IGNITOR
No full textIGNITOR is the only experiment today designed with the ambitious goal of achieving ignition. During the discharge, the First-Wall Limiter (FWL) will receive about 20 MW [B. Coppi, A. Airoldi, F. Bombarda, et al., Nucl. Fusion 41 (2001) 1253-1257] power, split between conduction/convection and radiation channels. Previous estimates suggested a peak heat flux on the FWL close to 1 MW/m2. This value should be re-evaluated, accounting for the latest developments in the design of the IGNITOR first wall and changes in the operational scenarios, in order to assess the risk of damages to the FWL deriving from the combination of thermal and mechanical stresses. For this purpose, the development of the ASPOEL code, implementing a 2D model of the edge plasma and including a detailed representation of the FWL, was started at Politecnico di Torino. Here we present the main features of the new code, and illustrate its potential via a preliminary application to IGNITO
How and to What Degree Does Physical Structure Differ Between Natural and Artificial Habitats? A Multi-Scale Assessment in Marine Intertidal Systems
No full textMarine infrastructures are increasing, generating a variety of impacts and introducing artificial habitats which have low ecological value and support assemblages that differ significantly from those on natural rocky coasts. While in the past there was little ecological consideration as to how artificial structures were built, now the trend is to look for “greener” designs inspired by or mimicking nature. These greening efforts have had a strong focus on enhancing physical habitat structure to support more diverse assemblages, driven by the untested assumption that artificial habitats lack the physical structure proper to natural habitats. We tested this assumption by comparing five descriptors of physical structure (inclination; exposure; roughness; abundance, and diversity of surface morphological microelements) across a combination of natural and artificial habitats of regular and irregular morphologies (seawalls = artificial regular; cliffs = natural regular; breakwaters = artificial, irregular; and boulder fields = natural irregular) in the North Adriatic Sea. Most structural descriptors were similar between artificial and natural habitats. Only inclination was consistently steeper in the artificial than in the natural habitats. Other minor differences in roughness or in the abundance of some surface microelements were related to the general morphology (regular or irregular) of the habitat rather than to its artificial or natural identity. The outcomes challenge the widespread assumption that artificial habitats lack the physical structure proper to natural habitats and stimulate renewed consideration about other structural and non-structural elements that could enhance the performance and sustainability of artificial marine structures, such as construction material, environmental setting or maintenance. They also encourage a wider reflection about what makes an artificial building surface “greener”: structural complexity is an important ecological parameter, and its deliberate increase will lead to responses in the biota, however, this may not necessarily match “more natural” conditions
Artificial marine structures facilitate the spread of a non-indigenous green alga, Codium fragile ssp. tomentosoides, in the north Adriatic Sea.
No full textGli assetti istituzionali delle imprese: risultati e prospettive di ricerca
No full textGli assetti istituzionali delle imprese, ossia gli assetti proprietari e di governance, sono stati oggetto di numerosi studi di varia natura soprattutto a partire dalla metà degli anni 1980. Qui si svolgono quattro temi: 1) i ruoli, le strutture e i processi del Consiglio di Amministrazione; 2) la diffusione e gli impatti dei codici di autodisciplina in materia di corporate governance; 3) la retribuzione come strumento di allineamento degli obiettivi tra proprietà e amministratori; 4) le relazioni tra strategia, proprietà e governance. Per ciascun tema si tracciano brevemente i risultati e le prospettive di ricerca
Anthropogenic disturbance can determine the magnitude of opportunistic species responses on marine urban infrastructures
No full textBackground: Coastal landscapes are being transformed as a consequence of the increasing demand for infrastructures to sustain residential, commercial and tourist activities. Thus, intertidal and shallow marine habitats are largely being replaced by a variety of artificial substrata (e.g. breakwaters, seawalls, jetties). Understanding the ecological functioning of these
artificial habitats is key to planning their design and management, in order to minimise their impacts and to improve their potential to contribute to marine biodiversity and ecosystem functioning. Nonetheless, little effort has been made to assess the role of human disturbances in shaping the structure of assemblages on marine artificial infrastructures. We tested the
hypothesis that some negative impacts associated with the expansion of opportunistic and invasive species on urban
infrastructures can be related to the severe human disturbances that are typical of these environments, such as those from maintenance and renovation works.
Methodology/Principal Findings: Maintenance caused a marked decrease in the cover of dominant space occupiers, such as mussels and oysters, and a significant enhancement of opportunistic and invasive forms, such as biofilm and macroalgae. These effects were particularly pronounced on sheltered substrata compared to exposed substrata. Experimental application of the disturbance in winter reduced the magnitude of the impacts compared to application in spring or summer. We use these results to identify possible management strategies to inform the improvement of the ecological value of artificial marine infrastructures.
Conclusions/Significance: We demonstrate that some of the impacts of globally expanding marine urban infrastructures, such as those related to the spread of opportunistic, and invasive species could be mitigated through ecologically-driven planning and management of long-term maintenance of these structures. Impact mitigation is a possible outcome of policies that consider the ecological features of built infrastructures and the fundamental value of controlling biodiversity in marine urban systems
Introduzione e diffusione in Mediterraneo di specie algali alloctone
No full textIl Comune di Livorno ha da sempre perseguito l'obiettivo della valorizzazione del patrimonio storico culturale della città anche attraverso l'edizione di volumi, che negli anni sono andati a costituire delle vere e proprie collane. Tra questi i Quaderni dell'acquario di Livorno, su cui ho presentato questo breve lavoro focalizzato sull'introduzione in Mediterraneo di specie algali allocton
Flussi di sostanza organica Early patterns of recovery of a filamentous algal turf on a rocky subtidal shore (Mediterranean Sea)
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