Simplicial Complexes From Graphs Toward Graph Persistence

Persistent homology is a branch of computational topology which uses geometry and topology for shape description and analysis. This dissertation is an introductory study to link persistent homology and graph theory, the connection being represented by various methods to build simplicial complexes from a graph. The methods we consider are the complex of cliques, of independent sets, of neighbours, of enclaveless sets and complexes from acyclic subgraphs, each revealing several properties of the underlying graph. Moreover, we apply the core ideas of persistence theory in the new context of graph theory, we define the persistent block number and the persistent edge-block number

Beyond topological persistence: Starting from networks

Persistent homology enables fast and computable comparison of topological objects. However, it is naturally limited to the analysis of topological spaces. We extend the theory of persistence, by guaranteeing robustness and computability to significant data types as simple graphs and quivers. We focus on categorical persistence functions that allow us to study in full generality strong kinds of connectedness such as clique communities, $k$-vertex and $k$-edge connectedness directly on simple graphs and monic coherent categories.Comment: arXiv admin note: text overlap with arXiv:1707.0967

Exergo-economic and exergo-environmental assessment of two large CHP geothermal power plants

An Exergo-Economic and Exergo-Environmental Analysis is presented for two large geothermal power plants located in Iceland – Hellisheidi and Nesjavellir. The latest configuration of the power plants - including for Hellisheidi acid gas removal and Carbon capture - is analyzed. Cost and LCA data available within the EU H2020 GECO project were processed with an exergy approach, with the purpose to identify the major points of cost build-up or environmental impact along the energy conversion process. A considerable relevance of the cost and impact due to the activity of wells drilling was confirmed for geothermal energy systems; within the operation of the plant, the major effects of exergy destruction are found at the turbines and condensers. The inefficiencies and the buildup of cost and environmental impact along the energy conversion chain are highlighted and the outcomes are discussed with a comparison between the two plants. These are confirmed as performing very well both from the economics and sustainability points of view: recent and foreseen improvements for emissions and carbon capture will not change substantially the economics and will be very effective from the point of view of environmental performance

Gruppi di omotopia di ordine superiore

Scopo di questa tesi è presentare i concetti topologici legati alla nozione di gruppo di omotopia, con particolare riferimento ai gruppi di omotopia delle sfere. Il capitolo introduttivo riguarda il gruppo fondamentale e il secondo capitolo la sua generalizzazione ai gruppi di omotopia di ordine superiore. Nel terzo capitolo è trattato il cobordismo con framing tra sottovarietà e la sua relazione con la teoria dell'omotopia. Negli ultimi due capitoli sono enunciati teoremi e risultati ottenuti nel problema ancora irrisolto del calcolo dei gruppi di omotopia delle sfere

Topological graph persistence

Graphs are a basic tool in modern data representation. The richness of the topological information contained in a graph goes far beyond its mere interpretation as a one-dimensional simplicial complex. We show how topological constructions can be used to gain information otherwise concealed by the low-dimensional nature of graphs. We do this by extending previous work in homological persistence, and proposing novel graph-theoretical constructions. Beyond cliques, we use independent sets, neighborhoods, enclaveless sets and a Ramsey-inspired extended persistence

Topological graph persistence

Graphs are a basic tool in modern data representation. The richness of the topological information contained in a graph goes far beyond its mere interpretation as a one-dimensional simplicial complex. We show how topological constructions can be used to gain information otherwise concealed by the low-dimensional nature of graphs. We do this by extending previous work in homological persistence, and proposing novel graph-theoretical constructions. Beyond cliques, we use independent sets, neighborhoods, enclaveless sets and a Ramsey-inspired extended persistence

LCA and Exergo-Environmental Evaluation of a Combined Heat and Power Double-Flash Geothermal Power Plant

This study deals with the life cycle assessment (LCA) and an exergo-environmental analysis (EEvA) of the geothermal Power Plant of Hellisheiði (Iceland), a combined heat and power double flash plant, with an installed power of 303.3 MW for electricity and 133 MW for hot water. LCA approach is used to evaluate and analyse the environmental performance at the power plant global level. A more in-depth study is developed, at the power plant components level, through EEvA. The analysis employs existing published data with a realignment of the inventory to the latest data resource and compares the life cycle impacts of three methods (ILCD 2011 Midpoint, ReCiPe 2016 Midpoint-Endpoint, and CML-IA Baseline) for two different scenarios. In scenario 1, any emission abatement system is considered. In scenario 2, re-injection of CO2 and H2S is accounted for. The analysis identifies some major hot spots for the environmental power plant impacts, like acidification, particulate matter formation, ecosystem, and human toxicity, mainly caused by some specific sources. Finally, an exergo-environmental analysis allows indicating the wells as significant contributors of the environmental impact rate associated with the construction, Operation & Maintenance, and end of life stages and the HP condenser as the component with the highest environmental cost rate

Sustainable Management of Anaerobic Digestate: From Biogas Plant to Full-Scale Cultivation of <i>Pleurotus ostreatus</i>

In the last decades, the number of studies about the valorization of agricultural by-products has strongly increased due to the growing focus on the circular economy. In this context, mushroom cultivation is raising attention for its nutritional properties and adaptability to different growing conditions. The goal of this project is, therefore, to create a link between two production chains, valorizing the solid anaerobic digestate fraction from the biogas plant as a potential substrate for Pleurotus ostreatus full-scale cultivation. A preliminary in vitro trial shows that the mycelia can colonize at the same rate in both the conventional substrate, which was wheat straw added with sunflower cake and the experimental ones supplemented with corn digestate. The most important and innovative part of the work was full-scale cultivation. Quantitative analyses demonstrate that P. ostreatus is capable of growing on the conventional substrate as well as on the substrate containing 15% of digestate without reducing the mushroom harvest. Even better, digestate seems to stimulate a precocious and more homogeneous production. Chemical and spectroscopic analyses on the fruiting bodies confirm the results; in fact, mushrooms show a comparable structural composition, highlighted with FTIR and SERS spectroscopic evaluations. Moreover, the nutrient content did not change due to the addition of digestate. These promising results demonstrate that anaerobic digestate can become a resource for P. ostreatus cultivation without production losses and maintaining the same qualitative characteristics