169 research outputs found
Multi-epoch machine learning for galaxy formation
In this thesis I utilise a range of machine learning techniques in conjunction with hydrodynamical cosmological simulations. In Chapter 2 I present a novel machine learning method for predicting the baryonic properties of dark matter only subhalos taken from N-body simulations. The model is built using a tree-based algorithm and incorporates subhalo properties over a wide range of redshifts as its input features. I train the model using a hydrodynamical simulation which enables it to predict black hole mass, gas mass, magnitudes, star formation rate, stellar mass, and metallicity. This new model surpasses the performance of previous models. Furthermore, I explore the predictive power of each input property by looking at feature importance scores from the tree-based model. By applying the method to the LEGACY N-body simulation I generate a large volume mock catalog of the quasar population at z=3. By comparing this mock catalog with observations, I demonstrate that the IllustrisTNG subgrid model for black holes is not accurately capturing the growth of the most massive objects. In Chapter 3 I apply my method to investigate the evolution of galaxy properties in different simulations, and in various environments within a single simulation. By comparing the Illustris, EAGLE, and TNG simulations I show that subgrid model physics plays a more significant role than the choice of hydrodynamics method. Using the CAMELS simulation suite I consider the impact of cosmological and astrophysical parameters on the buildup of stellar mass within the TNG and SIMBA models.
In the final chapter I apply a combination of neural networks and symbolic regression methods to construct a semi-analytic model which reproduces the galaxy population from a cosmological simulation. The neural network based approach is capable of producing a more accurate population than a previous method of binning based on halo mass. The equations resulting from symbolic regression are found to be a good approximation of the neural network
A multiscale strategy for fouling prediction and mitigation in gas turbines
Gas turbines are one of the primary sources of power for both aerospace and land-based applications. Precisely for this reason, they are often forced to operate in harsh environmental conditions, which involve the occurrence of particle ingestion by the engine. The main implications
of this problem are often underestimated. The particulate in the airflow ingested by the machine can deposit or erode its internal surfaces, and lead to the variation of their aerodynamic geometry, entailing performance degradation and, possibly, a reduction in engine life. This issue affects the compressor and the turbine section and can occur for either land-based or aeronautical turbines. For the former, the problem can be mitigated (but not eliminated) by installing filtration systems. For what concern the aerospace field, filtration systems cannot be used. Volcanic eruptions and sand dust storms can send particulate to aircraft cruising altitudes. Also, aircraft operating in remote locations or low altitudes can be subjected to particle ingestion, especially in desert environments. The aim of this work is to propose different methodologies capable to mitigate the effects
of fouling or predicting the performance degradation that it generates. For this purpose, both hot and cold engine sections are considered. Concerning the turbine section, new design guidelines are presented. This is because, for this specific component, the time scales of failure events due to hot deposition can be of the order of minutes, which makes any predictive model inapplicable. In this respect, design optimization techniques were applied to find the best HPT vane geometry that is less sensitive to the fouling phenomena. After that, machine learning methods were adopted to obtain a design map that can be useful in the first steps of the design phase. Moreover, after a numerical uncertainty quantification
analysis, it was demonstrated that a deterministic optimization is not sufficient to face highly aleatory phenomena such as fouling. This suggests the use of robust or aggressive design techniques to front this issue. On the other hand, with respect to the compressor section, the research was mainly focused on the building of a predictive maintenance tool. This is because the time scales of failure events due to cold deposition are longer than the ones for the hot section, hence the main challenge for this component is the optimization of the washing schedule. As reported in the previous sections, there are several studies in the literature focused on this issue, but almost all of them are data-based instead of physics-based. The innovative strategy proposed here is a mixture between physics-based and data-based methodologies. In particular, a reduced-order model has been developed to predict the behaviour of the whole engine as the degradation proceeds. For this purpose, a gas path code that uses the componentsâ characteristic maps has been created to simulate the gas turbine. A map variation technique has been used to take into account the fouling effects on each engine component. Particularly, fouling coefficients as a function of the engine architecture, its operating conditions, and the contaminant characteristics have been created. For this purpose, both experimental and computational results have been used. Specifically for the latter, efforts have been done to develop a new numerical deposition/detachment model.Le turbine a gas sono una delle pricipali fonti di energia, sia per applicazioni aeronautiche che terrestri. Proprio per questa ragione, esse sono spesso costrette ad operare in ambienti non propriamente puliti, il che comporta lâingestione di contaminanti solidi da parte del motore. Le principali implicazioni di questo problema sono spesso sottovalutate. Le particelle solide presenti nel flusso dâaria che il motore ingerisce durante il suo funzionamento possono depositarsi o erodere le superfici interne della macchina, e portare a variazioni alla sua aerodinamica, quindi a degrado di performance e, molto probabilmente, alla diminuzione della sua vita utile. Questo problema aflligge sia la parte del compressore che la parte della
turbina, e si manifesta sia in applicazioni terrestri che aeronautiche. Per quanto riguarda la prima, la questione può essere mitigata (ma non eliminata) dallâinstallazione di sistemi di filtraggio allâingresso della macchina. Per le applicazioni aeronautiche invece, i sistemi di filtraggio non possono essere utilizzati. Questo implica che il particolato presente ad alte quote, magari grazie ad eventi catastrofici quali eruzioni vulcaniche, o a basse quote, quindi ambienti deseritic, entra liberamente nella turbina a gas.
Lo scopo principale di questo lavoro di tesi, è quello di proporre differenti metodologieallo scopo di mitigare gli effetti dello sporcamento o predirre il degrado che esso comporta nelle turbine a gas. Per questo scopo, sia la parte del compressore che quella della turbina sono state prese in considerazione. Per quanto riguarda la parte turbina, saranno presentate nuove guide progettuali volte al trovare la geometria che sia meno sensibile possibile al problema dello sporcamento. Dopo di ciò, i risultati ottenuti verranno trattati tramite tecniche di machine learning, ottenendo una mappa di progetto che potrĂ essere utile nelle prime fasi della progettazione di questi componenti. Inoltre, essendo lâanalisi fin qui condotta di
tipo deterministico, unâanalisi delle principali fonti di incertezza verrĂ eseguita con lâutilizzo di tecniche derivanti dallâuncertainty quantification. Questo dimostrerĂ che lâanalisi deterministica è troppo semplificativa, e che sarebbe opportuno spingersi verso una progettazione robusta per affrontare questa tipologia di problemi. Dâaltro canto, per quanto concerne la parte compressore, la ricerca è stata incentrata principalmente sulla costruzione di uno strumento predittivo, questo perchè la scala temporale del degrado dovuto alla deposizione a "freddo" è molto piĂš dilatata rispetto a quella della sezione "calda". La trategia proposta in questo lavoro di tesi è unâinsieme di modelli fisici e data-driven. In particolare, si è sviluppato un modello ad ordine ridotto per la previsione del comportamento del motore soggetto a degrado dovuto allâingestione di particolato, durante unâintera missione aerea. Per farlo, si è generato un codice cosiddetto gas-path, che modella i singoli componenti della macchina attraverso le loro mappe caratteristiche. Questâultime vengono modificate, a seguito della deposizione, attraverso opportuni coefficienti di degrado.
Tali coefficienti devono essere adeguatamente stimati per avere una corretta previsione degli eventi, e per fare ciò verrĂ proposta una strategia che comporta lâutilizzo sia di metodi sperimentali che computazionali, per la generazione di un algoritmo che avrĂ lo scopo di fornire come output questi coefficienti
Modes of Esports Engagement in Overwatch
This Open Access book provides a comprehensive review of the rapidly developing esport phenomenon by examining one of its contemporary flagship titles, Overwatch (Blizzard Entertainment 2016), through three central themes and from a rich variety of research methods and perspectives. As a game with more than 40 million individual players, an annual international World Cup, and a franchised professional league with teams from Canada, China, Europe, South Korea, and the US, Overwatch provides a multifaceted perspective to the cultural, social, and economic topics associated with the development of esports, which has begun to attract attention from both commercial and academic audiences. The book starts with an introduction chapter to Overwatch and esports engagement in general, co-authored by the editors. This is followed by 15 unique chapters from scholars within the field of game cultures and esports, representing ten different nationalities. The contributions construct thematic sections that divide the book into three parts: Players, Diverse Audiences? and Fan & Fiction Work. As such, the parts provide a wide-ranging overview of esport engagement, thus disclosing the phenomenonâs cross-cultural, transmedial, and interconnected relations that have not been probed earlier in a single anthology
Modes of Esports Engagement in Overwatch
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Exploring the dynamics of knowledge sharing in the online affinity apaces of "Let's Play" Youtube Channels
With this dissertation the goal is to analyze the novel medium of video game streaming and more specifically the âLetâs Playâ video format as seen on YouTube and other online platforms. The practice has experienced a rapid growth in popularity over the course of the last decade since its emergence, which means many of its intricacies are yet to be accounted for by academic research. The intent is to engage with it from the perspective of learning and knowledge exchange and see whether such processes take place within the channels dedicated to this type of content, and if so to map out their dynamics, and reflect critically on the picture that emerges from the exploration of these virtual spaces.El objetivo de esta tesis es analizar el nuevo medio para retransmisiĂłn de videojuegos y, en particular, el formato de vĂdeo "Let's Play" como el que estĂĄ en YouTube y otras plataformas en lĂnea. La prĂĄctica ha experimentado un rĂĄpido crecimiento de popularidad en el transcurso de la Ăşltima dĂŠcada desde su apariciĂłn, lo que significa que muchas de sus complejidades aĂşn deben tenerse en cuenta por la investigaciĂłn acadĂŠmica. La intenciĂłn es abordar este formato desde la perspectiva del aprendizaje y el intercambio de conocimientos y ver si tales procesos tienen lugar dentro de los canales dedicados a este tipo de contenido y, en caso de ser asĂ, trazar la dinĂĄmica y reflexionar crĂticamente sobre el panorama que surge de la exploraciĂłn de estos espacios virtuales.L'objectiu d'aquesta tesi ĂŠs analitzar el nou mitjĂ de retransmissiĂł de videojocs i, mĂŠs concretament, el format de vĂdeo "Let's Play" que es veu a YouTube i altres plataformes en lĂnia. La popularitat d'aquesta prĂ ctica ha crescut rĂ pidament durant l'Ăşltima dècada des de la seva apariciĂł, cosa que significa que moltes de les seves complexitats encara no han estat considerades per la investigaciĂł acadèmica. La intenciĂł ĂŠs abordar-lo des de la perspectiva de l'aprenentatge i l'intercanvi de coneixements i veure si aquests processos es desenvolupen dins dels canals dedicats a aquest tipus de continguts i, en cas afirmatiu, establir-ne la dinĂ mica i reflexionar de manera crĂtica sobre el panorama que es desprèn de l'exploraciĂł d'aquests espais virtuals
Law and Policy for the Quantum Age
Law and Policy for the Quantum Age is for readers interested in the political and business strategies underlying quantum sensing, computing, and communication. This work explains how these quantum technologies work, future national defense and legal landscapes for nations interested in strategic advantage, and paths to profit for companies
Innovation and Nanotechnology
This book is available as open access through the Bloomsbury Open Access programme and is available on www.bloomsburycollections.com. This book defines 'nanowares' as the ideas and products arising out of nanotechnology. Koepsell argues that these rapidly developing new technologies demand a new approach to scientific discovery and innovation in our society. He takes established ideas from social philosophy and applies them to the nanoparticle world. In doing so he breaks down the subject into its elemental form and from there we are better able to understand how these elements fit into the construction of a more complex system of products, rules and regulations about these products. Where existing research in the field has tended to focus on potential social harm, Koepsell takes a different approach by looking at ways in which developments in distributed design and fabrication can be harnessed to enable wealth creation by those with good ideas but no access to capital. He argues that the key challenge facing us is the error implicit in current intellectual property regimes and presents new modes of relating inventors to artifacts in this new context. In conclusion he offers contractual models which he believes encourage innovation in nano-media by embracing open source and alternative means of protection for innovators
Identity dissolved in isolation: the contrasting notions of density and âthin-nessâ in haunted places in the literature of the supernatural from the 18th century to the modern age, with particular reference to works by Shirley Jackson, Stephen King and John Langan, and the development of these themes in the writing of no man.
My aim is to illustrate the development of inter-related themes of personal identity and isolation, in both physical and psychological senses, within the literature of the supernatural and to trace the development of a treatment of the horror of physical and mental disintegration which is increasingly psychologically-aware both in authors and readership through the introduction of âthe thin placeâ as a trope as it became an explicit feature of stories within âhorror fictionâ. To begin this thesis I will offer explanations of some key terms relating to the literature of the supernatural, incorporated within a necessarily brief historical review in Chapter 1, DEFINING THE INDEFINABLE: The Development of Themes of âThin-nessâ Within Stories of the Supernatural From Early History to The Gothic. In literary works predating the arrival of âthe Gothicâ as a distinctly identified form, I will show that there is no clear boundary demarcating the ânaturalâ from the âsupernaturalâ. This boundary becomes more clearly defined in later literature wherein the âsupernaturalâ is increasingly seen as a wholly separate, often inimical realm. I will demonstrate that the notion of âdensityâ which I will identify as emerging more fully and precisely in the later twentieth century should be seen as representing a âconsensual realityâ in contrast to the âindeterminacyâ which is one characteristic of the supernatural. In the course of this investigation, I will draw upon a number of different approaches, including definitions of the various associated genres in Section 1.2, with an exploration in sections 1.3 and 1.3.3 CRITICAL ENGAGEMENT: The Horrors of Isolation and The Dissolution of Identity, of some major critical currents shaping the treatment of these themes. This will be linked to the psychological insight which views irruption through âthin-nessâ as a transgressive motif, often including both metaphorical and literal âpenetration of the boundariesâ - metaphysical, as between planes of existence, and physical, as in penetration of the flesh. Thus a new understanding of a hitherto familiar literary trope in this stream of fiction was developed, combining the psychological horror of isolation, the physiological horror of âpenetrationâ (with concomitant death a likely outcome) and a third, metaphysical element of horror in the face of modes of existence wholly inimical to humanity. In Chapter 2, the works of Shirley Jackson, Stephen King and John Langan, along with material from other authors working within broadly similar traditions, will be examined and compared to reveal common threads in their treatment of isolation in âthin placesâ along with the subsequent dissolution of the âdensityâ of identity suffered by their characters. I will reference the ways in which particular settings have been used in stories by these authors, namely the âhaunted placesâ, increasingly described as âthin placesâ, where the boundary between natural and supernatural is easily traversed. In the course of this examination, I will demonstrate the continuing emergence, and import of, the notion of âdensityâ as a marker of normality, in contrast to the âthinâ nature of the boundary with the transgressive supernatural, and also show some of the ways in which this treatment manifests in modern stories of the supernatural. This trope, I contend, has developed following a conscious âpsychologisationâ of the experience of writing and reading tales of the supernatural which suggests a blurring of traditional boundaries of inner and outer experience, and, by extension, of reality and fantasy. I will also demonstrate some of the ways in which this particular stream of literature of the transgressive has developed to reflect the concerns of readerships of the time. There will be a focus upon elements which became of central importance in attempts to define the genre: issues concerning setting as character; and of identity and ontology, the latter in the sense of exploring what there is. I will seek to show how dissolution of identity plays a key part in many related genre stories, and how this dissolution is reflected in the themes and language used in the texts as âthinningâ. The notion of âdensityâ is taken as being of fundamental importance in modern novels of the supernatural placed within the tradition of âContemporary Gothicâ (as opposed to the more thematic concerns of the ânew Gothicâ). In modern times, physical and mental injury have both become seen as methods for demonstrating the dissolution of identity, in which both body and psyche wear thin (as examined in section 2.2.5). In the third chapter, the thesis sets out a thematic record of the process of the creation of my novel of the supernatural, No Man, tracing influences, techniques and methodologies employed in two sections: looking at characters and settings in section 3.1, and at autobiographical influences on the roots of the story in section 3.2. I will identify where the novel draws upon the methodologies outlined previously, and where it consciously draws upon contrasts of exteriority and interiority and where the boundary which separates these contrasts becomes foregrounded. Finally, I will attempt to place my novel within the literary tradition of tales of the supernatural, and bring to bear an authorial analysis, with explanations of the ways in which elements described above are developed within the story. This element of the thesis will aim to illuminate ways in which traditional themes, tropes and motifs of isolation and the dissolution of identity have been incorporated in a modern novel of the supernatural, developing the contrasting notions of density and âthin-nessâ as major thematic concerns and plot elements
Coastal Landform Change Influences on Endangered Five-Lined Skink Distribution at Northwest Beach, Point Pelee National Park, Canada
As park visitation increased to Point Pelee National Park up until its peak in 1963, the installation of infrastructure for the purpose of supporting the recreational interest grew with it. At Northwest Beach, large parking lots were built into the coastal landscape and by the 1970s large areas of sand dunes continued to be heavily impacted by the installation of visitor associated infrastructure. The infrastructure resulted in the stabilization of sand on the beach side of the parking lot, resulting in an artificially stabilized and heavily vegetated dune. Over the last few decades, the park slowly reduced the size and number of infrastructure and facilities to accommodate current visitor use trends.
This research focuses on determining the success of past management interventions that were implemented at Northwest Beach and the influence those interventions have had on restoring coastal ecosystem function and the endangered five-lined skink population. Since restoration is a long-term process, monitoring land use and land cover changes as well as outcomes of restoration activities is vital in progressing toward restoring ecosystem function and ecological integrity. The overall goal of this research is to identify the influence that coastal landform changes at Northwest Beach, Point Pelee National Park, have had on the endangered five-lined skink species abundance and distribution and to determine the success of past management interventions at Northwest Beach. Specific research objectives were to analyze change in land-use and land-cover at Northwest Beach and the influence past management interventions have had on landform change, to examine the abundance and distribution of the endangered five-lined skink population at Northwest Beach and determine the desired and most suitable habitat for the species, and to determine the coastal landform changes influence on the five-lined skink population abundance and distribution at Northwest Beach.
This research involves the land use land cover classification of aerial imagery from five sperate time periods across the Northwest Beach study area. The skink sighting abundance at Northwest Beach was comparatively analyzed with the abundance recorded throughout the entire Point Pelee National Park. The variation in abundance at Northwest Beach was evaluated along with the species distribution between the four research zones. The correlations between Northwest Beach management interventions and corresponding changes in land use and land cover as well as five-lined skink distribution and abundance were identified. Based on results of this research, additional management strategies for coastal restoration at Northwest Beach, Point Pelee were recommended. This study offers insight on the importance of specific rehabilitation practices for coastal habitat restoration to maintain ecological integrity and endangered species populations within Point Pelee National Park and broader practices that can be implemented in all coastal restoration projects
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