320 research outputs found
A fluid mechanic view on urban wind energy
No full textThe world energy demand is rising with an increasing need for renewable and sustainable energy sources. Wind energy plays a key role in this transition. Urban areas are largely unexploited for wind energy extraction. Urban wind energy offers great potential as a decentralized renewable energy source. However, one of the main issues to date is a limited understanding of the urban wind resources. The flow in an urban environment is naturally sheared, as part of the atmospheric boundary layer, and in addition, highly turbulent, due to the many obstructions in the flow. This thesis aims to contribute to an improved understanding of the urban wind resources. Specifically, the performance and flow field of a roof-mounted vertical axis wind turbine is examined, as well as the interaction of freestream turbulence and a turbulent boundary layer.
The thesis presents experimental work in which these problems are investigated on a lab-scale. Experiments are conducted in a wind tunnel and a water channel, enabling controlled flow conditions. Specific parameters in the flow, such as turbulence intensity and velocity shear, are deliberately varied using active grids. The flow is primarily evaluated with Particle Image Velocimetry and Laser Doppler Velocimetry, complemented by Constant Temperature Anemometry and surface pressure measurements. Two model buildings are placed in the flow, represented by surface-mounted cubes. A drag-driven vertical axis wind turbine of the Savonius type is positioned on the roof of the model buildings and its power output is measured. Both the streamwise position and the height of the turbine above the roof are varied, and the impact on the flow field and power output is assessed. In addition, the influence of varying wind directions and vertically sheared in flow on the turbine performance are examined. The influence of turbulence intensity is investigated fundamentally on the evolution of a turbulent boundary layer and on the flow around the model buildings. Again, the impact on the turbine's power output at various positions is evaluated.
It is demonstrated that a turbulent boundary layer is not permanently matured ahead of its natural evolution by the presence of freestream turbulence and that the relative state of evolution of both the boundary layer and the freestream turbulence has to be considered when assessing the turbulent boundary layer. A key finding is the substantial impact of a roof-mounted wind turbine on the flow field and, thus, on the available power. This suggests that in contrast to common practice, including an actual turbine in the analysis is significant. A central high turbine position is found to maximize the power output for a uniform wind rose. However, for individual wind directions, the ideal turbine position and height vary. Turbulence intensity has a significant impact on the flow around the model buildings and consequently also on the power output of the turbine. High levels of turbulence intensity reduce flow separation on top of the building, resulting in higher velocities where the turbine is placed and, thus, higher power output. Conversely, velocity shear has only limited influence on the flow field and power output of the roof-mounted turbine. Overall, a methodology to assess a roof-mounted vertical axis wind turbine in a controlled environment was developed, examining the influence of various parameters, such as in flow conditions and turbine position
Wave-front phase retrieval in transmission electron microscopy via ptychography
No full textThere are many different strategies that allow the solving of the well-known phase problem corresponding to the loss of phase information during a physical measurement. In microscopy, and, in particular, in transmission electron microscopy, most of these strategies focus on the retrieval of high-resolution information with the importance of lower resolution data often overlooked. Ptychography offers a means to investigate such data. Ptychography is a robust diffractive imaging technique with fast convergence for phase retrieval but, until now, has not been applied at the nanoscale. In this paper, we use the ptychographical iterative engine to retrieve the phase change at the exit plane of metallic nanoparticles using a conventional transmission electron microscope. Ptychographical reconstructions yielded images with a phase resolution of π/10 and a spatial resolution of 1 nm. These results stand as a first step toward aberration-free lensless imaging. The technique lends itself to be an alternative to off-axis electron holography or focal series reconstructio
Influence of site, turbine height and wind direction on the performance of vertical-axis wind turbines on model buildings
No full textVindturbiner som opererer i det bygde miljøet er utsatt for lavere gjennomsnittshastigheter og høyere
turbulente svingninger enn i åpent terreng. Likevel er det regioner rundt bygninger der strømmen blir
akselerert og hvor det kan være gunstig å plassere en vindturbin. I dette arbeidet er en Savonius vindturbin plassert i et modellert bymiljø bestående av et kunstig gulv og to veggmonterte kuber med avstand
på to kubehøyder, 2H. En parametrisk studie utføres for å bestemme idealposisjonen for å høste energi
uavhengig av vindretningen. Dette gjøres ved å undersøke hvilken innvirkning ulike tilførselsvinkler har
på effekten når to turbiner som er forhøyet forskjellig, er plassert i tre posisjoner på taket. Effekten
beregnes ved å innhente data på estimert mekanisk dreiemoment og rotasjonshastighet. Det oppnås
full effektkurver for fem innstrømningsvinkler, og enkeltoperasjonsmålinger utføres for finere diskretisering med tretten innstrømningsvinkler. Basert på gjennomsnittseffekten som er anskaffet over en full
rotasjon, er det vist at midten på taket er det ideelle stedet å plassere den høyeste forhøyede turbinen
som er undersøkt, og som spenner over 1.16 ≤ z/H ≤ 1.48, hvor z er høyden målt fra kunstgulvet.
Gjennomsnittlig effektutbytte er omtrent 20% høyere enn effekten i en "ren strøm" uten kubene i denne
posisjonen. Effekten er vist å være sensitiv til turbinhøyder, og den nedre monterte turbinen er mindre
effektiv. Det observeres videre at nabokuben har en betydelig innvirkning på effekten som ekstraheres
av turbinen på taket
La cosmétologie à travers les âges
No full textDie Kosmetologie im Laufe der Zeit.
Die Verfasserin gibt eine kurze Übersicht der Kosmetologie vom alten Aegypten an bis zum 19. Jahrhundert.Cosmetology across the ages.
The author paints a quick sketch of cosmetology from Ancient Egypt to the 19th century.de Roeck-Holtzhauer Yannick. La cosmétologie à travers les âges. In: Revue d'histoire de la pharmacie, 76ᵉ année, n°279, 1988. pp. 397-399
Révisions transatlantiques : une expérience de télécollaboration entre l’Université Ca’ Foscari et Bentley University
No full textThe aim of this work is to present the ins and outs of a telecollaboration project between an American university (Bentley University) and Ca\u27 Foscari University. This project targets oral production and revision skills around an authentic language object, the video CV. Between March and April 2021, the author and a colleague from Bentley University set up a collaborative video CV revision project between 10 American FLE students and 13 students from Ca\u27 Foscari University of Venice, Italy (CEFR level B1-B2 for both groups). After a preparation phase started in December 2020 on both sides of the Atlantic, the device was implemented with work phases in synchronous and asynchronous modality. First, we will provide a theoretical framework concerning the use of telecollaboration mediated by computer for didactics of French as a foreign language. Then, we will go into more detail on the organisation, the setting up of the project and the modalities, the course of the exchanges and the tools used. Finally, we will present the first results obtained through this project and raise some issues about some negative outcomes.L’objectif de ce travail est d’exposer les tenants et aboutissants d’un projet de télécollaboration entre une université américaine (Bentley University) et l’université Ca’ Foscari de Venise. Ce projet vise les compétences de production et de révision orales autour d’un objet langagier authentique, le CV vidéo. Entre Mars et Avril 2021 compris, l’auteur et une collègue de l’université américaine de la Bentley University ont mis en place un projet de révision collaborative de curriculum vitae au format vidéo entre 10 étudiant.es de FLE américains et 13 étudiant.es de l’université Ca’ Foscari (niveau B1-B2 du CECRL). Après une phase de préparation engagée dès décembre 2020 des deux côtés de l’Atlantique, le dispositif a été mis en œuvre avec des phases de travail en modalité synchrone et asynchrone. Dans un premier temps, nous fournirons un cadre théorique concernant le recours à la télécollaboration médiée par ordinateur en didactique du Français Langue Etrangère. Ensuite, nous reviendrons plus en détail sur l’organisation, la mise en place du projet et les modalités, le déroulement des échanges et les outils utilisés. Nous présenterons enfin les premiers résultats obtenus par le biais de ce projet et soulèverons les problématiques qui ressortent de résultats mitigés
A fluid mechanic view on urban wind energy
No full textThe world energy demand is rising with an increasing need for renewable and sustainable energy sources. Wind energy plays a key role in this transition. Urban areas are largely unexploited for wind energy extraction. Urban wind energy offers great potential as a decentralized renewable energy source. However, one of the main issues to date is a limited understanding of the urban wind resources. The flow in an urban environment is naturally sheared, as part of the atmospheric boundary layer, and in addition, highly turbulent, due to the many obstructions in the flow. This thesis aims to contribute to an improved understanding of the urban wind resources. Specifically, the performance and flow field of a roof-mounted vertical axis wind turbine is examined, as well as the interaction of freestream turbulence and a turbulent boundary layer.
The thesis presents experimental work in which these problems are investigated on a lab-scale. Experiments are conducted in a wind tunnel and a water channel, enabling controlled flow conditions. Specific parameters in the flow, such as turbulence intensity and velocity shear, are deliberately varied using active grids. The flow is primarily evaluated with Particle Image Velocimetry and Laser Doppler Velocimetry, complemented by Constant Temperature Anemometry and surface pressure measurements. Two model buildings are placed in the flow, represented by surface-mounted cubes. A drag-driven vertical axis wind turbine of the Savonius type is positioned on the roof of the model buildings and its power output is measured. Both the streamwise position and the height of the turbine above the roof are varied, and the impact on the flow field and power output is assessed. In addition, the influence of varying wind directions and vertically sheared in flow on the turbine performance are examined. The influence of turbulence intensity is investigated fundamentally on the evolution of a turbulent boundary layer and on the flow around the model buildings. Again, the impact on the turbine's power output at various positions is evaluated.
It is demonstrated that a turbulent boundary layer is not permanently matured ahead of its natural evolution by the presence of freestream turbulence and that the relative state of evolution of both the boundary layer and the freestream turbulence has to be considered when assessing the turbulent boundary layer. A key finding is the substantial impact of a roof-mounted wind turbine on the flow field and, thus, on the available power. This suggests that in contrast to common practice, including an actual turbine in the analysis is significant. A central high turbine position is found to maximize the power output for a uniform wind rose. However, for individual wind directions, the ideal turbine position and height vary. Turbulence intensity has a significant impact on the flow around the model buildings and consequently also on the power output of the turbine. High levels of turbulence intensity reduce flow separation on top of the building, resulting in higher velocities where the turbine is placed and, thus, higher power output. Conversely, velocity shear has only limited influence on the flow field and power output of the roof-mounted turbine. Overall, a methodology to assess a roof-mounted vertical axis wind turbine in a controlled environment was developed, examining the influence of various parameters, such as in flow conditions and turbine position
Law & Economics Perspectives on Electricity Regulation
No full textThis paper first reviews some of the main contributions of the new institutional economics to the analysis of the process of competitive transformation of network industries. It shows that neoinstitutional analysis is complementary to the microeconomics of rational pricing, since it accounts for the decisive role of an institutional framework adapted to new transactions. It emphasizes the importance of the political reform process, which draws on the conditions of attractiveness and feasibility to define an initial reorganization of property rights in these industries. The paper then analyzes in this light some of the main challenges ahead for electricity regulation: the question of investment in generation capacities and the link to long term contracts, the regulation of wholesale market power, the support to Renewable Energy Sources for Electricity (RES-E) and the design of new regulatory authorities.Electricity Markets; New Institutional Economics; Law & Economics
« Notte pour faire la pomade pour plusieurs maux » ou la recette d'un guérisseur vendéen
No full text« Notiz zur Bereitung der Salbe für mehrere Gebrechen » oder das Rezept eines Heilkunstlers aus der Vendée.
Der Verfasser untersucht die Zusammensetzung der Formel eines Empirikers aus der Vendée in der zweiten Hälfte des 19. Jahrhunderts fur Flechten, Brandwunden, Frostbeulen und Hamorrhoiden. Er ziecht daraus den Schluss auf Stichhaltigkeit dieser Formel welche der damaligen gebrauchten Polytherapie entspricht.« Notes on How to Make the Pommade for Several Illnesses » or the recipe of a healer from Vendée.
The author examines the composition of a formula from an empiric of Vendée, from the second half of the 19th century, for skin eruptions, burns, chilblains and hemorrhoids. He concludes that the components of the formula are valid, and conform to the polytherapy in use at that time.Romieux Yannick. « Notte pour faire la pomade pour plusieurs maux » ou la recette d'un guérisseur vendéen. In: Revue d'histoire de la pharmacie, 78ᵉ année, n°287, 1990. pp. 449-452
Toucher au plus vivant. Poétique et politique de l’amour dans 'Je cherche l’Italie' de Yannick Haenel
No full textÀ travers une lecture du roman 'Je cherche l’Italie' (2015) de Yannick Haenel est soulignée la manière toute singulière suivant laquelle la littérature (le poétique) permet d’étendre la compréhension que l’on se fait habituellement du politique, la plupart du temps réduit à une lutte pour la conquête d’un pouvoir de l’État ou dans l’État, à l’organisation des pouvoirs ou à un art/exercice de gouverner. Il s’agit ainsi de mettre en lumière la façon dont l’écrivain français, par son récit, fait de l’amour, qui a été peu à peu relégué au cercle intime, le cœur d’une possible reconfiguration du politique au sein de la société occidentale contemporaine en crise(s) et comment Haenel établit l’amour en tant que principe politique solide et déterminant pouvant venir revitaliser voire restructurer anarchiquement le vivre ensemble.Throughout a focused reading of Yannick Haenel’s novel Je cherche l’Italie (2015) is underlined the incongruous ability of literature (the poetics) to extend usual understanding of politics, which is often reduced to a conquest of power by the State or in the State, the organization of power(s) or the art (practice) of governing. This article aims to highlight the way the French author puts love, which was gradually relegated to the intimate sphere, at the heart of a possible reconfiguration of politics in the crisis-stricken contemporary western society. It shows how Haenel establishes love as a strong and decisive political principle that could revitalize or even restructure anarchically the vivre ensemble
D'un pot de pharmacie à la vie d'une famille de pharmaciens vendéens
No full textVon einem Apotheken-Gefäss zur Lebensskizze einer Apotheker-Familie aus der Vendée.
Um einen Salbentopf aus Faience von Creil und Montereau zu datieren und den Apotheker auszumachen dessen Name und Adresse auf dem Gefäss figuriert, sieht sich der Verfasser veranlasst das Leben von François Chassant (1804-1883), Apotheker in La Roche-sur-Yon, aufzuzeichnen. Sein Sohn Auguste wurde sein Nachfolger. Der Topf kann um 1849-1852 datiert werden.From a pharmacy jar to the life of a family of pharmacists from the Vendée.
In order to date a pommade jar of Creil and Montereau faience, and to identify the pharmacist whose name and address it bears, the author was brought to retrace the life of François Chassant (1804-1883), pharmacist of La Roche-sur-Yon, succeeded by his son Auguste. The pot can be dated from 1849-1852.Romieux Yannick. D'un pot de pharmacie à la vie d'une famille de pharmaciens vendéens. In: Revue d'histoire de la pharmacie, 75ᵉ année, n°272, 1987. pp. 57-64
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