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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Time-domain Simulation of Multibody Floating Systems based on State-space Modeling Technology

Yu, Xiaochuan 2011 August 1900 (has links)
A numerical scheme to simulate time-domain motion responses of multibody floating systems has been successfully proposed. This scheme is integrated into a time-domain simulation tool, with fully coupled hydrodynamic coefficients obtained from the hydrodynamic software - WAMIT which solves the Boundary Value Problem (BVP). The equations of motion are transformed into standard state-space format, using the constant coefficient approximation and the impulse response function method. Thus the Ordinary Differential Equation (ODE) solvers in MATLAB can be directly employed. The time-domain responses of a single spar at sea are initially obtained. The optimal Linear Quadratic Regulator (LQR) controller is further applied to this single spar, by assuming that the Dynamic Positioning (DP) system can provide the optimized thruster forces. Various factors that affect the controlling efficiency, e.g., the time steps ∆τ and ∆t, the weighting factors(Q,R), are further investigated in detail. Next, a two-body floating system is studied. The response amplitude operators (RAOs) of each body are calculated and compared with the single body case. Then the effects of the body-to-body interaction coefficients on the time-domain responses are further investigated. Moreover, the mean drift force is incorporated in the DP system to further mitigate the motion responses of each body. Finally, this tool is extended to a three-body floating system, with the relative motions between them derived.
2

Optimization of floating PV systems : Case study for a shrimp farm in Thailand

Louise, Wästhage January 2017 (has links)
The use of solar photovoltaic (PV) systems have expanded rapidly the last decade and today’s market includes several different solar utilizations, where floating PV is one of them. Previous studies have shown how floating PV systems increase the PV efficiency and at the same time reduce the water evaporation. The purpose of this study is to evaluate and optimize energy solutions using floating PV systems for a shrimp farm cultivation in Thailand, where the technical, environmental and economic aspects will be included. The optimizations have been done in the open source model OptiCE, where genetic algorithm (AG) have been used to maximize the renewable reliability and minimize the Levelized Costs of Electricity (LCOE). In order to find the optimal renewable solution for the investigated shrimp farm, four scenarios have been compared considering different PV system combinations. The simulated results showed how the scenarios considering floating PV system generated a higher reliability than the scenarios considering ground-mounted PV system. The scenario considered tracking PV system increased the system´s renewable reliability compared to fixed PV system. However the shrimp farm is connected to the national electric grid or not will have a huge impact on the LCOE due to the low electric price and the implemented feed-in-tariff (FIT) program. The size of the installed PV capacity significantly affects the reliability results were the capacity of 200 kWp reaches a reliability of almost 100%. The optimal solution for the investigated shrimp farm to become independent is therefore to install a combined floating PV and battery storage system.
3

Characterization and selection of globe artichoke and cardoon germplasm for biomass, food and biocompound production / Caractérisation et sélection de germoplasmes d'artichaut et de cardon pour l'alimentation et la production de biomasse et de biocomposés

Ciancolini, Anna 06 July 2012 (has links)
L'artichaut et le cardon, appartenant à la famille des Asteraceae (Compositae), sont des plantes pérennes herbacées natives du bassin méditerranéen, et qui sont traditionnellement cultivées comme plantes maraîchères, respectivement pour leurs têtes et leurs cardes. L'Italie est le pays possédant la plus importante collection de germoplasmes autochtones d'artichaut. Dans le centre de l'Italie, le type Romanesco est étendu. Ces dernières années, le développement des techniques in vitro a permis la multiplication de l'artichaut Romanesco et sa rapide expansion. Le clone Romanesco C3 a ainsi remplacé de nombreuses races locales de Romanesco, contribuant de la sorte à une érosion significative des ressources génétiques locales. Concernant le germoplasme de cardon cultivé, seules quelques études sont disponibles sur son identification et sa caractérisation génétique. Le cardon sauvage, n'est pas du tout cultivé; il est davantage considéré comme une adventice dans le paysage italien. La grande variabilité existant entre les espèces de Cynara n'est pas correctement décrite et il existe plusieurs cas d'homonymes. Le secteur de l'artichaut italien a du faire face ces dernières années à une crise causée principalement par l'apparition sur le marché de produits étrangers et par les coûts élevés de mise en culture et de récolte. Afin de surmonter cette crise, de nombreuses valorisations du Cynara ont été envisagées. Ces potentielles applications pour la culture ont pu voir le jour grâce au support de l'Union européenne pour la recherche sur les co-poduits issus de l'agriculture, et ont mené à un intérêt croissant pour la biomasse entière d'artichaut. Considérant ces remarques préliminaires, une stratégie, qui permettrait de valoriser le germoplasme italien par la production concomitante de biomasse et de biocomposés, a été mise en place durant ces trois ans de doctorat. Le premier objectif de ce travail de doctorat consistait en i) la caractérisation agro-morphologique du germoplasme italien par le biais de descripteurs UPOV, ii) l'évaluation de la variabilité génétique à l'intérieur et entre les races/clones et iii) l'identification et la préservation des ressources génétiques pour le développement de futurs programmes d'amélioration des plantes. Suite à cette caractérisation, trois génotypes ont été sélectionnés et enregistrés sous les noms de Michelangelo, Donatello and Raffaello. Afin d'analyser le germoplasme italien de Cynara d'un point de vue de la biomasse, différents traits expliquant la vigueur de la plante et la production de matière sèche ont été considérés. Le rendement en biomasse aérienne s'est révélé très élevé, soulignant la possibilité d'utiliser cette culture comme matière première industrielle. Un point particulier du programme de thèse était de mettre au point les méthodes d'extraction de biocomposés et les techniques d'analyse afin d'optimiser le rendement en polyphénols à partir de la biomasse de Cynara à l'échelle laboratoire. L'ASE a été reconnue comme étant la meilleure technique. De plus, les cinétiques de production de biomasse et de biocomposés ont été évaluées et le stade physiologique optimal pour collecter le matériel végétal en champ a été identifié. La caractérisation biochimique a été réalisée grâce aux méthodes mises au point et en collectant le matériel végétal au stade physiologique optimal identifié afin de distinguer les génotypes les plus appropriés pour la production de biocomposés. Le dernier point du programme de thèse était centré sur le développement d'une technique alternative de production de biomasse et de biocomposés en conditions de croissance sous serre. Les résultats obtenus mettent en exergue la possibilité d'utiliser avec succès certains génotypes de Cynara pour la production de biomasse et de biocomposés. La perspective réelle d'utiliser certains génotypes d'artichaut pour une double valorisation alimentaire et non-alimentaire a ainsi été soulignée. / Globe artichoke and cardoon, belonging to the Asteraceae (Compositae) family, are herbaceous perennial plants native to the Mediterranean area, which are traditionally grown as vegetables for the heads and the fleshy petiole leaves, respectively. Italy is the richest reserve of globe artichoke autochthonous germplasm, which is vegetatively propagated and well adapted to the different pedoclimatic conditions of the Country. In Central Italian environments, the Romanesco type is widespread. In the last years, the development of in vitro technologies allowed the propagation of Romanesco globe artichoke type and its rapid expansion. As a result, the micropropagated Romanesco clone C3 has replaced many landraces traditionally grown in the Latium Region and has led either to a significant erosion of local genetic resources. As regards Italian cultivated cardoon germplasm, there are few studies on its genetic characterization and identification and there is a lack of information about the genetic variability existing within and among accessions. For the wild cardoon, no specialized crop is present and it represents mainly a weed in Italian environments. The great variability existing in Cynara spp. has not been described, the nomenclature of Italian germplasm is not always very clear since there are many cases of homonyms. In addition, Italian globe artichoke sector is facing a crisis due principally to the appearance on the market of foreign products and to the high labor cost required for crop cultivation and harvesting. In order to overcome this crisis several possible industrial uses were considered for the species. Considering these preliminary remarks, a strategy for valorizing Italian germplasm using biomass and biocompound production has been carried out during the three years of PhD program. The first objective of PhD work consisted in (i) characterizing agro-morphologically Italian germplasm using UPOV descriptors, (ii) assessing the genetic variability existing within and among landraces/clones and (iii) identifying and preserving genetic resources for the development of future plant breeding programs. As a result of this characterization, three genotypes have been selected and registered under the names of Michelangelo, Donatello and Raffaello. In order to analyze Italian Cynara spp. germplasm also from a biomass point of view, different traits explaining plant vigor and dry matter production have been considered. The aerial biomass yield resulted very high underlining the possibility of using this crop as raw industrial material. A focal point of PhD program was to set up biocompound extraction methods and analysis techniques to optimize polyphenol recovery from biomass of Cynara spp at a laboratory scale. In particular, ASE was found as the best extraction technique which allows to reduce extraction time and solvent consumption, increase nutraceutical yield and improvement of extract quality. Moreover, the kinetics of biomass and bio-compound production has been evaluated and the optimal physiological stage to collect plant material grown in open field has been identified. Biochemical characterization has been performed using the methods set up and collecting plant material in the optimal physiological stage identified in order to distinguish which genotypes were more suitable for bio-compound production purpose. The last focal point of PhD program was the development of an alternative technique for biomass and biocompound production in greenhouse grown conditions. Results obtained in the three PhD years, highlighted the possibility of using successfully some Cynara spp. genotypes for biomass and bio-compound production, in particular in open field condition. Also the real prospect of using some globe artichoke genotypes for food and non-food dual-production (biomass for biocompound extraction and heads for human food) has been underlined.
4

Proměna Šumavy za industrializace: zapomenuté stopy dřevařů / The Transformation of Šumava Mountains at the time of industrialization: Forgotten Traces of Woodworkers

Blažková, Tereza January 2018 (has links)
The aim of the thesis is to show the changes and the development of the landscape and the settlement of the region of central Šumava mountains due to industrialization in the 19th century. The thesis is based theoretically and methodologically in the field of anthropology of landscape and industrial archeology. It combines archive written and cartographic sources with non-destructive field research of anthropogenic relics. The industrialization of the area of interest meant the woodworking expansion that was caused by the lack of firewood in Prague and its surroundings and was realized as a business plan by the noble Schwarzenberg family. Schwarzenberg forest exploatation and timber floating system for firewood transport have brought significant landscape changes to hitherto almost untouched mountaneous forested areas. The field research has identified elements of the floating timber system, such as water reservoirs, watercourse troughs or the Vchynicko-Tetovský floating canal, as well as traces of both, permanent and seasonal settlement of woodcutters. The work divides the area into four zones, depending on how they were used, settled and transformed during the 19th century. The greatest attention is devoted to zone no. I, the remote forest area, which has become a major resource area for the Schwarzenberg...
5

Proměna Šumavy za industrializace: zapomenuté stopy dřevařů / The Transformation of Šumava Mountains at the time of industrialization: Forgotten Traces of Woodworkers

Blažková, Tereza January 2018 (has links)
The aim of the thesis is to show the changes and the development of the landscape and the settlement of the region of central Šumava mountains due to industrialization in the 19th century. The thesis is based theoretically and methodologically in the field of anthropology of landscape and industrial archeology. It combines archive written and cartographic sources with non-destructive field research of anthropogenic relics. The industrialization of the area of interest meant the woodworking expansion that was caused by the lack of firewood in Prague and its surroundings and was realized as a business plan by the noble Schwarzenberg family. Schwarzenberg forest exploatation and timber floating system for firewood transport have brought significant landscape changes to hitherto almost untouched mountaneous forested areas. The field research has identified elements of the floating timber system, such as water reservoirs, watercourse troughs or the Vchynicko-Tetovský floating canal, as well as traces of both, permanent and seasonal settlement of woodcutters. The work divides the area into four zones, depending on how they were used, settled and transformed during the 19th century. The greatest attention is devoted to zone no. I, the remote forest area, which has become a major resource area for the Schwarzenberg...

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