• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 89
  • 83
  • 51
  • 16
  • 10
  • 10
  • 6
  • 5
  • 5
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 319
  • 143
  • 80
  • 60
  • 53
  • 47
  • 41
  • 34
  • 32
  • 28
  • 27
  • 26
  • 25
  • 24
  • 23
  • 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.
241

Les collections d’estampes en Europe (v. 1450-v. 1610) / Print Collecting in Europe (ca. 1450-ca. 1610)

Gallian, Nastasia 07 December 2019 (has links)
La naissance des collections de gravures constitue un phénomène mystérieux, qui ne peut être ni daté, ni localisé avec une précision absolue. Les premières manifestations remontent au milieu du XVe siècle, à une époque où les estampes sont collectées dans le but d’être collées dans des textes manuscrits ou imprimés. À partir des années 1470-1480, ces pratiques archaïques sont relayées progressivement par une approche proprement moderne des collections de gravures, qui se diffusent alors dans toute l’Europe, jusqu’à être largement répandues dans certaines couches de la société au moment où l’on bascule dans l’âge baroque. Plusieurs types d’ensembles coexistent à cette époque. Les collections d’amateurs tels que Fernand Colomb, Willibald Imhoff ou Abraham Ortelius témoignent d’une affinité particulière pour l’art de l’estampe et mettent en place les premiers outils pour sélectionner, conserver et classer les gravures. De nombreux princes, tels que Ferdinand de Tyrol et Philippe II d’Espagne, s’intéressent également à ces œuvres, auxquelles ils consacrent une section dans leurs collections encyclopédiques ou leurs bibliothèques. D’autres collections, à but utilitaire, émergent également à cette période. On trouve ainsi des fonds d’estampes dans de nombreux ateliers d’artistes et d’artisans, où elles sont employées pour former les apprentis et servir de modèles ou de supports à la création. Les érudits s’emparent également des gravures et constituent des fonds documentaires spécialisés en histoire, géographie et sciences naturelles. Cette grande diversité dans les pratiques est une des caractéristiques essentielles des premières collections d’estampes. / The origins of print collecting are ill documented and cannot be dated nor located with certainty. The early signs can be traced back to ca. 1450, when prints were collected to be pasted in manuscripts and printed books. From the 1470s-1480s onwards, these archaic practices tended to be replaced by modern collecting. It then spread throughout Europe and became a common practice at the dawn of the Baroque era. There are several types of print collectors at that time. Enthusiasts and connoisseurs such as Ferdinand Columbus, Willibald Imhoff and Abraham Ortelius created special methods for selecting, storing and classifying high quality engravings and woodcuts. Ferdinand of Tyrol, Philip II of Spain and others princes gathered prints in their encyclopedic collections and libraries. Other collectors were interested in using them as sources. Artists and craftsmen kept prints to train apprentices and use them as models and tools in the creative process. Scholars purchased them for their subject-matter and used them as historical, geographical, and scientific documents. This wide range of practices is maybe what define the most early print collecting.
242

Optimisation biénergie d'un panneau solaire multifonctionnel : du capteur aux installations in situ / Bienergetical optimisation for a multifunctional solar panel : from module to in situ installations

Brottier, Laetitia 29 March 2019 (has links)
Dans un contexte de lutte contre le réchauffement climatique, le bâtiment est un secteur stratégique du fait de sa forte consommation de chaleur et d’électricité. Le solaire, thermique et photovoltaïque, a de forts atouts pour répondre à cet enjeu avec une compétitivité qui s’accélère. En particulier, le solaire hybride PVT est prometteur avec un double gain : l’extraction de la chaleur sous le module photovoltaïque apporte à la fois un gain de rendement électrique, et un gain de par l’utilisation de cette chaleur pour les besoins du bâtiment. L’état de l’art permet de toucher du doigt la diversité des concepts de solaire hybride, et le PVT plan non survitré à eau a été retenu dans cette thèse. Pour faire face à des problématiques de durabilité et de performance, DualSun a conçu un module hybride avec un échangeur en acier inoxydable directement laminé pendant le process du module photovoltaïque.L’analyse de ces capteurs est faite en Partie I, d’abord avec un modèle 3D de l’échangeur. Ce modèle permet de déterminer des débits minimaux, de quantifier l’intérêt à ne pas isoler les bords du module et de visualiser que la perte de charge pour ce concept est principalement liée aux entrées et sorties du module mais reste tout à fait acceptable. Devant les limitations en termes de périmètre et de temps de calcul de ce modèle 3D, des modèles simplifiés sont proposés et comparés. Les résultats de ces modèles simplifiés corroborent une température de stagnation du concept DualSun de l’ordre de 75°C, ce qui confirme que le design est intrinsèquement résiliant à la surchauffe même en l’absence de besoins. Enfin les performances thermiques sur 9 prototypes avec des variations de composition couche par couche ont confirmé que le modèle est robuste. La puissance thermique(non isolé) est de 758W thermique pour un besoin à 30°C et la puissance photovoltaïque de 250Wc électrique dans des conditions extérieures standards (STC).Une analyse système de ces modules intégrés dans un ensemble complexe est réalisée dans la Partie II. Pour le système dit préchauffage d’eau sanitaire en maison individuelle (CESI), les quatre logiciels PVSyst, PVGis, Polysun, Solo sont comparés au logiciel Trnsys avec les Type 295 et Type 816 qui intègrent les deux modèles simplifiés du module définis dans la partie I. Les modèles physiques de ces logiciels sont cohérents entre eux dans le domaine d’utilisation.Les résultats de ces logiciels utilisés à partir de données statistiques pour la météo et les habitudes de consommation sont comparés à des mesures terrain sur 28 installations CESI hybride chez des particuliers. L’objectif a été de quantifier les erreurs d’estimation des prédictions statistiques par rapport au réel. Si l’écart type sur productible photovoltaïque et les températures maximales atteinte par les modules reliés à l’incertitude sur la météo est faible (environ 10%), l’écart type sur l’estimation du besoin sur la base d’un volume moyen consommé est beaucoup plus forte (de l’ordre de 30%) du fait d’un comportement très irrégulier de consommation chez les particuliers en terme d’heure et de volume de puisage en fonction des jours. Les températures moyennes atteintes au niveau des modules sont supérieures à 45°C pendant la moitié de l’année et permettent un préchauffage effectif du ballon sanitaire. Des couvertures solaires des besoins d’eau chaude de 57-58% sont mesurées près de Lyon.Dans le chauffage d’eau sanitaire collectif en couplage pompe à chaleur (HP+) ou en chauffage piscine (SP), les modèles statistiques permettent une évaluation des productibles du fait d’une stabilité des besoins.En conclusion, le solaire hybride devrait être une technologie clé de la transition énergétique pour les bâtiments dans les années à venir, sa compétitivité avec le vecteur électrique est déjà réelle. La technologie est appelée à évoluer pour réduire ses coûts d’année en année à l’instar du photovoltaïque et renforcer ainsi son positionnement face au gaz. / In the context of the fight against climate change, the building is a strategic sector to address because of its high consumption of heat and electricity. Solar energy, both thermal and photovoltaic, has strong assets to meet this challenge and is becoming more and more cost-competitive. In particular, the PVT hybrid solar is a promising solution with a double advantage: the extraction of heat under the photovoltaic module brings both a gain in electrical efficiency, and a gain by generating heat for the needs of the building. The state of the art demonstrates the diversity of solar hybrid technologies, and this thesis specifically addresses the unglazed flat-plate design with water as the heat transfer fluid. To address sustainability and performance issues, the company DualSun designed a PVT hybrid module with a stainless steel heat exchanger directly laminated during the photovoltaic module process.The analysis of the DualSun collector is done in Part I, first with a 3D model of the exchanger. This model makes it possible to determine minimum flows, to quantify the interest not to insulate the edges of the module and to visualize that the pressure drop for this concept is mainly related to the inlets and outlets of the module but remains acceptable. Given the limitations in terms of scope and calculation time of this 3D model, simplified models are proposed and compared. The results of these simplified models corroborate a stagnation temperature of the DualSun concept of around 75°C, which confirms that the design is intrinsically resilient to overheating even in the absence of hot water consumption. Finally, thermal performance on 9 prototypes with layer-by-layer composition variations confirm that the model is robust. The models demonstrate that the 250Wp non-insulated version of the PVT panel has a thermal power output of 758 Wth for hot water needs at 30°C.A system analysis of these modules integrated in a complex system is carried out in Part II. For the preheating Domestic Hot Water system (DHW), four software programs, PVSyst, PVGis, Polysun, Solo are compared to Trnsys with the Type 295 and Type 816, which integrate the two simplified models of the module defined in the section I. The physical models of these software programs are consistent with each other in the field of use.The results of these software programs used from statistical data for the weather and consumption habits are compared to field measurements on 28 DHW (domestic hot water) hybrid installations in private homes. The objective was to quantify the errors of estimation of the statistical predictions with respect to the reality. While the standard deviation of PV output and maximum temperatures reached by the modules related to the uncertainty on the weather is low (about 10%), the standard deviation of estimated hot water needs based on an average consumption is much higher (about 30%) because of irregular consumption behavior in individuals in terms of time and volume depending on the days. The average temperatures reached at the level of the modules are higher than 45°C during half of the year and allow an effective preheating of the sanitary tank. Solar covering of hot water needs of 57-58% are measured near Lyon.For combined solar and heat pump (HP+) systems in multi-dwelling buildings and for pool heating (SP) systems, statistical models allow a reliable evaluation of the energy production because of stable hot water needs.In conclusion, solar hybrid should be a key technology for the energy transition of buildings in the coming years. PVT technology will evolve to reduce costs from year to year as observed with photovoltaic technology and thus strengthen its cost-competitive position against gas as a heat source for homes and buildings.
243

Moderní energie a snížení energetické náročnosti budov / Modern energy and decreasing the energy intensiveness of buildings

Kučera, Miroslav January 2009 (has links)
This diploma thesis deals with possible energy-savings in the municipal buildings of Spytihněv. Moreover, it discusses the possible improvements of heating features and making use of renewable resources. This is meant to be achieved by a wrapper which is less demanding on energy consumption than those which have been used until now. Attention is also paid to a more efficient system of energy distribution. Both energetic and financial points of view are taken into consideration. The thesis consists of a few parts. Introduction, the first part, deals with renewable resources issues on a theoretical level. The second part is divided according to each individual analysed premise/building. At this point energy-saving proposal, choice of a heating system, a heating pump, a solar collector as well as energy-saving and financial calculation are included.
244

Monitorování aktivit uživatelů na pracovních stanicích / Monitoring of User Activities on Workstations

Skopal, Aleš January 2009 (has links)
This master's thesis deals with proposal of a system for monitoring of user activities on workstations Windows XP over .NET 2.0 platform. The system should monitor running programs, processes and find out user activities in these programs like movement of the mouse or writing on the keyboard. A part of whole project is a suggestion of the system which contains specifications of requirements for this system, creation of the architecture, creation of important models, suggestion of the communication between separated part of system and final compile of results. The project should get information about user's activities and also information about usage of software installed on these workstations. The final system will be tested by use case study. Last but not least, project deals with ethic questions in the context of monitoring of users and discuss law questions about this project.
245

Free cooling and PVT integration in a ground-source heat pump (GSHP) system

Pourier, Christopher January 2023 (has links)
The performance of ground-source heat pump (GSHP) systems can be negatively affected over time by soil temperature degradation of boreholes (BH) in heating dominated climates. Land area is scarce in the dense urban environments typical of multi-family houses (MFH) and can lead to accelerated degradation- in tight BH fields. Heat extracted from photovoltaic thermal collectors (PVT) can help with BH regeneration; thus, limiting degradation. Additionally, free cooling (FC) is proposed in this study to tackle the anticipated cooling demandi ncrease in Sweden, while resolving the listed challenges of GSHP systems. A novel multi-source (MS) system integrating FC, PVT and GSHP together shall be investigated in this study. Firstly, implementing FC in a GSHP system for the scenario considered only provided marginal regeneration of the BH in the longterm. Both the SPF4+ and total life cycle cost (TLCC) of an FC+GSHP and GSHPsystem remained virtually constant. Furthermore, operation interference of FC and PVT in the MS system can be mitigated by considering their relative location in the system. In this study, cooling is the priority, thus placing the FC system after the BH field but before the PVT system in the brine loop is recommended. In that case, only 0.56% of the annual cooling is not delivered due to FC operation interference and the PVT thermal yield is decreased on average by 3.52%. By decreasing the BH spacing from 15 to 5 m, a slight SPF4+ increase to 3.22 is possible in a system with FC and 48 PVT collectors. With a sensitivity analysis it was shown that if a 15% decrease is achieved in electricity prices then the TLCC of this system can be lower than the TLCC of 2.13 MSEK for a GSHP system. / Prestandan hos ytjordvärmepump (GSHP) kan påverkas negativt över tid av försämrad marktemperatur i borrhål (BH) i klimat som domineras av uppvärmning. I täta stadsmiljöer med flerfamiljshus (MFH) är markytan knapp, vilket kan leda till accelererad nedbrytning i trånga BH-fält. Värme som utvinns från solfångare (PVT) kan bidra till regenerering av BH, vilket begränsar nedbrytningen. Dessutom föreslås frikyla (FC) i denna studie för att hantera den förväntade ökningen av kylbehovet i Sverige, samtidigt som man löser de listade utmaningarna med GSHP-system. Ett nytt multikällsystem (MS) som integrerar FC, PVT och GSHP tillsammans ska undersökas i denna studie. För det första gav implementeringen av FC i ett GSHP-system för det aktuella scenariot endast marginell regenerering av BH på lång sikt. Både SPF4+ och den totala livscykelkostnaden (TLCC) för ett FC+GSHP och GSHP-system förblev praktiskt taget konstant. Dessutom kan driftstörningar från FC och PVT i MS-systemet minskas genom att ta hänsyn till deras relativa placering i systemet. I denna studie prioriteras kylning, och därför rekommenderas att FC-systemet placeras efter BH-fältet men före PVT-systemet i brineslingan. Endast 0.56% av den årliga kylningen levereras inte på grund av störningar i FC-driften och PVT:s värmeutbyte minskar i genomsnitt med 3.52%. Genom att minska BH-avståndet från 15 till 5 m är en liten ökning av SPF4+ till 3.22 möjlig i ett system med FC och 48 PVT-kollektorer. En känslighetsanalys visade att om elpriserna minskar med 15% kan TLCC för detta system bli lägre än TLCC på 2.13 MSEK för ett GSHP-system.
246

Effects of solar parabolic- trough collectors in small- scale district heating systems

Monterrubio, Alejandro January 2022 (has links)
Reducing carbon emissions in our societies requires a massive shift towards renewables. In Sweden, biomass is the dominant source for the district heat production, but growing demand for biomass in other sectors may cause pressure on it. In this context, this thesis explores the possibility to supply heat with solar parabolic thermal collectors to a district heating system in Kosta, a locality in Lessebo municipality, Kronoberg county. The simulations and calculations are based on the locally available hourly data of weather conditions, supply and return temperatures of district heat and heat demand profiles. The energy production as well as the profitability of the installation is evaluated through the calculation of carbon abatement costs, considering that heat supplied from solar collectors spares biomass which can be made available for decarbonating the power sector. Results have shown that a solar installation that cover most of the heat demand during the months of summer, thus 10% of the annual heat demand, can be profitable. This study also investigates different scenarios with increased costs for the biomass resource to simulate the growing pressure around this resource and concludes that with growing costs of the biomass resource, solar application will become more attractive, allowing to make larger solar district heating plants profitable.
247

New Polyazine-Bridged Ru(II),Rh(III) and Ru(II),Rh(I) Supramolecular Photocatalysts for Water Reduction to Hydrogen Applicable for Solar Energy Conversion and Mechanistic Investigation of the Photocatalytic Cycle

Zhou, Rongwei 09 November 2014 (has links)
The goal of this research is to test the design constraints of active dpp-bridged RuII,RhIII (dpp = 2,3-bis(2-pyridyl)pyrazine)) supramolecular photocatalysts for water reduction to H2 and provide mechanistic insights into the catalytic cycle. Two member of a new RuII,RhIII motifs with only one Rh-'Cl bond, [(bpy)2Ru(dpp)RhCl(tpy)](PF6)4 ( bpy = 2,2'-bipyridine, tpy = 2,2':6,2"-terpyridine) and [(bpy)2Ru(dpp)RhCl(tpm)](PF6)4, (tpm = tris(1-pyrazolyl)methane), and a cis-RhCl2 model system, [(bpy)2Ru(dpp)RhCl2(bpy)](PF6)3, were prepared. This new motif was to test whether two Rh-'Cl bonds on RhIII are required for the photocatalytic water reduction. 1H NMR spectroscopic analysis of complexes prepared using deuterated ligands was used to characterize these three RuII,RhIII supramolecular complexes. Electrochemical studies suggested that replacing bpy with a tridentate ligand on RhIII shifts the RhIII/II and RhII/I reduction couples positively, which can modulate the orbital energetics of the RhIII LUMO (lowest-unoccupied molecular orbital). This substitute also changes the rate of ligand dissociation following the reduction of RhIII. In tpm and bpy systems, RhII intermediate is more stable than that in the tpy system. All three complexes were good light absorbers in the visible region and weak emitters from their emissive Ru(dπ)-'dpp(π*) 3MLCT (metal-to-ligand charge transfer) excited states at room temperature. The population of a low-lying 3MMCT (metal-to-metal charge transfer) ES (excited state) from the 3MLCT ES contributed to the weak emission, indicating an important intramolecular electron transfer process from dpp' to RhIII upon photoexcitation. The lower-lying 3MMCT excited state in the tpm and tpy systems relative to the bpy system result in a higher rate constant (ket = 2.6 x 10^7 vs 1.7 x 10^7 s-1) for intramolecular electron transfer. Spectrophotochemical analysis suggested that all three complexes were photoinitiated electron collectors capable of collecting two electrons on the RhIII center to generate the RuII,RhI species in the presence of DMA (N,N-dimethylaniline). The observed H2 production from water using [(bpy)2Ru(dpp)RhCl(tpm)](PF6)4 and [(bpy)2Ru(dpp)RhCl(tpy)](PF6)4 established that two halides on RhIII are not necessary in the dpp-bridge RuII,RhIII supramolecular photocatalytic-water-reduction system. This new discovery opens a new approach to the design of different RuII,RhIII motifs for photocatalysis. The active species for water reduction is proposed to be [(bpy)2Ru(dpp)RhICl(TL)]3+ from [(bpy)2Ru(dpp)RhCl(TL)](PF6)4 (TL (terminal ligand) = tpy or tpm) and [(bpy)2Ru(dpp)Rh(bpy)]3+ from [(bpy)2Ru(dpp)RhCl2(bpy)](PF6)3 respectively. Included here is the design and study of a RuII,RhI complex, [(bpy)2Ru(dpp)RhCl(COD)](PF6)3 (COD =1,5-cyclooctadiene) to provide more insights into the photophysical and photochemical properties of polypyridyl RuII,RhI species. Electrochemical and photophysical studies revealed a dpp-based LUMO in this RuII,RhI complex, suggesting dpp reduction upon photoexcitation. Photochemical study found that [(bpy)2Ru(dpp)RhCl(COD)](PF6)3 is an active photocatalyst for water reduction and that additional reduction(s) is (are) required after the generation of the RuII,RhI active species in the RuII,RhIII supramolecular photocatalytic H2 production system. This hypothesis was supported by the electrocatalytic behaviors of the RuII,RhIII supramolecular complexes for proton reduction. Cyclic voltammetry results in the presence of an acid suggested that the protonolysis of the RuII,RhIIH and RuII,RhIH species are electrocatalytic H2-evolution pathways. The mechanism is acid-dependent and influenced by terminal ligand. The studies of electrocatalytic proton reduction on these RuII,RhIII complexes suggested several possible intermediates involved in the photocatalytic water reduction cycle. The insights gained from this research can provide guidance in designing new type of RuII,RhIII and RuII,RhI complexes with better photocatalytic and/or electrocatalytic H2 production performance. / Ph. D.
248

The artist's role as collector of memory and self

Thomas, Lee Ann 11 1900 (has links)
Artworks that use found or appropriated images and objects often function as collections. These collections simulate the everyday collections of mementos and souvenirs that come to represent aspects of an individual's personality and past. The collections of objects mirror the individual's collection of memories that help to define himself and provide a means of communication with others. The artist as collector takes on roles similar to that of storyteller and anthropologist, providing a narrative of conscious preservation. Through various devices of display and denial a curiosity cabinet I Wunderkammer representing and simulating a Self is created and the role of collector is passed on to the viewer. / Art History, Visual Arts & Musicology / Thesis (M.A. (Art History))
249

Μελέτη ροϊκών φαινομένων για μεγιστοποίηση θερμανταλλαγής σε ολοκληρωμένο ηλιακό σύστημα συλλέκτη-αποθήκης / Flow field study for maximization of heat transfer in Integrated Collector Storage Solar System.

Γκέρτζος, Κωνσταντίνος 31 March 2008 (has links)
Τα ολοκληρωμένα ηλιακά συστήματα συλλέκτη αποθήκης αποτελούνται από μία δεξαμενή αποθήκευσης, της οποίας τμήμα της επιφάνειας της χρησιμοποιείται σαν ηλιακός συλλέκτης. Συνήθως το ρευστό της αποθήκης είναι το νερό χρήσης. Στο υπό εξέταση σύστημα το νερό χρήσης θερμαίνεται έμμεσα, διερχόμενο μέσα από σωληνώσεις εναλλάκτη θερμότητας που τοποθετείται στο εσωτερικό της παραλληλεπίπεδης δεξαμενής. Για την εντατικοποίηση της μετάδοσης θερμότητας προς το νερό χρήσης, δημιουργείται ανάδευση του ρευστού του δοχείου μέσω κυκλοφορητή, ο οποίος τίθεται σε λειτουργία μόνο όταν υπάρχει ζήτηση ζεστού νερού. Προς αποφυγή παραμορφώσεων τοποθετούνται πτερύγια συγκράτησης που ενώνουν τις δύο μεγάλες επιφάνειες της δεξαμενής. Στην παρούσα διδακτορική διατριβή διερευνήθηκαν τα ροϊκά φαινόμενα στο εσωτερικό του ICS που έχει περιγραφεί προηγουμένως, με στόχο τη μεγιστοποίηση της θερμανταλλαγής μεταξύ των δύο κυκλωμάτων νερού. Για την παρατήρηση του ροϊκού πεδίου καθώς και την λήψη μετρήσεων ταχυτήτων κατασκευάστηκε πειραματική συσκευή με διαφανή τοιχώματα από Plexiglas. Ελήφθησαν μετρήσεις ταχυτήτων και διακυμάνσεων με χρήση συστήματος Laser Doppler διπλής ακτίνας. Για την οπτικοποίηση του ροϊκού πεδίου τοποθετήθηκαν σωματίδια πολυστερίνης στο εσωτερικό της συσκευής. Ελήφθησαν ψηφιακές φωτογραφίες και βιντεοσκοπήσεις του ροϊκού πεδίου. Για την υπολογιστική προσομοίωση χρησιμοποιήθηκε το εμπορικό λογισμικό FLUENT. Αναπτύχθηκε υπολογιστικό μοντέλο και επιλύθηκε με όλα τα διαθέσιμα μοντέλα τύρβης. Στη συνέχεια πραγματοποιήθηκε σειρά υπολογιστικών προσομοιώσεων, στις οποίες διερευνήθηκε η βέλτιστη θέση και το μέγεθος των στομίων ανακυκλοφορίας, η βέλτιστη διάταξη των πτερυγίων συγκράτησης και η βέλτιστη θέση του εναλλάκτη. Επιπλέον προσδιορίστηκε υπολογιστικά και πειραματικά ο χρόνος αποκατάστασης του ροϊκού πεδίου. Τέλος, τα αποτελέσματα συγκρίθηκαν και με πειραματικά αποτελέσματα άλλων εργασιών. Τα συμπεράσματα που εξάγονται έχουν ως ακολούθως: Το μοντέλο τύρβης standard k-ω δίνει τα πιο αξιόπιστα αποτελέσματα. Το υπολογιστικό μοντέλο θεωρείται πιστοποιημένο μετά από πειραματική επιβεβαίωση ταχυτήτων και θερμοκρασιών. Το στόμιο ανακυκλοφορίας δεν πρέπει να τοποθετείται κάθετα στις μεγάλες επιφάνειες της δεξαμενής, ενώ η διάμετρος του πρέπει να είναι 1/2" ή και μικρότερη. Ο χρόνος αποκατάστασης του ροϊκού πεδίου είναι περίπου 35 s. Τα πτερύγια συγκράτησης πρέπει να ακολουθούν τις ροικές γραμμές. Ως βέλτιστη θέση του εναλλάκτη θεωρείται όταν τοποθετείται σε επαφή με το τοίχωμα. / Integrated Collector Storage (ICS) solar systems use part of the hot water storage as collector, i.e. half of the storage surface is used as absorber. Usually, the storage medium serves also as the energy transfer medium (service hot water). In the examined ICS, the service water is heated indirectly, passing through a serpentine heat exchanger placed inside the tank. The heat transfer from the stored water to the service water is intensified by the agitation of the stored water. A simple solution is the recirculation of the stored water by a small pump, which is functioning whenever a request for hot water exists. Fins in suitable positions, connect the front and back surface of the ICS, to withstand the deformation due to pressures by the tank water. In the present PhD thesis, the flow phenomena inside the ICS previous mentioned, are investigated. The aim is the maximization of the heat transfer between the two water circuits. An experimental device was constructed by transparent Plexiglas, for flow visualization and velocity measurements. A dual beam Laser Doppler Velocimetry (LDV) system was used to measure velocities. Polystyrene particles were added in the comprised water, for the visualization of the path lines. Photographs and video films were also taken. The commercial code FLUENT is used for the Computational Fluid Dynamics (CFD) simulations. A CFD model is developed and solutions are obtained using all the available turbulence models. Three main factors that influence the performance are optimized: the position and size of the recirculation ports, the arrangement and size of the interconnecting fins and the heat exchanger placement. The settling time, i.e., the time required for the flow field to be fully developed, is computed both numerically and experimentally. The previous analysis leads to the following conclusions: The standard k–ω model is selected as the most appropriate. The model is validated, with good agreement, against experimental measurements of velocities and temperatures. The placement of the inlet recirculation port perpendicular to the main surfaces of the ICS should be avoided, while its diameter should be 1/2" or less. The settling time is computed about 35s. The interconnecting fins, of the two main ICS surfaces should follow the flow filed path lines. The optimal placement of the tube heat exchanger is in contact with the two major surfaces of the storage tank.
250

The artist's role as collector of memory and self

Thomas, Lee Ann 11 1900 (has links)
Artworks that use found or appropriated images and objects often function as collections. These collections simulate the everyday collections of mementos and souvenirs that come to represent aspects of an individual's personality and past. The collections of objects mirror the individual's collection of memories that help to define himself and provide a means of communication with others. The artist as collector takes on roles similar to that of storyteller and anthropologist, providing a narrative of conscious preservation. Through various devices of display and denial a curiosity cabinet I Wunderkammer representing and simulating a Self is created and the role of collector is passed on to the viewer. / Art History, Visual Arts and Musicology / Thesis (M.A. (Art History))

Page generated in 0.055 seconds