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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.
41

Évaluation de la qualité environnementale, du fonctionnement énergétique des espaces batis à Madagascar : application des outils de simulation sur un site universitaire d’Antsiranana / Evaluation of environmental quality, energy operation spaces batis in madagascar : application of simulation tools on an Antsiranana university site

Ranjaranimaro, Manitra Pierrot 28 February 2019 (has links)
Le secteur du bâtiment participe à hauteur de plus de 50% de la consommation d’énergie à l’échelle mondiale. Cette consommation ne cesse d’augmenter depuis ces trente dernières années. L’impact environnemental de la consommation d’énergie au niveau de ce secteur est en évolution permanente malgré les recommandations prises durant les COP. Ces constatations sont valables pour la France métropolitaine et aussi pour le cas de Madagascar. Au-delà de la maitrise de la consommation d’énergie, en phase de fonctionnement d’un espace bâti, nous devons également prendre en compte les impacts environnementaux de la phase de construction notamment en ce qui concerne les indicateurs de changement climatique, des maitrises de ressources et de la pollution. Cette thèse s’articule autour de trois concepts. En premier lieu, il s’agit de l’analyse des flux matière autour de leurs caractéristiques techniques et de leurs impacts environnementaux et économiques lors de la construction de l’espace bâti. Dans un second temps, notre analyse se focalise sur l’analyse de flux d’énergie en vue de connaitre la signature énergétique et environnementale du fonctionnement de l’espace bâti et de la mise en œuvre d’un fichier horaire traduisant les caractéristiques de la consommation d’énergie (Profil de consommation journalier et annuel). En dernier lieu, nous abordons également la problématique du pilotage de la distribution de l’énergie électrique dans un espace bâti en vue de dimensionner un système de production d’EnR et un système de stockage et de lisser la courbe de consommation au niveau du réseau de distribution. / The building sector accounts for more than 50% of global energy consumption. This consumption has been increasing steadily over the last thirty years. The environmental impact of energy consumption in this sector is constantly changing despite the recommendations made during the COPs. These findings are valid for metropolitan France and also for Madagascar. Beyond the control of energy consumption, during the operating phase of a built space, we must also take into account the environmental impacts of the construction phase, particularly with regard to climate change indicators, resource management and pollution. This thesis is based on three concepts. First, it is about the analysis of material flows around their technical characteristics and their environmental and economic impacts during the construction of the built space. In a second step, our analysis focuses on the analysis of energy flows in order to know the energy and environmental signature of the functioning of the built space and the implementation of a time file reflecting the characteristics of energy consumption (Daily and annual consumption profile). Finally, we also discuss the problem of managing the distribution of electrical energy in a built-up area in order to size an renewable energy production system and a storage system and to smooth the consumption curve at the level of the distribution network.
42

Estudo computacional do perfil energético e dinâmica de reações químicas bimoleculares

PROENZA, Yaicel Gé 07 October 2016 (has links)
Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-24T19:39:36Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tesis Doutorado Yaicel 2016.pdf: 2623082 bytes, checksum: cafc3dec5768c69da2e77ed04124e96b (MD5) / Made available in DSpace on 2017-03-24T19:39:36Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tesis Doutorado Yaicel 2016.pdf: 2623082 bytes, checksum: cafc3dec5768c69da2e77ed04124e96b (MD5) Previous issue date: 2016-10-07 / Facepe / O mecanismo de várias reações químicas bimoleculares em fase gasosa foi analisado e interpretado usando a energética dos perfis de energia potencial combinado com a teoria estatística (RRKM) e a simulação de trajetórias quaseclássicas via dinâmica molecular de Born-Oppenheimer. Primeiramente, foi testado o desempenho de vários métodos da DFT (do inglês, density funcional theory) em relação ao método CCSD(T)/CBS na descrição tanto do perfil energético quanto da distribuição relativa de produtos iônicos para as reações X– + CH3ONO2 (X = F, OH e NCCH2) em fase gasosa. Na comparação, além dos critérios habituais baseados em desvios absolutos e relativos, foram usados critérios mais rigorosos como o intervalo de confiança estatístico e a capacidade dos funcionais em descrever as alturas de barreira relativas. Os funcionais duplo-híbridos (B2PLYP e B2GPPLYP) são os mais apropriados para estudos cinéticos e de seletividade. Em segundo lugar, foi discutido o mecanismo SN2 das reações HX– + CH3Y (X = O, S; Y = F, Cl, Br) em fase gasosa do ponto de vista dinâmico. As trajetórias de dinâmica quaseclássicas revelaram um forte comportamento não-estatístico para estas reações, em que o caminho de reação preferido não foi aquele sugerido pela coordenada intrínseca de reação (IRC, do inglês intrinsic reaction coordinate), ou seja, os complexos CH3XH⋯Y– (via ligação de hidrogênio) não foram observados. A análise dos perfis de energia potencial após o estado de transição não fornece uma racionalização que permita compreender o comportamento não-estatístico. No entanto, a análise do fluxo energético durante a dinâmica mostrou que as trajetórias quaseclássicas apresentam uma bifurcação em relação à energia rotacional e que a incapacidade de seguir o caminho da IRC surge dos períodos vibracionais para a flexão do modo X−CY serem longos, implicando em pouca energia rotacional nos fragmentos HXCH3. Por fim, o mecanismo e a seletividade das reações X– + CH3ONO2 (X = NCCH2, CH3COCH2 e PhCH2) em fase gasosa foram estudados para os canais ECO2, SN2@C e SN2@N. A concordância entre as distribuições relativas de produtos iônicos calculadas e experimentais foi quase perfeita, o que indicou a aplicabilidade das aproximações estatísticas tanto quanto a importância de considerar a regioseletividade dos nucleófilos ambidentados e a exploração detalhada da superfície de energia potencial na determinação de intermediários. / The mechanism of several bimolecular chemical reactions in the gas phase has been analyzed and interpreted by using the potential energy profiles along with the RRKM statistical theory and the simulation of quasiclassical trajectories via Born-Oppenheimer molecular dynamics. Firstly, the accuracy and robustness of several DFT (density functional theory) methods in describing the potential energy profiles and the ionic product distributions of the X– + CH3ONO2 (X = F, OH and NCCH2) gas phase reactions were compared to that of the CCSD(T)/CBS level of theory. In addition to the usual mean signed and unsigned deviations, this study used tighter criteria such as the statistical confidence interval and the consistency of the functionals to describe the relative barrier heights. The double-hybrid functionals (B2PLYP and B2GPPLYP) performed better for kinetics and selectivity. Secondly, the SN2 mechanism for the HX– + CH3Y (X = O, S; Y = F, Cl, Br) gas phase reactions is discussed from a dynamical point of view. The quasiclassical trajectories revealed a strong non-statistical behavior for these reactions, where the preferred reaction pathways did not follow the intrinsic reaction coordinate (IRC), i.e., the hydrogen bonded CH3XH⋯Y– postreaction complexes were not observed. The analysis of the potential energy profiles after the transition state does not provide a rationalization that allows us to understand the non-statistical behavior. However, the analysis of the energy flow during the dynamics showed that the quasiclassical trajectories cross a dynamical bifurcation related to the rotational energy on the system and that the inability to follow the IRC pathway arises from the long vibrational periods of the X−CY bending mode, implying a low fraction of rotational energy in the HXCH3 fragments. Finally, the ECO2, SN2@N and SN2@N mechanisms and selectivity of the X– + CH3ONO2 (X = NCCH2, CH3COCH2 e PhCH2) gas phase reactions have been investigated. The agreement between the calculated and experimental ionic products ratios was almost perfect, and indicated the reliability of the statistical approaches as well as the importance of considering the regioselectivity of ambidented nucleophiles and the detailed investigation of the potential energy surface to determine intermediates.
43

Emerging technologies for climate-neutral urban areas : An Industrial Ecology perspective

Papageorgiou, Asterios January 2021 (has links)
The ever-increasing concentration of human activity in urban areas induces environmental problems beyond their boundaries on scales ranging from local to regional to global, such as resource depletion, land degradation, air and water pollution and climate change. Human-induced climate change is widely acknowledged as one of the greatest sustainability challenges of the present century and it is inextricably linked to urbanization. As a response to climate change, urban areas around the world have committed to reach climate neutrality within the next decades. In this context, the deployment of new technologies can have a key role in achieving carbon neutrality in urban areas. As new technologies emerge, it is essential to assess their environmental performance considering the broader systems context in order to ensure that they can indeed contribute to achieving climate neutrality without compromising environmental sustainability. This thesis aims is to provide insight on the environmental performance of emerging technologies that can be deployed in urban areas in order to contribute to achieving climate neutrality. The two technologies in focus are grid-connected solar microgrids and biochar-based systems for treatment of biomass waste and remediation of contaminated soil. The methods applied to conduct the environmental assessments and fulfil the aim of the thesis are: case studies, Life Cycle Assessment (LCA), Material and Energy Flow Analysis and Substance Flow Analysis. Moreover, as part of the research efforts, a spreadsheet model based on LCA data was developed. The assessment of the solar microgrid highlighted the importance of using explicit spatial and temporal boundaries when analyzing the environmental performance of energy systems, as it can increase the accuracy of the results. It also revealed that the choice of modeling approach can influence the results of the assessment, which motivates the application of different methodological approaches. Within this context, the assessment showed that in a short-term perspective the integration of a grid-connected urban solar microgrid into the Swedish electricity grid would not contribute to climate change mitigation, as solar electricity from the microgrid would displace grid electricity with lower carbon intensity. The assessment also indicated that operational and structural changes in the microgrid could reduce its climate change impact, albeit not to the extent to generate GHG emission abatements. The assessment of the biochar-based systems showed that these systems have many environmental benefits compared to incineration of waste and landfilling of contaminated soil. They have great potential to contribute to achieving climate neutrality, as they can provide net negative GHG emissions, owing mainly to carbon sequestration in the biochar. Between the two biochar-based systems, a system for on-site remediation can provide additional environmental benefits, as it can lead to more efficient use of resources. However, these systems also entail environmental trade-offs due to increased consumption of auxiliary electricity, while the extent of ecological and human health risks associated with the reuse of biochar-remediated soils is for the moment unknown. / Den ständigt ökande koncentrationen av mänsklig aktivitet i urbana områden orsakar miljöproblem utanför deras gränser på skalor som sträcker sig från lokal till regional till global, såsom utarmning av resurser, markförstöring, luft- och vattenföroreningar och klimatförändring. Mänskligt driven klimatförändring är allmänt erkänd som en av de största hållbarhetsutmaningarna under nuvarande seklet och den är nära kopplad till urbanisering. Som ett svar på klimatförändringen har urbana områden runt om i världen åtagit sig att nå klimatneutralitet inom de närmaste decennierna. I detta sammanhang kommer införandet av ny teknik ha en nyckelroll för att uppnå klimatneutralitet i stadsområden. När ny teknik dyker upp är det viktigt att bedöma dess miljöprestanda med hänsyn till den bredare systemkontexten för att säkerställa att tekniken verkligen kan bidra till att uppnå klimatneutralitet utan att kompromissa med miljömässig hållbarhet. Denna avhandling syftar till att ge insikt om miljöprestanda för framväxande teknik som kan användas i urbana områden för att bidra till att uppnå klimatneutralitet. De två teknikerna i fokus är nätanslutna solmikronät och biokolbaserade system för behandling av biomassavfall och sanering av förorenad mark. Metoderna för att genomföra miljöbedömningarna och uppfylla avhandlingens syfte är: fallstudier, livscykelanalys (LCA), material- och energiflödesanalys och substansflödesanalys. Som en del av forskningsinsatserna utvecklades dessutom en kalkylmodell baserad på LCA-data. Analysen av solmikronätet visade att det är viktigt att använda explicita rums- och tidsgränser vid analys av energisystemens miljöprestanda, eftersom det kan öka resultatens noggrannhet. Analysen visade också att valet av modelleringsmetod kan påverka resultatet, vilket motiverar en användning  av flera olika metoder. Inom detta sammanhang visade bedömningen att i ett kortsiktigt perspektiv skulle integrationen av ett nätanslutet urbant solmikronät i det svenska elnätet inte bidra till att begränsa klimatförändringen, eftersom solenergi från mikronätet skulle ersätta el med lägre klimatpåverkan. Bedömningen indikerade också att operativa och strukturella förändringar i mikronätet kunde minska mikronätets klimatförändrings påverkan, om än inte i sådan utsträckning att det skulle ge växthusgasutsläppsbesparingar. Bedömningen av de biokolbaserade systemen visade att dessa system har många miljöfördelar jämfört med förbränning av avfall och deponering av förorenad mark. De har stor potential att bidra till att uppnå klimatneutralitet, eftersom de kan ge nettonegativa utsläpp av växthusgaser, främst på grund av kolbindning i biokol. Vi jämförelse av de två biokolbaserade systemen så kan ett system för sanering på plats ge ytterligare miljöfördelar, eftersom det kan leda till en mer effektiv resursanvändning. Dessa system medför emellertid också miljöavvägningar på grund av ökad förbrukning av elektricitet, medan omfattningen av ekologiska och människors hälsorisker förknippade med återanvändning av biokolbehandlad jord ännu är okända. / <p>QC 20210419</p>
44

Multi-scale approaches for the vibration and energy flow through piezoelectric waveguides : simulation strategies, control mechanisms and circuits optimization / Approches multi-échelles pour les vibrations et le transfert énergétique dans les guides d’ondes piézoélectriques : stratégies de simulation, mécanismes de contrôle et circuits d’optimisation

Fan, Yu 17 June 2016 (has links)
Cette thèse s’interesse au contrôle des flux d’énergie mécanique dans les structures périodiques. Les problèmes de dynamiques des structures considérés dans cette thèse sont abordés sous l'angle d'une description ondulatoire : la réponse forcée d’un système est calculée comme une superposition d’ondes dans la structure, tandis que les modes propres sont interprétés comme des ondes stationnaires.Un des avantages de l’approche ondulatoire est qu’elle permet de réduire de manière importante la taille des problèmes de dynamique. Ceci se révèle particulièrement utile dans le domaine des hautes et moyennes fréquences, où les calculs par éléments finis deviennent très coûteux en temps à cause du grand nombre de degrés de liberté nécessaire à la convergence du modèle. Afin de contourner ce problème, cette thèse s'appuie sur la méthode des éléments finis ondulatoires (Wave Finite Element Method (WFEM)). Une des principales améliorations proposées est l’utilisation de plusieurs méthodes de synthèses modales (Component Mode Synthesis (CMS)) pour accélérer l’analyse des guides d’ondes généraux en présence d’amortissement ou de matériaux piézo-électriques. Les erreurs numériques restent faibles du fait de l’utilisation d'une base de projection réduite constituée d'ondes propagatives. Une autre contribution est le procédé de modélisation multi-échelle pour les assemblages de structures périodiques et non-périodiques. L’idée principale est de modéliser les parties non-périodiques par la méthode des éléments finis, et les parties périodiques par WFEM. Les interactions entre les différentes sous-structures sont modélisées par des coefficients de réflexion ou des impédances mécaniques. Ces travaux réalisent une extension de la WFEM à des structures plus complexes et plus proches des applications industrielles. Un autre intérêt de la vision ondulatoire est qu’elle mène à de nouvelles idées pour le contrôle des vibrations. Dans cette thèse, des matériaux piézo-électriques et des circuits de shunt, distribués de façon périodique sont utilisés afin de modifier artificiellement la propagation des ondes grâce au couplage électromécanique. Un nouveau critère, nommé « Wave Electromechanical Coupling Factor (WEMCF) », est proposé pour évaluer, en termes énergétiques, l’intensité du couplage entre le champ électrique et le champ mécanique lors du passage d'une onde. Ce facteur peut être obtenu à partir des caractéristiques ondulatoires obtenues par la WFEM. On montre que le WEMCF est fortement lié à l'atténuation dans le guide d’ondes piézo-électrique. La conception des paramètres géométriques et électriques peut être ainsi être effectuée séparément. Ce principe est appliqué à la réduction des vibrations d’une poutre encastrée. Le WEMCF est utilisé comme fonction objectif pour l'optimisation durant la conception géométrique, la masse totale de matériau piézo-électriques étant contrainte. Un circuit à capacité négative est utilisé pour élargir le band-gap de Bragg. La stabilité du système est prise en compte comme une contrainte sur la valeur de cette capacité. Les vibrations sont localisées et facilement dissipées par l’introduction d’absorbeurs sur la frontière. Ce procédé de conception basée sur une approche ondulatoire aboutit à des solutions stables, légères, et insensibles aux conditions aux limites dans une large gamme de fréquence. Par conséquent, il est prometteur pour analyser les structures en moyenne et haute fréquence où il est difficile d’accéder aux informations modales exactes. / This thesis describes analysis and control approaches for the vibration and energy flow through periodic structures. The wave description is mainly used to address the structural dynamic problems considered in the thesis: forced response is calculated as the superposition of the wave motions; natural modes are understood as standing waves induced by the propagating waves that recover to the same phase after traveling a whole circle of the finite structure. One advantage of the wave description is that they can remarkably reduce the dimensions of structural dynamic problems. This feature is especially useful in mid- and high frequencies where directly computing the full Finite Element Method (FEM) model is rather time-consuming because of the enormous number of degree-of-freedoms. This thesis extends one widely used wave-based numerical tool termed Wave Finite Element Method (WFEM). The major improvements are the use of several Component Mode Synthesis (CMS) methods to accelerate the analysis for general waveguides with proportional damping or piezoelectric waveguides. The numerical error is reduced by using the proposed eigenvalue schemes, the left eigenvectors and the reduced wave basis. Another contribution is the multi-scale modeling approach for the built-up structures with both periodic and non-periodic parts. The main idea is to model the non-periodic parts by FEM, and model the periodic parts by WFEM. By interfacing different substructures as reflection coefficients or mechanical impedance, the response of the waveguide is calculated in terms of different scales. These two contributions extend WFEM to more complex structures and to more realistic models of the engineering applications.Another benefit of the wave perception is that it leads to new ideas for vibration control. In this thesis periodically distributed piezoelectric materials and shunt circuit are used to artificially modify the wave properties by electric impedance. A novel metrics termed the Wave Electromechanical Coupling Factor (WEMCF) is proposed, to quantitatively evaluate the coupling strength between the electric and mechanical fields during the passage of a wave. This factor can be post-processed from the wave characteristics obtained from WFEM through an energy formula. We show that WEMCF is strongly correlated to the best performance of the piezoelectric waveguide. Hence the design for the geometric and electric parameters can be done separately. An application is given, concerning the vibration reduction of a cantilever beam. WEMCF is used as an optimization objective during the geometric design, when the overall mass of the piezoelectric materials is constrained. Then the negative capacitance is used with a stability consideration to enlarge the Bragg band gap. The vibration is localized and efficiently dissipated by few boundary dampers. The wave-based design process yields several broadband, stable, lightweight and boundary condition insensitive solutions. Therefore, it is promising at mid- and high frequencies where exact modal information is difficult to access.
45

Sledování environmentálních nákladů v Kovohutích Příbram nástupnická, a.s. / Monitoring Environmental Costs in KOVOHUTĚ PŘÍBRAM nástupnická, a.s.

Kvapilová, Jana January 2009 (has links)
Environmental managerial accounting is one of voluntary tools of environmental policy. It helps company to recognize its influence on environment and it is a base for environmental management decision-making, which brings environmental and economical results. EMA consists from two parts. The first is input/output balance of materials and energies and the second is a statement of environmental costs and revenues. Environmental accounting evaluates financial and physical information. Statements show in which domain there is the biggest influence on environment. Target of this work has been to implement this accounting in the company Kovohutě Příbram nástupnická, a.s. It is a long process, which needs cooperation of many employees of company. In the process of identification of environmental costs there were defined facilities, which protect or injure environment. Costs with influence on environment were described as environmental costs. On the base of environmental statements company is able to make decisions, which will lead to cleaner production
46

Towards sustainable urban transportation : Test, demonstration and development of fuel cell and hybrid-electric buses

Folkesson, Anders January 2008 (has links)
Several aspects make today’s transport system non-sustainable: • Production, transport and combustion of fossil fuels lead to global and local environmental problems. • Oil dependency in the transport sector may lead to economical and political instability. • Air pollution, noise, congestion and land-use may jeopardise public health and quality of life, especially in urban areas. In a sustainable urban transport system most trips are made with public transport because high convenience and comfort makes travelling with public transport attractive. In terms of emissions, including noise, the vehicles are environmentally sustainable, locally as well as globally. Vehicles are energy-efficient and the primary energy stems from renewable sources. Costs are reasonable for all involved, from passengers, bus operators and transport authorities to vehicle manufacturers. The system is thus commercially viable on its own merits. This thesis presents the results from three projects involving different concept buses, all with different powertrains. The first two projects included technical evaluations, including tests, of two different fuel cell buses. The third project focussed on development of a series hybrid-bus with internal combustion engine intended for production around 2010. The research on the fuel cell buses included evaluations of the energy efficiency improvement potential using energy mapping and vehicle simulations. Attitudes to hydrogen fuel cell buses among passengers, bus drivers and bus operators were investigated. Safety aspects of hydrogen as a vehicle fuel were analysed and the use of hydrogen compared to electrical energy storage were also investigated. One main conclusion is that a city bus should be considered as one energy system, because auxiliaries contribute largely to the energy use. Focussing only on the powertrain is not sufficient. The importance of mitigating losses far down an energy conversion chain is emphasised. The Scania hybrid fuel cell bus showed the long-term potential of fuel cells, advanced auxiliaries and hybrid-electric powertrains, but technologies applied in that bus are not yet viable in terms of cost or robustness over the service life of a bus. Results from the EU-project CUTE show that hydrogen fuelled fuel cell buses are viable for real-life operation. Successful operation and public acceptance show that focus on robustness and cost in vehicle design were key success factors, despite the resulting poor fuel economy. Hybrid-electric powertrains are feasible in stop-and-go city operation. Fuel consumption can be reduced, comfort improved, noise lowered and the main power source downsized and operated less dynamically. The potential for design improvements due to flexible component packaging is implemented in the Scania hybrid concept bus. This bus and the framework for its hybrid management system are discussed in this thesis. The development of buses for a more sustainable urban transport should be made in small steps to secure technical and economical realism, which both are needed to guarantee commercialisation and volume of production. This is needed for alternative products to have a significant influence. Hybrid buses with internal combustion engines running on renewable fuel is tomorrow’s technology, which paves the way for plug-in hybrid, battery electric and fuel cell hybrid vehicles the day after tomorrow. / QC 20100722

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