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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.
61

Utvärderingsmetod av transportalternativ till komplexa anläggningar : En fallstudie på Svensk Kärnbränslehantering AB / Evaluation method of transport alternatives for complex facilities : A case study at Svensk Kärnbränslehantering AB

Hallenborg, Jesper, Häll, Hugo January 2021 (has links)
I vårt samhälle idag finns ett större energibehov än någonsin förr. För att förse detta energibehov har vi i Sverige en mängd olika sorters kraftverk. Alla sorters energikraftverk har sina nackdelar och fördelar. För just kärnkraftverk är en stor nackdel det radioaktiva avfallet som uppstår vid energiproduktion. I detta arbete har vi studerat en liten del av det stora projektet att förvara detta radioaktiva avfall, vilket bedrivs av företaget SKB, Svensk Kärnbränslehantering AB. Det slutförvar som kommer byggas har i uppgift att isolera det radioaktiva avfallet från miljö och samhälle.  En del av verksamheten i detta slutförvar är transport av bentonitmaterial, som är en typ av lermaterial. Bentonitens uppgift i detta fall är att försluta hål och tunnlar där det radioaktiva avfallet förvaras, 500 meter ner i berget. Vi har i denna studie tagit fram en utvärderingsmodell för att undersöka två transportalternativ för bentonit under jord, där vi främst studerat hur de skiljer sig i aspekt av: Energianvändning Start- och driftkostnad Tid De transportalternativ som studerats är transport med lastbil och transport med skip, som är en typ av gruvhiss. Slutsatsen vi kommit fram till är att lastbilstransport är det mer passande alternativet för den verksamhet SKB kommer att bedriva. Den övervägande styrkan av en skip är den höga hastighet den kan arbeta i, vilket i detta slutförvar inte är en nödvändig egenskap. Genom att i detalj studera den mängd material som ska flyttas samt de unika egenskaper båda transportalternativ besitter, har en jämförelse av olika aspekter kunnat utföras. Denna jämförelse har varit grund för de resultat och slutsatser vi kommit fram till. Resultatet vi presenterat kan användas som referensram för beslut gällande bentonittransporter då SKB’s slutförvar går i drift. / In our society today, the need for energy is greater than ever before. In order to supply this growing demand, Sweden uses a variety of power plants. All kinds of power plants have their advantages and disadvantages. For nuclear power plants in particular, a major disadvantage is the radioactive waste that arises during energy production. In this case study we have examined a small part of the large project to store the radioactive waste, which is run by the company SKB, Svensk Kärnbränslehantering AB. The final repository that is currently being planned has the task to isolate the radioactive waste from the environment and society.  A part of the operation in the final repository is the transport of the material bentonite, which is a type of clay. The bentonite's main function is, in this case, to seal the deposition areas where the radioactive waste is stored. Moreover, the material is stored 500 meters down into the bedrock. In this study, we have developed an evaluation method in order to examine two different means to transport bentonite underground, with focus on how they differ in aspects of: Energy consumption Startup- and operational costs Time The two alternatives for transportation that have been studied are trucks and skip, which is a type of mine elevator. Our conclusion is that transport by truck is the more suitable alternative for the operation that SKB will conduct. The predominant strength of a skip is the high speed it can operate at, which in this final repository is not a necessary feature. By studying the amount of material that needs to be moved, and the unique properties of both alternatives for transportation, a comparison of the different aspects has been made. This comparison has been the basis of the results achieved and the conclusions that have been reached. The results presented in this study can be used as a reference framework for decisions regarding how bentonite will be transported when SKB’s final repository goes operational.
62

Numerical Investigation of High Strength Structural Steel Gravity Columns at Elevated Temperature

Akhtar, Mohammad Farhan January 2020 (has links)
No description available.
63

Finite Element Analysis of a Femur to Deconstruct the Design Paradox of Bone Curvature

Jade, Sameer 01 January 2012 (has links) (PDF)
The femur is the longest limb bone found in humans. Almost all the long limb bones found in terrestrial mammals, including the femur studied herein, have been observed to be loaded in bending and are curved longitudinally. The curvature in these long bones increases the bending stress developed in the bone, potentially reducing the bone’s load carrying capacity, i.e. its mechanical strength. Therefore, bone curvature poses a paradox in terms of the mechanical function of long limb bones. The aim of this study is to investigate and explain the role of longitudinal bone curvature in the design of long bones. In particular, it has been hypothesized that curvature of long bones results in a trade-off between the bone’s mechanical strength and its bending predictability. This thesis employs finite element analysis of human femora to address this issue. Simplified human femora with different curvatures were modeled and analyzed using ANSYS Workbench finite element analysis software. The results obtained are compared between different curvatures including a straight bone. We examined how the bone curvature affects the bending predictability and load carrying capacity of bones. Results were post processed to yield probability density functions (PDFs) for circumferential location of maximum equivalent stress for various bone curvatures to assess the bending predictability of bones. To validate our findings on the geometrically simplified ANSYS Workbench femur models, a digitally reconstructed femur model from a CT scan of a real human femur was employed. For this model we performed finite element analysis in the FEA tool, Strand7, executing multiple simulations for different load cases. The results from the CT scanned femur model and those from the CAD femur model were then compared. We found general agreement in trends but some quantitative differences most likely due to the geometric differences between the digitally reconstructed femur model and the simplified CAD models. As postulated by others, our results support the hypothesis that the bone curvature is a trade-off between the bone strength and its bending predictability. Bone curvature increases bending predictability at the expense of load carrying capacity.
64

Intégration du concept de capacité de support d’un plan d’eau aux apports en phosphore à l’aménagement du territoire au Québec : Réalité ou utopie?

Laniel, Mélissa 12 1900 (has links)
Ce mémoire a comme objectif de présenter une revue de la littérature et une analyse comparative des différents modèles existants pour le calcul de la capacité de support d’un plan d’eau aux apports en phosphore. Ce document a aussi pour but d’évaluer les différentes options pour l’utilisation de ce genre d’outil au Québec, ainsi que d’amorcer une réflexion sur les applications possibles de ce concept au niveau local, en lien avec l’aménagement du territoire des bassins versants. L’analyse comparative des modèles théoriques, combinée à la réflexion d’acteurs clés impliqués actuellement dans un processus qui consiste à tester leur utilisation dans les Laurentides au Québec, a permis de mettre en relief l’importance de calibrer les modèles régionalement. De plus, certains avantages semblent résider dans l’utilisation d’un modèle de nature empirique afin d’effectuer les prédictions sur les apports naturels et totaux en phosphore pour les lacs de cette région. Par contre, l’utilisation d’une approche de type « bilan de masse », s’avère tout de même indispensable afin de relativiser l’importance des différents apports anthropiques en phosphore du bassin versant. Dans l’avenir, l’utilisation de tels modèles permettra possiblement de justifier certaines mesures restrictives au développement des bassins versants, qui pourront s’insérer parmi les outils d’urbanisme actuels. Ce sont principalement les municipalités qui détiennent les pouvoirs nécessaires afin d’intégrer les prescriptions découlant de ce genre d’analyse à l’aménagement du territoire des bassins versants. Plusieurs outils d’urbanisme, tels que les plans d’aménagement d’ensemble (PAE) ou bien les règlements de zonage et de lotissement, semblent donner assez de latitude afin de permettre aux municipalités d’intervenir en ce sens. Toutefois, les modèles de capacité de support ne pourront pas être utilisés afin de calculer un nombre précis d’habitations qu’il est possible de construire dans le bassin versant d’un lac. / This study presents a literature review of current carrying capacity models developed in Ontario and Quebec (Canada) for the estimation of phosphorus (P) loading in lakes. Another objective is to evaluate their applications to land and watershed management practices in Quebec. A comparison of theoretical and empirical models, combined with the observations of keys stakeholders, confirms the importance of calibrating models regionally. The analysis further reveals that empirical models estimate more accurately P concentrations in lakes. However, the use of traditional mass balance approaches is still a necessity for the estimation of different P sources in the watershed. These models can support decision makers and land managers in Quebec in the application of more restrictive measures in lakes where the carrying capacity is currently exceeded. In Quebec, the use of the models and their implementation in the legislation will be a municipal responsibility. Many urbanism tools already allow this kind of intervention (zoning, « outils à caractère discrétionnaire »). But, model use alone will not be sufficient to justify a total interdiction of land development in a watershed or to impose a strict limit to house and cottage development.
65

Ekologické determinanty klonálního růstu rostlin / Ecological determinants of plant clonal growth

Martincová, Nina January 2016 (has links)
The aim of this study is to provide a further insight into influence of environment on clonal plants. The study focuses particularly on effects of fertilization level and light availability on production and growth of clonal organs. Three experiments were carried out within the study, targeted to elicit influence of these environmental conditions or clonal interactions on six species of clonal plants. Interspecies dependencies on these conditions was compared, regarding habitat occurrence of these species. A comparison was made also between species producing rhizomes and stolons. The experiments revealed that five of six studied species show significant relationship among at least one environmental condition and parameters of clonal reproduction. Most of the species showed higher elongation and production of clonal organs in relation to fertilization level. On the contrary, only three species reacted significantly to the light availability level by alternation of at least one parameter of clonal reproduction and the light availability level affected each species differently. A strong influence on production and elongation of clonal organs had also a size of a plant. There was not found significant difference in influence of environmental conditions on clonal reproduction among plant families. It...
66

Sozioökonomische Rahmenbedingungen und Landnutzung als Bestimmungsfaktoren der Bodenerosion in Entwicklungsländern - Eine überregionale empirische Analyse im Kontext der Agrarentwicklung

Morgenroth, Silvia 06 September 1999 (has links)
Trotz des erheblichen Ausmaßes der Bodenerosion in vielen Entwicklungsländern ist bislang weitgehend unklar, welches ihre wesentlichen anthropogenen Ursachen sind, und damit auch, wo Politiken und Maßnahmen für den Erhalt der Nahrungs- und Produktionsressource Boden ansetzen sollten. Jenseits unmittelbarer natürlicher und landnutzerischer Ursachen stehen heute sozioökonomische Faktoren im Mittelpunkt der Diskussion, von denen angenommen wird, daß sie die Anbau- und Bodenschutzentscheidungen der Landnutzer und darüber das Ausmaß an Bodenerosion beeinflussen, insbesondere: (i) verstärkte Armut, (ii) zunehmender Bevölkerungsdruck, (iii) verzerrte Agrarpreise, (iv) unangepaßter technischer Fortschritt sowie (v) unsichere Landbesitzverhältnisse. Der Bedeutung dieser Bestimmungsfaktoren wird vorwiegend im Rahmen produktionsökonomischer Ansätze und der Theorie der Induzierten Innovation nachgegangen. Allerdings wird die Wirkung einzelner Ursachen in der Literatur sehr unterschiedlich eingeschätzt. So wird beispielsweise in eher optimistischen Szenarien davon ausgegangen, daß Armuts- und Bevölkerungsdruck langfristig zur Entwicklung und Verbreitung bodenschonender Innovationen führen. In negativen Szenarien überwiegen hingegen Stimmen, die gerade in diesem Druck bei gleichzeitigem Preisdruck die wesentlichen Ursachen für die kurzsichtige Übernutzung des Bodens sehen. Empirische Studien zur Fundierung der kontrovers diskutierten Hypothesen liegen bislang nur für einen jeweils begrenzten lokalen Kontext vor und sind kaum verallgemeinerbar. Vor diesem Hintergrund bieten die Daten der ersten weltweiten Erhebung zum Stand der Bodenerosion (GLASOD, UNEP/ISRIC, 1991) nunmehr die Möglichkeit, sozioökonomische und landnutzerische Determinanten der Bodenerosion auf überregionaler Ebene empirisch zu untersuchen. Anhand der Aggregation und Analyse der im GLASOD enthaltenen Informationen wird zunächst deutlich, daß Afrika und Südostasien flächenmäßig mit jeweils rd. 4,5 Mio km2 am meisten zur Degradation durch Bodenerosion und Nährstoffverluste[1] in Entwicklungsländern beitragen, während der Anteil erodierter Fläche an der jeweiligen Gesamtfläche des Subkontinents[2] in Südwestasien (37%), Mittelamerika und Südostasien (jeweils rd. 25%) am höchsten ist. Extrem stark erodierte Länder finden sich v.a. in Mittelamerika und Afrika: In El Salvador, Haiti und Costa Rica sind zwischen 60% und 90% der jeweiligen Landesfläche betroffen. In Afrika sind vor allem die nord- und westafrikanischen Sahelländer Tunesien, Mauretanien, Libyen, Niger, Burkina Faso und Mali, im Osten die Hochlandstaaten Burundi und Rwanda sowie schließlich die Kapverdischen Inseln, besonders stark erodiert (40% bis 80% der Landesfläche). Wassererosion hat den größten Anteil an der Erosionsfläche, in Mittelamerika und Südostasien sind sogar mehr als 70% der erodierten Fläche von Wassererosion betroffen. Für die empirische Analyse der Zusammenhänge zwischen Bodenerosion und möglichen Bestimmungsfaktoren wird ein exploratives, ökonometrisches Vorgehen auf Grundlage nationaler Daten gewählt[3]. Die spezifische Aufeinanderfolge verschiedener Korrelations-, Faktoren- und Regressionsanalysen wird der großen Anzahl in Frage kommender Indikatorvariablen für mögliche Erosionsdeterminanten sowie den zu erwartenden Problemen der Multikollinearität und Modellspezifizierung in besonderem Maße gerecht. Letztere ergeben sich einerseits aus anzunehmenden Abhängikeiten unter verschiedenen Erosionsdeterminanten. Andererseits macht der latente Charakter[4], den die aus einem mikroökonomischen Kontext abgeleiteten Erosionsursachen auf aggregierter Ebene haben, es notwendig, für jede der angenommenen Determinanten verschiedene, u.U. korrelierte Indikatorvariablen zu definieren, was zusätzlich Kollinearität bedingt. Für Bodenerosion werden auf der Basis der national aggregierten GLASOD-Daten verschiedene Erosionsindizes definiert, die prinzipiell den von Wasser- und Winderosion sowie durch Nährstoffverluste betroffenen Anteil der nutzbaren Landesfläche wiedergeben. Die Datengrundlage für mögliche Erosionsdeterminanten wird ausgehend von Datensammlungen internationaler Organisationen für den Zeitraum 1961-1990 zusammengestellt. Für eine große Anzahl der in der Literatur diskutierten sozioökonomischen, landnutzerischen und auch natürlichen Rahmenbedingungen können repräsentative Indikatorvariablen definiert werden. Mangels geeigneter Indikatoren und Daten bleiben allerdings die Art und Sicherheit der Landbesitzverhältnisse unberücksichtigt. Insgesamt umfaßt die Datengrundlage rund 150 Variablen. Die Ergebnisse der Einfachkorrelationsanalysen zwischen den Erosionsindizes und möglichen Determinanten dienen einer ersten Einschätzung der Zusammenhänge. Sie zeigen, daß länderübergreifend insbesondere Variablen des Bevölkerungsdrucks sowie der durchschnittliche Waldanteil mit dem Ausmaß Bodenerosion in Zusammenhang stehen. Die Abholzungsraten in den 80er Jahren sind vor allem mit dem Ausmaß der Wassererosion korreliert. Bei Betrachtung der Länder mittleren Klimas[5] können Zusammenhänge mit Variablen nachgewiesen werden, die die Landnutzungsintensität und die Ausdehnung der tatsächlichen Nutzfläche in Relation zur potentiellen Nutzfläche wiedergeben. Weiterhin stehen in der mittleren Klimazone tendenziell sinkende Produzentenpreise für Agrarprodukte in Zusammenhang mit dem Ausmaß der Erosion. Erwartungsgemäß ist die Bedeutung natürlicher Faktoren für einzelne Erosionsformen und Klimazonen charakteristisch. Insgesamt scheinen Variablen, die das Ergebnis einer vermutlich längerfristigen Entwicklung wiedergeben, mehr Bedeutung für das Ausmaß der Erosion zu haben als solche, die Veränderungen im Referenzzeitraum 1961-1990 erfassen. Anhand verschiedener Faktorenanalysen für 62 Variablen und 73 Länder mit annähernd vollständigen Datensätzen können sodann strukturelle Zusammenhänge unter der Vielzahl möglicherweise relevanter Erosionsdeterminanten aufgedeckt und die Variablenanzahl auf Grundlage dieser Zusammenhänge auf eine geringere Anzahl weitgehend voneinander unabhängiger Größen reduziert werden. Es zeigt sich, daß die Struktur der Variablen durch etwa zehn gut interpretierbare Faktoren bei rd. 75% erklärter Gesamtvarianz klar wiedergegeben werden kann, und daß diese Faktoren auch bei Variation der Ausgangsvariablen sowie der Faktorextraktions- und Rotationsmethode stabil bleiben. Bemerkenswert ist, daß viele der Faktoren einen deutlichen Bezug zu den in der Literatur diskutierten Wirkungsketten unter möglichen Erosionsdeterminanten haben. So werden in dem für die Erklärung der Gesamtvarianz wichtigsten Faktor Variablen gebündelt, die die langfristige Intensivierung der Landnutzung im Zusammenhang mit strukturellem Bevölkerungsdruck und begrenzter Verfügbarkeit landwirtschaftlich nutzbarer Flächen erfassen. Weitere wichtige Faktoren beziehen sich auf strukturelle Armut in Verbindung mit erhöhtem ländlichen Bevölkerungswachstum; auf die mit Bevölkerungsdruck einhergehende langfristige wie auch rezente Expansion der landwirtschaftlichen Nutzfläche und Abholzung von Naturwald; auf Entwicklungswege, die eher auf die Produktion hochwertiger Produkte statt auf eine Flächenexpansion abzielen. Für die Preisentwicklung im Referenzzeitraum kann anhand einer Faktorenanalyse mit reduzierter Länderanzahl[6] gezeigt werden, daß ein Zusammenhang zwischen langfristig geringen oder negativen Preiszuwächsen im Agrarsektor und dem Faktor "Rezente Abholzungsraten" besteht. Um die relative Bedeutung dieser Faktoren für Bodenerosion zu quantifizieren, werden schrittweise Regressionsanalysen mit Bodenerosion als abhängiger Variablen und ausgewählten Repräsentantenvariablen für jeden Faktor als angenommenen unabhängigen Variablen durchgeführt[7]. Es lassen sich drei besonders relevante anthropogene Entwicklungen identifizieren, anhand derer das Erosionsausmaß bis zu rund 75% erklärt werden kann: (1) die langfristige, historische Ausdehnung der landwirtschaftlichen Nutzfläche auf Kosten des Waldbestandes in Zusammenhang mit einem Gesamtbevölkerungsdruck, der gegen Ende der 80er Jahre die agrar-ökologische Tragfähigkeit überschreitet; (2) die rezente Abholzung von Naturwald, die in Zusammenhang mit dem Wachstum der Gesamtbevölkerung zu sehen ist. Hier scheinen weniger der Druck der Agrarbevölkerung und die Ausdehnung der landwirtschaftlichen Nutzfläche - also die Produktionsseite - im Vordergrund zu stehen, als vielmehr der Druck der Nachfrageseite, in Kombination mit einem tendenziell sinkenden Agrarpreisniveau, das den Expansionsdruck auf das Land verstärkt hat. (3) Die langfristige, bevölkerungsdruckinduzierte Intensivierung der Agrarproduktion, vor allem durch Umwandlung von Dauergrünland in Ackerland, verkürzte Brachezeiten und erhöhte Viehbesatzdichten. Ein weiteres Ergebnis ist, daß in keinem Fall ein wesentlicher Einfluß von Armut auf das landesweite Ausmaß der Bodenerosion nachgewiesen werden kann - wie bereits die Ergebnisse der Einfachkorrelationsanalysen für immerhin 15 verschiedene Armutsindikatoren vermuten lassen. Es bestehen Unterschiede in den Erklärungsmustern für verschiedene Erosionsformen und Klimazonen. Die rezenten Abholzungsraten haben für Wassererosion, insbesondere in Ländern der extrem humiden Klimazone, herausragende Bedeutung. Zusätzlich zu den Faktoren (1) und (2) ist die Intensität der landwirtschaftlichen Produktion (3) vor allem für Wassererosion und in Ländern der mittleren Klimazone von Bedeutung. Hier ist auch die negative Wirkung einer sinkenden Agrarpreisentwicklung am stärksten. Gleichzeitig gilt hier: je eher der eingeschlagene Entwicklungsweg auf die Produktion hochwertiger Produkte im Gegesatz zur reinen Flächenexpansion abzielt, desto geringer ist das Erosionsausmaß. Für das Ausmaß der Winderosion und der Degradation durch Nährstoffverluste hingegen sind insbesondere die agroklimatischen Bedingungen ausschlaggebend. Die als erosionsrelevant identifizierten anthropogenen Rahmenbedingungen sind mit zentralen theoretischen Hypothesen konsistent. Fraglos gehören sie eher zu den Größen, deren kurzfristige Beeinflussung durch politische Maßnahmen schwierig ist. Dennoch können folgende Ansätze für eine Schwerpunktsetzung bei der Gestaltung von Politikmaßnahmen zur wirksamen Erosionsverminderung abgeleitet werden: Die Reduktion des Bevölkerungsdrucks durch eine an die natürlichen Bedingungen und relativen Faktorknappheiten angepaßte Erhöhung des Produktionspotentials, gerade auch in Regionen mit relativ niedrigem Potential. Eine stärkere Fokussierung auf Forstpolitiken bzw. auf eine Regulierung der kommerziellen Nutzung von Wäldern, vor allem in humiden Klimazonen. .Eine selektive, langfristig angelegte Verbesserung der incentive-Struktur für bodenschonende Produkte und Anbaumethoden über wirtschaftspolitische Eingriffe sowie durch verbesserte institutionelle und rechtliche Rahmenbedingungen. Von Politiken zur Armutsbekämpfung ist hingegen nicht zu erwarten, daß sie maßgebliche Impulse zur Verminderung der Bodenerosion geben können. Es muß jedoch immer präsent bleiben, daß arme Landnutzer sicherlich am stärksten und häufig existentiell von Erosionsschäden betroffen sind. Die Qualität zukünftiger Forschungsbemühungen auf globaler Ebene wird vor allem von der zukünftigen Datenverfügbarkeit und -qualität bestimmt: Für den Stand der Bodenerosion sind Informationen für verschiedene Zeitpunkte erforderlich; für anthropogene Erosionsdeterminanten eröffnen georeferenzierte Daten der Forschung gänzlich neue Perspektiven. Parallel zu überregionalen Analysen sind weitere lokale, sub-nationale Studien unbedingt notwendig, um umfassend zu ergründen, warum und welche Landnutzer die Ressource Boden in einem konkreten sozioökonomischen Kontext degradieren. Fußnoten: [1]Neben der Wasser- und Winderosion wird eine weitere Degradationsform, der Verlust von Nährstoffen und organischer Substanz, mitberücksichtigt und vereinfachend mit "Nährstoffverluste" bezeichnet.[2]Gemeint ist die nutzbare Landesfläche, Ödland ausgenommen. [3]Georeferenzierte Daten liegen derzeit für sozioökonomische Erosionsdeterminanten noch nicht vor.[4]D.h. Größen, von denen a priori nicht bekannt ist, wie sie beobachtet und gemessen werden können. [5]Dies sind Länder, in denen weder extrem aride noch extrem humide Bedingungen vorherrschen. [6]Für die entsprechende Variable liegen nur Daten für 56 Länder vor.[7]Umgekehrte Wirkungen der Erosion auf die als unabhängig angenommenen anthropogenen Variablen sind im Betrachtungszeitraum - bis auf die Armutswirkung starker Erosion - unwahrscheinlich. / By the end of this century, soil erosion has reached an alarming extent in many developing countries. Still, uncertainty prevails regarding the human-induced causes of soil erosion. In consequence, many efforts to design efficient anti-erosion policies and instruments remain erratic. The actual discussion about human-induced causes of soil erosion focusses on socioeconomic factors that assumably influence the land users´ decisions on agricultural production and soil protection, and, hence, the degree of soil erosion. The most frequently discussed factors are: (i) poverty, (ii) population pressure, (iii) biased agricultural prices, (iv) the introduction of inadequate technical innovations and (iv) insecurity of land tenure. They are basically deduced from and discussed on base of production theory and the theory of induced innovation. Nevertheless, the different views on the importance to be assigned to the single factors are quite controverse. For example, in a rather optimistic scenario, it is argued that poverty and population pressure lead to the development of soil-conserving innovations in the long run. On the other side, poverty and population pressure, in combination with falling agricultural prices, are assumed to lead to a short-termist overuse of the soil. Empirical evidence that supports some of the controverse hypotheses on the causes of soil erosion is restricted to local studies based on local data on soil erosion, their results can hardly be generalized. In this context, the spatial data compiled within the global assessment of human-induced soil degradation (GLASOD; UNEP/ISRIC, 1991) for the first time permits a large-scale empirical analysis of socioeconomic and landuse factors relevant to erosion. By aggregating the information of the GLASOD data, countries and regions whith marked soil erosion can be identified. While Africa and Asia most contribute to the extent of soil erosion and the loss of nutrients[8] in absolute terms (4,5 mio sqkm each), it is in Southwest Asia (37%), Central America and Southeast Asia (25% each), where the proportion of of the land area - excluding wastelands - that is affected reaches the highest levels. Looked at on a national level, countries with an extreme extent of soil erosion are to be found in Central America and Africa: In El Salvador, Haiti and Costa Rica, 60 to 90 percent of the land area[9] are affected. In Africa, Sahelian Countries as Tunesia, Mauretania, Libya, Niger, Burkina Faso and Mali, as well as the eastafrican highlands of Burundi and Rwanda, and also Cape Verde show the highest proportions of eroded land area2 (40 to 80 %). Water erosion is the most widespread type of erosion, in Central America and Southeast Asia it even contributes with about 70% to the area affected by erosion and the loss of nutrients1. The methodological approach chosen for the empirical analysis of human-induced causes of soil erosion is an explorative, econometric one, based on national cross-country data[10]. A specific combination of correlation analyses, factor analysis, and regression analysis is designed, that can handle the great number of possible indicators for the assumed causes of erosion, and cope with related problems of multicollinearity and model specification. Those problems result from supposed interrelationships among different human-induced causes of soil erosion. At the same time, many of the causes of erosion have a latent character when considered on a national level[11], since they are deduced from a microeconomic context. This makes it necessary to define various indicator variables for each of them, which, again, implies additional multicollinearity. On the basis of the aggregated GLASOD data, a set of operational variables for soil erosion is defined. They basically indicate the proportion of a country´s degradable land area (i.e. land area minus wastelands) that is eroded through wind, water, or degraded by the loss of nutrients and organic matter by the end of the 80´s. In turn, the database for possible determinants of erosion is compiled departing from standard international data sets for the time span 1961-1990. Representative indicators can be defined for many of the causative factors discussed in literature, as well for socioeconomic ones, as for landuse, and also for natural factors. They are adapted in a way that they not only best fit and capture the hypothesized determinants, but also the ecological and timely dimension of the analysis. One important field that is not covered is land tenure. The resulting database comprises about 150 variables for possible causative factors, with a varying number of country-data available. The results of correlation analyses between the indicator variables for soil erosion and for possible causative factors facilitate a first assesion of relevant relationships. They show, that variables that quantify population pressure and the proportion of forested area are correlated with soil erosion for all countries. Deforestation rates in the 80´s are especially related to water erosion. Considering only countries without extreme climatic conditions[12] correlations are found between soil erosion and variables for the intensity of land use and the degree of expansion of the agricultural frontier. Producer price declines for relevant agricultural products are also found to be correlated with soil erosion in these countries. Corresponding to theoretical assumptions, the importance of different natural factors vary for different types of erosion and climatic zones. Altogether, variables that express structural conditions and can be regarded as the outcome of historical, long-term developments, seem to have stronger correlation with the extent of soil erosion than variables that quantify changes that took place within the time span under consideration, 1961 to 1990. The next methodological step consists in different factor analyses for 62 of the variables that express possible causative factors and for 73 countries with approximatively complete data sets. The principal objectives are to detect structural interrelationships among the multitude of variables and to reduce their number on the basis of these interrelations, in a way to obtain a set of variables that are largely independent of each other. It turns out that the structure of the 62 variables under consideration can clearly be reproduced by about 10 factors, with about 75% of their total variance being explained. These factors prove to be robust with respect to changes in the set of included variables, and in the methods of extraction and rotation. It is noteworthy, that many of the identified factors refer to cause-effect relationships that are discussed in literature. For instance, the factor that explains the greatest part of total variance, combines variables that quantify the long-run intensification of land use with others that stand for structural population pressure and a limited buffer for the expansion of the agricultural area. Other important factors relate to structural poverty, in combination with high rates of rural population growth; to the long-term and recent deforestation and to total population pressure; to development paths that aim at sopisticated animal procuction and permanent culture rather than at a mere expansion of the agricultural area. Other factors stand for the prevailing natural conditions. Based on a factor analysis for a reduced number of countries, it can be shown that declinig aggregate agricultural producer prices[13] are associated with the factor ´recent deforestation rates´. To quantify the relative importance of the identified factors, stepwise regression analyses are then carried out, with soil erosion as the dependent variable and selected representative variables for each of the factors as presumed independent variables[14]. Three human-induced factors, or developments, show to have particular relevance for the extent of soil erosion, that they can explain to up to 75%: (1) the long-run historical expansion of the agricultural frontier at the expense of the forested area, in combination with a population pressure well above the corresponding supporting capacities in the 80´s; (2) recent deforestation rates in conjunction with total population growth. This effect can rather be associated with a growth of demand for agricultural and forestral products and declining agricultural prices than with pressures directly resulting from agricultural population and expansion; (3) the long-run intensification of land use, mainly throug the conversion of permanent pastures to arable land, the shortening of fallow periods, and the increase of animal densities. This type of intensification is associated with and possibly induced by high structural population pressure in agricultural areas. Another important result is that poverty seems to have minor impact on the extent of soil erosion at the aggregate, national level. None of the included variables that represent the factor ´poverty´ shows a significant relative impact, neither in the models for the sum of erosion nor for specific types of erosion or climatic zones. This fact supports the low correlation coefficients for altogether 15 different poverty indicators that were calculated in the context of simple correlation analysis. Specific models for specific types of erosion and climatic zones show that there exist characteristic patterns of explanation for each type and zone. Recent deforestation rates and the associated features (factor (2))are particularily important in the explanation of water erosion, especially in countries with predominant humid climate. The impact of production-intensity in terms of factor (3) is specific for water erosion, and for countries without extreme climatic conditions, together with the factors (1) and (2). This is also where the negative effect of declinig agricultural prices appears to be strongest. At the same time, the development of sopisticated animal procuction and the growth of the area under permanent culture in contrast to a mere expansion of the agricultural area seem to be favourable to the soil in this context. In the explanation of wind erosion and loss of nutrients, natural factors are in the foreground. The identified, human-induced pressures related to long-term population growth, intesification, agricultural price decline and recent deforestation are consistent with important theoretical hypotheses. Those pressures are clearly not of the type that can be overcome over night through political intervention. Nevertheless, they lead to the following areas of intervention that should be given priority in the design of policy measures for the reduction of soil erosion: A reduction of population pressure through an increase in site-specific production potentials, based upon innovations that match the prevailing agro-ecological and economic conditions. Special attention should be given to low potential areas.A stronger focus on forest policy and the regulation of commercial forest use especially in the humid zone.A selective, long-term improvement of economic incentives for the production of soil-conserving crops with soil-conserving methods, by means of economic policy as well as through improved institutional conditions. Policies that aim at the reduction of poverty can not be expected to play a decisive role in the reduction of soil erosion. In spite of that, it is most necessary that policy makers keep in mind that the poor certainly are most affected by and vulnerable to erosion damages. At a global scale, the quality of future research on the topic will largely be determined by data availability and quality: concerning soil erosion, information at different points in time is necessary; for anthropogenic factors, spatial datasets will bring a new dimension into scientific research. Parallel with global analyses, further in depth local studies are necessary for a comprehensive and detailed insight into why and which land users degrade the resource they depend on in a specific socioeconomic context. footnotes: [8]The loss of nutrients and organic matter, independent of soil erosion, is also considered and is abbreviated with the term ´loss of nutrients´ in this text. [9]Again, it is the land area excluding wasteland that is being referred to. [10]Spatial data sets are not avaiable yet for socioeconomic factors related to soil erosion. [11]I.e. it is not known a priori, how these causes can be measured and quantified. [12]I.e. countries without predominant arid, hyper-arid or humid agroclimatioc conditions. [13]The availability of data for the variable in cause is limited to 56 coutries. [14]Reciprocal effects that soil erosion might have on anthropogenic factors are not very likely to occurr within the considered time span, except a possible increase of poverty due to erosion.
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Uso do espaço e seleção de hábitat pelo Mico-Leão-da-Cara-Preta (Leontopithecus caissara) / Space use and habitat selection by the Black-faced Lion Tamarin (Leontopithecus caissara)

Nascimento, Alexandre Túlio Amaral 20 June 2008 (has links)
Comprometida com a compreensão da relação entre hábitat e uso do espaço pelo mico-leão-da-cara-preta (Leontopithecus caissara), esta dissertação se norteia por três perguntas: Diferenças de hábitat entre ilha e continente influenciam o tamanho da área de vida? Há predileção da espécie por alguma classe de vegetação dentro da área de uso? Qual a capacidade suporte em sua área de ocorrência continental, bem como nas áreas potenciais para seu manejo conservacionista? Na tentativa de elucidar essas questões esta dissertação se divide em três capítulos. O primeiro contextualiza o trabalho e a apresenta o estado atual de conhecimento de L. caissara. Os capítulos segundo e terceiro concernem às questões centrais do trabalho - uso e seleção do hábitat pelo mico-leão-da-cara-preta. No capítulo dois apresentamos o uso do espaço pela espécie em sua região continental de ocorrência e comparamos os resultados obtidos com as informações disponíveis para a Ilha do Superagui. No capítulo três tratamos da seleção do hábitat por grupos insulares e continentais de L. caissara e estimamos a capacidade suporte para a espécie considerando seus limites de ocorrência e as áreas passíveis de receber animais em situação de manejo. Ao final desses capítulos apresentamos algumas considerações e recomendações para pesquisa e conservação do mico-leão-da-cara-preta. A preocupação com uma postura crítica e construtiva acerca das metodologias de estudos e análises sobre uso do espaço por espécies animais é transversal aos assuntos tratados ao longo de todo o trabalho. Os resultados apresentados confirmam as grandes áreas de vida de L. caissara, as quais parecem ser compensadas energeticamente pela incorporação de novas áreas e abandono de outras ao longo do tempo. Os tipos de hábitats mais intensamente utilizadas pelos mico-leão-da-cara-preta intercalaram áreas de floresta madura e em clímax edáfico com áreas antropizadas em sucessão, ambos hábitats sobre pouco desnível altimétrico. A capacidade suporte estimada é aparentemente incapaz de sustentar uma população viável e ressalta a urgência de pesquisas genéticas que colaborem para a compreensão do histórico ecológico/evolutivo de L. caissara. Potenciais translocações com vistas ao aumento populacional devem considerar as amplas áreas de diva, a espacialidade dinâmica, a relação uso/disponibilidade do hábitat e as diferenças entre ilha e continente. / This dissertation focuses on the interaction between habitat and space use by the black-faced lion tamarin (Leontopithecus caissara). We seek to answer three questions: 1) Do differences in vegetation between insular and continental habitats influence how the species use the space? 2) Does the species prefer a specific type of vegetation within its home-range? 3) What is the carrying capacity of the continental distribution and which are areas for potential conservation management? The first chapter of this dissertation relates the subjects discussed and introduces what is known about L. caissara. The second and third chapters develop the central questions of the research: the use and selection of habitat by the black-faced lion tamarin. In Chapter Two, we introduce space use by the species in its continental distribution and compare the results with data from Superagui Island. In Chapter Three, we address habitat selection by insular and continental groups of L. caissara and estimate the carrying capacity for the species given its distribution and areas potentially able to receive animals in a management context. The conclusion of each chapter presents considerations and recommendations for research and conservation. The study methods and analyses of space use aim to be critical and constructive and are relevant to the topics addressed throughout the text. The results presented confirm that the large home-ranges of L. caissara undergo dynamic turnovers, with some areas being abandoned and others incorporated throughout the year. The habitat types most intensively used by tamarins include areas of mature and forest mixed with areas of anthropic succession, both occurring at low altitudes. The estimated carrying capacity is apparently insufficient to maintain a viable population and highlights the importance of genetic studies that incorporate the ecological/evolutionary history of the species. Potential translocations meant to increase population size should consider the large home-ranges, dynamic spatial structure, relation of habitat use/availability and the differences between island and continent.
68

Informação ambiental sobre produtos para o consumo sustentável: os métodos de avaliação de impacto do ciclo de vida sob a ótica da sustentabilidade forte / Environmental information of products for sustainable consumption: Life cycle impact assessment methods from the perspective of strong sustainability.

Renato Inhasz Paiva 14 October 2016 (has links)
A degradação ambiental proporcionada pelo consumo de produtos (JORGENSON, 2003) é fruto tanto da evolução de uma sociedade que se distancia da natureza (MORAN, 2011), quanto de suas reais necessidades (FRY, 2005). Da mesma forma, os interesses do mercado, de governos e de consumidores enrijecem a manutenção de uma sociedade hiperconsumista (FRY, 2005). Este fato é observado pela existência de políticas governamentais de consumo (corrente do consumo verde) que prezam pela rotulagem ambiental, depositam a responsabilidade da redução da degradação ambiental no consumidor (AKENJI, 2014), e que não consideram que o aumento da ecoeficiência, sem questionar quais são os limites ambientais impostos para a realização das atividades humanas, provocam um efeito de rebote que pode elevar ainda mais a degradação ambiental (HANLEY et al., 2009). Em contrapartida, a corrente do consumo sustentável afirma ser necessário repensar os níveis de consumo de modo a não ultrapassarmos os limites impostos pelo ambiente à realização das nossas atividades (AKENJI, 2014). Desta forma, a informação necessária para a corrente do consumo sustentável é aquela que indica em que medida as capacidades de suporte do ambiente foram superadas (ALCOTT, 2008). Dentre todos os instrumentos capazes de fornecer informação sobre os aspectos ambientais de produtos, a Avaliação do Ciclo de Vida (ACV) é o único instrumento desenhado para avaliar as consequências ambientais relacionadas ao ciclo de vida de um produto (CHEHEBE, 1997). Entretanto, as evidências encontradas na bibliografia indicam que os métodos utilizados pela ACV para mensurar as consequências ambientais do produto (métodos de AICV - Avaliação do Impacto do Ciclo de Vida) foram estruturados para calcular majoritariamente a ecoeficiência dos produtos, pois são poucos (ou não indicados pela bibliografia) os casos em que a capacidade de suporte do ambiente é avaliada por estes métodos (POTTING; HAUSCHILD, 2006). Diante deste quadro, esta dissertação se propôs a avaliar se os métodos de AICV existentes estão alinhados à sustentabilidade forte ou se estão alinhados à sustentabilidade fraca. Dois critérios de avaliação foram definidos com base nos princípios da sustentabilidade forte: (i) O resultado do indicador da Categoria de Impacto deve apresentar quanto da capacidade de suporte foi ultrapassada ou não para as emissões relacionadas ao ciclo de vida do produto - alinhado ao princípio (a) da sustentabilidade forte, de que as atividades humanas devem ser limitadas à capacidade de suporte do ambiente (COSTANZA; DALY, 1992) - e, (ii) Todas as Categorias de Impacto (CIs) do método de AICV devem atender ao requisito (i) - alinhado ao princípio (b) da sustentabilidade forte, de que não há substitutabilidade completa entre os diferentes elementos do capital natural (COSTANZA; DALY, 1992). Dos métodos de AICV avaliados (CML 2002, Eco-Indicator 99, Eco-Factors 2006, EDIP 2003, IMPACT2002+, MEErP 2011) verificou-se que nenhum método está alinhado aos princípios da sustentabilidade forte, pois os critérios (i) e (ii) não foram atendidos concomitantemente. Desta forma, concluiu-se que por não estarem alinhados aos princípios da sustentabilidade forte, os métodos de AICV avaliados não são capazes de atender à demanda do consumo sustentável por informações. Sua utilização demonstra que as políticas de consumo verde continuam a depositar a maior responsabilidade pela reversão da degradação ambiental nos consumidores, sem alterar a estrutura sistêmica criada pelos governos, pelo mercado e consumidores na qual o hiperconsumo prevalece. / The environmental degradation provided by the consumption of products (JORGENSON, 2003) is the result of the evolution of a society that distances itself away from nature (MORAN, 2011) and from its real needs (FRY, 2005). At the same time, the interests of the market, governments and consumers maintain the hyper-consumption society (FRY, 2005). This fact is noticed by the presence of government consumption policies that appreciate environmental labeling, lay the responsibility for the reduction of the environmental degradation on the consumer (green consumption current) (AKENJI, 2014), and do not consider that the increase in eco-efficiency, without questioning the environmental limits for human activities, causes a rebound effect that can further raise environmental degradation (HANLEY et al., 2009). In contrast, the sustainable consumption current claims to be necessary to rethink consumption levels in order not to overpass the limits imposed by the environment for our activities (AKENJI, 2014). Thus, the necessary information for the sustainable consumption current is the one that indicates to what extent the environmental carrying capacity is exceeded (ALCOTT, 2008). Among all the instruments able to provide information on the environmental aspects of products, the Life Cycle Assessment (LCA) is the only instrument designed to assess the environmental consequences related to the life cycle of a product (CHEHEBE, 1997). However, the evidence found in the literature indicates that the methods used by LCA to measure the environmental impact of products (LCIA methods - Life Cycle Impact Assessment) were structured to mainly calculate the eco-efficiency of products, once there are only a few cases (or no indicated by references) in which the environmental carrying capacity is assessed by these methods (POTTING; HAUSCHILD, 2006). Given this context, this work aimed to evaluate whether existing LCIA methods are aligned to the strong or weak sustainability currents. Two evaluation criteria were defined on the basis of strong sustainability: (i) The results of the Impact Category indicator should present how much of the carrying capacity has been exceeded or not by the emissions related to the product life cycle according to the principle (a) of the strong sustainability, which states that human activities should be limited by the environmental carrying capacity (COSTANZA; DALY, 1992) - and (ii) All Impact Categories of a LCIA method must meet the requirement (i) - according to the principle (b) of the strong sustainability, which states that there is no complete substitutability between the different elements of natural capital (COSTANZA; DALY, 1992). From the evaluation of the LCIA methods (CML 2002, Eco-Indicator 99 Eco-Factors 2006, EDIP 2003 IMPACT2002+ and MEErP 2011) it was found that any of these methods are aligned with the principles of the strong sustainability, once the methods do not comply with criteria (i) and (ii ) concurrently. Thus, it was concluded that once they are not aligned to the principles of strong sustainability, the evaluated LCIA methods are not able to meet the demand of sustainable consumption for information. Its use demonstrates that green consumption policies continue to place the greatest responsibility for the reversal of the environmental degradation on consumers, without changing the systemic structure created by governments, the market and consumers in which hyper-consumption prevails.
69

Informação ambiental sobre produtos para o consumo sustentável: os métodos de avaliação de impacto do ciclo de vida sob a ótica da sustentabilidade forte / Environmental information of products for sustainable consumption: Life cycle impact assessment methods from the perspective of strong sustainability.

Paiva, Renato Inhasz 14 October 2016 (has links)
A degradação ambiental proporcionada pelo consumo de produtos (JORGENSON, 2003) é fruto tanto da evolução de uma sociedade que se distancia da natureza (MORAN, 2011), quanto de suas reais necessidades (FRY, 2005). Da mesma forma, os interesses do mercado, de governos e de consumidores enrijecem a manutenção de uma sociedade hiperconsumista (FRY, 2005). Este fato é observado pela existência de políticas governamentais de consumo (corrente do consumo verde) que prezam pela rotulagem ambiental, depositam a responsabilidade da redução da degradação ambiental no consumidor (AKENJI, 2014), e que não consideram que o aumento da ecoeficiência, sem questionar quais são os limites ambientais impostos para a realização das atividades humanas, provocam um efeito de rebote que pode elevar ainda mais a degradação ambiental (HANLEY et al., 2009). Em contrapartida, a corrente do consumo sustentável afirma ser necessário repensar os níveis de consumo de modo a não ultrapassarmos os limites impostos pelo ambiente à realização das nossas atividades (AKENJI, 2014). Desta forma, a informação necessária para a corrente do consumo sustentável é aquela que indica em que medida as capacidades de suporte do ambiente foram superadas (ALCOTT, 2008). Dentre todos os instrumentos capazes de fornecer informação sobre os aspectos ambientais de produtos, a Avaliação do Ciclo de Vida (ACV) é o único instrumento desenhado para avaliar as consequências ambientais relacionadas ao ciclo de vida de um produto (CHEHEBE, 1997). Entretanto, as evidências encontradas na bibliografia indicam que os métodos utilizados pela ACV para mensurar as consequências ambientais do produto (métodos de AICV - Avaliação do Impacto do Ciclo de Vida) foram estruturados para calcular majoritariamente a ecoeficiência dos produtos, pois são poucos (ou não indicados pela bibliografia) os casos em que a capacidade de suporte do ambiente é avaliada por estes métodos (POTTING; HAUSCHILD, 2006). Diante deste quadro, esta dissertação se propôs a avaliar se os métodos de AICV existentes estão alinhados à sustentabilidade forte ou se estão alinhados à sustentabilidade fraca. Dois critérios de avaliação foram definidos com base nos princípios da sustentabilidade forte: (i) O resultado do indicador da Categoria de Impacto deve apresentar quanto da capacidade de suporte foi ultrapassada ou não para as emissões relacionadas ao ciclo de vida do produto - alinhado ao princípio (a) da sustentabilidade forte, de que as atividades humanas devem ser limitadas à capacidade de suporte do ambiente (COSTANZA; DALY, 1992) - e, (ii) Todas as Categorias de Impacto (CIs) do método de AICV devem atender ao requisito (i) - alinhado ao princípio (b) da sustentabilidade forte, de que não há substitutabilidade completa entre os diferentes elementos do capital natural (COSTANZA; DALY, 1992). Dos métodos de AICV avaliados (CML 2002, Eco-Indicator 99, Eco-Factors 2006, EDIP 2003, IMPACT2002+, MEErP 2011) verificou-se que nenhum método está alinhado aos princípios da sustentabilidade forte, pois os critérios (i) e (ii) não foram atendidos concomitantemente. Desta forma, concluiu-se que por não estarem alinhados aos princípios da sustentabilidade forte, os métodos de AICV avaliados não são capazes de atender à demanda do consumo sustentável por informações. Sua utilização demonstra que as políticas de consumo verde continuam a depositar a maior responsabilidade pela reversão da degradação ambiental nos consumidores, sem alterar a estrutura sistêmica criada pelos governos, pelo mercado e consumidores na qual o hiperconsumo prevalece. / The environmental degradation provided by the consumption of products (JORGENSON, 2003) is the result of the evolution of a society that distances itself away from nature (MORAN, 2011) and from its real needs (FRY, 2005). At the same time, the interests of the market, governments and consumers maintain the hyper-consumption society (FRY, 2005). This fact is noticed by the presence of government consumption policies that appreciate environmental labeling, lay the responsibility for the reduction of the environmental degradation on the consumer (green consumption current) (AKENJI, 2014), and do not consider that the increase in eco-efficiency, without questioning the environmental limits for human activities, causes a rebound effect that can further raise environmental degradation (HANLEY et al., 2009). In contrast, the sustainable consumption current claims to be necessary to rethink consumption levels in order not to overpass the limits imposed by the environment for our activities (AKENJI, 2014). Thus, the necessary information for the sustainable consumption current is the one that indicates to what extent the environmental carrying capacity is exceeded (ALCOTT, 2008). Among all the instruments able to provide information on the environmental aspects of products, the Life Cycle Assessment (LCA) is the only instrument designed to assess the environmental consequences related to the life cycle of a product (CHEHEBE, 1997). However, the evidence found in the literature indicates that the methods used by LCA to measure the environmental impact of products (LCIA methods - Life Cycle Impact Assessment) were structured to mainly calculate the eco-efficiency of products, once there are only a few cases (or no indicated by references) in which the environmental carrying capacity is assessed by these methods (POTTING; HAUSCHILD, 2006). Given this context, this work aimed to evaluate whether existing LCIA methods are aligned to the strong or weak sustainability currents. Two evaluation criteria were defined on the basis of strong sustainability: (i) The results of the Impact Category indicator should present how much of the carrying capacity has been exceeded or not by the emissions related to the product life cycle according to the principle (a) of the strong sustainability, which states that human activities should be limited by the environmental carrying capacity (COSTANZA; DALY, 1992) - and (ii) All Impact Categories of a LCIA method must meet the requirement (i) - according to the principle (b) of the strong sustainability, which states that there is no complete substitutability between the different elements of natural capital (COSTANZA; DALY, 1992). From the evaluation of the LCIA methods (CML 2002, Eco-Indicator 99 Eco-Factors 2006, EDIP 2003 IMPACT2002+ and MEErP 2011) it was found that any of these methods are aligned with the principles of the strong sustainability, once the methods do not comply with criteria (i) and (ii ) concurrently. Thus, it was concluded that once they are not aligned to the principles of strong sustainability, the evaluated LCIA methods are not able to meet the demand of sustainable consumption for information. Its use demonstrates that green consumption policies continue to place the greatest responsibility for the reversal of the environmental degradation on consumers, without changing the systemic structure created by governments, the market and consumers in which hyper-consumption prevails.
70

Load-carrying and energy-dissipation capacities of ultra-high-performance concrete under dynamic loading

Buck, Jonathan J. 06 April 2012 (has links)
The load-carrying and energy-dissipation capacities of ultra-high-performance concrete (UHPC) under dynamic loading are evaluated in relation to microstructure composition at strain rates on the order of 10⁵ s⁻¹ and pressures of up to 10 GPa. Analysis focuses on deformation and failure mechanisms at the mesostructural level. A cohesive finite element framework that allows explicit account of constituent phases, interfaces, and fracture is used. The model resolves essential deformation and failure mechanisms in addition to providing a phenomenological account of the effects of the phase transformation. Four modes of energy dissipation are tracked, including pressure-sensitive inelastic deformation, damage through the development of distributed cracks, interfacial friction, and energy released through phase transformation of the quartz silica constituent. Simulations are carried out over a range of volume fractions of constituent phases to quantify trends that can be used to design materials for more damage-resistant structures. Calculations show that the volume fractions of the constituents have more influence on the energy-dissipation capacity than on the load-carrying capacity, that inelastic deformation is the source of over 70% of the energy dissipation, and that the presence of porosity changes the role of fibers in the dissipation process. The results also show that the phase transformation has a significant effect on the load-carrying and energy-dissipation capacities of UHPC for the conditions studied. Although transformation accounts for less than 2% of the total energy dissipation, the phase transformation leads to a twofold increase in the crack density and yields nearly an 18% increase to the overall energy dissipation. Microstructure-behavior relations are established to facilitate materials design and tailoring for target-specific applications.

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