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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.
91

Microbial Communities in Boreal Peatlands : Responses to Climate Change and Atmospheric Nitrogen and Sulfur Depositions

Genero, Magalí Martí January 2017 (has links)
Myrmarker har en stor roll i regleringen av den globala kolbalansen och koncentrationerna av koldioxid och metan i atmosfären, vilket gör dem till speciellt viktiga ekosystem ur ett klimatförandringsperspektiv. Förändringar av myrmarker genom naturlig utveckling eller antropogen påverkan kan därför få långtgående störningar av myrars klimatreglerande funktion. Mikroorganismer har en avgörande roll i biogeokemiska processer genom att t ex bryta ned organisk material i mark och därmed styra kolets kretslopp. För att förstå hur myrsystemen reagerar på störningar är det därför väsentligt att veta hur mikroorganismsamhällena reagerar genom förändringar i sammansättning och biogeokemisk aktivitet. Målet för studierna, som ligger till grund för denna avhandling, var att undersöka hur mikroorganismsamhällen i myrar reagerar på uppvärmning genom klimatförändring och ökade kväve- (N) och svavel- (S) halter i nederbörd. High through-put sekvensering användes för att studera taxonomiska och funktionella egenskaper hos mikroorganismerna i myrar och quantative PCR användes för att mer specifikt studera de metanbildande arkeorna. Två fältkampanjer vardera omfattande tre ombrotrofa myrar med olika klimatförhållanden och olika mängder N och S inederbörden användes för att undersöka lokala och storskaliga effekter på myrars mikrobiella samhällen. Resultaten visade att latudinell variation i geoklimatologiska förhållanden (temperatur ochnederbördsmängd) och deposition av näringsämnen hade en påverkan på sammansättningen av de mikrobiella samhällena och aktiva metanbildare förr än variationen i den kemiska miljön inom varje specifik myr. Myrväxtsamhällenas sammansättning för en specifik myr visades sig i stor utsträckning styra sammansättningen av motsvarande mikrobiella samhälle i torvprofilen. Detta framgick klart av i en analys av samexisterande nätverk av mikroorganismsamhällen och motsvarande växtsamhällen i en studie av tre geografiskt skilda myrar med olika kvävedeposition. Effekterna av klimatförändring och nederbörd med olika mängder av N och S studerades mer specifikt genom att analysera de mikrobiellasamhällena i  ett långliggande (18 år) försök. Påverkan av var och en av dessa manipulationer antingen förstärktes eller minskades, när de förekom i kombinationer. Ökad kvävedeposition var den faktor som hade starkast effekt. De långvariga störningarna medförde stora förändringar i den mikrobiella taxonomin inom samhällena. Detta återspeglades dock inte i den fysiologiska kapaciteten, vilket visar att det finns en stark buffring i myrarnas mikrobiella funktion. Detta tyder på att framtida utveckling av myrar i relation till olika störningar sannolikt inte kommer att påverka myrarnas roll för kolbalans och växthusgasutbyte med atmosfären. / Peatlands play a substantial role in regulating the global carbon balance and concentrations of the greenhouse gases CO2 and CH4 in the atmosphere, and are thus of utmost importance from a climate change perspective. Any changes of peatland functions due to natural or anthropogenic perturbations may result in changes in these ecosystem services. Soil microbial communities are essential drivers of biogeochemical processes, including the carbon cycle. In order to fully understand the effect of environmental perturbations on peatland functions, it is essential to understand how microbial communities are affected. The aim of the research presented in this thesis was to investigate the responses of the peat microbial communities to climate change and increased precipitation of nitrogen(N) and sulfur (S) compounds. High-throughput sequencing approaches were used to investigate the taxonomic and functional composition of microbial communities, and quantitative PCR was used to specifically target the methanogen community. Two field studies including three ombrotrophic peatlands each that differed in climatological conditions and atmospheric N and S depositions, were used to investigate and compare the effect of large- and local-scale environmental conditions on microbial communities. The results show that the variation in geo-climatological (temperature and precipitation) and atmospheric deposition conditions along the latitudinal gradient modulate the peat microbial community composition and the abundance of active methanogens to a greater extent thansite-related microhabitats. Furthermore, a tight coupling between the plant community composition of a site and the composition of its microbial community was observed, and was found to be mainly driven by plants rather than microorganisms. These co-occurrence networks are strongly affected by seasonal climate variability and the interactions between species in colder areas are more sensitive to climate change. The long-term effects of warming and increased N and S depositions on the peat microbial communities were further investigated using an 18-year in-situ peatland experiment simulating these perturbations. The impacts of each of these perturbations on the microbial community were found to either multiply or counteract one another, with enhanced N deposition being the most important factor. While the long-term perturbations resulted in a substantial shift in the taxonomic composition of microbial communities, only minor changes occurred in genome-encoded functional traits, indicating a functional redundancy. This could act as a buffer maintaining ecosystem functioning when challenged by multiple stressors, and could limit future changes in greenhouse gases and carbonexchange.
92

Havsstrandängar i Halland : Försvinnande och nyetablering vid framtida klimatförändringar / Coastal meadows in Halland : Disappearance and new establishment at future climate change

Redegard, Magnus January 2017 (has links)
Havsstrandängar av EU-kod 1330 har en utbredning från atlantkusten till Öresund. Längs med Hallands kust finns salta strandängar utspridda. Habitatet är hem för många hotade och ohotade arter och har krav på finkorniga jordarter samt topografi med låg höjd och sluttning. Genom bete eller slåtter hålls strandängarna öppna. Klimatförändringar påverkar den globala havsnivån och kommer påverka strandängarna negativt. Genom en GIS-analys går det att beräkna strandsförluster samt ta fram potentiella marker för nyetablering. Resultatet visar att stora areella försluter drabbar Hallands strandängar. 87,9% av befintliga strandängar kommer gå förlorade vid en havsnivåhöjning på 1m. Resultatet visar också att det finns möjligheter för nyetablering av salta strandängar. Arealen för potentiell nyetablering är större än den strandängsareal som finns idag vilket ses som ett positivt resultat. GIS-analysen ger en indikation om vad som kommer att ske med Hallands salta strandängar men för att nya marker ska kunna fungera som strandängar måste aktiva åtgärder vidtas. Både omföring av befintliga markslag och åtgärdsprogram som kan underlätta för strandängarna att återetablera sig vid eventuella havsnivåhöjningar. / Coastal meadows of the EU-code 1330 have a range reaching from the Atlantic coast to the Öresund including all along the coastline of Halland. The habitat is home to many species, including many that are threatened and have requirements for fine-grained soils with low height and slope. Grazing and haymaking keep these species rich meadows open. Climate change, however, affects global sea level and is projected to negatively affect on the salt meadows. Through a GIS analysis, meadow losses due to sea level rise are calculated. The result shows large losses of meadows in Halland, a full 87.9% of the existing meadows are projected to be lost in a sea level rise of 1m. In addition to these concerns, the result also shows that there are opportunities for establishment of new salt meadows. In fact, the area for potential new meadows is greater than what’s available today, which is considered as a positive result. In conclusion, GIS analysis provides an indication of what may happen with salt meadows in Halland due to climate change, losses and potential compensation. However, if new areas are to serve as meadows, active measures must be taken. Necessary actions include both change of existing land types and effort that can help the meadows to re-establish themselves in the event of sea level rises.
93

Evidence for birch forests and a highly productive environment near the margin of the Fennoscandian ice sheet in the Värriötunturit area, northeastern Finland

Bogren, Fredrik January 2019 (has links)
High-resolution records of early Holocene deposits are rare, and as a consequence reconstruction of terrestrial environments very soon after the deglaciation has often been difficult. In this study the palaeoenvironmental conditions of early Holocene (c. 10600-7500 cal. yr BP) are reconstructed in the Värriötunturit area of northeastern Finland, using evidence from plant macrofossils and pollen preserved in a lake sediment sequence retrieved from the small lake Kuutsjärvi. Special emphasis is put on the environment immediately following the deglaciation as the base of the sediment sequence is rich in minerogenic material interpreted to have been deposited by meltwater pulses from the retreating ice sheet. The abundance and variety of fossil remains in these early meltwater deposits provide evidence for a very productive ice-marginal environment in the area between the lake and the ice sheet, and the presence of tree-type Betula macro remains as well as high percentage values of tree-type Betula pollen suggests that a subarctic birch forest established just a few years after the deglaciation. In the following centuries the birch forest around the lake became rich in an under growth of ferns, and at c. 9400 cal. yr BP a transition into a mixed pine and birch forest took place. Due to absence of indicator plant taxa in the sediment it was not possible to reconstruct temperature conditions for any parts of the sequence in this study. However, the rapid colonisation of birch forests suggests that the climate was warm already during deglaciation, which is also in accordance with climatic conditions reconstructed for the early Holocene in the nearby Sokli area just 10 km away, as well as in other parts of Fennoscandia and Russia.
94

Managing knowledge sharing of extreme weather induced impacts on land transport infrastructure : Case study of the Swedish Transport Administration

Rydstedt Nyman, Monika January 2016 (has links)
Extreme weather events and effects of climate change are threats to the transport sector’s functionality and safety. Risk management in this context implies a necessity to focus on the connection between near-term experiences and coping strategies on one hand, and long-term adaptation analyses on the other. How learning from past events and subsequent knowledge sharing can be adopted is a question that needs to be explored, discussed and tested. A systematic approach to lessons learned calls for measures of investigation, reporting, planning, implementation and evaluation. A qualitative case study approach was used in this thesis. In the first paper the practices of accident investigation in operation and maintenance were inventoried within the Swedish Transport Administration (STA). Three accident investigation methods were applied and tested on a cloudburst event, causing flooding in a railway tunnel in Sweden. In the second paper, semi-structured interviews, documents, and archival records were used as means for penetrating deeper into the attitudes and understanding of lessons learned concerning extreme weather events within a procured public-private partnership. The results of the two studies showed weak signals of feedback on lessons learned. Partly, these weak signals could be traced back to weak steering signals. Various obstacles impeded learning curves from lessons learned. The obstacles were of both hard and soft values, e.g. resources in time and equipment, systematic investigation methods, incentives for lessons learned, education and knowledge, values, norms and attitudes towards how and why identified problems should be solved. Successful knowledge sharing requires that close attention is paid to such obstacles and that an adaptive approach is adopted. / Den pågående och framtida klimatförändringen sätter press på aktörer att möta risker som associeras med klimatförändring. Syftet med denna avhandling är att bidra med kunskap om lärande och kunskapsöverföring inom offentlig förvaltning av landtransportinfrastruktur. Eftersom lärande och kunskapsöverföring är grundläggande för planering och beslutsfattande om strategier och åtgärder som främjar ett robust transportsystem. Målet för detta arbete är att belysa lärande och kunskapsöverföring inom och mellan olika organisationer i det svenska samhället. Det socio-tekniska systemperspektivet - som används som analysram i båda studierna ger en djupare förståelse för bakomliggande faktorer. En kvalitativ ansats, som omfattar intervjuer, deltagande observationer och dokumentanalys, har används i detta licentiatarbete. I den första studien belyses möjligheten att använda sig av industriella utredningsmetoder på naturolyckor i en svensk kontext av en översvämning i en järnvägstunnel. De industriella utredningsmetoderna visade sig vara användbara för utredning av konsekvenser efter skyfall, med olika metodologiska fördelar och nackdelar. Den andra studien utforskar hur Trafikverkets verksamhetsområde Underhåll arbetar med lärande kopplat till väderextremer; hur de fångar upp erfarenheter och kunskap som finns hos kontrakterade entreprenörer, samt hur entreprenörerna uppfattar att lärande och erfarenhetsåterföring sker. Resultatet från båda studierna visar på både svaga styrsignaler och svaga återkopplingssignaler, vilket medför svaga lärandekurvor. Olika hinder sågs ligga bakom med svaga styr- och återkopplingssignaler bl.a. resurser i tid och processer, systematik i utredning av naturolyckor, incitament att lära av varandra, utbildning och kunskap, värderingar normer och attityder till hur och varför identifierade problem ska lösas. Ett adaptivt förhållningssätt innebär att man behöver ta hänsyn till dessa hinder på ett systematiskt sätt. / The agreement in Paris in 2015 was an historic manifestation that society has to work with both mitigation and adaptation to achieve a reduction of the adverse effects of climate change. One way to achieve adaptation is through the integration of present coping strategies. A first step is to study the existing processes and routines that support short-term coping. This licentiate thesis targets different aspects of learning as a strategy for coping and building adaptive capacity. Road infrastructure and maintenance in relation to extreme weather are used as the physical context and the Swedish Transport Administration as a case to study. Paper I shows the possibility to apply industrial accident investigation methods to an extreme weather event and get useful insights into underlying root causes. Paper II shows the intra- and interrelated patterns that exist in public-private partnerships (PPP) in Sweden. The paper describes a parallel of systems with infrequent overlaps regarding lessons learned.  In both papers the socio-technical perspective approach was used to highlight aspects of learning from and investigating damage due to extreme weather at different tiers in society. The socio-technical perspective provides an understanding of how decisions and legislation that affect our actions and behavior today may have been taken in different time and space settings. This thesis contributes to concept and theory building regarding the socio-technical system approach. / <p>Paper 2 ingick i licentiatuppsatsen som manuskript, nu publicerat.</p>
95

O impacto do fator humano na obtenção de alto desempenho: estudo de caso

Guerreiro, Renato de Oliveira 25 February 2003 (has links)
Made available in DSpace on 2015-04-22T22:11:11Z (GMT). No. of bitstreams: 1 Dissertacao-Renato de Oliveira Guerreiro.pdf: 3063091 bytes, checksum: c05ac9ee5becff678a7dd0cce752745f (MD5) Previous issue date: 2003-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Due to the changing environment being noticed nowadays, a new reality seems to be coming up. Inside the organizations, this new world is noticed by the attempts to build flexible working environments, towards the respect to people, changing the thinking of men while just part of manufacturing machinery, without however to decrease the performance and competitiveness very important in the current days assuring a improvement to the organization . Many organizations, therefore, are looking for satisfying human needs while implementing operational changes, which are usually focused on process reengineering and team work activities. Considering that management practices are critical factors for leading in this environment, this dissertation s goal is to identify some of those practices, required for the construction of a management behavior based on the link between process management and Organizational Learning. The database research method, adopted in this work, consisted of a theoretical study and a case study. In this case, the managers practices have been observed during the Process Management methodology implementation, taking into account their own feelings, as well the feelings of their employees, together with the researcher observations. The conclusions have highlighted the following issues: the need for developing management practices, which are able to provide process management understanding; gain people commitment; provide required conditions for team work; encourage systemic vision of reality and create a continuous information flow through all levels of the organization. Then, management practices are presented while implementing process management, based on the learning organizational disciplines: group work development; endomarketing planning; commitment behavior; generating creative tension and microworlds; respecting the corparative values and organizational culture; building a shared vision. / O momento de transição vivenciado hoje dá indícios de que uma nova realidade está tomando forma. No âmbito das organizações, essa nova realidade é refletida na crescente preocupação com a construção de espaços de produção mais flexíveis e direcionados à valorização do ser humano em sua totalidade, modificando a idéia deste enquanto mera engrenagem do maquinário de produção, sem, no entanto diminuir o desempenho e competitividade fundamentais nos dias atuais assegurando um futuro próspero para a organização. Neste sentido, muitas organizações estão buscando abordagens que incorporem as necessidades humanas às mudanças operacionais, normalmente centradas na reestruturação dos processos e no fortalecimento do trabalho em equipe. Considerando-se que as ações dos gerentes são fundamentais para guiar esse momento de transição, este trabalho foi desenvolvido com o objetivo de identificar algumas dessas ações, necessárias à construção de uma abordagem gerencial baseada na visão de complementaridade entre o aperfeiçoamento de processos e a aprendizagem organizacional. Em função desse objetivo, adotou-se a pesquisa de arquivo, que se constituiu da revisão bibliográfica dos temas em questão e de uma aproximação da realidade através de um estudo de caso prático, real e efetivo. Neste caso, as práticas administrativas tem sido observadas durante a implementação da metodologia de gerenciamento do processo onde se levou em conta seus próprios sentimentos, como também os sentimentos dos colaboradores, em conjunto com as observações de pesquisa. As conclusões demonstraram: a importância de se desenvolver ações gerenciais capazes de propiciar a clareza dos objetivos do aperfeiçoamento de processos; buscar o comprometimento das pessoas com os mesmos; proporcionar as condições necessárias à realização do trabalho através de equipes; estimular a formação de uma visão sistêmica da realidade; criar um fluxo contínuo de comunicação em todos os níveis organizacionais. Desta forma, foram traçadas algumas propostas de ações a serem adotadas pelos gerentes quando da implementação do aperfeiçoamento de processos, tendo como base as disciplinas da aprendizagem organizacional: desenvolvimento de dinâmicas de grupo; planejamento da comunicação; adoção de uma postura de comprometimento; respeito aos valores corporativos e a cultura organizacional; estímulo à prática do diálogo; construção de uma visão compartilhada.
96

Building Happy and Resilient Communities in the North of the European Union : A case study on Transition Movement in Sweden and its relationship with the EU

Cardona Shokotko, Vanessa January 2017 (has links)
When the world becomes drowned in multiple global problems and citizens do not see any real progressive solutions from their governments, they take the initiative in their own hands and start changing the world on their own. The Transition Town movement was born this way. It is a social movement which aims at building resilient local communities in response to climate change, peak oil and an unfair ecologically destructive economic system which is probably soon to break down. As a potentially strong actor of future social change, it is worth studying emerging local movements in Europe, and hopefully identifying new potentials for success of these grass-root innovations.The study, thus, aims to investigate the relation between the participants of the Transition Movement Sweden and the supranational/intergovernmental entity EU, which plays one of the key roles in economic, environmental and social aspects of Swedish citizens. By conducting interviews with participants of the movement in several Swedish cities, the nature of this relationship is being explored. Using the theory of Multi-Institutional Politics Approach the case study explains the connection between the movement and the EU.
97

Modeling hydrometeorological extremes in Alpine catchments / Modellering av hydrometeorologiska extremvärden i alpina avrinningsområden

Voulgaridis, Theo January 2017 (has links)
Uncertainties with a modeling framework consisting of a weather generator, two precipitation disaggregation models and the hydrological HBV model was assessed with respect to hydrometeorological extremes in Tyrol, Austria. Extreme precipitation events are expected to increase in intensity and frequency in the Alps during a warmer climate. The Alpine regions may be particularly vulnerable to such changes in climate where many floods in Europe occurred during recent years and caused major damage and loss of life. Weather generators typically provide time series at daily resolution. Different disaggregation methods have therefore been proposed and successfully tested to increase temporal resolution in precipitation. This is essential since flood peaks may be maintained for as little as minutes. Here, the non-parametric method of fragments was tested and compared with the multiplicative microcanonical cascade model with uniform splitting on the reproduction of precipitation extremes. It is also demonstrated that the method of fragments model can be transformed to disaggregate temperature with slight changes in the model structure. Preliminary test results show that the simulation of discharge peaks can be improved by disaggregating temperature in comparison with using daily averages as input in the HBV model.  Test results show that precipitation extremes were simulated within confidence bounds for Kelchsauer and Gurglbach when using historical observations as input. These two catchments had longer records of data available in comparison with Ruetz where the majority of simulated precipitation extremes were found outside confidence ranges. This indicates that the model is data driven. Synthetic data series were constructed with the weather generator from historical data and disaggregated with the two disaggregation models. The differences between the models were bigger for Ruetz where less observed data was available. The method of fragments simulates extremes with the closest resemblance to extremes. This is also true for the reproduction of wet spells and simulated variance. To account for parameter uncertainty in the HBV model, it is highly motivated to simulate discharge with different but suitable parameter sets to account for equifinality. However, the large amount of data produced when disaggregating the weather generated time series transcended the data capacity of the HBV model and made it crash. Other uncertainties related to the framework are the use of theoretical probability distributions in the weather generator and the dependence of high-resolution data for the disaggregation model. Despite these uncertainties, the framework is closer to a physical understanding of the causes of floods than the uncertain frequency analysis method. The framework is also applicable to land-use and climate change studies.
98

Dimensionering av markavvattningssystem för jordbruksmark i nuvarande och framtida klimat : En pilotstudie på olika typjordar / Design of drainage systems for cultivated lands in climates of today and the future

Gustafsson, Eric January 2017 (has links)
I Sverige finns idag inom jordbruket runt 30 000 markavvattningsföretag och det räknas med att 1,3 miljoner hektar av jordbruksmarken är dikad. Tidigare undersökningar har visat att flera av dessa dräneringssystem som byggdes för 60–100 år sedan inte längre är anpassade för det nuvarande klimatet och att dagens riktvärde på 1,2 m djup för dräneringsledningarna bör ses över. Detta, i samband med att klimatförändringarna väntas leda till bland annat en ökad årlig nederbörd, ställer Sverige inför stora utmaningar att anpassa dräneringssystemen därefter. En väldränerad jordbruksmark är en förutsättning för att minimera kväveläckage och säkra den nuvarande samt i framtiden ökade matproduktionen som krävs för att underhålla en växande befolkning. Syftet har varit att med hjälp av hydrologimodellen DRAINMOD dimensionera dräneringssystem för två fält med olika markfysikaliska egenskaper som är anpassade för dagens samt framtidens klimat. DRAINMOD simulerar grundvattennivån mellan två dräneringsrör och kan med hjälp av grödparametrar såsom rotdjup och längd på odlingssäsonger uppskatta den relativa avkastningen för en specifik gröda med hjälp av ett stressindex. Detta stressindex beräknas av DRAINMOD baserat på över- eller underskott av vatten i markprofilen. DRAINMOD beräknar även vattenförluster i form av dränering, ytavrinning samt evapotranspiration. Efter att modellen validerats mot historiska klimatdata testades varje fält mot genererad framtida klimatdata. Flera olika dräneringsdjup och avstånd analyserades med avseende på dränering, ytavrinning och relativ avkastning. Det ena fältet beläget i Östergötland, med ett dräneringsdjup på riktvärdet 1,2 m och ett dräneringsavstånd på 25–50 m ger en minimerad dränerad volym samt en relativ avkastning på 80–100 % i ett framtida klimat. Det andra fältet beläget i Skåne uppnådde en minimerad dränerad volym och en relativ avkastning på 100 % vid dräneringsdjup på 0,9 m och ett avstånd mellan ledningarna på 20–50 m. / About half of Sweden’s cultivated lands are estimated to be using artificial subsurface drainage. Earlier studies have shown that several of these drainage systems are obsolete and ill-equipped to handle the present climate conditions. Sweden has used a drain depth of 1.2 meters for the drainage systems as a guideline value, although studies have suggested it is necessary to be re-evaluated. Poorly dimensioned drainage systems in combination with an expected increase in precipitation due to climate change puts Sweden into challenges to adapt current drainage systems for the future. A well-drained soil is a crucial fundament to minimize nitrogen-losses and maximize crop yields to sustain a growing population. The aim was to model two different types of soils’ drainage systems with the hydrology model DRAINMOD and adapt these for today’s and the future’s climate. DRAINMOD simulates the hydrology of a soil for long periods of climatological records. The model predicts water table, soil water regime, drainage, run-off and crop yields associated with a certain drainage system design. Several different drainage depths and spaces for each of the two soils were analysed and evaluated. For the field located in the county of Östergötland, a drainage depth of 1.2 m and spacing of 25–50 m were sufficient to minimize drainage losses and maximize crop yield. Furthermore, a depth of 0.9 m and spacings of 20–50 m would be sufficient for the second field located in the county of Skåne.
99

Frontiers of Fracking : Underground Political Ecology and Unconventional Energy in the Contested Landscapes of North West England

Clifford, Joseph January 2015 (has links)
Gas obtained from previously unexploited shale rock strata has emerged as an economically viable way of sourcing additional fossil fuel energy resources after the so-called ‘shale gas revolution’ in the United States. In the United Kingdom, the incumbent government has committed to the development of its own shale gas resources. A highly polarised public debate has erupted on the risks and rewards of extracting the shale gas deposits that presently lie underneath large swathes of the country using the controversial method of hydraulic fracturing, or ‘fracking’. This thesis examines how different groups in North West England – the major frontier of fracking in the UK – are contesting, resisting and negotiating the current government’s decision to sanction and push ahead towards the development a domestic shale gas industry. Employing a theoretical framework drawn from political ecology as its core mode of examination, this thesis utilises qualitative methods including in-depth interviews and participant observation techniques. It documents a range of social groupings that are contesting shale gas in the UK in a number of ways, and argues that landscapes and risk are fundamental hinges in this ongoing environmental conflict.
100

Characterizing particulate carbon using dielectric property measurements

Syk, Madeleine, Vollmer, Joakim January 2018 (has links)
Interest in effects of carbonaceous particles in the atmosphere has recently taken an upswing due to knowledge of how these particles affect our environment. Carbonaceous aerosols are characterized by their dark color, giving them the ability to absorb both incoming and outgoing radiation of all wavelengths in the atmosphere. If these particles are deposited on snow or ice they blacken the surface, with an increased rate of melting as a consequence. These particles play a significant role in climate change and it is important to characterize the particles in order to determine their environmental impact and their origin. In this thesis, two non-destructive dielectric measurement approaches for characterizing carbonaceous particles at microwave frequencies were explored: measurements with an impedance analyzer and measurements using a cavity resonator. Measurements were carried out on quartz filters containing concentrations of carbon normally found in snow in northern Scandinavia. To validate the carbon concentration on the filters a field trip to northern Sweden was conducted. Snow samples were collected and analyzed in regards of carbon content, confirming that the amount of carbon on the filters were accurate. The impedance analyzer showed great uncertainty and the results were not precise enough to determine the credibility of the approach. Measurements with the cavity resonator showed some promising results due to its extreme sensitivity but require adjustments to distinguish different particle types from each other. Thus, it is expected that the use of a cavity resonator operating at microwave frequencies will become an applicable method for characterizing carbonaceous particles in the future.

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