• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 248
  • 86
  • 32
  • 30
  • 26
  • 22
  • 17
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 520
  • 246
  • 181
  • 109
  • 89
  • 87
  • 67
  • 56
  • 50
  • 44
  • 43
  • 41
  • 40
  • 39
  • 34
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

Landscapes that facilitate learning : Outdoor spaces that improve learner performance in Atteridgeville schools

Janse van Rensburg, Jako Stegmann 09 December 2013 (has links)
Low learner performance is one of the greatest challenges that confront South Africans in this post-apartheid era. Despite valiant efforts on the government’s part to improve the education system every year, successful learners are not coming through the ranks in sufficient numbers. In the case of Atteridgeville, an old township near the Pretoria Central Business District, the phenomenon of low learner performance is reflected in the quality of schoolyards and the behavior of learners. Schoolyards are degraded, learners lack confidence, they are not enthusiastic about their schools, they do not interact with the communities around their schools, and they do not venture into the physical landscape outside their schools. The question arises whether the landscape outside the classroom is not, in fact, contributing to the problem. If this is so then a way must be found to manipulate the landscape so that obstacles to learner performance are removed and learning is facilitated. This thesis explores the notion that the outdoor landscape in Atteridgeville can play a role in helping learners reach their potential. Therefore Atteridgeville will be the departure point for the investigation. The investigation will result in a project location which will be further investigated to identify its inherent opportunities and constraints. The design response to these opportunities and constraints, coupled with both theoretical and conceptual backing, will inform the project at master plan and detail design level. Methods must be found to unlock the didactic and experiential potential of the schoolyard and surrounding landscape in a township where open green spaces are under threat and physical and social obstacles to learner performance exist. / Dissertation ML(Prof)--University of Pretoria, 2014 / Architecture / ML(Prof) / Unrestricted
242

Efficacité de zones tampons humides à réduire les teneurs en pesticides des eaux de drainage / Effectiveness of constructed wetlands to reduce the pesticide concentrations in drain water

Vallée, Romain 24 April 2015 (has links)
En Lorraine, le drainage fréquent des sols argileux favorise les transferts des intrants agricoles (pesticides et engrais) vers les eaux de surface. Dans ce cas, les bandes enherbées réglementaires (BCAE de la PAC) installées en bordure de cours d’eau sont court-circuitées et ne jouent plus leur rôle épurateur vis-à-vis des eaux de surface. Ainsi, des zones tampons humides artificielles (ZTHA) sont préconisées pour prendre le relais des bandes enherbées. Généralement, ces ZTHA sont installées à l’échelle du bassin versant ou du groupe de parcelles et sont donc de taille conséquente, les rendant concurrentielles de la surface agricole utile (SAU). L’objectif de ce projet de recherche est donc d’évaluer l’efficacité de deux ZTHA de taille réduite, installées dans la bande enherbée entre la parcelle drainée et le ruisseau. Pour cela, une approche multi-échelles intégrant des expériences de laboratoire en batch, des suivis dynamiques en bacs pilotes et un monitoring à la parcelle a été mise en place. Afin d’évaluer l’efficacité des ZTHA au cours des saisons de drainage 2012/13 et 2013/14, le suivi des teneurs en nitrate et de 79 pesticides a été réalisé dans les eaux en entrée et en sortie des ZTHA, ainsi que dans diverses matrices environnementales (sols, sédiment, paille, végétaux). Pour les deux dispositifs, la réduction du flux de nitrate s’est montrée stable, comprise entre 5,4 et 10,9 %, alors que la réduction du flux de pesticides s’est montrée très variable, comprise entre -618,5 et 100 %. Cette variabilité a été expliquée par quatre comportements distincts des molécules. Les fortes valeurs négatives d’efficacité ont été expliquées par une contamination des dispositifs à la suite d’épisodes de ruissellement connexes pour des molécules solubles telles que le 2,4-MCPA ou l’isoproturon. Pour ces deux molécules, l’étude de sorption a montré leur faible affinité avec les matrices environnementales, facilitant leur transport par les eaux de ruissellement et de drainage. D’autres molécules, telles que le boscalide ou l’OH-atrazine, ont présenté des abattements proches de 0. Pour le boscalide, ce comportement a été montré au laboratoire, en accord avec ses fortes capacités d’adsorption et de désorption observées lors des études de sorption et en bacs pilotes. Enfin, certaines molécules ont montré des abattements, allant de 9,9 à 100 %, en lien avec leur faible persistance (2,4-MCPA, clopyralid, mésosulfuron-méthyl,…) ou leur forte affinité pour les matrices environnementales (diflufenicanil, propiconazole, propyzamide,…). Ces ZTHA de taille réduite, installées dans les bandes enherbées, sont donc efficaces pour limiter la contamination des eaux de surface par les eaux de drainage agricole. Ainsi, la multiplication de ces dispositifs à l’échelle de la parcelle dans le paysage agricole permettrait de réduire la contamination des eaux de surface par les pesticides et les nitrates tout en préservant la SAU. Toutefois, l’efficacité de ces ZTHA restant limitée vis-à-vis de certains pesticides présentant un Koc faible et une DT50 élevée, leur installation ne doit pas remettre en cause la réduction en amont des apports phytosanitaires sur les parcelles / In Lorraine, the drainage of clay soils contributes to transfer of agricultural inputs (pesticides and fertilizers) towards surface waters. In this case, the regulatory grass strips (CAP regulation) installed along rivers are bypassed and no longer effective in purifying surface water. Thus, constructed wetlands (CWs) are recommended to take over grass cover bands. Generally, these CWs are installed at watershed scale or at that of several plots and they are therefore quite huge, making them competitive in the cultivated land. The objective of this project is to assess the effectiveness of two small CW, installed in the grass cover band between the drained plot and the river. For this, a multi-scale approach was set up integrating laboratory experiments in batch, pilot study taking into account the water dynamics and monitoring at field scale. The effectiveness of CW was assessed during the 2012/13 and 2013/14 drainage seasons. The nitrate and 79 pesticides concentrations were monitored at inlet and outlet of CWs and in various substrates (soils, sediment, straw and plants). For both devices, the removal efficiencies measured for nitrate were stable and ranged from 5.4 to 10.9 % of inlet amounts while the reduction of pesticide flows was very variable, ranging from -618.5 to 100 %. This variability was explained by four distinct behaviors. The high negative efficiency values were attributed to neighboured runoff events after heavy rains, for soluble molecules such as 2,4-MCPA or isoproturon. For both molecules, the sorption study showed low affinity for environmental substrates, facilitating their transport by runoff and drainage water. Other molecules such as boscalid or OH-atrazine showed effectiveness close to 0 %. For boscalid, this behavior has been observed in laboratory sorption and pilots studies, in agreement with its strong adsorption and desorption capacities. Finally, some molecules have shown reductions ranging from 9.9 to 100 %, in agreement with their low persistence (2,4-MCPA, clopyralid, mesosulfuron-methyl, ...) or their high affinity for environmental substrates (diflufenican, propiconazole or propyzamide). These small CWs, located in the grass cover bands, are effective in minimizing the contamination of surface waters by agricultural drainage water. Thus, multiplying the number of these devices at the plot scale in the agricultural landscape would reduce the contamination of surface waters by pesticides and nitrates while preserving the cultivated land. However, the effectiveness of these CWs are limited for pesticides with a low Koc and a long DT50; thus their installation in plot must not call into question the reduction in the use of pesticides
243

Transparency on Corporate Websites and Social Media During Crises : A Rhetorical and Semiotic Analysis on the Rhetorical Constructions of Transparency Online

Væver Kronborg, Katja January 2017 (has links)
This research paper is examining how corporations can create a rhetorical construction of transparency on digital platforms in order to make their communication appear transparent during a crisis. Crisis communication theory and theories of rhetoric and transparency have been used in order to analyse the crises situations and the linguistic means used in crisis related messages. By using the methods of semiotics and digital rhetoric, an analytical framework was developed to be able to analyse the level of both the rhetorical construction of transparency as well as the actual transparency by identifying what information has been disclosed and what has been withheld. The two companies used for the analysis were Toyota and Samsung, who both experienced a crisis in 2016. It was found that the two companies used different strategies in their crisis communication, in which Toyota came across as the best prepared corporation in times of crises due to a clearer reaction, which was not changed. Both corporations managed to construct a level of transparency through their use of language, however, some information was found to have been withheld, causing the actual transparency to be of a lower degree than the constructed transparency. Thus, by using language in certain ways, corporations are able to convince their stakeholders that they are transparent while being able to withhold different information that could prove valuable to some groups of stakeholders.
244

Soil Aquifer Treatment (SAT) and Constructed Wetlands (CW) Applications for Nutrients and Organic Micropollutants (OMPs) Attenuation Using Primary and Secondary Wastewater Effluents

Hamadeh, Ahmed F. 06 1900 (has links)
Constructed wetlands (CW) and soil aquifer treatment (SAT) represent natural wastewater treatment systems (NWTSs). The high costs of conventional wastewater treatment techniques encourage more studies to investigate lower cost treatment methods which make these appropriate for developing and also in developed countries. The main objective of this research was to investigate the removals of nutrients and organic micropollutants (OMPs) through SAT, CW and the CW-SAT hybrid system. CWs are an efficient technology to purify and remove different nutrients as well as OMPs from wastewater. They removed most of the dissolved organic matter (DOC), total nitrogen (TN), ammonium and phosphate. Furthermore, CWs aeration could be used as one of the alternatives to reduce CWs footprint by around 10%. The vegetation in CWs plays an essential role in the treatment especially for nitrogen and phosphate removals, it is responsible for the removal of 15%, 55%, 38%, and 22% for TN, dissolved organic nitrogen (DON), nitrate and phosphate, respectively. CWs achieved a very high removal for some OMPs; they attenuated acetaminophen, caffeine, fluoxetine and trimethoprim (>90%) under different redox conditions. Moreover, it was found that increasing temperature (up to 36 C) could enhance the removals of atenolol, caffeine, DEET and trimethoprim by 17%, 14%, 28% and 45%, respectively. On the other hand, some OMPs, were found to be removed by vegetation such as: acetaminophen, caffeine, fluoxetine, sulfamethoxazole, and trimethoprim. Moreover, atenolol, caffeine, fluoxetine and trimethoprim, showed high removal (>80%) through SAT system. It was also found that, temperature increasing and using primary instead of secondary effluent could enhance the removal of some OMPs. The CWs performance study showed that these systems are adapted to the prevailing extreme arid conditions and the average percent removals are about, 88%, 96%, 98%, 98% and 92%, for COD, BOD and TSS, ammonium and phosphate, respectively. Additionally, the natural hybrid system (CW-SAT) can provide an effective treatment technology of reclaimed water for replenishing aquifers and subsequent reuse. This hybrid system embodied the performance advantages of both processes and exhibits a high potential for removal of OMPs, nutrients, metals as well as pathogens, bacteria and viruses.
245

Reconnecting man with nature : post industrial landscape development

Burmeister, Marina January 2014 (has links)
Industries became a permanent addition to cities in the 18th century, transforming the natural landscape and influencing the people directly dependant on it, this enforces to the consumer culture we experience every day. This industrial development all over the world has disregarded apparent and non-apparent relationships that humans have within nature, resulting in the connection between humans and nature to become estranged, leaving humankind searching for identity and purpose. This study investigates the connection between humans and nature through adapting the post-industrial landscape, to ultimately establish an identity of place for human well-being. The study proposes that apparent and non-apparent relationships between humans and nature can be introduced in the post-industrial landscape through the concepts of ecosystem services and commemorative design. By commemorating the natural landscape, memories and experiences will create an appreciation for the natural landscape, strengthening the connection between humans and nature. Different ecosystem services are generated by the design to establish ecological and human well-being. The sketch plan design intervention proposes that, these apparent and non-apparent relationships between humans and nature are revealed and celebrated. The non-apparent relationships are transformed into apparent design features within the landscape to make visitors aware of their unity with nature and the services it provides them with. The design proposal creates opportunities for interaction, education and appreciation by means of food gardens, utility gardens, biodiversity gardens and experiments of spontaneous succession. The purpose of these interventions is to restore the post-industrial landscape while creating a strong cultural connection to heritage within industries and nature to reconnect humankind with their own identity as part of nature. / Dissertation (ML(Prof))--University of Pretoria, 2014. / Architecture / ML(Prof) / Unrestricted
246

Analys av sedimentackumulation i våtmarker i Rååns avrinningsområde och undersökning av våtmarkernas renoveringsbehov / Analysis of sediment accumulation in wetlands in the catchment area of Råån and an investigation of the maintenance needs of the wetlands

Lumsén, Louise January 2021 (has links)
Inom Rååns avrinningsområde, som är beläget i kommunerna Helsingborg, Landskrona, Svalöv och Bjuv, har anläggning av våtmarker pågått sedan 1990-talet. De anlagda våtmarkerna syftar till att minska näringsförlusterna från omkringliggande jordbruksmarker till vattendrag och gynna den biologiska mångfalden. I denna studie har 28 anlagda våtmarker inom Rååns avrinningsområde studerats. Studien hade två övergripande syften varav det ena var att undersöka sambandet mellan sedimentackumulering och våtmarkernas utformning samt placering i landskapet. Det andra syftet var att undersöka våtmarkernas renoveringsbehov. Renoveringsbehov syftar på åtgärder som behöver utföras för att upprätthålla våtmarkernas ursprungliga funktion och utformning såsom flödesvägar, vegetation, djupprofil samt in- och utlopp. Studien baserades på observationer och mätningar som utfördes i oktober år 2020. Resultatet visade att sedimentackumuleringen varierade mellan 0,2–2,3 cm per år och att både utformnings- och placeringsfaktorer påverkade sedimentackumuleringen. Det uppskattade ursprungliga vattendjupet hade en positiv korrelation med sedimentackumulationen och sedimentdjupet blev högre med våtmarkens ålder. Uppgrundningen var högre närmare inloppet i fyra av sju långsmala våtmarker (Längd-breddförhållande, 𝐿 ∶ 𝐵 > 3). I de långsmala våtmarkerna fanns även en positiv korrelation mellan hydraulisk belastning (HL) och sedimentackumulering. I våtmarker med 𝐿: 𝐵 < 3 fanns en övre gräns där höga värden på HL istället hade en negativ påverkan på sedimentackumuleringen. Våtmarkens storlek i relation till avrinningsområdet hade ett negativt samband med sedimentackumuleringen. Att många faktorer påverkade sedimentackumulationen gjorde att uppgrundningen skedde olika snabbt i våtmarkerna. Därmed kunde inte ett exakt åldersintervall för urgrävning fastställas. Däremot kan urgrävning potentiellt begränsas till början av våtmarker i de fall våtmarken är långsmal med djuphåla vid inloppet. De undersökta våtmarkerna hade varierande grad av renoveringsbehov. Urgrävning bedöms vara den mest resurskrävande åtgärden. Det är dock en nödvändig åtgärd om våtmarkerna ska fortsätta fungera som näringsfällor. Andra renoveringsbehov innefattade exempelvis enklare skötsel av vegetation, reparation av teknisk utrustning såsom rör och brunnar samt uppföljning av avtal med markägare för att se till att våtmarkerna förvaltas på sådant sätt att deras miljönytta gynnas. / Wetlands have been constructed within the catchment area of Råån since the 1990s. Råån is a river flowing through the municipalities Helsingborg, Landskrona, Svalöv, and Bjuv. The constructed wetlands aim to reduce nutrient leakage from surrounding agricultural land and increase biodiversity. In this study 28 constructed wetlands were studied with two aims: (i) to investigate the relationship between sediment accumulation in wetlands and wetland design and location in the landscape and (ii) investigate maintenance needs of the wetlands. Maintenance needs involve taking efforts to restore flow paths, depth profile, vegetation, and inlet and outlet to return the original function and design of the wetland. The study is based on observations and measurements carried out in October 2020. The results showed that sediment accumulation varied between 0.2–2.3 cm per year and that both wetland design and location affected sediment accumulation. Estimated original water depth had a positive correlation with sediment accumulation and sediment depth had a positive correlation with wetland age. The level of shoaling was higher closer to the inlet in four of seven long narrow wetlands (length- width ratio, L: W, > 3). In the long narrow wetlands, there was also a positive correlation between HL and sediment accumulation. However, in shorter and wider wetlands (L: W <3), there was an upper limit where high values of HL instead had a negative effect on sediment accumulation. Wetland area in relation to catchment area had a negative correlation with sediment accumulation. Shoaling rate is different in the wetlands since sediment accumulation is affected by many parameters. Thus, an exact time interval for excavation could not be determined. However, excavation can potentially be limited to the inlet of the wetlands if the wetland is long and narrow with a deep area near the inlet. The result showed that the wetlands had varying degrees of maintenance needs. Excavation is considered to be the most resource-intensive measure. However, excavation is necessary to maintain the function of the wetlands. Other maintenance needs include maintenance of vegetation, repair of technical equipment, and extension and enforcement of contracts with landowners to ensure that the wetlands are managed in such a way that the environmental function of the wetlands are favored.
247

Srovnání účinnosti malých balených ČOV a kořenových ČOV / The comparison of two waste water treatment systems - constructed wetlands and mechanical.

Dudíková, Kristýna January 2010 (has links)
This thesis is focused to the comparison of two wastewater treatment systems - constructed wetlands and mechanical-biological wastewater treatment plant. The main goal of the theses is to compare two types of wastewater treatment systems and to evaluate hypothesis that constructed wetlands are cheaper and more efficient than mechanical-biological wastewater treatment plant. To be able to compare two various wastewater treatment systems 18 (9 constructed wetlands and 9 mechanical-biological plants, three size groups of both types of plants) wastewater treatment plant were chosen and compared. The treatment effectiveness, investment and operating costs, advantages and disadvantages of both the systems were compared. The information about all individual systems was obtained from the local municipalities, operators and partially from the Ministry of Environment of CR. Obtained data involved treatment technology, amount of annual treated water, building data and capital and operating costs. In some waste water treatment plant (WWTP) the water samples were taken and the analyses of chosen parameters (not measured in WWTP) were done. Once in 2010 year the samples of water, sediments and sludges were taken and the analyses of heavy metals was done. For assessment of operational problems in constructed...
248

Analys av bitumenåldring vid tillverkning- och användningsskedet : En jämförelse mellan hur olika tillsatser påverkar bitumenåldring / Analysis of bitumenaging in asphalt : Examine which additive has the most effect on aging of bitumen

Ceylan, Serkan, Elhassan, Mahmoud January 2014 (has links)
Det är viktigt att vägarna håller så länge som möjligt. En faktor som har en påverkan i asfaltens långvarighet är bitumen. När bitumenet föråldras försämras dess egenskaper som ökar risken att skador uppstår på asfalten. Med hjälp av olika tillsatser kan bitumenets egenskaper förbättras. En av dessa egenskaper är bitumenåldring. Sammanlagt finns det tre olika skeden i bitumenåldring. Av dessa tre skeden kommer tillverknings- och användningsskedet att undersökas. I detta examensarbete kommer tre olika tillsatsers påverkan i bitumenföråldring att undersökas. Detta kommer utföras genom laborationer där olika metoder som penetration, mjukpunkt, fraass brytpunkt, DSR, Iatroscan, GPC och FTIR kommer användas. Det kommer också utföras styvhetestester på de tillverkade asfaltskropparna. Resultaten som tas fram i detta examensarbete tyder på att Rediseten har bäst värden avseende åldring utav bitumen. Men detta tros inte vara på grund av tillsatsens inverkan i bitumen utan möjligheten att sänka temperaturen vid tillverkningen av asfalten. / It is important that roads last as long as possible. One factor that has a prolonged effect on asphalt is bitumen. When bitumen ages the characteristics deteriorates which increases the risk for damages on the asphalt. With the help of different additives the characteristics of bitumen could improve. One of these characteristics is bitumen aging. There are three different stages in bitumen aging. Of these three stages will the production and user stage be examined. In this thesis will three additives effect on bitumen aging be examined. This will be performed by doing laboratory experiments where different methods will be used such as penetration, softening point, fraass breaking point, DSR, latroscan, GPC and FTIR. Stiffness tests will be made on the constructed asphalt bodies. Results in this thesis interprets that Rediset has the best values when it comes to aging of bitumen. It is not believed to be the additives effect in the bitumen but the fact that the additive gives the opportunity to lower the temperature during the production of the asphalt.
249

Exploring the relationship between renewable energy development and people-place bonds : Insights from a rural recreation area in southern Sweden

Goudriaan, Yvonne January 2021 (has links)
The transition to a low carbon future is necessary to ensure humanity’s sustainable future, yet the expanding introduction of renewable energy technologies (RETs) is a central driver for transformations in rural landscapes worldwide. Introducing renewable energy (RE) infrastructures in rural landscapes raises concerns about the reduced naturalness and attractiveness of such landscapes for tourism and recreation as well as the transformation of people-place bonds as established through people’s interactions with and experiences in the surrounding landscapes. Few have examined how landscape transformation resulting from RE developments reshapes land users’ bonds with places. Furthermore, previous research has primarily relied on crosssectional quantitative data. This study addresses that literature gap and uses the Nature's Contributions to People (NCP) framework and the evolutionary theory of place attachment as theoretical underpinnings to examine how individuals perceive and experience evolving landscapes. By exploring individuals’ perceptions of and affective bonds with physical landscapes, this study provides a holistic understanding of the bonds that different groups of people may have with a certain place and how these bonds are manifested in the context of RE development and RET-related place change. In-depth interviews with private landowners and recreationists from the municipality of Mönsterås, Sweden, and observations in the Åby-Alebo wind park allow for the coconstruction of narratives reflecting individual accounts of meaning-making processes. The findings demonstrate that place attachment was evident in respondents’ descriptions of how they make a place meaningful to themselves through personal experiences and (recreational) practices. Along with landscape changes, for some individuals, meanings towards and bond with place evolved as well. The discussion shows that the emotional relationship to place reflects respondents’ particular journey in the world and over time. The study also highlights that differences in how recreationists and landowners bond with places is manifested in a changing context, disclosing the relationality of place attachment along social, practical, and temporal contextual factors. This points to encouraging possibilities for discussing the reconceptualization of humanity’s transition towards a low carbon future and fostering more sustainable landscape management in rural recreation areas.
250

Ecological Structure and Function of Bioretention Cells

Wituszynski, David Michael January 2020 (has links)
No description available.

Page generated in 0.2535 seconds