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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.
81

Using blue light reflectance from high-resolution images (6000 dpi) of Scots pine tree rings to reconstruct three centuries of Scottish summer temperatures / Temperaturrekonstruktion av skotska sommartemperaturer med hjälp av blå ljusreflektion från högupplösta skotska tallprover (6000 dpi)

De Schutter, Alice, Markendahl, Karin January 2021 (has links)
Advances in scanner technology have made it possible to obtain high resolution (6000 dpi) images of tree samples. Due to the images’ increased capability of resolving anatomical wood structures, the new technology could be of benefit to dendroclimatology.  This study attempts to expand on Rydval et al.’s (2017) previous 800 years reconstruction of Scottish summer temperatures by assessing whether a higher image resolution of samples has the ability to improve the accuracy of the region’s temperature reconstruction. Two independent blue intensity (BI) chronologies, based on differing image resolutions (6000 dpi and 2400 dpi) of Scots pine samples, were developed and subjected to standard detrending procedures. Raw data from Rydval et al.’s (2017) prior study was used to develop the chronology which was based on the 2400 dpi images. On the other hand, newly acquired data was utilized for the other chronology. In order to resolve the primary question that this paper explores, the characteristics and strength of the two BI chronologies’ climatic signals were compared. In addition, the newly acquired data was used to develop a 318 years reconstruction of mean July/August temperatures for Scotland.  Calibrations against meteorological data indicated that the improved image resolution did not generate a positive effect on the chronology’s ability to retain a reliable climatic signal. The study’s findings were thus inconclusive in showing that a higher image resolution of Scots pine samples improves the accuracy of temperature reconstructions for Scotland. Future studies are encouraged to investigate the applicability of dendroclimatic computer softwares (i.e. CooRecorder) with regard to a high image resolution.  From a broader perspective, this study contributes to setting climate change in a more accurate long term spatiotemporal context. This is crucial in predicting future climate variability, as well as understanding the role and extent of anthropogenic forcing. / Framsteg inom skannerteknik har gjort det möjligt att få bilder av trädprover med hög upplösning (6000 dpi). På grund av bildernas ökade förmåga att lösa anatomiska träd strukturer kan den nya tekniken vara till nytta för dendroklimatologi.  Denna studie strävar mot att utveckla Rydval et al.s (2017) tidigare 800 års rekonstruktion av skotska sommartemperaturer genom att bedöma om en högre bildupplösning av prover har förmågan att förbättra noggrannheten för regionens temperaturrekonstruktion. Två oberoende blåintensitet (BI) -kronologier, baserade på olika bildupplösningar (6000 dpi och 2400 dpi) av skotska träprover, framtogs och utsattes för standardförfaranden. Rådata från Rydval et al.s (2017) tidigare studie användes för att utveckla kronologin som baserades på 2400 dpi-bilderna. Å andra sidan användes nyförvärvade data för den andra kronologin. För att besvara den primära frågan som denna studie undersöker jämfördes egenskaperna och styrkan hos de två BI-kronologins klimat signaler. Dessutom används de nyförvärvade uppgifterna för att utveckla en 318 års rekonstruktion av genomsnittliga juli/augusti temperaturer för Skottland.  Kalibreringar mot meteorologiska data indikerade att den förbättrade bildupplösningen inte genererade en positiv effekt på kronologins förmåga att behålla en pålitlig klimat signal. Studiens resultat var således otvetydiga när de visade att en högre bildupplösning av skotsk tallprover förbättrar noggrannheten i temperatur rekonstruktioner för Skottland. Framtida studier uppmuntras att undersöka användbarheten av dendroklimatiska datorprogram (dvs CooRecorder) med avseende på en ultrahög bildupplösning.  Ur ett bredare perspektiv bidrar denna studie till att placera klimatförändringarna i ett mer exakt långsiktigt rumsligt tidsmässigt sammanhang. Detta är avgörande för att förutsäga framtida klimatvariationer samt förstå rollen och omfattningen av antropogen tvingande.
82

Obtenção e caracterização de compósito verde de casca de pinhão e poliuretana derivada do óleo de mamona / Preparation and characterization of pinhão husk and polyurethane derived from castor oil green composite

Protzek, Giuliana Ribeiro 13 December 2017 (has links)
Compósitos verdes são caracterizados por possuir matriz polimérica e reforço derivado de fontes naturais. Polímeros derivados do petróleo não são biodegradáveis e possuem solventes orgânicos na sua composição. Solventes orgânicos são tóxicos e poluentes. A poliuretana derivada do óleo de mamona é derivada de fonte renovável, biodegradável e não possui solventes orgânicos em sua composição. A casca de pinhão é um resíduo do pinhão, semente do pinheiro de Paraná. O objetivo desse trabalho é desenvolver e caracterizar o compósito de casca de pinhão com PU derivada do óleo de mamona. A fibra foi caracterizada quimicamente, por FTIR, TGA e MEV. A PU foi caracterizada por ensaio de resistência à flexão, FTIR e TGA e os compósitos, por testes de densidade, absorção de água, inchamento em espessura, resistência à flexão de três pontos, FTIR e TGA. A superfície da fratura foi avaliada por MEV e a homogeneidade dos compósitos por perfil de densidade e raios-X. O compósito de 35%PU apresentou resistência à flexão de 51,55 MPa, densidade de 1018 kg/m³, absorção de água em 24 horas de 7,95% e inchamento em espessura em 24 horas de 5,36%. O material apresenta propriedades mecânicas apropriadas para uso em mobiliário e artesanato. / Polymeric composites reinforced with natural fibers are denominated green composites. Polymers comes from petroleum source, a non-biodegradable material and has volatile organic compounds, VOC, in its composition. Organic solvent are toxics and pollute the environment. The Polyurethane derived from castor oil is polymer produced from renewable sources, biodegradable material and there are no VOC in its composition. Araucária pine nut shell is a residue from its Araucaria pine seed. The aim of this work is to develop and characterize composites of pine nut shell with polyurethane derived from castor oil. The fiber was chemically characterized, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). PU was characterized by flexural strength, FTIR and TGA and composites was characterizes by density test, water absorption and swelling in thickness, flexural strength, FTIR, TGA. SEM evaluated the fracture surface and X-ray and vertical density profile verified the composites homogeneity. 35%PU composites presented flexural strength of 51,55 MPa, density of 1018 kg/m³, 7,95% of 24h water absorption and 5,36% of 24h swelling in thickness of. The material exhibits properties suitable for use in furniture and handicrafts.
83

Implementación de un controlador difuso de temperatura prototipo usando la inferencia difusa de Takagi Sugeno

Huamán Bustamante, Jesús Omar January 2007 (has links)
No description available.

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