• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 180
  • 96
  • 42
  • 33
  • 16
  • 9
  • 6
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • Tagged with
  • 491
  • 80
  • 52
  • 39
  • 38
  • 28
  • 24
  • 23
  • 23
  • 22
  • 21
  • 21
  • 20
  • 19
  • 19
  • 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.
121

Alternativas para a diminuição da acidificação do bulbo molhado na cultura do citros

Foratto, Leticia Cecilia [UNESP] 13 November 2012 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-11-13Bitstream added on 2014-06-13T20:43:44Z : No. of bitstreams: 1 foratto_lc_dr_botfca.pdf: 786989 bytes, checksum: 01afbab1f868718232ccbf41ee3c4b81 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / O Brasil é o maior produtor mundial de laranja, sendo o estado de São Paulo, responsável por aproximadamente 85% da produção. Nos últimos anos, a citricultura nacional vem adotando o sistema de irrigação localizada que tem contribuído para o aumento de produtividade, bem como, a utilização crescente da fertirrigação. Entretanto, a característica ácida conferida aos fertilizantes solúveis comumente utilizados na fertirrigação, associados à forma de aplicação (irrigação localizada) e a característica dos solos brasileiros que, naturalmente são ácidos, promovem rápida acidificação da solução do solo, atingindo valores de pH prejudiciais ao desenvolvimento da cultura. Portanto, neste experimento foi proposto o estudo de alternativas para diminuir a acidez do solo causada pela adoção da técnica de fertirrigação na citricultura, monitorando a reação da solução do solo com o auxilio de extratores de solução. O experimento foi conduzido em Reginópolis/SP/Brasil, durante duas safras e em laranjeiras Hamlin sobre porta enxerto citrumelo Swingle. Os tratamentos consistiram de dois materiais corretivos e fontes de fertilizantes de caráter básico: 1 – controle (sem material corretivo); 2 – calcário aplicado em faixa de 1,40 m; 3 – calcário aplicado em faixa de 2,80 m; 4 – cal hidratada aplicada em faixa de 1,50 m com barra de herbicida; 5 – cal hidratada via sistema de fertirrigação e 6 – fontes de fertilizantes com caráter básico via sistema de fertirrigação (nitrato de cálcio+MAP). Para monitorar a reação do solo foi avaliada mensalmente a solução do solo e as análises de solo e folhas foram feitas duas vezes ao ano, para determinar, respectivamente, a fertilidade do solo e o estado nutricional da cultura. A uniformidade de aplicação de... / The Brazil is the largest producer of orange, and the state of São Paulo, which accounts for 85% of production. In recent years, the national citriculture is adopting the irrigation system that has contributed to increased productivity, as well as the increasing use of fertigation. However, given the characteristic acid soluble fertilizers commonly used in fertigation, associated with the form of application (drip irrigation) and the characteristic of the Brazilian soils that are naturally acidic, promote rapid acidification of soil solution, reaching values of pH affects the development of culture. Therefore, this experiment was proposed to study alternatives to reduce soil acidity caused by the adoption of fertigation technique in citrus, monitoring the reaction of the soil solution with the aid of solution extractors. The experiment was conducted in Reginópolis / SP / Brazil, during two growing seasons and an orange orchard variety Hamlin on the rootstock Swingle citrumelo. The treatments consisted of two corrective materials and fertilizer sources of basic character: 1 – control (without correction material); 2 – lime applied in the range fo 1.40 m; 3 – lime applied in the range of 2.80 m; 4 – hydrated lime applied in the range of 1.50 m with herbicide bar; 5 – hydrated lime via fertigation system and 6 – alternative sources of fertilizers through fertigation system. To monitor the soil reaction was evaluated monthly soil solution and analysis of soil and leaves were made twice a year to determine the nutritional status of the culture. The uniformity of water application and fertilizer was checked monthly due to the application of hydrated lime via fertigation system (5). In the final period of each crop production was quantified. The results observed in both seasons show differentiation between treatments occuring reducing... (Complete abstract click electronic access below)
122

Disponibilidade de fósforo em função da aplicação de calcário e silicatos em solos oxídicos /

Sandim, Aline da Silva, 1988- January 2012 (has links)
Orientador: Leonardo Theodoro Büll / Banca: Dirceu Maximino Fernandes / Banca: Renato de Mello Prado / Resumo: Partindo do princípio que a aplicação do silicato pode resultar em aumento na disponibilidade de fósforo no solo para as culturas, objetivou-se estudar a influência da silicatagem, em comparação à calagem, na dessorção de fósforo em solos com fósforo previamente adsorvido, avaliada por dois extratores e pelo crescimento da planta. O delineamento experimental utilizado foi em blocos casualizados, com quatro repetições, em esquema fatorial 3 x 3 x 5 , constituídos por três solos, três doses de fósforo e quatro corretivos de acidez, além de um tratamento sem correção da acidez, totalizando 180 parcelas experimentais. O experimento foi realizado em casa de vegetação, em vasos de 20 L. Os solos foram submetidos a três doses de P, (0, 50 e 150 mg dm-3), tendo como fonte superfosfato triplo em pó e mantidos incubados por 90 dias. Após o período de incubação foram realizadas amostragens, para análise química de rotina e determinações dos teores de P através dos métodos resina, Mehlich 1 e P remanescente. Com base nesses resultados foi realizada a aplicação dos corretivos de acidez calculando-se as doses visando a elevar a 70% o valor de saturação por bases. Os corretivos de acidez utilizados foram: calcário dolomítico, escória de aciaria, escória de aciaria forno de panela, e wollastonita. Após a aplicação dos corretivos, os solos permaneceram incubados por mais 60 dias e novas determinações dos níveis de P foram realizadas. A cultura utilizada foi o milho. Nos solos foram realizadas determinações químicas de P, demais nutrientes e Si. Na planta foram realizadas avaliações de produção de massa seca, acúmulo de nutrientes e de Si e determinação do índice de clorofila. Os dados foram submetidos à análise de variância e as médias dos tratamentos foram comparadas pelo teste Tukey a... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Assuming that the application of silicate can result in increased availability of phosphorus in the soil for crops, aimed to study the influence of silicatagem compared to lime, the desorption of previously adsorbed soil phosphorus as assessed by two extractors and the plant growth. The experimental design was randomized blocks with four replications in a factorial 5 x 3 x 3, consisting of three solos, three and four doses of phosphorus lime acidity, and a treatment without liming, totaling 180 plots . The experiment was conducted in a greenhouse in pots of 20 L. The soils were subjected to three levels of P, (0, 50 and 150 mg dm-3), and triple superphosphate as source powder and kept incubated for 90 days. After the incubation period was sampled for routine chemical analysis and determination of the levels of P by the methods resin, the remaining P and Mehlich 1. Based on these results was performed liming acidity calculating the doses in order to raise the value of 70% saturation. The different lime sources used were limestone, steel slag, steel slag pot furnace, and wollastonite. After liming, the soils were incubated for another 60 days and further determinations of P levels were made. The culture was maize. The soils were subjected to chemical P, Si and other nutrients in the plant were evaluated for dry matter production, nutrient accumulation and determination of Si and chlorophyll content. The data were submitted to ANOVA and treatment means were compared by Tukey test at 5% probability. The slag increased the levels of phosphorus in the soil, when compared to the limestone, suggesting positive interaction between Si and P in the soil. The Mehlich 1 and resin were highly correlated with P extracted and phosphorus uptake by plants, regardless of the soil. For all parameters analyzed in the plant, there was... (Complete abstract click electronic access below) / Mestre
123

Aplicação de escória de aciaria e calcário no solo e desenvolvimento do primeiro ciclo da grama bermuda /

Oliveira, Mauricio Roberto de, 1988- January 2012 (has links)
Orientador: Dirceu Maximino Fernandes / Co-orientador: Roberto Lyra Villas Bôas / Banca: Clarice Backes / Banca: Hélio Grassi Filho / Resumo: O mercado brasileiro de grama cultivada tem expandido em decorrência a maior demanda em áreas paisagísticas e esportivas. Para maximizar a produção de grama, de maneira econômica, os tapetes devem ser produzidos com qualidade e em um tempo reduzido, sendo assim, a preparação do solo tem grande influência na produtividade dos gramados. Diante disso, tem se estudado diferentes corretivos da acidez do solo, e o mais novo é um subproduto da fabricação do aço, conhecido como escória de aciaria. Uma das vantagens de sua utilização é a possibilidade da correção do solo em maior profundidade, visto que a solubilidade de seu principal componente, o silicato de cálcio, é 6.78 vezes maior que a do carbonato de cálcio, o componente fundamental do calcário, que ainda hoje é o corretivo mais utilizado. Além disso, a grama é uma planta acumuladora de silício, e, portanto, poderá responder com maior facilidade ao silicato de cálcio. Desta forma, o objetivo foi avaliar o efeito da aplicação de escória de aciaria, comparado ao calcário, na implantação de um sistema de produção de grama bermuda. O experimento foi instalado no município de Botucatu, em uma área experimental da Unesp - fazenda Lageado, cujo solo é classificado como latossolo vermelho distrófico com textura média. O delineamento experimental foi realizado em blocos ao acaso de quatro repetições e com subparcelas de quatro doses de escória, quatro doses de calcário e uma testemunha, elevando a saturação de base do solo a 30%, 50%, 70% e 90%, e foram avaliadas diversas características do solo e da planta, e os dois corretivos aplicados ao solo na influência da produção da grama bermuda. Com a análise dos resultados, observou-se uma modificação no solo, quando aplicado os corretivos, tendo uma elevação nos teores de P e Ca para à escória de aciaria, e nos... (Resumo completo, clicar acesso eletrônico aba / Abstract: The Brazilian market of cultivated grass has expanded due to increased demand in scenic and sports areas. To maximize the production of grass, cost-effectively, the rugs should be produced with quality and in a shorter timeframe, so the soil preparation has great influence on the productivity of grasslands. Whereupon, has studied various correctives of the acidity of the soil, and the youngest is a by-product from the manufacture of steel, known as steelmaking slag. One of the advantages of their use is the possibility of correction of soil in greater depth, since the solubility of its main component, calcium silicate, is 6.78 times greater than that of calcium carbonate, the basic component of limestone, which is still the most widely used concealer. In addition, the grass is a Silicon-accumulating plant, and therefore be able to respond more easily to calcium silicate. In this way, the objective was to evaluate the effect of the application of steelmaking slag, compared to limestone, in deploying a production system of bermuda grass. The experiment was installed in the city of Botucatu, in an experimental area of Unesp-farm Lageado, whose soil is classified as red latosol textured red latosol. The experiment was conducted in randomized blocks with four repetitions and subplots of four doses of slag, four doses of lime and a witness, raising the soil base saturation at 30, 50, 70 and 90, and were assessed several characteristics of soil and plant, and the two soil applied correctives in influences the production of bermuda grass. With the analysis of the results, it was observed a change in the soil when applied the correction, with an elevation in the levels of P and Ca for the steelmaking slag, and in Mg for limestone, and there is no difference for the other nutrients. The availability of micro-nutrients have increased with the use of correctives, having... (Complete abstract click electronic access / Mestre
124

Alternativas para a diminuição da acidificação do bulbo molhado na cultura do citros /

Foratto, Leticia Cecilia, 1980- January 2012 (has links)
Orientador: Roberto Lyra Villas Bôas / Coorientador: Thais Regina de Souza / Banca: Dirceu Maximino Fernandes / Banca: João Carlos Cury Saad / Banca: José Renato Zanini / Banca: José Eduardo Creste / Resumo: O Brasil é o maior produtor mundial de laranja, sendo o estado de São Paulo, responsável por aproximadamente 85% da produção. Nos últimos anos, a citricultura nacional vem adotando o sistema de irrigação localizada que tem contribuído para o aumento de produtividade, bem como, a utilização crescente da fertirrigação. Entretanto, a característica ácida conferida aos fertilizantes solúveis comumente utilizados na fertirrigação, associados à forma de aplicação (irrigação localizada) e a característica dos solos brasileiros que, naturalmente são ácidos, promovem rápida acidificação da solução do solo, atingindo valores de pH prejudiciais ao desenvolvimento da cultura. Portanto, neste experimento foi proposto o estudo de alternativas para diminuir a acidez do solo causada pela adoção da técnica de fertirrigação na citricultura, monitorando a reação da solução do solo com o auxilio de extratores de solução. O experimento foi conduzido em Reginópolis/SP/Brasil, durante duas safras e em laranjeiras Hamlin sobre porta enxerto citrumelo Swingle. Os tratamentos consistiram de dois materiais corretivos e fontes de fertilizantes de caráter básico: 1 - controle (sem material corretivo); 2 - calcário aplicado em faixa de 1,40 m; 3 - calcário aplicado em faixa de 2,80 m; 4 - cal hidratada aplicada em faixa de 1,50 m com barra de herbicida; 5 - cal hidratada via sistema de fertirrigação e 6 - fontes de fertilizantes com caráter básico via sistema de fertirrigação (nitrato de cálcio+MAP). Para monitorar a reação do solo foi avaliada mensalmente a solução do solo e as análises de solo e folhas foram feitas duas vezes ao ano, para determinar, respectivamente, a fertilidade do solo e o estado nutricional da cultura. A uniformidade de aplicação de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Brazil is the largest producer of orange, and the state of São Paulo, which accounts for 85% of production. In recent years, the national citriculture is adopting the irrigation system that has contributed to increased productivity, as well as the increasing use of fertigation. However, given the characteristic acid soluble fertilizers commonly used in fertigation, associated with the form of application (drip irrigation) and the characteristic of the Brazilian soils that are naturally acidic, promote rapid acidification of soil solution, reaching values of pH affects the development of culture. Therefore, this experiment was proposed to study alternatives to reduce soil acidity caused by the adoption of fertigation technique in citrus, monitoring the reaction of the soil solution with the aid of solution extractors. The experiment was conducted in Reginópolis / SP / Brazil, during two growing seasons and an orange orchard variety Hamlin on the rootstock Swingle citrumelo. The treatments consisted of two corrective materials and fertilizer sources of basic character: 1 - control (without correction material); 2 - lime applied in the range fo 1.40 m; 3 - lime applied in the range of 2.80 m; 4 - hydrated lime applied in the range of 1.50 m with herbicide bar; 5 - hydrated lime via fertigation system and 6 - alternative sources of fertilizers through fertigation system. To monitor the soil reaction was evaluated monthly soil solution and analysis of soil and leaves were made twice a year to determine the nutritional status of the culture. The uniformity of water application and fertilizer was checked monthly due to the application of hydrated lime via fertigation system (5). In the final period of each crop production was quantified. The results observed in both seasons show differentiation between treatments occuring reducing... (Complete abstract click electronic access below) / Doutor
125

Geochemistry in the Critical Zone: limestone-shale and kimberlite weathering in the Flint Hills, Kansas, USA

Gura, Colleen Marie January 1900 (has links)
Master of Science / Department of Geology / Saugata Datta / Pamela Kempton / The Critical Zone is the realm where rocks meet life. This study examines the physicochemical interactions that occur when interbedded limestone-shale systems and kimberlitic rocks weather to form soils. Fast weathering processes with extensive soil loss have been a major environmental concern in the Flint Hills for decades. Knowledge of soil formation processes, rates of formation and subsequent loss, and understanding how these processes differ in different systems are critical for managing soil as a resource. Kimberlites are CO₂-rich igneous rocks that are high in Mg and Fe; they are compositionally distinct from the Paleozoic limestones and shales found throughout the rest of the region. This study will compare the geochemistry and mineralogy of the Stockdale Kimberlite in Riley county to that of interbedded limestone-shale system typical of the Flint Hills as sampled from Konza Prairie LTER. Bulk composition and mineralogy of the soils overlying these different bedrock types have been analyzed using X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), bulk elemental extractions, and particle size analyses. Results show that the kimberlitic soils have higher concentrations of Fe, Mg, Ca, K and some trace elements in greater proportions (e.g. Ti, Ni, Cu). The weathering products differ mineralogically as well, e.g. lizardite is abundant in kimberlitic soils and absent from the limestone terranes. Kimberlite derived soils also contain minerals as well such as kleberite (an alteration product of illminite), phlogopite, and magnetite. Kimberlite-sourced soils have different physical properties than the thin limestone-sourced soils surrounding them. Particle size analysis shows that the limestone-shale soils have different proportions of the clay size fraction in different core locations (~47% in highlands, ~51% at watershed base, ~41% in lowlands) whereas kimberlitic soils have a larger sand fraction than Konza (~19% vs. 10%). Clay minerals from the limestone-shale system reveals clay micas, kaolinite, and some expandable 2:1 layer silicates. Clay minerals from kimberlite-sourced soils are identified as primarily smectites with clay micas and kaolinites. Similarities between the kimberlite and limestone-shale soils are primarily seen in the shallower portions of the soil profile, suggesting that loess/wind-blown dust make a significant contribution to the soils in both areas. It could be concluded that kimberlite-sourced and limestone-shale-sourced soils produce weathering products that differ both chemically and mineralogically and could potentially have agricultural significance in terms of water retention as well as ionic and nutrient mobilities in these soils.
126

Caracterização da molhabilidade de coquinas da formação Coqueiro Seco / Wettability characterization of coquinas from Coqueiro Seco formation

Espinosa Leon, Carlos 02 April 2013 (has links)
Orientador: Rosângela Barros Zanoni Lopes Moreno / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-22T07:30:06Z (GMT). No. of bitstreams: 1 EspinosaLeon_Carlos_M.pdf: 5382010 bytes, checksum: fdf960a158541b21f9deb9c7f4593f44 (MD5) Previous issue date: 2013 / Resumo: A molhabilidade tem sido reconhecida como um fator importante controlando a localização microscópica, distribuição e escoamento de fluidos em um meio poroso. Afeta a saturação de água irredutível e de óleo residual assim como as curvas de permeabilidade relativa e pressão capilar do meio poroso, impactando significativamente na recuperação final de óleo. Evidencias de estudos de laboratório têm mostrado que as rochas carbonáticas são de molhabilidade mista a preferencialmente molhadas por óleo. Estas condições são desfavoráveis para a embebição espontânea da água e, portanto, para projetos de injeção de água como método de recuperação. Conforme estudos sobre interações óleo/água/rocha, a composição e propriedades da água injetada podem alterar as propriedades de molhabilidade das rochas durante processos de injeção de água, melhorando a recuperação de petróleo. O principal objetivo deste trabalho é caracterizar a molhabilidade de um bloco de coquinas de afloramento provenientes da Formação Coqueiro Seco - Bacia Sergipe-Alagoas, que são equivalentes às rochas dos reservatórios do pré sal. As medidas do índice de molhabilidade foram realizadas pelo método de Amott, que combina a embebição espontânea e forçada de fluidos para determinar a molhabilidade média das amostras carbonáticas. Óleo mineral e soluções aquosas com salinidade variando de 10000 a 140000 ppm de NaCl foram usadas para representar o óleo e a água de injeção, respectivamente. Os resultados obtidos dos testes realizados neste estudo evidenciam que este tipo de rocha é de molhabilidade mista a preferencialmente molhadas por óleo / Abstract: Wettability has been recognized as an important factor controlling the microscopic location, distribution and fluid flow through a porous medium. It affects the irreducible water saturation and residual oil saturation as well as the relative permeability curves and capillary pressure impacting the ultimate recovery oil. Evidence from laboratory studies have shown that carbonate rocks are mixed wettability to preferentially oil wet which are unfavorable conditions for spontaneous imbibition of water and therefore in the design of a waterflooding process as a recovery method. As studies on oil/water/rock interactions the composition and properties of the injected water can alter the wetting properties of rocks during a waterflooding improving oil recovery. The main objective of this work is to measure the wettability of coquina outcrops from the Coqueiro Seco Formation - Sergipe-Alagoas Basin, which are equivalent to pre-salt reservoir rocks. Wettability index measurements were carried out with the Amott method which combines spontaneous and forced imbibition of fluids to determine the average wettability of carbonate cores. Mineral oil and brines with salinity ranging from 10.000 to 140.000 ppm of NaCl were used to represent crude oil and the injection brine respectively. The results of the tests addressed in this study provided evidences that these rocks are mixed-wet to preferentially oil-wet / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo
127

Late Pleistocene reef limestones, Northern Barbados, W.I.

James, Noel P. January 1971 (has links)
No description available.
128

A Kimberlite, Its Mineralogy, and Implications

Convery, Thie 03 May 1990 (has links)
<p> Kimberlite diatremes from a single genetic source were examined. Macrocryst and groundmass constituents were identified, as well as their alteration products. It was hypothesized that carbon dioxide and water vapour were present at the time of formation. Limestone inclusions and peridotite xenoliths were examined, as well as fabrics within the xenoliths. It was concluded that water is present in the upper mantle. Ilmenite nodules were determined to be phenocrysts, as opposed to xenocrysts. A paragenetic sequence for the kimberlite was resolved. Ilmenite was classified as the best indicator mineral for exploration purposes.</p> / Thesis / Bachelor of Science (BSc)
129

Dissolution Caves of Mississippi

Moore, Christopher Michael 13 May 2006 (has links)
The purpose of this project was to distinguish between the karst and pseudokarst caves throughout Mississippi, create an inventory and survey of representative caves and karst features, identify the geology of the rocks hosting the caves, and produce a GIS-based digital karst map. The State of Mississippi is not known for its karst features, yet there are three distinct limestone units that contain dissolution caves: 1) Paleozoic (Mississippian) Tuscumbia Formation limestone; 2) Mesozoic carbonate units; and 3) Cenozoic limestone, Marianna Formation. There are a total of 44 caves known within the state based on past documentation, however the caves listed are not always differentiated between karst or pseudokarst features. This study located and mapped 20 caves, of which 18 were karst caves from eight counties and two were pseudokarst caves from two counties. Four of these caves were newly discovered karst caves, increasing the state total to 48; however two separate karst caves were connected, which makes the final state total 47 caves. Of the remaining 28 caves not surveyed, 11 were pseudokarst caves from eight counties and were not studied because the focus was on dissolutional karst caves. The remaining 17 missing karst caves either had been destroyed, access permission could not be obtained, or the caves could not be located. No active caving organizations exist in Mississippi to preserve cave location data or the caves themselves. Mining, deforestation, and other land use procedures have altered the landscape, resulting in concealment of some caves, and completely or partially destroying other caves.
130

Taphonomic and Sedimentologic Study of the Cretaceous Tepee Buttes Limestone

Close, Hilary G. January 2006 (has links)
No description available.

Page generated in 0.0907 seconds