Tesis sobre el tema "Poor soil"
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Rwehumbiza, Filbert. "The effect of seed and soil physical conditions on establishment of sorghum". Thesis, University of Aberdeen, 1994. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU538899.
Texto completoSaidin, Fadzilah. "Behavior of geosynthetic reinforced soil walls with poor quality backfills on yielding foundations /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10124.
Texto completoDonaldson, Jason. "Are forests restricted by nutrient poor soils? : an analysis of soil nutrient stocks and associated vegetation in the fynbos biome, South Africa". Bachelor's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/26584.
Texto completoCAMELIN, ENRICO. "Waste meets poor soils: perspectives on sewage sludge recycling". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2842501.
Texto completoTurkoglu, Melih. "Two-dimensional Numerical Analysis Of Tunnel Collapse Driven In Poor Ground Conditions". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615456/index.pdf.
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k in the Bilecik Province. The collapsed section of the tunnel was driven into a highly weathered, weak to medium rock mass. Unanticipated geological/geotechnical circumstances caused excessive deformations at the section on which the primary support system was applied, leading eventually to collapse. To understand the response of the tunnel and the collapse mechanism, the construction sequence is simulated using two-dimensional plane-strain and axisymmetric finite element models. The analyses were carried out for the section with and without invert closure of the shotcrete liner. To implement the effects of likely unfavorable ground conditions on the tunnel response, a number of fault scenarios and possible creep effects were also considered with those two alternatives. Displacements in the tunnel periphery, forces and moments in the primary liner as well as the plastic deformation zones in the surrounding ground were determined for each case and comprasions were made accordingly. It is concluded that the unforseen ground circumstances might have substantially aggravated the deformations in the section and that the lack of ring closure of the primary liner at invert played the key role in the collapse.
Osorio, Leyton Javier Mauricio. "Assessment of SWAT to Enable Development of Watershed Management Plans for Agricultural Dominated Systems under Data-Poor Conditions". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/27747.
Texto completoPh. D.
Abou, El Goud Amal Karam Sayed Ahmed. "Effect of endomycorrhizal fungi and compost on the yield and quality of maize and sunflower plants in poor nutrients soil". Kassel Kassel Univ. Press, 2010. http://d-nb.info/1003132960/04.
Texto completoAbou, El Goud Amal Karam Sayed Ahmed [Verfasser]. "Effect of Endomycorrhizal Fungi and Compost on the Yield and Quality of Maize and Sunflower Plants in Poor Nutrients Soil / Amal Karam Sayed Abou El-Goud". Kassel : Kassel University Press, 2010. http://d-nb.info/1016840985/34.
Texto completoWadgaonkar, Shrutika. "Nouveaux procédés de bioremédiation pour le traitement des sols et des sédiments sélénifères". Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1105.
Texto completoThe aim of this Ph.D. was to develop a technology for the remediation of seleniferous soils/sediments and to explore microbial reduction of selenium oxyanions under different respiration conditions and bioreactor configurations.Seleniferous soil collected from the wheat-grown agricultural land in Punjab (India) was characterized and its soil washing was optimized by varying parameters such as reaction time, temperature, pH and liquid to solid ratio. In order to maximize selenium removal and recovery from this soil, effect of competing ions and oxidizing agents as chemical extractants for soil washing were also studied. Although oxidizing agents showed a maximum selenium removal efficiency (39%), the presence of oxidizing agents in the leachate and the agricultural soil may increase the cost of their post-treatment. Aquatic plants, Lemma minor and Egeria densa were used to study phytoremediation of the soil leachate containing oxidizing agents. However, the selenium removal efficiency by aquatic weeds was significantly affected by the high concentrations of these oxidizing agents in the soil leachate.Seleniferous soil flushing revealed the selenium migration pattern across the soil column. Migration of soluble selenium fraction from the upper to the lower layers and its subsequent reduction and accumulation in the lower layers of the soil column was observed during soil flushing. The selenium removal efficiency by the soil flushing method decreased with an increase in the column height. Furthermore, the soil leachate containing selenium oxyanions obtained from soil washing was treated in a UASB reactor by varying the organic feed. Effluent containing less than 5 μg L-1 selenium was achieved, which is in accordance with the USEPA guidelines for selenium wastewater discharge limit.Moreover, ex situ bioremediation of selenium oxyanions was studied under variable conditions. An aerobic bacterium (Delftia lacustris) capable of transforming selenate and selenite to elemental selenium, but also to hitherto unknown soluble selenium ester compounds was serendipitously isolated and characterized. Alternatively, anaerobic bioreduction of selenate coupled to methane as electron donor was investigated in serum bottles and a biotrickling filter using marine sediment as inoculum. Finally, the effect of contamination of other chalcogen oxyanions in addition to selenium was studied. Simultaneous reduction of selenite and tellurite by a mixed microbial consortium along with the retention of biogenic Se and Te nanostructures in the EPS was achieved during a 120-day UASB bioreactor operation
Rodriguez, Tiago Garcia. "Caracterização geotécnica de um solo de diabásio por meio de ensaios SPT e CPT". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258775.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: A presente dissertação tem por objetivo apresentar a caracterização geotécnica do solo de diabásio do Campo Experimental da Faculdade de Engenharia Civil da Unicamp, por meio de ensaios de campo SPT e CPT. Verificar a adequabilidade dos ensaios as condições do solo tropical, lateritico, típico da região de Campinas, por meio de proposicoes de classificação de comportamento de solos e da estimativa de parâmetros geotécnicos, assim como as possíveis correlações, teóricas e empíricas, entre os dois ensaios. Foram utilizados ensaios de cone, mecânico e elétrico, e ensaios SPT com medição de energia. As propostas para classificações dos tipos de solo, através do CPT, utilizadas indicaram duas camadas distintas a primeira de solos de comportamento arenosos a silto-arenosos e a segunda de solos de comportamento siltosos a siltoargilosos, em concordância com a classificação obtida em laboratório. As proposicoes utilizadas para estimativa de parâmetros geotécnicos tiveram que ser ajustadas para o solo do campo experimental. A correlação (qc/pa)/N60 obtida foi de 4 para o solos coluvionar (areno-siltoso) e 2,5 para o solo residual (siltoso) em concordância com os valores encontrados na literatura
Abstract: The purpose of this dissertation is to present the geotechnical characterization of the diabasic soil of the Experimental Field of the Unicamp School of Civil Engineering by means of SPT and CPT field trials, and to check the adequacy of such trials to the conditions of the tropical, lateritic soil, which is typical of the Campinas region by means of propositions to classify the behavior of the soils and estimation of geotechnical parameters, as well as possible theoretical and empirical correlations between the two trials. Cone, mechanical and electrical trials were used as well as SPT trials with measurement of energy. The proposals used to classify the types of soil via CPT indicated two separate layers: the first one with soils with sandy to silty-sandy behavior, and the second layer of soils with silty to silty-clayey behavior, in agreement with the laboratory classification. The propositions used to estimate the geotechnical parameters had to be adjusted to the soil of the experimental field. The correlation (qc/pa)/N60 obtained was 4 for colluvial soil (sandy-silty), and 2.5 for residual soil (silty) in agreement with the values found in the literature
Mestrado
Geotecnia
Mestre em Engenharia Civil
Barbosa, Luís Alfredo Pires. "Compactação do solo gerada por pneus de alta flutuação de eixo livre e trativo". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256834.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: O aumento da mecanização das lavouras gera o emprego de máquinas cada vez mais potentes e, a potência possui relação direta com o peso. Aumentando-se o tráfego de máquinas pesadas sobre o solo o emprego do pneu correto é de suma importância para se minimizar os efeitos da compactação. Com as diferenças entre os modelos de pneus de alta flutuação para eixos livres e trativos (com garras) e o comum emprego de pneus trativos em eixos livres devido ao seu custo de imposto ser reduzido, questionou-se a possibilidade de o emprego do pneu mais barato estar prejudicando a produtividade, pelo fato de apresentar uma área de contato possivelmente menor. Objetivou-se ao estudo comparativo entre dois modelos de pneus de alta flutuação da mesma medida, porém um para eixos livres e outro para eixos trativos. Os experimentos foram conduzidos em caixa de solos e também em superfície rígida, sob condições controladas, realizando-se ensaios estáticos para duas cargas radiais (16 e 29 kN), medindo-se deformações, áreas de contato e compactação do solo, sendo feita uma análise estatística fatorial, com os fatores pneu e carga, sendo realizados 8 ensaios, totalizando 32 observações. Obteve-se como resultados, deformações maiores para o pneu trativo, bem como área de contato maior e compactações menores, que o pneu de eixo livre, isso porque a área de contato do pneu trativo envolve não somente as garras, mas também o fundo íncavo (região entre garras), para o solo estudado, e o fato do pneu possuir uma quantidade de composto de borracha menor em sua banda de rodagem, quando comparado com o pneu de eixo livre, aumenta a flexibilidade da rodagem, melhorando sua capacidade de deformação e consequentemente aumentando sua área de contato com o solo
Abstract: The increased mechanization in farming generates employment of ever more powerful machines, and power has direct relationship with the weight. Increasing traffic of heavy machinery on the ground the use of correct tire is of paramount importance to minimize the effects of compaction. With the differences between models of high-flotation tires for free and trative axes, especially regarding the presence of claws, and the common use of tires trative on free axes because of the cost of tax be reduced, questioned the possibility of employment tire cheaply be hindering productivity, because this has a contact area possibly lower. The objective is then to the comparative study between two models of high-flotation tires the same size, but one for free axes and another for trative axes. The experiments were conducted in soil bin and also in rigid surface, under controlled conditions, performing static tests for two radial loads (16 and 29 kN), by measuring deformation, contact areas and soil compaction, and made a factorial statistical analysis with the tire and load factors, was conducted 8 tests, totaling 32 observations. Was obtained as result, larger deformations for the trative tire as well as larger contact area and less compaction of the soil that tire of free axis, that because the contact area of the tire tractive involves not just the claws, but also the region between them and the fact that the tire has a much lower rubber compound in its tread, when compared with tire of free axis, increases flexibility, enhancing their ability to deformation and consequently increasing its contact area with the ground, reducing the compaction of soil
Mestrado
Maquinas Agricolas
Mestre em Engenharia Agrícola
Fatras, Christophe. "Etude de la rétrodiffusion altimétrique pour la caractérisation des surfaces et de l'humidité des sols en Afrique de l'Ouest". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30106/document.
Texto completoThe radar altimetry interferometry satellite SWOT, which is to be launched in 2020, should provide for the first time a global coverage of a close-to-nadir radar altimeter in a few days using the Ka-band. Yet, the use of such a frequency band for continental hydrology is still poorly documented. In particular, the contrast of the backscattering coefficient over soils and over water bodies for nadir and close-to-nadir angles is a major issue. This is the reason for this work. First, the study of the backscattering coefficients from C- and Ku- band altimeters and scatterometers over West Africa has shown that there is a link between the surface soil moistureand the backscattering coefficient. In semi-arid regions, this link is seen through a rise of the backscattering coefficients during the rainy season compared to the dry season. The analysis with ancillary data such as the surface soil moisture and the precipitation estimations has also shown that nadir-looking radars detect more precisely the changes in surface soil moisture compared to side-looking radars. Still with the purpose to better understand the Ka-band surface scattering, poorly documented, two measurement campaigns were led, on the one hand over water surface with controlled roughness, on the other hand over bare soils with monitored roughness and surface soil moisture. In parallel, an altimetry backscattering simulation program has been developed to analyze the effect of a low number of variables on realistic grounds, with the aim of simulating the backscattering coefficient variations. These measurements and simulations were then compared with time series from the satellite altimeter AltiKa, which has been launched in 2013 and works at Ka-band, over different sites representaing the bioclimatic areas of West Africa. It led to a high sensitivity of the Ka-band to changes in the surface soil moisture. It has also been shown that backscattering coefficients at nadir-looking angle from AltiKa over grounds and over water bodies can be similar
Saenger, Anaïs. "Caractérisation et stabilité de la matière organique du sol en contexte montagnard calcaire : proposition d'indicateurs pour le suivi de la qualité des sols à l'échelle du paysage". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENS010/document.
Texto completoMountain soils are major reservoirs of carbon (C), potentially vulnerable to climate and land use changes that affect them significantly. However, the great variability of these soils, their limited accessibility and the lack of appropriate measurement tools restrict our knowledge. Today, our comprehension of the biogeochemistry of mountain soils remains very incomplete regarding stocks, chemistry and reactivity of soil organic carbon (SOC). Yet this information is necessary to understand the evolution of soil carbon in the current context of global change. The objectives of this work were (i) to gain a better understanding of the nature, stability and vulnerability of SOC in a mosaic of ecosystems in a calcareous massif in the Alps (Vercors massif), (ii) to search for fast and reliable characterization tools, suitable for the study and monitoring of COS at the landscape scale, and (iii) to propose indicators for the assessment and monitoring of soil quality in mountain regions. As a first step, we tested the application of Rock-Eval pyrolysis for the study of COS at large-scale on a set of ecosystem units. Then, we compared the Rock-Eval approach to two conventional techniques for soil organic matter (SOM) study: the particle-size fractionation of SOM, and the mid-infrared spectroscopy. These coupled analytical approaches allowed us to quantify C stocks across the study area, and explain the stability and the vulnerability of COS at various angles. Factors responsible for the patterns observed in the different eco-units are discussed. This work also confirmed the relevance of the Rock-Eval tool to achieve our previous objectives. Biological approaches allowed us to assess the significance of microbial pool in these soils. Finally, indices assessing the status of SOM (SOC storage, soil fertility, vulnerability COS) were proposed and constituted interesting management tools for decision-makers
Silva, Moreira Cindy. "Stocks de carbone du sol dans les zones de reboisement : bases pour projets de mécanisme pour un développement propre". Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20228/document.
Texto completoConsidering the great importance of carbon sequestration (C) in forest soils, there are fewCDM projects that include this compartment as an agent of global warming mitigation. Thisoccurs because the quantification of soil C stocks represents a bigger challenge whencompared to other components of forest ecosystems. Considering the economic difficultiesand environmental issues involved in adopting this type of project and the importance offorests in mitigating climate change, the objective of this study was to evaluate theperformance of methods for obtaining soil C stocks in two forestry areas and their respectivebaselines (land use prior to planting, i.e. pastures and native vegetation) as a basis forreducing the cost-benefit ratio of CDM projects. To achieve the main objective, this researchwas composed of the following steps: (i) estimating the spatial variability of soil C in an areareforested with native species, established in Cotriguaçú, MT (Area I) and a Eucalyptuschronosequence, located in Avaré, SP (Area II), (ii) determining the optimal amount of soilsamples and the plot size from the soil C spatial dependence range in the reforestation areas,(iii) estimating soil C content and bulk density (BD) by Near and Mid Infrared ReflectanceSpectroscopy (NIRS and MIRS, respectively) to reduce analytical costs without affecting thequality of the results, and (iv) calculating soil C stocks in both areas and estimating the carbonbalance of a CDM Project conducted in Area II, using EX-ACT ("Ex-Ante Carbon BalanceTool"). The results confirmed the existence of significant soil C spatial variability in bothareas and a strong spatial dependence at all plots. The analysis of the optimal number of soilsamples indicated that the sampling procedure with five points per plot is as accurate asintensive sampling. The optimum size of plots ranged from 361-841 m2 at Area I plantationsand from 900-3721 m2 at Area II. The performance of MIRS and NIRS to estimate the soilcarbon content was very satisfactory, especially when the models were calibrated withamounts between 5-10% of the total data set. The estimations of BD were slightly less precisethan those of soil C content. The soil C stocks obtained at Area I were higher than Area II.Considering only the soil compartment, it is clear that the potential for C credit generation in areforestation with native species on a clayey soil is higher than in a reforestation witheucalyptus on a sandy soil. The C balance of the CDM project conducted in Area I is expectedto sequester almost three million tones of CO2 eq in 40 years. We hope this study contributesto the increased inclusion of soil in CDM projects, by confirming the feasibility of reducingthe costs associated with both sampling and analytical procedures
Jahangir, Emad. "Phénomènes d'interaction sol-structure vis-à-vis de l'aléa retrait-gonflement pour l’évaluation de la vulnérabilité des ouvrages". Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL088N/document.
Texto completoClayey soils can present large volumetric deformations in response of water content change. This phenomenon of shrinkage and swelling of clayey soils is recognized as a costly natural hazard throughout the world. In France, this cost is reported between 1988 and 2007 to 5 million Euros, ranking in second class of the French natural hazards in terms of cost of damage after the floods. The individual masonry buildings with shallow foundations are the most affected by this phenomenon that causes a differential settlement of the building leading to cracks in facades and structural elements, especially in unreinforced masonry elements.The objective of this thesis was to study the vulnerability of the building, against the shrink-swell hazard through an analysis of soil-structure interaction. This work was focused on three major points: - Hydro-mechanical behavior of clay soils - Soil-structure interaction - Evaluation of structural damage.The hydro-mechanical behavior of clay soils was considered by the concept of state surface and integrated into a soil-structure interaction model, based on the Winkler model, with increasingly complex approaches: 1D, 2D and 3D by modeling the building behavior respectively by a spring system, the beam element and the plate element. These models of soil-structure interaction are able to calculate the relative deflection of the building, according to the values of imposed suction, mechanical properties of the structure and hydro-mechanical properties of the soil. The relative deflection of the building is then compared to threshold values of the classical damage categories to assess the building damage.Finally a feasibility study was conducted on the development of vulnerability curves adapted to the problem of shrinkage – swelling of clayey soils. These curves represent the average of structural damage versus suction, for each type of building. These curves were developed based on a classification of expansive soils and a building typology outcome from databases of affected buildings. The average damage is calculated by the Monte-Carlo method, taking into account the variability of the building parameters
Cauvier, Jacques. "Renouveler le rapport à son corps, pour un renouvellement de soi et de sa pratique À la recherche d'un équilibre entre le soin de soi et le soin des autres /". Thèse, [Rimouski, Québec] : Université du Québec à Rimouski, 2007.
Buscar texto completoTitre de l'écran-titre (visionné le 1er novembre 2007). Mémoire présenté à l'Université du Québec à Rimouski comme exigence partielle du programme de maîtrise en études des pratiques psychosociales. Comprend un résumé. CaQRU CaQRU CaQRU Bibliogr.: f. 151-158. Publié aussi en version papier. CaQRU
Maghoul, Pooneh. "Solutions fondamentales en Géo-Poro-Mécanique multiphasique pour l'analyse des effets de site sismiques". Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00599397.
Texto completoVan, der Poel Petrus W. "Plunge pool erosion in cohesive channels below a free overfall /". Connect to resource, 1985. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1202403267.
Texto completoBasmaji, Bakri. "Développement d’un modèle analytique d’interaction sol-structure pour l'étude du comportement mécanique des structures soumises à un mouvement de terrain : influence des déformations de cisaillement et de la plasticité". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0290/document.
Texto completoThis work is a continuation of the research work conducted in the Géoressources Laboratory and INERIS since several years. It concerns the assessment of the vulnerability of masonry structures influenced by natural or induced ground movements. The origins of the movement are may be, mining subsidence, tunneling, and shrinkage-swelling of clayed ground. The objective of the thesis is to develop an analytical model to evaluate the differential settlement of a structure in relation to the free field ground movement and given a set of phenomena: soil-structure interaction, influence of shear deformations in the structure and the ground, influence of non- linearities induced by the ground yielding. The soil was modeled by Pasternak elements to take into account the influence of shear deformations in the soil, while the building is modeled by the Euler-Bernoulli beam and by the beam of Timoshenko. The possibility of having a gap under the building was also taken into account. The deflection transmission ratio is then calculated and plotted according to are lative stiffness ratio which depend on both the structure and the soil stiffness A numerical model is also developed and results are compared with those of the analytical model. Other results of several numerical and experimental models principally developed at the University of Cambridge are also used for this comparison. Results show significant consistence between all these results. This demonstrates the significance of the analytical soil-structure model developed in this thesis
De, La Motte Saint Pierre Mathieu. "Microfluidique digitale pour la croissance de micro-organismes difficiles à cultiver". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET039/document.
Texto completoSoil is the natural medium containing the highest microbial diversity (109 cells from 104 different species per gram of soil). Yet we still can’t grow in laboratory more than 5 % of them. Having access to this diversity will lead to crucial applications for farming (production of organic fertilizers or environmentally friendly pesticides) and to pharmacology (discovery of new antibiotics or new anticancer molecules). This work focuses on the study of growth of non culturable micro-organisms from natural samples, like soil. This method uses microfluidics droplets as microreactors to obtain the growth of microbial species encapsulated inside. The first step is to achieve a solution with nothing but the microbes from our natural sample (no minerals) for a successful encapsulation and obtain diversity as close to the one found in the soil. The second step is to encapsulate the cells from this solution with different set of condition like : initial concentration, growth media and incubation time. By coupling observation of the droplets after growth and the rRNA 16S sequencing of their content we demonstrate that it is possible to obtain the growth of up to 40 % of the species. This microfluidic method, besides its use in growing unculturable species in laboratory, opens the way towards high-throughput screening of interactions between a given species (human or plant pathogens, phage/virus) and the microbiota it is likely to contaminate (gut flora, soil, sea …) and obtain the quantitative determination the reaction of microbiota
Noël, Annie-Françoise. "Pour une théorie du soin". Paris 10, 2010. http://www.theses.fr/2010PA100013.
Texto completoThe theoretical model that makes common reference for (in)dividual and institutional practices of care and cure, sets up contradictory oppositions between Good and Evil, health and illness, the good and the bad, the strong and the weak, the learned and the ignorant, etc, in a rational concept that makes, subsumes, assumes and surmounts the paradoxical unity of two kinds of forces a priori deemed to be antinomical : natural forces “dangerous” to thought (“Evil”), and transcendental forces (“Good”), “sentenced” to struggle against the threat they are representing, and/or vice versa. In practice, this dialectical model forges conflicting forces, determines lacks of thought and sensibility and ends up achieving the opposite of the “good” expected : defaced nature, life threatened and human relations more often cruel, deceitful or cynical. The paradoxical structure of the model, actually traps everybody in double bind situations witch are surmounted “in theory”, but impossible to overcome “in practice”, where the concept compels one to be hard with everything that resists the “Good” it pretends to achieve. Hence, the faiths in theory’s unrealistic nature, in humans’ badness, in final impossibility of cure, and in care’s contingency. In fact, this ironical concept, settled by a subject identified with Real and thus enslaved to the rational machinery that serves to him as thought, is symptomatic of authentic Care, witch is not given under transcendent authority of this alienated subject, but keeps necessarily united, each one in its order of reality, physical and transcendental forces, according to the radical immanence (of) Real-One. United in-the-last-Identity only, these incommensurable functions (of) Real-One work together according to the Unilateral-duality’s structure (non-philosophy), without God nor Master, nor paradox. Hence : no “Good”, no “Evil”, only thought, sensibility, gentleness, dignity, solidarity and cooperation. In two words : Force (of) Care
Freitas, Milena Cardoso de. "Avaliação de técnica de melhoria de solos colapsíveis por meio de colunas de solo laterítico compactado". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-28112016-095823/.
Texto completoThe use of shallow foundation is limited on collapsible soils due to the collapse effect pronounced in superficial layers. Considering this scenario, this research presents a new soil reinforcement technique in order to reduce the settlement of foundations due to the collapse. The proposed technique involves the execution of compacted lateritic soil columns inserted into the collapsible soil. The compaction of these columns causes the densification of the surrounding soil and consequently reduces compressibility of the reinforced soil mass. In this work, it was also evaluated the effect of the hummer geometry on the radial compaction of the soil around the column. For this evaluation, laboratory tests were conducted using two different geometries of hammer, one conical and other cylindrical (traditionally used in foundation engineering). The results showed that the conical geometry provided greater lateral compaction of the soil around the column compared to the cylindrical geometry. The efficacy of the compacted lateritic soil columns was evaluated by the results of plate load tests performed on the collapsible soil of the Experimental Field of the University of São Paulo in São Carlos city. The tests were carried out on a plate installed in the ground with and without reinforcement. The gain on bearing capacity and settlement reductions due to the reinforcement were verified by using these tests results. The tests were performed in natural and in flooded condition to verify the efficiency of the soil reinforcement in the flooding situation. Based on the results of the plate load tests, it was verified the efficacy of the method to reduce the effect of collapse. The load-displacement curves of the load tests showed that the solution evaluated provided an increase of 400% on the ultimate capacity of the plate installed on the collapsible soil tested in this investigation.
Baroni, Axelle. "Modélisation du couplage sol-fluide pour la sismique entre puits". Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0515.
Texto completoSalvia, Marie-Virginie. "Développement d’outils analytiques et méthodologiques pour l’analyse et le suivi de composés vétérinaires et stéroïdes hormonaux à l’état de traces dans l’eau et le sol". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10036/document.
Texto completoSeveral chemical products are dispersed in the environment and the consequences can be sometimes harmful for humans and the ecosystems. Among these substances appear the antibiotics and the hormonal steroids. Nowadays, only few data are available on the presence and the fate of these substances in the environment in particular for solid matrices, mainly due to a lack of methodologies. Consequently, methods to analyze traces of « emergent » contaminants in water and soil were carried out. Therefore, multi-residues and inter-families procedures based on LC-MS/MS analysis were established. Concerning the aqueous samples, 23 analytes are extracted with the SPE technique (OASIS HLB). MLQs are between 0.09 and 34 ng/L. For the solid matrix, the extraction procedure of 31 compounds is inspired from the method called QuEChERS and followed by a purification step. This methodology was validated and MLQs between 0.013 and 3 ng/g were obtained. Two antibiotics families, tetracyclines and fluoroquinolones, were studied separately as they have specific physical/chemical properties and are therefore difficult to extract from soil with an inter-families method. Then, the method developed for the soil matrix allowed a statistic study which showed the impact of the soil parameters on the recoveries and matrix effects. Finally, the methodologies were applied to a soil column study which allowed obtaining data on the transfer, accumulation and degradation of the substances in soil
Soares, Fábio Visnadi Prado. "Previsão de recalques por colapso de sapatas assentes em solo natural e compactado". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/152859.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O comportamento dos solos não saturados é um tema amplamente estudado, tanto por meio de ensaios de laboratório quanto de campo. Fenômenos como o colapso dos solos são relativamente bem explicados pelos modelos elastoplásticos existentes, dos quais o Modelo Básico de Barcelona é um dos mais utilizados e difundidos no meio acadêmico. Apesar dos avanços obtidos, ainda existe certa escassez de estudos que comparem o comportamento previsto por tais modelos a resultados de situações reais de engenharia. Esta pesquisa teve como objetivo simular numericamente resultados de recalques devidos a carregamentos e inundação de provas de carga em placa e de protótipos de sapata construídas sobre solo natural e compactado em cava. Com os resultados buscou-se analisar a eficiência da técnica de compactação para mitigar o problema do colapso do solo. Para isso, ensaios de compressão triaxial e edométricos com sucção controlada, bem como ensaios de curva de retenção e condutividade hidráulica foram realizados para determinação dos parâmetros constitutivos hidráulicos e mecânicos do solo natural e compactado que foram utilizados no programa Code_Bright para simulação numérica dos resultados de campo. Os resultados demonstraram a capacidade do modelo em reproduzir o comportamento do solo no campo. Demonstraram também que o uso da compactação do solo que preconiza compactar em cava uma camada de espessura equivalente à largura da sapata é viável para redução da colapsibilidade, mas depende do nível das tensões atuantes nas fundações e da tolerância aos recalques. Tensões propagadas para a camada de solo natural superiores à tensão de pré-adensamento do solo natural saturado provocarão recalques por colapso quando o solo for umedecido.
The behaviour of unsaturated soils is a widely studied theme around the world, both by utilising laboratory and field tests. Phenomena like soil collapsibility are relatively well explained by the existing elastoplastic models, among which the Barcelona Basic Model is the most widely used in the academic field. Despite the recent advances, there is still a scarcity of papers that compare the behaviour predicted by constitutive models and results of real engineering problems. This research aims to numerically simulate the results of settlement due to loading and wetting of load tests built both on undisturbed and compacted soil. The results were analysed in order to study the efficacy of the soil compaction technique in mitigating soil collapse. Suction controlled triaxial compression and oedometer tests, as well as soil water retention curve and hydraulic conductivity experiments were conducted to determine the hydraulic and mechanic parameters used in the software Code_Bright to numerically simulate field results. The results highlight the capability of the model in reproducing the analysed field behaviour. They also show that the technique that involves compaction of the soil equal to the footing’s width is viable to reduce its collapsibility, but its efficacy will also depend on the tensions applied on the foundation and on the tolerable settlement values. Tensions that are propagated to the natural soil layer that are higher than its preconsolidation stress will cause collapse settlements and wetted.
Vitale, Quentin. "Modélisation et conception d'antennes radar large bande pour la cartographie de la teneur en eau volumique des sols agricoles". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066189/document.
Texto completoThe research work submitted in this PhD dissertation is part of research project which aims to develop a new tool for mapping the soil water content in agricultural context with ground penetrating radar technology. The scope of this particular work is the development of two prototypes of wideband radar antennae. Hence, two prototypes of antennae have been numerically designed based on a 3D finite-difference in time-domain (FDTD) electromagnetic solver of Maxwell's equations. The guiding principles that have been followed during the design are mainly a small size antenna (A4 format) and achieving the wider bandwidth possible in the frequency range 100 MHz - 1 GHz (in the air). In order to study the behavior of our prototypes when put in presence of soils, we conducted a numerical study representing the soils by half-spaces. This numerical study was based on the analysis of the antennae reflection coefficient in the frequency domain (or return loss coefficient s11). To be as close as possible to field conditions, the effect of a non ideal contact between the antenna and the soil (represented by a small elevation of the antenna) as well as the effect of soil surface rugosity (represented by corrugated iron-like and eggbox-like surface) have been investigated. Based on this numerical study, two prototypes of antennae (one bow-tie-like and on elliptical dipole) have been physically built and tested in both lab and field conditions. The test in lab condition enabled us to: (i) check the similarity between measured s11 in a controlled environment and corresponding FDTD simulation of the antenna including all antenna parts, (ii) calibrate the antenna in both far field and near field conditions which enabled the use of an analytical model to simulated the antenna s11 in presence of soil, (iii) estimate the dielectric permittivity of a sand sample using both FDTD and analytical simulations. Finally, the prototypes were tested in field condition in order to verify their behavior for in situ measurements. These tests show that using unshielded coaxial cable has a very important impact on the data (noise) and that the prototypes demonstrate a good sensitivity to dielectric permittivity contrasts
Fares, Reine. "Techniques de modélisation pour la conception des bâtiments parasismiques en tenant compte de l’interaction sol-structure". Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4103/document.
Texto completoBuilding design according to European seismic code does not consider the effects of soil-structure interaction (SSI). The objective of this research is to propose a modeling technique for SSI and Structure-Soil-Structure Interaction (SSSI) analysis. The one-directional three-component (1D-3C) wave propagation approach is adopted to solve the dynamic soil response. The one-directional three-component wave propagation model is extended for SSI and SSSI analysis. A three-dimensional (3-D) soil is modeled until a fixed depth, where the soil response is influenced by SSI and SSSI, and a 1-D soil model is adopted for deeper soil layers until the soil-bedrock interface. The T-soil profile is assembled with one or more 3-D frame structures, in a finite element scheme, to consider, respectively, SSI and SSSI in building design. The proposed 1DT-3C modeling technique is used to investigate SSI effects and to analyze the influence of a nearby building (SSSI analysis), in the seismic response of frame structures. A parametric analysis of the seismic response of reinforced concrete (RC) buildings is developed and discussed to identify the key parameters of SSI phenomenon, influencing the structural response, to be introduced in earthquake resistant building design. The variation of peak acceleration at the building top with the building to soil frequency ratio is plotted for several buildings, loaded by a narrow-band motion exciting their fundamental frequency. In the case of linear behaving soil and structure, a similar trend is obtained for different buildings. This suggests the introduction of a corrective coefficient of the design response spectrum to take into account SSI. The parametric analysis is repeated introducing the effect of nonlinear behaving soil and RC. The seismic response of a RC building is estimated taking into account the effect of a nearby building, for linear behaving soil and structures, in both cases of narrow-band seismic loading exciting the fundamental frequency of the target and nearby building. This approach allows an easy analysis of structure-soil-structure interaction for engineering practice to inspire the design of seismic risk mitigation tools and urban organization
Lebeau, Benoit. "Les tensiometres pour l'irrigation en milieu tourbeaux". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22754.
Texto completoReviewing the different methods that are used in field production, tensiometer have shown the greatest potential of adaptation to potted plants.
Tests on the utilization of tensiometer were realized on two peat-vermiculite substrates, using two types of porous cup (1 bat--standard flow and 1 bar--high flow). The instruments were tested while permanently fixed in the growing medium, and temporarily fixed for three hours in the growing medium.
The results show that the instruments give excellent measurements for normal condition of growth, requiring saturation level between 50 and 100%, and that for both mode of operation.
Preferably, the choice of the instrument should be based on the hydraulic characteristics of the substrate. Little difference has been found using both instrument in the substrate 1, but in substrate 2 however, the high flow porous cups have given better response. The high flow cups have higher porosity and bigger pores that suit better substrate 2, which is made of coarser particles.
Svay, Angkeara. "Modélisation de la Variabilité Spatiale du Champ Sismique pour les Etudes d’Interaction Sol-Structure". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC016/document.
Texto completoIn seismic soil-structure interaction studies (SSI), the common practice in Civil Engineering is to consider a uniform movement of free field at any point on the ground surface. However, that assumption is not completely realistic since the seismic ground motions can vary spatially due to wave passage effects, dispersions and reflections of wave propagating in the random heterogeneous media "pure incoherence" and site effects. Therefore, in order to increase the security of buildings and equipment, it is important to do an analysis of seismic soil-structure interactions in the most realistic way. This can be achieved by taking into account the spatial variability of seismic ground motions. Several studies in the literature show that taking into account the spatial variability of seismic ground motions in SSI analyses can have remarkable effects on the structural responses. The spatial incoherence of seismic ground motions due to dispersions and reflections of wave "pure incoherence" can generally be modelled in such analysis by a "coherency function" in frequency domain. The principal goal of this Ph.D thesis is to construct a stochastic description of spatial variability of seismic ground motions by means of coherency functions. Accurately, it aims to propose a parametrical coherency model of spatial variability of seismic ground motions. This later should be related to some physical and statistical properties of the soil at the application sites so that it can be applied in any types of sites. Based on theoretical considerations on coherency of seismic wave propagation in random heterogeneous media, on experimental data analyses, and on numerical modelling of seismic wave propagation in random heterogeneous media, a coherency model is validated and proposed for the analyses of soil-structure interactions. The influence of spatial variability of seismic ground motions on the structural responses are also pointed out by using the validated coherency model
Do, Quoc Viet. "Impacts des mouvements de terrains sur une structure type "maison individuelle" : modélisation de l'interaction sol-structure pour l'évaluation de la vulnérabilité du bâti". Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1075.
Texto completoIn the present work, the considered natural hazards concern to ground movements resulting from two main phenomena : shrinkage and swelling of clay soils and ground subsidence due to the presence of underground cavities. These phenomena cause differential ground settlements which generate disorders on the structures erected in their neighborhood : damage and cracking of masonry load-bearing walls, especially at the building corners. These structural degradations cause important economic consequences and losses in the case of dwelling houses. These damages result from a lack of masonry resistance or a small stiffness of the foundation system as well as a limited effectiveness of bracing system.This research aims to analyze the vulnerability of buildings and to propose a reinforcement method for the existing constructions as well as design recommendations for structures. These topics require a thorough understanding of the ground movements phenomenon and their transfer as actions on a structure. For this purpose, four main steps were performed : a literature review, an analysis of soil-structure interaction, a development of a damage justification and a method for reinforcement or design, as well as a probabilistic analysis of risk.The literature review with functional and statistical analysis, as a first step, provides a profile of the house susceptible to natural hazard effects and typical cases of building disturbances. The development of finite element method is therefore considered in order to study soil-structure interaction.The analysis of the soil-structure interaction using finite element modeling provides stresses in the masonry. First, simplified analytical and numerical models have been developed for simple structures such as a strip footing, a system of strips foundation or a masonry wall lying on elastic soil (Winkler or Boussinesq). Afterwards, modeling of more complex structures with the whole building elements was made by developing a particular finite element code that allowed the calculation of masonry buildings on a Pasternak soil. To develop a damage justification as well as the reinforcement and design building methods suitable for risk of “ground movements”, this work focuses on the stresses distribution obtained by numerical models and analyzes the validity domain of the approach proposed by Eurocodes EC6 and EC8 for confined masonry or reinforced masonry. By coupling the developed finite element models with the Monte-Carlo method, the probabilistic analysis of risk allows to study the vulnerability of dwelling houses having representative structural characteristics of existing buildings, erected in areas that are the most affected by ground movements. The results of this analysis have been unified into a global methodology for assessing the vulnerability of structures. This methodology is used, in one hand, for the development of GIS mapping of risks and, in other hand, for the reinforcement processes
Daugé, Frédéric. "Architectures innovantes pour les transistors SOI". Grenoble INPG, 2005. http://www.theses.fr/2005INPG0044.
Texto completoThe aim of this work is the study of ultra-thin silicon film MOS/SOI transistors with multi-gate architecture. This study includes a thorough electrical characterization and an analytical modeling carried out using a new program, developed during this work, "CAPES". This program, based on the Poisson-Schrodinger coupling equations, takes into account the quantum confinement effect and their multidimensional impact. A modified version of Hänsch method is proposed and the integration in CAPES of the non bands parabolicity shows the need for considering this effect for Si films thinner than 5nm. Ln addition, a detailed study on the interfaces coupling effects in fully-depleted and double-gate MOS/SOI transistors is achieved. The impact of the gate misalignement in DG devices is also analysed Finally, thanks to a new extraction method, the transport properties of the various channels of the FinFETs transistors are compared
Lyu, Han. "EFFECTS OF CLIMATE AND GEOCHEMISTRY ON SECONDARY MINERAL DISTRIBUTION AND SOIL ORGANIC CARBON POOLS IN TROPICAL VOLCANIC REGIONS". Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263813.
Texto completoBoin, Elisa Aurora Santana Ferreira 1986. "Remediação de solo contaminado por chumbo por imobilização induzida por fosfato na região de Apiaí, Vale do Ribeira (SP)". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287088.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: A exposição humana ao chumbo pode ser reduzida a partir de um controle de disponibilidade e mobilidade do mesmo por meio da aplicação de fertilizante fosfatado, induzindo a adsorção do chumbo e a formação de compostos insolúveis como a piromorfita. Os objetivos desta pesquisa foram caracterizar, física, química e mineralogicamente, o solo e os materiais fosfatados para otimização do tratamento de remediação e, a partir destas caracterizações, avaliar um método de remediação de solo adaptado para a região do CIEM/CPRM, em Apiaí (SP), baseado na imobilização do chumbo por fosfato. Nos experimentos em bancada foram analisados dois tipos de material: fosfato diamônico (DAP), na razão molar (P:Pb) 1:5, e rocha fosfática, na razão molar (P:Pb) 3:5, além da granulometria dos materiais fosfatados (comercial e moída) e o tempo de tratamento (3, 6 e 9 meses) em solo com 3,5% de chumbo. Experimentos in situ fora realizados em 3 locais com diferentes concentrações de chumbo (1204 mg.kg-1, 94 mg.kg-1 e 5191 mg.kg-1) utilizando rocha fosfática na razão molar (P:Pb) 4:1 e analisados em em períodos de 3 e 6 meses. Foram realizadas análises de concentração de Pb, Zn, Cu, As e Cd na fração solúvel em solo e em extrato parcial mediante ataque com acetato de amônio 1M a pH 4,5. O DAP não se mostrou um bom imobilizador de Pb pois teve a eficácia diminuída com o tempo e induziu a redução do pH, liberando Pb e outros elementos-traço para as frações estudadas nesta pesquisa. A aplicação de rocha fosfática elevou o pH e reduziu da concentração de Pb e outros elementos-traço: 37% na fração solúvel em solo e 20% no extrato parcial de solo após 9 meses de tratamento. Além disso, não foram observadas alterações nas concentrações de outros elementos-traço. Nestes ensaios não houve diferenças expressivas nos resultados em relação à granulometria da rocha fosfática. Nos experimentos in situ a aplicação de rocha fosfática resultou na imobilização de até 99% do chumbo disponível na fração solúvel em solo e de até 81% do chumbo disponível em extrato parcial e reduziu a concentração de outros elementos-traço nestas frações. Foi observada a ocorrência de piromorfita no solo tratado, porém os principais processos de imobilização do chumbo foram a adsorção por minerais de argila, óxidos e na superfície da rocha fosfática. A utilização de rocha fosfática, como imobilizador de chumbo, se mostrou eficiente para remediação do solo do CIEM/CPRM em Apiaí, independente da concentração de Pb. É recomendado que o planejamento de remediação do local contemple as seguintes ações: remover e isolar a escória em cápsulas de concreto no subsolo e cobri-las com solo não contaminado; revolver o solo contaminado com rocha fosfática (4:1 - P:Pb), cobrindo esses locais com uma nova camada de solo não contaminado; cobrir toda a área com grama e plantas e monitorar a qualidade do solo e a da água, visto que há possibilidade de lixiviação de outros elementos-traço como As e Cd
Abstract: Human exposure to lead can be reduced with a control of availability and mobility of lead through application of phosphatic fertilizers, inducing adsorption of lead and formation of insoluble compounds like pyromorphite. The goals of this research were to characterize physically, chemically and mineralogically the soil and the phosphate materials to optimize the remediation treatment based on immobilization of lead by phosphate in order to adapt a soil remediation method to the region studied. In the laboratorial experiments two types of material were analyzed: diammonium phosphate (DAP) at 1:5 molar ratio (P:Pb) and phosphate rock at 3:5 molar ratio (P:Pb), in addition to phosphate materials particle size (ungrounded and grounded) and the time of treatment (3, 6 and 9 months) in soil with 3.5% of lead contamination. In-situ experiments were carried out in 3 locations with different concentrations of lead (1,204 mg.kg-1, 94 mg.kg-1and 5,191mg.kg-1) using phosphate rock at 4:1 molar ratio (P:Pb) and collecting data at 3 and 6 months. Pb, Zn, Cu, and Cd concentration analyses were carried out in water soluble fraction and partial extract of ammonium acetate at pH 4.5 1M. DAP was not effective as lead immobilizer as diminished effectiveness over time and induces pH decrease, releasing Pb and other metals to the fractions here studied. Phosphate rock increased pH and reduced lead and other metal concentrations in the water soluble fraction (37% reduction of metal after 9 months of treatment) and partial extract (20% reduction after 9 months of treatment). Besides, it did not alter the concentrations of metals in this fraction and increased its performance over time. There were no expressive alterations in the results when comparing phosphate rock particle sizes. In the experiments in-situ the application of phosphate rock immobilized up to 99% of the lead available in soluble fraction and up to 81% of the lead available in partial extract. It also reduced other metals concentrations in these fractions. Although formation of pyromorphite took place, the main mechanism was lead adsorption by clay minerals, oxides and the surface of the phosphate rock. The use of phosphate rock as lead immobilizer showed to be efficient for soil remediation in the region studied independently of the lead concentration. It is recommended that the site remediation planning contemplate the following actions: removal and isolation of the slag in concrete capsules in the underground covering them with uncontaminated soil; mixing contaminated soil with phosphate rock (4:1 - P:Pb) and depositing a new layer of uncontaminated soil on these spots; replanting all the area with grass and plants and monitoring soil and water quality, seeing that there is a possibility of lixiviation of other trace elements such as As and Cd
Mestrado
Geologia e Recursos Naturais
Mestre em Geociências
Ellili, Yosra. "Evaluation biophysique des services écosystémiques des sols cultivés - Adaptation de l’information pédologique pour la modélisation dynamique du fonctionnement des sols". Thesis, Rennes, Agrocampus Ouest, 2019. http://www.theses.fr/2019NSARD087.
Texto completoSoils provide many ecosystem services essential to sustain human life and socio-economic development. However, soils are subjected to increasing pressure from current activities, including intensive land use to satisfy demands of a growing population for food and energy. To improve soil management, decision-support tools that consider soil diversity are required to assess impacts of human activities on soil dynamics. The objective of this study was to develop and validate a methodology to enhance existing pedological information (1: 250,000) using spatial disaggregation technique in order to estimate in space soil ecosystem services.By combining field observations, disaggregated soil data with known accuracy and dynamic modelling, six soil ecosystem services indicators were firstly assessed, to be then used to evaluate the sensitivity of estimated soil ecosystem services to the source of soil information. The main results highlight the contribution of digital mapping to produce relevant pedological information for assessing soil ecosystem services from cultivated soils. Future research must be performed to improve pedological information availability and soil ecosystem services assessment procedure by coupling dynamic coupling and proxies. Overall, this work emphasize the need to produce soils consideration in sustainable management strategies and territorial planning
Dresler, Johanna. "Préformulation d'un soin anti-tâche pour la peau". Paris 5, 1999. http://www.theses.fr/1999PA05P135.
Texto completoTiberj, Antoine. "Matériau SOI pour capteur à effet Hall". Montpellier 2, 2003. http://www.theses.fr/2003MON20012.
Texto completoDainese, Roberta. "L'utilisation du tensiomètre de grande capacité dans le cadre d'un système intégré de surveillance du continuum sol-plante pour les applications géotechniques". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG094.
Texto completoThe stability of slopes, embankments and earth structures is determined by the shear strength that the soil can mobilise. The upper portion of the soil profile (vadose zone) and the earth structures are usually partially saturated and the shear strength is affected by the (negative) pore-water pressure and the degree of saturation. If the amount of water in the soil is reduced, pore-water pressure is depleted and the shear strength increases. Soil water removal can therefore be viewed as a technique to strengthen the ground and enhance stability.A natural, low-cost, and low-carbon approach to remove soil water consists in exploiting the evaporative demand of the atmosphere. Evaporation from bare soil is well studied, but it is difficult to ‘engineer’ the process to enhance soil water removal. The problem of plant transpiration is complex as it involves the coupling between soil, plant and atmosphere. However, it offers the chance to control actively the process of water removal if adequate species are selected to cover the ground surface. As a result, vegetation can potentially be ‘engineered’ to stabilise geotechnical structures.This work has developed an experimental framework to investigate the effectiveness of vegetation in removing soil water by transpiration and the overall methodology has been designed around the comparison between transpiration (from vegetated soil) and evaporation (from bare soil), both in the laboratory and in the field. Experimental investigation into transpiration processes therefore requires the monitoring of the water flow through the Soil-Plant-Atmosphere Continuum.A novel technique was developed to monitor xylem water pressure. The High-Capacity Tensiometer (HCT), developed by geotechnical researchers, was tested on the plant to measure the xylem water pressure. This technique was validated via comparison with techniques routinely used in plant science. The novel procedure for the measurement of negative xylem water pressure is a step change in the study of continuous flow along the soil-plant system, especially in the geotechnical field. This allows the use of a single instrument to monitor the entire soil-plant continuum.The transpiration process was then first investigated in the laboratory. Two soil columns were developed, one vegetated and one left bare to compare the transpiration and evaporation respectively under the same atmospheric conditions. The columns were instrumented to monitor the water content, (negative) pore-water pressure in the soil respectively and the transpiration rate.The straightforward outcome from these laboratory tests is that vegetation does not have necessarily a beneficial effect. In the energy limited regime, the combination of the aerodynamic and canopy resistances can play either in favour of the bare or the vegetated soils depending on the vegetation type. In the water-limited regime, the effect of vegetation is always beneficial due to the different mode of water extraction. This is reflected in the time at which the transpiration enters the water limited regime, which is definitely longer in the vegetated soil than the bare one. Both aspects have been clearly demonstrated in the laboratory experiments.The hydrological effects of vegetation where finally investigated in the field in a poplar plantation in Montpellier, France. The water content profile was monitored throughout the dry season and the following rainy period in a poplar vegetated area as well as in the adjacent ploughed (virtually bare) field. The conceptual framework developed on the basis of the laboratory experiments was therefore key to interpret the field data and show in which regime the vegetation has beneficial effects in this specific case.In conclusion, this dissertation has shown how the effects of plant transpiration in removing soils water and, hence, enhancing the stability of slopes and earth structures can be assessed based on quantitative measurements
Dorji, Tshering. "Soil organic carbon variability under montane ecosystems: assessing the influence of landscape attributes". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14811.
Texto completoBuske, Taise Cristine. "COMPORTAMENTO DA UMIDADE DO SOLO DETRMINADA POR MÉTODOS EXPEDITOS". Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/7564.
Texto completoThe knowledge of soil moisture is quite important because it indicates soil hydric conditions and it can help on saving water and electric energy, given that monitoring of soil moisture allows controlled and timely applications of water pointing out how much and when to irrigate, according to the crop water requirements. Therefore, soil moisture should be determined before the irrigation and will serve as a parameter for the amount of water to be applied by the system. There are any methods used for determination of soil water content, in this way, the present study aimed to compare the results of soil moisture obtained by different methods for expeditious determination of the water content of the soil in different textural classes. The study was conducted in the Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria . Four methods were tested (standard method, M0; electric oven method, M1, microwave oven method, M2; weighing method, M3) with three soil samples (S1, S2, S3) and three repetitions for each. The linear regression was made between the standard method and alternative methods, for obtaining the correlation coefficient (r), the linear coefficient and the slope, the Wilmott concordance index (Iw) and Performance Index (Id). From the results obtained can be stated that the electric oven method and the microwave oven method have excellent performance when compared to the standard method. The method of weighing presented a performance good and very good. In addition, it was concluded that the 20 minutes period for the electric oven method was efficient signifying a time reduction for the moisture content determination. For the microwave oven method the 5 minute drying period was sufficient and did not differ statistically from the standard method. The method of weighing was also reliable in determining soil moisture. Therefore, it is possible to use alternative methods to determine the soil moisture.
O conhecimento da umidade do solo é de fundamental importância, pois indica em que condições hídricas encontra-se o mesmo, podendo auxiliar na redução dos gastos com água e energia elétrica, haja vista que o monitoramento da umidade do solo possibilita aplicações controladas e pontuais de água, respondendo o quanto e quando irrigar em função das necessidades hídricas das culturas. Assim sendo, para a realização da irrigação, a umidade do solo deve ser determinada anteriormente e servirá de parâmetro para a quantidade de água a ser aplicada pelo sistema. Inúmeros são os métodos utilizados para a determinação do conteúdo de água no solo, dessa maneira, o presente trabalho objetivou comparar os resultados de umidade do solo obtidos pelos diferentes métodos expeditos para determinação do conteúdo de água no solo em diferentes classes texturais. O estudo foi desenvolvido no Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria. Foram testados quatro métodos (método padrão de estufa, M0; método do forno elétrico, M1, método do forno de micro-ondas, M2; método das pesagens, M3), com três amostras de solo (S1, S2, S3) e três repetições para cada. Foi feita a regressão linear entre os métodos alternativos e o método padrão de estufa, com a finalidade de se obter o coeficiente de correlação (r), o coeficiente linear e o coeficiente angular, o índice de concordância de Wilmott (Iw) e o índice de desempenho (Id). Através dos resultados obtidos pode-se afirmar que o método do forno elétrico e o método do forno de micro-ondas apresentaram desempenho ótimo quando comparados ao método padrão. O método das pesagens apresentou desempenho bom e muito bom. Também concluiu-se que o tempo de 20 minutos para o método do forno elétrico foi eficiente, significando redução no tempo para determinação da umidade. Para o método do forno de micro-ondas o tempo de 5 minutos de secagem foi suficiente, não diferindo estatisticamente do método padrão. O método das pesagens também se mostrou confiável na determinação da umidade do solo. Portanto, existe a possibilidade de usar os métodos alternativos para a determinação da umidade do solo.
Sousa, Daniel Vieira de. "Alterações eletroquímicas e sua relação com a produção de gás metano em solos alagados por barragens". Universidade Federal de Viçosa, 2011. http://locus.ufv.br/handle/123456789/5542.
Texto completoFundação de Amparo a Pesquisa do Estado de Minas Gerais
The emission of gases of the greenhouse effect has increased dramatically since the geological era until the present days. Currently the use of fossil fuels and the changing of the use of the Earth are most responsible for the emission of these gases to the atmosphere.The carbon in the soil represents more than three times the carbon in the terrestrial biomass and about two times the carbon in the atmosphere, been a potential source of CO2 and CH4.The biogeochemical process that occurs in the soil or sediments for the emission of gases such as carbon dioxide and methane are controlled by process like the reduction of mineral compounds mainly oxides and amorphous and poor crystalline in anaerobic environment. These process leads to the formation of a favorable habitat suitable to the population grows of Methanogenic bacteria consequently with the production of gases of greenhouse effective. Nowadays there are several projects that defend that the hydroelectric dam offers a great contribution to the emission of the effective of greenhouse gases. This project has the purpose of study what the characteristics has more influence for the production of the emission of greenhouse effective in flood soils in hydroelectric lakes. The chapter one is dedicated to literature review where are addressed the more relevant topics. The chapter II had the purpose of studying the electrochemical dynamics of the soil at Zona da Mata mineira subject to flood due to the construction of hydroelectric. As a result we obtained that how bigger is the of Fe, bigger will be reduction of the soil, which lead us to establish the habitats proper for the establishment of the growth of Methanogenic bacteria‟s. population. The contents of Fe, CO and N have more influence in the ox reduction of flood soil. The chapter III had the purpose of studying dynamics and reactivity of the soil organic carbon (SOC) such as it is also dedicated to estimate the production of CH4 in soils flooded by hydroelectric dams lake with the purpose of identifying which characteristics has more influence in the production of methane comes from an eventually flooded of soils. As a result were obtained that the reactivity of SOC receives influence of the texture of the soil, and the finer is the texture greater is the presence of free fractions. The N shows an important factor to be analyzed due to its relation with the degradation of organic compound and microbial activity.
As emissões de gases do efeito estufa (GEE) têm aumentado vertiginosamente desde eras geológicos até os dias atuais. Atualmente a utilização de combustíveis fósseis, e alterações no uso da Terra, são as maiores responsáveis pelas grandes emissões destes gases para a atmosfera. O carbono contido no solo representa mais de três vezes o carbono contido em toda a biomassa terrestre e cerca de duas vezes o carbono contido na atmosfera, sendo, dessa forma, uma potencial fonte emissora de CO2 e CH4. Os processos biogeoquímicos que ocorrem em solos e ou sedimentos para emissão de gases como o dióxido de carbono e metano, são controlados por processos como a redução de compostos minerais, principalmente óxidos, amorfos e mal cristalizados em ambientes anaeróbios. Estes processos levam a formação de um habitat propício para o crescimento populacional de bactérias metanogênicas, com a conseqüente produção de gases do efeito estufa. Atualmente há diversos trabalhos que defendem que barragem de usinas hidroelétricas oferece uma grande contribuição na emissão de gases do efeito estufa. Nesta pesquisa objetivou-se estudar quais as características do exercem mais influencia para a produção de gases do efeito estufa em solos alagados em lagos de hidroelétricas. O capítulo I é dedicado a revisão de literatura, onde são abordados temas que se julgam relevantes. No capítulo II se objetivou estudar a dinâmica eletroquímica de solos da zona da mata mineira passíveis de serem submetidos a alagamento devido a construção de hidroelétricas. Como resultado obteve-se que quanto maior for a atividade de Fe, maior será o potencial de redução do solo, o que leva ao estabelecimento de habitats, apropriados para o estabelecimento de populações de bactérias metanogênicas. Os teores de Fe, CO e N, são os que mais exercem influencia no processo de oxiredução de solos alagados. O capítulo III teve por objetivo estudar dinâmica e reatividade do carbono orgânico do solo (COS), bem como dedicado a estimar a produção de CH4 em solos alagados por lagos de usinas hidroelétricas, com o intuito de identificar quais características exerce mais influência na produção de metano, provinda do eventual alagamento dos solos. Como resultados foram obtidos que a reatividade do COS recebe influencia da textura do solo, sendo que quanto mais fina a textura maior a presença de frações livres. O N total se mostra um importante fator a ser analisado devido sua relação com a degradação de compostos orgânicos e atividade microbiana.
Michali, Aphrodite-Ioanna. "Méthode pour l'identification des paramètres d'une loi élastoplastique à partir d'essais de laboratoire et in-situ : Modélisation numérique du tassement d'un remblai sur sol compressible". Châtenay-Malabry, Ecole centrale de Paris, 1994. http://www.theses.fr/1994ECAP0384.
Texto completoAndrieux, Luc. "Pour une philosophie du tact relationnel dans le soin". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10260.
Texto completoThe concept of tact is usually associated with the idea of touching, which is the genuine etymology. However, relational tact concerns a very special aspect of touching, because it is a none physically touching act regarding a kind of attitude trying to preserve anyone from the humiliation of being taken as an object rather than as a subject. Healthcare relationships especially have to be examined thoroughly by the way of tact in order to understand the fundamental human need for respect hidden in tact. Different from politeness, tact is the specific art of respecting others without conventional and formalized rules. It needs a capacity of building an area in which the partnerships can find a mutual respect of each other. According to interactionism sociology tact is really a face work that needs an ability never really taught in medical studies. Thanks to interactionism we can emphasize the base of these relationship attitudes. They depend on the frame in which interactions take place. This area must be though together with other concepts because of the weakness of the former ones. So, tactilairity could translate the capacity of making an informal area in every meeting and especially in healthcare relationships. Tactilairian ability is one of the ways to efficiently succeed in pacified relationships
Roux, Julien. "Conception d'un capteur distribué pour la surveillance de l'état hydrique des sols". Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0031/document.
Texto completoOwing to the development of the smart farming, some new studies need to be lead on a distributed instrumentation to measure soil moisture to control the irrigation.In the project IRRIS context, we realize a smart soil moisture sensor. First, we have to realize the sensing element of this sensor. We choose a capacitive detection to get a reactive sensor despite low cost. The body is a cylinder to be easily buried in the soil. The electrodes are made by electrochemical deposition on the plastic tube. Then, we design the measurement electronic. We compare two solutions, one with discrete components and the other software on embedded microcontroller. We submit those electronics at thermic variations to observe their comportment to create the law of compensation. Next we assemble the sensor according to two ways. The first, the multi sensor, forces the depths of sensing but reduces the costs by pooling the measurement electronic. The second, the mono sensor, frees the choice of depth but multiplies the number of sensors. We create at this step the sensor network thanks a wireless communication placed on 868MHz, an ISM band that we characterize in terms of range depending on the flow rate to optimize this communication. Finally, we observe the results of three measurement campaigns to validate the operating for different soil and cultures.This study ends in the realization of a sensor to measure soil moisture with a reduced cost relative to the industrial sensor on the market. Experiments prove its ease of use as well as its proper functioning
CIRCELLI, Luana. "Integration Vis-NIR spectroscopy and satellite Sentinel-2 data to assess soil organic carbon pool of an organic farm in south of Italy". Doctoral thesis, Università degli studi del Molise, 2021. http://hdl.handle.net/11695/106279.
Texto completoThe soil plays an important role in the global carbon cycle and the balance between the rates of organic carbon input and output determines at large scale the amount and the turnover of soil organic carbon (SOC). Thus, soil can act as both carbon store and supplier of carbon emissions increasing atmospheric greenhouse gases (GHGs), having a great potential in climate change mitigation. Changes in land use are those particularly involved in SOC accumulation and in loss of carbon dioxide (CO2) in the atmosphere as GHG. With this purpose, sustainable land management are necessary to be applied for carbon storage and sequestration. However, assessing the composition of SOC is important to understand the mechanisms through which soil C pools can be directly linked with its potential to sequester atmospheric CO2. The study of the SOC composition span from the micro to the macro-scale, and the application of Vis-NIR spectroscopy technique can couple some positive aspects of the resolution of the fine scale with a wide and easy applicability. In this framework, as a rapid technique for measuring SOC based on the diffuse soil reflectance, the application of Vis-NIR spectroscopy and integration with satellite Sentinel-2 data were applied. With the aim to analyze the organic and inorganic C pools, the soils of an organic farm in South of Italy were chosen. In this farm, the principles of conservation agriculture are adopted in apple cultivation. The organic and inorganic C pools were measured on 56 georeferenced soil samples, for a total study area of about 3 hectares, applying different methods, from dry combustion at high temperature, CNS analyzer and furnace loss on ignition for total and organic C, to wet oxidation procedures, also for soluble forms of organic C. This differentiation in methods allowed making a distinction between the more stable (recalcitrant) organic C forms in the soil from the more labile ones and more subject to mineralization phenomena. Spatial regression models allowed taking into account the role of topographical parameters and other soil properties on dynamics of organic and inorganic C pools. Vis-NIR spectroscopy, as a proximal sensing technique, was used to model calibrations and validations for the prediction of the investigated soil C fractions. From the combinations between different spectral preprocessing and regression models, second derivative transformations and partial least squares (PLS) regression have achieved excellent results, made by the average values of R2=0.85 and RPD=2.5 for soil organic C predictions, and R2=0.75 and RPD=1.7 for soil inorganic C. The evaluation gap of soil C pools from field to farm scale was improved by the satellite Sentinel-2 data in Vis-NIR predictive models. The obtained accurate results proved that remote sensing could be a powerful tool to recognizing the various soil C pools, especially those most exposed to the risk of degradation and erosion. In addition, the combination between soil laboratory analysis and Vis-NIR spectroscopy and satellite data can be very useful with a precision agriculture approach.
Lima, Patricia Tavares de. "Cordierita : sintese por processamento sol-gel". [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249760.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado
Perusi, Maria Cristina [UNESP]. "Discriminação de argissolos e avaliação da estabilidade de agregados por vias seca e úmida em diferentes sistemas de uso e manejo". Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/101956.
Texto completoIn order to discriminate ARGISSOLOS and to evaluate aggregates stability by dry and humid ways under different use and management systems, it was studied soil profiles under agricultural and pasture for more than twelve five years on the following system: six years with annual crop rotation in areas that had been pasture for the same time period and forest, for comparison purposes. This study was done in a agricultural farm in the Anhumas county, São Paulo state, Brazil, where the predominant soil class - ARGISSOLO - are representative of the region. Stages to achieve the objectives: a) not deformed and deformed samples collection to perform chemical and physical analysis; b) determination of the aggregate percentage by dry and humid ways; c) computation of the weighted mean diameter of the aggregates (WMDA); d) soils classification; e) statistical analysis: variance analysis and Tuckey's test for average, at 5 % of probability. Main conclusions: soil classification; the organic matter content of the A horizon of the soil under forest is 64 % more than the soil under pasture e 79 % more than the soil under annual crop; the flocculation degree and amount of the clay fraction of this same horizon is 31 % more than the soil under pasture e 39 % more than the soil under annual crop; the weighted mean diameter of the aggregates obtained by dry (D) and (H) humid ways of the A horizon and its mean value for the soils decrease in the following sequence: PVAd - forest > PVe - pasture > PVd - annual culture, respectively, with the following values: 1.33560 and 1.445496 (D), 2.81114 and 2.351380 (H); 0.66748 and 1.011830 (D), 2.79642 and 1.624250 (H); 0.32468 and 0.993775 (D), 1.25808 and 0.983135 mm (H); the weighted mean diameters of the aggregates of the A horizon - obtained by dry (D) and humid (H) ways - decreased 50 % and 1 % in the soil under pasture... (Complete abstract click electronic access below)
Miqueloni, Daniela Popim [UNESP]. "Perda de solo em área de nascentes caracterizada por análise multivariada e modelos de geoestatística". Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/88295.
Texto completoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Devido sua importância, a perda de solo das microbacias de cabeceira do Córrego do Tijuco-SP foi estimada por meio da EUPS, e a variabilidade espacial dos fatores do processo erosivo foi investigada pelas análises multivariada e geoestatística. A perda de solo média estimada foi considerada alta, 118,50 Mg ha-1 ano-1, e a correlação de Pearson confirmou o fator erodibilidade do solo como o fator mais importante no processo erosivo. A erodibilidade local é condicionada pela distribuição das frações granulométricas e matéria orgânica, sendo o solo basicamente de textura média/arenosa de baixa coesão. Próxima a zona urbana, a interação do fator erosividade da chuva e do fator práticas conservacionistas se mostrou proeminente evidenciando alta perda de solo devido à concentração de água oriunda da camada impermeabilizada urbana e da falta de controle da velocidade do escoamento superficial da água. Em contraste, o fator cobertura vegetal mostrou maior atuação nas áreas de vegetação permanente, localizadas principalmente nas nascentes e canais de escoamento. Nas áreas mais convexas do terreno, localizadas nos divisores de águas, a atuação do fator erodibilidade foi proeminente, em contraste com o fator topográfico, este em áreas côncavas de maior declividade. Foram observadas ainda áreas com atuação conjunta dos fatores topográfico e erodibilidade, refletindo locais de inclinação mais suave, porém com alto potencial natural de erosão. Os resultados das análises multivariadas e geoestatística permitiram uma estratificação da área estudada identificando locais com propriedades específicas quanto à perda de solo o que contribui na compreensão do processo erosivo para a aplicação das práticas conservacionistas
Because of the importance of headwater watersheds of the Córrego do Tijuco-SP its soil loss was estimated by the USLE and the spatial variability of the erosion process factors was investigated by multivariate analysis and geostatistics. The estimated average soil loss was considered high, 118.50 Mg ha-1ano-1, and Pearson correlation confirmed the soil erodibility factor as the most important factor in the erosion process. Erodibility is conditioned by the local distribution of soil particle-size fractions and organic matter, and soil texture mostly medium/sandy of low cohesion. Near urban areas, the interaction of rainfall erosivity factor and conservation practices factor showed prominent high soil loss due to concentration of water coming from urban soil impermeabilization and the lack of speed control of runoff water. In contrast, the vegetation cover factor showed great performance in the areas of permanent vegetation, mainly located in the headwaters and drainage channels. In areas of more convex topography close to the watershed dividers, the action of erodibility factor was prominent, in contrast to concave areas of greater slope where the topographic factor was more prominent. We also observed areas with joint action of topographic factors and soil erodibility factor, with smoother topography, but with high natural potential of erosion. Results of multivariate and geostatistics analysis enabled to stratify the study area by identifying sites with specific properties of soil loss which helps in understanding the erosion process for the implementation of conservation practices
Augusto, Carlos Henrique. "Zonas homogêneas de manejo por meio de variáveis edafoclimáticas e de produtividade". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153199.
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O aumento da população mundial e a limitada área disponível para a produção de alimentos, exige que busquemos cada vez mais técnicas e tecnologias que aumentem a produtividade das áreas agrícolas. A produtividade de uma determinada cultura depende de diversos fatores, e conhecer os fatores que mais influenciam a determinação do seu potencial produtivo pode contribuir para a tomada de decisão em relação à utilização e gestão de recursos. Utilizando dados de monitores de colheita da cultura da soja nas safras de 08/09, 10/11, 11/12, 12/13, 14/15 e 15/16, dados de precipitação destes anos, mapa de Condutividade Elétrica (CE) e das características químicas do solo para as safras de 09/10, 13/14, 14/15 e 15/16, este trabalho teve o objetivo de identificar os fatores mais relevantes para a determinação da produtividade da soja para auxiliar na determinação de Zonas Homogêneas de Manejo (ZHM) baseadas nestas características críticas. Comprovou-se que a disponibilidade de água é a principal determinante da produtividade da soja nas condições estudadas, sendo que a precipitação no mês de setembro, mês de implantação da cultura, apresentou-se como o fator mais crítico. Utilizando o mapa de produtividade média da cultura durante os anos estudados e o mapa de CE, foi possível identificar as áreas de potencial produtivo, mas a definição de ZHM mostrou-se desafiadora pois as características químicas do solo apresentaram alta variabilidade temporal, dificultando a determinação do manejo que poderia melhor explorar as áreas de maior ou menor potencial produtivo.
The growing world population and the limited area available for food production requires us to progressively seek techniques and technologies that increase the yield of agricultural crops. The yield of a crop depends on several factors and knowing the factors that most influences its yield potential can contribute to the decision making process regarding the use and management of resources. Using data from soybean yield monitors of 08/09, 10/11, 11/12, 12/13, 14/15 and 15/16 season, precipitation data from these years, Electric Conductivity (EC) map and the chemical characteristics of the soil for the 9/10, 13/14, 14/15 and 15/16 crops, this work had the objective of identifying the most relevant factors that determine soybean yield to assist in the determination of Homogeneous Management Zones (HMZ) based on these critical characteristics. The availability of water was the main factor of soybean yield under the conditions the study was carried out, and the precipitation in September was the most critical factor, being the month in which the crop was seeded. Using the average productivity map and the EC map, it was possible to identify areas of yield potential, but the definition of HMZ was challenging because the chemical characteristics of the soil had high temporal variability, making it difficult to determine the best management to explore the areas of greater or lesser yield potential.
Fedrigo, Jean Kássio. "Recuperação de pastagens naturais degradadas por sobrepastejo, por meio do diferimento". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/128120.
Texto completoThe herbivory on natural grasslands has a prominent role in driving vegetation dynamics, determining changes in vegetation structure, biodiversity patterns and primary and secondary productivity. These changes, which generally contribute to the ecosystems sustainability at moderate grazing intensities, can cause environmental degradation when the stocking rate used is higher than the pasture carrying capacity. The objective of this study was to evaluate the efficiency of temporary grazing exclusion to restore diversity, botanical composition, forage biomass, sward height, light interception and soil seed bank from a natural grassland degraded by overgrazing based on a reference area. Three treatments based on seasonal grazing exclusions (spring deferment, autumn deferment and continuous stocking) with three replications were applied simultaneously in areas managed for a long period with two grazing intensities: severe and moderate (used as reference area). The pasture managed under severe grazing showed a rapid change in botanical composition and diversity patterns in response to grazing exclusions. After two years of temporary grazing exclusions, grass functional groups of the established vegetation and soil seed bank from overgrazed pasture changed toward the characteristic species of plant community under moderate grazing. We also verified significant increases in forage biomass, sward height and light interception. The plant community under moderate grazing intensity showed better balance between different functional groups of plants, especially among species with prostrate and cespitose growth habits. This condition favored the spatial structure of appearance in the distribution of plant species, greater diversity, species richness and better structural pasture conditions. The grazing exclusion in moderate intensity grazing provided dominance tussock species, determining decrease in the diversity and richness of plants. The deferment periods showed similar response patterns within each grazing intensity with higher magnitude for spring deferment. These results reveal the importance of grazing exclusion as a tool for the recovery of degraded pastures by overgrazing.
Pocaznoi, Diana. "Optimisation d'anodes microbiennes à partir de lixiviat de sol pour la conception de piles à combustible microbiennes". Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0053/document.
Texto completoMicrobial fuel cells (MFC) are devices capable to convert chemical energy from organic fuels directly into electrical energy. In these cells, the fuel oxidation is provided by micro-organisms known as "electro-active"; these microorganism form biofilms on the surface of the anode and act as a catalyst for electrochemical reactions. The aim of this work was the optimisation of microbial anodes formed from bacterial flora contained in garden soils. The chronoamperometric experiments performed in a three-electrode system showed for the very first time in these systems that current densities of 66 A/m2 could be obtained by forming microbial anodes on ultra-microelectrodes. On electrode of normal size, the development of a new technique (delayed polarisation) for designing microbial biofilms produced current densities of 9.4 A/m2 after 3 days of polarisation, while the conventional protocol asked a few weeks for obtaining 6 to 8 A/m2. The study of different electrode materials indicated that stainless steel allowed reaching current densities up to 21 A/m2, which makes it a suitable candidate for designing electro-active biofilms. Indeed, the carbon electrodes provided up to 34.4 A/m2, even 50 A/m2 in anaerobic conditions, but the electrodes benefited of a three-dimensional structure contrasting the stainless steel electrode. The use of optimised microbial anodes in MFCs insured the production of 6 W/m2. In addition, the development of a new prototype containing a removable cathode allowed extending the lifetime of the initial MFC from 2 weeks to over 2 months