982 resultados para Solos - Carbono


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Located in Apiaí, Vale do Ribeira, southern region of São Paulo state, the Usina do Calabouço areas (CIEM / CPRM) and Morro do Ouro (Parque Municipal do Morro do Ouro), were targeted for stud ies due to its old buildings, respectively a foundry in lead ore, called Experimental de Chumbo e Prata (Usina Calabouço), and a gold mine with processing plant of the gold-bearing ore produced there. Nowadays, the areas are used for public visitation, and in both places the rests of the buildings remains. Particularly in the CIEM/CPRM, due to the materials witch was produced before, it can suggest the existence of anomalous amounts of the involved metals (CIEM / CPRM) and possible contaminations by chemical products used in the improvement of the auriferous ore (P. M. Morro do Ouro). These potential contamination were confirmed with geochemical survey of soils and current sediments accomplished in both areas, for the elements arsenic, cadmium, lead, copper, mercury, silver and zinc, which were used as parameters guiding values for soil and groundwater the state of São Paulo (CETESB), and watershed values stipulated by CPRM (poor, background and anomalous), in it rising geochemistry during Folha Apiaí's execution (SG-22-X-B-V).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The monolithic glassy carbon is a carbonaceous material, isotropic, non graphitizable obtained by means of carbonization of resins up to 1000 °C. The good physicochemical properties make this material applied in several areas such as aerospace, medicine, electronics, chemistry, among others. It has generally been processed from the use of phenolic and furfuryl alcohol resins. These resins have high crosslink density and high fixed carbon content and are therefore widely applied in aerospace. The combination phenol / furfuryl alcohol resins search for obtaining the most suitable process for the glass-like carbon processing with phenolic resins currently available and of lower cost and easier to synthesize than the furfuryl alcohol resin. The main objective of this work is to obtain a phenol-furfuryl resin with high fixed carbon content combined with low porosity of the material. Different synthesis routes have been adopted along with thermal analysis techniques, FTIR and image analysis. The resin obtained through partial synthesis process presented the characteristics sought in this work

Relevância:

20.00% 20.00%

Publicador:

Resumo:

With the increasing demand for electricity, the retraining of transmission lines is necessary despite environmental restrictions and crossings in densely populated areas to build new transmission and distribution lines. Solution is reuse the existent cables, replacing the old conductor cables for new cables with higher capacity power transmission, and control of sag installed. The increasing demand for electrical power has increased the electric current on the wires and therefore, it must bear out temperatures of 150°C or more, without the risk of the increasing sag beyond the established limits. In the case of long crossings or densely populated areas, sag is due to high weight of the cable on clearance. The cable type determines the weight, sag, height and the towers dimensions, which are the items that most influence the investment of the transmission line. Hence, to reduce both cost of investment and maintenance of the line, the use of a lighter cable can reduce both number and the height of the towers, with financial return on short and long term. Therefore, in order to increase the amount of transmitted energy and reduce the number of built towers and sag, is recommended in the current work substitute the current core material (steel or aluminium) for alternatives alloys or new materials, in this case a composite, which has low density, elevated stiffness (elasticity module), thus apply the pultruded carbon fiber with epoxy resin as matrix systems and perform the study of the kinetics of degradation by thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), according to their respective standards

Relevância:

20.00% 20.00%

Publicador:

Resumo:

After confirming the high specific mechanical properties of composite materials by scientific studies conducted over the last decades, one of the challenges of this new class of materials is the ability to achieve mass production at a more affordable cost, which has become indispensable. The Resin Transfer Molding (RTM) is an excellent method for manufacturing composite materials. Despite being a process widely used by international companies in the production of high performance structural composites, only a short time the national aviation industry has shown interest in implementing this type of processing to more complex structures and greater structural responsibility. In aeronautical projects, the reproducibility and the relative low cost of this process, several studies have been performed in Brazil for learning and perfecting this technique. This process is suitable for producing polymer components both simple as complex geometry, and allows to achieve consistent thickness, with high quality finish and without limiting range. Polymeric composite components for the high mechanical stress applications such as aircraft structures, satellites, etc., require a strict control of volume fractions of the composite constituents, beyond the knowledge of their mechanical and thermal properties. Therefore, in this experimental work degree study on the mechanical, thermal and of porosity composites processed by RTM processed characterization was performed. This characterization was performed targeting a possible aerospace application of this composite material. For the production of composites, process equipment (RTM RTM injector Radius 2100cc) was used. The processed carbono/epoxy composites were characterized via flexure tests mechanically and thermally analysis via DMA, DSC and TGA. To determine the volume fraction of fibers, the composite samples were analyzed via matrix digestion (ASTM D3171) ... (Complete abstract click electronic access below)

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This work performs a comparative study of fatigue life of riveted lap joints involving classes of drilling which adjustment is made with interference or clearance. For this study, representative specimens of this joints were manufactured with four rivets distributed in two rows. In this context, are presented the test matrix, the methodology employed in performing of the tests, the used mathematical modeling, and that methods that are the basis for the latter are described through the theoretical foundation. Next, are present the results obtained in fatigue tests and images of the region of failure of the specimens. Finally, are present some comments and conclusions related to the results obtained

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Along the Earth globe we can find many types of psychoactive plants. Among them is the Ipomoea violacea, popularly known as Morning Glory. There are ergotalkaloids producer associated-fungus in its leaves and seeds. One of these alkaloids that can be found is the ergine (or LSA), a homologous substance of the lysergic acid diethylamide (LSD). There are many discussions around the world about the inclusion of LSA in the list of controlled substances. In Brazil, this was recently prohibited. One of the most important point of view in the study of isotopic composition of 13C and 15N of this plant is the fact that there is a total alkaloid variation in function of its geographic origin like was verified in 1960’s, besides to aggregate knowledge about it. This work was made to verify if the isotopic ratio can be used as a tool in tracing this illegal Brazilian plant. We could conclude that this plant presents a C3 photosynthetic pathway, its parts has different isotopic carbon and nitrogen composition and that stable isotope analysis can be successfully used as a tool to detect its geographic origin

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The oil and biodiesel are oily substances which, if spilled or thrown out in the environment, can cause serious damages. In this context, bioremediation techniques can be used to the recovering of sites degradated by mineral or vegetable oil, besides them, the biodegradation. However, it is necessary that there are microorganism strains used to degradate the contaminant, previously selected for the fast, efficient and minimum impact remediation. The main objective of this study was to isolate microorganism strains coming from different ecological recesses and verify their potentiality on biodegradating oil and biodiesel. Strains of bacteria, fungi and yeasts were isolated from soils contaminated by hydrocarbons (diesel, gasoline, grease) before, by doing striations on culture plates. On the biodegradation tests, it was used the redox indicator, 2,6-dichlorophenol indophenol (DCPIP), then, after the indicador’s discoloration, the absorbance of the suspension obtained was measured. 46 different microorganism strains were isolated, and the oil, when it was used as a carbon resource, it was degradate easier than the biodiesel. The experiments showed that, in a period, the site impacted by oil spills recovers itself by the biodegradation, in aerobic conditions, by the redox activity.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Environrnental issues are in focus lately, mainly due to climate change that have been registered in recent decades. Some of these changes are attributed to the increased atmospheric concentration of greenhouse gases induce, main1y due to anthropogenic emissions. These gases act by absorbing heat in the form of electromagnetic radiation emitted by the planet, and after a time interval, reissuing such radiation in various directions, including back to the surface, causing overheating of the same. Projections indicate that climate change wiIl tend to increase even more. Because of this, in recent years a number of studies are being conducted on the dynamics of inducers of greenhouse gases, especially C02, because that is primarily responsible for the development of that phenomenon. To better understand the flow of C02 are studied specific areas, as regions bordering the forests, soils that are under preparation for agriculture, urban areas, among others. Forests are an important sink for C02, because during the process of photosynthesis, this molecule is captured and used to obtain glucose. Thus, studies of the regions bordering the forests contribute enough to the understanding of the dynamics of C02. Because it requires a large amount of factors, the concentration of CO2 in a given location is very variable and this makes it much more difficult to understand their dynamics and, consequently, the action of the enhanced greenhouse effect. Being a relatively new area of study, there are many controversies about the consequences of the greenhouse effect, so that the community does not believe that climate change resulting from human action. According to them, such changes are merely natural phenomena and periodicals

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Hybrid composites combining metal plates and laminates with continuous fiber reinforced polymer, called fiber-metal (CHMF), have been particularly attractive for aerospace applications, due mainly to their high mechanical strength and stiffness associated with low density. These laminates (CHMF) consist of a sandwich structure consisting of layers of polymer composites and metal plates, stacked alternately. This setting allows you to combine the best mechanical performance of polymer composites reinforced with long fibers, to the high toughness of metals. Environmental effects should always be considered in the design of structural components, because these materials in applications are submitted to the effects of moisture in the atmosphere, the large cyclical variations of temperature around 82 ° C to -56 ° C, and high effort mechanical. The specimens of fibermetal composite were prepared at EMBRAER with titanium plates and laminates of carbon fiber/epoxy resin. This study aims to evaluate the effect of different environmental conditions (water immersion, hygrothermal chamber and thermal shock) of laminate hybrid titanium/carbon fiber/epoxy resin. The effects of conditioning were evaluated by interlaminar shear tests - ILSS, tensile, and vibration free

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Aiming to reduce the cost of electrocatalysts and a greater resistance to CO poisoning this work was to study the adsorption and oxidation of carbon monoxide on ordered intermetallic phases AuIn, AuSb2, AuSn, PdSb and PdSn using voltammetric techniques in alkaline electrolyte solution. The results suggest that the AuSn and PdSn intermetallics has some form of resistance to CO poisoning. It is assumed that this behavior is a result of electronic effect and the effect of the third body has been achieved by adding a second metal to Au and Pd. However, further studies should be conducted to confirm this hypothesis as to test these materials as electrocatalysts in the reaction of oxidation of fuels

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Air pollution is an environmental issue worldwide and frequently cause negative effects on population health and ecosystems on cities. The relationship between climate and atmospheric pollution can be used as a surrogate to the intensity of air pollution. The present and quantity of some gases can be used as indicators to air quality: particulate matter (PM), sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), and nitrogen dioxide (NO2). Among those gases, CO has its major source within the cities, where automobiles are the main emitter. But measure pollutant concentration are challenging, sometimes because the lack of good equipments due to high costs and of the large variability of models that varies in precision, way of measure and distribution of sellers. Modeling are useful when there are an intend to evaluate air pollution, its sources and evaluate scenarios. This work aims to use CAL3QHCR model developed by the U.S Environmental Protection Agency (EPA) to generate predictive surfaces of CO concentration distribution on a site within Campinas city, located in São Paulo state, Brazil. CAL3QHCR model use data urban automobile circulation to generate spatial results for CO distribution. We observed that the pollution concentration was lower on our modeling than the concentrations measured by Companhia Ambiental do Estado de São Paulo (CETESB), the main environmental company on the São Paulo state. Also the correlation between average estimates of our model and the measure by CETESB was weak, indicating that the model used on this study need to be or better parameterized, or the scale we measured of CO emissions need to be rescaled. Although the model failed to correlate to CETESB data, maybe one that explore the estimated emissions distributed within the sites to understand spatial distributions of CO on the regions. Also, the generated information can also be used to other studies, and come to be useful to explain heat island

Relevância:

20.00% 20.00%

Publicador:

Resumo:

O cultivo de citrus é uma das principais atividades agrícolas no Estado de São Paulo, sendo realizado em solos gerados a partir de diferentes materiais que conferem, naturalmente, variações na constituição química e mineralógica destes, além de poderem, ou não estar contaminados por metais tóxicos oriundos dos métodos defensivos. Com o objetivo de quantificar os atributos químicos e os teores de metais pesados do solo foi realizado um estudo comparativo entre solos assim cultivados, das regiões das cidades de Mogi Guaçu e São José do Rio Preto. Este estudo envolveu a determinação do pH do solo, análises volumétricas para quantificação dos teores de matéria orgânica, Ca+2, Mg+2 e Al+3 , espectrofotômetro de chama para o estabelecimento dos teores de Na+ e K+ e espectrofotômetro de absorção atômica para determinação dos teores de Cobre, Zinco, Cádmio, Cromo, Níquel e Chumbo. O solo da região de Mogi Guaçu apresentou-se mais ácido devido, provavelmente, a uma maior concentração de Al3+. Apresentou, também, teores mais elevados de matéria orgânica. Os solos de ambas as regiões apresentaramse deficientes em Na+ , K+ , Ca+2 e Mg+2 . A análise realizada para os metais pesados mostrou uma elevada quantidade de Níquel observada nas amostras de solo da região de São José do Rio Preto e, Níquel e Cobre, nas de Mogi Guaçu, com valores classificados como de prevenção, de acordo com os Parâmetros Orientadores da CETESB (2005). Estes teores de alerta devem-se, muito possivelmente, à adição exagerada de defensivos agrícolas.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Inúmeros são os trabalhos versando sobre a contaminação de águas e solos por metais potencialmente tóxicos, ou metais pesados. O destaque sempre é dado para chumbo, mercúrio e, mais recentemente, cádmio que, também é, comprovadamente, carcinogênico. Em contrapartida, estudos sobre a toxicidade do manganês são raros devido, provavelmente, ao fato do mesmo ser um metal essencial à vida. Porém, absorvido em doses elevadas pelo organismo, pode provocar uma série de patologias e disfunções, algumas muito graves como déficit intelectual. Nesse trabalho procurou-se avaliar a concentração de manganês em amostras de solos cultivados e não cultivados de várias regiões do Estado de São Paulo. Surpreendentemente, algumas dessas amostras apresentaram teores até cinco vezes mais elevados do que o limite estabelecido como alto pelo Governo do Estado de São Paulo (que é de 5 mg/dm³). A provável fonte desse excesso reside na liberação de produtos de combustão e/ou na forma de aditivos aos combustíveis.