No description available.

Light may traverse a turbid material, such as blood, without encountering any of its pigment particles, a phenomenon known as sieve effect. This phenomenon may result in a decrease in the amount of light absorbed by the material. Accordingly, the corresponding sieve factor needs to be accounted for in optical investigations aimed at the derivation of blood biophysical properties from light transmittance measurements. The existing procedures used for its estimation either lack the flexibility required for practical applications or are based on general formulas that incorporate other light and matter interaction phenomena. In this thesis, a ray optics framework is proposed to estimate the sieve factor for blood samples using a first principles approach. It consists in applying ray-casting techniques to determine the probability that light can traverse a blood sample without encountering any of the pigment (hemoglobin) containing cells. The thickness of the samples as well as the distribution, orientation and shape of the red blood cells are taken into account by the simulation algorithm employed in this framework. The predictive capabilities of the proposed approach are demonstrated through a series of in silico experiments. Its effectiveness is further illustrated by visualizations depicting the different blood parameterizations considered in the simulations.

Light may traverse a turbid material, such as blood, without encountering any of its pigment particles, a phenomenon known as sieve effect. This phenomenon may result in a decrease in the amount of light absorbed by the material. Accordingly, the corresponding sieve factor needs to be accounted for in optical investigations aimed at the derivation of blood biophysical properties from light transmittance measurements. The existing procedures used for its estimation either lack the flexibility required for practical applications or are based on general formulas that incorporate other light and matter interaction phenomena. In this thesis, a ray optics framework is proposed to estimate the sieve factor for blood samples using a first principles approach. It consists in applying ray-casting techniques to determine the probability that light can traverse a blood sample without encountering any of the pigment (hemoglobin) containing cells. The thickness of the samples as well as the distribution, orientation and shape of the red blood cells are taken into account by the simulation algorithm employed in this framework. The predictive capabilities of the proposed approach are demonstrated through a series of in silico experiments. Its effectiveness is further illustrated by visualizations depicting the different blood parameterizations considered in the simulations.

No description available.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-10-19T12:37:38Z No. of bitstreams: 1 MARIA ROSIANE DE ALMEIDA ANDRADE - DISSERTAÇÃO (PPGEQ) 2017.pdf: 4020246 bytes, checksum: 96bceac541ee13322a3c142ca97018a6 (MD5) / Made available in DSpace on 2018-10-19T12:37:38Z (GMT). No. of bitstreams: 1 MARIA ROSIANE DE ALMEIDA ANDRADE - DISSERTAÇÃO (PPGEQ) 2017.pdf: 4020246 bytes, checksum: 96bceac541ee13322a3c142ca97018a6 (MD5) Previous issue date: 2017-10-26 / Capes / A diminuição das reservas de combustíveis fósseis devido a grande demanda por energia e as alterações climáticas causadas pela emissão de gases do efeito estufa têm incentivado o desenvolvimento de novas fontes de energia, como o biodiesel. O biodiesel é um combustível biodegradável derivado de fontes renováveis, que pode ser produzido a partir de óleos vegetais, resíduos de óleos e gorduras animais. A principal rota de produção do biodiesel é a transesterificação metílica de triglicerídeos na presença de um catalisador básico homogêneo, mas este tipo de catalisador produz sabão e não é recuperado. Nesse sentido, estudos têm sidos desenvolvidos para produzir um catalisador heterogêneo capaz de obter elevadas conversões em ésteres e que seja facilmente recuperado e reutilizado. Dentre os catalisadores heterogêneos destacam-se os catalisadores de molibdênio devido a sua acidez de Lewis e Brønsted-Lowry, suportados em sílicas mesoporosas, como a peneira molecular MCM-41 que apresenta alta estabilidade térmica, elevada área superficial, grande volume de poros e distribuição de mesoporos ordenados que possibilitam a incorporação de metais em sua estrutura. Dessa forma o objetivo do presente trabalho é sintetizar o catalisador MoO3/MCM-41 e avaliar seu potencial catalítico na reação de transesterificação metílica do óleo de soja e testar sua atividade no seu reprocessamento. Para isso, inicialmente a peneira molecular MCM-41 foi obtida por um processo hidrotérmico a 30 °C por 24 h, utilizando o ortossilicato de tetraetila (TEOS), o brometo de cetiltrimetilamônio (CTABr), o hidróxido de amônio (NH4OH) e a água, e em seguida, passou por um processo de ativação por calcinação para remoção do direcionador estrutural. Posteriormente, foi incorporado na estrutura da MCM-41 o precursor heptamolibdato de amônio, por saturação de volume de poro, nas porcentagens (em massa) de 10, 20, 30, 40 e 45 %. A obtenção do MoO3 sob a peneira molecular MCM-41 se deu através do processo de ativação por calcinação. A partir dos resultados obtidos nos difratogramas de raios X foi possível confirmar a formação da peneira molecular MCM-41, bem como identificar os picos referentes ao MoO3. Os óleos obtidos nas reações de transesterificação apresentaram densidade e viscosidade dentro dos padrões estabelecidos pela resolução da Agencia Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP) N° 51 de 25/11/2015, porém o índice de acidez não ficou dentro do limite máximo permissível e apenas os catalisadores com 10, 20 e 30 % de MoO3 conseguiram converter ao valor mínimo de ésteres. Os catalisadores de 30, 40 e 45% de trióxido de molibdênio apresentaram uma boa estabilidade catalítica nos dois ciclos de reuso, com uma redução máxima da atividade catalítica de 2,38%. Os óleos obtidos com a reutilização destes catalisadores apresentaram densidade e viscosidade dentro dos limites estabelecidos pela ANP. / The decline in fossil fuel reserves due to high demand for energy and climate change caused by greenhouse gas emissions has encouraged the development of new energy sources such as biodiesel. Biodiesel is a biodegradable fuel derived from renewable sources, which can be produced from vegetable oils, waste oils and animal fats. The main production route of biodiesel is the methyl transesterification of triglycerides in the presence of a homogeneous basic catalyst, but this type of catalyst produce soap and are not recovered. In this sense, studies have been developed to produce a heterogeneous catalyst capable of obtaining high conversions into esters and that is easily recovered and reused. Among the heterogeneous catalysts, there is one that stands out the molybdenum catalysts due to their acidity of Lewis and Brønsted-Lowry, supported in mesoporous silicas, such as the MCM-41 molecular sieve, which presents high thermal stability, high surface area, large pore volume and distribution of ordered mesopores that allow the incorporation of metals in its structure. Thus the objective of the present work is to synthesize the MoO3/MCM-41 catalyst and to evaluate its catalytic potential in the reaction of methyl transesterification of soybean oil and to test its activity in its reprocessing. For this purpose, the molecular sieve MCM-41 was initially obtained by a hydrothermal process at 30 °C for 24 hours using tetraethyl orthosilicate (TEOS), cetyltrimethylammonium bromide (CTABr), ammonium hydroxide (NH4OH) and water and then passed by a calcination activation process to remove the structural driver. Subsequently, the ammonium heptamolybdate precursor was incorporated into the MCM-41 structure by pore volume saturation, in the percentages (in mass) of 10, 20, 30, 40 and 45%. The MoO3 under the MCM-41 molecular sieve was obtained by the calcination activation process. From the results obtained in the X-ray diffractograms it was possible to confirm the formation of the molecular sieve MCM-41, as well as to identify the peaks related to MoO3. The oils obtained in the transesterification reactions presented density and viscosity within the standards established by the Resolution of the National Agency of Petroleum Natural Gas and Biofuels. (ANP) N°. 51 of 11/25/2015, but the acidity index was not within the maximum allowable limit and only the Catalysts with 10, 20 and 30% MoO3 were able to convert to the minimum value of esters. The catalysts of 30, 40 and 45% of molybdenum trioxide showed good catalytic stability in the two cycles of reuse, with a maximum reduction of catalytic activity of 2.38%. The oils obtained with the reuse of these catalysts showed density and viscosity within the limits established by the ANP.

The objective of this study was to investigate the transport properties and the microstructure of CMS membranes derived from a carbon-rich intrinsically microporous polyimide precursor. CMS membranes were prepared by a heat treatment of the polyimide precursor using a well-defined heating protocol in a horizontal tube furnace up to 1000 °C. A nitrogen purge was kept inside the furnace to remove all the evolved by-products as the precursor started to decompose and carbonize. The microstructures of the carbon molecular sieve membranes (CMSMs) were examined using wide-angle x-ray diffraction, Raman spectra, N2 adsorption and CO2 adsorption. The average interlayer spacing (d002) between the graphite plates was estimated using the data obtained by the WXRD. The average d002 decreased as a result of increasing the pyrolysis temperature; average d002 distances for CMS prepared at 700 and 1000 °C were estimated to be 0.40 to 0.38 nm, respectively. Raman spectra confirmed the progressive structural ordering as heat-treatment temperature increased. A substantial decrease in the intensity of the D band was observed as a function of pyrolysis temperature, indicating a decrease in the disordered structure. Graphitic structure and turbostratic carbon coexist in the as-prepared carbon membranes, of which the microcrystal size La and the stacking height Lc were increasing as a function of pyrolysis temperature. N2 adsorption showed a remarkable increase in the BET surface area as a function of pyrolysis temperature. BET surface areas for the pristine and CMSs prepared at 700 to 900 °C were in the range of 650 to 680 m2/g with a remarkable shift in the pore size distribution toward the ultra- microporous region. CO2 adsorption was used to estimate the surface area for pores with sizes of less than 1 nm. Surface areas were observed to increase from 350 m2/g at 500 °C to 857 m2/g at 800 °C, and then started dropping slightly from 857 to 650 m2/g at 800 to 1000 °C, respectively. This is believed to be caused by pore shrinkage effect being severe after 800 °C, which caused some pores to be hard to spot by the CO2 adsorption technique. The transport properties of the pristine and CMS membranes were tested using pure gases He, H2, N2, CH4, CO2, and O2. From the pristine to SBFDA-DMN-700°C, the selectivity increased significantly, with a massive loss in the permeability except for He and H2. From SBFDA-DMN- 700 °C to 900 °C, a substantial increase in selectivity with a moderate decline in permeability was observed. Beyond 900 °C, the permeability again decreased moderately, but a tremendous increase in the selectivity for N2/CH4, CO2/CH4, and H2/CH4 was observed.

One form of Goldbach’s Conjecture asserts that every even integer greater than 4is the sum of two odd primes. In 1920 Viggo Brun proved that every sufficiently large even number can be written as the sum of two numbers, each having at most nine prime factors. This thesis explains the overarching principles governing the intricate arguments Brun used to prove his result. Though there do exist accounts of Brun’s methods, those accounts seem to miss the forest for the trees. In contrast, this thesis explains the relatively simple structure underlying Brun’s arguments, deliberately avoiding most of his elaborate machinery and idiosyncratic notation. For further details, the curious reader is referred to Brun’s original paper (in French).

No description available.

Orientador: Gustavo Paim Valença / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T23:01:25Z (GMT). No. of bitstreams: 1 LaSalvia_Nathalia_D.pdf: 7860896 bytes, checksum: 356f0e957d83d2daaba9cb36b26a4056 (MD5) Previous issue date: 2014 / Resumo: Peneiras moleculares do tipo MCM-41 foram sintetizadas com e sem alumínio estrutural e impregnadas com 5% de magnésio e 5 e 10% de cromo. As amostras foram então calcinadas e caracterizadas, e utilizadas na conversão catalítica de etanol. Esses materiais foram caracterizados por Espectroscopia de Infravermelho com Transformada de Fourier (FTIR), Difração de Raios X (DRX), Adsorção de Nitrogênio, Microscopia Eletrônica de Transmissão (TEM), Ressonância Magnética Nuclear (NMR), Espectrometria de Emissão Óptica por Plasma Acoplado Indutivamente (ICP-OES), Espectroscopia de Absorção Atômica (AAS), Análise Termogravimétrica (TGA), Dessorção a Temperatura Programada de NH3 (TPD-NH3), Quimissorção de CO2 e Picnometria de Hélio. Testes preliminares foram realizados para avaliar a eficiência do sistema reacional. Os testes catalíticos foram realizados em um reator de leito fixo, as temperaturas de reação utilizadas foram 600, 625, 650, 675, 700 e 725 K e as pressões de etanol de 4310, 3128 e 2240 Pa, as massas utilizadas foram 30 e 60mg, e o fluxo de etanol foi mantido constante em 2×10-6 m3 s-1. Os compostos identificados foram o etileno, acetaldeído, dietil-éter, 1.3-butadieno, etano, acetato de etila e, com seletividade abaixo de 2%, crotonaldeído, butiraldeído, butanol, acetona, propanol, propeno, metano e metanol. Foi realizado também o balanço de massa do sistema e foram determinados os valores dos graus de avanço de cada reação. Os cálculos dos efeitos difusivos demonstraram que a transferência de massa externa para reações a 675, 700 e 725 K podem ser limitantes da reação. Foram realizados testes de desativação de 48 horas. Foram realizados também os cálculos da taxa global de reação e da taxa de giro para todos os sólidos e em todas as condições de reação / Abstract: Molecular sieves of the MCM-41 type were synthesized and impregnated with 5% w/w Mg and loads of Cr: 5% and 10%. The solids were then calcined, characterized and tested as catalysts for the conversion of ethanol. These materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (DRX), N2 adsorption, Transmission Electron Microscopy (TEM), Nuclear Magnetic Resonance (NMR), Inductively Coupled Plasma Optical Emission Spectrometry (ICP- OES), Atomic Absorption Spectroscopy (AAS), Thermogravimetric Analysis (TGA), Temperature-Programmed Desorption of NH3 (TPD-NH3), CO2 Chemisorption and Helium Pycnometry . Preliminary tests were conducted to evaluate the efficiency of the reaction system. The catalytic test reaction of ethanol was carried out in a fixed bed microreactor under differential conditions at 600, 625, 650, 675, 700 e 725 K and at 4310, 3128 e 2240 Pa of ethanol partial pressure. The mass of catalyst used in all tests were ca. 30 and 60 mg and the volumetric flow of ethanol saturated N2 was 2×10-6 m3 s-1. The compounds identified ethylene, acetaldehyde, diethyl ether, 1,3-butadiene, ethanol, ethyl acetate and selectivity with less than 2%, crotonaldehyde, butyraldehyde, butanol, acetone, propanol, propylene, methane, and methanol. The mass balance of the system was also performed and it was determined the values of the extent of reaction. The criteria for diffusion limitations were used in all cases. Calculations based on the experimental data suggest that data at 675, 700 and 725 K may be diffusion-limited. Deactivation tests were performed for 48 hours. The calculations of the overall reaction rate and turnover rate for all solid and all reaction conditions were also performed / Doutorado / Desenvolvimento de Processos Químicos / Doutora em Engenharia Quimica

Large sparse matrices arise in many applications, especially in the major problems of Cryptography of factoring integers and computing discrete logarithms. We focus attention on such matrices called sieve matrices generated after the sieving stage of the algorithms for integer factoring. We need to solve large sparse system of equations Bx = 0, with sieve matrices B arising in this context. The traditional Gaussian elimination, with a cubic run time, is not efficient for handling such matrices. Better algorithms for such input matrices are the quadratic runtime algorithms based on Block Lanczos(BL) or Wiedemann techniques. Of these two, BL is even better for large integer factoring algorithms. We carry out an efficient implementation of the Block Lanczos algorithm for finding the vectors in the null space of the the sieve matrix. We report our test results using our implementation for matrices of sizes up to 106. We plan to use this implementation in our ongoing projects on factoring the large RSA challenge integers of sizes 640 bits(called RSA-640) and beyond. So it is useful to exploit possible parallelism. We propose a scheme for parallelizing certain steps of the Block Lanczos method, taking advantage of structural properties of the sieve matrix. The sizes of matrices arising in integer factoring context are quite large. Hence we also discuss some techniques that are used to reduce the size of the sieve matrix. We also consider the last stage of the NFS Algorithm for finding square roots of large algebraic numbers and outline a sketch of our algorithm.