Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: A desire to increase the efficiency of the comminution process in mineral process systems has led to the need of determining the size distribution of ore particles at various stages in the system. The objective of this research is to investigate the feasibility of the use of an acoustic sensor for measuring particle size distribution. The acoustic signal generated when the particles impact on a cantilever bar is analysed using digital signal processing techniques. As rocks fall onto a metal bar, the bar vibrates. The vibrations contain information th a t is extracted to determine the size of particles tha t impacted on the bar. The bar is modelled as a linear system which is excited by impulses (impact of particles). The response of the bar is deconvolved from the acoustic signal to obtain an impulse whose amplitude is proportional to the energy of the impact. In order to improve size estimates, deconvolution is performed using a statistical model of the impulse sequence (Bernoulli-Gaussian) and then estimated using MAP estimation. Size estimates are not only a function of the mass of particles, but also on the exact position of impact on the bar. Since there is always a variation in the position of impact, size estimates are erroneous. It was found that the position of impact can be determined as to reduce variances dramatically. Due to physical sampling in space, the sensor has a bias towards larger particles. We show how this can be represented mathematically and removed. This project is mainly concerned with rocks in the +8-25mm (+0,7-22 gram) size range. / AFRIKAANSE OPSOMMING: Vergruising van erts in die mineraalbedryf verg groot hoeveelhede energie. Daar is ’n behoefte gei'dentifiseer orn hierdie proses meer effektief te maak. Aangesien die effektiwiteit van ’n meul ’n funksie is van die ertsgroottes wat gemaal word, kan partikel grootte inligting aangewend word om effektiwiteit te bevorder. Die doel van hierdie tesis is om die lewensvatbaarheid van ’n akoestiese sensor vir die doel van partikelgrootte estimasie, te ondersoek. Erts partikels wat val vanaf ’n vervoerband op ’n kantelbalk, veroorsaak dat die balk vibreer. Deur hierdie vibrasies te meet en verwerk, kan inligting aangaande partikel grootte verkry word. Die stelsel word gemodelleer as ’n lineere sisteem met impulse as intree. Die geobserveerde sein is die konvolusie tussen die intree impulse en die impulsweergawe van die sisteem. Deur gebruik te maak van ’n statistiese model en MAP-estimasie, word die effek van die sisteem gedekonvuleer vanaf die geobserveerde sein om ’n benadering van die intree impuls sein te verkry. Die amplitudes van die impulse word gebruik as ’n aanduiding van partikel massa. Partikelgroottes soos benader deur die stelsel, is ’n funksie van die die posisie waar die partikel die balk tref. Deur van patroonherkenning tegnieke gebruik te maak, word die posisie van impak bepaal om sodoende grootte benaderings aan te pas en die variansie van grootte verspreidings te verminder. As gevolg van die feit dat partikels gemonster word deurdat slegs ’n klein persentasie van die hele omvang van partikels ondersoek word, onstaan daar ’n oorhelling ( “bias” ) na groter partikels. Die kans dat groter partikels die balk tref is groter as vir klein partikels. ’n Wiskundige model vir hierdie verskynsel word voorgestel en gewys hoe die die oorhelling geneutraliseer kan word. Hierdie projek het te doen met ertsgroottes +8-25mm (+0,7-22 gram).

Solid substrate cultivation (SSC) using lignocellulosic non-food feedstock, such as switchgrass, is an alternative for advanced biofuel production. Acetone-Butanol-Ethanol (ABE) fermentation in two stages using a sequential culture of microorganisms from the class Clostridia is an approach proposed to increase the butanol production. The goal was to test the efficacy of a sequential culture on high solid substrate cultivation in batch and continuous cultivation, and to evaluate conditions to optimize butanol production using switchgrass as substrate. Initial batch experiments were used to determine particle size effect, choice of solvent producer and pretreatment evaluation: The effect of particle size on gas production was surface area-dependent, 2 mm particle size of switchgrass was better fermented by clostridia than the other particle sizes. C. thermocellum improved switchgrass fermentation by C. beijerinckii. Moreover, C. saccharoperbutylacetonicum produced the highest butanol yield on glucose as substrate. The Fenton reaction was studied as a potential pretreatment for switchgrass. C. beijerinckii grew better on Fenton-treated material, but solvent production was low. The major conclusion of the continuous flow on SSC experiment was that there is no statistical difference in the effect of flow rate within the flow range tested.

Com a crescente diminuição de recursos minerais e o alto custo envolvido na construção da estrutura de uma mina, a recuperação máxima possível de uma jazida vem se tornando fundamental. Para isso além da escolha do método de lavra ter a necessidade de ser feito cautelosamente, é possível lançar mão de métodos adicionais de recuperação, como por exemplo, a recuperação de pilares. Essa pesquisa foi baseada na determinação da caracterização do enchimento (backfill cimentado) utilizado nas câmaras vazias que possibilita a posterior recuperação dos pilares. A caracterização do enchimento é composta da determinação da resistência simples do backfill necessária para que o enchimento cumpra com seu objetivo, desenvolvimento da classificação granulométrica ótima para os agregados e dosagem de cimento e água para alcançar a resistência proposta. A metodologia desenvolvida para obter a nova caracterização é composta de várias etapas que incluem pesquisas em campo e trabalhos em laboratório. Primeiramente, foram obtidos através de análise em campo os parâmetros de dosagem de cimento e classificação granulométrica dos agregados já utilizados na planta de fabricação do enchimento, bem como sua resistência correspondente. Em seguida definições teóricas da dosagem de cimento ideal e classificação granulométrica ótima foram realizadas com base na resistência à compressão simples que foi identificada como necessária para cumprir com as solicitações geomecânicas do maciço rochoso, então posteriormente, a nova caracterização definida teoricamente foi posta à prova através da confecção de corpos de prova de backfill, seguido de execuções de ensaios de compressão. Durante a primeira etapa da metodologia, já se pôde identificar que os agregados possuíam um alto índice de partículas tamanho argila que estavam afetando os resultados de resistência obtidos com a caracterização empregada inicialmente. A partir disso se optou por construir a curva granulométrica ótima sem essa fração. A resistência à compressão simples calculada de 2,69 MPa, foi obtida com base no planejamento de longo prazo que prevê a total recuperação dos pilares existentes na mina. Dessa maneira toda a área que será minerada foi considerada como um único bloco. Finalmente, foi identificada a dosagem de cimento sendo de 4% em peso, que juntamente com a granulometria ótima é capaz de alcançar os valores esperados de resistência. Para que o planejamento da produção da mina durante os próximos anos de vida útil seja efetivamente cumprido, o enchimento deverá prover à mina estabilidade geomecânica local a nível de câmaras abertas com paredes verticais de backfill estáveis e também estabilidade global a nível de contato entre níveis e galerias de acesso. Isso somente será alcançado se a nova caracterização for corretamente aplicada. / As a consequence of the ongoing reduction of mineral resources and the high cost involved in the construction of a mine, the maximum recovery of a mineral deposit becomes a fundamental issue. Therefore, besides the need of caution on the choice of the mining method, it is possible to make use of additional recovery methods, such as the recovery of pillars. This research was based on the determination of the characterization of the fill (cemented backfill) used in avoid stopes that allows the subsequent recovery of adjacent pillars. The characterization of the fill consists of determining the uniaxial compressive strength of the backfill required for an efficient filling, developing an optimal particle-size distribution for the aggregates and finding the cement-water ratio necessary to reach the desired resistance. The methodology developed to obtain the new characterization is comprised of several steps which include field work and laboratory tests. First, cement dosing parameters and particle size of the aggregates (already used at the filling manufacturing plant), as well as their corresponding strength, were obtained through analyses in the field work. Then, theoretical definitions of the ideal cement dosing and optimal particle-size analysis were carried out based on the uniaxial compressive strength that has been identified as necessary to comply with the geomechanical requests from the rock mass, and then later, the new theoretical characterization was tested by making backfill samples, followed by execution of compression tests. During the first stage of this methodology, it has been identified a high proportion of clay particle size for the aggregates, that have affected the strength results obtained from the characterization used initially. From this point, we decided to build the optimal particle-size curve without this fraction. Uniaxial compressive strength, calculated as 2.69 MPa, was obtained from the long-term planning that determines the full recovery of the existing pillars in the mine. In this way, the entire area to be mined was considered as a single block. Finally, the cement dosing has been identified as 4% by weight, which together with the optimal particle size, is able to achieve the expected strength values. In order to effectively fulfill the mine production planning over the next years of lifespan, the filling should provide the mine local geomechanical stability at open stopes level, with vertical walls of stable backfill, and also global stability at the contacts between levels and access galleries. This will only be achieved if the new characterization is correctly applied.

This work has involved the study of the magnetic behaviour of small magnetic nanoparticle systems. Due to the reduced size of magnetic nanoparticles they present distinctive properties, such as size and surface effects, that have been analysed in this work, as well as the effect of interactions in such systems. The samples chosen for the study were magnetite particles in the form of a ferrofluid and Co nanoclusters in a nonmagnetic matrix of Cu. Both systems present very narrow particle size distributions, which facilitates the interpretation of the data. The samples have been subjected to basic characterisation, which includes the determination of the distribution of magnetic particle sizes using the magnetisation curves at room temperatures, TEM microscopy and X-ray diffraction, in the case of the ferrofluid samples. For the nanoclusters, a time of flight spectrometer has been used to obtain the number of atoms per cluster. Many of the measurements have been performed at low temperatures, where thermal effects are minimised. For such measurements the samples have been frozen in a zero applied field, so that they have a random distribution of magnetic moments prior to the measurement. The energy barrier distributions have been calculated via the temperature decay of remanence (TDR). From this study, an effective anisotropy constant has been calculated. For the study of the interactions, surface and size effects, magnetisation, susceptibility (ZFC), remanence and delta-M curves, as well as the time dependence of magnetisation have been studied. The attempt frequency of the different particle size systems has been calculated using different techniques. The basic magnetic behaviour can be explained on the basis of the Neel blocking model. It has been found that the systems with the smaller particles have significant surface effects, which are enhanced at lower temperatures. Interactions, which are weak due to the low concentration of magnetic material in the samples (<10%), have been found to be overall demagnetising and the evolution of the magnetic properties with dilution has been explained. As is the case for the surface effects, interaction effects are stronger at low temperatures due the reduction of thermal effects. The experimental results have been compared with calculations from a Montecarlo model for fine particles, which includes the effects of concentration, anisotropy, particle size and temperature.

Made available in DSpace on 2014-06-11T19:28:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-03Bitstream added on 2014-06-13T19:16:22Z : No. of bitstreams: 1 benedetti_mp_me_botfmvz.pdf: 748638 bytes, checksum: c6ba19aeae78da3ed949dcdb78d6fa9a (MD5) / Universidade Estadual Paulista (UNESP) / Objetivou-se com o presente trabalho avaliar o efeito da textura e granulometria sobre o desempenho, rendimento de carcaça, digestibilidade dos nutrientes e morfologia dos órgãos de frangos de corte. Dois experimentos foram conduzidos no galpão experimental do Laboratório de Nutrição de Aves da FMVZ/UNESP – Botucatu/SP. No experimento 1 foram utilizados 720 pintos de corte, machos, da linhagem Cobb. As aves foram distribuídas em delineamento inteiramente casualizado com esquema fatorial 2 X 3, duas texturas (dura e dentada) e três granulometrias do milho da dieta avaliadas pelo DGM (fina – 0,46 mm; média – 0,73 mm e grossa – 0,87 mm), com 4 repetições de 30 aves cada. No experimento 2 foram utilizados 120 pintos de corte, com as mesmas características dos utilizados no experimento 1, sendo o primeiro ensaio metabólico realizado no período do 19º ao 22º dias de idade e o segundo no período do 38º ao 41º dias de idade, com coleta total de excretas. A análise estatística dos dados de desempenho, rendimento, digestibilidade e morfologia foram feitas pelo método de análise de variância e as médias comparadas pelo teste de Tukey no nível de 5% de probabilidade. No experimento 1 a textura e a granulometria influenciaram os parâmetros de desempenho aos 7 dias de idade. Aos 21 dias de idade apenas a granulometria influenciou o peso final, ganho de peso médio, consumo de ração e a conversão alimentar. Não houve efeito de textura e granulometria do milho para as variáveis de desempenho aos 43 dias de idade, exceto para o fator de produção. No experimento 2, não houve diferenças no rendimento de carcaça e de partes para as variáveis estudadas, exceto para porcentagem de moela. Conclui-se que apesar do melhor desempenho dos frangos de corte até 21 dias de idade ter sido observado com o uso de rações com milho de granulometria fina, aos 42 dias... / This study aimed to evaluate growth performance, carcass yield, nutrient digestibility and organ morphology of broilers fed diets compounded by two corn texture (dent and flint) and particle size (fine, medium and coarse). Two experiments were undertaken in the Broiler Nutrition Laboratory experimental barn of the FMVZ/UNESP – Botucatu/SP. In experiment 1, 720 all-male broiler chicks of Cobb line were randomly assigned to 24 boxes in a 2 X 3 factorial scheme, two corn textures (flint and dent) and three corn particle size evaluated by geometric mean diameter (fine – 0.46 mm; medium – 0.73 and coarse – 0.87), with four replicates of 30 chicken each. In experiment 2, 120 broiler chicks with the same characteristics from experiment 1 were used, although the first metabolic assay was performed among the 19th to 22th day old with total excretion collection. The metabolic assay was performed among 38th to 41th days old. All data was submitted to ANOVA and means compared by Tukey’s test at 5% probability. In experiment 1, corn textures influenced the final weight and weight gain, mean weight gain, feed intake and feed conversion ratio. There was no effect of corn texture and particle size on growth performance parameters at 43- day old, regardless the production factor. In experiment 2, there was no effect of corn texture and particle size on carcass and parts yield, regardless for gizzard percentage. It was concluded that the use of diets with fine particle size improves broilers growth performance until 21 years day-old. Dent and flint textures did not influence broilers growth performance.

Made available in DSpace on 2014-06-11T19:28:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-21Bitstream added on 2014-06-13T19:16:31Z : No. of bitstreams: 1 oriolijunior_v_me_jabo.pdf: 281953 bytes, checksum: 9238bc67a61b82c999924de463bd2a19 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O alto custo atual do cloreto de potássio e a grande dependência de sua importação para suprir a demanda nacional, sugerem a necessidade de estudos que procurem avaliar a eficiência de outras fontes de potássio, principalmente aquelas baseadas em matéria-prima nacional. Nesse sentido, foi conduzido um experimento em casa de vegetação com amostras de um Latossolo Vermelho distrófico textura média, adotando-se o delineamento inteiramente casualizado em esquema fatorial 4x3x2 (quatro doses de K, três fontes e duas granulometrias), com três repetições. Os fertilizantes potássicos utilizados foram o cloreto de potássio, o termofosfato magnesiano potássico (TK) e a mistura TK (70%) + cloreto de potássio (30%), todos fornecidos em duas granulometrias (100 e 60 mesh) e aplicados nas doses de 0, 60, 120 e 180 mg kg-1 de K. Verificou-se que a adubação potássica promoveu incrementos significativos na produção de massa seca (parte aérea) nos dois crescimentos do capim-marandu e nas concentrações de K no solo e na planta, não havendo diferenças entre as fontes e suas granulometrias. Os níveis críticos de K no solo e na parte aérea das plantas foram 1,5 mmolc dm-3 e 19 g kg-1, respectivamente. / The high acquisition cost of potassium chloride and the fact that Brazil has to import it justify the search for the new sources of potassium, mainly among raw materials which can be found in Brazil. With this in view, an experiment was conducted under greenhouse conditions with samples of a sandy clay loam Typic Haplustox in completely randomized design in factorial scheme 4x3x2 (four rates of K, three sources and two particle sizes), with three replications. The potassium fertilizers employed in the experiment were potassium chloride, fused magnesium potassium phosphate (TK) and a mixture of 70% of TK and 30% of potassium chloride. The particle sizes for each fertilizer were of 100 and of 60 mesh. The rates were of 0, 60, 120, and 180 mg kg-1 of K. The results showed that the potassium fertilization resulted in significant increments in the yield of shoot dry matter in the two cuttings of the Marandu grass and in the levels of K both in the plant and in the soil. Source and particle size had no significant effect on the evaluated parameters. K critical levels in the soil and in the shoot were found to be of 1.5 mmolc dm-3 and 19 g kg-1, respectively.

Made available in DSpace on 2014-10-09T12:46:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:01:24Z (GMT). No. of bitstreams: 1 07540.pdf: 5595475 bytes, checksum: 832f00e3a259330c79b1d3676cd33214 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:45:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:50Z (GMT). No. of bitstreams: 1 07314.pdf: 4739953 bytes, checksum: a48b44f01cecc873bb2fc11c29573811 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:43:30Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:43Z (GMT). No. of bitstreams: 1 06636.pdf: 4715244 bytes, checksum: 8df295514eae9493e07c3d6352c4bf32 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2015-04-01T12:17:41Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3689736 bytes, checksum: 727f212a3d43cfe51e158ce0f1485daf (MD5) Previous issue date: 2013-07-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In last years there has been a huge concern about environment. This present study aims to study the viability of using mollusk shell powder, as particulate reinforcement in polymer composites of High Density Polyethylene (HDPE), in order to this research contributes potentially to mitigate the environmental impact caused by increase of shell waste associated with mollusk commercial activities on the coast of Paraiba State. To this end, a study on influence of mollusk shell additions (for concentrations of 2, 5 and 8% in weight and for granulometries with both 200 and 325 meshes) in changing the mechanical, morphological, and thermal properties of pure HDPE is done. In addition, a titanate coupling agent was used to treat surfaces of mollusk shell powder of the composite having 5% in weight of shell. All composites were processed in a single-screw extruder with a mixing component (Madock) and specimens are molded by injection. It was performed a chemical characterization of the shell powder by X-ray fluorescence in order to identify its constituents and it was found 97.95% calcium oxide, which is the main constituent of calcium carbonate. In addition, it was performed a MFI analysis and thermal, morphological, and mechanical characterization for all composites as well as for pure HDPE. The MFI analysis of the composites showed only slight changed, therefore the mollusk shell did not influence definitely on rheological behavior of the pure HDPE.The cristalinity degree of the pure UHWPE increased when mollusk shell powder was increased. The composition of 5% in weight with granulometry of 325 mesh produced the highest increase of cristalinity degree of non-treated powders, almost 29%, whereas 38% cristalinity degree was obtained when a 200-mesh composition of 5% in weight was treated with the titanate coupling agent. This behavior suggest a probable effect of particles as nucleating agent. Fracture surfaces show there is both low bonding among the phases and particle agglomerates, mainly in 8% composite for both granulometries. The addition of shell powder changed tensile mechanical properties of pure HDPE, where in major cases its stiffness was increased excepted for 5% compositions. Both the impact strength and bending mechanical properties of the pure HDPE were increased when the thinner shell powders were additioned. Hence shell powder is a potential particle reinforcement for use in HDPE composites. / Nos últimos anos existe uma preocupação muito grande com meio ambiente. O presente estudo tem como objetivo estudar a viabilidade do uso de pó de conchas de moluscos, como carga particulada em compósitos poliméricos de polietileno de alta densidade, (PEAD) a fim de que essa pesquisa contribua potencialmente para amenizar o impacto ambiental causado pelo aumento da produção dessas conchas, associadas com as atividades comerciais de moluscos, ao longo de toda a costa do estado da Paraíba. Com este objetivo foi realizado um estudo sobre a influência da concha, nas concentrações de 2, 5, 8% em massa, nas granulometrias de 200 e 325 mesh, sobre as propriedades mecânicas, morfológica e térmica do PEAD puro. Neste estudo, um agente de acoplamento titanato também foi utilizado para tratar as superfícies das partículas do pó da concha do compósito contendo uma concentração de 5 % de concha. Os compósitos foram processados em uma extrusora mono rosca com um componente de mistura(Madock) e os corpos de prova foram moldados por injeção. Foi realizado uma caracterização química no pó da concha por fluorescência de Raio X para verificar seus constituintes, e encontrando 97,95% de oxido de cálcio constituinte principal do carbonato de cálcio. Também foi realizada análise de MFI, caracterização térmica, morfológica e mecânica para todos os compósitos e para o PEAD puro. O MFI dos compósitos teve pequena alteração, logo a carga não influenciou o comportamento reológico do PEAD. O grau de cristalinidade do PEAD puro aumentou à medida que o teor de pó de concha foi aumentado, sendo que a composição de 5% em massa, na granulometria de 325 mesh foi a que apresentou maior aumento, quase 29% com relação ao puro, já o compósito com 5% em massa de pó de concha(200 mesh) tratado com agente de acoplamento titanato teve um aumento de quase 38%. Esse comportamento indica um provável efeito nucleante dessas partículas. A superfície de Fratura mostrou que existe pouca adesão entre as fases presentes e que existem aglomerados das partículas, principalmente com a composição de 8% nas duas granulometrias. A adição da concha alterou as propriedades mecânicas sob tração do PEAD puro, de um modo geral, sua rigidez foi aumentada, exceto os compósitos contendo 5% em massa, que diminuíram o módulo de elasticidade do PEAD puro. A resistência ao impacto e as propriedades mecânicas sob flexão do PEAD puro foram aumentadas com a adição do pó de concha, com a granulometria mais fina. O pó da concha é um reforço particulado potencial para o uso em compósitos de PEAD.