Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Thesis (Ph.D.)--University of Wollongong, 2009. / Typescript. Includes bibliographical references: leaf 308-322.

No presente trabalho, efetuamos um extensivo estudo das propriedades eletrônicas e estruturais de nanofios de silcio (Si NWs) utilizando simulações computacionais totalmente ab-initio (metodo do DFT). Mostramos que nestes sistemas, diferentes facetas podem ser eletronicamente ativas ou inativas nos estados de borda dependendo apenas da maneira como os átomos de superfície se ligam aos átomos mais internos. Estes efeitos são causados pelo confinamento quântico nos fios, e por isso podem ser estendidas para outros tipos de fios semicondutores. Nossos resultados podem ser utilizados para guiar o processo de manufatura de sensores baseados em nanofios. Efetuamos cálculos ab-initio de transporte eletrônico nos nanofios com radicais de NH2 adsorvidos em diferentes facetas. Estas análises indicam que há diferenças entre a resposta do sistema a perturbações em superfícies distintas que são eletronicamente ativas. Em certas circunstâncias que serão discutidas, o nível de impureza gera centros espalhadores que reduzem o transporte eletrônico de maneira mais uniforme, enquanto em outros casos as quedas na transmitância são extremamente agudas, com perfil lembrando ressonâncias de fano. Investigamos ainda dopagem de Si NWs com boro e fósforo. Mostramos que estas impurezas se distribuem de maneira razoavelmente uniforme em sítios internos e superficiais dos fios. Embora o confinamento quântico tenda a tornar os níveis de impureza significativamente mais profundos nos fios que no cristal de Si, mostramos que rapidamente, para diâmetros acima de 30°A, dopagem com características de bulke recuperada. Efeitos associados as diferentes superfícies nas quais as impurezas estão localizadas também foram identificados, e acordo com nossas constatações anteriores. Estudamos outra importante impureza em nanofios de Si, que é o ouro, que é utilizado como catalisador no crescimento destes fios. Nossas analises indicam que ha uma forte tendência para estes átomos serem incorporados em sítios superficiais, onde eles não introduzem estados próximos ao gap de energia. Isso indica que ouro pode ser utilizado para catalisar estes fios sem afetar suas propriedades eletrônicas. Por fim analisamos as propriedades eletrônicas de heteroestruturas filiformes de silicio-germânio. Dispositivos eletrônicos baseados nestes materiais têm apresentado propriedades superiores a de equivalentes em arquitetura planar ou mesmo dispositivos baseados em outros nanofios. Nossas análises indicam que estes materiais podem apresentar tão variadas que os tornam candidatos `a diversas implementações tecnológicas, desde detectores de alta sensibilidade e grande liberdade de manipulação até materiais de propriedades eletrônicas robustas e pouco sujeitas a indesejáveis perturbações. / We have performed an extensive study on the electronic and structural properties of silicon nanowires (NWs) using parameter free computational simulations (DFT). We show that in Si NWs, surfaces whose atoms are connected to inner ones perpendicularly to the wires axes become electronically inactive at the band edges. However, when these bonds are oriented along the growth axes the surface states contribute significantly to the formation of the HOMO and LUMO, even for relatively large wires (diameters > 30 °A). This is the dimension of the smallest experimental as-grown wires. These effects are caused by the fact that the electronic wave function is confined in the two directions perpendicular to the wires axes but it is not along it. Therefore, these conclusions can be extended to other types of semiconductor NWs, grown along different directions, with different facets and even surface reconstructions. These results can be used to guide actual implementations of NW based chemical and biological sensors, in a fashion that is now being followed by experimentalists. Following this work, we have investigated the electronic transport in these NWs with a NH2 radical adsorbed on different types of facets. These investigations not only confirm our previous conclusions but also indicate different effects associated with impurities adsorbed on distinct active surfaces. In some cases, the impurity level induces scattering centres that reduce the transport in an uniform way, whereas on other types of facets the decrease in the eletronic transport is sharp, suggesting the occurence of fano resonance.

No description available.

No description available.

This thesis presents a detailed experimental programme on understanding the mechanics of drilling in porous brittle solids. Gypsum was used as a model material for this experimental study, in which the mechanics of drilling was decoupled into equivalent problems of indentation and cutting. A comprehensive understanding of the mechanics of indentation and cutting was gained by performing experiments in 2-D conditions. A camera and microscope assembly was used to capture images at high temporal and spatial resolution to measure the in situ deformation. Particle image velocimetry (PIV) algorithm was used to measure the deformation parameters such as velocity, strain-rate, strain and volume change. In the last part of this research, drilling experiments were performed in 3-D conditions and an attempt was made for understanding the mechanics of drilling by relating the drilling experiment results to that of indentation and cutting. A series of wedge indentation experiments were performed under 2-D plane-strain conditions. Development of a parabolic zone of deformation, surrounding the indenter, was observed, wherein this size of the deformation zone and the strain accumulation in the deformation zone was a function of the geometry of the indenter. The maximum effective strain decreased and the overall strain field was more diffuse with increase in the wedge angle. Significant volume change was also observed in this deformation zone and the amount of volume change increased with increase in the porosity of the material. The zones of high volume change (compaction bands) were stacked in the form of layers oriented perpendicular to the direction of indentation. These compaction bands were more localized for the case of lower angles of wedge indenter. The extent of the compaction bands was also a function of porosity and spread over a larger area for the case of low porosity samples. A change in the material response was also observed with change in porosity and geometry of the indenter. The appearance of the crack was delayed with increase in porosity and reduction of wedge angle. The experimental results were also used to validate an analytical cavity expansion model. A better prediction of indentation pressure and the size of the deformation zone was possible after volume change corrections were incorporated into the cavity expansion formulation. A series of orthogonal cutting experiments were performed in 2-D plane-strain conditions. The e ect of tool geometry and the depth of cut on the mechanics of cutting was studied with the help of image based measurements and cutting force signatures. Different types of cutting mechanisms were observed for the case of positive and negative rake angle tool. A cyclic increase and decrease in the cutting force was observed in case of positive rake angle cutting tool. The decrease in the cutting force corresponded to the initiation of crack from the tip of the tool. The crack traversed towards the surface of the material and resulted in the removal of a material chip. With progress of cutting, the tool scratched the material surface, giving rise to the gradual increase in the cutting force as it again reached local maxima when the tool completely re-engaged with the material. For the case of negative rake angle, apart from cyclic increase and decrease of the cutting force, there was a development of a triangular dead zone at the tip of the cutting tool. The size of the dead zone varied cyclically with the progress of cutting. The length of crack, which resulted in the removal of the chip from the material, was found to be a function of the rake angle and the depth of cut. Drilling experiments were performed on gypsum samples in 3-D conditions. Two types of twist drills with different helix angles were used for this research work. Experiments were performed on the samples with two different porosities. Thrust force and torque signatures were recorded for five values of depth of cut per revolution. Since these experiments were performed in 3-D, image analysis was not performed. However, in order to ascertain a qualitative understanding of the drilling process, few experiments were performed on the edge of the material surface so that a cylindrical groove with semicircular cross section is made and the exposed surface of the material and the drill were imaged. The normalized thrust force and normalized torque were compared with indentation pressure and cutting force signatures and remarkable similarities between them was found. A transition from ductile to brittle type of response was observed with increase in the depth of cut per revolution, which was similar to what was observed in case of indentation. The magnitude of torque was found to be higher for high helix angle drills, which was counter to what was observed in cutting, which was due to the deposition of the material in helix for high helix angle drills, resulting in the reduction of the effective helix angle. An approximate estimate of the effective helix angle was made with the help of analytical solutions as well as from the qualitative analysis of the images.

No description available.

This dissertation describes the development of software specifically designed to facilitate simulation analysis of bulk material transportation systems. Use of the term simulation analysis indicates a special variation of the systems analysis process in which the model developed is a digital computer simulation model. Specifically, the software aids in model development, execution, and presentation of the simulation results. Simulation analysis is currently utilized by bulk material transport operators in a limited manner. The problem is that use of available simulation languages requires knowledge concerning language syntax and semantics. Additionally, system operators are not typically trained in how to perform an analysis of their bulk material transportation system. The common solution to these problems is to retain analytical experts who are unfamiliar with the system to be analyzed. The system operators for whom the analysis is performed, and who are responsible for implementation of analytical results, are therefore removed from the analysis process. The considerably reduces the credibility of the analysis. The simulation software described in this dissertation provides a means for a system operator, or anyone not familiar with simulation language use, to develop and execute a simulation model of their system. By increasing the operator role in the analysis process, the acceptability of the analysis is increased. The software is specifically designed for bulk material transportation systems analysis, a research area which can be greatly benefited through the use of simulation model analysis. The simulation software package embodies concepts somewhat similar to those of expert systems, a concept derived from the study of artificial intelligence. The software is "expertly" structured to represent bulk material transportation systems. It contains a knowledge base oriented toward both simulation analysis and bulk material transportation systems analysis. The computer languages C and SIMAN were used for software development. The software is structured in three parts; 1) input interface, 2) SIMAN code generator, and 3) output interface. The user interacts with the input interface, providing information as to the system to be analyzed. This information is utilized by the code generator to create executable SIMAN simulation programs. The output interface provides the simulation output in the system terminology initially selected by the user. / Ph. D.

The Cannibal system, comprised of an activated sludge process integrated with a side stream anaerobic bioreactor, is capable of reducing excess sludge up to 60% compared to the conventional activated sludge process. The hydraulic retention time (HRT) in the Cannibal bioreactor and the interchange rate (the percent of sludge by mass interchanged between the activated sludge system and the bioreactor on daily basis) are the two important operational parameters in the optimization of the Cannibal process. This research was designed to investigate the effect of the Cannibal bioreactor hydraulic retention time and the interchange rate on the solids destruction in the system. The first phase of this study has looked at the effect of three different HRTs, 5 day, 7 day and 10 day. The interchange rate during phase I was 10%. The results showed that the 7 day HRT can be recommended as the minimum retention period for the Cannibal process. The 5 day HRT Cannibal system had some settling problems and high volatile fatty acid content compared to the 7 day HRT Cannibal system. The protein and polysaccharide tests showed that the Cannibal bioreactor is primarily involved in the release of biopolymers which are degraded in the aerobic environment. The second part of this study focused on the effect of the interchange rate (IR) on the solids destruction in the system. The interchange rates that were applied in the system were 15%, 10%, 7%, 5% and 4%.The HRT in the Cannibal bioreactor was 7 day. The results showed that the 10% interchange rate gave maximum solids destruction than the other interchange rates. This implies that 10% is an optimum IR for the Cannibal system. Apart from higher solids wastage, the 4% and 5% IR Cannibal systems had higher volatile fatty acid production. / Master of Science