Os aços microligados ao vanádio são usados em peças automotivas forjadas, tais como virabrequins e bielas. Através de equações matemáticas que descrevem a cinética de recristalização e de crescimento de grão, foi desenvolvida uma rotina em planilha para simular a evolução dos tamanhos de grão austeníticos durante os passes de laminação em função da temperatura, taxa de deformação, tempo entre passes e características do material. O resultado do tamanho de grão ferrítico calculado final, foi comparado com os tamanhos de grãos de amostras retiradas da laminação e de amostras realizadas por simulação física (ensaio de torção a quente). Esta comparação entre modelamento matemático e simulação física com o processo de laminação, demonstra que é possível calcular e descrever a evolução microestrutural e mostra que o principal mecanismo de controle do refino de grão envolvido em uma laminação de não planos com trens abertos é o de recristalização estática, para as condições existentes na usina onde foi efetuado o presente estudo. / Microalloyed steels are used as forging stock for many automotive parts such as crankshafts and connecting rods. Using mathematical equations describing the recrystallization kinetics and grain growth, a spreadsheet has been developed to simulate the austenitic grain size evolution during bar rolling mill schedules as a function of temperature, strain rate and time between passes. The calculated ferritic grain size was compared with samples taken from the process and physical simulation (torsion testing). Comparison between mathematical modeling and physical simulation with the plant bar rolling mill process shows that it is possible to predict the microstructural evolution and confirm the main grain refinement control mechanism as being static recrystallization, under the conditions prevailing in the plant where this study has been carried out.

A solução sólida céria-samária é uma das principais candidatas para aplicação como eletrólito sólido em células a combustível de óxido sólido, devido sua alta condutividade iônica em temperaturas intermediárias (500-750 ºC) de operação. Um dos problemas ainda não solucionados com relação a este material é sua relativamente baixa sinterabilidade. Nesse trabalho foi utilizado o método de sinterização em duas etapas visando melhorar a densificação com reduzido tamanho médio de grãos. Soluções sólidas comercial e obtida por mistura de óxidos de composição Ce0,8Sm0,2O1,9 foram utilizadas. Para fins comparativos também foi utilizado o método denominado sinterização em duas etapas tradicional que visa a obtenção de amostras densas independentemente do tamanho médio de grãos. Resultados de densidade aparente e retração linear revelaram que ambos os tipos de amostras têm comportamento distinto. Para a solução sólida comercial, a retração total até 1400 ºC foi de ~18%. Só foram obtidos resultados de densidade significativos ao utilizar temperaturas elevadas (igual ou superior a 1300 ºC). Para o material obtido por mistura de óxidos não foi possível atingir densidades maiores que 90% da densidade teórica. A sinterização em duas etapas tradicional produziu amostras densas, da mesma forma, que a não-tradicional, mas com tamanhos de grãos consideravelmente maiores. Amostras sinterizadas por ambos os processos foram analisadas por espectroscopia de impedância para a determinação da condutividade elétrica em função da temperatura, e não apresentaram variação significativa nas condutividades intra e intergranular. A sinterização em duas etapas não resultou em melhorias na densificação e nem na condutividade elétrica das amostras. Entretanto, a redução obtida no tamanho médio de grãos pode melhorar as propriedades mecânicas. / Samaria-doped ceria solid solution has been proposed to be used as solid electrolyte in Solid Oxide Fuel Cells due to its high ionic conductivity at intermediate temperatures (500-750 ºC). One of the main problems related to this solid solution is the relatively low sinterability. In this work, sintering of powder compacts was carried out by the two-step sintering method to improve the densification with simultaneous reduction of the mean grain size. Samaria-doped ceria, both commercial and prepared by solid state reactions, with composition Ce0.8Sm0.2O1.9 were investigated. For comparison purposes, the traditional two-step sintering method, by which dense specimens are produced, was also utilized. Apparent density and linear shrinkage results showed distinct features depending on the type of specimen. Total linear shrinkage for commercial solid solution up to ~ 1400 ºC was 18%, but high density values were obtained only for sintering experiments conducted at high temperatures ( 1300 ºC). Specimens prepared by solid state reactions did not attain density values higher than 90% of the theoretical one. The traditional method produced dense specimens as well as the two-step sintering, although the grain size was considerably higher in the former. Specimens sintered by the two methods were used for electrical conductivity measurements. No significant variation in both the grain and the grain boundary conductivities was obtained. The two-step sintering did not allow any improvement in the densification and in the electrical conductivity of samaria-doped ceria. However, the decrease in the mean grain size may contribute to improve the mechanical properties of this solid solution.

This study compares four different methods to measure hydraulic conductivity (K) at two sites on the East Tennessee State University Valleybrook Campus. It compares the K values to each other, to the different K values between the two sites, and to United States Department of Agriculture (USDA) K values. Two field methods, Well Bail Test and Auger Hole Test, and two lab methods, Constant Head Permeameter Test and Grain Size Distribution Test (GSD), were performed on the clay rich Ultisol soils on an East Tennessee hillslope in the Valley and Ridge Physiographic Province. One site was located close to a monitoring well and the other on the floodplain of an existing stream. The Hazen, Alyamani & Sen, and Slichter methods were used to compute K from the GSD Test. The Alyamani & Sen, Slichter, and permeameter methods produced similar K values ranging from 9.52 x 10-6 to 1.25 x 10-3 cm/sec. These are similar to the USDA K values ranging from 9.17 x 10-4 to 2.82 x 10-4 cm/sec. The Hazen method overestimated K and ranged from 8.10 x 10-3 to 1.09 x 10-1 cm/sec. The Well Bail Test yielded a lower K value (ranging from 8.16 x 10-9 to 1.19 x 10-8 cm/sec) than the USDA values as expected for water flow in deeper soil horizons at a depth of 8.50 meters. Comparing these values helped to better understand the difference between various methods to compute the hydraulic conductivity.

The need for assessment of benthic habitat characteristics may arise for many reasons. Such reasons may include but are not limited to, habitat mapping, environmental concerns and identification of submerged aquatic vegetation. Oftentimes, such endeavors employ the use of aerial photography, satellite imagery, diving transects and extensive sampling. Aerial photography and remote sensing techniques can be severely limited by water clarity and depth, whereas diver transects and extensive sampling can be time consuming and limited in spatial extent. Acoustic methods of seabed mapping, such as the acoustic sediment classification system QTC are not hampered by water clarity issues. The acoustic sediment classification system QTC is capable of providing greater spatial coverage in fractions of the time required by divers or point sampling. The acoustic classification system QTC VIEW VTM was used to map benthic habitats within Tampa Bay. The QTC system connected in parallel to an echo-sounder is capable of digitally extracting and recording echoes returning from the seabed. Recorded echoes were processed using QTC IMPACTTM software. This software partitions echo waveforms into groups or classes based on their similarity to one another using multivariate statistics, namely Principal Component Analysis and K-Means clustering. Data was collected at two frequencies, 50 kHz and 200 kHz. Side-scan sonar data was collected coincident with the QTC data and used to produce mosaics of the various habitats in Tampa Bay. Side-scan sonar data was classified using QTC SideviewTM in an attempt to identify changes in benthic habitats. Sediment samples used for ground-truth were subjected to grain size analysis. Also, the percentage of organic matter and carbonate within samples was determined. Results of acoustic classification appear to accurately reflect changes in the sediment type and structure of the seabed. Grain size, particularly percent mud, appears to have a strong influence on classification. Carbonate hard bottom habitats were found to be acoustically complex, a characteristic useful for their identification. The QTC system was able to detect seagrass, although some misclassification occurred between vegetated and non-vegetated seabeds.

Grain size, 14C age, and X-ray diffraction (XRD) analyses of sediments indicate possible tsunami deposits on the southern coast of Java near Pangandaran and Adipala. Previous studies that have described known recent and paleotsunami deposits were used for comparison. Fining-upward grain size trends, interbedded sand and mud, sediment composition, and trends in heavy mineral abundances are among the characteristics used for tsunami deposit identification. At Batu Kalde, an archaeological site south of Pangandaran, a layer of aragonitic sand with marine fossils was found atop a layer of archaeological fragments at an elevation of ~2-5 m. It is likely this layer was deposited by a tsunami, potentially generated by a mega-thrust earthquake. Archaeological material remains suggest that the tsunami occurred ~1300 years ago. A bivalve with an age of 5584-5456 cal YBP was buried within the deposit, perhaps long after its death. At Goa Panggung, a cave east of Batu Kalde, fining-upward grain size trends, composition of sediments, and radiocarbon ages suggest the presence of at least one tsunami deposit. A 5040-4864 cal YBP piece of charcoal overlying modern organic matter suggest that the tsunami first scoured the cave floor, reworking existing material and making interpretation difficult. At Adipala, in western Central Java, fining-upward grain size, upward decrease in heavy mineral abundances, and lateral continuity of sand layers revealed the existence of two possible tsunami deposits buried within the sediments in a swale ~1.6 km from the ocean. Age of the deposits is undetermined.

β-grain size is an influential microstructural parameter on the properties of titanium components. A reduction of β-grain size is generally associated with improvements to ductility, strength, corrosion and fatigue resistance of many α, α/β and β titanium alloys. During production of wrought titanium components, the β-grain size is carefully controlled during thermomechanical processing but there is currently no control of the β-grain size during solidification of cast components. As such, this inability to control the β-grain structure during solidification may limit the applications for solidification based technologies including casting, welding and direct metal deposition. Due to the limited knowledge of grain refinement practices and the lack of commercial grain refiners for the titanium system, this thesis investigates the mechanisms of β-grain refinement during solidification of cast titanium alloys. In this thesis, generalized theories for grain refinement that have been developed from research into other metallic systems are applied to the titanium system. Similar to the findings from aluminium and magnesium research, it is shown that grain refinement of cast titanium alloys requires the addition of growth restricting solutes which provide constitutional undercooling as well as the presence of potent nucleant particles. It is demonstrated that commercially pure titanium contains a natural distribution of nuclei particles which may originate from the mould wall and when powerful growth restricting solutes are introduced, significant prior-β grain refinement is achievable. All solutes investigated do not interact or poison the naturally occurring nucleants enabling the grain size of the titanium alloys to be predicted by an empirically determined relationship based on the growth restriction factor. A full list of growth restriction factors for various elements in titanium is determined and it is proven that growth restriction theory is valid in the titanium system. A further reduction in β-grain size is achievable by introducing additional nucleant particles to titanium castings in conjunction with growth-restricting solutes. Using a novel technique, titanium powder was introduced to the melt stream prior to solidification and was mixed throughout the liquid. The powder particles partially melted and the oxide surface layer dissolved allowing intimate substrate-liquid contact, enabling the titanium substrates to act as sites for heterogeneous nucleation. Using this technique, it was possible to grain refine commercially pure titanium without foreign elemental addition and when growth restricting solutes were present it was possible to obtain approximately an order of magnitude grain size reduction. The results and concepts developed from this work may aid the future development of a commercial grain refiner for titanium. If a grain refiner is developed, its application will not just be limited to the titanium casting industry but may also benefit other solidification based technologies such as welding, direct metal deposition and wrought billet production.

The Australian wheat production environments are typically water-limited, and both temperature and vapour pressure deficit increase as the season progresses. As a result, high incidences of small or shriveled wheat kernels (screenings) are commonly generated and can substantially reduce grain value. Previous studies suggest the incorporation of the tiller inhibition (tin) gene can reduce the production of infertile tillers and increase kernel weight (KW). It was hypothesised that the incorporation of the tin gene into wheat germplasm may a) contribute to the maintenance of large KW and reduction in screenings (SCR) in terminal water deficit environments; and b) not be associated with a grain yield (GY) penalty in terminal water deficit environments. Thus, the major objective of this thesis was to evaluate the expression and performance of tin gene in terms of GY and SCR: 1) in different genetic backgrounds and across Australian production environments; 2) in various northern production environments which are particularly prone to terminal water deficit conditions; and 3) to determine the mechanisms that contribute to the maintenance of large KW of tin lines in terminal stress conditions. To address the overall objective, populations of lines were genotyped for the presence/absence of the tin gene and were field tested. Line differences in GY, yield components, SCR and general growth and development attributes were determined in 22 field experiments conducted between 2005-2007. The experiments were grouped into those that evaluated: a large number of sister lines from four genetic backgrounds in multi-location experiments; selected lines from Silverstar population in multi-location experiments; and selected sister lines in detailed agronomic experiments examining the effect of plant density and controlled levels of water supply through the use of a rainout shelter facility. The effect of tin on GY and SCR varied with environment and genetic background. In the Brookton, Wyalkatchem and Chara background, there was no reduction in GY associated with tin in southern production environments. However, a 31% and 10%, advantage of free-tillering over reduced tillering Silverstar lines existed in the 2005 western and 2006 northern experiments respectively, and led to an average 12% reduction in GY of Silverstar tin lines. In northern experiments, tin lines in a Silverstar background produced up to 50% fewer SCR than Silverstar free-tillering lines. Averaged across experiments, KW of Silverstar tin lines was 10% greater than free-tillering lines. Based on stem number per plant, Silverstar lines were classified into three groups; the restricted (R) and semi-restricted (SR) tin and free-tillering lines attained 2.9, 3.4 and 4.8 stems per plant respectively. Expression of tin in terms of maximum stem number production was genetic background and genotype dependent, and unlike free-tillering lines, R tin lines in particular, were not as responsive to plant density. Head number per unit area rather than kernel number per head was strongly associated with KW determination. Therefore, to maximize KW under water limiting conditions it is more beneficial if high kernel number can be achieved via the production of low head number with more kernels per head, as can be achieved with the use of tin lines. The KW advantage of Silverstar R tin was associated with greater anthesis total dry matter, stem water soluble carbohydrate and nitrogen available per head relative to free-tillering lines, and thus R tin lines had more assimilate for translocation during the grain filling period. In a terminal water deficit experiment, individual KW data collected for Silverstar tin and free-tillering lines revealed that KW of tin lines (≈ 25 mg per kernel) was maintained for main stem to fourth tiller heads and across floret positions 1-4 within spikelets. In contrast, free-tillering lines (≈ 18 mg per kernel) generated small kernels across the entire plant, with the largest proportion originating from floret positions 3 and 4. Lines containing the tin gene had a greater mean KW and kernel width, and a higher frequency of wider kernels than free-tillering lines. The high frequency of large kernel widths was associated with significantly less SCR in tin lines. A strong positive association between maturity head number per plant and SCR indicated, for every fertile head produced, SCR increased by 11% in the terminal water deficit experiment. Reduction in SCR in the Silverstar tin material in the north, was associated with high KW and a tendency for lower GY, although tin lines with equivalent GY to Silverstar could be identified in each environment. The incorporation of the tin gene has the potential to significantly reduce the incidence of SCR in commercial wheat crops. The reduction in GY associated with the tin gene was dependent on genetic background, suggesting the potential for selection of higher-yielding tin progeny in commercial line development. However, a tailored agronomic package to optimize yield potential of tin lines needs to be developed for different target environments. With the incorporation of the tin gene into genetic material adapted to the northern wheat belt and optimisation of head density, there exists scope for simultaneous improvements in GY and KW and subsequent reduction in SCR for terminal water deficit environments.

<p>Detailed information on past oceanographic and climatic changes is crucial for our understanding of natural climate variability and for the assessment of future climate variations. Sediments strongly influenced by the North Atlantic Current accumulate at high rates in the northeastern Skagerrak, forming a potential highresolution archive for information on past climatic and oceanographic processes and events. Through a highresolution, multi-proxy study of the 32 meter long core MD99-2286 from the north-eastern Skagerrak, and interpretation of chirp sonar profiles from the coring area, this thesis provides new and detailed insights about the paleoceanographic development of the eastern North Sea region since the deglaciation.</p><p>The chronostratigraphic control of core MD99-2286 relies on 27 radiocarbon dates. Ages are presented in calibrated thousand years before present (abbreviated “kyr”). Core MD99-2286 was correlated to chirp sonar profiles using measured physical properties. This correlation demonstrates that a strong regional acoustic reflector, previously assumed to represent the Pleistocene/Holocene boundary, was formed as a result of rapid ice retreat during the latest Pleistocene. Based on the distribution of ice rafted debris in the core, ice berg calving in the Skagerrak ended at 10.7 kyr. Detailed grain-size analyses of the core were interpreted using a novel 3D-visualization technique. Between 11.3 and 10.3 kyr, clay-rich distal glacial marine sediments were deposited in the northeastern Skagerrak, derived from Baltic melt-water outflow across south-central Sweden through the Otteid-Stenselva strait. As a result of differential isostatic uplift, the route of the major outflow and the associated sediment deposition moved southwards along the Swedish west coast. After 10.3 kyr, sediment deposition in the north-eastern Skagerrak gradually adopted to a fully interglacial normal marine sedimentation dominated by Atlantic inflow and the North Jutland Current.</p><p>The establishment of the modern circulation system in the eastern North Sea is marked by abrupt coarsening of the sediments in core MD99-2286 at 8.5 kyr. This was a result of increased Atlantic inflow, opening of the English Channel and the Danish straits, and formation of the South Jutland Current. Mineral magnetic properties of the core show a distinct relationship reflecting general sediment source variability. After 8.5 kyr, sediments in the northeastern Skagerrak were derived predominantly from the Atlantic Ocean and the North Sea, with varying contributions from the South Jutland Current, the Baltic Current, and the currents along the coasts of western Sweden and southern Norway. Between 6.3 and 3.8 kyr, the eastern North Sea was further developed towards the modern situation by an increase of the South Jutland Current flow. The Skagerrak bottom currents were probably forced by strong Atlantic water inflow between 0.9 and 0.5 kyr, and after that by increased wind stress. The influence of regional climate on the eastern North Sea circulation has increased since the middle of the Holocene.</p>

<p>Treatment wetlands been showed efficient for reducing pollutant in waste water. In Lajeado – RS, Brazil the landfill has poor leachate water treatment. It is necessary to supplement the treatment plant because they need to reduce BOD, COD and nitrate of the water going to recipient. A subsurface flow wetland (SSF) can be a good choice.  In order to be able to design an efficient SSF it is important to understand how the grain sizes of a substrate affect the reducing of pollutants in waste water. This study focus on two substrate, sand with grain size of 0 - 3 mm and gravel with the grain size of 10 - 20 mm. To see the grain size reduces BOD, COD and nitrate best, the experiment used eight pilot scales SSF for leachate water treatment, four filled with sand and four filled with gravel. Two different flows, four with batch and four used continuous flow; two of each was planted with <em>Thypa angustifolia</em> <em>L</em>. Samples were taken from each wetland every week during a four week period. The results showed that the wetlands with the fine- grained substrate; sand gave the better reduction of BOD, COD and TKN (total kjeldahl kväve). It also showed great reduction in color. Important to notice in this study is the lack of time; more samples are required to be able to establish a pattern.</p>

The separation of natural and anthropogenically caused climatic changes is an important task of contemporary climate research. For this purpose, a detailed knowledge of the natural variability of the climate during warm stages is a necessary prerequisite. Beside model simulations and historical documents, this knowledge is mostly derived from analyses of so-called climatic proxy data like tree rings or sediment as well as ice cores. In order to be able to appropriately interpret such sources of palaeoclimatic information, suitable approaches of statistical modelling as well as methods of time series analysis are necessary, which are applicable to short, noisy, and non-stationary uni- and multivariate data sets. Correlations between different climatic proxy data within one or more climatological archives contain significant information about the climatic change on longer time scales. Based on an appropriate statistical decomposition of such multivariate time series, one may estimate dimensions in terms of the number of significant, linear independent components of the considered data set. In the presented work, a corresponding approach is introduced, critically discussed, and extended with respect to the analysis of palaeoclimatic time series. Temporal variations of the resulting measures allow to derive information about climatic changes. For an example of trace element abundances and grain-size distributions obtained near the Cape Roberts (Eastern Antarctica), it is shown that the variability of the dimensions of the investigated data sets clearly correlates with the Oligocene/Miocene transition about 24 million years before present as well as regional deglaciation events. Grain-size distributions in sediments give information about the predominance of different transportation as well as deposition mechanisms. Finite mixture models may be used to approximate the corresponding distribution functions appropriately. In order to give a complete description of the statistical uncertainty of the parameter estimates in such models, the concept of asymptotic uncertainty distributions is introduced. The relationship with the mutual component overlap as well as with the information missing due to grouping and truncation of the measured data is discussed for a particular geological example. An analysis of a sequence of grain-size distributions obtained in Lake Baikal reveals that there are certain problems accompanying the application of finite mixture models, which cause an extended climatological interpretation of the results to fail. As an appropriate alternative, a linear principal component analysis is used to decompose the data set into suitable fractions whose temporal variability correlates well with the variations of the average solar insolation on millenial to multi-millenial time scales. The abundance of coarse-grained material is obviously related to the annual snow cover, whereas a significant fraction of fine-grained sediments is likely transported from the Taklamakan desert via dust storms in the spring season. / Die Separation natürlicher und anthropogen verursachter Klimaänderungen ist eine bedeutende Aufgabe der heutigen Klimaforschung. Hierzu ist eine detaillierte Kenntnis der natürlichen Klimavariabilität während Warmzeiten unerlässlich. Neben Modellsimulationen und historischen Aufzeichnungen spielt hierfür die Analyse von sogenannten Klima-Stellvertreterdaten eine besondere Rolle, die anhand von Archiven wie Baumringen oder Sediment- und Eisbohrkernen erhoben werden. Um solche Quellen paläoklimatischer Informationen vernünftig interpretieren zu können, werden geeignete statistische Modellierungsansätze sowie Methoden der Zeitreihenanalyse benötigt, die insbesondere auf kurze, verrauschte und instationäre uni- und multivariate Datensätze anwendbar sind. Korrelationen zwischen verschiedenen Stellvertreterdaten eines oder mehrerer klimatologischer Archive enthalten wesentliche Informationen über den Klimawandel auf großen Zeitskalen. Auf der Basis einer geeigneten Zerlegung solcher multivariater Zeitreihen lassen sich Dimensionen schätzen als die Zahl der signifikanten, linear unabhängigen Komponenten des Datensatzes. Ein entsprechender Ansatz wird in der vorliegenden Arbeit vorgestellt, kritisch diskutiert und im Hinblick auf die Analyse von paläoklimatischen Zeitreihen weiterentwickelt. Zeitliche Variationen der entsprechenden Maße erlauben Rückschlüsse auf klimatische Veränderungen. Am Beispiel von Elementhäufigkeiten und Korngrößenverteilungen des Cape-Roberts-Gebietes in der Ostantarktis wird gezeigt, dass die Variabilität der Dimension der untersuchten Datensätze klar mit dem Übergang vom Oligozän zum Miozän vor etwa 24 Millionen Jahren sowie regionalen Abschmelzereignissen korreliert. Korngrößenverteilungen in Sedimenten erlauben Rückschlüsse auf die Dominanz verschiedenen Transport- und Ablagerungsmechanismen. Mit Hilfe von Finite-Mixture-Modellen lassen sich gemessene Verteilungsfunktionen geeignet approximieren. Um die statistische Unsicherheit der Parameterschätzung in solchen Modellen umfassend zu beschreiben, wird das Konzept der asymptotischen Unsicherheitsverteilungen eingeführt. Der Zusammenhang mit dem Überlapp der einzelnen Komponenten und aufgrund des Abschneidens und Binnens der gemessenen Daten verloren gehenden Informationen wird anhand eines geologischen Beispiels diskutiert. Die Analyse einer Sequenz von Korngrößenverteilungen aus dem Baikalsee zeigt, dass bei der Anwendung von Finite-Mixture-Modellen bestimmte Probleme auftreten, die eine umfassende klimatische Interpretation der Ergebnisse verhindern. Stattdessen wird eine lineare Hauptkomponentenanalyse verwendet, um den Datensatz in geeignete Fraktionen zu zerlegen, deren zeitliche Variabilität stark mit den Schwankungen der mittleren Sonneneinstrahlung auf der Zeitskala von Jahrtausenden bis Jahrzehntausenden korreliert. Die Häufigkeit von grobkörnigem Material hängt offenbar mit der jährlichen Schneebedeckung zusammen, während feinkörniges Material möglicherweise zu einem bestimmten Anteil durch Frühjahrsstürme aus der Taklamakan-Wüste herantransportiert wird.