Este trabalho teve como objetivo analisar os cavacos de dimensões reduzidas inseridos em cozimentos que se utilizam de menores tempos e maiores temperaturas, de maneira a se obter as bases para o estabelecimento de um novo processo e/ou a otimização dos sistemas atualmente utilizados em escala industrial. Amostras de cavacos de referência (3,6 mm, obtidas pelo processo convencional de picagem) e de cavacos com espessura de 0,5 mm, 1 mm e 2 mm (obtidas por um gerador de partículas), do híbrido de Eucalyptus urophylla x Eucalyptus grandis com 7 anos foram analisadas quanto à densidade básica, composição química e morfologia das fibras. Após a caracterização, os materiais foram submetidos à polpação kraft pelo processo convencional e foram testados três níveis de fator H com quatro níveis de álcali ativo de maneira a se estabelecer uma equação que representasse o processo e pudesse ser utilizada em cozimentos futuros. Através das equações obtidas foi possível calcular os parâmetros de rendimento depurado, álcali ativo residual, álcali ativo consumido, teor de sólidos secos, fator H e álcali ativo em função de um número kappa 18. Os resultados mostram que a densidade básica, a composição química e a morfologia das fibras da madeira não foram afetadas pelo processo de picagem. No entanto, a densidade a granel foi afetada pela espessura dos cavacos, sendo de 0,037, 0,081, 0,110 e 0,141 g.cm-³ para os cavacos de 0,5 mm, 1 mm, 2 mm e 3,6 mm respectivamente. No processo de polpação, as espessuras se comportaram de maneira semelhante, no entanto, a espessura de 2 mm apresentou o melhor número kappa para o fator H de 451, o de maior interesse, com o mesmo rendimento que as demais espessuras. Na análise de regressão, a espessura de 2 mm apresentou melhor rendimento, menor teor de sólidos e menor fator H (de 461), compatível com o que se pretende utilizar em processos de polpação com tempo reduzido de cozimento. / The objective of this work was to evaluate the performance of thin chips inserted on a short time and higher temperatures in cooking process, to obtain the basis for the establishment of a new process and / or the optimization of the currently systems used on an industrial scale. Samples of the reference chips (3,6 mm obtained by the conventional process of chipping) and thin chips with 0,5 mm, 1 mm and 2 mm (obtained by a particle generator) of the Eucalyptus urophylla x Eucalyptus grandis hybrid with 7 years of age had their density, chemical composition and fibers morphology evaluated. After the characterization, the materials were submitted to conventional kraft pulping process and three levels of H factor with four levels of active alkali were tested to establish an equation to represent the process that can be used on future cookings. Yield, residual active alkali, consumed active alkali, dry solids, H factor and active alkali were calculated through equations, according to a kappa number 18. The results show that the basic density, chemical composition and morphology of the wood fibers were not affected by the chipping process. However, the bulk density of 0,037, 0,081, 0,110 and 0,141 g.cm-³ for the 0,5 mm, 1 mm, 2 mm and 3,6 mm chips, respectively, was affected by the chip thickness. On the pulping process, the different chips had the same behavior, however, 2 mm chips showed the best kappa number to H factor 451, with the same yield as the other thickness. On the regression analysis, the 2 mm chips showed better performance, lower solids content and lower H factor (461), consistent with a short time pulping process.

Despite extensive research in the field of aging neuroscience, it still remains unclear whether age related cortical changes can be detected in different functional networks of younger adults and whether these networks respond identically to healthy aging. We collected high-resolution brain anatomical data from 56 young healthy adults (mean age = 30.8 +/- 8.1 years, 29 males). We performed whole brain parcellation into seven functional networks, including visual, somatomotor, dorsal attention, ventral attention, limbic, frontoparietal and default mode networks. We estimated intracranial volume (ICV) and averaged cortical thickness (CT), cortical surface area (CSA) and cortical volume (CV) over each hemisphere as well as for each network. Averaged cortical measures over each hemisphere, especially CT and CV, were significantly lower in older individuals compared to younger ones (one-way ANOVA, p < 0.05, corrected for multiple comparisons). There were negative correlations between age and averaged CT and CV over each hemisphere (p < 0.05, corrected for multiple comparisons) as well as between age and ICV (p = 0.05). Network level analysis showed that age was negatively correlated with CT for all functional networks (p < 0.05, corrected for multiple comparisons), apart from the limbic network. While age was unrelated to CSA, it was negatively correlated with CV across several functional networks (p < 0.05, corrected for multiple comparisons). We also showed positive associations between CV and CT and between CV and CSA for all networks (p < 0.05, corrected for multiple comparisons). We interpret the lack of association between age and CT of the limbic network as evidence that the limbic system may be particularly resistant to age-related declines during this period of life, whereas the significant age-related declines in averaged CT over each hemisphere as well as in all other six networks suggests that CT may serve as a reliable biomarker to capture the effect of normal aging. Due to the simultaneous dependence of CV on CT and CSA, CV was unable to identify such effects of normal aging consistently for the other six networks, but there were negative associations observed between age and averaged CV over each hemisphere as well as between age and ICV. Our findings suggest that the identification of early cortical changes within various functional networks during normal aging might be useful for predicting the effect of aging on the efficiency of functional performance even during early adulthood.

Additive manufacturing (AM) shows great promise for the manufacturing of next-generation engineering structures by enabling the production of engineered cellular structures, overhangs, and reducing waste. Melt-pool geometry prediction and control is critical for widespread implementation of laser powder bed processes due to speed and accuracy requirements. The process mapping approach used in previous work for different alloys and additive manufacturing processes is applied to the selective laser powder bed process for IN625 and 17-4 stainless steel alloys. The ability to predict the resulting steady state melt-pool geometry in terms of process parameters, specifically power and velocity, is explored in detail numerically and experimentally verified. A finite element model was created that simulates powder at the macro scale. This model correlates well with current experiments in showing that small amounts of powder relative to melt-pool depth have negligible effects on resulting geometry. Results indicate that the effect of powder may be negligible when comparing steady state widths of the no powder and one layer of powder cases. The work in this thesis investigates the effect of powder on the resulting steady-state melt-pool geometries for IN625 and 17-4 alloys. This analysis has been extended to the production of overhanging and cellular structures. The successful analysis will allow for better predictions and possible correction for cellular structure production issues as well as overhanging features.

Vertical-cavity surface-emitting lasers (VCSELs) are complex multi-layer structures whose operating characteristics are highly sensitive to variations in layer thickness and composition. They contain an active region of one or more quantum wells sandwiched between highly reflecting mirrors. Non-destructive optical characterisation techniques including reflectance spectroscopy, spectroscopic ellipsometry and photomodulated reflectance have been used to examine these structures and various components of them. In addition, the relatively novel technique of photomodulated spectroscopic ellipsometry has been examined in comparison with photomodulated reflectance in the characterisation of bulk, multi-layer and quantum well material. The distributed Bragg reflectors of VCSELs provide the high reflectance required over a selected wavelength range. Optical measurements were used to determine important information concerning layer thicknesses and compositions, which were confirmed with X-ray diffraction and transmission electron microscopy. The techniques were also used to provide important information concerning growth and uniformity, which could be readily applied for feedback to growers or for device fabrication. Novel reflectance and photomodulated reflectance measurements made on a range of laser structures designed to operate over a range of wavelengths from 650 nm to 1 ?m were used to examine the characteristics of the reflectors and the active region of the lasers. The cavity mode observed clearly indicates the lasing wavelength, and the interaction of the cavity and quantum well has been interpreted using new lineshapes. The cavity mode and quantum well resonance observed in photomodulated reflectance has been shown to provide a clear indication of where devices can be fabricated successfully from non-uniform material. The identification of the cavity and quantum well features has also enabled important information concerning the changes in structure and therefore in device performance with temperature and pressure. Measurements have also been able to provide important information to explain the variation in performance of some devices.

In a periglacial environment it is important to know the thickness, orientation and structureof sediments when assessing the landscape and its hydrological pathways. Using a groundpenetratingradar (GPR) I have profiled large areas of the subsurface in a catchment area to alake on western Greenland. Post-processing and calculations of the gathered data has revealedthat the sediment thickness is maximum 15 meters in the valleys. Due to the fact that nocorrelation data is available, such as boreholes or pits, this estimation has large error limits butthe profiles gathered reveals the structure in the subsurface to a great extent.

No description available.

Many systems for field-based, high-throughput phenotyping (FB-HTP) quantify and characterize the reflected radiation from the crop canopy to derive phenotypes, as well as infer plant function and health status. However, given the technology's nascent status, it remains unknown how biophysical and physiological properties of the plant canopy impact downstream interpretation and application of canopy reflectance data. In that light, we assessed relationships between leaf thickness and several canopy-associated traits, including normalized difference vegetation index (NDVI), which was collected via active reflectance sensors carried on a mobile FB-HTP system, carbon isotope discrimination (CID), and chlorophyll content. To investigate the relationships among traits, two distinct cotton populations, an upland (Gossypium hirsutum L.) recombinant inbred line (RIL) population of 95 lines and a Pima (G, barbaderise L.) population composed of 25 diverse cultivars, were evaluated under contrasting irrigation regimes, water-limited (WL) and well-watered pm conditions, across 3 years. We detected four quantitative trait loci (QTL) and significant variation in both populations for leaf thickness among genotypes as well as high estimates of broad-sense heritability (on average, above 0.7 for both populations), indicating a strong genetic basis for leaf thickness. Strong phenotypic correlations (maximum r = -0.73) were observed between leaf thickness and NDVI in the Pima population, but not the RIL population. Additionally, estimated genotypic correlations within the RIL population for leaf thickness with CID, chlorophyll content, and nitrogen discrimination (r(gij) = -0.32, 0.48, and 0.40, respectively) were all significant under WW but not WL conditions. Economically important fiber quality traits did not exhibit significant phenotypic or genotypic correlations with canopy traits. Overall, our results support considering variation in leaf thickness as a potential contributing factor to variation in NDVI or other canopy traits measured via proximal sensing, and as a trait that impacts fundamental physiological responses of plants.

Nowadays technology development places increasing demands on miniature and micro components and products, and micro-milling is one of the most flexible machining processes in manufacturing 3D structures and complex structured surfaces. A thorough and scientific understanding on fundamentals of the micro-milling process is essential for applying it in an industrial scale. Therefore, in-depth scientific understanding of the micro-cutting mechanics is critical, particularly on size effect, minimum chip thickness, chip formation, tool wear and cutting temperature, etc. so as to fulfil the gap between fundamentals and industrial scale applications. Therefore, three key fundamental research topics are determined for this research, and a comprehensive study on those topics is conducted by means of modeling, simulation, experiments. The topics include chip formation process in micro-milling, novel cutting force modeling in multiscale and study on the tool wear and process monitoring. The investigation into chip formation process in micro-milling consists of three stages; the micro-cutting process is firstly simulated by means of FEA with a primary focus on finding the minimum chip thickness for different tool/material pair and explaining the size effect; the simulation results are then validated by conducting micro-cutting experiment on the ultra-precision lathe. Experiments are carried out on aluminium 6082-T6 with both natural diamond and tungsten carbide tool. By knowing the minimum chip thickness for different tool/material pair, the chip formation process is investigated by performing comparative study by using the diamond and tungsten carbide micro-milling tools. As the minimum chip thickness for diamond micro-milling tool is smaller than that for tungsten carbide tool compared to nominal chip thickness, MCT is ignored in diamond micro-milling. Thus the comparative study is conducted by utilizing both tools with perfectly sharpened cutting edge and tools with the rounded cutting edge in micro-milling. The chips are inspected and associated with cutting force variations in the micro-milling process. The findings are further consolidated by comparing with research results by other researchers. The cutting force modeling is developed in three different aspects, e.g. cutting force on the unit length or area and cutting force on the unit volume in order to better understand the micro-cutting mechanics in aspects of size effect, tool wear mechanism and the cutting energy consumption. The mathematical modeling firstly starts with a novel instantaneous chip thickness algorithm, in which the instantaneous chip thickness is computed by taking account of the change of tool geometry brought about by the tool runout; then the collected cutting forces are utilized to calibrate the model coefficients. For accurate measurement on cutting forces, the Kalman Filter technique is employed to compensate the distortion of the measured cutting force. Model calibration is implemented using least-square method. The proposed cutting force model is then applied in micro-milling to represent the conditions of tool wear and the cutting energy consumption. Further study on the surface generation simulation is based on force model and its comparison with the machined surface is also performed. Cutting experiments using the new tungsten carbide tool are carried out and the tool wear is monitored offline at different machining stages. The dominant tool wear types are characterised. Tool wear is investigated by mainly analysing cutting force at different tool wear status. Frequency analysis by Fourier Transform and Wavelet Transform are carried out on the force signals, and features closely related to the tool wear status are identified and extracted. The potential of applying these features to monitoring the tool wear process is then discussed. Experimental studies to machine the structured surface and nano-metric level surface roughness are presented, the machining efficiency, dimensional accuracy and tool-path strategies are optimised so as to achieve the desired outcomes. Moreover, investigation on cutting temperature in micro-cutting is also studied to some extent by means of simulation; the influence of cutting edge radius on cutting temperature is particularly investigated. Investigation on above aspects provides systematic exploration into the micro-milling process and can contribute substantially to future micro-milling applications.

Introduction: Atherosclerosis remains asymptomatic until it progresses to cause flow-limiting disease. Identifying patients at high risk in the early stages of the atherosclerotic process may allow modification of cardiovascular risk by effective preventive strategies. Various non-invasive tests have been studied and have shown promising results in predicting future adverse cardiovascular events. The objective of this study was to establish the carotid ultrasonographic markers that best correlate with angiographic coronary artery disease (CAD) and the relationship between left ventricular geometry, carotid atherosclerosis, biomarkers and CAD in patients with unobstructed coronary arteries, chronic stable angina (CSA) and acute coronary syndromes (ACS). Methods: Carotid ultrasound examination, echocardiography and serum biomarker estimation were performed in consecutive patients who underwent coronary angiography for evaluation of stable or acute chest pain. Results: A total of 146 subjects were recruited into the study with a mean age of 56.9 ± 10.6 (range 29 to 85) years; 120 were men (82%) and 26 (18%) women. Twenty-one percent of the study population had unobstruced coronaries, 42% had stable CAD and 37% had presented with ACS. There was no significant difference in the carotid intima media thickness (CIMT) measurements between the three groups. CIMT correlated with abnormal left ventricular geometry but not with the presence or severity of CAD. The presence of carotid plaque and plaque score correlated with obstructive CAD, but was not significantly different between stable CAD and ACS patients. There was a trend towards more echogenic plaque in the stable CAD group. The composite score of IMT and plaque was positively correlated with the presence and severity of CAD. The averaged myocardial peak systolic and early diastolic velocities were significantly lower in those with obstructive CAD. CRP and osteopontin levels were higher in the ACS patients. Conclusions: Carotid plaque and not CIMT was associated with angiographic coronary artery disease. Averaged systolic and early diastolic myocardial velocities by tissue doppler imaging correlated with obstructive CAD. Novel serum biomarkers are promising and further studies are needed.

No description available.