993 resultados para Continued Fraction Method


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As the world population continues to grow past seven billion people and global challenges continue to persist including resource availability, biodiversity loss, climate change and human well-being, a new science is required that can address the integrated nature of these challenges and the multiple scales on which they are manifest. Sustainability science has emerged to fill this role. In the fifteen years since it was first called for in the pages of Science, it has rapidly matured, however its place in the history of science and the way it is practiced today must be continually evaluated. In Part I, two chapters address this theoretical and practical grounding. Part II transitions to the applied practice of sustainability science in addressing the urban heat island (UHI) challenge wherein the climate of urban areas are warmer than their surrounding rural environs. The UHI has become increasingly important within the study of earth sciences given the increased focus on climate change and as the balance of humans now live in urban areas.

In Chapter 2 a novel contribution to the historical context of sustainability is argued. Sustainability as a concept characterizing the relationship between humans and nature emerged in the mid to late 20th century as a response to findings used to also characterize the Anthropocene. Emerging from the human-nature relationships that came before it, evidence is provided that suggests Sustainability was enabled by technology and a reorientation of world-view and is unique in its global boundary, systematic approach and ambition for both well being and the continued availability of resources and Earth system function. Sustainability is further an ambition that has wide appeal, making it one of the first normative concepts of the Anthropocene.

Despite its widespread emergence and adoption, sustainability science continues to suffer from definitional ambiguity within the academe. In Chapter 3, a review of efforts to provide direction and structure to the science reveals a continuum of approaches anchored at either end by differing visions of how the science interfaces with practice (solutions). At one end, basic science of societally defined problems informs decisions about possible solutions and their application. At the other end, applied research directly affects the options available to decision makers. While clear from the literature, survey data further suggests that the dichotomy does not appear to be as apparent in the minds of practitioners.

In Chapter 4, the UHI is first addressed at the synoptic, mesoscale. Urban climate is the most immediate manifestation of the warming global climate for the majority of people on earth. Nearly half of those people live in small to medium sized cities, an understudied scale in urban climate research. Widespread characterization would be useful to decision makers in planning and design. Using a multi-method approach, the mesoscale UHI in the study region is characterized and the secular trend over the last sixty years evaluated. Under isolated ideal conditions the findings indicate a UHI of 5.3 ± 0.97 °C to be present in the study area, the magnitude of which is growing over time.

Although urban heat islands (UHI) are well studied, there remain no panaceas for local scale mitigation and adaptation methods, therefore continued attention to characterization of the phenomenon in urban centers of different scales around the globe is required. In Chapter 5, a local scale analysis of the canopy layer and surface UHI in a medium sized city in North Carolina, USA is conducted using multiple methods including stationary urban sensors, mobile transects and remote sensing. Focusing on the ideal conditions for UHI development during an anticyclonic summer heat event, the study observes a range of UHI intensity depending on the method of observation: 8.7 °C from the stationary urban sensors; 6.9 °C from mobile transects; and, 2.2 °C from remote sensing. Additional attention is paid to the diurnal dynamics of the UHI and its correlation with vegetation indices, dewpoint and albedo. Evapotranspiration is shown to drive dynamics in the study region.

Finally, recognizing that a bridge must be established between the physical science community studying the Urban Heat Island (UHI) effect, and the planning community and decision makers implementing urban form and development policies, Chapter 6 evaluates multiple urban form characterization methods. Methods evaluated include local climate zones (LCZ), national land cover database (NCLD) classes and urban cluster analysis (UCA) to determine their utility in describing the distribution of the UHI based on three standard observation types 1) fixed urban temperature sensors, 2) mobile transects and, 3) remote sensing. Bivariate, regression and ANOVA tests are used to conduct the analyses. Findings indicate that the NLCD classes are best correlated to the UHI intensity and distribution in the study area. Further, while the UCA method is not useful directly, the variables included in the method are predictive based on regression analysis so the potential for better model design exists. Land cover variables including albedo, impervious surface fraction and pervious surface fraction are found to dominate the distribution of the UHI in the study area regardless of observation method.

Chapter 7 provides a summary of findings, and offers a brief analysis of their implications for both the scientific discourse generally, and the study area specifically. In general, the work undertaken does not achieve the full ambition of sustainability science, additional work is required to translate findings to practice and more fully evaluate adoption. The implications for planning and development in the local region are addressed in the context of a major light-rail infrastructure project including several systems level considerations like human health and development. Finally, several avenues for future work are outlined. Within the theoretical development of sustainability science, these pathways include more robust evaluations of the theoretical and actual practice. Within the UHI context, these include development of an integrated urban form characterization model, application of study methodology in other geographic areas and at different scales, and use of novel experimental methods including distributed sensor networks and citizen science.

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Soviet sedimentologists use the term "coarse silt" to denote the size fraction 0.1 to 0.05 mm (50-100 µm). Petelin (1961) has shown that this fraction is most diagnostic for terrigeneous and volcanogenic mineral assemblages and provinces in Recent deep-sea sediments, because of its greatest variability of both heavy and light non-opaque minerals, which may be easily identified by the common immersion method. We believe that the fraction is suitable for mineralogical study of unconsolidated and friable sediments from DSDP cores as well, if the objective is to investigate their source area and transporation tracks. In the case of fine-grained oceanic sediments, mineral composition of the coarse silt does not differ markedly from that of the "coarse fraction" (>62 µm).

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The late Neogene was a time of cryosphere development in the northern hemisphere. The present study was carried out to estimate the sea surface temperature (SST) change during this period based on the quantitative planktonic foraminiferal data of 8 DSDP sites in the western Pacific. Target factor analysis has been applied to the conventional transfer function approach to overcome the no-analog conditions caused by evolutionary faunal changes. By applying this technique through a combination of time-slice and time-series studies, the SST history of the last 5.3 Ma has been reconstructed for the low latitude western Pacific. Although the present data set is close to the statistical limits of factor analysis, the clear presence of sensible variations in individual SST time-series suggests the feasibility and reliability of this method in paleoceanographic studies. The estimated SST curves display the general trend of the temperature fluctuations and reveal three major cool periods in the late Neogene, i.e. the early Pliocene (4.7 3.5 Ma), the late Pliocene (3.1-2.7 Ma), and the latest Pliocene to early Pleistocene (2.2-1.0 Ma). Cool events are reflected in the increase of seasonality and meridional SST gradient in the subtropical area. The latest Pliocene to early Pleistocene cooling is most important in the late Neogene climatic evolution. It differs from the previous cool events in its irreversible, steplike change in SST, which established the glacial climate characteristic of the late Pleistocene. The winter and summer SST decreased by 3.3-5.4°C and 1.0 2.1C in the subtropics, by 0.9°C and 0.6C in the equatorial region, and showed little or no cooling in the tropics. Moreover, this cooling event occurred as a gradual SST decrease during 2.2 1.0 Ma at the warmer subtropical sites, while that at cooler subtropical site was an abrupt SST drop at 2.2 Ma. In contrast, equatorial and tropical western Pacific experienced only minor SST change in the entire late Neogene. In general, subtropics was much more sensitive to climatic forcing than tropics and the cooling events were most extensive in the cooler subtropics. The early Pliocene cool periods can be correlated to the Antarctic ice volume fluctuation, and the latest Pliocene early Pleistocene cooling reflects the climatic evolution during the cryosphere development of the northern hemisphere.

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This study investigates topology optimization of energy absorbing structures in which material damage is accounted for in the optimization process. The optimization objective is to design the lightest structures that are able to absorb the required mechanical energy. A structural continuity constraint check is introduced that is able to detect when no feasible load path remains in the finite element model, usually as a result of large scale fracture. This assures that designs do not fail when loaded under the conditions prescribed in the design requirements. This continuity constraint check is automated and requires no intervention from the analyst once the optimization process is initiated. Consequently, the optimization algorithm proceeds towards evolving an energy absorbing structure with the minimum structural mass that is not susceptible to global structural failure. A method is also introduced to determine when the optimization process should halt. The method identifies when the optimization method has plateaued and is no longer likely to provide improved designs if continued for further iterations. This provides the designer with a rational method to determine the necessary time to run the optimization and avoid wasting computational resources on unnecessary iterations. A case study is presented to demonstrate the use of this method.

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A novel surrogate model is proposed in lieu of Computational Fluid Dynamics (CFD) solvers, for fast nonlinear aerodynamic and aeroelastic modeling. A nonlinear function is identified on selected interpolation points by
a discrete empirical interpolation method (DEIM). The flow field is then reconstructed using a least square approximation of the flow modes extracted
by proper orthogonal decomposition (POD). The aeroelastic reduce order
model (ROM) is completed by introducing a nonlinear mapping function
between displacements and the DEIM points. The proposed model is investigated to predict the aerodynamic forces due to forced motions using
a N ACA 0012 airfoil undergoing a prescribed pitching oscillation. To investigate aeroelastic problems at transonic conditions, a pitch/plunge airfoil
and a cropped delta wing aeroelastic models are built using linear structural models. The presence of shock-waves triggers the appearance of limit
cycle oscillations (LCO), which the model is able to predict. For all cases
tested, the new ROM shows the ability to replicate the nonlinear aerodynamic forces, structural displacements and reconstruct the complete flow
field with sufficient accuracy at a fraction of the cost of full order CFD
model.

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A novel surrogate model is proposed in lieu of computational fluid dynamic (CFD) code for fast nonlinear aerodynamic modeling. First, a nonlinear function is identified on selected interpolation points defined by discrete empirical interpolation method (DEIM). The flow field is then reconstructed by a least square approximation of flow modes extracted by proper orthogonal decomposition (POD). The proposed model is applied in the prediction of limit cycle oscillation for a plunge/pitch airfoil and a delta wing with linear structural model, results are validate against a time accurate CFD-FEM code. The results show the model is able to replicate the aerodynamic forces and flow fields with sufficient accuracy while requiring a fraction of CFD cost.

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Multiphase flows, type oil–water-gas are very common among different industrial activities, such as chemical industries and petroleum extraction, and its measurements show some difficulties to be taken. Precisely determining the volume fraction of each one of the elements that composes a multiphase flow is very important in chemical plants and petroleum industries. This work presents a methodology able to determine volume fraction on Annular and Stratified multiphase flow system with the use of neutrons and artificial intelligence, using the principles of transmission/scattering of fast neutrons from a 241Am-Be source and measurements of point flow that are influenced by variations of volume fractions. The proposed geometries used on the mathematical model was used to obtain a data set where the thicknesses referred of each material had been changed in order to obtain volume fraction of each phase providing 119 compositions that were used in the simulation with MCNP-X –computer code based on Monte Carlo Method that simulates the radiation transport. An artificial neural network (ANN) was trained with data obtained using the MCNP-X, and used to correlate such measurements with the respective real fractions. The ANN was able to correlate the data obtained on the simulation with MCNP-X with the volume fractions of the multiphase flows (oil-water-gas), both in the pattern of annular flow as stratified, resulting in a average relative error (%) for each production set of: annular (air= 3.85; water = 4.31; oil=1.08); stratified (air=3.10, water 2.01, oil = 1.45). The method demonstrated good efficiency in the determination of each material that composes the phases, thus demonstrating the feasibility of the technique.

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Surface flow types (SFT) are advocated as ecologically relevant hydraulic units, often mapped visually from the bankside to characterise rapidly the physical habitat of rivers. SFT mapping is simple, non-invasive and cost-efficient. However, it is also qualitative, subjective and plagued by difficulties in recording accurately the spatial extent of SFT units. Quantitative validation of the underlying physical habitat parameters is often lacking, and does not consistently differentiate between SFTs. Here, we investigate explicitly the accuracy, reliability and statistical separability of traditionally mapped SFTs as indicators of physical habitat, using independent, hydraulic and topographic data collected during three surveys of a c. 50m reach of the River Arrow, Warwickshire, England. We also explore the potential of a novel remote sensing approach, comprising a small unmanned aerial system (sUAS) and Structure-from-Motion photogrammetry (SfM), as an alternative method of physical habitat characterisation. Our key findings indicate that SFT mapping accuracy is highly variable, with overall mapping accuracy not exceeding 74%. Results from analysis of similarity (ANOSIM) tests found that strong differences did not exist between all SFT pairs. This leads us to question the suitability of SFTs for characterising physical habitat for river science and management applications. In contrast, the sUAS-SfM approach provided high resolution, spatially continuous, spatially explicit, quantitative measurements of water depth and point cloud roughness at the microscale (spatial scales ≤1m). Such data are acquired rapidly, inexpensively, and provide new opportunities for examining the heterogeneity of physical habitat over a range of spatial and temporal scales. Whilst continued refinement of the sUAS-SfM approach is required, we propose that this method offers an opportunity to move away from broad, mesoscale classifications of physical habitat (spatial scales 10-100m), and towards continuous, quantitative measurements of the continuum of hydraulic and geomorphic conditions which actually exists at the microscale.

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La fraction d’éjection du ventricule gauche est un excellent marqueur de la fonction cardiaque. Plusieurs techniques invasives ou non sont utilisées pour son calcul : l’angiographie, l’échocardiographie, la résonnance magnétique nucléaire cardiaque, le scanner cardiaque, la ventriculographie radioisotopique et l’étude de perfusion myocardique en médecine nucléaire. Plus de 40 ans de publications scientifiques encensent la ventriculographie radioisotopique pour sa rapidité d’exécution, sa disponibilité, son faible coût et sa reproductibilité intra-observateur et inter-observateur. La fraction d’éjection du ventricule gauche a été calculée chez 47 patients à deux reprises, par deux technologues, sur deux acquisitions distinctes selon trois méthodes : manuelle, automatique et semi-automatique. Les méthodes automatique et semi-automatique montrent dans l’ensemble une meilleure reproductibilité, une plus petite erreur standard de mesure et une plus petite différence minimale détectable. La méthode manuelle quant à elle fournit un résultat systématiquement et significativement inférieur aux deux autres méthodes. C’est la seule technique qui a montré une différence significative lors de l’analyse intra-observateur. Son erreur standard de mesure est de 40 à 50 % plus importante qu’avec les autres techniques, tout comme l’est sa différence minimale détectable. Bien que les trois méthodes soient d’excellentes techniques reproductibles pour l’évaluation de la fraction d’éjection du ventricule gauche, les estimations de la fiabilité des méthodes automatique et semi-automatique sont supérieures à celles de la méthode manuelle.

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La fraction d’éjection du ventricule gauche est un excellent marqueur de la fonction cardiaque. Plusieurs techniques invasives ou non sont utilisées pour son calcul : l’angiographie, l’échocardiographie, la résonnance magnétique nucléaire cardiaque, le scanner cardiaque, la ventriculographie radioisotopique et l’étude de perfusion myocardique en médecine nucléaire. Plus de 40 ans de publications scientifiques encensent la ventriculographie radioisotopique pour sa rapidité d’exécution, sa disponibilité, son faible coût et sa reproductibilité intra-observateur et inter-observateur. La fraction d’éjection du ventricule gauche a été calculée chez 47 patients à deux reprises, par deux technologues, sur deux acquisitions distinctes selon trois méthodes : manuelle, automatique et semi-automatique. Les méthodes automatique et semi-automatique montrent dans l’ensemble une meilleure reproductibilité, une plus petite erreur standard de mesure et une plus petite différence minimale détectable. La méthode manuelle quant à elle fournit un résultat systématiquement et significativement inférieur aux deux autres méthodes. C’est la seule technique qui a montré une différence significative lors de l’analyse intra-observateur. Son erreur standard de mesure est de 40 à 50 % plus importante qu’avec les autres techniques, tout comme l’est sa différence minimale détectable. Bien que les trois méthodes soient d’excellentes techniques reproductibles pour l’évaluation de la fraction d’éjection du ventricule gauche, les estimations de la fiabilité des méthodes automatique et semi-automatique sont supérieures à celles de la méthode manuelle.

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The success of childhood weight management programmes relies on family engagement. While attendance offers many benefits including the support to make positive lifestyle changes, the majority of families referred to treatment decline. Moreover, for those who do attend, benefits are often compromised by high programme attrition. This systematic review investigated factors influencing attendance at community-based lifestyle programmes among families of over-weight or obese children. A narrative synthesis approach was used to allow for the inclusion of quantitative, qualitative and mixed-method study designs. Thirteen studies met the inclusion criteria. Results suggest that parents provided the impetus for programme initiation, and this was driven largely by a concern for their child's psychological health and wellbeing. More often than not, children went along without any real reason or interest in attending. Over the course of the programme, however, children's positive social experiences such as having fun and making friends fostered the desire to continue. The stigma surrounding excess weight and the denial of the issue amongst some parents presented barriers to enrolment and warrant further study. This study provides practical recommendations to guide future policy makers, programme delivery teams and researchers in developing strategies to boost recruitment and minimise attrition.

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The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

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Long-acting reversible contraceptives (LARCs) include the copper-releasing intrauterine device (IUD), the levonorgestrel-releasing intrauterine system (LNG-IUS) and implants. Despite the high contraceptive efficacy of LARCs, their prevalence of use remains low in many countries. The objective of this study was to assess the main reasons for switching from contraceptive methods requiring daily or monthly compliance to LARC methods within a Brazilian cohort. Women of 18-50 years of age using different contraceptives and wishing to switch to a LARC method answered a questionnaire regarding their motivations for switching from their current contraceptive. Continuation rates were evaluated 1 year after method initiation. Sample size was calculated at 1040 women. Clinical performance was evaluated by life table analysis. The cutoff date for analysis was May 23, 2013. Overall, 1167 women were interviewed; however, after 1 year of use, the medical records of only 1154 women were available for review. The main personal reason for switching, as reported by the women, was fear of becoming pregnant while the main medical reasons were nausea and vomiting and unscheduled bleeding. No pregnancies occurred during LARC use, and the main reasons for discontinuation were expulsion (in the case of the IUD and LNG-IUS) and a decision to undergo surgical sterilization (in the case of the etonogestrel-releasing implant). Continuation rate was ~95.0/100 women/year for the three methods. Most women chose a LARC method for its safety and for practical reasons, and after 1 year of use, most women continued with the method.

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The present work compared the local injection of mononuclear cells to the spinal cord lateral funiculus with the alternative approach of local delivery with fibrin sealant after ventral root avulsion (VRA) and reimplantation. For that, female adult Lewis rats were divided into the following groups: avulsion only, reimplantation with fibrin sealant; root repair with fibrin sealant associated with mononuclear cells; and repair with fibrin sealant and injected mononuclear cells. Cell therapy resulted in greater survival of spinal motoneurons up to four weeks post-surgery, especially when mononuclear cells were added to the fibrin glue. Injection of mononuclear cells to the lateral funiculus yield similar results to the reimplantation alone. Additionally, mononuclear cells added to the fibrin glue increased neurotrophic factor gene transcript levels in the spinal cord ventral horn. Regarding the motor recovery, evaluated by the functional peroneal index, as well as the paw print pressure, cell treated rats performed equally well as compared to reimplanted only animals, and significantly better than the avulsion only subjects. The results herein demonstrate that mononuclear cells therapy is neuroprotective by increasing levels of brain derived neurotrophic factor (BDNF) and glial derived neurotrophic factor (GDNF). Moreover, the use of fibrin sealant mononuclear cells delivery approach gave the best and more long lasting results.

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Syngonanthus macrolepis, popularly known in Brazil as 'sempre-vivas', is a plant from the family Eriocaulaceae, it is found in the states of Minas Gerais and Bahia. The species contains a variety of constituents, including flavonoids with gastroprotective effect. In this work, a flavonoid-rich fraction (Sm-FRF) obtained from scapes of S. macrolepis was investigated for preventing gastric ulceration in mice and rats. The activity was evaluated in models of induced gastric ulcer (absolute ethanol, stress, non-steroidal anti-inflammatory drugs and pylorus ligation). The cytoprotective mechanisms of the Sm-FRF in relation to sulfhydryl (SH) groups, nitric oxide (NO) and antioxidant enzymes were also evaluated. The Sm-FRF (100 mg/kg, p.o.) significantly reduced gastric injury in all models, and did not alter gastric juice parameters after pylorus ligation. The results indicate significant gastroprotective activity for the Sm-FRF, which probably involves the participation of both SH groups and the antioxidant system. Both are integral parts of the gastrointestinal mucosa's cytoprotective mechanisms against aggressive factors.