Controle de Formações Flexíveis de Robôs Móveis com Desvio de Obstáculos

Este trabalho apresenta um esquema de controle multicamadas para controlar formações de n>3 robôs móveis, incluindo uma estratégia de desvio de obstáculos. O controlador proposto é capaz de conduzir os robôs para compor formações desejadas (controle de posição) e/ou seguir uma trajetória desejada (controle de seguimento de trajetória). A estratégia de evasão de obstáculos é baseada em forças virtuais, que são geradas em função das distâncias robô-obstáculo, sendo consideradas para alterar as velocidades (linear e angular) individuais dos robôs componentes da formação. Tal estratégia é implementada em cada robô da formação, enquanto que o controlador proposto é aplicável a agrupamentos de três robôs, ou seja, a formações triangulares. Além disso, é apresentada uma prova de estabilidade para o sistema de controle em malha fechada, com base na teoria de Lyapunov, incluindo limitação da magnitude dos sinais de controle, para evitar saturação dos atuadores. Finalmente, resultados de simulação e experimentais são apresentados para distintas formações de robôs móveis tipo uniciclo, demonstrando que o esquema de controle proposto é efetivo não somente em termos de assegurar que os robôs alcancem e/ou mantenham uma formação desejada, mas também em termos de evitarem obstáculos enquanto navegam no espaço de trabalho

Positron emission tomography in the diagnostic work-up of screening-detected lung nodules

Low-dose computed tomography (CT) screening for lung cancer can reduce lung cancer mortality, but overdiagnosis, false positives and invasive procedures for benign nodules are worrying. We evaluated the utility of positron emission tomography (PET)-CT in characterising indeterminate screeningdetected lung nodules. 383 nodules, examined by PET-CT over the first 6 years of the COSMOS (Continuous Observation of Smoking Subjects) study to diagnose primary lung cancer, were reviewed and compared with pathological findings (surgically-treated patients) or follow-up (negative CT for â\u89¥2 years, considered negative); 196 nodules were malignant. The sensitivity, specificity and accuracy of PET-CT for differentially diagnosing malignant nodules were, respectively, 64%, 89% and 76% overall, and 82%, 92% and 88% for baseline-detected nodules. Performance was lower for nodules found at repeat annual scans, with sensitivity ranging from 22% for nonsolid to 79% for solid nodules (p=0.0001). Sensitivity (87%) and specificity (73%) were high for nodules â\u89¥15 mm, better (sensitivity 98%) for solid nodules â\u89¥15 mm. PET-CT was highly sensitive for the differential diagnosis of indeterminate nodules detected at baseline, nodules â\u89¥15 mm and solid nodules. Sensitivity was low for sub-solid nodules and nodules discovered after baseline for which other methods, e.g. volume doubling time, should be used

Desenvolvimento de mapas de avaliação do desempenho de sistemas fotovoltaicos em diferentes ângulos de inclinação e de azimute

O Brasil, devido as suas dimensóes continentais, apresenta condicóes muito distintas de radiacáo solar e clima, o que toma difícil modelar um sistema foto voltaico baseado em dados que nao sejam locáis. A instalagáo de sistemas foto voltaicos fixos em inclina^oes e orientagoes adequadas é fundamental para otimizar o desempenho energético do mesmo. Este trabalho apresenta e desenvolve mapas de avalia^áo do desempenho de sistemas fotovoltaicos em distintos ángulos de inclinaváo e de azimute considerando diferentes perfis de radiacáo solar. Os mapas de avaliagáo foram desenvolvidos a partir de resultados obtidos de simulagbes computacionais com o software System Advisor Model (SAM) desenvolvido pelo Laboratorio Nacional de Energias Renováveis (NREL) do Departamento de Energia (DOE) dos Estados Unidos. Os mapas desenvolvidos permitem avaliar o desempenho energético de um sistema fotovoltaico genérico em duas regioes com perfis distintos de radia^áo solar.Brazil has very different conditions of solar radiation, which makes it difficult to model a PV system based on data that are not local. The installation of photovoltaic systems with angles of inclination and azimuth appropriate is critical to optimizing the energy performance of the same. This paper presents and develops evaluation maps of performance of photovoltaic systems at different angles of inclination and azimuth considering different profiles of solar radiation. The evaluation maps were developed from the results of computational simulations with System Advisor Model (SAM) that was developed by the National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy (DOE). Developed maps allow assessing the energy performance of a generic PV system into two regions with distinct profiles of solar radiation.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Dynamical mass measurements of two protoplanetary discs

ALMA observations of line emission from planet forming discs have demonstrated to be an excellent tool to probe the internal disc kinematics, often revealing subtle effects related to important dynamical processes occurring in them, such as turbulence, or the presence of planets, that can be inferred from pressure bumps perturbing the gas motion, or from detection of the planetary wake. In particular, we have recently shown for the case of the massive disc in Elias 2-27 how one can use such kind of observations to measure deviations from Keplerianity induced by the disc self-gravity, thus constraining the total disc mass with good accuracy and independently on mass conversion factors between the tracer used and the total mass. Here, we refine our methodology and extend it to two additional sources, GM Aur and IM Lup, for which archival line observations are available for both the 12CO and the 13CO line. For IM Lup, we are able to obtain a consistent disc mass of Mdisc=0.1 Msun, implying a disc-star mass ratio of 0.1 (consistent with the observed spiral structure in the continuum emission) and a gas/dust ratio of ~ 65 (consistent with standard assumptions), with a systematic uncertainty by a factor ~2 due to the different methods to extract the rotation curve. For GM Aur, the two lines we use provide slightly inconsistent rotation curves, that cannot be attributed only to a difference in the height of the emitting layer, nor to a vertical temperature stratification. Our best fit disc mass measurement is Mdisc=0.26Msun, implying a disc-star mass ratio of ~0.35 and a gas/dust ratio of ~130... ABRIDGEDComment: 14 pages, 10 figures, MNRAS in pres

Long-term outcomes of a pilot CT screening for lung cancer

Background: Low-dose computed tomography (CT) screening can detect early stage lung cancer in high-risk populations. However, no data on repeated annual screening over more than 5 years are available, and the impact of screening on lung cancer mortality is controversial. Methods: We analysed outcomes in high-risk asymptomatic volunteers (smokers and former smokers, >50 years) enrolled in a pilot study over 1 year from June 2000, who received annual low-dose CT for 7 years. Cumulative lung cancer incidence and survival were represented by Kaplan 12Meier curves. Standardized incidence and mortality ratios were used to estimate risks relative to the general Italian and US population. Results: Compliance was 86% at the end of the seventh year in 1035 recruited volunteers (71% men, mean age 58 years). Lung cancer was diagnosed in 54 (5.3%); radical surgery was possible in 48/54 (87%); 39/54 (72%) had stage I disease. Five-year survival was 63% overall, 89% for stage I cases. During 6308 person-years of observation, 47 participants had died versus 75 expected in the Italian general population standardised for age and sex. Fourteen lung cancer deaths were registered versus 27 expected in a standardised US smoker population. Conclusions: Seventy percent of screening-diagnosed patients had stage I disease, and the survival of screen-detected cancer patients was high. Lung cancer mortality was favourable compared to age- and sex-matched population of US smokers, suggesting that mortality can be lowered by screening, although larger trials with longer follow-up are necessary to confirm these findings

Solitary fibrous tumours : unusual aspects of a rare disease

Background: In literature there are only a few descriptions of the typical presentation of solitary fibrous tumours (SFT) and only a few case reports showing its unusual clinical and radiological features. Methods: We retrospectively evaluated the computed tomography scans of 36 patients presenting with a histological diagnosis of SFT between 1998 and 2008. Results: We present five cases of SFT with an atypical clinical presentation and radiological features. Conclusions: SFT can occasionally present with unusual radiological features making a differential diagnosis difficult. Even thought imaging plays a fundamental role in the initial diagnostic approach, final diagnosis in only confirmed by biopsy and histology

Characteristics of Convective Sources of Gravity Waves and Sprites Present in Satellite IR Images During the SpreadFEx 2005 Campaign

We developed a technique to identify and estimate the size, intensity, and Tropopause overshoot of thunderstorm convective cores expected to be significant sources of gravity waves. The work was based on GOES IR images of South America on the night of 30 September to 1 October and 25–26 October 2005, as part of the Spread F Experiment (SpreadFEx) in Brazil in 2005. We also characterized, for the first time, the convective activity of three small TLE producing thunderstorms that yielded 11 TLEs on 25–26 October 2005. The campaign occurred during the dry to wet season transition in central Brazil, marked by the presence of extra-tropical cyclogenesis over the Atlantic Ocean, and cold fronts penetrating inland. The Tropopause temperature was typically −76°C with a corresponding altitude of ~15 200 m. Vigorous convective cores capable of generating strong gravity waves were located in convective regions having areas with cloud top temperatures ≤−76°C. They had typical cloud-top temperature deficits of ΔT−2.0°C to −8.0°C from the average surroundings, implying overshoot heights of 200 to 3100 m, which are within the typical range. Fast vertical development and high horizontal growth rates were associated with a large number of simultaneously active vigorous convective cores, indicating that their dynamics may have determined the spatial-temporal development of the thunderstorms analyzed. Moderate convective cores were also present in areas with cloud top −76°C≤T≤−70°C. They had ΔT of −1.9°C to −5.3°C producing overshoots between 80–300 m. All convective cores had typical diameters of 5–20 km and their size tended to increase with ΔT, there was a 57% correlation between the two parameters. Analysis of the relationship of cloud top T with positive and negative cloud-to-ground lightning (+/−CG) occurrence rate and with peak current showed that lighting activity may provide an independent way to identify convective cores and measure their intensity, since they were characterized by a high incidence of low peak current −CGs that forms the bulk of the −CG population

Low-dose CT for quantitative analysis in acute respiratory distress syndrome

Introduction: The clinical use of serial quantitative computed tomography (CT) to characterize lung disease and guide the optimization of mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) is limited by the risk of cumulative radiation exposure and by the difficulties and risks related to transferring patients to the CT room. We evaluated the effects of tube current-time product (mAs) variations on quantitative results in healthy lungs and in experimental ARDS in order to support the use of low-dose CT for quantitative analysis. Methods: In 14 sheep chest CT was performed at baseline and after the induction of ARDS via intravenous oleic acid injection. For each CT session, two consecutive scans were obtained applying two different mAs: 60 mAs was paired with 140, 15 or 7.5 mAs. All other CT parameters were kept unaltered (tube voltage 120 kVp, collimation 32x0.5 mm, pitch 0.85, matrix 512x512, pixel size 0.625x0.625 mm ). Quantitative results obtained at different mAs were compared via Bland-Altman analysis. Results: Good agreement was observed between 60 mAs and 140 mAs and between 60 mAs and 15 mAs (all biases less than 1%). A further reduction of mAs to 7.5 mAs caused an increase in the bias of poorly and non aerated tissue (-2.9 and 2.4%, respectively) and determined a significant widening of the limits of agreement for the same compartments (-10.5 - 4.8 % for poorly aerated and -5.9 - 10.8% for non aerated tissue). Estimated mean effective dose at 140, 60, 15 and 7.5 mAs corresponded to 17.8, 7.4, 2.0 and 0.9 millisievert, respectively. Image noise of scans performed at 140, 60, 15 and 7.5 mAs corresponded to 10, 16, 38 and 74 Hounsfield Units, respectively. Conclusions: A reduction of effective dose up to 70% has been achieved with minimal effects on lung quantitative results. Low-dose computed tomography provides accurate quantitative results and could be used to characterize lung compartment distribution and possibly monitor time-course of ARDS with a lower risk of exposure to ionizing radiation. A further radiation dose reduction is associated with lower accuracy in quantitative results