262 research outputs found
Adaptive quadruped locomotion: learning to detect and avoid an obstacle
Dissertação de mestrado em Engenharia de InformáticaAutonomy and adaptability are key features in the design and construction of a robotic
system capable of carrying out tasks in an unstructured and not predefined environment.
Such features are generally observed in animals, biological systems that usually serve as an
inspiration models to the design of robotic systems. The autonomy and adaptability of these
biological systems partially arises from their ability to learn. Animals learn to move and
control their own body when young, they learn to survive, to hunt and avoid undesirable
situations, from their progenitors.
There has been an increasing interest in defining a way to endow these abilities into
the design and creation of robotic systems. This dissertation proposes a mechanism that
seeks to create a learning module to a quadruped robot controller that enables it to both,
detect and avoid an obstacle in its path. The detection is based on a Forward Internal Model
(FIM) trained online to create expectations about the robot’s perceptive information. This
information is acquired by a set of range sensors that scan the ground in front of the robot in
order to detect the obstacle. In order to avoid stepping on the obstacle, the obstacle detections
are used to create a map of responses that will change the locomotion according to what is
necessary. The map is built and tuned every time the robot fails to step over the obstacle and
defines how the robot should act to avoid these situations in the future. Both learning tasks
are carried out online and kept active after the robot has learned, enabling the robot to adapt
to possible new situations.
The proposed architecture was inspired on [14, 17], but applied here to a quadruped robot
with different sensors and specific sensor configuration. Also, the mechanism is coupled
with the robot’s locomotion generator based in Central Pattern Generators (CPG)s presented
in [22]. In order to achieve its goal, the controller send commands to the CPG so that the
necessary changes in the locomotion are applied.
Results showed the success in both learning tasks. The robot was able to detect the
obstacle, and change its locomotion with the acquired information at collision time.Autonomia e capacidade de adaptação são características chave na criação de sistemas
robóticos capazes de levar a cabo diversas tarefas em ambientes não especificamente preparados
nem configurados para tal. Estas características são comuns nos animais, sistemas biológicos
que muitas vezes servem de modelo e inspiração para desenhar e construir sistemas
robóticos. A autonomia e adaptabilidade destes sistemas advém parcialmente da sua capacidade
de aprender. Quando ainda jovens, os animais aprendem a controlar o seu corpo e a
movimentar-se, muitos mamíferos aprendem a caçar e a sobreviver com os seus progenitores.
Ultimamente tem havido um crescente interesse em como aplicar estas características
no desenho e criação de sistemas robóticos. Nesta dissertação é proposto um mecanismo
que permita que um robô quadrúpede seja capaz de detectar e evitar um obstáculo no seu
caminho. A detecção é baseada num Forward Internal Model (FIM) que aprende a prever
os valores dos sensores de percepção do robô, os quais procuram detectar obstáculos no seu
caminho. Por forma a evitar os obstáculos, os sinais de detecção dos obstáculos são usados
na criação de um mapa que permitirá ao robô alterar a sua locomoção mediante o que é
necessário. Este mapa é construído à medida que o robô falha e tropeça no obstáculo. Nesse
momento, o mapa é definido para que tal situação seja evitada no futuro. Ambos os processos
de aprendizagem são levados a cabo em tempo de execução e mantêm esse processo activo
por forma a possibilitar a readaptação a eventuais novas situações.
Este mecanismo foi inspirado nos trabalhos [14, 17], mas aplicados aqui a um quadrúpede
com uma configuração de sensores diferente e específica. O mecanismo será interligado
ao gerador da locomoção, baseado em Control Pattern Generator (CPG) proposto em [22].
Por forma a atingir o objectivo final, o controlador irá enviar comandos para o CPG a fim da
locomoção ser alterada como necessário.
Os resultados obtidos mostram o sucesso em ambos os processos de aprendizagem. O
robô é capaz de detectar o obstáculo e alterar a sua locomção de acordo com a informação
adquirida nos momentos de colisão com o mesmo, conseguindo efectivamente passar por
cima do obstáculo sem nenhum tipo de colisão
Increasing Vegetable Diversity Consumption Impacts the Sympathetic Nervous System Activity in School-Aged Children
Evidence about the impact of vegetable and fruit diversity consumption on the autonomic nervous system (ANS) functioning is scarce. In this cross-sectional study (513 participants, 49.9% girls aged 7 to 12 years), we evaluated the association between vegetable and fruit diversity consumption and the ANS in school-aged children. Dietary intake was collected using a single 24-h recall questionnaire. Fruit and vegetable diversity consumption was estimated by summing up all the different individual vegetables and fruits consumed in one day. Pupillometry was used to assess pupillary light response, which evaluated the ANS activity. Adjusted linear regressions estimated the association between vegetable and fruit diversity consumption with pupillary light response measures. There was a positive and significant association between vegetable diversity consumption and the average dilation velocity, a measure related to the sympathetic nervous system activity (beta-coefficient = 0.03, 95%CI: 0.002; 0.07). Our findings show that vegetable diversity consumption is associated with the ANS response, a possible early link between diet and health in school-aged children
LIBERALIZAÇÃO FINANCEIRA E DESEMPENHO MACROECONÔMICO BRASILEIRO: EVIDÊNCIAS EMPÍRICAS A PARTIR DO MODELO VEC [FINANCIAL LIBERALIZATION AND BRAZILIAN MACROECONOMIC PERFORMANCE: SOME EMPIRICAL EVIDENCE BASED ON VEC MODEL]
RESUMO: Este artigo avalia a relação entre liberalização financeira externa – tanto abertura quanto integração financeira – e desempenho macroeconômico da economia brasileira a partir da estimação de um modelo baseado em vetores autorregressivos com correção de erros (VEC). Como contribuição potencialmente original, foi encontrada a precedência, no sentido de Granger, dos movimentos do ciclo financeiro global diante do grau de integração financeira da economia brasileira, e deste diante do risco-país. Quanto aos demais resultados, um aumento do grau de abertura da conta capital e financeira não gerou efeitos macroeconômicos significativos. Já uma elevação do grau de integração financeira teve desdobramentos problemáticos em variáveis como volatilidade cambial e nível de atividade.PALAVRAS-CHAVE: liberalização financeira; desempenho macroeconômico; Brasil=========================ABSTRACT: This paper discusses the relationship between external financial liberalization – both in terms of capital account liberalization and financial integration – and the macroeconomic performance of Brazil’s economy by estimating vector error correction model (VEC). As a potentially original contribution, it has been found a causal relation, in Grange sense, between the global financial movements and the degree of financial integration and between the latter and the country risk. Also, evidence has been found that an increased degree of capital account liberalization did not produce relevant macroeconomic effects. Additionally, results show that a high degree of financial integration had problematic repercussions in variables such as exchange rate volatility and activity level.KEYWORDS: financial liberalization; macroeconomic performance; Brazi
The Influence of Eating at Home on Dietary Diversity and Airway Inflammation in Portuguese School-Aged Children
Considering the negative impact of a lack of dietary diversity on children's nutritional status, we aimed to describe dietary variety according to eating at home frequency and assessed its association with respiratory outcomes in school-aged children. This cross-sectional study included 590 children (49% girls) aged 7 to 12 years from 20 public schools located in city of Porto, Portugal. Daily frequency of eating at home groups were calculated and dietary diversity was calculated using a 10-food group score from a 24 h recall questionnaire. Spirometry and exhaled nitric oxide levels (eNO; = 35 ppb) were assessed. The comparison of diet diversity according to the groups was performed by ANOVA and ANCOVA. The association between dietary diversity and respiratory outcomes was examined using regression models. In multivariate analysis, children in the highest group of eating at home episodes (>= 4 occasions) obtained the lowest dietary diversity mean score, while the lowest group (= 5 food groups) significantly decreased the odds of having an eNO >= 35. Diet diversity might decrease the chance of airway inflammation among children. However, having more eating episodes at home could be a barrier to a more diverse diet
Dietary Acid Load: A Novel Nutritional Target in Overweight/Obese Children with Asthma?
Obesity has been repeatedly linked to asthma, and several potential mechanisms have been proposed in the etiologies of the obese-asthma phenotype. Considering that lungs play an important role in systemic pH and acidbase regulation, are a key organ in asthma development, and that nutritional inadequacy of several nutrients and high dietary acid load can affect airway inflammation and reactivity, we aimed to test the hypothesis that dietary acid load may be associated with asthma in children. Data on 699 children (52% females), aged 712 years, were analyzed. Anthropometric measurements were performed to assess body mass index. Dietary acid load was calculated using potential renal acid load (PRAL) equations from a 24 h dietary recall administrated to children. Adjusted PRAL for total energy intake was applied with the use of the residual method. Lung function and airway reversibility were assessed with spirometry. Asthma was defined by a positive bronchodilation or self-reported medical diagnosis with reported symptoms (wheezing, dyspnea, or dry cough) in the past 12 months. After adjustment for energy intake, sex, age, parents education level, and physical activity, positive and significant associations were found between asthma and PRAL [odds ratio (OR) = 1.953, 95% CI = 1.024, 3.730) in overweight/obese children. Our findings suggest that dietary acid load might be a possible mechanism in overweight/obese-asthma phenotype development.</jats:p
Microwave-assisted solvothermal : an efficient and new method to obtain hydrophobic wood surfaces
The objective of this work was to form a hydrophobic surface in a highly porous wood by coating and incorporating TiO2 micro/nano structures through the microwave-assisted solvotermal method, without need any pre- or post-modification of the wood substrate, using low temperatures and short times. The behavior and morphology of the TiO2-treated surfaces was characterized using scanning electron microscopy (SEM), while the elemental composition was determined via energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. The results indicated that the crystallization of the TiO2 anatase phase was efficient and fully coated the wood surface during the solvothermal process. The treated wood contained TiO2 particles agglomerate with an average diameter of 200 nm that also allowed to coat an abundant fraction of tracheids cell walls. When investigated through X-ray spectroscopy-mapping, the element titanium appeared abundantly throughout the wood. After TiO2 growth in wood through the microwave-assisted solvotermal method, a roughness at the micro/ nano scales structures was created on the wood surface, originating an increase in the contact angle up to 137°, which characterizes the appearance of a hydrophobic surface. The TiO2-treated wood demonstrated 85% of water absorption after 400 h of immersion, while untreated wood reached 160%, suggesting that the microwave-assisted solvotermal process promotes a delay in the progression of water absorption. This feature can improve the dimensional stability of wood, contributing to the increase of its durability and applications
Formation Control Driven by Cooperative Object Tracking
In this paper we introduce a formation control loop that maximizes the performance of the cooperative perception of a tracked target by a team of mobile robots, while maintaining the team in formation, with a dynamically adjustable geometry which is a function of the quality of the target perception by the team. In the formation control loop, the controller module is a distributed non-linear model predictive controller and the estimator module fuses local estimates of the target state, obtained by a particle filter at each robot. The two modules and their integration are described in detail, including a real-time database associated to a wireless communication protocol that facilitates the exchange of state data while reducing collisions among team members. Simulation and real robot results for indoor and outdoor teams of different robots are presented. The results highlight how our method successfully enables a team of homogeneous robots to minimize the total uncertainty of the tracked target cooperative estimate while complying with performance criteria such as keeping a pre-set distance between the teammates and the target, avoiding collisions with teammates and/or surrounding obstacles
Growth Performance, Carcass and Meat Traits of Autochthonous Arouquesa Weaners Raised on Traditional and Improved Feeding Systems
Arouquesa is an autochthonous bovine breed known for its Arouquesa PDO beef labeling.
There are several production systems under the definition of PDO labeling. This study aimed to
compare the effect of different production systems on carcass and meat traits for the Arouquesa breed.
Two trials differing in diet and weaning age were conducted. The first trial included a TF group
fed the traditional way and weaned at 9 months; a TF + S1 group, equal to TF, but with a starter
supplement; and finally, a S1 + S2 group that was fed with a starter and a growth supplement and
weaned at 5 months. The second trial was composed of a TF + S3 group fed like the TF + S1 group
but reared until 12 months with a finishing supplement, and finally, the S3 group fed like the S1 + S2
group but reared until 12 months. In the first trial, the TF + S1 and S1 + S2 groups showed higher final
live weight and average daily gain. In the second trial, we observed differences in the subcutaneous
fat that was higher in the S3 group. Regarding meat traits, we observed differences in exudative
and cooking losses in the first trial. In general, supplementation improved meat production without
affecting meat quality parametersinfo:eu-repo/semantics/publishedVersio
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