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Zuin A.,University of Sao Paulo | Cousseau T.,Federal University of TechnologyParana | Sinatora A.,University of Sao Paulo | Sinatora A.,Instituto Tecnologico Vale | And 3 more authors.
Tribology International | Year: 2017

Lipophilic magnetite nanoparticles (MagNP; d≈10 nm) functionalized with stearic acid were synthetized and tested as additive in polyalphaolefin synthetic base oil (PAO8) in a model system. The thermal properties of the starting base oil and of the base oil mixed with nanoparticles were evaluated using TG/DTA under inert and oxidizing atmosphere. The frictional response of the lubricants was evaluated under a broad range of operating conditions at the boundary lubrication regime using a 10 mm AISI 52,100 bearing steel ball against the flat face of an AISI H13 steel disc. The results showed that: i) MagNP improved the thermal stability of the base oil; ii) reduced the friction values, mostly during load step transition; iii) reduced significantly the wear marks. © 2017 Elsevier Ltd


Pereira S.,University of Porto | Gomes T.N.,University of Porto | Borges A.,University of Porto | Santos D.,University of Porto | And 5 more authors.
International Journal of Environmental Research and Public Health | Year: 2015

Day-to-day variability and stability of children’s physical activity levels across days of the week are not well understood. Our aims were to examine the day-to-day variability of moderate-to-vigorous physical activity (MVPA), to determine factors influencing the day-to-day variability of MVPA and to estimate stability of MVPA in children. The sample comprises 686 Portuguese children (10 years of age). MVPA was assessed with an accelerometer, and BMI was computed from measured height and weight. Daily changes in MVPA and their correlates (gender, BMI, and maturity) were modeled with a multilevel approach, and tracking was calculated using Foulkes & Davies γ. A total of 51.3% of boys and 26.2% of girls achieved 60 min/day of MVPA on average. Daily MVPA was lower during the weekend (23.6% of boys and 13.6% of girls comply with the recommended 60 min/day of MVPA) compared to weekdays (60.8% and 35.4%, boys and girls, respectively). Normal weight children were more active than obese children and no effect was found for biological maturation. Tracking is low in both boys (γ = 0.59 ± 0.01) and girls (γ = 0.56 ± 0.01). Children’s MVPA levels during a week are highly unstable. In summary, boys are more active than girls, maturation does not affect their MVPA, and obese children are less likely to meet 60 min/day of MVPA. These results highlight the importance of providing opportunities for increasing children’s daily MVPA on all days of week, especially on the weekend. © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Pereira S.,University of Porto | Katzmarzyk P.T.,Louisiana State University | Gomes T.N.,University of Porto | Borges A.,University of Porto | And 8 more authors.
Nutrients | Year: 2015

Obesity in children is partly due to unhealthy lifestyle behaviours, e.g., sedentary activity and poor dietary choices. This trend has been seen globally. To determine the extent of these behaviours in a Portuguese population of children, 686 children 9.5 to 10.5 years of age were studied. Our aims were to: (1) describe profiles of children’s lifestyle behaviours; (2) identify behaviour pattern classes; and (3) estimate combined effects of individual/ socio-demographic characteristics in predicting class membership. Physical activity and sleep time were estimated by 24-h accelerometry. Nutritional habits, screen time and socio-demographics were obtained. Latent Class Analysis was used to determine unhealthy lifestyle behaviours. Logistic regression analysis predicted class membership. About 78% of children had three or more unhealthy lifestyle behaviours, while 0.2% presented no risk. Two classes were identified: Class 1-Sedentary, poorer diet quality; and Class 2-Insufficiently active, better diet quality, 35% and 65% of the population, respectively. More mature children (Odds Ratio (OR) = 6.75; 95%CI = 4.74–10.41), and boys (OR = 3.06; 95% CI = 1.98–4.72) were more likely to be overweight/obese. However, those belonging to Class 2 were less likely to be overweight/obese (OR = 0.60; 95% CI = 0.43–0.84). Maternal education level and household income did not significantly predict weight status (p ≥ 0.05). © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Gomes T.N.,University of Porto | Katzmarzyk P.T.,Louisiana State University | Dos Santos F.K.,Federal University of Pernambuco | De Chaves R.N.,Federal University of TechnologyParana | And 5 more authors.
Nutrients | Year: 2015

The purpose of this research was to investigate the relationship between body mass index (BMI) and sedentariness (Sed) in children and to examine the influence of child and school correlates on their variation. The sample comprises 580 children (337 girls, 9–11 years). Sedentariness was assessed with an accelerometer, and BMI was computed. Child- and school-level covariates were analyzed using multilevel models. No significant correlation between Sed and BMI was found. School context explains 5% and 1.5% of the total variance in Sed and BMI, respectively. At the child level, only moderate-to-vigorous physical activity was associated with both Sed (β = -0.02 ± 0.002) and BMI (β = -0.005 ± 0.002). Sleep time is related to Sed (β = -0.42 ± 0.04), while sex (β = 1.97 ± 0.13), biological maturity (β = 1.25 ± 0.07), media in the bedroom (β = 0.26 ± 0.08) and healthy (β = -0.09 ± 0.03) and unhealthy (β = -0.07 ± 0.04) diet scores were associated with BMI. None of the school-level covariates were related to BMI, but access to cafeteria (β = -0.97 ± 0.25), playground equipment (β = -0.67 ± 0.20) and restaurants (β = 0.16 ± 0.08) were related to Sed. In conclusion, Sed and BMI were not correlated. Further, they have different correlates, while children’s traits seem to play more relevant roles in their differences in Sed and BMI than the school milieu. This information should be taken into account when strategies to reduce Sed and BMI are implemented. © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Santos-Sanz P.,Institute Astrofisica Of Andalucia | French R.G.,Wellesley College | Pinilla-Alonso N.,University of Tennessee at Knoxville | Stansberry J.,US Space Telescope Science Institute | And 12 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2016

In this paper, we investigate the opportunities provided by the James Webb Space Telescope (JWST) for significant scientific advances in the study of Solar System bodies and rings using stellar occultations. The strengths and weaknesses of the stellar occultation technique are evaluated in light of JWST's unique capabilities. We identify several possible JWST occultation events by minor bodies and rings and evaluate their potential scientific value. These predictions depend critically on accurate a priori knowledge of the orbit of JWST near the Sun–Earth Lagrange point 2 (L2). We also explore the possibility of serendipitous stellar occultations by very small minor bodies as a byproduct of other JWST observing programs. Finally, to optimize the potential scientific return of stellar occultation observations, we identify several characteristics of JWST's orbit and instrumentation that should be taken into account during JWST's development. © 2016. The Astronomical Society of the Pacific. All rights reserved.


Oliveira E.A.S.,Federal Institute of Science Education TechnologyMA | Xavier A.A.P.,Federal University of TechnologyParana | Michaloski A.,Federal University of TechnologyParana
Occupational Safety and Hygiene III - Selected Extended and Revised Contributions from the International Symposium on Safety and Hygiene | Year: 2015

Environmental Ergonomics has been researching the effects of temperature on human performance for the purpose to understand how man reacts in different thermal environments. This paper presents the results of an observational study which evaluated the subjective productivity of office workers subjected to two different temperatures. The equipment Confortimetro Sensu, Hobo 03 and NASA TLX was used to measure the indoor environmental temperature upon subjective productivity through workload. After statistical analysis of the scores, the results showed that there is no statistically significant difference between the ambience; but at higher temperature the scores show greater variability. This sample suggests that the thermal conditions affect productivity of office workers, changing their performance. © 2015 Taylor & Francis Group, London.


Guarneri G.A.,Federal University of TechnologyParana | Pipa D.R.,Federal University of TechnologyParana | Neves F.,Federal University of TechnologyParana | de Arruda L.V.R.,Federal University of TechnologyParana | Zibetti M.V.W.,Federal University of TechnologyParana
Sensors (Switzerland) | Year: 2015

Ultrasound imaging systems (UIS) are essential tools in nondestructive testing (NDT). In general, the quality of images depends on two factors: system hardware features and image reconstruction algorithms. This paper presents a new image reconstruction algorithm for ultrasonic NDT. The algorithm reconstructs images from A-scan signals acquired by an ultrasonic imaging system with a monostatic transducer in pulse-echo configuration. It is based on regularized least squares using a l1 regularization norm. The method is tested to reconstruct an image of a point-like reflector, using both simulated and real data. The resolution of reconstructed image is compared with four traditional ultrasonic imaging reconstruction algorithms: B-scan, SAFT, ω-k SAFT and regularized least squares (RLS). The method demonstrates significant resolution improvement when compared with B-scan—about 91% using real data. The proposed scheme also outperforms traditional algorithms in terms of signal-to-noise ratio (SNR). © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Mafra S.B.,Federal University of TechnologyParana | Alves H.,Federal University of TechnologyParana | Alves H.,University of Oulu | Costa D.B.,Federal University of Ceará | And 2 more authors.
Eurasip Journal on Wireless Communications and Networking | Year: 2015

In this paper, a new full-duplex (FD) relaying scheme for a cooperative cognitive underlay network is proposed. The secondary network is composed of one secondary transmitter, one full-duplex secondary relay, and one secondary destination. The relay employs the selective-decode-and-forward (SDF) protocol. The secondary destination jointly decodes the signals from the secondary transmitter and the FD secondary relay so that the direct link can be seen as useful information rather than interference. The analysis includes the effect of the interference from the primary transmitter and the self-interference at the relay. Under equal power allocation strategy, closed-form expressions for the outage probability are derived for the proposed FD cooperative cognitive scheme, and the feasibility of FD relaying under cognitive constraints is shown. Our results also reveal that the proposed full-duplex joint-decoding (FDJD) cognitive network considerably outperforms the known full-duplex dual-hop (FDDH) scheme. Moreover, we propose an optimal power allocation (OPA) scheme. On the basis of the signal-to-interference-plus noise of the secondary network, the OPA strategy can choose between two modes of operation, cooperation between source and relay or source transmission only. Our results show that the FDJD scheme under the proposed OPA policy presents the best performance among all schemes investigated in this paper. © 2015, Mafra et al.; licensee Springer.

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