Search

Background: Published data suggests that lockdowns during the COVID-19 pandemic may have negatively affected children's weight development. This study aims to assess the prevalence of overweight and obesity after the COVID-19 lockdowns as well as anthropometric development among primary school children in the Rhein-Neckar Region, Germany. Methods: In this cross-sectional study, schools were selected in cooperation with the local health authority to include different socioeconomic backgrounds. Participation was voluntary at school and individual level, requiring written informed consent from legal guardians. Study visits in schools were conducted between October 2021 and July 2022. Anthropometric data from nationally recommended medical examinations at 4 years (U8) and 5 years (U9), data on nutrition, physical activity, and socioeconomic data was collected using questionnaires. zBMI and weight category were calculated based on German reference data. Results: 256 children with a mean age of 8.0 years (7.1–9.3 years) were included in the study. Most participants were from households with an above average income. 5.1% of the children were overweight, 4.7% were obese, 15.6% were underweight, and 74.6% were normal weight with a mean zBMI of -0.25 (SD 1.10), which is significantly lower than the mean zBMI of the German reference population (p < 0.001). No significant changes in zBMI were observed between U8 and U9 (p = 0.16). The mean zBMI decreased by 0.17 (SD 0.72) between U9 and the study visit (p = 0.02). A zBMI decrease of 0.5 was documented for the subgroup of overweight and obese children (p = 0.028) as well as a decrease of 0.23 (SD 0.63) for the normal-weight children subgroup (p < 0.001). Conclusions: Contrary to previous reports mean zBMI decreased significantly in the children studied. No significant changes in zBMI were observed between U8 and U9 examinations, which supports the hypothesis that the decrease in zBMI could be attributed to lockdown measures. The study was registered at clinicaltrials.gov on September 21st 2021 under the registration number NCT05077059. [ABSTRACT FROM AUTHOR]

This article presents an accurate method to determine the mandatory rotor position to control a permanent magnet synchronous machine from misplaced Hall-effect switch sensors. The main feature of this technique is the estimated speed from two consecutive edge transitions in the same phase to dodge the inaccurate information. Besides, when a new electrical cycle starts, a gradual compensation algorithm corrects the initial speed estimation to cancel the electrical angle error in order to prevent current distortions. Furthermore, a first-order Taylor series approximation estimates the rotor position from the compensated speed calculation, reducing the possible torque ripple and noise due to an inaccurate control strategy. The proposed method has been compared with other state-of-the-art approaches through simulation and experimental results obtained from a low-voltage powertrain, showing more straightforward implementation and delivering the best balance performance during steady-state and transient operation. [ABSTRACT FROM AUTHOR]

This article presents an enhanced flux weakening (FW) control scheme for permanent magnet synchronous motors, focused on electric vehicle applications. The novelty of the proposed algorithm is the integration in a unified scheme of both the accelerator pedal as torque reference and the cruise speed limiter as speed limit, without interfering between them until this limit is achieved. The dq-axis current references are calculated from the proposed algorithm by using a polar coordinate system and a per-unit system. The latter is based on the characteristic machine parameters, which aim to ease and simplify the algorithm implementation. Moreover, it takes advantage of the smooth transition between the low back electromotive force zone and the FW zone thanks to a voltage loop, which changes the current-vector angle. Another fundamental merit of the proposed scheme is its capacity to work in all the dq plane throughout the maximum torque per ampere, constant torque, current and voltage limit, maximum torque per voltage, and constant speed strategies without switching the algorithm. Simulations and experimental results from a real exterior-rotor interior permanent magnet synchronous motor direct-drive e-motorbike verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper deals with multiterminal voltage source converter (VSC) HVDC transmission systems for the connection of offshore wind power plants to the main land ac grid. A droop-based control scheme is considered. The droop controllers have been designed base on a mixed sensitivity criterion by solving a convex optimization problem with linear matrix inequalities. The system is analyzed by means of simulations and experimentally in a scaled platform. Simulations show the control performance during a wind speed change and a voltage sag in the main ac grid. Experimental results include wind power changes (increase and decrease) and an eventual VSC loss (both considering grid-side and wind farm VSC loss). In all the cases, the simulation and the experimental results have shown a good system performance. [ABSTRACT FROM PUBLISHER]

In this paper, a high-accuracy all-digital resolverto-digital (R/D) converter is presented. The two basic components of a conventional tracking R/D converter, the phase detector and the loop filter, are software implemented by frequency-shifting techniques and a decoupled double synchronous reference frame-based phase-locked loop (DSRF-PLL). This PLL allows the simultaneous extraction of the angular position and speed of the rotatory resolver, even in the presence of gain and phase errors in the resolver. In order to increase accuracy and to minimize the time lag of the whole system, oversampling methods and downsampling finite-impulse response digital filters are introduced. Finally, DSP implementation issues, like the use of techniques to synchronize the resolver output signals with the excitation one, are discussed. Using these combined techniques and a standard DSP with a 12-bit analog-to-digital converter, resolutions of up to 14 bits can be achieved with a computation cost of about 13% of the total (100 MIPs). The paper presents the main techniques, simulation, and experimental results. [ABSTRACT FROM AUTHOR]