Urban–rural disparity in blood pressure among Chinese children: 1985–2010

Background: Understanding the urban-rural gap in childhood blood pressure (BP) is crucial to alleviate the urban-rural disparity in burden of hypertension in the future. This study investigated trends in urban-rural BP disparity and the influence of body mass index among Chinese children between 1985 and 2010. Methods: Data included 1 010 153 children aged 8-17 years enrolled in the Chinese National Survey on Students' Constitution and Health, a successive national cross-sectional survey. High BP was defined according to age-sex- and height-specific 95th percentile. Multi-variable linear and logistic regression models were used to assess the urban-rural BP differentials. Results: Although urban children had greater prevalence of overweight and obesity than rural counterparts, rural children revealed higher levels of BP across the consecutive 25-year periods. The urban-rural disparity in prevalence of high systolic BP decreased from 2.3 (95% confidence interval: 2.3, 2.6) % to 0.2 (-0.1, 0.4) % in boys and 3.7 (3.5, 4.0) % to 0.6 (0.3, 0.8) % in girls between 1985 and 2010 after adjusting for confounding factors. Further adjustment of body mass index did not change the urban-rural disparity and its trend. The similar results were also observed for diastolic BP. Conclusions: Despite the urban-rural disparity in BP decreased between 1985 and 2010, rural children constantly showed higher BP levels than their urban counterparts. Since these differentials in BP cannot be explained by obesity, study of other potential factors could provide further opportunity to bridge this gap

On Control System Design for the Conventional Mode of Operation of Vibrational Gyroscopes

This paper presents a novel control circuitry design for both vibrating axes (drive and sense) of vibrational gyroscopes, and a new sensing method for time-varying rotation rates. The control design is motivated to address the challenges posed by manufacturing imperfection and environment vibrations that are particularly pronounced in microelectromechanical systems (MEMS) gyroscopes. The method of choice is active disturbance rejection control that, unlike most existing control design methods, does not depend on an accurate model of the plant. The task of control design is simplified when the internal dynamics, such as mechanical cross coupling between the drive and sense axes, and external vibrating forces are estimated and cancelled in real time. In both simulation and hardware tests on a vibrational piezoelectric beam gyroscope, the proposed controller proves to be robust against structural uncertainties; it also facilitates accurate sensing of time-varying rotation rates. The results demonstrate a simple, economic, control solution for compensating the manufacturing imperfections and improving sensing performance of the MEMS gyroscopes

A Robust Decentralized Load Frequency Controller for Interconnected Power Systems

A novel design of a robust decentralized load frequency control (LFC) algorithm is proposed for an inter-connected three-area power system, for the purpose of regulating area control error (ACE) in the presence of system uncertainties and external disturbances. The design is based on the concept of active disturbance rejection control (ADRC). Estimating and mitigating the total effect of various uncertainties in real time, ADRC is particularly effective against a wide range of parameter variations, model uncertainties, and large disturbances. Furthermore, with only two tuning parameters, the controller provides a simple and easy-to-use solution to complex engineering problems in practice. Here, an ADRC-based LFC solution is developed for systems with turbines of various types, such as non-reheat, reheat, and hydraulic. The simulation results verified the effectiveness of the ADRC, in comparison with an existing PI-type controller tuned via genetic algorithm linear matrix inequalities (GALMIs). The comparison results show the superiority of the proposed solution. Moreover, the stability and robustness of the closed-loop system is studied using frequency-domain analysis

On Control System Design for the Conventional Mode of Operation of Vibrational Gyroscopes

This paper presents a novel control circuitry design for both vibrating axes (drive and sense) of vibrational gyroscopes, and a new sensing method for time-varying rotation rates. The control design is motivated to address the challenges posed by manufacturing imperfection and environment vibrations that are particularly pronounced in microelectromechanical systems (MEMS) gyroscopes. The method of choice is active disturbance rejection control that, unlike most existing control design methods, does not depend on an accurate model of the plant. The task of control design is simplified when the internal dynamics, such as mechanical cross coupling between the drive and sense axes, and external vibrating forces are estimated and cancelled in real time. In both simulation and hardware tests on a vibrational piezoelectric beam gyroscope, the proposed controller proves to be robust against structural uncertainties; it also facilitates accurate sensing of time-varying rotation rates. The results demonstrate a simple, economic, control solution for compensating the manufacturing imperfections and improving sensing performance of the MEMS gyroscopes

Numerical study of vapor bubble effect on flow and heat transfer in microchannel

Flow boiling in a microchannel is characterized by nucleation and dynamic behavior of vapor bubbles in the channel. In the present study, the effect of vapor bubble on fluid flow and heat transfer in a microchannel is investigated via lattice Boltzmann (LB) modeling. With respect to boiling flow in a single microchannel, the bubble nucleation, growth, and departure are simulated by using an improved hybrid LB model. Relating bubble behavior with fluid flow and boiling heat transfer provides some insight into the relevant fundamental physics on flow boiling in the microchannel. It is found that the bubble growth before its departure from the wall induces an obvious resistance to the fluid flow. The processes of nucleation and motion of different bubbles interact, leading to an alternate, either enhanced or weakened, effect of bubble behavior on the flow boiling. (C) 2011 Elsevier Masson SAS. All rights reserved.</p

Active Disturbance Rejection Control for MEMS Gyroscopes

A new control method is presented to drive the drive axis of a Micro-Electro-Mechanical Systems (MEMS) gyroscope to resonance and to regulate the output amplitude of the axis to a fixed level. It is based on a unique active disturbance rejection control (ADRC) strategy, which actively estimates and compensates for internal dynamic changes of the drive axis and external disturbances in real time. The stability analysis shows that both the estimation error and the tracking error of the drive axis output are bounded and that the upper bounds of the errors monotonously decrease with the increase of the controller bandwidth. The control system is simulated and tested using a field-programmable-gate-array-based digital implementation on a piezoelectric vibrational gyroscope. Both simulation and experimental results demonstrate that the proposed controller not only drives the drive axis to vibrate along the desired trajectory but also compensates for manufacture imperfections in a robust fashion that makes the performance of the gyroscope insensitive to parameter variations and noises. Such robustness, the fact that the control design does not require an accurate plant model, and the ease of implementation make the proposed solution practical and economic for industrial applications

Inverse Problem Solution and Regularization Parameter Selection for Current Distribution Reconstruction in Switching Arcs by Inverting Magnetic Fields

Current density distribution in electric arcs inside low voltage circuit breakers is a crucial parameter for us to understand the complex physical behavior during the arcing process. In this paper, we investigate the inverse problem of reconstructing the current density distribution in arcs by inverting the magnetic fields. A simplified 2D arc chamber is considered. The aim of this paper is the computational side of the regularization method, regularization parameter selection strategies, and the estimation of systematic error. To address the ill-posedness of the inverse problem, Tikhonov regularization is analyzed, with the regularization parameter chosen by Morozov’s discrepancy principle, the L-curve, the generalized cross-validation, and the quasi-optimality criteria. The provided range of regularization parameter selection strategies is much wider than in the previous works. Effects of several features on the performance of these criteria have been investigated, including the signal-to-noise ratio, dimension of measurement space, and the measurement distance. The numerical simulations show that the generalized cross-validation and quasi-optimality criteria provide a more satisfactory performance on the robustness and accuracy. Moreover, an optimal measurement distance can be expected when using a planner sensor array to perform magnetic measurements