The relationship between body mass index (BMI) and quality of life in Iranian primary school students in Tehran, Iran

Background: This study aimed to investigate the relationship between Body Mass Index (BMI) and quality of life in primary school students in Tehran. Method: In this cross-sectional study 829 primary school children and their parents participated. Healthrelated quality of life (HROOL) was evaluated with the Persian version of Pediatric Quality of Life Inventory (PedsQL�4.0) questionnaire. According to objective measures of height and weight, children BMI computed, and adapted for age and gender. For data analysis we used Pearson correlation test, Independentsample t-test and ANOVA using SPSS version 18. Results: Mean of children self-reported HRQOL total score was 82.05 ± 12.04 and mean of parent proxyreported HRQOL total score was 81.66 ± 12.81. Based on HRQOL subscale scores, social functioning was the highest subscale score of HRQOL (84.67 ± 15.07) and the emotional subscale score was the lowest (77.79 ± 17.26). Lower HRQOL scores were significantly correlated with Higher BMI and normal weight children had significantly higher HRQOL total score than obese children (P < 0.05). The difference between normal weight and overweight children in HRQOL total scores were not significant. Same results were obtained from parent proxy-reports and a good harmony between children self-report and parent proxy-report of HRQOL was perceived. Conclusion: This study showed that HRQOL of obese children were at the lower level in comparison to normal weight and overweight children. At further interventional studies these outcomes can be very important for improving quality of life in obese children. © Author(s) 2018. This article is published with open access by China Medical University

A novel switching table for a modified three-level inverter-fed DTC drive with torque and flux ripple minimization

The use of a direct torque control (DTC) drive is a well-known control strategy that is applied frequently to induction motors. Although torque and stator flux ripples are major disadvantages of this approach, using a higher-level inverter helps to overcome these issues. In this paper, we propose a novel switching table with a modified control strategy for a three-level inverter to achieve ripple minimization, as well as smooth switching and neutral point balance; the latter features are generally ignored in many works. The proposed model is compared with a conventional DTC and an improved three-level inverter-fed voltage vector synthesis model in the Matlab/Simulink® environment with low, normal, and high-speed operation under load torque disturbances. The performance indexes and the comparative results confirm the effectiveness of the proposed model in reducing the torque and stator flux ripples by up to 70% and 78%, respectively, generating a lower total harmonic distortion (THD%) in all scenarios, in addition to maintaining the neutral point balance and preventing voltage jumps across the switches of the inverter

Nonlinear mechanics of nanoscale tubes via nonlocal strain gradient theory

A size-dependent nonlinear nonlocal strain gradient model for nanoscale tubes is proposed in this investigation and the forced mechanical behaviour is examined. This continuum model is better capable of incorporating size effects as it includes two independent length-scale parameters. The scale-dependent elastic energy and motion energy as well as the work carried out by the excitation load are formulated. The non-classical nonlinear differential equation of motion of the nanoscale tube is obtained using Hamilton's work/energy principle together with the nonlocal strain gradient elasticity. A precise numerical solution is presented for the nonlinear dynamic characteristics within the framework of Galerkin's scheme in conjunction with a continuation approach. The influences of nanosystem parameters such as the scale parameters, the length-to-gyration-radius ratio as well as the amplitude of the excitation force on the frequency/force responses are explored and discussed in details.Mergen H. Ghayesh, Ali Farajpou

A review on the mechanics of nanostructures

Understanding the mechanical behaviour of nanostructures is of great importance due to their applications in nanodevices such as in nanomechanical resonators, nanoscale mass sensors, electromechanical nanoactuators and nanogenerators. Due to the difficulties of performing accurate experimental measurements at nanoscales and the high computational costs associated with the molecular dynamics simulations, the continuum modelling of nanostructures has attracted a considerable amount of attention. Since size influences have a crucial role in the mechanics of structures at nanoscale levels, classical continuum-based theories have been modified to incorporate these effects. Among various modified continuum-based theories, the nonlocal elasticity and the nonlocal strain gradient elasticity have been employed to estimate the mechanical behaviour of nanostructures. In this review paper, first these two modified elasticity theories are briefly explained. Then, the nonlocal motion equations for different nanostructures including nanorods, nanorings, nanobeams, nanoplates and nanoshells are derived. Several papers which reported on the size-dependent mechanical behaviour of nanostructures using modified continuum models are reviewed. Furthermore, important results reported on the vibration, bending and buckling of nanostructures as well as the results of size-dependent wave propagation analyses are discussed.Ali Farajpour, Mergen H.Ghayesh, Hamed Farokh

Nonlinear coupled mechanics of nanotubes incorporating both nonlocal and strain gradient effects

The coupled nonlinear mechanical behavior of nonlocal strain gradient nanotubes subject to distributed excitation forcing is investigated for the first time. Both longitudinal displacements and transverse deflection are taken into consideration in both the continuum-based formulation and the numerical solution. The influences of being at the nanoscale level are modeled with the use of the nonlocal strain gradient theory. The coupled large amplitude motion characteristics are extracted via Galerkin's approach and a continuation method. The influences of scale coefficients, the slenderness ratio, and the force amplitude of the external forcing on the motion are examined.Mergen H. Ghayesh and Ali Farajpou