Objective To explore the influence of secular trends in body height and weight on the prevalence of overweight and obesity among Chinese children and adolescents.Methods The data were obtained from five cross-sectiona...Objective To explore the influence of secular trends in body height and weight on the prevalence of overweight and obesity among Chinese children and adolescents.Methods The data were obtained from five cross-sectional Chinese National Surveys on Students' Constitution and Health.Overweight/obesity was defined as BMI-for-age Z-score of per the Wold Health Organization(WHO) reference values.Body height and weight for each sex and age were standardized to those reported in 1985(standardized height: SHY;standardized weight: SWY) and for each sex and year at age 7(standardized height: SHA;standardized weight: SWA) using the Z-score method.Results The prevalence of overweight/obesity in Chinese children was 20.2% among boys and 10.7% among girls in 2010 and increased continuously from 1985 to 2010.Among boys and girls of normal weight,SHY and SHA were significantly greater than SWY and SWA,respectively(P < 0.001).Among boys and girls with overweight/obesity,SHY was significantly lower than SWY(P < 0.001),and showed an obvious decreasing trend after age 12.SHA was lower than SWA among overweight boys aged 7-8 years and girls aged 7-9 years.SHY/SHW and SHA/SWA among normal-weight groups were greater than among overweight and obese groups(P < 0.001).Conclusion The continuous increase in the prevalence of overweight/obesity among Chinese children may be related to a rapid increase in body weight before age 9 and lack of secular increase in body height after age 12.展开更多
Objective Over the last century, a progressive rise in stature, known as the ‘secular trend’, was documented worldwide, and especially in Sardinia, it has reached a peak in Europe. However, this situation recently c...Objective Over the last century, a progressive rise in stature, known as the ‘secular trend’, was documented worldwide, and especially in Sardinia, it has reached a peak in Europe. However, this situation recently ceased in several populations. In this study, we tested the hypothesis that the stature secular trend has significantly leveled off in the Sardinian younger generations.Methods Height measurements were retrieved from a database of patients undergoing digestive endoscopy, spanning generations between 1920 and 1990. Sex-specific principal component regression models were fitted to decompose stature variation into the contribution of age, period, and birth cohort.Results A steady increase in stature was observed in generations born after 1920, with an upward surge in those born after 1950. However, a significant leveling off was observed among cohorts born after 1970 among both sexes, as mean heights stabilized at 171.1 cm with a standard error(SE) of 0.9 cm among men and a mean of 160.1 cm(SE = 0.9 cm) among women.Conclusion Our findings support a significant slowdown in the secular trend of stature among the latest Sardinian generations. Several factors, including the consumption of low-quality food, lack of physical activity, and late motherhood, among others, may explain the decline in the secular trend.展开更多
To reduce the damages of pavement,vehicle components and agricultural product during transportation,an electric control air suspension height adjustment system of agricultural transport vehicle was studied by means of...To reduce the damages of pavement,vehicle components and agricultural product during transportation,an electric control air suspension height adjustment system of agricultural transport vehicle was studied by means of simulation and bench test.For the oscillation phenomenon of vehicle height in driving process,the mathematical model of the vehicle height adjustment system was developed,and the controller of vehicle height based on single neuron adaptive PID control algorithm was designed.The control model was simulated via Matlab/Simulink,and bench test was conducted.Results show that the method is feasible and effective to solve the agricultural vehicle body height unstable phenomenon in the process of switching.Compared with other PID algorithms,the single neuron adaptive PID control in agricultural transport vehicle has shorter response time,faster response speed and more stable switching state.The stability of the designed vehicle height adjustment system and the ride comfort of agricultural transport vehicle were improved.展开更多
基金supported by the National Natural Science Foundation of China(81502823)
文摘Objective To explore the influence of secular trends in body height and weight on the prevalence of overweight and obesity among Chinese children and adolescents.Methods The data were obtained from five cross-sectional Chinese National Surveys on Students' Constitution and Health.Overweight/obesity was defined as BMI-for-age Z-score of per the Wold Health Organization(WHO) reference values.Body height and weight for each sex and age were standardized to those reported in 1985(standardized height: SHY;standardized weight: SWY) and for each sex and year at age 7(standardized height: SHA;standardized weight: SWA) using the Z-score method.Results The prevalence of overweight/obesity in Chinese children was 20.2% among boys and 10.7% among girls in 2010 and increased continuously from 1985 to 2010.Among boys and girls of normal weight,SHY and SHA were significantly greater than SWY and SWA,respectively(P < 0.001).Among boys and girls with overweight/obesity,SHY was significantly lower than SWY(P < 0.001),and showed an obvious decreasing trend after age 12.SHA was lower than SWA among overweight boys aged 7-8 years and girls aged 7-9 years.SHY/SHW and SHA/SWA among normal-weight groups were greater than among overweight and obese groups(P < 0.001).Conclusion The continuous increase in the prevalence of overweight/obesity among Chinese children may be related to a rapid increase in body weight before age 9 and lack of secular increase in body height after age 12.
文摘Objective Over the last century, a progressive rise in stature, known as the ‘secular trend’, was documented worldwide, and especially in Sardinia, it has reached a peak in Europe. However, this situation recently ceased in several populations. In this study, we tested the hypothesis that the stature secular trend has significantly leveled off in the Sardinian younger generations.Methods Height measurements were retrieved from a database of patients undergoing digestive endoscopy, spanning generations between 1920 and 1990. Sex-specific principal component regression models were fitted to decompose stature variation into the contribution of age, period, and birth cohort.Results A steady increase in stature was observed in generations born after 1920, with an upward surge in those born after 1950. However, a significant leveling off was observed among cohorts born after 1970 among both sexes, as mean heights stabilized at 171.1 cm with a standard error(SE) of 0.9 cm among men and a mean of 160.1 cm(SE = 0.9 cm) among women.Conclusion Our findings support a significant slowdown in the secular trend of stature among the latest Sardinian generations. Several factors, including the consumption of low-quality food, lack of physical activity, and late motherhood, among others, may explain the decline in the secular trend.
基金the National Natural Science Foundation of China(Grant No.51375212,71373105)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20133227130001)+1 种基金Research and Innovation Project for College Graduates of Jiangsu Province of China(Grant No.CXZZ12_0663)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20131255)。
文摘To reduce the damages of pavement,vehicle components and agricultural product during transportation,an electric control air suspension height adjustment system of agricultural transport vehicle was studied by means of simulation and bench test.For the oscillation phenomenon of vehicle height in driving process,the mathematical model of the vehicle height adjustment system was developed,and the controller of vehicle height based on single neuron adaptive PID control algorithm was designed.The control model was simulated via Matlab/Simulink,and bench test was conducted.Results show that the method is feasible and effective to solve the agricultural vehicle body height unstable phenomenon in the process of switching.Compared with other PID algorithms,the single neuron adaptive PID control in agricultural transport vehicle has shorter response time,faster response speed and more stable switching state.The stability of the designed vehicle height adjustment system and the ride comfort of agricultural transport vehicle were improved.
