In order to analyze the influence rule of experimental parameters on the energy-absorption characteristics and effectively forecast energy-absorption characteristic of thin-walled structure, the forecast model of GA-B...In order to analyze the influence rule of experimental parameters on the energy-absorption characteristics and effectively forecast energy-absorption characteristic of thin-walled structure, the forecast model of GA-BP hybrid algorithm was presented by uniting respective applicability of back-propagation artificial neural network （BP-ANN） and genetic algorithm （GA）. The detailed process was as follows. Firstly, the GA trained the best weights and thresholds as the initial values of BP-ANN to initialize the neural network. Then, the BP-ANN after initialization was trained until the errors converged to the required precision. Finally, the network model, which met the requirements after being examined by the test samples, was applied to energy-absorption forecast of thin-walled cylindrical structure impacting. After example analysis, the GA-BP network model was trained until getting the desired network error only by 46 steps, while the single BP-ANN model achieved the same network error by 992 steps, which obviously shows that the GA-BP hybrid algorithm has faster convergence rate. The average relative forecast error （ARE） of the SEA predictive results obtained by GA-BP hybrid algorithm is 1.543%, while the ARE of the SEA predictive results obtained by BP-ANN is 2.950%, which clearly indicates that the forecast precision of the GA-BP hybrid algorithm is higher than that of the BP-ANN.展开更多
A simple and reliable method has been developed for separation and preconcentration of trace amounts of copper ions in cereals food for subsequent measurement by flame atomic absorption spectrometry （FAAS）. The Cu^2...A simple and reliable method has been developed for separation and preconcentration of trace amounts of copper ions in cereals food for subsequent measurement by flame atomic absorption spectrometry （FAAS）. The Cu^2＋ ions are adsorbed selectively and quantitatively during the passage. The retained copper ions were desorbed from the potassium tetratitanate whisker with 10.0mL of 2mol/L sulphuric acid solutions as eluent and were determined by FAAS. The linear range was 0.05μg/mL-0.20μg/mL in the original solution with a correlation coefficient of 0.9998. The detection limit of the proposed method is 2. lng/mL in the original solution （3σ, n=9）. Determination of copper in standard ions showed that the proposed method has good accuracy （recovery was more than 95%）. The method was successfully applied for recovery and determination of copper in cereals food samples展开更多
Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected f...Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage(Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd(0–4 mg kg^(-1)) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions. The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil p H from 4.7 to 7.5. However, further increase in soil pH to > 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg^(-1) for the tested soils. The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil p H in combination with soil organic matter or clay content.展开更多
The present study focuses on the prediction of acoustic absorption performance of a perforated plate with air jets by theoretical calculations. In addition, we experimentally measured the flow rate, internal pressure,...The present study focuses on the prediction of acoustic absorption performance of a perforated plate with air jets by theoretical calculations. In addition, we experimentally measured the flow rate, internal pressure, acoustic pressure, and transfer function using an acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. We investigated the influences of background air space, flow velocity, thickness, aperture rate, and aperture diameter of a perforated plate on the acoustic absorption characteristics. The frequency characteristics of the acoustic absorption coefficient showed a maximum value at a local frequency. As the background air space increased, the peak frequency of acoustic absorption characteristics decreased. As the flow velocity passing through the apertures increased, the peak level of the acoustic absorption coefficient also increased. The theoretical results agreed well with the experimental ones qualitatively.展开更多
基金Project(50175110) supported by the National Natural Science Foundation of ChinaProject(2009bsxt019) supported by the Graduate Degree Thesis Innovation Foundation of Central South University, China
文摘In order to analyze the influence rule of experimental parameters on the energy-absorption characteristics and effectively forecast energy-absorption characteristic of thin-walled structure, the forecast model of GA-BP hybrid algorithm was presented by uniting respective applicability of back-propagation artificial neural network （BP-ANN） and genetic algorithm （GA）. The detailed process was as follows. Firstly, the GA trained the best weights and thresholds as the initial values of BP-ANN to initialize the neural network. Then, the BP-ANN after initialization was trained until the errors converged to the required precision. Finally, the network model, which met the requirements after being examined by the test samples, was applied to energy-absorption forecast of thin-walled cylindrical structure impacting. After example analysis, the GA-BP network model was trained until getting the desired network error only by 46 steps, while the single BP-ANN model achieved the same network error by 992 steps, which obviously shows that the GA-BP hybrid algorithm has faster convergence rate. The average relative forecast error （ARE） of the SEA predictive results obtained by GA-BP hybrid algorithm is 1.543%, while the ARE of the SEA predictive results obtained by BP-ANN is 2.950%, which clearly indicates that the forecast precision of the GA-BP hybrid algorithm is higher than that of the BP-ANN.
基金Imburse Fund of Science and Technology Office (05C26213100474)
文摘A simple and reliable method has been developed for separation and preconcentration of trace amounts of copper ions in cereals food for subsequent measurement by flame atomic absorption spectrometry （FAAS）. The Cu^2＋ ions are adsorbed selectively and quantitatively during the passage. The retained copper ions were desorbed from the potassium tetratitanate whisker with 10.0mL of 2mol/L sulphuric acid solutions as eluent and were determined by FAAS. The linear range was 0.05μg/mL-0.20μg/mL in the original solution with a correlation coefficient of 0.9998. The detection limit of the proposed method is 2. lng/mL in the original solution （3σ, n=9）. Determination of copper in standard ions showed that the proposed method has good accuracy （recovery was more than 95%）. The method was successfully applied for recovery and determination of copper in cereals food samples
基金supported by the Special Fund for Environment-Scientific Research in the Public Interest of China (No. 201409041)the Special Fund for Agro-Scientific Research in the Public Interest of China (No. 201403015)the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institute, China
文摘Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage(Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd(0–4 mg kg^(-1)) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions. The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil p H from 4.7 to 7.5. However, further increase in soil pH to > 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg^(-1) for the tested soils. The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil p H in combination with soil organic matter or clay content.
基金supported by JSPS KAKENHI Grant Numbers JP17K06232
文摘The present study focuses on the prediction of acoustic absorption performance of a perforated plate with air jets by theoretical calculations. In addition, we experimentally measured the flow rate, internal pressure, acoustic pressure, and transfer function using an acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. We investigated the influences of background air space, flow velocity, thickness, aperture rate, and aperture diameter of a perforated plate on the acoustic absorption characteristics. The frequency characteristics of the acoustic absorption coefficient showed a maximum value at a local frequency. As the background air space increased, the peak frequency of acoustic absorption characteristics decreased. As the flow velocity passing through the apertures increased, the peak level of the acoustic absorption coefficient also increased. The theoretical results agreed well with the experimental ones qualitatively.
