The developed technique of diffusive gradients in thin film( DGT) has been suggested as a promising tool for evaluation of cadmium( Cd) availability in soils,but there exists considerable debate on its suitability. In...The developed technique of diffusive gradients in thin film( DGT) has been suggested as a promising tool for evaluation of cadmium( Cd) availability in soils,but there exists considerable debate on its suitability. In this study,Cd bioavailability in soils was systemically investigated by comparing this technique with seven traditional methods, including soil solution concentration and six commonly used extraction methods( HAc,EDTA,Na c,NH4Ac,CaCl2 and MgCl2). Two typical plants( wheat and maize) were examined for Cd uptake. Maize was more sensitive to increasing exposure to Cd in soils than wheat when the added amounts of Cd ranged from 3. 5 to 5. 0 mg · kg-1,accompanied by the significant decreases of shoot and root biomasses. Cd concentrations in shoots and roots of two plants increased continuously with increasing levels of Cd in soils. Cd uptake was higher in wheat than that in maize. The bioavailable concentrations of Cd measured by all methods increased nearly linearly with increasing addition of Cd in soils. Positive correlations were observed between various bioavailable indicators of Cd in soils and Cd concentrations in two plants. The extractable Cd by six chemical extractants was considerably higher for maize than for wheat,while the DGT-measured and soil solution concentrations of Cd were lower for maize than for wheat,following the same trend as plant Cd uptake. The results imply that DGT measurement can effectively predict the bioavailable levels of Cd in soil solutions and that it is an ideal tool for prediction of Cd bioavailability in soils.展开更多
The paper investigates continuously changing wrinkle patterns of thin films bonded to a gradient substrate. Three types of gradient substrates including exponential, power-law, and symmetry models are considered. The ...The paper investigates continuously changing wrinkle patterns of thin films bonded to a gradient substrate. Three types of gradient substrates including exponential, power-law, and symmetry models are considered. The Galerkin method is used to dis- cretize the governing equation of film bonded to gradient substrates. The wavelength and the normalized amplitude of the wrinkles for substrates of various material gradients are obtained. The numerical simulation based on the finite element method （FEM） is used to evolve the wrinkle patterns. The result agrees well with that of the analytical model. It is concluded that localization of wrinkle patterns strongly depends on the material gradient. The critical membrane force depends on both the minimum value of wrinkle stiffness and the gradient of wrinkle stiffness when the wrinkle stiffness is at its minimum. This work provides a better understanding for local wrinkle formation caused by gradient substrates.展开更多
The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonline...The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.展开更多
热点温度是影响金属化薄膜电容器(metallized film capacitors,MFC)绝缘寿命的重要因素之一,但由于其无法直接测量,因此通常采用热仿真分析或温度反演的方法获得。该文提出了基于共轭梯度法(conjugategradient method,CG)的热点温度反...热点温度是影响金属化薄膜电容器(metallized film capacitors,MFC)绝缘寿命的重要因素之一,但由于其无法直接测量,因此通常采用热仿真分析或温度反演的方法获得。该文提出了基于共轭梯度法(conjugategradient method,CG)的热点温度反演模型,建立了内部传热过程的温度分布目标函数,采用有限差分法求解电容器温度场,再通过CG对内部温度分布进行迭代求解。同时,通过交流温升试验校核了仿真模型以及反演模型。研究结果表明:热点温升与表面温升存在线性关系,热点温度出现在MFC中央靠近芯轴处,反演模型与仿真模型最大误差为4.35%,说明该模型可实现现场工况下的温度分布、热点分布等的有效预测。展开更多
针对沉积物中沉积磷(P)通过微生物活动再释放,致使湖泊富营养化反复的问题,采集郑州大学眉湖上覆水和沉积物,搭建一个沉积式微生物燃料电池(Sediment Microbial Fuel Cell,SMFC)系统,研究了通过SMFC限制沉积磷向上覆水体释放的方法。实...针对沉积物中沉积磷(P)通过微生物活动再释放,致使湖泊富营养化反复的问题,采集郑州大学眉湖上覆水和沉积物,搭建一个沉积式微生物燃料电池(Sediment Microbial Fuel Cell,SMFC)系统,研究了通过SMFC限制沉积磷向上覆水体释放的方法。实验周期内监测SMFC的电压和阳极电极电位、上覆水温度pH、沉积物磷的Standards Measurements and Testing(SMT)法分级提取;并在实验开始与结束收集阳极微生物样进行微生物群落及基因分析;首次使用氧化锆薄膜扩散梯度技术(Zr-Oxide Diffusive Gradients in Thin-films,Zr-Oxide DGT)可视化了SMFC沉积物中不稳定磷亚毫米分辨率的浓度分布。结果表明:SMFC阳极电极电位从-100 mV升至230 mV;上覆水pH从7.15升至7.46;SMFC沉积物烧失量(Loss on Ignition,LOI)从18.31%±0.7%降至13.09%±1.10%,低于对照组的14.29%±2.10%;SMFC显著促进了孔隙水磷向沉积物磷的矿化过程,在沉积物垂向方向上,Na OH-P和HCl-P出现了明显的区域性增加;根据沉积物DGT磷的二维(2D)图像,SMFC使沉积物DGT磷的浓度最低降至初始值的66%;基于京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes,KEGG)数据库的功能基因分析,SMFC使磷相关功能基因丰度显著增加。证明SMFC对于沉积物磷和水相磷分布有显著影响,通过基质竞争、提高阳极电位等方式减弱固相磷的溶解,促进水相磷向沉积相磷的转化,可用于富营养化水体原位底泥磷稳定化。该文深入研究了SMFC固磷作用机理,为修复水体内源磷污染提供了一种新思路。展开更多
采集我国15个省份的耕作土壤进行盆栽试验,通过外源添加不同浓度梯度的Pb并种植小白菜,比较梯度薄膜扩散技术(Diffusive gradients in thin-films,DGT)与传统化学方法(土壤溶液法、EDTA法、HAc法、CaCl_2法和全量法)评价土壤中Pb生物有...采集我国15个省份的耕作土壤进行盆栽试验,通过外源添加不同浓度梯度的Pb并种植小白菜,比较梯度薄膜扩散技术(Diffusive gradients in thin-films,DGT)与传统化学方法(土壤溶液法、EDTA法、HAc法、CaCl_2法和全量法)评价土壤中Pb生物有效性。简单回归分析表明,各评价方法测定的土壤Pb含量与小白菜Pb含量都呈显著相关关系,但DGT技术相关性(R^2=0.97)最高。通过逐步多元线性回归分析,融合土壤pH值、有机碳(OC)含量、阳离子交换量(CEC)、粘粒含量等土壤基本理化性质,建立多元回归模型,结果表明:各传统评价方法融合了pH值、OC含量等土壤性质,R^2较对应的简单回归分析有所提高,都能用于评价土壤Pb的生物有效性,但通过DGT技术所构建的模型方程(R^2=0.97,p<0.01)几乎不受土壤性质的影响,且较传统化学方法相关性更高,因此,DGT技术是一种可以用于评价土壤中Pb生物性的较优方法。展开更多
基金National Natural Science Foundation of China(No.41001334)Fundamental Research Funds for the Central Universities,China(No.2009B00814)+1 种基金the Project of Knowledge Innovation for the 3rd period,the Chinese Academy of Sciences(No.KZCX2-YW-JS304)Project of the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
文摘The developed technique of diffusive gradients in thin film( DGT) has been suggested as a promising tool for evaluation of cadmium( Cd) availability in soils,but there exists considerable debate on its suitability. In this study,Cd bioavailability in soils was systemically investigated by comparing this technique with seven traditional methods, including soil solution concentration and six commonly used extraction methods( HAc,EDTA,Na c,NH4Ac,CaCl2 and MgCl2). Two typical plants( wheat and maize) were examined for Cd uptake. Maize was more sensitive to increasing exposure to Cd in soils than wheat when the added amounts of Cd ranged from 3. 5 to 5. 0 mg · kg-1,accompanied by the significant decreases of shoot and root biomasses. Cd concentrations in shoots and roots of two plants increased continuously with increasing levels of Cd in soils. Cd uptake was higher in wheat than that in maize. The bioavailable concentrations of Cd measured by all methods increased nearly linearly with increasing addition of Cd in soils. Positive correlations were observed between various bioavailable indicators of Cd in soils and Cd concentrations in two plants. The extractable Cd by six chemical extractants was considerably higher for maize than for wheat,while the DGT-measured and soil solution concentrations of Cd were lower for maize than for wheat,following the same trend as plant Cd uptake. The results imply that DGT measurement can effectively predict the bioavailable levels of Cd in soil solutions and that it is an ideal tool for prediction of Cd bioavailability in soils.
基金Project supported by the National Natural Science Foundation of China(No.11472163)the National Key Basic Research Project of China(No.2014CB04623)the Shanghai Municipal Commission of Eduction(No.13ZZ067)
文摘The paper investigates continuously changing wrinkle patterns of thin films bonded to a gradient substrate. Three types of gradient substrates including exponential, power-law, and symmetry models are considered. The Galerkin method is used to dis- cretize the governing equation of film bonded to gradient substrates. The wavelength and the normalized amplitude of the wrinkles for substrates of various material gradients are obtained. The numerical simulation based on the finite element method （FEM） is used to evolve the wrinkle patterns. The result agrees well with that of the analytical model. It is concluded that localization of wrinkle patterns strongly depends on the material gradient. The critical membrane force depends on both the minimum value of wrinkle stiffness and the gradient of wrinkle stiffness when the wrinkle stiffness is at its minimum. This work provides a better understanding for local wrinkle formation caused by gradient substrates.
文摘The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.
文摘热点温度是影响金属化薄膜电容器(metallized film capacitors,MFC)绝缘寿命的重要因素之一,但由于其无法直接测量,因此通常采用热仿真分析或温度反演的方法获得。该文提出了基于共轭梯度法(conjugategradient method,CG)的热点温度反演模型,建立了内部传热过程的温度分布目标函数,采用有限差分法求解电容器温度场,再通过CG对内部温度分布进行迭代求解。同时,通过交流温升试验校核了仿真模型以及反演模型。研究结果表明:热点温升与表面温升存在线性关系,热点温度出现在MFC中央靠近芯轴处,反演模型与仿真模型最大误差为4.35%,说明该模型可实现现场工况下的温度分布、热点分布等的有效预测。
基金National Natural Science Foundation of China(52102133)Natural Science Foundation of Jiangsu Province,China(BK20210354)+1 种基金Fundamental Research Funds for the Central Universities(30921011217)Young Elite Scientists Sponsorship Program by CAST(2021-2023QNRC001)。
文摘针对沉积物中沉积磷(P)通过微生物活动再释放,致使湖泊富营养化反复的问题,采集郑州大学眉湖上覆水和沉积物,搭建一个沉积式微生物燃料电池(Sediment Microbial Fuel Cell,SMFC)系统,研究了通过SMFC限制沉积磷向上覆水体释放的方法。实验周期内监测SMFC的电压和阳极电极电位、上覆水温度pH、沉积物磷的Standards Measurements and Testing(SMT)法分级提取;并在实验开始与结束收集阳极微生物样进行微生物群落及基因分析;首次使用氧化锆薄膜扩散梯度技术(Zr-Oxide Diffusive Gradients in Thin-films,Zr-Oxide DGT)可视化了SMFC沉积物中不稳定磷亚毫米分辨率的浓度分布。结果表明:SMFC阳极电极电位从-100 mV升至230 mV;上覆水pH从7.15升至7.46;SMFC沉积物烧失量(Loss on Ignition,LOI)从18.31%±0.7%降至13.09%±1.10%,低于对照组的14.29%±2.10%;SMFC显著促进了孔隙水磷向沉积物磷的矿化过程,在沉积物垂向方向上,Na OH-P和HCl-P出现了明显的区域性增加;根据沉积物DGT磷的二维(2D)图像,SMFC使沉积物DGT磷的浓度最低降至初始值的66%;基于京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes,KEGG)数据库的功能基因分析,SMFC使磷相关功能基因丰度显著增加。证明SMFC对于沉积物磷和水相磷分布有显著影响,通过基质竞争、提高阳极电位等方式减弱固相磷的溶解,促进水相磷向沉积相磷的转化,可用于富营养化水体原位底泥磷稳定化。该文深入研究了SMFC固磷作用机理,为修复水体内源磷污染提供了一种新思路。
文摘采集我国15个省份的耕作土壤进行盆栽试验,通过外源添加不同浓度梯度的Pb并种植小白菜,比较梯度薄膜扩散技术(Diffusive gradients in thin-films,DGT)与传统化学方法(土壤溶液法、EDTA法、HAc法、CaCl_2法和全量法)评价土壤中Pb生物有效性。简单回归分析表明,各评价方法测定的土壤Pb含量与小白菜Pb含量都呈显著相关关系,但DGT技术相关性(R^2=0.97)最高。通过逐步多元线性回归分析,融合土壤pH值、有机碳(OC)含量、阳离子交换量(CEC)、粘粒含量等土壤基本理化性质,建立多元回归模型,结果表明:各传统评价方法融合了pH值、OC含量等土壤性质,R^2较对应的简单回归分析有所提高,都能用于评价土壤Pb的生物有效性,但通过DGT技术所构建的模型方程(R^2=0.97,p<0.01)几乎不受土壤性质的影响,且较传统化学方法相关性更高,因此,DGT技术是一种可以用于评价土壤中Pb生物性的较优方法。
