In this article, we have considered the simultaneous influence of ohmic heating and chemical reaction on heat and mass transfer over a stretching sheet. The effects of applied magnetic field are also taken into consid...In this article, we have considered the simultaneous influence of ohmic heating and chemical reaction on heat and mass transfer over a stretching sheet. The effects of applied magnetic field are also taken into consideration while the induced magnetic field is not considered due to very small magnetics Reynolds number. The governing flow problem comprises of momentum, continuity, thermal energy and concentration equation which are transformed into highly nonlinear coupled ordinary differential equations by means of similarity transforms, which are then, solved numerically with the help of Successive Linearization method(SLM) and Chebyshev Spectral collocation method. Numerical values of skin friction coefficient, local Nusselt number, and Sherwood number are also taken into account with the help of tables. The physical influence of the involved parameters of flow velocity, temperature and concentration distribution is discussed and demonstrated graphically. The numerical comparison is also presented with the existing published results and found that the present results are in excellent agreement which also confirms the validity of the present methodology.展开更多
The breakup reaction of ~9Li on a Pb target has been measured at 32.7 MeV/nucleon for the first time. Two peaks of ~6He+t coincident fragments at 9.8 and 12.5 MeV were observed and agreed with the results of the gener...The breakup reaction of ~9Li on a Pb target has been measured at 32.7 MeV/nucleon for the first time. Two peaks of ~6He+t coincident fragments at 9.8 and 12.5 MeV were observed and agreed with the results of the generator coordinate method calculation. The experiment was carried out thanks to a specially arranged detection system around zero degrees at the Heavy Ion Research Facility in Lanzhou, Radioactive Ion Beam Line in Lanzhou(HIRFL–RIBLL).展开更多
For the first time a mathematical modelling of porous catalyst particles subject to both internal mass concentration gradients as well as temperature gradients, in endothermic or exothermic reactions has been reported...For the first time a mathematical modelling of porous catalyst particles subject to both internal mass concentration gradients as well as temperature gradients, in endothermic or exothermic reactions has been reported. This model contains a non-linear mass balance equation which is related to rate expression. This paper presents an approximate analytical method (Modified Adomian decomposition method) to solve the non-linear differential equations for chemical kinetics with diffusion effects. A simple and closed form of expressions pertaining to substrate concentration and utilization factor is presented for all value of diffusion parameters. These analytical results are compared with numerical results and found to be in good agreement.展开更多
以六氟双酚A(BPAF)与2,6-二氯苯甲腈(DCBN)为主要原料,采用经典的亲核芳香取代缩聚反应,优化合成与纯化工艺,得到了高纯度双酚AF型聚芳醚腈(BPAF-PEN)树脂粉末,为制备聚芳醚类微孔材料提供了新思路。采用红外光谱和核磁共振氢谱法表征了...以六氟双酚A(BPAF)与2,6-二氯苯甲腈(DCBN)为主要原料,采用经典的亲核芳香取代缩聚反应,优化合成与纯化工艺,得到了高纯度双酚AF型聚芳醚腈(BPAF-PEN)树脂粉末,为制备聚芳醚类微孔材料提供了新思路。采用红外光谱和核磁共振氢谱法表征了BPAF-PEN的结构,并通过热失重分析(TGA)研究了BPAF-PEN的热分解动力学。首先利用无模型的Friedman法确定了该热分解反应是一个复杂的过程,活化能约为230~260 k J/mol。采用了基于动力学模型的非线性优化拟合方法揭示了反应机理,得到双酚AF型聚芳醚腈热分解过程可以通过连串反应的动力学模型进行描述,实验值和模拟值的相关系数为0.997。其中,第一步为成核生长反应,第二步为N级反应。展开更多
建立超高效液相色谱-串联质谱同时、快速分析18种酚类物质的方法,测定比较铁皮石斛茎、叶、花部位含量差异。样品用甲醇-水溶液提取,提取液中的目标化合物经Waters T3 C_(18)柱梯度洗脱分离,电喷雾串联三重四极杆质谱仪正、负离子扫描...建立超高效液相色谱-串联质谱同时、快速分析18种酚类物质的方法,测定比较铁皮石斛茎、叶、花部位含量差异。样品用甲醇-水溶液提取,提取液中的目标化合物经Waters T3 C_(18)柱梯度洗脱分离,电喷雾串联三重四极杆质谱仪正、负离子扫描方式多反应监测模式检测。结果表明:以18种酚类物质标准品作为对照,在铁皮石斛样品中共检出15种酚类组分,分别为3,5-二羟基苯甲酸、橘皮素、绿原酸、槲皮素、芦丁、对羟基苯甲酸、咖啡酸、丁香酸、香草酸、山柰酚、对香豆酸、芥子酸、阿魏酸、3-羟基肉桂酸、水杨酸。铁皮石斛不同部位多酚组分含量为花>叶>茎,相对于其他酚类组分,芦丁在铁皮石斛茎、叶、花中的含量均为最高。铁皮石斛不同部位主要酚类组分表现出一定的差别:铁皮石斛花中主要含有芦丁、咖啡酸、阿魏酸和对羟基苯甲酸,铁皮石斛叶中芦丁和阿魏酸的含量相对较高,而铁皮石斛茎部主要酚类组分则为芦丁、阿魏酸与香草酸。实验结果可为铁皮石斛不同部位酚类组分的利用提供一定的科学依据。展开更多
Dynamic interfacial properties are investigated for solvent extraction systems of metals by organophosphoric or phosphonic acid. The relationship between interfacial properties and kinetic parameters shows that the dy...Dynamic interfacial properties are investigated for solvent extraction systems of metals by organophosphoric or phosphonic acid. The relationship between interfacial properties and kinetic parameters shows that the dynamic interfacial properties are important to mass transfer processes in liquid-liquid extraction. The authors develop a two-film adsorption model which may offer a basis for researching interfacial activity in mass transfer processes.展开更多
文摘In this article, we have considered the simultaneous influence of ohmic heating and chemical reaction on heat and mass transfer over a stretching sheet. The effects of applied magnetic field are also taken into consideration while the induced magnetic field is not considered due to very small magnetics Reynolds number. The governing flow problem comprises of momentum, continuity, thermal energy and concentration equation which are transformed into highly nonlinear coupled ordinary differential equations by means of similarity transforms, which are then, solved numerically with the help of Successive Linearization method(SLM) and Chebyshev Spectral collocation method. Numerical values of skin friction coefficient, local Nusselt number, and Sherwood number are also taken into account with the help of tables. The physical influence of the involved parameters of flow velocity, temperature and concentration distribution is discussed and demonstrated graphically. The numerical comparison is also presented with the existing published results and found that the present results are in excellent agreement which also confirms the validity of the present methodology.
基金supported by the National Natural Science Foundation of China(Nos.U1432247 and 11575256)the National Basic Research Program of China(973 Program)(Nos.2014CB845405 and2013CB83440x)
文摘The breakup reaction of ~9Li on a Pb target has been measured at 32.7 MeV/nucleon for the first time. Two peaks of ~6He+t coincident fragments at 9.8 and 12.5 MeV were observed and agreed with the results of the generator coordinate method calculation. The experiment was carried out thanks to a specially arranged detection system around zero degrees at the Heavy Ion Research Facility in Lanzhou, Radioactive Ion Beam Line in Lanzhou(HIRFL–RIBLL).
文摘For the first time a mathematical modelling of porous catalyst particles subject to both internal mass concentration gradients as well as temperature gradients, in endothermic or exothermic reactions has been reported. This model contains a non-linear mass balance equation which is related to rate expression. This paper presents an approximate analytical method (Modified Adomian decomposition method) to solve the non-linear differential equations for chemical kinetics with diffusion effects. A simple and closed form of expressions pertaining to substrate concentration and utilization factor is presented for all value of diffusion parameters. These analytical results are compared with numerical results and found to be in good agreement.
文摘以六氟双酚A(BPAF)与2,6-二氯苯甲腈(DCBN)为主要原料,采用经典的亲核芳香取代缩聚反应,优化合成与纯化工艺,得到了高纯度双酚AF型聚芳醚腈(BPAF-PEN)树脂粉末,为制备聚芳醚类微孔材料提供了新思路。采用红外光谱和核磁共振氢谱法表征了BPAF-PEN的结构,并通过热失重分析(TGA)研究了BPAF-PEN的热分解动力学。首先利用无模型的Friedman法确定了该热分解反应是一个复杂的过程,活化能约为230~260 k J/mol。采用了基于动力学模型的非线性优化拟合方法揭示了反应机理,得到双酚AF型聚芳醚腈热分解过程可以通过连串反应的动力学模型进行描述,实验值和模拟值的相关系数为0.997。其中,第一步为成核生长反应,第二步为N级反应。
文摘建立超高效液相色谱-串联质谱同时、快速分析18种酚类物质的方法,测定比较铁皮石斛茎、叶、花部位含量差异。样品用甲醇-水溶液提取,提取液中的目标化合物经Waters T3 C_(18)柱梯度洗脱分离,电喷雾串联三重四极杆质谱仪正、负离子扫描方式多反应监测模式检测。结果表明:以18种酚类物质标准品作为对照,在铁皮石斛样品中共检出15种酚类组分,分别为3,5-二羟基苯甲酸、橘皮素、绿原酸、槲皮素、芦丁、对羟基苯甲酸、咖啡酸、丁香酸、香草酸、山柰酚、对香豆酸、芥子酸、阿魏酸、3-羟基肉桂酸、水杨酸。铁皮石斛不同部位多酚组分含量为花>叶>茎,相对于其他酚类组分,芦丁在铁皮石斛茎、叶、花中的含量均为最高。铁皮石斛不同部位主要酚类组分表现出一定的差别:铁皮石斛花中主要含有芦丁、咖啡酸、阿魏酸和对羟基苯甲酸,铁皮石斛叶中芦丁和阿魏酸的含量相对较高,而铁皮石斛茎部主要酚类组分则为芦丁、阿魏酸与香草酸。实验结果可为铁皮石斛不同部位酚类组分的利用提供一定的科学依据。
文摘Dynamic interfacial properties are investigated for solvent extraction systems of metals by organophosphoric or phosphonic acid. The relationship between interfacial properties and kinetic parameters shows that the dynamic interfacial properties are important to mass transfer processes in liquid-liquid extraction. The authors develop a two-film adsorption model which may offer a basis for researching interfacial activity in mass transfer processes.
