The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures fr...The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures from 923 to 1123 K,system pressure of 3 Pa and holding time of 30 min.The mass transfer coefficients and apparent activation energies of Pb and its alloys were determined at various temperatures.Additionally,a kinetics model was developed to describe Pb vacuum volatilization in high-temperature melts.It is obtained that the vapor mass transfer is the factor limiting the vacuum volatilization rates of Pb and In-Pb alloys under the above specified conditions.展开更多
The substitution of traditional blast furnaces with steel-belt furnaces for antimony smelting was proposed.The influence of various parameters on the oxidative volatilization of stibnite was studied according to the p...The substitution of traditional blast furnaces with steel-belt furnaces for antimony smelting was proposed.The influence of various parameters on the oxidative volatilization of stibnite was studied according to the production practice of steel-belt furnaces.Furthermore,the kinetics of oxidative volatilization was elucidated using differential thermal gravimetric analyses and non-isothermal analysis methods.The results indicated that the oxygen concentration and the temperature were pivotal variables in the oxidative volatilization process.Notably,the volatilization efficiency of antimony was 97.25%under optimal conditions.Moreover,the kinetic control stages were divided into chemical reaction control(440-490°C),internal diffusion control(500-550°C),and chemical reaction control(560-580°C).These stages corresponded to activation energies of 16.40-18.79,120.86-195.96,and 24.00-28.31 kJ/mol,respectively.展开更多
Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methyl...Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methylation and volatilization under non-fooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with strawderived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440(GE P. putida). Under fooded conditions, the application of biochar(BC), rice straw(RS)and their combination(BC+RS) increased total As in porewater. However, these effects were greatly attenuated under non-fooded conditions. Compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization,and the promotion percentage under non-fooded conditions were significantly higher than that under fooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation(88 μg/L) and volatilization(415.4 μg/(kg·year)) in the non-fooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOC and p H in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/BC+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-fooded conditions.展开更多
Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to ...Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great importance.In this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the VOC.The devolatilization rate and liquid phase volume(KLa)have been evaluated.The results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 MPa.The dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of acetone.This work provides a promising path for the removal of volatiles from polymers in combination with high-gravity technology.It can provide the basis for the application of RPB in viscous fluids.展开更多
采用顶空固相微萃取-气相色谱-质谱联用(HS-SPME-GC-MS)技术、16 S rRNA和内在转录间隔区(ITS)高通量测序技术,探究了安化红茶的深发酵和浅发酵工艺过程中红茶的香气特征成分和微生物多样性。结果表明,在不同发酵工艺的安化红茶中共检测...采用顶空固相微萃取-气相色谱-质谱联用(HS-SPME-GC-MS)技术、16 S rRNA和内在转录间隔区(ITS)高通量测序技术,探究了安化红茶的深发酵和浅发酵工艺过程中红茶的香气特征成分和微生物多样性。结果表明,在不同发酵工艺的安化红茶中共检测出82种挥发性成分,主要为醇类、酯类和醛类,占比约为85%;挥发性成分总量随着加工过程的进行呈现先增加后降低的趋势。以气味活度值(OAV)>1且变量投影重要性(VIP)>1为依据,在浅发酵与深发酵工艺的安化红茶中筛选出柠檬醛、芳樟醇、苯乙醇、苯乙醛、水杨酸甲酯、β-月桂烯等14种关键差异挥发性成分。安化红茶的优势细菌为鞘氨醇单胞菌属(Sphingomonas)、甲基杆菌属(Methylobacterium)、橙黄单胞菌属(Aureimonas),优势真菌为枝孢属(Cladosporium)、链格孢属(Alternaria)、Setophoma。橙黄单胞菌属、肠杆菌属(Enterobacter)、曲霉属(Aspergillus)、Pseudopithomyces与不同发酵过程显著相关。研究结果为安化红茶科学加工、风味解析提供理论参考与依据。展开更多
如何对期权的隐含波动率曲面建模,一直以来是金融衍生品领域的难点问题之一。已有文献针对某些特定结构的随机波动率模型,推导出期权的隐含波动率解析表达式(Analytical formula of implie dvolatility,AFIV),但通用性差、或精度不够好...如何对期权的隐含波动率曲面建模,一直以来是金融衍生品领域的难点问题之一。已有文献针对某些特定结构的随机波动率模型,推导出期权的隐含波动率解析表达式(Analytical formula of implie dvolatility,AFIV),但通用性差、或精度不够好。本文针对一般形式的随机波动率模型,给出获取高精度AFIV的通用方法:首先应用特征函数局部结构微扰法,推导出一般形式随机波动率模型的特征函数表达式;然后基于特征函数与期权价格的关系式,应用参数微扰法推导出隐含波动率的渐近表达式。数值实验和实证结果表明:(1)与同类最新研究(如Ait-Sahalia等,2021)[1-2]相比,本文方法在长到期期权上的定价精度有显著提升,在短到期期权上的定价精度也略优些;(2)与孙有发等(2022)[3]提出的基于特征函数局部结构微扰的期权定价方法相比,本文提出的AFIV方法不仅定价精度高,且拥有更优越的定价效率和参数校准的稳健性。本文提出的AFIV方法,不仅解决了众多性能良好的随机波动率模型在期权市场的运用问题,而且还为公平比较不同标的模型的市场刻画性能提供一种可行方法。展开更多
基金financially supported by the Fundamental Research Project of Yunnan Province,China(Nos.202301AW070020,202201AT070229,202105AC160091,202202AB080018).
文摘The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures from 923 to 1123 K,system pressure of 3 Pa and holding time of 30 min.The mass transfer coefficients and apparent activation energies of Pb and its alloys were determined at various temperatures.Additionally,a kinetics model was developed to describe Pb vacuum volatilization in high-temperature melts.It is obtained that the vapor mass transfer is the factor limiting the vacuum volatilization rates of Pb and In-Pb alloys under the above specified conditions.
基金supported financially by the National Natural Science Foundation of China(No.52074362)。
文摘The substitution of traditional blast furnaces with steel-belt furnaces for antimony smelting was proposed.The influence of various parameters on the oxidative volatilization of stibnite was studied according to the production practice of steel-belt furnaces.Furthermore,the kinetics of oxidative volatilization was elucidated using differential thermal gravimetric analyses and non-isothermal analysis methods.The results indicated that the oxygen concentration and the temperature were pivotal variables in the oxidative volatilization process.Notably,the volatilization efficiency of antimony was 97.25%under optimal conditions.Moreover,the kinetic control stages were divided into chemical reaction control(440-490°C),internal diffusion control(500-550°C),and chemical reaction control(560-580°C).These stages corresponded to activation energies of 16.40-18.79,120.86-195.96,and 24.00-28.31 kJ/mol,respectively.
基金supported by the National Natural Science Foundation of China (No.42107048)the National Key Research and Development Program of China (No.2021YFC1809205)the Open Foundation of the State Key Laboratory of Urban and Regional Ecology of China (No.SKLURE2021-2-5)。
文摘Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methylation and volatilization under non-fooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with strawderived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440(GE P. putida). Under fooded conditions, the application of biochar(BC), rice straw(RS)and their combination(BC+RS) increased total As in porewater. However, these effects were greatly attenuated under non-fooded conditions. Compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization,and the promotion percentage under non-fooded conditions were significantly higher than that under fooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation(88 μg/L) and volatilization(415.4 μg/(kg·year)) in the non-fooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOC and p H in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/BC+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-fooded conditions.
基金the financial support from the Scientific Research Program of Taiyuan University (23TYQN23)
文摘Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental problems.The removal of VOCs from polymers has become a key problem.The effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great importance.In this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the VOC.The devolatilization rate and liquid phase volume(KLa)have been evaluated.The results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 MPa.The dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of acetone.This work provides a promising path for the removal of volatiles from polymers in combination with high-gravity technology.It can provide the basis for the application of RPB in viscous fluids.
文摘采用顶空固相微萃取-气相色谱-质谱联用(HS-SPME-GC-MS)技术、16 S rRNA和内在转录间隔区(ITS)高通量测序技术,探究了安化红茶的深发酵和浅发酵工艺过程中红茶的香气特征成分和微生物多样性。结果表明,在不同发酵工艺的安化红茶中共检测出82种挥发性成分,主要为醇类、酯类和醛类,占比约为85%;挥发性成分总量随着加工过程的进行呈现先增加后降低的趋势。以气味活度值(OAV)>1且变量投影重要性(VIP)>1为依据,在浅发酵与深发酵工艺的安化红茶中筛选出柠檬醛、芳樟醇、苯乙醇、苯乙醛、水杨酸甲酯、β-月桂烯等14种关键差异挥发性成分。安化红茶的优势细菌为鞘氨醇单胞菌属(Sphingomonas)、甲基杆菌属(Methylobacterium)、橙黄单胞菌属(Aureimonas),优势真菌为枝孢属(Cladosporium)、链格孢属(Alternaria)、Setophoma。橙黄单胞菌属、肠杆菌属(Enterobacter)、曲霉属(Aspergillus)、Pseudopithomyces与不同发酵过程显著相关。研究结果为安化红茶科学加工、风味解析提供理论参考与依据。
文摘如何对期权的隐含波动率曲面建模,一直以来是金融衍生品领域的难点问题之一。已有文献针对某些特定结构的随机波动率模型,推导出期权的隐含波动率解析表达式(Analytical formula of implie dvolatility,AFIV),但通用性差、或精度不够好。本文针对一般形式的随机波动率模型,给出获取高精度AFIV的通用方法:首先应用特征函数局部结构微扰法,推导出一般形式随机波动率模型的特征函数表达式;然后基于特征函数与期权价格的关系式,应用参数微扰法推导出隐含波动率的渐近表达式。数值实验和实证结果表明:(1)与同类最新研究(如Ait-Sahalia等,2021)[1-2]相比,本文方法在长到期期权上的定价精度有显著提升,在短到期期权上的定价精度也略优些;(2)与孙有发等(2022)[3]提出的基于特征函数局部结构微扰的期权定价方法相比,本文提出的AFIV方法不仅定价精度高,且拥有更优越的定价效率和参数校准的稳健性。本文提出的AFIV方法,不仅解决了众多性能良好的随机波动率模型在期权市场的运用问题,而且还为公平比较不同标的模型的市场刻画性能提供一种可行方法。
