Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study, the migration behavi...Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study, the migration behavior of rare earth during the thermal decomposition of Zhijin phosphorus ore and the separation and extraction of rare earth in phosphorus slag are discussed systematically. During the thermal decomposition process of phosphorus ore, almost all of the associated rare earth enters into the phosphorus slag phase but does not enter into the ferrophosphorus or gas phases. Amorphous calcium metasilicate and calcium fluosilicate are major components of phosphorus slag, and rare earth mainly exists as a calsil solid solution. Hydrochloric acid was used for acidolysis of the phosphorous slag. Under the following conditions, 96% of the rare earth in the phosphorous slag can be dissolved in the acidolysis solution: acid excess coefficient of 1.5, reaction time of 50 min and reaction temperature of 50℃. The rare earth in the acidolysis solution was separated and recycled using oxalic acid as a precipitator and NaOH as a pH modifier. At pH of 1.7, rare-earth-enriched matter with rare-earth content of 2.1 wt% was obtained, and the recovery of the rare earth was 88%.展开更多
Objective To estimate the relationship between migration and HIV risky behavior when controlling for gender, age, and educational levels and to evaluate the gender differences in migration, HIV knowledge, and HIV risk...Objective To estimate the relationship between migration and HIV risky behavior when controlling for gender, age, and educational levels and to evaluate the gender differences in migration, HIV knowledge, and HIV risky behaviors among rural youth in China. Methods A cross-sectional, anonymous, investigative questionnaire for 1710 unmarried, out-of-school rural youth, aged between 15 and 24 years, was handed out in Gongzhuling county of Jilin province, China. Results 58.5% of participants had a history of migration, irrespective of gender. There were gender differences observed in other factors such as drug abuse(4.3% for males and 5.5% for females, P〈0.01), multiple sexual partners(24.1% for males and 44.1% for females, P〈0.01), and HIV knowledge rate(35.2% for males and 25.5% for females, P〈0.001). While controlling for gender, age, and educational levels, the relationships between migration and drug abuse, selling sex, and non usage of condoms during last instance of sexual activity were found to be significant. The cases of premarital sex and multiple sexual partners were both not found to be related to migration. Conclusion Among rural youth, the HIV risky behavior such as drug abuse, selling sex, and lack of condom use, is significantly related to migration, while premarital sex and multiple sexual partners seem unrelated to migration.展开更多
First-principles calculations are performed to investigate the effect of strain on the electrochemical performance of Janus MoSSe monolayer.The calculation focuses on the specific capacity,intercalation potential,elec...First-principles calculations are performed to investigate the effect of strain on the electrochemical performance of Janus MoSSe monolayer.The calculation focuses on the specific capacity,intercalation potential,electronic structure,and migration behavior of Li-ion under various strains by using the climbing-image nudged elastic band method.The result shows that the specific capacity is nearly unchanged under strain.But interestingly,the tensile strain can cause the intercalation potential and Li-ion migration energy barrier increase in MoSSe monolayer,whereas the compressive strain can lead to the intercalation potential and energy barrier decreasing.Thus,the rate performance of the MoSSe anode is improved.By analyzing the potential energy surface of MoSSe surface and equilibrium adsorption distance of Li-ion,we explain the physical origin of the change in the intercalation potential and migration energy barrier.The increase of MoSSe potential energy surface and the decrease of adsorption distance caused by tensile strain are the main reason that hinders Li-ion migration.展开更多
The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding o...The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding of Al alloy retaining continuous oxide layers was successfully achieved in the air by a low-temperature and low-pressure diffusion bonding mothed using a Zn interlayer.During the bonding processes,conducted at 360℃ and 3 MPa,Zn diffused into Al through cracks of thin oxide layers to form the joint composed Al/(diffusion layer)/(oxide layer)/(Zn)/(oxide layer)/(diffusion layer)/Al.The diffusion layers were composed of Zn-Al eutectoid,and the oxide layer included nanocrystals and amorphous Al_(2)O_(3).The shear strength of joints containing continuous oxide layers was about 30 MPa.Interestingly,the migration behavior toward the joint center of the interfacial oxide layers was observed with consuming of the Zn interlayer.The cracking phenomenon,the“subcutaneous diffusion”and the migration behavior of oxide layers were verified and analyzed by the diffusion bonding of anodized 6063Al-6063Al.Subsequently,the dynamic migration mechanism of oxide layers with elements diffusion and bonding interface strengths were discussed in detail.The ability to join Al alloys in the air at low temperatures and low pressure suggests a highly practical and economic method for diffusion bonding.展开更多
The present study sought to investigate the migration of target bisphenols,such as bisphenol-A(BPA),bisphenol-F(BPA),bisphenol-A diglycidyI ether(BADGE),bisphenol-A(2,3-dihydroxypropyl)glycidyl ether(BADGE.H_(2)O),bis...The present study sought to investigate the migration of target bisphenols,such as bisphenol-A(BPA),bisphenol-F(BPA),bisphenol-A diglycidyI ether(BADGE),bisphenol-A(2,3-dihydroxypropyl)glycidyl ether(BADGE.H_(2)O),bisphenol-A bis(2,3-dihydroxypropyl)ether(BADGE.2H_(2)O),and bisphenol F diglycidyl ether(BFDGE)in 102 samples of several canned seafood,namely canned Antarctic krill,scallop,oysters,mussel,clam,and mantis shrimp stored for months at different temperatures through a high-performance liquid chromatographic-fluorescence detector com-bined with a microwave-assisted extraction method.Except for BFDGE,the other five bisphenols were observed in most of the analyzed sam-ples.The canned shrimp showed the highest migration of BPA(0.089 mg/kg),exceeding the specific migration limit(SML)of BPA(0.05 mg/kg)specified by the European Union,while the migration levels of BADGE and its derivatives were within their SMLs.The migration behavior of bisphenols in the canned seafood was majorly affected by the analytes,storage conditions,and food types.BPA,BADGE.H_(2)O,and BADGE 2H_(2)O were characterized by a rapid migration during the first half of the shelf life,which increased with the increase of temperature,followed by a stabilization or decline of their concentrations for prolonged durations.Besides,the migration of target bisphenols was significantly influenced by the storage temperature in some seafood species.Notably,higher migration level of BPA was found in samples with higher fat content.The average dietary exposure of Chinese adults to BPA,BPF,BADGE.2H_(2)O,BADGE.H_(2)O,and BADGE of canned seafood was estimated at 11.69,1.21,6.47,8.74,and 4.71 ng/(kg d),respectively.The target hazard quotient values of all the analyzed bisphenols were below 1 for the Chinese adults,suggesting an insignificant exposure to these bisphenols through canned seafood consumption.展开更多
基金Project supported by Key Industrial Engineering Project of Guizhou Province([2013]3041)High-level Talent Project of Guizhou Province(TZJF-2011-54)Guizhou Science and Technology Support Plan Project([2017]2892)
文摘Zhijin phosphorus ore is a moderate and low-grade phosphorus rare-earth ore contained in mines. The separation and extraction of associated rare earth are important research topics. In this study, the migration behavior of rare earth during the thermal decomposition of Zhijin phosphorus ore and the separation and extraction of rare earth in phosphorus slag are discussed systematically. During the thermal decomposition process of phosphorus ore, almost all of the associated rare earth enters into the phosphorus slag phase but does not enter into the ferrophosphorus or gas phases. Amorphous calcium metasilicate and calcium fluosilicate are major components of phosphorus slag, and rare earth mainly exists as a calsil solid solution. Hydrochloric acid was used for acidolysis of the phosphorous slag. Under the following conditions, 96% of the rare earth in the phosphorous slag can be dissolved in the acidolysis solution: acid excess coefficient of 1.5, reaction time of 50 min and reaction temperature of 50℃. The rare earth in the acidolysis solution was separated and recycled using oxalic acid as a precipitator and NaOH as a pH modifier. At pH of 1.7, rare-earth-enriched matter with rare-earth content of 2.1 wt% was obtained, and the recovery of the rare earth was 88%.
基金supported by the 2006 Chinese National AIDS Prevention Social Mobilization Project 06-I-37
文摘Objective To estimate the relationship between migration and HIV risky behavior when controlling for gender, age, and educational levels and to evaluate the gender differences in migration, HIV knowledge, and HIV risky behaviors among rural youth in China. Methods A cross-sectional, anonymous, investigative questionnaire for 1710 unmarried, out-of-school rural youth, aged between 15 and 24 years, was handed out in Gongzhuling county of Jilin province, China. Results 58.5% of participants had a history of migration, irrespective of gender. There were gender differences observed in other factors such as drug abuse(4.3% for males and 5.5% for females, P〈0.01), multiple sexual partners(24.1% for males and 44.1% for females, P〈0.01), and HIV knowledge rate(35.2% for males and 25.5% for females, P〈0.001). While controlling for gender, age, and educational levels, the relationships between migration and drug abuse, selling sex, and non usage of condoms during last instance of sexual activity were found to be significant. The cases of premarital sex and multiple sexual partners were both not found to be related to migration. Conclusion Among rural youth, the HIV risky behavior such as drug abuse, selling sex, and lack of condom use, is significantly related to migration, while premarital sex and multiple sexual partners seem unrelated to migration.
基金Project supported by the Education Department of Jiangxi Province,China(Grant No.GJJ160337)。
文摘First-principles calculations are performed to investigate the effect of strain on the electrochemical performance of Janus MoSSe monolayer.The calculation focuses on the specific capacity,intercalation potential,electronic structure,and migration behavior of Li-ion under various strains by using the climbing-image nudged elastic band method.The result shows that the specific capacity is nearly unchanged under strain.But interestingly,the tensile strain can cause the intercalation potential and Li-ion migration energy barrier increase in MoSSe monolayer,whereas the compressive strain can lead to the intercalation potential and energy barrier decreasing.Thus,the rate performance of the MoSSe anode is improved.By analyzing the potential energy surface of MoSSe surface and equilibrium adsorption distance of Li-ion,we explain the physical origin of the change in the intercalation potential and migration energy barrier.The increase of MoSSe potential energy surface and the decrease of adsorption distance caused by tensile strain are the main reason that hinders Li-ion migration.
基金supported by the National Natural Science Foundation of China under Grant No.51975152.
文摘The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding of Al alloy retaining continuous oxide layers was successfully achieved in the air by a low-temperature and low-pressure diffusion bonding mothed using a Zn interlayer.During the bonding processes,conducted at 360℃ and 3 MPa,Zn diffused into Al through cracks of thin oxide layers to form the joint composed Al/(diffusion layer)/(oxide layer)/(Zn)/(oxide layer)/(diffusion layer)/Al.The diffusion layers were composed of Zn-Al eutectoid,and the oxide layer included nanocrystals and amorphous Al_(2)O_(3).The shear strength of joints containing continuous oxide layers was about 30 MPa.Interestingly,the migration behavior toward the joint center of the interfacial oxide layers was observed with consuming of the Zn interlayer.The cracking phenomenon,the“subcutaneous diffusion”and the migration behavior of oxide layers were verified and analyzed by the diffusion bonding of anodized 6063Al-6063Al.Subsequently,the dynamic migration mechanism of oxide layers with elements diffusion and bonding interface strengths were discussed in detail.The ability to join Al alloys in the air at low temperatures and low pressure suggests a highly practical and economic method for diffusion bonding.
基金the National Key Research and Development Program of China(No.2018YFD0901006).
文摘The present study sought to investigate the migration of target bisphenols,such as bisphenol-A(BPA),bisphenol-F(BPA),bisphenol-A diglycidyI ether(BADGE),bisphenol-A(2,3-dihydroxypropyl)glycidyl ether(BADGE.H_(2)O),bisphenol-A bis(2,3-dihydroxypropyl)ether(BADGE.2H_(2)O),and bisphenol F diglycidyl ether(BFDGE)in 102 samples of several canned seafood,namely canned Antarctic krill,scallop,oysters,mussel,clam,and mantis shrimp stored for months at different temperatures through a high-performance liquid chromatographic-fluorescence detector com-bined with a microwave-assisted extraction method.Except for BFDGE,the other five bisphenols were observed in most of the analyzed sam-ples.The canned shrimp showed the highest migration of BPA(0.089 mg/kg),exceeding the specific migration limit(SML)of BPA(0.05 mg/kg)specified by the European Union,while the migration levels of BADGE and its derivatives were within their SMLs.The migration behavior of bisphenols in the canned seafood was majorly affected by the analytes,storage conditions,and food types.BPA,BADGE.H_(2)O,and BADGE 2H_(2)O were characterized by a rapid migration during the first half of the shelf life,which increased with the increase of temperature,followed by a stabilization or decline of their concentrations for prolonged durations.Besides,the migration of target bisphenols was significantly influenced by the storage temperature in some seafood species.Notably,higher migration level of BPA was found in samples with higher fat content.The average dietary exposure of Chinese adults to BPA,BPF,BADGE.2H_(2)O,BADGE.H_(2)O,and BADGE of canned seafood was estimated at 11.69,1.21,6.47,8.74,and 4.71 ng/(kg d),respectively.The target hazard quotient values of all the analyzed bisphenols were below 1 for the Chinese adults,suggesting an insignificant exposure to these bisphenols through canned seafood consumption.