than 2.2, the electromagnetic pressure acting on melt can be simply expressed as Pm =B^2/wμ, and the melt shape would be known only by measuring the distribution of magnetic flux density. As a is small and makes the ...than 2.2, the electromagnetic pressure acting on melt can be simply expressed as Pm =B^2/wμ, and the melt shape would be known only by measuring the distribution of magnetic flux density. As a is small and makes the ratio a/8 less than 2.2, the melt shape and electromagnetic pressure for confining and shaping are determined not only by magnetic flux density B but also by melt thickness a, electromagnetic parameter μγ and current frequency f. In this paper, an equation used to calculate electromagnetic pressure acting on 'thin plate-form melt' is brought forward. The equation gives a precise relationship between electromagnetic pressure factor p and melt thickness a, electromagnetic parameter μγ and current frequency f.展开更多
目的研究马口铁包装水果罐头中锡的浓度变化和形态分布。方法采用电感耦合等离子体串联质谱法(inductively coupled plasma tandem mass spectrometry,ICP-MS/MS)测定马口铁包装水果罐头的锡含量,并分析锡浓度随储存时间、加热次数的变...目的研究马口铁包装水果罐头中锡的浓度变化和形态分布。方法采用电感耦合等离子体串联质谱法(inductively coupled plasma tandem mass spectrometry,ICP-MS/MS)测定马口铁包装水果罐头的锡含量,并分析锡浓度随储存时间、加热次数的变化特点;采用高效液相色谱电感耦合等离子体串联质谱法(high performance liquid chromatography-inductively coupled plasma tandem mass spectrometry,HPLC-ICP-MS/MS)测定并分析罐头中锡的形态分布。结果镀锡马口铁包装水果罐头中锡含量在生产日期3个月内为27.17~183.81mg/kg,生产日期12个月时为54.56~265.44mg/kg,锡浓度随储存时间、加热次数而明显增加,溶出锡为无机形态,以二价锡Sn[II]为主,未检测到锡的有机形态。结论马口铁包装水果罐头中锡随储存时间和加热次数而大量增加,但都以无机锡的形态存在,因吸收利用率低,毒性较低;尽量选择靠近生产日期的产品,且不要罐内加热食用。展开更多
基金National Natural Science Foundation! No. 59995440National PostDoctor Science Foundation !([19971 11)of China
文摘than 2.2, the electromagnetic pressure acting on melt can be simply expressed as Pm =B^2/wμ, and the melt shape would be known only by measuring the distribution of magnetic flux density. As a is small and makes the ratio a/8 less than 2.2, the melt shape and electromagnetic pressure for confining and shaping are determined not only by magnetic flux density B but also by melt thickness a, electromagnetic parameter μγ and current frequency f. In this paper, an equation used to calculate electromagnetic pressure acting on 'thin plate-form melt' is brought forward. The equation gives a precise relationship between electromagnetic pressure factor p and melt thickness a, electromagnetic parameter μγ and current frequency f.
文摘目的研究马口铁包装水果罐头中锡的浓度变化和形态分布。方法采用电感耦合等离子体串联质谱法(inductively coupled plasma tandem mass spectrometry,ICP-MS/MS)测定马口铁包装水果罐头的锡含量,并分析锡浓度随储存时间、加热次数的变化特点;采用高效液相色谱电感耦合等离子体串联质谱法(high performance liquid chromatography-inductively coupled plasma tandem mass spectrometry,HPLC-ICP-MS/MS)测定并分析罐头中锡的形态分布。结果镀锡马口铁包装水果罐头中锡含量在生产日期3个月内为27.17~183.81mg/kg,生产日期12个月时为54.56~265.44mg/kg,锡浓度随储存时间、加热次数而明显增加,溶出锡为无机形态,以二价锡Sn[II]为主,未检测到锡的有机形态。结论马口铁包装水果罐头中锡随储存时间和加热次数而大量增加,但都以无机锡的形态存在,因吸收利用率低,毒性较低;尽量选择靠近生产日期的产品,且不要罐内加热食用。
基金supported by the National Key Research and Development Program of China(No.2018YFA0707300)the National Natural Science Foundation of China(Nos.51901151,51905372,52275362,52171122)China Postdoctoral Science Foundation(Nos.2020M680918,2021T140503)。