A detailed mineralogical characterization of a tin-polymetallic ore from Mengzi,Yunnan Province,China,was undertaken by automated electron microprobe-based mineral mapping and quantitative analysis methods.The results...A detailed mineralogical characterization of a tin-polymetallic ore from Mengzi,Yunnan Province,China,was undertaken by automated electron microprobe-based mineral mapping and quantitative analysis methods.The results show that the most valuable metal is Sn（0.98%,mass fraction）.The main tin minerals are cassiterite and stannite,which account for 94.90% of total tin.Other metals,such as Cu（0.261%）,Zn（0.612%） and Pb（0.296%） can also be seen as valuable metal to be recovered.Minerals such as pyrrhotite,pyrite,arsenopyrite,sphalerite,galena and chalcopyrite are disseminated in the ore.Quartz,sericite and dolomite are the main gangue.The optimal grinding fineness should be chosen as 0.037 mm to make sure that most of the tin minerals can be liberated from other minerals.展开更多
In this paper,effects of conditions in phenol sulfonic acid(PSA) plating for tin coating of MR low carbon aluminum killed steel on trace Pb were examined.Trace Pb was measured by atomic absorption spectrometry(AAS)and...In this paper,effects of conditions in phenol sulfonic acid(PSA) plating for tin coating of MR low carbon aluminum killed steel on trace Pb were examined.Trace Pb was measured by atomic absorption spectrometry(AAS)and glow discharge spectrometry,and coating morphology was observed by scanning electronic microscopy(SEM).Corrosion resistance of the tin coating was analyzed by electrochemical methods.The results indicated that Pb content in the tin coating reduced as bath temperature increased.When the temperature exceeded40 ℃,the grains in the coating were coarse and loose,reducing the corrosion resistance.As current density increased,Pb content increased rapidly,while low current density plating could lead to drain regions.The plating speed had no obvious effect on trace Pb in tin coating.In the tin plating layer,Pb was enriched at the surface and gradually reduced to zero along the depth.At bath temperature of 40 ℃ and current density of 20 A·dm^(-2),the amount of Pb could be less than 100 mg·kg^(-1) with excellent corrosion resistance.展开更多
A novel process for preparing tin oxide thin films directly on copper foil by electrodeposition was developed. An optimal preparation technology to obtain SnOz thin films was proposed with current density of 8 mA/cm^2...A novel process for preparing tin oxide thin films directly on copper foil by electrodeposition was developed. An optimal preparation technology to obtain SnOz thin films was proposed with current density of 8 mA/cm^2, the time of deposition of 120 min, the concentration of tin dichloride of 0.02 mol/L and the concentration of dissociated acid of 0. 03 mol/L. The phase identification, microstructure and morphology of the thin films were investigated by thermogravimetric analysis and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectra,scanning electron microscopy and transmission electron microscopy. The as-deposited thin film was composed of SnO2·xH2O was obtained by drying at room temperature. Nanocrystalline SnO2 thin film having tetragonal structure with average grain size in the range of 8 to 20 nm and porous, uniform surface was obtained by heat-treating the as-deposited film at 400 ℃ for 2 h. Electrochemical characterization shows that SnO2 film can deliver a discharge capacity of 798 mAh/g and the SnO2 film with smooth surface and annealed at 400 ℃ for 2 h has better cycle performance than that with rough surface and annealed at 150℃ for 10 h.展开更多
Under the globalization, the coastal China becomes a hot area of the international manufacturing investment due to its priority location, excellent environment, lower labor and land costs, etc. However, the fast indus...Under the globalization, the coastal China becomes a hot area of the international manufacturing investment due to its priority location, excellent environment, lower labor and land costs, etc. However, the fast industrialization has aroused the great demolishment to the local ecological environment. For example, the heavy water eutrophication in Taihu Lake has affected the source of drinking water for the cities around the lake. Anyway, in order to keep the economic increase and reduce the resource ex- pense and pollution at the same time, it is necessary to encourage the greening of industrial enterprises actively for sustainable de- velopment. On the basis of the investigation of industrial enter- prises in Wuxi city within Taihu Basin, the relatively developed region in coastal China, this paper analyzed the development process of green industry. This article concluded that governmen- tal principal is the main pressure for enterprises to protect envi- ronment while the market factor plays a part role. Moreover, en- terprises in the high technology development zone work better in environmental protection than those in the villages and towns, while the large enterprises work better than those small enterprises.展开更多
Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable, which is widely applied to the third generation (3G) mobile communication system. However, in ...Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable, which is widely applied to the third generation (3G) mobile communication system. However, in the traditional horizontal tin-plating process, disadvantages such as the pinhole defects and low productivity effect cannot be avoided. In this paper, a vertical tin-plating process was proposed to reduce the pinhole defects and improve the tincoating quality. Compared with the traditional horizontal tin-plating process, the immersion length was reduced from 300-400 mm to 10-100 mm and the tin-plating time was reduced from 7 s to 3 s in the proposed method. The experimental results indicate that immersion length and time are key parameters for the tin-plating quality. With this new tin-plating process, the experimental results show that the pinhole defects can be eliminated effectively by controlling the immersion depth below 100 mm and tin-plating time at 3 s. The thickness of tin-coating increased from not more than 5 μm to 12.3 μm with the proposed vertical tin-plating process. Meanwhile, the thickness of the intermetallic compounds (IMCs) layer between the tin-coating and copper wires was reduced from 3.26 μm to 0.62 μm if the immersion time decreased from 30 s to 1 s. Besides, a self-developed flux, which possesses a boiling point or decomposed temperature of active components over 300℃, exhibits a better efficiency in reducing the pinhole formation.展开更多
The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry...The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand （COD） and NH4＋-N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 mE/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.展开更多
AT the"International Exchanges on Open Innovation"held in San Francisco in 2015,one question was raised:"If you were an engineer and would like to make a creative idea into a product within one or two w...AT the"International Exchanges on Open Innovation"held in San Francisco in 2015,one question was raised:"If you were an engineer and would like to make a creative idea into a product within one or two weeks,which city would be your choice?"Founder&CTO of Spark Labs Global Ventures,Zachary Crockett’s answer was Shenzhen.Known as entrepreneurs’heaven,Shenzhen gives priority to innovation education and make students’dreams reality.展开更多
In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and th...In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and the hardness and electrical conductivity properties of the Cu-Cr-Sn-Zn alloy was set up.The results show that the ANN model is a very useful and accurate tool for the property analysis and prediction of aging Cu-Cr-Sn-Zn alloy.Aged at 470-510 ℃ for 4-1 h,the optimal combinations of hardness 110-117(HV) and electrical conductivity 40.6-37.7 S/m are available respectively.展开更多
PtSnNa/AlSBA-15 catalysts with different amounts of Sn were prepared for propane dehydrogenation.The catalysts were characterized by XRF,BET,H2 chemisorption,NH3-TPD,H2-TPR,and TPO techniques.Test results indicated th...PtSnNa/AlSBA-15 catalysts with different amounts of Sn were prepared for propane dehydrogenation.The catalysts were characterized by XRF,BET,H2 chemisorption,NH3-TPD,H2-TPR,and TPO techniques.Test results indicated that the presence of tin not only modified the acid function and the interfacial character between metal and support,but also reduced the coke deposition effectively.Among these catalysts investigated thereby,the PtSn(0.7%)Na/AlSBA-15 catalyst had the best catalytic performance in terms of propane conversion and stability.With the continuous addition of Sn,more amounts of Sn0 species appeared,which was unfavorable to the reaction.The PtSn(0.7%)Na/AlSBA-15 catalyst was parametrically characterized in order to obtain necessary information to integrate the process operating conditions.A weight hourly space velocity of 3 h-1,a reaction temperature of 610 ℃ and a H2/C3H8 molar ratio of 0.25 were found to be optimum conditions for achieving a higher dehydrogenation activity of the catalyst.展开更多
While professional associations connected to higher education such as the American Association of University Professors fought to defend its members against the anti-communism of the 1950s, evidence suggests that teac...While professional associations connected to higher education such as the American Association of University Professors fought to defend its members against the anti-communism of the 1950s, evidence suggests that teachers＇ unions failed in this role. Drawing upon the archival records and publications of the American Federation of Teachers and National Education Association, the following paper argues that the ideological inclinations of union leaders hindered their efforts to protect K-12 public school teachers. The attacks on academic freedom rights during the McCarthy era would thus have implications for years to come in regard to the ability of K-12 teachers to exercise their intellectual autonomy.展开更多
Natural grasslands are increasingly subjected to the dual stresses of grazing pressures and climate change.However,the contribution of human activities,especially grassland ecology conservation projects,to grassland i...Natural grasslands are increasingly subjected to the dual stresses of grazing pressures and climate change.However,the contribution of human activities,especially grassland ecology conservation projects,to grassland improvement remains ambiguous.Utilizing MODIS satellite data in conjunction with the VPM model,the gross primary productivity(GPP)changes in the Xilingol grassland from 2000 to 2020 were assessed.Based on GPP data derived from remote sensing,this study quantitatively assessed the spatiotemporal dynamics of the impacts of climate change and human activities on the productivity of grassland in the Xilingol League.From 2000 to 2020,the grasslands exhibited a greening trend characterized by a significant annual GPP increment of 2.66 gC m^(-2) yr^(-1)(P<0.05).Climate change and human activities jointly contributed to this greening trend,with relative contribution rates of 55%and 45%,respectively.However,the relative contributions of climate change and human activities to the trend of GPP varied greatly in different regions.Climate change emerged as the principal driver in the central and eastern regions of Xilingol League with robust grass growth,accounting for more than 65%of the GPP enhancement.Conversely,human activities were the dominant factors in less verdant western regions and the agro-pastoral ecotone,representing more than 60%of the GPP change.Grassland productivity was sensitive to grassland ecological restoration measures,with significant changes in the trends of grassland productivity attributed to human activities in pivotal policy implementation years such as 2005 and 2011.Specifically,measures such as the control of wind/sand sources and returning grazing land to grassland from 2000 to 2005 gradually alleviated the pressure of human activities on grassland productivity,as they significantly improved vegetation growth in high-quality grasslands.Under the forage-livestock balance policy from 2005 to 2011,inadequate compensation for grassland ecological protection led to a significant reduction in GPP,as some herders increased their livestock holdings despite grazing restrictions,and this particularly affected the high-quality grasslands.The implementation of the Grassland Ecological Protection Subsidy and Reward Program from 2011 to 2020 generally promoted the recovery of productivity in eastern and western Xilingol League grasslands,but significant ecological pressure persisted.This study provides theoretical support for optimizing grassland ecosystem management and forming a virtuous cycle of grassland conservation in pastoral areas.展开更多
基金Project(50774094) supported by the National Natural Science Foundation of ChinaProject(2010CB630905) supported the National Basic Research Program of China
文摘A detailed mineralogical characterization of a tin-polymetallic ore from Mengzi,Yunnan Province,China,was undertaken by automated electron microprobe-based mineral mapping and quantitative analysis methods.The results show that the most valuable metal is Sn（0.98%,mass fraction）.The main tin minerals are cassiterite and stannite,which account for 94.90% of total tin.Other metals,such as Cu（0.261%）,Zn（0.612%） and Pb（0.296%） can also be seen as valuable metal to be recovered.Minerals such as pyrrhotite,pyrite,arsenopyrite,sphalerite,galena and chalcopyrite are disseminated in the ore.Quartz,sericite and dolomite are the main gangue.The optimal grinding fineness should be chosen as 0.037 mm to make sure that most of the tin minerals can be liberated from other minerals.
基金Supported by the Fundamental Research Funds for the Central Universities(04040022212005)
文摘In this paper,effects of conditions in phenol sulfonic acid(PSA) plating for tin coating of MR low carbon aluminum killed steel on trace Pb were examined.Trace Pb was measured by atomic absorption spectrometry(AAS)and glow discharge spectrometry,and coating morphology was observed by scanning electronic microscopy(SEM).Corrosion resistance of the tin coating was analyzed by electrochemical methods.The results indicated that Pb content in the tin coating reduced as bath temperature increased.When the temperature exceeded40 ℃,the grains in the coating were coarse and loose,reducing the corrosion resistance.As current density increased,Pb content increased rapidly,while low current density plating could lead to drain regions.The plating speed had no obvious effect on trace Pb in tin coating.In the tin plating layer,Pb was enriched at the surface and gradually reduced to zero along the depth.At bath temperature of 40 ℃ and current density of 20 A·dm^(-2),the amount of Pb could be less than 100 mg·kg^(-1) with excellent corrosion resistance.
文摘A novel process for preparing tin oxide thin films directly on copper foil by electrodeposition was developed. An optimal preparation technology to obtain SnOz thin films was proposed with current density of 8 mA/cm^2, the time of deposition of 120 min, the concentration of tin dichloride of 0.02 mol/L and the concentration of dissociated acid of 0. 03 mol/L. The phase identification, microstructure and morphology of the thin films were investigated by thermogravimetric analysis and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectra,scanning electron microscopy and transmission electron microscopy. The as-deposited thin film was composed of SnO2·xH2O was obtained by drying at room temperature. Nanocrystalline SnO2 thin film having tetragonal structure with average grain size in the range of 8 to 20 nm and porous, uniform surface was obtained by heat-treating the as-deposited film at 400 ℃ for 2 h. Electrochemical characterization shows that SnO2 film can deliver a discharge capacity of 798 mAh/g and the SnO2 film with smooth surface and annealed at 400 ℃ for 2 h has better cycle performance than that with rough surface and annealed at 150℃ for 10 h.
基金Under the auspices of the National Natural Sci-ence Foundation of China (No.40371031).
文摘Under the globalization, the coastal China becomes a hot area of the international manufacturing investment due to its priority location, excellent environment, lower labor and land costs, etc. However, the fast industrialization has aroused the great demolishment to the local ecological environment. For example, the heavy water eutrophication in Taihu Lake has affected the source of drinking water for the cities around the lake. Anyway, in order to keep the economic increase and reduce the resource ex- pense and pollution at the same time, it is necessary to encourage the greening of industrial enterprises actively for sustainable de- velopment. On the basis of the investigation of industrial enter- prises in Wuxi city within Taihu Basin, the relatively developed region in coastal China, this paper analyzed the development process of green industry. This article concluded that governmen- tal principal is the main pressure for enterprises to protect envi- ronment while the market factor plays a part role. Moreover, en- terprises in the high technology development zone work better in environmental protection than those in the villages and towns, while the large enterprises work better than those small enterprises.
基金Supported by Science and Technology Support Project of Tianjin Science and Technology Commission (No.10ZCKFGX3500)
文摘Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable, which is widely applied to the third generation (3G) mobile communication system. However, in the traditional horizontal tin-plating process, disadvantages such as the pinhole defects and low productivity effect cannot be avoided. In this paper, a vertical tin-plating process was proposed to reduce the pinhole defects and improve the tincoating quality. Compared with the traditional horizontal tin-plating process, the immersion length was reduced from 300-400 mm to 10-100 mm and the tin-plating time was reduced from 7 s to 3 s in the proposed method. The experimental results indicate that immersion length and time are key parameters for the tin-plating quality. With this new tin-plating process, the experimental results show that the pinhole defects can be eliminated effectively by controlling the immersion depth below 100 mm and tin-plating time at 3 s. The thickness of tin-coating increased from not more than 5 μm to 12.3 μm with the proposed vertical tin-plating process. Meanwhile, the thickness of the intermetallic compounds (IMCs) layer between the tin-coating and copper wires was reduced from 3.26 μm to 0.62 μm if the immersion time decreased from 30 s to 1 s. Besides, a self-developed flux, which possesses a boiling point or decomposed temperature of active components over 300℃, exhibits a better efficiency in reducing the pinhole formation.
基金Projects(5114703,51004059/E041601)supported by the National Natural Science Foundation of China
文摘The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand （COD） and NH4＋-N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 mE/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.
文摘AT the"International Exchanges on Open Innovation"held in San Francisco in 2015,one question was raised:"If you were an engineer and would like to make a creative idea into a product within one or two weeks,which city would be your choice?"Founder&CTO of Spark Labs Global Ventures,Zachary Crockett’s answer was Shenzhen.Known as entrepreneurs’heaven,Shenzhen gives priority to innovation education and make students’dreams reality.
基金Project(2006AA03Z528) supported by the National High-Tech Research and Development Program of ChinaProject(102102210174) supported by the Science and Technology Research Project of Henan Province,ChinaProject(2008ZDYY005) supported by Special Fund for Important Forepart Research in Henan University of Science and Technology
文摘In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and the hardness and electrical conductivity properties of the Cu-Cr-Sn-Zn alloy was set up.The results show that the ANN model is a very useful and accurate tool for the property analysis and prediction of aging Cu-Cr-Sn-Zn alloy.Aged at 470-510 ℃ for 4-1 h,the optimal combinations of hardness 110-117(HV) and electrical conductivity 40.6-37.7 S/m are available respectively.
基金the Production and Research Prospective Joint Research Project(BY2009153)the Science and Technology Support Program(BE2008129) of Jiangsu Province of Chinathe National Nature Science Foundation of China(50873026) for financial supports
文摘PtSnNa/AlSBA-15 catalysts with different amounts of Sn were prepared for propane dehydrogenation.The catalysts were characterized by XRF,BET,H2 chemisorption,NH3-TPD,H2-TPR,and TPO techniques.Test results indicated that the presence of tin not only modified the acid function and the interfacial character between metal and support,but also reduced the coke deposition effectively.Among these catalysts investigated thereby,the PtSn(0.7%)Na/AlSBA-15 catalyst had the best catalytic performance in terms of propane conversion and stability.With the continuous addition of Sn,more amounts of Sn0 species appeared,which was unfavorable to the reaction.The PtSn(0.7%)Na/AlSBA-15 catalyst was parametrically characterized in order to obtain necessary information to integrate the process operating conditions.A weight hourly space velocity of 3 h-1,a reaction temperature of 610 ℃ and a H2/C3H8 molar ratio of 0.25 were found to be optimum conditions for achieving a higher dehydrogenation activity of the catalyst.
文摘While professional associations connected to higher education such as the American Association of University Professors fought to defend its members against the anti-communism of the 1950s, evidence suggests that teachers＇ unions failed in this role. Drawing upon the archival records and publications of the American Federation of Teachers and National Education Association, the following paper argues that the ideological inclinations of union leaders hindered their efforts to protect K-12 public school teachers. The attacks on academic freedom rights during the McCarthy era would thus have implications for years to come in regard to the ability of K-12 teachers to exercise their intellectual autonomy.
基金The National Key Research and Development Program of China(2022YFF1301802)。
文摘Natural grasslands are increasingly subjected to the dual stresses of grazing pressures and climate change.However,the contribution of human activities,especially grassland ecology conservation projects,to grassland improvement remains ambiguous.Utilizing MODIS satellite data in conjunction with the VPM model,the gross primary productivity(GPP)changes in the Xilingol grassland from 2000 to 2020 were assessed.Based on GPP data derived from remote sensing,this study quantitatively assessed the spatiotemporal dynamics of the impacts of climate change and human activities on the productivity of grassland in the Xilingol League.From 2000 to 2020,the grasslands exhibited a greening trend characterized by a significant annual GPP increment of 2.66 gC m^(-2) yr^(-1)(P<0.05).Climate change and human activities jointly contributed to this greening trend,with relative contribution rates of 55%and 45%,respectively.However,the relative contributions of climate change and human activities to the trend of GPP varied greatly in different regions.Climate change emerged as the principal driver in the central and eastern regions of Xilingol League with robust grass growth,accounting for more than 65%of the GPP enhancement.Conversely,human activities were the dominant factors in less verdant western regions and the agro-pastoral ecotone,representing more than 60%of the GPP change.Grassland productivity was sensitive to grassland ecological restoration measures,with significant changes in the trends of grassland productivity attributed to human activities in pivotal policy implementation years such as 2005 and 2011.Specifically,measures such as the control of wind/sand sources and returning grazing land to grassland from 2000 to 2005 gradually alleviated the pressure of human activities on grassland productivity,as they significantly improved vegetation growth in high-quality grasslands.Under the forage-livestock balance policy from 2005 to 2011,inadequate compensation for grassland ecological protection led to a significant reduction in GPP,as some herders increased their livestock holdings despite grazing restrictions,and this particularly affected the high-quality grasslands.The implementation of the Grassland Ecological Protection Subsidy and Reward Program from 2011 to 2020 generally promoted the recovery of productivity in eastern and western Xilingol League grasslands,but significant ecological pressure persisted.This study provides theoretical support for optimizing grassland ecosystem management and forming a virtuous cycle of grassland conservation in pastoral areas.
