A helicon wave plasma source in a tube of ring permanent magnets(PMs)has been constructed to study the effect of the conflguration of the magnetic fleld with zero magnetic points on plasma parameters.This device also ...A helicon wave plasma source in a tube of ring permanent magnets(PMs)has been constructed to study the effect of the conflguration of the magnetic fleld with zero magnetic points on plasma parameters.This device also serves as an exploration platform for a simple,compact helicon wave plasma source adaptable to engineering applications.A small-diameter(26 mm)highdensity(~10^(18)m^(-3))blue core plasma is produced in~1 Pa argon by helicon RF(radiofrequency)discharge using a NagoyaⅢantenna under magnetic fleld(~2 k G)of compact ring PMs(length~204 mm).Operational parameters,i.e.RF power and neutral gas pressure are scanned and plasma density is measured by an RF compensated probe to explore the operating characteristics of the device.Iconic feature of a helicon discharge,such as blue core plasmas and E-H-W mode transitions are well observed in the device,despite the wavelength calculated using the conventional dispersion relation of a bounded whistler waves(Chen 1991 Plasma Phys.Control.Fusion 33339)is order of magnitudes longer than the length of the plasma in this device which seems to suggest that such helicon device is impossible.Surprisingly,the wavelength calculated by the unbounded whistle wave dispersion formula in turn suggests the occurrence of a half wavelength resonance.展开更多
In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behav...In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behavior was investigated.By reducing the electron beam power instantly and gradually at reduction rates of 1,3 and 5 kW/min,it is found that W is enriched at the bottom of ingots as the melt solidifies.The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases,attributed to the k0(W)>1 andρ(W)>ρ(Ce).Overall,the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot,and the purity of Ce increases from 99.932 wt%to 99.995 wt%by this combined method.Additionally,this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.展开更多
The stellarator has inherent advantages over the tokamak in achieving steady-state operation,especially due to its absence of disruptions and lack of need for current drive and the associated recirculating power.In re...The stellarator has inherent advantages over the tokamak in achieving steady-state operation,especially due to its absence of disruptions and lack of need for current drive and the associated recirculating power.In recent years,there have been remarkable advances in the field of stellarator optimization,where precisely quasi-symmetric and precisely quasi-isodynamic magnetic configurations have been achieved with coils,allowing the neoclassical transport and energetic particle losses of stellarators to be reduced to levels comparable to those of tokamaks.At the same time,the development of high-temperature superconducting magnet technology will potentially double the magnetic field strength of stellarators.While these strong fields are expected to introduce new challenges,and while turbulent transport remains a common challenge for both stellarators and tokamaks,the combination of these physical and technological advances results in the expectation that stellarators will become a competitive approach to tokamaks for realizing steady-state fusion.展开更多
Inorganic-organic hybrid WOx-ethylenediamine (WO/-EDA) nanowires have been produced by a simple, low-cost and high-yield solvothermal method. These WO/-EDA hybrid nanowires have unique lamellar mesostructures with a...Inorganic-organic hybrid WOx-ethylenediamine (WO/-EDA) nanowires have been produced by a simple, low-cost and high-yield solvothermal method. These WO/-EDA hybrid nanowires have unique lamellar mesostructures with an alternate stacking of an interconnected [WO6] octahedral layer and a monolayer of ethylenediamine molecules. This hybrid structure integrated the functionality of ethylenediamine with the stability of the WOx frameworks. In situ synchrotron- radiation X-ray diffraction is used to elucidate a possible formation mechanism of the hybrid WOx-EDA. The nanowire morphology, lamellar structure and abundant functional amino groups endow them with versatile abilities. For example, in heavy metal ion adsorption the WOx-EDA nanowires display exceptional adsorption capabilities of 925 mg·g^-1 for Pb^2+ and 610 mg·g^-1 for UO2^2+. The nanowires also show outstanding stability and activity as a heterogeneous base catalyst in the Knoevenagel condensation reaction at room temperature. The catalyst can be recycled and reused for 20 cycles with nearly 100% yields. This study provides a new strategy to design inorganic-organic hybrid materials, and offers a multifunctional material that is a highly efficient adsorbent and sustainable catalyst.展开更多
Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indi...Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indicate that,the evaporation coefficient of Fe in La metal is 35-175 at 1800-3000 K,and Fe impurity can be removed by EBM;the removal efficiency of Fe impurity is improved with the increasing EBM power,the Fe concentration is significantly decreased from 1482 to 0.1 μg/g under 50 kW and 2400 s;the reaction of Fe removal by EBM follows the first-order rate law,and Fe impurity is removed by evaporation as a single atom;transport from the La melt to the liquid boundary layer of the Fe atom is rate-controlling step in the EBM when the EBM power is 30-50 kW.展开更多
In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound...In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques.The results show that the reduction of Y(Ⅲ)at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons,which is controlled by the mass transfer rate.The diffusion coefficient of Y(Ⅲ)in the fluoride salt at a temperature of 1323 K is 5.0238×10^(-3)cm^(2)/s.Moreover,the thermodynamic properties associated with the formation of Y-Al intermetallic compounds were estimated using a steady-state electrochemical method.Y-Al intermediate alloy containing 92 wt%yttrium was prepared by constant current electrolysis at 1323 K in the LiF-YF_(3)-AIF_(3)-Y_(2)O_(3)(6 wt%)-Al_(2)O_(3)(1 wt%)system at a cathodic current density of 8 A/cm^(2)for 2 h.The Y-Al intermediate alloy is mainly composed ofα-Y2Al and Y phases.The development and application of this innovative technology have solved major technical problems,such as a long production process,high energy consumption,and serious segregation of alloy elements at this stage.展开更多
The bogie is a crucial component of urban rail vehicles,and its performance plays a decisive role in the safe operation of vehicles.Aiming at the intelligent operation and maintenance requirements of rail transit equi...The bogie is a crucial component of urban rail vehicles,and its performance plays a decisive role in the safe operation of vehicles.Aiming at the intelligent operation and maintenance requirements of rail transit equipment,in this paper,it takes several key parts of the urban rail vehicle bogie system as research objects,such as motor bearings,frames,fasteners,etc.,and proposes a three-dimensional(3D)visual collaborative maintenance method.Firstly,a multi-sensor urban rail vehicle bogie running simulation experiment analysis platform was constructed,thereby establishing a database of running state and performance characteristics of the bogie in the whole life cycle.Then,the health status of key components of bogie was predicted by the state interval prediction model.Finally,the three-dimensional visual collaborative maintenance model proposed in this paper was integrated to realize the early warning of the bogie operation faults,3D precise guidance of automatic location and maintenance operation information,and collaborative sharing of visual information among multiple users.展开更多
基金supported by National Natural Science Foundation of China(No.U19A20113)。
文摘A helicon wave plasma source in a tube of ring permanent magnets(PMs)has been constructed to study the effect of the conflguration of the magnetic fleld with zero magnetic points on plasma parameters.This device also serves as an exploration platform for a simple,compact helicon wave plasma source adaptable to engineering applications.A small-diameter(26 mm)highdensity(~10^(18)m^(-3))blue core plasma is produced in~1 Pa argon by helicon RF(radiofrequency)discharge using a NagoyaⅢantenna under magnetic fleld(~2 k G)of compact ring PMs(length~204 mm).Operational parameters,i.e.RF power and neutral gas pressure are scanned and plasma density is measured by an RF compensated probe to explore the operating characteristics of the device.Iconic feature of a helicon discharge,such as blue core plasmas and E-H-W mode transitions are well observed in the device,despite the wavelength calculated using the conventional dispersion relation of a bounded whistler waves(Chen 1991 Plasma Phys.Control.Fusion 33339)is order of magnitudes longer than the length of the plasma in this device which seems to suggest that such helicon device is impossible.Surprisingly,the wavelength calculated by the unbounded whistle wave dispersion formula in turn suggests the occurrence of a half wavelength resonance.
基金Project supported by the National Key Research and Development Program of China(2022YFC2905203)the NationalScience and Technology Major Project of China(J2019-VI-0023-0140)。
文摘In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behavior was investigated.By reducing the electron beam power instantly and gradually at reduction rates of 1,3 and 5 kW/min,it is found that W is enriched at the bottom of ingots as the melt solidifies.The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases,attributed to the k0(W)>1 andρ(W)>ρ(Ce).Overall,the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot,and the purity of Ce increases from 99.932 wt%to 99.995 wt%by this combined method.Additionally,this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.
基金This work was supported by the National Magnetic Confinement Fusion Energy Program of China(grant no.2019YFE03030000).
文摘The stellarator has inherent advantages over the tokamak in achieving steady-state operation,especially due to its absence of disruptions and lack of need for current drive and the associated recirculating power.In recent years,there have been remarkable advances in the field of stellarator optimization,where precisely quasi-symmetric and precisely quasi-isodynamic magnetic configurations have been achieved with coils,allowing the neoclassical transport and energetic particle losses of stellarators to be reduced to levels comparable to those of tokamaks.At the same time,the development of high-temperature superconducting magnet technology will potentially double the magnetic field strength of stellarators.While these strong fields are expected to introduce new challenges,and while turbulent transport remains a common challenge for both stellarators and tokamaks,the combination of these physical and technological advances results in the expectation that stellarators will become a competitive approach to tokamaks for realizing steady-state fusion.
基金Acknowledgements We are grateful for financial support from the National Basic Research Program of China (2009CB930400), the National Natural Science Foundation of China (NSFC 21121063) and the Joint Research Project funding (GJHZ1224) from the Chinese Academy of Sciences and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). We thank the Institute of Modem Physics, Chinese Academy of Sciences for providing the UO2(NO3)2"6H20 salts and uranium content measurements. We acknowledge the Australian Synchrotron for access to the Powder Diffraction beamline. We thank Ian Madsen (CSIRO Process Science and Engineering) for providing access to the in situ XRD instrument and for a critical reading of the manuscript. The CSIRO Office of the Chief Executive (OCE) Postdoctoral and Science Leader Schemes are acknowledged for supporting this work. R. A. C. acknowledges the Australian Research Council for a Future Fellowship (FT0990583).
文摘Inorganic-organic hybrid WOx-ethylenediamine (WO/-EDA) nanowires have been produced by a simple, low-cost and high-yield solvothermal method. These WO/-EDA hybrid nanowires have unique lamellar mesostructures with an alternate stacking of an interconnected [WO6] octahedral layer and a monolayer of ethylenediamine molecules. This hybrid structure integrated the functionality of ethylenediamine with the stability of the WOx frameworks. In situ synchrotron- radiation X-ray diffraction is used to elucidate a possible formation mechanism of the hybrid WOx-EDA. The nanowire morphology, lamellar structure and abundant functional amino groups endow them with versatile abilities. For example, in heavy metal ion adsorption the WOx-EDA nanowires display exceptional adsorption capabilities of 925 mg·g^-1 for Pb^2+ and 610 mg·g^-1 for UO2^2+. The nanowires also show outstanding stability and activity as a heterogeneous base catalyst in the Knoevenagel condensation reaction at room temperature. The catalyst can be recycled and reused for 20 cycles with nearly 100% yields. This study provides a new strategy to design inorganic-organic hybrid materials, and offers a multifunctional material that is a highly efficient adsorbent and sustainable catalyst.
基金Project supported by the National Key Research and Development Program of China(2017YFB0405901)the National Natural Science Foundation of China(51504036,51604033)。
文摘Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indicate that,the evaporation coefficient of Fe in La metal is 35-175 at 1800-3000 K,and Fe impurity can be removed by EBM;the removal efficiency of Fe impurity is improved with the increasing EBM power,the Fe concentration is significantly decreased from 1482 to 0.1 μg/g under 50 kW and 2400 s;the reaction of Fe removal by EBM follows the first-order rate law,and Fe impurity is removed by evaporation as a single atom;transport from the La melt to the liquid boundary layer of the Fe atom is rate-controlling step in the EBM when the EBM power is 30-50 kW.
基金Project supported by the Financial Science and Technology Special Projects of China(XCSTS-TI2020-28)。
文摘In this study,a molten salt co-reduction method was proposed for preparing Y-Al intermediate alloys and the electrochemical co-reduction behaviors of Y(Ⅲ)and Al(Ⅲ)and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques.The results show that the reduction of Y(Ⅲ)at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons,which is controlled by the mass transfer rate.The diffusion coefficient of Y(Ⅲ)in the fluoride salt at a temperature of 1323 K is 5.0238×10^(-3)cm^(2)/s.Moreover,the thermodynamic properties associated with the formation of Y-Al intermetallic compounds were estimated using a steady-state electrochemical method.Y-Al intermediate alloy containing 92 wt%yttrium was prepared by constant current electrolysis at 1323 K in the LiF-YF_(3)-AIF_(3)-Y_(2)O_(3)(6 wt%)-Al_(2)O_(3)(1 wt%)system at a cathodic current density of 8 A/cm^(2)for 2 h.The Y-Al intermediate alloy is mainly composed ofα-Y2Al and Y phases.The development and application of this innovative technology have solved major technical problems,such as a long production process,high energy consumption,and serious segregation of alloy elements at this stage.
基金the Key Project of Research and Development Plan of HunanProvince under Grant 2018GK2044in part by the Natural Science Foundation of Hunan Provinceunder Grant 2018JJ4084+1 种基金in part by the National Natural Science Youth Fund Project under Grant51805168in part by the Science and Technology Talent Project of Hunan Province – HuxiangYouth Talent under Grant 2019RS2062.
文摘The bogie is a crucial component of urban rail vehicles,and its performance plays a decisive role in the safe operation of vehicles.Aiming at the intelligent operation and maintenance requirements of rail transit equipment,in this paper,it takes several key parts of the urban rail vehicle bogie system as research objects,such as motor bearings,frames,fasteners,etc.,and proposes a three-dimensional(3D)visual collaborative maintenance method.Firstly,a multi-sensor urban rail vehicle bogie running simulation experiment analysis platform was constructed,thereby establishing a database of running state and performance characteristics of the bogie in the whole life cycle.Then,the health status of key components of bogie was predicted by the state interval prediction model.Finally,the three-dimensional visual collaborative maintenance model proposed in this paper was integrated to realize the early warning of the bogie operation faults,3D precise guidance of automatic location and maintenance operation information,and collaborative sharing of visual information among multiple users.