No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel...No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel stacked-tape structure leads to new current redistribution among stacked tapes in each turn during local quenches,which also considerably changes the current redistribution behavior through inter-turn contacts.Therefore,quench behaviors of parallel-wound no-insulation(PWNI)coil should differ from its counterpart wound with single tape,which are still unknown.This study is to illustrate quench behaviors of PWNI HTS coils induced by local hot spot.A multi-physics model integrating an equivalent circuit network,a FEM heat transfer module,and a FEM T-A model is developed to analyze the electromagnetic and thermal characteristics of PWNI HTS coils during quench.Results show that the transport currents are mainly redistributed among parallel-stacked tapes through terminal resistances when a local hot spot happens on one tape,while being less dependent on turn-to-turn electrical contacts.It leads to a coupling current within PWNI coils that is not present in NI coils wound with single tape(single-wound no-insulation(SWNI)coil),resulting in a highly non-uniform transport current distribution among parallel-wound tapes.The reduced terminal joint resistances further enhance the coupling current,potentially leading to an extra overcurrent quench risk in PWNI coils.Moreover,the current redistribution between parallel-stacked tapes inhibits the turn-to-turn current redistribution in the PWNI coil,thus significantly reducing its magnetic field degradation under a high heat disturbance,which can be almost less than half of the SWNI counterpart in this study.These results offer important theoretical guidance to safety operation and robustness improvement of high-field HTS magnets wound by PWNI technique.展开更多
A cationic poly(p-phenylene vinylene) related copolymer without bulky phenylene substitutents attached to the conjugated backbone was prepared through Wittig reaction.The molecular structure and optical properties wer...A cationic poly(p-phenylene vinylene) related copolymer without bulky phenylene substitutents attached to the conjugated backbone was prepared through Wittig reaction.The molecular structure and optical properties were highly investigated through ~1H-NMR,UV and PL spectroscopy.The quenching behavior was also investigated,and the results demonstrate that incomplete quenching exists,which is consistent with the cationic poly(p-phenylene vinylene) related copolymer containing bulky phenylene substitutents,prob...展开更多
By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angl...By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angle of die (90 °-120 °), hardness after quenching and tempering (HRC21-29) and lubricated condition on the forming load was analyzed. The results show that there is no central bursting and micro crack in the inner of the extruded specimen, and the forming quality is good. The double-peak phenomenon takes place at the front-end of the specimen; the double-peak index increases with deformation extent, and larger deformation can avoid the double-peak phenomenon. The deformation extent is the most important influencing factor, and the lubricated condition almost has no influence, which means that the phosphate coating plus soap process is still a proper lubrication method for cold extrusion of medium carbon steel after quenching and tempering. By investigating the microscopic structure before and after deformation, the initial equiaxed grain is elongated in the extrusion direction, and this feature is more significant at the front-end of specimen.展开更多
A model considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is presented to examine metallo-thermo-mechanical behavior during carburized and nitrided quenchi...A model considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is presented to examine metallo-thermo-mechanical behavior during carburized and nitrided quenching. Coupled simulation of diffusion, phase transformation and stress/strain provides the final distribution of carbon and nitrogen contents as well as residual stress and distortion. Effects of both transformation and lattice expansion induced by carbon and nitrogen absorption were introduced into calculating the evolution of the internal stress and strain. In order to verify the method and the results, the simulated distributions of carbon and nitrogen content and residual stress/strain of a ring model during carburized and nitrided quenching were compared with the measured data.展开更多
The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission...The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.展开更多
The effects of 5%Ni addition on the glass forming ability,thermal stability and crystallization behavior of Mg65Cu25Tb10 bulk metallic glass were investigated using X-ray diffractometry,differential scanning calorimet...The effects of 5%Ni addition on the glass forming ability,thermal stability and crystallization behavior of Mg65Cu25Tb10 bulk metallic glass were investigated using X-ray diffractometry,differential scanning calorimetry and transmission electron microscopy.The small amount of Ni addition reduces the glass forming ability and thermal stability due to a significant decrease in the crystallization activation energy.Analyses of crystallization kinetics give evidence to the existence of quenched-in nuclei in amorphous Mg65Cu20Ni5Tb10.Final crystallization products are basically same for Mg65Cu25Tb10 and Mg65Cu20Ni5Tb10.展开更多
基金sponsored by National Key R&D Program of China(No.2023YFE0118100)The work is also sponsored by National Natural Science Foundation of China(No.52207028)+1 种基金The work is also spon-sored by Shanghai Science&Technology Innovation Action Program(No.23511101800)The work is also sponsored by Natural Science Foundation of Chongqing(No.2022NSCQ-MSX1512).
文摘No-insulation(NI)high-temperature superconducting(HTS)coil wound with parallel-stacked tapes emerges as a prospective choice for high-field fusion magnets owing to lower inductance and faster ramping rate.The parallel stacked-tape structure leads to new current redistribution among stacked tapes in each turn during local quenches,which also considerably changes the current redistribution behavior through inter-turn contacts.Therefore,quench behaviors of parallel-wound no-insulation(PWNI)coil should differ from its counterpart wound with single tape,which are still unknown.This study is to illustrate quench behaviors of PWNI HTS coils induced by local hot spot.A multi-physics model integrating an equivalent circuit network,a FEM heat transfer module,and a FEM T-A model is developed to analyze the electromagnetic and thermal characteristics of PWNI HTS coils during quench.Results show that the transport currents are mainly redistributed among parallel-stacked tapes through terminal resistances when a local hot spot happens on one tape,while being less dependent on turn-to-turn electrical contacts.It leads to a coupling current within PWNI coils that is not present in NI coils wound with single tape(single-wound no-insulation(SWNI)coil),resulting in a highly non-uniform transport current distribution among parallel-wound tapes.The reduced terminal joint resistances further enhance the coupling current,potentially leading to an extra overcurrent quench risk in PWNI coils.Moreover,the current redistribution between parallel-stacked tapes inhibits the turn-to-turn current redistribution in the PWNI coil,thus significantly reducing its magnetic field degradation under a high heat disturbance,which can be almost less than half of the SWNI counterpart in this study.These results offer important theoretical guidance to safety operation and robustness improvement of high-field HTS magnets wound by PWNI technique.
基金supported by the National Natural Science Foundation of China(Nos.20774043,20874048)the Fok Ying-Tong Education Foundation(No.111051)+1 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK2008453)the Scientific Research Foundation of Nanjing University of Posts and Telecommunications (NUPT)(Nos.NY207035 and NY207011)
文摘A cationic poly(p-phenylene vinylene) related copolymer without bulky phenylene substitutents attached to the conjugated backbone was prepared through Wittig reaction.The molecular structure and optical properties were highly investigated through ~1H-NMR,UV and PL spectroscopy.The quenching behavior was also investigated,and the results demonstrate that incomplete quenching exists,which is consistent with the cationic poly(p-phenylene vinylene) related copolymer containing bulky phenylene substitutents,prob...
文摘By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angle of die (90 °-120 °), hardness after quenching and tempering (HRC21-29) and lubricated condition on the forming load was analyzed. The results show that there is no central bursting and micro crack in the inner of the extruded specimen, and the forming quality is good. The double-peak phenomenon takes place at the front-end of the specimen; the double-peak index increases with deformation extent, and larger deformation can avoid the double-peak phenomenon. The deformation extent is the most important influencing factor, and the lubricated condition almost has no influence, which means that the phosphate coating plus soap process is still a proper lubrication method for cold extrusion of medium carbon steel after quenching and tempering. By investigating the microscopic structure before and after deformation, the initial equiaxed grain is elongated in the extrusion direction, and this feature is more significant at the front-end of specimen.
文摘在压水堆冷却剂丧失事故(Loss-of Coolant Accident,LOCA)中,处于高温条件下的燃料棒由于棒内压力过高,可能导致包壳发生鼓胀。包壳形变会造成堆芯局部流道堵塞,进而影响失水事故再淹没阶段的堆芯换热。然而,大多数系统分析程序都是基于假设的流道堵塞率来模拟事故进程,导致模拟结果与实际情况不符合。本文将已开发的燃料棒热-力行为分析模块(Fuel Rod Thermal-Mechanical Behavior,FRTMB)集成在自主开发的严重事故分析程序ISAA(Integrated Severe Accident Analysis Code)中,通过改进已有的流道堵塞模型,使其能够模拟由于燃料棒形变导致的冷却剂流量变化。最后,使用ISAA-FRTMB模拟QUENCH-LOCA-0实验,通过对比包壳峰值温度,验证改进的流道堵塞模型的正确性和有效性,并在此基础上研究包壳形变对堆芯换热以及后续事故进程的影响。
文摘A model considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is presented to examine metallo-thermo-mechanical behavior during carburized and nitrided quenching. Coupled simulation of diffusion, phase transformation and stress/strain provides the final distribution of carbon and nitrogen contents as well as residual stress and distortion. Effects of both transformation and lattice expansion induced by carbon and nitrogen absorption were introduced into calculating the evolution of the internal stress and strain. In order to verify the method and the results, the simulated distributions of carbon and nitrogen content and residual stress/strain of a ring model during carburized and nitrided quenching were compared with the measured data.
基金the National Natural Science Foundation of China (50571052)
文摘The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.
基金Projects(50601011,50432020) supported by the National Natural Science Foundation of ChinaProject(A2720060295) supported by the Basic Research Project of National Defense of China+1 种基金Project(BK2006533) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject supported by the New Century Excellent Talents in University Program
文摘The effects of 5%Ni addition on the glass forming ability,thermal stability and crystallization behavior of Mg65Cu25Tb10 bulk metallic glass were investigated using X-ray diffractometry,differential scanning calorimetry and transmission electron microscopy.The small amount of Ni addition reduces the glass forming ability and thermal stability due to a significant decrease in the crystallization activation energy.Analyses of crystallization kinetics give evidence to the existence of quenched-in nuclei in amorphous Mg65Cu20Ni5Tb10.Final crystallization products are basically same for Mg65Cu25Tb10 and Mg65Cu20Ni5Tb10.
