排序方式: 共有36条查询结果,搜索用时 15 毫秒
11.
The vortex pinning determining the current carrying capacity of a superconductor is an important property to the applications of superconducting materials.For layered superconductors,the vortex pinning can be enhanced by a strong interlayer interaction in accompany with a suppression of superconducting anisotropy,which remains to be investigated in iron based superconductors(FeSCs)with the layered structure.Here,based on the transport and magnetic torque measurements,we experimentally investigate the vortex pinning in two bilayer FeSCs,CaKFe4As4(Fe1144)and KCa2Fe4As4F2(Fe12442),and compare their superconducting anisotropyγ.While the anisotropyγ≈3 for Fe1144 is much smaller thanγ≈15 in Fe12442 around Tc,a higher flux pinning energy as evidenced by a higher critical current density is found in Fe1144,as compared with the case of Fe12442.In combination with the literature data of Ba0.72K0.28Fe2As2 and Nd Fe AsO0.82F0.18,we reveal an anti-correlation between the pinning energy and the superconducting anisotropy in these Fe SCs.Our results thus suggest that the interlayer interaction can not be neglected when considering the vortex pinning in Fe SCs. 相似文献
12.
13.
The density functional calculations of the energy band structure and density of state for the tetragonal PbO-type phase α-FeSe and hexagonal NiAs-type phase β-FeSe are reported in this paper. The structural phase transition from tetragonal to hexagonal FeSe under high pressure is investigated, it is found that the calculated transition pressure for the α → β phase transformation is 8.5 GPa. Some fluctuations in the transition pressure maybe occurred by different external factors such as temperature and stress condition. There is about 17% volume collapse accompanying the α → β phase transformation. 相似文献
14.
15.
16.
17.
采用微波辅助凝胶燃烧法制备了Ca2MgSi2O7∶Eu3+红色荧光粉,运用XRD、荧光分光光度计等对合成样品进行分析表征,并探讨了焙烧温度、助熔剂用量、Eu3+浓度等对样品发光性能的影响。结果表明:所得样品为四方晶系的Ca2MgSi2O7晶体结构。Ca2MgSi2O7∶Eu3+的激发光谱由一宽带和一组锐线峰组成,分别归属于Eu3+-O2-之间的电荷迁移态和Eu3+的f→f跃迁。样品的发射光谱主要由两个强发射峰组成,分别位于591 nm和619 nm处,属于Eu3+的5D0→7F1磁偶极跃迁和5D0→7F2的电偶极跃迁。研究发现:当焙烧温度为1000℃、助熔剂H3BO3用量为15%时,样品发光性能较好;Eu3+浓度(x)对样品Ca2-xMgSi2O7∶Eu3x+的发光强度影响较大,当Eu3+浓度x在0.02~0.16范围内变化时,随着Eu3+浓度的增加,样品的发光强度不断增加,未出现明显的浓度猝灭现象。 相似文献
18.
通过分析研究气体栓子的超声多普勒信号的特征及其成因,建立气体栓子的超声多普勒仿真模型,为后续的气体栓子与固体栓子的分类提供理论基础。先利用超声辐射力和液体黏滞阻力的模型计算气体栓子所受的超声辐射力和黏滞阻力,然后计算气体栓子在血管内的径向加速度和轴向加速度,并从加速度得到气体栓子在血管内的运动轨迹,最后建立气体栓子的计算机仿真模型。实验中仿真合成气体栓子和固体栓子的超声多普勒信号,对信号的分析结果表明,相比于固体栓子,仿真的气体栓子信号受到作用力而产生的加速度将导致气栓信号在多普勒声谱图上频域的展宽,当气体栓子由低速区域加速到高速区域再由高速区减速至低速区将会在声谱图上体现为"V"型,若只有单一的加速或减速运动将只表现为斜线型。将仿真的气栓信号与临床采集的气栓信号进行比较,发现两者的特征是吻合的,说明气栓超声多普勒信号的仿真方法是合理的。 相似文献
19.
CS模型线圈运行电流为47.65k A,储能高达407MJ,可靠的失超保护系统是线圈安全运行的重要保障。本文根据线圈的设计参数和运行要求,进行了失超保护系统的初步设计,介绍了高灵敏度失超检测方法,确定了失超保护回路的拓扑结构。针对回路中的主要器件,设计了50k A级直流快速断路器,估算了熔断器的关键参数,计算了移能电阻在线圈i2t≤7.95×108A2s、端电压U≤2500V条件下,阻值选取范围为12.5mΩ≤R≤52.47mΩ。同时开展了失超保护控制系统的设计,为后期失超保护系统工程设计及线圈实验运行提供依据。 相似文献
20.
The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an excellent mid-temperature thermoelectric material due to its suitable intrinsic thermoelectric properties.So tremendous efforts have been done to improve the thermoelectric performance of Pb Te,and figures of merit,z_T 2.0,have been reported.Main strategies for optimizing the thermoelectric performance have been focused as the main line of this review.The band engineering and phonon scattering engineering as two main effective strategies are systemically summarized here.The band engineering,like band convergence,resonant levels,and band flatting have been addressed in improving the power factor.Additionally,phonon scattering engineerings,such as atomic-scale,nano-scale,meso-scale,and multi-scale phonon scatterings have been applied to reduce the thermal conductivity.Besides,some successful synergistic effects based on band engineerings and phonon scatterings are illustrated as a simultaneous way to optimize both the power factor and thermal conductivity.Summarizing the above three main parts,we point out that the synergistic effects should be effectively exploited,and these may further boost the thermoelectric performance of Pb Te alloys and can be extended to other thermoelectric materials. 相似文献