排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
2.
3.
Nb3Sn 超导复合股线在强磁场工程中有着重要的应用,其拉伸强度为保证和评估其长期服役安全的一个关键参数。本文从 “剪滞”理论出发,利用基于Weibull/Possion统计理论的复合材料纤维断裂的Curtin-Zhou模型,较好地描述复合股线中Nb3Sn超导纤维碎片化过程,建立了分析超导复合股线统计拉伸强度和失效概率的模型。计算结果表明,青铜法Nb3Sn超导复合股线的拉伸强度随着初始损伤参数的增大而迅速减小;在4.2K服役温度下,当Weibull模量为8时,随着初始损伤参数的增加,股线的拉伸强度约从900MPa衰减至480MPa,与已有实验结果吻合良好;初始损伤参数约为1时,正规化方差最大。初始损伤和Weibull模量对Nb3Sn复合股线统计拉伸强度和失效概率函数的分布有着显著影响。 相似文献
4.
Spin-dependent negative differential conductance in transport through single-molecule magnets 下载免费PDF全文
Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance (NDC) emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor. 相似文献
5.
We propose a continuous-wave(CW)middle infrared(MIR)and long infrared(LIR)dual-band laser for the calibration and effect research of infrared detecting and imaging systems.A total output power of 18 W is achieved by the proposed dual-band laser through one DF gain medium module and one parallel placed CO2 gain medium module using a common stable resonator and output mirror with nominal transmissivities of ~5%in the MIR band and~10%in the LIR band.Spectra of dual-band laser are acquired.The power extracting efficiency of this dual-band laser can be significantly improved,as validated by a single-band test of optimized parameters. 相似文献
6.
In this paper, the contents and methods of small-class teaching of chemical principles were introduced in detail, including the allocation of teaching time, the allocation of lecturing and self-study contents, organizing seminar and literature reading, as well as the cultivation of students' innovation ability. The reform of teaching content and teaching method in the process of implementing were introduced. 相似文献
7.
制备了聚({4,8-双[(2,5,8,11,14,17,20-七氧二十二烷-22-基)氧基]苯并[1,2-b∶4,5-b']二噻吩}-交替-[2,5-二(噻唑-2-基)吡嗪])(P7O-2N-2N)和聚({4,8-双[(2,5,8,11,14,17,20-七氧二十二烷-22-基)氧基]苯并[1,2-b∶4,5-b']二噻吩}-交替-[3,6-双(5-溴-2-噻吩基)-1,2,4,5-四嗪])(P7O-4N)2个亲水性共轭聚合物, 通过调节主链含氮杂环上氮原子的位置, 系统研究了主链结构对材料吸收光谱、 能级、 氢结合自由能及光催化性能的影响. 研究发现, 与P7O-2N-2N相比, P7O-4N表现出更强的链间聚集、 更低的氢结合自由能及更好的光催化制氢性能. 相似文献
8.
9.
沥青混凝土有效性能的预测和评估是其在道路工程与大坝防渗等应用中的关键问题。本文利用细观随机建模技术和有限元方法研究了级配曲线对沥青混凝土有效弹性模量的影响。首先,基于改进的蒙特卡洛法分别实现了服从工程筛分级配曲线或给定函数级配曲线的沥青混凝土细观随机模型的高效生成;然后,利用建立的模型分析了骨料的含量、弹性模量和试样尺寸对沥青混凝土的有效弹性模量的影响,并与实验结果进行对比,验证了所建模型的可靠性;从而,预测了在AC-13级配范围内级配曲线的凹凸程度,即粗细骨料的组成比例对沥青混凝土有效弹性模量的影响。结果表明,级配曲线的凹凸程度对其有效弹性模量影响存在较大差异,级配曲线的下凹(粗骨料占比增大)会导致有效弹性模量迅速增大,级配曲线的上凸(细骨料占比增大)也会引起有效弹性模量略有上升;另外提出的随机建模方法可实现对级配曲线,即对粗细骨料组成比例的定制设计. 相似文献
10.
Grain Size Effect on Electrical Conductivity and Giant Magnetoresistance of Bulk Magnetic Polycrystals 下载免费PDF全文
By solving the Boltzmann transport equation and considering the spin-dependent grain boundary scattering, the distribution of electrons in grains and the electrical transport properties in the applied magnetic field are studied. With regard to the dominant influence of grain boundary scattering which is taken as a boundary condition for the electrical transport, the grain size-dependent electrical conductivity is investigated. In addition, the reorientation of the relative magnetization between grains brings the change of the electron spin when the magnetonanocrystailine material is subjected to the magnetic field, resulting in the remarkable giant magnetoresistance effect. 相似文献