接近亏损系统的矩阵摄动法

随着系统参数的变化，带有重频的系统可转变成带有密集频率的系统，反之亦然．本文讨论了亏损系统与接近亏损系统之间的关系．并提出了接近亏损系统的平均移位的摄动方法．算例表明了此方法的有效性．     

Gatemon Qubit Based on a Thin InAs-Al Hybrid Nanowire

We study a gate-tunable superconducting qubit(gatemon) based on a thin InAs-Al hybrid nanowire.Using a gate voltage to control its Josephson energy,the gatemon can reach the strong coupling regime to a microwave cavity.In the dispersive regime,we extract the energy relaxation time T₁～0.56 μs and the dephasing time T₂*～0.38 μs.Since thin In As-Al nanowires can have fewer or single sub-band occupation and recent transport experiment shows the existence of nearly quantized zer...     

Epitaxial Growth and Magnetic Properties of NiMnAs Films on GaAs Substrates

Single-phase Ni_(0.92)Mn_(1.08) As films with strained C_(1b) symmetry are grown on GaAs(001) substrates. In addition,a preferred epitaxial configuration of(110)-orientated Ni_(0.92)Mn_(1.08) As on(001)-orientated GaAs is revealed by synchrotron radiation measurement. The magnetic properties of the films are found to be significantly influenced by the growth temperature and the optimized growth temperature is determined to be ~370℃. According to the results of x-ray absorption spectroscopy, these phenomena can be attributed to the variation of the local electronic structure of the Mn atoms. Our work provides useful information for the further investigations of NiMnAs, which is a theoretically predicted half-metal.     

Tunneling Anisotropic Magnetoresistance in L1_0-MnGa Based Antiferromagnetic Perpendicular Tunnel Junction

We report on the tunneling anisotropic magnetoresistance in antiferromagnetic perpendicular tunnel junction consisting of L1_0-MnGa/FeMn/AlO_x/Pt grown on GaAs(001) substrates by molecular-beam epitaxy. The temperature-dependent perpendicular exchange bias effect reveals an exchange coupling between ferromagnetic L1_0-MnGa and antiferromagnetic FeMn. The rotation of antiferromagnetic spins in FeMn can be driven by perpendicularly magnetized L1_0-MnGa due to the exchange-spring effect at the interface and leads to roomtemperature tunneling anisotropic magnetoresistance ratio of 0.86%. We also find that the tunneling anisotropic magnetoresistance strongly depends on temperature and angle. These results have broadened the material selection range for high performance antiferromagnetic spintronic devices.     

双喷嘴挡板力反馈伺服阀的阀芯振荡分析

基于双喷嘴挡板力反馈伺服阀的结构特点,根据伺服阀内部的压力-流量方程、阀芯运动学方程,首次建立了伺服阀阀芯振动的数学模型,推导了伺服阀固有频率及幅值放大系数的数学表达式;并以国产某型号伺服阀为例进行了理论分析,研究了阀芯质量、反馈杆刚度对于伺服阀固有频率及幅值放大系数的影响。结果表明:固有频率随阀芯质量的增加、弹簧杆刚度的降低而依次降低;幅值放大系数随阀芯质量、载荷频率、弹簧杆刚度的增加而依次降低。本文研究为双喷嘴挡板力反馈伺服阀的设计提供了理论基础。     

红外光谱分辨率对气体定量分析的影响研究

利用不同分辨率(1, 2, 4, 8 cm-1)的红外光谱建立对多组分气体样本(一氧化碳、二氧化碳、一氧化氮)的定量分析模型,研究了分辨率对气体定量测量精确性的影响。研究发现：对于样本中的各气体组分,在合适的分辨率下都有其最佳的测量精确性;而对于模型的整体精确性,在高分辨率1和2 cm-1以及低分辨率8 cm-1时模型都有较好的精确性,各组分相关系数(r)均值达到0.999 5以上,校正均方根误差(RMSEC)和验证均方根误差(RMSEP)的均值分别为18.36和15.43以下,而在分辨率为4 cm-1时,模型测量精确性陡然降低,r均值降到0.989 66,RMSEC均值为90.37,RMSEP均值为64.33。实验结果表明：光谱分辨率对气体定量分析有明显的影响。为提高定量分析测量的精确性,需要针对不同的待测气体和应用场合采用合适的分辨率参数。     

血液中流淌着艺术的物理大师——记Stephan von Molnár教授

说起磁性半导体研究先驱,业内人士可能会想到日本东北大学现任校长,Hideo Ohno教授。可Ohno教授在最近给我的email中评价Stephan von Molnár 教授：“He was a great and joyful mentor to us all”。Stephan一生充满传奇色彩：出生于有着高贵艺术血统的家庭,儿童时辗转躲避纳粹的迫害成为小移民,青少年时期活跃在观众欢呼的戏剧舞台,博士毕业后成为IBM Watson研究中心出色的资深研究员和高管,最后归宿佛罗里达州立大学物理系。     

缺陷对Pt在Graphene上吸附影响的研究

本文利用第一原理方法计算了空位缺陷和硼（B）掺杂时对Pt在graphene上吸附的影响.结果表明：Pt在graphene上吸附的稳定位置是Pt吸附在桥位;悬挂键的存在极大的增强了Pt在graphene空位处的吸附;B替位掺杂有利于Pt原子在杂质附近的吸附.     

沙尘大气物理约束方程研究

基于风沙两相流的相互作用和气块质量变化的观点,推导出了闭合的沙尘大气物理约束方程组.理想状况下对之分析发现:沙尘大气密度比同体积洁净大气大,一定程度上会减缓气块的运动速度;沙尘与空气间的速度差异会使得细粒子处于高流速区,而粗粒子位于低流速区;温度差异会使得沙尘在上升运动中充当热源,下沉运动中充当冷源,从而加强对流;沙尘大气质量定容热容会在等压面上诱发新的温度梯度,促进沙尘云边界处的夹卷;沙尘大气气体常数会在等温面上诱发新的气压梯度,促进沙尘云边界处的夹卷;质量变化会对气块密度、速度和温度造成较大影响.总之,沙尘云要比基于被动标量的方程组模拟结果更高大、内部对流更强、边界处夹卷更活跃、水平运动更迟缓.     

FeSi2单晶化学气相生长

利用化学气相输运方法, 以碘作为传输剂, 在封闭的石英安瓿中制备出了优质新型的光电及热电半导体材料β-FeSi₂单晶. 在大量实验基础上深入研究了生长工艺对单晶质量、形态的影响, 除了得到大尺寸针状β-FeSi₂单晶外, 还获得了大尺寸颗粒状单晶. 通过改变衬底温度, 得到了四面体柱状优质的α-FeSi₂单晶.