撕裂模实时主动控制系统

在HL-2A装置上发展了一套撕裂模实时主动控制系统。该系统在放电期间用电子回旋发射/软X射线诊断实时确定撕裂模的几何位置,结合实时剖面重建和电子回旋波沉积计算,得到电子回旋波反射镜的控制角度值。通过电机实时驱动电子回旋波反射镜到达指定角度,使得电子回旋波功率沉积在撕裂模的有理磁面附近,改变当地局部的电流剖面,从而控制撕裂模,改善等离子体约束。该系统已经在2015年以后的实验中投入使用,并取得了良好的控制效果。它不仅能够实时发现并控制经典撕裂模,并且具有控制新经典撕裂模的潜力。     

Asymmetric d-wave superconducting topological insulator in proximity with a magnetic order

In the framework of the Dirac–Bogoliubov–de Gennes formalism, we investigate the transport properties in the surface of a 3-dimensional topological insulator-based hybrid structure, where the ferromagnetic and superconducting orders are simultaneously induced to the surface states via the proximity effect. The superconductor gap is taken to be spin-singlet d-wave symmetry. The asymmetric role of this gap respect to the electron–hole exchange, in one hand, affects the topological insulator superconducting binding excitations and, on the other hand, gives rise to forming distinct Majorana bound states at the ferromagnet/superconductor interface. We propose a topological insulator N/F/FS junction and proceed to clarify the role of d-wave asymmetry pairing in the resulting subgap and overgap tunneling conductance. The perpendicular component of magnetizations in F and FS regions can be at the parallel and antiparallel configurations leading to capture the experimentally important magnetoresistance (MR) of junction. It is found that the zero-bias conductance is strongly sensitive to the magnitude of magnetization in FS region $m_{zfs}$ and orbital rotated angle α of superconductor gap. The negative MR only occurs in zero orbital rotated angle. This result can pave the way to distinguish the unconventional superconducting state in the relating topological insulator hybrid structures.     

Perturbation theories behind thermal mode spectroscopy for high-accuracy measurement of thermal diffusivity of solids

Thermal mode spectroscopy (TMS) has been recently proposed for accurately measuring thermal diffusivity of solids from a temperature decay rate of a specific thermal mode selected by three-dimensional (anti)nodal information [Phys. Rev. Lett., 117, 195901 (2016)]. In this paper, we find out the following advantages of TMS by use of perturbation analyses. First, TMS is applicable to the measurement of high-thermal diffusivity with a small-size specimen. Second, it is less affected by thermally resistive films on a specimen in the sense that the resistance at the interface does not affect the first-order correction of thermal diffusivity. Third, it can perform doubly accurate measurement of the thermal diffusivity specified at a thermal equilibrium state even if the diffusivity depends on temperature in the sense that the measurement can be performed within tiny temperature difference from the given state and that the decay rate of the slowest decaying mode is not affected by the dependence.     

Josephson current through a quantum dot molecule with a Majorana zero mode and Andreev bound states

Based on the Green's function method, we investigate the interplay between Majorana zero mode (MZM) and Andreev bound states (ABSs) in a quantum dot molecule side coupled to a topological superconducting nanowire with a pair of MZMs forming a Josephson junction. Since the strong electron–hole asymmetry induced by the nanowire with a topologically non-trivial phase, the MZM suppress the ABSs. The suppression induced by the MZM is robust against the Coulomb repulsion. The interplay between the MZM and the ABSs in Josephson junction presents a feasible experimental means for distinguish between the presence of MZM and ABSs.     

Massless and quantized modes of kinks in the phase space of superconducting gaps

We investigated quantized modes of kinks in the phase space of superconducting gaps in a superconductor with multiple gaps. The kink is described by the sine-Gordon model in a two-gap superconductor and by the double sine-Gordon model in a three-gap superconductor. A fractional-flux vortex exists at the edge of the kink, and a fractional-flux vortex will be stable in a three-gap superconductor with time-reversal symmetry breaking. The kink and fractional-flux vortex exhibit massless modes as a sliding motion. We show further that there are one zero-energy mode (massless mode) and quantized excitation modes in kinks, which are characteristic features of multi-gap superconductors. The equation of quantized modes for the double sine-Gordon model is solved numerically. The correction to the ground-state energy is calculated based on the renormalization theory.     

混合表面等离子体激元的纳米激光器设计

为了实现纳米激光器的性能优化,设计了一种基于纳米线、半圆形氟化镁、三角形空气槽和金属脊结构的纳米激光器模型。模型中耦合在低折射率电介质层中的SPP模式和纳米线波导可以在低折射率间隙下像电容器那样存储光能,从而使低折射率的空气槽场强明显增大。应用有限元法在COMSOL Multiphysics软件下,分析了该纳米激光器模型的电场分布、模式特性、品质因数和增益阈值随着设计结构几何参数变化的规律,通过各部分折线图的综合分析来得出模型性能的数据。分析表明：该模型的光场约束能力较强且传播损耗较低,其中归一化面积最小可达到0.004 8,有效传输损耗最小可达到0.002。波导模场区域和限制因素表明,该激光器模型可以实现输出光场的亚波长约束。该模型基本实现了低增益阈值、低传输损耗和高品质因数的要求。     

以间质隔离法研究CH3O分子在p-H2间质中的红外吸收光谱

本研究利用低温间质隔离技术搭配红外光谱仪研究CH3ONO在p-H2间质中的光解产生CH3O。实验观察到位于689.3/694.6cm-1、945.9/951.7cm-1、1041.8cm-1、1224.7cm-1、1235.5cm-1、1347.7cm-1、1365.4cm-1、1427.5cm-1、1519.5cm-1、1522.3cm-1等处的CH3O红外吸收谱线,并分析得出各振动模式分别为电子态E1/2a1对称性的ν6、电子态E1/2a2对称性的ν6、电子态E3/2对称性的ν2、电子态E3/2e对称性的ν6、电子态E1/2e对称性的ν6、电子态E1/2a1对称性的ν5、电子态E3/2对称性的ν2、电子态E1/2对称性的ν2、电子态E3/2e对称性的ν5及电子态E1/2e对称性的ν5。     

HHT时频分析土壤光谱的重金属铜离子污染信息提取模型

土壤中不同浓度Cu2+含量映射到土壤光谱上的信息量十分微弱,并且这些高光谱数据中也存在着难以避免的噪声,因而本研究的关键是如何在土壤光谱复杂的噪声环境中提取微弱Cu2+信息。经验模态分解算法(EMD)能够有效去除高光谱数据中的噪声,且EMD是Hilbert变换对“非线性非稳定”信号时频分析的前提,当引入Huang变换后,可利用Hilbert-Huang变换(HHT)模型时频分析高光谱数据以实现降噪处理与信息提取。通过时频的HHT分析不同浓度Cu2+污染下的土壤光谱,完成从原始光谱经EMD分解出各本征模态函数(IMF)分量的包络线、调制信号和频谱等曲线中挖掘土壤光谱的Cu2+污染信息。研究结果表明,相同浓度Cu2+污染时的土壤光谱HHT时频分析结果相同,不同浓度时则不同,所以也可依据IMF分量反演土壤Cu2+含量。因此,高光谱数据的HHT时频分析能为土壤光谱的信息挖掘、光谱诊断和Cu2+含量反演等提供一种新的方法和思路。     

基于简正波分解的不同阵列匹配场定位性能分析

针对利用不同阵列对浅海环境中水下目标的定位问题,基于简正波分解方法,对组合阵的目标声源定位性能进行了研究,着力解决在实际实验环境下定位性能不够高的问题,并降低实验设备布放难度.在浅海环境下,基于匹配场理论的声接收阵可实现目标的定位,但定位性能受阵形、阵元数目等影响.通过研究不同声接收阵的简正波分解矩阵,可以有效辨别不同阵形定位性能的优劣.仿真实验表明,当某一子阵简正波分解效果较差时,会降低组合阵的定位性能.基于实际实验的需求,在对短垂直阵和组合阵性能的研究中发现,由于水平阵对接收声场的定位模糊度函数中的旁瓣有抑制效果,从而造成模糊度函数表面上旁瓣较低,定位目标的主旁瓣比有所提升的现象.仿真实验表明,不同组合阵形的定位准确度均在90%以上,基于实际应用的考虑,组合阵无疑是对定位性能和实验复杂度的折中选择.     

Finite deformation analysis of slip-induced crystalline rotations during tensile and compressive tests on bcc iron crystals

This work compares slip-induced lattice rotations calculated from double-slip, finite-deformation analytical solutions to electron-back-scattering-diffraction (EBSD) rotation measurements from SEM in situ, room temperature straining of bcc iron crystals. The finite-deformation modelling assumes slip proportionality between the two dominant active systems. Four experimental cases from a recently published work (2015) are examined, two in axial tension and two in axial compression. They correspond to mixed double-slip on {110} and {112} planes, with slip on the latter in both ‘easy’ and ‘hard’ orientations. In the experiments, EBSD rotation measurements were made on three faces of the iron samples and the dominant active systems were identified from slip traces. Here the relative contributions of the two systems for the best match with available rotation data are determined for each case, and the results discussed in relation to initial shear stress and (probable) critical shear-strength ratios. The analyses provide insight into achievable accuracy in crystal-slip quantification, based on slip-trace observations and rotation measurements of a sample’s load and lateral axes, and some assessment of the relative hardening of active slip systems.