Photon-assisted electronic and spin transport through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm interferometer

We investigate the time-modulated electronic and spin transport properties through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm(A-B) interferometer. By using the Keldysh non-equilibrium Green's function technique, the photon-assisted spin-dependent average current is analyzed. The T-shaped three-quantum-dot molecule A-B interferometer exhibits excellent controllability in the average current resonance spectra by adjusting the interdot coupling strength, Rashba spin-orbit coupling strength, magnetic flux, and amplitude of the time-dependent external field.Efficient spin filtering and multiple electron-photon pump functions are exploited in the multi-quantum-dot molecule A-B interferometer by a time-modulated external field.     

自聚集在纳米金粒上的烷基硫醇单分子层的NMR驰豫时间研究

通过质子的自旋-晶格驰豫时间（T_1）、自旋-自旋驰豫时间（T_2）研究烷基 巯基[X(CH_2)_nS-]单分子层保护的纳米金粒中配体分子的运动。本研究涉及两种 典型配体：CH_3(CH_2)_7SH和Py(CH_2)_(12)SH及该两配体的不同配比的测合配体 。实验监测了配体中不同位置的质子的NMR驰豫时间随空间距离及配体比例改变的 变化情况。不同位置的质子,因主要影响因素的不同,表现出各自特殊的运动特征 。配体与金粒配位后,2,3位T_1,T_2值减少,1,4位T_1,T_2值增加。混合配体 中Py(CH_2)_(12)SH含量增加,1,2,3位T_1,T_2值都会减小;而4位T_1值减小, T_2值却增加;不同位置T_1,T_2值变化快慢有别。2位因其特殊位置,在配体配比 PY:C_8 = 1:1[PY代表Py(CH_2)_(12)SH,C_8代表CH_3(CH_2)_7SH]时,分子运动最 自由。实验结果显示T_1总是大于T_2,这说明配体处于低频运动区。     

苷类化合物研究 IV: 熊果苷类似物的合成

本文报道以1-溴-2,3,4,6-四-O-乙酰基-a-D-吡喃糖与苯二酚在氢氧化钠的丙酮-水溶液中反应, 生成熊果苷类似物. 由^1HNMR测定了糖苷的端基异构体.     

LAMOST medium-resolution spectroscopic survey of binarity and exotic star (LAMOST-MRS-B): Observation strategy and target selection

LAMOST-MRS-B is one of the sub-surveys of LAMOST medium-resolution ($R\sim7500$) spectroscopic survey. It aims at studying the statistical properties (e.g., binary fraction, orbital period distribution, mass ratio distribution) of binary stars and exotic stars. We intend to observe about 30000 stars ($10 {\rm mag}\leq G < 14.5$ mag) with at least 10 visits in five years. We first planned to observe 25 plates around the galactic plane in 2018. Then the plates were reduced to 12 in 2019 because of the limitation of observation. At the same time, two new plates located at the high galactic latitude were added to explore binary properties influenced by the different environments. In this survey project, we set the identified exotic and low-metallicity stars with the highest observation priorities. For the rest of the selected stars, we gave the higher priority to the relatively brighter stars in order to obtain high quality spectra as many as possible. Spectra of 49129 stars have been obtained in LAMOST-MRS-B field and released in DR8, of which 28828 and 3375 stars have been visited more than twice and ten times with $\rm SNR \geq 10$, respectively. Most of the sources are B-, A-, and F-type stars with $\rm -0.6< [Fe/H] < 0.4 $ dex. We also obtain 347 identified variable and exotic stars and about 250 stars with $\rm [Fe/H] <-1$ dex. We measure radial velocities (RVs) by using 892233 spectra of the stars. The uncertainties of RV achieve about $1$ ${\rm km \cdot s^{-1}}$and $10$ ${\rm km \cdot s^{-1}}$ for 95% of late- and early-type stars, respectively. The datasets presented in this paper are available at http://www.doi.org/10.57760/sciencedb.j00113.00035.     

基于视觉测量的应变片空间定位及应用

在大型航天结构舱段试验中，通常需要粘贴大量的应变片来获取结构的应变测试数据。为了能够准确定位结构舱段上的应变片位置，本文研究了基于单目视觉测量技术的应变片空间坐标重建方法。该方法采用一台单反相机，从不同视角连续对构件进行拍摄，获得一组包含圆环编码点和应变片的图像序列；通过检测编码点图像坐标，构建相邻帧之间的匹配关系，然后基于相对定位原理估计相机姿态信息；再利用深度学习技术提取图像中的应变片坐标，结合估计的姿态信息对提取的应变片进行立体匹配，并且采用三角测量方法重构应变片空间坐标，从而实现应变片的三维定位。利用所研究的方法，分别对铝质平板和圆筒上粘贴应变片的三维坐标、碳纤维标尺的长度进行了定位。定位结果表明，该方法的重复定位精度优于0.05mm,三维点距离测量精度优于0.1mm。