The Structure–Property Correlations in the Isomerism of Au21(SR)15 Nanoclusters by Density Functional Theory Study

Isomerism of atomically precise noble metal nanoclusters provides an excellent platform to investigate the structure–property correlations of metal nanomaterials. In this study, we performed density functional theory (DFT) and time‐dependent (TD‐DFT) calculations on two Au₂₁(SR)₁₅ nanoclusters, one with a hexagonal closed packed core (denoted as Au₂₁ ^hcp ), and the other one with a face‐centered cubic core (denoted as Au₂₁ ^fcc ). The structural and electronic analysis on the typical Au–Au and Au–S bond distances, bond orders, composition of the frontier orbitals and the origin of optical absorptions shed light on the inherent correlations between these two clusters.     

非对称空间外差光谱仪自适应频率跟踪处理方法

非对称空间外差光谱技术是一种新型的超高分辨率遥感探测技术,要求后期的数据处理技术也具有相应的超高准确度.从数字信号处理的角度,提出了一种自适应的频率跟踪处理方法,根据信号的空间频率来插值补偿信号的相位偏移,并且递归迭代出最接近真实值的相位信息.经仿真实验对比验证表明,在噪声干扰强度不大的条件下,相较于传统傅里叶变换方法,本文算法对信号频率和相位提取的准确度提高了约100倍以上,能够有效降低非对称空间外差光谱技术的系统误差.     

An analysis of the wide area differential method of geostationary orbit satellites

This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between the dilution of precision (DOP) of four-dimensional (4D) calculation including satellite clock errors and ephemeris errors and that of three-dimensional (3D) calculation only including ephemeris errors with the inverse positioning theory of GPS shows the conclusion that all the 3D PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock errors and ephemeris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock errors are separated in a master station with time synchronization, and all the remaining pseudo-range errors after the satellite clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid for GEO constellation. Supported by the National Natural Science Foundation of China (Grant No. 10778715), the National Key Basic Research Development Program of China (Grant No. 2007CB815502), and the Scientific Research Fund of Hunan Provincial Education Department (Grant No. 08B039)     

恒温恒湿空调三种工况下自动控制研究

针对恒温恒湿空调在夏季、冬季和过渡季节三种典型工况下的自动控制,详细分析了三种工况下空气处理过程,对温度和湿度的控制进行了分解、给出了实现框图并分析了控制系统本身造成的控制精度问题,为恒温恒湿空调的控制改进提供参考。     

基于计数法测量激光多普勒测速仪的测速精度

为了测量所设计的激光多普勒测速仪(LDV)的测量精度,用均匀转动的斩波片代替高精度的转台作为标准的速度源,并基于单片机AT89S52,采用光计数的方法测量斩波片上某一固定位置的切向运动速度,LDV的测量结果与之相比较。实验结果表明,LDV测速的相对精度不超过8‰,稳定性较好。     

高精度消色差相位延迟器的新设计

消色差相位延迟器是在某一宽度光谱范围内使用的光相位延迟器件。从相位延迟的全反射相变理论出发,对斜入射消色差相位延迟原理进行阐述,参考菲涅耳棱镜的具体设计形式,对引起相位延迟变化的参量进行分析,通过选择合适的材料新设计出了特殊角度入射的高精度相位延迟器,其理论曲线显示,在365~1150nm的光谱区域内延迟偏差小于0.4°,是常规相位延迟器在相同条件下的五分之一,是一种宽广谱范围内、负延迟偏差小、精度高的消色差相位延迟器。     

光纤Sagnac温度传感器

介绍了一种新型的基于光纤Sagnac干涉仪的高精度光纤温度传感器———光纤Sagnac温度传感器。讨论了此传感器的测温原理,推导了被测温度与传感器输出之间的关系,设计并调测了一个具体传感器系统。实验结果表明,此温度传感器具有很高的精度和大的测量范围。     

大口径平面光学元件超精密加工技术的研究

为了解决激光核聚变装置中大口径平面光学元件的批量制造难题,将先进制造技术和传统抛光技术相结合,提出了一种新的工艺方法,即使用ELID(在线电解)磨削代替传统的铣磨和初抛工序,以提高生产效率。利用数控抛光将工件抛光至最终的面形精度,以提高生产效率和减少边缘效应。将连续抛光作为最终加工工序,使加工工件的表面粗糙度和波纹度达到工程要求。实验证明这一新的工艺方法是可行的。     

四象限探测器用作激光准直的特性分析

以四象限光电探测器用作激光准直为例,对其探测原理、光电转换特性、影响探测精度的因素进行了理论分析。用数值模拟、实验验证了分析结果,并对影响探测精度的因素进行了深入的探讨,从而为四象限探测器用作激光准直提供了有力的理论依据。     

Performance comparison using the GUESS mixture to evaluate counter-current chromatography instruments

Comparing the performance of different counter-current chromatography (CCC) J-type centrifuges has and will always be difficult. This is due to the number of variables such as speed of rotation, swung radius, β-value, column bore, column length that can be chosen during the design of an instrument. This situation is further complicated by the implication that some of these variables are intrinsically linked, such that if one is changed another or others can also change. The chromatographer has no influence on these hardware parameters once the instrument designer has chosen them. However, the chromatographer wants a CCC column that retains the most liquid stationary phase in order to achieve the best separation of the components in a mixture. What matters most is column performance in terms of: sample loading per injection, speed of separation, purity of target and yield of target. The instrument that has the best performance in all these areas is called a “high-performance” CCC system. This paper demonstrates to the modern chromatographer that a “high-performance” CCC instrument has shorter, lower volume columns that are rotated faster to provide quicker separations, even with the same sample loading.