Modifying the generalized singular value decomposition with application with application in direction-of-arrival finding

We consider updating and downdating problems for the generalized singular value decomposition (GSVD) of matrix pairs when new rows are added to one of the matrices or old rows are deleted. Two classes of algorithms are developed, one based on the CS decomposition formulation of the GSVD and the other based on the generalized eigenvalue decomposition formulation. In both cases we show that the updating and downdating problems can be reduced to a rank-one SVD updating problem. We also provide perturbation analysis for the cases when the added or deleted rows are subject to errors. Numerical experiments on direction-of-arrival (DOA) finding with colored noises are carried out to demonstrate the tracking ability of the algorithms. The work of the first author was supported in part by NSF grants CCR-9308399 and CCR-9619452. The work of the second author was supported in part by China State Major Key Project for Basic Researches.     

试论高比能量电池进展

在综述电化学近５０年来比能量提高情况的基础上，讨论了现代科技发展对电池比能量的要求，以及当今电池能在多大程度上满足这些要求，并讨论了进一步提高电池比能量的可能性及可能途径．     

碳酸盐岩储层流体包裹体差分拉曼光谱的研究

拉曼微探针分析法对单个气液包裹体的化学成分和相态的无破坏性测量来说,目前几乎是唯一最好的方法.但是由于众多因素的影响,特别是主矿物具有较强荧光时,提高信噪比的问题急待解决.本工作对碳酸盐岩储层包裹体样品制成的薄片进行了显微观察、荧光测试及拉曼分析,并进行了空间上横向XY扫描、纵向上深度剖析(Z扫描)和冷热台上变温的流体包裹体筹分拉曼光谱测量方法的研究.结果表明,所得到的差谱揭示了包裹体更真实的光谱曲线,消除了主矿物对包裹体的干扰,以较高的信噪比显现出包裹体中流体(-170℃温度下的冰)位于位移波数3 098 cm-1附近的宽拉曼散射峰,明显的改善了信噪比.     

Molecular dynamics study of mechanical properties of carbon nanotube-embedded gold composites

The mechanical properties of nano-single crystal gold and carbon nanotube-embedded gold (CNT/Au) composites under axial tension were investigated using molecular dynamics (MD) simulation method. The interactions between atoms were modeled using the many-body tight-binding (TB) potential and the empirical Tersoff potential coupled with the Lennard-Jones (L-J) potential. We get the yield strain and the yield stress of nano-single crystal gold 0.092, 5.74 GPa, respectively. The computational results show that the increase in Young's modulus of the long CNT-embedded gold composite over pure gold is much large. From the simulation, we also find that the yield stress and the yield strain of short CNT-embedded gold composite are evidently less than that of the nano-single crystal gold.     

利用一个三粒子W态隐形传送N粒子GHZ态

杨洪钦等提出一个用两个三粒子W态作为量子信道将N粒子GHZ态从发送者传送给两个接收者中任意一个的量子隐形传送方案. 给出其理论分析,并提出了一个仅用一个三粒子W态作为量子信道将N粒子GHZ态传送给两个接收者之一的量子隐形传送的方案. 关键词： 隐形传态 GHZ态 W态量子信道     

化学让生活多姿多彩——记中国科学技术大学化学科普活动

用"化学让大自然丰富多彩、色彩斑斓——天然色素的五彩世界""化学很魔幻——揭秘化学小魔术""化学让我们生活得更智慧、更安全、更健康——引导大众消除生活误区""化学也诗意——以诗入‘化’——打造诗意化学科普"和"化学让大自然更为奇特绝妙——走进大自然,学习化学知识,感悟化学的魅力"五个主题,介绍了中国科学技术大学化学实验教学中心在化学科普教育内容方面的一些探索和经验。     

色彩斑斓的自然,五颜六色的化学

通过介绍菠菜中色素的提取分离及紫甘蓝中花青素的提取两个实验,揭示大自然色彩背后的化学奥秘,并介绍了两个实验作为科普实验项目在化学科普活动中展示和互动的效果及特点。     

Semiconductor SERS on Colourful Substrates with Fabry-Pérot Cavities

Non-metallic materials have emerged as a new family of active substrates for surface-enhanced Raman scattering (SERS), with unique advantages over their metal counterparts. However, owing to their inefficient interaction with the incident wavelength, the Raman enhancement achieved with non-metallic materials is considerably lower with respect to the metallic ones. Herein, we propose colourful semiconductor-based SERS substrates for the first time by utilizing a Fabry-Pérot cavity, which realize a large freedom in manipulating light. Owing to the delicate adjustment of the absorption in terms of both frequency and intensity, resonant absorption can be achieved with a variety of non-metal SERS substrates, with the sensitivity further enhanced by ≈100 times. As a typical example, by introducing a Fabry-Pérot-type substrate fabricated with SiO₂/Si, a rather low detection limit of 10⁻¹⁶ M for the SARS-CoV-2S protein is achieved on SnS₂. This study provides a realistic strategy for increasing SERS sensitivity when semiconductors are employed as SERS substrates.     

Reversible Solid–Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium–Sulfur Batteries by Weakly Solvating Ether Electrolytes

Despite carbonate electrolytes exhibiting good stability to sulfurized polyacrylonitrile (SPAN), their chemical incompatibility with lithium (Li) metal anode leads to poor electrochemical performance of Li||SPAN full cells. While the SPAN employs conventional ether electrolytes that suffer from the shuttle effect, leading to rapid capacity fading. Here, we tailor a dilute electrolyte based on a low solvating power ether solvent that is both compatible with SPAN and Li metal. Unlike conventional ether electrolytes, the weakly solvating ether electrolyte enables SPAN to undergo reversibly “solid–solid” conversion. It features an anion–rich solvation structure that allows for the formation of a robust cathode electrolyte interphase on the SPAN, effectively blocking the dissolution of polysulfides into the bulk electrolyte and avoiding the shuttle effect. What's more, the unique electrolyte chemistry endowed Li ions with fast electroplating kinetics and induced high reversibility Li deposition/stripping process from 25 °C to −40 °C. Based on tailored electrolyte, Li||SPAN full cells matched with high loading SPAN cathodes (≈3.6 mAh cm⁻²) and 50 μm Li foil can operate stably over a wide range of temperatures. Additionally, Li||SPAN pouch cell under lean electrolyte and 5 % excess Li conditions can continuously operate stably for over a month.