300 W侧面分布式抽运掺Yb全光纤放大器

采用角度磨抛的方式, 在纤芯/包层为20/400 μm双包层掺Yb光纤上制作了侧面抽运耦合器. 该耦合器对975 nm的半导体二极管抽运光的耦合效率最高可达97%, 对1080 nm信号光的泄漏比小于2%. 分析了侧面抽运耦合器的性能以及多个侧面抽运耦合器的级联分布对抽运耦合效率的影响; 同时, 在前向抽运和双向抽运方式下, 分析了级联耦合器的分布及信号光泄漏比对激光器整体效率的影响, 并进行了数值模拟. 采用自行研制的侧面抽运耦合器, 搭建了侧面耦合分布式抽运、掺Yb双包层全光纤主振荡功率放大器, 获得了波长为1080 nm、功率为303 W 的基模激光输出. 进一步增加抽运点个数, 提高抽运功率, 可获得更高的输出功率.     

Two New Steroidal Saponins from the Fresh Leaves of Agave sisalana

A new furostanol saponin, sisalasaponin C ( 1 ), and a new spirostanol saponin, sisalasaponin D ( 2 ), were isolated from the fresh leaves of Agave sisalana, along with three other known steroidal saponins and two stilbenes. Their structures were identified as (3β,5α,6α,22α,25R)‐3,26‐bis[(β‐D ‐glucopyrano‐ syl)oxy]‐22‐hydroxyfurostan‐6‐yl β‐D ‐glucopyranoside ( 1 ), (3β,5α,25R)‐12‐oxospirostan‐3‐yl 6‐deoxy‐α‐L ‐mannopyranosyl‐(1→4)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐xylopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 2 ), (3β,5α,6α,22α,25R)‐22‐methoxyfurostane‐3,6,26‐triyl tris‐β‐D ‐glucopyranoside, cantalasaponin‐1, polianthoside D, (E)‐ and (Z)‐2,3,4′,5‐tetrahydroxystilbene 2‐O‐β‐D ‐glucopyranosides. The last three known compounds were isolated from the fresh leaves of Agavaceae for the first time. The structures of the new compounds were elucidated by detailed spectroscopic analysis, including 1D‐ and 2D‐NMR experiments, and chemical techniques.     

Ex situ FTIR spectroscopy study of LiVPO4F as cathode material for lithium-ion batteries

The LiVPO₄F as cathode material for lithium-ion batteries was synthesized through two steps of solid-state reactions and investigated by ex situ Fourier transform infrared (FTIR) spectroscopy for the initial charge and discharge cycle. The characterization of the effect on the structure of the LiVPO₄F in the process of lithium-ion insertion/extraction at a molecular level by ex situ FTIR spectroscopy is helpful for the mechanism research for lithium-ion insertion/extraction and the improvement of the performance of lithium-ion batteries. In the process of the initial cycle, new bands of VPO₄F appear in the charge and the featured bands of LiVPO₄F reappear in the discharge. In this paper, ex situ FTIR spectra indicates that the structure of the LiVPO₄F in the process of lithium-ion insertion/extraction is almost not affected, which clearly states that the LiVPO₄F possesses stable structure as cathode material. Consequently, the LiVPO₄F might be expected as a potential cathode replacement for commercial lithium-ion batteries.     

Investigation on NIR, coating mechanism of PS-b-PAA coated calcium carbonate particulate

Particulate calcium carbonate is treated by polystyrene (PS)/polyacrylic acid (PAA) block copolymer with varied amount. Coating efficiency is obtained by measuring the dissolve curve. The results of near-infrared (NIR) analysis reveal the thickness and structural information of the surface polymer layer. The alignment of PS-b-PAA chain on and the interaction of carboxyl with the calcite surface are deduced on the basis of X-ray photoelectron spectroscopy (XPS) results.     

利用铜激光与光纤技术测量光速

利用脉冲式铜激光技术与光纤技术测量了光速，该实验结合光电技术，提高了测量精度．     

L—Fuzzy拓扑空间中的可数F紧性与几乎可数F紧性

本文在Ｌ－ｕｚｚｙ拓扑空间中引入可数Ｆ紧性与几乎可数Ｆ紧性的概念，并讨论了它们的性质及其相互关系。     

日冕扰动传播的数值模拟

本文应用一种新的磁流体力学模式和球坐标中的Euler全隐式计算格式,重新考察了太阳日冕扰动的传播特征。为了模拟太阳大气的磁场结构,文中采用解析和数值相结合的方法,得出了溪流状的磁场位形。在这种磁场模式下,我们讨论了太阳表面赤道附近冷物质径向喷射所引起的日冕动力学响应和伴随的物理过程,揭示了一些很有意义的物理现象。这些结果可以解释日珥的形成及伴随的日冕瞬变。     

Thermal Properties of Materials Characterized by Scanning Electron-Acoustic Microscopy

A modified technique of scanning electron-acoustic microscopy is employed to determine thermal diffusivity of materials. Using the dependence of the electron-acoustic signal on modulation frequency of the electron beam, the thermal diffusivity of materials is characterized based on a simplified thermoelastic theory. The thermal diffusivities of several metals characterized by the modified scanning electron-acoustic microscopy are in good agreement with the referential values of the corresponding materials, which proves that the scanning electronacoustic microscopy can be used to characterize the thermal diffusivity of materials effectively. In addition, for micro-inhomogeneous materials, such as biological tissues, the macro-effective （average） thermal diffusivities are characterized by the technique.     

CCD用于建立惯性坐标系

本文详细叙述了CCD测量用于建立惯性坐标系的方法,重点讨论了测定河外星系与定标星相对位置的重迭露光测量方法,并给出了在1m望远镜上利用CCD进行的试验及得到的结果。文中还给出了利用三个历元的观测确定岁差常数和章动常数采用值的改正△P₁,△q,△ρ和△ε的条件方程,并进行了精度估计。最后还将本文提出的方法与利用干板的照相方法作了比较,采用这种方法能以较高的精度把基本坐标系过渡到惯性坐标系。     

小麦花药诱导单倍体植株的减数分裂分析

本文研究了由花药诱导的72株小麦单倍体的减数分裂过程。阐述了减数分裂各期染色体的行为,特别是二价体和单价体在中期Ⅰ和中期Ⅱ的分布。根据单倍体花粉母细胞减数分裂染色体行为的特点,讨论了同源染色体间的交换、染色体向赤道面排列的机制和次级联会的原因等问题。