Two new benzopyran derivatives from Gouania leptostachya DC. var. tonkinensis Pitard.

Two new benzopyran derivatives,1-[(rel 2S,3R)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone(1),and 1-[(rel 25,35)-3,5,7-trihydroxy-3,4-dihydro-2H-chromen-2-yl]ethanone(2),along with four known flavonoids,prodelphinidin C,prodelphinidin B3,(-)-epi-gallocatechin and(+)-gallocatechin,were isolated from the stems of Gouania leptostachya DC.var. tonkinensis Pitard.Their structures were determined on the basis of spectroscopic methods including HR-ESI-MS,1D and 2D NMR.Prodelphinidin C exhibited significant inhibitory activity forα-glucosidase.     

Comparable Studies of Adsorption and Magnetic Properties of Ferrite MnFe_2O_4 Nanoparticles,Porous Bulks and Nanowires

The spinel ferrites MnFe2O4 nanowires were synthesized by hydrothermal route,porous MnFe2O4 and nanoparticles morphologies were synthesized by sol-gel method with egg white.The structures,morphologies,magnetic properties and adsorption properties of these obtained ferrites with different morphologies were studied contrastively.Results show that the obtained samples exhibit ferromagnetic properties.This realizes convenient magnetic separation from solution when they are used in the treatment of organic dyes ...     

Ozone profiles retrieval from SCIAMACHY Chappuis-Wulf limb scattered spectra using MART

The Scanning Imaging Absorption spectroMeter for Atmospheric ChartographY(SCIAMACHY) instrument,launched on the Envisat satellite in March 2002,measures the earthshine radiance,simultaneously from the ultraviolet(UV) to the near infrared(NIR),in the three viewing geometries:nadir,limb,and occultation.These measurements are used to retrieve both the total amount and vertical profiles of a large number of atmospheric constituents.In this paper,stratospheric ozone profiles between 15 and 40 km altitude are ret...     

Underwater moving noise source identification based on hybrid near-field acoustical holography

Near-field acoustical holography (NAH) is a powerful tool for identifying noise sources and visualizing acoustic field. By recording the acoustic pressures in the near-field, the acoustic quantities in the whole 3-D field can be reconstructed and predicted. However, the current theory of NAH is not applicable to tracking large scale moving noise sources. Therefore, the hybrid near-field acoustical holography is developed for reconstructing acoustic radiation, which is derived from statistically optimized ne...     

起偏器参量对光学电流传感器性能的影响

以琼斯矩阵为数学工具,利用理论分析、计算机仿真和实验研究的方法,考察了偏振片的消光比和预偏角误差对光学电流传感器输出特性的影响.研究结果表明,上述偏振片参量均可在光学电流传感器的输出中引入直流分量,并使尺度因子发生一定的改变.当最终输出信号用交流电表度量时,输出信号中引入的直流分量可被交流电表中自带的隔直电容滤除,尺度因子的改变可用后续信号处理电路中的放大单元矫正.本研究结果可为光学电流传感器的设计人员提供有用的参考.     

窄脉冲外差体制CO2激光主动成像研究

根据大目标外差探测时发射功率P_T与距离R₂成正比规律的脉冲激光雷达方程和天线定理,利用国内最新研制的小型高重频电光调Q波导CO₂激光器,采用非线性扫描和激光器不等时发射技术,设计研制了一套窄脉冲外差体制CO₂激光主动成像系统,对室内20m处大目标实现了像元素64×32、成像速率10帧/s实时成像显示,图像质量较好,激光器峰值功率约为60W、脉冲重复频40KHz、前沿50ns、脉宽300ns.     

光学玻璃电流传感头线性双折射的一种测量方法

报告了一种测量光学玻璃电流传感头线性双折射的方法,以琼斯矩阵为数学工具给出了对该方法的理论分析、测量不确定度计算公式,并用实验方法给出了应用实例.此方法的主要优点是光路所用元件容易获得且测量结构简单实用.     

航天柔性结构振动控制的若干新进展

围绕航天柔性结构的振动控制，从结构及材料的数学模型、材料及器件、基本理论与方法和一体化振动控制几个方面对一些研究的最新进展进行了介绍．主动控制和被动控制的一体化技术研究是当今航天柔性结构振动控制研究的重点，两种控制方法的结合不仅优点互补，而且提高了控制系统的性能．控制用材料和器件的研究在工程应用的推动下，也取得了较快的发展，并促进了振动控制技术的实用化     

Controlled Growth Morphology of Porous Nanocrystal Iron Oxide by Electrodeposition

Fe(II) was deposited into the bottom of the mesopores of highly ordered large caged cubic mesoporous silica by electrodeposition. And the deposited Fe mesoporous silica thin film was treated by 1%―4% HF to remove the SiO2 template and then calcined. It was found that nanowire bundles, dendritic plates of porous iron oxide, dense parallel backbones of porous iron oxide were obtained at 1.4―-1.6 V and 0.08―0.1 mol/L electrolyte concentration after calcinations; the dendritic pattern of porous iron oxide film ...