高功率全固态绿光激光技术研究进展

 报道了高功率全固态腔内和腔外倍频两种绿光激光器研究进展。腔内倍频绿光激光器采用L型腔双棒串接结构,在重复频率10 kHz时,用三硼酸锂晶体倍频获得绿光功率186 W,光-光效率达15.8%。腔外倍频绿光激光器采用主振荡和功率放大器,在重复频率400 Hz时,获得基频激光单脉冲能量1.2 J,采用Ⅱ类相位匹配KTP晶体腔外倍频,获得525 mJ的绿光输出,倍频效率为43.7%。采用偏振合成技术获得了单脉冲能量大于1 J的绿光输出。在该激光放大器实验装置上,进行了双模块热效应补偿技术和受激布里渊散射相位共轭技术实验研究,改善了激光光束质量。     

Thickness determination of molecularly thin lubricant films by angle-dependent X-ray photoelectron spectroscopy

An angle-dependent X-ray photoelectron spectroscopy (XPS) method used to measure the thickness of molecularly thin lubricants was developed. The method was built based on an island model of patched overlayer on a flat substrate by using the photoemission signal solely from the lubricant film. Typical molecularly thin Zdol films on the CHx overcoat of unused commercial magnetic disks were measured to verify the metrology. The lubricant thickness determined by the metrology was equal to the recent result by thermostatic high vacuum atomic force microscopy. The measured deduction in the thickness of the molecularly thin lubricant films, successively irradiated by the monochromatic source operated at 14 kV/250 W, was as low as 1 ? during the first irradiation hour. XPS spectra showed that no hydrocarbons, water or oxygen were adsorbed over the Zdol outer surfaces in the tested XPS conditions. The inelastic mean free path (IMFP) of C 1s in Zdol or in CHx was found to be independent of take off angle (TOA) when TOA < 40°. The IMFP of C 1s in Zdol was ∼63.5 ? and the lubricant island thickness was ∼35 ?.     

Dispersion effect on the current voltage characteristic of AlGaN/GaN high electron mobility transistors

The current voltage (IV) characteristics are greatly influenced by the dispersion effects in AlGaN/GaN high electron mobility transistors. The direct current (DC) IV and pulsed IV measurements are performed to give a deep investigation into the dispersion effects, which are mainly related to the trap and self-heating mechanisms. The results show that traps play an important role in the kink effects, and high stress can introduce more traps and defects in the device. With the help of the pulsed IV measurements, the trapping effects and self-heating effects can be separated. The impact of time constants on the dispersion effects is also discussed. In order to achieve an accurate static DC IV measurement, the steady state of the bias points must be considered carefully to avoid the dispersion effects.     

珙桐叶总黄酮提取工艺及体外抗氧化性

运用正交试验设计探讨了绵竹白云山珙桐叶黄酮的微波辅助提取工艺条件,并对提取液的抗氧化性能进行了研究。结果表明,珙桐叶总黄酮提取的最佳工艺参数：微波功率700W,料液比（g/mL）1∶40,乙醇质量分数浓度为70%,提取时间为2min,测得每克干叶中总黄酮含量为71.03mg。对提取液的抗氧化性研究表明,珙桐叶总黄酮对超氧阴离子自由基、羟基自由基的清除率较好,在实验所选浓度范围内,总还原能力随浓度增加而增强。     

紫外-可见分光光度法在植物多糖含量测定中的应用

紫外-可见分光光度法(UV-Vis)是目前国内比较常见的一种光谱学测量方法.且近年来,其在植物多糖含量测定领域的应用越来越多.本文从UV-Vis测定植物多糖含量过程中的显色剂选取、各种条件的优化以及具体应用等方面进行综述.     

水母雪莲不同器官中铅和镉的含量分析

应用石墨炉原子吸收光谱法分析了水母雪莲不同器官中铅、镉的含量。结果表明水母雪莲各器官铅含量由多到少的顺序是叶〉根〉苞片〉茎〉花萼〉花〉种子,各器官镉含量由多到少顺序是花〉苞片〉根〉茎〉叶〉花萼〉种子。本实验方法简便快速,结果准确可靠。     

Effect of annealing on structural and optical properties of lead tungstate microcrystals

Shuttle-like lead tungstate (PbWO₄) microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning electron microscopy show that the lattice distortions of the PbWO₄ microcrystals are reduced significantly when the annealing temperature is increased to 873 K. The result from the ultraviolet-visible diffuse reflectance spectroscopy shows that the exciton absorption appears in the sample annealed at 673 K. The self-trapped exciton luminescence due to the Jahn-Teller effect is also observed in the blue band. The interstitial oxygen ions in the WO₄^2- groups are mainly resposible for the enhancement effect of the green luminescence of the annealed samples. The above results are supported by the spectrum analysis of the as-grown and the post-annealed samples using the X-ray photoelectron spectroscopy.     

成都市绿地系统土壤总汞的测定

拟定了成都市绿地系统各土壤功能区总汞含量的测定方法。样品经湿法消解后,用氢化物发生-原子荧光光谱法测定绿地土壤中的总汞。在选定的条件下,仪器检出限可达0.01ng/mL。相对标准偏差（RSD）为1.7%。样品回收率在91.0%—94.0%之间;成都市绿地土壤中公共绿地总汞含量在0.1491—9.719mg/kg之间;交通干道绿地总汞含量在0.1841—2.879mg/kg之间;居住绿地总汞含量在0.3111—2.861mg/kg之间。     

Surface modification of polytetrafluoroethylene film using single liquid electrode atmospheric- pressure glow discharge

Polytetrafluoroethylene films are treated by room temperature helium atmospheric pressure plasma plumes, which are generated with a home-made single liquid electrode plasma device. After plasma treatment, the water contact angle of polytetrafluoroethylene film drops from 114°to 46°and the surface free energy increases from 22.0 mJ/m2 to 59.1 mJ/m2. The optical emission spectrum indicates that there are reactive species such as O2+ , O and He in the plasma plume. After plasma treatment, a highly crosslinking structure is formed on the film surface and the oxygen element is incorporated into the film surface in the forms of -C-O-C-, -C=O, and -O-C=O groups. Over a period of 10 days, the contact angle of the treated film is recovered by only about 10 , which indicates that the plasma surface modification is stable with time.     

First-principles study on the crystal, electronic structure and mechanical properties of hexagonal Al3RE (RE = La, Ce, Pr, Nd, Sm, Gd) intermetallic compounds

The structural properties, elastic properties and electronic structures of hexagonal Al₃RE intermetallic compounds are calculated by using first-principles calculations based on density functional theory. Since there exists strong on-site Coulomb repulsion between the highly localized 4f electrons of RE atoms, we present a combination of the GGA and the LSDA+U approaches in order to obtain the appropriate results. The GGA calculated lattice constants for the hexagonal Al₃RE intermetallic compounds are in good agreement with available experimental values. The results of cohesive energy indicate that these compounds can be stable under absolute zero Kelvin and the stability of Al₃Gd is the strongest in all of the hexagonal Al₃RE compounds. The densities of states for GGA and LSDA+U approaches are also obtained for the Al₃RE intermetallic compounds. The mechanical properties are calculated from the GGA method in this paper. According to the computed single crystal elastic constants, Al₃La, Al₃Sm and Al₃Gd are mechanically unstable, while Al₃Ce, Al₃Pr and Al₃Nd are stable. The polycrystalline elastic modulus and Poisson’s ratio have been deduced by using Voigt-Reuss-Hill (VRH) approximations, and the calculated ratio of bulk modulus to shear modulus indicates that Al₃La compound is ductile material, but Al₃Ce, Al₃Pr, Al₃Nd, Al₃Sm and Al₃Gd are brittle materials.