普洱茶茶褐素类主要组分特征及光谱学性质研究

利用不同分子截留量的透析袋可有效将茶褐素类物质分离。随分子量增大,茶黄素(TF)、茶红素(TR)、茶褐素(TB)、茶多糖(TPS)含量逐渐增加,分子量大于25 000Da的样品中TB含量最高。羧基和羟基含量随分子量增大而增加,特别是总羧基含量在分子量大于25 000Da的样品中增幅最大。AFM显示,不同分子量茶褐素粒子形貌并不均一,单分子呈岛屿状态或颗粒状聚集物结构。当粒子聚集较多时,呈线状链接且有较多分支或形成网状结构。CP-MAS NMR表明,在3 500～25 000Da的茶褐素属含有多苯环的苯多酚类高聚物,结合多糖、蛋白质残基,富含羧基、羟基、甲基等基团,具有酚类物质特性。其酸未水解物经CP-MAS NMR分析表明为多苯环高聚物,CP-GC/MS共鉴定出16种可能存在的化合物。     

YBCO高温超导磁体临界电流密度快速确定方法

基于绘图法基本原理,以及YBCO高温超导带材的临界电流特性,采用有限元电磁场分析软件AnsoftMaxwell建立了空心圆柱磁体模型.根据磁场分布、并考虑到带材的临界电流密度随磁场大小和方向的变化关系,给出了影响磁体工作电流特性的磁场的分布.基于以上工作提出了一种利用Ansoft电磁场分析软件快速确定YB-CO高温超导带材临界电流密度的方法.     

栅漏间表面外延层对4H-SiC功率MESFET击穿 特性的改善机理与结构优化

本文提出了一种带栅漏间表面p型外延层的新型MESFET结构并整合了能精确描述4H-SiC MESFET工作机理的数值模型,模型综合考虑了高场载流子饱和、雪崩碰撞离化以及电场调制等效应. 利用所建模型分析了表面外延层对器件沟道表面电场分布的改善作用,并采用突变结近似法对p型外延层参数与器件输出电流(I_ds)和击穿电压(V_B)的关系进行了研究.结果表明,通过在常规MESFET漏端处引入新的电场峰来降低栅极边缘的强电场峰并在栅漏之间的沟道表面引入p-n结内建电场进一步降低电场峰值,改善了表面电场沿电流方向的分布.通过与常规结构以及场板结构SiC MESFET的特性对比表明,本文提出的结构可以明显改善SiC MESFET的功率特性.此外,针对文中给定的器件结构,获得了优化的设计方案,选择p型外延层厚度为0.12 μupm,掺杂浓度为5× 10¹⁵ cm^-3,可使器件的V_B提高33%而保持I_ds基本不变.     

交联聚乙烯电缆绝缘材料中电树枝的导电特性研究

利用光学显微观察、局部放电测量和共聚焦Raman光谱分析相结合的方法, 研究了交联聚乙烯(XLPE)电缆绝缘材料中两种典型电树枝的导电特性.尽管具有相似的培养条件, 两种电树枝却呈现出完全不同的形态,其中9 kV下典型电树枝为枝-松枝状, 11 kV下为枝状, 而且电树枝生长及局部放电规律呈现出明显的差异.枝-松枝状电树枝主干通道内存在无序石墨碳的沉积, 根据石墨碳G带与D带的相对强度,估算碳层厚度约为8 nm,树枝通道单位长度电阻小于 10 Ω· μm^-1,足以抑制电树枝内局部放电的发展,电树枝呈现出导电型电树枝特征. 枝状电树枝通道内观察到荧光背景,存在材料劣化的产物,但不存在无序石墨碳的聚集, 通道具有明显的非导电特性而不足以抑制电树枝内局部放电的连续作用. 最后提出了XLPE电缆绝缘材料中导电型和非导电型电树枝的单通道生长模型, 利用等效电路理论对XLPE电缆绝缘材料中两种不同导电特性电树枝的生长机理进行了探讨.     

Physical and analytical characteristics of an atmospheric pressure argon–helium radiofrequency capacitively coupled plasma

A very low power radiofrequency capacitively coupled plasma (13.56 MHz, 5–70 W), was generated in our laboratory on a sharp Kanthal tip without any counter electrode, as an intrinsic part of RLC series resonant circuit. Physical characteristics of this plasma obtained in Ar–He mixture, were studied as function of observation height or gas mixture composition. The excitation temperature of Ar (1500–2100 K), He (3000–3500 K) and H (2500–3200 K), the rotational temperature of the OH band (1300–2900 K), the electron temperature (5500–6500 K) and the electron number density (8 · 10¹³–2 · 10¹⁴ cm^− 3) were determined. The evolution of several atomic emission lines or molecular bands was studied in order to investigate the fundamental processes that take place in such plasma. From the point of view of analytical applications it was found that the optimum conditions of excitation (most intense emission lines and lowest detection limits) are met for a 42% He in the gas mixture and an observation height of 1 mm above the electrode. The optimum atomic emission analysis parameters were established for 7 elements (Na, Li, Ca, K, Cd, Zn and Hg) using pneumatically nebulized liquid solutions. It was found that the presence of He in the plasmogenic gas has an enhancing effect on the emission intensities and detection limits.     

不同钙基CO_2吸收剂的循环特性研究

对石灰石和白云石这两种不同钙基CO2吸收剂的循环特性进行了实验研究,考察了晶格结构不同的钙基CO2吸收剂,随着循环次数的增加,吸收剂的表面形态、分子孔径及比表面积等微观结构的变化,分析了影响吸收剂不同衰减趋势的主要原因。结果表明,白云石基B-CaO吸收剂循环吸收容量稳定性明显高于石灰石基C-CaO吸收剂;白云石中含有的MgO起到原子骨架的作用,减少吸收过程中由于生成碳酸钙产品层引起的孔堵塞,从而有效的保持了吸收剂的活性。     

UV-B辐射对2种海洋微藻生长和生理生化特征的影响

通过实验生态学和生物化学的方法,研究了UV-B辐射对杜氏盐藻、小角毛藻的生长、叶绿素含量、可溶性蛋白含量、超氧化物歧化酶活力的影响.结果表明：（1）UV-B辐射对小角毛藻的生长起促进作用,高剂量UV-B辐射对盐藻的生长具有一定抑制作用.（2）2种微藻叶绿素含量均低于对照组,UV-B辐射使盐藻叶绿素含量先下降后升高,而小角毛藻则随辐射剂量的增加呈现下降趋势.（3）2种微藻可溶性蛋白含量均低于对照组,且随辐射剂量的增加而下降;2种微藻超氧化物歧化酶活力较对照组呈现出升高的趋势.     

大环二芳基庚烷类化合物的波谱特征

通过查阅国内外相关文献和书籍,对大环联苯型二芳基庚烷和大环二苯醚型二芳基庚烷类化合物的结构特征,紫外,红外,核磁共振波谱和改良Mosher法测定绝对构型进行综述. 现已研究的来源于天然产物的大环二芳基庚烷类化合物结构上各具特征,尤以大环二苯醚型二芳基庚烷类化合物6位H最有代表性. 大环二芳基庚烷类化合物波谱特征的研究为人们鉴定结构提供了重要的依据.     

Investigation of Simultaneous Generation of Arsenic,Bismuth and Antimony Hydrides Using Inductively Coupled Plasma Optical Emission Spectrometry

Hydride generation from solution containing As(III), Bi(III), and Sb(III) by means of different borane reductants and acids using inductively coupled plasma optical emission spectrometry as a detection system was investigated. The As, Bi, Sb, B, C, H, and N lines as well as the OH and CN molecules were recorded. Their intensities in relation to hydride formation conditions were measured. Effects of the HCl, CH₃COOH, and C₆H₈O₇ acids as well as the NaBH₄, H₃B-NH(CH₃)₂, and H₃B-NH₂C(CH₃)₃ reductants on efficiency of the As, Sb, and Bi hydride generation were investigated and discussed. Influence of hydride generation conditions on plasma was studied.     

Etching of Silicon Nitride in CCl2F2, CHF3, SiF4, and SF6 Reactive Plasma: A Comparative Study

Silicon nitride is an important material layer in various types of microelectronic devices. Because of continuous integration of devices, patterning of this layer requires a highly selective and anisotropic etching process. Reactive ion etching is one of the most simple and popular plasma processes. The present work is an experimental analysis of primary etch characteristics in reactive ion etching of silicon nitride using chlorine- and/or fluorine-based organic and inorganic chemistries (CCl ₂ F ₂+O ₂ , CHF ₃+O ₂ , SiF ₄ +O₂, SF₆+O ₂ , and SF ₆+He) in order to obtain a simultaneous etch selectivity against polysilicon and silicon dioxide. A recipe, in CCl ₂ F ₂ /O ₂ plasma chemistry, which provides acceptable etch characteristics, along with a reasonable simultaneous selectivity against polysilicon and silicon dioxide, has been formulated.