On the limiting behavior of randomly weighted partial sums

We study the almost sure limiting behavior and convergence in probability of weighted partial sums of the form where {W_nj, 1jn, n1} and {X_nj, 1jn, n1} are triangular arrays of random variables. The results obtain irrespective of the joint distributions of the random variables within each array. Applications concerning the Efron bootstrap and queueing theory are discussed.     

基片及其上方回转椭球粒子极化光散射

基于BV理论建立基片及其上方回转椭球粒子的复合散射模型,通过矢量球谐函数展开,对散射过程进行了分析,对散射场及微分散射截面详细求解,并给出了数值计算结果,与离散源方法做了比较,同时退化为球粒子与扩展Mie理论做了比较,说明了此方法的有效性。并详细讨论分析了微分散射截面随不同入射角,散射角,回转椭球粒子的尺寸、长短轴比例,距基片的距离,介电常数,粒子取向角的变化关系。结果表明:同一散射角下入射角越大,其微分散射截面越大;粒子尺寸越大,相互作用越大,其微分散射截面越大;长短轴比例越大,其微分散射截面越小;距离基片的距离越大,微分散射截面越大;微分散射截面的变化主要依赖于相对介电常数实部、虚部数值较大的一方,并且随粒子取向角的增大而增大。     

Migration and Annihilation of Triplet Excitation Energy in the Charge-Transfer Anthracene-Tetrachlorophtalic Anhydride Crystal

Abstract

The emission spectra of the charge-transfer crystal of anthracene-tetrachlorophtalic anhydride were studied in the 1.7-300 K temperature range. Delayed fluorescence was observed over the whole temperature range. At temperatures below ～40 K it results from heterogenous (mobile exciton-trapped exciton) triplet-triplet annihilation. At higher temperatures it is due to homogenous triplet-triaplet annihilation. The existence of mobile excitons is also proved by the character of the ESR lines which are very narrow Lorentzians. The phosphorescence, observed only in the range 1.7–40 K, originates from at least two different kinds of traps with energies ～6 cm^?1 and ～140 cm^?1, respectively. The vibrational structure of the phosphorescence is identical to that of anthracene, with 0—0 band blue-shifted by ～400cm^?1. A kinetic model of trapping and detrapping of triplet excitons as well as the nature of the traps are discussed.     

Microstructure and mechanical properties of nano-Y2O3 dispersed ferritic steel synthesized by mechanical alloying and consolidated by pulse plasma sintering

Ferritic steel with compositions 83.0Fe–13.5Cr–2.0Al–0.5Ti (alloy A), 79.0Fe–17.5Cr–2.0Al–0.5Ti (alloy B), 75.0Fe–21.5Cr–2.0Al–0.5Ti (alloy C) and 71.0Fe–25.5Cr–2.0Al–0.5Ti (alloy D) (all in wt%) each with a 1.0?wt% nano-Y₂O₃ dispersion were synthesized by mechanical alloying and consolidated by pulse plasma sintering at 600, 800 and 1000°C using a 75-MPa uniaxial pressure applied for 5?min and a 70-kA pulse current at 3?Hz pulse frequency. X-ray diffraction, scanning and transmission electron microscopy and energy disperse spectroscopy techniques have been used to characterize the microstructural and phase evolution of all the alloys at different stages of mechano-chemical synthesis and consolidation. Mechanical properties in terms of hardness, compressive strength, yield strength and Young's modulus were determined using a micro/nano-indenter and universal testing machine. All ferritic alloys recorded very high levels of compressive strength (850–2850?MPa), yield strength (500–1556?MPa), Young's modulus (175–250?GPa) and nanoindentation hardness (9.5–15.5?GPa), with up to 1–1.5 times greater strength than other oxide dispersion-strengthened ferritic steels (<1200?MPa). These extraordinary levels of mechanical properties can be attributed to the typical microstructure of uniform dispersion of 10–20-nm Y₂Ti₂O₇ or Y₂O₃ particles in a high-alloy ferritic matrix.     

Comparative analysis of the full set of methylated β‐cyclodextrins as chiral selectors in capillary electrophoresis

The chiral separation ability of the full library of methylated‐β‐cyclodextrins towards pharmacologically significant racemic drugs including basic compounds was studied by chiral CE. The syntheses of all the methylated, single isomer β‐cyclodextrins were revised and optimized and the aqueous solubility of the derivatives was unambiguously established. The three most relevant commercially available methylated isomeric mixtures were also included in the screening, so a total of ten various methylated CDs were investigated. The effects of the selector concentration on the enantiorecognition properties at acidic pH were investigated. Among the dimethylated β‐cyclodextrins, the heptakis (2,6‐di‐O‐methyl)‐β‐cyclodextrin isomer (2,6‐DIMEB) resulted to be the most versatile chiral selector. Terbutaline was selected as a model compound for the in‐depth investigation of host‐guest enantiodiscrimination ability. The association constants between the two terbutaline enantiomers and 2,6‐DIMEB were determined in order to support that the enantioseparation is driven by differences is host‐guest binding. The migration order of the enantiomers was confirmed by performing spiking experiments with the pure enantiomers. 1D and 2D NMR spectroscopy was applied to the 2,3‐, and 2,6‐DIMEB/terbutaline systems to rationalize at molecular level the different enantioseparation ability of the dimethylated β‐cyclodextrin selectors.     

电控聚合物分散液晶全息透镜及特性研究

报道位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜的研制及特性研究,理论上,根据耦合波理论,研究了不同的相分离程度系数下,理想位相型电控聚合物分散液晶(H-PDLC)全息衍射透镜在可见光波长(400—800nm)的衍射特性.实验研制了衍射效率最高为70%的电控H-PDLC变焦透镜样品,研究表明H-PDLC透镜具有优良的成像特性,和快速响应的电控开关特性,在光学成像系统,光通信系统中具有良好的应用前景.     

高分散纳米薄水铝石和纳米氧化铝的制备及其对甲基橙的吸附性能

以硝酸铝为铝源,尿素为沉淀剂,采用无模板水热法合成纳米薄水铝石(γ-AlO(OH))。在不同温度下煅烧后,得到氧化铝产物(γ-Al2O_3和θ-Al2O_3)。利用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、氮气吸附-脱附法和紫外-可见分光光度计(UV-Vis)对产物进行了表征分析。并且研究了产物对甲基橙(MO)的吸附性能,系统地考察了吸附时间、溶液的pH值、甲基橙浓度及循环使用对产物吸附性能的影响。此外,还对吸附过程进行了相关吸附理论研究。结果表明:与其他方法所制备的产物相比,通过该方法获得的产物的分散性更高,形态更均匀和完整。产物为高度分散的纳米捆扎状结构。γ-AlO(OH)对甲基橙的最大吸附量达1 492.5 mg·g~(-1)。另外,产物的吸附机制包含化学作用吸附机制和静电作用吸附机制等。3种产物对甲基橙的吸附均符合Langmuir单分子层吸附模型,吸附过程均符合二级动力学特征。     

A personal journey on using polymerization in aqueous dispersed media to synthesize polymers with branched structures

This short review is dedicated to celebrate Prof.Shoukuan Fu's 80 th birthday by discussing several of my accomplished projects over the past twenty years,which all applied radical polymerization in aqueous dispersed media for producing polymers with branched structures.These projects include the use of microemulsion polymerization for syntheses of fluorescent nanoparticles,hairy nanoparticles and hyperbranched polymers;the use of miniemulsion polymerization for synthesis of star polymers and light-emitting nanoparticles;the use of seeded emulsion polymerization for synthesis of hairy nanoparticles and hyperstar polymers;and the use of precipitation polymerization for synthesis of hollow polymer nanocapsules.Discussion of these projects demonstrates intriguing features of polymerization in biphasic dispersed media via either conventional radical polymerization or controlled radical polymerization to effectively regulate the branched structure of functional polymers.     

水产品中11种海洋生物毒素的高效液相色谱-四极杆/静电场轨道阱高分辨质谱检测方法研究

建立了水产品中11种海洋生物毒素的高效液相色谱-四极杆/静电场轨道阱高分辨质谱(HPLC-Q-Orbitrap HRMS)检测方法。该方法采用分级提取原理,结合分散固相萃取技术(dSPE)和载体辅助液液萃取技术(SLLE),建立了对亲水性及亲脂性海洋生物毒素的"一站式"提取净化体系。在优化条件下,11种毒素在一定质量浓度范围内具有良好的线性关系,相关系数(r)均大于0.99。该方法对11种毒素的检出限为1～10μg/kg,定量下限为2～20μg/kg,加标回收率为55.6%～122%,相对标准偏差为5.4%～16%。方法快速高效,可操作性强,解决了不同理化性质的海洋生物毒素的通用性检测问题,可满足水产品中海洋生物毒素的快速筛查要求。