Radiative lifetimes of Rydberg 6pnd J=2 states of Pb I by multichannel quantum defect theory

Energy levels of the odd-parity 6pnd J=2 Rydberg states of Pb I are analysed by the multichannel quantum defect theory (MQDT) in the frame of a five-channel three-limit calculation model. With optimal MQDT parameters, channel admixture coefficients are obtained and used to calculate the theoretical lifetimes of the levels by comparing to the previously measured lifetimes. The predicted lifetimes for higher-lying Rydberg states are given and discussed. These predicted lifetimes are very different from those obtained by the four-channel two-limit model pl:eviously used, which means that introduction of the additional interacting channel is important for studying the 6pnd J=2 Rydberg states of Pb I.     

一种高温超导磁悬浮装置

本文介绍一个基于倒挂吸引式(EMS)原理的高温超导磁悬浮试验装置．这个装置由高温超导磁体、单臂梁金属导轨、位置传感器、控制电路等组成．绕制超导磁体线圈所用的是Bi-2223／Ag高温超导线材．超导磁体工作在激磁电流为3．2A时，在5mm的空气间隙中产生0．21T的磁通密度，与单臂梁金属导轨可产生72N的垂直悬浮力．通过引入压控电流源，利用常规的超前一滞后校正实现了该磁悬浮装置的稳定悬浮和鲁棒控制，在负载变化87．5%的情况下仍能实现超导磁悬浮装置的稳定悬浮．该试验装置首次验证了高温超导线圈的可控性问题，为进一步探索高温超导线圈用于磁悬浮轨道交通系统的可行性打下了基础．     

超高介电常数非铁电单晶

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Effect of unidirectional solidification rate on Jc for current lead

The dependence of transport J_c value on the traveling rate and the nominal composition was investigated by taking different nominal compositions of YBa₂Cu₃O_6+x (Y123) + n mol% Y₂BaCuO₅ (Y211) (n = 10, 20, 30, 40 and 50) with addition of 0.5 wt% of Pt on samples processed by different unidirectional solidification rates, namely 1, 3 and 5 mm/h. The highest J_c was found in the sample with 30% Y211 addition by the higher traveling rate adjusted to prevent the formation of polycrystals. In this φ 1.56 × 60 mm sample the values of transport I_c and J_c were 1370 A and 71 700 A/cm², respectively, which were obtained by the conventional DC four-probe method with criterion of 1 μV/cm at 77 K and self-field.     

Lead Fractionation Analysis in Lipstick Samples by Inductively Coupled Plasma-Mass Spectrometry

A new analytical approach based on fractionation was introduced for lead in lipstick samples. Different separation techniques including n-hexane, glycerol extraction, and activated carbon adsorption were used to characterize the lipid fraction, polar and aromatic components of the samples. Additionally, artificial saliva and food stimulant extractions were used for the risk assessment studies. Trace metal levels in fractions were determined by inductively coupled plasma-mass spectrometry. Method validation parameters in the total element determinations were defined in terms of detection limits, accuracy, and precision. The limits of detection and quantification were 0.02 and 0.07 mg kg^?1 for Pb; whereas the repeatability and reproducibility of the results based on percent relative standard deviation were 3.0% and 7.2% for lead, respectively.     

Analytical Study of Raw Materials of Zinc Oxide Used for Enamels on Industrial Ceramics: Quantitative Analysis of Zinc,Lead, and Sulfur in These Samples by X‐ray Fluorescence and Flame Atomic Absorption Spectrometry

An analytical study is carried out to optimize X‐ray fluorescence (XRF) and flame atomic absorption spectrometry (FAAS) quantitative analysis of Zn, Pb, and S in ZnO samples commonly used to obtain industrial ceramic enamels. Pb and S in the raw materials often contaminate ZnO and are very detrimental in industrial applications. Thus, very accurate analytical determination of these elements in ceramic samples is extremely important. First of all, a mineralogical study by X‐ray diffraction (XRD) on the different components in these raw materials and the materials produced during the firing process is performed in order to establish the mineral forms in a reference sample for analysis by XRF spectrometry. The working conditions are optimized for XRF multielemental analysis, using the sample in the form of pellets, due to high loss on ignition (LOI) values. The preparation of suitable standards and working conditions for FAAS analysis have also been optimized. The content of these elements was determined by FAAS for the reference sample and several samples for industrial use, and the results were compared with those obtained by XRF. Comparison of the results obtained from XRF and FAAS analysis of Pb and Zn show more accurate values for FAAS. For ZnO, an accuracy of 0.11% with ±0.1% precision by FAAS and 0.46% accuracy with ±0.2% precision by XRF are found. For PbO, 1.06% accuracy and ±0.06% precision using FAAS and 5.6% accuracy and ±0.35% precision by XRF were found. For SO₃ determined only by XRF, accuracy was 4.76% with ±0.25% precision. These values are highly satisfactory given that these two elements are only found in small proportions.     

Solid Introduction to an ICP-Atomic Emission Spectrometer for the Analyses of Metals Contents of Air Filters

The direct introduction of solid samples (air filters) to the inductively coupled plasma source of an atomic emission spectrometer using a furnace atomizer has been studied. Conditions have been found for the analysis of elements which volatilize with varyling degrees of difficulty. Lead, copper and vandaium compounds retained on glass fibre filters from air pollution studies have been determined. The results are in good agreement with those obtained by means of established sample dissolution/atomic emision methods.     

Renormalization phenomena in Ba-diluted ferroelastic lead phosphate, (Pb1-x Ba x )3(PO4)2

Abstract

In the improper ferroelastic palmierite-type lead phosphate order parameter coupling with a defect induced conjugate field leads to the renormalization of the two different critical temperatures of three order parameter components {Q ₃} and {Q ₁ Q ₂}. The influence of the lead dilution by barium on the ferroelastic domain pattern, the critical temperature of the ferroelastic transformation R m–C2/c and the development of the intermediate regime in (Pb_1–x Ba _x )₃(PO₄)₂ is studied using optical birefringence measurements, Raman and infrared spectroscopy. At the ferroelastic transition temperature T _c the orientational contribution of the three-states Potts model becomes critical. T _c is reduced from 453 K (x = 0) to zero K at x? 0.12. Modifications of the shape of zigzag needle domains as well as the angle between the monoclinic binary axis and the W walls along [031] with temperature and increasing Ba-content are reported. Above the ferroelastic transition point the component Q ₃, which corresponds to the displacive part in the Gibbs free energy, leads to dynamic short-range monoclinic deformation in the trigonal matrix. The temperature where Q ₃ shows critical behaviour is renormalized to 720 K (x = 0.12) as compared with 563 K in pure lead phosphate. For x>0.13 no monoclinic precursor clusters were found.     

氮化镓基感光栅极高电子迁移率晶体管器件设计与制备

GaN基高电子迁移率晶体管(HEMT)作为栅控器件,具有AlGaN/GaN异质结处高浓度的二维电子气(2DEG)及对表面态敏感等特性,在栅位置处与感光功能薄膜的结合是光探测器领域重要的研究方向之一.本文首先提出在GaN基HEMT栅电极上引入光敏材料锆钛酸铅(PZT),将具有光伏效应的铁电薄膜PZT与HEMT栅极结合,提出一种新的"金属/铁电薄膜/金属/半导体(M/F/M/S)"结构;然后在以蓝宝石为衬底的AlGaN/GaN外延片上制备感光栅极HEMT器件.最后,通过PZT的光伏效应来调控沟道中的载流子浓度和通过源漏电流的变化来实现对可见光和紫外光的探测.在365 nm紫外光和普通可见光条件下,对比测试有/无感光栅极的HEMT器件,在较小V_(gs)电压时,可见光下测得前者较后者的饱和漏源电流I_(ds)的增幅不下降,紫外光下前者较后者的I_(ds)增幅大5.2 mA,由此可知,感光栅PZT在可见光及紫外光下可作用于栅极GaN基HEMT器件并可调控沟道电流.     

PbMoO4晶体生长基元和生长习性的高温拉曼光谱研究

应用高温拉曼光谱研究了PbMoO₄熔体中的生长基元.通过对不同温度下PbMoO₄晶体拉曼光谱和熔点温度附近熔体高温拉曼光谱的研究,发现PbMoO₄熔体中存在Pb²⁺阳离子和［MoO₄］^2－阴离子生长基元.进一步讨论了PbMoO₄晶体生长基元和各个低指数晶面间的相互作用,解释了晶体的生长习性和枝晶生长的原因,并指出:PbMoO₄晶体生 关键词： 钼酸铅晶体 枝晶 籽晶取向 拉曼光谱