一种漂移室定位子性能反常现象的研究

研究了一种漂移室定位子性能的反常现象,它关系到定位子的使用寿命．着重测量了暗电流和随机噪声与时间、高压及温度的关系.     

Banach空间中全纯映射的若干性质

本文将全纯映射的若干性质推广到Ｂａｎａｃｈ空间，并应用这些性质研究有界域中的凸映射与星形映射．     

北京谱仪大型精密圆柱漂移室dE/dx粒子识别的研究

本文简要描述了北京谱仪主漂移室的dE/ds粒子识别方法,给出在物理实验应用中dE/dx性能测量的主要结果.经过系统效应的软件修正和绝对的能量刻度后,对最小电离粒子(0.4—0.5GeV/c的π)大于30次dE/dx取样的能量分辨率为7.5%.大于3σK/π分离的动量p≤0.65GeV/c.大于3σe/π分离的相应动量范围为0.2≤p≤4GeV/c.     

Size control of mesoscale aqueous assemblies of quantum dots and block copolymers

Dropwise addition of water to blend solutions of block copolymer-stabilized quantum dots (QDs) and amphiphilic block copolymer stabilizing chains PS(665)-b-PAA(68) (PS = polystyrene, PAA = poly(acrylic acid)) in DMF induces self-assembly to form photoluminescent mesoscale QD/block copolymer colloids in water termed QD compound micelles (QDCMs). Here we demonstrate reproducible kinetic control of QDCM particle size and chain stretching within the external PAA stabilizing layer via changes in the initial polymer concentration and rate of water addition. By increasing the initial polymer concentration or decreasing the rate of water addition for a constant blend composition, larger QDCM particles are obtained. From a combination of transmission electron microscopy and dynamic light scattering, the thickness of the external PAA layer is determined for various QDCM sizes, showing that PAA stretching in the external brush layer increases with increasing particle size, reaching the limit of fully extended chains for sufficiently large particles. The photoluminescence spectra from QDCMs in pure water indicate that photoluminescence properties of the block copolymer-stabilized QD building blocks are retained during self-assembly. The demonstrated control of mesoscale particle size and conformation of the stabilizing PAA layer, among other related structural parameters, via simple variation of experimental conditions is a promising step toward the application of QDCM assemblies in photonics and biolabeling.     

Square wave voltammetric determination of Hg(II) using thiol functionalized chitosan-multiwalled carbon nanotubes nanocomposite film electrode

Covalent tethering of cysteamine to chitosan using glutaraldehyde yields thiol-functionalized chitosan (CS-SH). It was cast on a glassy carbon electrode which is found to be very stable in acidic solutions and to possess a strong affinity for Hg(II) ions as confirmed by quartz crystal microbalance measurements. A glassy carbon electrode modified with a nanocomposite made from CS-SH and multiwalled carbon nanotubes was applied for square wave voltammetric determination of Hg(II). The procedure comprises the steps of (a) chemical accumulation of Hg(II) under open-circuit condition and (b) electrochemical determination of Hg(II). Linear responses are obtained in the range from 10 to 140 nM, with a limit of detection of 3 nM (S/N?=?3) under optimized conditions. The electrode was applied to the determination of Hg(II) in water samples with satisfactory recoveries.     

核探测器中混合气配制新方法

以质量流敏感器件和系统控制器为主要部件,建立起一套新的混合气配制系统,其配比误差小于满量程的1%,动态响应时间小于3s,有很好的长期稳定性,能满足核探测器对混合气体的多种需要.     

ABTS‐Multiwalled Carbon Nanotubes Nanocomposite/Bi Film Electrode for Sensitive Determination of Cd and Pb by Differential Pulse Stripping Voltammetry

A 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonate) diammonium salt (ABTS)‐multiwalled carbon nanotubes (MWCNTs) nanocomposite/Bi film modified glassy carbon (GC) electrode was constructed for the differential pulse stripping voltammetric determination of trace Pb²⁺ and Cd²⁺. This electrode was more sensitive than ABTS‐free Bi/GC and Bi/MWCNTs/GC electrodes. Linear responses were obtained in the range from 0.5 to 35 μg L^?1 for Cd²⁺ and 0.2 to 50 μg L^?1 Pb(II), with detection limits of 0.2 μg L^?1 for Cd²⁺ and 0.1 μg L^?1 for Pb²⁺, respectively. This sensor was applied to the simultaneous detection of Cd²⁺ and Pb²⁺ in water samples with satisfactory recovery.     

Towards large eddy simulations of flame extinction and carbon monoxide emission in compartment fires

The general objective of this research is to adapt current combustion modeling capabilities used in computational fluid dynamics solvers to the treatment of under-ventilated compartment fires. More specifically, we consider in the present study two models proposed to describe: diffusion flame extinction due to air vitiation; and the emission of carbon monoxide (CO) and unburnt hydrocarbon (HC) mass in a compartment fire. The flame extinction model is based on a flammability diagram parametrized in terms of vitiated air properties. The CO/HC mass model is based on: a transport equation for fuel mass; a comparison of this fuel mass to a Burke–Schumann chemical-equilibrium expression; and an interpretation of the difference as a measure of incomplete combustion. Both models are implemented into a large eddy simulation solver developed by the National Institute of Standards and Technology, USA. The models performance is tested via detailed comparisons with an experimental database corresponding to reduced-scale compartment fires. The study considers two cases that correspond to different values of the fire room global equivalence ratio and are representative of strikingly different flame behaviors. The comparative tests serve to evaluate the general ability of the models to describe the transition from extinction-free conditions to conditions in which the flame experiences partial or total quenching, as well as the transition from fire regimes with no or little CO emission to regimes that emit hazardous levels.     

光生电子和由还原剂提供的电子在卤化银颗粒中性能的比较

本文研究了光生电子和还原剂提供的电子在卤化银晶体中的行为。光灰化和还原剂灰化生成的灰雾中心的位置不同。光灰化时灰雾中心优先在卤化银颗粒内部形成,表明光生电子可以直接进入卤化银晶体的导带。还原灰化时内部灰雾中心只有在灰化剂量足够多时才形成,而且滞后于表面灰雾中心的形成,表明还原剂提供的电子虽然可以进入卤化银的导带,但它们进入导带的方式与光生电子不同。     

内敏乳剂的ESR研究

本文制备了具有化学结构缺陷以及具有物理晶格缺陷的两种内敏核壳乳剂,并研究了它们的电子自旋共振波谱。随着化学增感时间的增加,ESR信号强度增强,达到一最大值后又下降。ESR信号强度随核壳比的下降而下降;随灰化程度的上升而下降。不同减感染料由于其减感机理的不同,对内部感光性能和ESR信号强度的影响也不同。上述结果可以用空穴在颗粒内部的行为来解释。