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101.
1 引言 多重网格作为求解椭圆偏微分方程的快速有效方法而倍受欢迎.多重网格方法有两大要素:一是光滑,二是粗网格校正. 相似文献
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选择3种典型光电耦合器开展了反应堆中子辐照实验,中子注量为3×1011~5×1012cm-2时,位移效应导致电流传输比下降,饱和压降提高。发光器件相同,探测器为Si PIN光电二极管的光电耦合器比探测器为Si NPN光敏晶体管的光电耦合器的初始电流传输比要小,但其抗位移损伤能力更强。探测器均为Si NPN光敏晶体管,发光器件为异质结LED要比硅两性掺杂LED的光电耦合器的电流传输比抗位移损伤能力提高2个量级;以光敏晶体管为探测器的光电耦合器,在较大的正向电流和输出负载电阻条件下工作可提高抗辐射水平。此外,光电耦合器的位移损伤存在加电退火效应。 相似文献
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中子作为一种具有独特性质的亚原子粒子,在很多研究领域都具有重要且无法替代的优势. 中子三轴谱仪通过能量守恒和动量守恒原理就可以测量某一系统的弹性或非弹性散射性质,从而获得该系统的结构或动力学信息. 中子三轴谱仪得名于其3个核心部分:单色器、样品和分析器,每一部分都可以独立转动.由于三轴谱仪在物理学尤其是凝聚态物理学研究中所发挥的重要作用,中国科学院物理研究所将联合中国原子能科学研究院,在后者新建成的中国先进研究堆搭建一台现代化的热中子三轴谱仪.文章结合该谱仪,介绍了中子三轴谱仪的基本原理、技术以及应用范围 相似文献
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《应用光谱学评论》2013,48(1):19-55
ABSTRACT This review is intended to present an introduction to the use of thermal neutron activation analysis (TNAA) as an analytical technique for the determination of elements in almost all kinds of matrices. This method of analysis is generally multi-element and experimental conditions can be designed to be nondestructive to the sample. This review will focus on thermal neutron activation as this technique allows determination of approximately two-thirds of the elements on the periodic chart. There are also more and wider spread facilities in the United States that offer these services. The available facilities are located across the United States and are generally accessible to everyone. The review will also detail the advantages and disadvantages of TNAA compared to other common spectroscopic methods. An outline of the general procedure for performing the analysis of the elements using activation analysis is presented to emphasize the ease of using this technique. The outline is divided into sections that give the general procedure, how to choose the correct nuclear reaction and reaction product, and the main sources of errors that can affect the results of the study. These sources of error are subdivided into general types of errors. The general types of errors are divided into those related to pre-chemistry, problems associated with the irradiation of the samples, errors associated with the use of nuclear constants (cross sections, half-lives, transition probabilities, etc.), the choice of the correct reaction and reaction product, and those associated with the counting of the irradiated samples. The general theory of activation analysis is presented and summarizes the derivation of the equations used and the development of the comparator method of analysis. The comparator method is used to simplify the method by irradiating samples along with standards. This reduces the need for using the nuclear constants and thus reducing errors. The use of radiochemical separations to isolate analytes of choice from the radioactive matrix is also described. Some current literature is also included to give a feel for current applications of the use of thermal neutron activation analyses. The summary also describes some of the different matrices that have been used for analyses. 相似文献
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Prof. Dr. Axel G. Griesbeck Dr. Johannes Uhlig Dr. Thomas Sottmann Dr. Lhoussaine Belkoura Prof. Dr. Reinhard Strey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(50):16161-16165
Pluronic F‐127 hydrogels are highly efficient microenvironments for photochemical reactions, as demonstrated for singlet oxygen reactions of monoalkenes. Nonpolar substrates are localized in the nanosized polymer compartment, which can be visualized by neutron scattering. The efficiency of 1O2 reactions is strongly increased for tiglate derivatives and the regioselectivity of the ene reaction of trisubstituted alkenes is completely switched in comparison with solution phase and inverted in comparison with intrazeolite photo‐oxygenations. 相似文献
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