Baseline drift effect on the performance of neutron and γ ray discrimination using frequency gradient analysis

Frequency gradient analysis (FGA) effectively discriminates neutrons and γ rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift similar to other pulse shape discrimination methods. The baseline drift effect is attributed to factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and γ rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSample/s 8-bit oscilloscope. The theoretical and experimental results both show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.     

C*-代数交叉积上的渐近同态(英文)

林华新和松井宏树提出了可分C~*-代数上的渐近同态的概念,以及Cantor极小系统上弱逼近共轭的概念.设A为Ko群有限生成的AF代数,α,β为A上的具有Rokhlin性质的*-自同构.则α和β弱逼近共轭的充要条件是,存在两列渐近同态{φ_n}:A_α→A_β和{ψ_n}:A_β→A_α,以及两列*-自同构{Φ_n},{Ψ_n}:A→A,满足对任意的a∈A,均有lim_(n→∞)‖φ_noj_α(a)-jβoΦ_n(a)‖=0和lim_(n→∞)‖ψ_nojβ(a)-jα·Ψ_n(a)‖=0.     

超声波空化作用对ICP光源辐射强度的影响

为了增大电感耦合等离子体辐射强度,降低分析检出限,实验研究了水样品经过超声波空化处理以后样品表面张力和粘度的变化,并探索了空化效应对光谱强度和信背比的影响。实验结果证明,样品溶液的表面张力和黏度随着超声波功率和空化时间的增加均呈现出先减小后增大的变化规律,在功率为50 W、时间为15min时水样品的表面张力和粘度最低。经此条件处理的水样品引入ICP以后,元素Al,Cd,Mn,Ni,Pb和Zn的谱线强度比无空化处理时分别提高了56.73%,57.23%,44.57%,43.20%,39.04%和40.19%,光谱信背比分别提高了61.54%,64.86%,44.95%,52.27%,40.84%和40.85%。可见,空化处理水溶液能够改善ICP发射光谱质量。     

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??A class of backward doubly stochastic differential equations driven by white noises and Poisson random measures are studied in this paper. The definitions of solutions and Yamada-Watanabe type theorem to this equation are established.     

强场亚周期光脉冲研究

强场亚周期光脉冲的产生是未来激光光源发展所追求的先进内容之一,其不仅标志了超快激光技术的前进方向,并且将开启新型强场光与物质相互作用研究的大门。作为当前强场物理研究的一个重要课题——阿秒脉冲技术,强场亚周期光脉冲的出现将带给它新的发展机遇。强场亚周期光脉冲不仅可以直接产生极紫外波段孤立阿秒脉冲,而且其光电场的可裁剪性能够用来优化阿秒脉冲的产生。然而,亚周期光脉冲对应的超宽带光谱,使强场亚周期光脉冲的产生面临很大的挑战性。将多个中心波长不同的少周期超短脉冲进行合并的光场相干合成技术是实现强场亚周期光脉冲的有效技术。文章将介绍亚周期光脉冲的研究进展,着重描述基于光场相干合成技术的强场亚周期光脉冲产生方法。     

关于数学建模课程的一些思考

数学建模课程的教学目标是培养学生应用数学解决实际问题的能力.根据多年的教学实践经验,本文探讨如何在教学过程中注重数学思想方法的传授和能力的培养.对目前教学过程中存在的一些问题进行了剖析.介绍了我们在课程的课外延拓方面所做的一些工作.     

改进的口腔微生物种群模型及其Lyapunov稳定性

考察人体口腔异味现象,利用恒化器建模方法,改进了人体口腔系统中微生物种群关系的模型,利用Lyapunov稳定性理论分析了系统的平衡点及其稳定性.进而得到结论,口腔异味作为疾病,需要专业医治才能治愈.数值模拟结果证实了理论分析的正确性.     

在类比系统中研究引力和黑洞的性质

引力和量子力学的融合是理解时空起源和引力本质的重要问题,也是一个长期悬而未决的基础物理学根本问题。理论物理学家们对此提出了诸多理论猜想,也做出了许多预言。然而一些相关的预言涉及的效应极其微弱,因此难以通过实验观测加以证实。通过类比引力系统,人们可以将这些引力效应转化为实验室可测可控系统的一些效应。对这些类比系统的研究一方面可以帮助人们更深入地理解引力的性质本身,另一方面也可以为其他相关领域的研究提供启发和新的思路。文章将以几个具体的类比系统为例简要介绍类比引力研究的历史和最近的一些研究进展。     

Extension Operators Preserving Biholomorphic Mappings on Hartogs Domains*

In this paper, the authors extend the Roper-Suffridge operator on the generalized Hartogs domains. They mainly research the properties of the extended operator.By the characteristics of Hartogs domains and the geometric properties of subclasses of spirallike mappings, they obtain the extended Roper-Suffridge operator preserving almost starlikeness of complex order λ, almost spirallikeness of type β and order α, parabolic spirallikeness of type β and order ρ on the Hartogs domains in different co...     

A Note on the Pair Excitation Across Major Shell in Deformed Nuclei

Valence nucleons usually play a dominant role in low energy nuclear spectra. The original version of the Interacting Boson Model[1](IBM) with the assumption that all degrees of freedom arise from the valence shell reproduces well large amount of experimental data. However this assumption does not work well in some cases, for instance, in the even isotopes of Sn, Cd, and Hg, Pb rather well developed intruder bands121 lie outside the IBA model space. K. Heyde et al. attributed these low lying intruder states to the pair excitation (PE) across major shell131. In the well deformed nuclei one can hardly think of the closed shell core as being spherical and inert. The rapid change of Nilsson levels with deformation seems to indicate that there should be excitations of nucleons across major shells in the well deformed nuclei.