一种改进的计算探测器校正因子的相关抽样方法

对于小尺寸探测器处于大块介质的情形, 在探测器的校正因子的Monte Carlo模拟中, 存在两个难题: 一是由于探测器尺寸很小粒子难以到达探测器并发生碰撞; 二是两个随机变量比值难以达到要求精度. 本文使用经过改进的粒子碰撞自动重要抽样方法, 再结合相关抽样方法, 解决了这两个难题, 并在MCNP-4C程序平台上加以实现. 除了粒子碰撞自动重要抽样以外, 还选用了其他3种方法: 直接模拟、区域分裂、强迫碰撞+Dxtran球分别与相关抽样方法结合, 对一个简化的探测器校正因子计算模型进行了计算. 实际计算结果表明, 相关抽样方法无论与哪种方法结合, 都起到了提高相关量计算效率的作用; 而它与粒子碰撞自动重要抽样结合, 比其他方法具有明显的优越性.     

平面坡体渐进破坏模型及其应用

平面坡体渐进破坏模型旨在通过在坡体稳定性分析中引进渐进坡坏的概念,来较合理地考虑岩土材料的峰值强度和残余强度在稳定性分析中的不同作用。通过与其它稳定性分析方法进行比较以及实例应用研究,证明该计算模型可用于初步判断坡体稳定状态并估算其破坏变形范围。这一研究也说明了水对边坡破坏的重要作用。     

热力学数据对1, 3-丁二烯燃烧特性的影响

基于G4方法, 计算了1,^{3-丁二烯框架燃烧反应机理中102个物种的热力学数据, 并考察了振动非谐性、 频率校正因子以及受阻内转动对结果的影响. 结果表明, 考虑振动非谐性或采用不同的频率校正因子, 对热力学数据的影响不大; 考虑内转动后, 对热力学数据有较大影响. 而且考虑内转动后, 得到的热力学数据与实验热力学数据吻合得更好. 用所得热力学数据模拟了1,3-丁二烯的绝热燃烧温度以及点火延迟时间, 结果显示, 要得到可靠的绝热火焰温度, 对小分子(如CO和CO₂等)的热力学数据需要采用实验结果. 将用所得热力学数据模拟得到的点火延迟时间, 与机理本身的热力学数据所得点火延迟时间进行对比, 二者差别显著, 表明所得热力学数据主要通过改变一些反应的逆反应速率常数来影响点火延迟时间. 进一步确定了用所得热力学数据对点火延迟时间有显著影响的一些物种.}     

Determination of relative molecular weights of fluorescent components in dissolved organic matter using asymmetrical flow field-flow fractionation and parallel factor analysis

Dissolved organic matter in aquatic systems is of variable structure and composition. Asymmetrical flow field-flow fractionation coupled to UV/vis diode array and fluorescence detectors (AF4–DAD–EEM) was used to assess the size and optical properties of dissolved organic matter. The results were analyzed using parallel factor analysis (PARAFAC) and statistical fractogram deconvolution to correlate fluorescing components with molecular weight fractions. This coupling, which is shown for the first time in this work, is a powerful method capable of revealing novel information about the size properties of PARAFAC components. Tyrosine/polyphenol-like fluorescence (peak B) was significantly correlated (p < 0.05) with the smallest size group (relative molecular weight = 310 ± 10 Da), microbial humic-like and terrestrial visible humic-like fluorescence (peaks M, C, A) with the intermediate size group (1600 ± 150 Da), and terrestrial fulvic-like and tryptophan/polyphenol-like fluorescence (peaks A and T) with the largest size group (4300 ± 660 Da).     

斜角入射沉积法制备渐变折射率薄膜的折射率分析

斜角入射沉积法是一种制备薄膜的新颖方法,它可以用来制备渐变折射率薄膜.本文首先探讨了膜料的沉积入射角为α,薄膜柱状生长倾斜角为β时的薄膜的填充系数;之后利用drude理论,分析研究了斜角入射沉积法制备渐变折射率薄膜的折射率与薄膜的入射角和生长方向的关系. 关键词： 斜角入射沉积 渐变折射率 填充系数     

Electromagnetic form factors of nucleons in a relativistic square-root potential model of independent quarks

The nucleon electromagnetic form factorsG _E ^P (q²),G _M ^P (q²) and the axial-vector form factor G_A(q²) are studied in a relativistic model of independent quarks confined by an equally mixed scalar-vector square root potentialV _q(r)=1/2(1+γ ⁰)(ar ^1/2+ν ₀) taking into account the appropriate centre-of-mass corrections. The respective root-mean-square radii associated withG _E ^P (q²) and G _A (q²) come out as [〈r ²〉 _E ^P ]^1/2=0.86 fm and 〈r _A ² 〉^1/2=0.88 fm. Restoration of chiral symmetry in this model is discussed to derive the pion-nucleon form factorG _πNN(q²) and consequently the pion-nucleon coupling constant is obtained asg _πNN(q²)=12.81 as compared tog _πNN(q²)_exp⋍13.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

基于空间光调制器的计算全息成像特性

把基于高分辨空间光调制器(SLM)的动态计算全息波面变换系统看作一个相干光学成像系统,分析并推导了该系统的点扩展函数（PSF）,进而研究了SLM像素结构所引起的固有切趾和展宽效应. 通过计算机模拟考察了SLM填充因子和衍射距离对系统分辨率的影响,给出了满足抽样定理所要求的系统的最小衍射距离. 最后提出了一种消除SLM像素结构影响的物波频谱预处理方法. 这一研究为优化系统设计,完善波面变换系统提供了新的途径.     

炸药水中爆炸冲击因子的新型计算方法

针对水中爆炸冲击因子在近场范围内的一些不足,利用水中爆炸冲击波的最大峰值压力与正相冲量的乘积推导了冲击因子的表达式。通过水中爆炸实验,得到了几种典型炸药的冲击波参数及其相似方程。利用该公式计算了水中爆炸冲击因子及其装药指数,并与基于平面波的水下爆炸冲击因子进行了对比。结果表明：冲击因子中的装药指数n＝0.5不仅适合所有以TNT为基本组分的炸药,也适合于RDX、HMX基的炸药。在修正冲击波形状的基础上,由峰值压力与冲量的乘积推导的冲击因子计算公式,从冲击波的毁伤作用的角度表述了水中爆炸冲击因子的物理意义,在计算近场冲击因子时具有更高的准确性。