基于CBS的人体安检图像组合增强方法

在X射线人体康普顿背散射(CBS)安检系统中,图像的清晰度对于识别隐匿在人体上的违禁品非常重要.根据人体CBS图像的特点,从人眼视觉感知的特点出发,提出了一种图像组合增强方法,明显改善了图像质量,获得了层次清晰、轮廓分明、背景均匀的CBS图像.     

形态滤波在快中子图像降噪处理中的应用

在基于CCD耦合闪烁光纤阵列的快中子照相系统中,快中子图像受噪声污染较为严重.针对快中子图像中的椒盐噪声和泊松噪声,研究了形态滤波技术在降噪方面的应用.结果表明在对快中子图像处理过程中,基于二维多方向结构元素的形态滤波在滤除噪声和保持图像细节等方面效果较佳.     

基于BM3D算法的快中子图像降噪方法

在快中子照相过程中,由于受到各种因素影响,快中子图像严重降质,呈现大量噪声,不利于无损检测和后续的定量分析。通过噪声分析得出了快中子图像的噪声统计分布符合高斯噪声模型,探讨了将BM3D算法应用到快中子图像降噪处理的方法。实验结果表明,BM3D算法不仅能够有效滤除快中子图像的噪声,而且保护了图像的细节和边缘信息,可为快中子图像的降噪处理提供参考。     

基于BM3D frames和方差稳定化变换的中子图像复原方法

中子照相是无损检测中应用较为广泛的一种技术。然而中子成像系统诸多不可避免的物理因素会导致所得中子图像严重降质,如噪声污染和空间模糊等。针对此问题,本文提出了一种将BM3D frames和方差稳定化变换相结合的中子图像复原方法。此方法首先对图像中的泊松高斯噪声进行变换,变换后数据成为符合高斯分布的噪声,然后用BM3D frames滤除变换后的高斯噪声,最后对去噪结果进行逆变换即得复原图像。该方法对强泊松高斯噪声有很强的抑制作用,且可很好地保留降质中子图像中的细节。实验结果表明,该方法在客观数据和视觉感受上均表现出稳健高质的复原性能。     

基于PCA和BM3D的噪声估计方法及其在中子图像去噪中的应用

针对中子图像的去噪问题,本文提出了一种弱化残差图像特征值的噪声估计方法。该方法将残差图像作为噪声图像,利用主成分分析（PCA）分析了残差图像特征值,估计了噪声强度。根据噪声强度,应用三维块匹配方法（BM3D）去除了噪声,逐步弱化残差图像特征值,得到了最终噪声估计值。实验结果表明,该方法能估计模拟噪声图像和实际含噪中子图像的高斯噪声,计算效率高,可实现较好的去噪复原效果。     

卷积反投影法重建康普顿背散射图像过程中的数据修正

CBS机是近几年才兴起的无损探测技术。它与CT技术不同之处是传统CT技术是利用射线穿过人体时,各个部位对射线吸收的衰减量的积分来重建图像,而CBS机是利用入射射线在人体各个部位中的某点产生背散射(散射角α大于90°)的光子数来重建图像。重点分析了利用经典的卷积反投影算法重建康普顿背散射扫描图像过程中的数据修正问题。     

X射线背散射透射一体成像系统设计

介绍了X射线检测技术在安检领域的应用情况,讨论了背散射成像系统组成结构。提出2种可经过一次扫描获得背散射图像与透射图像的一体机模型,并且搭建了相应的实验平台,完成了透射和背散射成像获取实验。特别是在双源结构平台上对藏匿在箱包中的TNT、硝酸铵爆炸物与水作为检材的透射、背散射图像内容做了对比说明;分析了单源并联一体机透射图像分辨率低的问题,为进一步改进背散射透射一体机图像信号噪声比和图像分辨率指出解决方法。     

基于剪切波变换的辐射图像泊松噪声降噪技术研究

为了降低由统计涨落引起的辐射图像噪声，提出了一种基于剪切波变换的降噪方法。该方法以低剂量射线或质量厚度大的物体的辐射图像为研究对象，对此类辐射图像进行了噪声分析，利用Anscombe变换将统计涨落引起的泊松噪声转换为高斯噪声，再运用剪切波分解、阈值去噪、剪切波重构和Anscombe逆变换得到降噪图像。结果表明，当剪切波分解层数为5，采用改进阈值函数及极小极大原理阈值时可达到最优降噪效果，该方法能较好地去除辐射图像中的泊松噪声并保留边缘、细节信息，在视觉和量化指标上均优于传统降噪方法。     

60Co γ射线对视频质量的影响与消噪方法的初步研究

视频装置受γ射线照射后,视频图像出现不同强度噪声,影响图像的清晰度.为消除此类图像噪声,深入研究γ射线对视频装置各组成元件的影响机制,总结视频图像噪声产生机理,根据视频监控装置的实际使用环境,提出了从软、硬件两方面采取措施以提高视频图像质量的方法.设计了一套完善的硬件辐射防护装置,并结合特定的软件消噪算法用于图像消噪....     

基于结构特征对齐的γ辐射环境场景图像配准方法

针对γ辐射环境场景图像中位置、形状、颜色多样的斑块噪声在图像配准过程中比场景信息更加显著，严重干扰场景信息的特征表达，导致场景图像难以实现准确图像对齐的问题，本文提出一种联合去噪策略与结构特征对齐的γ辐射环境场景图像配准方法，该方法从降低噪声干扰和改善场景信息的特征表达两个方面提升配准精度。首先，针对γ辐射环境场景图像中斑块噪声多样性的问题，通过金字塔滑动取样策略将γ辐射环境场景图像下采样为无损子图像集，使斑块噪声被拆分为子图像中的孤立点噪声，并利用中值滤波方法对此类噪声进行去除。其次，针对场景信息特征显著性不足的问题，采用Sobel边缘特征提取方法获取场景信息的稳定结构特征，实现对斑块噪声边缘弱纹理的抑制及场景信息特征表达的提升。最后，利用傅里叶-梅林变换方法进行结构特征的准确对齐，实现γ辐射环境场景图像的准确配准。在⁶⁰Co γ辐射环境采集的图像上进行了大量对比实验，待配准图像的尺度量解析误差小于0.01,旋转量解析误差小于0.4°,平移量解析误差小于±0.6像素，实验结果表明了本文方法的有效性。     

Intensity Ratio of 2,158keV and 2,505keV Gamma-Rays in the Decay of 60Co

The intensity ratio of the 2,158 and 2,505keV γ-rays in the decay of ⁶⁰Co was measured by applying the photonuclear reactions ⁹Be(γ, n) and ²D(γ, n). The result obtained was an intensity ratio of {I (2,158)I(2,505)}–237, which exceeded all the values reported in available literature on previous measurements.     

Investigation of the space-dependent noise induced by propagating perturbations

The space-dependent behaviour of the neutron noise, induced by perturbations represented by the fluctuations of the absorption cross sections, propagating with the coolant of a PWR, is investigated in a one-dimensional one-group approach. The general space–frequency dependent problem is solved for this specific noise source with the help of the Green’s function technique. All calculations are made in the frame of first-order perturbation theory. The solution is investigated for different frequencies and system sizes. The limits of point kinetic and space-dependent behaviour were investigated. An interesting interference phenomenon was found between the point kinetic and the pure space dependent components of the noise for certain domains of the frequency and system size. The results bear some significance for the dynamics of Molten Salt Reactors (MSR), which is reported on in a companion paper.     

Determination of Microamount of Aluminum,Chromium, Copper,Iron, Manganese,Molybdenum and Nickel in Pure Water by Extraction Photometry

Aluminum, iron (III), copper, and molybdenum 8-quinolinol complexes, chromium (III) and manganese 8-hydroxyquinaldine complexes and nickel dimethylglyoxime complex can be quantitatively extracted into chloroform from large volumes of aqueous phases adjusted to an approriate pH for each metal. These metals can be determined by measuring the absorbance of the organic phases containing their complexes at an appropriate wavelength for each metal. By the proposed method, quantities exceeding 3 p.p.b. of aluminum, chromium, and manganese, and 5 p.p.b. of copper, iron, molybdenum and nickel can be determined when a 500 ml sample of water is available.     

Exact noise in three-region coupled reactors

The theory of space-dependent neutron noise is applied to the coupled core problem. The geometry modeled is a three region configuration consisting of two sub-cores with a central non-multiplying region of one-fourth to four diffusion lengths resulting in a tightly to loosely coupled system. The solution sought is the auto-spectral density function (ASDF) for the system. The results obtained show the space-dependency of the ASDF as a change in the higher frequency asymptotic form due to detector location. Those forms encountered were proportional to ω⁻² for detectors near the center of the system, ω^−3/2 when approaching the core — non-multiplying region interface and within the core region, and ω^−1/2 for locations at the outer boundaries. Break frequencies, ω_b, were correctly determined only by applying the appropriate higher frequency asymptotic form. This proves the importance of spatial effects on noise studies.     

Calculation of the ex-core neutron noise induced by individual fuel assembly vibrations in two PWR cores

Calculation of the neutron noise induced by fuel assembly vibrations in two pressurized water reactor(PWR) cores has been conducted to investigate the effect of cycle burnup on the properties of the ex-core detector noise. An extension of the method and the computational models of a previous work have been applied to two different PWR cores to examine a hypothesis that fuel assembly vibrations cause the corresponding peak in the auto power spectral density(APSD) increase during the cycle. Stochastic vibrations along a random two-dimensional trajectory of individual fuel assemblies were assumed to occur at different locations in the cores. Two models regarding the displacement amplitude of the vibrating assembly have been considered to determine the noise source. Then, the APSD of the ex-core detector noise was evaluated at three burnup steps. The results show that there is no monotonic tendency of the change in the APSD of ex-core detector; however, the increase in APSD occurs predominantly for peripheral assemblies. When assuming simultaneous vibrations of a number of fuel assemblies uniformly distributed over the core, the effect of the peripheral assemblies dominates the ex-core neutron noise.This behaviour was found similar in both cores.     

Geometrical Interpretation of Mutual Relatonship between Ordinary Coherence and Noise Power Contribution Ratio

Angular neutron fluxes leaking from the surface of lithium-oxide and graphite slab assemblies have been measured with irradiation of D-T neutrons. The spectrum measurement was performed using the time-of-flight technique with an NE213 scintillation detector. The thicknesses of the slabs were 0.6 to 5 mean free path for 14.8 MeV neutrons, and the measured leaking angles of the angular fluxes were 0.0°, 12.2°, 24.9°, 41.8° and 66.8°. The experimental results have been compared with the results calculated by the continuous energy Monte Carlo transport code MCNP, using the data in the JENDL-3PR1, ?3PR2, and ENDF/B-V nuclear data files. The comparisons between the experimental and calculated results show that the data of ⁷Li in JENDL-3PR2 is improved for the secondary emission spectra of the 4.63 MeV level and (n, 2n) reactions; the angular distributions of 3rd-and 4th-level inelastic reactions of C in the JENDLs are questionable. The thickness dependences for high energy neutrons also suggest that the total cross section of ⁷Li and the elastic cross sections of C are slightly inadequate.     

脉冲堆瞬发负温度系数的噪声测量法

根据反应堆堆内中子信号和温度信号的相关性，以及中子动力学方程和热力学绝热方程，利用噪声信号分析技术，在频域内建立了测量脉冲堆堆芯瞬发负温度系数的物理模型，同时，利用反应堆稳态运行是中子信号以及温度信号和扰动信息，通过自回归滑动和ＡＲＭＡ模型，得到中子噪声信号以温度噪声信号的功率谱密度（ＰＳＤ）再在频域内，通过最优化方法得到脉冲堆堆芯瞬发负温度系数值，该值与理论值相符。     

工业控制机数据采集系统用RC模拟滤波器的计算和选用

一、引言RC模拟滤波器,是一种低通滤波器。虽然人们对它并不陌生,但把它用于工业控制机的输入部分,并且合理地选用它,也并不是一件容易的事。随着计算机技术的发展,工业用数据采集系统得到了广泛的应用。由于它的输入讯号来自于生产过程中的各种测量仪表,而这些仪表又多安装在充满各种电磁干扰的环境中,     

光电倍增管的噪声模型

光电倍增管作为一个高灵敏的检测器．能够在来自阴极的单个光电子脉冲这样低的检测水平下工作。也就是说．在一个给定的时间间隔里输出脉冲的计数提供了光子撞击光阴极速率的测量。在这种情况下．光电倍增管本身的噪声变得更加重要了。着重讨论了光电倍增管的噪声来源,噪声特征及噪声模型。