Fusion Core Imaging Experiment Based on the Shenguang Ⅱ Facility

A laser fusion experiment was performed based on the Shenguang Ⅱ Facility ,An image of thermonuclear burning region was obtained with a Fresnel zone plate-coded imaging technique,where the laser-driver target was served as an α-particle soure ,and the coded image obtained in the experiment was reconstructed by a numerical way.     

单气泡破裂产生膜液滴空间分布实验研究

本文研究了常温、常压条件下自由液面单气泡破裂产生的膜液滴现象。利用染色液滴撞击熟宣纸表面不洇散特性,加工宣纸纸筒进行稀释墨水中气泡破裂产生膜液滴空间分布实验,并通过后续图片扫描及编写Matlab图像处理程序获得膜液滴在圆柱纸筒上的尺寸分布、空间分布信息。通过改变实验条件,讨论分析气泡尺寸及纸筒半径对膜液滴空间分布结果的影响,获得了常温、常压条件下自由液面单气泡破裂产生膜液滴空间分布规律。     

EAST等离子体图像采集与位置识别技术

本工作采用快速CCD相机采集并保存托卡马克等离子体放电时的图像。根据放电时等离子体图像的位置特点,采用改进的主动轮廓模型算法实时获得等离子体边界位置,并通过最小二乘法对其边界进行拟合,以此获得等离子体的中心位置,为进一步进行等离子体的实时控制提供了基础。该方法已成功应用于EAST装置的放电实验中,并取得了良好的效果。     

用于激光产生的高能X射线源能谱诊断的滤片堆栈谱仪的研制

为了诊断基于激光的短脉冲、高强度的高能X射线源能谱特性,本文利用不同材料和厚度的金属滤片和记录介质研制了一套滤片堆栈谱仪。基于Greval算法发展了能谱反解程序,并使用蒙特卡罗程序Geant4模拟得到了谱仪的响应函数。在星光Ⅲ激光装置上验证了谱仪的可靠性,获得了ps激光与固体靶相互作用产生的10 keV~3 MeV轫致辐射能谱,从而验证了谱仪的可靠性。     

基于卷积神经网络的大尺寸气泡体积二维图像测定方法

由于表面张力与惯性力作用,静止流场内较大尺寸气泡[500<气泡雷诺数（Re）<2000]形成不规则几何形状,造成二维图形处理方法等效球体或椭球获取三维体积的方式误差较大。此外,由于不规则界面的散射和反射,引起二维图像处理中边界模糊,难以辨识。本文以高速摄像机获得的静止流场内大尺寸气泡二维灰度图像作为卷积神经网络（CNN）的输入,以图像内气泡二维投影面积及实验获得三维体积训练网络,并用训练好的网络预测气泡体积。实验采用小气泡叠加法获得真实气泡体积,与网络预测结果进行对比。结果表明,该方法与传统图像处理方法相比,不需要对气泡形状进行假设,提高了对大尺寸气泡的适用性。      

基于APV25读出电子学系统的GEM探测器的位置分辨与X射线成像研究

采用3层GEM膜制作了有效面积为10 cm×10 cm的GEM探测器,该探测器采用二维条读出方式,条间距为400 μm,每个维度有256个读出通道。探测器的读出采用APV25读出电子学系统,根据GEM探测器的需要,设计并改进了电子学系统使用的背板连接器。实验测得GEM探测器空间分辨为76 μm。进行了X射线二维成像研究,获得了清晰的二维图像,探测器与电子学运行稳定可靠。     

噪声图象最小方差模块滤波方法

用噪声图象平滑滤波的算法对一幅加了多种噪声的图象作了平滑。结果表明，本滤波算法在既不模糊图象边缘，又不损害图象内部细节的前提下，达到了很好的去除噪声、增强图象边缘的目的．     

Characteristics of two-phase condensing flow by visualization using computed image processing

The mechanics of the condensing behavior of vapor bubbles in a subcooled bulk flow is complicated and influenced by both heat and mass transfer. To examine the characteristics of such thermal-nonequilibrium two-phase flow, experimental and analytical researches have been made. In the experiment, the movement of each vapor bubble in a flowing channel was recorded on video tapes and analyzed by an image processing system. As result, the distributions of void fraction along the test section were obtained. In the analysis, a simple analytical model was introduced to predict the distributions of void fraction and liquid subcooling temperature. By considering the rate of vapor condensation along the flow direction, the differential equation of energy balance between two phases was obtained. Integration of this equation yielded the void fraction and bulk liquid subcooling at any position. The condensation rate was estimated as a function of the local liquid subcooling, interfacial area and mass velocity. Finally, a close fit between calculated results and experimental data was obtained.     

基于图像熵的数字化核电站人机界面复杂度快速评价

计算机画面是数字化核电站人机界面的基本组成元素,画面的复杂程度会影响操纵员对核电站情况的掌握。为对单幅画面进行快速有效的复杂度定量评价,本文提出了一种基于图像熵的定量评价方法。首先对画面做图像化处理,并转化为灰度图,然后利用图像熵的定义,计算整个画面的熵值,并将其作为画面复杂度的度量。实验结果表明,图像熵作为画面复杂度的定量评价指标,与人工评价结果具有一致性,能反映人对画面复杂度的综合感受。此方法可应用于实际工程设计,特别是在设计初期不具备实验评价和专家评价的条件时,用来对画面进行复杂度测量,可避免画面过度复杂、改善人机交互。     

Development of hybrid photon detectors with integrated siliconpixel readout for the RICH counters of LHCb

We report on the ongoing work towards a hybrid photon detector with integrated silicon pixel readout for the ring imaging Cherenkov detectors of the LHCb experiment at the Large Hadron Collider at CERN. The photon detector is based on a cross-focussed image intensifier tube geometry where the image is demagnified by a factor of 4. The anode consists of a silicon pixel array, bump-bonded to a fast, binary readout chip with matching pixel electronics. The developments and tests of full-scale prototypes with 80% active area are presented. Specific requirements for pixel front-end and readout electronics in LHCb are outlined, and recent results obtained from pixel chips applicable to hybrid photon detector design are summarized     

基于卷积神经网络的辐射图像降噪方法研究

为了抑制探测器中统计涨落引起的噪声,提出了一种基于卷积神经网络的辐射图像降噪方法。该方法利用引入残差网络结构的卷积神经网络模型,对训练集中的辐射图像样本进行了训练,拟合出含噪声图像和无噪声图像的映射关系。实验结果表明,本文方法在降低统计噪声的同时保留了图像的细节。与传统的降噪方法相比,本文方法在量化指标和视觉效果上均有较大的改善。     

Simulation of Flow Around Cylinder Actuated by DBD Plasma

The electric-static body force model is obtained by solving Maxwell's electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge(DBD) plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry(PIV) experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around the cylinder.     

基于深度学习的辐射图像超分辨率重建方法

安全检查系统中,数字化X射线摄影技术获得的辐射图像空间分辨率较低,影响图像的视觉效果。为了对单幅低分辨率辐射图像的空间分辨率进行提升,提出一种基于深度学习的超分辨率重建方法。该方法利用引入残差网络结构的卷积神经网络模型,对训练集中的辐射图像样本进行了训练,拟合出低分辨率图像和高分辨率图像的映射关系。实验结果表明,与传统的超分辨率重建方法相比,本方法在量化指标和视觉效果上均有较大的改善,且具备较快的处理速度。研究结果表明,深度学习方法在辐射图像处理中有较大的潜力。     

Analysis of Dieaway Experiments in a Uranium-238 Sphere

To analyze dieaway experiments in a highly subcritical fast system, a method is proposed that utilizes the image method to seek the solution of the time-dependent diffusion equation relevant to the early part of the time scale. Inverse Fourier and Laplace transformations are performed numerically to obtain the solution.

The method was applied to the analysis of dieaway experiments on a depleted uranium spherical system. The YOM 20-group constant set, and the JAERI-FAST 20-group constant set collapsed from the original 70 energy group set, were used in the analysis. The results of calculation agree well with the plots obtained by experiment except for the very early part of the time scale, where the uncollided neutrons from the source predominate.     

Radiation imaging using a compact Compton camera mounted on a crawler robot inside reactor buildings of Fukushima Daiichi Nuclear Power Station

ABSTRACT

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown in the aftermath of a large tsunami caused by the Great East Japan Earthquake of 11 March 2011. Measurement of radiation distribution inside the FDNPS buildings is indispensable to execute decommissioning tasks in the reactor buildings. We conducted a radiation imaging experiment inside the reactor building of Unit 1 of FDNPS by using a compact Compton camera mounted on a crawler robot and remotely visualized gamma-rays streaming from deep inside the reactor building. Moreover, we drew a radiation image obtained using the Compton camera onto the three-dimensional (3-D) structural model of the experimental environment created using photogrammetry. In addition, the 3-D model of the real working environment, including the radiation image, was imported into the virtual space of the virtual reality system. These visualization techniques help workers recognize radioactive contamination easily and decrease their own exposure to radiation because the contamination cannot be observed with the naked eye.     

一个启发式的图像边缘检测方法

用启发式图像边缘检测的方法对图像做了实验，并与经典边缘检测方法进行了比较。结果表明，此方法比经典法在检测质量上有较大的改善，能准确有效地将图像目标的边缘从背景中提取出来．     

Image reconstruction from Compton scattering data

A new image reconstruction method was developed for a Compton camera. A simulation to determine a γ-ray source position was performed by using the simulation tool, GEANT4. An image reconstruction was made in two steps. First, a three dimensional image was constructed and projected in one selected plane, then the points from each ellipse was picked up by taking the peak points of a density distribution of crossing points between the ellipse and the first step image. The second step procedure improved the accuracy and the spatial resolution of a position determination significantly, comparing with the image obtained by only the first step. The accuracy and the resolution for a point source were obtained to be about 0.02 mm and (1.35 0.15) mm, respectively. The same procedure was applied to an imaging of the distributed y-ray source.     

Experimental observations of flow modifications in nanofluid boiling utilizing particle image velocimetry

In order to understand the effects of nanofluids upon boiling, pool boiling experiments involving both pure water and water based nanofluids were investigated. Point temperature and full velocity field measurements were obtained during pool boiling conditions using state-of-the-art dynamic particle image velocimetry (DPIV). Specifically, results of nanofluid's effect upon nucleate boiling heat transfer are investigated, in an effort to find engineering solutions in critical applications such as nuclear energy. A change in the hydrodynamic behavior of bubbles was observed with the introduction of nanoparticles. The measured velocity fields exhibited different fluid behavior for the various cases investigated which in turn highlights the complexity of the fluid flow in the pool boiling experiment. The results show a relation between wall temperature and nanofluid concentration.     

Natural Convection Heat Transfer in the Horizontal Dry Storage System for the LWR Spent Fuel Assemblies

A heat transfer and flow visualization experiment was conducted with a one-fifth scale model simulating a dry shielded canister (DSC) with 24 PWR spent fuel assemblies in order to elucidate the heat transfer characteristics and the velocity distribution for natural convection inside a DSC filled with air or water at atmospheric pressure. It was found that the average heat transfer coefficients were proportional to the one-fourth power of the Rayleigh number despite the complicated geometry inside the DSC. Flow patterns inside the DSC were visualized clearly through a digital image processing system. The velocity distributions inside the DSC were obtained quantitatively from the Particle Tracking Velocimetry. In comparison with the results of a two-dimentional thermal hydraulic analysis, computed flow patterns were similar to the experimental results and the computational temperature distributions on the sleeve surfaces agreed well with the experiments within 8%, except at the top point of the center gap. It was also found that the difference in the heat transfer coefficient was within 25% for air as the working fluid, while a satisfactory agreement was not obtained when water was the working fluid.     

基于波带片纳米聚焦装置的快速扫描X射线荧光成像实验系统

在上海光源硬X射线微聚焦光束线站BL15U1,为提高波带片纳米聚焦装置的X射线荧光成像实验效率,设计实现了一种快速扫描荧光成像实验装置。该装置包括运动控制系统、样品荧光探测系统和实验数据同步获取系统。运动控制系统设计了闭环反馈控制、样品台电机运动控制和扫描轨迹,实现了快速扫描过程中样品的准确定位。样品荧光探测系统和实验数据同步获取系统实现了硬件同步触发计数器获取荧光计数,保证了荧光成像的准确性。实验结果表明,运动控制系统三角波形跟踪误差小于20 nm,满足光斑在样品处的重复定位精度小于光斑尺寸1/10的要求。用该系统获取了标准铜网的元素分布图像,图像获取时间是“走停”扫描模式的1/5,验证了实验系统的可行性和高效性。