Geant4 simulation of fast-electron bremsstrahlung imaging at the HL-3 tokamak

To further research on high-parameter plasma,we plan to develop a two-dimensional hard X-ray(HXR)imaging system at the HL-3 tokamak to measure HXRs with energies ranging from 20 to 300 keV.The application of an array-structured detector ensures that this system can measure HXR-radiation spectra from the entire plasma cross section.Therefore,it is suitable for the study of fast-electron physics,such as radio-frequency wave current drives,fast electrons driving instabilities,and plasma disruptions in fusion research.In this study,we develop a simulation for calculating fast-electron bremsstrahlung in the HL-3 tokamak based on the Monte Carlo simulation code Geant4,in which the plasma geometry and forward scattering of fast-electron bremsstrahlung are considered.The preliminary calculation results indicate that the HXR energy deposi-tion on the detector is symmetrically distributed,even though the plasma distribution is asymmetric owing to the toroidal effect.These simulation results are helpful in constructing the relationship between the energy deposition on the detector and parameter distribution on the plasma cross section during HL-3 experiments.This is beneficial for the reconstruction of the fast-electron-distribution function and for optimizing the design of the HXR-imaging system.

Research on Clothing Simulation Design Based on Three-Dimensional Image Analysis

Traditional clothing design models based on adaptive meshes cannot reflect.To solve this problem,a clothing simulation design model based on 3D image analysis technology is established.The model uses feature extraction and description of image evaluation parameters,and establishes the mapping relationship between image features and simulation results by using the optimal parameter values,thereby obtaining a three-dimensional image simulation analysis environment.On the basis of this model,by obtaining the response results of clothing collision detection and the results of local adaptive processing of clothing meshes,the cutting form and actual cutting effect of clothing are determined to construct a design model.The simulation results show that compared with traditional clothing design models,clothing simulation design based on 3D image analysis technology has a better effect,with the definition of fabric folds increasing by 40%.More striking contrast between light and dark,the resolution increasing by 30%,and clothing details getting a more real manifestation.

Image processing based three-dimensional model reconstruction for cross-platform numerical simulation

Numerical simulation is the most powerful computational and analysis tool for a large variety of engineering and physical problems.For a complex problem relating to multi-field,multi-process and multi-scale,different computing tools have to be developed so as to solve particular fields at different scales and for different processes.Therefore,the integration of different types of software is inevitable.However,it is difficult to perform the transfer of the meshes and simulated results among software packages because of the lack of shared data formats or encrypted data formats.An image processing based method for three-dimensional model reconstruction for numerical simulation was proposed,which presents a solution to the integration problem by a series of slice or projection images obtained by the post-processing modules of the numerical simulation software.By means of mapping image pixels to meshes of either finite difference or finite element models,the geometry contour can be extracted to export the stereolithography model.The values of results,represented by color,can be deduced and assigned to the meshes.All the models with data can be directly or indirectly integrated into other software as a continued or new numerical simulation.The three-dimensional reconstruction method has been validated in numerical simulation of castings and case studies were provided in this study.

Clinical application of improved 2D computer-assisted fluoroscopic navigation through simulating a 3D vertebrae image to guide pedicle screw internal fixation

Objective To study the effect of using improved 2D computer-assisted fluoroscopic navigation through simulating 3D vertebrae image to guide pedicle screw internal fixation.Methods Posterior pedicle screw internal fixation,distraction

真空冷喷涂BaTiO_(3)颗粒加速过程研究

以BaTiO_(3)陶瓷颗粒为例,模拟了在不同真空冷喷涂工艺参数下的加速过程,探讨了工艺参数对颗粒速度的影响,并通过粒子成像测速装置进行验证,最后采用真空冷喷涂制备了BaTiO_(3)陶瓷涂层并测试涂层性能。模拟结果表明:颗粒速度随着气体压力和气体预热温度的增大而增大;在相同气体压力和预热温度下,颗粒粒径越小受弓形激波的影响越大;多颗粒的加速规律与单颗粒相似。粒子成像测速结果表明在0.2 MPa、300 K或373 K条件下,BaTiO_(3)颗粒速度与模拟结果分别相差约10.2%和8.1%。在该工艺参数下,采用真空冷喷涂制备得到2~3μm连续且致密的BaTiO_(3)涂层,结合力大小为8 N。研究结果表明,数值模拟结合粒子成像测速得到的工艺参数及其影响规律是可靠的,可用于指导柔性陶瓷薄膜的制备。

混凝土CT图像的3维重建技术

为了建立更加真实的3维混凝土细观模型,进行破损机理的分析。利用3维图像处理软件MIMICS对原始的CT图像进行预处理,实现了混凝土真实细观结构的3维重建,将重建结果导入到大型商业有限元软件ANSYS中,建立了更加能准确表征混凝土细观非均质性的3维有限元数值模型。在此基础上,对重建的细观有限元模型进行了数值模拟,并与其它有限元模型的分析结果进行了比较。结果表明:所建立的3维混凝土细观模型可以弥补传统随机混凝土骨料模型的不足,较好地反映出混凝土材料内部的力学特性,为最终能够深入研究混凝土材料的细观破损机理开辟新的途径。

FY-3/中分辨率光谱成像仪星上黑体的在轨太阳污染模拟与抑制

对风云三号(FY-3)中分辨率光谱成像仪(MERSI)的黑体进行了在轨太阳污染模拟,以掌握在轨太阳污染对面源黑体的影响,同时研究了抑制太阳污染的措施。模拟了FY-3卫星轨道及全轨道周期内太阳光的入射角,使用Tracepro软件建立了太阳污染模拟的模型,利用太阳光入射与MERSI的相对位置对太阳污染进行仿真,分析了污染随光谱成像仪扫描镜旋转和卫星飞行位置的变化。最后,根据分析结果设计了太阳污染抑制措施,并对抑制效果进行了仿真验证。结果表明:在扫描镜附近区域设置遮光板,有效地抑制了太阳光的污染,使辐射量级小于0.1 W,整个太阳污染功率下降了97%以上,对黑体有良好的保护效果。另外,提出的方法提高了面源黑体温度的均匀性和稳定性,保证了红外通道星上定标精度。

基于5/3提升小波的图像压缩算法及其FPGA仿真实现

传统小波变换具有很好的时间和频率特性,适合于突变信号分析,被广泛的应用于解决边缘提取和图像压缩问题.但传统小波变换依赖于傅立叶变换、计算量大,不适用于高速实时信号处理领域.相比传统小波变换,提升小波变换则不依赖于傅立叶变换,有效的降低了计算复杂度、适合硬件实现、且可以节省存储空间.因此,设计了一种基于5/3提升小波的图像压缩算法,并对其FPGA仿真实现进行了研究.实验结果表明,该方法对数字图像压缩是有效的.

基于蒙特卡罗模拟3-D PET图像重建的研究

应用蒙特卡罗模拟软件GATE对Ge Discovery LS PET/CT扫描系统进行模拟,获得三维投影数据,分别采用三维有序子集最大期望值法(3-D OSEM)与三维滤波反投影法(3-D FBP)进行图像重建,从空间分辨率、成像的对比度以及信噪比等方面对3-D OSEM法与3-D FBP法的重建结果进行比较。结果显示,对蒙特卡罗方法模拟获得的三维投影数据,采用3-D OSEM法重建比3-D FBP法重建得到的图像质量好。

Study on Wave Field Characteristics and Imaging of Collapse Column in Three-Dimensional Detection with Love Channel Wave Reflected outside the Working Face

The safety accidents caused by collapse column water diversion occur frequently, which has great hidden danger to the safety production of coal mine. Limited by the space of underground, the detection of collapse column on the outside of working face has been a difficult problem. Based on this, numerical simulation and imaging research were carried out in this paper. The results indicate that when a seismic source near the roadway is excited, a part of seismic wave propagates along the roadway direction, namely direct P-wave, direct S-wave and direct Love channel wave. When the body waves and Love channel wave propagating to the outside of working face meet the interface of collapse column, the reflected Love channel wave and reflected body waves are generated. Reflection body waves and direct waves are mixed in time domain, which is difficult to identify in seismic records, while reflected Love channel wave whose amplitude is relatively strong. The reflected Love channel wave which has a large interval from other wave trains in the time domain is easily recognizable in seismic record, which makes it suitable for advanced detection of collapse column. The signal-to-noise ratio of X component is higher than that of Y component and Z component. According to the seismic records, polarization filtering was carried out to enhance the effective wave, which removed the interference waves, and the signal was migrated to get the position parameters of collapse column interface, which was basically consistent with the model position.

Device topological thermal management of β-Ga_(2)O_(3) Schottky barrier diodes

The ultra-wide bandgap semiconductor β gallium oxide(β-Ga_(2) O_(3)) gives promise to low conduction loss and high power for electronic devices. However, due to the natural poor thermal conductivity of β-Ga_(2) O_(3), their power devices suffer from serious self-heating effect. To overcome this problem, we emphasize on the effect of device structure on peak temperature in β-Ga_(2) O_(3) Schottky barrier diodes(SBDs) using TCAD simulation and experiment. The SBD topologies including crystal orientation of β-Ga_(2) O_(3), work function of Schottky metal, anode area, and thickness, were simulated in TCAD, showing that the thickness of β-Ga_(2) O_(3) plays a key role in reducing the peak temperature of diodes. Hence, we fabricated β-Ga_(2) O_(3) SBDs with three different thickness epitaxial layers and five different thickness substrates. The surface temperature of the diodes was measured using an infrared thermal imaging camera. The experimental results are consistent with the simulation results. Thus, our results provide a new thermal management strategy for high power β-Ga_(2) O_(3) diode.

单幅高分辨率SAR图像建筑物三维模型重构

提出了一种利用高分辨率SAR图像进行建筑物提取和三维重构的方法.首先,分析了高分辨率SAR图像建筑物产生的电磁散射的类型,给出了不同类型散射区域的后向散射计算方法,并在此基础上给出了一种利用建筑物三维CAD模型进行SAR建筑物特征区域图像仿真的方法;其次,给出了利用建筑物的二次散射结构确定建筑物底部轮廓位置和方向的方法,并提出了一种基于分布密度函数差异的仿真图像迭代匹配方法,进行建筑物高度的反演.仿真SAR图像后向散射系数用来划分建筑物不同的散射区域,通过计算特征区域之间的分布密度函数差异,以取得最大匹配度值的仿真图像对应的检验高度作为建筑物的反演高度;最后,选用了两幅不同屋顶类型的实际机载高分辨率SAR图像进行建筑物提取和三维重构实验,试验结果较为理想,验证了所提方法的可行性和有效性.

基于OpenGL的AWX格式红外云图三维仿真技术应用

针对AWX格式红外云图数据特点,依据红外云图三维仿真原理,通过构建DEM模型和应用OpenGL技术,提出了适合云图自身特点真实感表现的颜色及透明度获取方法,实现了对AWX格式红外云图三维仿真显示,并给出了实现方法及流程。通过应用验证,该方法对AWX格式红外云图三维仿真显示速度快,更好地反映了云团的空间分布特征,增强了云图的显示效果。

基于CT扫描的计算机模拟薄木刨切

基于CT扫描和计算机模拟技术,本文介绍了一种制定原木截断和木方锯剖方案的方法。通过扫描获得原木内部结构的相关信息、图象处理和三维重建,在计算机上进行原木模拟刨切加工,并在屏幕上显示虚拟刨切薄木的图象。可对同一木段进行多方案的重复加工,通过对显示图象的比较分析,制定出优化加工方案。

红外成像系统噪声测量仿真研究

介绍了红外成像系统的噪声模型和测量方法,首先分析了二代红外成像系统不同于一代红外成像系统的特性。将红外成像系统噪声按时空三维空间划分为7个分量,就三维噪声各个分量表现方式进行了分析,并给出了不同红外成像系统的主要噪声分量;其次,结合噪声模型给出了红外系统噪声测量方法;最后给出了实验结果,对模型结合实测数据用于噪声仿真进行了尝试,并在某试验中得到了初步应用。

泰伯衍射光场的三维分布特征

采用菲涅尔近似公式和傅里叶级数展开的方法，分析了罗奇光栅、正弦强度光栅、正弦振幅光栅的泰伯衍射光场的三维强度分布特征，给出了计算机模拟的三维强度分布图，并讨论了一些在三维传感领域有应用前景的性质。

油基钻井液环境下电成像仪器对裂缝响应的数值模拟

基于电磁场理论及三维有限元素法,提出一种用于模拟电成像仪器对裂缝响应的算法。该算法适用于电成像仪器在油基钻井液环境下对裂缝(包括水平裂缝、倾斜裂缝和交叉裂缝)响应的数值模拟。当裂缝张开度大于1 mm时,随着裂缝张开度的减小,裂缝处响应值也相应减小,算法对裂缝有较好的分辨效果;算法对裂缝的识别能力受背景地层与裂缝流体电阻率对比度的影响;仿真结果可以清晰地反映裂缝所处地层位置及方位角,对于倾斜裂缝,通过后续处理还可进一步获取裂缝倾角。

基于间接校正的高分三号正射影像生成

由于高分三号卫星(gaofen-3 satellite, GF-3)数据问世时间较短、参数不足,现有软件未针对GF-3数据添加传感器支持,导致难以利用现有各类软件生成其正射影像。提出一种基于间接校正的GF-3正射影像生成方法。模拟待校正区域卫星成像过程,采用RD模型利用与该区域对应的DEM数据构建模拟GF-3影像;在模拟与真实GF-3影像中分别提取特征点,并配准提取的特征点对,进而建立两影像间的映射关系;利用模拟GF-3影像分别与DEM数据和真实GF-3影像之间的映射关系,间接完成正射校正,生成正射影像。针对GF-3多成像模式的特点,选取3种具有代表性成像模式的影像进行正射影像生成试验,取得了较好的实验结果。将真实GF-3影像与模拟GF-3影像的对应像元坐标进行比较表明,x和y方向误差均小于一个像元,精度较高。提出算法充分考虑到了GF-3系统的成像特点,在不同的地形细节均取得了较好的结果。定性和定量的分析实验结果验证了提出方法的可行性及有效性。

基于实测数据的红外成像系统噪声测量仿真

介绍了红外成像系统的噪声模型、测量方法和基于实测数据的噪声仿真法。通过分析二代红外成像和一代红外系统的不同特性,导出了更适合二代红外成像系统的三维噪声模型。就三维噪声各个分量表现方式进行了分析,给出了影响噪声分量的原因。结合噪声模型给出了红外成像系统噪声测量方法;最后进行了试验,给出了实验结果,并对模型结合实测数据用于红外图像噪声仿真进行了尝试,并在某试验中得到了初步应用。

三维流场立体仿真软件研发

根据三维立体成像原理,利用计算机三维显示技术,以软件产品(TK-Animator)形式实现了对三维流场、波浪场的立体式仿真模拟,软件同时能实现对温度、盐度等三维标量场的仿真模拟。它运用微软最先进的WPF(Windows Presentation Foundation)技术建立三维场景,采用高效三维质点追踪算法、多线程编程技术,使得三维仿真模拟能够在普通计算机上完成。立体仿真模拟技术的采用,使三维场景包括流场中的示踪粒子可以有景深、分层次地展示出来。软件生成的三维立体片源可用于任何立体播放设备。