Study of a millimeter-wave squint indirect holographic algorithm suitable for imaging with large field-of-view

In this paper a millimeter-wave （MMW） squint indirect holographic method is presented, which is suitable for imaging with a large field-of-view. The proposed system employs the squint operation mode to remove the background and twin- image interferences, which achieves a similar effect to off-axis holography but leaves out the large-aperture quasi-optical component. The translational scanning manner enables a large field of view and ensures the image uniformity, which is difficult to realize in off-axis holography. In addition, a corresponding imaging algorithm for the presented scheme is developed to reconstruct the image from the recorded hologram. Some imaging results on typical objects, obtained with electromagnetic simulation, demonstrate good performance of the imaging scheme and validate the effectiveness of the image reconstruction algorithm.     

SPSO同时反演乙烯火焰温度和碳黑浓度的实验研究

本文用一台测量范围为500～1100nm的便携式光谱仪对乙烯火焰30mm和50mm两个高度进行扫描,通过黑体炉标定对测量值进行修正得到单色辐射强度,进一步采用随机微粒群算法(SPSO)同时重建出火焰在这两个高度处的温度和碳黑浓度分布.与Abel逆变换以及Tikhonov正则化算法的对比,表明了SPSO方法在同时重建轴对...     

低温高密核物质测量谱仪时间投影室的集团重建

低温高密核物质测量谱仪(CEE)是研究高重子数密度区核物质性质的重离子碰撞实验谱仪。使用了先进的 SAMPA 电子学读出芯片的时间投影室(TPC)是 CEE 最核心的探测器。在集团重建的过程中,同一排读出板的信号被首先重建成 2 维集团,然后根据 2 维集团的 ADC 加权平均位置重建击中点。当信号 ADC 随漂移时间变化呈峰-谷-峰结构时,一个集团可能被重建成两个或更多击中点,从而提高双径迹分辨能力。使用模拟信号的测试显示,该重建算法在$x/ y$方向可以达到0.100/0.043 cm的位置分辨能力和1.1/2.8 cm的双径迹分辨能力。     

MCNP Dose Calculations in a CT Phantom for Therapeutic External Photon Beam

In this paper, we have addressed the problem of the radiation transport with the Monte Carlo N particle(MCNP) code. This is a general purpose Monte Carlo tool designed to transport neutron, photon and electron in three dimensional geometries. To examine the performance of MCNP5 code in the field of external radiotherapy, we performed the modeling of an Electron Density phantom (EDP) irradiated by photons from 60Co source. The model was used to calculate the Percent Depth Dose (PDD) at different depths in an EDP. One field size for PDD has been examined. A 60Co photons source placed at 80 cm source to surface distance (SSD). The results of calculations were compared to TPS data obtained at National Institute of Oncology of Rabat.     

基于全变分正则化的高能闪光照相消模糊图像重建算法

 针对高能闪光照相投影图像消模糊难度大的问题,提出了一种基于全变分正则化的消模糊图像重建算法,该算法根据闪光照相的成像特点,将客体的纵向截面作为一个整体来进行建模,并在重建方程中考虑了模糊因素,然后采用全变分范数作为正则项,构建了用于消模糊图像重建的展平泛函,将消模糊图像重建问题转化为能量泛函极小化问题,通过固定点迭代算法求解图像重建问题的最小化解。数值模拟结果表明：该算法由于考虑了闪光照相成像时的图像模糊因素,在重建时能够较好地消除模糊对重建结果的影响,在抑制噪声的同时能较好地保持图像的边缘信息,有利于提高重建图像的质量。     

螺旋锥束CT中两种解析重建算法的研究

 研究了锥束螺旋Katsevich和FDK重建算法,并对这两种算法进行比较。实验结果表明：当投影数据没有噪声的时候,FDK算法和Katsevich算法均能取得较好的效果,当对实际物体进行重建的时候,投影数据含有噪声, Katsevich算法需要对投影数据求导,而它对投影数据的噪声较敏感,重建质量有所下降。     

Performance of third-order ghost imaging with second-order intensity correlation

The third-order ghost imaging with the second-order intensity correlation is theoretically and experimentally demonstrated.The resolution and visibility of the reconstructed image are discussed,and the relationship between resolution and visibility is analyzed.The theoretical results show that a tradeoff exists between the visibility and resolution of the reconstructed image;the better the image resolution,the worse the image visibility.Numerical simulations are carried out to verify this theory,and a ghost...     

Modified adaptive algebraic tomographic reconstruction of gas distribution from incomplete projection by a two-wavelength absorption scheme

A modified adaptive algebraic reconstruction technique (MAART) with an auto-adjustment relaxation parameter and smoothness regularization is developed to reveal the tomographic reconstruction of H 2 O distribution in combustion from incomplete projections. Determinations of relaxation parameter and regularization factor are discussed with regard to the consideration of improvement in reconstruction and reduction of computational burden. A two-wavelength scheme from tunable diode laser absorption measurement, 7444.36 and 7185.59 cm 1 , is used to simplify the nonlinear solution problem for obtaining the tomographic distributions of concentration and temperature simultaneously. Results of calculations demonstrate that MAART can perform the reconstruction results more efficiently with little complex modification and much lower iterations as compared with the traditional algebraic reconstruction technique (ART) or simultaneous iterative reconstruction technique (SIRT) methods. The stability of the algorithm is studied by reconstruction from projections with random noise at different levels to demonstrate the dependence of reconstruction results on precise line-of-sight measurements.     

一种测量多相流流型的ECT图像重建算法

提出了一种新的电容层析成像图像重建算法-IMNSNOF算法.该算法在分析极小范数解的基础之上针对ECT逆问题的特点对其进行改进,并利用奇异值分解定理证明这种改进的数值稳定作用.在此基础上建立新的日标泛函,并在求解该泛函的过程中采用正则技巧对其进行改进确保数值解的稳定性.利用非闭合电极ECT传感器实测了多相流沿流向的流型...     

中子半影成像的计算机断层重建技术

实际用于中子半影成像重建的方法都是线性方法,而计算机断层重建是一种能够用于中子半影成像重建的新方法.介绍了中子半影成像的断层重建原理,将半影成像的诊断图像沿径向等角度提取、微分后就可以使用断层重建方法重建.给出了使用卷积反投影方法重建不同噪声诊断图像的结果,并分析了断层重建的优缺点.重建结果表明,断层重建方法能够重建出...