Reconstructing the landing trajectory of the CE-3 lunar probe by using images from the landing camera

An accurate determination of the landing trajectory of Chang＇e-3 （CE-3） is significant for verifying orbital control strategy, optimizing orbital planning, accu- rately determining the landing site of CE-3 and analyzing the geological background of the landing site. Due to complexities involved in the landing process, there are some differences between the planned trajectory and the actual trajectory of CE-3. The land- ing camera on CE-3 recorded a sequence of the landing process with a frequency of 10 frames per second. These images recorded by the landing camera and high-resolution images of the lunar surface are utilized to calculate the position of the probe, so as to reconstruct its precise trajectory. This paper proposes using the method of trajectory reconstruction by Single Image Space Resection to make a detailed study of the hov- ering stage at a height of 100 m above the lunar surface. Analysis of the data shows that the closer CE-3 came to the lunar surface, the higher the spatial resolution of im- ages that were acquired became, and the more accurately the horizontal and vertical position of CE-3 could be determined. The horizontal and vertical accuracies were 7.09 m and 4.27 m respectively during the hovering stage at a height of 100.02 m. The reconstructed trajectory can reflect the change in CE-3＇s position during the powered descent process. A slight movement in CE-3 during the hovering stage is also clearly demonstrated. These results will provide a basis for analysis of orbit control strategy, and it will be conducive to adjustment and optimization of orbit control strategy in follow-up missions.

基于LS-SVM的超声导波管道缺陷二维重构

针对当前超声导波检测中的缺陷成像技术难点,提出了基于支持向量机的缺陷轮廓重构方法.通过实验和有限元仿真相结合的方式,获得不同大小缺陷的检测信号.采用最小二乘网络学习算法,选取缺陷回波数据作为支持向量机的输入,缺陷轮廓数据作为输出.建立了缺陷回波到缺陷二维轮廓的非线性映射,实现了缺陷轴向宽度和径向深度的二维轮廓重构,并与径向基神经网络重构效果进行了对比.实验结果表明,该方法速度快、精度高、泛化能力好,是管道超声导波定量化、可视化检测的一种可行方法.

Example-based super-resolution for single-image analysis from the Chang'e-1 Mission

Due to the low spatial resolution of images taken from the Chang＇e-1 （CE-I） orbiter, the details of the lunar surface are blurred and lost. Considering the limited spatial resolution of image data obtained by a CCD camera on CE-1, an example-based super-resolution （SR） algorithm is employed to obtain high- resolution （HR） images. SR reconstruction is important for the application of image data to increase the resolution of images. In this article, a novel example-based algorithm is proposed to implement SR reconstruction by single-image analysis, and the computational cost is reduced compared to other example-based SR methods. The results show that this method can enhance the resolution of images using SR and recover detailed information about the lunar surface. Thus it can be used for surveying HR terrain and geological features. Moreover, the algorithm is significant for the HR processing of remotely sensed images obtained by other imaging systems.

A super-high angular resolution principle for coded-mask X-ray imaging beyond the diffraction limit of a single pinhole

High angular resolution X-ray imaging is always useful in astrophysics and solar physics. In principle, it can be performed by using coded-mask imaging with a very long mask-detector distance. Previously, the diffraction-interference effect was thought to degrade coded-mask imaging performance dramatically at the low energy end with its very long mask-detector distance. The diffraction-interference effect is described with numerical calculations, and the diffraction-interference cross correlation reconstruction method （DICC） is developed in order to overcome the imaging performance degradation. Based on the DICC, a super-high angular resolution principle （SHARP） for coded-mask X-ray imaging is proposed. The feasibility of coded mask imaging beyond the diffraction limit of a single pinhole is demonstrated with simulations. With the specification that the mask element size is 50 × 50 μm^2 and the mask-detector distance is 50 m, the achieved angular resolution is 0.32arcsec above about 10keV and 0.36arcsec at 1.24keV （λ = 1 nm）, where diffraction cannot be neglected. The on-axis source location accuracy is better than 0.02 arcsec. Potential applications for solar observations and wide-field X-ray monitors are also briefly discussed.

多种超声影像技术在乳腺癌诊断中的研究进展

乳腺癌是我国女性发病率最高的恶性肿瘤,常规超声是乳腺癌筛查常用的影像检查方法。弹性成像、超声造影、自动乳腺超声成像系统、S-detect技术及超声引导下穿刺活检等新技术正在飞速发展并逐渐应用于临床,为乳腺癌的诊断提供了更有价值的信息。本文就多种超声影像技术诊断乳腺癌的临床应用进展进行综述。

Wavelet Analysis of Space Solar Telescope Images

The scientific satellite SST (Space Solar Telescope) is an important research project strongly supported by the Chinese Academy of Sciences. Every day, SST acquires 50 GB of data (after processing) but only 10GB can be transmitted to the ground because of limited time of satellite passage and limited channel volume. Therefore, the data must be compressed before transmission. Wavelets analysis is a new technique developed over the last 10 years, with great potential of application. We start with a brief introduction to the essential principles of wavelet analysis, and then describe the main idea of embedded zerotree wavelet coding, used for compressing the SST images. The results show that this coding is adequate for the job.

Manifestations of bright points observed in G-band and CaⅡH by Hinode/SOT

An algorithm was developed for identifying and tracking a magnetic bright point, or bright point （BP） for short, observed in both the photosphere （G-band） and chromosphere （Ca II H）, as well as for pairing a photospheric BP （PBP） with its conjugate chromospheric BP （CBP）. Two sets of data observed by Hinode/SOT in the quiet Sun near the disk center were analyzed. About 278 PBP-CBP pairs were identified and tracked. Lifetimes of both the PBPs and CBPs follow an exponential distribution with average lifetimes of 174 s and 163 s, respectively. We found that the differences in appearance time, in disappearance time and in lifetime of the two kinds of BPs all follow Gaussian distributions,which may indicate that the mechanisms of PBP and CBP formation/disintegration are different. However, the lifetimes of PBPs and CBPs are positively correlated with one another, with a correlation coefficient of 0.8. Furthermore, we calculated the horizontal displacement between the PBP and its conjugate CBP, which follows a Gaussian function with an average and standard deviation of （67.7 ± 38.5）km. We also calculated the amplitude of the flux tube shape change which might be caused by MHD waves propagating along the flux tube, and found that it follows an exponential distribution very well.

Optical fiber positioning based on four-quadrant detector with Gaussian fitting method

With the development of large-scale spectral surveys, fiber positioning technology has been developing rapidly. Because of the performance advantages of a four-quadrant（4Q） detector, a fiber positioning and real-time monitoring system based on the 4Q detector is proposed. The detection accuracy of this system is directly determined by the precision of the center of the spot. A Gaussian fitting algorithm based on the 4Q detector is studied and applied in the fiber positioning process to improve the calculated accuracy of the spot center. The relationship between the center position of the incident spot and the detector output signal is deduced. An experimental platform is built to complete the simulated experiment. Then we use the Gaussian fitting method to process experimental data, compare the fitting value with the theoretical one and calculate the corresponding error.

Ghost Images in Schmidt CCD Photometry

The wide field of the Schmidt telescope implies a greater chance of the field containing bright objects, and the presence of a corrector lens produces a certain type of ghost images. We summarize and confirm the features of such ghost images in Schmidt CCD photometry. The ghost images could be star-like under special observational conditions. The zenith distance of the telescope, among other factors, is found to correlate with different patterns of the ghost images. Some relevant issues are discussed and possible applications of our results are suggested.

LAMOST CCD camera-control system based on RTS2

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope（LAMOST） is the largest existing spectroscopic survey telescope, having 32 scientific charge-coupled-device（CCD） cameras for acquiring spectra. Stability and automation of the camera-control software are essential, but cannot be provided by the existing system. The Remote Telescope System 2 nd Version（RTS2） is an open-source and automatic observatory-control system. However, all previous RTS2 applications were developed for small telescopes. This paper focuses on implementation of an RTS2-based camera-control system for the 32 CCDs of LAMOST. A virtual camera module inherited from the RTS2 camera module is built as a device component working on the RTS2 framework. To improve the controllability and robustness, a virtualized layer is designed using the master-slave software paradigm, and the virtual camera module is mapped to the 32 real cameras of LAMOST. The new system is deployed in the actual environment and experimentally tested. Finally, multiple observations are conducted using this new RTS2-frameworkbased control system. The new camera-control system is found to satisfy the requirements for automatic camera control in LAMOST. This is the first time that RTS2 has been applied to a large telescope, and provides a referential solution for full RTS2 introduction to the LAMOST observatory control system.

Algorithm Design and Test of the Solar Guide Telescope

The Solar Guide Telescope (SGT), an important solar attitude sensor of theSST (Space Solar Telescope, a space solar observing instrument being developed in China), canaccurately produce pointing error signals of the SST for attitude control at high speed. We analyzein detail the error algorithm of the heliocentric coordinates and the edge judging of solar images.The measuring accuracy of +- 0.5 arcsec of the SGT is verified by experiments on the tracking of theSun and by testing a sun simulator. Some factors causing the pointing errors are examined.

基于改进群稀疏正则化的稀疏角度图像重建

计算机断层扫描(Computer Tomography,CT)是临床医学中广泛使用的医学图像,可以清楚地显示人体的精细结构细节,为医生诊断疾病提供很大帮助。通过最近的研究表明,基于群稀疏正则化的联合代数重建技术(Simultaneous Algebraic Reconstruction Technique,SART)重建在稀疏角度采样背景下可以获得较好的性能。然而,群稀疏正则化在去掉伪影的同时,可能将边缘或细节过度平滑,使得对比度降低,无法获得符合人类视觉效果的高分辨率图像。因此,该文提出了一种基于改进群稀疏正则化的稀疏角度图像重建方法。首先对稀疏角度下的Shepp-Logan模型进行SART重建,再利用群稀疏正则化去除图像伪影,最后利用滚动引导滤波(Rolling Guided Filtering,RGF)进行对比度提升,再次作为SART的输入进行迭代。实验结果表明,该方法在视觉上以及PSNR(Peak Signal-to-Noise Ratio),MSE(Mean Squared Error)和FSIM(Feature Similarity)上均优于其他算法,并且在迭代初始阶段就具有较好的收敛性能。

An active coronagraph using a liquid crystal array for exoplanet imaging:principle and testing

High-contrast imaging coronagraphs, used for the detection of exoplanets, have always adopted passive coronagraph optical components. It is therefore impossible to actively optimize the coronagraphs to achieve their best performance. To solve this problem, we propose a novel high-contrast imaging coronagraph which combines a liquid crystal array （LCA） for active pupil apodization and a deformable mirror （DM） for phase correction. The LCA we use is an amplitude-only spatial light mod- ulator. The LCA is well calibrated and compensates for its amplitude non-uniformity and nonlinear intensity responsivity. We measured the imaging contrasts of the coron- agraph system with the LCA only and without the DM deployed. Imaging contrasts of 10-4 and 10-5 can be reached at an inner working angular distance of 2.5 and 5A/D, respectively. A simulation shows that the phase errors on the coronagraph pupil limit the contrast performance. The contrast could be further improved if a DM is deployed to correct the phase errors induced by the LCA and coronagraph optics.

三维成像技术联合精确定位导向器用于股骨颈骨折中的临床价值

目的分析三维成像技术联合精确定位导向器在股骨颈骨折中的临床应用。方法选取我院150例股骨颈骨折患者为研究对象,其中2012年6~12月收治的50例股骨颈骨折患者为对照组,利用螺旋CT的三维成像技术观察骨的解剖外形并对骨折进行复位操作;2013年1~12月收治的100例股骨颈骨折患者为观察组,采用三维成像技术联合精确定位导向器进行治疗,两组患者采用不同方法模拟出骨折部位的移位情况及健侧部位骨骼形态的三维数据并做好统计,观察疗效。结果经不同治疗,观察组治疗优良率(94.00%)与对照组(70.00%)相比明显要高,差异有统计学意义(P<0.05);经随访,观察组患者骨折部位预后良好,需要实施二次手术的比例(3.00%)明显少于对照组(30.00%),差异有统计学意义(P<0.05);观察组患者日常生活、社会活动、抑郁和烦躁各方面评分均高于对照组,差异有统计学意义(P<0.05)。结论三维成像技术联合精确定位导向器对骨折情况进行分析后,实施相应治疗,能够提高手术质量,减少二次手术比例,有利于骨折的早期愈合。

鼻内镜手术中影像导航系统的作用

目的评价鼻内镜手术中使用影像导航系统的作用。方法回顾2000年1月～2003年5月进行的76例影像导航鼻内镜下手术,对比不同手术中影像导航使用次数：采用视觉模拟尺量化评估术者对影像导航的需求程度及对术中影像导航的满意程度；对鼻腔鼻窦骨化纤维瘤切除术和垂体腺瘤切除术时使用和不使用影像导航鼻内镜下手术时手术时间、麻醉时间、术中出血量、术中并发症情况进行对比分析。结果不同疾病间影像导航使用次数存在统计学差异,术者对影像导航的需求程度和满意程度也有差别。进行鼻内镜下鼻腔鼻窦骨化纤维瘤切除术和垂体腺瘤切除术时,使用和不使用影像导航,所观察的客观数据无显著性差异。从骨化纤维瘤切除情况看,还不能认为使用影像导航手术比不使用更能完全切除肿瘤。结论不同病变手术时导航使用的程度不同,涉及重要部位和结构的手术才有使用的必要；病例越复杂,越能证明影像导航系统作用强。使用导航系统操作达到最佳状态可能需要经过很长的时间。

基于导波理论的管道缺陷成像研究

在导波传播理论和频散波形预测理论的基础上,研究了超声导波在检测管道时,如何利用时域波形重构缺陷图像的问题。由于根据导波检测理论可以获得在任意时间管道表面任意位置的波形信息,而且管道上缺陷的存在直接影响导波信号的幅值,并被包含在回波信号中为传感器接收,所以通过对接收信号进行相应的处理便可预测缺陷处的波形用以成像。针对管道中的单通孔人工缺陷和轴向位置不同的双槽形人工缺陷,利用非轴对称端面加载的传感器激励L(0,2)模态导波进行检测,通过改变传感器周向位置获得一组检测信号以实现缺陷形状的成像。成像结果不仅能反映缺陷的类型,还能实现缺陷在轴向和周向的二维定位,对轴向双缺陷的定位取决于时间参数的选择。

以密度为导向的条纹正则优化方法

在光学干涉测量技术中,准确地实现条纹正则化是提取条纹图中的相位信息的前提.文中基于双重正交带通滤波器的正则优化法,提出了以条纹密度信息为质量评估标准来引导条纹正则化的优化方法,包含条纹图局部优化与整体优化两部分,是对双重正交带通滤波器的正则化方法的改进.首先以条纹背景强度和振幅具有的局部线性与连续性特征设计能量函数,并通过最小化能量函数获取背景强度和条纹振幅的值;然后根据高低密度区域条纹的分析,提出密度对正则化过程的导向作用以及局部优化的可行性.实验结果表明,以密度为导向的条纹正则优化法具有均方误差低、抗噪性高等优点;提出的条纹正则优化方法在操作上不需要对噪声严重的条纹图进行除噪预处理,对背景强度与振幅的线性与非线性变化可同时处理,具有较高的条纹处理效率和准确性,可应用于复杂的条纹图正则化处理.

关于放疗位置验证方式的探讨

目的:探讨放疗全程进行位置验证的意义。方法:测量使用0.6 MU的剂量拍摄位置验证片时患者实际的吸收剂量,用计划系统计算患者整个疗程吸收剂量的改变。每次治疗前采用单次曝光成像技术拍摄正、侧位位置验证片,与首次位置验证片比对,记录左右、腹背和头脚方向的误差值,若超出误差阈值则纠正摆位后再进行治疗。前五次误差,首次、中间和末次误差以及全程位置验证的误差利用方差分析方法进行统计分析。结果:获取位置验证图像过程中患者平均吸收剂量为0.3 cGy,经过计划系统重新计算剂量分布,对靶区剂量无影响。三种位置验证方式中,全程位置验证的左右、腹背和头脚方向的误差均为最大,且差异有统计学意义(P<0.05)。三种位置验证方法中,腹背方向的误差均值最小,左右方向的误差均值最大,且差异有统计学意义(P<0.05)。结论:全程位置验证对于保证病人靶区位置的精确性是有意义的。

影像学引导下不可逆电穿孔消融治疗肝脏恶性肿瘤专家共识(2022版)

不可逆电穿孔(IRE)为消融治疗肿瘤技术,尤其适用于特殊部位实体肿瘤,可不损伤血管及胆道等肿瘤周围结构,常用于消融治疗肝脏恶性肿瘤。近年来国内专家对于IRE消融治疗肝脏肿瘤已获得了成熟经验。为更好发挥IRE优势和规范临床操作、最大限度避免相关并发症,特召集国内相关专家讨论制定此共识,供临床参考。

飞机对抗红外成像导弹的方法

红外成像导弹已经得到了广泛的发展,具有较强的抗干扰能力,论文通过对红外成像制导导弹的工作原理、制导特点、成像条件和抗干扰方法的分析,针对飞机干扰红外成像制导弹的方法进行了分析研究。